In present paper a new niobate materials Ba5LixTixNb10-xO30 were synthesized by doping Li+ in the system BaO- TiO2- Nb2O5 in millimeter wave field. X-ray diffraction (XRD) quantitative and scanning transition spectros...
In present paper a new niobate materials Ba5LixTixNb10-xO30 were synthesized by doping Li+ in the system BaO- TiO2- Nb2O5 in millimeter wave field. X-ray diffraction (XRD) quantitative and scanning transition spectroscopy (SEM) analysis were employed to study crystal structure and microstructure of reaction products. It was found that pure products could be obtained at temperature 900°, 8 min which is lower comparing with that by conventional method. The XRD data shown the crystal belongs to tetragonal tungsten bronze structure with space group P4bm. The grain size synthesized in millimeter wave field had smaller size, narrower distribution, better sinter-ability, and without hard agglomeration comparing whit that obtaining from conventional synthesis. At lower temperature Ba5LiTiNb9O30 is a tetragonal ferroelectric phase.
A high performance thermosetting epoxy resin crosslinkable at room temperature was obtained via directly moulding diglycidyl ether of bisphenol A（DGEBA） and flexibleα,ω-bisamino（n-alkylene）phenyl terminated poly...
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A high performance thermosetting epoxy resin crosslinkable at room temperature was obtained via directly moulding diglycidyl ether of bisphenol A（DGEBA） and flexibleα,ω-bisamino（n-alkylene）phenyl terminated poly（ethylene glycol）.The influences of the n-alkylene inserted in aminophenyl of flexible amino-terminated polythers（ATPE） on the mechanical properties,fractographs and curing kinetics of the ATPE-DGEBA cured products were *** results show that the insertion of n-alkylene group into the aminophenyl group of the ATPE,on one hand,can significantly increase the strain relaxation rate and decrease glass transition temperature of the ATPE-DGEBA cured products,resulting in slight decrease of the Young’s modulus and tensile strength,and significant increase of the toughness and elongation of the ATPE-DGEBA cured *** the other hand,it can remarkably enhance the reactivity of amine with epoxy,much accelerating the curing rate of the ATPE-DGEBA *** activation energy of DGEBA cured by BAPTPE,BAMPTPE and BAEPTPE was 53.1,28.5 and 25.4 kJ·mol;,*** as-obtained ATPE-DGEBA cured products are homogeneous, transparent,and show excellent mechanical properties including tensile strength and *** they are promising to have important applications in structure adhesives,casting bulk materials,functional coatings,cryogenic engineering, damping and sound absorbing materials.
ZnO sub-millimeter crystals were synthesized by microwave heating from ZnO powders without any catalyst or transport agent. Zinc oxide raw materials were evaporated from the high-temperature zone in an enclosure and c...
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ZnO sub-millimeter crystals were synthesized by microwave heating from ZnO powders without any catalyst or transport agent. Zinc oxide raw materials were evaporated from the high-temperature zone in an enclosure and crystals were grown on the self-source substrate. The thermodynamics analysis method was used to estimate the partial pressure of gases in the chamber, which shows that the pressure of ZnO could be neglected entirely in the range of experiment temperature. The kinetics analysis was employed to estimate the growth rate in different conditions, which shows a remarkable temperature gradient and a high system temperature would enhance the growth rate. Optics photos reveal that these products are hexagon crystals with 0.2-0.3 mm in diameter and 0.5-1 mm in length. A vapor-solid mechanism is proposed to explain the growth process of ZnO crystals. The temperature distribution in microwave oven is mainly determined by properties of electric field and it is different from that of a conventional method.
Fe doped In2O3 samples （In1-xFex）2O3 （x=0, 0.05, 0.1, 0.2 and 0.3） on glass substrate were prepared by sol-gel method. The XRD results demonstrate that the solubility of Fe ions in In2O3 matrix is around 20%, abov...
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Fe doped In2O3 samples （In1-xFex）2O3 （x=0, 0.05, 0.1, 0.2 and 0.3） on glass substrate were prepared by sol-gel method. The XRD results demonstrate that the solubility of Fe ions in In2O3 matrix is around 20%, above which impurity phase can be observed. The transmittance of the samples with x=0, 0.05, 0.1 and 0.2 are above 80% in the visible region while the transimittance of the glass is 90%. The transmittance curves slightly red-shifts as x increasing. All of the samples except x=0 are ferromagnetic at room temperature. The highest saturation magnetization moment is reached in the sample x=0.2 with 330 emu/cm3, and the coercive force is 169 Oe which is also the largest in our samples. The results indicate that the addition of Fe ions could tune the structure, the ferromagnetism and optical property in the In2O3 matrix.
About 300 μm thickness uniform thermal barrier coatings （TBCs） were deposited on the 1Cr18Ni9Ti samples by solution precursor plasma spray （SPPS）.The analysis methods,such as TEM,SEM,and XRD were used to characte...
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About 300 μm thickness uniform thermal barrier coatings （TBCs） were deposited on the 1Cr18Ni9Ti samples by solution precursor plasma spray （SPPS）.The analysis methods,such as TEM,SEM,and XRD were used to characterize the coatings in the aspects of microstructure and phase *** samples were quenched from 1121 ℃ to room temperature by forced-air to measure the thermal cycling *** density were measured by means of water *** experimental results show that grain size of the SPPS TBCs is about 30 nm with desired tetragonal phase ZrO2,and the SPPS TBCs（with 16% porosity） consist of arcuate pores,gelatin and melted *** hardness of the coatings is HR45Y38.5 and bond strength between coatings and substrates is 24.2 *** thermal shock test show the coatings have a average life of 500 cycles which is about 2.5 times than that of conventional air plasma spray （APS） TBCs.
Polycrystalline samples of Sr5PrTi3Ta7O30 （SPTT） and Sr5EuTi3Ta7O30 （SETT） compounds were prepared by high-temperature solid-state reaction method and their formation, structure and dielectric properties were stud...
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Polycrystalline samples of Sr5PrTi3Ta7O30 （SPTT） and Sr5EuTi3Ta7O30 （SETT） compounds were prepared by high-temperature solid-state reaction method and their formation, structure and dielectric properties were studied. They are found to be ferroelectric phase of filled tetragonal tungsten bronze （TB） structure at room temperature and undergoes diffuse type of ferroelectric-paraelectric phase transition around 34 ℃ and 31 ℃, respectively. At 1 MHz SPTT exhibits high dielectric constants of 177 and low dielectric losses of 3.5×10^-4 and SETT has high dielectric constants of 125 and low dielectric losses of 2.4×10^-3.
Graphene was prepared and used as an adsorbent for removal of cationic red X-GRL from aqueous solutions. The physico-chemical properties of graphene were characterized by the transmission electron microscope (TEM), th...
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Graphene was prepared and used as an adsorbent for removal of cationic red X-GRL from aqueous solutions. The physico-chemical properties of graphene were characterized by the transmission electron microscope (TEM), the Brunauer-Emmett-Teller (BET) specific surface area measurement, atomic force microscope (AFM), and Raman microscope. The adsorption properties of cationic red X-GRL onto graphene were studied as a function of pH, adsorbent dosage, contact time, and temperature. Kinetic data were well fitted by a pseudo second-order model. Langmuir and Freundlich adsorption models were applied to describe the isotherms and isotherm constants. Equilibrium data agreed very well with the Langmuir model. Thermodynamic studies showed that the adsorption was a spontaneous and endothermic process.
A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly invol...
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A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core–shell particles by a controllable liquid reduced reaction of Ag[（NH3）2]＋ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy （SEM）, transmitted electron microscopy （TEM）, X-ray photoelectron spectra （XPS）, X-ray diffraction （XRD） and energy dispersive X-ray （EDX） etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.
A 3-D finite element model of two-stage thermoelectric generator based on low-temperature thermoelectric material bismuth-telluride and medium-temperature thermoelectric material skutterudites is established. Based on...
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ISBN:
(纸本)9781424480364
A 3-D finite element model of two-stage thermoelectric generator based on low-temperature thermoelectric material bismuth-telluride and medium-temperature thermoelectric material skutterudites is established. Based on the formal model, structural optimization of the two-stage thermoelectric generator is carried out. Results show that, reasonable design of the structure of two-stage thermoelectric generator can take full advantage of the characteristics of thermoelectric materials and effectively improve the performance of power generation. If contact resistance and all heat losses are neglected, the conversion efficiency of the two-stage thermoelectric generator can reach a value of 17.02%.
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