WC-6Co-1.5Al合金高能球磨-电场活化烧结工艺的研究

采用高能球磨-电场活化烧结工艺制备了WC-6Co-1.5Al超细晶硬质合金块体,并对球磨粉末特性,以及合金的微观组织进行了分析测试。研究结果表明,WC-6Co-1.5Al复合粉末的球磨过程是一个晶粒逐渐细化、晶格畸变逐渐增加、粉末体系能量逐渐增大的过程;利用电场活化烧结技术能在电流为1 560 A,压力为30 MPa,烧结时间为6 min的情况下获得较为致密的硬质合金块体;合金中WC晶粒分布均匀,且没有出现异常长大现象。     

Fundamentals of liquid phase sintering for modern cermets and functionally graded cemented carbonitrides (FGCC)

Metallurgical reactions and microstructure developments during sintering of modern cermets and functionally graded cemented carbonitrides (FGCC) were investigated by modern analytical methods such as mass spectrometer (MS), differential thermal analysis (DTA), differential scanning calorimeter (DSC), dilatometer (DIL), microscopy and analytical electronic microscopy with energy dispersive spectrometer (EDS). The complex phase reactions and phase equilibria in the multi-component system Ti/Mo/W/Ta/Nb/C,N-Co/Ni were studied. The melting behavior models in the systems of TiC–WC/MoC–Ni/Co, TiC–TiN–WC–Co and TiCN–TaC–WC–Co have been established. By an in-depth understanding of the mechanisms that govern the sintering processing and metallurgical reactions, new cermets and different types of FGCC with desired microstructures and properties were developed.     

Formation of (W,V)Cx layers at the WC/Co interfaces in the VC-doped WC-Co cemented carbide

The (W,V)C_x thin layers at the WC/Co interfaces in the oil-quenched WC-12mass%Co-0.5mass%VC hard metal were investigated by high resolution transmission electron microscopy. The (W,V)C_x thin layers are formed on the liquid phase sintering state, because they are observed on the micro-facets and some of them are included inside the WC grains. The grain growth rate strongly depends on whether the thickness of the (W,V)C_x layers is more than one layer or less during liquid-phase sintering.     

Microstructural adjustment of Ni–BaCe0.9Y0.1O3−δ cermet membrane for improved hydrogen permeation

Dense ceramic membranes are usually hybridized with an electronically conductive metallic phase to enhance their hydrogen permeation fluxes, thereby increasing the hydrogen-production efficiency of hydrogen separation membranes. Herein, the hydrogen-separation properties of membranes fabricated from cermets containing BaCe_0.9Y_0.1O_3−δ (BCY) as the proton-conducting ceramic phase and Ni as the electronic-conducting metal phase were investigated with respect to the compositions of the Ni–BCY mixture. Because the hydrogen permeability of a cermet membrane is seriously affected by microstructural parameters such as grain size and homogeneity of the cermet mixture used to fabricate it, we tried to optimize the microstructures and compositions of the Ni–BCY cermets by controlling their fabrication conditions. A high-energy milling process was employed to fabricate fine-grained, dense membranes that exhibited high levels of mixing homogeneity. From the adjustment of composition and microstructure of Ni–BCY composites, the hydrogen permeability of Ni–BCY cermet membranes can be significantly increased so that hydrogen fluxes of ~0.76 cm³/(min cm²) at 800 °C can be achieved.     

Cermets Ni/(Ce0.9Ln0.1O1.95) (Ln = Gd,La, Nd and Sm) prepared by solution combustion method as catalysts for hydrogen production by partial oxidation of methane

Catalysts based on Ni/(Ce_0.9Ln_0.1O_1.95) (Ln = Gd, La, Nd and Sm) have been developed and tested for hydrogen production by partial oxidation of methane. The synthesis method (SCS, solution combustion synthesis) produces macroporous composite materials composed of ceramic (cer, Ce_0.9Ln_0.1O_1.95) and metallic (met, Ni) phases, without the need of an activation stage prior to the catalytic reaction. The catalysts have been characterized by different techniques: X-ray diffraction, N₂ adsorption-desorption, Hg porosimetry, Scanning Electron Microscopy, Temperature Programmed Reduction, H₂ and O₂ pulse chemisorption, X-ray photoelectron spectroscopy and Raman spectroscopy. With the exception of the lanthanum-loaded catalyst, the catalysts are highly active, selective and stable; being the one doped with gadolinium the most efficient. Correlations structure-activity point out that the excellent catalytic performance is related to the high catalytic surface area per unit mass of catalyst and to an appropriate balance of nickel dispersion to oxygen vacancies of the support.     

Anodes for Direct Oxidation of Dry Hydrocarbons in a Solid‐Oxide Fuel Cell

The manufacture of fuel cells that can operate directly on various hydrocarbon fuels, without the need for reforming, has the potential of greatly speeding the application of fuel cells for transportation and distributed‐power applications. This paper will briefly review the literature in this area and describe recent developments in solid‐oxide fuel cells (SOFCs) that demonstrate that direct‐oxidation fuel cells are possible with Cu‐based anodes. A new method for synthesizing thin‐electrolyte, anode‐supported cells is described that is based on tape casting with graphite pore formers (see Figure), followed by impregnation with aqueous solutions of Cu(NO₃)₂ and Ce(NO₃)₃. The performance of model SOFCs for direct conversion of n‐butane and methane is shown. Finally, future developments that are needed for this technology to be commercialized are discussed.     

Nb添加量对金属陶瓷显微组织和磁学性能的影响

Ti(C,N)基金属陶瓷具有硬度高、耐蚀性好及密度低等一系列优点,在工业领域具有广泛的应用前景。但它室温时易呈铁磁性,阻碍了其进一步推广应用。采用粉末冶金法制备了系列TiC-l0TiN-xNb-30Ni-4C(摩尔分数)金属陶瓷,用X射线衍射仪(XRD)、扫描电镜(SEM)、振动样品磁强计(VSM)、物理性能测试系统(PPMS)、洛氏硬度计和万能试验机研究了金属陶瓷的磁学性能、力学性能以及显微组织在不同Nb添加量下的变化。结果表明,所有金属陶瓷由陶瓷晶粒和Ni基粘结相组成,添加的Nb组元在烧结过程中基本完全固溶于粘结相和陶瓷相。整体上,陶瓷晶粒随着Nb添加量的增加变细。未添加Nb的金属陶瓷呈现典型的铁磁性,当Nb添加量为8%(摩尔分数)时,金属陶瓷转变为顺磁性。随着Nb添加量的增加,Ti(C,N)基金属陶瓷的室温饱和磁化强度和剩磁都呈现下降趋势,然后逐渐趋近于0。Nb含量的增加,也使得Ti(C,N)基金属陶瓷的抗弯强度和硬度呈现先增加后逐渐减小的趋势。当Nb含量为4%(摩尔分数)时,Ti(C,N)基金属陶瓷保持较好的抗弯强度(1 470 MPa)和硬度(87.0 HRA)。研究可为制备...     

In-situ combustion synthesis and densification of TiC–xNi cermets

The combustion synthesis reaction was combined with quasi-isostatic pressing (QIP) technique to fabricate full density TiC–xNi composites in a single processing operation. Combustion wave velocity and temperature of Ti–C–Ni were measured and the microstructure of the product was characterized by X-ray diffraction and scanning electron microscopy. With increasing Ni content in TiC–xNi, both the combustion wave velocity and temperature decrease. The Ni additive, mainly as a diluent and the binder of TiC grains in a matrix, formed a quasi-continuous phase enveloping spheroidal TiC particles and brought about a grain size decrease from 9 to 1 μm. TiC-20 wt% Ni cermet produced by the combustion synthesis/quasi-isostatic pressing process under 160 MPa for 20 s show near full density, high hardness and transverse rupture strength (1024.2 MPa).     

Effect of various carbides on the dissolution behavior of Ti(C0.7N0.3) in a Ti(C0.7N0.3)–30Ni system

HfC, TaC, or WC were individually added to a Ti(C_0.7N_0.3)–30 wt% Ni system, in order to investigate microstructural changes and the dissolution behaviors of Ti(C_0.7N_0.3) and the carbides. Of these systems, the Ti(C_0.7N_0.3)–WC–Ni system proved to be the most favorable for the refinement of microstructure. The fraction for the cross-sectional area of the Ti(C_0.7N_0.3) cores, which is related to the amount of Ti(C_0.7N_0.3) dissolved, increases and the thickness of solid solution rims decreases in the order of HfC, TaC, and WC added. This finding indicates that the dissolution rate of Ti(C_0.7N_0.3) in a Ni melt is the lowest when WC is added. In addition, it was found that the average dissolution rate of Ti(C_0.7N_0.3) in the HfC-containing system is 1.6 and 1.9 times higher than those for Ti(C_0.7N_0.3) in the TaC- and WC-containing systems at the same sintering conditions. Further, the dissolution rates of TaC and WC were 80% of the rate found for HfC during the formation of the outer rim.     

气氛控制烧结制备17M/(10NiO-NiFe2O4)金属陶瓷的抗氧化性能研究

采用等温热重法,测试了冷压-烧结和气氛控制烧结两种方法制备的17M/(10NiO-NiFe2O4)(M=Cu和Ni)金属陶瓷惰性阳极的高温抗氧化性能。考察了氧化温度和氧化时间对17M/(10NiO-NiFe2O4)金属陶瓷氧化行为的影响,并对其氧化产物层微观结构进行了分析。结果表明,气氛控制烧结有利于提高金属陶瓷材料的抗氧化性,表面的致密氧化层能够有效阻挡氧的向内扩散。17Cu/(10NiO-NiFe2O4)金属陶瓷材料表面氧化层中的Cu的质量分数占到37.58%比过渡层中11.28%高,说明Cu有向表面迁移后再氧化的现象。