微波场中不同配碳量钛精矿的吸波特性

采用微波谐振腔微扰法测定了碳质还原剂和钛精矿混合物料的吸波特性,研究了碳质还原剂配入钛精矿不同比例时混合物的吸波特性与材料的复介电常数（ε″）、微波场内热源强度p的关系。分析结果表明：当粒度为147～175μm时,钛精矿的吸波特性优于椰壳碳、焦碳和无烟煤的;且通过比较复介电常数的大小确定了椰壳碳和钛精矿最佳配比为20%,焦碳和钛精矿最佳配比为14%,无烟煤和钛精矿最佳配比为5%;并在此配比条件下得到了ε″和p的最大值。     

微波活化焙烧辉钼矿生产低硫氧化钼

对比研究了微波功率、作用时间及物料质量对辉钼矿预活化焙烧后的脱硫效果的影响,并采用气-固多相反应的未反应收缩核模型研究了辉钼矿氧化焙烧的动力学。结果表明,辉钼矿的吸波性能良好,在微波功率0.64 k W、物料质量30 g、微波作用6 min的条件下,微波可比常规处理方式显著降低硫含量0.256%;辉钼矿氧化焙烧是强放热反应,温度越高,辉钼矿氧化速率越快;540~630℃时转化率明显增高,界面化学反应是控制性环节。微波对于辉钼矿在常规氧化焙烧之前的活化作用已得到试验验证,若应用于工业生产,可采用短时间活化焙烧预处理来辅助常规的氧化焙烧。     

微波活化焙烧辉钼矿生产低硫氧化钼（英文）

对比研究了微波功率、作用时间及物料质量对辉钼矿预活化焙烧后的脱硫效果的影响,并采用气-固多相反应的未反应收缩核模型研究了辉钼矿氧化焙烧的动力学。结果表明,辉钼矿的吸波性能良好,在微波功率0.64 k W、物料质量30 g、微波作用6 min的条件下,微波可比常规处理方式显著降低硫含量0.256%;辉钼矿氧化焙烧是强放热反应,温度越高,辉钼矿氧化速率越快;540~630℃时转化率明显增高,界面化学反应是控制性环节。微波对于辉钼矿在常规氧化焙烧之前的活化作用已得到试验验证,若应用于工业生产,可采用短时间活化焙烧预处理来辅助常规的氧化焙烧。     

微波加热浸出初级富钛料非等温动力学及吸波特性

研究微波加热浸出初级富钛料非等温动力学,测定浸出体系的温度和压力曲线及浸出前后混合液体的吸波特性.动力学研究以铁浸出率为衡量指标,在本研究条件下推导出微波浸出初级富钛料动力学表观总速率方程.温度和压力曲线表明,浸出体系温度和压力的提高都有利于提高铁的浸出率;浸出前后混合液体吸波特性表明,15%盐酸浸出液和经20%盐酸浸出后的混合液都存在吸波特性的突变.     

微波场下渗硼介质的温度特性研究

利用渗硼介质吸收微波的特性可实现钢铁表面渗硼层的制备，渗硼介质与微波作用产生的温度特性是影响渗硼层形成最主要的因素。用热电偶精确测定微波场下渗硼介质的温度，采用MATLAB对实验数据进行了曲面插值拟合和分析，结果表明：微波功率（900-3600W）和渗硼剂质量（40-160g）对升温速率和稳定温度有较大影响，且当微波功率为1800W和2700W时，加热温升曲线符合Boltzmann方程；加热过程可以分为开始升温阶段、升温阶段和温度稳定三个阶段。     

响应面法优化微波焙烧氧化锌烟尘脱氟、氯工艺参数（英文）

研究微波焙烧烟化炉产氧化锌烟尘脱除氟氯工艺,采用响应曲面法对焙烧温度、保温时间和搅拌速度三个重要工艺参数进行优化。结果表明:焙烧温度和保温时间对氟、氯脱除效果影响最显著,搅拌速度的次之;在焙烧温度为700℃、保温时间为80 min和搅拌速度为120 r/min的条件下,氟和氯的脱除率分别达到92.6%和90.2%。上述结果表明,微波焙烧烟化炉产氧化锌烟尘脱氟氯工艺稳定可靠,效果显著。     

碳纤维复合吸波材料的频散特性影响规律研究

目的归纳总结碳纤维长度和含量对碳纤维复合吸波材料(CFCAM)频散特性的影响规律。方法以水性聚氨酯(PR)为基体树脂,碳纤维(CF)为填料,制备了不同长度和含量的CFCAM,采用扫描电镜和X射线衍射仪对CF改性前后的微观形貌和物质结构进行表征,用矢量网络分析仪测试CFCAM介电常数(ε),归纳总结出CF长度、含量对CFCAM的频散特性的影响规律。结果随着CF长度的增大,CFCAM的ε先增大后减小,当CF长度为3 mm时,CFCAM不仅具有较好的频散特性,实部(ε′)和虚部(ε′′)都较大;随着CF含量增大,CFCAM的?增大,当CF质量分数为0.9%时,ε′达到18左右,ε′′达到9左右,预示着该含量下CFCAM有较大的储存能量的能力,并且对电磁波有较强的电损耗能力。结论 3 mm碳纤维在质量分数为0.9%时具有较好的频散特性,适宜用来制备吸波性能强、频带宽的雷达吸波涂层材料。     

纳米铁纤维与羰基铁粉共混制备轻质宽带吸波涂层材料

为降低羰基铁粉吸波剂的密度、提高介电常数,采用轻质、高介电常数的纳米铁纤维与羰基铁粉共混,制备了轻质宽带吸波涂层.研究了纳米铁纤维含量对复合吸波剂微波电磁与吸收特性的影响.结果表明,随纳米铁纤维含量的提高,复合吸波剂的介电常数和磁导率增大.当复合吸波剂中纳米铁纤维含量(质量分数)为2.2%-4.4%时,吸波涂层有更低的面密度和更宽的有效带宽,这是由于在一定范围内提高介电常数,可以改善吸波涂层的匹配吸收特性.     

钛精矿的微波干燥特性及动力学

研究微波功率及物料量对钛精矿微波干燥的含水率、脱水速率、水分比等干燥特性的影响.实验微波功率范围为119～700 W,物料量为5～25 g.不同的干燥条件下干燥过程均延续2～8 min.研究发现微波功率密度对含水率和干燥速率的影响较大,所有干燥过程都有一个明显的特征,即在初始阶段有加速干燥峰.固定物料量为25 g和微波...     

微波场中矿物及其化合物的升温特性

研究了微波场中矿物及其化合物的升温特性，并对其升温曲线进行了定量描述，旨在为探求冶金新工艺提供理论依据。结果表明，矿物在微波场中的升温速率取决于其自射特性以及对微波的吸收性，其升温速度方程可表达为：Ｔ＝ａｔ＋ｂ（第一阶段）和Ｔ＝（ｃｔ＋ｄ）＾１／２（第二阶段）。     

温度对低品位攀枝花钛铁矿的介电性能和微波加热行为的影响

采用实验和理论计算相结合的同轴探头反射法测定低品位钛铁矿粉末在2.45 GHz频率下和20~100℃之间的介电特性,并测定钛铁矿在微波场下的升温特性。结果表明：低品位钛铁矿的复介电常数的实部和虚部都随着矿物温度的升高而显著增大;矿物的损耗角正切和温度有二次函数关系;矿物的穿透深度随温度的升高而不断降低。微波场下钛铁矿的升温曲线表明温度和微波辐射时间具有非线性关系。复介电常数与温度的相互作用关系使微波能和钛铁矿的相互作用不断增强,矿物产生更多热量并产生温升,进一步加剧微波能和矿物的耦合作用。当2.45 GHz的微波从两侧加热钛铁矿时,随着温度从室温上升到100℃,优化的物料厚度是从10 cm逐渐降低到5 cm。     

锌浸渣还原焙烧-磁选回收铁

在查明锌浸渣工艺矿物学的基础上,采用还原焙烧将铁酸锌分解为氧化锌和磁性氧化铁,再通过磁选的方法回收铁,达到锌、铁分离的目的。实验考查了焙烧温度、焙烧时间、还原剂用量对铁酸锌分解率、铁回收率和铁品位的影响。结果表明:在焙烧温度为950℃、焙烧时间为1 h及还原剂添加量为10%和5%的条件下,铁酸锌分解率达到72.05%,铁回收率可达到91.79%,精矿中铁的品位为50%左右。焙烧及磁选过程中颗粒的团聚包裹是铁精矿品位不高的主要原因。     

Preparation and microwave properties of Ba4ZnzCo2_zFe36O60 hexaferrites by a sol-gel process

Ba4ZnzCo2_zFe36O60 hexaferrites with Z = 2.0, 1.5, 1.0, 0.5, and 0.0 were prepared by a citrate sol-gel process.The complex dielectric constant and complex permeability of hexaferrite-paraffin wax composites were measured in the range from 0.1 to 6.0 GHz. Measured results showed that both the complex dielectric constant and the dielectric loss exhibited no significant change as the measuring frequency increasing except for the sample with Z = 0.0. The real part of permeability decreased with increasing frequency for all samples in the whole measuring frequency range, and the natural resonance phenomena were observed in allμ" spectrum but Co2U. The results also indicate that the content of zinc closely affects the microwave properties of Ba4ZnzCo2_zFe36O60 felTites, and the greater the zinc content, the lower the natural resonance frequency is.     

Atmosphere Plasma-Sprayed Carbon Nanotubes/Cordierite Nanocomposite Coatings for Microwave Absorption Applications

Multi-walled carbon nanotubes (MWCNTs)/cordierite (MAS) nanocomposite coatings with different MWCNT contents were prepared via atmosphere plasma spraying method. The characteristics of the MWCNTs/MAS powders and as-sprayed coatings, such as microstructure and phase constitution, were observed and measured. The dielectric properties and microwave absorption properties of MWCNTs/MAS powders and nanocomposite coatings have been investigated at the frequency of 8.2-12.4 GHz with different MWCNT contents and sample thicknesses. When the MWCNT content increased to 7%, the nanocomposite coating revealed the highest dielectric constant and optimal microwave absorption property. Further increase in MWCNT content led to severe oxidation of MWCNTs during the plasma spray process, which resulted in lower dielectric constants and poor microwave absorption property. Moreover, the sample thickness has a noticeable influence on the reflection loss (RL) of the MWCNTs/MAS coatings, and the coating of 2.4-mm thickness shows optical microwave absorption with a minimum RL of ?15.61 dB and bandwidth of 2.35 GHz.     

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.     

Effects of rare earth addition on sintering process and dielectric property of cordierite based glass-ceramics

The effects of rare earth oxide on the sintering and dielectric property of cordierite-based glass-ceramics with non-stoichiometric composition prepared by quenching of molten droplets were investigated. The results show that the addition of rare earth oxide can lower the sintering temperature of cordierite glass-ceramics, improve the densification process and obviously reduce sintering activation energy. It is found that the densification of cordieritebased glass-ceramics is a liquid phase sintering process. The dielectric constant of the sintered compacts enhances with the increase of the density. When the sintering temperature is identical, the rare earth addition is found to have a noticeable effect on the dielectric loss of glass-ceramics. The properties of the glass-ceramics containing rare earth oxide appear to be correct for low firing temperature substrates.     

MoSi_2含量对MoSi_2/Al_2O_3复合涂层介电与力学性能的影响(英文)

通过喷雾干燥法制备MoSi2包覆Al2O3的壳核结构混合粉,利用该混合粉以等离子喷涂技术制备MoSi2/Al2O3复合涂层材料。研究MoSi2/Al2O3质量比涂层材料的力学和介电性能的影响。结果表明:随着MoSi2含量从0增加到45%,复合材料的抗弯强度和断裂韧性分别从198MPa和3.05MPa·m1/2增加到324MPa和4.82MPa·m1/2,随后又降到310MPa和4.67MPa·m1/2。在8.2-12.4GHz微波频率波段内,随着MoSi2含量的增加,复合材料的介电损耗增加,而介电常数的实部却呈减小趋势。这主要是由于MoSi2颗粒熔化后的凝聚及导电网络结构的形成导致电导率的增加引起的。     

微波作用下铝酸钙炉渣非等温浸出动力学

研究了微波作用下铝酸钙炉渣非等温浸出动力学，考察了不同微波辐射功率对炉渣中氧化铝浸出率的影响以及相应微波功率下反应体系温度随时间的变化规律。结果表明：该浸出动力学过程的控制步骤为界面化学反应控制，表观反应活化能为40kJ／mol左右；微波作用可改变反应的频率因子，对反应活化能影响不明显；随着微波辐射功率的增大，频率因子增加，宏观表现出微波功率的增加对反应有促进作用。     

Sinterability and microwave dielectric properties of nano structured 0.95MgTiO3-0.05CaTiO3 synthesised by top down and bottom up approaches

0.95MgTiO₃-0.05CaTiO₃ (MCT) nano powders were synthesised using sol-gel method and high energy ball milling (HEBM). Synthesised powders were characterised using X-ray diffraction analysis to ensure phase purity and HRTEM to determine the fine microstructural features like particle size, interplanar spacing, etc. The powder pellets were heat treated to study the sinterability and microwave dielectric properties and these properties were then compared with the microwave dielectric properties of micron sized sample. Nano powder synthesised using HEBM shows better dielectric properties, sinterability and gets densified to 90% of theoretical density (TD) at 1200 °C/2 h. Dielectric resonators prepared using chemically synthesised nano powder showed poor sinterability and microwave dielectric properties, but, dielectric properties of HEBM samples were very near to that of solid state synthesised samples. Sintered HEBM powders retain the microwave dielectric properties almost to the same level as the solid state synthesised powder with considerable lowering of sintering temperature.