Optimization of Process Parameters for in High-Energy Ball Milling of CNTs/Al2024 Composites Through Response Surface Methodology

The mathematical models are developed to evaluate the ultimate tensile strength( UTS) and hardness of CNTs / Al2024 composites fabricated by high-energy ball milling. The effects of the preparation variables which are milling time,rotational speed,mass fraction of CNTs and ball to powder ratio on UST and hardness of CNTs / Al2024 composites are investigated. Based on the central composite design( CCD),a quadratic model is developed to correlate the fabrication variables to the UST and hardness. From the analysis of variance( ANOVA),the most influential factor on each experimental design response is identified. The optimum conditions for preparing CNTs / Al2024 composites are found as follows: 1. 53 h milling time,900 r / min rotational speed,mass fraction of CNTs 2. 87% and Ball to powder ratio 25 ∶ 1. The predicted maximum UST and hardness are 273.30 MPa and 261.36 HV,respectively. And the experimental values are 283.25 MPa and256.8 HV,respectively. It is indicated that the predicted UST and hardness after process optimization are found to agree satisfactory with the experimental values.

Effects of high-energy ball milling oxide-doped and varistor ceramic powder on ZnO varistor

ZnO varistor ceramics doped with Bi2O3, Sb2O3, CO2O3, Cr2O3, and MnO2 were prepared separately by two high-energy ball milling processes： oxide-doped and varistor ceramic powder. A comparison in the electrical and microstructural properties of the samples obtained by both methods was made. The best results on these characteristics were achieved through the high-energy ball milling varistor ceramic powder route, obtaining a nonlinear coefficient of 57 and a breakdown field of 617 V/mm at a sintering temperature of 1000 ℃ for 3 h. The samples synthesized by this technique show not only high density value, 95% of the theoretical density, but also a homogeneous microstructure, which compete with those obtained by the high-energy ball milling oxide-doped powder route. With the advantage that the high-energy ball milling varistor ceramic powder route can refine grain, increase the driving force of sintering, accelerate the sintering process, and reduce the sintering temperature.

Bimodal-grained Ti fabricated by high-energy ball milling and spark plasma sintering

Bimodal-grained Ti containing coarse and fine grains was fabricated by high-energy ball milling and spark plasma sintering (SPS). The microstructure and mechanical properties of the compacts sintered by Ti powders ball-milled for different time were studied. Experimental results indicated that when the ball-milling time increased, the microstructure of sintered Ti was firstly changed from coarse-grained to bimodal-grained structure, subsequently transformed to a homogeneous fine-grained structure. Compared with coarse-grained Ti and fine-grained Ti, bimodal-grained Ti exhibited balanced strength and ductility. The sample sintered from Ti powders ball-milled for 10 h consisting of 65.3% (volume fraction) fine-grained region (average grain size 1 μm) and 34.7% coarse-grained region (grain size > 5 μm) exhibited a compress strength of 1028 MPa as well as a plastic strain to failure of 22%.

Microstructure and electrical properties of Y_2O_3-doped ZnO-based varistor ceramics prepared by high-energy ball milling

Y2O3-doped ZnO-based varistor ceramics were prepared using high-energy ball milling （HEBM） and low-temperature sin- tering technique, with voltage-gradient of 1934-2197 V/mm, non-linear coefficients of 20.8-21.8, leakage currents of 0.59-1.04 μA, and densities of 5.46-5.57 g/cm3. With increasing Y2O3 content, the voltage-gradient increases because of the decrease of ZnO grain size; the non-linear coefficient and the leakage current improve but the density decreases because of more porosity; the donor con- centration and density of interface states decrease, whereas the barrier height and width increase because of the acceptor effect of Y2O3 in varistor ceramics.

Microstructure and Electrical Properties of Er_2O_3-Doped ZnO-Based Varistor Ceramics Prepared by High-Energy Ball Milling

The microstructure, electrical properties and density of ZnO-based varistor ceramics with different Er2O3 content prepared by high-energy ball milling （HEBM） and sintered at 800℃ were investigated. With increasing Er2O3 content, the ZnO grain size decreases due to the Er-rich phases inhibiting grain growth ; and nonlinear coefficient （ α ） decreases because of the decrease of barrier height （φB） The breakdown voltage （Eb） and density increase, whereas leakage current （IL） decreases with increasing Er2O3 content. The barrier height （φB）, donor concentration （Nd）, density of interface states （Ns） decrease and barrier width （ω） increases with increasing Er2O3 content due to acceptor effect of Er2O3 in varistor ceramics.

Modelling of the High-Energy Ball Milling Process

In this paper, the milling parameters of high energy ball mill (Fritsch Pulverisette 7) like vial geometry, number and size of balls and speed of the mill were modelled and discussed. Simulations through discrete element method (DEM) provide correlation between the milling parameters. A mathematical model is used to improve and develop this process. The results show that the loss of powder mass can remarkably improve the performance of milling. The balls made of stainless-steel have a positive effect on the milling efficiency. The simulation shows that the high ball milling velocities can contribute to faster particle size reduction.

Manufacturing a TiAl alloy by high-energy ball milling and subsequent reactive sintering

A TiAl alloy was fabricated by high-energy ball milling and subsequent reactive sintering from the mixed powders of Ti and Al. High-energy ball milling produced a kind of particular composite powders with an extremely fine altemative Ti and Al lamella structure. The composite powders not only possessed good consolidation and densification characteristics, but also resulted in the augment of nucleation rate of α and γ titanium aluminides during solid-phase reactive sintering After a series of processing, pressing, degassing, extrusion, and sintering, the resultant TiAl alloy presented high relative density and refined grain sizes of （α2 ＋ γ） lamella and γ phases. The compressive yield strength of the sintered TiAl reached 600 MPa at 800℃.

Mssbauer study on Fe-doped TiO_2 by high-energy ball milling

The structural evolution of Fe-doped TiO2 by high-energy ball milling was investigated by X-ray diffraction and Mǒssbauer spectroscopy, The results show that the original anatase-TiO2 transforms to srilankite-type and rutile-type during ball milling. Iron atoms are preferable to dissolve in rutile-TiO2 and there are two relative doublets appearing in Mǒssbauer spectra. A doublet is found in the condition of Fe atoms dissolved in srilankite TiO2 lattice. Mǒssbauer spectra show that the composition distribution is nonuniform in TiO2 during the mechanical alloying with Fe atoms rich at the interface or surface of TiO2 crystalline.

Synthesis of cathode material LiMn_(2)O_(4)for lithium-ion batteries by high-energy ball milling

Using electrolytic manganese dioxide and Li 2CO 3 as starting materials, the precursor of LiMn 2O 4 as cathode materials for lithium ion batteries was obtained by high energy ball milling. The LiMn 2O 4 powder was synthesized by calcinating the as milling powder at 750 ℃ for 24 h. X ray diffraction, SEM, cyclic voltammograms and charge discharge were carried out to investigate the property of LiMn 2O 4 cathode materials. Results show that the synthesized material, which is of standard spinel structure, possesses high reversibility of electrochemistry. The capacity in EC DMC(1∶1)+1 mol/L LiPF 6 electrolyte during first discharge is determined to be 125 mA·h/g.[

Preparation of Bi_(4)Ti_(3)O_(12)(BIT)Ceramics via a High-Energy Ball Milling Process Doped with Multi-Walled Carbon Nanotubes(MWNTs)

We prepared the Nano-sized bismuth titanate Bi4Ti3O12 (BIT) powders, through a high-energy ball milling process from their oxides Bi2O3 and TiO2. This BIT phase can be formed after a milling process for 40 min. With an increasing milling time, this particle size of mixture is gradually reduced, thus, we have mostly an amorphous phase. The BIT ceramics were duly obtained by sintering the synthesized powders at temperatures ranging from 850°C to 1000°C. The BIT ceramics sintered at 1020°C for 1 h, exhibiting a density with 7.52 g/cm3 of a crystaline phase and a dielectric of K = 288.11 (100 Hz), as well as a dielectric loss of 0.05 (100 kHz). The High-energy ball milling process is a promising way to prepare BIT ceramics. After the preparation of the BIT, we doped it with the Multi-Walled Carbon Nanotubes which are properly obtained by a chemical vapour deposition (CVD), using nickel as a catalyst, as well as using acetilene at 720°C, and then proceeded with the dielectric and optical measurements.

New Method to Measure the Fill Level of the Ball Mill I——Theoretical Analysis and DEM Simulation

The accurate measurement of the fill level in the ball mill has not been resolved because of the interplay of many variable factors, which led the mill to be operated under the uneconomical condition and lost a lot of energy. At present, some methods, such as vibration method and acoustic method, have been applied for measuring the fill level by the researchers. Aiming at the problem of the traditional methods for measuring the fill level, that is, the feature variables of the fill level suffer the influences of the ball load and the water content of the coal, a novel method to measure the fill level is proposed and a possible relation between the fill level and the angular position of the maximum vibration point on the mill shell is investigated. The angular positions of the maximum vibration point on the mill shell for different fill level cases are calculated theoretically under two assumptions, respectively. Meanwhile the charge motions of the mill for different fill level cases are simulated with the discrete element method （DEM）. And the simulation results are verified by comparing the motion trajectories of steel balls and power draft of the mill. The simulated movement trajectories of the outmost layer steel balls in the mill are monitored and analyzed to obtain the angular positions of the maximum vibration point on the mill shell. Both the results of the theoretical calculation and the 3D DEM simulation show that the position of the maximum vibration point on the mill shell moves to a lower angular positions as the fill level decreasing, which provides a new idea for measuring the filllevel accurately.

Simulation of a Laboratory Scale Ball Mill via Discrete Element Method Modelling

Discrete Element Method (DEM) is a powerful tool for simulating different types of mills. It also used for computing different types of particles such as rocks, grains, and molecules. DEM has been widely used in the field of rock mechanics. In the present work, DEM approach is applied to model the milling media (powder particles and balls) inside a planetary ball mill and to estimate the distribution of particles of a dry powder during milling. In fact, the efficiency of the DEM strongly depends on the input parameters. The DEM simulation results indicated that DEM is a promising tool for the simulation of the dynamic particles motion and interactions within planetary ball mill. These results could be utilized to further develop the synthesis performance, anticipate the reaction, and reduce the wear in the dry milling reactions.

Role of milling time and Ni content on dehydrogenation behavior of MgH_2/Ni composite

The effects of ball milling time and Ni content on the dehydrogenation performance of MgH2/Ni composite weresystematically investigated.The structural evolution of ball milled MgH2+x%Ni(x=0,2,4,8,20,30,mass fraction)samples duringmechanical milling process and dehydrogenation properties were investigated by a series of experimental techniques.The resultsshow that the desorption kinetics is independent of particle size,grain size and defects as the temperature is above380oC.Thedesorption kinetics is improved by prolonged milling time due to refined and uniformly distributed Ni.The formation of Mg2Ni afterdehydrogenation is proposed to explain the degradation of hydrogen storage properties of MgH2during de-/hydrogenation cyclingprocess.The desorption activation energy of MgH2decreases with the increase of Ni content due to the catalytic effect of Ni.It isfound Ni favors the nucleation of magnesium phase and accelerates the recombination of hydrogen atoms.

Calibration of DEM Parameters to Simulate a Planetary Ball Mill

Planetary ball mill is a powerful tool, which has been used for milling various materials for size reduction. The discrete element method (DEM) was used to simulate the dynamics of particle processes in a planetary ball mill. This work includes the calibration of DEM parameters to simulate a planetary ball mill using EDEM Altair 2021.2 software, which provides both faster workflows and results. The iterative input parameters changed to a close correlation between the simulation and experimental results are attained. The results showed that the standard tests could be used to generate various experimental reference values for the calibration. The numerical modeling results agree with theexperimental, indicating that the calibrated parameters are accurate.

Evaluating the Effects of Crystallinity on Drug Release Behaviour in Itraconazole- or Miconazole-Loaded PLGA Microparticles Prepared Using a Co-Grinding Method

This study aimed to prepare and characterize itraconazole (ITCZ)- or miconazole (MCZ)-loaded poly (lactide-co-glycolide) (PLGA) microparticles (MP) using a co-grinding method with ball milling, which is a solvent-free and convenient procedure. PLGA MP was prepared by grinding for 60 min, and the fixed theoretical drug loading was set at 9.1% and 16.7% for both drugs. The obtained loading efficiency for both drugs was estimated to be approximately 100%. The average diameters of the drug-loaded PLGA MP were approximately 20 - 35 μm. Powder X-ray diffraction (PXRD) or differential scanning calorimetry (DSC) confirmed amorphization of ITCZ and MCZ in ITCZ- or MCZ-loaded PLGA MP in all formulations. The drug release percentage from 9.1%-loaded ITCZ-PLGA7505 MP at 24 h was almost 50%, which was higher than that of ITCZ powder. The drug release percentage from MCZ-loaded PLGA7505 MP at 4 h was over 80%, which was higher than that of MCZ powder. This enhancement of release rate is caused by the amorphization of ITCZ or MCZ in the PLGA matrix. MCZ-loaded PLGA7510 MP showed a sustained release profile up to 24 h, suggesting that MCZ exists in an amorphous form in the PLGA matrix;however, the release rate declined owing to the large molecular weight of PLGA. Therefore, the release enhancement of antifungal drugs loaded on PLGA MP could be achieved by their amorphization using a co-grinding method with ball milling.

玛瑙球磨法制备微米介孔球状材料催化剂及其应用

利用玛瑙球磨法合成出一种负载酸催化剂三氟甲磺酸铜的微米级球状介孔材料,研究了催化剂的微观结构、微观形貌和催化反应活性。通过对环己酮和乙二醇的催化反应表明,样品作为催化剂具有较高活性。初次使用时环己酮转化率为97%,环己酮缩酮的选择性为99%,经过4次使用后依旧具有较高催化活性-环己酮转化率为96%。环己酮缩酮的选择性为99%,远远高于工业用硫酸催化剂的环己酮转化率(90%)和环己酮缩酮的选择性(91%)。

球磨法制备堇青石负载Fe/Ce载氧体的甲烷化学链重整性能

通过球磨法制备一系列堇青石负载Fe/Ce的复合载氧体,并在固定床装置上评价复合载氧体的甲烷化学链重整的反应性能。系统考察了堇青石质量分数、Fe/Ce摩尔比、椰壳添加量以及球磨参数对复合载氧体的氧化还原性能的影响,并进行了一系列表征(XRD、H2-TPR、BET、SEM、XPS)。研究发现,在球料比10∶1、转速500r/min、时间1h的球磨参数下制备质量分数30%堇青石负载Fe/Ce摩尔比为1∶9的复合载氧体具有较优的氧化还原性能。质量分数15%椰壳炭的添加使复合载氧体的实际出氧量提升了38.7%,并且在还原氧化循环反应中表现出良好的稳定性和氧释放能力。

四苯基甲烷球磨法合成多孔碘蒸气吸附材料

【目的】避免在核能利用过程中产生的常见放射性污染核素129I和131I等碘蒸气泄漏对环境和生物产生危害,制备并探讨具有丰富孔道的有机多孔聚合物对碘蒸气的吸附性能。【方法】采用简便快捷的机械合成法,以具有正四面体结构的四苯基甲烷为单体,利用高能行星式球磨机球磨2 h制备3种具有较大比表面积和丰富孔道的有机多孔聚合物T-FDA、T-DCM和T-DCE,并利用碘单质在温度为75℃的密闭体系内升华模仿放射性碘蒸气,分别测试3种多孔材料的碘蒸气吸附性能。【结果】T-FDA、T-DCM、T-DCE的碘蒸气吸附质量分数分别可达461%、486%、444%,达到饱和吸附量的时间分别为5、8、6 h,且多孔材料在循环使用5次后碘吸附性能仅有轻微下降(≤6.8%)。【结论】以四苯基甲烷为单体,通过快速球磨法合成的多孔材料具有良好的碘蒸气吸附性能,有望在放射性碘蒸气吸附领域发挥重要作用。

废旧LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)材料球磨-喷雾法再生研究

为了改善再生锂离子电池材料的电化学性能,提出了一种球磨-喷雾法对废旧LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)进行回收再生。该方法是通过对预处理后的废旧正极材料进行球磨细化,经过喷雾干燥迅速制备再生材料的前驱体,并结合高温煅烧制备再生NCM523材料。采用SEM、EDS、XRD、HRTEM、FT-IR、XPS、TG-DSC等对再生过程中材料的形貌、成分、物相及化学变化等进行了分析,且对再生NCM523组装的电池进行了电化学性能分析。结果表明,再生材料具有多孔结构,锂镍混排程度降低,电化学性能得到改善。在实验条件下得到的再生NCM523材料在0.11 C下的首圈放电比容量为159.053 mA·h/g,循环100圈后放电比容量为145.615 mA·h/g,容量保持率为91.55%,具有良好的容量保持率;电流密度为5 C的首圈放电比容量为126.974 mA·h/g。相较于传统的直接再生方法,球磨-喷雾再生法制备的NCM523的电化学性能得到明显改善。

Al-Mg共掺杂钴酸锂的合成及其电化学性能研究

钴酸锂(LCO)作为锂电池正极材料,在电子产品领域有非常广泛的应用,但由于高电压下会导致其晶相的不可逆相变从而导致循环稳定性降低,因此如何提高钴酸锂在高电压下的电化学稳定性一直是研究热点。为了改善钴酸锂的电化学稳定性,采用固相球磨-烧结法合成了Al-Mg共掺杂的LCO材料。采用X射线衍射(XRD)和扫描电镜(SEM)及电化学性能测试表征晶体结构、形貌和测量其循环稳定性。结果表明:Mg、Al进入钴酸锂晶格内部后有效地提高了其电化学稳定性,当Al掺杂量为0.1%,Mg掺杂量为1%时,在0.5C的倍率,3~4.5V的电压下,首圈放电比容量可达136.7mAh/g,100圈后的容量保持率可达76.2%,同时也表现出了良好的倍率性能。