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。     

柠檬酸盐溶胶-凝胶法制备La2(CexZr1-x)2O7纳米粉体

采用柠檬酸盐溶胶凝胶法制备出了La2(CexZr1-x)2O7纳米粉体,利用TG-DTA、XRD、SEM等方法对粉体进行了研究。结果表明:制备出的纳米粉晶粒在25 nm左右;粉体在600℃附近具有稳定的晶体结构;La2Zr2O7为烧绿石结构,La2(CexZr1-x)2O7的晶体结构为近似Ce4O7的萤石结构;随着柠檬酸含量的增大,得到蓬松絮状的粉体。     

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.     

NiO纳米粉体的溶胶-凝胶法制备及表征

采用溶胶-凝胶(Sol-gel)并结合热处理工艺制备氧化镍粉体,考察烧结条件对NiO粉体组成、结构和形貌的影响,并对其电化学性能进行研究.结果表明:以醋酸镍为镍源,PAA为整合剂合成了均匀稳定的溶胶;在热处理过程中,干凝胶前驱体在450℃基本分解完全并逐渐形成纳米晶NiO粉体;在粉体热处理过程中随着温度的升高,凝胶中的有机物去除更加完全,NiO晶型趋于完整,晶粒逐渐增大;在600℃烧结获得的晶型完整、颗粒分布均匀,同时也表现出了良好的充放电稳定性.     

合成温度对正极材料Li3V2（PO4）3/C性能的影响

以V2O5、NH4H2PO4、Li2CO3和C6H8O7·H2O为原料,采用溶胶-凝胶法在600～800℃下合成了锂离子电池正极材料Li3V2(PO4)3/C,利用XRD和蓝电测试系统对材料进行表征,研究了合成温度对材料电化学性能的影响。结果表明:650℃下合成产物中开始出现Li3V2(PO4)3相,700、750和800℃下合成纯相的Li3V2(PO4)3正极材料;750℃合成的样品在放电电流密度为0.1C下首次放电容量为123.5mAh·g-1,并且随电流密度增大到10C时也有较好的循环稳定性。     

等离子喷涂Al2O3/TiO2复合粉末的Sol-Gel法制备

传统热喷涂粉末由小颗粒粉体混合团聚制得,流动性差、致密度低,制得的涂层均匀性差、性能不稳定。以有机金属盐为原料,采用溶胶-凝胶法及喷雾干燥法制备出氧化钛质量分数为13%的氧化铝-氧化钛(AT-13)复合前驱体粉末。采用TG-DSC、XRD、FESEM、霍尔流量计研究了粉体反应机理、物相组成、微观结构及流动性能,同时利用维氏硬度计、FESEM-EDS对制得的涂层性能进行了分析比较。结果表明,凝胶经喷雾干燥工艺后可获得球形Ti(OH)4/Al OOH复合粉体,直径约为40μm;与传统团聚粉体相比,前驱体粉末流动性更为优异,为43 s/50 g;由该粉末制得的涂层表面光滑、元素分布均匀、力学性能稳定、耐磨损性能优良,平均显微硬度达873.8 HV0.3,磨损量较团聚粉末涂层减少三分之一。     

溶胶-凝胶法合成导电SrVO3 粉末

通过溶胶-凝胶法结合热处理合成了导电SrVO₃粉末。在溶胶配制过程,对Sr:V摩尔比进行精确调控,再通过对凝胶热分解行为的表征,确定其煅烧温度和除去残余碳,从而获得前驱体粉末,再将其在H₂中还原以获得最终产物。研究了煅烧温度、Sr:V摩尔比对产物形貌、结构和组成的影响,并采用标准直流四探针技术对样品的电导率进行测试。结果表明,当Sr:V摩尔比为1:1.06,煅烧温度500 ℃,再在850 ℃氢气还原,可以制备没有残余碳或钒的氧化物杂质的单相SrVO₃粉末。SrVO₃粉末的电导率达到714.3 S/cm,比石墨粉末的电导率（500 S/cm）高。     

Sol-Gel法合成纳米羟基磷灰石及晶粒生长、结晶度的研究

以Ca(NO3)2·4H2O与H3PO4为前躯体,采用溶胶-凝胶法制备出纳米羟基磷灰石(HA)粉体。通过差热分析仪、X-射线衍射仪、SEM对HA粉体及烧结体进行了表征和分析,采用阿基米德排水法测试了样品密度。结果表明:粒径分布均匀、呈球形、团聚极少,a轴方向和c轴方向的晶粒尺寸分别为10~30nm和20~50nm,随着温度的升高颗粒的尺寸和结晶度增大。600℃烧结2h得到纯度高、晶化好的HA;800和900℃烧结样品中出现的少量Ca3(PO4)2和CaO是由于HA的分解和含磷前躯体的挥发所致。     

常压干燥法制备CNTs掺杂TiO2气凝胶

以钛酸丁酯为原料,乙酸为有机配体,甲酰胺为干燥控制化学添加剂(DCCA),采用溶胶凝胶法制备碳纳米管(CNTs)掺杂TiO2复合醇凝胶,并结合常压干燥等后续工艺,制备了CNTs掺杂TiO2块体气凝胶。采用XRD、BET、TEM、SEM、EDS、DSC及FT-IR等对样品进行表征。结果表明:制备态CNTs掺杂TiO2气凝胶晶型为无定型,比表面积为601.7 m2/g;在氮气保护下,经950℃热处理后,比表面积为136.8 m2/g,TiO2以锐钛矿相存在,且均匀密集包覆在CNTs表面,对甲基橙光降解具有较高光催化活性。     

Bi3.25La0.75Ti3O12籽晶层对Ca0.4Sr0.6Bi4Ti4O15铁电薄膜的影响

用溶胶-凝胶法在Si(100)基片上沉积Ca0.4Sr0.6Bi4Ti4O15/Bi3.25La0.75Ti3O12双层膜,薄膜置于空气气氛在退火炉中700℃退火处理。用X射线衍射(XRD)和扫描电镜(SEM)分别对薄膜的相结构、取向度和微观形貌进行表征,并测试了样品的电滞回线。结果表明:与纯的Ca0.4Sr0.6Bi4Ti4O15铁电薄膜相比,双层膜具有更高的a轴取向度,表面均匀致密无孔隙,多为球形晶粒,且晶粒尺寸约为80nm,并且具有较高的剩余极化强度Pr=13.34μC/cm2,对应的矫顽场强为68.32kV/cm;Bi3.25La0.75Ti3O12的引入对Ca0.4Sr0.6Bi4Ti4O15铁电薄膜的形核生长和晶体学取向具有一定的促进作用,有利于样品的铁电性能。     

Influence of pH value and chelating reagent on performance of Li3V2(PO4)3/C cathode material

The Li₃V₂(PO₄)₃/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid, salicylic acid and polyacrylic acid) at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%.     

溶胶凝胶过程的控制因素对堇青石陶瓷制备的影响

堇青石具有低介电系数和低烧结温度，常用在片式电感和陶瓷基板中。用溶胶．凝胶法制备堇青石粉体，通过研究溶胶-凝胶过程中的pH值对烧结性能、介电性能和微观结构的影响，探讨了溶胶．凝胶过程的工艺条件对堇青石制备的影响。发现水的量和混合溶液的pH值影响水解反应速度和一次粒子的聚集速度，从而影响粉体性能。当溶胶的pH为7时粉体的烧结性能最好。最终获得了介电系数约为4（1MHz），损耗约为0．001的低介电系数堇青石陶瓷材料。     

pH值对溶胶-凝胶法制备La0.65Sr0.35MnO3的影响

利用溶胶-凝胶法制备亚锰酸盐化合物La0.65Sr0.35MnO3,通过XRD和SEM研究不同pH值对合成粉体相组成和微观形貌的影响。结果发现:在pH值为0.5的酸性环境和pH为8.0的弱碱性环境中,均可以获得具有钙钛矿结构且尺寸均匀的La0.65Sr0.35MnO3粉体。在pH值为0.5的酸性环境中,有利于形成二维层状结构的凝胶,而在pH为8.0的弱碱性环境中,有利于形成三维空间网络结构的凝胶,金属离子可以有效地分散于这两种凝胶中,避免了后期热处理过程中化学组分的偏差及团聚的生成。     

Microstructure of nano precursors of La-Mg hydrogen storage alloy synthesized by sol-gel technology at different pH values

Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5,1.5,8.0 and 9.0) of reaction solution.The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR),thermo-gravimetric and differential thermal analysis (TG/DTA),X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM).IR results indicate that the chelating agent,citric acid,is not fully ionized,and carboxyl groups are not entirely used to complex metal ions in acidic solutions.The efficiency of complexing metal ions is enhanced in basic solutions.TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH＜1.5.On the contrary,the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles.XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La2O3 and MgO.The morphology of the particles is almost flake with the size of～30 nm when pH is 8.0.     

Determination of lattice parameters, diffracting crystallite size, and thermal stability in mechanically alloyed Cu-Zn solid solutions

Four copper-zinc (Cu-Zn) alloy powders are produced by mechanical alloying to investigate the effects of zinc composition on the lattice parameter, diffracting crystallite size (DCS), and thermal stability. The DCS versus either milling time or composition data indicates that the substitutional zinc solutes alter the dislocation generation, organization, and recovery processes. Lattice parameter determinations agree well with published values at small compositions, but are slightly less than the expected values for larger compositions. Annealing the powders at 823 and 1023 K for 6 h resulted in a substantial decrease of rootmean-square (rms) atomic-level strain and slight increases in the lattice parameters. In spite of the high annealing temperatures, the DCS remains less than 30 nm for all compositions. Furthermore, this high degree of thermal stability was inversely related to the concentration of zinc in the alloy.     

pH值对镁合金表面氧化硅溶胶凝胶成膜及膜层性能的影响

采用溶胶-凝胶(Sol-Gel)浸渍提拉法在AZ91D镁合金表面制备不同pH值下的SiO2溶胶-凝胶膜层;对膜层耐酸性、耐碱性、抗氧化性及耐蚀性等性能进行测试和表面形貌分析.结果表明,当SiO2溶胶组分比(正硅酸乙酯:无水乙醇:蒸馏水的物质的量之比)为1:15:9.5,浸渍时间为120 s,浸渍次数为1,干燥温度为12...     

用XRD线形分析法表征TiC粉体中的镶嵌尺寸与晶格畸变

采用XRD线形分析(双Voigt函数)法对球磨行星96h的TiC粉和纳米TiC粉中的镶嵌尺寸和晶格畸变进行了对比分析和表征,并采用TEM法印证。研究结果表明,球磨粉的平均镶嵌尺寸大约为纳米粉的40%,而球磨粉的平均晶格畸变大约为纳米粉的5倍。TEM的分析结果与XRD表征结果相吻合。     

PCVD法制备的Ti-Si-C-N纳米复合超硬薄膜的高温氧化行为

用脉冲直流等离子体辅助化学气相沉积(PCVD)方法在高速钢基体上沉积出Ti-Si-C-N超硬薄膜.XRD,XPS及HRTEM等测试表明,薄膜由纳米晶/非晶复合结构组成(nc-Ti(C,N)/a-Si3N4/a-C-C或nc-Ti(C,N)/h-Si3N4/a-Si3N4/a-C-C).Ti(C,N)显示(200)晶面择优取向.高温氧化实验显示:随Ti含量降低和Si含量增大,Ti-Si-C-N薄膜的抗氧化温度逐步提高;当Ti含量为8.7%、Si含量为17.8%时,薄膜中出现少量晶化的密排六方结构的h-Si3N4,弥散分布在非晶基体中,薄膜抗氧化温度达到900℃.Ti-Si-C-N薄膜的氧化过程分为增重和失重两个阶段,进入失重阶段后薄膜很快失效.     

Microstructure of alloy MlNi_(3.75)Co_(0.75)Mn_(0.3)Al_(0.2) (Ml—La-rich mischmetal) during electrochemical hydriding-dehydriding process

1　INTRODUCTIONIt s well known that the hydrogen absorptionand desorption cycling in the LaNi5 based AB5 type alloys always induces high isotropic or aniso tropic strains and therefore accelerates the rate ofpulverization, which has been considered as themain reason for the degradation of hydrogen stor age alloys in the electrochemical cycling[1]. There fore, it s necessary to study the properties of thehydrogen cycling induced strains and other strain related microstructu…