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Showing papers on "Carbide published in 1996"


Book
31 Dec 1996
TL;DR: The Refractory Nitrides Interstitial Carbides, Structure and Composition Carbides of Group IV: Titanium, Zirconium, and Hafnium Carbides.
Abstract: The Refractory Carbides Interstitial Carbides, Structure and Composition Carbides of Group IV: Titanium, Zirconium, and Hafnium Carbides Carbides of Group V: Vanadium, Niobium and Tantalum Carbides Carbides of Group VI: Chromium, Molybdenum, and Tungsten Carbides Covalent Carbides: Structure and Composition Characteristics and Properties of Silicon Carbide and Boron Carbide The Refractory Nitrides Interstitial Nitrides: Structure and Composition Interstitial Nitrides: Properties and General Characteristics Covalent Nitrides: Composition and Structure Covalent Nitrides: Properties and General Characteristics Processing of Refractory Carbides and Nitrides (Powder, Bulk, and Fibers) Processing of Refractory Carbides and Nitrides (Coatings) Applications of Refractory Carbides and Nitrides

1,160 citations



Journal ArticleDOI
01 Jan 1996-Nature
TL;DR: In this paper, a boron-containing silicon nitride/carbide ceramic that does not degrade at temperatures up to 2,000 °C even in nitrogen-free environments is presented.
Abstract: CERAMICS based on silicon nitride and carbide are strong and stable at high temperatures, and are therefore under investigation for the fabrication of motor and turbine parts1–3. But silicon nitride decomposes at about 1,400 °C in vacuum and 1,775 °C in 0.1 MPa nitrogen4,5, limiting the high-temperature range of its technological uses. Here we describe a boron-containing silicon nitride/carbide ceramic that does not degrade at temperatures up to 2,000 °C even in nitrogen-free environments. We synthesize the material in a polymer-to-ceramic transformation6 from a single polymeric polyborosilazane precursor. On heating at 1,000 °C in argon we obtain a ceramic with the composition Si3.0B1.0C4.3N2.0. The ceramic begins to convert to a polycrystalline composite of silicon nitride and carbide (with some non-crystalline boron nitride) at 1,700 °C, a process that is completed (without substantial change in elemental composition) at 2,000 °C.

634 citations


BookDOI
01 Jan 1996
TL;DR: In this paper, the authors present an overview of safety issues in non-oxide materials and their application in the development of complex composites and solid solutions, including a discussion of the safety issues of carbide and nitride powders.
Abstract: Part 1 Introduction: overview safety issues. Non-oxide materials - properties and applications engineering: introduction advanced ceramics - origin, current status, trends: origins of advanced ceramics recent status monolithic ceramics ceramics composites manufacturing applications engineering: the market wear components ceramic armour high temperature applications electrically conductive ceramics corrosion resistant applications automotive applications electronic substrates special applications. Critical powder characteristics: introduction Tungsten carbide: effects of Tungsten/carbon stoichiometry hard metal composition silicon carbide: effect of oxygen sintering developments effect of impurities effect of particle size and method of synthesis silicon nitride: sintering developments effect of particle size effect of impurities effect of synthesis method aluminum nitride: sintering developments effect of oxygen effect of impurities effect of synthesis method summary references. Part 2 Carbothermal reduction synthesis processes: overall process safety issues. Thermochemistry and kinetics: introduction thermochemistry kinetics importance of the gas phase synthesis of carbide and nitride powders references. Acheson process: introduction, history basic silicon carbide process description manufacturing cost factors summary references. Electric arc process: introduction boron carbide manufacturing other non-oxide ceramics references. Tube/pusher/moving bed furnace processes: introduction fundamental physio-chemical considerations system design considerations process scale-up considerations safety considerations conclusions acknowledges nomenclature references. Rotary tube reactor processes: introduction rotary furnace design configurations process considerations operating difficulties applications to non-oxide powder synthesis references. Fluidized bed reactor processes: background application to carbothermal reduction processes references. Part 3 Combustion synthesis processes: overall process safety issues. Thermochemistry and kinetics: principles of combustion synthesis thermodynamics and thermochemistry combustion front structure and stability analysis gasless combustion gas solid combustion synthesis of complex composites and solid solutions nomenclature references. Processes: introduction solid-solid reactions gas-solid reactions summary nomenclature references. Part 4 Gas phase synthesis processes: overall process safety issues references. (Part contents).

436 citations


Journal ArticleDOI
TL;DR: The sonochemical decomposition of volatile organometallic compounds produces high surface area solids that consist of agglomerates of nanometer clusters, which are active heterogeneous catalysts for hydrocarbon re-forming and CO hydrogenation as discussed by the authors.
Abstract: The sonochemical decomposition of volatile organometallic compounds produces high surface area solids that consist of agglomerates of nanometer clusters. For iron pentacarbonyl and tricarbonylnitrosylcobalt, nanostructured metals and alloys are formed; for molybdenum hexacarbonyl, the metal carbide is produced. These sonochemically produced nanostructured solids are active heterogeneous catalysts for hydrocarbon re-forming and CO hydrogenation. The sonochemical synthesis, characterization, and catalytic studies will be discussed in this review.

264 citations


Journal ArticleDOI
TL;DR: In this paper, a simple sonochemical synthesis of nanostructured molybdenum carbide from the ultrasonic irradiation of hexacarbonyl was presented.
Abstract: The preparation of nanophase materials has been the focus of intense study in materials science1,2 A variety of chemical and physical preparative methods have been applied to produce materials with nanometer structure, including metal evaporation,3 decomposition of organometallic compounds,4 and reduction of metal salts5,6 Sonochemical decomposition of transition metal carbonyl compounds has also been proven to be a useful technique to generate nanophase transition metals7,8 Recently, molybdenum and tungsten carbides have been examined as heterogeneous catalysts because their activity is often similar to that of the platinum group metals9-11 For catalytic applications, high surface area materials are generally needed; the preparation of interstitial carbides of molybdenum and tungsten with high surface areas, however, is very difficult We present here a simple sonochemical synthesis of nanostructured molybdenum carbide from the ultrasonic irradiation of molybdenum hexacarbonyl In addition, we have examined the catalytic activity and selectivity of these materials for the dehydrogenation of alkanes The chemical effects of ultrasound arise from acoustic cavitation: the formation, growth, and implosive collapse of bubbles in a liquid12,13 The collapse of bubbles generates localized hot spots through adiabatic compression or shock wave formation within the gas of the collapsing bubble This local heating produces a wide range of high-energy chemistry The conditions formed in these hot spots have been experimentally determined, with transient temperatures of ∼5000 K, pressures of∼1800 atm, and cooling rates in excess of 1010 K/s14,15 Using these extreme conditions, we have explored a variety of applications of ultrasound to materials chemistry16 A slurry of molybdenum hexacarbonyl (1 g in 50 mL of hexadecane) was sonicated with a high-intensity ultrasonic horn (Sonic and Materials, model VC-600, 05 in Ti horn, 20 kHz, 100 W cm-2) at 90 °C for 3 h under argon to yield a black powder The powder was filtered inside an inert atmosphere box (Vacuum Atmospheres, <1 ppm O2), washed several times with purified, degassed pentane, and heated at 100 °C under vacuum X-ray powder diffraction17 (XRD) showed extremely broad peaks centered at a d spacing of 24, 15, and 13 A (Figure 1), which did not match body-centered cubic (bcc) lines of molybdenum metal After the heat treatment at 450 °C under helium flow for 12 h, sharper peaks in the XRD were observed at d spacing values of 239, 149, and 127 A which accurately correspond to face-centered cubic (fcc) molybdenum carbide, Mo2C (Figure 1) The synthesis of Mo2C is particularly prone to substantial oxygen contamination9 Even after heat treatment at 450 °C under helium, oxygen was still present at about 4 wt % Since the presence of oxygen could poison the catalytic activity, it was removed prior to catalytic studies by heating in a flowing 1:1 CH4/H2 mixture at 300 °C for 1 h, then at 400 °C for 1 h, and finally at 500 °C for 48 h The flow rate of the CH4/H2 mixture was 275 cm3 (STP)/min After this carburization, excess carbon, hydrogen, and oxygen had been largely removed The elemental analysis results showed the sample was very pure (theoretical for Mo2C, 9411 % Mo, 589 % C; exptl, 9386 % Mo, 568 % C, 008 % H, 006 % N), which corresponds to a stoichiometry of Mo2C097 The XRD was essentially unchanged by carburization

256 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructures, secondary phases, and grain boundaries were characterized using a range of analytical techniques including TEM, SEM, AES, and XRD, and the fracture toughness was derived either from bend tests of beam-shaped samples with a controlled surface flaw or from standard disk-shaped compact-tension specimens precracked in cyclic fatigue.
Abstract: “In situ toughened” silicon carbides, containing Al, B, and C additives, were prepared by hot pressing. Densification, phase transformations, and microstructural development were described. The microstructures, secondary phases, and grain boundaries were characterized using a range of analytical techniques including TEM, SEM, AES, and XRD. The modulus of rupture was determined from fourpoint bend tests, while the fracture toughness was derived either from bend tests of beam-shaped samples with a controlled surface flaw, or from standard disk-shaped compact-tension specimens precracked in cyclic fatigue. The R-curve behavior of an in situ toughened SiC was also examined. A steady-state toughness over 9 MPa·m1/2 was recorded for the silicon carbide prepared with minimal additives under optimum processing conditions. This increase in fracture toughness, more than a factor of three compared to that of a commercial SiC, was achieved while maintaining a bend strength of 650 MPa. The mechanical properties were found to be related to a microstructure in which platelike grain development had been promoted and where crack bridging by intact grains was a principal source of toughening.

204 citations


Journal ArticleDOI
TL;DR: In this article, a model was proposed for the active catalytic surface of the alumina-supported Mo carbide and nitride catalysts in which a thin layer of highly dispersed sulfided Mo was present on the surfaces of the catalysts.

180 citations


Patent
29 Jul 1996
TL;DR: Hardfacing to protect wear surfaces of drill bits and other downhole tools having coated diamond particles (44) dispersed within and bonded to a metallic matrix deposit was proposed in this paper.
Abstract: Hardfacing to protect wear surfaces of drill bits and other downhole tools having coated diamond particles (44) dispersed within and bonded to a metallic matrix deposit (20). The coating (42) on the diamond particles (44) may be formed from materials and alloys such as particles of tungsten carbide, and tungsten carbide/cobalt and cermets such as metal carbides and metal nitrides. The coated diamond particles (40) are preferably sintered and have a generally spherical shape. The coated diamond particles (40) are pre-mixed with selected materials such that welding and cooling will form both a metallurgical bond and a mechanical bond within the solidified metallic matrix deposit (20). A welding rod (70) is prepared by placing a mixture of coated diamond particles (40), hard particles such as tungsten carbide/cobalt (30), and loose filler material (74) into a steel tube (72). A substrate (24) is hardfaced by progressively melting the welding rod into a selected surface of the substrate (24) and allowing the melted material to solidify, forming the desired hardfacing with coated diamond particles (40) dispersed therein on the substrate surface (22).

175 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the kinetics of wetting in the reactive pure aluminium/vitreous carbon (Cv) system by the sessile drop technique in high vacuum and found that the curve showing the radius of the metal drop base R as a function of time t consisted of a central part where the radial spreading of the drop is a linear function and two extremal parts where significant deviations from linearity are observed.

163 citations


Journal ArticleDOI
TL;DR: In this paper, the catalytic performance of molybdenum nitride (Mo2N), supported on alumina (Mo 2 C Al 2 O 3 ) was compared with commercial sulfided MoS 2Al 2O 3 > and NiMoS Al 2O3 > for hydrotreating coal-derived gas oil and residuum at 633 K (360°C) and 13.7 MPa (2000 psig).
Abstract: Unsupported molybdenum nitride (Mo2N) and molybdenum carbide supported on alumina ( Mo 2 C Al 2 O 3 ) were compared against commercial sulfided MoS 2 Al 2 O 3 > and NiMoS Al 2 O 3 for hydrotreating coal-derived gas oil and residuum at 633 K (360°C) and 13.7 MPa (2000 psig). When the catalytic rates were compared on the basis of active sites measured by chemisorption, the nitrides and carbides were estimated to have activities as much as five times that of NiMoS Al 2 O 3 and MoS 2 Al 2 O 3 . The comparison was based on sites titrated by CO on the carbide and nitride and by O2 on the sulfided catalysts. The gas oil and resid product quality from the carbide and nitride catalysts was significantly better than the thermal blank, indicating that the materials were active under practical hydrotreating conditions. X-ray photoelectron spectroscopy analysis after reaction of the Mo2N and Mo 2 C Al 2 O 3 catalysts indicated that surface sulfiding was not extensive.

Journal ArticleDOI
01 Apr 1996-Wear
TL;DR: Wear surfaces of cutting tools are analyzed to study the wear mechanism of cemented carbide tools in turning in Inconel 718 superalloys as mentioned in this paper, and it is shown that during high speed turning condition (V = 35 m min−1) was caused by diffusion of elements (Ni or Fe) in workpiece into tool's binder (Co) by a grain boundary diffusion mechanism.

Journal ArticleDOI
TL;DR: The linear rule of mixtures first proposed by Stern for heterogeneous alloys was re-examined in this article, showing that the corrosion behavior of the hard metal composites cannot be predicted from that of tungsten carbide and pure cobalt.
Abstract: Accurate measurements of the polarisation curves of tungsten carbide-cobalt composites as well as those of the individual components (tungsten carbide, pure cobalt and a cobalt-tungsten-carbon alloy representing the composition of the binder phase of the liquid-phase sintered composites) in normal sulphuric acid were carried out. The linear rule of mixtures first proposed by Stern for heterogeneous alloys was re-examined. The corrosion behaviour of the hardmetal composites cannot be predicted from that of tungsten carbide and pure cobalt. Two models were tested, one in which the carbide crystals are separated from the binder alloy by a thin layer of cobalt low in both carbon and tungsten, and one where this layer is not considered. The second model agrees very well with the experimental results while the first one shows significant deviations. Calculations of the relative removal rates show that the binder corrodes faster than the carbide and is leached out in spite of exhibiting a pseudopassive behaviour owing to the formation of a porous corrosion layer. The influence of the carbide grain size and of the cobalt content on the corrosion kinetics is shown to be too small as to be of any practical importance.

Journal ArticleDOI
TL;DR: In this paper, an example of the selection of metal-ceramic Ti-TiN-TiCN supporting interlayers is given based on studies of their morphology, structure and mechanical properties.

Journal ArticleDOI
TL;DR: In this paper, twenty elements were codeposited with carbon in an arc discharge between graphite electrodes, and the majority of them were evaporated from composite anodes that contained the elements or their oxides stuffed into central bores in the graphite rods.
Abstract: Twenty elements were codeposited with carbon in an arc discharge between graphite electrodes. The majority of them were evaporated from composite anodes that contained the elements or their oxides stuffed into central bores in the graphite rods. The deposits, found in the soot at the reactor walls or as slag at the cathode, were characterized using scanning and transmission electron microscopy, electron energy loss spectroscopy, and x‐ray diffraction. The products fall into four categories: (1) elements that can be encapsulated in the form of their carbides (B, V, Cr, Mn, Y, Zr, Nb, Mo); (2) elements that are not encapsulated but tolerate the formation of graphitic carbon cages (Cu, Zn, Pd, Ag, Pt); (3) elements that form stable carbides, competing with and pre‐empting the carbon supply for the graphitic cage formation (Al, Si, Ti, W); and (4) the iron‐group metals (Fe, Co, Ni) that stimulate the formation of single‐walled tubes and strings of nanobeads in the conventional arc discharge condition, and produce the nanometer‐size carbon‐coated ferromagnetic particles in a modified arc discharge in which metals are in molten form in graphite crucible anodes exposed to a helium jet stream. The criterion determining the formation according to one of the four categories is discussed on the basis of this extended study. It is apparent that the physical properties such as vapor pressure, melting and boiling points, the completeness of the electronic shells of the elements, or their heat of carbide formation are not sufficient to explain the selectivity of the encapsulation without exceptions. A hypothesis is advanced that emphasizes the existence of the carbide, interfacial compatibility with the graphitic network, as well as the transport and supply parameters in the reaction space.

Patent
12 Mar 1996
TL;DR: In this paper, a polycrystalline diamond cutter has a coating of refractory material applied to the diamond surface to increase the operational life of the diamond cutter, which can be applied using conventional plating or other physical or chemical deposition techniques.
Abstract: A polycrystalline diamond cutter having a coating of refractory material applied to the polycrystalline diamond surface increases the operational life of the cutter. The coating typically has a thickness in the range of from 0.1 to 30 μm and may be made from titanium nitride, titanium carbide, titanium carbonitride, titanium aluminum carbonitride, titanium aluminum nitride, boron carbide, zirconium carbide, chromium carbide, chromium nitride, or any of the transition metals or Group IV metals combined with either silicon, aluminum, boron, carbon, nitrogen or oxygen. The coating can be applied using conventional plating or other physical or chemical deposition techniques.

Journal ArticleDOI
TL;DR: In this paper, a WC-Co coating was sprayed by the high-velocity oxyfuel process using a feedstock of tungsten carbide clad with cobalt, and the structure of the sprayed coating was characterized by x-ray diffraction, differential scanning calorimetry (DSC), and differential thermal analysis (DTA).
Abstract: A WC-Co coating was sprayed by the high-velocity oxyfuel process using a feedstock of tungsten carbide clad with cobalt. The structure of the sprayed coating was characterized by x-ray diffraction (XRD), differential scanning calorimetry (DSC), and differential thermal analysis (DTA). It was found that an amorphous phase of Co-W-C ternary alloy observed as a large, broad peak in the XRD pattern can be formed in the as-sprayed WC-Co coating. The DSC, DTA, and XRD analyses revealed that the amorphous phase crystallized at a temperature of around 873 K to metallic cobalt, Co6W6C, and tungsten with appreciable precipitation of free carbon. The heat treatment of as-sprayed WC-Co coating at a high temperature of 1173 K suggests that annealing at a temperature higher than about 1104 K will promote the reaction of tungsten and cobalt with carbon to form the complex carbide C06W6C.

Journal ArticleDOI
TL;DR: CVD diamond sheet tools have been available for several years as discussed by the authors, however, commercially useful thin-film (thick film, > 250 μm) tools have not yet been available.

Journal ArticleDOI
TL;DR: In this article, a comparative analysis of the surface reaction of ethylene with clean Mo(110) and carbide-modified Mo (110) has been carried out using high-resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD).
Abstract: A comparative investigation of the surface reaction of ethylene with clean Mo(110) and carbide-modified Mo(110) has been carried out using high-resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD). As typically observed for early transition metals, the clean Mo(110) surface interacts very strongly with ethylene, as indicated by the decomposition of ethylene to produce C2H2 surface species at temperatures as low as 80 K. The surface acetylene species further decompose to atomic carbon and hydrogen at higher temperatures. The strong reactivity of the Mo(110) surface can be modified by the formation of carbide. The surface reactivity is modified in such a way that the reaction mechanism of ethylene on C/Mo(110) is very similar to those typically observed on Pt-group metal surfaces: At 80 K, ethylene molecules bond to the C/Mo(110) surface in the di-σ bonded configuration; a new surface reaction intermediate, which can be best described as ethylidyne species, is d...

Journal ArticleDOI
TL;DR: In this paper, the growth of transition-metal carbide nanorods from spatially separated Ti metal and carbon nanotubes in the presence of iodide has been studied.
Abstract: Transition-metal carbide nanorods have been prepared by reacting carbon nanotubes with volatile Ti and Nb iodides. Systematic temperature-dependent growth studies of TiC nanorods produced from spatially separated Ti metal and carbon nanotubes in the presence of iodine have shown that reaction proceeds initially via the formation of a thin, uniform carbide coating and that further reaction proceeds via inward growth of this coating with a concomitant consumption of the carbon nanotube until a solid nanorod is formed. Transmission electron microscopy, selected area diffraction, and X-ray powder diffraction have been used to show that the coatings and nanorods are polycrystalline, cubic TiC. Similar results were also obtained in growth studies of of NbC nanorods from Nb metal and carbon nanotubes. These data show that the growth of TiC and NbC nanorods involves a template mechanism in which the carbon nanotubes define the overall morphology and, furthermore, demonstrate that new TiC and NbC nanotubes can be ...

Journal ArticleDOI
TL;DR: In this article, the wear rate of alumina-silicon carbide nanocomposites was measured and compared with those for pure polycrystalline aluminas of similar grain size.
Abstract: Wet erosive wear rates for alumina-silicon carbide nanocomposites have been measured and compared with those for pure polycrystalline aluminas of similar grain size. In pure materials for mean grain sizes >2 μm the dominant wear mechanism appears to be grain-boundary microfracture, leading to grain pullout; for finer grain sizes the worn surfaces are smooth. Within both grain size ranges significant reductions in wear rate are found for the nanocomposite materials, thus extending the span of established benefits obtained through the incorporation of silicon carbide nanoparticles into ceramic materials.

Patent
09 Sep 1996
TL;DR: In this paper, a polycrystalline diamond layer is bonded to a cemented metal carbide substrate by a multiple roller process, where diamond particles become rounded instead of angular due to high shear compaction.
Abstract: A polycrystalline diamond layer (27) is bonded to a cemented metal carbide substrate (21) by this process. A layer of dense high shear compaction material (27) including diamond or cubic boron nitride particles is placed adjacent to a metal carbide substrate (21). The particles of diamond have become rounded instead of angular due to high shear compaction in a multiple roller process. The volatiles in the high shear compaction material are removed and binder decomposed at high temperature, for example, 950 °C, leaving residual amorphous carbon or graphite in a layer of ultra hard material particles on the carbide substrate. The substrate and layer assembly is then subjected to a high pressure, high temperature process, thereby sintering the ultra hard particles to each other to form a polycrystalline ultra hard layer (27) bonded to the metal carbide substrate (21). The layer of high shear compaction material is also characterized by a particle size distribution including larger and smaller particles that are distributed uniformly throughout the layer.

Journal ArticleDOI
01 Jan 1996-Carbon
TL;DR: In this paper, micro-coiled carbon fibers were prepared by the impurity-activated chemical vapor deposition using the powders of metal carbides, metal oxides, and a Ni single crystal.

Journal ArticleDOI
TL;DR: In this paper, an electrochemical permeation technique was performed on mild steel and S45C medium carbon steel and the results showed that mild steel has higher permeability and diffusivity than medium carbon steels.

Patent
02 Feb 1996
TL;DR: The multiple region cermets of the present invention may be used in materials processing technology including, for example, compression technology, extrusion, supercritical processing, chemical processing, materials processing, and ultrahigh pressure.
Abstract: Methods for making, methods for using and articles including cermets, preferably cemented carbides and more preferably tungsten carbide, having at least two regions exhibiting at least one property that differs are discussed. Preferably, the cermets further exhibit a portion that is binder rich and which gradually or smoothly transitions to at least a second region. The multiple-region cermets are particularly useful in compressively loaded application wherein a tensile stress or fatigue limit might otherwise be excessive for monolithic articles. The cermets are manufactured by juxtaposing and densifying at least two powder blends having different properties (e.g., differential carbide grain size, differential carbide chemistry, differential binder content, differential binder chemistry, or any combination of the preceding). Preferably, a first region of the cermet includes a first ceramic component and a prescribed binder content and a second region, juxtaposing or adjoining the first region, of the cermet includes a second ceramic component and a second binder content less than the prescribed binder content. The multiple region cermets of the present invention may be used in materials processing technology including, for example, compression technology, extrusion, supercritical processing, chemical processing, materials processing, and ultrahigh pressure.

Journal ArticleDOI
TL;DR: In this paper, the effect of boron carbide (B 4 C) additions on the densification and sintering behavior of a titanium diboride (TiB 2 ) matrix was determined.
Abstract: The effect of boron carbide (B 4 C) additions on the densification and sintering behavior of a titanium diboride (TiB 2 ) matrix was determined. Due to the milling process, iron and tungsten carbides (WC-Co) were included as a contaminant or a third phase in the composite. When adding from 10 to 30 wt% of B 4 C to TiB 2 along with 0.5 wt% Fe sintered densities were increased from 96 to 99.9%. A small amount (0.5 wt% Fe) enhanced densification of TiB 2 . However, larger quantity (5 wt% Fe) leads to volatilization of the iron when sintering at high temperature and exaggerated grain growth. Solid solutions of (Ti,W)B 2 were also detected when 3 wt% WC-Co was present. Microstructural coarsening was inhibited by incorporation of B 4 C particles and mechanical properties were consequently improved.

Journal ArticleDOI
TL;DR: In this paper, the characteristics of hydride nucleation and growth on certain surfaces of pure uranium and of U-0.1 wt.% Cr samples were studied (under I atm H, at temperatures of 50-75 C) using the hot-stage microscope, microprobe analyzer and atomic force microscope techniques.

Patent
26 Jan 1996
TL;DR: A cutting element comprises a diamond layer and a metal carbide substrate, which form an egg-carton-shaped interface as mentioned in this paper, and the diamond layer is used to cut the substrate.
Abstract: A cutting element comprises a diamond layer and a metal carbide substrate. The diamond layer and the metal carbide substrate form an egg-carton shaped interface.

Patent
08 May 1996
TL;DR: In this article, the atomic ratio of platinum to aluminum is from 80:20 to 60:40 and the alloy is present on the carbon carrier in carbidized form with the structure of platinum-aluminum carbide Pt 3 AlC 0.5.
Abstract: A catalyst for use in a fuel cell containing a platinum-aluminum alloy on a conductive carbon carrier, wherein the atomic ratio of platinum to aluminum is from 80:20 to 60:40 and the alloy is present on the carbon carrier in carbidized form with the structure of platinum-aluminum carbide Pt 3 AlC 0 .5. Also disclosed are multimetallic alloy catalysts for use as electrode catalysts in fuel cells. Catalysts with high activity and stability are obtained on the basis of carbidized platinum-aluminum alloy catalysts by adding alloying elements of the groups VIB, VIIB, VIII and IB of the Periodic Table of Elements.

Journal ArticleDOI
TL;DR: In this article, three laser surface modified samples were prepared, one by laser melting, and the other two by laser melt/particle injection processing with tungsten carbide and titanium carbide (TiC) particles, respectively.
Abstract: Seawater corrosion behavior of laser surface processed Inconel 625 alloy was investigated. Three laser surface modified samples were prepared, one by laser melting, and the other two by laser melt/particle injection processing with tungsten carbide (WC) and titanium carbide (TiC) particles, respectively. Particle injection involved embedding the carbide particles into a laser melted surface and resulted in a metal matrix-particulate composite surface layer which was both hard and wear-resistant. While Inconel 625 is a corrosion resistant alloy suitable for marine applications, and WC and TiC are generally inert to chemical attack, results from this study showed that laser surface modification produced microstructures that were susceptible to seawater corrosion to varying degrees. Nominal corrosion was observed in the dendritic structure produced by laser melting of the alloy surface. In the particle injected samples, the WC particulate phase in contact with the Inconel alloy matrix showed different kinds of attack, while the TiC particulate phase showed none. In both particle injected samples, resolidification of the Inconel alloy melt produced significant departures in composition and microstructure from those of the base alloy. Eutectic and dendritic carbides and, in WC, interphase carbides were some of the resolidification byproducts that formed in the matrix surrounding the particulate. Alloyed with solute elements from the base alloy, each product phase contributed to unique forms of corrosion. A qualitative analysis of the corrosion behavior of the injected samples showed that corrosive damage was more severe in the WC injected sample than in the TiC injected sample and in the laser melted sample. This paper describes the processing, microstructural and compositional characterization, and seawater corrosion behavior of the laser surface modified samples, and attempts to explain the observations as a consequence of the formation of galvanic cells.