首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 296 毫秒
1.
Poly(vinyl chloride) (PVC) nanocomposites with different contents of copper alumina (Cu-Al2O3) nanoparticles were prepared by the solution casting method. The effects of the nanoparticles on structural, thermal, electrical, contact angle and mechanical properties were thoroughly examined. The presence of Cu-Al2O3 in the macromolecular chain was confirmed through Fourier transform infrared (FTIR) spectroscopy. The X-ray diffraction (XRD) analysis of PVC nanocomposites showed the systematic arrangement of Cu-Al2O3 nanoparticles within the polymer, which indicated the higher crystallinity of the nanocomposites. The surface morphology of PVC was changed into hemispherical shaped particles by the inclusion of nanofiller was analyzed from SEM images. The glass transition temperature of the nanocomposites obtained from differential scanning calorimetry (DSC) was found to be increased with an increase in loading of nanoparticles in the polymer. The AC conductivity and dielectric studies revealed that the inclusion of nanofiller increases the electrical properties of the material and the composite with 7 wt.% sample showed the maximum conductivity and dielectric constant. The mechanical properties such as modulus, tensile strength, hardness, and impact properties of the PVC nanocomposites were significantly enhanced by the reinforcement of nanoparticles into the PVC matrix. The reinforcing mechanism behind the increase in tensile strength with the addition of nanoparticles was correlated with different theoretical models. The highest mechanical and electrical properties were observed for 7 wt.% Cu-Al2O3 loaded nanocomposite. Contact angle measurements of PVC with various loadings of Cu-Al2O3 nanofillers demonstrated that the nanoparticle attachment increased the hydrophobicity of the polymer matrix.  相似文献   

2.
The distribution of a filler in a polymeric matrix is one of the most important factors affecting the physical properties of the final product. For this reason, the main objective of this study was to introduce aluminum oxide (Al2O3), acting as a dispersing agent, to reduce the filler–filler interaction and enhance the filler–polymer interaction. To achieve this aim, the electrical behavior of a styrenated polyester resin filled with different amounts of high‐abrasion furnace black in the presence of 5% Al2O3 was studied in the vicinity of the percolation threshold to evaluate the effect of the addition of Al2O3 in an attempt to reduce the filler–filler interaction through the polyester matrix. At a certain concentration of carbon black, an abrupt increase was noticed through electrical conductivity, permittivity, and dielectric loss investigations. With this increase, the tendency of conductive chain formation increased through the aggregation of a carbon black particle network. The addition of 5% Al2O3 improved the filler distribution by lowering the aggregate size and consequently enhanced the formation of the network. From the Arrhenius temperature dependence of the electrical conductivity, the activation energy and pre‐exponential factor were obtained, and they confirmed the validity of the compensation law for the semiconducting composite systems. The composites were also analyzed by thermogravimetric analysis. Al2O3 improved the thermal stability of the composites in comparison with that of a sample free of Al2O3. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

3.
Fully dense and magnetically controllable glass ceramics was successfully synthesized by method of hot pressing using CaO-Al2O3-SiO2-Na2O glass powder and Fe3O4 powder as raw materials. The influences of sintering temperature and time, content and particle size of Fe3O4, as well as particle size of glass powder on the densification and magnetic properties of samples were investigated. It was found that the saturation magnetization gradually increased with increasing magnetite content. In addition, the samples containing smaller size magnetite particles had a higher coercivity. However, for samples using smaller size glass powder, magnetite particles could partially dissolve into the glass matrix, which led to the decrease of saturation magnetization and the increase of coercivity. It was also concluded that the precipitation of crystalline phase from smaller size glass powder caused the decrease of degree of densification, and after decreasing the sintering temperature, the degree of densification of product was enhanced.  相似文献   

4.
Li2O–ZrO2–SiO2–Al2O3 (LZSA) glass ceramic systems are usually obtained from powder technology to obtain materials with a low thermal expansion coefficient (CTE). However, in these cases, there is a high residual porosity. An alternative to reduce the porosity involves the production of monoliths. Nevertheless, there is still a lack of crystallisation kinetics and the final properties of glass ceramic monoliths are affected such as electrical properties. This study aims to evaluate the electrical behaviour as function of the crystalline layer thickness formed on the monolith surface of a 17.7Li2O·5.2ZrO2·68.1SiO2·9.0Al2O3 (molar basis) glass ceramic LZSA composition. Monoliths thermally treated at 750, 800, and 850 °C were chosen to evaluate based on the range of the crystalline layer growth. Electrochemical impedance spectroscopy was used for the electrical characterisation of LZSA glass and the glass ceramics. The resistivity increased with increasing thermal treatment temperature due to the formation of lithium-based crystalline phases. The electrical conductivity at 25 °C of the glass ceramic thermally treated at 850 °C decreased to 1.4 × 10?13 S cm?1 from 8.7 × 10?11 S cm?1 for LZSA glass. Based on the electrical behaviour, monoliths thermally treated at 850 °C can be considered potential for dielectric industrial applications.  相似文献   

5.
In this study, phosphate glasses embedded with Fe2O3 quantum dots were prepared via a conventional melt quenching technology with further heat treatment. The effect of Fe2O3 content on the structural, optical and magneto-optical properties was investigated. The results showed that the addition of Fe2O3 had no obvious influence on the structure units that built up the host glass and the amorphous nature of glass. In the glass matrix, the existence of Fe2O3 quantum dots was confirmed by high resolution transmission electron microscope. Meanwhile, optical study clearly demonstrated a red shift in optical cut-off wavelength resulted from the size quantization effect. The highest Verdet constant (22.33°/T-cm) was measured for the glass containing 1 mol% Fe2O3, which was ~ 7 times higher than that of the glass matrix. As the increment of Fe2O3 contents, a phase evolution of Fe2O3 quantum dots from amorphous phase to γ-Fe2O3 phase was recorded due to the Ostwald Ripening effect. Interestingly, a concentration quenching phenomenon in Verdet constant was observed along with the phase evolution of Fe2O3 quantum dots. When the content of Fe2O3 is up to 2 mol%, the glass exhibited paramagnetism with the Verdet constant of ? 2.833°/T-cm. This finding can provide a new idea for the development of quantum dot embedded magneto-optical glass.  相似文献   

6.
The addition-type liquid silicone rubber (ALSR) co-filled with spheroidal Al2O3 and flaky BN was prepared by the mechanical blending and hot press methods to enhance the thermal, electrical, and mechanical properties for industrial applications. Morphologies of ALSR composites were observed by scanning electron microscopy (SEM). It was found that the interaction and dispersion state of fillers in the ALSR matrix were improved by the introduction of BN sheets. Thermal, electrical, and mechanical performances of the ALSR composites were also investigated in this work. The result indicated that the thermal conductivity of ALSR can reach 0.64 W m−1 K−1 at the loading of 20 wt% Al2O3/20 wt% BN, which is 3.76 times higher than that of pure ALSR. The addition of Al2O3 particles and BN sheets also improve the thermal stability of ALSR composites. Moreover, pure ALSR and ALSR composites showed relatively lower dielectric permittivity (1.9–3.1) and dielectric loss factor (<0.001) at the frequency of 103 Hz. The insulation properties including volume resistivity and breakdown strength were improved by the introduction of flaky BN in the ALSR matrix. The volume resistivity and characteristic breakdown strength E0 are 6.68 × 1015 Ω m and 93 kV/mm, respectively, at the loading of 20 wt% Al2O3/20 wt% BN. In addition, the mechanical characteristics including elongation at break and tensile strength of ALSR composites were also enhanced by co-filled fillers. The combination of these improved performances makes the co-filled ALSR composites attractive in the field of electrical and electronic applications.  相似文献   

7.
Zinc borate glasses with different concentrations of Nb2O5 were prepared and later were heat treated for prolonged times. Prepared samples were characterized by XRD, SEM, DSC, IR and optical transmission spectroscopy techniques. Later, dielectric properties viz., dielectric constant, loss tangent, electric modulii, electrical impedance and a.c. conductivity over wide ranges of frequency and temperature, were investigated as a function of Nb2O5 concentration. Finally, the dielectric breakdown strength was measured in air medium at ambient temperature. The results of characterization techniques viz., XRD, SEM and DSC indicated that multiple crystal grains (with sizes varying from 0.1 to 1 μm) are dispersed in the residual glass phase. The concentration of crystal grains found to increase with increase in Nb2O5 content. The XRD studies have further revealed that the bulk samples are composed of columbite ZnNb2O6 crystal phases. Using generalized gradient approximation (GGA) quantitative information on these crystal phases viz., the lattice parameters, optical band gap and band structure were evaluated. The analysis of results of IR spectral studies have indicated that there is an increasing degree of polymerization of glass network with increase in Nb2O5 content due to the increased connectivity between various structural groups in the glass network. The optical absorption spectra indicated an increase in optical transmittance of the bulk samples with increase in Nb2O5 content. The dielectric parameters are observed to decrease, whereas the dielectric breakdown strength is observed to increase to a large extent due to the crystallization of the glass with the Nb2O5. The increase is attributed to the formation of ZnNb2O6 crystalline phases that contain intertwined ZnO6 and NbO6 structural units. As a whole, zinc borate glasses exhibited a significant increase in the electrical insulating strength due to the crystallization with Nb2O5 as the crystallizing agent. Further, the value of dielectric constant is also found to be the optimal with no dispersion with frequency up to 450 K. Overall, the studied glass‐ceramics meet the necessary physical conditions to be used as insulating layers in the display panels and hence may be considered for such applications.  相似文献   

8.
《Ceramics International》2016,42(10):12064-12073
The band structure and thermoelectric properties of inkjet printed ZnO and ZnFe2O4 thin films have been investigated. The bulk pellets were prepared by a solid-state method and thin films were deposited using an inkjet printing method. Multiple print cycles were required to fabricate homogeneous films and the composition of the thin films can be varied by varying the relative amounts of liquid deposited. It was possible to obtain high thermoelectric properties of ZnO by controlling the ratios of dopant added and the temperature of the heat treatments. XRD analysis showed that the fabricated samples have a wurtzite structure and an additional ZnAl2O4 phase was formed with increasing Al content and sintering temperature. It was found that the band gap of Al doped ZnO becomes smaller with increasing Al content and thus the electrical conductivity of Alx doped ZnO (x=0.04) thin films showed the highest electrical conductivity (114.10 S/cm). The ZnFe2O4 samples were compared against the ZnO samples. The formation of single phase cubic spinel structure of the sintered ZnFe2O4 samples was found and confirmed by X-ray diffraction technique. Secondary phase Fe2O3 was also detected for compositions with Zn (x≤0.4). Finally, we want to report that the electrical conductivity of ZnxFe3−xO4 was lower than the conductivity of the Al-doped ZnO.  相似文献   

9.
To improve the properties of polyimide (PI), different mass fractions of alumina (Al2O3) nanoparticles, unmodified or modified by KH550, were incorporated into PI matrix to form PI/Al2O3 hybrid films by in situ polymerisation. The effects of Al2O3 additives on the structure, dielectric and mechanical properties of the films were studied. Fourier transform infrared spectroscopy confirmed the successful preparation of PI/Al2O3 hybrid films, and the microstructures of the samples showed a more uniform dispersion of the modified Al2O3 nanoparticles than the unmodified ones in the matrix. The dielectric constant of the films increased with increasing filler content, and the maximum electrical breakdown strength of 311 MV m?1 was obtained with a filler content of 8.0 wt-% modified Al2O3 in the matrix. Both unmodified and modified Al2O3-reinforced PI hybrids demonstrated improved mechanical properties compared with the PI matrix. Moreover, the properties of films with Al2O3 modified by KH550 were better.  相似文献   

10.
Nano-Al2O3-reinforced monomer casting nylon (NA/MCN) composites were prepared by using in situ polymerization. The average molecular weight of the matrix nylon was measured using gel permeation chromatography. The thermal-mechanical properties of the NA/MCN composites were characterized by thermo-dynamic mechanical analysis, and the results were compared with micro-Al2O3-reinforced nylon (MA/MCN) composites. A tensile property test was conducted to investigate the mechanical properties of neat nylon and composites. Experimental results showed that the average molecular weight of the matrix nylon filled with nano-alumina had little change and was higher than that with micro-alumina. The glass transition temperature (Tg) and storage moduli of NA/MCN composites were higher than that of neat nylon. During the experiment, it was also found that the tensile strength increased up to 52% when 3 wt.% of nano-Al2O3 particles were added. The thermal and tensile properties of NA/MCN composites were better than those of the MA/MCN composites when the same weight percentage of Al2O3 particles was used.  相似文献   

11.
Nextel? 610 alumina fibers and alumina‐YAG (yttrium‐aluminum garnet) matrices were used to make oxide‐oxide ceramic matrix composites (CMCs) with and without monazite (LaPO4) fiber‐matrix interfaces. Twelve sequential aluminum oxychloride (AlOCl) infiltrations with 1 hour heat treatments at 1100°C and a final 1 hour heat treatment at 1200°C were used for matrix densification. This matrix processing sequence severely degraded CMC mechanical properties. CMC tensile strengths and interlaminar tensile (ILT) strengths were less than 10 MPa and 1 MPa, respectively. Axial fracture of Nextel? 610 fibers was observed after ILT testing, highlighting the extreme degradation of fiber strength. Extensive characterization was done to attempt to determine the responsible degradation mechanisms. Changes in Nextel? 610 fiber microstructure after CMC processing were characterized by optical microscopy, SEM, and extensively by TEM. In AlOCl degraded fibers, grain boundaries near the fiber surface were wetted with a glass that contained Y2O3/SiO2 or Y2O3/La2O3/P2O5/SiO2, and near‐surface pores were partially filled with Al2O3. This glass must also contain some Al2O3 and initially some chlorine. AlOCl decomposition products were predicted using the FactSage® Thermochemical code, and were characterized by mass spectrometry. Effects of AlOCl precursors on monazite coated and uncoated Nextel? 610 fibers tow and filament strength were evaluated. A mechanism for the severe degradation of the oxide‐oxide CMCs and Nextel? 610 fibers that involves subcritical crack growth promoted by release of chlorine containing species during breakdown of intergranular glasses in an anhydrous environment is proposed.  相似文献   

12.
Y.T. Sung  K.H. Song  H.S. Lee  J. Joo 《Polymer》2006,47(12):4434-4439
Rheological and electrical properties of the polycarbonate (PC)/multi-walled carbon nanotube (MWNT) were studied. The MWNT was funtoinalized by treating with the hydrogen peroxide (H2O2). The H2O2 treated MWNT was dried by thermal and freeze drying methods. From the morphological studies, the degree of entanglement of the MWNT was decreased after treating with the H2O2. For the H2O2 treated MWNT (thermal drying), the length of the MWNT was shortened compared that of the H2O2 treated MWNT (freeze drying). The rheological and electrical properties of the PC/MWNT (H2O2 treated) composites increased compared that of the PC/MWNT (untreated) composites. Also, the electrical conductivity showed higher value for the PC/MWNT (H2O2 treated, freeze drying) composites compared that of the PC/MWNT (H2O2 treated, thermal drying) composites. From the results of the morphological, rheological, and electrical properties of the PC/MWNT composites, it is suggested that the electrical and rheological properties of the PC/MWNT composites are affected by the MWNT-MWNT network structure, which is related with the MWNT morphologies such as the degree of aggregation and aspect ratio of the MWNT.  相似文献   

13.
We report Eu3+ doped transparent glass-ceramics (GCs) containing bismuth layer-structured ferroelectric (BLSF) CaBi2Ta2O9 (CBT) as the major crystal phase. The CBT crystal phase was generated in a silica rich glass matrix of SiO2-K2O-CaO-Bi2O3-Ta2O5 glass system synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. Non-isothermal DSC study was conducted to analyze crystallization kinetics of the glass in order to understand the crystallization mechanism. The optimum heat-treatment protocol for ceramization of precursor glass that has been determined through crystallization kinetics analysis was employed to fabricate transparent GCs containing CBT nanocrystals, which was otherwise difficult. Structural analysis of the GCs was carried out using XRD, TEM, FESEM and Raman spectroscopy and results confirmed the existence of CBT nanocrystals. The transmittance and optical band gap energies of the GCs were found to be less when compared to the precursor glass. The refractive indices of the GCs were increased monotonically with increase in heat-treatment time, signaling densification of samples upon heat-treatment. The dielectric constants (εr) of the GCs were progressively increased with increase in heat-treatment duration indicating evolution of ferroelectric CBT crystals phase upon heat-treatment.  相似文献   

14.
A potential low temperature co-fired ceramics system based on zinc borate 3ZnO–2B2O3 (3Z2B) glass matrix and Al2O3 filler was investigated with regard to phase development and microwave dielectric properties as functions of the glass content and sintering temperature. The densification mechanism for 3Z2B–Al2O3 composites was reported. The linear shrinkage of 3Z2B glass–Al2O3 composites exhibited a typical one-stage densification behavior. XRD patterns showed that a new crystalline phase, ZnAl2O4 spinel, formed during densification, indicating that certain chemical reaction took place between the 3Z2B glass matrix and the alumina filler. Meanwhile, several zinc borate phases, including 4ZnO·3B2O3, crystallized from the glass matrix. Both of the reaction product phase and crystallization phases played an important role in improving the microwave dielectric properties of composites. The optimal composition sintered at 850–950 °C showed excellent microwave dielectric properties: ?r = ∼5.0, Q·f0 = ∼8000 GHz, and τf = ∼−32 ppm/°C at ∼7.0 GHz.  相似文献   

15.
The glasses, in which oxygen was partially replaced with sulfur, have been synthesized in the Na2O-P2O5-Na2S system. The chemical and chromatographic analyses of the glasses synthesized have been performed. The temperature-concentration dependences of electrical conductivity of the glasses have been studied over a wide temperature range; the glass transition temperatures and the nature of charge carriers have been determined. The IR spectra and Raman spectra have been recorded at room temperature; the density and microhardness of the glasses and ultrasound velocity have been measured. A comparison of the electrical conductivities of the investigated glasses with those of the earlier studied glasses in the Na2O-P2O5 system has shown their fair coincidence. The introduction of sodium sulfide into the Na2O-P2O5 system is accompanied by an approximately threefold increase in electrical conductivity, although the concentrations of charge carriers (sodium ions) in the glasses amount to ∼17 and ∼26 mmol/cm3, respectively. The rise in electrical conductivity has been assumed to be caused by the increase in the degree of dissociation of polar structural chemical units including sulfide ions and by the higher mobility of sodium ions in the oxygen-free matrix.  相似文献   

16.
The combined effect of nano-Al2O3 and TiO2 fillers on residual mechanical and thermal properties of glass fiber-reinforced polymer composites has been evaluated. The results reveal that the addition of 0.1?wt% of Al2O3 and 0.1?wt% of TiO2 into the epoxy matrix reduces the water diffusivity by 12%. The residual flexural and interlaminar shear strength of the nanocomposite have been increased by 19 and 21%, respectively, as compared to those of neat epoxy glass fiber-reinforced polymer composite. In spite of reduction in water diffusivity and increase in strength, there was no improvement in glass transition temperature of the nanocomposites.  相似文献   

17.
Nitrogen (N)-doped conductive silicon carbide (SiC) of various electrical resistivity grades can satisfy diverse requirements in engineering applications. To understand the mechanisms that determine the electrical resistivity of N-doped conductive SiC ceramics during the fast spark plasma sintering (SPS) process, SiC ceramics were synthesized using SPS in an N2 atmosphere with SiC powder and traditional Al2O3–Y2O3 additive as raw materials at a sintering temperature of 1850–2000°C for 1–10 min. The electrical resistivity was successfully varied over a wide range of 10−3–101 Ω cm by modifying the sintering conditions. The SPS-SiC ceramics consisted of mainly Y–Al–Si–O–C–N glass phase and N-doped SiC. The Y–Al–Si–O–C–N glass phase decomposed to an Si-rich phase and N-doped YxSiyCz at 2000°C. The Vickers hardness, elastic modulus, and fracture toughness of the SPS-SiC ceramics varied within the ranges of 14.35–25.12 GPa, 310.97–400.12 GPa, and 2.46–5.39 MPa m1/2, respectively. The electrical resistivity of the obtained SPS-SiC ceramics was primarily determined by their carrier mobility.  相似文献   

18.
La2O3–Ga2O3M2O5 (M = Nb or Ta) ternary glasses were fabricated using an aerodynamic levitation technique, and their glass‐forming regions and thermal and optical properties were investigated. Incorporation of adequate amounts of Nb2O5 and Ta2O5 drastically improved the thermal stabilities of the glasses against crystallization. Optical transmittance measurements revealed that all the glasses were transparent over a wide wavelength range from the ultraviolet to the mid‐infrared. The refractive indices of the glasses increased and the Abbe number decreased upon substituting Ga2O3 with Nb2O5, and the decrease in the Abbe number was significantly suppressed when Ta2O5 was incorporated into the glass. As a result, excellent compatibility between high refractive index and lower wavelength dispersion was realized in La2O3–Ga2O3–Ta2O5 glasses. Analysis based on the single‐oscillator Drude–Voigt model provided more systematical information and revealed that this compatibility was due to an increase in the electron density of the glass.  相似文献   

19.
Y-TZP (YZ) and Al2O3-doped Y-TZP (AYZ) bioceramics with addition of different contents of a refractory bioglass were fabricated. The influence of the glass addition and sintering temperature on the densification behavior, microstructure, and mechanical properties of YZ and AYZ was studied. The developed ceramics contained small amounts of ZrSiO4 and Ca2P2O7 phases within the ZrO2 matrix. The incorporation of glass to YZ promoted the ZrO2 phase partitioning and enhanced the ZrO2 grain growth at all the sintering temperatures, whereas the glass addition in AYZ prevented the Y2O3 redistribution between ZrO2 grains and limited the ZrO2 grain growth at 1300–1400°C. The hardness of the samples with glass was not significantly altered by using either YZ or AYZ. A slight increase in the fracture toughness with increasing glass content was found for YZ, while the fractured toughness of AYZ decreased by the glass addition. The more pronounced ZrO2 phase partitioning of YZ with glass decreased the flexural strength, whereas AYZ maintained almost unaltered its flexural strength at a high level by the glass incorporation.  相似文献   

20.
We modified a polycarbonate (PC)/polystyrene (PS) blend by loading alumina (Al2O3) into the blend. X-ray diffraction (XRD) shows a decrease in crystallinity. The optical microscopy and atomic force microscopy (AFM) confirms the homogeneous dispersion of alumina. The differential scanning calorimetry (DSC) data shows improved results in glass transition (Tg) and melting temperature (Tm) of blend systems. The electrical properties of polymer blends modified by Al2O3 were studied as a function of frequency (50 Hz–35 MHz) at 323 K. The alumina showed a significant effect in resulting in a high dielectric constant with low dielectric loss and dissipation factor.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号