排序方式: 共有43条查询结果,搜索用时 31 毫秒
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采用热压烧结法对块状菱镁矿进行煅烧,研究了温度为1400 ℃,压力P分别为1 MPa、5 MPa和9 MPa,热压时间为2h条件下煅烧后试样的结晶度.结果表明,压力P=1 MPa时,方镁石晶粒间间隙较大,液相分布不均匀,晶粒各个方向晶界移动速率不均匀,晶粒多为半自形晶,结晶程度较差;压力P=5 MPa时,方镁石晶粒紧密排布,液相分布均匀,晶粒的结晶度最高,晶粒发育最好;压力P=9 MPa时,试样组织结构产生应力和应变,晶粒发生形变、损毁和晶面断裂,试样中方镁石晶粒结晶程度最低,晶粒发育最差. 相似文献
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采用TG法对块度为20 mm、30 mm 、40 mm和50 mm的立方体状菱镁矿的热分解进行了研究.结果表明:在相同转化率条件下,块状菱镁矿的分解活化能随块度增加而增大,块度(L =20 ~50 mm)与活化能的关系为:E=4.795×L+34.070(kJ·mol-).块状菱镁矿在不同的分解阶段,受不同的机理函数控制:分解前期,Anti-Jander方程控制的n=2的3D模型为最概然机理函数,动力学方程为:dα/dT=6.111×1010 ×β-1 exp[(4.098-0.577 × L)×T-1](1+α)2/3[(1+α)1/3-1]-1;分解中期,Avrami-Erofeev方程控制的n=3(Code:AE3)的随机成核和随后长大模型为最概然机理函数,动力学方程为:dα/dT=1.422×109×β-exp[(4.098-0.577×L)×T-1](1-α)[-ln(1-α)]-2;分解后期,Avrami-Erofeev方程控制的n=3/2的随机成核和随后长大模型为最概然机理函数,动力学方程为:dα/dT =2.477×109 ×β-1exp[(4.098-0.577L)×T-1](1-α)[-ln(1-α)]-2.本项研究为制定块状菱镁矿生产MgO工艺提供了理论依据. 相似文献
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采用高温电炉对块状菱镁矿进行煅烧,研究了块状菱镁矿烧结末期(1600~ 1800℃)方镁石晶粒长大和致密化行为.结果表明:在烧结末期,随着温度升高,晶界快速移动,气孔“汇聚-排除”的速率和晶界向曲率中心的移动的速率增加,致使颗粒致密化迅速,方镁石晶粒长大明显.温度在1600~1700℃期间,晶界扩散是控制烧结致密化的主导机制,晶粒生长活化能为1.382×103 kJ·mol-1,晶粒以结晶长大方式为主;温度在1700 ~ 1800℃期间,体积扩散是控制烧结致密化的主导机制,晶粒生长活化能为1.164×103 kJ·mol-1,晶粒以聚晶长大方式为主.随温度的升高,晶粒长大活化能逐渐减小,晶粒长大速率增加. 相似文献
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Controlling the collision between two solitons in the condensates by a double-barrier potential 下载免费PDF全文
We present an analytical solution of two solitons of Bose-Einstein condensates trapped in a double-barrier potential by using a multiple-scale method.In the linear case,we find that the stable spots of the soliton formation are at the top of the barrier potential and at the region of barrier potential absence.For weak nonlinearity,it is shown that the height of the barrier potential has an important effect on the dark soliton dynamical properties.Especially,in the case of regarding a double-barrier potential as the output source of the solitons,the collision spots between two dark solitons can be controlled by the height of the barrier potential. 相似文献
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以硅溶胶和炭黑为原料,三氧化二铁、硅铁合金为催化剂,研究分析碳化硅晶须的合成条件,催化剂种类对合成碳化硅晶须的影响.用X'pert plus软件对X射线衍射图进行拟合,通过半定量法对试样品相组成进行计算,用SEM对合成的碳化硅晶须进行微观形貌分析.结果表明:合成β-SiCw的热力学条件为:T=1823 K时,Pco>0.23×105 Pa;晶须生成量随Fe2O3、Si-Fe加入量增加而增多;Si-Fe加入量为1;时,虽然合成的晶须量少,但生成的B-SiCw直径均匀,为0.1~0.6 μm,长度适中,为1O~50 μm,直晶率达95;. 相似文献
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Bifurcation of a periodic instanton and quantum-classical transition in the biaxial nano-ferromagnet with a magnetic field along hard axis 下载免费PDF全文
Crossover from classical to quantum regimes of the barrier transition rate in a biaxial ferromagnetic magnet with a magnetic field applied along hard anisotropy axis is investigated. We show that the type of action-temperature diagrams can he determined by counting the number of bifurcation points. The model possesses not only the known type I and Ⅱ, hut also the interesting type Ⅲ and Ⅳ of transition which do not occur in general. 相似文献
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