New Borate Precursors for Boron Nitride Powder Synthesis

Abstract

The thermal decomposition of guanidinium tetraborate, pentaborate, and nonaborate has been characterized under nitrogen and ammonia atmospheres, and conditions have been defined for bulk powder and aqueous aerosol transformations of these precursors to boron nitride (BN). The bulk pyrolyses under ammonia (600-1400 °C) produce micrometer-and sub-micrometer-sized platelet morphology particles with oxygen contents of 3-18 wt. %. Subsequent pyrolysis of these powders at 1600 °C under NH 3 reduces the oxygen contents to <1 wt. %. Pyrolysis of aqueous aerosols containing the guanidinium borates gives submicrometer spherical morphology BN particles. The chemistry and processing of guanidinium borates are compared with the behavior of alternative precursors.

Comparative study of boron compounds and aluminum trihydroxide as flame retardant additives in epoxy resin

“…. The detailed spectrum analysis of MB and GB was made in the previous studies, and the results were in accordance with these studies …”

Thermal stability and flame retardancy of guanidinium and imidazolium borate finished cotton fabrics

“…The calculated TG curves are obtained on the basis of common additive rules. As already demonstrated in the literature [23,24], the degradation of GB (Fig. 2) and IB (Fig.…”

“…3) occurs in two steps in nitrogen via dehydration (first step) and the degradation of amine moiety (second step). The detailed analysis carried out by Schubert et al [23] and Wood et al [24] showed that the gaseous products of water, CO 2 , and NH 3 are formed during the degradation of both boron compounds. Also in our case, the same mechanism has been observed, and at the end of the test at 1,073 K, GB and IB retain 46 and 58 % of their mass, respectively.…”

“…The borate ester formation via reaction with boric acid and cellulose favors the char formation [2,22,30]. During the thermal degradation of GB and IB, nitrogencontaining intermediates which are basic in nature are formed [23,24]. As stated in the previous studies that investigate the effect of nitrogen-containing flame retardants including guanidine compounds on thermal stability of cellulosic materials, the basic intermediates can react with cellulose to form more thermally stable char [31,32].…”

“…The peaks seen between 1,050 and 890 cm -1 are the characteristics of asymmetric stretching modes of B-O in tetrahedral boron (BO 4 ). The bands seen at 1,650 and 1,595 cm -1 arise from the bending vibrations of N-H group for GB and IB, respectively [24][25][26][27].…”