{"title":"Self-diffusivity of nitrogen in γ'-iron nitride (“Fe4N”)","authors":"C.T. Cheung, G. Simkovich","doi":"10.1016/0168-7336(89)80022-1","DOIUrl":"10.1016/0168-7336(89)80022-1","url":null,"abstract":"<div><p>The growth of γ'-iron nitride (“Fe<sub>4</sub>N”) on pure iron plate samples was followed by a thermogravimetric technique in the temperature range of 450–550 ° C at various nitrogen activities (fixed by H<sub>2</sub>/NH<sub>3</sub> gas mixtures). The growth kinetics were characterized by an initial stage of nucleation and growth control followed by nitrogen diffusion controlled growth. At 450 ° C, the self-diffusivity of nitrogen <em>D</em><sup>*</sup> is independent of nitrogen activities. At 500 ° C, <em>D</em><sup>*</sup> decreases with increasing nitrogen activities. At 550°C, <em>D</em><sup>*</sup> decreases to a minimum and then increases again with increasing nitrogen activities. It is suggested that the nitrogen diffusion mechanism in γ'-iron nitride is strongly related to the non-stoichiometry of this phase. At 450 and 500 ° C, the growth kinetics can be explained by a mechanism that involves the mixed control of two processes: (i) nitrogen diffusion via a small number of vacant regular sites (<span><math><mtext>1</mtext><mtext>2</mtext></math></span>, <span><math><mtext>1</mtext><mtext>2</mtext></math></span>, <span><math><mtext>1</mtext><mtext>2</mtext></math></span>) and (ii) nitrogen diffusion via a large number of disordered sites (<span><math><mtext>1</mtext><mtext>2</mtext></math></span>, 0, 0), (1, <span><math><mtext>1</mtext><mtext>2</mtext></math></span>, 0), (0, 0, <span><math><mtext>1</mtext><mtext>2</mtext></math></span>) as interstitials. At 550°C, the diffusion mechanism is controlled by nitrogen diffusion via the vacant regular sublattice sites at low nitrogen activities. At high nitrogen activities, the diffusion mechanism again becomes mixed control of the two diffusion processes. At the nitrogen activities of 100 and 174, <em>D</em><sup>*</sup> can be represented, respectively, by: <em>D</em><sup>*</sup> = (5.81 × 10<sup>−7</sup>cm<sup>2</sup>/s) · exp((−19.05 <span><math><mtext>kcal</mtext><mtext>mole</mtext></math></span>)/<em>RT</em>) and <em>D</em><sup>*</sup> = (2.45 × 10<sup>−9</sup>cm<sup>2</sup>/s) · exp((−11.16 <span><math><mtext>kcal</mtext><mtext>mole</mtext></math></span>)/<em>RT</em>) It appears that the activation energy of diffusion for nitrogen diffusion via the disordered sites is higher than that via the regular sites.</p></div>","PeriodicalId":101061,"journal":{"name":"Reactivity of Solids","volume":"7 2","pages":"Pages 115-129"},"PeriodicalIF":0.0,"publicationDate":"1989-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0168-7336(89)80022-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78810252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Real space imaging of adsorbed organic molecules by STM","authors":"FalkoP. Netzer","doi":"10.1016/0168-7336(89)80030-0","DOIUrl":"10.1016/0168-7336(89)80030-0","url":null,"abstract":"","PeriodicalId":101061,"journal":{"name":"Reactivity of Solids","volume":"7 2","pages":"Page 189"},"PeriodicalIF":0.0,"publicationDate":"1989-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0168-7336(89)80030-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"112081744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Entropy of activation as a possible structure-sensitive parameter in the dehydroxylation of kaolinite","authors":"I. Horváth, G. Kranz, Yu.G. Fedorenko","doi":"10.1016/0168-7336(89)80027-0","DOIUrl":"10.1016/0168-7336(89)80027-0","url":null,"abstract":"<div><p>The kinetics of the dehydroxylation on 14 kaolinites having varying structural disorder (crystallinity) was studied by use of an isothermal TG method. Second-order kinetics were found to control the rate of water release during the dehydroxylation with up to 60% of conversion regardless of the crystallinity and/or temperature of the isothermal heating.</p><p>There is no simple relationship between crystallinity and activation energy (<em>E</em>). Unexpectedly high values of <em>E</em> have been determined for some extremely disordered structures. To explain this, the role of intracrystalline pressure of the gaseous product as well as the character of its diffusion paths in the decomposition reaction have been considered.</p><p>The crystallinity (index HWB) and activation entropy (Δ<em>S</em><sup>≠</sup>) are related by empirical straight-line function: HWB = (0.07064 Δ<em>S</em><sup>≠</sup>) + 17.65 (correl. coeff. <em>r</em> = 0.873) in which Δ<em>S</em><sup>≠</sup> values increase with decreasing of kaolinite crystallinity (index HWB increases).</p></div>","PeriodicalId":101061,"journal":{"name":"Reactivity of Solids","volume":"7 2","pages":"Pages 173-181"},"PeriodicalIF":0.0,"publicationDate":"1989-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0168-7336(89)80027-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84971494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Calendar of forthcoming events","authors":"","doi":"10.1016/0168-7336(89)80035-X","DOIUrl":"https://doi.org/10.1016/0168-7336(89)80035-X","url":null,"abstract":"","PeriodicalId":101061,"journal":{"name":"Reactivity of Solids","volume":"7 2","pages":"Pages 197-198"},"PeriodicalIF":0.0,"publicationDate":"1989-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0168-7336(89)80035-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136924992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Oxidation behaviour of ytterbium sulphides","authors":"L.C. Otero-Diaz, M.J. Torralvo-Fernández, R.M. Rojas ∗","doi":"10.1016/0168-7336(89)80024-5","DOIUrl":"10.1016/0168-7336(89)80024-5","url":null,"abstract":"<div><p>Thermal studies (at up to ~1500 ° C) carried out on some ytterbium sulphides in air or under nitrogen show that complex decomposition processes undergone before the ultimate formation of the ytterbium oxide. The decompositions take place as overlapping and incomplete reactions to give mixtures of various intermediates, such as Yb<sub>2</sub>O<sub>2</sub>S and Yb<sub>2</sub>O<sub>2</sub>SO<sub>4</sub>. Electron microscopy diffraction studies on the intermediate Yb<sub>2</sub>O<sub>2</sub>SO<sub>4</sub> reveals a complex microstructure because of intergrowth with small precipitates of cubic phase Yb<sub>2</sub>O<sub>3</sub>.</p></div>","PeriodicalId":101061,"journal":{"name":"Reactivity of Solids","volume":"7 2","pages":"Pages 143-156"},"PeriodicalIF":0.0,"publicationDate":"1989-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0168-7336(89)80024-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91047826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"An alternative route to copper antimony oxide, Cu9Sb4O19","authors":"Shiro Shimada, Tadao Ishii","doi":"10.1016/0168-7336(89)80028-2","DOIUrl":"10.1016/0168-7336(89)80028-2","url":null,"abstract":"","PeriodicalId":101061,"journal":{"name":"Reactivity of Solids","volume":"7 2","pages":"Pages 183-186"},"PeriodicalIF":0.0,"publicationDate":"1989-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0168-7336(89)80028-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89075155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}