Boron nitride boric acid

The microstructure of products of ferroboron combustion in nitrogen has various morphological forms. At the same time, a significant difference is visible in shape of particles of external and central parts of the burned sample. The presence of amorphous boron in the original material influences the process of nitride formation because (according to XRD analysis) amorphous boron contains boric acid which decomposes during combustion forming boric anhydride and water. 

Hexagonal boron nitride is relatively stable in oxygen or chlorine up to 700°C, probably because of a protective surface layer of boric oxide. It is attacked by steam at 900°C, and rapidly by hot alkaU or fused alkaU carbonates. It is attacked slowly by many acids as well as alcohols (to form borate esters), acetone, and carbon tetrachloride. It is not wetted by most molten metals or many molten glasses. 

Preparation. Hexagonal boron nitride can be prepared by heating boric oxide with ammonia, or by heating boric oxide, boric acid, or its salts with ammonium chloride, alkaU cyanides, or calcium cyanamide at atmospheric pressure. Elemental nitrogen does not react with boric oxide even in the presence of carbon, though it does react with elemental boron at high temperatures. Boron nitride obtained from the reaction of boron trichloride or boron trifluoride with ammonia is easily purified. 

Molybdenum disulhde (M0S2), graphite, hexagonal boron nitride, and boric acid are examples of lamella materials commonly applied as solid lubricants. The self-lubricating nature of the materials results from the lamella crystalline structure that can shear easily to provide low friction. Some of these materials used to be added to oils and greases in powder forms to enhance their lubricity. Attention has been shifted in recent years to the production and use of nanosize particles of M0S2, WS2, and graphite to be dispersed in liquid lubricants, which yields substantial decreases in friction and wear. 

Boron trichloride Boron trifluoride Fluoroboric acid Potassium tebafluoroborate Boric acid Boron nitride Sodium perborate Diborane... 

A colorless gel formed which was isolated by vacuum evaporation of the volatiles. The resulting colorless glassy solid was pyrolyzed in vacuo at 900°C for 24 hours in a quartz tube and the evolved volatiles identified as NH3 and NH4CI. The remaining solid was briefly (2 hours) heated in air at 1200°C in order to remove minor carbon impurities and to improve crystallinity. This solid was then treated at room temperature with 40% aqueous HF to remove boric acid and silica formed in small quantities. The solid obtained at 900°C was identified as boron nitride however, the majority of the material was amorphous. After treatment at 1200°C, white crystalline boron-nitride was obtained in about 55% yield. 

The c-BN phase was first obtained in 1957 [525] by exposing hexagonal boron nitride phase (h-BN) to high pressures and low temperatures. A pressure of more than 11 GPa is necessary to induce the hexagonal to cubic transformation, and these experimental conditions prevent any practical application for industrial purposes. Subsequently, it has been found that the transition pressure can be reduced to approximately 5 GPa at very high temperature (1300-1800°C) by using catalysts such as alkali metals, alkali metal nitrides, and Fe-Al or Ag-Cd alloys [526-528]. In addition, water, urea, and boric acid have been successfully used for synthesis of cubic boron nitride from hexagonal phase at 5-6 GPa and temperature above 800-1000°C [529]. It has been... 

Heating with metal oxides at elevated temperatures produces anhydrous borates. Reactions with halogens in the presence of carbon at temperatures above 500°C give boron trdialides. Heating a mixture of boric acid, ammonia and calcium phosphate in an electric furnace produces boron nitride. 

Nitride Boron nitride, BN, white solid, insoluble, reacts wiLh steam Lo form NHj and boric acid, formed by heating anhydrous sodium borate with ammonium chloride, or by burning boron in air. 

The traditional method for the preparation of boron nitride is by the fusion of urea with boric acid in an atmosphere of ammonia at 750 °C.54 The product from these reactions is hexagonal boron nitride with a layer structure like that of graphite. Unlike graphite, it is colorless and is not an electronic conductor. Conversion of the hexagonal form to a cubic modification requires heating at 1,800 °C at 85,000 atmospheres pressure. 

Boron nitride (BN) can normally be prepared from the reaction of boric acid and urea or melamine. For example, the pyrolysis of MB can yield hexagonal BN. It is commonly referred to as white graphite because of its platy hexagonal structure similar to graphite. Under high pressure and at 1600°C, the hexagonal BN is converted to cubic BN, which has a diamond-like structure. 

Bando and co-workers271 have prepared BN nanolubes by the reaction of MgO, FeO and B in the presence of NH, at 1400 °C. Reaction of boric acid or B20, with N2 or NH, at high temperatures in the presence of carbon or catalytic metal particles has been employed in the preparation of BN nanotubes.2 2 Boron nitride nanotubes can be grown directly on substrates at 873 K by a plasma-enhanced laser-deposition technique.172 Recently, GaN nanotube brushes have been prepared using amorphous carbon nanotubes templates obtained using AAO membranes.274... 

A mixture of boric acid (1 g) and urea (11.8 g) was taken in 40 ml distilled water and heated at 70 °C until the solution became viscous the a-CNTs were soaked in it for nearly 2 h. They were later separated physically and dried in air at 40 C overnight. The dried sample was thermally treated at 970 °C for 3 h for 40 nm nanotubes in a N2 atmosphere, and for 12 h in the case of the larger diameter (170 nm) nanotubes, and then cooled down to room temperature. The product was subsequently heated in an NHt atmosphere at 1050 °C in case of 170 nm nanotubes and 900 C in case of 40 nm nanotubes for three hours to give black-coloured boron-carbon-nitride nanotube brushes. The products were investigated by transmission electron microscopy and other physical techniques. 

The main source of boron is a complex compound of boron called borax. About half of the world supply of borax comes from a large deposit in California s Mojave Desert. Borax is used as a cleaning agent and as fireproof insulation. Another compound of boron, boric acid, is used as a disinfectant and as an eye wash. A form of boron nitride is the second hardest known material only diamond is harder. These materials are classified as superabrasives. They are used in grinding wheels, which shape manufactured parts and tools. 

The preparation of boron nitride from orthoboric acid and urea is described by T. E. O Connor [81]. Special measures are required to remove the last traces of boric oxide commercial preparations are likely to be significantly contaminated with 820 and water. Deacon and Goodman [11] found a small loss of volatiles at 373-423 K from boron nitride subjected to thermogravimetric analysis in air and a large increase in weight at 1123-1173 K, which is the temperature range of the active oxidation of BN to B2O2. 

BORON FLUORIDE (7637-07-2) BF3 Noncombustible gas. A powerful oxidizer. Reacts with moist air, water, or steam, producing hydrogen fluoride boric acid and fluoboric acid. Reacts violently with reducing agents, including hydrides, nitrides. 

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