俄独特方法生产碳化钨纳米粉简单经济

正俄罗斯托木斯克理工大学开发出一种生产碳化钨和其他超硬材料的独特方法。该方法比同类技术简单、经济、可靠,同时,还能用含有相似材料的废物作为生产原材料。相关研究成果近日发表在《国际难熔金属与硬质材料》期刊上。碳化钨是一种超硬材料,广泛用于生产钻头、刀具和其他耐磨零件。     

钨酸三乙醇胺热分解法合成碳化钨陶瓷涂层工艺及其对农药废水的电催化氧化能力初探

提出了一种制备碳化钨陶瓷的新方法-钨酸三乙醇胺浸渍热分解法。研究表明,用该法可成功制得碳化钨涂层材料。经过综合热分析仪的测定可得出,碳化钨生成温度为954.5℃。通过碳化钨的X射线衍射(XRD)分析可知,该工艺合成的碳化钨主要成份为W_2C。将所制备的碳化钨陶瓷作电极电解含甲胺磷的农药废水。实验证明,在电压为30V,电流为0.03A时,随着通电时间的加长,有机磷转化为无机磷的程度随之增大。当电解时间为165min时,有机磷的转化率可达9.8%,高于同等条件下碳电极的1.6%。     

混捏机碳化钨搅刀的补焊修复工艺

介绍了修复混捏机动搅刀表层的一种新型耐磨材料--碳化钨,根据工作实践,主要阐述了使用碳化钨材料进行动搅刀表层补焊修复时的工艺要求及经验总结.     

RF-PCVD法制备纳米碳化钨微晶的研究

采用高频等离子体化学气相沉积法(RF-PCVD),以WCl6 C2H2 H2的反应体系来制备纳米碳化钨微晶,实验制得了粒径小于100nm,平均粒径为50nm的纳米碳化钨微晶样品。理论分析和实验结果都表明:RF-PCVD法制备的碳化钨样品比较复杂,含有WC,W2C,WC1-x等三种碳化钨。其中WC的硬度较高,而W2C,WC1-x的催化活性较好。     

新型硼化钨超硬材料出现,可能会取代碳化钨的地位

正近日,国际上久负盛名的团队报道了一种可用于钻井、机械制造以及其他应用的新型超硬材料。他们发现的新型硼化钨材料性能比广泛使用的pobedit要优异很多,pobedit是一种穿插人造金刚石碳化钨和钴的复合材料,他们的研究结果发表在著名的科学杂志《物理化学快报》上。     

使用离子注渗碳化钨耐磨材料的效果分析

水泥行业立磨、高效选粉机、燃烧器等设备中的耐磨件，采用高能离子注渗碳化钨材料，其耐磨性是堆焊或热喷涂碳化钨材料的5—6倍。     

溶胶-凝胶法制备高表面积碳化钨

本文采用溶胶一凝胶法制备高表面积的碳化钨.CRD结果表明,该碳化钨为WC和β-W2C的混合物,其中β-W2C的含量很少.TEM观察显示,该碳化钨主要由无规则颗粒组成.N2吸附结果显示,碳化钨样品的表面积为150m2g-1,孔径分布主要集中在3-5nm范围内.     

一种纳米级碳化钨粉的制备方法

本发明公开了一种纳米级碳化钨粉[粒度≤0．2μm、w（化合碳）≥6．10％]的制备方法，它是以纳米（粒度≤0．2μm）钨粉、纳米炭黑为原料，将纳米钨粉与纳米炭黑放入容器，并向容器内通入惰性气体，在惰性气体保护状态下将纳米钨粉与纳米炭黑进行搅拌混合，混合过程中加入0．5％～3％的有机活性材料，待混合均匀后，在500～1500kg／cm^2压力下压制成块，煅烧压块（W＋C），使纳米钨粉、纳米炭黑化合形成碳化钨（WC），待碳化钨形成后，采用气流研磨方式将碳化钨研磨、打散形成纳米级碳化钨粉。该方法具有工艺流程短、投资少、产量大、产品质量及稳定性均可得到大幅度提高的特点，是一种环保型的制备方法。     

高比表面积碳化钨制备及其在锂空气电池中电催化性能研究

锂空气电池具有高能量密度和良好的发展前景,但其循环性能仍不能满足使用要求,而空气电极侧(即正极)的电化学反应对电池的循环可逆性具有显著影响,正极催化剂的引入可以显著改善电池的循环性能。以高比表面积的石墨相氮化碳介孔材料作为模板和碳源,以六氯化钨为钨源,通过高温反应制备具有较高比表面积的碳化钨材料,并以该碳化钨作为锂空气电池的正极催化剂。利用透射电子显微镜(TEM)、X射线衍射(XRD)、物理吸附等对合成的样品进行表征,结果表明制备的样品为碳化钨材料,并且具有较高的比表面积。采用电化学测试方法研究了碳化钨材料在锂空气电池中的电催化效果,结果表明该碳化钨材料在锂空气电池中具有良好的电催化性能,电池可以保持较长时间的稳定循环状态。     

WC/MMT纳米复合材料制备及其对PNP的电催化活性

以剥离后的蒙脱石(MMT)为载体,将浸渍法与原位还原技术相结合制备了碳化钨/蒙脱石(WC/MMT)纳米复合材料。采用X射线衍射、扫描电子显微镜和透射电子显微镜等手段对样品进行了表征。结果表明,剥离后蒙脱石的片层厚度为10～15 nm,层间距增大,边缘发生卷曲;复合材料由碳化钨(WC)、碳化二钨(W₂C)和蒙脱石组成,碳化钨颗粒均匀地分布于蒙脱石外表面。采用循环伏安法测试了样品对对硝基苯酚(PNP)的电化学还原性能,结果表明,WC/MMT纳米复合材料对对硝基苯酚具有良好的电催化活性,且具有较好的稳定性。蒙脱石是碳化钨基复合电催化材料良好的载体。     

碳纳米管、碳化钨在直接法合成过氧化氢中的应用

选用新型纳米材料——碳纳米管（CNTs）作为催化剂载体,用沉积沉淀法制备负载型钯-铂合金催化剂。同时选用过渡金属碳化物材料（碳化钨）为催化剂,其具有类似于Pt的表面电子结构,有望替代贵金属催化剂。探讨了Pd-Pt/CNTs及碳化钨在氢氧直接合成过氧化氢反应中的催化性能。     

Tungsten Carbide Synthesized by Polystyrene Sphere Template Method Promoting Pd Electrocatalyst for Alcohol Oxidation in Alkaline Media

Tungsten carbide (WC) particles loading on hollow carbon spheres (HCS) have been synthesized by using ammonium metatungstate as W source, glucose as carbon source, P123 as dispersant and polystyrene sphere as template. The typical WC‐HCS composite has the WC particle sizes of 5–20 nm, specific surface area of 445 m² g⁻¹, pore volume of 0.24 cm³ g⁻¹ and hollow spherical structure. The above structures of WC‐HCS favor dispersion of Pd particles and mass transfer. Therefore, the Pd/WC‐HCS electrocatalyst has 4.6 times higher peak current density and 130 mV more negative onset potential than that of Pd/C for ethanol oxidation in alkaline solution. The mass transfer property of WC‐HCS (due to structure effect) and promotion effect of WC on Pd are believed to be the origins of the excellent performances.     

Colloidal processing and sintering of WC-based ceramics with low Ni content as sintering aid

To soften the extreme sintering conditions of Tungsten Carbide (WC), a 3 wt.% of metallic nickel (Ni) was added to the starting powders. To ensure a fair distribution of the second phase and an intimate mixture of the phases, the colloidal process was adopted. A commercial Ni and a in-house synthesised nanosized nickel were used as sintering aids. Rheological studies allowed a high dispersion of the nickel in the final composite powders. Sintering studies by Hot-Pressing route (HP) proved the great benefices of Ni as a sintering aid, decreasing the maximum temperature necessary to achieve full densification, from 1900 to 1450 °C and dwell times from 20 to 7 min. Among all the materials obtained, the best results in terms of density, microstructure and properties were obtained for WC-nNi, which achieved hardness of 14.8 GPa and toughness comparable to conventional cermets with much higher content of metallic phase.     

α-硝基萘在介孔结构碳化钨催化剂上的电化学还原行为

以喷雾干燥处理的偏钨酸铵为前驱体，分别采用CH₄/H₂和CO/CO₂为还原碳化气氛，利用固定床气固反应法制备了两种具有介孔结构的碳化钨（WC）粉体.以WC粉末作为电催化材料制成了碳化钨粉末微电极（WC-PME），并采用循环伏安和线性扫描等方法研究了酸性溶液中两种介孔结构WC对α-硝基萘（NP）电还原过程中的电催化行为.结果表明，以CH₄/H₂为还原碳化气氛所制备的WC粉末，其制成的粉末微电极对NP具有更良好的电催化活性，这主要与该WC粉末的结构形貌及其制备后的处理工艺有关，同时该WC-PME具有良好的化学稳定性.     

超细碳化钨制备过程及机理研究进展

超细碳化钨（WC）具有硬度高、耐磨性好、强度高和韧性较高的特点,是制备硬质合金最基础的原料。因此,超细碳化钨的制备成为学术界和工业界关注的焦点,也是硬质合金制备领域研究的重点。从反应体系的角度综述了超细碳化钨粉体制备技术,对相关反应路径机理进行了分析,并展望了超细碳化钨制备技术的发展趋势。     

Dense tungsten carbide bulks by self-densification reaction sintering of nanodiamond with tungsten at 1700 °C

Tungsten carbide (WC) bulks from the sintering of WC powders possess excellent physical and chemical properties, widely used in high-precision optical molds, seals, nozzles and many other scenarios. To produce dense WC bulks, however, needs a very high sintering temperature (>1900 °C) and super fine WC powders due to the poor sinterability. The high sintering temperature required puts a huge strain on processing equipment, and the preparation of super fine WC powders involves many complex steps. In this work, dense WC bulks are prepared by spark plasmas sintering via self-densification reaction of nanodiamond with tungsten at 1700 °C. The use of nanodiamond enables dense WC bulks of a density of 98.1% and Vickers hardness of 21.8 GPa for a volume expansion associated with the change of diamond to graphite greatly reduces the porosity of as-prepared WC bulks, demonstrating a novel mechanism of self-densification reaction sintering. Besides, reaction between tungsten and diamond produces far less volume shrinkage than other allotropes of carbon, partly contributing to the densification of the as-prepared WC bulks. Our creative strategy has significant advantages over prevailing methods in preparing high-density WC bulks, facilitating the application of WC bulk materials in industrial production and providing a new insight into the preparation of dense bulks of other metal carbides.     

火柴棒状纳米碳管的制备及其生长机理

以钨酸钠为钨源,氯化钠为诱导剂,通过水热法制备了三氧化钨(WO₃)纳米棒,再以葡萄糖为碳源,经再次水热反应对WO₃表面进行碳包覆,然后在氢气和甲烷混合气氛中反应一段时间获得了具有火柴棒状结构的纳米碳管。采用X射线衍射分析、场发射扫描电子显微镜、透射电子显微镜和X射线能量散射谱等手段对样品的晶型、形貌、微结构和表面化学元素进行了表征与分析。结果表明,样品由纳米碳管和碳化钨(WC)构成。其中,纳米碳管为火柴棒状,长度0.5～1.0 μm,直径100 nm左右;WC颗粒位于纳米碳管内部,其大小决定了火柴棒状纳米碳管的内径。这充分说明WC在碳管的生长过程中充当催化剂的作用。     

废金刚石刀具中铜钴镍的回收工艺研究

为了使废金刚石刀具循环再生和综合利用，以废金刚石刀具为原料，通过盐酸浸溶、氧化还原、钴镍分离等过程，系统地研究了金刚石、碳化钨、铜粉、钴粉和镍粉的回收工艺，并优化了最佳工艺参数。结果表明，金属钴和镍的回收率可达96％，而纯度在98％以上。该方法工艺简单，回收率高，经济效益显著。     

Microstructural Properties of Air Plasma Sprayed Coating Consisting of Tungsten Carbide and Yttria‐Stabilized Zirconia

Thermal Spraying technologies are proven to be capable of producing composite materials and structures. In the present work, an innovative composite coating was produced to achieve high wear and thermal resistant properties in a single‐step process using air plasma spraying (APS) technique. Tungsten carbide has shown high wear resistance and zirconia coatings exhibited excellent tribological and insulation properties. It is speculated that a composite material consisting of zirconia and tungsten carbide exhibits excellent thermomechanical properties. A powder mixture of 50wt% WC‐10wt% Ni (WC‐Ni) and 50wt% ZrO₂‐8wt% Y₂O₃ (YPSZ) was deposited on a low carbon steel substrate using APS technique. Important microstructural properties of WC‐Ni/YPSZ coating such as splat boundaries, pore and grain morphology, microcracks, phase composition, elemental distribution of coatings, and lattice parameters of the crystals were investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive X‐ray (EDS), and X‐ray diffractometry (XRD). A good adhesion was observed between different phases in tungsten carbide mixed with zirconia coatings. Decarburization process which occurred during APS process resulted in formation of tungsten hemi‐carbide (W₂C) phase in plasma sprayed samples. The calculated crystal size for APS‐deposited coating was smaller than those of feedstock powder.     

Study of processing routes for WC-MgO composites with varying MgO contents consolidated by FAST/SPS

Two different preparation routes were applied to process WC-MgO composites with varying MgO contents (4.1 wt.% and 5.9 wt.% MgO). WC-MgO powder mixtures were synthesized by a milling process at 600 rpm for 6 h of partially oxidized WC (WC + WO₃), Mg₃N₂ and C. Alternatively, WC and MgO as initial powders were used. For consolidation of the powder mixtures the field-assisted sintering technology (FAST) was used. X-ray diffraction shows that samples out of different powder mixtures and sintered between 1600 °C and 1750 °C exhibited WC, MgO and the W₂C phase independent of the preparation route of the powder mixtures. A higher density and better mechanical properties (hardness and indentation fracture toughness) of WC-MgO were achieved of pure WC and MgO as initial powders were consolidated by FAST. It was found that a lower MgO content results in higher hardness values and in a slightly decreased indentation fracture toughness.