共查询到20条相似文献,搜索用时 15 毫秒
1.
Poly(vinyl chloride)/calcium carbonate (PVC/CaCO3) composites with micrometer or nanometer CaCO3 as fillers were prepared by the solution blending method. The thermogravimetric analysis (TGA) of the composite films conducted in N2 atmosphere showed that the addition of the CaCO3 fillers could improve their thermal stabilities. It was also found that the nanometer CaCO3 filler provided better thermal stabilities than the micrometer fillers even with a smaller amount. The mechanism of the improvements was investigated by a facile chemical analysis developed to examine the thermal stabilizing effect of calcium carbonate particles with different sizes in PVC/CaCO3 composites after the pyrolysis of the samples in an air atmosphere in an oven. 相似文献
2.
Ling Zhang Meifang Luo Shuisheng Sun Jan Ma Chunzhong Li 《Journal of Macromolecular Science: Physics》2013,52(5):970-982
To study the effect of different surface structures on resultant mechanical and rheological properties, nano-CaCO3 particles were treated with isopropyl tri-stearyl titanate (H928), isopropyl tri-(dodecylbenz-enesulfonyl) titanate (JN198), and isopropyl tri-(dioctylpyrophosphato) titanate (JN114). Scanning electron microscopy (SEM) and dynamic mechanic analysis (DMA), carried out to characterize the effective interfacial interaction between the nano-CaCO3 particles and a poly(vinyl chloride) (PVC) matrix, indicated that JN114 treated nano-CaCO3 particles had the strongest interfacial interaction with a PVC matrix, while H928 treated nano-CaCO3 had the weakest. The rheological and mechanical properties of PVC/nano-CaCO3 composites were investigated as a function of surface structure and filler volume fraction. The tensile yield stress and elongation at break decreased with the increasing of calcium carbonate content while tensile modulus increased. PVC filled with JN114 treated nano-CaCO3 had the highest tensile modulus and tensile yield stress, while those filled with H928 treated nano-CaCO3 had the highest elongation at break at the same filler content. The impact strength of PVC/nano-CaCO3 composites increased with the increasing of CaCO3 content, and PVC composites filled with JN198 treated nano-CaCO3 particle had a higher impact strength than those with JN114 or H928 treated, with the value reaching 23.9 ± 0.7 kJ/m2 at 11 vol% CaCO3, four times as high as that of pure PVC. Rheological properties indicated that a suitable interfacial interaction and a good dispersion of inorganic filler in a PVC matrix could reduce the viscosity of PVC/nano-CaCO3 composites. The interfacial interaction was quantitatively characterized by semiempirical parameters calculated from the tensile strength of PVC/nano-CaCO3 composites to confirm the results from the SEM and DMA experiments. 相似文献
3.
Shadpour Mallakpour Mohammad Dinari 《Journal of Macromolecular Science: Physics》2013,52(11):1651-1661
The surface of α-alumina (Al2O3) nanoparticles was first modified with γ-aminopropyltriethoxy silane as a coupling agent. Then a series of poly(vinyl alcohol)/ surface modified Al2O3 nanocomposite suspensions were prepared in ethanol by a simple ultrasonic irradiation process. Composite films with 5, 10, and 15 wt % of inorganic Al2O3 nanoparticles were achieved after solvent evaporation. The formation of the composite materials were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and optical transparencies. The FE-SEM and TEM results showed a homogenous dispersion of nanoscale inorganic particles in the poly(vinyl alcohol) matrix. TGA thermographs showed that the thermal stability of the prepared Al2O3-reinforced nanocomposites was improved, increasing with increasing content of the nanoparticles. According to the optical transparencies, the optical clarity of poly(vinyl alcohol)/Al2O3 nanocomposite films was only slightly affected by the presence of the Al2O3 content. 相似文献
4.
Poly(vinyl alcohol) (PVA)/montmorillonite (MMT) nanocomposites were prepared by combining solid-state shear milling (S3M) technology with melt intercalation. Compared with the composite obtained by simple melt intercalation, more MMT layers were exfoliated and apparently oriented along the injection molding direction in the nanocomposite prepared by combining S3M technology and melt intercalation, which greatly increased the orientation degree of MMT, resulting in the greater interactions between PVA and MMT layers. Simultaneously, this also promoted the orientation of PVA molecules and produced effective nucleation of the crystallization of PVA. Consequently, the thermal stability and mechanical properties of PVA were obviously improved. For instance, when the MMT content was 3 wt%, the tensile strength and modulus of the nanocomposite with MMT prepared by S3M were 98.9 MPa and 3.1 GPa, respectively, increasing by 52% and 63.2% compared with PVA. 相似文献
5.
Binary composites of poly(lactic acid) (PLA)/calcium carbonate whiskers (CCW) with different weight fractions were prepared with a vane mixer based on extensional rheology. The mechanical properties, thermostability, crystallization behavior, rheology behaviors and micromorphology of the composites were analysed to study the effect of the CCW fibers on the composite's properties; a pure PLA sample was also prepared for comparison. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) revealed that the CCW fibers had excellent compatibility with the PLA matrix and the CCW fibers were dispersed and distributed evenly in the PLA matrix under the action of the extensional flow field produced by the vane mixer. Differential scanning calorimetric (DSC) analysis showed that introducing a vane mixer into the PLA processing could increase the degree of crystallization (χc) of the composites significantly, and moderate CCW fibers adding could further increase its χc value. Thermogravimetric analysis (TGA) revealed that adding the CCW fibers reduced the thermostability of the composites. The G′, G″, η* and the torque, TN, of the composites, obtained from rheology analyses, declined obviously, because of the hydrolysis and chains scission induced by residual water and fatty acid when the CCW content less than 4%. Tensile tests proved that filling moderate amounts of CCW fibers into PLA could increase its tensile strength and strain at break, increasing by 5% and 29.6%, respectively. 相似文献
6.
7.
The properties of TiO2/polyamide 6 (PA6) and ZnO/PA6 nanocomposite filament yarns produced on a pilot-plant melt spinning machine were compared. Concentrated masterbatches were prepared using a twin screw extruder. Then continuous multifilament yarns were produced by blending nylon 6 chips and various amounts of the prepared masterbatches. Melt spinning was carried out at the spinning temperature of 265°C and take-up speed of 4000 m/min. As-spun multifilament yarns were then drawn and textured. Morphological properties of the produced yarns were studied. Thermal behavior and physical properties, including shrinkage and tensile properties, were measured. Weft-knitted fabrics were evaluated for their ultraviolet protection properties. Although both kinds of the nanoparticles had a positive effect on the ultraviolet protection properties of their nanocomposite fabrics as compared to pure PA6 fabric, the efficiency of the TiO2 nanoparticles was more than that of the ZnO ones for the same concentrations. The differences between the different properties of the two kinds of nanocomposites are discussed based on their interaction with the polymeric matrix, specific surface area, steric hindrance effect, and band gap energies. 相似文献
8.
采用固相反应法制备了Y2O3施主掺杂的92 mol%BaTiO3-8 mol%(Bi1/2Na1/2)TiO3(BBNT8)高温无铅正温度系数电阻(positive temperature coe?cient resistivity,PTCR)陶瓷.利用透射电镜观察材料的显微结构,发现陶瓷的显微结构主要包括晶粒和晶界两部分,观察不到明显的壳层结构.进一步利用交流阻抗谱研究了陶瓷的宏观电学性能,发现陶瓷的总电阻是晶粒和晶界两部分的贡献,而晶粒电阻很小,在居里温度以上变化不大,材料的PTCR效应主要是晶界部分的贡献.当温度高于居里温度时,随着温度的升高,晶界介电常数逐渐减小,导致势垒增加,晶界电阻增大,从而产生正温度系数效应.最后,通过测试材料的介电频谱特性,研究计算了陶瓷的室温电阻率. 相似文献
9.
Optical birefringence, calorimetric, thermal expansion, powder and single crystal X-ray diffraction investigations of mixed proton conductors [Rb1-x(NH4)x]3H(SeO4)2 were performed with the aim of studying the influence of partial substitution of cations on the superprotonic phase transition, on the atomic structure and on other characteristic features of this type of crystals. 相似文献
10.
The nano-structured Fe(III)-doped TiO2 photocatalysts with anatase phase have been developed for the oxidation of non-biodegradable different organic dyes like methyl orange (MO), rhodamine B (RB), thymol blue (TB) and bromocresol green (BG) using UV-Hg-lamp. The different compositions of FexTi1−xO2 (x = 0.005, 0.01, 0.05, and 0.1) nanocatalysts synthesized by chemical method (CM), have been characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, specific surface area (BET), transmission electronic microscopy (TEM) analysis, XPS, ESR and zeta potential. From XRD analysis, the results indicate that all the compositions of Fe(III) doped in TiO2 catalysts gives only anatase phase not rutile phase. For complete degradation of all the solutions of the dyes (MO, RB, TB, and BG), the composition with x = 0.005 is more photoactive compared all other compositions of FexTi1−xO2, and degussa P25. The decolorization rate of different dyes decreases as Fe(III) concentration in TiO2 increases. The energy band gap of Fe(III)-doped TiO2 is found to be 2.38 eV. The oxidation state of iron has been found to be 3+ from XPS and ESR show that Fe3+ is in low spin state. 相似文献
11.
Jian-Lan Tang Man-Kang Zhu Chuan Chen Yu-Dong Hou Hao Wang Hui Yan 《Journal of nanoparticle research》2009,11(2):355-363
A novel surfactant-modulated precipitation method is proposed to produce pure perovskite Pb(Sc1/2Nb1/2)O3 (PSN) nanopowders at a low temperature of 700 °C. The samples were characterized by XRD, SEM, TEM, and HRTEM, respectively.
The results indicate that the powders exhibit a granular shape of 80 nm in diameter. It is believed that the nanosize of as-prepared
PSN powders is dependent on the well-dispersed performance, which arouse from the combined effects of both precipitant TMAH
and surfactant CTAB. The mechanism of the formation of the pure perovskite PSN nanopowders is discussed in detail. Our method
is expected to create a new, low-cost route to produce the promising nanopowders of multi-component perovskite systems. 相似文献
12.
Dan Zhao 《Journal of luminescence》2010,130(3):424-428
This paper reports the growth and spectroscopic characterization of Er3+:Sr3Y(BO3)3 crystal. Er3+:Sr3Y(BO3)3 crystal with dimensions up to ∅20×35 mm3 has been grown by Czochralski method. The polarized spectroscopic properties of Er3+:Sr3Y(BO3)3 crystal were investigated. Based on the Judd-Ofelt theory, the effective intensity parameters Ωt were obtained: Ω2=1.71×10−20 cm2, Ω4=1.39×10−20 cm2, Ω6=0.74×10−20 cm2 for π-polarization, and Ω2=1.77×10−20 cm2, Ω4=1.44×10−20 cm2, Ω6=0.65×10−20 cm2 for σ-polarization. The emission cross-section σem was calculated to be 4.75×10−21 cm2 for π-polarization at 1536 nm and 6.30×10−21 cm2 for σ-polarization at 1537 nm. The investigated results showed that Er3+:Sr3Y(BO3)3 crystal may be regarded as a potential laser host material for 1.55 μm IR solid-state lasers. 相似文献
13.
Alkaline polymer electrolytes (ASPE) have been prepared by using poly(vinyl alcohol) (PVA) polymer and which different weight percentages of potassium hydroxide (KOH), ceramic filler (α-Al2O3), and propylene carbonate (PC) have been added. The pure PVA/H2O weight ratio (1.00:1.49), the PVA/KOH/H2O (1.00:0.67:2.22), the PVA/KOH/α-Al2O3/H2O (1.00:0.67:0.09:7.56), and PVA/KOH/α-Al2O3/PC/H2O (1.00:0.67:0.09:2.64:1.32) were studied. The hysteresis phenomena in the conductivity temperature of ASPE were investigated. The polymer electrolytes prepared were characterized using X-ray diffraction and scanning electron microscopy. 相似文献
14.
In this contribution, photoluminescence and time-resolved photoluminescence spectra of Ca(NbO3)2 doped with Pr3+ obtained at high hydrostatic pressure up to 72 kbar applied in a diamond anvil cell are presented. At ambient conditions, the emission spectrum obtained in the time interval 0-1 μs is dominated by spin-allowed transitions from the 3P0 state. On the other hand, transitions from 1D2, characterized by a decay time equal to 30 μs dominate the steady-state luminescence.At pressures lower than 60 kbar, the continuous wave emission spectrum consists of sharp lines peaking between 600 and 625 nm, related to the 1D2→3H4 transition and three lines at 500, 550 and 650 nm related to emission transitions originating from the 3P0 level of Pr3+. The emission from the 1D2 excited state depends weakly on the pressure. Its decay time decreases from 33 μs at ambient pressure to less than 22 μs at 68 kbar. On the other hand, the 3P0 emission is strongly pressure dependent. At pressures of 60 kbar and higher, the Pr3+ emission intensity from the 3P0 state decreases. This is accompanied by a strong shortening of the luminescence decay time.The observed pressure quenching of the f-f emission transitions and the concomitant lifetime shortening have been attributed to increasing crossover from the 3P0 state of Pr3+ to a Pr3+-trapped exciton state. 相似文献
15.
采用机械合金化制备了n型(Bi1-xAgx)2(Te1-ySey)3合金粉体,对其进行XRD分析表明Bi,Te,Ag,Se单质粉末,经2h球磨后实现了合金化;SEM分析表明随着机械合金化时间延长粉体颗粒变得均匀、细小,颗粒尺寸在微米至亚微米数量级.采用放电等离子烧结制备了块体样品,研究了合金成分和球磨时间对热电性能的影响.结果表明材料的热电性能与掺杂元素有密切关系,Ag有利于提高功率因子和降低晶格热导率,球磨10h的(Bi0.99Ag0.01)2(Te0.96Se0.04)3合金粉末的烧结块体具有最大的功率因子和最低的晶格热导率,并在323K取得最高ZT值0.52.
关键词:
1-xAgx)2(Te1-ySey)3合金')" href="#">(Bi1-xAgx)2(Te1-ySey)3合金
机械合金化
放电等离子烧结
热电性能 相似文献
16.
Microstructure and properties of Ni-Co/nano-Al2O3 composite coatings by pulse reversal current electrodeposition 总被引:1,自引:0,他引:1
Ni-Co/nano-Al2O3 (Ni-Co/Al2O3) composite coatings were prepared under pulse reversal current (PRC) and direct current (dc) methods respectively. The microstructure of coatings was characterized by means of XRD, SEM and TEM. Both the Ni-Co alloy and composite coatings exhibit single phase of Ni matrix with face-centered cubic (fcc) crystal structure, and the crystal orientation of the Ni-Co/Al2O3 composite coating was transformed from crystal face (2 0 0) to (1 1 1) compared with alloy coatings. The hardness, anti-wear property and macro-residual stress were also investigated. The results showed that the microstructure and performance of the coatings were greatly affected by Al2O3 content and the electrodeposition methods. With the increasing of Al2O3 content, the hardness and wear resistance of the composite coatings enhanced. The PRC composite coatings exhibited compact surface, high hardness, better wear resistance and lower macro-residual stress compared with that of the dc composite coatings. 相似文献
17.
Yumashev K. V. Posnov N. N. Prokoshin P. V. Kalashnikov V. L. Mejid F. Poloyko I.G. Mikhailov V. P. Kozich V. P. 《Optical and Quantum Electronics》2000,32(1):43-48
The nonlinear refractive index n2 of Yb3+:KY(WO4)2 crystal has been measured using picosecond Z-scan technique. The magnitude of n2 was found to be 8.7 × 10–16 cm2/W at wavelength of 1.08 m. The numerical modeling based on fluctuation model showed a great potential of this crystal as active medium for Kerr-lens mode-locking. 相似文献
18.
B. Pispisa C. Mazzuca A. Palleschi L. Stella M. Venanzi F. Formaggio C. Toniolo J.-P. Mazaleyrat M. Wakselman 《Journal of fluorescence》2003,13(2):139-147
The ground- and excited-state properties of two conformationally constrained hexapeptides of general formula Boc-Bin-A1-A2-T-A1-A2-OtBu, where A1 and A2 are -aminoisobutyric acid (Aib) or L-alanine (Ala), Bin is an optically pure, axially chiral 1,1-binaphthyl-substituted Aib, and T (Toac) is a stable nitroxide free radical-containing Ac6c analog, were investigated in methanol solution. These peptides are denoted as (R)-Bin/Toac and (S)-Bin/Toac, depending on the chirality of the binaphthyl moiety. Electronic spectra in methanol indicate the occurrence of intramolecular exciton interaction between the naphthyl moieties of Bin, and time-resolved fluorescence measurements show a biexponential decay for both peptides examined. According to infrared (IR) absorption data in the NH stretching frequency region, and to earlier X-ray diffraction results on (S)-Bin/Toac in the crystal state, both (R)-Bin/Toac and (S)-Bin/Toac populate a 310-helix in solution with opposite screw sense, the helical handedness being determined by the chirality of binaphthyl and not by that of the Ala residues in the main chain. The combination of molecular mechanics calculations with fluorescence decay data indicate that the two observed lifetimes for each peptide arise from two conformations having different interprobe distance and orientation, in which electronic energy transfer from excited Bin to Toac takes place. 相似文献
19.
R. Martínez-Martínez A. Speghini M. Bettinelli C. Falcony U. Caldio 《Journal of luminescence》2009,129(11):1276-1280
The photoluminescence of Ce3+, Tb3+ and Mn2+ ions was investigated in the Zn(PO3)2 glass. The blue and green emissions of Tb3+ ions and the red emission of Mn2+ ions are enhanced upon UV excitation through a non-radiative energy transfer from Ce3+ to Tb3+ and Mn2+ ions. The efficiency of this transfer was estimated in at least 62%. It is demonstrated that this glass activated with three ions (Ce3+, Tb3+ and Mn2+) can generate white light emission (x=0.420 and y=0.423 chromaticity coordinates and 3440 K colour temperature) under excitation at 254 nm, i.e., using an AlGaN-based LED as excitation source. 相似文献
20.
Abstract A complete vibrationalassignment of the title compounds is performed from their IR and Raman Spectra. A normal coordinate treatment of these molecules based on a simplified model allow us to confirm most of the experimental assignments. A comparison of some structural aspects of these complexes with Cp?Re(CO)3 are also discussed. Additionally, the preparation and characterization of the trimethylphosphite derivative is reported. 相似文献