General classification of hydride compounds and their main characteristics [15, 16, 17, 18, 19, 20].
\r\n\t
",isbn:"978-1-83969-603-9",printIsbn:"978-1-83969-602-2",pdfIsbn:"978-1-83969-604-6",doi:null,price:0,priceEur:0,priceUsd:0,slug:null,numberOfPages:0,isOpenForSubmission:!0,isSalesforceBook:!1,isNomenclature:!1,hash:"63deca41156136bb9fc21e070181a5dd",bookSignature:"Associate Prof. Monjur Ahmed",publishedDate:null,coverURL:"https://cdn.intechopen.com/books/images_new/11851.jpg",keywords:"Peptic Ulcer, Ischemic Ulcer, Crohn's Ulcer, Duodenal Infections, Adenoma, Carcinoma, Gastrointestinal Stromal Tumors, Neuroendocrine Tumors, Ampullectomy, Bariatric Surgery, Duodenal Resurfacing, Duodenal Stenting",numberOfDownloads:null,numberOfWosCitations:0,numberOfCrossrefCitations:null,numberOfDimensionsCitations:null,numberOfTotalCitations:null,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"April 26th 2022",dateEndSecondStepPublish:"May 24th 2022",dateEndThirdStepPublish:"July 23rd 2022",dateEndFourthStepPublish:"October 11th 2022",dateEndFifthStepPublish:"December 10th 2022",dateConfirmationOfParticipation:null,remainingDaysToSecondStep:"3 days",secondStepPassed:!0,areRegistrationsClosed:!1,currentStepOfPublishingProcess:3,editedByType:null,kuFlag:!1,biosketch:"Trained and board-certified in Internal Medicine and Gastroenterology in the United Kingdom and the United States. Has worked in many academic medical centers such as Temple University Hospital and Marshall University. He has a passion for teaching, training, doing clinical research, and publishing and is a member of the American College of Gastroenterology, American Gastroenterology Association, and the Royal College of Physicians of the United Kingdom.",coeditorOneBiosketch:null,coeditorTwoBiosketch:null,coeditorThreeBiosketch:null,coeditorFourBiosketch:null,coeditorFiveBiosketch:null,editors:[{id:"206355",title:"Associate Prof.",name:"Monjur",middleName:null,surname:"Ahmed",slug:"monjur-ahmed",fullName:"Monjur Ahmed",profilePictureURL:"https://mts.intechopen.com/storage/users/206355/images/system/206355.jpeg",biography:"Monjur Ahmed, MD, FRCP, is an Associate Professor of Medicine at Thomas Jefferson University, Philadelphia, Pennsylvania, USA. He has been a practicing gastroenterologist for twenty-two years. He has a special interest in inflammatory bowel disease, eosinophilic esophagitis, gastrointestinal motility, and dysphagia. Dr. Ahmed also serves as an editor in chief for the World Journal of Gastrointestinal Oncology.",institutionString:"Thomas Jefferson University",position:null,outsideEditionCount:0,totalCites:0,totalAuthoredChapters:"8",totalChapterViews:"0",totalEditedBooks:"2",institution:{name:"Thomas Jefferson University",institutionURL:null,country:{name:"United States of America"}}}],coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"16",title:"Medicine",slug:"medicine"}],chapters:null,productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},personalPublishingAssistant:{id:"466997",firstName:"Patricia",lastName:"Kerep",middleName:null,title:"Ms.",imageUrl:"https://mts.intechopen.com/storage/users/466997/images/21565_n.jpg",email:"patricia@intechopen.com",biography:"As an Author Service Manager my responsibilities include monitoring and facilitating all publishing activities for authors and editors. From chapter submission and review, to approval and revision, copyediting and design, until final publication, I work closely with authors and editors to ensure a simple and easy publishing process. I maintain constant and effective communication with authors, editors and reviewers, which allows for a level of personal support that enables contributors to fully"}},relatedBooks:[{type:"book",id:"6550",title:"Cohort Studies in Health Sciences",subtitle:null,isOpenForSubmission:!1,hash:"01df5aba4fff1a84b37a2fdafa809660",slug:"cohort-studies-in-health-sciences",bookSignature:"R. Mauricio Barría",coverURL:"https://cdn.intechopen.com/books/images_new/6550.jpg",editedByType:"Edited by",editors:[{id:"88861",title:"Dr.",name:"R. Mauricio",surname:"Barría",slug:"r.-mauricio-barria",fullName:"R. Mauricio Barría"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9500",title:"Recent Advances in Bone Tumours and Osteoarthritis",subtitle:null,isOpenForSubmission:!1,hash:"ea4ec0d6ee01b88e264178886e3210ed",slug:"recent-advances-in-bone-tumours-and-osteoarthritis",bookSignature:"Hiran Amarasekera",coverURL:"https://cdn.intechopen.com/books/images_new/9500.jpg",editedByType:"Edited by",editors:[{id:"67634",title:"Dr.",name:"Hiran",surname:"Amarasekera",slug:"hiran-amarasekera",fullName:"Hiran Amarasekera"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"1591",title:"Infrared Spectroscopy",subtitle:"Materials Science, Engineering and Technology",isOpenForSubmission:!1,hash:"99b4b7b71a8caeb693ed762b40b017f4",slug:"infrared-spectroscopy-materials-science-engineering-and-technology",bookSignature:"Theophile Theophanides",coverURL:"https://cdn.intechopen.com/books/images_new/1591.jpg",editedByType:"Edited by",editors:[{id:"37194",title:"Dr.",name:"Theophile",surname:"Theophanides",slug:"theophile-theophanides",fullName:"Theophile Theophanides"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"3161",title:"Frontiers in Guided Wave Optics and Optoelectronics",subtitle:null,isOpenForSubmission:!1,hash:"deb44e9c99f82bbce1083abea743146c",slug:"frontiers-in-guided-wave-optics-and-optoelectronics",bookSignature:"Bishnu Pal",coverURL:"https://cdn.intechopen.com/books/images_new/3161.jpg",editedByType:"Edited by",editors:[{id:"4782",title:"Prof.",name:"Bishnu",surname:"Pal",slug:"bishnu-pal",fullName:"Bishnu Pal"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"371",title:"Abiotic Stress in Plants",subtitle:"Mechanisms and Adaptations",isOpenForSubmission:!1,hash:"588466f487e307619849d72389178a74",slug:"abiotic-stress-in-plants-mechanisms-and-adaptations",bookSignature:"Arun Shanker and B. Venkateswarlu",coverURL:"https://cdn.intechopen.com/books/images_new/371.jpg",editedByType:"Edited by",editors:[{id:"58592",title:"Dr.",name:"Arun",surname:"Shanker",slug:"arun-shanker",fullName:"Arun Shanker"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"3092",title:"Anopheles mosquitoes",subtitle:"New insights into malaria vectors",isOpenForSubmission:!1,hash:"c9e622485316d5e296288bf24d2b0d64",slug:"anopheles-mosquitoes-new-insights-into-malaria-vectors",bookSignature:"Sylvie Manguin",coverURL:"https://cdn.intechopen.com/books/images_new/3092.jpg",editedByType:"Edited by",editors:[{id:"50017",title:"Prof.",name:"Sylvie",surname:"Manguin",slug:"sylvie-manguin",fullName:"Sylvie Manguin"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"72",title:"Ionic Liquids",subtitle:"Theory, Properties, New Approaches",isOpenForSubmission:!1,hash:"d94ffa3cfa10505e3b1d676d46fcd3f5",slug:"ionic-liquids-theory-properties-new-approaches",bookSignature:"Alexander Kokorin",coverURL:"https://cdn.intechopen.com/books/images_new/72.jpg",editedByType:"Edited by",editors:[{id:"19816",title:"Prof.",name:"Alexander",surname:"Kokorin",slug:"alexander-kokorin",fullName:"Alexander Kokorin"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"2270",title:"Fourier Transform",subtitle:"Materials Analysis",isOpenForSubmission:!1,hash:"5e094b066da527193e878e160b4772af",slug:"fourier-transform-materials-analysis",bookSignature:"Salih Mohammed Salih",coverURL:"https://cdn.intechopen.com/books/images_new/2270.jpg",editedByType:"Edited by",editors:[{id:"111691",title:"Dr.Ing.",name:"Salih",surname:"Salih",slug:"salih-salih",fullName:"Salih Salih"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"117",title:"Artificial Neural Networks",subtitle:"Methodological Advances and Biomedical Applications",isOpenForSubmission:!1,hash:null,slug:"artificial-neural-networks-methodological-advances-and-biomedical-applications",bookSignature:"Kenji Suzuki",coverURL:"https://cdn.intechopen.com/books/images_new/117.jpg",editedByType:"Edited by",editors:[{id:"3095",title:"Prof.",name:"Kenji",surname:"Suzuki",slug:"kenji-suzuki",fullName:"Kenji Suzuki"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"3828",title:"Application of Nanotechnology in Drug Delivery",subtitle:null,isOpenForSubmission:!1,hash:"51a27e7adbfafcfedb6e9683f209cba4",slug:"application-of-nanotechnology-in-drug-delivery",bookSignature:"Ali Demir Sezer",coverURL:"https://cdn.intechopen.com/books/images_new/3828.jpg",editedByType:"Edited by",editors:[{id:"62389",title:"PhD.",name:"Ali Demir",surname:"Sezer",slug:"ali-demir-sezer",fullName:"Ali Demir Sezer"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}]},chapter:{item:{type:"chapter",id:"23559",title:"Metastatis of Soft Tissue Sarcomas",doi:"10.5772/25294",slug:"metastatis-of-soft-tissue-sarcomas",body:null,keywords:null,chapterPDFUrl:"https://cdn.intechopen.com/pdfs/23559.pdf",chapterXML:null,downloadPdfUrl:"/chapter/pdf-download/23559",previewPdfUrl:"/chapter/pdf-preview/23559",totalDownloads:2581,totalViews:68,totalCrossrefCites:0,totalDimensionsCites:0,totalAltmetricsMentions:0,impactScore:0,impactScorePercentile:27,impactScoreQuartile:2,hasAltmetrics:0,dateSubmitted:"January 20th 2011",dateReviewed:"June 24th 2011",datePrePublished:null,datePublished:"November 16th 2011",dateFinished:null,readingETA:"0",abstract:null,reviewType:"peer-reviewed",bibtexUrl:"/chapter/bibtex/23559",risUrl:"/chapter/ris/23559",book:{id:"810",slug:"soft-tissue-tumors"},signatures:"Fethi Derbel, Sonia Ziadi, Medi Ben Hadj Hamida, Jaafar Mazhoud, Mohamed Ben Mabrouk, Abdallah Mtimet, Sabri Youssef, Ajmi Chaouch, Ali Ben Ali, Ibtissam Hasni, Mrad Dali Kaouthar, Jemni Hela, Moncef Mokni and Ridha Ben Hadj Hamida",authors:[{id:"62900",title:"Prof.",name:"Fethi",middleName:null,surname:"Derbel",fullName:"Fethi Derbel",slug:"fethi-derbel",email:"fethi.derbel@gmail.com",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/62900/images/system/62900.jpeg",institution:null},{id:"69162",title:"Dr.",name:"Sonia",middleName:null,surname:"Ziadi",fullName:"Sonia Ziadi",slug:"sonia-ziadi",email:"sonia.ziadi@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:null},{id:"69163",title:"Dr.",name:"Medi",middleName:null,surname:"Ben Hadj Hamida",fullName:"Medi Ben Hadj Hamida",slug:"medi-ben-hadj-hamida",email:"mbh@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:{name:"Hôpital Sahloul",institutionURL:null,country:{name:"Tunisia"}}},{id:"69166",title:"Dr.",name:"Jaafar",middleName:null,surname:"Mazhoud",fullName:"Jaafar Mazhoud",slug:"jaafar-mazhoud",email:"jaafar.mazhoud@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:{name:"Hôpital Sahloul",institutionURL:null,country:{name:"Tunisia"}}},{id:"69168",title:"Prof.",name:"Sabri",middleName:null,surname:"Youssef",fullName:"Sabri Youssef",slug:"sabri-youssef",email:"sabri.youssef@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:{name:"Hôpital Sahloul",institutionURL:null,country:{name:"Tunisia"}}},{id:"69170",title:"Prof.",name:"Ali",middleName:null,surname:"Ben Ali",fullName:"Ali Ben Ali",slug:"ali-ben-ali",email:"ali.benali@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:{name:"Hôpital Sahloul",institutionURL:null,country:{name:"Tunisia"}}},{id:"69171",title:"Prof.",name:"Moncef",middleName:null,surname:"Mokni",fullName:"Moncef Mokni",slug:"moncef-mokni",email:"moncef.mokni@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:null},{id:"69172",title:"Prof.",name:"Ridha",middleName:null,surname:"Ben Hadj Hamida",fullName:"Ridha Ben Hadj Hamida",slug:"ridha-ben-hadj-hamida",email:"ridha.bhhamida@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:{name:"Hôpital Sahloul",institutionURL:null,country:{name:"Tunisia"}}},{id:"117074",title:"Dr.",name:"Mohamed",middleName:null,surname:"Ben Mabrouk",fullName:"Mohamed Ben Mabrouk",slug:"mohamed-ben-mabrouk",email:"mohamed.benmabrouk@rns.tn",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",institution:null}],sections:null,chapterReferences:null,footnotes:null,contributors:null,corrections:null},book:{id:"810",type:"book",title:"Soft Tissue Tumors",subtitle:null,fullTitle:"Soft Tissue Tumors",slug:"soft-tissue-tumors",publishedDate:"November 16th 2011",bookSignature:"Fethi Derbel",coverURL:"https://cdn.intechopen.com/books/images_new/810.jpg",licenceType:"CC BY 3.0",editedByType:"Edited by",isbn:null,printIsbn:"978-953-307-862-5",pdfIsbn:"978-953-51-6730-3",reviewType:"peer-reviewed",numberOfWosCitations:12,isAvailableForWebshopOrdering:!0,editors:[{id:"62900",title:"Prof.",name:"Fethi",middleName:null,surname:"Derbel",slug:"fethi-derbel",fullName:"Fethi Derbel"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"1088"}],productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},chapters:[{id:"23546",type:"chapter",title:"Considerations for Treatment Development in Rhabdomyosarcoma: In Vitro Assessment of Novel DNA Binding Drugs",slug:"considerations-for-treatment-development-in-rhabdomyosarcoma-in-vitro-assessment-of-novel-dna-bindin",totalDownloads:2125,totalCrossrefCites:0,signatures:"Steven J. Wolf, Laurence P.G. Wakelin and Daniel R. Catchpoole",reviewType:"peer-reviewed",authors:[{id:"63157",title:"Dr.",name:"Daniel",middleName:null,surname:"Catchpoole",fullName:"Daniel Catchpoole",slug:"daniel-catchpoole"},{id:"93018",title:"Dr.",name:"Steven",middleName:null,surname:"Wolf",fullName:"Steven Wolf",slug:"steven-wolf"},{id:"93776",title:"Prof.",name:"Laurence",middleName:null,surname:"Wakelin",fullName:"Laurence Wakelin",slug:"laurence-wakelin"}]},{id:"23547",type:"chapter",title:"Telomere Maintenance Mechanisms in Soft Tissue Sarcomas",slug:"telomere-maintenance-mechanisms-in-soft-tissue-sarcomas",totalDownloads:2251,totalCrossrefCites:0,signatures:"Matthew J. Plantinga and Dominique Broccoli",reviewType:"peer-reviewed",authors:[{id:"68514",title:"Dr.",name:"Dominique",middleName:null,surname:"Broccoli",fullName:"Dominique Broccoli",slug:"dominique-broccoli"},{id:"70078",title:"Dr.",name:"Matthew",middleName:null,surname:"Plantinga",fullName:"Matthew Plantinga",slug:"matthew-plantinga"}]},{id:"23548",type:"chapter",title:"Classification of Soft Tissue Tumors by Machine Learning Algorithms",slug:"classification-of-soft-tissue-tumors-by-machine-learning-algorithms",totalDownloads:2489,totalCrossrefCites:2,signatures:"Jaber Juntu, Arthur M. De Schepper, Pieter Van Dyck, Dirk Van Dyck, Jan Gielen, Paul M. Parizel and Jan Sijbers",reviewType:"peer-reviewed",authors:[{id:"71416",title:"Dr.",name:"Jaber",middleName:null,surname:"Juntu",fullName:"Jaber Juntu",slug:"jaber-juntu"}]},{id:"23549",type:"chapter",title:"Medical Theory on Orthopedics Combining Molecular Imaging with Clinical Practice",slug:"medical-theory-on-orthopedics-combining-molecular-imaging-with-clinical-practice",totalDownloads:2157,totalCrossrefCites:0,signatures:"Jing jing Peng",reviewType:"peer-reviewed",authors:[{id:"63345",title:"Prof.",name:"Jing-Jing",middleName:null,surname:"Peng",fullName:"Jing-Jing Peng",slug:"jing-jing-peng"}]},{id:"23550",type:"chapter",title:"Imaging Findings of Adipocytic Tumors",slug:"imaging-findings-of-adipocytic-tumors",totalDownloads:4491,totalCrossrefCites:0,signatures:"Jun Nishida, Shigeru Ehara and Tadashi Shimamura",reviewType:"peer-reviewed",authors:[{id:"64117",title:"Dr.",name:"Jun",middleName:null,surname:"Nishida",fullName:"Jun Nishida",slug:"jun-nishida"},{id:"120250",title:"Prof.",name:"Shigeru",middleName:null,surname:"Ehara",fullName:"Shigeru Ehara",slug:"shigeru-ehara"},{id:"120251",title:"Prof.",name:"Tadashi",middleName:null,surname:"Shimamura",fullName:"Tadashi Shimamura",slug:"tadashi-shimamura"}]},{id:"23551",type:"chapter",title:"Pediatric Soft Tissue Tumors",slug:"pediatric-soft-tissue-tumors",totalDownloads:3457,totalCrossrefCites:0,signatures:"Ezequiel Trejo-Scorza, Belinda Beatriz Márquez Álvarez, Carlos José Trejo-Scorza and Simón Paz-Ivannov",reviewType:"peer-reviewed",authors:[{id:"62913",title:"Prof.",name:"Ezequiel",middleName:null,surname:"Trejo-Scorza",fullName:"Ezequiel Trejo-Scorza",slug:"ezequiel-trejo-scorza"},{id:"119812",title:"Dr.",name:"Carlos José",middleName:null,surname:"Trejo-Scorza",fullName:"Carlos José Trejo-Scorza",slug:"carlos-jose-trejo-scorza"}]},{id:"23552",type:"chapter",title:"Head and Neck Soft Tissue Sarcoma",slug:"head-and-neck-soft-tissue-sarcoma",totalDownloads:3923,totalCrossrefCites:3,signatures:"Rogelio Gonzalez – Gonzalez, Ronell Bologna – Molina, Omar Tremillo – Maldonado, Ramon Gil Carreon – Burciaga and Marcelo Gomez Palacio - Gastelúm",reviewType:"peer-reviewed",authors:[{id:"63162",title:"Dr.",name:"Rogelio",middleName:null,surname:"Gonzalez",fullName:"Rogelio Gonzalez",slug:"rogelio-gonzalez"},{id:"69549",title:"Dr.",name:"Ronell",middleName:null,surname:"Bologna - Molina",fullName:"Ronell Bologna - Molina",slug:"ronell-bologna-molina"},{id:"115308",title:"Dr.",name:"Omar",middleName:"Alejandro",surname:"Tremillo - Maldonado",fullName:"Omar Tremillo - Maldonado",slug:"omar-tremillo-maldonado"},{id:"116369",title:"Dr.",name:"Ramón Gil",middleName:null,surname:"Carreon - Burciaga",fullName:"Ramón Gil Carreon - Burciaga",slug:"ramon-gil-carreon-burciaga"},{id:"117748",title:"MSc.",name:"Marcelo",middleName:null,surname:"Gomez Palacio - Gastelum",fullName:"Marcelo Gomez Palacio - Gastelum",slug:"marcelo-gomez-palacio-gastelum"}]},{id:"23553",type:"chapter",title:"Dermatofibrosarcoma Protuberans – Special Challenges of Management in Resources Constrained Countries",slug:"dermatofibrosarcoma-protuberans-special-challenges-of-management-in-resources-constrained-countries",totalDownloads:2939,totalCrossrefCites:0,signatures:"Titus Osita Chukwuanukwu and Stanley Anyanwu",reviewType:"peer-reviewed",authors:[{id:"63108",title:"Dr.",name:"Titus",middleName:"Osita",surname:"Chukwuanukwu",fullName:"Titus Chukwuanukwu",slug:"titus-chukwuanukwu"},{id:"140097",title:"Dr.",name:"Stanley",middleName:null,surname:"Anyanwu",fullName:"Stanley Anyanwu",slug:"stanley-anyanwu"}]},{id:"23554",type:"chapter",title:"Clinical and Molecular Biology of Angiosarcoma",slug:"clinical-and-molecular-biology-of-angiosarcoma",totalDownloads:3747,totalCrossrefCites:3,signatures:"N.J. Andersen, R.E. Froman, B.E. Kitchell and N.S. Duesbery",reviewType:"peer-reviewed",authors:[{id:"62952",title:"Prof.",name:"Nicholas",middleName:null,surname:"Duesbery",fullName:"Nicholas Duesbery",slug:"nicholas-duesbery"},{id:"62955",title:"Dr.",name:"Nicholas",middleName:null,surname:"Andersen",fullName:"Nicholas Andersen",slug:"nicholas-andersen"},{id:"62956",title:"Prof.",name:"Roe",middleName:null,surname:"Froman",fullName:"Roe Froman",slug:"roe-froman"}]},{id:"23555",type:"chapter",title:"Gastrointestinal Stromal Tumours: A Contemporary Review on Pathogenesis, Morphology and Prognosis",slug:"gastrointestinal-stromal-tumours-a-contemporary-review-on-pathogenesis-morphology-and-prognosis",totalDownloads:2206,totalCrossrefCites:0,signatures:"Muna Sabah",reviewType:"peer-reviewed",authors:[{id:"66389",title:"Dr.",name:"Muna",middleName:null,surname:"Sabah",fullName:"Muna Sabah",slug:"muna-sabah"}]},{id:"23556",type:"chapter",title:"Treatment of Synovial Sarcoma in Children",slug:"treatment-of-synovial-sarcoma-in-children",totalDownloads:2221,totalCrossrefCites:0,signatures:"Shvarova Anna Viktorovna, Rykov Maxim Yurjevich, Karseladze Appolon Irodionovich and Ivanova Nadezhda Mikhailovna",reviewType:"peer-reviewed",authors:[{id:"63914",title:"Dr.",name:"Anna",middleName:null,surname:"Shvarova",fullName:"Anna Shvarova",slug:"anna-shvarova"},{id:"66902",title:"Prof.",name:"Maxim",middleName:null,surname:"Rykov",fullName:"Maxim Rykov",slug:"maxim-rykov"},{id:"66903",title:"Dr.",name:"Rano",middleName:null,surname:"Ravshanova",fullName:"Rano Ravshanova",slug:"rano-ravshanova"},{id:"66904",title:"Prof.",name:"Nadeghda",middleName:null,surname:"Ivanova",fullName:"Nadeghda Ivanova",slug:"nadeghda-ivanova"}]},{id:"23557",type:"chapter",title:"Novel Therapeutic Targets in Soft Tissue Sarcomas",slug:"novel-therapeutic-targets-in-soft-tissue-sarcomas",totalDownloads:2317,totalCrossrefCites:0,signatures:"Quincy S.C. Chu and Karen E. Mulder",reviewType:"peer-reviewed",authors:[{id:"70468",title:"Dr.",name:"Quincy",middleName:null,surname:"Chu",fullName:"Quincy Chu",slug:"quincy-chu"},{id:"71290",title:"Dr.",name:"Karen",middleName:null,surname:"Mulder",fullName:"Karen Mulder",slug:"karen-mulder"}]},{id:"23558",type:"chapter",title:"Prognostic Factors in Soft Tissue Sarcoma",slug:"prognostic-factors-in-soft-tissue-sarcoma",totalDownloads:2601,totalCrossrefCites:1,signatures:"Luiz Eduardo Moreira Teixeira, Jose Carlos Vilela and Ivana Duval De Araujo",reviewType:"peer-reviewed",authors:[{id:"64388",title:"Prof.",name:"Luiz Eduardo Moreira",middleName:null,surname:"Teixeira",fullName:"Luiz Eduardo Moreira Teixeira",slug:"luiz-eduardo-moreira-teixeira"},{id:"70392",title:"Dr",name:"Jose Carlos",middleName:null,surname:"Vilela",fullName:"Jose Carlos Vilela",slug:"jose-carlos-vilela"},{id:"70393",title:"Dr",name:"Ivana Duval",middleName:null,surname:"De Araujo",fullName:"Ivana Duval De Araujo",slug:"ivana-duval-de-araujo"}]},{id:"23559",type:"chapter",title:"Metastatis of Soft Tissue Sarcomas",slug:"metastatis-of-soft-tissue-sarcomas",totalDownloads:2581,totalCrossrefCites:0,signatures:"Fethi Derbel, Sonia Ziadi, Medi Ben Hadj Hamida, Jaafar Mazhoud, Mohamed Ben Mabrouk, Abdallah Mtimet, Sabri Youssef, Ajmi Chaouch, Ali Ben Ali, Ibtissam Hasni, Mrad Dali Kaouthar, Jemni Hela, Moncef Mokni and Ridha Ben Hadj Hamida",reviewType:"peer-reviewed",authors:[{id:"62900",title:"Prof.",name:"Fethi",middleName:null,surname:"Derbel",fullName:"Fethi Derbel",slug:"fethi-derbel"},{id:"69162",title:"Dr.",name:"Sonia",middleName:null,surname:"Ziadi",fullName:"Sonia Ziadi",slug:"sonia-ziadi"},{id:"69163",title:"Dr.",name:"Medi",middleName:null,surname:"Ben Hadj Hamida",fullName:"Medi Ben Hadj Hamida",slug:"medi-ben-hadj-hamida"},{id:"69166",title:"Dr.",name:"Jaafar",middleName:null,surname:"Mazhoud",fullName:"Jaafar Mazhoud",slug:"jaafar-mazhoud"},{id:"69168",title:"Prof.",name:"Sabri",middleName:null,surname:"Youssef",fullName:"Sabri Youssef",slug:"sabri-youssef"},{id:"69170",title:"Prof.",name:"Ali",middleName:null,surname:"Ben Ali",fullName:"Ali Ben Ali",slug:"ali-ben-ali"},{id:"69171",title:"Prof.",name:"Moncef",middleName:null,surname:"Mokni",fullName:"Moncef Mokni",slug:"moncef-mokni"},{id:"69172",title:"Prof.",name:"Ridha",middleName:null,surname:"Ben Hadj Hamida",fullName:"Ridha Ben Hadj Hamida",slug:"ridha-ben-hadj-hamida"},{id:"117074",title:"Dr.",name:"Mohamed",middleName:null,surname:"Ben Mabrouk",fullName:"Mohamed Ben Mabrouk",slug:"mohamed-ben-mabrouk"}]}]},relatedBooks:[{type:"book",id:"2649",title:"Abdominal Surgery",subtitle:null,isOpenForSubmission:!1,hash:"cf9e8d49b05e1e65874842c5bbf4bccc",slug:"abdominal-surgery",bookSignature:"Fethi Derbel",coverURL:"https://cdn.intechopen.com/books/images_new/2649.jpg",editedByType:"Edited by",editors:[{id:"62900",title:"Prof.",name:"Fethi",surname:"Derbel",slug:"fethi-derbel",fullName:"Fethi Derbel"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"},chapters:[{id:"38233",title:"Abdominal Trauma Imaging",slug:"abdominal-trauma-imaging",signatures:"Nadia Mama, Hela Jemni, Nadia Arifa Achour, Ould Chavey Sidiya, Kaled Kadri, Mehdi Gaha, Ibtisem Hasni and Kalthoum Tlili",authors:[{id:"62900",title:"Prof.",name:"Fethi",middleName:null,surname:"Derbel",fullName:"Fethi Derbel",slug:"fethi-derbel"},{id:"143773",title:"Prof.",name:"Hela",middleName:null,surname:"Jemni",fullName:"Hela Jemni",slug:"hela-jemni"},{id:"143774",title:"Prof.",name:"Nadia",middleName:null,surname:"Arifa",fullName:"Nadia Arifa",slug:"nadia-arifa"},{id:"143775",title:"Dr.",name:"Ibtissam",middleName:null,surname:"Hasni",fullName:"Ibtissam Hasni",slug:"ibtissam-hasni"},{id:"143778",title:"Dr.",name:"Khaled",middleName:null,surname:"Kadri",fullName:"Khaled Kadri",slug:"khaled-kadri"},{id:"143779",title:"Dr.",name:"Mehdi",middleName:null,surname:"Ben Haj Hamida",fullName:"Mehdi Ben Haj Hamida",slug:"mehdi-ben-haj-hamida"},{id:"143780",title:"Dr.",name:"Jaafar",middleName:null,surname:"Mazhoud",fullName:"Jaafar Mazhoud",slug:"jaafar-mazhoud"},{id:"143782",title:"Prof.",name:"Ridha",middleName:null,surname:"Ben Haj Hamida",fullName:"Ridha Ben Haj Hamida",slug:"ridha-ben-haj-hamida"},{id:"143783",title:"Prof.",name:"Kalthoum",middleName:null,surname:"GraiessTtlili",fullName:"Kalthoum GraiessTtlili",slug:"kalthoum-graiessttlili"}]},{id:"38232",title:"Anesthetic Management of Abdominal Surgery",slug:"anesthetic-management-of-abdominal-surgery",signatures:"Aysin Alagol",authors:[{id:"150058",title:"Dr.",name:"Aysin",middleName:null,surname:"Alagol",fullName:"Aysin Alagol",slug:"aysin-alagol"}]},{id:"38231",title:"Abdominal Surgery: Advances in the Use of Ultrasound-Guided Truncal Blocks for Perioperative Pain Management",slug:"abdominal-surgery-advances-in-the-use-of-ultrasound-guided-truncal-blocks-for-perioperative-pain-man",signatures:"Jens Børglum and Kenneth Jensen",authors:[{id:"141182",title:"Dr.",name:"Jens",middleName:null,surname:"Børglum",fullName:"Jens Børglum",slug:"jens-borglum"},{id:"145845",title:"Dr.",name:"Kenneth",middleName:null,surname:"Jensen",fullName:"Kenneth Jensen",slug:"kenneth-jensen"}]},{id:"38229",title:"Study of Vitamin C Administration Effect on Postoperative Plasma IL-6 Concentrations in Septic Patients After Abdominal Surgery",slug:"study-of-vitamin-c-administration-effect-on-postoperative-plasma-il-6-concentrations-in-septic-patie",signatures:"Ignacio Ferrón-Celma, Carmen Olmedo, Alfonso Mansilla, Ana Garcia-Navarro, Karim Muffak, Pablo Bueno and Jose-Antonio Ferrón",authors:[{id:"147593",title:"PhD.",name:"Pablo",middleName:null,surname:"Bueno",fullName:"Pablo Bueno",slug:"pablo-bueno"}]},{id:"38230",title:"Hydatid Cysts of the Liver - Diagnosis, Complications and Treatment",slug:"hydatid-cysts-of-the-liver-diagnosis-complications-and-treatment",signatures:"Fethi Derbel, Mohamed Ben Mabrouk, Mehdi Ben Hadj Hamida, Jaafar Mazhoud, Sabri Youssef, Ali Ben Ali, Hela Jemni, Nadia Mama, Hasni Ibtissem, Arifa Nadia, Chedia El Ouni, Walid Naija, Moncef Mokni and Ridha Ben Hadj Hamida",authors:[{id:"62900",title:"Prof.",name:"Fethi",middleName:null,surname:"Derbel",fullName:"Fethi Derbel",slug:"fethi-derbel"}]},{id:"38228",title:"Abdominal Advanced Oncologic Surgery",slug:"abdominal-advanced-oncologic-surgery",signatures:"Enrico Maria Pasqual and Serena Bertozzi",authors:[{id:"74449",title:"Dr.",name:"Serena",middleName:null,surname:"Bertozzi",fullName:"Serena Bertozzi",slug:"serena-bertozzi"},{id:"139756",title:"Prof.",name:"Enricomaria",middleName:null,surname:"Pasqual",fullName:"Enricomaria Pasqual",slug:"enricomaria-pasqual"}]}]}],publishedBooks:[{type:"book",id:"827",title:"Tumor Suppressor Genes",subtitle:null,isOpenForSubmission:!1,hash:"deeb41ed72b58d5215b7cee7b72243a1",slug:"tumor-suppressor-genes",bookSignature:"Yue Cheng",coverURL:"https://cdn.intechopen.com/books/images_new/827.jpg",editedByType:"Edited by",editors:[{id:"71501",title:"Dr.",name:"Yue",surname:"Cheng",slug:"yue-cheng",fullName:"Yue Cheng"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"963",title:"Hodgkin's Lymphoma",subtitle:null,isOpenForSubmission:!1,hash:"a107026375308f4f7f45cf2ed535b4e8",slug:"hodgkin-s-lymphoma",bookSignature:"Nima Rezaei",coverURL:"https://cdn.intechopen.com/books/images_new/963.jpg",editedByType:"Edited by",editors:[{id:"116250",title:"Dr.",name:"Nima",surname:"Rezaei",slug:"nima-rezaei",fullName:"Nima Rezaei"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"1133",title:"Germ Cell Tumor",subtitle:null,isOpenForSubmission:!1,hash:"004a109c6be9c54e2ece2ca511d7e3d9",slug:"germ-cell-tumor",bookSignature:"Angabin Matin",coverURL:"https://cdn.intechopen.com/books/images_new/1133.jpg",editedByType:"Edited by",editors:[{id:"100071",title:"Dr.",name:"Angabin",surname:"Matin",slug:"angabin-matin",fullName:"Angabin Matin"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}],publishedBooksByAuthor:[{type:"book",id:"9163",title:"The Eye and Foot in Diabetes",subtitle:null,isOpenForSubmission:!1,hash:"0702b8cb35abbd7ac1fe4d80a7d092ad",slug:"the-eye-and-foot-in-diabetes",bookSignature:"Jeffery Grigsby and Fethi Derbel",coverURL:"https://cdn.intechopen.com/books/images_new/9163.jpg",editedByType:"Edited by",editors:[{id:"83508",title:"Dr.",name:"Jeffery",surname:"Grigsby",slug:"jeffery-grigsby",fullName:"Jeffery Grigsby"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}]},onlineFirst:{chapter:{type:"chapter",id:"64686",title:"Tailoring the Kinetic Behavior of Hydride Forming Materials for Hydrogen Storage",doi:"10.5772/intechopen.82433",slug:"tailoring-the-kinetic-behavior-of-hydride-forming-materials-for-hydrogen-storage",body:'\nIn the last two centuries, the energy supply has been based on fossil fuels (natural gas, liquid fuels, and coal). This strong dependence of our modern society on fossil fuels has economic- and geo-political consequences and causes detrimental environmental footprints. Figure 1A shows the world fossil fuel demand-supply trend from the 1990s until 2017. In 2017, the world fossil fuel demand (97.8 barrel per day) is over the supply (97.4 barrel per day) [1]. For these reasons, in the last decades, many efforts have been put for the development and research of energy renewable sources. The market of the renewable energies achieved a new global record in 2015 with $285 billion investment on this technology, exceeding the previous record of $278 billion on 2011 [2]. The use of renewable energy has many potential benefits, including a reduction in CO2 emissions, the diversification of energy vectors, and a reduced dependency on fossil fuel markets. In this regard, hydrogen (H2) is considered as a potential energy vector because it is abundant and its combustion generates a large amount of energy and water: H2 + ½ O2 → H2O + Energy. Figure 1B shows that H2 exhibits far higher gravimetric energy density than other traditional fossil fuels: 33.3 kWh/kg for H2, 13.9 kWh/kg for natural gas, and 12.4 kWh/kg for liquid hydrocarbons [3, 4, 5, 6]. Furthermore, H2 can be directly produced from clean sources such as, for instance, from electrolysis of water or from biomass with light from the sun and biological micro-organism. These renewable methods for hydrogen production can avoid the coal reforming, though this technology is under development and it is not available on industrial scale yet [7].
\n(A) Evolution of the world demand and supply of fossil fuels in millions of barrels per day (includes all kinds of fossil fuels) [
Nowadays, H2 is used as feedstock in the petrochemical and fertilizers industries. There are restricted technological applications of H2 as for example in portable devices like mobile phones, computers, and even some hydrogen driven cars. In spite of all the advantages of H2 to be considered as the new energy carrier and the evolution of the hydrogen technology showing some technological applications, there are some major issues to be solved before introducing the “hydrogen technology” into the massive market [8]. The hydrogen technology is still under early research and development phase, the current costs of this new technology and the lack of established infrastructure are the main constraints [9, 10, 11]. Among the technological problems for the implementation of the “hydrogen economy,” one of the main bottleneck is the lack of safe, compact, energetic-, and cost-efficient hydrogen storage system, especially for mobile applications such as means of transports [12, 13].
\nOn one hand, H2 has the highest gravimetric energy density in comparison with the traditional fossil fuels, Figure 1B. On the other hand, H2 has extremely low density at room temperature (0.089 g/dm3 under 1 bar), hence its volumetric energy density is extremely low (0.003 kWh/dm3). Figure 2A shows that the volumetric energy density of H2 is notably lower than the traditional fossil fuels (0.008 kWh/dm3 for natural gas, 10.5 kWh/dm3 for liquid hydrocarbons, and 35 kWh/dm3 for processed coal). Figure 2B shows the volumetric storage density for different traditional and hydrogen storage systems. As seen, there is a huge gap between the volumetric energy density of the light and cheap tank system for liquid hydrocarbons such as gasoline and the volumetric energy density of hydrogen storage systems.
\n(A) Volumetric energy density for pure: hydrogen, liquid hydrocarbons, natural gas, and coal [
Liquefaction and compression are the traditional physical methods to store hydrogen. Nowadays, available liquid hydrogen storage systems can achieve energy densities of 1.2 kWh/dm3. However, cryogenic hydrogen storage systems work at −253°C (liquefied hydrogen temperature) and this requires 20–30% of its energy content. Moreover, hydrogen losses because of evaporation are between 0.3 and 3% per day. On the contrary, gas storage systems can confine hydrogen for long periods without losses. The gas hydrogen vessels need similar technology and infrastructure to that of the established compressed natural gas tanks. Reinforced gas hydrogen containers for 350 and 700 bar of pressure are commercially available. These gas storage systems can achieve volumetric energy densities up to 0.9 kWh/dm3, but about 15% of the fuel energy content is required for compression. Solid storage systems in hydride compounds are so far tested on small and middle scale in laboratories. As an example, a tested solid storage system has lower volumetric energy density (0.8 kWh/dm3) than the traditional physical storage systems [14]. However, solid storage systems work at milder temperature and pressure conditions than the physical storage systems, i.e., in the range of temperatures between 25 and 400°C and under pressure in the range of 10–100 bar of H2, depending on the hydride material. This means that extreme cryogenic temperature of −253°C or extreme high pressure of 700 bar is not necessary. It brings two main advantages from the safety and energy point of view: (1) mechanical properties of the vessel’s material are not demanding as for gas storage containers, (2) energy losses because of hydrogen liquefaction, compression, or boil-off are avoided. Nonetheless, the volumetric energy density of the solid storage hydrogen system is still low, particularly comparing with the gasoline storage system. Moreover, there are critical topics like materials’ properties (hydride material), charging and discharging conditions of the systems (pressure, time, and heat transfer), charging cycles, and cost that are still matter of intensive research. Improving mainly the properties of the hydride forming material and optimizing the weight and operative conditions of the solid hydrogen storage system is challenging. However, there are several promising materials under research and development, and besides unexplored system configurations, which can lead to an efficient and safe hydrogen storage system for the future hydrogen economy.
\nThe solid storage system is based on hydride forming materials, i.e., the system consists basically in a vessel filled with the hydride forming material. Of course, the complexity of the storage system including pipes, heat transfer system, and control instrumentations is in this simplified description neglected. In this section, it is presented basic concepts regarding the chemical reaction for the hydride formation and its thermodynamics.
\nHydrogen interacts with a large number of elements and materials for the formation of hydride compounds. Hydride forming materials can be classified as: metals (alkaline, alkaline earth, transition, and rare earth), intermetallic (Mg2Ni, LaNi5, etc.), non-intermetallic (Mg-Fe, Mg-Co, etc.), and the combination of boron (B), aluminum (Al), or nitrogen (N) with alkaline or alkaline earth metals. Furthermore, a general classification considering the main feature of different hydride compounds is shown in Table 1. There are two main groups of hydride: the room temperature hydrides where hydrogen is located in the interstices of the metal’s lattice, without forming a strong metal-hydrogen bond. This kind of hydride works at low temperatures, i.e., 20–50°C, and under low and high pressures, depending on the type of alloy. For instance, LaNi5 alloy works at low pressure, between 10 and 50 bar, while TiCrMo alloy uptake hydrogen under high pressures, over 100 bar. The main constraint of the room temperature hydride compounds is the low gravimetric hydrogen storage capacities ranging from 1 to 3 wt.% H2, though they do have considerable hydrogen volumetric capacity of about 100 kg/m3. The other categories are binary and complex hydrides, where hydrogen is chemically bound. They work in a broad range of temperatures and pressures, but the most common ranges are temperatures over 100°C and pressures from 10 to 200 bar. There are some exceptions such as non-stable hydride compounds at room temperature, as for example Ti(BH4)3, Fe(BH4)2, Ni(AlH4)2, among others. Moreover, several binary and complex hydrides are not even reversible [15, 16, 17, 18, 19, 20]. These hydrides show large gravimetric hydrogen storage capacities ranging from 4 to about 20 wt.% H2 and also considerable volumetric hydrogen capacity from 100 to 150 kg/m3.
\nThe chemical reaction for the hydride formation can be described as a reversible gas-solid reaction. For the sake of clarity, the most simple reaction between a solid metal (M(s)) and gas hydrogen (H2(g)) is herein explained. At certain temperature (T) and under certain pressure (P), M(s) reacts with H2(g) to form a hydride compound (MHx(s)) according to reaction (1):
Reaction (1) shows the overall process for the reversible formation of a hydride compound without any detail about reaction intermediates. As seen, the hydride compound formation is exothermic, while its decomposition is endothermic. Moreover, the formation and decomposition of a hydride compound occur under certain T and P conditions, which depend on the kind of M(s) and the resulting hydride compound. Thus, these T and P conditions are determined by the thermodynamics and kinetics of the metal-hydrogen (M-H2) system.
\nThermodynamic properties for the M-H2 systems are usually characterized by measuring pressure-composition-isotherms (PCIs). Figure 3A shows ideal PCIs (without slope and hysteresis), where the x-axis is the hydrogen concentration (CH) expressed as the ratio between atomic hydrogen and metal (H/M), and y-axis is the hydrogen pressure (pH2). The procedure to measure a PCI consist in introducing the hydride forming metal or material in a sealed vessel connected to hydrogen supply and increase steeply the hydrogen pressure at a constant temperature. There are different steps involved during the hydrogen absorption process in a metal under equilibrium conditions. For example, taking the PCI at T2 (Figure 3A), a detailed description of the process during PCI characterization can be done as follows [4, 21]:
At the beginning of the process, molecular hydrogen (H2) near the metal’s surface suffers van der Waals interactions. This H2-M interaction process is called physisorption.
Molecular H2 dissociates on the metal’s surface (H2 → H + H) and forms a M-H bond. This process is called chemisorption and the required energy for it depends on the elements on the metal’s surface.
Chemisorbed H diffuses to the interstitial site of the metal’s lattice and exothermically dissolves to form a solid solution (α phase). This process occurs in the low hydrogen concentration zone (H/M < 0.1), as shown in Figure 3A—point (a) and is described by reaction (2):
Increasing the hydrogen pressure, the solid solution (α phase) reaches a hydrogen saturation concentration at H/M = 0.1. From this hydrogen concentration, the hydride phase (β phase) starts to form as shown in Figure 3A—point (b). Significant expansions of the metal’s lattice causes strong H–H interactions which result in the nucleation and then further growth of the hydride phase. In an ideal case, the overall process of formation of the hydride phase occurs under constant pressure and is called plateau region in the PCI curve, Figure 3A—from point (b) to point (d). In this region, the solid solution (α phase) and the hydride phase (β phase) co-exist in equilibrium conditions, Figure 3A—point (c). The pressure associated to the plateau region is called equilibrium pressure (Peq.). Reaction (3) describes the process:
Once the formation of the hydride phase is finished, the hydrogen pressure increases again, as shown in Figure 3A—from point (d). This phenomenon is ascribed to the atomic hydrogen dissolution in the hydride phase.
(A) Ideal PCIs for the description of the hydrogen absorption-desorption process through hydride compound formation in equilibrium conditions. (B) van’t Hoff plot built from PCIs. (C) PCIs showing the real behavior with slope and hysteresis.
Under experimental conditions, the equilibrium pressure during the “plateau region” is not perfectly constant, as shown in Figure 3C. The sloppy plateau is attributed to expansions of the lattice of the hydride and relaxations of the metallic matrix, which causes a slight increase of the equilibrium pressure during the chemical reaction of the hydride phase (β phase) formation. Furthermore, it is also observed in Figure 3C that the equilibrium pressure for the hydrogenation process is lower than the equilibrium pressure for the dehydrogenation process. This phenomenon is called hysteresis and it is ascribed to localized defects in the metallic lattice and inhomogeneity on the metal’s surface [21, 22, 23]. Therefore, different equilibrium pressures for the hydrogenation and dehydrogenation processes are usually reported.
\nThe dependence of the equilibrium pressure (Peq.) on the temperature (T) is given by the van’t Hoff Eq. (4):
\nwhere ΔH and ΔS are the enthalpy and entropy changes for the chemical reaction of the hydride phase formation, respectively, and R is the ideal gas constant. Values for ΔH and ΔS can be obtained from the slope and intercept of the linear correlation between the ln(Peq) and 1/T, as shown in Figure 3B. This linear correlation is built from the equilibrium pressures determined by the PCI measurements (pH2 during the plateau region—Figure 3A—from point (b) to point (d)) at each temperature (T1, T2, etc.). ΔS indicates the entropy change for hydrogen, i.e., from molecular gas hydrogen to hydrogen in the hydride phase. For metal-hydrogen systems, the standard entropy change for hydrogen is 130 kJ/K mol, but it can have a different value for other kind of hydride systems as for example for hydrides composed of boron, aluminum, or nitrogen and alkaline or alkaline earth metals [4, 21]. ΔH of the hydride compound or system characterizes the stability of the metal-hydrogen bond (M–H) and it takes a negative value for the exothermic hydrogenation and a positive value for the endothermic dehydrogenation. These two thermodynamic parameters, i.e., ΔH and ΔS, are quite important for hydride forming material design and hence for practical applications. They allow calculating the temperature for the hydrogen release from hydride phase under atmospheric pressure (∼1 bar), which refers to the minimum temperature for the dehydrogenation process without any kind of kinetic restriction. Additionally, the thermodynamic properties of the hydride phase provide information about the range of temperature and pressures at which the hydride system works. Table 2 shows the experimental enthalpy, entropy values, and decomposition temperature under 1 bar H2 for some hydride compounds and systems, which have been under intensive research [24, 25, 26, 27, 28, 29, 30, 31].
\nHydride compound/Hydride system | \nΔH [kJ/mol H2] | \nΔS [J/K mol H2] | \nTdecomposition = ΔH/ΔS at 1bar [°C] | \nRef. | \n
---|---|---|---|---|
LaNi5H6 | \n31.8 | \n110.0 | \n16 | \n[24] | \n
MgH2 | \n74 | \n135 | \n275 | \n[25] | \n
Mg2FeH6 | \n80 | \n137 | \n311 | \n[26] | \n
LiBH4 | \n74 | \n115 | \n370 | \n[27] | \n
(1)NaAIH4 | \n42 | \n124 | \n66 | \n[28] | \n
LiNH2 | \n45 | \nn.a. | \n- | \n[29] | \n
(2)2LiBH4+MgH2 | \n40.5 | \n81.3 | \n255 | \n[30] | \n
Mg(NH2)2+2LiH | \n38.9 | \n107(3) | \n90 | \n[31] | \n
Dehydrogenation thermodynamic parameters and decomposition temperature under 1 bar H2 for some hydride compounds and systems.
Table 2 clearly indicates that the use of some hydride compounds and systems for solid-state hydrogen storage system working under mild temperature conditions is thermodynamically feasible. Moreover, other cases such as Mg2FeH6 are more suitable for energy storage because of its large enthalpy value. All efforts toward the design of hydride compounds, especially for mobile applications, have been focused on reaching enthalpy values ranging between 40 and 50 kJ/mol H2, leading to an operative temperature between 20 and 90°C. It seems that some materials such as room temperature hydride fulfill these requirements, but the thermodynamic stability is not the unique parameter that determines the practical application of the hydride compound, since the capacity plays a major role. For this reason, high gravimetric hydrogen capacities are required as well, and room temperature hydrides do not meet this requirement at the time to work at low hydrogen pressure.
\nMost of the hydride compounds and hydride systems cannot work at the temperature predicted by the thermodynamics. This fact is related to kinetic constraints, leading to notable higher operative temperatures than that thermodynamically feasible. For this reason, enhancing the kinetic behavior of hydride compounds and hydride systems has been matter of intensive research. To start with a comprehensive development about the strategies to improve the kinetic behavior of the hydride compounds and systems, it is important to introduce fundamental concepts and details about the experimental method used to understand and to tailor the hydrogenation/dehydrogenation rates, respectively.
\nThe kinetic behavior for the formation/decomposition of a hydride compound gives information about the time required for the material to uptake/release hydrogen in non-equilibrium (dynamic) conditions. Figure 4 shows experimental kinetic hydrogenation and dehydrogenation curves for Nb2O5-doped MgH2. These curves show hydrogen concentration as a function of time. For the sake of clarity, all the explanation and description is referred to a nominal metal hydride (MHx(s), M = metal, H = hydrogen). The absorbed/desorbed hydrogen concentration is expressed in terms of fraction (α), which is the ratio between the absorbed/desorbed hydrogen concentration at each time during the process and the maximum absorbed/desorbed hydrogen concentration. Under dynamic conditions, the hydrogenation reaction happens when the operative pressure (Pa) is over the equilibrium pressure (Peq) of the hydride phase at the operative temperature (T), Figure 4A. On the contrary, for dehydrogenation under dynamic conditions, the operative pressure (Pd) has to be below the equilibrium pressure (Peq) of the hydride phase at the operative temperature (T), Figure 4B. The procedure to measure a kinetic curve for the hydrogenation/dehydrogenation consist in introducing the hydride forming metal or material in a sealed vessel connected to hydrogen supply and suddenly increase/decrease the hydrogen pressure at a constant temperature, respectively. After the sudden pressure increase/decrease, the operative pressure is kept constant and higher/lower than the Peq for the hydrogenation/dehydrogenation dynamic processes, respectively. The measurement of the kinetic curve runs until reaching saturation, i.e., α = 1.
\n(A) Hydrogenation kinetic behavior and (B) dehydrogenation kinetic behavior for metal-hydrogen system.
In order to clarify the complexity of the hydrogenation/dehydrogenation processes under dynamic conditions, the sequence of involving steps can be simply described as follows:
\n\n
The
Steps involved in the hydrogenation and dehydrogenation processes under dynamic conditions.
In the previous description (Figure 5), any fluid dynamic and heat transfer restrictions associated to large amounts of material are not taken into account. For instance, fluid dynamic restriction occurs when hydrogen can flow into the material’s bed. For the case of the heat transfer restrictions, it is referred to the notable temperature increase or decrease during the exothermic or endothermic hydrogenation or dehydrogenation reaction, respectively. The heat transfer through the hydride bed is not efficient because the thermal conductivity of the hydride compounds is rather low. For these reasons, the analysis on the kinetic behavior and tailoring will be performed for a punctual mass of hydride bed without any fluid dynamic and heat transfer restriction.
\nThere are functional dependences of the hydrogenation/dehydrogenation reaction rates on the temperature, pressure, and morphology of the material. The rates for gas-solid reactions, such as the ones occurring during the hydride formation and decomposition, can be described by Eq. (5) [32, 33]:
\nwhere the overall reaction rate,
At constant temperature and pressure, the reaction rate depends on intrinsic factors and morphological changes of the solid (defects, crystalline structure, size and morphology of the particles, etc.), i.e., G(α) [34, 35]. Thus, Eq. (5) can be expressed:
k is the kinetic constant and it contains the temperature and pressure dependences as seen in Eq. (7). Reordering Eq. (6), it is possible to obtain an expression for the evaluation of G(α):
\nwhere g(α) is the integral form of the gas-solid kinetic models for the material’s changes. The gas-solid kinetic models describe different physical phenomena. There are four main sets of models: (1) nucleation and growth models, (2) geometrical contracting models, (3) diffusion models, and (4) autocatalytic models. In Table 3, the integral form of the gas-solid kinetic models is described. There are more gas-solid models, but it is not the aim to perform exhaustive description of them.
\n\nAmong the steps involved in the hydrogenation/dehydrogenation processes (Figure 5), it is usually found a slowest one, which limits the overall reaction rate of the process. Thus, the slowest step is commonly called “rate-limiting step.” The determination of the rate-limiting step depends on the kind of hydride and the experimental conditions. Identifying the rate-limiting step requires the application of gas-solid models shown in Table 3. The determination of the rate-limiting step is carried out by measuring kinetic curves under constant temperature and pressure, as the ones shown in Figure 4. Once, the hydrogen uptake and release against time is expressed in terms of hydrogen fraction, α, the integral models can be applied to build a graph of g(α) as function of time.
\nA first approach to study which process limits the hydrogenation/dehydrogenation kinetic behavior is to find which model has the best linear fitting of the integral form, g(α), of the solid-state models against time. First, the hydrogen fraction range considered for the fitting is usually from 0.1 to 0.9. On one hand, at the beginning of the process the initial points involve a high degree of uncertainty, mainly for fast rates in the range of seconds. On the other hand, the final stage of the process, reaching the saturation of the material, does not play any role in the determination of the rate-limiting step. As an example, Figure 6 exhibits g(α) generated from each model, Table 3, as a function of time in the range of α between 0.10 and 0.90 for the hydrogenation and dehydrogenation process shown in Figure 4. Then, a liner fitting was performed in each curve.
\nApplication and fitting of the integral form of the solid-state models (
As seen, the simple linear fitting of the integral form of the solid state-models does not provide a clear clue about the rate-limiting step for the hydrogenation and dehydrogenation rates. There are several models with suitable fitting goodness (highlighted in bold). For these reason, it is possible to apply other procedure such as the reduced time method proposed by Sharp and Jones [37, 38]. By applying this method, a plot for the theoretical reduced time (t/t0.5)theoretical as a function of the experimental reduced time (t/t0.5)experimental is built as shown in Figure 7. The (t/t0.5)theoretical is obtained by expressing the equation of the integral form of solid-state models in terms of the time at α = 0.5, i.e., t0.5. As an example, for the case of the integral form of the solid-gas model JMA with n = 1, the (t/t0.5)theoretical is obtained as follows:
Reduced time method: Plots (t/t0.5)theoretical vs. (t/t0.5)experimental and fitting for (A) hydrogenation and (B) dehydrogenation rates.
The right term of Eq. (10) is equal to 0.69. Replacing 0.69 in Eq. (10) and dividing (9) over (10), Eq. (11) provides the (t/t0.5)theoretical
The (t/t0.5)experimental is directly obtained from the experimental results, Figure 4, by dividing the time during the measurement (t) over the time at α = 0.5. The rate-limiting step is determined by three parameters, i.e., the fitting goodness, slope, and intercept of the linear fitting. This represents an advantage in comparison with the simple linear fitting of the integral form of the solid-state models, with just the fitting goodness as one decision parameter. The best fitting obtained from the reduced time method is the one showing linear fitting goodness and slope equal to 1 and intercept equal to 0.
\nFigure 7 shows that for the case of the hydrogenation rate the model JMA, n = 1, Table 3, provides the best linear fitting (slope = 1, intercept = 0 and goodness ≈ 1). For this reason, the overall reaction rate is limited by one-dimensional growth with interface-controlled reaction rate. This rate-limiting step is related to the step (f) described in Figure 5. For the dehydrogenation rate, the rate-limiting step is the two-dimensional growth of contracting volume with constant interface rate (CA), related to the step (a) shown in Figure 5.
\nIn fact, the kinetic analysis based on the solid-state models should be also based on additional experimental evidence obtained from the material science characterizations for morphological and microstructural changes before and after and upon hydrogenation and dehydrogenation kinetic processes.
\nUnder constant pressure, the hydrogenation/dehydrogenation reactions speed up as the temperature increases and this temperature dependence is described by the Arrhenius expression. The dependence of the hydrogenation/dehydrogenation reaction rates on the temperature follows Eq. (12):
\nwhere A is the pre-exponential factor or frequency factor and represents the frequency of collisions between reactant molecules, Ea is the apparent activation energy, which is the energy required to start the reaction, R is the gas constant, and T is the absolute temperature.
\nThe activation energy is a relevant kinetic parameter to evaluate the kinetic performance of a hydride forming material. Isothermal and non-isothermal measurements can be performed to obtain the activation energy. Two procedures are commonly used. The first consists in performing isothermal measurements at different temperature and constant pressure, such as the ones shown in Figure 4. Then, by the application of the gas-solid models, it is possible to calculate the kinetic constant “k,” once identified the rate-limiting step as explained in Section 3.1. As expressed in Eq. (7), k depends on K(T) and F(P). Considering isobaric measurements, k is only function of K(T) following the Arrhenius expression:
Applying natural logarithm to Eq. (13):
Plotting lnk against 1/T, the slope of the linear fitting provides the Ea in kJ/mol H2 and the intercept the frequency factor A, as seen in Figure 8A. The second method involves non-isothermal measurements done via calorimetric methods such as scanning differential calorimetry (DSC) and differential temperature analysis (DTA) [39]. This method is the Kissinger one [40]. The method consists in determining temperature maxima (Tm) of the exothermal (hydrogenation)/endothermal (dehydrogenation) events obtained from the DSC or DTA measurements at different constant heating rate (ø). The change of Tm with ø is directly related to the nature of the reaction.
\nActivation energy determination: (A) isothermal method, (B) DSC curves for the (C) non-isothermal method.
At a constant heating rate (ø), constant pressure (F(P)) and considering k has an Arrhenius dependence on the temperature, Eq. (13), Eq. (5) can be expressed:
Assuming that the fraction at the peak maximum and G(α) are independent on ø, reordering and applying natural logarithm to expression (15), it is possible to write:
Figure 8B shows the DSC curves at different ø for a dehydrogenation process, from which the peak maxima are selected. Then, a plot of the ln(ø/Tm2) against 1/T is built and the Ea in kJ/mol H2 is obtained from the slope of the linear fitting, as shown in Figure 8C.
\nTable 4 shows examples for experimental activation energy (Ea) values, reaction mechanism, and rate-limiting steps for different materials. As seen, the lowest Ea values are related to surface controlled process such as physisorption and chemisorption (Figure 5: Hydrogenation process—Steps
Activation energies, reaction mechanisms, and rate-limiting steps.
It is important to point out that the isothermal method for
At constant temperature, the hydrogenation/dehydrogenation reactions show a dependence on a functional relationship between the operative pressure (P) and the equilibrium pressure (Peq) for both hydrogenation and dehydrogenation processes. This dependence is called
Pressure dependencies, their physical mining, and rate-limiting step.
In this section, all the basics concepts for the right understanding of the kinetic behavior of the hydride compounds and dependencies of the hydrogenation/dehydrogenation reaction rates were exposed. Now, it is possible to describe the main strategies applied to improve the hydrogenation/dehydrogenation rates for some hydride compounds and hydride systems under extensive research.
\nInvestigations on the kinetic tailoring to improve the hydrogen storage properties of hydride compounds and hydride systems involve knowledge about the thermodynamic behavior and kinetic behavior of the hydride system. First, equilibrium pressures at different temperatures are needed to plan the experimental pressure and temperature for the characterization of the kinetic behavior. Second, some knowledge about the mechanism(s) that constraint the overall reaction rates is also required. For this reason, it is important to know or at least have clues about possible rate-limiting steps for the hydrogenation/dehydrogenation processes, as well as the influence of the temperature and pressure dependences on the reaction rates. In this regard, knowledge about K(T) allows quantifying in terms of Ea the effects of a tailoring strategy. In this line, knowledge of F(P) dependence is usually necessary to properly determine K(T). All these understanding about the thermodynamics and kinetics of the hydride compound or system matter of investigation enormously contribute to seek the best strategy to improve it hydrogenation/dehydrogenation reaction rates. Of course, there are several opportunities in which kinetic improvements for a hydride compound or system are proposed based just on a simple experimental procedure; without any previous systematic study about the thermodynamics and kinetics. This approach is also possible, but it leads to a superficial knowledge about the actual kinetic improvement and to a poor understanding of the behavior of the hydride compound or system.
\nThe most relevant approaches to enhance the kinetic behavior of hydride compounds and systems are: (1) improving the microstructural refinement via mechanical milling, (2) doping with transition metal and transition metal compounds, (3) forming in situ catalyst, and (4) nanoconfinement. In this section, the concepts of these strategies are explained and examples for their practical application to hydride compounds and systems are also described [58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96].
\nIn general, two or three of these strategies are applied together, as for example mechanical milling, transition metal, or transition metal compound addition and in situ catalyst formation or nanoconfinement and transition metal or compound addition, etc. However, it is possible to put emphasis on the each strategy in order to understand what the specific effects are on the hydride forming, regardless the combined application of them.
\nThe mechanical milling process is a powder processing method. This processing technique allows producing homogeneous materials starting from powder mixtures [58]. Moreover, the mechanical milling causes particle and grain size reduction (microstructural refinement). Furthermore, mechanical milling is also applied for the synthesis of hydrides, i.e., mechanochemical synthesis [59]. This process can be carried out at laboratory scale and at industrial scale. Herein, the laboratory scale milling process of hydride compounds and systems are discussed. In general, the milling process for improving the microstructural characteristics of hydrides is performed with amounts of material ranging between 1 and 20 g. The milling vessels are usually made of stainless steel and with a volume between 50 and 250 cm3. As grinding medium stainless steel balls are used. There are several laboratory milling devices that can be classified by the injected shock power per unit mass of grinding medium (Pg), which is a parameter that determines the reached microstructural refinement of a material (powder) subjected to milling procedure. Indeed, the reached degree of microstructural refinements also depends on the milling time and the numbers of ball (grinding medium), which are parameters that can be changed at the time to perform the milling process. Among the most commonly utilized mill devices for hydride compounds and system preparation at laboratory scale, it is possible to mention: (1) Magneto Uni-ball mill device (low energy, Pg: 0.0003–0.002 W/g), (2) Planetary Fritsch-P6 (middle energy, Pg: 0.01–0.22 W/g), and Vibratory Spex 8000 M mill device (high energy, Pg < 0.24 W/g) [60, 61]. Owing to the pyrophoric nature of the hydride compounds and their easiness to get hydrolyzed and/or oxidized, the milling process is done under inert atmosphere or hydrogen atmosphere in the case of mechanochemical synthesis. The effects of mechanical milling on the material are: (1) creation of grain boundaries and defects, (2) higher degree of microstructural refinement, and (3) intimate mixture of powders. In this regard, the first two effects improve the activation process of the material for the initial hydrogen absorption and the hydrogenation/dehydrogenation kinetic processes due to the enhancement of hydrogen diffusion through new pathways and shorter distances. Grain boundaries and defects are created by the mechanical energy provided during the milling process. More grain boundaries provide larger surface area and shorter diffusion distance for hydrogen, while the presence of defects acts as channels for hydrogen diffusion. Both effects ease the contact between hydrogen and fresh hydride forming material, enhancing the kinetic behavior. The third effect contributes to the homogeneous distribution and intermixture of the main components of the material and an additive. Moreover, the milling process can promote interactions between the main components and the additive, leading to the formation of other species with favorable effects on the kinetic behavior. This effect will be addressed in a following section. Figure 9 shows the effects of mechanical milling under hydrogen (0.5 bar) atmosphere for 150 h on a mixture of Mg + 10 wt.%Fe in a Magneto Uni-ball mill device. As seen in the SEM photos (Scanning Electron Microscopy), the particle sizes are notably reduced and the surface has porous characteristic in comparison to the starting material. These results account for the mechanical effects of the milling process as well as the fragilization of Mg (ductile material) because of the
SEM photos for (A) Mg starting material and (B) Mg + 10 wt.%Fe after 150 h of milling under 0.5 bar H2 in a magneto Uni-ball device.
In 1997, Zaluska et al. [63] reported a pioneering work about the properties of different as-milled hydride forming materials such as Mg, Mg2Ni, FeTi, and LaNi5. It was found that the materials after milling presented a nanocrystalline nature, causing notable improvements in the hydrogenation/dehydrogenation kinetic behavior. These effects are also noticed in complex hydrides and hydride system [64]. Despite the beneficial effects of milling, there are also some disadvantages. In the case of room temperature hydrides, the effects of milling are not always beneficial. For example, it was also reported that FeTi alloys undergo hydrogen capacity loss after milling process. This is due to the creation of amorphous regions induced by the mechanical deformation and it is not possible to store hydrogen interstitially in the amorphous regions [65]. Furthermore, taking into account that the milling vessel and grinding medium are usually made of stainless steel, Fe contamination is also a concern, particularly at the time to perform the milling process in a high-energy mill device. For instance, as demonstrated by Puszkiel et al., the presence of Fe for the 2LiBH4 + MgH2 hydride system causes detrimental effects in the kinetic behavior since FeB species without any beneficial effects are formed. It was found that an appreciable amount of Fe came mostly from the grinding medium [66]. Despite the described disadvantages, the milling process is quite effective and efficient at the time to prepare and tailor hydride compounds and systems and additionally it is possible to scale-up for practical applications. Reducing the grain and particle sizes, creating more boundary surfaces and defects are the most relevant effects of the milling process. These effects mainly improve the diffusion processes for the hydride formation and decomposition by shortening the diffusion pathways and generating channels for more efficient hydrogen transport.
\nSince the beginning of the investigations on hydride compounds, it was discovered that the addition of transition metal and metal compounds were able to improve their kinetic characteristics. The addition of amounts from 1 to 10 wt.% of these transition metals and compounds was performed by milling procedures in most of the cases. Therefore, the “doping strategy” also involves the milling process to reach a high degree of intermixture and microstructural refinement. The doping strategy results in reductions of the hydrogenation and/or dehydrogenation activation energies, changes in the reaction paths and consequently different rate-limiting steps. Figure 10 shows the concept of doping
Concept of doping via mechanical milling. TM = transition metal. MHy = hydride, M = metal, ΔH = enthalpy,
In the case of room temperature hydrides, the presence of transition metals like Pd and Ni notably improves their activation behavior and kinetic properties. This fact was attributed to the active sites of these transition metals, located on the metal or alloy surface, which facilitated the hydrogen molecule dissociation and penetration across the oxides generated on the metal or alloy surface [67, 68, 69]. These hydrides are commonly prepared by arc melting since, as mentioned in Section 4.2, the milling process can cause hydrogen capacity losses.
\nIn 1997, Bogdanović et al. [70] achieved reversible hydrogen uptake and release from NaAlH4 under mild conditions by doping with Ti-based catalyst (TiCl3). However, the catalytic mechanism of the Ti-based catalyst was not clear at those times. In 2015, Züttel et al. [71] reported a work about the catalytic mechanism of Ti-compound in the hydrogen uptake/release of alkali alanates. In this work, based on an atomistic model, it was proposed that Ti works as a bridge to transfer H− and M+ (M+---Ti---H−) from MAlH4 (M = Li, Na, K), reducing their charge separation and thus lowering the activation energies for hydrogenation and dehydrogenation processes.
\nAmong the most interesting hydrides, MgH2 is very attractive because of its low cost and high gravimetric hydrogen capacity (7.6 wt.%). However, its high thermodynamic stability (74 kJ/mol H2) required high operative temperature over 300°C [25]. Pure MgH2 has sluggish kinetic behavior. Upon hydrogenation, the rate-limiting step is three-dimensional diffusion controlled contracting volume. This fact is attributed to the low diffusion coefficient of MgH2 covering fresh Mg; the diffusion coefficient of MgH2 was found to be three orders of magnitude lower that the one for Mg). Upon dehydrogenation, the rate-limiting step for pristine MgH2 turned to be surface controlled and related to the recombination of the hydrogen molecule [72, 73]. Several transition metals and transition metal compounds exhibited excellent catalytic effect on de-/hydrogenation of MgH2. The main effect of these additives was related to the dehydrogenation mechanism, since they ease the recombination of the hydrogen molecule [74, 75]. One of the most effective additives was Nb2O5, leading to 7 wt.% H2 capacity in about 60 s and fast dehydrogenation in about 130 s. Moreover, the presence of Nb2O5 reduced the dehydrogenation temperature down to 250°C [76]. Nb2O5 had a “pathway effect” mainly on the hydrogenation of MgH2. Upon milling and subsequent hydrogen cycling, the formation of Mg-Nb oxides created diffusion pathways by the formation of metastable niobium hydrides, hence avoiding the large diffusion constraints. The effect and mechanism of Nb2O5 on MgH2 is similar but slower when MgH2 is physically doped with Nb2O5 [77, 78].
\nLiBH4 also caught the attention due to the extremely high gravimetric capacity of 18.3 wt.% H2, though just 13.8 wt.% H2 is available because LiH and B are formed upon desorption. However, LiBH4 is quite stable and needs harsh temperature and pressure conditions for de-/re-hydrogenation [79]. Several dopants such as metal oxides and metal halides were tried for improving the kinetic behavior of LiBH4. However, LiBH4 reacts with the dopants because this complex hydride is a strong reduction agent. The interactions between LiBH4 and dopants also lead to gas byproducts such as B2H6. In this regard, complex hydrides such as borohydrides and amides are combined with binary hydrides to form “thermodynamically destabilized systems” and then the kinetic behavior of these hydride systems is tailored by doping [30, 31]. In almost all the cases, the added dopants interact with the hydride system itself by forming other species
This strategy is applied to binary hydrides, to complex hydrides and mainly to destabilized hydride systems. In this section, the
One of the most representative examples of this approach is the addition of transition metal compounds to the 2LiBH4 + MgH2 hydride system. Under dynamic conditions, this borohydride system uptake hydrogen in one step, but releases hydrogen in two steps as described in reactions (17)–(19), respectively [80].
For the hydrogenation process, temperature and pressures of about 350°C and 50 bar are required. These conditions for the formation of LiBH4 are notably milder than that needed for the re-hydrogenation of LiBH4 from LiH and B [79]. For the dehydrogenation process, temperatures above 350°C and hydrogen overpressures higher than 3 bar of hydrogen overpressure are required. These conditions are harsher than those predicted by the thermodynamics (Table 2). The hydrogen overpressure upon dehydrogenation assures the reversibility of the hydride system since MgB2 is only formed under backpressure conditions. As seen in the reactions, LiBH4 is in liquid state because this complex hydride undergoes from solid to liquid state at about 270°C [81]. Furthermore, mainly upon dehydrogenation the kinetic behavior is sluggish, particularly the second step described by reaction (19), taking more than 10 h for the full hydrogen release. Therefore, one of the most effective strategies was the addition of transition metal compounds [82]. Through this strategy, transition metal halides TiCl3, TiF4, NbF5 among others, notably improved the dehydrogenation kinetic behavior of 2LiBH4 + MgH2 hydride system. In this case, the transition metal halide additive interacts with LiBH4 during the preparation stage during milling and subsequent heating to reach the operative temperature for hydrogen interactions. This interaction results in the formation of stable and nanostructure boride species such as TiB2 and NbB2 with similar hexagonal crystal structure as MgB2. The
Other example with the same 2LiBH4 + MgH2 hydride system is the addition of TiO2, leading to the
Mg(NH2)2 + 2LiH was also investigated as a potential hydrogen storage material due to its hydrogen capacity of about 5 wt.% and operative temperature roughly 220°C [83]. This hydride system uptake/release hydrogen in two steps according to reactions (20) and (21):
Several additives such as halides and hydrides were used to try to improve the kinetic behavior of this system [84, 85, 86, 87, 88, 89]. However, it was found that the addition of just 0.1 mol of LiBH4 improves not only the kinetic behavior, but also reduces the reaction enthalpy from 38.9 to 36.5 kJ/mol H2 [31, 90]. Moreover, the 6 Mg(NH2)2 + 9LiH + LiBH4 molar composition is the optimum one for the kinetic-destabilization effect.
Further improvement for the 6 Mg(NH2)2 + 9LiH + LiBH4 was achieved by co-adding YCl3 and Li3N. The
Figure 11 depicts the concepts of the
Concept of
This strategy consists in confining the dimensions of hydride particles to sizes lower than 25 nm by introducing them into a nanoporous matrix. For a simple hydride formation/decomposition reaction (23), the contribution of the excess surface area given by the nanosize of the metal (M(s)) and metal hydride (MH2(s)) must be taken into account as part of the reaction enthalpy as described in reaction (24), where Vm is the molar volume,
Nanoconfinement was basically proposed as a promising strategy to make hydride compounds reversible under mild conditions, as for example LiBH4, NaAlH4, and MgH2, and to further destabilized hydrogen systems such as 2LiBH4 + MgH2. However, in most of the cases, the main effect was observed on the kinetic behavior of the hydride compounds and systems. The nanometric range of the particles provide extremely large grain boundaries and notable shorter diffusion paths as well as optimized contacting for the materials, hence these properties account for improvements in terms of kinetic behavior and cycling stability. Carbon frames such as scaffolds, nanotubes, and aerogels are used for confining hydrides due to its light weight and inter condition. Despite the fact that this strategy usually leads to improved kinetic behavior without actually changing the thermodynamics of the hydride compound and system, the main constraint lay on the reduced capacity because of the introduction of the hydride into the nanoporous frame. Furthermore, it is hard to figure out in a possible scale-up for practical application [94, 95, 96].
\nHydrogen can be considered as future energy carrier because of its large gravimetric energy density, abundance as combined with oxygen in water and its environmentally friendly condition at the time to release its energy. However, its low volumetric energy density owing to its gas conditions demands an efficient and a safe method to store hydrogen. One of the most attractive methods consists in storing hydrogen in solid state by forming a hydride compound. Much effort has been put in designing hydride forming materials and hydrogen storage systems based on hydride forming materials. One of the main constraints for the design of commercial solid-state hydrogen storage systems is the lack of a hydride forming material able to have proper thermodynamic stability as well as kinetic behavior. There are already materials with suitable experimental thermodynamic properties which would allow to reversibly uptake and release hydrogen at low temperature of about 90°C and under low pressures. Nonetheless, these conditions predicted by the thermodynamics of the system cannot be reached because of kinetic constraints. Therefore, strategies to tailor the kinetic behavior of hydride compounds and system of technical interest have been intensively developed. In this chapter, all the basics concepts about the chemical reaction, thermodynamics and kinetics for the right understanding of the solid-state hydrogen storage as hydride compounds or systems were explained. Then, the main strategies to tune the kinetic behavior of hydride compounds or systems were described. Among the most interesting strategies, milling process, transition metal, and transition metal compound doping,
The author acknowledges CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) and Alexander von Humboldt Foundation (Fellowship Number: ARG-1187279-GF-P).
\nThere is no conflict of interest.
The company was founded in Vienna in 2004 by Alex Lazinica and Vedran Kordic, two PhD students researching robotics. While completing our PhDs, we found it difficult to access the research we needed. So, we decided to create a new Open Access publisher. A better one, where researchers like us could find the information they needed easily. The result is IntechOpen, an Open Access publisher that puts the academic needs of the researchers before the business interests of publishers.
",metaTitle:"Our story",metaDescription:"The company was founded in Vienna in 2004 by Alex Lazinica and Vedran Kordic, two PhD students researching robotics. While completing our PhDs, we found it difficult to access the research we needed. So, we decided to create a new Open Access publisher. A better one, where researchers like us could find the information they needed easily. The result is IntechOpen, an Open Access publisher that puts the academic needs of the researchers before the business interests of publishers.",metaKeywords:null,canonicalURL:"/page/our-story",contentRaw:'[{"type":"htmlEditorComponent","content":"We started by publishing journals and books from the fields of science we were most familiar with - AI, robotics, manufacturing and operations research. Through our growing network of institutions and authors, we soon expanded into related fields like environmental engineering, nanotechnology, computer science, renewable energy and electrical engineering, Today, we are the world’s largest Open Access publisher of scientific research, with over 4,200 books and 54,000 scientific works including peer-reviewed content from more than 116,000 scientists spanning 161 countries. Our authors range from globally-renowned Nobel Prize winners to up-and-coming researchers at the cutting edge of scientific discovery.
\\n\\nIn the same year that IntechOpen was founded, we launched what was at the time the first ever Open Access, peer-reviewed journal in its field: the International Journal of Advanced Robotic Systems (IJARS).
\\n\\n2004
\\n\\n2005
\\n\\n2006
\\n\\n2008
\\n\\n2009
\\n\\n2010
\\n\\n2011
\\n\\n2012
\\n\\n2013
\\n\\n2014
\\n\\n2015
\\n\\n2016
\\n\\n2017
\\n\\nWe started by publishing journals and books from the fields of science we were most familiar with - AI, robotics, manufacturing and operations research. Through our growing network of institutions and authors, we soon expanded into related fields like environmental engineering, nanotechnology, computer science, renewable energy and electrical engineering, Today, we are the world’s largest Open Access publisher of scientific research, with over 4,200 books and 54,000 scientific works including peer-reviewed content from more than 116,000 scientists spanning 161 countries. Our authors range from globally-renowned Nobel Prize winners to up-and-coming researchers at the cutting edge of scientific discovery.
\n\nIn the same year that IntechOpen was founded, we launched what was at the time the first ever Open Access, peer-reviewed journal in its field: the International Journal of Advanced Robotic Systems (IJARS).
\n\n2004
\n\n2005
\n\n2006
\n\n2008
\n\n2009
\n\n2010
\n\n2011
\n\n2012
\n\n2013
\n\n2014
\n\n2015
\n\n2016
\n\n2017
\n\n\r\n\tScientists have long researched to understand the environment and man’s place in it. The search for this knowledge grows in importance as rapid increases in population and economic development intensify humans’ stresses on ecosystems. Fortunately, rapid increases in multiple scientific areas are advancing our understanding of environmental sciences. Breakthroughs in computing, molecular biology, ecology, and sustainability science are enhancing our ability to utilize environmental sciences to address real-world problems.
\r\n\tThe four topics of this book series - Pollution; Environmental Resilience and Management; Ecosystems and Biodiversity; and Water Science - will address important areas of advancement in the environmental sciences. They will represent an excellent initial grouping of published works on these critical topics.