Preparation and properties ofX-sialon

X-sialon has been produced by hot pressing Si₃N₄-Al₂O₃-SiO₂ powder mixtures and Si₃N₄ Powder-mullite gel mixtures at 1650 °C. The formation mechanism ofX-sialon has been studied and is correlated with the processing technique for the two preparation routes. Microprobe analysis of the obtainedX-sialon phase, combined with previous observed compositions and literature formulae suggests that, at 1650 °C,X-sialon exists as a narrow solid solubility region on the Si₃N₄-mullite line in the Si₃N₄-SiO₂-Al₂O₃-AIN phase diagram. The physical, mechanical and chemical properties ofX-sialon have been evaluated.X-sialon has a modest hardness of 1280 kg mm^–2, a fracture toughness of 1.7 Mpa m^1/2, and an elastic modulus of 213 GPa.X-sialon exhibits excellent chemical stability in contact with iron-based alloys at 1200 °C.     

碳纳米管-石墨烯气凝胶的制备与性能

以混合均匀的碳纳米管(CNTs)-石墨烯(GR)分散液为前驱液,质量分数为3.0%的1788-聚乙烯醇(PVA)溶液为有机物黏结剂,通过冷冻干燥法制备了轻质、平整和易切削的CNTs-GR气凝胶。采用TEM、SEM、压缩试验机和比表面积测试仪等对样品的微观形貌结构和力学性能进行了表征。结果表明,CNTs-GR混合分散液的质量分数为3.0%、CNTs与GR的质量比为5∶3时,得到的气凝胶呈现不同尺寸等级的气孔且分布最均匀;PVA在气凝胶的形成中有效地抵抗样品收缩变形;固体物的质量与样品的密度严格线性负相关,满足y=-0.125x+106.26函数关系式;N2吸附脱附检测显示气凝胶的比表面积为138.77m2/g,介孔在气凝胶中占主导部分,平均孔直径为46.6nm,孔隙率可达97%;且样品的压缩过程出现了三个不同阶段的弹性变形,并能最终恢复到原始尺寸。     

壳聚糖水凝胶的制备及性能研究

以壳聚糖为原料,用戊二醛作为交联剂,在醋酸溶液中合成壳聚糖水凝胶。用正交实验优化了制备壳聚糖水凝胶的工艺条件,实验结果表明:当壳聚糖浓度为3%、戊二醛浓度为3%、凝胶温度为55℃时制得的水凝胶硬度最大;当壳聚糖浓度为2%、戊二醛浓度为1%、凝胶温度为45℃时,制得的水凝胶溶胀度最大。壳聚糖水凝胶具有良好的生物相容性。     

磁性累托石的制备及其性能

采用化学共沉淀法制备了纳米Fe3O4磁性微粒,将其与累托石复合制得一系列不同Fe3O4,载量的磁性累托石,分别用XRD,SEM,TEM和VSM对样品的物相组成、微观形貌特征、磁学性质等进行了表征;研究了磁性累托石对废水中重金属离子的吸附性能及其磁分离回收效果.结果表明,Fe3O4粒度为10～25nm、结晶良好、具尖晶石...     

Preparation and properties of alumina-baria nano-composites

Barium doped alumina was prepared by calcination of gels obtained from metal chloride solutions by homogeneous precipitation with urea. The gels were either air-dried, oven-dried, microwave-dried or autoclave treated. The materials were analysed by SAXS, XRD, DTA/TG and TEM. The phase composition of the calcined products depended on the gel drying procedure. Barium aluminates formed directly at low temperatures in the microwave treated gel because of the uniform distribution of barium in the dried gel. After calcination at 1200 °C the aluminates were uniformly distributed as nanoscale particles within an -Al₂O₃ matrix. In contrast, autoclave treated samples initially consisted of boehmite crystals coated with barium carbonate which reacted on calcination to form a surface layer of BaAl₂O₄. The autoclaved material withstood 1 h at 1400 °C in air without transformation to -Al₂O₃. This increased thermal stability of transition alumina (-Al₂O₃) is attributed to the presence of the BaAl₂O₄ surface layer. The final transformation to -Al₂O₃ was associated with the transformation of a surface layer of BaAl₂O₄ to nanoscale particles of BaAl_9.2O_14.8.     

掺铝氧化锌粉末的制备及其性能研究

采用溶胶凝胶燃烧合成法制备了ZAO(掺铝氧化锌)粉末,借助于DSC-TG、XRD、SEM、反射率测试、红外辐射率测试对制得的ZAO粉末的形貌、微观结构、激光吸收性能和红外辐射性能进行表征.研究结果表明,制备的ZAO粉末属于六方晶系纤锌矿结构.XRD分析表明煅烧温度提高到700℃后,ZA0的晶相形成的更好.SEM图中可以看出,随着Al离子的掺杂量增加,ZAO粉末的粒径越来越小,形状越来越不规则.反射率图谱表明,在900～1200nm波长范围,存在较强的激光吸收.红外辐射率测试表明ZAO粉末具有中等红外辐射率.     

微晶纤维素的制备及性质研究

分别用HCl和H2SO4处理从棉纤维和稻秆中提取的纤维素，制备得到微晶纤维素。研究了酸处理对微晶纤维素的聚合度、结晶度、体积密度和热稳定性的影响．X射线衍射结果表明，纤维素微晶化后仍保持原来的晶型和晶区和非晶区两相共存的微细结构。扫描电子显微镜测试结果表明，不同原料，酸处理后所得产物的形态不同．     

河流水环境容量计算模型分析

河流水环境容量计算模型包括有机物环境容量计算模型和重金属环境容量计算模型。本文对各种河流水环境计算模型进行了科学分析，并对各种模型适用的范围和计算方法进行了论述。     

Preparation and properties of some alumina-chrome refractories

Preparative procedures, grain growth, densification and change in corundum lattice dimensions in sintered compacts made from chromium (III) oxide/aluminium (III) oxide mixtures were evaluated in a study of some alumina-chrome refractories. High-energy milling using A17 reactive alumina gave densification at low temperature and rapid grain growth, also a low variability in modulus of rupture. X-ray diffraction studies confirmed solid solution formation, the corundum lattice dimensions decreasing with 7 wt% chromium (III) oxide, other compositions giving lattice expansion. The modulus of rupture at 1150 °C for a series of ethyl silicate-bonded alumina-chrome refractories containing 5 to 12 wt% chromium (III) oxide was also minimal at 7 wt% chromium (III) oxide. The composition of this series is typical of ethyl silicate-bonded alumina-chrome refractories used in the steel industry.     

CNx薄膜的制备和光电性能

以单晶硅片(100)和镀Pt硅片为衬底,用电化学沉积方法在阴极制备出CNx薄膜(x接近于1),薄膜的表面平滑,颗粒均匀.热处理后得到了β-C3N4和α-C3N4多晶结构薄膜.热处理温度的提高使薄膜中的C≡N键逐渐减少而消失,氮元素的流失使薄膜中非晶碳的成分增多,但是薄膜中碳氮逐渐以sp3C-N为主.薄膜的能带在1.1～1.8 eV之间,氮含量对能带大小影响较大.热处理使薄膜的电阻率(高于108Ω@cm)变化不大.氮含量影响PL谱中3.0和3.5 eV处发射峰的峰强,不影响峰位.     

纤维素离子凝胶的制备及性能

开发高性能的导电凝胶已经成为推动柔性电子设备进一步发展的基石。以天然纤维素为凝胶骨架,以离子液体为导电介质,通过加热溶解-冷却凝胶化过程可以制备高性能的绿色离子液体-纤维素复合凝胶(CGel)。复合凝胶中的纤维素基体呈现三维网络结构,并包含大量的孔洞,可以有效吸附和储存离子液体,实现离子液体在纤维素基体中的均匀分布。纤维素离子复合凝胶具有较高的模量(G′>G″)、优异的透明度(88%)、良好的电学性能(2.2 mS/cm)及柔韧性。进一步通过高温加热-冷却凝胶化过程能够实现纤维素离子凝胶体系的再循环生产过程。纤维素离子凝胶展现了对水分子的高度敏感性,其电导率正比于工作湿度,有望应用于环境湿度及人体皮肤状况的高效监督检测。      

Preparation of alginate-gelatin capsules and its properties

Capsules based on alginate and gelatin prepared by extrusion method could increase the cell numbers of Lactobacillus casei ATCC 393 to be 10⁸ CFU·g⁻¹ in the wet state of the capsules. The capsules were spherical, smooth-surfaced and non-aggregated with a diameter of (4.0 ± 0.3) mm. The behavior of the samples were quite similar at low relative humidity (33%, 52%) and the ratio of weight change reached 93%. Four kinds of capsules in simulated gastric fluid (SGF) exhibited shrinkage while the beads eroded accompanied with slight swelling in simulated intestinal fluid (SIF). The pH values affected the stability of the capsules and with the increase in pH, the capsules changed from shrank then swelled and finally, broke into pieces. The capsules behaved differently under different ion intensities and the introduction of gelatin weakened the stability of capsules compared with the alginate ones. Cells of L. casei ATCC 393 could be continuously released from the capsules in the simulated gastrointestinal tract (GIT) and the release amounts and speeds in SIF were much higher and faster than those in SGF.     

抗静电模压成型热固性复合材料的制备与性能研究

以不饱和聚酯树脂为原料,研究抗静电剂炭黑用量对热固性复合材料力学性能和抗静电性能的影响。结果表明:当炭黑含量1.0%时,复合材料的力学性能和抗静电性最好。     

壳聚糖基多孔膜的制备及性能研究

为研制出一种配方简单、性能良好的壳聚糖基伤口敷料,以壳聚糖为主体,采用冷冻干燥法制备了壳聚糖基多孔膜.通过单因素实验,探讨了不同配方和工艺条件下的成膜性、pH、吸水性和透气性能,并采用扫描电镜(SEM)、热重分析(TGA)对膜的结构和性能进行表征.通过实验得到最佳配方和工艺条件:3%的壳聚糖31.5mL,甘油3.5mL,羧甲基纤维素钠0.40g,碳酸氢钠0.1g,剧烈搅拌混匀,预冷冻7h后冷冻干燥.抑菌实验和降解实验表明,该多孔膜对大肠杆菌和金黄色葡萄球菌均有较强的抑菌作用,降解性能良好,是一种理想的伤口敷料.     

Preparation and properties of Yb-Ti02 photocatalysts

采用溶胶-凝胶法制备了稀土Yb掺杂纳米Ti02光催化剂（Yb-TiO2）,采用XRD、UV-Vis、FT-IR等方法对其进行表征和分析,并以亚甲基蓝（MB）作为目标降解物,考察了热处理温度以及Yb掺杂量对样品性能的影响。实验结果表明,Yb掺杂样品均为金红石相和锐钛矿相的混晶相,Yb的掺入拓展了TiO2对可见光的吸收范围,有效地抑制了光生电子-空穴对的复合,提高了TiO2的光催化活性。当pH值-2．5、n（Yb）：n（Ti）-0．005、热处理温度为650℃时,制备的样品其光催化活性明显优于Degussa P25。     

海藻酸钡纤维的制备和性能研究

以海藻酸钠为原料,0.5mol/L氯化钡水溶液为凝固浴,通过湿法纺丝制备了海藻酸钡纤维.利用扫描电镜、红外光谱仪对制得的纤维进行了表征,并对纤维进行了单纤维拉伸测试和防辐射性能测试.研究表明,海藻酸钠在凝胶化过程中形成明显的螯合结构,海藻酸钡纤维的平均断裂强度20.69cN/tex,线密度为3.86dtex,与普通粘胶纤维相比海藻酸钡纤维有明显的防辐射性能.     

Bi-Pb-Sn-Cd易熔合金的制备与性能研究

利用差热分析仪和拉伸试验机,研究了易熔合金Bi-Pb-Sn-Cd的成分对合金熔点和剪切强度的影响.结果表明合金的液相线随Cd元素含量的增加逐渐降低.Cd元素对合金的剪切强度的影响最大,Sn元素次之,Pb元素的影响最小;合金钎焊接头剪切强度的提高是通过Pb7Bi3、Sn和Cd相的强化实现的.     

Preparation and properties of alumina-ceria nano-nano composites

Alumina-ceria composites were prepared by the calcination in air of gels obtained by homogeneous precipitation from dilute chloride and nitrate solutions, followed by either microwave treatment, autoclave treatment or air-drying. Microwave treatment and air-drying of the gels yielded amorphous powders whereas autoclave treatment yielded well-crystallised boehmite. The phase evolution during calcination was investigated by in-situ X-ray diffraction (XRD) and by differential thermal analysis and thermogravimetry (DTA/TG). The structures of the calcined powder were investigated by transmission electron microscopy (TEM) and high resolution TEM. A variety of morphologies was found depending on the processing route. The calcined microwave treated gels consisted of nano-size particles of ceria in nanostructured transition alumina i.e. a nano-nano composite structure suitable for catalysis applications. In comparison, the calcined autoclave treated gels consisted of a coarser composite of large agglomerates of ceria in transition alumina which, however, was more stable against transformation to alpha alumina at high temperature. Boehmite sols made with the autoclave treated gels were suitable for making thin films by dip-coating. This revised version was published online in September 2006 with corrections to the Cover Date.     

Preparation of alginate-gelatin capsules and its properties

Capsules based on alginate and gelatin prepared by extrusion method could increase the cell numbers of Lactobacillus casei ATCC 393 to be 10⁸ CFU·g^-1 in the wet state of the capsules. The capsules were spherical, smooth-surfaced and non-aggregated with a diameter of (4.0 ± 0.3) mm. The behavior of the samples were quite similar at low relative humidity (33%, 52%) and the ratio of weight change reached 93%. Four kinds of capsules in simulated gastric fluid (SGF) exhibited shrinkage while the beads eroded accompanied with slight swelling in simulated intestinal fluid (SIF). The pH values affected the stability of the capsules and with the increase in pH, the capsules changed from shrank then swelled and finally, broke into pieces. The capsules behaved differently under different ion intensities and the introduction of gelatin weakened the stability of capsules compared with the alginate ones. Cells of L. casei ATCC 393 could be continuously released from the capsules in the simulated gastrointestinal tract (GIT) and the release amounts and speeds in SIF were much higher and faster than those in SGF.     

Preparation and electrical properties of TbSb films

Thin polycrystalline TbSb films have been grown by thermal evaporation in vacuum from two separate sources on glass-ceramic, sapphire, and single-crystal silicon substrates. The substrate material has been shown to have no significant effect on the phase composition and crystallinity of the films. The optimal substrate temperature is 1120–1145 K. The films have a cubic structure (NaCl type), their composition is 49 ± 0.01 at % Tb + 50.1 ± 0.01 at % Sb, and their components are uniformly distributed both on the surface and in the bulk of the films. The resistivity, Hall coefficient, and thermoelectric power of the films have been measured as functions of temperature in the temperature range 95–700 K. It has been shown that charge carriers in the films are electrons, with a concentration of ~10²⁶ m^–3 and mobility of ~10^–3 m²/(V s). According to the electrical measurements, TbSb is a semimetal.