Production of boron nitride

Download

index.pdf

Date

2008

Author

Özkol, Engin

Metadata

Show full item record

Item Usage Stats

225
views

108
downloads

Boron nitride is found mainly in two crystal structures; in hexagonal structure (h-BN) which is very much like graphite and in cubic structure (c-BN) with properties very close to those of diamond. h-BN is a natural lubricant due to its layered structure. It is generally used in sliding parts of the moving elements such as rotating element beds in turbine shafts. Since c-BN is the hardest known material after diamond it is used in making hard metal covers. In addition to its possible microelectronics applications (can be used to make p-n junction), its resistance to high temperatures and its high forbidden energy gap are its superiorities over diamond. Recent studies have shown that c-BN can be produced by Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) in plasma. But these studies have failed to determine how all of the production parameters (boron and nitrogen sources, composition of the gas used, substrate, RF power, bias voltage, substrate temperature) affect the c-BN content, mechanical stress and the deposition rate of the product with a systematic approach. The systematic study was realized in the range of available experimental ability of the present PVD and CVD equipment and accessories. The BN films were produced in the plasma equipment for CVD using RF and MW and magnetron sputtering and were studied with the measurement and testing facilities. It is believed that with this approach it will be possible to collect enough experimental data to optimize production conditions of BN with desired mechanical and optoelectronic properties. h-BN films were successfully deposited in both systems. It was possible to deposit c-BN films with the MW power, however they were weak in cubic content. Deposition at low pressures eliminated the hydrogen contamination of the films. High substrate temperatures led to more chemically and mechanically stable films.

Subject Keywords

Chemical engineering.

URI

http://etd.lib.metu.edu.tr/upload/12609646/index.pdf
https://hdl.handle.net/11511/18192

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Chemical vapor deposition of boron carbide Karaman, Mustafa; Özbelge, Önder; Department of Chemical Engineering (2007) Boron carbide was produced on tungsten substrate in a dual impinging-jet CVD reactor from a gas mixture of BCl3, CH4, and H2. The experimental setup was designed to minimise the effect of mass transfer on reaction kinetics, which, together with the on-line analysis of the reactor effluent by FTIR, allowed a detailed kinetic investigation possible. The phase and morphology studies of the products were made by XPS, XRD,micro hardness and SEM methods. XPS analysis showed the existence of chemical states attrib...
Dynamic Behavior of continuous flow stirred slurry reactors in boric acid production Yücel Çakal, Gaye Ö; Eroğlu, İnci; Department of Chemical Engineering (2004) One of the most important boron minerals, colemanite is reacted with sulfuric acid to produce boric acid. During this reaction, gypsum (calcium sulfate dihydrate) is formed as a byproduct. In this study, the boric acid production was handled both in a batch and four continuously stirred slurry reactors (4-CFSSR̕s) in series system. In this reaction system there are at least three phases, one liquid and two solid phases (colemanite and gypsum). In a batch reactor all the phases have the same operating time (...
Determination of degree of mixing in solid rocket propellants Yeşilırmak, Yener; Yılmazer, Ülkü; Department of Chemical Engineering (2006) Composite propellants are mainly composed of: crystalline oxidizer, metallic fuel, and polymeric binder. Additives, such as plasticizers, catalysts, bonding agents and curing agents may also be incorporated to propellant compositions in small amounts. These ingredients should be mixed rigorously in order to obtain a uniform microstructure throughout the cast propellant profile. The quality of the propellant mixture has to be determined quantitatively to improve the product quality and to reduce costs. In th...
Dissolution of colemanite and crystallization of gypsum during boric acid production in a batch reactor Erdoğdu, Anıl; Eroğlu, İnci; Department of Chemical Engineering (2004) One of the most commonly used boron compounds, boric acid, is produced by dissolving colemanite (2CaO₉3B2O3₉5H2O) in aqueous sulfuric acid whereby gypsum (CaSO4₉2H2O) is formed as a byproduct and must be separated from the main product. This process consists of two steps, dissolution of colemanite and formation of gypsum. The amount of boric acid formed depends on the first step, dissolution of colemanite. In the latter step, gypsum crystals are formed and stay in the reaction mixture to grow up to a size l...
Biological hydrogen production on acetate in continuous panel photobioreactors using rhodobacter capsulatus Androga, Dominic Deo; Eroğlu, İnci; Department of Chemical Engineering (2009) Photobiological hydrogen production from organic acids occurs in the presence of light and under anaerobic conditions. Stable and optimized operation of the photobioreactors is the most challenging task in the photofermentation process. The main aim of this study was to achieve in long term, a stable and high hydrogen production on acetate, using the photosynthetic bacteria Rhodobacter capsulatus in continuous panel photobioreactors. Rhodobacter capsulatus (DSM 1710), heat adapted Rhodobacter capsulatus (DS...

Citation Formats

E. Özkol, “Production of boron nitride,” M.S. - Master of Science, Middle East Technical University, 2008.