氮气气氛高能球磨Al2O3相变研究

研究了高能球磨过程中A1203相结构的变化。结果表明：随着球磨时间的延长，粉末中发生了γ-Al2O3→a—Al2O3的转变，这一点对于降低碳热还原反应激活能是不利的；高能球磨20h，A1203部分非晶化，而且有立方结构AIN生成：高能球磨过程中形成的AIN，结构不同于常规六方结构氮化铝；增加球磨能量，立方AIN生成量增加；650r／min高能球磨40h，AIN生成量达到72％。     

球磨能量对Mo－Si混合粉末机械合金化的影响

利用Ｘ射线衍射，ＳＥＭ和ＴＥＭ研究了Ｍｏ－Ｓｉ（原子比为１：２）混合粉末在不同球磨条件下的机械合金化过程．Ｍｏ／Ｓｉ相变与球磨强度密切相关，高能球磨有利于稳定相α－ＭｏＳｉ_２的形成，而低能球磨有利于亚稳相β－ＭｏＳｉ_２的形成。对不同球磨条件下的相变动力学和热力学进行了讨论．     

制备Cu-TiB_2合金高能球磨及后续热处理过程的研究

利用高能球磨以及高温热处理研究了原位合成高浓度Cu-2.5 wt%TiB2合金过程,并对其不同状态的组织、性能以及原位反应模型进行了研究。结果表明,随着球磨时间的延长,复合合金粉末显微硬度分三个阶段变化,即快速上升阶段,缓慢上升阶段和平稳波动阶段;组织经历相互焊合、形成交替分布的层状组织以及层状组织消失后的均匀分布组织;SEM和X射线衍射分析均表明长时间高能球磨不能在复合粉末基体内形成TiB2粒子;高能球磨60 h后的复合粉末其第二个DSC放热峰向低温区发生了明显的推移,初步判定激发其发生原位反应的最低温度为660℃。SEM观察发现复合粉末经后续900℃高温热处理后能够合成了大量细小的TiB2粒子,并绘制了原位合成TiB2粒子形成模型图。     

高能球磨Si还原Cu的固态还原反应

通过对Ｓｉ和ＣｕＯ粉末进行高能球磨制备了Ｃｕ和ＳｉＯ２的复合材料。表明了一般条件下难以进行的固态还原反应，在高能球磨时可以发生，还原产物为纳米级的Ｃｕ和非晶的ＳｉＯ２，还原反应的进行有整于高能球磨的条件；利用高能球磨可以直接制纳米级氧化物、金属复合材料。     

高能球磨Si还原CuO的固态还原反应

通过对Ｓｉ和ＣｕＯ粉末进行高能球磨制备了Ｃｕ和ＳｉＯ２的复合材料。表明了一般条件下难以进行的固态还原反应，在高能球磨时可以发生；还原产物为纳米级的Ｃｕ和非晶的ＳｉＯ２，还原反应的进程有赖于高能球磨的条件；利用高能球磨可以直接制备纳米级氧化物金属复合材料     

高能球磨Mg／B复合粉体的反应烧结致密行为

采用高能球磨Mg／B复合粉体作为前驱粉制备了MgB2超导块材，研究了球磨时间、烧结温度和时间等参数对MgB2超导块材致密度的影响，并理论分析了高能球磨Mg／B复合粉体的反应烧结致密行为。     

高能反应球磨制备氧化铝/碳化钛纳米复合粉体

研究了以二氧化钛、铝和石墨为原料,采用高能球磨制备α-Al2OdTiC纳米复合材料的可行性.对球磨不同时间后的粉末进行X射线衍射分析,并利用扫描电镜观察其微观形貌.结果表明:以微米尺寸的TiO2、A1和C为原料,利用高能反应球磨法可以制备出纳米尺寸的α-Al2O3/TiC复合粉末;球磨250 min后,原料粉完全反应,合成的α-A12OdiC复合粉体晶粒尺寸为15nm.     

等离子体辅助球磨对Al+C_4H_4N_4合成超细AlN的影响机制

对铝(Al)和二氨基马来腈(C_4H_4N_4)的混合物分别进行等离子体辅助球磨和普通球磨,研究等离子体辅助球磨活化对合成AlN的作用机制。结果表明:相对于普通球磨,等离子体辅助球磨更有利于Al粉的晶粒细化和晶格畸变,并有利于形成Al-C_4H_4N_4纳米级的复合结构。辅助球磨中的等离子体促进C_4H_4N_4的脱胺,使C_4H_4N_4分解出更多的游离含N基团,加速与活化的Al合成AlN,辅助球磨14 h后AlN的转化率达到91%,远高于普通球磨合成AlN的产率83%。等离子体辅助球磨8 h的Al+C_4H_4N_4前驱体发生氮化反应的激活能为353.46 kJ/mol,在Ar中于800℃保温1 h可以通过固-固反应机制全部转化为超细AlN,而普通球磨8 h的前驱体反应激活能高达441.21 kJ/mol,Al需熔化后才能进行氮化反应,导致部分C_4H_4N_4先行受热分解蒸发,AlN产率仅为86%。辅助球磨促进AlN合成的主要原因是等离子体放电的高频脉冲轰击和瞬态"电火花"对粉体产生协同球磨作用。     

高活性无定形硼粉的制备及表征(英文)

采用高能球磨-燃烧合成法制备高活性无定形纳米硼粉。考察球磨转速、球磨时间等因素对无定形硼粉结晶度、微观形貌以及反应活性等性能的影响。结果表明:无定形纳米硼粉结晶度只有22.5%,纯度达92.86%;高能球磨预处理显著细化了硼粉粒径,平均粒径在50 nm以下,比表面积达70.03 m2/g。当透射电子束照射到试样时,试样快速熔化。由试样熔化痕迹可看出无定形硼粉单体颗粒粒径小于30 nm,说明试样具有极高的反应活性。     

高能球磨诱发Al,Si/CuO固态还原反应动力学

采用差热分析（DTA）和X射线衍射（XRD）技术研究了球磨燃烧反应发生前不同球磨时间下Al／CuO和Si／CuO体系反应动力学和微观结构变化。结果表明：高能球磨诱发燃烧反应的发生是粉末颗粒细化和均匀化与局部反应、球磨介质污染两方面竞争的结果。球磨时CuO的缺陷形成速率或者氧离子从CuO点阵中通过短路扩散路径向反应界面迁移是球磨诱发Al／CuO燃烧反应的控制步骤。     

Synthesis of TiCr<Subscript>2</Subscript> intermetallic compound from mechanically activated starting powders via calcio-thermic co-reduction

Effect of mechanical activation of TiO2 and Cr2O3 oxides as starting materials was investigated for direct synthesis of TiCr₂. Differential thermal analysis (DTA) indicated that increasing the ball milling time resulted in lower exothermic reaction temperatures between molten Ca–Cr2O3 and molten Ca–TiO2. A model-free Kissinger type method was applied to DTA data to evaluate the reaction kinetics. The results reveal that the activation energy of the exothermic reactions decreased with increasing the milling time. The structure, oxygen content, and average particle sizes of the obtained TiCr₂ product were affected by the ball milling time of the starting materials. Increasing the milling time from 10 to 40 h decreased the average particle size and oxygen content of the obtained TiCr₂ from 10 to 2 μm and from 1690 to 1290 ppm, respectively. The X-ray diffraction (XRD) results showed that TiCr₂ compounds with metastable bcc phase can be produced using nano-sized starting materials, while only a slight amount of bcc phase can be obtained in the TiCr₂ compounds, using micron-sized starting materials. The TiCr₂ obtained by this method had a hydrogen absorption capability of 0.63 wt % and the kinetics of the hydrogen absorption increased for the 40 h milled sample.     

表面机械活化粉煤灰提取氧化铝及其动力学研究

采用高能球磨活化粉煤灰,并对球级配、球料比、转速以及球磨时间进行正交试验,将经不同时间活化的粉煤灰与Na2CO3按一定比例煅烧溶出,得到Al2O3.通过测试分析,研究了高能球磨活化各工艺参数对Al2O3溶出率的影响,得到了最优化工艺条件,并对Al2O3溶出过程的动力学进行了验证分析.结果表明:当表面机械活化6h、溶出温度90℃、液固比L/S=6、硫酸浓度4 mol/L时,效益最高;此反应属于收缩未反应芯模型,表观活化能为60.87 kJ/mol,反应级数为0.1701.     

钼硅混合粉末在机械合金化过程中的结构演变

采用X射线衍射仪（XRD）和差热分析仪（DTA）研究了Mo-67at%Si元素混合粉末在中等强度的机械研磨（合金化）过程中的结构变化过程，结果表明，在中等强度的研磨过程中，β－MoSi2是初生相，且在随后的研磨过程中非晶化；在高研磨强度下生成α－MoSi2的量大于β－MoSi2,且α－MoSi2的含量随研磨时间的增加而增加，差热分析表明亚稳相β－MoSi2随温度的升高会向α－MoSi2转变。     

GRAIN SIZE AND ACTIVATION ENERGY OF SERRATED YIELDING

The apparent activation energy of serrated yielding was measured by two different methodsfor a commercial brass H68.The results showed that the apparent activation energy of serrat-ed yielding measured by a method involving(m+β)values increases with the grain size.Incontrast,those measured by another method without involving(m+β)values are all the samefor specimens with different grain sizes.Combining with the observation of themicrostructures,the above phenomena have been explained.The method to measure the trueactivation energy of serrated yielding has also been proposed.     

ACTIVATION MECHANISM OF AlCl_3 DURING THE LEACHING OF Cu-Ni ORE WITH FeCl_3

After Cu-Ni ore powder pre-soaked in AlCl_3 solution.the leaching ratios of copper andnickel can increase obviously.By X-ray diffraction analyses,electron energy spectrum analysesand electrochemical experiments,it is affirmed that,the activation of aluminum ion includestwo aspects:one is the surface change of the ore by the absorption of hydrolysates,and the oth-er is the change of semiconductor characteristics of the metal sulfides by impurity aluminum ionentering the lattice,so that leaching reactions are accelerated.     

铁基合金中热驱动和应力驱动的马氏体形核动力学

根据马氏体相变的经典形核理论，对铁基合金中马氏体形核激活能进行了重新估算。结果表明：在非低温时形核激活能比热能低一个数量级，从而证实了铁基合金中马氏体相变的热致形核，深入研究了马氏体形核的动力学，确定了马氏体形核激活能－界面能、激活能－相变驱动以及相变驱动力－激活体积的关系，这些关系与相关的实验研究结果相一致。在此基础上，探讨了热能和应力在马氏体形核中的驱动作用，提出了马氏体相变的形核机制。高温条件下的形核由热驱动来完成，而在低温时应力驱动起重要作用。     

冷塑变对氮在38CrMoAlA钢中扩散激活能的影响

将冷压３０％与未变形的３８ＣｒＭｏＡｌＡ钢试样在不同温度下进行不同时间的气体渗氮。利用扫描电镜对试样进行波谱分析，由碳浓度曲线精确确定了渗氮层深。利用公式，计算了未变形与３０％变形度试样氮的扩散激活能。最后，借助电镜对试验结果进行了初步探讨。     

Effect of processing history of pyrite on its leaching kinetics

1　INTRODUCTIONThereliableknowledgeaboutleachingkineticofmineralsisofgreatimportancefordevelopinghy drometallurgical processes .Butmanyatime ,re searchersobtainedscatteredresultsforthesamepro cess .Forexample ,theapparentactivationenergyforthedigestionofpyritebyoxygeninsulfateacidsolu tionrangeswidelyfrom 39to 84kJ/mol[13] .Usual ly ,thedifferenceisascribedtothevarietyinmineralresource ,chemicalcompositionand ,accuracyofex perimentalmethods.Howeveronlythisisstillunsat isfactoryforexplain…     

Synthesis of nano-structured La0.8Ba0.2MnO3 perovskite via a mechano-thermal route

In this study, barium-doped lanthanum manganite, La_0.8Ba_0.2MnO₃, was synthesized via a mechano-thermal route employing high energy ball milling and subsequent heat treatment. The structural evolution, morphology and thermal behaviour of the powders were evaluated using XRD, FESEM, and DTA/TGA, respectively. DTA/TGA results showed that the calcination temperature of the carbonates significantly decreased by increasing the milling time. The results revealed that single phase perovskite was formed at 900 °C in a milled sample for 2 h and this temperature decreased to 600 °C by increasing the milling time to 30 h. The mean crystallite size also decreased from 32 to 20 nm by increasing the milling time from 2 to 30 h. The reaction sequence of La_0.8Ba_0.2MnO₃ formation via the mechano-thermal route is proposed using XRD and DTA/TGA results. FESEM micrographs showed that the mean particle size of the perovskite phase is increased slightly from 30 to 40 nm by increasing the heat treatment temperature from 600 to 900 °C.     

Formation of NiAl intermetallic by gradual and explosive exothermic reaction mechanism during ball milling

NiAl intermetallic has been produced by mechanical alloying in a high energy vibrator mill using elemental Ni and Al powder mixture. The NiAl powders were formed in two ways. One by a gradual exothermic reaction mechanism during a long time continuous milling and the other by explosive exothermic reaction mechanism that occurred when opening the milling vessel to the air atmosphere after a short time milling. Prolonged milling for both cases resulted in change of morphology and refinement of grain size down to nano scale.