溶胶-凝胶法制备YAG颗粒及在电接触材料中的应用

以硝酸钇(Y(NO₃)₃6H₂O)、硝酸铝(Al(NO₃)₃9H₂O)为主要原料,六次甲基四胺作为催化剂,采用溶胶-凝胶法合成Y₃Al₅O₁₂(YAG)纳米颗粒,并以YAG颗粒为第二相增强材料,通过粉末冶金工艺制备Ag/YAG电接触复合材料;采用X-射线衍射仪(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),傅里叶红外光谱(FT-IR)、硬度计、电导率仪等方法对其进行表征。结果表明：在水浴温度为50℃的条件下成功采用sol-gel法合成YAG纳米颗粒,物相纯度高;随着催化剂六次甲基四胺加入量的增加,YAG粉末颗粒粘连在一起,并出现大孔;以YAG为第二相增强材料制备的Ag/YAG电接触复合片材电阻率较低,维氏硬度大于80。     

溶胶-凝胶法制备SiC/YAG复合粉体

以硝酸铝和硝酸钇为先驱体,采用无机盐溶胶-凝胶法将YAG引入到SiC粉体中制备siC/YAG复合粉体;并采用IR,TG/DTA,XRD,TEM,能谱等测试手段对YAG凝胶及SiC/YAG复合粉体进行表征;探讨YAG凝胶在SiC表面的包裹情况,分析热处理条件对SiC/YAG复合粉体性能的影响.结果表明,YAG凝胶呈网状结构,SiC颗粒嵌入在凝胶网络中;干凝胶在920℃左右已完全转变成YAG相,最终获得YAG粒径小、均匀分散的SiC/YAG复合粉体.     

无机盐先驱体溶胶-凝胶法制备YAG超细粉体

以硝酸铝和硝酸钇为先驱体,采用溶胶-凝胶法制备超细YAG粉体;并采用IR,TG/DTA,XRD,TEM,能谱分析等测试手段对YAG凝胶及粉体进行表征;探讨溶胶-凝胶过程参数和热处理条件对粉体性能的影响.研究结果表明,YAG凝胶呈网状结构,YAG干凝胶在920℃已完全转变成YAG相,最终获得单分散、窄分布、形状规则的YAG超细粉体.     

酸催化剂对TiO2溶胶晶粒形貌及光催化性能的影响

采用溶胶-凝胶法,以钛酸丁酯为前驱体,常温合成含有一定晶型晶粒的TiO2溶胶,考察了不同种类的酸催化剂对二氧化钛纳米晶形貌和光催化活性的影响.采用X射线衍射、透射电镜、扫描电镜等测试手段分析样品中纳米晶的微观形貌与结构,并以罗丹明B为目标催化物测试了溶胶的光催化性能.实验发现,酸根对纳米晶的结晶类型有很大的影响盐酸和硝酸作催化剂时,为锐钛矿和板钛矿;硫酸、氢氟酸和醋酸为催化剂时则为锐钛矿.其中,硫酸为催化剂制备的溶胶光催化性能较好.     

溶胶凝胶燃烧法合成YAG纳米粉

以硝酸钇、硝酸铝为原料,采用溶胶-凝胶/燃烧合成结合法合成了钇铝石榴石(Y3Al5O12,YAG)超细微粉.用X射线衍射仪(D/Max-2550V型)及傅立叶红外光谱(FT-IR)确定前驱体和不同温度处理的粉末的相组成;借助于德国NETZSCH STA449C TG-MS热分析仪(升温速率为10℃/min)对前驱体粉末的热分解过程进行了研究,由JEM-200CX型透射电镜观察粉体的形貌.结果表明过多的柠檬酸和羧酸盐在400℃分解形成碳酸盐,在800℃YAG相开始逐渐形成,在900℃形成了结晶完全的YAG相,而没有中间相产生.经1000℃热处理获得了超细、分散良好、粒度为80nm左右的均匀粉体.     

EDTA络合溶胶-凝胶法合成YAG:Ce黄色荧光粉及其性能

以金属硝酸盐为原料,乙二胺四乙酸(EDTA)为络合剂,采用溶胶-凝胶法制备YAG:Ce黄色荧光粉,利用X射线衍射仪、扫描电镜、荧光分光光度计等检测方法研究制备过程工艺参数对粉体结构、形貌和发光性能的影响。结果表明:EDTA络合所得的凝胶经1000℃煅烧就得到纯的钇铝石榴石相(YAG),其晶相转变温度比柠檬酸(CA)络合剂溶胶-凝胶法的降低约200℃,且所得YAG:Ce荧光粉的发光强度随着煅烧温度升高而增大;凝胶经1500℃高温煅烧所得荧光粉的发光强度比柠檬酸(CA)络合剂的提高66.2%,这是由粉体结晶度好、颗粒形貌更规整、呈球形且尺寸更加均匀所致;在原料液中添加Na2SO4-K2SO4复合熔盐后,凝胶经1500℃煅烧后所得荧光粉发光强度比采用非熔盐法所得荧光粉的增大约10%。     

溶胶—凝胶法制备纳米粉体

介绍了溶胶－凝胶法的原料、原理以及无机盐和金属醇盐的水解特点以及溶胶－凝胶方法的最新进展，存在的问题，并结合作者自己的研究工作，以二氧化锡为例，介绍了溶胶－凝胶法的工艺流程，最后对溶胶－凝胶法的未来发展进行了展望。     

溶胶-凝胶法制备铁酸铋及其可见光催化性能

为了获得新型的窄带隙半导体BiFeO3,以硝酸铁、硝酸铋为主要原料,以无水乙醇和冰醋酸为溶剂,采用溶胶-凝胶法制备干凝胶,然后将干凝胶在氮气条件下、马弗炉中煅烧1h得到BiFeO3粉末样品。采用X射线衍射光谱(XRD)、差热(DTA)分析和漫反射吸收谱(DRS)对BiFeO3的物性进行表征,并以偶氮染料甲基橙作为模拟污水研究BiFeO3的可见光催化性能。结果表明:BiFeO3接近纯相、在832℃附近有一个相变峰,带隙为2.03eV,具有良好的可见光催化活性,是一类具有广泛应用前景的新型窄带隙半导体可见光催化剂。     

Pt/Co双金属纳米溶胶的制备及催化制氢性能

采用化学共还原法制备了聚乙烯吡咯烷酮(PVP)稳定的Pt/Co双金属纳米溶胶,利用UV-Vis、TEM等对所合成的Pt/Co双金属纳米溶胶进行了表征,并系统研究了PVP用量,还原剂用量,双金属比例对该溶胶型纳米双金属催化剂活性的影响。结果表明:所制备的Pt/Co双金属纳米溶胶的平均粒径在2~3 nm之间,大部分双金属纳米溶胶催化剂催化NaBH4制氢的活性都优于单金属Pt和Co纳米溶胶,Pt10Co90双金属纳米溶胶的催化活性最高,其催化NaBH4制取氢气的活性可以达到8800 mol-H2·mol-催化剂-1·h-1,该双金属纳米溶胶催化NaBH4水解反应的活化能为61.8 kJ/mol。所制备的Pt/Co双金属纳米溶胶催化剂具有很好的稳定性,即使在4次催化试验后该催化剂仍然保持着较高的催化活性。     

超声场中溶胶凝胶法制备纳米氧化铝粉体的研究

近年来，超声空化处理已被证明是一种制备纳米材料十分有效的技术，当将超声空化作用应用于溶胶凝胶法制备纳米粉体过程时，将为防止团聚体的生成创造一个独特的条件。本文以六次甲基四胺为沉淀剂，研究了超声场下溶胶凝胶法制备纳米Al2O3粉体的工艺，对产物进行了扫描电镜（SEM），X射线衍射（XRD）分析及粒度分析。实验结果表明，超声波的引入可显著提高粉体的性能。超声处理过的前驱体在1100℃煅烧2小时制得了团聚少，平均粒径在30nm左右的α-Al2O3粉体。超声波的辐射作用有利于纳米α—Al2O3粉体的制备，它的作用主要体现在防止胶粒之间的团聚和长大，及破碎团聚体的作用上。     

Pd/ZrO2-Al2O3催化剂中载体制备对CH4转化活性的影响

为推动ZrO2-Al2O3在天然气汽车尾气净化催化剂中的实际应用,并阐明其制备条件对负载催化剂转化活性的影响机制,文章以ZrO2-Al2O3复合氧化物为载体,采用等体积浸渍法制备了Pd/ZrO2-Al2O3催化剂,并在连续流动固定床反应器上研究了ZrO2-Al2O3复合氧化物的制备对催化剂低温CH4氧化活性的影响。结果表明：制备方法中,相比于浸渍法和胶溶法,沉淀法更能提高催化剂活性;锆源、铝源优选中,以Zr(NO3)4为锆源、拟薄水铝石为铝源时能获得较高的催化活性;组分配比中,以w (ZrO2): w (Al2O3)=10:90的催化活性最高。XRD、低温N2吸附、CO脉冲吸附的结构表征表明,ZrO2-Al2O3复合氧化物的大的比表面积、孔容、孔径是促进贵金属Pd分散,提升催化剂低温CH4转化活性的关键因素。     

Surface tuning of LaCoO_3 perovskite by acid etching to enhance its catalytic performance

The stoichiometric LaCoO_3 and nonstoichiometric LaCo_(1.2)O_3 perovskite catalysts were prepared by citric acid sol-gel method,and then,LaCoO_3 perovskite was etched with nitric acid.The structure,surface composition and reducibility of the catalyst were studied by X-ray diffraction(XRD),nitrogen desorption,transmission electron microscope(TEM),temperature program reduction of H_2(H2-TPR) and X-ray photoelectron spectroscopy(XPS).It was found that nitric acid etching did not change the crystal structure and the overall morphology of the LaCoO_3 catalyst,but it can cause the exposure of B-site Co metal to the surface of the catalyst.As a result,after acid etching,the reducibility of the LaCoO_3 catalyst was improved,leading to the improvement in the catalytic activity of the LaCoO_3 catalyst for CO oxidation and C_3 H_8 combustion.Moreover,the catalytic activity of the LaCoO_3 catalyst after acid etching was higher than that of LaCo_(1.2)O_3 and CoO_x/LaCoO_3 catalyst.     

Preparation and properties of K2NiF4-type perovskite oxides La2NiO4 catalysts for steam reforming of ethanol

The performance of La₂NiO₄ perovskite catalysts, prepared using a citric acid complexation method, for the steam reforming of ethanol was studied. The catalysts were characterized by X-ray diffractometry (XRD), specific surface area measurements (BET), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The experimental results show that the calcination temperature and the amount of citric acid (CA) have a significant influence on the characteristics of the catalysts and their catalytic activity. Among the catalysts tested, the La₂NiO₄ catalyst calcined at 700 °C with n(La):n(Ni):n(CA) of 2:1:3 exhibits the best activity and excellent stability as well as very low coke formation.     

Yttrium aluminum garnet （Y3Al5O12） nanopowders synthesized by the chemical method

1 Introduction The transparent polycrystalline yttrium aluminum garnet, laser ceramic matrix materials with pre-dominantly chemical stability, excellent optical per-formance and high temperature stability, is gradually becoming a substitute for single cry…     

Deterioration and film forming abilities of the slurries used for preparing La0.8Sr0.2MnO3 films through composite sol-gel method

The slurries, used for preparing La_1−xSr_xMnO₃ (LSM) films through composite sol-gel method with citric acid, were made up of LSM particles and precursor sol with different pH values. The reasons and key factors for the deterioration of the acidic slurry were analyzed by XRD, SEM and TG/DSC. Furthermore, the LSM films were fabricated with different slurries for studying their film forming abilities. It has been found that the deterioration of the acidic slurry is determined by the abundant H⁺ ions, generated from ionization of the citric acid. Discoloration of the alkaline sol and slurry is considered as a result of complicated complexes of Mn²⁺ ions, which have a good effect on the film forming ability of the alkaline slurry, together with the complexes of La³⁺ and Sr²⁺ ions. The alkaline slurry has better long-term stability than the acidic slurry, and the films made from it are more homogeneous, thicker and have lower sheet resistance.     

柠檬酸法制备热障涂层用La2Ce2O7粉体

以ZrO(NO3)2·2H2O、Ce(NO3)·6H2O和La2O3为原料,采用柠檬酸法制备了La2Ce2O7粉体,研究了pH值、乙二醇及柠檬酸用量、煅烧温度等工艺参数对La2Ce2O7粉体的影响。结果表明,采用该方法能够制备纯净的La2Ce2O7粉体,最佳实验条件是pH值为5,乙二醇、柠檬酸与金属离子的摩尔比分别是1.8和2,煅烧温度为400℃。     

Influence of the structure of TiO2, CeO2, and CeO2-TiO2 supports on the activity of Ru catalysts in the catalytic wet air oxidation of acetic acid

Ru catalysts, supported on TiO 2 , CeO 2 , and CeO 2 -TiO 2 , were prepared by the impregnation method. The effect of the structure of the supports on the activity of Ru catalysts was investigated in the catalytic wet air oxidation (CWAO) of acetic acid under 230℃ and 5 MPa in a batch reactor. Physical properties including the surface area, crystalline phase, and surface components of the Ru catalysts were characterized by N 2 adsorption, X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy ...     

包覆型镍基催化剂DRM反应研究

Ni纳米颗粒是甲烷干重整反应(DRM)中的高效催化剂。然而,当应用于实际条件下的DRM反应时,克服由于烧结和积碳引起的催化剂失活,提高催化剂耐久性是其面临的巨大挑战。通过原子层沉积(ALD)技术制备了不连续包覆的FeOx-Ni复合纳米催化结构,显著改善了催化活性,并有效抑制了DRM反应中的碳沉积。通过精确调控Ni纳米颗粒上FeOx包覆层的密度可以实现最佳的催化性能,在650℃下,CH4的转化率由52.21%提高到64.27%。一方面,不连续的包覆结构将Ni表面分隔开,以防止形成碳纳米管钝化催化剂。另一方面,FeOx提供了部分甲烷分解的活性位点,这有利于催化剂活性的提升。同时,FeOx的添加,增强了CO2的吸附和活化,减少了碳中间体的形成。Fe含量为0.1%(质量分数)的FeOx/Ni/Al2O3在650℃反应72 h后活性(CH4转化率)仅降低7%,耐久性良好。     

Bi3.25La0.75Ti3O12纳米管的制备工艺研究

研究了一种Bi3.25La0.75Ti3O12 (BLT)铁电存储材料纳米管的简单有效合成方法。通过阳极氧化铝模板(AAO)辅助溶胶凝胶法,合成了BLT纳米管。其基本过程是以次硝酸铋、硝酸镧和钛酸四丁酯为原料,以冰醋酸和乙二醇甲醚为溶剂配制BLT溶胶,然后将BLT溶胶滴在AAO模板表面,浸润后烘干并反复多次,而后将材料在500 ℃下保温1 h,除去有机物,最后在750 ℃下保温30 min晶化,用KOH腐蚀去除氧化铝模板,即得到BLT纳米管。结果表明,BLT纳米管具有[117]择优取向;BLT纳米管管壁光滑,直径与模板孔径相当,约300 nm,且分布均匀,管壁厚度约25 nm,纳米管是多晶体,由粒径为8~12 nm晶粒组成     

季鏻盐对高氯酸铝溶液中铝的缓蚀作用

季鏻盐对高氯酸铝溶液中铝的缓蚀作用何祚清,李金良（徐州师范学院化学系徐州２２１００９）１前言为降低以Ａｌ（ＣｌＯ４）３作为电解液的Ａｌ－ＭｎＯ２干电池中Ａｌ的腐蚀速率,选用合适的缓蚀剂并对缓蚀机理进行研究是一项有意义的工作。有关季盐对钢铁及锌的缓蚀作用己有一些研究［１,２］,但对铝的缓蚀作用尚罕见报导。本工作在１ｍｏｌ／ＬＡＩ（ＣｌＯ４）３底液中用微分极化电阻测量技术和交流阻抗法研究三种季盐?...