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1.
In this study, we report highly transparent Y2O3 ceramics fabricated by hot-pressing only at 1500 °C without a HIP treatment, featuring in-line transmittance levels of 77% and 84% at a wavelength of 400 and 1100 nm, respectively with the grain size suppressed to 710 nm. The effect of the ball size during the grinding of Y2O3 powders on the correlation between the thus-prepared Y2O3 powders and the optical properties of the hot-pressed samples is demonstrated for the first time. With a decrease in the diameter of the ZrO2 balls from 5 mm to 1 mm, the milling efficiency was enhanced and admirable transparency of Y2O3 was attained at a short milling time. However, several micron-sized pores remained in the transparent specimens prepared with 1 mm balls, originating from the inhomogeneously packed region of the green body. Finally, the 2 mm was found to be optimum for obtaining a fine-grained and pore-free microstructure with the best in-line transmittance of Y2O3 ceramics.  相似文献   
2.
立铣刀高速铣削方式加工可显著提高淬硬钢模具的加工效率,但同时也存在切削温度高、刀具磨损快的问题。对刀具与工件的切削接触区域进行充分冷却及润滑是解决此问题的有效方法。对气体风冷高速切削展开刀具磨损研究,涉及两种气体冷却方法—压缩气体冷却法以及涡流管冷却法。实验结果表明,涡流管冷却法相比压缩气体冷却法可降低切削区域温度,有效减轻切屑粘结及粘结磨损现象,最终有效降低立铣刀刀刃的剥落宽度以及刀具磨损程度。  相似文献   
3.
Magnesium aluminate-based materials were prepared by applying different methods: (i) mechanochemical milling of the initial mixture of magnesium and aluminium nitrate powders (in appropriate stoichiometric amounts) followed by heat treatment at temperatures of 650 °C and 850 °C and (ii) melting of the mixture of nitrate precursors at 240 °C followed by thermal treatment at 650 °C, 750 °C and 850 °C. The effect of synthesis method on the structure and morphology of the obtained solids was studied by using various techniques such as: nitrogen adsorption-desorption isotherms, powder XRD, IR spectroscopy and SEM. It was shown that the mechanochemical milling performed before calcination procedure leads to obtaining of nanocrystalline magnesium aluminate spinel phase at lower temperature of 650 °C in comparison with the method using thermal treatment only (at 750 °C). The obtained nanomaterials exhibit mesoporous structure.  相似文献   
4.
《Ceramics International》2015,41(7):8742-8747
The polyaluminium chloride (PACl) precursor was used for a simple and scaled-up mechanochemical-molten salt synthesis of α-Al2O3 platelets. PACl, as a low temperature α-Al2O3 precursor, was firstly mechanically activated by high-energy ball milling for 5 min, followed by a next 5 min ball milling in the presence of a NaCl–KCl salt mixture. The starting formation temperature of the α-Al2O3 phase was 600 °C. In the subsequent annealing in the temperature range of 660–1000 °C, the α-Al2O3 phase with a well developed plate-like morphology was obtained. The products were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), and thermal analysis (DTA, TG) and solution 27Al NMR spectroscopy.  相似文献   
5.
The effects of Ni content and ball milling time on the hydrogen storage thermodynamics and kinetics performances of asmilled La_5Mg_(95-x)Ni_x(x = 5, 10, 15) ternary alloys have been investigated.The evolution of microstructure and phase of experimental alloys in the absorption/desorption process has been characterized by XRD, SEM and HRTEM.The hydrogen storage kinetics and thermodynamics performances and PCI curves have been tested using the Sievert apparatus.It is found that the rising of Ni content remarkably improves the hydrogen storage kinetic performance, but reduces hydrogen storage capacity.And with the increase in milling time, hydrogen desorption activation( E_a) value decreases firstly and then increases; the minimum value is 47.6 kJ/mol, and the corresponding milling time is 10 h for La_5Mg_(85)Ni_(10) alloy.As for the thermodynamics properties, the hydrogenation enthalpy(Δ H) and hydrogenation entropy(Δ S) both decrease firstly and then increase with the rising of Ni content and milling time.The composite La_5Mg_(85)Ni_(10)alloy milled for 10 h exhibits the best thermodynamics and kinetics performances, the lowest E_a of 47.6 kJ/mol, absorption of 5.4 wt.% within 5 min and desorption of 5.2 wt.% within 3 min at 360 ℃ and the lowest Δ H and Δ S of 72.1 kJ/mol and 123.2 J/mol/K.  相似文献   
6.
ABSTRACT

This study reports the energy-efficient performance of three different brands of rice polisher machines operating at different rice mills. The observations of feed screws, sieves and cams have been recorded and we have analysed the chemical composition, microstructure, hardness of cams of different rice mills and given solutions for the performance enhancement of cams. Our objective is to enhance the production of rice variety with quality characteristics and general appearance as required by the consumers.  相似文献   
7.
提出了基于颜色特征和BP神经网络判别大米加工精度的方法。设计了基于机器视觉的大米加工精度检测装置采集大米图像,利用图像处理技术对获取的大米图像进行预处理,提取大米籽粒目标图像;在大米籽粒腹部确定半径为R的圆形区域作为颜色特征值提取区域,将颜色特征值提取区域按面积平均分成5个同心圆子区域,提取每个子区域的R、G、B颜色值,并将颜色值转成色调H值作为描述大米籽粒表面加工精度的颜色特征值,以5个颜色特征值作为输入值,采用BP神经网络对大米的加工精度进行检测。试验结果表明:该方法对4种不同加工精度大米样品籽粒检测的平均准确率为92.17%。  相似文献   
8.
《Ceramics International》2015,41(7):8894-8903
The differences in the set of the process parameters measured before and after mica mechanical activation and their influence on the grain size distribution related characteristics have been studied. The modification of the behavior for activated samples has been correlated to the particle size distribution effect produced by activation via an ultra centrifugal mill. The mechanical treatments are energetically and economically unsustainable procedures, therefore the mica activation was optimized on basis of assessment of the process variables effect on the final quality of product parameters. Response surface method, standard score analysis and principal component analysis were used as means of the optimization. Developed models showed r2 values in the range of 0.816–0.988 and they were able to accurately predict quality parameters in a wide range of processing parameters. Standard score analysis highlighted that the optimal sample was obtained using sieve mesh of 80 μm set of processing parameters (SS=0.81). Multiple comparison tests revealed that the optimal variation in the processing parameters could reduce the negative effect of mica samples inherent properties on the final score and improve activation procedure energetic and economic sustainability.  相似文献   
9.
《Advanced Powder Technology》2021,32(8):2950-2961
The effect of the SiC content on the microstructural, mechanical, and magnetic properties of Cu(1 − x)SiC(x) composite powders (x = 0, 2, 10 and 15 wt%) prepared by high energy milling for 30 h was investigated. The results showed that Cu particles were severely deformed and formed plate like particles of different sizes, while SiC particles were fragmented and embedded in the Cu phase, thus, forming composite particles. As the SiC content increased, the average particle size decreased from 40.75 to 12.84 µm. Besides, XRD data showed a decrease in the crystallite sizes of the Cu phase (from 23.66 to 21.56 nm), accompanied by an increase in the lattice micro-strain (from 0.41 to 0.46%). Changes in the lattice parameters of the Cu phase were observed. The Vickers microhardness were measured in compacted powder samples and reached a maximum value of 135.22 HV for the sample with 15 wt% SiC. The samples showed hysteresis magnetic behavior at 300 K, and with a maximum saturation magnetization of 0.123 emu/g. The weak magnetic signal is mainly due to Co impurities present in the WC from the milling media.  相似文献   
10.
邓集松 《机械制造》2022,60(1):59-61
针对螺纹加工中存在的主要问题,研究总结螺纹铣削的工艺和编程方法。在此基础上,开发了通用螺纹和锥螺纹的铣削程序,并进行简化,由此解决小直径螺纹、特殊螺纹的加工问题。应用所开发的螺纹铣削程序,可以降低螺纹加工的不合格率,提高加工效率。  相似文献   
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