CeO_2微结构的水热合成和光学性质（英文）

以Ce(NO_3)_3·6H_2O作为铈源、尿素作为沉淀剂、K-30型PVP作为表面活性剂,采用水热法成功制备二氧化铈微结构.采用X射线衍射仪(XRD)、热重/差热分析(TG/DTA)、傅里叶变换红外谱(FT-IR)、扫描电子显微镜(SEM)、拉曼光谱(Raman)、紫外可见近红外分光光度计(UV-Vis)和荧光分光光度计(PL)对此CeO_2样品进行表征,结果表明:制备的CeO_2样品具有萤石立方结构,样品中存在氧空位和Ce~(3+)离子,样品具有较强的紫外吸收和室温光致发光性能.吸收边和拉曼峰位的移动与样品中氧空位和Ce~(3+)离子有关.     

DFT+U方法研究Ni掺杂对CeO2结构和储放氧性能影响

铈基材料具有优异的储放氧性能和催化活性,在当今催化领域有着广泛的应用.本研究通过DFT+U方法计算了Ni掺杂引起的Ce02局域结构及全局结构扰动.并分析了原子位置排布与储放氧性能之间的构效关系.当Ni以间隙位形式进入CeO2晶胞时,Ni具有四面体配位特征,部分氧离子远离其初始位置.向类间隙位移动;在产生氧空位之后,全局结构弛豫现象明显.当Ni以取代位形式进入CeO2晶胞时,Ni具有八面体配位特征,与纯NiO结构类似;在产生氧空位之后,由Ni及其最近邻氧离子构成的局域空间发生扩张.结合氧空位生成能计算结果,间隙位Ni离子对储放氧性能的促进较小,取代位Ni离子可促进体系自发产生氧空位.     

紫外及真空紫外光激发下K_2Y(WO_4)(PO_4):Ce~(3+)的发光性质

通过高温固相法制备了新型Ce~(3+)掺杂K_2Y(WO_4)(PO_4)发光材料,研究了其在紫外和真空紫外光激发下的光致发光性能.在254nm激发下,K_2Y(WO_4)(PO_4):xCe~(3+)系列样品均显示出3个宽带发射,最高峰分别位于330,355和550nm,依次归属于Ce~(3+)的5d-~2F_(5/2),5d-~2F_(7/2)跃迁和O_2的p轨道到W~(6+)的d轨道的电荷转移跃迁.此外,在172nm激发下K_2Y(WO_4)(PO_4):0.05Ce~(3+)的CIE坐标为(0.309,0.3329),接近白光发射,暗示以Ce~(3+)掺杂K_2Y(WO_4)(PO_4)的白光发射材料在实现无汞荧光灯或等离子平板显示方面具有重要的应用前景.     

PbO_2电极在库仑分析中应用的研究

按照PbO_2电极具有高的氧化电位和氧析出超电位,我们研究了以PbO_2代替pt作阳极的可能性.在硫酸介质中,将其用于屯生Co~(3+)、Ce~(4+)、MnO_4~-等强制氧化荆,恒电流库仑法滴定Fe~(2+)、Ti~(3+)、C_2O_4~(2-)等离子,在选定的条件下电流效率可达100%。方法用于硫酸中微量铁的测定。     

BaFBr:Ce~(3+)的发光特性

研究了Ce~(3+)在BaFBr基质中的发光性质。根据不同激发(发射)条件下的发射(激发)光谱,鉴别出BaFBr:Ce~(3+)具有两种不同的发光中心。对发射光谱中的发射峰作了高斯峰分解,发现BaFBr:Ce~(3+)的发射峰是成对出现的双峰,分别对应于Ce~(3+)的两种不同的发光中心。它们可归属为~2D_(3/2)低能级到~2F_(5/2),~2F_(7/2)的双基态的跃迁。 实验表明,BaFBr:Ce~(3+)具有较好的发光性质,可以用作X射线或光致发光材料。     

Ce~(3+)/Tb~(3+)共掺的自析晶Sr_2YF_7微晶玻璃的发光性能

通过熔融淬冷法成功制备了Ce~(3+)/Tb~(3+)共掺的自析晶Sr_2YF_7微晶玻璃.用X-射线衍射和透射电镜分析了样品的微观结构;利用荧光光谱和荧光寿命系统地研究了样品的荧光特性.调节Tb~(3+)的掺杂浓度,可以得到从蓝光到白光,最终到黄绿光的可调发光.结果表明,Ce~(3+)/Tb~(3+)共掺的自析晶Sr2YF7微晶玻璃有望应用在白光LED和光转换器件中.     

氧化铈和氧化钪掺杂对氧化锆材料中点缺陷的影响

介绍了两种稀土元素掺杂的氧化锆(ZrO_2)材料:氧化铈(CeO_2)掺杂ZrO_2和氧化钪(Sc_2O_3)掺杂ZrO_2.CeO_2掺杂ZrO_2材料的研究重点是温度和氧分压对其氧空位形成的影响,以及由此带来的其热力学参数的变化.Sc_2O_3掺杂ZrO_2材料的研究重点在ZrO_2的掺杂含量对其氧空位数量的影响,以及氧空位作为离子导通的载体在晶体和晶界上的变化对材料导电性能的作用.     

共沉淀法制备的含Sm2O2S钐铈复合物的表征及紫外–可见光屏蔽性能

氧化铈是一种应用比较广泛的无机紫外屏蔽剂，但是太阳光中的成分不只是紫外线会对人体产生伤害，400–450 nm之间的高能短波蓝光也会对人的皮肤或者眼睛产生一定的伤害，所以，本文旨在制备一种既能屏蔽紫外光又能屏蔽高能短波蓝光的光屏蔽剂。本文通过共沉淀法合成了含有Sm₂O₂S的钐铈复合物。 这种复合物不仅可以阻挡紫外光，还可以阻挡蓝光。钐铈复合物的平均透射率(360–450 nm)和禁带宽度最小值分别为8.90%和2.76 eV，低于CeO₂的13.96%和3.01 eV。元素分析 (EA)、X 射线衍射 (XRD)、傅里叶变换红外光谱(FTIR)和拉曼光谱(Raman)确定了实验中制备的钐铈复合物样品由Ce₄O₇、Sm₂O₂S、Sm₂O₃和Sm₂O₂SO₄组成。通过扫描和透射电子显微镜(SEM和TEM)分析了钐铈复合物样品的微观结构。 X射线光电子能谱(XPS)表明，铈元素具有Ce3+和Ce4+两种价态，氧元素具有晶格氧和氧空位两种存在形式。Sm3+和Ce3+在氧化铈晶格中的掺杂以及氧空位的存在是导致钐铈复合物具有较小的禁带宽度以及优异的紫外–可见光屏蔽性能的重要原因。     

溶胶–凝胶温度对Cu_(0.5)Ce_(0.375)Zr_(0.125)O_x结构及催化降解甲苯性能的影响

采用简单的溶胶–凝胶法在不同的温度下制备Cu_(0.5)Ce_(0.375)Zr_(0.125)O_x复合氧化物催化剂,通过XRD、H_2-TPR、O_2-TPD和Raman技术表征催化剂的结构,在固定床反应器中对其降解甲苯性能进行研究.结果表明:溶胶–凝胶的温度对催化剂的结构和活性具有一定影响,适宜的溶胶–凝胶温度有利于增强金属离子的流动性,促进CuO和CeO_2的相互作用,使Cu~(2+)更容易进入到CeO_2晶格中形成Cu-Ce固溶体,形成缺陷结构,产生更多的氧空位.当催化剂制备的溶胶–凝胶温度为70℃时,催化剂降解甲苯的活性最好,其完全降解甲苯的温度为250℃.这归因于该催化剂具有高达0.95的氧空位浓度和对活性起主要作用的活性物种较高的耗氢量.     

3DOM-TiO_(2-x)的制备及其光催化降解性能

将模板法制得的三维有序大孔TiO_2(3DOM-TiO_2)置于H_2中还原,得到具有氧空位的3DOM-TiO_(2-x)(x为氧空位值)。采用X线衍射仪(XRD)、扫描电子显微镜(SEM)、拉曼光谱仪、紫外-可见漫反射光谱仪(UV-Vis DRS)和电化学工作站等对产物的结构和性能进行表征。通过固定床反应器中模拟太阳光催化降解罗丹明B(RhB),对3DOM-TiO_(2-x)的光催化活性进行评价,并对光催化活性提高的原因和反应机制进行分析。结果表明:3DOM-TiO_(2-x)具有较高的光催化活性源于3DOM结构和氧空位的协同作用,3DOM结构通过提高比表面积增加氧空位的生成量,从而增强光催化的活性,同时,3DOM结构有利于光的穿透,提高了光催化效率。·OH、空穴(h~+)和·O~-_2在罗丹明B的降解中均起着重要作用,它们对罗丹明B降解的贡献度由大到小的顺序为·O~-_2、·OH、h~+。3DOM-TiO_(2-x)具有较好的稳定性,采用周期性注入清水清洗的方法可以去除吸附在3DOM-TiO_(2-x)表面上的罗丹明B,以保证反应过程稳定进行。     

Preparation and characterization of highly active nanosized strontium-doped lanthanum cobaltate catalysts with high surface areas

The volatile organic compounds (VOCs) emitted from the sources of industries are a kind of main pol-lutants to the atmosphere. The Environmental Protec-tion Agency (EPA) of the United States lists more than 300 VOC pollutants. 70% of the toxic compounds t…     

TFEL of Ce3+ in zine sulpho-oxide

A new TFEL material ZnS_xO_1−x: Ce³⁺ is prepared. The EL brightness of ZnS_xO_1−x: Ce³⁺ is at least one order higher than that of ZnS: Ce³⁺ at the same doping concentration of Ce³⁺. The EL emission wavelength of ZnS_xO_1−x: Ce³⁺ (X = 0.5) ranges from 400 to 600 nm. The emission of ZnS_xO_1−x: Ce³⁺ may be used as the blue part of white TFEL.     

二维NiFe-LDH/Mo(OS)x纳米片协同促进电催化析氧反应

过渡族金属基二维纳米材料作为电催化析氧反应（oxygen evolution reaction, OER）催化剂具有巨大的潜力。通过原位电沉积法,在泡沫镍基底表面制备了二维层状镍铁双氢氧化物（NiFe-LDH）和氧硫化钼Mo(OS)_x纳米片异质结构。NiFe LDH/Mo(OS)_x电极在1 M KOH溶液中表现出优异的OER性能和长效稳定性,在10 mA/cm²电流密度下过电势仅为220 mV。在100、500 mA/cm²的高电流密度下,也能达到253、304 mV的低过电势。研究结果表明,NiFe-LDH/Mo(OS)_x电极优异的OER性能归因于Mo(OS)_x和NiFe LDH的协同作用,极大地促进了Fe²⁺向Fe³⁺活性物质的转化,并促进了氧空位的形成。这种协同制备方法为合理构建和设计异质结构电催化剂,实现高效的水分解提供了帮助。     

Mn-ion-enhanced red spectral emission from yttrium aluminum garnet doped cerium phosphor

Mnions were co-doped in yttrium aluminum garnet doped cerium(YAG:Ce) phosphors as a co-activator and host lattice element using the co-precipitation method.These ions broadened the emission spectra of the pure YAG:Ce phosphor,which is caused by the 2E-4A2,5E-5T2 or 1T2-5T2 transition.From our X-ray diffraction results,we observed that Ce3+(1.032 ) was substituted at the Y3+(0.900 ) site,and Mn4+(0.538 ) and Mn3+(0.67 ) were substituted at the Al3+(0.535 ) site.The chromaticity color co-ordinates of YAG:Ce0.06 is(0.203,0.167),and the indices of YAG:Ce0.06,Mn0.04 and YAG:Ce0.06,Mn0.08 are(0.249,0.181) and(0.233,0.194),respectively.The manganese co-doped yttrium aluminum garnet doped cerium blended with the YAG:Ce phosphor showed improved white light emission.     

Present status and future prospect of design of Pt–cerium oxide electrodes for fuel cell applications

In the research field of proton exchange membrane fuel cells, the design of electrocatalytic activities on Pt-oxide promoter in the anode side has attracted attention for improvement of CO tolerance of Pt in anode side and a lowering of large over-potential loss of the oxygen reduction reaction on the cathode in the fuel cells. In the Pt-oxide promoter series, Pt–CeOx/C is one of the unique systems. It is because the unique behavior of CeOx such as electrochemical redox reaction between Ce3t and Ce4t in the anodic and cathodic reactions of fuel cell is observed. The present short review gives an overview of the recent works for improvement of the CO tolerance of Pt in the Pt–CeOx/C anodes and enhancement of the oxygen reduction reaction activity on Pt in the Pt–CeOx/C cathodes for fuel cell application. To show the design paradigm for fabrication of high quality Pt–CeOx/C electrodes, the authors re-introduced parts of our research results to highlight the important role of interface structure of Pt–CeOx based on the ultimate analysis results. The usefulness of the combined approach of microanalysis and the processing route design is presented.     

Effect of Ce addition on hot tearing behavior of AZ91 alloy

A small amount of cerium (below 1.0 wt%) addition to AZ91 alloy have been investigated on the hot tearing susceptibility (HTS) at a cooling rate of 1.5Ks^?1. The HTS increased to a maximum value with a cerium addition of 0.6 wt% and then decreased to a stable status as cerium was gradually added. Due to high chemical activity, cerium into the melts can react with aluminum to form an Al₁₁Ce₃ intermetallic compound. X–ray diffraction results also confirmed the existence of Al₁₁Ce₃. The Al₁₁Ce₃ increased with the presence of the needle-like and block morphology. As cerium levels increased, the amount of Mg₁₇Al₁₂ decreased. The variations between Mg₁₇Al₁₂ and Al₁₁Ce₃ resulted in a similar normal distribution of the HTS in AZ91 alloy. The findings were further verified through the microstructure evolution and the surface morphology of fracture.     

Preparation and luminescence characteristics of Sr3SiO5：Eu^2＋ phosphor for white LED

The Sr3SiO5：Eu^2＋ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5：Eu^2＋ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5：Eu^2＋ is influenced by the Eu^2＋ concentration. The relative emission spectra of the white-emitting InGaN-based YAG：Ce^3＋ LED and Sr3SiO5：Eu^2＋ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5：Eu^2＋ is better than that of InGaN-based YAG：Ce^3＋, and the CIE chromaticity of InGaN-based Sr3SiO5：Eu^2＋ is （x=0.348, y=0.326）.     

High-pressure synthesis and properties of CeO2-ZrO2 solid solution

Using nanoparticles of CeO₂ and ZrO₂ prepared by the chemical precipitation method as starting materials, the singlephase cubic Ce_0.5Zr_0.5O₂ solid solution (cCe_0.5Zr_0.5O₂) has been synthesized under 3.1 GPa at 1073 K for the first time. The structure of the c-Ce_0.5Zr_0.5O₂ has not been changed before and after annealing at 773 K for 1 h. Only an unknown EPR signal (g =1.990) has been observed in the c-Ce_0.5Zr_0.5O₂ and not varied after annealing at 773 K for 1 h, which exhibited that there exists no Ce³⁺ in the c-Ce_0.5Zr_0.5O₂ and the Ce⁴⁺ has not been reduced into Ce³⁺ after annealing. The transport mechanism is ionic for the c-Ce_0.5Zr_0.5O₂. The bulk conductivity (σ =1.2 ×10⁻⁵ S/cm at 823 K, σ=2.1 × 10⁻³ S/cm at 1123 K) is the same as that of CeO₂, but smaller than that of Y₂O₃-stabilized ZrO₂. A marked curvature at T = 823 K has been observed in the Arrhenius plot of the bulk conductivity. The activation energy below 823 K is lower than that above 823 K, and the reason has been discussed.     

铝含量对B2铁铝空位浓度和硬度的影响

[目的]铁铝合金在高温结构材料、加热元件等方面有广泛的应用,对其强化和韧化机理的研究对设计和开发新型铁铝基高温合金具有重要意义。[方法]采用真空熔炼方法制备不同铝含量的铁铝合金,经过不同的退火温度热处理后,用XRD方法测量其晶格常数,确定其X射线密度,采用阿基米德法测量其体密度,从而确定其空位浓度;用显微硬度计测量其硬度。[结果]空位浓度随着铝含量的增加而增加,随热处理温度的升高合金中空位浓度增加;显微硬度随铝含量的增加或热处理温度的升高而增大。[结论]随着铝含量的增加,空位形成能下降,空位浓度增加;随着热处理温度的升高,合金中空位浓度增大;合金显微硬度增大主要是由于空位浓度增加对位错的阻碍作用增强所致。显微硬度与空位浓度的关系可近似表示为H_V=1.922+2.179C_Vac^1/2。     

Effects of synthetic conditions on the structure and morphology of open-ended vanadium oxide nanotubes and study of their growth mechanism

Vanadium oxide nanotubes (VOx-NTs) have been synthesized by using n-butylamine as structuredirecting template and V2O5 as precursor under hydrothermal conditions. XRD, FTIR, SEM, TEM, BET and TG-DTA characterizations have been performed to both optimize the synthetic conditions and understand the growth mechanism of VOx-NTs. The results showed that open-ended VOx-NTs were obtained under the optimized conditions (hydrothermal temperature: 150―160°C, hydrothermal time: 5―7 d, the molar ratio of V2O5 to n-butylamine is 1:1) with diameters ranging from about 30 to 100 nm and several micrometers in length. The BET surface area and the desorption cumulative pore volume of pores of the as-synthesized sample were about 27.4609 m2/g and 0.191087 cm3/g, respectively. The result presents that the synthesis of VOx-NTs is controlled by the "rolling" mechanism and temperature is primary driving force for rolling.