制备条件对Pd/TiO_2催化剂上对羧基苯甲醛加氢性能的影响

采用浸渍法以TiO2成型载体制备了Pd/TiO2催化剂,考察了浸渍液pH值、Pd负载量、焙烧温度以及还原温度等因素对粗对苯二甲酸(CTA)中的主要杂质对羧基苯甲醛(4-CBA)的加氢精制性能的影响,并采用BET、XPS、XRD、H2-TPR等手段对催化剂进行了表征。结果表明,浸渍液pH值的升高会造成催化剂表面Pd原子富集,导致催化剂比表面积降低。Pd负载量0.5%时,催化剂所提供的活性中心数目足以满足4-CBA加氢所需。适当提高催化剂焙烧温度,有利于含钯前驱体的分解,催化剂还原温度过高时,会造成Pd/TiO2催化剂活性的迅速降低。Pd/TiO2催化剂的适宜制备条件为:浸渍液pH=2.0、Pd负载量0.5%、催化剂焙烧温度400℃、还原温度低于200℃。     

Effects of precoating and calcination on microstructure of 3D silica fiber reinforced silicon nitride based composites

1 Introduction Continuous fiber reinforced ceramic matrix composites, such as C/SiC, C/Si-C-N, C/Si-O-C and SiC/SiC systems[1?5], have received considerable attention because of their excellent thermal stability, light mass and high toughness, etc. Among…     

高温水蒸气毒化对钯膜表面状态与渗氘能力的影响

采用H2O(g)在300℃与900℃之间对Pd膜表面进行了毒化,将毒化后的Pd膜在常温下与氢气进行反应,并在500℃进行了氘气渗透试验。采用XPS、SEM等对反应前后Pd膜表面状态进行了表征与分析,研究了H2O(g)的毒化作用与吸氢反应对Pd膜表面形貌与化学成分的影响与机理。实验表明:当毒化温度低于500℃时,H2O(g)对Pd膜表面无明显影响;当毒化温度高于500℃,H2O(g)会导致Pd膜表面出现微孔,且随着毒化温度升高,微孔数量与体积逐渐增加;当温度达到600℃以上时,H2O(g)毒化会造成Pd膜表面出现细微裂纹。H2O(g)与Pd膜在300℃与900℃之间不但不会产生化学变化,其表面原有的吸附杂质反而得到了明显的去除,且在600℃以上反应后钯膜的透氘性能也得到了提高。     

Modeling of the beam transportation behavior in selective laser transmission sintering the translucent core–shell composite powder

In the paper, selective laser transmission sintering the 2%PF/silica sand core–shell composite powders was studied based on a developed optical model by using a Zemax optical design program. The construction of the powder bed was made by the particle stacking model with the composite particle assumed as a three-component optical system. It showed that simulation results agreed well with the experimental data. A focus point after the first layer particle was produced by the translucent spherical lens of particles and then laser beam was quickly diverged by subsequent particles along the beam transportation path. The occurrence of the vaporization at the focus point had little effect on the whole properties of the sintered sample because of its relatively small size. Since no melting pool was produced in the sintering process owing to the thin polymer binder, the rearrangement of the powder bed was not remarkable which led to a constant porosity of the powder bed before and after laser sintering. Laser transmission sintering of core–shell composite powders was basically “contaction” sintering, where particles near to each other as well as within the beam transportation path had an opportunity to sinter together.     

KH560改性纳米硅溶胶对苯丙涂层性能的影响

目的提高硅溶胶-苯丙复合涂层的综合性能,为有机-无机复合涂层的应用提供一定的参考意义。方法采用水浴加热机械搅拌/超声分散法,用KH560对硅溶胶进行表面改性,并将改性前后的硅溶胶与苯丙乳液共混,制备了含改性前后硅溶胶15%、30%、45%(质量分数,全文同)的硅溶胶-苯丙复合涂层。用红外光谱仪证实改性成功。用紫外/可见/近红外分光光度计、力学性能测试仪、扫描电子显微镜对改性前后硅溶胶-苯丙复合涂层综合性能及微观结构进行表征。结果含有改性后硅溶胶的复合涂层综合性能得到明显提高,当改性硅溶胶掺量为30%时,复合涂层综合性能最好,此时复合涂层磨耗值为0.078 g,附着力为1级,抗冲击性为62 mm,拉伸强度为4.74 MPa,断裂伸长率为215.90%,附着力、抗冲击性、拉伸强度和断裂伸长率分别比相同掺量下未改性硅溶胶复合涂层提高1级、6 mm、0.59 MPa和10.34%。结论 KH560可成功地对硅溶胶进行表面改性,将改性后的硅溶胶替代未改性的硅溶胶可提高硅溶胶-苯丙复合涂层的综合性能,实际应用时改性硅溶胶掺量以30%为宜。     

响应曲面法优化偏钒酸铵煅烧制备V2O5的工艺（英文）

采用响应曲面法中的中心组合模式对偏钒酸铵煅烧制备V2O5工艺条件进行优化,建立偏钒酸铵煅烧制备V2O5的二次多项式数学模型,探讨主要因素的影响及其交互作用。方差分析结果表明:煅烧温度和煅烧时间对偏钒酸铵的分解率都有显著的影响。采用响应曲面法优化得出的最佳工艺条件为:煅烧温度669.71K,煅烧时间35.9min,物料量4.25g。在最佳工艺条件下,偏钒酸铵的分解率预测值为99.71%,其与实验值99.27%相近,证实回归方程拟合度良好。XRD分析表明,采用响应曲面法所得的煅烧工艺参数是可行的。     

INFLUENCE OF FIBER COATING ON TENSILE BEHAVIOR OF UNIDIRECTIONAL C/Mg COMPOSITES

1.Intr0ductionAm0ngtheseveralmethodsavailablef0rcombiningamagnesiummatrixwithacar-bonfiberreinforcement,l0wpressureinfiltrati0nprocesseshavetheadvantages0frelativesimplicityandpotentialf0rl0w-costpr0ductionofnet-0rnear-net-shapec0mpositecom-ponents.Unfortunately,thereexistcomplexproblemsatfiber/matrixinterfacesuchasinterfacialwetting,illterfacialreacti0nandinterfacialb0nding,allofwhichneedtobesolvedsimultaneously.Afunctionalgradientcoating0nfibersurface,C/SiC/SiO2,wasthuspresentedinourprevio…     

氮化钛含量对热塑性涂层光热效应及自修复性能的影响

为了实现涂层破损的高效自修复,将纳米氮化钛与热塑性聚氨酯混合,制备了不同氮化钛含量的复合涂层。 利用扫描电子显微镜(SEM)、X 射线衍射仪(XRD)和紫外可见分光光度计(UV-Vis)分析了氮化钛的结构和光谱吸收特征;利用差示扫描量热仪(DSC)、热电偶、光学显微镜、扫描电子显微镜( SEM)、交流阻抗谱(EIS)等对复合涂层的热力学性能、光热转换性能、自修复性能及防腐性能进行测试。 结果表明:基于纳米氮化钛的表面等离激元特性,在热塑性聚氨酯中添加质量分数为 2%的氮化钛后,复合涂层具有良好的光热转换性能,在近红外激光照射后其表面温度高于聚氨酯的玻璃化转变温度。 当涂层表面有划口时,通过激光照射可以提高涂层的局部温度,使聚合物分子链运动并流向划痕界面,复合涂层的结构和防腐性能均得到恢复,并且修复后涂层中氮化钛仍分布均匀。 此外,氮化钛纳米颗粒还有助于填补涂层的微观孔隙,使复合涂层的防腐性能提高。     

钼系光催化抗菌材料的制备及性能研究

以水玻璃和碳酸氢钠作为硅胶原料,采用溶胶-凝胶法将钼离子负载到硅胶表面以制备钼系抗菌硅胶,通过单因素实验得到了其最佳制备条件。利用XRD、ICP、SEM、EDS、XPS、BET等对材料的晶体结构、离子浓度、表观形貌、负载形式、比表面积等进行了表征。另外,通过平板涂布法对样品的抗菌性能进行了检测;观察不同光源下亚甲基蓝溶液的降解情况,检测了复合材料的光催化效果。结果表明:在未改变硅胶结构形态的基础上成功制备钼系光催化抗菌材料,且在最佳制备条件下对大肠杆菌的杀菌效果可达99%以上;在紫外光持续照射240 min后可以将98%的染料降解,可见光在持续照射360 min后降解率为93.5%。最后,结合表征和检测结果探讨了光催化抗菌机理,证明该材料主要杀菌方式为活性氧杀菌。     

Evaluation of corrosion inhibition performance of silica sol–gel layers deposited on galvanised steel

The present work reports a comparative investigation of the electrochemical behaviour of some new types of silica sol–gel coatings with enhanced corrosion resistance deposited on electrolytically or thermally (hot-dip) zinc-coated steel. The coatings were rendered hydrophobic by silylation. Dichlorodimethylsilane or trimethylchlorosilane were used as silylating agents and cetyltrimethylammonium bromide or Pluronic PE 10300, as templating agents. The morpho-structural and optical properties of compact and mesoporous silica coatings were characterised with different methods. The corrosion behaviour of the coatings was evaluated by open circuit potential measurements, Tafel interpretation of the polarisation curves and electrochemical impedance spectroscopy. Both silylating agents improve significantly the corrosion resistance of both porous and compact coatings by reducing the corrosion current density with at least one order of magnitude. The possibility to use the porous structure of the coatings as corrosion inhibitor carriers was explored by loading of mesoporous silica layers with 1H-benzotriazole.     

Morphology and carbon content of WC-6%Co nanosized composite powders prepared using glucose as carbon source

Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method. The effects of carbon source on microstructure characteristic of composite powders were investigated, and the effects of heat-treatment parameter on carbon content of composite powders were also discussed. The results of SEM and XRD revealed that the carbon decomposing from glucose was more active than carbon black. Therefore, WC-Co nanosized composite powders could be synthesized at 900 °C for 1 h under a hydrogen atmosphere. The individual WC grains were bonded together into a long strip under the action of cobalt. The results of carbon analysis revealed that the total carbon content decreased with the increase of the temperature in the range of 800–1000 °C. Moreover, the total carbon content and the compounded carbon increased with the increase of the flow rate of H₂ in the range of 1.1–1.9 m³/h.     

铬镀层及其阴极化修饰镀层的钝化行为

用电沉积方法在ＡＩＳＩ ４３０不锈钢上得到铬、铬钯交替镀层和铬钯复合镀层，凭借钯的阴极修饰效应，含钯的铬镀层在除氧的非氧化性酸中具有自钝化能力，极化曲线和阻抗频谱测定表明，在相庆铬镀层处于活化－钝化的电位区间，含钯镀层都表现出净阴极电流；活化溶解与钝化过程随电位的相对发展变化可由低频段容抗圈的演变来推定，铬钯复合镀层具有更大的钝化膜阻抗。     

还原-插锂和碳包覆同步制备磷酸铁锂/碳复合材料及其性能

以聚丙烯酸为碳源,用低温还原-插锂与聚合物高温分解相结合的方法制备LiFePO4/C复合正极材料;FePO4被还原插锂与含碳聚合物化学包覆同时进行,简化了制备工艺,降低了制备成本。经X射线粉末衍射(XRD)、扫描电镜(SEM)以及恒电流充/放电测试,研究了不同焙烧温度对合成产物的物相、晶胞参数、表面形貌及电化学性能的影响。研究发现,焙烧温度为600℃时,合成产物的0.1 C倍率放电具有最高的放电容量和最好的循环稳定性。在0.1 C下LiFePO4/C复合材料的首次放电容量高达141.3 mAh/g,库伦效率为98.0%,100次循环后,其容量保持率为108.3%。     

Formation of gradient palladium-hydrogen alloy and the change in the form of a palladium plate during one-sided hydrogen saturation

Forming of a palladium plate (60 × 5.5 × 0.27 mm) saturated one-sidedly with hydrogen at 240°C at various hydrogen pressures from 0.03 to 0.43 MPa has been investigated experimentally. It has been established that forming of a palladium plate during its saturation with hydrogen is time-dependent and occurs in two functionally different stages. At the first stage, the plate becomes bent and its bending quickly reaches the maximum value. At the second, much longer stage, the plate straightens back almost completely. An increase in pressure of gaseous hydrogen leads to a sharp rise in the maximum possible bending of the plate. The degree of reversibility of hydrogen-induced bending of the plate also grows with an increase in hydrogen pressure. The experimental research and an analysis within the framework of the elasticity theory has shown that the palladium plate investigated demonstrates during mechanical loading the elastic reversible bending at deflections approximately three times smaller than those observed upon hydrogen loading. It is concluded that the mechanism of bending of the palladium plate upon saturation with hydrogen is fundamentally different from that under mechanical loading. A fundamental feature of the process of hydrogen-induced shape change is in that it is always implemented through the formation and development of the temporary gradient material of a metal-hydrogen type. Under experimental conditions of this work, the hydrogen-induced reversible bending of the palladium plate results from the “work” of the temporal gradient elastically stressed coherent alloy α-PdH _n .     

Inhibition effect of phosphate on the crystal grain growth of nanosized titania

The inhibitory effect of phosphate on the crystal grain growth of nanosized titania during high temperature calcination was investigated. Nanosized titanium dioxide powders prepared by hydrolysis of titanium tetrachloride were soaked in phosphate solutions with different con-centrations. The obtained powders calcined at various temperatures were characterized by X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), and X-ray photoelectronic spectroscopy (XPS). The grain size of the samples without phosphate treatment in-creased quickly when calcined at high temperatures, while the grain size of the samples with phosphate modification increased slowly when calcined at the same temperature. This phenomenon implies that phosphate treatment plays an important role in inhibiting the crystal grain growth of titania. The possible mechanism of the inhibition effect of phosphate on titania is discussed.     

Investigation of reactions between lead/tin solder and palladium surface finishes

The role of palladium as a surface finish for the electronics industry was investigated. Of particular interest were the metallurgical phases that form during and following soldering operations of palladium thin films. The formation of PdSn₄ intermetallics on composite substrates (gold/palladium/nickel) with varying palladium chemistry and layer thickness were soldered at 220 °C and observed using scanning electron microscope combined with energy dispersive X-ray (SEM/EDX) analysis. Thin layers of palladium approximately 1 μm thick, combined with a fast dissolution rate also resulted in the formation of Ni₃Sn₄ intermetallics. The role of phosphorus in palladium thin films was also investigated. Its presence was found to increase the solubility of palladium in molten solder producing intermetallic crystals that are confined to the bulk. A thin gold layer, used to protect the palladium was found to dissolve rapidly into the solder and to redeposit, forming a thin layer just outside the PdSn₄ intermetallic structure.     

生物模板法结合溶胶-凝胶技术制备二氧化硅中空微球材料(英文)

生物模板法与溶胶凝胶技术的结合是实现无机中空微球材料快捷、高效制备的有效途径。本研究利用油菜花粉为模板,以正硅酸四乙酯为前驱体,通过溶胶-凝胶包裹的方法制备了二氧化硅中空微球。通过将二氧化硅溶胶吸附到花粉颗粒表面形成包裹层,再经过烧结处理将花粉模板去除的方法,可以方便地制备表面有一定特殊形貌的二氧化硅中空微球材料。利用扫描电子显微镜,电子能谱仪以及傅里叶变换红外光谱对花粉颗粒和所制备的二氧化硅中空微球进行表征。结果表明:利用花粉颗粒为模板,结合溶胶-凝胶方法可以成功制备具有特殊表面结构的无机中空微球材料,在这一过程中,物理吸附作用是主要的影响因素。     

ELECTROPLATED Zn-Ni-SiO2 COMPOSITE COATINGS TREATED WITH A SILANE COUPLING AGENT TO REPLACE CHROMATING

The fixing of a silane coupling agent to Zn-Ni-silica (SiO2) composite coatings was studied for the purpose of developing a coating process as an alternative to chromating. The corrosion resistance of Zn-Ni-silica composite coatings was remarkably improved by the silica nanoparticles in the composite, which were dispersed in the surface of this film. The silane coupling agent formed chemical bonds with the inorganic silica particles during the silane coupling treatment on these composite coatings. The treatment suppressed the formation of white corrosion products to the same extent as chromating, as measured in salt spray tests. It is concluded that treating Zn-Ni-silica composite coatings with silane coupling agents is a viable alternative technique to chromating.     

多孔钯块材的脉冲烧结制备及其气体载氘行为(英文)

钯材的高速载氘对金属-氢同位素系统和氢能应用领域的研究具有重要的意义.本文研究了以海绵钯粉为原料通过脉冲烧结制备多孔钯块材的新工艺,用SEM和XRD分析了制备的多孔钯块材的微观结构形貌和相组成,并进一步研究了多孔钯块材的气体载氘行为.结果表明,采用脉冲烧结工艺可制备出孔隙率为81.6%的纯净多孔钯块材,氘在该钯材中的初始载入速度较高但迅速降低,80 s内即可完成约90%氘的载入;载氘开始约10 s后,氘的载入速度下降到较低的水平并缓慢衰减.     

Synthesis and characterization of aluminum particles coated with uniform silica shell

The silica coated aluminum composite particles were prepared by hydrolysis-condensation polymerization of tetraethylorthosilicate（TEOS） on the surface of aluminum particle. The structure, morphology, and properties of the silica coated aluminum were studied. The peaks of Si-O-Si are presented in the Fourier transform infrared （FT-IR） spectrum of the composite particles. The thickness of the silica shell is about 80 nm according to the results of transmission electron microscopy（TEM） and laser particle size analysis, while the mean diameter of the aluminum particle is 7.13 μm. The mass fraction of silica in the sample was determined by fluorescent X-ray spectrometry（XRF）. Result of the thermogravimetric analysis（TGA） indicates that thermal stability of silica coated aluminum particles is better than that of pure aluminum particles at low temperature while more reactive at high temperature.