Carbide

About: Carbide is a research topic. Over the lifetime, 36331 publications have been published within this topic receiving 503586 citations.

Microstructural Studies of the Interfacial Zone of a SiC-Fiber-Reinforced Lithium Aluminum Silicate Glass-Ceramic

Abstract: Transmission electron microscopy studies have been conducted on interfaces in a lithium aluminum silicate/SiC-fiberreinforced composite. In the as-processed state, interphases of amorphous C and carbides of Nb have been confirmed, with circumferential thermal debonds evident in the C layer. After heat treatment in air at 800°C, the C is found to be replaced by amorphous SiO2, and the carbides of Nb replaced by oxides. The SiO2 thickens with exposure time and typically contains circumferential separations. Some Mg and Al diffusion also accompanies the heat-treatment process and eventually leads to the formation of MgO and Mg silicates in the interfacial zone.

Wear-Resistant Cobalt-Base Alloys

Abstract: Cobalt-base alloys have enjoyed extensive use in wear-related engineering applications for well over 50 years because of their inherent high-strength, corrosion resistance, and ability to retain hardness at elevated temperatures. Microstructurally, wear-resistant cobalt-base alloys consist of hard particles (Cr7C3) dispersed in cobalt-rich (Co > 50%) solid solution matrix alloys (generally Co-Cr-W/Mo). Recent investigations in the Cabot Corporation Technology Laboratories have shown that the adhesive and cavitation-erosion wear characteristics of these alloys are determined by the composition of the matrix alloy and are influenced to a large extent by a strain-induce fee → hep allotropie transformation in the matrix alloy. Further, it has been shown that the cobalt content in the matrix alloy can be decreased to approximately 30% without significantly degrading relevant wear or corrosion properties. Toughness and abrasive wear resistance, on the other hand, are determined primarily by carbide volume fraction and morphology. Large, hypereutectic carbides are generally preferred for good abrasive wear resistance but are detrimental to toughness considerations. The tribological measurements and microstructural correlations associated with these Cabot investigations are summarized and discussed in this paper.

Correlation of the electrical properties of metal contacts on diamond films with the chemical nature of the metal-diamond interface. I. Gold contacts: A non-carbide-forming metal.

Abstract: The I-V characteristics of titanium contacts on polycrystalline diamond have been correlated with x-ray-photoelectron-spectroscopy (XPS) and Auger-electron-spectroscopy (AES) characterizations of the interface. As-deposited titanium contacts were rectifying in nature because of minimal interaction between as-deposited titanium and diamond as confirmed via XPS and AES. Once annealed, however, these contacts became Ohmic. The change was related to the formation of a carbide at the interface as observed by XPS. The Schottky-barrier height of the titanium contacts, which was determined by valence-band XPS, decreased from 1.3 to 0.8 eV as a result of the postdeposition annealing. It is believed that the carbide formation at the interface creates a diamond surface layer rich in electrically active defects which lower the barrier height of the metal and increase the leakage current. The interface between titanium and an argon-sputtered diamond surface was also characterized. Titanium formed as-deposited Ohmic contacts on the sputtered surface. A high density of ion-radiation-induced defects and a formation of a carbide during deposition both contributed to the Ohmic-contact formation. These contacts remained Ohmic after postdeposition annealing despite the fact that the annealing did not increase the carbide formed at the interface. It is believed that the carbide formed by the deposition of titanium behaved as a diffusion barrier to prevent the damaged layer from being annealed out into the titanium overlayer. It is concluded that most materials will yield rectifying contacts on a clean diamond surface. Ohmic contacts can be obtained by modifying the interface in some way (i.e., carbide formation, sputtering, etc.).

Heart pacemaker system

Abstract: Provided in order to avoid or at least reduce the problems produced by the passive electrode of a heart pacemaker system is a layer having a high double layer capacitance at the phase boundary with the bodily fluid. Advantageous to that end is a porous layer comprised of a carbide, nitride or carbonitride of at least one of the metals titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum or tungsten. The layer can also be comprised of activated carbon with a microporous exposed surface. The layer is produced in the simplest manner by means of roughening the existing electrode surface at its active area.