CeO2包覆对TiO2传感器材料的氧敏性能的影响

针对CeO2具有良好的催化性和稳定性,以及TiO2的优良的氧敏特性,采用溶及－凝胶法制备CeO包覆TiO2S材料,并在自行设计的实验装置中对材料进行了氧化敏制试。该材料的温度系数低于纯TiO2材料,且氧敏性能比纯TiO2材料显著提高,其原因在于壳层中CeO颗粒为氧离子进出包覆体内的TiO2提供通道,并利用CeO储、放氧能力,促进TiO2电导率变化。     

CeO2掺杂对HfO2栅介质电学特性的影响

采用磁控共溅射的方法在p-Si(100)衬底上沉积了掺杂和不掺杂CeO2的HfO2薄膜。通过X射线光电子能谱(XPS)研究了薄膜中元素的化学计量比及结合能,制备MOS结构并对漏电流及电容等电学性能进行表征。结果表明,掺入CeO2后,整个体系的氧空位生成能增大,氧空位数目减少,漏电流较纯HfO2下降了一个数量级,满足作为高k材料的要求。     

TiO2掺杂CeO2催化超声降解甲基橙

以合成TiO2掺杂CeO2作为催化剂,以超声降解甲基橙反应为模型,研究了各种因素对TiO2掺杂CeO2催化超声降解甲基橙溶液的影响。结果表明,在TiO2(掺杂CeO2)催化剂作用下超声降解甲基橙的效果明显优于单纯以锐钛矿型TiO2催化时的情况。TiO2(掺杂CeO2)用量为0.5 g/L～1.0 g/L、超声波频率为25 kHz、输出功率为1.0 W/cm2、pH值为1.0～3.0时,初始浓度为20 mg/L的甲基橙水溶液在80 min左右基本可降解完全,COD的去除率达到了99.0%。     

十二烷基磺酸钠改性纳米CeO2的研究

采用十二烷基磺酸钠(SDS)对纳米CeO2粉体进行表面改性以提高其在有机材料中的分散性,以活化指数表征改性效果,并用IR、TG-DSC、TEM和LPSA表征了改性纳米CeO2的效果和结构。结果表明,最佳改性工艺条件为:十二烷基磺酸钠用量4%,反应温度70℃,反应时间6h,pH=7。SDS以化学键合的方式吸附在纳米CeO2的表面,并形成了有机包覆层,经SDS改性过的纳米CeO2的分散性明显提高,粒度降低44%。     

LnO2-δ-ZrO2(Ln=Ce,Tb,Pr)储氧材料的制备与结构

迄今为止,国际普遍使用的储氧材料主要是以具萤石四方结构CeO2-δ-ZrO2为基体掺杂Y2O3的固溶氧化物.为进一步提高储氧材料的储氧、催化、高温稳定性和抗老化性能,本研究采用 "超声膜扩散"法制备了(LnO2-δ)x-(ZrO2)1-x ( Ln = Ce,Pr,Tb)储氧材料.通过热重(TG)、微分扫描热分析(DSC)和XRD对其固溶过程和结构特征进行了研究.结果表明,(PrO2-δ)x-(ZrO2)1-x和(TbO2-δ)x-(ZrO2)1-x显示出具有(CeO2-δ)x-(ZrO2)1-x同样晶体结构,较后者更稳定的固溶体组织,为进行储氧催化等性能的研究提供了基础.     

铈掺杂TiO2光催化降解甲基橙的研究

采用溶胶-凝胶法制备纯的及掺杂不同量Ce的TiO2纳米粒子,利用UV-Vis漫反射光谱及XRD等对所制备样品进行表征和解释,以高压汞灯为光源,甲基橙水溶液的脱色为模型反应,研究了CeO2/TiO2的光催化降解反应活性.实验发现掺杂Ce的TiO2纳米粒子反射光谱特性向可见光方向红移到了500 nm;掺杂Ce的TiO2纳米粒子比纯的TiO2纳米粒子对光的吸收率高、吸收能力强;掺杂的Ce4+仅有少量进入TiO2晶格中,而大部分的Ce4+没有进入TiO2晶格中,而是以小团簇的CeO2形态均匀地分散在TiO2纳米粒子中或者是覆盖在其表面上,说明掺杂Ce能提高TiO2光催化反应活性,且掺杂Ce量有最佳值.实验结果表明在TiO2中掺杂Ce的摩尔百分含量为2%,甲基橙起始浓度为20 mg·L-1,CeO2/TiO2用量为0.400 g,双氧水用量为5.88 mmol·L-1,pH值为6.4时,光照8 h,甲基橙的脱色率可达96.8%.     

储氧材料CeO_2-ZrO_2-La_2O_3-Pr_6O_(11)的制备与表征

采用共沉淀法制备了稀土复合氧化物CeO2-ZrO2-La2O3-Pr6O11储氧材料,通过调节分散剂和表面活性剂浓度、改变工艺参数,得到了比表面积大和高温抗老化能力强的储氧材料,并对该材料进行表征。结果表明,该材料铈、锆、镧、镨的摩尔比约为40∶50∶5∶5;粒径分布D10=1.508μm,D50=3.348μm、D90=6.824μm,材料的新鲜比表面积和1 000℃老化4h后的比表面积分别达到了101.5m2/g和40.21m2/g,具有优异的抗高温老化能力。     

尖晶石LiMn2O4的表面修饰改性

尖晶石LiMn2O4是很有发展前途的锂离子电池正极材料,但它在循环过程中存在着容量衰减的问题。介绍了几种容量衰减机理:Mn的溶解,Jahn Teller效应以及氧的缺陷。表面修饰是1种抑制尖晶石LiMn2O4容量衰减的有效方法。还介绍了几种表面修饰尖晶石LiMn2O4的方法:锂硼氧化物玻璃(LBO)包覆,碳酸盐包覆,乙酰丙酮包覆,LiCoO2包覆,金属氧化物包覆。其中用Li CoO2包覆的方法具有优异的效果。     

TiO2应用性能的影响因素及其改善措施

分析了影响TiO2遮盖力、耐候性、分散性等应用性能的因素,重点阐述了金红石型TiO2表面包覆硅铝氧化物的方法及对这些应用性能的影响,在此基础上对包覆机理进行探讨。同时分析了我国TiO2包覆技术存在的主要问题并指出相应对策。     

CeO_2基固体氧化物燃料电池电解质研究

固体氧化物燃料电池(SOFCs)被誉为21世纪最具有发展潜力的能源技术之一.由于用稀土或碱土金属氧化物掺杂的CeO2在较低的温度下具有较高的氧离子电导率,是用作中低温固体氧化物燃料电池较理想的电解质材料.本文综述了近年来以掺杂的CeO2作电解质的SOFCs性能的研究情况,总结了提高、改善CeO2基固体电解质电性能的几种方法,并对今后的研究提出了自己的看法.     

Characteristic of macroporous CeO2-ZrO2 oxygen carrier for chemical-looping steam methane reforming

Chemical-looping steam methane reforming （CL-SMR） is a novel process towards the production of pure hydrogen and syngas, consisting ofa syngas production reaction and a hydrogen production reaction. Macroporous CeQ-ZrO2 oxygen carders with different pore sizes prepared by colloidal crystal templating method and characterized by techniques of scalming electron microscopy （SEM）, transmission electron microscopy （TEM）, Brunauer-Emmett-Teller （BET）, X-ray diffraction （XRD） and temperature pro- grammed reduction （H2-TPR） were tested in CL-SMR process. For comparison, nonporous CeO2-ZrO2 oxygen carrier prepared by precipitation method was also investigated. It was found that macroporous CeO2-ZrO2 oxygen carriers owned higher reducibility and reactivity in CL-SMR process than nonporous samples. For the macroporous CeO2-ZrO2 sample, the decline of pore size could im- prove the reducibility and reactivity. The macroporous sample with a pore size of 100 nm （labeled as Ce-Zr-100） showed the highest performance for the co-production of syngas and hydrogen during the successive CL-SMR redox cycles. After 10 redox cycles, it still retained good porous structure and reducibility. It was found that the porous structure could accelerate the oxygen release from bulk to surface, leading to a good mobility of oxygen and higher reducibility. In addition, it was also favorable for diffusion and penetration of methane and water steam into the sample particles to accelerate the reaction rate.     

A rationale for the development of thermally stable nanostructured CeO2-ZrO2-containing mixed oxides

CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermaUy treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.     

A comparative study of formaldehyde and carbon monoxide complete oxidation on MnOx-CeO2 catalysts

MnOx-CeO2 composite catalysts were prepared by a coprecipitation method and tested for formaldehyde (HCHO) and carbon monoxide (CO) oxidation. X-ray photon spectroscopy (XPS) results indicated that the average oxidation state of surface Mn species in CeMn composite catalyst was higher compared to the pure MnOx. The enhancement of reactivity for HCHO oxidation was due to the activation of the lattice oxygen species in MnOx by the addition of CeO2, which was confirmed by the H2 temperature programmed reduction (H2-TPR) results. The remarkable enhancement of reactivity for CO oxidation by the addition of CeO2 was due to the active oxygen species generated on the CeO2 surface which directly participated in the reaction.     

Si(100)衬底上CeO2薄膜的脉冲激光制备及性能研究

用CeO2陶瓷靶材,使用脉冲激光沉积(PLD)技术在Si(100)衬底上制备了CeO2薄膜.研究了衬底温度、沉积氧压对薄膜性能的影响,实验制备出了高度(111)取向的CeO2薄膜.使用X射线衍射(XRD)、反射式高能电子衍射(RHEED)对薄膜进行晶体结构的表征.结果表明:随着衬底温度的增加,薄膜中的残余宏观应力(拉应力)及微观应力逐渐减小,薄膜结晶质量不断提高,而沉积氧压对此影响较小.RHEED图像显示使用PLD方法在Si衬底上沉积的薄膜具备较高的结晶性及原子级平整的表面.使用原子力显微镜(AFM)对样品进行表面粗糙度分析,发现不同温度下生长的薄膜均具有光滑的表面,方均根粗糙度(RMS)均在0.4 nm以下.使用Keithley 4200半导体测试仪、椭偏仪对薄膜进行电性能及光学性能分析,发现衬底温度对薄膜的电学性能有显著影响,并且CeO2薄膜结晶状态与电学性能有直接的联系.     

Catalytic Reduction of SO2 on CeO2-La2O3 Rare Earth Mixed Compounds

Adding rare earth oxide CeO2 with variable valences to La2O3 formed a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers were all γ-Al2O3, were used as the catalyst for the reduction of SO2 by CO. The activation process of this catalyst and the impact of temperature and reactant concentration on the activation process were investigated. Using X-ray diffraction, the structure characteristics of catalyst before and after reaction were analyzed to reveal the change of phase structure. The result shows that the rare earth oxide mixtures composing of CeO2 and La2O3, as the catalyst for the reduction of SO2 by CO, diminish activation temperature 50～100℃ less and have higher activity than a single oxide CeO2 or La2O3. The reason possibl is that La2O3 goes into in the lattice of CeO2 to form solid phase complex CeO2-La2O3 and increases the capability of CeO2-La2O3/γ-Al2O3 catalyst to store oxygen, which supplies the redox of CeO2 reaction with a better condition. At the same time, elemental sulfur formed in the redox reaction impels La203 to be transformed to activation phase La2O2S in a lower temperature, which can be explained with the synergism between redox reaction and COS intermediate mechanism reaction.     

Temperature Programmed Reduction Studies on CeO2-Containing Catalysts

Temperature programmed reduction (TPR) study was carried out for CeO2/A12O3 and CeO2/ZrO2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO2/ZrO2 catalyst possesses excellent oxygen storage activity at 373 K after reduction above 1173 K although the oxygen storage of CeO2/Al2O3 catalyst after reduction above 1173 K is poor because of the formation of CeAlO3. Consequently, the oxygen storage on the CeO2/ZrO2 catalyst smoothly occurs from low temperatures when the catalyst is reduced even at high temperatures.     

Structures and oxygen storage capacities of CeO2-ZrO2-Al2O3 ternary oxides prepared by a green route： supercritical anti-solvent precipitation

CeO2-ZrO2-Al2O3 ternary oxides were successfully prepared by a green route of supercritical anti-solvent precipitation with supercritical CO2 as anti-solvent and methanol as solvent.The structures and oxygen storage capacities of these ternary oxides were characterized by XRD,Raman spectra and oxygen storage capacity measurements.It was found that Al 3+ and Zr 4+ inserted into CeO2 lattice,forming CeO2-ZrO2-Al2O3 solid solution.The concentration of aluminium isopropoxide in the solution affected the concentration of oxygen vacancy and the distortion of oxygen sublattice which were responsible for the oxygen storage capacity.The rapidest oxygen uptake/release rate and maximum total oxygen storage capacity(122.0 mmolO2/molCeO2)were obtained with the aluminium isopropoxide concentration at 0.2 wt.% in the solution.     

Preparation and Characterization of Cex Th1-xO2 Solid Solutions Prepared by Sol-Gel Method

Ceriumoxidehasbeenwidelystudiedinrecent yearsbecauseofitsusefulnessindifferentareasof chemistry.Incatalyticfield,forexample,CeO2has beenusedasanimportantcomponentofautomotive three waycatalystsforreducingtheexhaust.The mainroleofceriainthree waycatalystsi…     

Preparation, Characterization of CuO／CeO2 and Cu／CeO2 Catalysts and Their Applications in Low-Temperature CO Oxidation

CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.