Synthesis of cBN by Emulsion Detonation Synthesis
Abstract
In the proposed research program, Rutgers will examine the amorphous B-C-N-O system. They propose to synthesize a metastable amorpho"us material that contains sp3 bond which will be utilized to help reducing the temperature and pressure requirement for conversion t"o c-BN. They will employ Emulsion Detonation Synthesis (EDS) method. In their approach, they will utilize amorphous boron-nitrogen-o""xygen-carbon compounds (a-BCNO) as starting materials, which will undergo a transformation under non-equilibrium conditions that pos""sesses extreme pressure and temperatures during the explosion. Dramatic quenching, which will provide desired metastable supercoole""d phase or phases with sp3 hybridization, will be followed. They state that significantly lower pressures and temperatures can be ut""ilized to successfully synthesize c-BN by employing a metastable, amorphous and sp3 bonded starting material. The revolutionary oppo""rtunity lies in the ability to reduce the transformation pressure to achieve high pressure phase and to produce a sinterable, bulk s""hape at lower pressures consistent with normal material processing pressures (<1 GPa), which would be the first scalable methodology" for the production of high pressure phase of superhard cBN materials.Abstract:Friction stir welding is energy efficient solid st"ate joining technique that creates high quality, high strength joints with low distortion without the use of fusion or filler materi""al. In this process, a rotation tool containing a pin and a shoulder is employed to generate heat between the two facing pieces by f""riction without melting the workpiece material1, 2, 3. Friction stir welding has initially been applied to metals and their alloys w""ith relatively low melting points such as aluminum,copper, magnesium etc. And it has later been employed for the joining process of"" materials with higher melting points such as steels, stainless steels, titanium and nickel based alloys through the improvement of" tool material1. The requirements for the tool material are critical since it has to stand up to the high stresses and temperatures" needed for the process. Necessity of high strength, resistance to fatigue, fracture, wear and chemical reactions with both environm""ent and the weldmaterial are the essential physical and chemical properties for the tool materials. In meeting theserequirements," cubic form of boron nitride (c-BN) has recently been utilized1. c-BN has unique properties including extreme hardness (~45 or 70 GP"a), which is only next to diamond, great compressive strength and stiffness, high thermal conductivity and high electrical resistivi"ty. Higher temperature oxidation resistance and higher chemical stability against ferrous metals makes c-BN more suitable for engine"ering hardened or alloyed steels than diamond4, 5. Thus, it has been usedas abrasive in the fields of grinding and cutting and also" tool material for friction stir welding process. 1. c-BN is typically synthesized using hexagonal BN (h-BN) as a starting material and it requires very high pressure (>8 GPa) processing due to the fact that there are two high activation energy barriers to overcome to transform h-BN to c-BN.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712532
Entities
People
- Richard A Haber
Organizations
- Office of Naval Research
- Rutgers University
- United States Navy