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, and those calculated by non-isothermal calculation method using Kissinger methods were 57, 82 and 99 kJ/mol, respectively. The values of Avrami parameter, n, from isothermal calculation, during...: Al-Zn-Mg alloys; precipitation kinetics; DSC; JMAK model; activation energy; Avrami parameter 1 Introduction Aluminum alloys of 7xxx series AlZnMg are extensively used in the automotive and aerospace......
Ozawa, Boswell and Kissinger methods, were around 151 and 144 kJ/mol, respectively. The Avrami parameter of growth morphology (indicating the crystallization mode) was found to be around 1.57 using... of metakaolinite with polyhedron-like morphology controlled by diffusion from a constant number of nuclei. Key words: kaolinite; decomposition kinetics; Avrami parameter; activation energy; growth morphology 1......
:黑钨矿在该体系中的浸出过程可用Avrami方程描述,其模型特征参数为0.83,反应的表观活化能为67.54 kJ/mol,属化学反应控制,建立硫磷混酸浸出黑钨矿的反应动力学方程. 关键词:黑钨矿;硫酸;磷酸;Avrami方程;浸出动力学 文章编号:1004-0609(2018)-01-0175-08 中图分类号:TF111.31  ... images of wolframite concentrate(a) and residues(b) Avrami方程最早多用于结晶与固相转变动力学方程,之后被应用于描述多种矿物的浸出反应动力学过程[19-24],其动力学方程如下:  ......
growth on the derivations from Johnson-Mehl-Avrami kinetics [J]. Acta Materialia, 2007, 55(5): 1629-1639. [14] STARINK M J. On the meaning of the impingement parameter in kinetic equations... and then a regular behavior of varying Avrami exponent. Following previous analytical model, the formulations of Avrami exponent and effective activation energy accounting for blocking effect were......
agreement with each other. In addition, the isothermal transformation kinetics in Zr55Cu30Ni5Al10 bulk metallic glasses was described by the Johnson-Mehl-Avrami (JMA) model. For Zr55Cu30Ni5Al10 bulk metallic glass, the Avrami exponent n ranges from 2.2 to 2.9, indicating that crystallization mechanism in the bulk metallic glass was mainly diffusion-controlled; crystal growth is controlled by long range......
聚己内酯等温结晶的Avrami动力学研究于翔,朱诚身,何素琴,刘文涛郑州大学材料科学与工程学院摘 要:利用示差扫描量热仪(DSC)分析了3种不同分子量的聚己内酯(PCL)在30~45℃的等温结晶,并通过Avrami方程对其进行了等温结晶动力学研究.在此温度范围内,PCL的结晶度与等温结晶时间的关系曲线都呈现S型,说明其均采用异相成核的方式.根据Avrami关系式解出的双对数图都存在很好的直线关系部分,推导出Avrami指数(n)的值大都约为整数,在相同的Tc下,PCL生长方式类似,与分子量基本无关.lnK(结晶速率常数)随Tc的升高逐渐减小,说明晶体生长速率逐渐下降.在相同的Tc下,随着分子量的增加,结晶速率逐渐下降.半结晶时间(t1/2)随Tc的升高而降低,说明在此温度范围内晶体的生长速率随着Tc的......
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Johnson-Mehl-Avrami (JMA)方程描述合金的等温晶化过程,在不同等温温度下计算得出Avrami指数大于3.0,合金的主要晶化过程为三维形核长大过程.在Arrhenius方程的基础上,得到合金的区域Avrami指数和阶段晶化激活能随晶化体积分数变化的关系曲线. 关键词:Y基大块非晶合金;晶化动力学;Avrami指数;晶化激活能 中图分类号:TG139.8  ... of continuous heating and the isothermal annealing. The activation crystallization energy is determined by Kissinger method, i.e. Ec=3.02 eV. And the isothermal kinetics is modeled by the Johnson–Mehl–Avrami......
文章编号:1004-0609(2009)06-1087-06 温度对Mg-3Ni-2MnO2储氢材料吸放氢过程 相转变行为的影响 张文丛,贾彬彬,于元春 (哈尔滨工业大学 (威海) 材料科学与工程学院,威海264209) 摘 要:利用充氢反应球磨工艺制备氢化态Mg-3Ni-2MnO2储氢复合材料,测试材料的吸放氢动力性能,并利用Avrami指数研究储氢材料吸放氢过程中相转变行为特征.结果表明:在研究的温度范围内,温度越高,越有利于提高Mg-3Ni-2MnO2储氢复合材料的吸放氢速度;在150~200 ℃范围内吸氢时,其Avrami指数由初始阶段的1.0~1.5很快变为0.5,即储氢材料很快进入已形成相的增厚阶段;在150~200 ℃范围内,温度变化对吸氢相转变影响不大,但影响相转变速率;放氢过程中,根据Avrami 指数的变化,相转变基本过程为形核长大阶段和新相继续......
Trans. Nonferrous Met. Soc. China 22(2012) s851-s858 Development of micro milling force model and cutting parameter optimization Shih-ming WANG, Da-fun CHEN, Min-chang JANG, Shambaljamts TSOOJ... and effectiveness of the model and method. Key words: micro-milling; cutting force; spindle run out; cutter deflection; optimal parameter 1 Introduction Miniaturization has become the design trend......