采用等离子体化学工艺制备技术陶瓷压制粉

介绍了采用等离子体化学工艺制备技术陶瓷压制粉的原理及其工艺流程，并对制备的压制粉及其陶瓷材料的性能进行了研究。

用溶胶－凝胶工艺制备技术陶瓷压制粉

介绍了采用溶胶一凝胶工艺制各技术陶瓷压制粉的工艺过程和原理，以及制备工艺参数对陶瓷结果和性能的影响。采用此工艺可获得特定性能、成分、颗粒度和形状的压制粉，为制备高机械、物理性能的技术陶瓷奠定了基础。

正压制粉系统煤仓下煤不畅的治理

以益阳发电公司二期工程2×600 MW超临界直流锅炉机组制粉系统为研究对象,分析正压直吹式制粉系统煤仓下煤不畅的原因和对锅炉安全经济运行的直接影响,结合现场条件、燃煤火电厂煤仓堵煤常用的处理办法,提出了符合实际的解决方案:改善煤仓流线,"相对缩短"原煤下落高程,分段疏松,定期降煤位,入仓落煤口尽量靠中,加强燃料管理,规范运行操作等。

火电厂正压制粉系统煤仓下煤不畅的治理

分析正压制粉系统煤仓下煤不畅的原因和对锅炉安全经济运行的影响,结合现有条件对煤仓进行改造、分段疏松,加强运行管理等措施,问题得以解决。说明了解决煤仓下煤不畅的重要意义。

粉料压制成型螺旋压力机工艺性分析

较系统地分析了粉料压制成型的机理与成型过程 ,并对粉料压制力和压制能与成型件密度的关系、粉料压制螺旋压力机的工艺性进行了较全面的论述 ,为设计及选择粉料成型螺旋压力机提供借鉴。

基于EDEM软件的粉料压制过程仿真与分析

为了验证在陶瓷墙地砖粉料压制过程中运用离散元软件EDEM分析的可行性,利用EDEM对陶瓷墙地砖粉料压制过程进行数值模拟分析,采用控制变量方法进行多组粉料压制过程的动态仿真实验,通过对实验数据的分析得出压制速度和压制力之间的关系。结果表明,在其他条件相同时,压制力与压制坯体密度均随着粉料压制速度的增大而增大,采用EDEM软件仿真的结果与压力机的实际工作情况是相符的。

Mo-15Cu复合材料的制备

以MoO3为原料配置悬浮料浆,采用喷雾干燥-氢气还原工艺制备钼粉,并以Mo预烧坯为骨架,采用熔渗法制备Mo-15Cu复合材料。借助X射线衍射和扫描电镜分别分析Mo粉物相组成和颗粒形貌;通过分析粉末的压缩特性,确定预烧骨架密度变化、径向收缩率以及熔渗样理论密度变化;借助金相显微镜观察熔渗样金相组织,借助热导仪和热膨胀分析仪测定合金的热性能。结果表明:所制备的钼粉纯度高、球形度高、压缩性好。在压制压力720 MPa、预烧温度1 250℃时,钼骨架中钼的体积分数为83.2%,Mo-15Cu复合材料的致密度为99.6%,热导率153 W/(m-K),线膨胀系数为7.0×10-6/K。熔渗样中存在极少孔隙,钼颗粒细小,钼与铜两相分布均匀。

试论中速磨煤机新型焊接结构旋转风环的设计与应用

火电厂的发电能源主要以煤炭为主,目前在大多数发电厂中,煤炭能源的使用方式通常为混煤掺烧,这对于磨煤机的要求更高.本文针对某大型火电厂的磨煤需求进行分析,结合具体的磨煤方式实践,对中速磨煤机HB型的旋转风环进行了重新设计,并在具体的应用环节对其应用效率进行了分析,为火电厂中速磨煤机选用提供帮助.

Die wall lubricated warm compaction behavior of non-lubricant admixed iron powders

The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Steel Corporation was used. With compacting and sintering, compared with cold compaction, the density of warm compacted samples increases by 0.07 - 0. 22 g/cm^3 at the same pressed pressure. The maximum achievable green density of warm compacted samples is 7.12 g/cm^3 at 120℃, and the maximum sintered density is 7.18 g/cm^3 at 80℃. Compared with cold compaction, the ejection force of warm compaction is smaller; the maximum discrep- ancy is about 7 kN. The warm compacted mechanism of densification of iron powders can be obtained： heating the powder contributes to improving plastic deformation of powder particles, and accelerating the mutual filling and rearrangement of powder particles.

Improvement of deformation capacity of gas-atomized hypereutectic Al-Si alloy powder by annealing treatment

Gas-atomized pure metal or alloy powders are widely used as raw material in the preparation of high performance materials by powder metallurgy route（compaction and sintering）. However, cold compactibility of gas-atomized Al-Si alloy powder is inhibited due to the high strength as a result of the refined Si phases and the supersaturated Al matrix. The effect of annealing on improving the compactibility of Al-Si alloy powder was studied. The densification was investigated by the HECKEL compaction equation in terms of deformation capacity. Moreover, the microstructures and bending fracture surfaces of the green compacts were examined to clarify the densification behavior. The results show that a maximum relative density of 96.1% is obtained when the powder is annealed at 400 °C. The deformation capacity is significantly improved by annealing treatment due to the softening of Al matrix, precipitation of supersaturated Si phases, dissolution of needle-like eutectic phase, and spheroidization of Si phases.

Electrochemical properties of powder-pressed Pb-Ag-PbO_(2) anodes

Pb?Ag?PbO2 composite anodes with different mass fractions(1%,2%,3%,4%and 5%)ofβ-PbO2 were prepared by powder-pressed(PP)method.The galvanostatic polarization curves,Tafel curves and anodic polarization curves were tested in sulfuric acid solution.The morphologies and phase compositions of the anodic layers formed after galvanostatic polarization were investigated by using scanning electron microscope(SEM)and X-ray diffractometer(XRD),respectively.The results showed thatβ-PbO2 can improve the electrocatalytic activity of anodic oxide.The anode containing 3%β-PbO2 had the lowest overpotential of oxygen evolution reaction(OER)and the best corrosion resistance.The morphologies of the anode surfaces were gradually transformed from regular crystals to amorphous ones as the content ofβ-PbO2 increased in anodes.

Comprehensive study on quasi-static and dynamic mechanical properties and wear behavior of Mg–B4C composite compacted at several loading rates through powder metallurgy

The present study aims to fabricate and evaluate the mechanical properties and wear behavior of Mg metal matrix composite,reinforced by 0,1.5,3,5 and 10 vol.%B4C microparticles.Mg−B4C samples were fabricated at 450℃ and under different loading rates by using split Hopkinson bar(SHB),drop hammer(DH)and Instron(QS)at strain rates of 1600,800 and 0.008 s–1,respectively.The mechanical properties including microhardness,quasi-static and dynamic compressive strengths and wear behavior of samples were experimentally investigated.The results show that,the hardness of SHB and DH samples is obtained to be 20.2%and 5.7%higher than that of the QS sample,respectively.The wear rate and wear mass loss of Mg–10.0%B4C samples fabricated by SHB were determined lower than those of the QS sample by nearly 33%and 39%,respectively.The quasi-static compressive strengths of Mg−5.0%B4C are improved by 39%,30%and 29%for the SHB,DH and QS samples,respectively,in comparison with the case of pure Mg.Furthermore,it is discovered that the dynamic compressive strength of samples is 51%−110%higher than their quasi-static value with respect to the B4C content.

Effects of warm compaction on mechanical properties of sintered P/M steels

The green and sintered densities,and tensile strength of sintered P/M steels produced by cold compaction,warm compaction,warm compaction combined with die wall lubrication(DWL)were measured under various compaction pressures using polytetrafluoroethylene(PTFE)emulsion as the die wall lubricant.The effects of warm compaction on the mechanical properties were studied.The tensile fracture behaviors of cold compaction and warm compaction were studied using scanning electron microscope(SEM).The results show that the density of sintered P/M steel prepared by warm compaction or warm compaction with DWL is higher than that by cold compaction under all compaction pressures.Meanwhile,the highest tensile strength is obtained by combination of warm compaction and die wall lubrication under all compaction pressures.The SEM results show that the fracture modes of the sintered samples prepared by cold compaction and warm compaction at 700 MPa are the mixed mode of ductile fracture and brittle fracture,and obvious dimples can be found in some regions.The fracture of sample prepared by cold compaction is uneven and has irregular and big pores,but that by warm compaction is relatively even and the pores are round mostly,and the samples have many obvious dimples on the whole fracture surface.

Precision Tension Control System Using Magnetic Particle Clutch

The control of the stability of the filament tension is one of the crucial techniques ensuring the component quality of the composite materials. The open-loop tension control system, with industrial control computer as the core, magnetic particle clutch as the actuator, equipped with compensation technique is researched and manufactured. It can assure the tension control stability of the yarn in filament winding process and increase the control precision of the whole system.

Active disturbance rejection control for hydraulic width control system for rough mill

The highly nonlinear behavior of the system limits the performance of classical linear proportional and integral （PI） controllers used for hot rolling. An active disturbance rejection controller is proposed in this paper to deal with the nonlinear problem of hydraulic servo system in order to preserve last response and small overshoot of control system. The active disturbance rejection （ADR） controller is composed of nonlinear tracking differentiator （TD）, extended state observer （ESO） and nonlinear feedback （NF） law. An example of the hydraulic edger system case study is investigated to show the effectiveness and robustness of the proposed nonlinear controller, especially, in the circumstance of foreign disturbance and working condition variation, compared with classic PI controller.

Cemented backfill technology based on phosphorous gypsum

Physical-chemical properties of phosphorous gypsum, proportion and cemented mechanism of slurry with gypsum as aggregate were studied to remove the harms of gypsum pile, combining with difficult problems of excessive mined-out gobs, enormous ore body under roadway and low recovery ratio of Yongshaba Mine, Kaiyang Phosphor Mine Group, Guizhou Province, China. An appropriate backfill system and craflwork were designed, using shattering milling method to crush gypsum, double-axles mixing and strong activation mixing way to mix slurry, cemented slurry and mullock backfill alternately process. The results show that gypsum is fit for backfilling afterwards by adding fly ash, though it is not an ideal aggregate for fine granule and coagulate retardation. The suggested dosage （the mass ratio of cement to fly ash to gypsum） is 1：1：6-1：1：8 with mass fraction of solid materials 60%-63%. Slurry is transported in suspend state with non-plastic strength, and then in concretion state after backfilling. The application to mine shows the technology is feasible, and gypsum utilization ratio is up to 100%. Transportation and backfill effect is very good for paste-like slurry and drenching cemented slurry into mullock, and the compressive strength and recovery ratio are 2.0 MPa and 82.6%, respectively, with the maximum subsidence of surface only 1.307 mm. Furthermore, the investment of system is about 7 × 10^6 yuan （RMB）, only 1/10 of that of traditional paste backfill system.

Control of Mechanical Properties According to Content Ratio of Copper Coated Carbon Nanotubes in Alumimum Composites

The main objective of this study is to enhance the strength of CNTs （carbon nanotubes） which reinforced AI matrix composites by introducing an appropriate amount of Copper（Cu） into the composite material. AI-Cu/MWCNTs （multi-walled carbon nanotubes） nanocomposites were produced via compaction, sintering and hot extrusion process of AI-Cu/MWCNTs powders, which were fabricated by a conventional ball mill process with AI powders and Cu-MWCNTs composite powders which were synthesized by molecular level mixing technique. Also the change of mechanical properties with different content ratio of Cu/MWCNT composite powders in A1 matrix is analyzed. It is found that the addition of the proper Cu/MWCNTs powders which are well distributed in AI matrix leads to high mechanical stiffness. The 2 wt% Cu/MWCNTs reinforced A1 composites which exhibited 3.2 times higher tensile strength and 4.4 times higher yield strength than pure AI.

Microstructures and mechanical properties of SiBCNAl ceramics produced by mechanical alloying and subsequent hot pressing

Amorphous SiBCNAl powders were prepared via a mechanical alloying (MA) technique using crystalline silicon (Si), hexagonal boron nitride (h-BN), graphite (C), and aluminum (Al) as starting materials. SiBCNAl powders were consolidated by a hot pressing (HP) technique at 1800 °C under a pressure of 30 MPa in argon and nitrogen. The sintering atmosphere had a great influence on the microstructures and mechanical properties of the ceramics. The two ceramics had different phase compositions and fracture surface morphologies. For the ceramics sintered in argon, flexural strength, fracture toughness, elastic modulus and Vickers hardness were 421.90 MPa, 3.40 MPa·m1/2, 174.10 GPa, and 12.74 GPa, respectively. For the ceramics sintered in nitrogen, the mechanical properties increased, except for the Vickers hardness, and the values of the above properties were 526.80 MPa, 5.25 MPa·m1/2, 222.10 GPa, and 11.63 GPa, respectively.