嵌有纳米碳颗粒凝胶玻璃的制备及其发光特性

以磷酸三乙酯、硝酸铝和正硅酸乙酯为原料,通过它们的水解制备了ｘＡｌ_２Ｏ_３·ｘＰ_２Ｏ₅·１００ＳｉＯ_２（ｘ＝０．２５～３）凝胶．在６００℃对凝胶进行热处理,使其中的有机基团炭化,从而制备出了镶嵌有碳纳米颗粒的ｘＡｌ_２Ｏ_３·ｘＰ_２Ｏ_５·１００ＳｉＯ_２（ｘ＝０．２５,０．５）凝胶玻璃．在室温下以５３２ｎｍ激光（Ｎｄ：ＹＡＧ）激发,在 ６３０ｎｍ处有一强的发光峰,该发光现象是由镶嵌在凝胶玻璃中的纳米碳颗粒产生的．     

溶胶—凝胶法制备的SiO2膜的结构与性质

本文用ＴＥＯＳ和硅溶胶作原料，用溶胶－凝胶法制备了无支撑体和有支撑体的ＳｉＯ２膜。用ＴＥＯＳ制得的无支撑体ＳｉＯ２膜，无１．７ｎｍ以上的微孔，由硅溶胶制得的无支撑体ＳｉＯ２膜平均孔径为７．５ｎｍ，且孔径分布集中，这种差异主要来自于由不同原料制备的溶胶，其聚合物分子具有不同的形态和生长模式。用ＴＥＯＳ作原料，在无过滤层的α－Ａｌ２Ｏ３多孔支撑体上制得了无大孔缺陷、厚约１５μｍ的ＳｉＯ２膜，膜对ＢＳＡ     

医用NiTi合金表面溶胶-凝胶法制备TiO2-SiO2薄膜

采用溶胶－凝胶法在ＮｉＴｉ形状记忆合金表面制备了ＴｉＯ_２－ＳｉＯ_２复合薄膜,在提高医用ＮｉＴｉ合金的抗腐蚀性方面,收到了显著的效果．运用电化学方法对不同组成的ＴｉＯ_２－ＳｉＯ_２薄膜在模拟体液中的腐蚀行为进行了研究,结果表明,随薄膜中 Ｔｉ／Ｓｉ比的增加,ＴｉＯ_２－ＳｉＯ_２薄膜的抗腐蚀性增强．划痕试验表明 ＴｉＯ_２－ＳｉＯ_２（Ｔｉ／Ｓｉ＝４：１）膜与ＮｉＴｉ合金基体具有较高的界面结合强度．用原子力显微镜（ＡＦＭ）对ＴｉＯ_２－ＳｉＯ_２薄膜的表面形貌及表面粗糙度进行观察和分析,解释并讨论了ＴｉＯ_２－ＳｉＯ_２薄膜的配方组成与其抗腐蚀性的关系,ＳｉＯ_２含量较少时,薄膜结构致密,膜层均匀平滑,且膜基结合力好,作为医用ＮｉＴｉ合金的表面保护层,可以使其耐腐蚀性有显著提高．     

聚乙烯醇(PVA)对无支撑氧化铝膜微观结构的影响

聚乙烯醇（ＰＶＡ）能够避免溶胶－凝胶法制备的Ａｌ_２Ｏ_３膜在干燥阶段产生微裂纹,同时也对Ａｌ_２Ｏ_３膜的微观结构产生影响．利用ＸＲＤ、ＤＴＡ、ＴＧＡ、ＦＴ－ＩＲ及Ｎ_２吸附等手段研究掺杂ＰＶＡ对Ａｌ_２Ｏ_３膜的物相组成、热稳定性以及比表面积、孔径分布、孔表面分形性等微观结构的影响．研究表明,经过４００℃煅烧ＰＶＡ完全排除．与纯Ａｌ_２Ｏ_３膜相比,添加ＰＶＡ的Ａｌ_２Ｏ_３膜吸附量较大,比表面积有所增大,但并不随着ＰＶＡ含量的增多而增加．ＰＶＡ有利于 Ａｌ_２Ｏ_３膜孔径的调整,使孔径分布更狭窄,孔体积也有较大程度的增加．随着 ＰＶＡ的加入,Ａｌ_２Ｏ_３膜的孔表面分形维数降低．     

ZrO2及ZrO2:CdS薄膜的制备和表征

利用ｓｏｌ－ｇｅｌ方法合成了ＺｒＯ_２薄膜,并通过在ＺｒＯ_２薄膜中复合ＣｄＳ纳米粒子成功地制备了ＺｒＯ_２：ＣｄＳ薄膜．制得的ＺｒＯ_２薄膜透明并具有较好的光透射性,而ＺｒＯ_２的含量及膜厚是影响其光透射性的主要因素．分散在ＺｒＯ_２：ＣｄＳ薄膜中的ＣｄＳ纳米粒子为六方相结构,并具有较好的分散性,其平均尺寸为４～６ｎｍ．实验结果表明：ＺｒＯ_２颗粒的晶化会对薄膜的光学性能及表面形貌产生影响,但ＣｄＳ的形成可以抑制薄膜表面ＺｒＯ_２颗粒的晶化,从而得到较为平滑的薄膜．     

由SiO2/3Y-TZP包裹复合粉体制备ZrSiO4/3Y-TZP细晶陶瓷

对湿化学法制备的ＳｉＯ_２／３Ｙ－ＴＺＰ包裹复合粉体进行了热压烧结研究,并利用Ｘ射线衍射和透射电镜表征了烧结体的物相和显微结构．在低于１３００℃,复合粉体发生瞬时粘性烧结,材料密度迅速提高;随着烧结温度的升高,ＳＩＯ_２和ＺｒＯ_２发生反应生成ＺｒＳｉＯ_４．在１５００℃热压条件下,制备了平均晶粒尺寸为３５０ｎｍ的ＺｒＳｉＯ_４／３Ｙ－ＴＺＰ细晶复相材料．我们认为,在烧结过程中形成的第二相ＺｒＳｉＯ_４,特别是ＳｉＯ_２包裹层对抑制基体晶粒长大起主要作用．     

疏水型SiO2气凝胶

以多聚硅为硅源,通过溶胶-凝胶、表面修饰及超临界干燥过程制备出了疏水型ＳｉＯ_２气凝胶．表面修饰后ＳｉＯ_２气凝胶孔洞由修饰前的２３．１ｎｍ减小到１８．２ｎｍ;比表面积由修饰前的 ４７７ｍ２ｇ^－１增加到 ５６３ｍ２ｇ^－１,骨架颗粒比修饰前略大,饱和水蒸汽吸附量由吸附前的０．０４（重量比）降低到０．００１２,且与水不浸润．     

溶胶－凝胶法制备的SiO_2膜的结构与性质

本文用ＴＥＯＳ和硅溶胶作原料，用溶胶一凝胶法制备了无支撑体和有支撑体的ＳｉＯ２膜．用ＴＥＯＳ制得的无支撑体ＳｉＯ２膜，无１．７ｎｍ以上的微孔，由硅溶胶制得的无支撑体ＳｉＯ２膜平均孔径为７．５ｎｍ，且孔径分布集中，这种差异主要来自于由不同原料制备的溶胶，其聚合物分子具有不同的形态和生长模式．用ＴＥＯＳ作原料，在无过渡层的α－Ａｌ２Ｏ３多孔支撑体上制得了无大孔缺陷、厚约１５μｍ的ＳｉＯ２膜，膜对ＢＳＡ的百分截留率为７５．８％．在有过渡层的α－Ａｌ２Ｏ３上制得的ＳｉＯ２膜的纯Ｎ２渗透表现为Ｋｎｕｄｓｅｎ扩散特征．起超滤和扩散作用的是ＳｉＯ２膜层内部的缺陷微孔．     

醇-水溶液加热法制备纳米ZrO2粉体及相关过程的研究

分析了醇－水溶液加热法制备纳米ＺｒＯ_２（３Ｙ）粉体的过程及加热温度、时间对反应过程及最后所得粉体的影响．研究结果表明：该法制备纳米ＺｒＯ_２粉体过程中发生了一系列化学反应,这些反应使Ｙ_２Ｏ_３前趋体在ＺｒＯ_２前驱体中均匀分布,Ｙ_２Ｏ_２在粉体煅烧期间逐渐渗透到ＺｒＯ_２颗粒中使之转变为四方相．只有当加热的温度足够高使得溶液的介电常数＜２５时,沉淀才可能发生．加热时间必须足够长,使反应完全．过短的加热时间致使沉淀不够完全时,容易产生团聚．     

高分子网络凝胶法制备纳米α-Al2O3粉体

用高分子网络凝胶法制备Ａｌ_２Ｏ_３粉体,通过网络的阻碍作用,阻止Ａｌ_２Ｏ_３的团聚,获得颗粒大小在 １０ｎｍ左右的α－Ａｌ_２Ｏ_３粉体,其煅烧温度比通常低 １００℃．     

原位合成La_2Zr_2O_7-YSZ复合材料及高温热稳定性研究

以硝酸锆、硝酸镧、硝酸钇和柠檬酸为原料,原位合成了La2Zr2O7、氧化钇稳定氧化锆(YSZ)及其La2Zr2O7-YSZ复合材料。采用X射线衍射和拉曼光谱对样品进行分析和表征,研究La2Zr2O7、YSZ和La2Zr2O7-YSZ复合材料的物相组成与高温热稳定性。结果表明:合成的La2Zr2O7和YSZ均为单一纯相。在1 200℃煅烧6 h条件下合成的系列复合材料(物质的量比n(La2Zr2O7)∶n(YSZ)=1∶8~10∶1)中均未发现单斜ZrO2相和其他化合物的生成。在1 400℃煅烧24 h条件下合成的LZYZ11中出现单斜ZrO2相,此时La2Zr2O7对YSZ的稳定效果不大。     

La2O3-Y2O3-ZrO2纳米陶瓷粉末的制备及高温相稳定性

用化学共沉淀法制备4.5%Y2O3-ZrO2(YSZ)和0.6%La2O3-YSZ、0.8%La2O3-YSZ、1.2%La2O3-YSZ(0.6La、0.8La、1.2La)(摩尔分数)纳米复合陶瓷粉末,研究了四组粉末的高温相稳定性.结果表明:采用正向滴淀方法制备的0.6La粉末(粒径～50 nm)团聚严重,而用反向...     

Y2O3与Gd2O3共掺杂SrZrO3热障涂层材料的热物理性能

采用固相反应法合成了5mol%Y2O3与5mol%Gd2O3共掺杂SrZrO3(Sr(Zr0.9Y0.05Gd0.05)O2.95,SZYG)粉末.采用X射线衍射(XRD)和差示扫描量热仪(DSC)分别研究了SZYG粉末在1450℃长期热处理后以及200~1400℃范围内的相稳定性.采用高温热膨胀仪测量了SZYG块材的热膨胀系数,结果表明:通过Y2O3与Gd2O3共掺杂改性可以明显抑制SrZrO3的相转变.在1000℃下SZYG块材的热导率是～1.36 W/(m.K),与SrZrO3和8YSZ块材相比降低~35%SZYG分别与8YSZ和Al2O3在1250℃热处理24 h表现出很好的化学相容性.     

Single-step fabrication of nanolamellar structured oxide ceramic coatings by metal-organic chemical vapor deposition

Oxide ceramic coatings in the system Y2O3-Al2O3-ZrO2 were fabricated in laboratory scale by using a MOCVD unit. A hot wall reactor was used along with different precursor feeding systems. Most experiments were carried out by using powder flash evaporation including a screw feeder for precursor powder delivery. For comparison, further samples were fabricated by using band flash evaporation and continuous evaporation from a crucible. Oxygen was used in all cases as reactant gas. Aluminium-tris-2,4-pentanedione (Al(acac)3), yttrium-tris-2,2,6,6-tetramethyl-3,5-heptanedione (Y(thd)3) and zirconium-tetrakis-2,2,6,6-tetramethyl-3,5-heptanedione (Zr(thd)4) were applied as metal-organic precursors because of their similar vaporization behaviour under the given conditions. The coating stoichiometry was varied from pure alumina to complex ternary compositions in the system Y2O3-Al2O3-ZrO2. Both kinds of ternary coatings fabricated by using flash evaporation methods show a nanolamellar microstructure in the as deposited state. Heat treating experiments at 1200 degrees C for up to 5 days enhance the lamellar character of the coating deposited by using powder flash evaporation. The lamellar microstructure is due to alternating YSZ enriched layers and YAG enriched layers in this state. However, the coating fabricated by using band flash evaporation shows a dense interpenetrating network of YSZ and YAG after heat treating instead of a lamellar microstructure observed in the as deposited state.     

Sol–gel synthesis and characterization of mesoporous yttria-stabilized zirconia membranes with graded pore structure

Mesoporous yttria-stabilized zirconia (YSZ) membranes can be used for liquid phase applications in harsh environments and as supports for ultra-thin dense ceramic, carbonate, or metallic membranes. This article reports on the synthesis and characterization of three-layer mesoporous ceramic membranes consisting of a mesoporous YSZ layer, a macroporous YSZ intermediate layer, and macroporous α-alumina support. The macroporous YSZ intermediate layer was coated on the alumina support using a suspension of submicron-sized YSZ powders, and the mesoporous YSZ layer was obtained by dip-coating with diluted zirconia sol doped with yttrium nitrate. The mesoporous YSZ layer has desired cubic phase structure. Crack-free mesoporous YSZ membranes could be obtained by multiple dip-coating, drying, and calcination using a dilute YSZ sol at a concentration of 0.014 M with the help of using a drying control chemical additive. The 5 times dip-coated mesoporous YSZ membranes were about 1 μm in thickness with an average pore diameter of 3 nm. The mesoporous YSZ membranes exhibited Knudsen separation factor. The characteristics of the dip-coating process for the mesoporous YSZ membranes on the macroporous YSZ support are similar to those on the macroporous alumina support.     

Synthesis of SiC/BN nanocomposite powders by carbothermal reduction and nitridation of borosilicate glass, and the properties of their sintered composites

A new synthetic method for the fabrication of SiC/BN nanocomposites was devised to attain strong machinable ceramics. SiC/BN nanocomposites that contained 10, 20, and 30?vol% hexagonal BN (h-BN) were successfully fabricated by sintering SiC-BN nanocomposite powders by carbothermal reduction and nitridation of borosilicate glass powders. Homogeneous mixtures of silica (SiO(2)), boric acid (H(3)BO(3)), and carbon powder were heated in a nitrogen atmosphere to synthesize SiC-BN nanocomposite powders. Borosilicate glass was obtained by reacting SiO(2) and B(2)O(3) above 800?°C, and SiC and turbostratic BN (t-BN) were obtained by reacting borosilicate glass with carbon powder and nitrogen gas at 1500?°C. Carbothermal reduction followed by nitridation yielded SiC-BN nanocomposite powder composed of nanosized SiC and t-BN. By hot-pressing nanocomposite SiC-BN powders containing 7?wt% Al(2)O(3) and 2?wt% Y(2)O(3), machinable SiC/BN nanocomposites were obtained without a significant decrease in their fracture strength.     

基于氢敏材料的WO_3溶胶稳定性的影响因素研究

采用钨粉和双氧水反应制备了WO3溶胶,考察了双氧水(H2O2)加入量、无水乙醇加入量、陈化温度和时间对溶胶稳定性的影响。研究表明,H2O2和乙醇的加入能增强WO3溶胶的稳定性,当H2O2与钨酸的物质的量比为1∶2、乙醇与WO3溶胶体积比为1∶2时,所制备的WO3溶胶在室温下可稳定存在3个月以上,溶胶成膜质量最佳。WO3溶胶陈化温度越高,溶胶的稳定时间越短。研究了WO3溶胶陈化时间与粘度的关系,并试验得出了最佳的成膜条件,即陈化时间越长,WO3溶胶粘度越大,当WO3溶液粘度为180～300mPa.s时成膜质量较好。     

硼硅酸凝胶包覆层对铜粉抗氧化性和导电性的影响

铜电子浆料作为银电子浆料最为理想的替代材料,其越来越受到人们青睐,但铜的性质活泼,极易被氧化.为解决铜电子浆料在高温烧结时铜粉易被氧化的问题,以无水乙醇、正硅酸乙酯、硼酸三丁酯为原料制作SiO_2-B_2O_3溶胶,用SiO_2-B_2O_3溶胶对经过盐酸酸洗过的铜粉进行包覆,将包覆后的铜粉制成浆料并印刷到陶瓷模板上,600℃烧结制备得到铜导电膜层.通过四探针测试仪测试铜导电膜层的电导率,利用扫描电子显微镜(SEM)观察不同量溶胶包覆的铜粉的表面形貌,采用X射线衍射仪(XRD)及热重分析仪(TGA)考察溶胶包覆铜粉700℃烧结后的氧化情况.结果表明,在m(SiO_2-B_2O_3)∶m(Cu)=10%时,硼硅酸溶胶恰好均匀包覆铜粉而无多余溶胶堆积铜粉之间,此时铜导电膜层导电性能最好,其相对电导率为57%;铜粉700℃高温烧结后几乎没有被氧化,铜粉表面仅有极少量的氧化亚铜生成.实验结果证明,在合适的硼硅酸溶胶包覆率下,铜粉在700℃以下具有良好的抗氧化性,铜导电膜层也具有良好的导电性能.     

溶胶-凝胶法制备纳米Si_3N_4(Y_2O_3)粉末的研究

本文以硅溶胶、尿素和炭黑为原料，采用溶胶-凝胶碳热氮化法在1500℃、2h条件下制得粒径为50～80nm的Si3N4纳米粉末．比较了由硅溶胶与尿素经氨解合成的前驱体和硅溶胶二种不同起始物料的反应活性，研究了氮化条件对合成反应的影响．结果表明：氨解前驱体使硅溶胶中的结构水排除，有助于加快反应速率，提高产物氮含量．本文同时以Y（NO3）3为添加剂，在溶液状态与硅源混合，合成了Si3N4－Y2O3纳米复合粉末.     

Preparation and Properties of Sintering Additives Coated Si3N4 from Heterogeneous Nucleation Processing

The sintering additives such as Al2O3 and /or Y2O3 were coated on the surfaces of Si3N4 particles via heterogeneous nucleation processing using a buffered pH solution as the precipitation reagent .They nucleated and grew only on the surfaces of Si3N4 and did not form sol particles in solution by TEM observation .The isoelectric point(IEP) of coated Si3N4 was different from that of as-received Si3N4.The IEP of Al(OH)3-coated Si3N4 occurred at pH8.4, which is close to that of alumina .When Al(OH)3-coated Si3N4 particles were coated with Y(OH)3,the IEP of coated Si3N4 powder shifted from pH8.4 to pH9.2 ,similar to that of yttria.In addition ,the rheological data showed that Al2O3 and /or Y2O3 coated Si3N4 suspension is nearly Newtonian and that added Si3N4 suspension shows a shear rate thinning behavior.