Effect of temperature on dielectric property and microwave heating behavior of low grade Panzhihua ilmenite ore

The permittivity of low grade Panzhuhua ilmenite ore at 2.45 GHz in the temperatures from 20 ℃ up to 100 ℃ was measured using the technology of open-ended coaxial sensor combined with theoretical computation. The results show that both the real （ε′） and imaginary （ε′） part of complex permittivity （ε′-jε′） of the ilmenite significantly increase with temperature. The loss tangent （tanδ） is a quadratic function of temperature, and the penetration depth of ilmenite decreases with temperature increase from 20 ℃to 100 ℃ The increase of the sample temperature under microwave radiation displays a nonlinear relationship between the temperature （T） and microwave heating time （t）. The positive feedback interaction between complex permittivity and sample temperature amplifies the interaction between ilmenite and the microwave radiation. The optimum dimensions for uniform heat deposition vary from 10 cm to 5 cm （about two power penetration depths） in a sample being irradiated from both sides in a 2.45 GHz microwave field when temperature increases from room temperature to 100 ℃

Synthesis and Characterization of SiCOF/a-C∶F Double-Layer Films with Low Dielectric Constant for Copper Interconnects~*

A novel double-layer film of SiCOF/a-C ： F with a low dielectric constant is deposited using a PECVD system. The chemical structure of the film is characterized with Fourier transform infrared spectroscopy （FTIR）. The measurements of the film refractive index reveal that the optical frequency dielectric constant （n^2） of the film is almost constant as a function of air exposure time, however, with increasing annealing temperature, the value of n^2 for the film decreases. Possible mechanisms are discussed in detail. The analysis of SIMS profiles for the metal-insulator-silicon structures reveal that in the Al/a-C ： F/Si structure,the annealing causes a more rapid diffusion of F in AI in comparison with C, but there is no obvious difference in Si. In addition, no recognizable verge exists between SiCOF and a-C ： F films,and the SiCOF film acts as a barrier against the diffusion of carbon into the aluminum layer.

The Impact of the Inclusion of MgO Nano-Fillers in a Polyethylene Matrix on Dielectric Strength and Resistance to Partial Discharges

One commonly used strategy to enhance polymers specific properties such as the resistance to partial discharges erosion is the incorporation into the polymeric matrix of inorganic micro or nanoparticles. This study focused on the dielectric properties of Low-Density Polyethylene (LDPE) filled with nano-sized Magnesium Oxide (MgO) particles compounded by thermo-mechanical process and one of the purposes was to establish appropriate processing parameters in order to reach the desired dielectric properties. LDPE was used as a matrix and was reinforced by MgO particles having a nominal average size of 30 nm. The MgO nanoparticles were treated with a silane coupling agent (3-Glycidyloxypropyl Trimethoxysilane). The samples were initially prepared in a melt-mixing chamber with a MgO content of 1% wt. These pre-mixed samples were further treated by the means of thermo-mechanical mixing in a conical co-rotating twin-screw extruder in order to improve the dispersion and distribution of the MgO particles. In this report, both lifetime under a PD activity and AC dielectric strength of pure and nano-filled LDPE samples have been measured and compared. Nano-filled LDPE samples were found to exhibit an improve lifetime, without any detrimental impact on their short-term dielectric strength. This suggests that nano-filled LDPE may be for electric applications for which the dielectric materials may be exposed to partial discharge activities. This is significant result for the use of MgO-reinforced PE as an insulating material for HV cables since the resistance to PD is closely related to treeing resistance which is the main electrical degradation mechanism that leads to failure for shielded extruded power cables.

Dielectric Permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies

Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate capacitors.In the present investigation biopolyol was synthesized from Latvia-grown rapeseeds’oil by the transesterification method with triethanolamine,in an environmentally friendly process,without emission of harmful substances,at temperatures 175℃±5℃.Rigid,closed-cell rapeseed oil polyol polyurethane biofoams and petrochemical foams were made ensuring content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.Dielectric permittivity of the polyurethane foams and the underlying monolithic petrochemical-origin polyurethane and biopolyurethane was measured with a non-destructive dielectric spectrometer equipped with a capacitive sensor of one-side access type at 16 discrete frequencies distributed geometrically over the band 10 Hz,…,330 kHz.Permittivity value of the gaseous phase in the closed-cells was estimated to beεg≈1.001 that corresponds to the values,characteristic for the most of gases.Dielectric permittivity of petrochemical polyurethane foams and the mentioned biofoams was compared with permittivity of polyurethane foams from industrial producers Sika JSC and General Plastics Manufacturing Co.Polyurethane foams of the developed formulation exhibit competitive,low dielectric permittivity,not exceeding that of the foams from industrial producers:petrochemical foams up to 550 kg/m^(3) and the mentioned biofoams,comprising the renewable rapeseed oil polyol,up to densities 230–250 kg/m^(3).Considering petrochemical-origin polyurethane foams as a heterogeneous media“Polymer—gaseous phase”,the applicability of the rule of mixture and Maxwell–Garnett equation to model mathematically the dependence of effective dielectric permittivity on the volume fraction of phases was showed.

Low Frequency Dispersion Mechanism of Dielectric Response for Oil-paper Insulation Diagnosis

Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low fre- quencies, especially at ultra-low frequencies under conditions of different moisture concentrations and temperatures, which is recognized as the low frequency dispersion (LFD). In order to explain this dispersion, a new mechanism of dielectric response of LFD of oil-paper insula- tion is proposed. A simplified one-dimensional mathematical model of concentration polarization carrier caused by slow migration is developed and solved, which indicates that ion mobility is closely related to the size of gap and the adsorption capacity of cellulose molecu- lar chains to ions. A stochastic statistical model of the carrier mobility induced LFD is also developed. Moreover, actual tests under 50 °C and 2% moisture content were put forward, as well as simulations with according current waveforms. The simulation results agreed well with the experimental data in that concentration polarization of carriers caused by slow migration is the probable cause of low frequency dispersion of dielectric response for oil-paper insulation diagnosis.

Structure and properties of low-dielectric-constant poly(acetoxystyrene-co-octavinyl-polyhedral oligomeric silsesquioxane) hybrid nanocomposite

Low-dielectric-constant poly(acetoxystyrenezhi-co-octavinyl-polyhedral oligomeric silsesquioxane)(PAS-POSS) organicinorganic hybrid nanocomposite was successfully synthesized via one-step free radical polymerization and characterized by FTIR,high-resolution ~1H NMR,^(29)Si NMR,DSC,TGA,AFM,spectroscopic elhpsometry and dielectric constants measurements. The results show T_g and T_(dec) were elevated dramatically due to the incorporation of inorganic POSS cores.Spectroscopic ellipsometry and dielectric consta...

Destruction of Gaseous Styrene with a Low-Temperature Plasma Induced by a Tubular Multilayer Dielectric Barrier Discharge

The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge（DBD）.The results indicate that the applied voltage,gas flow rate,inlet styrene concentration and reactor configuration play important roles in styrene removal efficiency （ηstyrene） and energy yield（EY）.Values of ηstyrene and EY reached 96%and 15567 mg/kWh when the applied voltage,gas flow rate,inlet styrene concentration and layers of quartz tubes were set at 10.8 kV,5.0 m/s,229 mg/m^3 and 5 layers,respectively.A qualitative analysis of the byproducts and a detailed discussion of the reaction mechanism are also presented.The results could facilitate industrial applications of the new DBD reactor for waste gas treatment.

A novel partial silicon on insulator high voltage LDMOS with low-k dielectric buried layer

A novel partial silicon-on-insulator （PSOI） high voltage device with a low-k （relative permittivity） dielectric buried layer （LK PSOI） and its breakdown mechanism are presented and investigated by MEDICI. At a low k value the electric field strength in the dielectric buried layer （EI） is enhanced and a Si window makes the substrate share the vertical drop, resulting in a high vertical breakdown voltage; in the lateral direction, a high electric field peak is introduced at the Si window, which modulates the electric field distribution in the SOI layer; consequently, a high breakdown voltage （BV） is obtained. The values of EI and BV of LK PSOI with ki = 2 on a 2μm thick SOI layer over 1μm thick buried layer are enhanced by 74% and 19%, respectively, compared with those of the conventional PSOI. Furthermore, the Si window also alleviates the self-heating effect.

Synthesis of Organic Modified SiC_w/PVDF Composite Membrane and Its Dielectric Properties under Low Temperature

Cetyltrimethylammonium bromide(CTAB) was incorporated into silicon carbide whiskers(SiCw) to improve their hydrophobicity. The solution casting method was employed to develop composite membranes of polyvinylidene fluoride(CTAB-SiCw/PVDF) with different feed ratios. FT-IR spectroscopic studies proved that CTAB was successfully incorporated into the SiCw. SiCw phase structure was maintained after modification by CTAB according to XRD results. SEM studies indicated that the surface became smoother with CTAB dispersal in the PVDF membrane. The dielectric properties of the composite membranes containing various amounts of CTAB-SiCw were measured at low temperature. It was found that the dielectric constant of the composite membranes with 13.0 wt% whiskers reached a maximum value of 25 at low frequency, and decreased to nine at high frequency(from 500 Hz to 1 MHz) at 0 ℃. The dielectric loss of each composite membrane increased with increasing temperature and reached a maximum value. The value shifted with corresponding frequency increases. In addition, the dielectric loss reached a maximum value of 0.2 when 16.7 wt% of CTAB-SiCw was fed at each frequency(from-30 ℃ to 10 ℃). At room temperature, the dielectric constant could be maintained at 42 and the loss factor decreased to 0.8 at 100 Hz when 13.0 wt% of CTABSiCw was incorporated. Additionally, TGA experiments indicated that the decomposition temperature of a PVDF membrane was increased by 10 ℃ and its heat resistance was improved by adding 13.0 wt% of CTAB-SiCw. This PVDF composite membrane has potential for use as an insulator and capacitor.

Low-Temperature Sintering and Microwave DielectricProperties of Ba_2Ti_3Nb_4O_(18) Ceramics

The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 （ 〈3.5 wt%） remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.Ba2Ti3Nb4O18 ceramics sintered at 1 050 ℃ for 4 h with the addition of 1.0 wt% CuO and 3.5 wt% H3BO3 exhibited good microwave dielectric properties：er=33.74,Q？f=13 812 GHz,and tf=-5.35 ppm/°C at about 5.0 GHz.

Synthesis and applications of low dielectric polyimide

With the advent of the 5 G era,advanced packaging applications such as wafer-level fan-out packaging have emerged thanks to efforts to reduce signal loss and increase signal transmission rates.As one of the key materials employed in telecommunication devices,the interlayer dielectric material directly affects signal transmission and device reliability.Among them,polyimide(PI)has become an important interlayer dielectric material because of its excellent comprehensive properties.However,in order to meet the needs high-frequency and high-speed circuits for 5 G networks,it will be necessary to further reduce the dielectric constant and dielectric loss of PI.PI is widely used as a flexible dielectric material due to its excellent electrical insulation properties(dielectric constant≈3.0-4.0,dielectric loss≈0.02),mechanical properties,and thermal resistance.However,further reduction in the dielectric constant will be needed in order for PI-based materials to better meet the current high integration development needs of the microelectronics industry.This article starts from strategies to prepare low dielectric PI that have been developed in the last decade,based on a more systematic and inductive analysis,and prospects the development potential of low dielectric PI.

Design of a low-sidelobe-level and wideband dielectric resonator antenna array for 60 GHz millimeter wave communication

A low-sidelobe-level( SLL) and wideband linear dielectric resonator antenna( DRA) array is proposed for 60 GHz millimeter wave communication. The array consists of 10 wideband DRAs which work at 60 GHz and it is fed by a Chebyshev feeding network to get a low SLL. To avoid the influence from the feeding network,a U-shaped substrate and a conformal ground are used,which can separate the DRA array and the feeding network. The parameter analysis and simulated results are presented.

Alumina/Polyimide Composite Porous Nanosolid:Dielectric Characteristics and Compressive Strength

Al2O3 porous nanosolid was prepared via solvothermal hot-press（SHP） method.The dielectric constant of Al2O3 porous nanosolid is as low as 2.34,while its compressive strength is very poor.In order to improve the compressive strength and maitain low dielectric constant,polyimide was introduced to prepare Al2O3 /polyimide composite porous nanosolid.Compared to Al2O3 porous nanosolid,Al2O3 /polyimide composite porous nanosolid possesses much higher compressive strength,which reaches its saturation value when the mass loading of polyimide is 7.75%.In addition,the in situ Fourier transformation infrared（FTIR） monitoring result reveals that Al2O3 /polyimide composite porous nanosolid is stable up to 400 °C.

The Experimental Investigations of Dielectric Barrier Discharge and Pulse Corona Discharge in Air Cleaning

The dielectric barrier discharge (DBD) and pulse corona discharge(PCD) plasma generator was used to remove NH3, H2S, C7H8 etc. from atmosphere. The principle and characteristic of the two ways was discussed in the article. The test shows the result of PCD is better than that of DBD.

Study on BaO-Sm_2O_3-TiO_2 Microwave Dielectric Ceramics Doped with Bismuth and Zinc

BaO-Sm2O3-TiO2 microwave dielectric ceramics doped with Bi and Zn was studied. The experiment was based on BST microwave dielectric ceramics doped with Bi2O3, which is shown by Ba4(Sm1-yBiy )28/3Ti18O54. When y =0.15, ZnO was added and the effects of ZnO on this system were studied. The result shows that the dielectric characteristics of BST microwave dielectric ceramics are the most excellent when the content of ZnO is 3% , and the optimal sintering temperature is 1200℃.

Experimental Study on Inactivation of Bacterial Endotoxin by Using Dielectric Barrier Discharge

The low-temperature plasma （LTP） generated by dielectric barrier discharge （DBD） was used to sterilize the E.coli endotoxin, which is usually difficult to kill by traditional methods. Three different concentrations of bacterial endotoxin （1 EU/mL, 0.5 EU/mL and 0.25 EU/mL） were treated by LTP for different time （20 s, 40 s and 60 s）. Tachypleus amebocyte lysate （TAL） method was employed to detect the concentration variation of bacterial endotoxin before and af- ter the plasma treatment, and endotoxic shock mice model was used to evaluate the inactivation effects of LTP on endotoxin for further study. Experimental results demonstrated that, DBD plasma can inactivate the bacterial endotoxin quickly and effectively, and when the LTP treatment time was increased, the concentrations of bacterial endotoxin decreased gradually （after 60 s plasma treatment, its inactivation effect was beyond the Chinese pharmacopoeia standard）, and the average survival time of mice gradually extended. The possible inactivation mechanisms are proposed to be related to reactive oxygen species （ROSs）.

Temperature-frequency dependence and mechanism of dielectric properties for γ-Y_2Si_2O_7

This paper reports that single-phase γ-Y2Si2O7 is prepared via a sufficient blending and cold-pressed sintering technique from Y2O3 powder and SiO2 nanopowder. It studies the dielectric properties of γ-Y2Si2O7 as a function of the temperature and frequency. The γ-Y2Si2O7 exhibits low dielectric loss and non-Debye relaxation behaviour from 25 to 1400℃ in the range of 7.3 18 GHz. The mechanism for polarization relaxation of the as-prepared γ-Y2Si2O7 differing from that of SiO2 is explained. Such particular dielectric properties could potentially make specific attraction for extensive practical applications.

A Hybrid Dielectric Ink Consisting of up to 50 wt% of TiO2 Nanoparticles in Polyvinyl Alcohol （PVA）

PVA （Polyvinyl Alcohol） is a water soluble organic dielectric, easily solution processed to fabricate films by spin coating, dip coating or inkjet printing. It has been used as a dielectric layer in OTFTs （organic thin film transistors）, and its dielectric constant is around 3.5-10. For OTFTs operating at lower voltage, it is desirable to increase the dielectric constant. Here, we report a technique to incorporate upto 50 wt% of TiO2 nanoparticles （15-25 nm） in PVA to increase its dielectric constant. Rutile phase of TiO2 is used, because of its higher dielectric constant （e = 114） compared to anatase phase （E = 31）. We have made inks containing 10 and 50 wt% （of PVA） TiO2 nanoparticles, which is stable upto six months. PVA-TiO2 dispersions and PVA （without TiO2） were spin coated on indium tin oxide coated polyethylene terephthalate substrate. Film structure was studied using SEM （scanning electron microscopy）. Absorption study of the films confirms presence of TiO2 nanoparticles. M-I-M capacitors were fabricated by thermally evaporating aluminium on top of the dielectric films. We observed enhancement in dielectric constant by a factor of 2 for PVA containing 50 wt% TiO2 in comparison to PVA＇s dielectric constant. There is no concomitant increase in the leakage current.

Effects of V₂O₅Addition on Microwave Dielectric Properties of Li₂ZnTi₃O₈Ceramics for LTCC Applications

The sintering temperature of Li2ZnTi3O8 ceramics is still high for LTCC-based applications. In this work, V2O5 was doped as the sintering aid. The sintered density, phase composition, grain size, as well as microwave dielectric properties of Li2ZnTi3O8 ceramics with the addition of V2O5 were investigated. Based on our research, V2O5 doping effectively promoted the densification of Li2ZnTi3O8 ceramics at about 900°C, without affecting the main crystal phase of the ceramics. Li2ZnTi3O8 ceramics with 0.5 wt% V2O5 doping (sintered at 900°C) exhibited the best microwave dielectric properties (Qf =?22,400 GHz at about 6 GHz, εr = 25.5, and τf = -10.8 ppm/°C). The V2O5-doped Li2ZnTi3O8 ceramics were well cofired with Ag inner paste without cracks and diffusion, indicating its significant potential for LTCC applications.

6LoWPAN中基于Mesh-under的备用缓存机制

在基于Mesh-under的IPv6低功耗无线个域网(IPv6over low-power wireless personal area networks,6LoWPAN)中,针对传输路径上中间节点重传缓存溢出导致重传数据分片丢失,造成网络性能下降等问题,提出一种基于Mesh-under的备用缓存机制。本文所提机制根据传输路径上各节点重传缓存使用情况及数据分片剩余跳数等信息,设置动态重传缓存门限,并为超过该门限的节点从其邻居节点中挑选合适的备用缓存节点,从而完成数据分片的缓存与重传过程,达到均衡使用各节点重传缓存的目的。结果表明,所提机制能够有效避免重传缓存溢出,减小网络能耗,同时进一步提高目的端重组成功率。