更全的杂志信息网

Dielectric Properties and Microwave Heating of Molybdenite Concentrate at 2.45 GHz Frequency

更新时间:2016-07-05

Molybdenum trioxide is an important multiphase crystals[1] that occurs in various nanostructure[2]with a very wide range of uses in areas such as oxidation catalysis[3], photo degradation[4], gas sensors[5], battery electrodes, smart windows[6] , ion conductors[7], imaging devices[8] and lubricants[9]. Traditionally, molybdenum trioxide is produced for industrial use through sublimation and calcination[10] after ammonia leaching of raw molybdenite concentrate. Molybdenite however, high energy consumption and short equipment life are major downsides of the sublimation[11] of molybdenite concentrate by conventional heating. Additionally, the hydrometallurgy process used during ammonia leaching is not efficient as it requires a longer production procedure.

Microwave technology is a highly efficient, low energy consuming, rapid and uniform, clean and easy-controlling heat source because of its two main advantages compared to traditional thermal processing. Firstly, the microwave energy can be directly generated from the intensive exercises among inner molecules under microwave irradiation. Secondly, heat diffusing from the interior to the surface of the material can enhance heat transfer effect[12]. In a dielectric material, there is a close relationship between the microwave absorption property and its dielectric permittivity (dielectric property) [13-14]. Many studies have been done on the basic applications of dielectric property.Maurya[15] described the dielectric behaviors of multiplayer ceramic configurations for a design of high-performance capacitors. Rujun Tang[16] investigated the dielectric permittivity of Sr3Co2Fe24O41 Z-type hexaferrite to determine the performance of a magneto electronic device operating in the microwave region. Boreddy[17] reported the egg white powder with a temperature-dependent dielectric property can be treated by microwave in order to improve its functional properties.

2)由于拆装设备的数量及课程学时的限制,不可能做到每人一组,学生在分组拆装操作过程中实际动手操作机会少;

不过,警察问我:“钱包里有没有个人证件?”我说有,有在留卡。他打开东京警视厅失物招领网站,输入我的名字,结果居然看到我的钱包已经出现在“拾到物”的名录上。

Therefore, it is essential to understand the relational physical parameters in several corresponding change factors to acquire the actual process conditions.In this work, dielectric properties of molybdenite concentrate with different apparent densities were measured using the cavity perturbation method. The temperature rising behavior was investigated under the different conditions to provide a theoretical foundation to prepare high purity MOO3 in fields of microwave.

论文提出的自适应卡尔曼滤波实现的前提是,系统模型参数已知,而噪声统计参数Q和R未知。由于 增益矩阵K值会影响噪声的最终统计参数Q和R,从而影响滤波值。因此在进行自适应滤波时,可以在未估计Q和R等参数的情况下,直接根据量测数据调整K的值。自适应滤波的输出相关法的基本方法是通过量测数据对输出函数序列{ CK}进行估计,然后由{ CK}再进一步推算出系统的 K值,即最佳增益矩阵,使得增益矩阵 K不断的调整,以为 K与实际量测数据{ CK}相匹配。

1 Experimental

1.1 Experimental materials

The molybdenite concentrate with a particle size of 50-300 mesh was provided by Jiangsu Hengxing Tungsten & Molybdenum Co., Ltd. of China. Its chemical composition and XRD analysis are shown in Tab. 1 and Fig. 1 respectively.

Tab.1 Main chemical compositions of molybdenite concentrate

MoSSiO2CuCaOPb44.6428.1711.370.920.900.16

Tab.1 shows the elements molybdenum and sulphur occupy a large proportion in the molybdenite concentrate without any treatments. The main impurities are copper, oxides of calcium and lead, etc.

Fig.1 XRD spectrum of molybdenite concentrate sample

In Fig. 1, the sharp diffraction peaks of MoS2 indicate that MoS2 is the main morphology for this molybdenite concentrate sample. Some weak diffraction peaks corresponding to WS2 as well as CdBrCl were also detected.

From Fig. 2, it can be seen that molybdenite concentrate particle has a layer structure and a wide grain size distribution ranging from several microns to more than 100 μm.

Fig.2 SEM micrograph of molybdenite concentrate sample

1.2 Dielectric property measurements

完善的公司治理对于涉农企业的发展起着关键作用,可有效提高企业经营业绩和投资回报,改善企业的经营状况,实现企业价值最大化目标。公司治理是涉农企业经营和发展的重要条件,优化配置企业的有限资源,提高效率;公司治理有助于解决涉农企业委托代理关系,降低代理成本,规范代理制度;公司治理促进股权结构的优化调整,充分发挥董事会和监事会的职能,保证规章制度的有效贯彻执行;公司治理有效促进涉农企业内控制度的完善,加速整个涉农行业的发展,助推我国“三农”问题的有效解决,更好地化解我国人民日益增长的美好生活需要和不平衡不充分的发展之间的矛盾。

1—vertical cylindrical cavity; 2—vector network analyser (E5071C); 3—laptop Fig.3 Schematic of the developed system for the dielectric measurement

As seen clearly in Fig. 6, with an increase in the apparent density, Dp decreases inversely. Similarly, a quadratic polynomial regression written in Tab. 2 has been used to model the data which shows a high value of correlation coefficient R2(=0.999 3) that indicates the fitting equation can accurately predict the relationship between penetration depth and density. Through the foregoing analysis, it is known that with the increase in the apparent density, the material can absorb more microwave energy. The energy density at the surface of material is maximum when microwave is fed into a material. While the microwave energy would be converted into heat, the microwave field strength and power are constantly being attenuated as the microwave permeates into the interior of material. The attenuation state determines the material penetration. This finding correlates with the study done by Peng[23]. When microwave penetration depth is greater than the size of the specimen heated, the influence was negligible. Conversely, when the penetration depth is less than the size of specimen heated, microwave energy penetration will be limited resulting in anon-uniform heating of the specimen. On the other hand, as the apparent density increases, the dielectric loss factors of material may increase greatly. If the value of the dielectric loss is too high, the microwave energy will attenuate quickly on the surfaces of the material and will not be heated internally. However, a material with low dielectric loss and smaller particle size can be heated wholly and evenly because of a larger microwave penetration depth. Therefore, the investigation for the microwave penetration depth is necessary. Appropriate thickness of material or microwave intensity can be caught from the size of penetration depth of the material treated by microwave.

(1)

(2)

(3)

(4)

2007年起,江西省开始实施山洪灾害防御非工程措施建设,到目前,全省山洪灾害防御非工程体系初步建立,并在近年山洪灾害防御中发挥了重要作用。

1.3 Temperature curves

where T is the material heating temperature, T0 is the material initial temperature, E is the electric field strength, τ is the time, m is the mass of material, cp is the specific heat capacity of material, f is the frequency of microwave and ε0 is the dielectric permittivity in a vacuum.

Fig.4 Microwave high-temperature material treatment equipment (linking cooling device in operation)

2 Results and Discussion

2.1 Dielectric properties

The three dielectric parameters represent specific features of the dielectric material undergoing microwave irradiation. ε′ is the measure of the ability of a material to store electric energy(or the polarization ability of molecules under electric field). ε″ (also called loss factor) represents how much energy is lost during the interaction of the material with radiation. Loss tangent (tanδ) is a measure of how much energy coming from the material can be converted into heat under microwave stimulation at the specific frequency and particular temperature. The dielectric parameters of molybdenite concentrate as a fitting function of apparent density under required measurement condition were shown in Fig.5; Tab. 2 shows each regression curve equation and the corresponding correlation coefficient (R2).

Fig.5 Effect of apparent density on dielectric permittivity

From this plot, we can clearly observe the shifting trends of dielectric permittivity under room temperature. The three parameters are proportional to the apparent density of samples that increase monotonically with the increase inapparent densities within the experimental condition. The possible reason is that the air between material particles was continuously discharged with the increase of apparent density resulting in the significant change of data trend of dielectric characteristics (ε′, ε″ and tan δ). Additionally, clearance between material particles is reduced as the apparent density increases and the sufficient contacti between the particles lead to a greater contact proportion, which leads to a strengthening of space charge polarization, interfacial polarization and dipole polarization[21] (these three types of polarization can be equivalent to the orientation polarization)generating in the microwave frequency range. Therefore, within a microwave penetration depth there is more microwave energy that can be absorbed by dielectric material, hence the material will be heated more efficient.

The resonant cavity perturbation method is widely adopted for microwave dielectric property measurements since it has a high measurement accuracy and simple requirements[18] for preparing the desired specimen and operating in measurement procedure.To take this measurement, a dielectric resonator was centered on a Teflon support positioned in the center of a resonant cylindrical cavity (Fig. 3). The cavity was excited using a coaxial probe where the electromagnetic wave was incident into the dielectric resonator at the desired frequency. The complex permittivity was determined from a calculation that was performed by a computer based on those reflection coefficients measured using a vector net-work analyzer.

2.2 Microwave penetration depth

Penetration depth (Dp) is defined as the distance from the surface of the material to the inner part where microwave power is reduced to 1/e of its surface value.It is the measure of how deep a microwave radiation can penetrate into a material and a critical criterion for designing any microwave heating system. Penetration depth is affected by temperature, characteristics of the heating material and the frequency of microwave incident. Penetration depth can be calculated as[22]

(5)

where λ0=c/f refers to the wavelength of microwave in free space, c is the velocity of light in free space and f is the frequency of microwave radiation. The microwave penetration depth of the molybdenite concentrate was obtained from the derivation relative to series of values of apparent density, and determined the heating uniformity for the material by microwave at 2.45 GHz (λ=12.24 cm). The effect of apparent density on microwave penetration depth is illustrated in Fig. 6.

where fc and fs are the resonant frequencies, Vc and Vs are the volumes of cavity and the sample, Qc and Qs are the measured quality factors of the cavity without and with a lossy sample inside the cavity respectively. Qc is the modification from Qc based on the fact that the quality factor of the cavity will increase for the specimen that is considered to be lossless (Qc>Qc) because of the direct proportion in quality factor to dielectric constant ε′. Qd is also a quality factor that calculates the value of the loss tangent by its reciprocal. The dielectric constant and loss factor were calculated based on the reflection coefficient and resonance frequency variation under the empty sensor and filled with the sample, respectively.

Fig.6 Effect of apparent density on microwave penetration depth for molybdenite concentrate

According to perturbation theory, the fundamental concept of the perturbation technique is that the appearance of a small piece of the dielectric specimen in the resonant cavity will cause a subtle change in the resonant frequency and a decrease in the quality factor of the cavity. This assures that the change of electromagnetic field,when the sample is introduced, will be small.The amended formulas derived for the measurements of dielectric permittivity and loss tangent are expressed as [19-20]

Tab.2 Regression equations for dielectric parameters and penetration (ρ: apparent density)

ItemLinearregressionequationR2ε'ε'=1.41428ρ2+0.13668ρ+2.057870.9979ε″ε″=0.6231ρ2-0.8501ρ+0.47945tanδ=0.05726ρ2-0.05782ρ+0.070620.9993tanδDp=7.01575ρ2-32.05589ρ+39.6610.9993Dp0.9993

2.3 Temperature rising behavior

2.3.1 Effect of sample mass on temperature rising behavior

As expected, the time required to increase temperature up to 800 ℃ became longer with the increase in thickness of molybdenite concentrate. This means that heating rate was gradually reduced. In addition, in Fig.8, the intersection and displacement of curves may be caused by non-uniformly heating due to the presence of large particles and lumps in the material.According to the transmission line theory[25], the reflection loss (RL) based on the complex permittivity and permeability can be calculated. A larger specimen thickness will match a smaller RL peak[26] that represents a larger value of RL, which thus indicates a lower absorption rate on microwave energy for the test samples (when other variables are constant). On the other hand, as the sample thickness increases, the microwave penetration resistance increases as well. Moreover, when the microwave is gradually penetrated into the interior of material, the energy density will appear to exponentially decay[27] along with the diffusion depth. Simultaneously, part of the microwave energy is absorbed by the material and transformed into other forms of energy. Thus in a thicker sample, delivering the same heat needs more microwave energy(microwave power). In summary, within the same microwave power, a thicker specimen can only absorb less microwave power thus exhibiting a relatively slow heating rate.

Fig.7 Temperature rising behaviors for molybdenite concentrate for different sample masses

From Fig.7, the temperature trends among different sample masses can be clearly compared in any same time intervals until the temperature is raised to 800 ℃. Since the oxidation roasting temperature was usually set between 550-650 ℃, it is possible to select the experimental temperature upper limit of 800 ℃ for a better preparation selection. The microwave power was set to a lower value of 0.5 kW in order to achieve a slower temperature increase rate so that changing trends would be observed clearly. The sample thickness was set as 4.0 cm to ensure uniform heating and precise measurement of temperature. Results show that the slope of the curve is different within the same time period, indicating that different materials possess different heating rates. The time required for temperature up to 800 ℃ increased when the materials mass increased. The average heating rates of molybdenite concentrate at the sample mass of 70 g, 90 g, 110 g, and 130 g were 97 ℃/min, 70.5 ℃/min, 55.4 ℃/min and 43.1 ℃/min respectively. Hence a smaller mass of sample indicates a faster apparent heating rate. In fact in a microwave field, the effect of the specimen mass of molybdenite concentrate on the heating rate can be calculated as [24]

会上,公司安监部(应急指挥中心)通报了“三种人”和《安规》调考的情况,与会人员听取了楚雄、普洱、德宏、怒江供电局,大理巍山5家供电局就“三种人”管理的专题交流,普洱供电局“三种人”代表谈了个人感想,玉溪供电局分享了安全文化建设的经验,普洱思茅供电局六顺供电所从切身体会出发,汇报了在供电所安全管理方面的工作,最后公司参会各部门进行发言。会议现场大家还共同观看了昆明供电局的安全文化微电影。

(6)

The microwave reactor employed in the present study is made by the Key Laboratory of Unconventional Metallurgy, Ministry of Education, Kunming University of Science and Technology, and has the ability to alter the power intensity in the range of 0-3 kW at a frequency of 2.40 GHz (Fig.4). The temperature was measured through a K-type thermocouple placed inside a thermos well. The crucible that held the sample material is made of ceramic materials. Using the microwave power, sample mass and thickness required, temperature values were recorded per second by the temperature-display panel that was connected to the thermocouple. In the process of roasting, plenty of air was blown into the heating chamber.

As shown in Eq.(6), there is an inversely proportional relationship between the heating rate and the specimen mass.The greater the concentrate mass, the smaller the heating rate is. This correlates with the experimental testing results. This is because the increase of specimen mass can lead to a decrease of microwave power density and a larger contact area between the sample particles, thus resulting in increasing heat dissipation to the external environment. Furthermore, when apparent density is constant, a larger amount of molybdenite concentrate indicates a thicker sample and the need for more microwave power. Consequently with increasing specimen mass, the power density of the specimen decreases, which leads to an insufficient microwave energy supply, and a slower increase rate of temperature during the microwave heating.

2.3.2 Effect of thickness on temperature rising behavior

Fig. 8 shows how temperature varies with thickness of concentrate sample filled in the corundum cylinder crucible when the sample mass and microwave power were set to 100 g and 0.5 kW respectively.

Fig.8 Temperature rising behaviors of molybdenite concentrate at different specimen thickness

Fig. 7 shows the time-dependent temperature plots for various sample masses of molybdenite concentrate at microwave power 0.5 kW and sample thickness 4.0 cm.

2.3.3 Effect of microwave power on temperature rising behavior

The temperature rising behavior of molybdenite concentrate pertaining to microwave power is shown in Fig. 9.

Fig.9 Temperature rising behaviors for molybdenite concentrate under different microwave power

From Fig. 9, it is clear that the heating rates of molybdenite concentrate increases with the increase in microwave power. The average heating rates successively increase from 43.1 ℃/min to 96.9 ℃/min against an increase in microwave power. The increasing microwave power infers that increasing electric field strength when other conditions were unchanged. Microwaves could penetrate the deeper interior of the material and thus would result in stronger heating uniformity. Because the molybdenite concentrate specimen absorbed more microwave energy with the increase in E, this results in the increase of temperatures. Therefore, increasing the microwave power properly can reduce the heating time and improve the apparent average heating rate of molybdenite concentrate, as same as the heating situation of pyrite, hematite, galena, rutile and coal, etc. Chen[28] also proved this experimentally.

1.我国老年教育发展过程中的差异性。我国老年教育发展过程中的差异性主要表现为城乡差异和东西差异两个方面。有学者表示,根据国家统计局的数据显示,2016年底,全国有2.22亿老年人,全国平均老龄化水平是16.15%。其中,农村是18.47%,城市是14.34%,也就是说中国乡村的老龄化水平比城市已高出4个百分点。而与之相对的是,超过90%以上的老年大学和社区学习中心都集中在城市。此外,中国东部发达地区和西部欠发达地区也存在巨大差异。

2.4 Characterization of products

Fig.10 SEM images of products of molybdenite concentrate samples boasted in air atmosphere

After the molybdenite concentrate sample was roasted in the field of microwave for five minutes at 800 ℃, the products obtained were examined by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). As seen in Fig. 10, the products present a compact plate-shape structure with a smooth surface, which correlates with the results of molybdenum trioxide nanobelts from a preparation by thermal evaporation technique[29]. The XRD pattern of the plate-shape crystal is shown in Fig.11. The positions of strong diffraction peaks at (0 2 0), (1 1 0), (0 4 0), (0 6 0) and (0 10 0) planes are in good agreement with those reported in literature for the orthorhombic α-MoO3 crystalline phase. Nevertheless, some weak peaks of impurities such as unseperated BaSi4O9, unreacted MoS2 and the MoO2, which formed as an intermediate product, are also detected. The occurrence of these constituents may be explained by a limited local supply of O2 during the oxidation process, or an unavailable adequate reaction time. The X-ray fluorescence (XRF) results of roasting products are presented in Tab.3. MoO3 accounts for a major proportion (>90%). The presence of other elements in the product produced infers that this presented work still needs to be improved in order to achieve MoO3 product in a better quality. For example, considering the melting point of MoO3 crystals of 795, the production for high-purity MoO3 would be feasible through sublimating the liquefied MoO3 crystals at a higher temperature and then collecting them using a condensation process. Since the melting points of those impurities are much higher they will remain in the solid phase while the purified MoO3 is collected. This perspective can be illustrated through further research. In any case, the findings have provided a solid foundation to produce high purity molybdenum trioxide by using microwave energy.

1.7 统计学处理 所有数据均采用SPSS 20.0软件包进行。数据由2人重复录入、核查、纠错。计数资料用频数、率表示,采用χ2检验或Fisher′s确切概率法分析。计量资料采用x±s表示,统计推断采用方差分析。多因素分析采用logistic风险模型进行。P<0.05为差异有统计学意义。

Fig.11 X-ray diffractogram of products after roasting of molybdenite concentrate

Tab.3 XRF test results of products obtained from microwave roasting for the concentrate sample at corresponding conditions %

MoO3SiO2Fe2O3SO3Al2O3K2OCuOCaOPbO90.2096.8681.0610.4640.3790.3140.2210.2010.073

3 Conclusion

The dielectric properties and temperature rising behavior were investigated to illustrate the feasibility of preparing high-purity MOO3 from molybdenite concentrate through microwave heating. The results show that the dielectric constant, dielectric loss, and loss tangent are proportional to the apparent density of molybdenite concentrate in the range 0.9-1.4 g/cm3 and the apparent heating rate of the molybdenite concentrate increases with the increase in microwave power and decreases with the increase in the sample mass and thickness. The temperature of the samples reach approximately 800 ℃ after microwave treatment 100 g of the sample for 5 min at 0.5 kW. The products obtained from microwave roasting for molybdenite concentrate at air atmosphere were examined by XRD, SEM and XRF characterization techniques, Thed MOO3 crystals in good quality have been confirmed to be prepared. Molybdenite concentrate can be heated up to a high temperature by microwave, it is feasible to prepare high purity MOO3 from molybdenite concentrate via microwave energy technology.

References:

[1] Sharma R K, Reddy G B. Effect of substrate on the growth of α-MOO3 nanostructures via plasma assisted sublimation process[J]. Physical B, 2015,456: 197-205.

[2] Ette P M, Gurunathan P, Ramesha K. Self-assembled lamellar α-molybdenum trioxide as high performing anode material for lithium-ion batteries [J]. Journal of Power Sources, 2015, 278: 630-638.

[3] Fernandes C I, Capelli S C, Vaz P D, et al. Highly selective and recyclable MoO3 nanoparticles in epoxidation catalysis[J].Applied Catalysis A: General, 2015, 504: 345-456.

[4] Kumar V V, Gayathri K, Anthony S P. Synthesis of α-MoO3nanoplates using organic aliphatic acids and investigation of sunlight enhanced photodegradation of organic dyes[J]. Materials Research Bulletin, 2016, 76: 147-154.

[5] Alaie M M, Jahangiri M, Rashidi A M, et al. Selective hydrogen sulfide (H2S) sensors based on molybdenum trioxide (MoO3) nanoparticle decorated reduced graphene oxide[J].Materials Science in Semiconductor Processing, 2015, 38: 93-100.

[6] Deki S, Béléké A B, Kotani Y, et al. Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films[J]. Journal of Solid State Chemistry, 2009, 182(9): 2362-2367.

[7] Julien C, Nazri G A. Transport properties of lithium-intercalated MoO3[J]. Solid State Ionics, 1994, 68(1-2): 111-116.

[8] Zhang Qixiu, Zhao Qinsheng. Metallurgy of tungsten and molybdenum[M]. Beijing: Metallurgical Industry Press, 2005. (in Chinese)

[9] Ye Yinping, Chen Jianmin, Zhou Huidi. An investigation of friction and wear performances of bonded molybdenum disulfide solid film lubricants in fretting conditions[J]. Wear Volume, 2009, 266(7-8): 859-964.

[10] Ellefson C A, Flores O M, Ha S. Synthesis and applications of molybdenum (IV) oxide[J]. Journal of Materials Science, 2012, 47: 2058-2059.

[11] Xiang Tiegen. Molybdenum metallurgy[M]. Changsha: Central South University Press, 2002. (in Chinese)

[12] Bergman T L, Lavine A S, Incropera F P, et al. Fundamentals of heat and mass transfer [M]. Hoboken: John Wiley, 2011.

[13] Hassan M N, Mahmoud M M, Fattah A A, et al. Microwave-assisted preparation of nano-hydroxyapatite for bone substitutes[J].Ceramics International, 2016, 42: 3725-3744.

[14] Tuichai W, Srepusharawoot P, Swatsitang E, et al. Giant dielectric permittivity and electronic structure in (Al+Sb)co-doped TiO2 ceramics [J]. Microelectronic Engineering, 2015, 146: 32-37.

[15] Maurya D, Sun Fuchang, Alpay S P, et al. A new method for achieving enhanced dielectric response over a wide temperature range[J].Scientific Reports, 2015, 15144.

[16] Tang Rujun, Jiang Chen, Qian Wenhu, et al. Dielectric relaxation, resonance and scaling behaviors in Sr3Co2Fe24O41 hexaferrite [J]. Scientific Reports, 2015,13645.

[17] Boreddy S R, Subbiah J. Temperature and moisture dependent dielectric properties of egg white powder [J].Journal of Food Engineering, 2016, 168: 60-67.

[18] Salema A A, Yeow Y K, Ishaque K, et al. Dielectric properties and microwave heating of oil palm biomass and biochar [J]. Industrial Crops and Products, 2013, 50: 366-374.

[19] Sheen J. Measurements of microwave dielectric properties by an amended cavity perturbation technique[J]. Measurement, 2009, 42: 57-61.

[20] Sheen J. Amendment of cavity perturbation technique for loss tangentmeasurement at microwave frequencies[J]. Journal of Applied Physics, 2007, 014102.

[21] Xu Feng, Dong Bo, Hu Xiaofang, et al. Discussion on magnetic-induced polarization Ampere’s force by in situ observing the special particle growth of alumina during microwave sintering [J]. Ceramics International, 2016, 42(7): 8296-8302.

[22] Tripathi M, Sahu J N, Ganesan P, et al. Effect of temperature on dielectric properties and penetration depth of oil palm shell(OPS) and OPS char synthesized by microwave pyrolysis of OPS[J]. Fuel, 2015, 153: 257-266.

[23] Peng Jinhui,Yang Xianwan. New applications of microwave power[M].Kunming: Yunnan Science and Technology Press,1997.(in Chinese)

[24] Zhang Libo, Ma Aiyuan, Liu Chenhui, Dielectric properties and temperature increase characteristics of zinc oxide dust form fuming furnace [J].Transactions of Nonferrous Metals Society of China, 2014, 24(12): 4004-4011.

[25] Pozar D M. Microwave engineering [M]. Hoboken: John Wiley, 2012.

[26] Han Rui, Li Wei, Pan Weiwei, et al.1D magnetic materials of Fe3O4 and Fe with high performance of microwave absorption fabricated by electrospinning method[J]. Scientific reports, 2014: 7493.

[27] Gao Enyu, Bilén S G, Yang Shuxing. Analysis and numerical modeling of a 20 W microwave electrothermal thruster[J].Journal of Beijing Institute of Technology, 2010, 19(3): 324-330.

[28] Chen Xiaoyu. Researches on preparing molybdenum trioxide by the oxidation boasting by microwave[D]. Kunming: Kunming University of Science and Technology,2015, 36-37.(in Chinese)

[29] Siciliano T, Tepore A, Filippo E. Characteristics of molybdenum trioxide nanobelts prepared by thermal evaporation technique [J].Materials Chemistry and Physics, 2009, 114: 687-691.

Yonglin Jiang,Bingguo Liu,Jinhui Peng,Libo Zhang
《Journal of Beijing Institute of Technology》2018年第1期文献

服务严谨可靠 7×14小时在线支持 支持宝特邀商家 不满意退款

本站非杂志社官网,上千家国家级期刊、省级期刊、北大核心、南大核心、专业的职称论文发表网站。
职称论文发表、杂志论文发表、期刊征稿、期刊投稿,论文发表指导正规机构。是您首选最可靠,最快速的期刊论文发表网站。
免责声明:本网站部分资源、信息来源于网络,完全免费共享,仅供学习和研究使用,版权和著作权归原作者所有
如有不愿意被转载的情况,请通知我们删除已转载的信息 粤ICP备2023046998号