沉淀法制备纳米Eu：Y2O3荧光粉

试验分别以微米级Y2O3、Eu2O3粉体为原料，碳酸氢铵为沉淀剂，三乙醇胺为络合剂，采用三乙醇胺络合沉淀法制备了化学组成为NC6H12（NH4）Y2（CO3）（NO3）2·nH2O的前驱体。研究了前驱体在不同的煅烧温度下的物相变化，结果表明，前驱体在500℃保温2h即可直接生成立方相的Eu：Y2O3，在1000℃保温2h的条件下得到了结晶度高、分散性好、平均粒径为50～60nm、近球形的纳米Eu：Y2O3荧光粉。     

两步沉淀法合成Bi3.25La0.75Ti3O12(BLT)粉体及其表征

以五水硝酸铋(Bi(NO3)3·5H2O)、水合硝酸镧(La(NO3)3·nH2O)和钛酸四丁酯((C4H9O)4Ti)为原料,氨水为沉淀剂,分两步沉淀Ti离子和Bi、La离子,利用沉淀法合成了Bi3.25La0.75Ti3O12(BLT)粉体.利用差热分析(DTA)和热失重(TG)对两步沉淀法制备的前驱体粉体的热行为进行了分析,用X射线衍射(XRD)研究了其晶相演化过程,利用场发射扫描电子显微镜(FESEM)对BLT粉体粒度和形貌进行了观察.结果显示两步法制备的前驱体粉体经低温煅烧直接转化为单一的铋层状钙钛矿相BLT粉体,在700℃煅烧2 h合成的BLT粉体颗粒不大于100nm,颗粒间结合疏松,具有良好的分散性.     

Ca0．6Mg0．4Zr4（PO4）6纳米粉体的共沉淀法合成与表征

采用直接共沉淀法，以等化学计量比的Ca（NO3）2·4H2O、Mg（NO3）2·6H2O、ZrO（NO3）2·8H2O和NH4H2PO4等无机盐为原料，控制共沉淀反应过程pH=9时，合成了单相的Ca0．6Mg0．4Zr4（PO4）6（C0．6M0．4ZP）纳米粉体，并采用TG-DSC、XRD、纳米粒度分析、SEM和TEM等分析测试手段对合成的Ca0．6Mg0.4Zr4（PO4）6（C0．6M0．4ZP）纳米粉体进行了测试表征。TG-DSC和XRD分析表明，沉淀物经900℃左右热处理即可获得单相的C0．6M0．4ZP纳米粉体。SEM和TEM分析表明，沉淀物在900℃煅烧3h，可获得颗粒粒径为30nm左右的C0．6M0．4ZP纳米粉体，粉体颗粒呈球形，但合成纳米粉体存在团聚现象，导致采用纳米粒度分析仪测定的纳米粉体颗粒尺寸主要分布在30～70nm之间，平均粒径达到45nm。合成C0．6M0．4ZP纳米粉体制备的干压试样，在1300℃保温3h烧成后相对密度达到95．3％，抗弯强度为125．7MPa。     

微波法制备LaF3超细粉

以La2O3、HCl为原料制备了LaCl3,并直接用双柱法,以LaCl3溶液同NH4HCO3溶液作用合成了粒度较小的La2(CO3)3粉体;以粉体La2(CO3)3为镧源与NH4F混合,在微波作用下经过固相化学反应,合成了LaF3超细粉;研究了不同分散剂等反应条件对合成LaF3超细粉的粒度和纯度的影响;通过X射线衍射(XRD)检测了不同途径合成的LaF3超细粉体的纯度,通过扫描电镜(SEM)、透射电镜(TEM)测试了不同途径合成的LaF3超细粉体颗粒的粒度和形貌.结果表明:用乙醇作为分散剂经微波加热固相合成得到了纯度较高,平均粒度约为50 nm的LaF3超细粉.     

利用低冰镍制备铁酸镍前躯体

以低冰镍为原料,采用草酸盐共沉淀法合成颗粒细小的铁酸镍前躯体 NiFe2(C2O4)3·6H2O。NiCl2?FeCl2?(NH4)2C2O4?H2O体系的热力学研究表明：Ni2+和Fe2+的理论最佳共沉淀pH值为2,2?24C O 对Ni2+、Fe2+离子具有较强的络合作用。在理论研究的基础上,考察沉淀参数对沉淀率和前躯体粒度的影响。结果表明：最佳共沉淀条件为溶液pH=2,反应温度为45°C,(NH4)2C2O4加入量为理论值的1.2倍,PEG400加入量为3%。在此条件下,Ni2+和Fe2+的沉淀率达99.8%,所得前躯体的粒径为1~2 um。XRD和TG?DTA分析表明：所得前躯体为单相置换固溶体,反应过程中镍、铁原子相互取代。     

脉冲电磁场对CoC_2O_4·2H_2O粒度的影响

在脉冲电磁场(PEMF)作用下,采用常规沉淀方法制备了草酸钴(CoC2O4·2H2O)粉体.利用XRD,TGDSC,松装密度仪以及激光粒度仪对产物的物相、热分解过程及粒度进行了表征.并基于PEMF和反应体系内微观粒子之间的相互作用提出了CoC2O4·2H2O粒度改变的机理.实验结果表明,施加及未施加PEMF条件下,以CoCl2·6H2O为原料,(NH4)2CoC2O4·2H2O为沉淀剂制备的产物均为β-CoC2O4·2H2O;脉冲电压为800 V时,产物松装密度为0.393 g/cm3,平均粒径为3.5403 μm,与未施加PEMF条件下制备的样品相比,分别降低了26.95%和60.13%;以PEMF制备的CoC2O4·2H2O为前躯体,在Ar气氛下加热分解获得了fcc结构的金属Co粉.     

以NH4FePO4·H2O制备LiFePO4及其性能研究

用FeSO4,H3PO4,NH3·H2O为原料合成NH4FePO4·H2O前驱体,再与Li2CO3和蔗糖均匀混合,通过高温固相反应法合成了LiFePO4正极材料.用X射线衍射和扫描电镜分析对NH4FePO4·H2O和LiFePO4的结构进行了表征.研究了不同含碳量对LiFePO4晶体结构和电化学性能的影响.结果表明,NH4FePO4·H2O前驱体和LiFePO4具有结构相似性,在高温固相反应时NH4FePO4·H2O与Li2CO3发生置换反应.材料具有较好的电化学性能.     

超声沉淀法制备纳米Al2O3粉体

将超声辐射应用于以硫酸铝铵 (NH4Al(SO4) 2 ·12H2 O )和碳酸氢铵 (NH4HCO3 )为原料的沉淀法制备Al2 O3 纳米粉体的化学反应工艺过程 ,制备了粒径为 12nm的α Al2 O3 纳米粉体。通过SEM、TEM等分析手段研究了超声辐射对前驱体NH4Al(OH) 2 CO3 沉淀物及最终粉体尺寸、形貌及其团聚行为的影响 ,并探讨了其作用机理。结果表明 :超声辐射由于其自身的空化作用不仅细化了前驱体颗粒、抑制了其间的团聚 ,而且延缓了其向凝胶的转变过程 ,从而有效地细化α Al2 O3 颗粒 ,但过高的频率却易导致颗粒间的进一步聚合     

以NH4FeP04·H2O制备LiFePO4及其性能研究

用FeSO4,H3PO4,NH3·H2O为原料合成NH4FePO4·H2O前驱体,再与Li2CO3和蔗糖均匀混合,通过高温固相反应法合成了LiFePO4正极材料.用X射线衍射和扫描电镜分析对NH4FePO4·H2O和LiFePO4的结构进行了表征.研究了不同含碳量对LiFePO4晶体结构和电化学性能的影响.结果表明,NH4FePO4·H2O前驱体和LiFePO4具有结构相似性,在高温固相反应时NH4FePO4·H2O与Li2CO3发生置换反应.材料具有较好的电化学性能.     

纳米W-Cu粉末的均相沉淀法制备及其烧结性能

采用湿化学工艺--蒸氨均相沉淀法,制备了纳米CuWO4·2H2O/Cu2WO4(OH)2均相沉淀物,然后煅烧、还原,得到含Cu 30%的W-Cu复合粉.将该复合粉压坯在H2气氛中于不同温度下烧结后,对烧结体的微结构和物理、力学性能等进行了测试分析.实验结果表明:蒸氨均相沉淀法制备的W-Cu复合粉体具有纳米粒度和均匀的化学组成,其烧结活性高,在较低温度下烧结即可达很高的致密化程度.由上述W-Cu粉体所制备的烧结体具有良好的物理、力学性能.     

Preparation of highly dispersed antimony-doped tin oxide nanopowders by azeotropic drying with isoamyl acetate

Antimony-doped tin hydroxide colloid precipitates were prepared by hydrolysis of SnCl4·5H2O and SbCl3 ethanol solutions. Isoamyl acetate was selected as azeotropic drying solvent and was compared with the most commonly used n-butanol solvent on treating precipitate for low hard agglomeration precursor powders. The FT-IR, BET, XRD, and TEM results of the precursor powders and calcinated antimony-doped tin oxide powders were recorded. The results demonstrate that isoamyl acetate is an excellent azeotropic drying solvent that can effectively prevent the agglomeration of particles and greatly improve the fluffiness of the obtained dried powders. After these precursor powders are calcined, antimony-doped tin oxide nanopowders with tetragonal futile structure and high dispersivity can be obtained.     

均相沉淀法制备YAG球形粉体及透明陶瓷

以Y(NO3)3.6H2O和Al(NO3)3·9H2O为原料,尿素为沉淀剂,采用均相沉淀法合成了成分为5[Al(OH)CO3]·3[Y(OH)CO3]的钇铝石榴石(YAG)先驱体粉末。在沉淀过程中通过控制硫酸根离子的含量可以避免晶核生长时的方向性,有效防止了纳米颗粒硬团聚的形成,先驱体颗粒逐渐球化。经1 100℃煅烧分解,获得平均尺寸为200~400 nm、低团聚的高纯YAG球形粉体。该粉体经模压成型、1 700℃真空烧结,得到晶粒分布均匀、完全透明的YAG陶瓷。     

Preparation of Sn-doped In2O3 nanopowders by a solvothermal process

Sn-doped In2O3 (ITO) nanopowders in square shape were prepared in ethylene solvent by a solvothermal process,using In (4N) and SnCl4·5H2O as starting materials.The effects of solvothermal temperature and coprecipitation pH on the products were investigated using XRD,XPS,and TEM.Mixtures of InOOH crystals and In4Sn3O12 crystals were prepared at 210℃ or 230℃ and ITO nanopowders with cubic structure were obtained at 250℃ or above 250℃.When the coprecipitation pH was 6,the product was ITO with impurity Sn3O4- When the pH was 9,the product was single phase ITO.     

Thermal property and microstructure of Al nanopowders produced by two evaporation routes

Al nanopowders with diameters ranging from 20 to 50 nm passivated by Al2O3 coatings were produced by two different evaporation routes: induction heating evaporation (IHE) and laser-induction complex heating evaporation (LCHE). Thermal property of the nanopowders was investigated by differential thermal analysis (DTA) in dry oxygen environment. The results show that Al nanopowders produced by LCHE have the oxidation enthalpy change (ΔH) of 3.54 kJ/g, while the ΔH of Al produced by IHE is 1.18 kJ/g. The phase constitution and microstructures of these nanopowders were revealed using X-ray diffraction (XRD) analysis, transmission electronic microscopy (TEM) and high-resolution transmission electronic microscopy (HRTEM). The results show that the two powders have the same composition and mean particle size, as well as the thickness of Al2O3 coatings (3-5 nm). Defects were observed on the surfaces of the particles by LCHE. However, the defects were not detected by HRTEM on the surfaces of the particles by IHE. The results prove that there exists excessive stored energy in Al nanopowders by LCHE because of the nonequilibrium condition brought by laser and the defects are the storage area of the excessive stored energy. Propellants composed of Al nanopowders by LCHE show higher energy level and specific impulse.     

液料等离子热喷法制备Fe3+/TiO2纳米粉末

通过对液料等离子热喷前驱物添加掺杂成分实现了液料等离子热喷TiO2纳米粉末的掺杂改性,并利用TEM,XRD及XPS对其进行表征.结果表明,采用液料等离子热喷法可以制备Fe3 掺杂TiO2纳米粉末,所制备粉末形貌基本呈球形或近球形,粒径分布为10～35 nm,掺杂量小于2.0%时粉末为锐钛矿及金红石相混晶,Fd3 掺杂促进锐钛矿向金红石相的转变,掺杂量为10.0%时析出了Fe2Ti3O9相.Fe3 掺杂不会引起TiO2粒径的大范围波动.粉末中含有O,Ti,Fe和C等元素,Fe元素在TiO2中仍为 3价.     

Al-Mg-Sc中间合金的制备

在非真空条件下用氟化物熔盐体系镁 (铝 )热还原法制备了Al Mg Sc中间合金 ,讨论了金属还原剂的选择及还原温度、时间等工艺条件对钪收率的影响 ,并研究制定了氧化钪固相氟化制备氟化钪熔盐工艺。采用Al Mg合金熔体为还原剂经二次还原后钪收率 >80 %,制备的Al Mg Sc中间合金铸锭中钪含量 >1.9%,最佳的还原反应温度为 110 0K ,还原时间 40min .。氟化钪还原产生的初生态钪与铝作用形成稳定的Al3 Sc化合物 ,促进了还原的进行 ,使钪收率得到了大幅度提高。     

纳米铝粉的固相化学还原法制备、表征及对ADN热分解性能的影响

以山梨糖醇酐三油酸酯(Span-85)作为过程控制剂,通过氢化铝锂还原无水氯化铝,采用高能机械球磨法制备了纳米铝粉(n-Al)。利用扫描电镜(SEM)、高分辨率透射电镜(TEM)、X射线衍射(XRD)仪、傅里叶变换红外光谱(FTIR)仪及X射线光电子能谱(XPS)仪对其形貌和结构进行了表征。用差示扫描量热仪(DSC)对ADN(二硝酰胺铵)、n-Al/ADN的热分解反应特性进行了研究。结果表明:纳米铝粉属立方晶系,表面包覆有无定型Al2O3氧化物及部分表面活性剂Span-85,同时制备的纳米铝粉试样中含少量Al Cl3·6H2O杂质;此方法制备的n-Al粒子对ADN液化温度几乎没有影响,但放热分解温度明显增大,且ADN分解由多重峰变为单一的尖峰。     

Effect of vanadium on synthesis of WC nanopowders by thermal processing of V-doped tungsten precursor

The effect of vanadium on the synthesis of WC nanopowders by carbon thermal processing of V-doped tungsten precursor has been discussed. The V-doped tungsten precursor was prepared by a wet chemical method with ammonium tungstate and ammonium vanadate as its starting materials. The precursor was carbonized in the vacuum furnace using phenol formaldehyde resin as a carbon agent. The results of XRD revealed that the tungsten oxide and vanadium oxide obtained from the precursor preparation formed V–O–W bronze with the structure of WO₃ · 0.33H₂O. The carbonization reactions of WO₃ with 1 wt% of vanadium took place in a temperature range from 900 to 1050 °C to obtain V-doped WC nanopowder. The results of particle size measurement and morphological analysis show that the vanadium effectively inhibits the particle growth of tungsten carbide powder during carbonization processes, resulting in the particle size to be within the range from 64 to 184 nm after heat treatment in the temperature range from 900 to 1200 °C. V₂O₃ particles decomposed from V–O–W bronze can act as a nucleation aid for tungsten during reduction, and those on the surface of tungsten powder can hinter the growth of tungsten carbide crystal by the pinning effect.     

等离子喷涂超高温热障涂层用纳米结构La2(Zr0.75Ce0.25)2O7球形喂料的研究

目的通过纳米粉体造粒技术制备出适合热喷涂超高温用纳米结构La2(Zr(0.75)Ce(0.25))2O7球形喂料,进而采用热喷涂方法制备出纳米结构的热障涂层,以满足下一代热障涂层服役温度需求。方法以化学共沉淀法合成的纳米La2(Zr(0.75)Ce(0.25))2O7粉末为原料,通过球磨、喷雾干燥及热处理工艺制备出纳米结构的La2(Zr(0.75)Ce(0.25))2O7喂料,进而采用大气等离子喷涂方法制备出纳米结构La2(Zr(0.75)Ce(0.25))2O7热障涂层。利用扫描电镜(SEM)和透射电镜(TEM)对原始纳米粉体、纳米喂料及喷涂态涂层进行显微形貌和组织结构分析。此外,通过电感耦合等离子体原子发射光谱法(ICP-AES)对制备的纳米喂料进行成分分析。结果制备出的纳米结构La2(Zr(0.75)Ce(0.25))2O7喂料表面光滑、呈球形,成分与化学计量比基本一致。相对于原始纳米粉末,喂料晶粒长大并不显著。喷涂态涂层部分晶粒长大,但仍保留纳米结构。结论成功制备出纳米结构La2(Zr(0.75)Ce(0.25))2O7球形喂料及纳米结构热障涂层,有望作为下一代超高温热障涂层材料。     

不同前驱体制备的锡锑中间层对Ti／SnO2＋Sb2O3／PbO2电极性能的影响

研究了以乙二醇与柠檬酸反应制得的乙二醇柠檬酸酯溶液、乙二醇、乙醇、正丁醇为前驱体溶剂制备的锡锑中间层对Ti/SnO2 Sb2O3/PbO2电极性能的影响,用XRD、ESEM对不同前驱体制备的锡锑中间层和对应的二氧化铅活性层进行了表征,并用极化曲线法和阳极寿命快速检测法比较了不同前驱体对Ti/SnO2 Sb2O3/PbO2电极的阳极寿命和在1．0mol/L硫酸溶液中的电催化活性的影响。结果表明,不同前驱体溶剂对锡锑中间层的结构和形貌有着显著的影响;以乙二醇与柠檬酸反应制得的聚合前驱体为溶剂制备的锡锑中间层表面致密,锡锑含量相对较高,该中间层的均匀度和平整度明显好于其它3种前驱体。由聚合前驱体中间层制得的Ti/SnO2 Sb2O3/PbO2电极的使用寿命明显提高,但不同中间层前驱体对电极的电催化活性影响不大。