铷、铯钨青铜粉末及其透明隔热薄膜的研究

研究不同形貌的铷、铯钨青铜粉末及其薄膜的性能。通过水热反应制备棒状和片状的铷、铯钨青铜纳米粉末,并对粉末进行热处理,之后使用旋涂法在玻璃上制备钨青铜透明隔热薄膜。通过X射线衍射、扫描电镜、透射电镜等对粉末进行表征,并研究其光热性能。使用紫外可见近红外光谱分析钨青铜薄膜近红外屏蔽性能,并测试其隔热性能。结果表明,热处理后的钨青铜粉末具有优异的光热性能,具有光热治疗癌症的应用前景。相比于棒状,片状的铷、铯钨青铜薄膜具有更高的近红外屏蔽率,分别为95%和98.8%。使用片状铷、铯钨青铜薄膜的玻璃室内温度相比使用空白玻璃分别下降了9.4℃和8.5℃。综上,片状铷、铯钨青铜具有优异的近红外屏蔽性能,在节能和光热治疗领域具有巨大的应用前景。     

电子束焊接Ta—10W合金的机械性能研究

前言钽具有很高的熔点(2996℃),具备用于高温结构的潜力,它的使用温度仅低于钨,而且,钽有良好的加工性能和焊接性能。就塑性、加工性和可焊性而言钽比钨要优越的多。为充分发挥这些优点,同时提高钽的高温强度,国内外,对钽合金的发展和研     

钽粉的低温掺氮及氮在钽中的分布

叙述了钽粉在镁还原脱氧后引入氮气对钽粉进行掺氮,在200℃以下0．1MPa以上,保温时间大于2h时,得到的钽粉粒子间含氮差别率在20％以下。用俄歇电子能谱仪对渗氮的钽表面进行元素分布研究,发现氮在钽中分布是不均匀的,对于每个粒子也是外表面氮浓度大于钽内部的氮浓度。     

钽及钽合金的制备方法和力学性能研究

钽是过渡族金属元素,其强度低、塑性极佳。钽-钨合金的熔点高、热强性和加工性能良好,是重要的结构材料和功能材料。制备钽和钽合金的方法有粉末冶金法和电子束熔炼法等。简要介绍了钽和不同含钨量的钽-钨合金的力学性能、化学性能、冷变形加工(主要是冷轧)性能、轧制后的退火工艺以及应用等。     

碱钨青铜粉体的溶胶-凝胶法合成与表征

采用溶胶-凝胶法合成了碱钨青铜(M_xWO_3,M=Cs,Rb中的1种或2种)粉体,探究了铯、铷分别单掺杂和铯、铷共掺杂对钨青铜粉体晶相、形貌的影响。利用X射线衍射仪(XRD)、X射线能谱仪(EDS)、扫描电子显微镜(SEM)、X射线光电子能谱仪(XPS)、紫外可见近红外光谱(UV-Vis-NIR)、隔热膜温度测试仪对所合成碱钨青铜粉体的物相、形貌、光学性能和隔热性能进行了表征。结果表明:溶胶-凝胶法所合成的碱钨青铜粉体结晶性较好、粒径较小;Cs、Rb共掺杂的透明绝热指数K=157.34比Rb单掺杂提高了23.92,改善了Cs单掺杂在1076 nm处透过率突变的情况;Cs、Rb共掺杂的温差(与起始温度相比)为4.9℃,比Rb单掺杂的温差下降了5.7℃。     

Ti／IrO2-Ta2O5阳极的制备及其析氧电催化性能研究

通过热氧化技术在500℃条件下制备了一系列Ti／IrO2-Ta2O5阳极。采用线性扫描和循环伏安技术分析了不同铱钽比阳极涂层的析氧电流、电位和伏安电荷的变化规律，并结合扫描电镜（SEM）及X射线衍射（XRD）技术研究了Ti／IrO2-Ta2O5阳极的表面形貌、组成、结构对析氧电催化性能的影响。研究表明，在IrO2-Ta2O5涂层中，铱钽由于存在一定的互溶度而形成固溶体结构，铱钽互溶度与涂层中铱钽比有关且影响IrO2晶胞的大小。随着涂层组元IrO2含量的增加，涂层表面细小的IrO2晶体聚集体增多，析氧电催化活性增强；但当IrO2含量过多时，涂层附着力的下降和机械强度的降低对析氧电催化性能产生负面影响。IrO2-Ta2O5涂层的活性表面积不仅取决于活性组元IrO2的含量，还与涂层的结构有关。适宜的铱钽比才具有最大的催化活性。其原因可能在于涂层中加入的适量惰性元素钽与IrO2晶胞形成部分固溶体结构，增强了涂层附着力与机械强度，同时形成了多裂纹的网状表面结构，增加了涂层活性表面积，提高了电极的析氧电催化活性与电解稳定性。     

纳米碳化钽对SPS烧结钨显微结构的影响

通过放电等离子体烧结(SPS)方法在1700℃下制备纳米碳化钽(TaC)弥散强化钨块,研究钨粉原始粉末粒度大小和添加碳化钽的量对烧结钨块微观组织的影响。结果表明:不同粒度钨粉(30nm、200nm和3μm)制备的钨块,烧结后的粒径随原始粉末粒度的增大而增大,3μm钨粉烧结后的晶粒平均直径为22.19μm;同一种粒度钨粉(如200nm)中分别添加质量分数为0%,1%,2%和4%的碳化钽,烧结后钨晶粒的平均直径随碳化钽添加量的增加而减小,加入量为4%时晶粒平均直径为5.91μm。通过SEM分析可以看出,碳化钽在烧结钨中是以球形状态存在的。从断口可以看出,纯钨烧结体为穿晶断裂,加入碳化钽的钨烧结体为晶间断裂。     

化学共沉淀法制备钨铜合金

首先采用化学共沉淀法制备钨铜复合氧化物粉末,再用氢还原得到纳米级钨铜复合粉末,经成形和烧结得到超细弥散分布钨铜合金.研究结果表明,采用化学共沉淀法结合氢还原工艺制备的W-20%Cu纳米复合粉,W颗粒粒度为30～50 nm,形状呈多边形,Cu相均匀分布在W相之间将W颗粒粘结.所制得的钨铜复合粉表现出高的烧结活性,经1250℃烧结其相对密度达到99.7%,热导率达到223.1 W/m·K,导电性、抗弯强度以及硬度等性能也比传统产品有大幅度提高.     

Pt-WC/Mnt三元纳米复合材料的制备及其电催化性能

以剥离后的蒙脱石(Mnt)片层为载体、六氯化钨(WCl6)为钨源,通过浸渍负载及原位还原碳化获得了碳化钨(WC)与蒙脱石(Mnt)纳米复合材料,然后将氯铂酸(H2PtCl6)通过浸渍负载于复合材料上,并在氢气(H2)中还原得到Pt-WC/Mnt三元纳米复合催化材料。采用X射线粉末衍射和透射电子显微镜对三元纳米复合催化材料的物相、形貌和结构进行表征,采用三电极体系和循环伏安法测试了样品的电催化性能。结果表明:样品物相主要为WO3和WC,蒙脱石片层结构明显,铂(Pt)纳米粒子均匀分布于WC/Mnt复合材料的外表面。Pt-WC/Mnt三元纳米复合材料对甲醇电催化氧化具有较高的催化活性,并且在酸碱体系中均具有良好的稳定性。     

钨的还原机理(述评Ⅱ)

本研究的目的是:探讨氢还原钨氧化物成钨粉的机理,澄清一般文献中一些矛盾的说法。试验条件近于专业厂生产条件。当还原温度为750℃和1000℃时,中断还原工艺,中间出现的氧化物彼此分开,且各具特色。热力学计算证实了这些观点,阐述了钨经由气相迁移的机理。     

Electrocatalytic properties of electrodeposited Ni–Mn–S system in alkaline electrolytes

Abstract

Ni–Mn–S was electrodeposited on mild steel from sulphate–thiocyanate baths. The resultant materials were evaluated for electrocatalytic activity towards hydrogen evolution reaction in 30 wt-% KOH. Incorporation of sulphur in Ni–Mn improves the electrocatalytic activity giving a sizeable increase in exchange current density j ₀. In Ni–Mn the hydrogen evolution reaction is through a Volmer–Tafel mechanism whereas in the Ni–Mn–S system follows a Tafel mechanism. The influence of deposition current density (CD) was investigated. Electrocatalytic activity increased with increase in the deposition CD and was maximum in samples deposited at 80 mA cm^?2.     

Electrodeposition, characterization and long term stability of NiW and NiWZn coatings on copper substrate in alkaline solution

This paper describes the electrodeposition of Ni, NiW and NiWZn coatings onto copper surfaces from electrolyte solutions containing Na₃C₆H₅O₇, Na₂WO₄, NiSO₄ and ZnSO₄. The electrocatalytic effects of electrodeposited coatings were investigated for hydrogen evolution reactions in 1 M NaOH solution. Surface characterization studies were carried out by energy dispersive X-ray spectroscopy, scanning electron microscopy, atomic force microscopy and cross-section analysis. The effect of operating conditions on the chemical composition, microstructure and electrocatalytic properties of Ni-W coatings was studied. The Zn ions were used to improve the active surface area and catalytic activity of the electrodeposited surface. The electrocatalytic activity of NiW and NiWZn coated electrodes for the hydrogen evolution reaction in alkaline solution was compared with that of an electrodeposited Ni electrode and copper substrate by using cathodic polarization curves and electrochemical impedance spectroscopy techniques over 96 h of electrolysis. The results proved that the NiWZn coated electrode showed better electrocatalytic activity and durability than bare Cu, Ni and NiW coatings.     

Engineered Three-Dimensional Electrodes by HVOF Process for Hydrogen Production

High velocity oxy-fuel process was used to prepare nickel electrode coatings for hydrogen production by alkaline water electrolysis. To further increase the active surface area of the electrodes, pyramidal fin arrays with two different sizes were deposited on the top surface of the electrodes using mesh screen masks. The surface microstructure, topology and roughness of the coatings were studied using scanning electron microscope, optical microscopy and confocal laser scanning microscopy. Steady-state polarization curves were used to evaluate the electrocatalytic activity of the electrodes. The performance of the electrodes coated using mesh outperformed the electrode deposited without using mesh. In addition, the electrode that was coated using the coarse mesh was characterized with the highest activity with the exchange current density and overpotential values of 9.3 × 10^?3 A/cm² and ?306 mV, respectively. Formation of different roughness levels due to the combination of normal and off-normal impact of the coating particles on the surface of the fins was identified as the main factor for the increased activity of this electrode toward the hydrogen evolution reaction.     

Hydrogen evolution on microstructured polypyrrole films modified with nickel

Enhancement of electrocatalytic activity of polypyrrole (PPy) for hydrogen evolution reaction (HER) has been carried out by the deposition of Ni layer of different thickness. By formation of three-dimensional microcontainers on the PPy surface an increase in surface area of the PPy/Ni catalytic layer could be obtained, providing an increased overall electrocatalytic activity. The PPy/Ni layers offer a significantly higher electrocatalytic activity in the HER than PPy or Ni electrode. The best catalytic activity was detected for composite PPy/Ni electrodes produced by electrodeposition of Ni on pre-deposited microstructured PPy substrate in 2 cycles.     

钌基双金属聚酞菁电催化析氧性能研究

电解水制氢阳极电催化析氧反应(OER)动力学缓慢，可采用阳极OER催化剂提高。采用简单的低温热解法制备出钌(Ru)、铁钌(Fe Ru)和钴钌(CoRu)复合聚酞菁等一系列催化剂，通过X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)对催化剂的形貌和结构进行表征，并采用电化学工作站对催化剂的析氧等电催化性能进行测试。测试结果表明，催化剂Fe₃Ru-PPc在碱性环境下电流密度为50 mA·cm^-2时的过电位为303.5 mV，塔菲尔斜率仅为42.3 mV·dec^-1，相比于商业Ir O₂具有更好的OER活性。对其结构分析可知，Fe与Ru的结合使得材料的电子结构发生变化，促进了OER的动力学过程，从而使其具有更好的OER活性和载流子迁移率。     

Electrolytic Synthesis of Ni-W-MWCNT Composite Coating for Alkaline Hydrogen Evolution Reaction

Nickel–tungsten multi-walled carbon nanotube (Ni-W-MWCNT) composite films were fabricated by an electrodeposition technique, and their electrocatalytic activity toward hydrogen evolution reaction (HER) was studied. Ni-W-MWCNT composite films with a homogeneous dispersion of MWCNTs were deposited from an optimal Ni-W plating bath containing functionalized MWCNTs, under galvanostatic condition. The presence of functionalized MWCNT was found to enhance the induced codeposition of the reluctant metal W and resulted in a W-rich composite coating with improved properties. The electrocatalytic behaviors of Ni-W-MWCNT composite coating toward HER were studied by cyclic voltammetry (CV) and chronopotentiometry techniques in 1.0 M KOH medium. Further, Tafel polarization and electrochemical impedance spectroscopy (EIS) studies were carried out to establish the kinetics of HER on the alloy and composite electrodes. The experimental results revealed that the addition of MWCNTs (having a diameter of around 10-15 nm) into the alloy plating bath has a significant effect on the electrocatalytic behavior of Ni-W alloy deposit. The Ni-W-MWCNT composite coating was found to show better HER activity than the conventional Ni-W alloy coating. The enhanced electrocatalytic activity of Ni-W-MWCNT composite coating is attributed to the MWCNT intersticed in the deposit matrix, evidenced by surface morphology, composition and phase structure of the coating through SEM, EDS and XRD analyses, respectively.     

Preparation and electrocatalytic properties of tungsten carbide electrocatalysts

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Activation in situ de la cathode de nickel par le molybdate de sodium

In situ activation of a solid nickel cathode was achieved by adding sodium molybdate during the electrolysis of an aqueous solution of 30 wt.% KOH at 70 °C. The resulting improvement in the electrocatalytic activity with regard to the hydrogen evolution reaction reaches a maximum when 4 × 10^-3 M of molybdenum is added. This is attributed to the formation of a spongy deposit on the electrode surface resulting from the deposition of molybdenum and iron. A continuous growth of nodules on the surface is observed while the current, for a constant applied potential of -1.5 V_Hg/HgO increases linearly with the logarithm of time, the slope being 230 mA cm^-2 (decade time)^-1 for t < 50 000 s.     

Vacuum plasma spraying of high-performance electrodes for alkaline water electrolysis

Electrode coatings for advanced alkaline water electrolysis were produced by applying the vacuum plasma spraying (VPS) process. The characteristics of the used VPS equipment that were essential for the development of effective electrocatalytic electrode layers are presented. Molybdenum-containing Raney nickel coatings were applied for cathodic hydrogen evolution, and Raney nickel/Co₃O₄ matrix composite layers were developed for the anodic oxygen evolution reaction. For the preparation of Raney nickel coatings, a precursor alloy such as Ni-Al was sprayed that had to be leached subsequently in caustic solution to remove the aluminum content, forming a porous, high-surface-area nickel layer. The spray powders and the resulting VPS layers were studied by metallography, x-ray diffraction (XRD), and scanning electron microscopy/energy dispersive analysis by x-ray (SEM/EDX). For spraying of thermally sensitive oxide electrocatalysts (e.g., Co₃O₄), special process conditions involving plasma-chemical effects (reactive plasma spraying) had to be developed. The electrocatalytic activity of the electrode coatings was investigated by performing polarization curves free of ohmic losses (IR-free) and long-term tests under conditions of continuous and intermittent operation, which showed excellent electrochemical properties.     

Synthesis of effective electrocatalyst for water splitting application from simple Cu-Ni bath

Electrocatalytically active Cu-Ni alloy coatings have been developed from a simple electrolyte having only Cu⁺² and Ni⁺² ions, without the use of any additive. Electrocatalytic character of the coatings was tested for their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH medium, alongside with their corrosion behaviours. Cyclic voltammetry and chronopotentio-metry study revealed that the deposition current density has a prominent role on the alkaline water splitting behaviour of the coatings, depending on their phase structure, composition and surface morphology. It was found that the c.d. has an inverse dependence on HER and OER. The Cu-Ni alloy coatings developed, respectively at 3.0 and 4.0 A dm^–2, were found to be the best coatings for HER and OER, depending on the surface morphology. The electrocatalytic activity of Cu-Ni alloy coating for HER, deposited at 3.0 A dm^–2 (optimal), was further improved through electrochemical dissolution of the as-deposited coating. The increase in the electrocatalytic activity for HER has been attributed to the enhancement in the exposed surface area of Ni active sites due to the leaching of Cu from the alloy matrices, evidenced by the energy-dispersive X-ray spectroscopy and scanning electron microscopy. The dependencies of HER and OER on to the surface of Cu-Ni alloy coatings were analysed in terms of deposition c.d. of the coatings, and the results are discussed.