微波辐射下热塑性酚醛树脂的合成

首次将微波这种能量形式引入热塑性酚醛树脂的合成反应中,在详细分析了微波辐射下树脂合成特点的基础上,结合基础化学试验室的实际情况,以家用微波炉为基础,设计改装了一套能初步适用于热塑性酚醛树脂连续化试验的微波合成装置.利用此装置,采用微波直接辐射及水浴协同加热相结合的方式合成出壳法用热塑性酚醛树脂.结果表明,与传统加热相比,微波辐射下热塑性酚醛树脂聚合及脱水时间分别缩短了87.5%和74%左右,所得树脂流动性能及其覆膜砂强度也得到了显著改善.     

微波辐射下壳法用高邻位酚醛树脂的合成

在传统加热合成高邻位壳法用酚醛树脂的基础上,就催化剂类型、微波功率及辐射时间等对微波辐射下树脂合成的影响进行了研究.结果表明:在微波辐射下,采用某类二价金属弱酸盐催化,可在相当短的时间内获得具有强烈邻位联接特征的壳法用高邻位酚醛树脂,与传统加热相比,微波辐射具有回流温度高,反应速度快,合成时间短的特点.     

Kinetics of the reactions of carbon containing zinc oxide composites under microwave irradiation

As a fundamental study for the recycling of EAF dust using microwave heating, the reduction rate of a zinc oxide composite by solid carbon under microwave irradiation was investigated. It was found that the reduction of zinc oxide by solid carbon under microwave irradiation was much faster than the conventional method, and the activation energy for the reaction under microwave irradiation was estimated to be 335 kJ/mol.     

KINETICS OF LEACHING SPHALERITE WITH PYROLUSITE SIMULTANEOUSLY BY MICROWAVE IRRADIATION

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An Evaluation of Fracture Toughness of Vinyl Ester Composites Cured under Microwave Conditions

The shrinkage of vinyl ester particulate composites has been reduced by curing the resins under microwave conditions. The reduction in the shrinkage of the resins by microwaves will enable the manufacture of large vinyl ester composite items possible (H.S. Ku, G. Van Erp, J.A.R. Ball, and S. Ayers, Shrinkage Reduction of Thermoset Fibre Composites during Hardening using Microwaves Irradiation for Curing, Proceedings, Second World Engineering Congress, Kuching, Malaysia, 2002a, 22-25 July, p 177-182; H.S. Ku, Risks Involved in Curing Vinyl Ester Resins Using Microwaves Irradiation. J. Mater. Synth. Proces. 2002b, 10(2), p 97-106; S.H. Ku, Curing Vinyl Ester Particle Reinforced Composites Using Microwaves. J. Comp. Mater., (2003a), 37(22), p 2027-2042; S.H. Ku and E. Siores, Shrinkage Reduction of Thermoset Matrix Particle Reinforced Composites During Hardening Using Microwaves Irradiation, Trans. Hong Kong Inst. Eng., 2004, 11(3), p 29-34). In tensile tests, the yield strengths of samples cured under microwave conditions obtained are within 5% of those obtained by ambient curing; it is also found that with 180 W microwave power, the tensile strengths obtained for all duration of exposure to microwaves are also within the 5% of those obtained by ambient curing. While, with 360 W microwave power, the tensile strengths obtained for all duration of exposure to microwaves are 5% higher than those obtained by ambient curing. Whereas, with 540 W microwave power, the tensile strengths obtained for most samples are 5% below those obtained by ambient curing (H. Ku, V.C. Puttgunta, and M. Trada, Young’s Modulus of Vinyl Ester Composites Cured by Microwave Irradiation: Preliminary Results, J. Electromagnet. Waves Appl., 2007, 20(14), p. 1911-1924). This project, using 33% by weight fly ash reinforced vinyl ester composite [VE/FLYSH (33%)], is to further investigate the difference in fracture toughness between microwave cured vinyl ester particulate composites and those cured under ambient conditions. Higher power microwaves, 540 and 720 W with shorter duration of exposure are used to cure the composites. Short-bar method of fracture toughness measurement was used to perform the tests. Plastic (PVC) re-usable molds were designed and manufactured for producing the test samples. The results show that the fracture toughness of specimens cured by microwave conditions are generally higher than those cured under ambient conditions, provided the power level and duration of microwave irradiation are properly and optimally selected.     

微波法合成介孔WO_3 ·NiO ·0.33H_2O及光催化降解气相甲醛

以复合表面活性剂为模板,采用微波辐射、二甲苯萃取脱除模板剂法制备了介孔材料WO_3·0.33H_2O、WO_3·NiO·0.33H_2O,利用XRD、TGA、TEM、BET等手段表征了材料的结构、形貌、比表面积、孔径分布.结果表明,微波辐射比传统加热法制备的材料晶粒小,结晶度高,孔径分布更均匀,比表面积更大;制备的材料WO_3·NiO·0.33H_2O介孔呈现蠕虫状,掺杂Ni~(2+)能稳定介孔结构,抑制晶粒长大,其比表面积达66.37m~2·g~(-1).分别以WO_3·NiO·0.33H_2O催化剂考察在紫外光(UV)、黑光灯、可见光3种光源下对气相甲醛光催化降解反应动力学规律及紫外光下的催化稳定性,其光催化降解气相甲醛降解率为传统加热法样品的3倍,在可见光下达76.8%.     

Microwave assisted atmospheric acid leaching of nickel from laterite ore

The recovery of nickel from laterite ore with sulphuric acid under the effect of microwave irradiation was studied.The experimental results indicated that the extraction rate of nickel was influenced by reaction time,sulphuric acid concentration,and temperature,especially by microwave power.The results obtained from the experiments of orthogonal arrays showed that the optimum conditions of sulphuric acid concentration,reaction time,microwave power,and temperature were 25 vol.%,1.5 h,600 W,and 90°C,respectively.Under the optimal conditions,the nickel recovery could reach approximately 90.8%,which was higher than that obtained by conventional water bath heating.Kinetic experiments showed that the leaching of nickel in a sulphuric acid medium was controlled by chemical reaction occurring on the surface of laterite ore.The apparent activation energy was 38.9 kJ/mol.Microwave heating technology is efficient,clean,and easy to control and facilitate continuous processing of materials.     

中等加载速率下微波损伤砂岩的动态抗压强度及破坏机理（英文）

为了研究微波加热对岩石动态特性和破坏机制的影响,使用改进的分离式霍普金森压杆系统对微波辐射砂岩试样进行动态压缩试验。结果表明,微波辐射能有效降低砂岩的抗压强度。冲击荷载作用下试样呈现出3种不同的破坏模式：拉伸破坏、拉伸-剪切复合破坏和压缩-剪切破坏。利用实测的纵、横波速度计算得到的动态泊松比来描述砂岩的变形特征。随着微波功率和加热时间的增加,泊松比先下降后略有增加,转折点温度出现在244.6°C。此外,微观结构特征表明,微波辐射对岩石产生脱水、扩孔和致裂效应。基于岩石内部热应力和蒸汽压力,探讨微波辐射对岩石的损伤机理,为实验结果提供合理的解释。     

Probing of the microwave radiation effect on the green fluorescent protein luminescence in solution

Microwaves have a larger effect on the green fluorescent protein (GFP) fluorescence intensity than is observed by conventional thermal heating. Our measurements show that thermally heating a GFP solution from 7 to 40 °C results in a ∼1% decrease in fluorescence for every 1 °C. On the other hand, under 250 mW of localized microwave irradiation, the fluorescence can decrease by up to 3–10% with an accompanying temperature rise of only 1 °C.     

THE RATE OF TEMPERATURE INCREASE AND THE KINETICS OF PbS AND PbO IRRADIATED WITH MICROWAVE

The rate of temperature increase and the kinetics of PbS and PbO, irradiated with microwaves, have been studied. According to the experimental data, the interaction between PbS and PbO is nonisothermal, and the activation energy becomes lower and the rate of interaction becomes faster with microwave irradiation than with conventional heating.     

Pyrolysis of polyurethane by microwave hybrid heating for the processing of NiCr foams

Reticulated polyurethane foams are often used as templates for the processing of metal and ceramic foams, since polyurethane foams with a high homogeneity and uniformity of pores and a wide variety of porosities and pore sizes are commercially available. Current conventional methods to pyrolyse polyurethane have brought attention to issues such as long processing time, high costs and high contents of carbon residue. Microwave hybrid heating, as a new pyrolysis method, has been investigated in this research to overcome these issues. Two microwave hybrid and one conventional heating process as comparison were performed to pyrolyse binder and polyurethane for the processing of NiCr8020 foams, which were fabricated by dip-coating method in a powder metallurgical route. Compared to the conventional process, the processing time and residual carbon content of the pyrolysed and pre-sintered foams can be reduced significantly by utilizing microwave hybrid heating techniques, whereas the stability of microwave hybrid heating must be improved and a compromise must be made between the heating rate and the residual carbon content due to the formation of burst holes during the rapid decomposition of polyurethane.     

Leaching Behavior of Complex Copper Sulphide Concentrate with Ferric Chloride by Microwave Irradiation

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微波辐射时间对木质陶瓷导电性能影响的研究

以烟杆和酚醛树脂为原料,采用微波辐射制备了高导电性能的烟杆基木质陶瓷。同时,研究了微波辐射时间对木质陶瓷体积电阻率的影响,并采用X射线衍射技术、激光喇曼光谱和扫描电镜对其微观结构进行了研究。实验结果表明:与常规加热制备木质陶瓷相比,采用微波辐射的方法可将制备时间缩短99.4%。当微波辐射时间为80s时,木质陶瓷的体积电阻率仅为0.97Ω·cm。通过样品XRD谱图和激光喇曼谱图的分析,随着微波辐射时间的延长,样品有序化程度的提高,根据Tuinstra-Koening经验公式计算所得的石墨微晶面网直径La与通过XRD图谱计算得到的值相近。通过SEM观察可知,当微波辐射时间达到80s时,样品中由酚醛树脂形成的玻璃炭与由烟杆炭形成的无定形炭已融合为一个整体,呈多孔状。     

覆膜砂用酚醛树脂/MMT纳米复合材料制备与性能研究

利用己内酰胺同时作为热塑性酚醛树脂内增韧和蒙脱石（MMT）有机改性剂，通过一步原位插层法制备了改性酚醛树脂／MMT纳米复合材料。结果表明，酚醛树脂能较好地插层至4MMT的片层，用于覆膜砂时，由于树脂强韧性和耐热性的综合改善，覆膜砂的综合性能得到明显提高，特别是当MMT加入量为4％左右时，覆膜砂冷态抗拉、抗弯强度分别提高了25％和30％以上。     

Microwave irradiation effects on reversible hydrogen desorption in sodium aluminum hydrides (NaAlH4)

The effect of microwave irradiation on the reversible desorption reaction in sodium aluminum hydride (NaAlH₄) is explored. NaAlH₄ is doped with 2 mol% TiCl₂ and pre-activated by high energy ball milling and aging to show the presence of metallic aluminum phase. As a catalyst, Ti²⁺ has been used to improve desorption kinetics in sodium alanate. X-ray diffraction was performed on the samples exposed to microwave irradiation for 10, 20, 30, 40 and 50 min. Results show that when the powders show the presence of aluminum, a steady increase in the formation of the hexahydride (Na₃AlH₆) phase and Al occurs during microwave irradiation; and is accompanied by a steady reduction in the NaAlH₄ phase XRD peak (h k l) intensities. This data suggests that microwave irradiation drives the reversible H₂ desorption reaction in NaAlH₄. NaAlH₄ doped with 2 mol% TiCl₂ which does not show the presence of Al phase, undergoes a reduction in NaAlH₄ peak intensities with increasing microwave exposure (and no reversible product phases are detected in this case). Dielectric studies on NaAlH₄ indicate that microwave penetration is low. Therefore, it is proposed that microwave irradiation heating of the Al particulate phase is responsible for the hydrogen desorption reaction pathway which is similar to that of conventional heating.     

Research on Properties of Carbon Fiber/Epoxy Resin Composite Material by Microwave Curing

Microwave irradiation was used to reduce the curing time of carbon fiber/epoxy resin composite material.The properties of carbon fiber/epoxy resin composite material under microwave curing were investigated by thermogravimetry(TG),dynamic mechanical analysis(DMA),impact strength test and scanning electron microscope(SEM).The results show that composite materials patch have high thermal stability after microwave curing.The initial degradation temperature is 330.9℃,the maximum thermal decomposition rate is at 368.1℃.When the layer of composite materials patchis 4 layers,the dynamic mechanical properties are the best after microwave curing.The initial storage modulus is 43.2 GPa,increased 28.3 GPa and 27.1 GPa than 3 layers and 5 layers,the glass transition temperature(Tg)is 67.48℃,increased about 12 ℃than 3 layers and 5 layers.Microwave curing can significantly improve the infiltration capacity of epoxy resin,enhance interfacial bonding,and increase the impact strength of composite patch.Under microwave curing,the impact strength of 3,4,5-layers composite material patches increases 35.9%,6.4% and 15.1%,respectively than heating curing.The SEM analysis of impact fracture surface shows that microwave curing can improve the interface of carbon fiber and epoxy resin.     

Effect of sintering techniques on the microstructure and tensile properties of nano-yttria particulates reinforced magnesium nanocomposites

In the present study, magnesium nanocomposites were fabricated using magnesium as matrix and nano-yttria as reinforcement. Nanocomposites with 0.2 and 0.7 vol.% of Y₂O₃ particulates with an average size of 29-50 nm were synthesized blend-press-sinter powder metallurgy technique followed by hot extrusion. Conventional slow heating and microwave assisted rapid heating sintering techniques were used. Microstructural characterization of the materials revealed fairly uniform distribution of reinforcement with the presence of minimal porosity in all of the processed materials, while significant grain refinement in the cases of conventionally sintered materials. Tensile properties characterization of the conventional and microwave sintered nanocomposites revealed that significant and resembling increase in the 0.2% yield strength and ultimate tensile strength of magnesium matrix with the increasing presence of reinforcement. The ductility and work of fracture of magnesium matrix increased significantly in the case of conventionally sintered nanocomposites when compared to the microwave assisted sintered nanocomposites.     

The influence of microwave heating on the mechanical properties of wood

The drying of wood can be a time-consuming process. The timber industry has been using several methods to reduce the drying time of timber for many years; these include drying the wood at elevated temperatures in conventional ovens or kilns, drying in radio frequency or microwave ovens, or a combination of the two. Little attention has been given to quantifying the effect of drying method on the mechanical properties of the wood, especially where this involves microwave energy with its interior to exterior heating characteristics. In this study, Carribean pine timber was dried to pre-determined moisture contents using several drying methods. The wood specimens were then subjected to tensile loading in order to determine the mechanical properties of the dried timber samples. The wood was dried in air at ambient temperature, in a conventional oven at two elevated temperatures and in a microwave oven at two different power settings. The results of the mechanical tests were then compared for the various drying methods. These revealed that microwave drying reduced the strength of the dried timber by as much as 60%.     

Effect of heating mode and sintering temperature on the consolidation of 90W-7Ni-3Fe alloys

The present study compares the sintering response of 90W-7Ni-3Fe alloys consolidated in a 2.45 GHz microwave furnace and a conventional furnace. The W-Ni-Fe compacts were sintered in a temperature range of 1200-1500 °C corresponding to solid-state as well as liquid phase sintering. The compacts were successfully sintered in a microwave furnace with about 80% reduction in the overall processing time. For both the heating modes, the W-Ni-Fe alloys exhibited significant densification prior to melt formation through solid-state sintering. The in situ dilatometric studies revealed that the contribution to densification from solid-state sintering is higher at lower heating rates. In comparison to conventional sintering, microwave sintered compacts showed relatively refined microstructure and higher hardness and flexural strength.     

Microwave synthesis of LiCoO2 cathode materials

1INTRODUCTION LiCoO2isacommerciallyusedcathodemateri alforlithiumionbattery.Comparedwithothercathodematerials,suchasLiNiO2,LiMn2O4and theirdopedcompounds,LiCoO2hastheadvanta gesofhighpotential,excellentreversibility,longcyclelifeandreliableperformance[14].Thereare mainlyseveralmethodsforsynthesisofLiCoO2,suchasconventionalceramicmethod[5,6],sol gel synthesis[7],andlow temperaturesolutioncom bustion[8].Amongthesemethods,theconvention alceramicmethodhasbeenappliedtoindustrial productio…