Reinforcement boron nitride

Cera.micA.bla.tors, Several types of subliming or melting ceramic ablators have been used or considered for use in dielectric appHcations particularly with quartz or boron nitride [10043-11 -5] fiber reinforcements to form a nonconductive char. Fused siHca is available in both nonporous (optically transparent) and porous (sHp cast) forms. Ford Aerospace manufactures a 3D siHca-fiber-reinforced composite densified with coUoidal siHca (37). The material, designated AS-3DX, demonstrates improved mechanical toughness compared to monolithic ceramics. Other dielectric ceramic composites have been used with performance improvements over monolithic ceramics (see COMPOSITE MATERIALS, CERAMIC MATRIX). 

Method b, the so-called hot pressing method is suitable for making dense composites. A 2D woven Hi-Nicolon tissue with or without a boron nitride coating (BN) is used as reinforcement. All of this is illustrated by the following photographs. 

Metals and ceramics (claylike materials) are also used as matrices in advanced composites. In most cases, metal matrix composites consist of aluminum, magnesium, copper, or titanium alloys of these metals or intermetallic compounds, such as TiAl and NiAl. The reinforcement is usually a ceramic material such as boron carbide (B4C), silicon carbide (SiC), aluminum oxide (A1203), aluminum nitride (AlN), or boron nitride (BN). Metals have also been used as reinforcements in metal matrices. For example, the physical characteristics of some types of steel have been improved by the addition of aluminum fibers. The reinforcement is usually added in the form of particles, whiskers, plates, or fibers. 

Recent research has explored a wide variety of filler-matrix combinations for ceramic composites. For example, scientists at the Japan Atomic Energy Research Institute have been studying a composite made of silicon carbide fibers embedded in a silicon carbide matrix for use in high-temperature applications, such as spacecraft components and nuclear fusion facilities. Other composites that have been tested include silicon nitride reinforcements embedded in silicon carbide matrix, carbon fibers in boron nitride matrix, silicon nitride in boron nitride, and silicon nitride in titanium nitride. Researchers are also testing other, less common filler and matrix materials in the development of new composites. These include titanium carbide (TiC), titanium boride (TiB2), chromium boride (CrB), zirconium oxide (Zr02), and lanthanum phosphate (LaP04). 

Wider use of fiber-reinforced ceramic matrix composites for high temperature structural applications is hindered by several factors including (1) absence of a low cost, thermally stable fiber, (2) decrease in toughness caused by oxidation of the commonly used carbon and boron nitride fiber-matrix interface coatings, and (3) composite fabrication (consolidation) processes that are expensive or degrade the fiber. This chapter addresses how these shortcomings may be overcome by CVD and chemical vapor infiltration (CVI). Much of this chapter is based on recent experimental research at Georgia Tech. 

Because most development work has been done on non-oxide materials, particularly SiC fiber-reinforced SiC CMCs (SiC/SiC) with fiber interfacial coatings of either carbon or boron nitride, non-oxide CMCs are more advanced than oxide CMCs. Non-oxide CMCs have attractive high temperature properties, sueh as creep resistance and microstructural stability. They also have high thermal conductivity and low thermal expansion, leading to good thermal stress resistance. Therefore, non-oxide CMCs are attractive for thermally loaded components, such as combustor liners (see Figure 1-4), vanes, blades, and heat exchangers. 

Fiber reinforced ceramic matrix composites (CMCs) are under active consideration for large, complex high temperature structural components in aerospace and automotive applications. The Blackglas resin system (a low cost polymer-derived ceramic [PDC] technology) was combined with the Nextel 312 ceramic fiber (with a boron nitride interface layer) to produce a sihcon oxycarbide CMC system that was extensively characterized for mechanical, thermal, and electronic properties and oxidation, creep mpture, and fatigue. A gas turbine tailcone was fabricated and showed excellent performance in a 1500-hour engine test. 

This chapter will describe the processing and properties of an oxide fiber reinforced ceramic matrix composite with a silicon oxycarbide matrix based on a PDC technology, introduced by AlliedSignal (now Honeywell International) under the trademark of Blackglas ceramic. The oxide fiber in this CMC system is the Nextel 312 fiber (3M, Inc.) that has been treated to form a boron nitride surface coating. The information that follows was primarily developed from Low Cost Ceramic Matrix Composites (LC ) program funded by DARPA from 1991-1997. 

S. Campbell, Silicon Caiboxide Composite Reinforced with Ceramic Fibers Having a Surface Enriched in Boron Nitride , U.S. Patent 5,955,194, Sept 99. 

Metal matrix nanocomposites are those having metal as the continuous phase or matrix and other nanoparticles like carbon nanotube as the reinforced materials. These types of composites can be classified as continuous and noncontinuous. One of the more important nanocomposites is Carbon nanotube reinforced metal matrix composite, which is an emerging new material with the high tensile strength and electrical conductivity of carbon nanotube materials. In addition to carbon nanotube metal matrix composites, boron nitride reinforced metal matrix composites and carbon nitride metal matrix composites are the new research areas on metal matrix nanocomposites [9,10]. 

Alumina 9- lu-m9-n9 [NL, fr. L alumin-. alumen alum] (1801) (corundum) n. The oxide of aluminum, AI2O3, very refractory and next to diamond and boron nitride in hardness, obtained by the calcinations of bauxite. Alumina powder is used as a fire-retardant filler in plastics and, over the past two decades, alumina fibers have enjoyed increasing use as reinforcements for plastics, metals, and even ceramics. Its density is 3.965 g/cm. ... 

Lahiri D et al (2010) Boron nitride nanotube reinforced polylactide-polycaprolactone copolymer composite Mechanical properties and cytocompatibility with osteoblasts and macrophages in vitro. Acta Biomater 6(9) 3524—3533... 

The different types of boron nitride composites cited can be reinforced with fibrous materials such as titanium alloy fibers [287], Si/Zr oxynitride fibers [288], SiOg/TiOg/ZrOg fibers [289], and carbon fibers [290 to 292, 313] (see also Section 4.1.1.10.1, p. 58). BN-containing oxide and carbide ceramics are used to protect graphite from being attacked in metallurgical processes [293 to 295]. Porous ceramics and ceramic foams which can be infiltrated either with metals or lubricants may contain a-BN or are produced in boron nitride ceramic molds [296 to 299]. 

Silicon carbide and alumina still dominate the abrasive industry at the present time. However their performance in the grinding of superalloys, ceramics, reinforced plastics, and other hard materials is generally unsatisfactory. This has led to the development of new abrasives such as synthetic diamond and cubic boron nitride. Cubic boron nitride was first synthesized in 1957 and has been available commercially since the 1970 s. Although not as hard as diamond, c-BN does not react with carbide formers such as Fe, Co. Ni, Al, Ta, and B at 1000 (while diamond does). However, it reacts with aluminum at 1050°C, with Fe and Ni alloys containing Al above 12S0"C, and with water and water-soluble oils.1 1... 

Twin-screw extrusion is used to blend additives, fillers, and reinforcements to polymers as well as blending of two or more polymers. For instance, additives are combined with biopolymers in a twin-screw extruder to increase the strength and mechanical properties. PHA materials are compounded with acrylic impact modifiers and boron nitride nucleating agent in a twin-screw extruder to improve the strength of PHA and increase the crystallinity percentage (Greene 2013). 

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