介孔结构空心球状WC粉体催化剂的制备与表征

以偏钨酸铵为钨源, CO为还原性气体和碳源, 采用喷雾干燥微球化处理—气固反应法制备了具有介孔结构空心球状的WC粉体. 采用XRD, SEM, EDS和TG-DTA等分析手段对样品的形貌、物相组成、化学成分以及在空气中的热稳定性进行了表征. 结果表明, 碳化钨粉体为缺碳含氧的WC相, 化学成分为W, C, O, W与C的原子比接近1∶1; 碳化钨颗粒为分散性良好的空心球状, 表面具有介孔结构; TG-DTA曲线表明, 样品在空气中具有良好的热稳定性.     

Pt/WC/TiO2催化剂的制备及其电催化性能研究

以TiO2为载体制备了Pt/WC/TiO2三元复合催化剂,并由XRD、SEM和TEM等表征催化剂样品的形貌和结构特征.用循环伏安法测定了三元复合催化剂在酸性条件下对甲醇氧化的电催化性能,并将其与二元复合催化剂Pt/TiO2和Pt/WC的电催化性能进行比较.结果表明：三元复合催化剂具有更好的催化活性.进一步研究了二氧化钛晶相对Pt/WC/TiO2催化剂电催化活性的影响.     

聚苯胺/碳化钨导电复合材料的合成

以苯胺和过硫酸胺为原料,采用原位聚合方法合成了聚苯胺/碳化钨(PANI/WC)导电复合材料。研究了反应体系中碳化钨的含量对复合材料电导率的影响,确定了较佳的聚合条件,并且通过FT-IR、XRD、XPS和DSC-TGA等手段对复合材料的结构和性能进行了表征和分析。结果表明:碳化钨(WC)的加入提高了聚苯胺的电子导电性能,复合材料中聚苯胺组分为无定型,WC的晶型在反应前后并未发生变化,复合材料的热稳定性好并且质子化程度更高。     

片层WC/C的原位合成及其在甲醇氧化中的应用

以片层二硫化钨(WS2)为前驱体,氯化钠(Na Cl)为介质,CO为气体碳源,采用程序升温法一步合成片层碳化钨/碳复合材料(WC/C)。通过X射线衍射(XRD),X射线近边吸收谱(XANES)和扫描电镜(SEM)等一系列手段对样品的化学组成、形貌、结构等进行表征。研究发现,在高温渗碳过程中,不仅利用WS2的片层结构和Na Cl的锚定作用合成了具有薄层孔洞的WC,而且Na Cl和WS2金属面对碳膜生长的催化作用使WC表面覆有原位生长的碳膜,为电子传输提供了有效通道。将该材料作为载体材料进行电化学性能测试,结果表明:负载少量Pt后制得的Pt/WC/C电催化剂,在甲醇氧化反应(MOR)中表现出良好的电催化活性、稳定性及优异的抗CO中毒能力。     

微波合成Pt/WC催化剂及其对甲醇的电催化性能

分别采用微波加热乙二醇还原法(MW)和浸渍还原法(IR)制备以碳化钨(WC)为载体的Pt/WC催化剂, 并分别标记为: MW-Pt/WC及IR-Pt/WC. 用XRD、SEM对两种方法制备的复合材料的结构与形貌进行表征. 循环伏安测试结果表明MW-Pt/WC催化剂在酸性条件下的甲醇氧化性能比IR-Pt/WC催化剂更优, 表现在同一电位下MW-Pt/WC催化剂具有更高的电流且其氧化起始电位负移约30 mV, 还具有更大的电化学比表面积. 此外计时电流法实验结果表明MW-Pt/WC催化剂的稳定性高于IR-Pt/WC催化剂.     

Ion‐beam synthesis of 3C‐SiC surface layers on silicon

The attempt to grow 3C‐SiC thin films on silicon substrates has become an area of significant scientific interest, largely as a consequence of the impressive electrical properties that this polytype displays. In this paper, we have utilized low‐energy (20 keV) high‐fluence carbon implantation and a subsequent annealing step to form layers of 3C‐SiC directly on a silicon surface, and have investigated the effect of implantation fluence on the resultant materials properties. The quality of the Si/SiC interface is shown to be highly fluence‐dependent, with the formation of voids decreasing significantly with increased fluence. The conversion of carbon into 3C‐SiC is found to be most efficient at near‐stoichiometric concentrations, while at higher implantation fluences clusters of excess carbon are discovered to form within the silicon and to diffuse to the surface of the grown 3C‐SiC layer upon annealing. Copyright © 2011 John Wiley & Sons, Ltd.     

Non‐hydrogenated amorphous germanium carbide with adjustable microstructure and properties: a potential anti‐reflection and protective coating for infrared windows

Amorphous non‐hydrogenated germanium carbide (a‐Ge_1?xC_x) films have been deposited using magnetron co‐sputtering technique by varying the sputtering power of germanium target (P_Ge). The effects of P_Ge on composition and structure of the a‐Ge_1?xC_x films have been analyzed. The FTIR spectrum shows that the C–Ge bonds were formed in the a‐Ge_1?xC_x films according to the absorption peak at ~610 cm^?1. The Raman results indicate that the amorphous films also contain both Ge and C clusters. The XPS results reveal that the carbon concentration decreased as P_Ge increased from 40 to 160 W. The fraction of sp³ C–C bonds remains almost constant when increasing P_Ge from 40 to 160 W. The sp² C–C content of a‐Ge_1?xC_x film decreases gradually to 35.9% with P_Ge up to 160 W. Nevertheless, sp³ C–Ge sites rose with increasing P_Ge. Furthermore, the hardness and the refractive index gradually increased with increasing P_Ge. The excellent optical transmission of annealed a‐Ge_1–xC_x double‐layer coating at 400 °C suggests that a‐Ge_1?xC_x films can be used as an effective anti‐reflection coating for the ZnS IR window in the wavelength region of 8–12 µm, and can endure higher temperature than hydrogenated amorphous germanium carbide do. Copyright © 2012 John Wiley & Sons, Ltd.     

碱处理对PtRu/WC电极材料结构及甲醇电催化氧化性能的影响

本文采用不同pH值的KOH溶液对WC材料进行了不同时间的碱处理,并以该WC为载体通过微波加热还原法制备PtRu/WC 复合材料. 采用XRD对材料进行结构表征,通过循环伏安法和计时电流法测试电极对甲醇的电催化氧化性能. 结果表明,经不同碱性条件处理的WC材料表面更易于铂钌的负载,其中经强碱（pH = 14）的KOH溶液处理后可在WC表面得到结晶度最好的铂钌合金,且所得电催化剂PtRu/WC电极的性能最佳,而经碱处理5 h的WC负载的PtRu/WC电极对甲醇氧化的效果最优.     

Investigation of synthesis and microstructure of bismuth titanates with TiO<Subscript>2</Subscript> rich compositions

Preliminary examinations regarding formation of bismuth titanates in a part of Bi₂O₃—TiO₂ system rich with TiO₂ have been carried out. Bismuth titanates have been synthesized from mixtures of Bi₂O₃ and TiO₂ (anatase) by the conventional solid-state method at the temperatures ranged from 1273 to 1473 K. Differential thermal analysis (DTA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to study the formation of bismuth titanates. The following compounds have been achieved: Bi₄Ti₃O₁₂, Bi₂Ti₂O₇ and Bi₂Ti₄O₁₁. Existence of controversial bismuth titanate of formula Bi₂Ti₃O₉ in the Bi₂O₃—TiO₂ system has not been confirmed.     

Ethanol to Acetaldehyde Conversion under Thermal and Microwave Heating of ZnO-CuO-SiO2 Modified with WC Nanoparticles

The nonoxidative conversion of ethanol to acetaldehyde under thermal and microwave heating was studied on mixed oxide ZnO-CuO-SiO₂ catalysts modified with additives of tungsten carbide nanoparticles. The results revealed that the WC-modified catalyst exhibited superior activity and selectivity under microwave heating conditions. It is assumed that when microwave heating is used, hot zones can appear at the contact points of WC nanoparticles and active centers of the mixed oxide ZnO-CuO-SiO₂ catalyst, which intensively absorb microwave energy, allowing the more efficient formation of acetaldehyde at moderate temperatures. Thermodynamic calculations of equilibrium concentrations of reagents and products allowed us to identify the optimal conditions for effective acetaldehyde production. The initial catalyst and the catalyst prepared by the coprecipitation of the oxides with the addition of WC were characterized by physicochemical methods (TPR-H₂, XRD, DRIFTS of adsorbed CO). The active centers of the oxide catalyst can be Cu⁺ cations.     

介孔空心球状WC微球结构与晶相形成机理

采用喷雾干燥微球化处理-气固反应法制备了介孔空心球状WC微球，应用扫描电子显微镜(SEM)对微球的形貌变化进行了表征。结果表明，介孔空心球状结构是逐步形成的。其中，空心球状结构形成于前驱体微球化处理过程中，介孔结构形成于空心微球还原碳化过程中。在与样品制备工艺条件相同的情况下，采用原位X射线衍射技术(in situ XRD)对样品的晶相演变规律进行了监测。结果表明，样品在CO/CO₂气氛中进行还原碳化时，当温度缓慢而连续上升到750 ℃时，其晶相变化遵循AMT → WO₃ → WO₂ → W₂C → WC规律;当采用“阶跃式”升温，即温度缓慢而连续上升到400 ℃，然后再快速上升到750 ℃，并在750 ℃下进行还原碳化时，其晶相变化规律为AMT → WO₃ → WO₂ → WC。这说明，样品的晶相演变不仅与还原碳化温度和时间有关，而且与升温方式和升温速率有关。     

Selective Production of Renewable para‐Xylene by Tungsten Carbide Catalyzed Atom‐Economic Cascade Reactions

Tungsten carbide was employed as the catalyst in an atom‐economic and renewable synthesis of para‐xylene with excellent selectivity and yield from 4‐methyl‐3‐cyclohexene‐1‐carbonylaldehyde (4‐MCHCA). This intermediate is the product of the Diels–Alder reaction between the two readily available bio‐based building blocks acrolein and isoprene. Our results suggest that 4‐MCHCA undergoes a novel dehydroaromatization–hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W₂C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio‐based building blocks, thus potentially providing a petroleum‐independent solution to valuable aromatic compounds.     

双功能WC/HZSM-5催化剂上正己烷芳构化反应性能

以HZSM-5(SiO2/Al2O3=38)为载体,偏钨酸铵为钨源制备了双功能催化剂WC/HZSM-5,考察了其催化正己烷芳构化反应性能,并采用X射线衍射、扫描电子显微镜、X射线能量散射谱和程序升温氨脱附等手段对催化剂进行了表征,探讨了制备方法和WC含量对WC/HZSM-5催化剂性能的影响.结果表明,采用原位还原碳化法制备的WC/HZSM-5(RC)催化剂上正己烷芳构化反应性能优于浸渍法制备的WC/HZSM-5(IP).5%WC/HZSM-5(RC)样品在反应初始阶段芳烃选择性为10.28%,而HZSM-5上的仅为2.56%.WC/HZSM-5(RC)催化剂上反应产物中轻质芳烃(苯、甲苯和二甲苯)含量增加,重质芳烃C9+含量降低,其催化性能优于Pt/HZSM-5催化剂.产物分布的变化可能是由于WC与分子筛间的协同作用所致.     

碳化钨/碳化二钨核壳结构纳米复合材料的制备及电化学性能

以偏钨酸铵为钨源, 铁黄(FeOOH)为载体, 将表面包覆法与原位还原碳化技术相结合, 制备出了具有核壳结构的碳化钨(WC)/碳化二钨(W₂C)纳米复合材料; 应用X射线衍射(XRD)分析、透射电子显微镜(TEM)和X射线能量散射谱(EDS)等手段对不同阶段样品的晶相、形貌、微结构和化学组成等特征进行了表征. 结果表明, 负载体经煅烧后, 载体及包裹层的物相均发生了变化, 形貌也相应地发生了改变; 经盐酸处理及还原碳化后, 样品由WC和W₂C纳米颗粒构成, 并构成了以W₂C为壳, 以WC为核的典型核壳结构; 结合表征结果对核壳结构的形成机理进行了探讨. 采用三电极体系循环伏安法测试了样品在酸性、中性和碱性溶液中对甲醇的电催化氧化活性. 结果表明, 与颗粒状碳化钨和介孔空心球状碳化钨相比, 样品的电催化活性有了明显的提高. 这说明W₂C与WC构成核壳结构纳米复合材料后, 其电化学性能有了明显的提升, 核壳结构纳米复合材料是提高碳化钨催化材料活性的有效途径之一.     

沸石负载碳化钨的制备及其电催化性能

 以天然丝光沸石和偏钨酸铵为原料制备了沸石负载的碳化钨复合材料. 先用稀盐酸水热处理沸石原料,真空干燥后再用偏钨酸铵水溶液浸泡,干燥后置于一氧化碳和二氧化碳混合气体中进行还原和碳化即得. 用X射线衍射、扫描电镜和X射线能量分散谱对样品进行了表征. 结果表明,样品主要由碳化钨和沸石等组成,碳化钨颗粒主要位于沸石外表面. 在样品表面,W元素的分布与C元素的分布呈正相关,Si元素的分布与O元素的分布也呈正相关,W和C的分布与Si的分布呈负相关. 采用粉末微电极对样品的电化学性能进行了测试,结果表明样品对碱性溶液中的对硝基苯酚还原反应具有电催化活性.     

WC/CNT纳米复合材料制备及其对甲醇氧化的电催化性能

采用表面修饰技术将碳纳米管(CNT)表面羧基化, 通过羧基将钨离子基团修饰到碳纳米管的外表面, 再通过原位还原碳化技术, 将钨离子基团还原成碳化钨(WC)纳米微粒, 制备出WC/CNT纳米复合材料. 采用FTIR、XRD、SEM、HRTEM和N2吸附等分析测试手段对样品的形貌、晶相组成和微观结构特征进行了表征. FTIR和N2吸附结果表明, 硝化后, 在碳纳米管表面羧基化的同时比表面积增加; XRD结果表明, WC/CNT样品由碳纳米管、WC以及非化学计量比的氧化钨组成; SEM和HRTEM结果表明, WC纳米颗粒均匀地分散于碳纳米管的外表面,并与碳纳米管构成了复合材料. 采用循环伏安法测试了样品在碱性条件下对甲醇氧化的电催化性能, 结果表明, 复合材料对甲醇氧化的电催性能明显强于WC 和碳纳米管, 并在实验结果的基础上探讨了复合材料催化性能提高的原因.     

The heteroscorpionate ligand 2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,1‐diphenylethanol and an easy preparation of its tungsten complex

The heteroscorpionate ligand 2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,1‐diphenylethanol, C₂₄H₂₆N₄O, features in the solid state an intramolecular O—H…N hydrogen bond. A heteroscorpionate tungsten complex, cis‐[2,2‐bis(3,5‐dimethylpyrazolyl)‐1,1‐diphenylethanolato]chloridodioxidotungsten(VI) tetrahydrofuran monosolvate, [W(C₂₄H₂₅N₄O)ClO₂]·C₄H₈O, was prepared by the simple mixing of solutions of the ligand and WOCl₄ in tetrahydrofuran. The tungsten complex was isolated after standing for several weeks. The complex exhibits a κ³N,N′,O‐coordination of the ligand. This simple synthetic procedure allows access to the cis isomer in high yield without additional purification steps. The Hirshfeld surface analysis shows a change of the intermolecular contacts due to the coordination of the WO₂Cl unit with the ligand molecule.     

WC/纳米碳管复合材料制备及其电化学性能

碳化钨具有类铂催化性能和较强的抗中毒能力, 但其催化活性远低于铂等贵金属催化剂. 如何提高其催化活性是碳化钨应用研究所面临的主要难点与热点之一. 为寻找改善碳化钨催化性能的技术方法, 本文将表面修饰与原位还原碳化技术相结合, 成功制备了碳化钨/纳米碳管复合材料, 采用XRD, HRTEM等手段对其形貌和晶相组成进行了表征, 并应用粉末微电极对其电催化性能进行了评价. 实验结果表明, 样品由碳化钨颗粒和纳米碳管组成, 碳化钨为形态不规则纳米颗粒, 均匀地生长于纳米碳管的外表面; 在碱性溶液中, 复合材料对对硝基苯酚的电催化性能明显强于具有介孔结构的纯碳化钨样品. 这说明将碳化钨复合到纳米碳管的外表面是提高碳化钨电催化活性的有效技术方法之一.     

纳米晶WC-Co-Ni复合材料的制备及其电催化性能

采用喷雾干燥-气固反应法制备了具有介孔结构的纳米晶碳化钨-钴-镍(WC-Co-Ni)复合材料. 通过XRD, SEM, EDS和粒径分析等测试手段对样品的形貌、物相组成、化学成分、粒径分布进行了表征, 采用线性扫描法对WC-Co-Ni复合材料在氢析出反应中的电催化性能进行了评价. 结果表明, WC-Co-Ni复合材料由缺碳六方WC相、立方Co相和立方Ni相组成, 化学成分为W, C, Co和Ni, W与C的原子比接近1∶1; WC-Co-Ni复合材料具有空心球状或层状形貌, 其表面具有介孔结构; 样品颗粒的粒径集中分布在3～30 µm, 该区间内样品分布呈单分散性, 其中位径(d50)为10 µm; 在碱性溶液中, 复合材料对氢析出反应的电催化性能明显强于具有介孔结构的碳化钨样品.