Introduction:

We report depressurization amorphization of single-crystal boron carbide (B4C) investigated by in situ high-pressure Raman spectroscopy. It was found that localized amorphization of B4C takes place during unloading from high pressures, and nonhydrostatic stresses play. Silicon carbide is composed of tetrahedra of carbon and silicon atoms with strong bonds in the crystal lattice. This produces a very hard and strong material. Silicon carbide is not attacked by any acids or alkalis or molten salts up to 800°C. In air, SiC forms a protective silicon oxide coating at 1200°C and is able to be used up to 1600°C. YAP Single Crystal; Yttria Stabilized Zirconia (YSZ) Single Crystal; Safety Data Sheets (pdf) Get in touch. Open here for our page navigation. Boron Carbide Powder B4C 99.5% pure. Applications: Boron Carbide is an exceptionally hard chemical product used in the Grinding, Lapping. The results show that air-cooling and water-cooling have little effect on TiC content of molten carbide blast furnace slag, and have great effect on crystal structure and grain size. TiC content in slag is different when carbide blast furnace slag is crushed in argon atmosphere and air atmosphere.

Boron carbide (B4C) is an extremely hard material with a melting temperature above 2000°C; its electronic properties vary strongly with the precise composition.

PARADIM’s Tilting Laser Diode Floating Zone Furnace enables users to routinely grow B4C single crystals for further study. The in-situ monitoring of gas-phase species during the growth provides insights on the underlying mechanism by which the composition changes and enables the successful growth of single crystals with controlled stoichiometry. Various growth rates were explored to mitigate microstructure defects (including stacking faults, SF) and zone refinement allowed for a significant reduction of trace impurities. Initial analysis by powder x-ray diffraction confirms that the crystals are indeed rhombohedral B4C, with a hardness of 41±1 GPa and a Young’s modulus of 520±14 GPa revealed by nano-indentation. Laser light was found to induce graphitization in the presence of air, enabling a new process to fabricate electronic structures in boron carbide with micron or nanoscale precision.

M. Straker et al. J. Cryst. Growth543, 125700 (2020).

M.V.S. Chandrashekhar et al., U.S. Patent No. US20190352234-A1 (21 November 2019).

Figure 1: (top left) Photograph of a boron carbide crystal. (bottom left) View into the laser diode floating zone furnace (right) Scanning electron microscopy images of a B₄C single crystal with indicated stacking fault lines.

Technical details: We report the growth of 4 mm diameter × 50 mm long Boron Carbide (B₄C) with large single crystal regions using a Laser Diode Floating Zone (LDFZ) method at varying growth rates of 5–20 mm/hr. These materials were grown using polycrystalline B₄C as a seed. Microstructural characterization shows the presence of a significant number of twinning-boundaries along the growth direction ([0 0 1]_h) oriented in the (1210)_h plane. At faster growth rates >10 mm/hr, the crystal orientation was reproducible, suggesting a twin-plane mediated growth mechanism. On the contrary, at slower growth rates <10 mm/hr the crystal orientation was not reproducible, suggesting a critical rate for twin-plane mediated growth to dominate.

Zone refinement of these crystals led to a significant reduction of trace impurities to better than 99.999 wt% purity, at the expense of increased twinning. Powder x-ray diffraction confirms that the bulk is rhombohedral B₄C, consistent with the microstructural analysis. The X-ray reciprocal space maps reveal the growth direction to be close to the [001]_hdirection, and the corresponding ω-rocking curve width is ~530 arcsec. The rocking curve consisted of 3 distinct peaks, indicating in-plane mosaicism, consistent with the twinning observed. Berkovich nano-indentation of the key (001)_h plane showed 41 ± 1 GPa hardness, with a Young’s modulus of 520 ± 14 GPa, comparable to literature reports. In addition, it was discovered that the laser field could induce graphitization of boron carbide in air, a new, previously unknown phenomena that led to a patent application due to the potential uses of the technique in fabricating electronic structures in single crystal boron carbide substrates.

Researchers of Morgan State University initialized and performed the work at the PARADIM Bulk Crystal Growth Facility located at John Hopkins University.

Full references:

Michael Straker, Ankur Chauhan, Mekhola Sinha, W. Adam Phelan, M.V.S. Chandrashekhar, Kevin J. Hemker, Christopher Marvel, and Michael Spencer, “Growth of high purity zone-refined Boron Carbide single crystals by Laser Diode Floating Zone method,” J. Cryst. Growth543, 125700 (2020).

M.V.S. Chandrashekhar, Joshua Letton, Travis Williams, Abdulganiyu Ajilore, and Michael Spencer “Laser Induced Graphitization of Boron Carbide in Air,” U.S. Patent No. US20190352234-A1 (21 November 2019) https://patents.google.com/patent/US20190352234A1/en.

Silicon Carbide is the only chemical compound of carbon and silicon. It was originally produced by a high temperature electro-chemical reaction of sand and carbon. Silicon carbide is an excellent abrasive and has been produced and made into grinding wheels and other abrasive products for over one hundred years. Today the material has been developed into a high quality technical grade ceramic with very good mechanical properties. It is used in abrasives, refractories, ceramics, and numerous high-performance applications. The material can also be made an electrical conductor and has applications in resistance heating, flame igniters and electronic components. Structural and wear applications are constantly developing.

.Key Silicon Carbide Properties
Low density
High strength
Low thermal expansion
High thermal conductivity
High hardness
High elastic modulus
Excellent thermal shock resistance
Superior chemical inertness
. Silicon Carbide Typical Uses
Fixed and moving turbine components
Suction box covers
Seals, bearings
Ball valve parts
Hot gas flow liners

.Key Silicon Carbide Properties

Silicon Carbide Typical Uses

B4c Single Crystal