Papers by Keyword: Thermal Decomposition

Abstract: The present study aimed to identify the potential of modified nanoreinforcement (multiwalled carbon nanotubes; m-MWCNTs) to attenuate the thermal transport/decomposition/transition and mechanical aspects of three different polymeric matrices. In order to develop strong interfacial interaction between the host matrix and the incorporated nanotubes, 3-aminopropyletrimethoxy silane (APTMS) was used to m-MWCNTs. IR spectra confirmed the silane chemical moiety attachment on the upper surface of the MWCNTs. Conventional elastomeric mixing techniques were adopted to disperse m-MWCNTs within the three polymeric matrices (Acrylonitrile butadiene rubber, Silicone rubber, and Styrene Butadiene rubber) separately. SEM images assured the uniform dispersion of m-MWCNTs within the host polymeric matrices. Experimental evaluation of thermal conductivity revealed the reduction of thermal transport through the developed composite specimens by increasing the host polymer matrix to nanofiller concentration (m-MWCNTs). The utmost insulation effect was perceived in the F-MWCNTs incorporated silicone rubber nanocomposite comparatively. Glass transition/crystallization temperatures of the nanocomposites were lessened however melting temperatures were enhanced by impregnating nanotubes into the host polymeric matrices. Maximum thermal stability improvement due to the addition of m-MWCNTs was observed in the silicone elastomeric nanocomposite as compared to the other two systems. Proper dispersion and compatibility of m-MWCNTs with the polymeric matrices effectively enhanced the ultimate tensile strength (UTS)/elongation at break along hardness of rubber of the nanocomposites. The insulation character of m-MWCNTs/silicone rubber system was found best among the explored nanocomposite formulations.

Abstract: We investigated an alternative technology to conventional organic material removal that replaces sulfuric acid and hydrogen peroxide (SPM). We assumed that the removal model of organic material by ozone gas was absorption of oxygen radicals, generated by thermal decomposition of ozone, on a surface and subsequent reaction with organic materials. Then we characterized the correlation between removal rate and process parameter, and the validity of the model was verified. It also showed that this method is effective for high dose, ion-implanted photoresists.

Abstract: An entirely novel preparation method of calcium carbonate (CaCO₃) from calcium hydrogen carbonate (Ca (HCO₃)₂) solution was presented and named as thermal decomposition. The variation of the polymorphs and morphologies of CaCO₃ particles with reaction temperature was investigated. XRD result indicates that high temperature favors the formation of calcite. Cubic or rhombohedra calcite crystals, lamellar and spherical vaterite crystals and rod– and needle–like aragonite crystals are found in powder synthesized at different temperatures. The reaction process was also discussed in the present work.

Abstract: Magnesium-stabilized aluminum titanate powder was prepared via non-hydrolytic sol-gel method using titanium tetrachloride and anhydrous aluminium chloride as precursors, anhydrous ethanol as the oxygen donor, magnesium powder, magnesium fluoride, magnesium ethoxide and anhydrous magnesium acetate as stabilizers. The effect of magnesium stabilizers on low temperature synthesis of aluminum titanate was investigated, and their role and mechanism in stabilizing aluminum titanate were also studied by XRD, FT-IR and thermal expansion dilatometer. The results show that introducing magnesium powder or magnesium fluoride can’t stabilize aluminum titanate, they also lead to the failure of aluminum titanate low-temperature synthesis at 750 °C due to its promotion of non-hydrolytic homogeneous condensation. Anhydrous magnesium acetate and magnesium ethoxide can react with aluminum alkoxide and titanium alkoxide in the precursor mixture to form heterogeneous condensation bonds, which promotes magnesium ion to dope into aluminum titanate lattice at 750 °C, and hence to improve its thermal stability.

Abstract: The conjugate problem of aerodynamic heating of a blunted cone moving in the atmosphere at angle of attack at supersonic speed is considered. Three modifications of a thermal protection material based on coal-plastic with different proportions of a phenol-formalhyde binder and a carbon cloth are investigated. The effect of the material composition on the surface temperature and the mass loss characteristics is analyzed.

Abstract: The adsorption and desorption of water molecules from α, β and γ-cyclodextrins were studied by gravimetric and thermogravimetric analysis. Cyclodextrins like all the other carbohydrates have tendency to adsorb water molecules. However, their cyclic nature tends to affect the adsorption patterns. The cyclic nature of the cyclodextrins facilitates the formation of hydrogen bondings between OH groups of the neighbouring glucose units. The C2(1)-OH forms hydrogen bonding with C3(2)-OH. The extent of the hydrogen bond formation and strength of the hydrogen bond affect the way the adsorption and dehydration of water molecules from cyclodextrins take place.

Abstract: BaCe_0.54Zr_0.36Y_0.1O_2.95 (BCZY10) ceramic powder was synthesized by a modified sol-gel method using metal nitrate salt as pre-cursors. The sample was prepared using three different types of surfactants namely polyethylene glycol (PEG) 6000, sodium dodecyl sulphate (SDS) and cetyltrimetylammonium bromide (CTAB). Thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectrometry was used to analyze the thermal decomposition of the dried (T=325 °C) and calcined (T=1100 °C) powder. Standard sample prepared without surfactant is denoted as A1 while the sample that prepared using PEG, SDS and CTAB as surfactant was denoted as A2, A3, and A4 respectively. TGA results indicate that all the samples were almost completely decomposed at ~800 °C except for A2. It showed the lowest thermal decomposition temperature T_td=739 °C. The highest total weight loss ~94.7% is shown by sample A4 than others. The sample with the presence of surfactant exhibits faster reaction rate for the first decomposition stage which is t = 8 min, 11 min, and 13 min for sample A2, A3, and A4 respectively compared to A1 (t = 18 min). The A2 sample shows faster reaction rate indicates that BCZY10 compound might be formed earlier faster due to the long carbon chain posses by PEG surfactant. The higher number of carbon chain present in the surfactant may accelerate the combustion process and the formation of metal oxide compounds. FTIR spectra illustrated that the carbonate residue still remained in all the samples even after calcined at 1100 oC. This result indicates that the used of surfactant does not give a significant effect on preventing the formation of BaCO₃. However, the intensity of metal-oxygen band at ~450 cm^-1 become stronger indicates that the formation of BCZY10 compound was being enhanced.

Abstract: Graphene oxide (GO) was prepared by Hummers method and GO/1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) composite was prepared via an ultrasonic compounding method. The structure of GO was characterized using XRD and SEM, the thermal decomposition of HMX and GO/HMX composite was analyzed by DSC/TG test. The results show that interlayer space of GO increases markedly, the thermal decomposition process of HMX can be promoted with the nanolayer structure of GO, resulting the reduced thermal decomposition activation energy of about 50 kJ/mol with 1% GO.

Abstract: Due to high reaction activity and high combustion heat release, magnesium is widely used in the field of explosives. The research focus of this article is the effect of magnesium powder size and content on the thermal decomposition of PTFE. Two different particle sizes of magnesium powder are regarded as research objects. The thermal behavior of Mg/PTFE energetic system was investigated by TG-DSC analyzer. The experimental results show that magnesium has a catalytic effect on the thermal decomposition of PTFE. With the increase of magnesium content , the decomposition peak temperature of PTFE decreased firstly and when passed the ratio 50% increased, the best mixing ratio is Mg: PTFE =50:50. Within nanopowder, the activation energy of PTFE decreased by 150kJ∙mol^-1 compared to 112 kJ∙mol^-1 by mixing with micro powder. Obviously nanopowder has a better reactivity than micro powder, so has a more obvious catalytic effect.

Abstract: The printed circuit board (PCB) in the electronic waste contains a variety of metals and organic materials, including bromine, heavy metals and other pollutants. Thermal treatment is an effective method for harmless disposal of waste circuit boards with resources recycle. In this study, the composition of RF4 type waste game PCB was determined by elemental analysis and proximate analysis, followed by thermogravimetric analysis of the weight lost process in CO₂、N₂ or air, at 10°C/min, 20°C/min or 30°C/min programmable heating rate, and the thermal decomposition reaction kinetics parameters were calculated with the Kissinger method. The results show that under the CO₂ atmosphere, the weight loss process of the sample consists of the 250°C～410°C and 750°C~960°C temperature intervals; under the N₂ atmosphere, the rapid weight loss stage is between 263°C and 420°C; under the air atmosphere, the weight loss process is from 178°C to 675°C, including three minor weight loss stages. The phenolic volatile components are mainly released around 260°C～360°C under three different atmospheres, while the residual carbon is further oxidized under the air atmosphere or gasified in CO₂ at temperatures above 800°C.