Xiangyang Li, Jianjun Ding, Lin Chen, Xingyou Tian
{"title":"Modeling small-angle X-ray scattering in quiescently crystallized polymers in the absence of long-period dispersity","authors":"Xiangyang Li, Jianjun Ding, Lin Chen, Xingyou Tian","doi":"10.1107/S1600576725002705","DOIUrl":"https://doi.org/10.1107/S1600576725002705","url":null,"abstract":"<p>To explain the single and wide first-order long-period peak observed in semicrystalline polymers, classical small-angle X-ray scattering (SAXS) theory regards the dispersity in lamellar thickness/long period as the key structural feature of semicrystalline polymers. Other factors affecting the SAXS pattern such as the lateral size of a lamellar stack, the number of lamellar crystals in a stack and linear crystallinity have been overlooked as secondary factors, preventing structure extraction from SAXS. In this study, we attempted to establish a scattering equation for semicrystalline polymers formed during quiescent crystallization without considering dispersity in the long period/lamellar thickness. The results indicate that the lateral size is the key factor leading to the unique SAXS pattern in semicrystalline polymers and the absence of the linear region in the correlation function. SAXS in semicrystalline polymers results from minor lamellar stacks with small intersection angles with the incident X-rays. On the basis of the results, we suggest employing a revised interface distribution function to obtain structural information after recovering higher-order weak long-period peaks by a difference method. Half of the <i>q</i><sup>4</sup> correction is to eliminate the influence of the form factor, while the other half is to remove the factor of 1/<i>q</i><sup>2</sup> in the structure factor. This study helps to further our understanding of SAXS in semicrystalline polymers.</p>","PeriodicalId":48737,"journal":{"name":"Journal of Applied Crystallography","volume":"58 3","pages":"948-962"},"PeriodicalIF":5.2,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jiaming Kang, Mingke Tan, Zhenling Huang, Tai Li, Xiang Zhou, Guoqiang Lv, Xingwei Yang, Wenhui Ma
{"title":"Effect of gap design of a double-layer heater on melt flow behavior in a single-crystal furnace","authors":"Jiaming Kang, Mingke Tan, Zhenling Huang, Tai Li, Xiang Zhou, Guoqiang Lv, Xingwei Yang, Wenhui Ma","doi":"10.1107/S1600576725002699","DOIUrl":"https://doi.org/10.1107/S1600576725002699","url":null,"abstract":"<p>The application of double-layer heaters in single-crystal furnaces holds great promise for single-crystal silicon rod production, but the absence of sufficient supporting research literature has hindered rapid progress in practical applications. In the current work, the relationship between the design of the double-layer heater and the flow behavior in the melt was obtained by investigating the lengths of the upper and lower layers of the double-layer heater and the gap position. The <i>FEMAG</i> single-crystal growth simulation platform (https://www.femagsoft.com) was adopted to simulate the growth model of M10 large-sized <i>n</i>-type single crystals. The mechanism of influence of the double-layer heater gap design on the melt flow behavior was obtained by taking the melt heating and heater radiation characteristics as the entry point and finally adopting the oxygen content in the crystal as a quality criterion. The results indicate that movement of the gap position can alter the heat-transfer conditions, thereby changing the intensity or volume of the three main vortices in the melt, which in turn affect the oxygen transport capacity.</p>","PeriodicalId":48737,"journal":{"name":"Journal of Applied Crystallography","volume":"58 3","pages":"832-844"},"PeriodicalIF":5.2,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Artem S. Borisov, Veronika R. Abdulina, Oleg I. Siidra, Victoria A. Ginga, Alexander A. Tsirlin, Astrid Holzheid, Annika Zapfe, Yurii Skourski, Annette Setzer
{"title":"Thermal behavior of römerite over a Mars surface relevant temperature range: single-crystal and powder X-ray crystallography and magnetic properties","authors":"Artem S. Borisov, Veronika R. Abdulina, Oleg I. Siidra, Victoria A. Ginga, Alexander A. Tsirlin, Astrid Holzheid, Annika Zapfe, Yurii Skourski, Annette Setzer","doi":"10.1107/S1600576725002572","DOIUrl":"https://doi.org/10.1107/S1600576725002572","url":null,"abstract":"<p>A number of hydrous iron sulfate minerals have been detected on the surface of Mars under extraterrestrial conditions. Nonetheless, certain inquiries regarding the properties and phase evolution of hydrous iron sulfate minerals remain unresolved and subject to debate at present. In our research, the behavior of römerite, Fe<sup>2+</sup>Fe<sup>3+</sup><sub>2</sub>(SO<sub>4</sub>)<sub>4</sub>(H<sub>2</sub>O)<sub>14</sub>, was examined by utilizing <i>in situ</i> single-crystal and powder X-ray diffraction while simultaneously acquiring data upon heating. Römerite is stable under low-vacuum conditions. It exhibits a significant negative thermal expansion in the α<sub>33</sub> direction throughout the entire temperature range from −173 to 77°C and on up to decomposition. There is a cooperative interaction between the rotation of the sulfate tetrahedra in the [Fe<sup>3+</sup>(SO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sup>−</sup> clusters and the features of the hydrogen-bond system that determines the thermal expansion of römerite. The structure of römerite shows that the sulfate tetrahedra are the most rigid complexes, followed by the Fe2<sup>3+</sup>O<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub> octahedra, and the Fe1<sup>2+</sup>(H<sub>2</sub>O)<sub>6</sub> octahedra are the most flexible. High-temperature powder X-ray diffraction, thermogravimetry and differential scanning calorimetry were used to determine the phase transformations and the eventual decomposition of römerite at higher temperatures up to 740°C. The decomposition of römerite at 60°C is followed by an amorphization, a transformation into a mikasaite-like phase at ∼275°C and a further decomposition into a hematite-like phase above 550°C, associated with the high-temperature form of magnetite, Fe<sub>3</sub>O<sub>4</sub>, above 575°C. The magnetic behavior of römerite reveals weak interactions between the Fe<sup>2+</sup> and Fe<sup>3+</sup> centers, in line with the large spatial separation between these ions.</p>","PeriodicalId":48737,"journal":{"name":"Journal of Applied Crystallography","volume":"58 3","pages":"822-831"},"PeriodicalIF":5.2,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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