脉冲电流密度对Ni-W合金镀层耐蚀性的影响

采用脉冲电沉积方法在黄铜基体上制备Ni-W合金镀层。研究了脉冲电流密度对镀层的表面形貌、微观结构及耐蚀性的影响。当脉冲电流密度小于15A/dm2时,Ni-W合金镀层主要由纳米晶和非晶的混合物构成;当脉冲电流密度大于20A/dm2时,镀层转变为完全非晶。脉冲电流密度为20A/dm2时制备的NiW合金镀层在质量分数为3.5%的NaCl溶液中的耐蚀性最好,自腐蚀电流密度最小,约为2.532μA/cm2;自腐蚀电位最正,约为-327mV;电荷转移电阻最大,约为5 412Ω/cm2。所有Ni-W合金镀层的表面均致密平整,W的质量分数约为(40.5±3.5)%。     

电沉积非晶合金的形成条件

通过对Fe-W、Ni-W等9种非晶合金电沉积过程的分析,总结了电沉积条件(镀液组成、电流密度、镀液温度、pH)及镀层组成对镀层结构的影响,认为电沉积条件直接影响镀层中添加元素的含量,间接影响镀层结构。添加元素及其含量才是形成非晶镀层的决定性因素。     

Ni-W-Fe-P四元合金镀层在酸碱盐溶液中的腐蚀行为

在Ni-W-P合金镀液中加入硫酸亚铁,并通过适当的工艺在Q235钢表面制备了Ni-W-FeP四元合金镀层。采用扫描电子显微镜观察了镀层的表面形貌,通过能谱仪测试了镀层中各元素的质量分数,通过X射线衍射仪分析了镀层的结构,并借助极化曲线和交流阻抗曲线方法考察了镀层和Q235钢在体积分数为5%的H2SO4溶液、质量分数为5%的NaOH溶液和质量分数为3.5%的NaCl溶液中的腐蚀行为。结果表明:Ni-W-Fe-P合金镀层为非晶态结构,表面较为均匀,W和Fe的质量分数分别约为2.71%和1.56%。在上述三种腐蚀介质中,镀层的耐蚀性远优于Q235钢的,主要是镀层在酸、碱、盐介质中表面形成钝化膜所致。     

脉冲频率对Ni-W合金镀层耐蚀性的影响

采用脉冲电沉积方法在黄铜基体上制备出Ni-W合金镀层。研究不同脉冲频率(0.5~20.0kHz)对镀层表面形貌、微观结构、硬度及耐蚀性的影响。所有Ni-W合金镀层的表面均致密平整,W的质量分数为42.41%~48.92%。脉冲频率为5.0kHz时制备的Ni-W合金镀层在3.5%的NaCl溶液中的耐蚀性最好,自腐蚀电流密度为2.532μA/cm2,自腐蚀电位为-327mV。     

锡钴合金镀层表面膜的X光电子能谱研究

从焦磷酸盐型槽液中电沉积Sn-Co合金镀层(Sn 69.99原子%,Co 30.01原子%),用X光电子能谱(XPS)研究镀层在空气中形成的氧化膜与在铬酸盐溶液中形成的钝化膜的组成.发现未经钝化的氧化膜可能是由CO(OH)_2、SnO和SnP_2·YH_2O组成的水合复合氧化物,而钝化后的表面膜可能是由CoO、SnO、Cr_2O_3和CrO_3·XH_2O组成的水合复合氧化物.对峰值变化研究的结果说明,钝化后的表面膜比未钝化的表面膜薄.     

化学镀镍磷合金镀层碱性无铬钝化膜的耐蚀性研究

为了解决六价铬钝化工艺的毒性问题,采用碱性无铬钝化工艺对A3钢上化学镀Ni–P合金镀层进行钝化处理,在镀层表面获得了抗氧化性与耐蚀性良好的钼酸盐钝化膜。研究了钝化液组分(包括碳酸钠和钼酸钠)的质量浓度以及钝化温度对镀层耐硝酸点滴腐蚀时间的影响,获得了最佳的钝化工艺:NaOH 10 g/L,Na2CO3 4.0 g/L,钼酸钠40.0 g/L,复合添加剂(四硼酸钠与亚硝酸钠组成的复合缓冲体系)5 g/L,温度60°C,时间15 min。通过扫描电镜(SEM)和电化学测试,对比研究了钝化前、后Ni–P合金镀层的表面形貌及耐蚀性能,采用X射线光电子能谱仪(XPS)分析了最佳工艺得到的钝化膜的组成。经最佳钝化工艺处理得到的钝化膜无色透明,由Ni、P、O、Mo等元素组成。钝化后,Ni–P合金镀层在3.5%Na Cl溶液(p H=6.8)中的电荷转移电阻由钝化前的11.6 k?·cm2增大至448.2 k?·cm2,耐硝酸点滴腐蚀时间提高了60倍以上,耐蚀性明显提高。     

电流密度对Ni-W合金镀层性能的影响

采用脉冲电沉积技术,通过改变电流密度制备出非晶Ni-W合金镀层。利用XRD对镀层的晶粒尺寸和相结构进行表征,利用电化学工作站测试镀层在3.5%的NaCl溶液中的极化曲线和交流阻抗谱。结果表明:镀层的非晶程度随电流密度的增大而增大。当电流密度为15A/dm~2时,镀层的耐蚀性最好,自腐蚀电位和自腐蚀电流密度分别为-288mV和49.4μA/cm~2。     

Zn-Fe合金镀层黑色钝化工艺研究Ⅱ--工艺条件的优化及钝化膜耐蚀性能的研究

在钝化膜组成成分研究的基础上，详细研究了工艺条件对Zn-Fe合金钝化膜耐蚀性的影响，从而得到了最佳的工艺条件。对Zn-Fe合金钝化膜性能进行了测试，并采用5％NaCl中性溶液浸泡试验对Zn镀层、Zn-Fe合金镀层及Zn-Fe-TiO2复合镀层黑色钝化膜的耐蚀性进行了比较。结果表明，经黑色钝化后，Zn-Fe合金镀层及Zn-Fe-TiO2复合镀层的耐蚀性都有很大的提高；Zn-Fe合金镀层的耐蚀性是纯锌镀层的3倍多，而Zn-Fe-TiO2复合镀层的耐蚀性是Zn-Fe合金镀层的2倍多，是纯锌镀层的5倍左右。     

热浸锌-5%铝合金镀层硅酸盐钝化工艺

采用含5%(质量分数)SiO_2的硅酸盐溶液对热浸Zn-5%Al合金镀层进行钝化,研究了溶液模数(即SiO_2与Na_2O的摩尔比)、钝化温度、时间以及烘干温度对钝化膜耐中性盐雾腐蚀性能的影响。硅酸盐的最优工艺条件为:模数4.0,钝化温度80℃,钝化时间60s,烘干温度125℃。采用扫描电镜(SEM)和电化学阻抗谱(EIS)表征了最优工艺条件下所得膜层的表面形貌和耐蚀性。在最优工艺下所得硅酸盐转化膜均匀、完整、透明,能有效改善热浸Zn-5%Al合金镀层的耐蚀性。     

脉冲占空比对Ni-W合金镀层耐蚀性的影响

采用脉冲电沉积方法在纯铜基体上制备出Ni-W合金镀层。研究了脉冲占空比(30%~60%)对镀层表面形貌、结构、成分和耐蚀性的影响。结果表明:制得的Ni-W合金镀层表面致密、平整,W的质量分数在46.84%~49.24%范围内窄幅波动,具有非晶态结构。脉冲占空比为50%时制得的镀层的耐蚀性最好。在3.5%的NaCl溶液中,自腐蚀电位较正,自腐蚀电流密度最小,电荷转移电阻最大。     

Dual-grained (Ti,W)C–Ni cermets by two-step carbonization: Hot isotropic press sintering of NiTiW alloys and colloidal graphite

Reactive sintering of crushed metals and carbon is advantageous for preparing toughened complete solid-solution cermets (CSCs). Here, dual-grained (Ti_0.6, W_0.4)C–18Ni cermets were prepared using a two-step carbonization method. High-energy milling of Ni–Ti–W–C (Ni(Ti_0.6, W_0.4)₄C) mixture afforded NiTiW solid solution, which was then transformed into Ni₆W₆C by heating at 1250°C. Twinned (Ti, W)C platelets were formed by the carbonization of Ni₂W₄C during liquid sintering. W atoms that accumulated in the (111) planes of TiC promoted the {111} twin formation, leading to sandwich-type (Ti, W)C platelets. Dense (Ti_0.6, W_0.4)C–18Ni cermets were obtained by hot isostatic press sintering in Ar with satisfactory Hv of 12.8 ± 0.2 GPa, high strength of 1960 ± 84 MPa and toughness of 15.80 ± 0.6 MPa·m^1/2. A higher sintering temperature or graphite content accelerated the carbonization, resulting in coarser platelets with decreased aspect ratio. This study provides a new approach to modify the microstructure of CSCs and a method for preparing dual-grained cermets.     

Fabrication and characterization of medium-entropy carbide ceramics in low temperature sintering

The medium-entropy carbide (W,Ti,V)C_0.8 ceramics were prepared by sparking plasma sintering at temperatures between 1400 and 1700°C. The effects of sintering temperature on the microstructure and mechanical properties of the medium-entropy carbide (W,Ti,V)C_0.8 ceramics were investigated. X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer were used to confirm the formation of single-phase face-centered cubic (FCC) solid solution of the medium-entropy carbide (W,Ti,V)C_0.8 ceramics prepared at a sintering temperature of 1600°C. It was found that the mechanical properties of the material were improved by solid solution strengthening during the formation of single-phase FCC solid solution, and the best overall performance of the medium-entropy carbide (W,Ti,V)C_0.8 ceramics was achieved at 1600°C, when the hardness value was 22.3 ± 1.8 GPa, the fracture toughness was 5.7 ± 0.8 MPa·m^1/2, the flexural strength was 605 ± 4 MPa, and the compressive strength was 1.84 GPa. Most importantly, the addition of TiC_0.4 promoted the diffusion among the elements of the medium-entropy carbide (W,Ti,V)C_0.8 ceramics, which contributed to the formation of single-phase FCC solid solution and significantly reduced the sintering temperature of the medium-entropy carbide (W,Ti,V)C_0.8 ceramics due to the effect of vacancies. This study provides a new idea for the preparation of medium-entropy carbide ceramics.     

Isotropic magnetization response of electrodeposited nanocrystalline Ni–W alloy nanowire arrays

Isotropic magnetization response was demonstrated in electrodeposited nanocrystalline Ni–15 % W alloy nanowire arrays, which can be applied to nanoscale magnetic field sensors. The Ni–W alloy nanowire arrays were electrochemically synthesized on a nanochannel template electrode from an aqueous electrolytic solution. X-ray and electron diffraction patterns revealed that Ni–15 % W alloy deposits were composed of ultrafine crystal grains with a supersaturated solid solution phase. The magnetization of the Ni–15 % W alloy thin films reached saturation at around 2.5 kOe in a perpendicular direction to the film plane, whereas the pure Ni thin films hardly magnetized in the perpendicular direction. On the contrary, Ni–15 % W alloy nanowire arrays were easily magnetized, and reach saturation at around 1.0 kOe, even in a perpendicular direction to the array film plane that corresponds to the long-axis direction of the alloy nanowires.     

二水合氯化铜与对甲基苯胺固相配位反应的热化学研究

用新型的具有恒定温度环境的反应热量计,以一定比例的４ ｍ ｏｌ· Ｌ－ １ Ｈ Ｃｌ与无水乙醇混合溶液作为量热溶剂,分别测定了反应物和产物的溶解焓,设计了一个新的热化学循环,得到了固相配位反应的反应焓△ｒ Ｈθｍ ＝ ５４．７８０ ｋ Ｊ·ｍ ｏｌ－ １,估算了配合物 Ｃｕ Ｃｌ２·（ Ｃ７ Ｈ９ Ｎ）２ 标准生成焓△ｆ Ｈθｍ ＝ － ３４８．８０２ ｋ Ｊ·ｍ ｏｌ－ １。     

Glucose hydrogenation on Co–B amorphous alloy catalysts and the promoting effect of metal additives

Two kinds of ultrafine Co–B amorphous alloy catalysts, denoted as P‐1 Co–B and P‐2W Co–B, were prepared by chemical reduction with borohydride in aqueous or 50% (v/v) ethanol/water solution, respectively. In comparison with the corresponding Co‐based crystalline catalysts and Ni‐based catalysts, these catalysts exhibited higher activity during the liquid phase glucose hydrogenation, possibly due to the unique amorphous characteristics and the lower d‐band electron density, which was favorable for hydrogen dissociative chemisorption. Addition of Cr‐, Mo‐ or W‐promoters could further increase the conversion of Co–B amorphous catalyst, which was mainly attributed to the dispersion effect of promoters and the adsorption and polarization of carbonyl groups by these promoters. The different effects of W‐ from Cr‐ and Mo‐promoters on the conversion were observed and are discussed. © 2001 Society of Chemical Industry     

Characterization of calcination temperature on a Ni-substituted lanthanum-strontium-zirconate pyrochlore

A lanthanum strontium zirconate pyrochlore material was substituted with Ni, and the effect of calcination temperature on important catalytic properties was evaluated. The introduction of the Ni into the pyrochlore decreased the BET surface as compared to non-Ni containing materials due to enhanced sintering. The presence of Ni dispersed in the precursor material produced oxygen vacancies which improved solid state diffusion of the pyrochlore cations, and lowered the onset of crystallization by almost 100 °C compared to the baseline material without Ni. Furthermore, only a small amount of Ni was found to be soluble in the structure up to 1000 °C, at which point almost no Ni occupies lattice positions in the pyrochlore crystal structure. The Ni was found to exsolve to the surface and grain boundary regions of the pyrochlore and reside on the surface as NiO. Heating to temperatures greater than 800 °C also led to the formation of a La₂ZrNiO₆ perovskite phase. Surface composition, as measured by XPS, showed a decrease in Ni concentration at the surface as the calcination temperature was increased. This was likely due to the formation of larger Ni particles with increasing temperature, as well as the migration of the Ni into the bulk through the formation of the La₂ZrNiO₆ phase. Temperature programmed reduction results showed that increasing the calcination temperature resulted in particle growth of the NiO and a weaker interaction with the pyrochlore surface, which made the NiO more reducible at lower temperatures. Multiple reduction-oxidation TPR/TPO cycles showed that the results were not reproducible from cycle-to-cycle for the lowest calcination temperature material (700 °C) due to an amorphous La-Zr-O phase initially present. However, materials calcined at all other temperatures showed an almost identical TPR/TPR profiles after the second cycle.     

微乳状液体系应用研究进展

综述了微乳状液体系在医药、化学化工等领域的应用研究现状。着重介绍了微乳超声造影剂和微乳燃料等。     

Facile preparation of asymmetric Ni/PVC film with controlled structure: Application as a high‐performance EMI shielding material

Controlling the spatial configuration of conductive fillers in thin composites by a facile strategy is critical to widely commercial use these materials for electromagnetic interference (EMI) shielding applications. In this work, a series of free‐standing thin Ni/polyvinyl chloride (PVC) films with the same composition just systematically varied Ni particles dispersion states was prepared by solution casting method. The relationships between the structure and properties were also investigated. Ni particles motion was governed by evaporation and sedimentation during solvent evaporation with the presence of soluble PVC influencing the casting solution viscosity. The experimental results fit the 1D model. In dilute casting system, the effective concentration of Ni particles in the lower part of the film was significantly enhanced and a dense, closed packed conductive network was formed. This special distribution of Ni particles was found to play a key role in the corresponding properties. Compared to the uniform film, the film which was fabricated from the casting solution containing 0.03 g/mL PVC, exhibited much better electrical conductivity and EMI shielding performance. Furthermore, the detailed study shows that the obtained thin film exhibited excellent EMI SE values per unit film thickness of 200 dB/mm. Meanwhile, the resultant films possessed thermal conductivity of 0.32～0.59 W/(m·K) depended on whether a Ni continuous network formation throughout the whole film in the temperature range of 30～60°C. Our study results pave thus the way for scalable fabrication of substrate‐free systems that have advantages in multifunctional complex devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42560.     

Study on porous silk fibroin materials. I. Fine structure of freeze dried silk fibroin

Silk fibroin solution was prepared by dissolving the silk fibroin in triad solvent CaCl₂ · CH₃CH₂OH · H₂O. In this article we tested and analyzed the state of frozen silk fibroin solution and fine structure of freeze dried porous silk fibroin materials. The results indicated that the glass transition temperature of frozen silk fibroin solution ranges from −34 to −20°C, and the initial melting temperature of ice in frozen solution is about −8.5°C. When porous silk fibroin materials are prepared by means of freeze drying, if freezing temperature is below −20°C, the structure of silk fibroin is mainly amorphous with a little silk II crystal structure, and if freezing temperature is above −20°C, quite a lot of silk I crystal structure forms. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2185–2191, 2001     

Analysis of pressureless sintering of titanium diboride ceramics with nickel,cobalt, and tungsten carbide additives

The mechanisms during pressureless sintering of TiB₂ with 0–50 wt.% Ni were analysed by differential dilatometry after mechanical alloying with hard metal beads. Three main stages of sintering could be identified by means of the changing dilatation rate. The first interval (200–600 °C) comprises reactions with oxygen and moisture (H₃BO₃, B₂O₃ formation, melting, evaporation). The second stage (600–700 °C) is governed by solid state sintering and reactions of Ni and/or Co with TiB₂ yielding Ni₃B, Ni₂B, the corresponding Co-compounds and the ternary ω-phase of W₂NiB₂-type. The third main shrinkage interval is due to liquid phase sintering (987–1640 °C) and is accompanied by a significant weight-loss. Both precipitation of ω-phase as well as a (Ti,W)B₂ solid solution in form of a core-shell structure are responsible for a grain growth retardation and the homogeneous microstructure. The results explain well all features reported in the corresponding literature while encountering the role of WC, too.