Ti基RuO2-CeO2-SnO2涂层阳极的电催化性能

利用热分解法制备了不同CeO2含量的Ti基RuO2-CeO2-SnO2涂层阳极, 通过循环伏安曲线和电化学阻抗谱测试了所制备的涂层阳极的电催化性能, 并用扫描电镜对涂层阳极的表面形貌进行了观察. 结果表明 制备温度对涂层阳极的性能有很大影响, 在涂层阳极中引入CeO2可以增加RuO2-CeO2- SnO2涂层的有效活性表面积, 从而提高涂层阳极的电催化活性, 且CeO2含量的最佳摩尔分数为0.4.     

ZrB2/Al2O3 composite powders prepared by self-propagating high-temperature synthesis

Self-propagating high-temperature synthesis（SHS） method was used to synthesize ZrB2/Al2O3 composite powders from B2O3-ZrO2-Al system. X-ray diffractometry（XRD） and scanning electron microscopy（SEM） analyses show the presence of ZrB2 and Al2O3 as the primary phases in the composite powders, while the presence of a very small amount of ZrO2 is thought to be unreacted zirconium oxide. Transmission electron microscopy（TEM） and high resolution electron microscopy（HREM） observations of microstructure of the composite powders indicate that the interfaces of ZrB2/Al2O3 bond well without any interracial reaction products. It is proposed that the good interfacial bonding of composite powders results from the ZrB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

Low temperature synthesis of nanocrystalline lanthanum monoaluminate powders by chemical coprecipitation

Nanocrystalline lanthanum monoaluminate (LaAlO₃) powders were prepared by chemical coprecipitation using 25 vol.% of NH₄OH, 0.05 M La(NO₃)₃·6H₂O and 0.05 M Al(NO₃)₃·9H₂O aqueous solutions as the starting materials. Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analyses (TGA/DTA), X-ray diffraction (XRD), Raman spectrometry, specific surface area (BET) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) were utilized to characterize the LaAlO₃ powders prepared by chemical coprecipitation. The crystallization temperature of the LaAlO₃ precursor gels precipitated at pH 9 is estimated as 810 °C by TG/DTA. The XRD pattern of the LaAlO₃ precursor gels precipitated at pH 8–12 and calcined at 700 °C for 6 h shows a broad arciform continuum exist between 24° and 32° and sharp peaks of LaAlO₃ except the precursor gels precipitated at pH 9. For the LaAlO₃ precursor gels precipitated at pH 9 and calcined at 700 °C for 6 h, the formation of the perovskite LaAlO₃ phase occurs and the presence of crystalline impurities is not found. The crystallite size of LaAlO₃ slightly increases from 37.8 to 41.5 nm with calcination temperature increasing from 700 to 900 °C for 6 h. The LaAlO₃ powders prepared by chemical coprecipitation have a considerably large specific surface of 30 m²/g. The relative density greater than 97% is obtained when these nanocrystalline LaAlO₃ powders are sintered at 1550 °C for 2 h.     

Chemical synthesis and electrochemical analysis of nickel cobaltite nanostructures for supercapacitor applications

Nickel cobaltite (NiCo₂O₄) films containing nanorods and nanoflakes are synthesized on indium tin oxide (ITO) substrates by a chemical bath deposition method and calcination process at 300 °C for 3 h. The NiCo₂O₄/ITO films are used as electrodes for supercapacitor applications, and electrochemical properties of the NiCo₂O₄ nanostructures are examined by cyclic voltammetry and charge-discharge experiments. NiCo₂O₄ nanorods exhibit the largest specific capacitance, with a value of 490 F g⁻¹at energy and power densities of 45 Wh kg⁻¹ and 2 kW kg⁻¹, respectively. This is significantly better than the performance of NiCo₂O₄ nanoflakes. Cycle-life tests show that the specific capacitance of NiCo₂O₄ is stable even after 1000 cycles, indicating its high potential for supercapacitor applications. The low cost and environmental friendliness of NiCo₂O₄ nanorods, coupled with its high supercapacitor performance, offer advantages over other transition metal oxides used for supercapacitors.     

Low temperature synthesis of nanocrystalline titanium nitride from a single-source precursor of titanium and nitrogen

Nanocrystalline titanium nitride has been prepared via a convenient route from a single-source precursor of titanium and nitrogen (ammonium fluotitanate) in an autoclave at 650 °C. X-ray powder diffraction patterns indicate that the product is cubic titanium nitride, and the cell constant is a = 4.235 Å. Transmission electron microscopy image shows that it consists of particles with an average size of about 40 nm in diameter. The product was also studied by BET and TGA.     

One step synthesis of complex fluoride powders for solid-state lasers

One step, wet chemical synthesis of several complex fluorides is described. Formation of single phase compounds was confirmed by XRD. In some cases study of photoluminescence by Eu²⁺ activation supported the conclusions. It is suggested that availability of such powders will greatly facilitate growth of single crystals for solid-state lasers.     

Structural, magnetic and Mössbauer spectral studies of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite powders

Nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ powders, synthesized by a combustion method are investigated by X-ray diffraction, vibrating sample magnetometry and Mössbauer spectroscopic techniques. We adopt a strategy to systematically control the particle sizes between 4 and 45 nm simply by changing the elemental stoichiometric coefficient, Φ_e, of the combustion mixture. Curie temperature of the superparamagnetic particles of size 4 nm is higher than that of the bulk particles. Interestingly, bigger particles (45 nm) show a comparable room temperature saturation magnetization and exceptionally very high Curie temperature of 833 K, when compared to that of the bulk Ni_0.5Zn_0.5Fe₂O₄ material (563 K).     

On the synthesis and crystallization process of nanocrystalline PZT powders obtained by a hybrid sol–gel alkoxides route

Sol–gel synthesis has been a very successful and efficient route for obtaining high quality ferroelectric materials. Particularly, the alkoxides based route has proven its advantages due to the better homogeneity and easier controlled gelation rate. In this work, butoxides and propoxides are used to obtain nanocrystalline PZT powders in order to determine the influence of each B-site precursor on crystallization. Along with this, we study the involved chemical reactions (reactants and intermediates) and the crystallization process by using several spectroscopic techniques (Raman, FT-IR and XRD) as well as thermogravimetric (TGA) and calorimetric (DTA) analysis. The evolution of the initial gel solution and the amorphous powder into the final perovskite PZT phase is traced. According to our results, the propoxy route tends to be the more suitable for good PZT crystallization under our experimental conditions.     

A convenient thermal reduction–nitridation route to nanocrystalline molybdenum nitride (Mo2N)

Nanocrystalline molybdenum nitride (γ-Mo₂N) was synthesized via a thermal reduction–nitridation route by the reaction of metallic sodium with anhydrous molybdenum pentachloride and ammonium chloride in an autoclave at 550 °C. X-ray powder diffraction pattern indicated that the product was cubic Mo₂N, and the cell constant was a = 4.161 Å. Scanning electron microscopy image showed that it consisted of particles with an average size of about 30 nm. The product was also studied by BET and TGA. It had good thermal stability and oxidation resistance below 400 °C in air.     

纳米结构ZrO2/SiO2粒子的逐层自组装及催化性

用自组装技术合成了以通过溶胶凝胶法得到的纳米ZrO2包覆的SiO2粒子,并研究了其作为固体超强酸的催化性能。样品采用TG-DTA,SEM,EDS,XPS和XRD进行了表征。结果表明:SiO2粒子表面的纳米ZrO2具有较好的均匀性和致密性,ZrO2的含量随覆盖层的增加而增多,纳米ZrO2具有四方相结构;SO42--ZrO2/SiO2固体超强酸具有较好的催化性及重复使用性。     

Facile synthesis of La2Mo2O9 nanoparticles via an EDTA complexing approach

A facile EDTA (ethylene diamine tetraacetic acid) complexing technique has been successfully employed to prepare La2Mo2O9 nanoparticles.The as-synthesized products are characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscopy (TEM),and Fourier transform infrared spectroscopy (FT-IR).The results show that a homogeneous transparent gel can be obtained with EDTA as the organic complexing reagent under the pH value of 3.0.Further thermal decomposition of the as-synthesized transparent gel by increasing the temperature up to 600℃ for 3 h results in the formation of La2Mo2O9 nanoparticles with a crystal size of about 30 nm.Moreover,the nanoparticles tend to form micrometer-sized aggregates with a three-dimensional network structure,which shows promising applications in solid oxide fuel cells (SOFC),catalysts and so on.     

Room-temperature synthesis of crystallized LiCoO2 thin films by electrochemical technique

LiCoO₂ thin films have been directly synthesized on cobalt substrate in LiOH solution at room temperature by electrochemical method. The obtained LiCoO₂ thin films were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of electrochemical reaction time, current density and concentration of LiOH solution on the crystal structure and morphology of the obtained LiCoO₂ thin films was discussed emphatically. Our results show that the as-synthesized LiCoO₂ films all are pure hexagonal structure. The crystallinity, densification and uniformity of the films increase with increasing electrochemical reaction time, current density as well as concentration of LiOH solution and then decrease. The preferable electrochemical reaction conditions were optimized as: electrochemical reaction time is 50 h, current density is 1 mA cm⁻² and concentration of LiOH solution is 3 mol dm⁻³.     

ZrO2+SiC颗粒强韧化MoSi2复合材料的显微组织和性能

通过显微组织观察和力学性能测试 ,初步探讨了ZrO2 SiC颗粒对MoSi2 基体材料的强韧化效果和机制。结果表明 ,材料复合具有较好的强韧化协同效应 ,复合材料中ZrO2 相和少量SiC颗粒在基体的间层作用 ,可抑制MoSi2 晶粒长大 ;断口呈现晶粒细小、裂纹扩展曲折和沿晶与穿晶混合型断裂等特征 ;ZrO2 SiC颗粒通过弥散强化和细化晶粒使复合材料强度提高 ,通过晶粒细化、裂纹偏转和分支、微裂纹形成等机制的综合作用使复合材料增韧     

Effects of tourmaline on microstructures and photocatalytic activity of TiO2/SiO2 composite powders

The SiO2/TiO2 composite powders including mineral tourmaline powders （T/SiO2/TiO2） were prepared from a sol made by a two-step hydrolysis method, using metasilicate ester as precursor. The powders were characterized by scanning electron microscopy （SEM）. The photocatalytic activity of the sample was evaluated by the photocatalytic degradation of methyl orange. The effects of heat-treatment on the photocatalytic activity were discussed. It is found that the T/SiO2/TiO2 composite powders show higher photocatalytic activity when including 10% SiO2 and 4% tourmaline. Moreover, the photocatalytic mechanism of tourmaline on the powders was proposed.     

ZrO2增韧MoSi2的作用机制与KIC测试方法的响应关系

采用两种具有代表意义的KIC测试方法 ,对两类试验材料 (0Y ZrO2 /MoSi2 基复合材料和2 5Y ZrO2 /MoSi2 基复合材料 )的断裂韧度进行了对比和分析 ,探讨了两类ZrO2 增韧机制所伴随的两类显微结构对断裂韧度测试方法的不同响应关系和内在作用机制。     

纳米晶复合物Mg-Ni-Cr_2O_3的吸放氢性能

在氢气作为保护气氛条件下 ,用机械合金化方法制备成Mg Ni Cr2 O3 纳米晶复合物。该复合物具有很好的吸放氢性能 ,在球磨过程中能发生吸氢反应 ,经过较长时间球磨之后 ,基本能完成吸氢 ,其放氢温度也有所降低。该复合材料充氢量在 2 0 0℃可以于 5 0s内达到 6 .0 %以上 ;在 30 5℃ ,0 .1MPa下 ,放氢量在 5 0 0s内可达到6 .0 %以上。对该复合物的热力学性能进行了研究 ,测出了PCT曲线及吸放氢的生成热ΔH等数据 ,并分析了其吸放氢的机理。     

ZrO2/Al2O3复相泡沫陶瓷过滤器制备工艺研究

采用有机泡沫浸渍法制备泡沫陶瓷,研究了各种不同工艺因素对泡沫陶瓷性能的影响。采用XRD、SEM对泡沫陶瓷的相组成及微观结构作了分析与探讨。结果表明,在粘结剂聚乙烯醇加入量为0.5%,减水剂木质素磺酸钙加入量为0.5%,流变剂苏州土加入量为1.5%时,调整分散剂的加入量,当浆料中分散剂四甲基氢氧化铵的质量分数为0.9%时,可获得具有较佳分散性能的浆料。浆料的固相含量为85%时最适合挂浆的需求。对氧化锆氧化铝复合浆料进行进一步分析表明,氧化铝的加入量为20%时,浆料具有较小的粘度。烧结体的XRD分析表明,氧化铝加入量为20%时较好地抑制了t-ZrO2→m-ZrO2转变的发生,将大量的能发挥应力诱导相变的亚稳态四方相氧化锆保留了下来,从而提高了烧结体的力学性能。SEM分析也表明加入适量的氧化铝可有效抑制氧化锆晶粒的长大,并且起到颗粒弥散增强的作用。