桦甸油页岩的微波干馏特性

在自行设计的微波干馏装置上研究了桦甸油页岩、半焦及其混合物在微波场中的升温特性。发现油页岩本身是一种微波弱吸收物质,纯油页岩在微波场中升温能力较差;油页岩热解产物半焦在微波场中升温很快,可以作为油页岩微波干馏的微波吸收剂,将油页岩和半焦的混合物放入微波场中能达到良好的热解效果。实验研究了半焦和油页岩的混合比、微波功率、粒径等因素对微波干馏效果的影响,结果发现,随着半焦比例加大,产油率增加,半焦产率降低;在相同时间内,微波功率越大,产油率和气体损失产率越大,半焦产率降低;油页岩粒径对微波热解影响较小,但当粒径小于0.2mm时实验中出现了较严重的夹带现象。     

微波用于高粘原油脱水的研究

文章分析了微波破乳的机理,并以脱水率为考查依据,采用正交设计的方法对影响稠油微波脱水的主要因素,即原油含水量、微波辐射时间、微波功率进行了系统研究。结果表明,原油含水量为影响稠油微波脱水的主要因素,含水量越高,脱水率越大。另外,微波辐射时间与辐射功率对脱水率也存在着一定的影响。对于实验所用的稠油,当微波辐射功率为420 W,辐射时间为120 s,原油含水量为80%时,稠油脱水率最高,达到93.88%。     

微波辐射处理亚甲基蓝染料废水的实验研究

考察了微波辐射后GAC和ACF的SEM形貌,研究了微波辐射处理亚甲基蓝染料模拟废水情况。结果表明：微波辐射后GAC和ACF的烧蚀程度加深,GAC的孔隙直径增大;ACF纤维丝断头增多,纤维丝表面变得粗糙不平;GAC和ACF加入量越大,亚甲基蓝染料的去除率越高;微波辐射时间越长,脱色率越高;微波辐射功率越大,去除率越高;微波辐射催化能够增强GAC和ACF在液相中的吸附能力。ACF吸附性能较GAC好。     

微波化学反应用聚四氟乙烯容器的透波性能

因聚四氟乙烯（PTFE）具有较低的复介电常数,其作为透波材料而被广泛用作微波化学反应用容器。透波材料的介电特性和透波性能对微波化学反应的速率和效果具有重要影响。本研究首先利用谐振腔微扰法测量了PTFE在23~250℃范围内的复介电常数,并分析了该材料介电属性的温度特性;其次,基于电磁波传输原理,计算了该材料受到不同因素影响下的功率透过系数（T²）,并对该材料的透波性能进行了分析。研究表明,随着温度的增加,PTFE的介电常数逐渐减小,损耗正切逐渐增大,但是二者变化幅度较小;在水平（TM）极化中存在一个布儒斯特角θ_B,当微波以该角度入射时会发生全透射现象;TM极化下的T²随着入射角的增大先增大后减小,垂直（TE）极化下的T²随着入射角的增加而减小,TM极化下的整体透波性能要优于TE极化;随着容器壁厚的增加,透波性能波动变化,存在极大值和极小值;在相同容器壁厚范围内（0~0.1m）,2450MHz频率下对应高透波性能的厚度值要多于915MHz。研究还表明,微波入射角度较小时,PTFE的T²始终保持在0.87~0.99之间,透波性能较好。最后给出了微波以不同频率入射时PTFE的优选壁厚以供实际应用过程中进行参考。     

微波法制备膨胀石墨影响因素分析

以不同粒径的可膨胀石墨为原料,采用微波法制备蠕虫状膨胀石墨。通过控制可膨胀石墨的颗粒度、单次膨胀质量、膨胀容器大小和膨胀时间等参数,进一步探究微波法制备膨胀石墨的影响因素。结果表明:可膨胀石墨粒径越大,膨胀石墨空隙率越大,蠕虫状越明显。当微波时间为30~50 s,单次膨胀质量为0.4~0.7g,容器选用500 m L时,石墨膨胀完全,得到的膨胀石墨体积最大,基本没有烧蚀。50、80、100目的可膨胀石墨最大膨胀体积分别为357 m L/g、234 m L/g、180 m L/g。     

陶瓷材料新术语诠释(十四)

微波是指频率范围为0．3～300GHZ、相应波长为1～0．00lm的高频电磁波。微波烧结是利用微波加热对材料进行烧结的技术。其基本原理是利用微波与材料的相互作用,由高频率电磁波场引起电介质内部的自由或束缚电荷(为偶极子、离子和电子等)的反复极化和剧烈运动,在分子间产生碰撞、摩擦和内耗,将微波能转变为热能,从而产生高温,达到烧结的目的。     

不同干燥因素对天然橡胶微波干燥过程的影响

使用动态称量微波干燥设备研究了不同微波功率密度、不同胶样厚度和不同初始含水率3种因素对湿天然橡胶微波干燥过程及表观质量的影响。结果表明,3种因素对湿天然橡胶微波干燥过程和胶样表观质量的影响较大;微波功率密度越大,失水速率就越大,干燥时间就越短,胶样易出现干燥发粘现象;胶样厚度越厚,失水速率越小,干燥时间就越长,易出现部分夹生和发粘现象;初始含水率越高,失水速率就越大,干燥时间就越长,胶样易出现部分发粘现象。微波干燥湿天然橡胶较为合适的微波功率密度、胶样厚度和初始含水率分别为30.14-34.2W/dm3,5~15mm和10%-20%。     

微波加热对活性炭表面性质的影响

采用了微波加热技术，在不同功率和加热时间下对BN-09颗粒炭进行改性，研究了改性前后活性炭的表面基团变化。结果表明，经微波加热处理后，活性炭表面酸性基团分解，同时碱性特征增强。微波功率越大，加热时间越长，氧含量减少越多，活性炭的碱性特征也越强。     

微波消解—荧光光度法测定化学需氧量

探讨了一种微波消解制样、荧光光度法快速测定水样化学需氧量的新方法.确定最佳消解条件为:氢离子浓度1.0 mol·L-1、微波消解功率585 W、消解时间6 min,无需催化剂,当氯离子浓度小于800.0 mg·L-1时无需氯离子掩蔽剂.在激发波长为250 nm、发射波长为366 nm条件下用荧光光度法测定Ce(Ⅲ)的荧光强度.结果表明,荧光强度与COD值在0～200.0 mg·L-1范围内呈良好的线性关系,检测限为0.9 mg·L-1,回收率为94.4%～111.0%.     

褐煤微波加热除湿研究

采用正交实验设计方法,研究了微波加热功率、时间及褐煤粒度、质量四因素对褐煤除湿率的影响情况;通过极差和方差分析,得出主要影响因素为微波功率,其次是加热时间,褐煤质量及粒度影响较小;在相同时间内微波功率越大,褐煤水分越高、质量越轻,除湿率越大。     

复合材料的微波无损检测研究

简单介绍了微波无损检测技术的基本原理和方法,利用反射法对复合材料缺陷进行检测。对不同材质、不同孔径大小、不同缺陷类型（包括体积型和平面型）试件的检测,得出了与理论分析比较一致的结果。结果表明微波对复合材料缺陷反应灵敏,可检出的最小缺陷孔径为１．０ｍｍ,并得出了微波的误差与缺陷孔的深度以及缺陷孔径的关系。     

Dielectric properties and electromagnetic wave transmission performance of polycrystalline mullite fiberboard at 2.45 GHz

Refractory lining is an indispensable part of high temperature microwave heating equipment, and its wave transmission performance exerts an important impact on the mode and efficiency of microwave heating, while the complex dielectric constant (dielectric constant and dielectric loss) of the material is the decisive factor in determining the wave transmission performance of the material. In this work, we measured the complex dielectric constant of polycrystalline mullite fiber board (PMF) in the temperature range of 25–1000 °C, and the effect of temperature on dielectric constant and dielectric loss was analyzed; The wave-transmission properties of the material were calculated according to the theory of electromagnetic wave transmission line, and the effects of temperature, material thickness, polarization modes of electromagnetic wave and incident angle on the wave transmission performance were analyzed. The results reveal that the dielectric constant of PMF does not change much with the increase of temperature, which is about 1.6; The dielectric loss does not change much within 200 °C, but when the temperature is higher than 200 °C, the change presents approximately exponential increase with the rise of temperature. The wave transmission performance fluctuates with the increase of the thickness, and there are maximum value and minimum value, and the overall wave transmission performance decreases with the increase of the material thickness. In a transverse electric (TE) field, the overall wave transmission performance decreases with the increase of the incident angle, and better wave transmission performance can be obtained by priority selection of vertical incidence of electromagnetic wave. In a transverse magnetic (TM) field, with the increase in the incident angle, the wave transmission performance firstly climbs up then declines, and there is an optimal incident angle where total transmission can occur. Finally, this work selected the thickness corresponding to different temperature as the preferred thickness. This work is of important theoretical significance for understanding the mechanism of the dynamic change of the wave transmission performance of the thermal insulation materials in microwave heating, and provides important practical guidance for the design and optimization of microwave heating equipment.     

The electromagnetic absorbing properties of plasma-sprayed TiC/Al2O3 coatings under oblique incident microwave irradiation

High performance absorbing coatings attract great interest because of the urgent demand for radar stealth technology. However, most reported absorbing coatings focused on the incident microwave were perpendicular to the surface of the coatings. Here, a kind of absorber of TiC/Al₂O₃ was prepared by plasma spraying method and the influence of TiC content and oblique incident microwave irradiation on the absorbing properties of TiC/Al₂O₃ were reported. The absorbing performance firstly increased and then decreased with increasing the TiC content due to the impedance matching and attenuation constant cannot match well at the same time. Meanwhile, compared with TE polarization, TM polarization of the plasma-sprayed TiC/Al₂O₃ coatings was more sensitive to the incident angle. This study demonstrates the feasibility of plasma-sprayed TiC/Al₂O₃ absorbing coatings for electromagnetic applications.     

A review on electrospinning nanofibers in the field of microwave absorption

As important functional materials for absorbing and attenuating incident electromagnetic waves, microwave absorption (MA) materials have found a wide range of applications in civil and military fields. In addition to the study of the compositions, the structural design of the MA materials is also a research hotspot in the field. Among the various structures, the one-dimensional (1D) structure has drawn wide attention because of the unique shape anisotropy and spatial confinement effect. Electrospinning technology has become one of the main ways to prepare continuous 1D micro-nano fibers due to the advantages of many types of spinnable materials, low spinning cost, and high controllability of process parameters. This review involves an introduction and a classification of the research progresses achieved in electrospinning technology concerning MA nanofibers from the perspective of compositions, as well as the list of their minimum reflection loss (RL_min) and effective absorption bandwidth (EAB).     

Formation of Sn filled CNTs nanocomposite: Study of their magnetic,dielectric properties and enhanced microwave absorption performance at gigahertz frequencies

The Simplistic formation, advantageous configuration, non-colossal magnetoresistance and broadband absorption are important parameters for microwave absorbent materials. In this study, a core-shell nanocomposite comprising of Sn-filled carbon nanotubes (Sn/CNTs) was prepared by arc discharge method. The microstructure, morphology and surface composition of Sn/CNTs-based core-shell nanocomposites were characterized in detail. Sn/CNTs nanocomposite showed a magnetic signal due to the broken bonds and defects at interfaces in Sn/CNTs. The weak ferromagnetism was found to be helpful in improving magnetic permeability in the Sn/CNTs which confirms its role as a magnetic loss material under incident electromagnetic wave. Sn-filled CNTs revealed an appropriate value of dielectric constant, which plays an important role in impedance matching upon incident electromagnetic wave. The composite of Sn-CNTs and paraffin with a 50 wt % loading showed the lowest reflection loss (RL) of ?43.87 dB at 10 GHz, with a wide effective absorption band (RL ≤ ?10 dB) of 3 GHz in thickness of 2.3 mm. This enhanced performance is attributed to the combined effect of the conduction loss in one-dimensional core-shell architecture, the interfacial loss Sn-CNT interface, the magnetic loss due to defects-induced ferromagnetism in Sn shell, and in the carbon-containing atomic layers of CNTs.     

Strong light coupling effect for a glancing-deposited silver nanorod array in the Kretschmann configuration

In this work, three slanted silver nanorod arrays (NRAs) with different thicknesses are fabricated using the glancing angle deposition method. Each silver NRA in the Kretschmann configuration is arranged to form a prism/NRA/air system. Attenuated total reflection occurs over the visible wavelengths and wide incident angles of both s- and p-polarization states. The extinctance is inversely proportional to the thickness of the Ag NRA. The thinnest NRA, with a thickness of 169 nm, exhibits strong extinctance of more than 80% over the visible wavelengths. The associated forward scatterings from the three NRAs are measured and compared under illumination with a laser beam with a wavelength of 632.8 nm.     

Effect of the Inside Placement of Electrically Conductive Beads on Electric Field Uniformity in a Microwave Applicator

Non-uniform heating is a major issue in microwave applications, mainly due to inherently uneven distribution of electromagnetic energy in the microwave applicator. In this work, our aim is to improve electric field distribution uniformity by utilizing microwave reflection from electrically conductive beads placed in the microwave oven. The effects of position, size, and number of electrically conductive beads on the electric field distribution were numerically investigated, and validated through water-load experiments in the cavity. It is found that uniform electric field distribution was realized to some extent by appropriate placement of electrically conductive beads; meanwhile, average electric field intensity in the microwave oven was increased.     

Fabrication and microwave absorbing property of WO3@WC with a core-shell porous structure

Special microstructure can significantly improve the microwave absorption property of rare materials. In this paper, porous WC powders were successfully synthesized by spray granulation method. Then, WO₃@WC materials with core-shell porous structure can be prepared after 410 °C heating treatment at different time to form the outer WO₃ oxidation layer. In addition, the microstructure, morphology, phase analysis and electromagnetic property were fully studied by investigating the WC-based materials in different structures. For WO₃@WC core-shell porous materials, when the coating thickness was 2.1 mm, the maximum reflection loss can reach ?19.4 dB at 12.6 GHz, which shows quite good microwave absorbing effects. The core-shell porous structure enhances the original microwave absorption performance due to the multiple reflection reflections and polarizations.     

微波在高分子材料表面处理中的应用

采用微波等离子体处理高分子材料表面可以提高其表面能。通过测定被处理材料的接触角,确定了处理压力、时间对处理的影响及材料处理后的时效性;通过Ｘ射线光电子能谱（ＸＰＳ）分析、获得了被处理表面成分改变情况。材料处理后粘接强度大大提高。     

光谱增感AgBrI-T颗粒乳剂光电子特性

用微波吸收相敏技术检测了光谱增感AgBrI T颗粒乳剂的自由光电子时间分辨谱 ,观察到增感样品在染料增感吸收峰位置有明显的光电子信号 ,在AgBrI T颗粒固有吸收带自由光电子衰减时间比未增感样品的衰减时间短。