搜索到3541篇“ TETRAGONAL“的相关文章
Local tetragonal distortion of Pt alloy catalysts for enhanced oxygen reduction reaction efficiency
2024年
Platinum-based alloy nanoparticles are the most attractive catalysts for the oxygen reduction reaction at present,but an in-depth understanding of the relationship between their short-range structural information and catalytic performance is still lacking.Herein,we present a synthetic strategy that uses transition-metal oxide-assisted thermal diffusion.PtCo/C catalysts with localized tetragonal distortion were obtained by controlling the thermal diffusion process of transition-metal elements.This localized structural distortion induced a significant strain effect on the nanoparticle surface,which further shortened the length of the Pt-Pt bond,improved the electronic state of the Pt surface,and enhanced the performance of the catalyst.PtCo/C catalysts with special short-range structures achieved excellent mass activity(2.27 Amg_(Pt)^(-1))and specific activity(3.34 A cm^(-2)).In addition,the localized tetragonal distortion-induced surface compression of the Pt skin improved the stability of the catalyst.The mass activity decreased by only 13%after 30,000 cycles.Enhanced catalyst activity and excellent durability have also been demonstrated in the proton exchange membrane fuel cell configuration.This study provides valuable insights into the development of advanced Pt-based nanocatalysts and paves the way for reducing noble-metal loading and increasing the catalytic activity and catalyst stability.
Xiaoke LiXiao DuanKang HuaYongkang WuZhiyan RuiRui DingAidong LiChen OuyangJia LiTing LiJianguo Liu
关键词:ELECTROCATALYSTS
四方相锆钛酸铅陶瓷制备及温度稳定性研究
2024年
采用传统固相法制备了Pb(Zr_(1-x)Ti_(x))O_(3)陶瓷,通过调节锆钛摩尔比将其定位于四方区域以改善温度稳定性,并通过优化烧结温度改善电学性能。实验结果表明,当x=0.52时,体系处于四方区域,此时陶瓷的温度稳定性有所提升,在室温~300℃时,d33变化率为±14.7%。在1250℃下烧结的Pb(Zr_(0.48)Ti_(0.52))O_(3)陶瓷具有最佳的电学性能:压电常数d_(33)=183 pC/N,居里温度TC=402℃,相对介电常数ε_(r)=1209。
杨洋侯育冬杜红亮张阿梅侯鸿平
关键词:压电陶瓷锆钛酸铅四方相温度稳定性烧结温度
基于异丙醇溶剂热合成四方相BaTiO_(3)工艺探索及机理研究
2024年
以Ba(OH)_(2)·8H_(2)O和Ti(OC_(4)H_(9))_(4)为原料、异丙醇(IPA)为溶剂,通过溶剂热法合成富四方相纳米钛酸钡(BTO)粉体,研究了钡钛比、体系pH值、溶剂热温度及时间等因素对制备高四方性纳米BTO粉体的影响,利用X射线衍射和扫描电镜等表征方法研究了IPA在溶剂热制备BTO过程中的作用机理。结果表明,溶剂热工艺合成过程中,IPA会优先提供一定的—OH以促进Ti(OC_(4)H_(9))_(4)的水解,生成TiO_(6)八面体并与Ba^(2+)连接。在低碱度环境中,经相转变、小颗粒溶解与重结晶等过程逐步转变为形貌规整的四方相BTO。钡钛比1.6、体系pH值10、溶剂热温度220℃、时间24 h、煅烧温度950℃、煅烧时间2 h时制备的富四方相纳米BTO粉体分散均匀、形貌规整,呈四方形或近四方形,c/a值达1.009 4,平均粒径为124 nm。
盖卉妍戴超华杨林
关键词:四方相陶瓷电容器合成制备
Defects in the grain interiors of 3 mol%yttria-stabilized tetragonal zirconia polycrystal ceramics with 0.25 wt%alumina
2024年
The presence of high-density defects is rarely observed in bulk 3 mol%yttria-stabilized tetragonal zirconia polycrystal(3Y-TZP)ceramics obtained through conventional pressureless sintering.In the present work,fine-grained dense 147 nm 3Y-TZP ceramics were prepared by pressureless sintering of commercial 0.25 wt%alumina-doped zirconia powders at 1300℃.A novel discovery was reported in which large amounts of defects were present in the grain interiors of the sample.The phenomenon was further examined using three types of powder samples,and the reasons for defect formation were investigated by microstructural characterization using high-resolution transmission electron microscopy(HRTEM)analysis and Rietveld refinement.The results confirmed the essential dependence of the defect formation on the alumina addition.The authors attributed the defect formation to the significant difference in ionic radii of the solvent and solute during the dissolution of alumina into the zirconia lattice.The sintering kinetics were proposed to be enhanced by the presence of substantial defects,which consequently favored the low-temperature sintering of the alumina-doped zirconia ceramics.
Yan XiongLian LuoYao ChengZhi LiuQi LiuWeimin WangWei Ji
极低温环境下立方相和四方相Nb_(3)Sn超导晶体力学及力-电耦合行为分析
2024年
Nb_(3)Sn超导相转变中的力电耦合效应给超导磁体装备的电磁性能指标和安全运行带来不利影响。鉴于Nb_(3)Sn具有立方相和四方相两种相结构,建立了Nb_(3)Sn立方相、四方相和混合相晶体力学模型,以及考虑变形-临界温度退化和变形-正常态电阻率变化的力电耦合响应模型。研究结果表明,相结构会导致单晶体弹性力学性能有所区别,但静水压作用下不同相结构的Nb_(3)Sn多晶体,其局部应力状态与相结构无关,仅取决于晶粒形貌和取向。由于不同的相结构在外载下的费米面上电子态密度的演变规律基本一致,使得变形诱导的临界温度退化行为对相结构没有依赖性。对于混合相Nb_(3)Sn正常态电阻率变化而言,温度低于马氏体相变温度时,可以采用基于电子-电子散射假设得到的T_(2)规律来描述;当温度高于马氏体相变温度时,由于四方相向立方相的转变,需要考虑电-声子耦合作用对正常态电阻率的贡献,可以采用拓展的Woodard-Cody电阻率模型来描述宏观电阻率的应变效应。研究结果提高了对不同相的临界性能退化机理的认识。
王涛何宇新乔力
关键词:四方相立方相
From Topological Nodal-Line Semimetals to Quantum Spin Hall Insulators in Tetragonal SnX Monolayers(X=F,Cl,Br,I)
2024年
Two-dimensional(2D)topological materials have recently garnered significant interest due to their profound physical properties and promising applications for future quantum nanoelectronics.Achieving various topological states within one type of materials is,however,seldom reported.Based on first-principles calculations and tightbinding models,we investigate topological electronic states in a novel family of 2D halogenated tetragonal stanene(T-SnX,X=F,Cl,Br,I).All the four monolayers are found to be unusual topological nodal-line semimetals(NLSs),protected by a glide mirror symmetry.When spin-orbit coupling(SOC)is turned on,T-SnF and TSnCl are still ascertained as topological NLSs due to the remaining band inversion,primarily composed of Sn pxy orbitals,while T-Sn Br and T-SnI become quantum spin Hall insulators.The phase transition is ascribed to moving up in energy of Sn s orbitals and increasing of SOC strengths.The topology origin in the materials is uniformly rationalized through elementary band representations.The robust and diverse topological states found in the 2D T-SnX monolayers position them as an excellent material platform for development of innovative topological electronics.
朱晔赵宝薛阳徐玮徐文婷杨中芹
关键词:TOPOLOGICAL
四方相纳米钛酸钡粉体的制备及性能研究被引量:1
2024年
在传统固相法制备四方相纳米钛酸钡粉体中,碳酸钡前驱体的分散性与粒径对所得钛酸钡的形貌、粒径以及介电性能起重要作用。本研究以氢氧化钡与干冰为原料,通过控制氢氧化钡的浓度,制备了碳酸钡粉体,然后以此为原料,制备了钛酸钡粉体和陶瓷,并研究了钛酸钡陶瓷的介电性能。结果表明:本研究制得粒径为180 nm的短棒状碳酸钡粉体,和粒径为400 nm的高分散、高均匀、纯四方相的钛酸钡粉体。在1250℃下煅烧制得钛酸钡陶瓷,其介电常数为4885,介质损耗因数为0.0189。
上官明楠王超莹赵昀云张秀云朱归胜徐华蕊
关键词:碳酸钡钛酸钡固相法
低温合成四方相BaTiO_(3)及其压电催化性能
2024年
基于淀粉糊化机制低温合成了四方相BaTiO_(3)粉体。采用扫描电子显微镜、透射电子显微镜、X射线衍射、傅里叶变换红外光谱、紫外可见吸收光谱、X射线光电子能谱对合成粉体的形貌、物相进行表征;在超声条件下,以系列典型染料为降解对象测试BaTiO_(3)压电催化性能。结果显示,煅烧温度为600℃时即可获得四方相BaTiO_(3)粉体,且随着温度的提升,结晶度逐渐增加;当煅烧温度为700℃时,合成的BaTiO_(3)粉体尺寸分布均匀,分散度良好,呈现类立方体状;在超声驱动下,BaTiO_(3)降解罗丹明B、刚果红、甲基橙染料时均展现出良好的效果,反应速率常数分别为1.090×10^(-2)、1.113×10^(-2)、1.084×10^(-2)min^(-1),并以降解刚果红为对象揭示其压电催化的机理,即空穴和超氧自由基是降解过程中的主要反应物质。
胡志文董伟霞董伟霞李萍
关键词:淀粉糊化
四方-正交相界处的PLZST反铁电陶瓷电性能研究
2024年
采用固相法烧结制备(Pb_(0.97)La_(0.02))(Zr_(y)Sn_(1-x-y)Ti_(x))O_(3)反铁电陶瓷样品(x=0.01,0.03,0.05,0.07;y值沿La^(3+)掺杂PZST三元相图反铁电相界处取得),系统研究了B位不同Ti含量对PLZST体系反铁电陶瓷结构、微观形貌、铁电、介电特性的影响。结果表明:该体系PLZST反铁电陶瓷为简单钙钛矿(ABO_(3))结构;且随Ti含量增加,其晶粒尺寸、陶瓷致密度均增大,材料最大极化强度相应提高,同时耐击穿电场强度有所降低;在B位Ti的质量分数为5%时储能特性最佳(W_(re)=1.7 J/cm^(3),η=90.14%);同时,该系列陶瓷具有良好的介电温度稳定性(350℃时介电损耗低于5%)和介电频率稳定性(测试频率在1MHz时介电常数变化率约为10%)。
申震夏翔李怡李荣杨晓禹程英晔史秀梅
关键词:电子陶瓷反铁电体
Discovery of controllable high Chern number quantum anomalous Hall state in tetragonal lattice FeSIn
2024年
Quantum anomalous Hall(QAH) insulators have excellent properties driven by fancy topological physics, but their practical application is greatly hindered by the observed temperature of liquid nitrogen, and the QAH insulator with high Chern number is conducive to spintronic devices with lower energy consumption. Here, we find that monolayer Fe SIn is a good candidate for realizing the QAH phase;it exhibits a high magnetic transition temperature of 221 K and tunable C = ±2 with respect to magnetization orientation in the y–z plane. After the application of biaxial strain, the magnetic axis shifts from the x–y plane to the z direction, and the effect of the high C and ferromagnetic ground state on the stress is robust. Also, the effect of correlation U on C has been examined. These properties are rooted in the large size of the Fe atom that contributes to ferromagnetic kinetic exchange with neighboring Fe atoms. These findings demonstrate monolayer Fe SIn to be a major template for probing novel QAH devices at higher temperatures.
任小浪张昌文

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