Effect of Grinding Media Shapes on Breakage Parameters

In the present study, the effect of grinding media shape on breakage parameters was investigated. Balls and cylpebs were used as the grinding media. It was observed that the grinding of quartz obeyed first‐order breakage kinetics in the case of balls and cylpebs. Higher breakage rates were noted with cylpebs than with balls. Furthermore, it was found that the primary breakage distribution function is dependent on the feed size (i.e., non‐normalizable), but independent of the grinding media shape. The effect of grinding time on the product size distribution has also been investigated. Following four and ten minute grindings, cylpebs produced a relatively finer product compared to balls.     

球磨法对不同基质上转换发光的影响

分别利用高温固相法和高能球磨法,在反应温度为1 100℃、反应时间为2 h的条件下合成了以Y2O3、La2O3、LiTaO3为基质的双掺和三掺Tm3+、Er3+、Yb3+发光粉。XRD测试结果表明,高能球磨法制备的Y2O3、La2O3、LiTaO3材料的相纯度高于高温固相法。用980 nm红外激光分别对两种合成方法制得的样品粉末进行发光性质的检测,结果表明高能球磨法制得样品的发光强度高于高温固相法样品。不同基质样品的上转换发光性质表现为:Tm3+、Yb3+掺杂呈蓝光;Er3+、Yb3+掺杂呈黄光;Tm3+、Er3+、Yb3+三掺样品的发光减弱,颜色可调。     

球磨法对不同基质上转换发光的影响

分别利用高温固相法和高能球磨法,在反应温度为1 100 ℃、反应时间为2 h的条件下合成了以Y₂O₃、La₂O₃、LiTaO₃为基质的双掺和三掺Tm³⁺、Er³⁺、Yb³⁺发光粉。XRD测试结果表明,高能球磨法制备的Y₂O₃、La₂O₃、LiTaO₃材料的相纯度高于高温固相法。用980 nm红外激光分别对两种合成方法制得的样品粉末进行发光性质的检测,结果表明高能球磨法制得样品的发光强度高于高温固相法样品。不同基质样品的上转换发光性质表现为：Tm³⁺、Yb³⁺掺杂呈蓝光;Er³⁺、Yb³⁺掺杂呈黄光;Tm³⁺、Er³⁺、Yb³⁺三掺样品的发光减弱,颜色可调。     

水基型光学高速精磨冷却液的化学作用

本文介绍的是以丙三醇－三乙醇胺－水与基本组份，并添加适量的硫酸铝钾盐，ＥＤＴＡ二钠盐为澄清、沉淀剂的水基型光学玻璃高速精磨冷却液的化学作用，它不仅冷却、清洗和润滑性能好，且具有良好的化学作用；不仅对金刚石磨具的“自锐”性能好，且能保持冷却液和磨具表面清洁，为此，进一步提高了冷却液和磨具的使用性能和使用寿命，以及光学玻璃零件加工的效率和表面质量。     

球磨法制备Tm~(3+)/Yb~(3+)掺杂NaGdF_4的上转换发光及顺磁性质研究

利用球磨法制备了Na源及其比例不同的Tm3+/Yb3+掺杂的NaGdF4发光粉,并对部分样品高温处理。讨论了Na源及其比例的不同和高温对样品上转换发光的影响。结果表明在所选比例中,当各离子的量比n(RE)∶n(Na)∶n(F)=1∶1∶4时,样品在高温处理前后的上转换发光均为最强。高温处理改变了上转换荧光发射的比例,可见光区的发射强度有大幅增加。XRD测试结果表明,Tm3+和Yb3+掺入到了NaGdF4的晶格内,高温处理改变了部分样品的结晶度和相态,从而导致可见光的发射强度大幅增加。HRTEM图像显示样品中有α相与β相NaGdF4共存。对上转换发光和顺磁性质之间相互影响的研究结果表明,980 nm红外激光的激发对样品的顺磁性基本没有影响,而变化磁场的存在对上转换发光有负面的影响。     

High-Energy Ball Milling of Some Intermetallics

High-energy ball milling of metallic powders has been used in recent years for the synthesis of alloys through reactions mainly occurring in solid state. The diffusive phenomena accompanying and promoting the reactions of formation are related to the microstructure acquired by the powders as a consequence of the intense mechanical deformations. The process induces a remarkable comminution of powder particles, inside of which domains of nanometric size are formed and compositional variations often occur. Several analytical techniques are suitable for following the structural evolution of the powders during milling. Among them, Mössbauer spectroscopy is suitable for obtaining detailed local information on the atomic arrangement of the treated materials, if one of the constituents is a Mössbauer isotope, and for detecting little changes occurring at an atomic scale. For these reasons Mössbauer spectroscopy is more sensitive than other analytical techniques especially in the early stages of the process. Some recent results are presented regarding in particular the Fe–Cu, Fe–Al, Fe–Al–Cu, NiAl(Fe) and Fe–Mn systems.     

Partial Reduction of MgFe2O4 with Al and Mg via Ball Milling

Nanocomposites consisting of metallic Fe particles and a nonmagnetic oxide were prepared by reducing MgFe₂O₄ with Al or Mg in a ball mill. The reaction takes place as a fast self-propagating process sometime between 0.5 and 1 h of milling. Combining XRD and Mössbauer spectroscopy reveals that the bcc Fe phase contains a few percents of dissolved Al, it has a high defect concentration, and the surface tension of the ultrafine (about 15 nm) grains results in local compressive strains. The magnetization is 25% less than expected for pure ferromagnetic Fe.     

High-Energy Ball Milling of NiAl(Fe) System

High-energy ball milling was used to promote the solubilization of iron into NiAl powder for an iron concentration range of 10–30 wt.%. The microstructural evolution induced by the intense mechanical deformations, under different milling conditions, was followed by X-ray diffraction and Mössbauer spectroscopy. The Mössbauer spectra are dominated by a magnetic sextet of about 33 T. Increasing the time and the speed of milling gives rise to a non-resolved doublet, having parameters typical of a NiAl compound with Fe atoms in solution. At the same time a reduction of lattice parameter occurs, which can be correlated to composition variations and partial disordering of the NiAl structure. Subsequent annealing modifies the Mössbauer spectra noticeably. In particular, the non-magnetic component becomes a broad singlet. Both diffraction analysis and Mössbauer spectroscopy indicate that a fcc Ni(Al,Fe) solid solution is forming in samples milled in agate. It is observed that the grain size of the milled products remains in the nanometric range even after thermal treatment, which adds interest to possible applications.     

Dry Grinding of Mefenamic Acid Particles for Enhancement of its Water Dissolution Rate

This paper details an investigation into the enhancement of the water dissolution rate of mefenamic acid (MA) by means of a dry grinding treatment. The physico‐chemical properties of the ground MA particles were analyzed by measurements of specific surface area, powder X‐ray diffraction patterns, differential scanning calorimetry thermograms and infrared spectra, and the effects of the change in the physico‐chemical properties (especially, crystalline structure) on the dissolution rate were studied. The polymorphic transition from Form I (original) to II and the change of the molecular structure of MA did not occur in the grinding treatments. However, the specific surface area of the MA particles increased, and the crystallinity decreased (i.e., the amorphization level increased) as the grinding progressed. Hydrogen bonds formed between the carboxyl groups of the opposed asymmetric MA molecules were broken gradually after the grinding limit was attained in the grinding system, resulting in an effective improvement of the initial dissolution rate.     

Milling of Organic Solids in a Jet Mill. Part 2: Checking the Validity of the Predicted Rate of Breakage Function

The particle size distribution of fine chemicals in the solid state, like active pharmaceutical ingredients, is often a critical parameter. To achieve the desired particle size distribution, milling of such materials is usually the method of choice. Since these chemicals are often scarcely available, experimental optimization of milling is not possible. Therefore, a model to predict the milling conditions has been developed. The model estimates the rate of breakage function, and needs mechanical properties like hardness and yield strength as input to calculate the rate of breakage function. This paper attempts to check the validity of the model by a series of experiments. A comparison of the experimental results with the outcomes of the model using five different model compounds has been performed. It appears that the rate of breakage function can be estimated by: The model is able to rank the compounds by degree of fracture as an effect of milling. It was also possible to perform a quantitative prediction of the impact of milling pressure on the milling behavior. Finally, it appeared that the prediction of the large particles in the distribution was significantly better than small ones. Because the oversized material is usually the most critical parameter, the conclusion is that the model has acceptable practical applicability.     

球磨处理的TiO2光谱特征及其光催化性能研究

为改变TiO₂的颗粒尺寸和提高其光催化性能,采用高能球磨法处理TiO₂粉末,研究球磨时间对样品微观形貌、晶体结构、拉曼光谱、荧光光谱和光催化性能的影响;分析荧光光谱和光催化性能之间的关系,确定光催化机理为快速判断其光催化性能提供依据。结果表明：随着球磨时间的增加样品颗粒由规则形状变成无规则形状且表面变得粗糙。所有样品均主要为锐钛矿结构,有少量的金红石结构,随着球磨时间的增加金红石结构的(110)衍射峰逐渐增强说明在球磨过程中少量的TiO₂发生了相转变,晶粒尺寸先减小后增加。所有样品均出现锐钛矿型TiO₂拉曼散射峰,而未发现金红石晶型的拉曼散射峰。各个拉曼峰的半高宽随着球磨时间的增加都有所增加,这表明样品的表面质量下降,表面缺陷和氧空位逐渐增加导致。所有样品在470 nm附近均出现荧光峰,且球磨后的样品该荧光峰得到增强,经过球磨后的TiO₂样品在397, 452, 483, 500和536 nm等处出现荧光峰,且球磨4 h后的TiO₂荧光峰强度最强,表明其表...     

钡铁氧体前驱体高能球磨过程的红外拟合光谱分析

高能球磨法是材料制备过程中常用的方法,通过物料在高速运转的过程中进行磨合而产生晶体空位缺陷,实现元素的掺杂,进而发生化学吸附或化学反应,合成产生新的物相,对于后续合成材料的性能有很大影响.钡铁氧体具有良好的磁性能,被用于功能材料制备的诸多领域.采用高能球磨法制备钡铁氧体前驱体,利用XRD,SEM和FTIR检测方法考察不...     

高能球磨对碳纳米管形貌及场致发射显示特性的影响

用化学气相沉积法制备了碳纳米管,进行了不同时间的球磨处理。用扫描电镜、拉曼光谱对其形貌和结构进行了表征。对不同球磨条件下的碳纳米管制备成阴极,进行了场致发射特性的测试。结果表明,高能球磨会对碳纳米管的形貌、结构及场致发射性能有明显的影响。球磨时间为0．5～1h时,可以使碳纳半管变短而均匀,且场致发射电性能与未处理时相近,即有低的阈值电场和高的发射电流密度,从而使发射时在阳极上产生的荧光点密度大大增加,发光均匀。但研磨时间过长会改变碳纳半管结构,使其非晶化或石墨化,导致其场致发射性能和显示效果变差。     

Simulation of ball motion and energy transfer in a planetary ball mill

A kinetic model is proposed for simulating the trajectory of a single milling ball in a planetary ball mill, and a model is also proposed for simulating the local energy transfer during the ball milling process under no-slip conditions. Based on the kinematics of ball motion, the collision frequency and power are described, and the normal impact forces and effective power are derived from analyses of collision geometry. The Hertzian impact theory is applied to formulate these models after having established some relationships among the geometric, dynamic, and thermophysical parameters. Simulation is carried out based on two models, and the effects of the rotation velocity of the planetary disk and the vial-to-disk speed ratio ω/Ω on other kinetic parameters is investigated. As a result, the optimal ratio ω/Ω to obtain high impact energy in the standard operating condition at = 800 rpm is estimated, and is equal to 1.15.     

地表柯石英的实验室模拟合成及其形成机制的研究

 静高压合成柯石英的压力和温度的实验条件是提出地球板块折返假说的基础,然而,静高压没有反映局部碰撞和剪切应力的因素。考虑这些因素,提出了一种利用高能机械球磨与静高压相结合的、可以模拟地表柯石英合成的实验室研究方法,发现了一种由机械碰撞引起的α-石英中间亚稳相,其静高压致晶化成柯石英的条件为3.0 GPa、923 K、<1.0 min。如果沿袭传统的板块折返假设,对应此条件的板块俯冲深度应比Jr.L.Coes的结果浅20 km。发现了10 s量级的柯石英的短时间快速合成现象。由本方法合成的柯石英的Raman峰,涵盖了以前得到的天然柯石英和人工合成的柯石英的Raman信息。阐明了由本方法合成的柯石英在地质科学上的涵义,并提出了另一种可能的地表柯石英形成机制。     

Phase Transformations in Fe–Mn Alloys Induced by Ball Milling

Hyperfine Interactions - We have studied the dependence on the milling time of the amounts of metastable fcc and hcp phases produced by ball milling on Fe-13.7 wt% Mn alloys by Mössbauer...     

光学零件镜面磨削加工技术

本文主要阐述了光学零件镜面磨削加工的机床、超微粒金刚石砂轮及其修整技术。     

Disordered Magnetic Phase in Partially Oxidized Bulk Nanocrystalline Iron

Magnetically frozen partially disordered state was observed in nanocrystalline bulk iron prepared by ball-milling of microcrystalline Fe. Role of nanostructure and oxidized fraction is pointed out. Altough we have found a small constituent which is proportional to 1/T in the ZFC curve, the magnetization scaling with T ^3/2 at high fields and the hysteretic behavior in FC-ZFC curves signalizes the presence of frozen ferromagnet at low temperatures.     

细磨抛光中镜片腐蚀的一般特征及其解决方法

本文对ＺＦ７玻璃材料在细磨、抛光加工过程中造成镜片的腐蚀进行了分析，并通过试验提出了新的、简易的控制腐蚀的方法。     

一维取向LTL型分子筛荧光阵列的快速组装

通过有效控制合成液配比,合成出了形貌规则、结晶度高且具有不同长径比的LTL型分子筛晶粒。采用"瓶中造船法",在不同长径比的LTL型分子筛晶粒孔道中组装稀土有机配合物,制得LTL分子筛/Eu-TTA主-客体荧光材料。荧光光谱表征结果表明,在激发波长为350 nm时,长径比为0.2的LTL分子筛/Eu-TTA晶粒在617 nm处的5D0→7F2发光强度最大,而长径比为3的晶粒发光强度最小。最后,将长径比为0.2的LTL分子筛/Eu-TTA晶粒在PEI修饰的玻璃表面快速擦涂10 s后,就制得厘米尺寸的一维取向LTL型分子筛荧光阵列。SEM表征结果证实,该分子筛荧光阵列中几乎所有的LTL分子筛晶粒都沿着与底基表面垂直的c轴方向一维高密度、单层有序排列。在激发波长为365 nm时,该一维取向LTL分子筛荧光阵列发出鲜艳的红色荧光。