Global insight into microwave stoneware firing: Macro and microstructural changes

Industrial competition and environmental concerns lead to the exploration of alternative and energy-efficient technologies for ceramic materials processing. The main objective of this work was to present microwave heating as a viable option for stoneware processing. Stoneware functional properties are presented and discussed, with emphasis on impact strength, water absorption, porosity, and color. Microstructure analyses show that microwave- and gas-fired samples have higher densifications than electrically fired samples. A relevant finding for processing conditions is that microwave firing requires temperatures approximately 100°C lower than those required by conventional firing. Microwave-fired samples’ rupture energies are approximately twice (0.57 ± 0.06 (J)) those of the reference samples (0.26 ± 0.03 (J)), and their water absorptions are approximately one-half (1.5% at 1170°C and 0.8% at 1190°C) of those of the reference samples (2.0%), whereas the water absorption of electrically fired samples at 1180°C has been estimated to be 7.5%. Color analysis also evidences a shift to lower microwave firing temperatures, what is attributed to the enhanced transformations promoted by microwave heating when comparing with the transformations promoted by conventional (gas or electric) heating.     

Effect of deposition conditions on the properties and annealing behavior of cold-sprayed copper

The deposition of copper by cold gas dynamic spraying has attracted much interest in recent years due to the capability to deposit low-porosity oxide-free coatings. However, it is generally found that as-deposited copper has a signicantly greater hardness, and potentially lower ductility, than bulk material. In this article, copper was deposited by cold spraying using helium as the driving gas at both 298 and 523 K. Evidence is presented indicating that the material sprayed at the lower temperature exhibits a lower dislocation density throughout the grain structure than the material sprayed at the higher temperature. The low stacking fault energy of copper restricts recovery during annealing, and thus microstructural changes during annealing only proceed once recrystallization begins. The material sprayed at low temperature (with the low dislocation density) exhibited recrystallization at annealing temperatures as low as 373 K with a corresponding reduction in hardness. However, the copper sprayed with helium at 523 K was resistant to annealing at temperatures up to 473 K where the dislocations in the structure prevented recrystallization. However, at higher temperatures, recrystallization did proceed (with corresponding reductions in hardness). The fracture behavior of the copper that was cold sprayed with helium at 523 K, both in the as-sprayed condition and following annealing, was measured and explained in terms of the annealing mechanisms proposed. The original version of this paper was published in the CD ROM Thermal Spray Connects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany.     

铜冶炼渣尾矿综合利用现状及研究

铜冶炼炉渣含有大量的有价金属元素,经过选矿工艺处理后,大部分铜被回收,选出的渣精矿返回熔炼炉,渣尾矿外售至水泥厂,尾矿中有价金属仍存在较大利用价值,在现有工艺流程后增加磁选工艺,磁选后的铁精粉用作炼钢配料,尾矿外售。主要介绍了熔炼渣及尾矿成分,现有工艺尾矿处理方式,新工艺的应用及实践。     

HVOF喷涂NiCr-Cr3C2过程中Laval管壁结瘤成因的探讨

围绕超音速火焰喷涂NiCr-Cr3C2涂层时在Laval管内壁产生结瘤的问题，在分析结瘤产物显微结构的基础上探讨了形成结瘤的原因。研究发现，结瘤产物具有层状组织结构，说明结瘤的形成机制与涂层形成机制相似；在HVOF喷涂时，导致Laval管内壁结瘤的原因主要包括：喷涂材料、喷涂粉末颗粒粒度、喷涂工艺参数、Laval管的内表面粗糙度。     

U形件弯曲影响回弹因素模拟分析

板材在弯曲过程中存在的最突出的问题是弯曲回弹难以精确控制.弯曲卸载后产生的回弹,使弯曲件的形状和尺寸与模具工作部分的形状和尺寸不符.弯曲件的最后形状与整个变形过程有关,模具几何参数、材料性能参数等都会对回弹产生很大影响.在板材弯曲成形智能化控制系统中,准确确定实时识别和预测模型的输入、输出参数是弯曲智能化控制的成功与否以及回弹控制精度高低的关键.本文采用Ls-dyna软件,对U形件弯曲影响回弹的因素进行了分析,得出了影响回弹规律的主要因素.为U形件弯曲智能化控制神经网络参数识别及预测模型输入、输出参数的选择提供依据.     

乳液聚合中乳化剂对聚合物乳液稳定性的影响

简要叙述了聚合物乳液稳定性的测定方法，详细地讨论了乳化剂的类型、用量及加入方式等对丙烯酸酯类聚合物乳液的化学稳定性、机械稳定性及贮存稳定性的影响。     

水泥色度控制方法

总结了国内某水泥企业多年对水泥色度进行控制的实际经验,参照国外资料,分析、对比了水泥色度的各类影响因素,给出这些影响因素影响程度的相对大小。提出了水泥企业色度控制指标的推荐数值。针对顾客最容易提出的水泥色度问题,从效果评价、可操作性、负面影响、实施的优先程度等方面介绍了水泥色度的控制方法。     

Isobutane/2-butene alkylation on MCM-22 catalyst. Influence of zeolite structure and acidity on activity and selectivity

The catalytic behavior of the novel MCM-22 zeolite for the continuous alkylation of isobutane with 2-butene has been investigated at a temperature of 50°C, 2.5 MPa total pressure, and a variety of olefin space velocities. At high olefin conversions the MCM-22 zeolite showed a very high initial cracking activity attributable to strong Brønsted acid sites, as well as to the existence of strong diffusional restrictions of the TMP's (formed inside the zeolite) to exit through the channels. At short times on stream (TOS), TMP's account for ca. 40% of the C₈ fraction. The olefin conversion and the cracking activity rapidly decline with TOS, while the alkylate product became richer in dimethylhexenes, indicating a predominance of 2-butene dimerization and a loss of hydrogen transfer activity as the catalyst aged. Moreover, MCM-22 gives less TMP's than large-pore zeolites (USY, beta, mordenite), but more than the mediumpore ZSM-5 at similar 2-butene conversion. The latter catalyst was much more selective for olefin dimerization than for isobutane alkylation, presumably because formation of the bulkier TMP's was strongly impeded in its smaller pores.     

基于RKNN的选址算法及其应用研究

为了使各个设施的整体利用效果最佳, 结合空间位置影响力查询技术, 提出了基于RKNN的选址算法。针对空间对象对空间位置的贡献具有多重性, 建立了一种新的空间位置影响力的度量模型, 该模型更加符合实际应用情况; 然后, 利用该模型计算选址方案中各个设施的影响力, 并引入均衡系数评价选址方案的合理性, 均衡系数越小, 方案越合理。实际应用表明基于RKNN的选址算法使村镇基础设施的选址更加合理、有效。     

氟对硝酸磷肥生产的影响

介绍在硝酸分解磷矿生产硝酸磷肥的过程中 ,杂质氟对酸不溶物过滤、硝酸钙结晶及过滤、母液的氨中和及料浆蒸发过程的影响。由于氟的存在使物料粘度增加 ,结晶细小 ,过滤变得困难。目前还没有除去液相中氟的成熟方法 ,该公司是采取精料政策及一些工艺措施使生产基本能正常运行。