By kissinger and Ozawa kinetic methods the activation energies and the reaction orders of the phase transitions in ammonium thiocyanate for heat storage in air were calculated from the DSC curve of phase transition at...By kissinger and Ozawa kinetic methods the activation energies and the reaction orders of the phase transitions in ammonium thiocyanate for heat storage in air were calculated from the DSC curve of phase transition at different heating rates.展开更多
The phase transition kinetics of thennotropic liquid crystalline aromatic-aliphatic regular copolyester: were studied by DSC. By means of Kissinger's method the kinetic equation and parameters including activation...The phase transition kinetics of thennotropic liquid crystalline aromatic-aliphatic regular copolyester: were studied by DSC. By means of Kissinger's method the kinetic equation and parameters including activation energy, rate order and preexponential factor for phase transition from nematic to isotropic were obtained. The activation energy from crystal to nematic was also presented.展开更多
Barium titanate powder on nanometer scale was synthesized by means of co-precipitation. The thermal mass loss, crystal grain growth and phase transition of the barium titanate nanometer powder were investigated by TG ...Barium titanate powder on nanometer scale was synthesized by means of co-precipitation. The thermal mass loss, crystal grain growth and phase transition of the barium titanate nanometer powder were investigated by TG (Thermogravimetric)-DTA (Differential scanning calorimetric) and XRD (X-ray powder diffractometer) at different heat treatment temperatures. The results show that amorphous barium titanate powder can transfer into tetragonal symmetry structure after heat treatment. When the heat treatment temperature is below 900℃, the grains grow rapidly because the activation energy at low temperature is greatly less than that at high temperature. By controlling the heat treatment temperature, the optimization of the barium titanate crystallite size and formation of tetragonal phase can be realized.展开更多
采用差示扫描量热法(DSC)热分析设备进行了奥氏体相变激活能的研究,通过测定10Mn5试验钢冷轧和温轧两种状态下的热流-温度曲线计算了逆相变激活能和相变激活能。绘制了相变体积分数与温度之间的关系曲线。结果表明,钢温轧态奥氏体逆相...采用差示扫描量热法(DSC)热分析设备进行了奥氏体相变激活能的研究,通过测定10Mn5试验钢冷轧和温轧两种状态下的热流-温度曲线计算了逆相变激活能和相变激活能。绘制了相变体积分数与温度之间的关系曲线。结果表明,钢温轧态奥氏体逆相变激活能(788.5 k J/mol)小于冷轧态奥氏体逆相变的激活能(1030 k J/mol);温轧态奥氏体逆相变能量门槛低,转变较容易。当相变体积分数大于50%后,冷轧和温轧的奥氏体相变激活能的变化趋势是随着奥氏体体积分数的增加而逐渐减小。展开更多
采用示差扫描量热分析(DSC)研究了固溶、时效阶段施加电流场对7B04铝合金时效析出行为的影响。试验结果表明:固溶阶段施加500 A直流电抑制了η'相和η'+η相的析出,促进了GPⅠ区的析出;时效阶段施加600 A直流电促进了η相的析...采用示差扫描量热分析(DSC)研究了固溶、时效阶段施加电流场对7B04铝合金时效析出行为的影响。试验结果表明:固溶阶段施加500 A直流电抑制了η'相和η'+η相的析出,促进了GPⅠ区的析出;时效阶段施加600 A直流电促进了η相的析出和长大,η相的最大析出速率较常规时效的提高了67.6%,形成激活能由常规时效的233.8 k J/mol降低至162.9 k J/mol。展开更多
文摘By kissinger and Ozawa kinetic methods the activation energies and the reaction orders of the phase transitions in ammonium thiocyanate for heat storage in air were calculated from the DSC curve of phase transition at different heating rates.
文摘The phase transition kinetics of thennotropic liquid crystalline aromatic-aliphatic regular copolyester: were studied by DSC. By means of Kissinger's method the kinetic equation and parameters including activation energy, rate order and preexponential factor for phase transition from nematic to isotropic were obtained. The activation energy from crystal to nematic was also presented.
文摘Barium titanate powder on nanometer scale was synthesized by means of co-precipitation. The thermal mass loss, crystal grain growth and phase transition of the barium titanate nanometer powder were investigated by TG (Thermogravimetric)-DTA (Differential scanning calorimetric) and XRD (X-ray powder diffractometer) at different heat treatment temperatures. The results show that amorphous barium titanate powder can transfer into tetragonal symmetry structure after heat treatment. When the heat treatment temperature is below 900℃, the grains grow rapidly because the activation energy at low temperature is greatly less than that at high temperature. By controlling the heat treatment temperature, the optimization of the barium titanate crystallite size and formation of tetragonal phase can be realized.
文摘采用差示扫描量热法(DSC)热分析设备进行了奥氏体相变激活能的研究,通过测定10Mn5试验钢冷轧和温轧两种状态下的热流-温度曲线计算了逆相变激活能和相变激活能。绘制了相变体积分数与温度之间的关系曲线。结果表明,钢温轧态奥氏体逆相变激活能(788.5 k J/mol)小于冷轧态奥氏体逆相变的激活能(1030 k J/mol);温轧态奥氏体逆相变能量门槛低,转变较容易。当相变体积分数大于50%后,冷轧和温轧的奥氏体相变激活能的变化趋势是随着奥氏体体积分数的增加而逐渐减小。
文摘采用示差扫描量热分析(DSC)研究了固溶、时效阶段施加电流场对7B04铝合金时效析出行为的影响。试验结果表明:固溶阶段施加500 A直流电抑制了η'相和η'+η相的析出,促进了GPⅠ区的析出;时效阶段施加600 A直流电促进了η相的析出和长大,η相的最大析出速率较常规时效的提高了67.6%,形成激活能由常规时效的233.8 k J/mol降低至162.9 k J/mol。
文摘目的 通过关注纳米8YSZ粉末在不同温度下烧结过程中的晶粒长大行为及相结构组成变化,获得纳米8YSZ粉末的高温稳定性,防止高温烧结导致纳米8YSZ涂层性能明显衰减,致使涂层在正常服役过程中过早失效。方法 采用共沉淀工艺合成低杂质含量的8YSZ纳米粉末,经过低温煅烧预处理后,在900～1200℃温度区间进行3～12 h的烧结。通过X射线衍射仪和扫描电子显微镜对纳米颗粒进行物相结构和形貌分析,根据Scherrer公式计算热处理后的颗粒平均晶粒尺寸,采用Arrhenius公式得到晶粒生长活化能,进而确定晶粒的生长机制。结果 经过低温煅烧预处理后,粉末绝大多数仍然保持非晶态结构,经过高温热处理后,粉末均完成了晶态转化,相结构基本为单一四方相。温度为900～1100℃时,晶粒生长的活化能为42.638 k J/mol;温度为1100～1200℃时,晶粒生长的活化能为3.849 k J/mol。结论 高温热处理后,纳米8YSZ粉末物相结构为单一四方相,可以保持高温稳定性,防止涂层性能明显衰减。温度为900～1200℃时,晶粒生长机制以表面扩散为主的聚合生长。
