Abstract: K1-xNaxNb1-ySbyO3 lead-free piezoelectric ceramic powders were prepared by hydrothermal route. The samples were sintered under normal pressure at 1060 °C for 2 h. The structure of piezoelectric ceramics is perovskite and crystalline grain shows a block shape. With the different ceramics component and microstructure, piezoelectric constant d33 varies from 20 to 73. When x=0.54, y=0.04, reached the maximum.
Abstract: In this paper, (K0.5Na0.53)0.932Nb0.932O3-0.008BF-0.06LS (abbreviated as KNN-BF-LS) piezoelectric ceramic was prepared by sol-gel method. Structure and properties of ceramics were analyzed.Through analysis of the results, when sintering temperature is 1080°C, ceramic has good perovskite structure. At this temperature, grain size is more uniform, and structure is the most dense. Piezoelectric constant d33, electromechanical coupling coefficient Kp, dielectric constant εr reached the maximum value, respectively, 113pC/N, 0.33, 591. Dielectric loss tanδ reached the minimum 0.11.
Abstract: Ba0.5Sr0.5TiO3 powders were prepared via a new sol-gel method with titanium oxide, strontium nitrate, and barium nitrate as raw materials. The microstructure and electrical properties were characterized by field scanning electron microscopy, x-ray diffraction and impedance analyser. When the PH = 4, n (CA): n (metal oins) = 3:1 and the synthesis temperature is 800 °C, Ba0.5Sr0.5TiO3 powders were obtained with good crystallinity. BST ceramics sintered at 1250 °C for 2h exhibited good dielectric properties (εr = 930, tanδ = 0.08) at room temperature and f =1 KHz. The relatively low sintering temperature and excellent dielectric properties would make these ceramics promising for applications in electronics.
Abstract: (Ba0.5Sr0.5)1-xMnxTiO3(x=0,0.01,0.03,0.05)ceramics were prepared via a new sol-gel method with titannium oxide, strontium nitrate, barium nitrate and manganous nitrate as raw materials.The effect of Mn doping on the microstructure and dielectric properties of the BST were characterized by field scanning electron microscopy,x-ray diffraction and impedance analyser.It was found that the dopted ions could not alter the basic crystal strcuture and they only improved the material properties as modified ions when x≤0.3.The (Ba0.5Sr0.5)1-xMnxTiO3 ceramics sintered at 1250°C for 2h exhibited good dielectric properties(er=1330,tand=0.03)at room temperature and f=1KHz when x=0.03 and the grains were regular and uniform ,indicating a dense microstrcture.
Abstract: Lead-free (K0.5Na0.5)0.992Nb0.992-0.008BF-xNa (KNN-BF-xNa) piezoelectric ceramics with excess Na doping were synthesized using the sol-gel method at the sintering temperature of 1100°C. The effects of excess Na-doping on microstructure and properties of the lead-free piezoelectric ceramics were systematically investigated with x from 0.00 to 0.04. As x increased into 0.03, the acutest peak of x-ray diffraction patterns appeared; the SEM fig.1(c) showed regular and dense crystal shape. KNN-BF-0.03Na ceramics showed excellent properties of d33=149pC/N, εr=641(f=1KHz), tanδ=0.06(f=1KHz), ρ=4.15g/cm3. The results indicated that excess Na doping can make up for the Na volatilized while sintering under atmosphere pressure, but as x was 0.04, too much more Na dropping would lower the sintering temperature. Therefore, there would be quantities of liquid phases, as was shown in the fig.1(d), which caused the inferior properties of piezoelectric ceramics.
Abstract: We studied the effect of annealing and Co ion doping on the structure, leakage current, ferroelectric polarization and magnetism of BiFeO3 samples. X-ray diffraction patterns demonstrate that an appropriate Co doping concentration is favor of suppressing the secondary phase but annealing treatment is apt to the growth of both the main and the secondary phases. The current density as a function of an electric field indicates that Co doping increases the leakage current density as samples before annealing but suppresses it after annealing. Annealing treatment improves the leakage for Co-doped sample and reduces it for the undoped sample. Ferroelectric hysteresis loops reflect that Co ions doping is liable to increase the ferroelectric polarization, while the sample is annealed it will do opposite effect. However the annealing treatment do improve the ferroelectricity for pure BiFeO3 sample. The magnetic hysteresis at room temperature shows the obvious enhancement of ferromagnetic properties with the sample after annealing.
Abstract: To research the effect of a elastic modifier on the mechanical properties of epoxy/rubber concrete, series of epoxy/rubber concretes were prepared with different elastic modifier content, the relationship between elastic modifier content and stress-strain curve of epoxy/rubber concretes were investigated. Results show: as the increase of elastic modifier content, both the compressive and bending stress-strain curves of epoxy/rubber concretes experience a stage transition of elastic-elastoplasticity-plastic apparently; the slope in the rising and falling section of stress-strain curves are gradually decreased; the peak stress decrease while the corresponding strain and stain energy increase. Content of elastic modifier between 40pbw and 60 pbw is proposed in order to attain better properties of epoxy/rubber concrete. Compared with ordinary concrete and rubberized concrete, Improved epoxy/rubber concrete has better comprehensive mechanical properties and larger rubber content.
Abstract: The recent trend in automotive industry is characterized by the replacement of existing metal materials with composite ones or the combination of both for lightweight parts. This study 1) created single lap joint specimens of SPCC used for automobile frame and four adhesives; epoxy, urethane, acrylic, mixed (urethane and acrylic) and rivets to bind dissimilar materials of CFRP necessary for weight lightening, and 2) performed a tensile shear test on adhesive bonding versus adhesive bonding with rivets. In summary, this study investigated on the bonding performance of different specimens: bonding strength, shapes of the failure surface, and the effect of rivets on bond strength.
Abstract: The application of structural insulated panels (SIP) was mainly limited to wall panels in the past. In order to evaluate the flexural performance of SIP two-way slabs, an experimental research on the flexural behavior of four full-size two-way slabs, made of SIP panels or fiber reinforced structural insulated panels, was presented in this paper. The bending capacities and the strains in the face layers were studied and compared with those of ordinary reinforced concrete two-way slabs. Testing results verified that, strengthening of glass fiber reinforced polymer sheets could obviously improve the flexural capacity of SIP slab. Fiber reinforced structural insulated panels could substitute ordinary reinforced concrete slabs in residential or light commercial buildings.