Thermal stability of aluminas by hydrothermal treatment of an alkoxide-derived gel

Alumina precursors were prepared by hydrothermal treatment of alkoxide-derived alcogels. The crystalline structure of precursor beohmites and their microstructural change during heat treatment were examined and the specific surface area of the alumina precursors after heating was measured. The alumina prepared by hydrothermal treatment at 270 °C retained high specific surface areas at high temperatures; e.g. 35.0, 8.3 and 5.4 m²g^–1 at 1200, 1400 and 1500 °C, respectively. The thermal stability of the aluminas depended on the hydrothermal temperatures. For excellent thermal stability, the following factors are necessary: (1) grain growth of beohmite as an alumina precursor, and a grain size of more than 20 nm for the (1 2 0) plane; (2) a crystallite size for the (2 0 0) plane exceeding that for the (0 0 2) plane; (3) anisotropic growth of the beohmite crystal. In the transition alumina region ( 1200 °C), the thermal stability of the alumina is caused by raising the transformation temperature, resulting from decreasing the number of grain boundaries by beohmite growth. In the -alumina region (> 1200 °C), inhibiting the three-dimensional grain growth achieves thermal stability, resulting from preservation of the anisotropic structure introduced into the beohmite.     

Preparation of thermally stable nanocrystalline hydroxyapatite by hydrothermal method

Thermally stable hydroxyapatite (HAp) was synthesized by hydrothermal method in the presence of malic acid. X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA) was done on the synthesized powders. These analyses confirmed the sample to be free from impurities and other phases of calcium phosphates, and were of rhombus morphology along with nanosized particles. IR and Raman analyses indicated the adsorption of malic acid on HAp. Thermal stability of the synthesized HAp was confirmed by DTA and TGA. The synthesized powders were thermally stable upto 1,400 degrees C and showed no phase change. The proposed method might be useful for producing thermally stable HAp which is a necessity for high temperature coating applications.     

Preparation and characterization of thermally stable nanohydroxyapatite

Rod-like hydroxyapatite was synthesized by precipitating calcium nitrate tetrahydrate and ammonium dibase phosphate in the presence of polyacrylic acid followed by hydrothermal treatment. Both polyacrylic acid and the hydrothermal treatment stabilised the hydroxyapatite.     

新型耐高温复合反渗透膜的制备与性能

以杂萘联苯聚芳醚腈酮超滤膜为基膜,间苯二胺作为水相单体、均苯三甲酰氯作为有机相单体,通过界面聚合法制备了新型耐高温聚芳香酰胺复合反渗透膜.研究了单体浓度、反应时间对膜性能的影响,用扫描电子显微镜和红外光谱仪表征了界面聚合反应前后膜表面形貌和化学结构的变化,并对膜的耐高温性能进行了考察.随着操作温度从20℃升高到95℃,膜的脱盐率保持在97.9%,通量从7.4 L/(m~2·h)上升至31.4 L/(m~2·h);膜在沸水中煮沸至3 h,其脱盐率基本不变而通量先增加后趋于稳定,表明杂萘联苯聚芳醚腈酮复合反渗透膜具有优良的耐高温性能.     

Preparation of anatase nanocrystals deposited on hydroxyapatite by hydrothermal treatment

TiO₂-deposited hydroxyapatite (HAp) crystals have been successfully synthesized by hydrothermal treatment of nearly neutral suspension of HAp powders in 10 vol.% of TAS-FINE™ (Titanium amine complex) solutions at 120 or 180 °C. Resultant products were characterized by XRD, SEM–EDX, Vis-Raman and TEM. SEM and TEM observation showed that small rodlike TiO₂, identified as anatase crystals of 100–150 nm in length, were deposited on HAp plates/crystals. The anatase crystals seem to be formed by heterogeneous nucleation on the surfaces of HAp crystals. A higher temperature and a longer reaction period promoted the cystallization of anatase TiO₂.     

Improving the efficiency of organic electroluminescent devices by introducing an electron-accepting and thermally stable polymer

A new hole-transporting material for multi-layer organic electroluminescent devices (OELDs) was prepared by the copolymerization of a hole-transporting material (9-vinyl carbazole) and an electron-retarding material (bis-4-vinylbenzyl-4,4^′-dipyridinium chloride). The resulting polymer has good thermal stability and electron-retarding property, due to its chemical structure and the 4,4^′-dipyridyl groups, respectively. The OELDs were fabricated with a multi-layer structure of an anode/new polymeric hole-transporting layer (HTL)/emitter/cathode. It was found that the electroluminescence efficiency was improved by using an electron-retarding material in a HTL.     

镁合金表面水热一步法制备生物膜层及其表征

针对镁合金作为生物体植入材料,因其活性高易腐蚀问题,对其做表面改性研究。提出了一种相对简易、低成本的方法——水热一步法,在低成本的Na2CO3处理液中,直接在AZ91D镁合金上制备了具有相应保护性能及生物相容性膜层。采用XRD、SEM表征膜层的结构及微观形貌,结合电化学手段及腐蚀浸泡实验测试膜层在模拟体液中的耐蚀性能。研究结果将为镁合金应用于生物体植入材料的表面改性提供一条新途径。     

水热法制备CdS纳米结构

利用氯化镉(CdC12)、硫脲(CO(NH2)2)和聚乙烯吡咯烷酮(PVP),在水热条件下获得了玉米棒状和花状等不同形貌的CdS纳米结构.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、荧光发光光谱(PL)、紫外可见光分光光度计(UV-vis)对产物进行表征.结果表明:PVP对不同形貌CdS纳米结构的形成起关键作用,随着PVP量的增加,PVP选择性地吸附(102)晶面,抑制了该(102)晶面方向的生长,使产物的形貌由玉米棒状转变为花状;而花状纳米结构的紫外的吸收产生了红移现象,荧光性能无明显变化.     

超临界水热合成法制备TiO_2纳米粉体

采用超临界水热合成法制备TiO_2纳米粉体,研究反应条件包括温度、压力、反应时间对纳米粉体颗粒的粒径大小、形貌及结晶度的影响。结果表明,随着温度从亚临界升高到超临界,TiO_2颗粒粒径急剧减小,且结晶度增大,最终合成10 nm左右结晶度良好的椭球形颗粒。颗粒在26~30 MPa的压力范围内,结晶度随着反应压力的增大而增大,但粉体粒径大小差别不大。在1 min的反应时间内即检测出了TiO_2物相,而在5 min后生成了结晶良好的椭球形晶体,随着反应时间的增加,棒状的颗粒逐渐增多,这是由于发生了溶解-结晶机理。     

一步水热法制备核壳型纳米粉体

液相法制备核壳纳米粉体具有反应温度低、设备简单、能耗少的优点,而一步水热法在液相法中具有其它方法无法比拟的优越性。重点讨论了一步水热法制备核壳纳米粉体的工艺流程和机理。     

Preparation of amino-acid-regulated hydroxyapatite particles by hydrothermal method

The hydroxyapatite nanorods (about 80 nm in length and 15 nm in width) with uniform size were achieved by hydrothermal method at 100 °C and pH 10 in the presence of alanine and glutamic acid. A special instillment order was used and the prepared powders were characterized for phase composition by X-ray diffraction and Fourier Transform infrared spectroscopy. The size and morphology of HAP nanoparticles were studied by Transmission electron microscopy. The characterization showed that the amino acid could induce the synthesis of hydroxyapatite nanoparticle and control HAP crystal growth when HAP crystal was formed. An instable monetite phase (CaPO₃OH) was found in the progress of ACP transforming to HAP.     

Preparation of CuZr2P3O12 from alkoxide-derived gels: phase formation as a function of heat treatment

The phase formation in alkoxide gels with composition corresponding to CuZr₂P₃O₁₂ has been studied as a function of gel preparation and heat treatment. Two preparational methods have been examined. The chemicals used include Cu(NO)₃ · 3H₂O, Zr(n-OC₃H₇)₄ and either P₂O₅ or H₃PO₄, respectively. The P₂O₅ method results in the formation of di-phase gels. Heat treatment of these invariably gives multi-phase materials. Gels prepared by the H₃PO₄ method are completely amorphous and can be converted into porous glasses by heating to 500 °C. Calcination in the range 650 to 750 ° C results in the formation of a new CuZr₄P₆O₂₄ phase ( . Later, this prevents formation of mono-phase materials during heating to 1200 ° C. It is suggested that this behaviour is related to mixing of Cu²⁺ and Zr⁴⁺ in the normal copper and zirconium positions in the low-temperature -Nasicon. Calcination in the range 750 to 850 ° C results in the formation of the normal C2/c Cu²⁺-Nasicon which readily converts to mono-phase Cu⁺-Nasicon (CuZr₂P₃O₁₂) above 880 ° C. Only gels calcined in the range 750 to 850 ° C are useful for the fabrication of mono-phase CuZr₂P₃O₁₂ ceramics.     

溶胶-凝胶水热法制备纳米晶体PbTiO3

以醋酸铅和钛酸丁酯为原料，乙二醇单甲醚为溶剂，分别用溶胶－凝胶直接水解法和溶胶－凝胶水热合成法制备纳米晶体PbTiO3，用XRD、TEM、Raman、ICP和氮吸附表面积测量等测试手段对纳米PbTiO3进行了分析。单纯sol-gel直接水解法（无酸催化）合成样品经400℃处理后仍为无定形结构，但同样条件下经溶胶－凝胶水热过程处理过的样品经400℃热处理可得到形状均一，颗粒较小，平均粒径在20－30nm左右，具有单相钙钛矿结构的钛酸铅纳米粉。在sol-gel酸性条件下水解合成的样品300℃形成晶相，但颗粒分布不均匀，经400℃处理的样品平均粒径在50nm左右。     

Preparation of novel CdSe microstructure by modified hydrothermal method

Wurtzite CdSe nanoparticles-assembled microspheres with macropores have been successfully synthesized through a modified hydrothermal method with Cd(NO₃)₂ and Na₂SeO₃ as precursors and hydrazine hydrate as a reductant in the presence of 1-n-butyl-3-methylimidazolium bromide ([Bmim]Br). The crystalline structure and morphology of the resulting samples were investigated by means of X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The results indicated that the CdSe microspheres have an average size of about 3 μm and were assembled by CdSe nanoparticles with size ranging from 20 to 40 nm. It was found that the pH and [Bmim]Br have influence on the morphologies of the products, and the potential formation mechanism of CdSe was discussed.     

Surfactant/co-polymer template hydrothermal synthesis of thermally stable, mesoporous TiO2 from TiOSO4

Industrial TiOSO₄ solution was used as inorganic precursor to prepare mesoporous titania via composite template route, using cetyl-trimethylammonium bromide (CTAB) and tri-block copolymer EO₂₀PO₇₀EO₂₀ (P-123) as structure-directing agents (SDA) under high acidic conditions. Mesoporous TiO₂ with high thermal stability was obtained via controlling the hydrolysis and condensation rate of industrial TiOSO₄ solution by adjusting the pH value and post hydrothermal treating. The as-prepared materials were characterized by XRD, nitrogen adsorption-desorption, SEM and HRTEM. The powder calcined at 723 K for 2 h showed higher thermal stability, with BET specific surface area of 218.7 m²/g and an average pore diameter of 3.63 nm.     

泡沫复制法制备多孔钛及表面水热碱处理改性

采用聚氨酯泡沫复制法成功的制备出孔径可控、孔隙率高且三维贯通的多孔钛.采用水热碱处理法对多孔钛进行表面改性,以提高其生物活性.改性后多孔钛的表面形貌发生了改变,呈均匀分布的三维网状微纳米结构.将改性后的多孔钛浸泡在SCPS中检测其矿化能力.研究结果表明,改性后的多孔钛能加速磷灰石的矿化,其中三维网状微纳米结构是加速矿化的主要因素.同时考察了改性后的多孔钛表面大鼠颅盖骨成骨细胞(MC3T3-E1)的黏附铺展情况.细胞培养表明细胞在改性后的多孔钛表面能较好的黏附铺展.上述研究结果表明水热碱处理改性后的多孔钛具有较好的生物活性及生物相容性.