The combustion characteristics of brown coal, anthracite and their blends were investigated by thermogravimetric analysis. The combustion characteristic parameters, including temperature corresponding to ignition, burnout, maximum fractional conversion and mean conversion for the whole process, were analyzed, and the comprehensive combustion characteristic index was calculated as well. A double parallel reactions random pore model (DRPM) was applied to thermal data obtained by non-isothermal thermogravimetric analysis from room temperature to 1173 K at different heating rates in air to calculate the kinetic parameters of anthracite coal–brown coal blends with different ratios. The DRPM provides a good prediction of the fractional conversion curves for co-combustion with coefficient over 0.988. The agreement between experimental and calculated data indicates the accuracy of the DRPM. The activation energy of blends was calculated by DRPM model in the present work as well, and the activation energy of blends decreases with increasing the ratio of brown coal, which show that with increasing the ratio of brown coal in the blends, the combustion reactivity get improved.

Characteristics and kinetic analysis of co-combustion of brown coal and anthracite

Solution Processing of Boron Nitride Nanotubes and Bending Behavior of Carbon Nanotube Fibers

Solution processing of boron nitride nanotubes and Bending behavior of carbon nanotube fibers

Reaction of CVD BN ceramics in water vapor at 1023–1173 K using different kinetic model

In contrast to a mass of powder in air at 900 °C, the oxidation rate of hexagonal boron nitride does not tend to a plateau when present as a coating on austenitic stainless steel type 304 and type 310, and a real-world hot forming tool alloy. As with a mass of powder, a molten boron trioxide diffusion barrier encapsulates each hexagonal boron nitride grain around the basal plane. These subsequently merge to form a dispersion of remnant grains throughout a molten matrix. Boron trioxide is semipermeable, and as such, the substrate oxidizes concurrently. As it does so, outwardly diffusing chromium (III) ions react with boron trioxide to form chromium borate, which depletes the diffusion barrier. This causes the oxidation of hexagonal boron nitride to be sustained at an enhanced rate and the overlayer ultimately undergoes complete decomposition. During this process, the scale comprises chromium borate and chromia only. While manganese chromium spinel and iron chromium spinel form readily at the oxide-atmosphere interface of equivalently heat-treated uncoated substrates, they do not form until after the coating has completely decomposed.

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Oxidation‐led decomposition of hexagonal boron nitride coatings on alloy substrates at 900 °C: Chromia‐formers

The oxidation behavior of SiC Sylramic fibers coated with chemically vapor deposited Si-doped boron nitride (BN) was investigated at temperatures between 800 and 1200°C in dry and wet O2 atmospheres. Thermogravimetric analysis was used to study the oxidation kinetics of the fiber and the influence of the BN layer and the environment. The morphology and composition of the thermally grown oxide scale was determined posttest by scanning electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission spectrometry. This study gives new insights into the synergistic effects of BN and water vapor on the oxidation behavior SiC Sylramic fibers. The vulnerability of the BN fiber interphase and the behavior of the fiber under conditions relevant to high-temperature turbine applications are discussed. 

High‐temperature oxidation of BN‐coated sylramic SiC fibers in dry and wet atmosphere

The reaction of hexagonal BN powder in wet air at 1073–1373 K for 18 h was investigated using TG, XRD, and SEM analysis. Initially, the oxidation occurred rapidly with simultaneous volatile reaction. At long times, a steady state was achieved and the degradation rate was determined by the volatilization reaction. Temperature affected the reaction behavior. At 1073 K, it consisted of two linear processes. With temperature increasing, initially, the paralinear kinetics was observed and then followed the linear rate. The sample shape also affected the reaction behavior. The reaction kinetics was dealt with Chou's model and gotten good agreement.

Liu Yanxiang

Papers

Effect of Temperature on Reaction of Hexagonal BN Powder in Wet Air Between 1073 and 1373 K

Reaction of CVD BN ceramics in water vapor at 1023–1173 K using different kinetic model