Preparation of AZ91D magnesium alloy semi-solid billet by new strain induced melt activated method

New strain induced melt activated (new SIMA) method for preparing AZ91D magnesium alloy semi-solid billet is introduced by applying equal channel angular extrusion into strain induced step in SIMA method, by which semi-solid billet with fine spheroidal grains and average grain size of 18 μm can be prepared. Furthermore, average grain size of semi-solid billet is reduced with increasing extrusion pass of AZ91D magnesium alloy obtained in ECAE process. By using semi-solid billet prepared by new SIMA, thixoforged magazine plates component with high mechanical properties such as yield strength of 201.4 MPa, ultimate tensile strength of 321.8 MPa and elongation of 15.3%, can be obtained.

Improvement of X-Band Polarization Radar Melting Layer Recognition by the Bayesian Method and ITS Impact on Hydrometeor Classification

Using melting layer(ML)and non-melting layer(NML)data observed with the X-band dual linear polarization Doppler weather radar(X-POL)in Shunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation processes.The prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian method.When PBB>PNB the gate belongs to the ML,and when PBB<PNB the gate belongs to the NML.The ML identification results with the Bayesian method are contrasUsing melting layer(ML)and non-melting layer(NML)data observed with the X-band dual linear polarization Doppler weather radar(X-POL)in Shunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation processes.The prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian method.When PBB>PNB the gate belongs to the ML,and when PBB<PNB the gate belongs to the NML.The ML identification results with the Bayesian method are contrasted under the conditions of the independent PDDs and joint PDDs of the ZH,ZDR and CC.The results suggest that MLs can be identified effectively,although there are slight differences between the two methods.Because the values of the polarization parameters are similar in light rain and dry snow,it is difficult for the polarization radar to distinguish them.After using the Bayesian method to identify the ML,light rain and dry snow can be effectively separated with the X-POL observed data.ted under the conditions of the independent PDDs and joint PDDs of the ZH,ZDR and CC.The results suggest that MLs can be identified effectively,although there are slight differences between the two methods.Because the values of the polarization parameters are similar in light rain and dry snow,it is difficult for the polarization radar to distinguish them.After using the Bayesian method to identify the ML,light rain and dry snow can be effectively separated with the X-POL observed data.

Structural and electrical characterization of Cu_(2)ZnSnS_(4) ingot material grown by melting method

In this work,a Cu_(2)ZnSnS_(4)(CZTS)ingot is grown via a melting method,then cooled;the resulting molten stoichiomet-ric mixture is sealed off in a quartz ampoule under vacuum.The CZTS powder chemical composition analyses are determined us-ing energy dispersive spectroscopy,and revealing the slightly Cu-rich and Zn-poor character of the ingot.Powder X-ray diffrac-tion analysis reveals a crystalline structure with a kesterite phase formation,and a preferred orientation of(112)plane.The lat-tice constants of the a-and c-axes,calculated based on the XRD analyses,are a=5.40Åand c=10.84Å.Based on Hall measure-ments at room temperature,we find that the crystal exhibits p-type conductivity,with a high concentration of 1018 cm^(-3),a res-istivity of 1.7Ωcm,and a mobility of 10.69 cm^(2)V-1s-1.Activation energies are estimated based on an Arrhenius plot of conductiv-ity versus 1/T,for a temperature range of 80-350 K,measuring 35 and 160 meV in low-and high-temperature regimes,respect-ively,which is attributed to complex defects(2CuZn+SnZn)and antisite defects(CuZn),respectively.The observed scattering mech-anisms are attributed to ionized impurities and acoustic phonons at low and high temperatures,respectively.The extracted band-gap is 1.37 eV.

Preparation of Thermosensitive Microcapsules Containing Water Soluble Powder by Melting Dispersion Cooling Method

It was tried to prepare the thermosensitive microcapsules containing the water soluble solid powder by the melting dispersion cooling method and to establish the optimum preparation conditions. As a model water soluble solid powder, sodium hydrogen carbonate was adopted in order to generate carbon dioxide gas and as a thermosensitive shell material, olefin resin with the melting point of ca. 40°C was used. In the experiment, the concentration of olefin resin in the shell material solution was mainly changed together with the concentrations of the oil soluble surfactant species and the α-tocopherol as a modifier of shell. Addition of α-tocopherol into the shell material solution could prevent the core from breaking away during the microencapsulation process and result in the higher microencapsulation efficiency, because the dispersion stability of solid powder in the shell material solution could be increased due to the increase in affinity between the shell material solution and solid powder. Also, the microencapsulation efficiency increased with the concentration of olefin resin, became maximum at 50 wt% and then, decreased. The microcapsules were found to begin melting at 36°C and to generate carbon dioxide gas.

Preparation of Microcapsules Containing Aqueous Solution of Azur B with Melting Dispersion Cooling Method and Application to DNA Amplification Detector

Microcapsules containing the aqueous solution of Azur B of a water soluble dye were prepared with the melting dispersion cooling method and applied to the amplification detector of plant DNA. Paraffin wax with melting temperature of 75°C was used as the shell material. In the experiment, the aqueous solution (W) of Azur B as the core material was dispersed in the melted paraffin wax (O) to form the (W/O) emulsion and then, the (W/O) emulsion was dispersed in the silicon oil (O’) as the continuous phase to form the (W/O)/O’ emulsion at 85°C. After formation of the (W/O)/O’ emulsion, the microcapsules were prepared by cooling the (W/O)/O’ emulsion to 50°C. The microcapsules were prepared by changing the concentration of oil soluble surfactant in the (W/O) emulsion and the volume of the (W/O) emulsion in the (W/O)/O’ emulsion. The microencapsulation efficiency increased with the concentration of oil soluble surfactant and finally became 100% under the optimum conditions. Furthermore, the microcapsules were melted down at temperature of 85°C to reveal the sharp thermal responsibility and to release the aqueous solution of Azur B. As a result, it was found that the microcapsules were able to be applied to the amplification detector of plant DNA by utilizing the reaction between DNA and Azur B.

Organic Melt Crystallization as a Method for Synthesis of Supramolecular Complexes

The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4'-bipyridine, BZP = benzophenone], is proposed. Although CMCR by itself is high melting point compound (above 300°C), CMCR was found to be dissolved in melt mixture of BPY and BZPeven below 120°C. In the mixture of the three components, the reaction occurs to form CMCR·2BPY·BZP supramolecular complex.

A Data Treatment Method of Carbon Saturated Solubility in Fe-C-Cr Melt

Based on the current situation of studying the thermodynamic property of Fe-C-Cr melt using the carbon saturated solubility, an experimental data treatment method of the carbon saturated solubility was put forward. With this method a linear relationship ex- pression of the carbon saturated solubility in Fe-C-Cr melt was obtained, which intercept is dependent on temperature and independent of third component [Cr], but which slope is dependent on third component [Cr] and independent of temperature. Through this expression activity interaction coefficients at different temperatures were calculated and the relationship between activity interaction coefficients and temperature is also obtained.

Dissolution improvement of fenofibrate by melting inclusion in mesoporous silica

In this study,using mesoporous silica for the solubility enhancement of poorly watersoluble drug was investigated.Although the incorporating drug into mesoporous silica is generally performed through the solvent method,the new melting method was proposed in the present study.Fenofibrate,a poorly water-soluble drug,was incorporated into mesoporous silica by solvent method and melting method.The obtained samples were observed by SEM and their physicochemical properties were evaluated by PXRD and DSC measurement.The dissolution and supersaturated property were also investigated.The results from SEM,PXRD and DSC measurement showed that drug could be loaded into pore via the melting method as well as by the solvent method.The drug loaded quantity depended on the pore volume.Drug up to 33%could be incorporated into mesoporous silica and existed in amorphous state.When drug was overloaded or difficulty in incorporation into pore was found,recrystallization of drug occurred at the outer surface of mesoporous silica.From the dissolution test,samples prepared by solvent method and melting method gave the supersaturated drug concentration which sample from melting method showed superior dissolution to the one from solvent method.From this study,drug was efficiently incorporated into mesoporous silica by the melting method which is a simple and solvent-free process,and the aqueous solubility enhancement of poorly watersoluble drug was achieved.

Microstructure and Electrochemical Characteristics of Melt-Spinning Alloy Ml(NiCoMnAl)_5

The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies show that the microstructure of melt spinning alloys is columnar structure. With increasing melt spinning rate, the crystal grains become finer and preferentially grow along (111)[111] direction. The melt spinning and cast alloys belong to CaCu 5 type hexagonal crystal structure. The electrochemical measurements show that the initial capacities of melt spinning alloy electrodes are all above 210 mAh·g -1 with good activation behavior, reaching their maximum capacities after two charge discharge cycles. The maximum capacity (294 mAh·g -1 ) of melt spinning (10 m·s -1 ) alloy electrodes is as the same as that of as cast alloy electrode, and stability of charge discharge cycles of all melt spinning alloy electrodes is better than that of the as cast alloy electrodes. When charged at 600 mA·g -1 , the capacity of melt spinning (10 m·s -1 ) alloy electrode could reach 65% of its maximum capacity about 45 min with high rate discharge capability; but with the cycle number increasing, the stability of its capacity is less than that electrodes of melt spinning rate.

Effects of melt spinning process parameters and wheel surface quality on production of 6060 aluminum alloy powders and ribbons

The aim of this study is to investigate the surface quality of the melt spinning wheel, which was changed from smooth type to textured structure, to atomize liquid metal to form powders. The effects of melt spinning process parameters like wheel speed, gas ejection pressure, molten metal temperature, nozzle–wheel gap and wheel surface quality on the morphological and microstructural features of 6060 aluminum alloy powders and ribbons were investigated. It was observed that ribbon type material was obtained with the smooth wheel and the powder was produced with textured type. The sizes of produced ribbons with smooth surface wheel varied in the range of 30-170 μm in thickness, 4-8 mm in width, and 0.5-1 m in length. The average powder size of the powders manufactured using the textured wheel was in the range of 161-274 μm, depending on the process parameters.Increasing the wheel speed, melt temperature and decreasing gas ejection pressure, nozzle-wheel gap resulted in the decrease of both ribbon thickness and powder size. The microstructures of the powders and ribbons were the equiaxed cellular type, and the average grain sizes diminished with decreasing the ribbon thickness and powder size. The maximum cooling rates were 2.00×10^5 and 1.26×10^4 K/s for the ribbon with thickness of 30 μm and for the powder with size of 87 μm, respectively.

Superelasticity of Cu–Ni–Al shape-memory fibers prepared by melt extraction technique

In the paper, a melt extraction method was used to fabricate Cu–4Ni–14Al（wt%） fiber materials with diameters between 50 and 200 μm. The fibers exhibited superelasticity and temperature-induced martensitic transformation. The microstructures and superelasticity behavior of the fibers were studied via scanning electron microscopy（SEM） and a dynamic mechanical analyzer（DMA）, respectively. Appropriate heat treatment further improves the plasticity of Cu-based alloys. The serration behavior observed during the loading process is due to the multiple martensite phase transformation.

Melting phenomenon in magneto hydro-dynamics steady flow and heat transfer over a moving surface in the presence of thermal radiation

The Lie group method is applied to present an analysis of the magneto hydro-dynamics（MHD） steady laminar flow and the heat transfer from a warm laminar liquid flow to a melting moving surface in the presence of thermal radiation.By using the Lie group method,we have presented the transformation groups for the problem apart from the scaling group.The application of this method reduces the partial differential equations（PDEs） with their boundary conditions governing the flow and heat transfer to a system of nonlinear ordinary differential equations（ODEs） with appropriate boundary conditions.The resulting nonlinear system of ODEs is solved numerically using the implicit finite difference method（FDM）.The local skin-friction coefficients and the local Nusselt numbers for different physical parameters are presented in a table.

Computerized Simulation of Structure of NaAIO_2 Melt

The structure of NaAlO_2 melt has been studied by computerized simulation using Monte Carlo method.The radial distribution functions and Local structure of this melt are calculated.It has been found that NaAlO_2 melt contains ionic clusters formed by corner-sharing AlO_4 tetrahedra,sodium ions and xNa^+.yO^(2-) ionic clusters.

LIQUID SEPARATION OF TUNGSTEN-TIN-BEARING GRANITIC MELT AT 85℃ AND 150 MPa

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基于改进SHRP融冰试验的氯盐融雪剂性能研究

氯盐融雪剂因其融冰除雪性能优异、价格低廉、易于获取而得到广泛应用。为探究氯盐融雪剂的温度适用性不同、标准不统一、撒布方式粗略等问题,该文通过改进的SHRP融冰试验,分析了温度、固液态及撒布方式对NaCl、CaCl_(2)、MgCl_(2) 3种常用氯盐融雪剂除冰性能的影响。试验结果表明:氯盐融雪剂的除冰性能对温度具有显著的敏感性;MgCl_(2)、CaCl_(2)两种融雪剂在融化过程中存在“放热”效应;同种氯盐融雪剂在固态下的融冰效率高于液态下的;同种氯盐融雪剂在不同撒布方式下融冰效率不同,其中,在线性撒布下除冰能力最强。根据试验结果,建议使用固态线性撒布的方式,并根据环境温度选择适宜的融雪剂。

Simulation and Analysis of Electromagnetic Force in Laser Melting Deposition by Electromagnetic Impact

Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil.Axial electromagnetic force shows repulsion in one cycle.The experimental results indicate that the magnetic field is beneficial for grain refinement,microhardness increasement and decline of quantities and average sizes of pores.

Preparation of Al-Si-Ti Master Alloys by Electrolysis of Silica and Titania in Cryolite-Alumina Melts

Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al Si Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al Si Ti master alloys.

基于离散元法的SLM刮刀倾角对粉末铺展行为的影响研究

刮刀倾角对选区激光熔化过程粉末铺展行为有重要影响.基于离散元法建立铺粉数值模型,对不同刮刀倾角的铺粉过程及粉层质量进行模拟研究.针对不同的刮刀倾角,提出一个量化指标对粉层铺展的致密度和均匀性进行综合评估,获得刮刀倾角对粉层质量的影响规律.根据颗粒分布及运动特征将粉堆颗粒体系划分为底层区、斜坡区、刮刀影响区和内部区4个区域.针对各区域进行铺粉过程动力学机理的深入研究,包括颗粒运动轨迹和速度场、刮刀前方剪切带、颗粒间力链分布及演化等.研究发现:刮刀倾角小于0时,颗粒体系难以形成完整的环流运动,剪切带较小,流向沉积层的颗粒较少,颗粒间强力链较少,刮刀间隙前方易形成力拱导致颗粒堵塞,进而形成空斑使得沉积层的致密度和均匀性较低.刮刀倾角大于0时,颗粒体系的环流运动较充分,剪切带较大,流向沉积层的颗粒增多,随倾角增大强力链增多,刮刀压实作用增强,有利于沉积层致密度和均匀性的提高.本研究为优化工艺参数、提高粉层沉积质量提供了理论基础.

致密铼粒的制备研究

为了制备致密铼粒,采用粉末冶金法和电弧熔炼法分别处理5N铼粉。结果表明:当压坯压力为20 MPa、烧结温度2 000℃、烧结时间4 h时,在氢气气氛下烧结后制得致密铼粒,其致密度达到92.33%,且晶粒尺寸为8~20μm,其微观形貌呈现多孔状且具有较多孔洞缺陷;而电弧熔炼法所得铼粒微观形貌平整无缺陷,其致密度高达99.95%,优于粉末冶金法所得铼粒的致密度,但其晶粒尺寸偏大,其值为700~1 500μm。

一种基于物质点法的熔冰仿真方法

为了解决拉格朗日法模拟熔冰时产生的穿模现象,提出一种基于物质点法的熔冰仿真方法。首先,将欧拉空间中的每个拉格朗日粒子视为固-液双相耦合的集合体,实现固相到液相的平稳过渡;其次,在物质点法背景网格上计算热能,采用预处理共轭梯度法求解相变过程的温度线性系统;最后,对潜热现象进行处理,引入虚拟水模型,通过限制虚拟水的移动来实现对冰块外部水流现象的仿真。实验结果表明,该方法不仅能够利用物质点法处理自碰撞的优势解决穿模现象,而且能模拟出真实的潜热过程的水流现象。