Influence of high energy ball milling on structural,microstructural and optical properties of TiO2 nanoparticles

The influence of high-energy ball milling on structural, microstructural, and optical properties of TiO₂ by modifying the nanoparticle size was studied. Five samples were extracted at different milling times (0, 2, 4, 8, and 13 h). The average particle sizes estimated by dynamic light scattering (DLS) were 205, 155.8, 116.8, 82.9, and 82.7 nm at 0, 2, 4, 8, and 13 h, respectively. X-ray diffraction analysis confirmed progressive broadening of the peaks as the milling time elapsed. Besides, a correlation was found between d spacing and the average crystal size. The UV–Vis diffuse reflectance spectra of TiO₂ revealed a decrease in reflectance due to particle size reduction. Similarly, an alteration of the bandgap transition energy was presented, whose values gradually decreased from 2.966 eV to 2.861 eV for the sample without and with the maximum duration milling performed (13 h), respectively. Likewise, the SEM analysis showed a distribution in nanoparticle size that became more homogeneous and smaller average grain size as the milling duration was longer.     

New horizon in mechanochemistry—high-temperature,high-pressure mechanical synthesis in a planetary ball mill—with magnesium hydride synthesis as an example

A new route of materials synthesis, namely, high-temperature, high-pressure reactive planetary ball milling (HTPRM), is presented. HTPRM allows for the mechanosynthesis of materials at fully controlled temperatures of up to 450 °C and pressures of up to 100 bar of hydrogen. As an example of this application, a successful synthesis of magnesium hydride is presented. The synthesis was performed at controlled temperatures (room temperature (RT), 100, 150, 200, 250, 300, and 325 °C) while milling in a planetary ball mill under hydrogen pressure ($>$50 bar). Very mild milling conditions (250 rpm) were applied for a total milling time of 2 h, and a milling vial with a relatively small diameter (φ = 53 mm, V = ～0.06 dm³) was used. The effect of different temperatures on the synthesis kinetics and outcome were examined. The particle morphology, phase composition, reaction yield, and particle size were measured and analysed by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry (DSC) techniques. The obtained results showed that increasing the temperature of the process significantly improved the reaction rate, which suggested the great potential of this technique for the mechanochemical synthesis of materials.     

Structural and electrical studies of excessively Sm2O3 substituted soft PZT nanoceramics

The solid solution of Pb_1-x Sm_2x/3 (Zr_0.6 Ti_0.4) O₃ ceramics with x = 0.1, 0.2, 0.3, and 0.4 was prepared via the high-energy ball milling technique. Further, the effect of excessive Sm₂O₃ substitution at Pb-site on structural, dielectric, and dc-conductivity properties was studied. The X-ray diffraction (XRD) analysis confirmed that all samples were crystallized with perovskite and pyrochlore diphase form. Excess Sm³⁺ substitution in the PZT system increases the pyrochlore volume fraction from 5 to 20% and induces a structural phase transition from rhombohedral to a tetragonal structure. The microstructural study by TEM and SEM indicated that the particles were spherical with an average size of 43–55 nm. The frequency and temperature-dependent dielectric constant for all compositions was carried out and it is obtained that the dielectric constant decreases with Sm³⁺ content. The phase transition temperature first decreases up to x = 0.2 and then increases for the higher concentration of samarium. The dc-conductivity studies revealed that all samples showed an unusual mixed TCR effect (both positive and negative temperature coefficient of resistance). Such properties of the studied samples indicate that the material is suitable for potential applications in thermistors, and temperature sensors of the automotive, and petroleum industries.     

碘化多壁碳纳米管制备含有Ag/MWCNTs复合材料的银-环氧树脂浆料

提出一种将多壁碳纳米管碘化后制备银/多壁碳纳米管（Ag/MWCNTs）复合材料的方法。通过球磨对碘化多壁碳纳米管进行了功能化，并通过透射电子显微镜（TEM）、X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、拉曼光谱和热重分析（TG）对其进行了表征。结果表明，经碘化处理后，银纳米粒子（Ag-NPs）能更好地粘附在碳纳米管表面，改善了银纳米粒子与碳纳米管之间的连接。羟基（-OH）基团的伸缩振动明显增强，激活了碳纳米管的表面，增加了碳纳米管表面Ag⁺形核的数量。在260 ℃以下，Ag/MWCNTs复合材料的质量损失小于MWCNTs的质量损失。最后，制备了银-环氧树脂浆料，发现使用Ag/MWCNTs复合物制备的浆料具有最低的电阻率和最高的热导率。     

汽车悬架球头拉杆冷成形技术

为提高生产效率、改变原来通过车削加工汽车悬架球头拉杆的方式,提出了一种球头拉杆的多工位冷镦成形工艺。基于DEFORM-3D软件建立了有限元模型,对球头拉杆的塑性成形过程进行了仿真,研究了预成形凸模入模角α、预成形凹模圆角R1、终成形凹模圆角R2以及终成形凹模入模角β等工艺参数对球头拉杆成形的影响,并进行了正交试验,以模具在球头拉杆成形过程中所受载荷及工件损伤值为优化目标,获得了合理的工艺参数组合。结果表明:在保证工件成形质量及模具寿命的前提下,当预成形凸模入模角α为30°、预成形凹模圆角R1为12 mm、终成形凹模圆角R2为3 mm、终成形凹模入模角β为60°时,模具载荷及工件损伤有显著的降低。采用优化后的参数进行试模生产,工件成形质量较好,验证了模拟结果的可信性,能够有效地指导工艺设计人员的设计工作。     

Preparation of YSZ porous ceramics with precise porosity control

Conventional preparation of porous ceramics often hard to accurately control the porosity of the samples. In this paper, by improving the foaming method, the foaming process is placed in the limited space of the ball mill tank, and YSZ porous ceramics with different porosity are obtained by changing the amount of slurry. Initial results showed that the porosity of the sample varies linearly with the increasing of addition of slurry. From the microscopic morphology, it can be seen that the increase in slurry content will reduce the number of pore with little changed size, which lead to the decrease in porosity. Therefore, with simple calculation YSZ porous ceramics with 85%, 80%, 75%, 70%, and 65% porosity can be obtained using the method of foaming in limited space by ball milling.     

自旋对角接触球轴承弹流润滑与油膜刚度的影响

根据角接触球轴承自旋运动特征，同时考虑弹流润滑效应，建立角接触球轴承考虑自旋运动的弹流润滑模型；采用多重网格法求解弹性变形，利用有限差分法迭代求解雷诺方程，得到较为精确的数值解；分析不同赫兹接触压力、滚道表面粗糙度下自旋对角接触球轴承弹流润滑和油膜刚度的影响。结果表明：考虑自旋时随着Hertz接触压力、自旋角速度增大，油膜厚度减小，油膜压力增大，油膜承压区域呈细长状，并向接触中心靠近；随着滚道表面粗糙度幅值增大，油膜压力和膜厚均出现了波动，且考虑自旋运动时，轴承油膜厚度明显减小，油膜局部压力峰值更大；随着卷吸速度、润滑油黏度增大，油膜刚度减小，而考虑自旋运动时油膜刚度值更大；随着自旋角速度增大，油膜刚度逐渐增大。     

大型球磨机订购（制造）设计联络中零部件结构优化的探讨

针对大型球磨机使用中存在的问题，对球磨机主要零部件结构缺陷进行分析并提出解决方案。通过设计联络，提前对球磨机主要零部件结构进行优化，消除设备缺陷。大型球磨机设计联络中对主要零部件结构进行优化，对提高球磨机的运转率有着事半功倍的作用。