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Enhanced conductivity and stability of Co_(0.98)Cu_(x)Mn_(2.02−x)O_(4)ceramics with dual phases and twin structures

Journal of Advanced Ceramics 2023年第9期12卷 1742-1757页

作者： Chengjian Ma Longhua He Lei Bi Hong Gao Jianxiang Ding Analytical and Testing Center Yancheng Institute of TechnologyYancheng 224051China School of Materials Science and Engineering Yancheng Institute of TechnologyYancheng 224051China School of Resource Environment and Safety Engineering University of South ChinaHengyang 421001China School of Mathematics and Physics Yancheng Institute of TechnologyYancheng 224051China School of Materials Science and Engineering Anhui University of TechnologyMa’anshan 243002China

Semiconductor materials with heterogeneous interfaces and twin structures generally demonstrate a higher concentration of carriers and better electrical stability.A variety of Cu-doped Co_(0.98)Cu_(x)Mn_(2.02−x)O_(4)(0≤x≤0.5)negative temperature coefficient(NTC)ceramics with dual phases and twin structures were successfully prepared in this *** refinement indicates that the content of a cubic spinel phase increases with increasing Cu *** addition of Cu can promote grain growth and ***-level structural characterization reveals the evolution of twin morphology from large lamellae with internal fine lamellae(LIT lamellae)to large lamellae without internal fine lamellae(L lamellae)and the distribution of twin boundary ***-principles calculations reveal that the dual phases and twin structures have lower oxygen-vacancy formation energy than those in the case of the pure tetragonal and cubic spinel,thereby enhancing the transmission of ***,the three-dimensional charge-density difference shows that metal ions at the interface lose electrons and dwell in high valence states,thereby enhancing electrical stability of the NTC ***,the additional Cu ions engage in electron-exchange interactions with Mn and Co ions,thereby reducing *** comparison to previous Cu-containing systems,the Co_(0.98)Cu_(x)Mn_(2.02−x)O_(4)series exhibit superior stability(aging value≤2.84%),tunable room-temperature resistivity(ρ),and material constant(B)value(17.5Ω·cm≤ρ≤7325Ω·cm,2836 K≤B≤4315 K).These discoveries lay a foundation for designing and developing new NTC ceramics with ultra-high performance.

关键词： negative temperature coefficient(NTC)ceramics Cu-containing spinel high electrical stability twin structure first-principles calculation electron-exchange interaction

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Barrellite and Pillarrite: A Description and a Mode of Formation of a Novel Post-Sedimentary twin structures from As-Subbiyah, North of Kuwait Bay, Kuwait

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International Journal of Geosciences 2021年第7期12卷 625-634页

作者： Ali T. Al-Mishwat Department of Earth and Environmental Sciences Kuwait University Safat Kuwait

I report on the occurrence of a pair of novel and related post-sedimentary structures that form in the Neogene cross-bedded red sandstones in the As-Subbiyah area, north of Kuwait Bay, Kuwait. I named them barrellite and pillarrite. Barrellite forms as vertical tubes of concentric sheaths of siltstone with partially hollow interior or intervening homogeneous and structure-less sandstone. It stands as barrels above the background sandstone. Pillarrite forms as discrete, vertical and solitary spines of homogeneous sandstone and siltstone, or inside barrellite masses from which successive siltstone sheaths were stripped. The structures range in diameter from one-centimeter poke marks to one-meter-wide barrels and hunks, and their vertical length exceeds two meters. Barrellite, pillarrite and their complex intergrowths develop near thin quartz veins and chaotic zones, and form with them complex geometrical relationships. The dual structures are genetically related and fall within the general class of tubular structures in sedimentary rocks. I consider them as a special type of sand injectites. The mode of formation of these structures is enigmatic. They develop in a geological setting that displays evidence of a widespread and vigorous oil field brine. I suggest a tentative scenario for their formation, involving flushing of the brine through hydraulic fracturing of the sedimentary succession above the Ebharah Oil Field reservoir in the As-Subbiyah area. The brine plucks mineral and rock fragments and mixes with them along its paths, producing a heterogeneous slurry. Ultimately, the slurry solidifies as barrellite and pillarrite, chaotic zones and quartz veins. The vertical nature of the structures, ci

关键词： Barrellite Pillarrite As-Subbiyah Kuwait Post-Sedimentary twin structure

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Study of δ-hydrides in Ti-2Al-2.5Zr and Ti-4Al-2V alloys

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Rare Metals 2006年第1期25卷 16-20页

作者： YU Huang GU Jialin LIU Qing LIU Yanzhang Department of Materials Science and Engineering Laboratory of Advance Materials Materials Research Center Tsinghua University Beijing100084 China Nuclear Power Institute of China Chengdu 610005 China

The α alloy Ti-2Al-2.5Zr and near α alloy Ti-4Al-2V were hydrogenated to various levels. The morphology, orientation relation （OR）, and habit plane of the hydrides were studied by means of transmission electron microscopy （TEM）. It was found that in the two alloys most of the precipitates are δ-hydrides which have fcc structure with the lattice parameter a = 0.44 nm. Two basic orientation relationships and habit planes of the precipitates are determined. twin structure was observed in both alloys.

关键词： titanium alloy hydride orientation relation habit plane twin structure

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Stability of twins in Mg alloys-A short review

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Journal of Magnesium and Alloys 2020年第1期8卷 66-77页

作者： Tingting Liu Qingshan Yang Ning Guo Yun Lu Bo Song School of Materials and Energy Southwest UniversityChongqing 400715China School of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China Graduate School of Science and Engineering Chiba UniversityChiba 263-8522Japan

In this article,the stability of twins,especially{10–12}twins,in Mg alloys was critically *** the last decade,pre-twinning is considered to be an effective method for adjusting the microstructure and properties of wrought Mg ***,formation of twin-texture can remarkably improve formability of rolled Mg ***,the stability of{10–12}twins determines the effect of this *** work revealed that initial{10–12}twins may either grow or shrink under further deformation,and may be removed by static recrystallization under thermal *** is considered that improving the stability of twin structure could enhance the contribution of twin-texture on subsequent plastic *** on this background,stress stability and thermal stability of{10–12}twin structure were summarized and reviewed in this ***,a few critical scientific problems in this research field were pointed out.©2020 Published by Elsevier *** behalf of Chongqing University.

关键词： Mg alloys twin structure Stability Texture Recrystallization

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