Thermal degradation mechanism and kinetics of aluminum-copper green bodies prepared by gelcasting
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摘要: 通過凝膠注模工藝,采用非水基凝膠體系,成功地制備鋁銅坯體.通過掃描電鏡觀察脫脂前聚合物完全包裹粉末顆粒,脫脂后金屬坯體中聚合物完全脫除.通過反應機理得出聚合物三維網絡結構的化學式.采用熱分析手段、熱重和紅外連用系統分析金屬坯體的脫脂過程,根據Coats-Redfern方法對非等溫熱失重率曲線的數據進行動力學研究,建立動力學方程.在不同的升溫速率下聚合物脫脂反應級數為1,活化能在79.86-108.63 k J·mol-1范圍內,指前因子反應指數在106-107min-1,活化能的結果表明反應對溫度和動力學比較敏感.脫脂主要分為兩個階段,在240-350℃主要是聚合物鏈段的分解,在350-470℃主要是聚合物網狀結構的解聚和解交聯反應,同時脫脂階段主要產生CO2、CO、NO2和H2O揮發性氣體.Abstract: Aluminum-copper green bodies were successfully prepared by a non-aqueous gelcasting system. Scanning electron microscopy observations showed that the powder particles were completely wrapped by the polymer before degreasing,and the polymer in the metal body was completely removed after degreasing. A three-dimensional network polymer structure was obtained by the reaction mechanism. The degreasing process of the metal body was investigated by means of differential scanning calorimetry,thermogravimetry-derivative thermogravimetry and thermogravimetry-Fourier transform infrared spectroscopy. The kinetic equations and parameters were gotten according to Coats-Redfern method for non-isothermal weight loss curves. The results indicate that at different heating rates the reaction order is 1,the activation energy and pre-exponential factor are ranging from 79.86 to 108.63 kJ·mol-1 and 106 to 107 min-1,respectively. The activation energy reaction is sensitive to temperature and dynamics. The degreasing process is divided into two stages:a slight weight loss over a wide temperature range of 240-350℃ is due to the random chain scission and the main weight loss around 380 to 425℃ is attributed to depolymerization of monomers from the main chains and decrosslinking of the network polymer. The emissions of CO2,CO,NO2 and H2O are identifled during the degreasing process.
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Key words:
- gelcasting /
- aluminum-copper alloys /
- degreasing /
- kinetics
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