Effect of Molecular Structure of Polyols with Different Molecular Characteristics on Synthesis of Boron Carbide Powder

Abstract

Crystalline boron carbide (B4C) powder was synthesized by the carbothermal reduction of condensed products formed from boric acid (H3BO3) and polyols with different molecular characteristics, i.e., glycerin, mannitol, and poly (vinyl alcohol) (PVA). The effect of the molecular structure of the polyol on the thermal decomposition conditions and the obtained morphology of the B4C powder was discussed in this study. The thermal decomposition in air of each condensed product was performed before the carbothermal reduction in order to eliminate the excess carbon, where the decomposition conditions varied with the type of polyol. Crystalline B4C powder with less residual free carbon was synthesized from the thermally decomposed products by heating at 1250 °C for 5 h in an Ar flow. The thermal decomposition conditions and the particle size of the obtained B4C powder reflected the molecular characteristics of the polyols.

Low‐Temperature Synthesis of Calcium Hexaboride Powder via Transient Boron Carbide Formation

“…]. This formation temperature of B 4 C is consistent with our previous results for the low‐temperature synthesis of B 4 C . The intensity of the peaks attributed to B 4 C increased with increasing heat treatment temperature up to 1350°C.…”

“…The morphology of the obtained CaB 6 particles is affected by the size of the B 4 C particles used as a raw material . In our low‐temperature synthesis method for B 4 C powder, a fine B 4 C powder is obtained without a postgrinding process . This is because the number of nucleation sites increased with the dispersion of the boron and carbon sources.…”

“…To achieve this approach, we focused on our low‐temperature synthesis method for B 4 C powder . This method is described as follows: a B 4 C precursor consisting of B 2 O 3 and carbon components is prepared from a condensed boric acid (H 3 BO 3 )‐polyol product by thermal decomposition in air.…”

“…The carbon content in the precursor (C/B 2 O 3 ratio) is controllable by varying the thermal decomposition conditions in air. Within the obtained precursor powder, a B 2 O 3 /carbon structure with a homogeneous arrangement at the nanometer scale is spontaneously formed . The diffusion of reacting species becomes facile with increased contact area of the B 2 O 3 and carbon components, enabling synthesis at a low temperature compared with the conventional carbothermal reduction process.…”

Synthesis of Boron Carbide Without Excess Carbon over Local Boric Acid

“…Fakat karbon kaynağı olarak kullanılan hammadde, son üründeki karbon kalıntısını da doğrudan etkilemektedir (Bigdeloo et al 2009, Alizadeh et al 2004. B4C, içerdiği safsızlık ve parçacık boyutuna göre pek çok yöntemle üretilse de, düşük sıcaklıkta gerçekleştirilen sentez yöntemlerinden son zamanlarda en çok çalışılanı polimer başlangıç malzemelerinden sentez yöntemidir (Mondal et al 2008, Sudoh et al 2007, Zakharova et al 2013, Kakiage et al 2012, Kakiage et al 2013, Tahara et al 2013. Polimer başlangıç malzemelerinden B4C sentezi konusunda gerçekleştirilen çalışmalar, B-O-C bağlarını oluşturma, ürünlerdeki C/B2O3 oranını ayarlama ve B4C oluşum koşullarının optimizasyonu üzerinde yoğunlaşmaktadır (Hadian et al 2008, Kakiage et al 2012, Tahara et al 2013, Sinha et al 2002, Yanase et al 2009.…”