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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - THz Properties of Fe and Ti Oxides Nanoparticles Obtained by Pulsed Laser Ablation
摘要： We present Dielectric properties of Fe and Ti oxides nanoparticles (NPs) measured by THz-TDS. The NPs were obtained via ns pulsed laser ablation (PLA) of the metals in air and water and were annealed at different temperatures. In the paper, we exhibit the dependence of absorption spectra on NPs structure: from magnetite to hematite for Fe, and from anatase to rutile for Ti. The prospects for their use as materials for the THz photonics are discussed.
关键词： THz-TDS,Fe and Ti oxides nanoparticles,THz photonics,dielectric properties,pulsed laser ablation
更新于2025-09-12 10:27:22
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Study on Detecting Dielectric Properties of Typical Electrical Insulation Materials by Terahertz Wave Spectroscopy
摘要： The dielectric properties of the electrical insulation materials is of great importance to the safe operation of the power system. As a promising technique in the field of material testing and with the very adaptive physical modeling of wave transmission process, terahertz wave was used to measure the dielectric properties of five commonly used insulation materials by two methods in this paper. When excluding the echo pulse from the reference signal and the sample signal, a better signal-noise ratio and a wider effective frequency band of spectrums can be obtained. Alternatively, the dielectric properties can also be achieved by separating the main pulse and echo pulse from the sample signal. The latter method makes the sampling of reference signal unnecessary. Furthermore, the dielectric properties of materials were also measured on a relative lower frequency band (1Hz-1MHz) by the broadband dielectric spectrometer. Compared with a relatively lower frequency band, due to the polarization, the dielectric constant of the tested insulation materials was lower on the terahertz band while the dielectric loss tangent was generally higher except the epoxy resin.
关键词： Dielectric properties,Terahertz wave,Insulation materials,Broadband dielectric spectrometer
更新于2025-09-11 14:15:04
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Facile preparation and properties of polyvinylidene fluoride dielectric nanocomposites <i>via</i> phase morphology control and incorporation of multiwalled carbon nanotubes conductive fillers
摘要： A novel PVDF dielectric nanocomposite was achieved by controlling phase morphology and incorporating conductive ?llers simultaneously, and the mechanical, thermal, dielectric properties of the resultant dielectric nanocomposites were investigated. Mechanical analysis showed that incorporation of modi?ed MWCNTs (MWCNTs-COOH) in the PVDF nanocomposites resulted in signi?cant improvements on the tensile strength (Ts) and elasticity modulus (Em). When the ?ller content was 12 wt%, the Ts of MWCNTs-COOH/PVDF could reach 64.6 MPa. XRD test showed that the addition of MWCNTs-COOH and MWCNTs promoted the formation of β-phase of PVDF. DMA analysis showed that the glass-transition temperature of the PVDF nanocomposites slightly increases on loading of original MWCNTs and this effect was more pronounced on loading MWCNTs-COOH. The dielectric property analysis showed that the original MWCNTs were more likely to form local conductive networks in the PVDF matrix, promoting the electron displacement polarization, and improving the dielectric constant. When the contents of MWCNTs was 12 wt%, the percolation threshold was obtained and the dielectric constant (ε0) reached 286, which was 36 times of pure PVDF. Our work provides a simple way to fabricate polymer blends with excellent dielectric performances, good mechanical properties as well as good processing capability but low cost.
关键词： polyvinylidene ?uoride (PVDF),thermal performance,dielectric properties,multi-walled carbon nanotubes (MWCNTs),mechanical properties
更新于2025-09-11 14:15:04
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Structure, crystallization, and dielectric properties of the Al <sub/>2</sub> O <sub/>3</sub> filled CaO–B <sub/>2</sub> O <sub/>3</sub> –SiO <sub/>2</sub> –Al <sub/>2</sub> O <sub/>3</sub> glass composites for LTCC applications
摘要： The glass structures and crystallization behaviors of CaO–B2O3–SiO2 (C1) and CaO–B2O3–SiO2–Al2O3 (C1A03) glasses are investigated. The addition of Al3+ into CaO–B2O3–SiO2 glass acts as a glass former and bonds with the silicon tetrahedron with non-bridged oxygen to form Si–O–Al–O–Si, which increases the Q4 structural unit. The relative dielectric constants for C1 and C1A03 glass systems were all about 7.8–8.4. Compared to the C1 glass, the size and amount of pores decreased for the C1A03, leading to a higher dielectric constant. The C1A03 glass system exhibits better Qxf value than the C1 system due to the decrease in the size and amount of pores. The Qxf value roughly decreased with increasing glass addition for the densified samples. The C1A03 glasses with 50 wt% alumina exhibited the highest dielectric constant (8.4) and Qxf value (3150 GHz) due the maximum densification and highest amount of anorthite were obtained.
关键词： crystallization,dielectric properties,CaO–B2O3–SiO2–Al2O3 glass,LTCC,Al2O3
更新于2025-09-11 14:15:04
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Precipitation of Silver Nanoparticles in Borate Glasses by 1064?nm Nd:YAG Nanosecond Laser Pulses: Characterization and Dielectric Studies
摘要： This work aims to present a modern process to synthesis nanoparticles in a glassy matrix. Borate glasses doped by silver nitrate (AgNO3) via the melt annealing technique were irradiated by a (1064 nm wavelength) Nd:YAG (Neodymium–doped Yttrium Aluminum Garnet) laser to yeild precipitation of silver nanoparticles (AgNPs) in borate glasses. The characterization of the irradiated glasses was investigated using ultraviolet/visible (UV/Vis.), x-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM), ?eld emission-scanning electron microscopy (FE-SEM), and dielectric properties. XRD patterns depict the presence of sharp diffraction peaks at 111 and 200 planes that can be attributed to the precipitated AgNPs in the borate glass sample after laser irradiation. A signi?cant change in color was observed within the borate glass after laser irradiation, which was attributed to the appearance of surface plasmon resonance and con?rmed the presence of AgNPs in the borate glass. The morphological properties and the distribution of the observed AgNPs inside the sample were performed via HR-TEM and FE-SEM. The behavior of dielectric constant and dielectric loss progressively decreased as the frequency increased. The values of AC conductivity increased as the temperature of the borate glass matrix increased.
关键词： Borate,UV/Vis.,Nd:YAG,dielectric properties,AgNPs,XRD,FE-SEM,HR-TEM
更新于2025-09-11 14:15:04
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Effect of CdSeS/ZnS quantum dot concentration on the electro-optical and dielectric properties of polymer stabilized liquid crystal
摘要： Our research paper has been discussed electro-optical and dielectric characterization of polymer stabilized liquid crystal (PSLC) and its doped form with different concentration of CdSeS/ZnS quantum dot (QD). PSLC composite was prepared using a nematic liquid crystal (E63) and Poly(methyl methacrylate) (PMMA) polymer. In order to improve physical properties, composites were dispersed with different concentration of CdSeS/ZnS QD. The electro-optical and dielectric properties of the composites were investigated depending on the frequency and voltage. Considerable physical parameters such as threshold voltage, dielectric anisotropy, relaxation frequency and response time were obtained from the experimental data. The results show that QD contribution and polymer networks change the electro-optical and dielectric properties of PSLC and these can become a focus of interest for new applications of PSLC composites in the future.
关键词： polymer network,quantum dot,dielectric properties,Polymer stabilized liquid crystal
更新于2025-09-11 14:15:04
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Preparation and characterization of pyrochlore-free 0.655Pb(Mg <sub/>1/3</sub> Nb <sub/>2/3</sub> )O <sub/>3</sub> -0.345PbTiO <sub/>3</sub> piezoelectric ceramics by tape-casting process
摘要： Piezoelectric ceramics of the perovskite solid solution 0.655Pb(Mg1/3Nb2/3)O3-0.345PbTiO3 (0.655PMN-0.345PT) were synthesized by tape-casting process. Highly dense ceramics lacking parasitic pyrochlore phases were fabricated by using precursor method and adding moderate PbO. The influences from sintering temperature on the physical and electrical properties of the 0.655PMN-0.345PT ceramics were initially investigated by phase and microstructure analyses. High piezoelectric, dielectric and ferroelectric properties of d33?700 pC/N, kp?0.605, er?4770, tand ? 0.016, Pr?30.68 lC/cm2 were obtained for the specimens sintered at 1200 (cid:2)C. Compared with the traditional solid-state sintering method, the performance of ceramics formed by tape-casting achieved an improvement.
关键词： tape-casting,PMN-PT,ferroelectric properties,dielectric properties,piezoelectric properties
更新于2025-09-11 14:12:44
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Improving the electroactive phase, thermal and dielectric properties of PVDF/graphene oxide composites by using methyl methacrylate-co-glycidyl methacrylate copolymers as compatibilizer
摘要： In this work, graphene oxide sheets (GO) filled polyvinylidene fluoride (PVDF) nanodielectric composites with methyl methacrylate-co-glycidyl methacrylate copolymer (MG) as compatibilizer were fabricated by solution blend process. MG improved the dispersion of GO and enhanced the interface strength between GO and PVDF matrix. The strong dipolar interaction between MG on the surface of GO and PVDF resulted in the crystal transformation of PVDF from a-phase to b/c-phase and nearly 81% b/c-phase PVDF formed for PVDF/MG@GO7.0 composite. The thermal stability, mechanical property, melting and crystallization behaviors of PVDF/MG@GO composites were improved obviously due to the enhanced interface strength between GO and PVDF matrix with the aid of MG. MG copolymers not only contributed to the uniform dispersion of GO in PVDF, but also prevented the direct connection of GO and effectively inhibited the occurrence of leakage current in composites. Therefore, the dielectric properties of PVDF/MG@GO composites were also enhanced significantly with the addition of MG compared with the PVDF/GO composites, which supported the fact that the dielectric properties of resulted composites could be tailored by using MG copolymer as compatibilizer.
关键词： thermal properties,PVDF,graphene oxide,compatibilizer,dielectric properties
更新于2025-09-10 09:29:36
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Enhanced dielectric, electromechanical and hydrophobic behaviors of core-shell AgNWs@SiO2/PDMS composites
摘要： This paper reports a feasible method to prepare polymeric nanocomposites with enhanced dielectric, electromechanical and hydrophobic performance by introducing the core-shell AgNWs@SiO2 filler into polydimethylsiloxane (PDMS). The homogenous core-shell AgNWs@SiO2 was firstly synthesized through a two-step sol-gel process. The thicknesses of AgNWs and SiO2 coating layer are approximately 70 nm and 20 nm, respectively. The dielectric constant is improved effectively due to enhanced interfacial polarization, while extremely low dielectric loss and conductivity are achieved by introducing the insulating SiO2 interlayer to moderate the internal surface area of core-shell nanowires and restrict the electron transfer between Ag nanowires. Typically, the PDMS nanocomposites with 20 wt% AgNWs@SiO2 have a dielectric constant of 6.7, nearly 2.7 times larger than that of pure PDMS, and remains a quite low loss of 0.02 at 1 kHz. Meanwhile, nanocomposites also show improved electromechanical and hydrophoic properties. Nanocomposites with 10 wt% AgNWs@SiO2 exhibit the highest electromechanical sensitivity (β=9.04), about 12.6 times higher than that of pure PDMS at 1 kHz. The static contact angle of nanocomposties with 20 wt% AgNWs@SiO2 reaches 129°. All the improved performances show great potential application for dielectric elastomer material and electrowetting devices.
关键词： Dielectric properties,Electromechanical properties,Core-shell structure,Interfacial polarization
更新于2025-09-10 09:29:36
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Investigations on synthesis, growth and physicochemical properties of semi-organic nonlinear optical crystal: l-arginine sodium nitrate
摘要： Single crystals of l-arginine sodium nitrate semiorganic nonlinear optical crystal were grown by slow evaporation process at room temperature. The single crystal X-ray diffraction study confirms that the unit cell parameters of the grown l-arginine sodium nitrate crystal. Fourier transform infrared spectrum analysis was used to identify the functional groups of the grown crystal. The thermal stability of the l-arginine sodium nitrate was determined using thermogravimetric analysis and differential thermal analysis. The linear optical property of LARSN crystal has been studied using Ultraviolet–visible spectroscopy studies in the wavelength range 200–800 nm. The relative second harmonic efficiency of the l-arginine sodium nitrate compound is found to be 0.49 times that of Potassium Di-hydrogen phosphate. The mechanical property of the grown crystals was determined by Vicker’s micro hardness test and it proved the hard nature of the grown crystal. Dielectric study reveals that both dielectric constant and dielectric loss decreases with increase in frequency.
关键词： thermal analysis,l-arginine sodium nitrate,slow evaporation process,FTIR,nonlinear optical crystal,microhardness,dielectric properties,X-ray diffraction,SHG efficiency,UV–Vis spectroscopy
更新于2025-09-10 09:29:36