微波热力辅助粉碎研究

微波加热是向被加热物质内部辐射微波电磁场,推动其偶极子运动,使之相互碰撞、摩擦而生热.利用微波加热技术对矿石进行快速加热,使矿石在热应力作用下产生裂纹,可以改善矿石的易磨性,起到辅助粉碎效果.本文选用6种物料进行微波加热、并经自然和水淬冷却处理,通过Hardgrove磨的易磨性指数对比测试,表明微波加热后自然冷却的物料易磨性提高5～36%,而经水淬冷却的物料易磨性提高38～150%左右.     

高长径比硅灰石的制备及相关研究

硅灰石的化学分子式为Ca[SiO_3],理论含CaO 48.3%、SiO_2 51.7%,是一种链状偏硅酸盐类矿物。硅灰石产品可分为两大类:一类是高长径比的硅灰石产品;一类是细磨硅灰石粉;高长径比超细硅灰石针状粉可以取代其他的短纤维矿物原料(如石棉、玻璃纤维等)及其他合成晶体,用作功能性增强材料,且由于它价格低廉,在工业应用中具有极高的应用价值和巨大的潜在市场[1]。因此,高长径比超细硅灰石针状粉的加工制备已成为世界各硅灰石加工企业备受重视的研究热点。本文主要介绍了高长径比硅灰石的制备方法及相关研究。     

硅灰石的微粉碎与物性研究

以硅灰石矿物粉末为对象，用自动玛瑙乳钵进行干式微粉碎，研究了微粉碎过程中的机械力化学效应，考察分析了硅灰石在微粉碎过程中粉体粒度（激光衍射法）、比表面积（ＢＥＴ吸附法）、结晶构造畸变（有效德拜瓦洛参数－Ｂｅｆ）的变化特征，阐述了硅灰石从三斜晶系向单斜晶系的多型转变过程。     

硅灰石深加工及应用进展

硅灰石是天然产出的偏硅酸盐纤维矿物 ,具有许多优异的工业应用特性。磨细硅灰石是优质的陶瓷原料、冶金助剂 ;高长径比硅灰石是石棉和玻纤的理想代用品 ,可用作橡胶、塑料和油漆涂料的填料 ,起补强和增量的双重作用。本文介绍了硅灰石的工业应用及其深加工进展     

粉碎针状硅灰石粉体的剪搓磨研究与应用

剪搓磨是一种先进、新型生产针状硅灰石粉的专用设备，它以剪切破碎的原理，使物料颗粒细化，并能保持物料纤维状的特性（长径比12-20：1），它节能、高产、不破坏硅灰石特性的优点，是干法生产针状硅灰石扮体的理想设备。     

矿物的微波处理

文中介绍了微波加热的原理和优点,对微波技术在矿物处理的应用情况进行了综述分析,并对微波技术在矿物领域中的应用前景进行了展望。     

填料形貌对导热胶渗流阈值的影响研究

采用微波辅助乙二醇法,通过调节微波处理时间,制备了不同长径比的纳米银材料。用TEM和XRD对不同长径比的纳米银进行了表征。以不同长径比的纳米银作为导热填料制备导热胶,研究发现对于填充不同长径比的纳米银材料,导热胶的阈值填充量是不同的。长径比越大阈值越小。运用修正的Nielsen-lewis阈值理论对这一实验现象进行了合理解释,模拟结果表明,修正的阈值理论与实验结果非常吻合。     

不同含水量木质生物质的粉碎特性研究

为考察不同含水量木质生物质的粉碎特性,用人工喷洒方式制备一定含水量的木质生物质,并利用配有热风炉的超级涡流磨在最大加工能力条件下进行粉碎实验。结果表明,木质生物质产品的粒度、均匀性系数先增加后减小;长径比总体呈增长趋势;振实密度和松装密度逐渐减小;压缩比先变化缓慢,然后增加;产品的含水量、生产能耗逐渐增加。     

淀粉接枝丙烯腈共聚物的微波皂化

通过微波加热，使淀粉接枝丙烯腈共聚物在氢氧化钠水溶液中水解，制得高吸水性树脂。对反应时间、微波功率、氢氧化钠溶液体积对水解反应的影响进行了探讨。实验表明只需选择９５Ｗ，加碱８％ＮａＯＨ８０ｍＬ，反应时间为１８ｍｉｎ的反应条件即能制得高吸水性树脂，与常规皂化反应比较，微波加热能大大加快反应速度。     

两种无机填料改性双马来酰亚胺的摩擦学性能研究

利用盘销摩擦磨损试验机，分别研究了氧化铜和硅灰石两种无机填料对双马来酰亚胺与硬铝合金的滑动摩擦损性能的影响。结果表明：两种填料加入都可以改善双马来酰亚胺的摩擦学性能，随氧化铜用量增加，滑动副的摩擦系数和耐磨性均增加；随硅灰石用量增加和粒径减小，滑动副的耐磨性提高，摩擦系数减小。扫描电镜的分析表明，硅灰石和氧化铜提高滑动副磨性的原因是它们促进了双马来酰亚胺在铝环表面形成牢固的转移膜。     

粉体堆积空隙率对介电常数的影响

通过对不同粒级的石英、方解石、滑石、硅灰石等粉体进行介电性能测量，获得不同频率激励下的电容值和损耗值，分析了粉体粒度及空隙率对粉体堆积态介电常数之间的变化关系。实验结果表明，堆积体空隙率随粒度的增大而提高，堆积态介电损耗随粒度增大而减小，即介电损耗随堆积体空隙率减小而增大。     

Application of Microwave Radiation to Extractive Metallurgy

In applying the microwave radiation to extractive me-tallurgy,it is essential first of all to find the extent ofmicrowave energy absorbed by various minerals experi-mentally.In this paper,more than 25 kinds of commonuseful minerals have been individually irradiated by a 500W,2450 MHz microwave source in an enclosed quartzcrucible to ascertain their heating temperature in a definitetime.In addition,the reduction and cbloridization testswere also carried out on the titanomagnetite concentrateand pentlandite with microwave heating,respectively.These experiments indicate potential applications of util-izing microwave energy in extractive metallurgy.     

Carbothermic reduction roasting for processing of ferruginous chromite ore using conventional and microwave heating

The present study investigates the recovery of chromite from a low-grade ferruginous ore through the carbothermic magnetization route using conventional and microwave heating sources. The carbothermic magnetization of ore is studied in both a horizontal tube furnace and a microwave oven by varying different process variables. The main objective of the study is to enhance the magnetic susceptibility of iron-bearing gangue minerals to enable the separation in a magnetic field. Alteration of crystalline structure and magnetic property of these minerals enables separation of low-grade ore by using magnetic separation. It is found that low-grade ferruginous chromite ore can be upgraded by reduction roasting, and 61.2% Cr₂O₃ was recovered with a chromium-to-iron ratio of 1.93 from a feed chromium-to-iron ratio of 1.01. The optimum result is achieved at a roasting temperature of 800 °C, with a roasting time of 60 min and a reductant dosage of 7.5%. Similarly, under microwave radiation, the chromium-to-iron ratio was upgraded to 1.81 with a recovery of 22%Cr₂O₃. The optimum result achieved under microwave radiation is at a microwave power of 900 W and exposure time of 7.5 min, with a reductant dosage of 10%. The findings of these two processing routes are discussed through characterization tools.     

The hydrothermal analogy role of ionic liquid in transforming amorphous TiO2 to anatase TiO2: elucidating effects of ionic liquids and heating method

In this study, the specific coexistence of water and ionic liquid being the lower temperature thermal annealing condition for anatase crystallization of amorphous titania at ambient pressure was found. The test ionic liquids were 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium tetrafluoroborate. After deep investigation, we found that there existed an analogy between our lower temperature thermal annealing treatment system (LTTAT) and hydrothermal treatment system. In LTTAT system, the ionic liquid played an important role in driving surface crystallization of amorphous TiO₂ to the anatase phase by retaining a suitable amount of water through a dissolution–crystallization mechanism. We could observe higher hydroxyl group ratio of hydroxylated titanium compound from X-ray photoelectron spectroscopy (XPS) data during initial thermal annealing period. The self-assembly ability of ionic liquid then lead to kinetical dehydration and crystallization of hydroxylated titanium compound around it during the following annealing process. Based upon this proposition, the effects of different types of ionic liquid and its amount, temperature effect, and heating method on anatase crystallinity, characterized by X-ray diffraction (XRD), were investigated. It was found that different temperatures and microwave heating effect were observed for different types of ionic liquid. From these observations, it was pointed out that we could get better anatase crystallinity and good photodegradation performance by using the system containing ionic liquid having higher water-adsorbing ability and microwave heating annealing.     

基于非线性超声技术的热损伤混凝土微裂纹检测实验研究

混凝土结构在受热或者火灾作用后其内部极易形成微裂纹,这将严重影响混凝土的耐久性与强度等特性。基于非线性声场调制理论,提出边带峰计数法及损伤指标概念,以评估热损伤混凝土微裂纹的发展。通过高温制备热损伤混凝土,对热损伤混凝土微裂纹的检测结果表明,损伤指标会随微裂纹的发展而增大,与理论研究吻合。证明了非线性声场调制法的可行性,并引入非线性声场共振法进行对比实验,分析了调制法的优越性。并对不同水灰比、骨料比与升温速率的热损伤混凝土微裂纹的检测实验发现,损伤指标峰值会随混凝土水灰比或骨料比的增大而增大,缓慢升温方式对混凝土的损伤较快速升温方式大,并建立起了残余强度与损伤指标峰值之间的关系,为混凝土材料的热损伤评估奠定基础。     

Microwave-assisted generation of standard gas mixtures

Microwave heating was employed for preparation of the standard gas of volatile organic compounds (VOCs) and semivolatile organic compounds (semi-VOCs) by using a 1000 W commercial domestic microwave oven and 1 L gas-sampling bulbs. The VOCs investigated were benzene, chloroform, 1,3-dichlorobenzene, tetrachloroethylene, toluene, and 1,1,2-trichloroethane, and the semi-VOCs used were the polychlorinated biphenyls (PCBs) PCB 1016 and PCB 1248. Since these weakly or nonpolar molecules are very poor absorbers of microwave energy, an appropriate amount of water was introduced to accept microwave radiation and act as the thermal source to accelerate their evaporation. The glass bulb may also contribute thermal energy to the VOCs/semi-VOCs by accepting microwave energy to a small degree. For 0.5 microL of liquid VOCs on 10 mg of glass wool, it was shown that 15 microL of H2O and 60 s of microwave heating yielded a very efficient evaporation [97.2-106.4%, compared with a classic method (Muller, L; Gorecki, T.; Pawliszyn, J. Fresenius' J. Anal. Chem. 1999, 364, 610-616)]. For 1 microL of PCB solution (1000 microg/mL in hexane), 15 microL of H2O and 90 s of microwave heating also provided a complete evaporation. The addition of water was particularly significant for microwave-assisted evaporation of PCBs because semi-VOCs are much more difficult to evaporate than VOCs. This developed microwave technique proved to be quite simple, powerful, rapid, accurate, and safe for the preparation of VOC/semi-VOC standard gas. Solid- phase microextraction combined with gas chromatography was used for the gas analysis.     

微波辅助聚氯乙烯-苯酚之间的Friedel-Crafts接枝反应及对聚氯乙烯热稳定性的影响

在四氢呋喃溶液中通过微波辐照实现了聚氯乙烯(PVC)与苯酚的Friedel-Crafts接枝反应;通过紫外分光光度法表征了PVC-g-苯酚接枝物的接枝率,考察了加热方式、反应温度、催化剂用量及反应时间对接枝反应的影响,并通过红外光谱表征了接枝物的结构;通过刚果红试验、热重分析研究了接枝苯酚对PVC热稳定性的影响。结果表明,相同反应时间,水浴加热接枝率仅为0.1,而微波辐照接枝率可达2.12,其优化工艺条件为无水AlCl_3的用量为PVC质量的8%,反应时间30 min,反应温度为65℃;接枝样品的刚果红试验热稳定时间为6 min46 s,比空白PVC延长了3 min,在空气气氛和氮气气氛中的热降解第一阶段活化能比空白PVC分别提高11.2 kJ/mol和13.8 kJ/mol,而在第二和第三阶段,接枝样品的活化能反而低于空白PVC。证明苯酚取代了容易导致PVC降解的活性氯,抑制了PVC热降解的第一阶段,即脱HCl反应,提高了PVC的热稳定性。     

Suitability of alternative fatty food simulants to study the effect of thermal and microwave heating on overall migration of plastic packaging

The suitability of alternative fatty food simulants on overall migration determination under thermal treatment and microwave heating were analysed for different plastic materials commonly used for packs subjected to thermal treatment or microwave heating. Elevated temperature and microwave heating increased overall migration. The results demonstrated that polymer–simulant affinity plays a large role in determining the suitability of the alternative simulant. For PA/PE, ethanol 95% represented the best alternative fatty food simulant to reproduce overall migration with olive oil. PVC presented a high overall migration. Microwave heating increased migration up to 45 mg/dm². For PVC, isopropanol was able to reproduce olive oil even after microwave heating. For PP, none of the alternative fatty food simulants were able to reproduce overall migration with olive oil. PP presented high inert behaviour. Microwave heating did not produce a significant increase in overall migration; meanwhile, the time of exposure produced a more significant migration. Copyright © 2004 John Wiley & Sons, Ltd.     

Hygrothermal properties of glass fiber reinforced cements subjected to elevated temperature

The effect of elevated temperatures on basic hygric and thermal properties of three types of glass fiber reinforced cement composites (GFRC) is analyzed in the paper. The main difference in the composition of particular GFRC is the use of wollastonite and vermiculite in two of them instead of usual sand aggregates. The composites containing wollastonite and vermiculite are found to have about four times lower thermal conductivity and two to three times lower thermal diffusivity in room temperature conditions. After heating the samples to 800°C and subsequent cooling, a decrease in room-temperature thermal conductivity as high as 50% and an increase in moisture diffusivity in the range of one to two orders of magnitude are observed for all types of studied materials. The application of wollastonite and vermiculite exhibits a positive effect on the high temperature linear thermal expansion coefficient. On the other hand, for temperatures higher than 450°C the thermal diffusivity of materials with wollastonite and vermiculite is higher than of common GFRC with sand aggregates.

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Résumé L'effet des températures élevées sur les principales propriétés hygriques et thermiques de trois types de matériaux composites à base de ciment renforcés par des fibres de verre (GFRC) est analysé dans cet article. La différence majeure de composition de ces matériaux est l'utilisation de wollastonite et de vermiculite dans deux d'entre eux au lieu des granulats de sable habituels. Les matériaux composites contenant de la wollastonite et de la vermiculie s'avèrent posséder une conductivité thermique environ quatre fois inférieure et une diffusivité thermique deux à trois fois inférieure en conditions de température ambiante. Après avoir chauffé les échantillons à 800°C puis les avoir refroidis, on observe pour tous les types de matériaux étudiés une diminution de la conductivité thermique à température ambiante, à hauteur de 50%, et une augmentation de la diffusivité d'humidité, d'environ un à deux ordres de grandeur. L'application de la wollastonite et de la vermiculite montre un effet positif sur le coefficient linéaire à haute température de dilatation thermique. D'autre part, pour les températures supérieures à 450°C, la diffusivité thermique des matériaux contenant de la wollastonite et de la vermiculite est plus élevée que celle des GFRC communs avec des granulats de sable.

     

Development of microwave assisted zeolite–water adsorption heat pump

A microwave assisted zeolite–water adsorption heat pump system was designed, manufactured and investigated experimentally. The influence of operation time of microwave oven on performance of the adsorption heat pump was studied. The performance criteria: coefficient of performance, specific cooling power and volumetric cooing power, were calculated for the designed and tested adsorption heat pump system. The regeneration of adsorbent bed was achieved very rapidly (35 min) by using microwave heating system. The poor thermal conductivity of adsorbent did not affect the periods of isosteric heating and isobaric desorption processes.