Applied Mechanics and Materials Vol. 740

Abstract: KNN-BF piezoelectric ceramics synthesized by sol-gel method in this experiment. By controlling bismuth and iron content in the system to study effects of them. We selected citric acid as metal chelator and ethylene glycol as esterification agent. PH maintained 5-6 during preparation of the sol. Sintering temperature of ceramic selected 1100°C. Preparation ceramics under these conditions and comparative analysis, the structure of ceramics is single perovskite and shap of crystals are square block. With the increase of x, properties of ceramics firstly increases and then decreases: d₃₃, ε_r, Q_m, K_p reaching the maximum, values of them were 136pC/N, 630(f =1KHz), 212, 0.41 respectively; dielectric loss to minimum is 0.07(f =1KHz); at this point, ceramics had best performance.

Abstract: In this paper, the sol-gel method was used to systematic study of the preparation conditions and sintering conditions about KNN-0.008BF powders. At the same time, microstructure and electrical properties of ceramics were studied and analyzed. In this experiment, citric acid(CA) as metal chelator, ethylene glycol(EG) as esterification and chelating agents. Through a large number of experiments, n(citric acid):n(ethylene glycol)=2:1, n(citric acid):n(Nb⁵⁺)=1.5:1 is the best equipped ratio. This ratio can obtained pale yellow transparent solution. Under the experiments condition, PH of the precursor solution and the sintering temperature of powders have great influence on experimental. Experiments confirmed that PH=5-6 and temperature=1100°C is the best preparation condition, in which condition piezoelectric ceramics can obtained excellent structures and piezoelectric properties.

Abstract: In order to enhance the thermal conductivity of high-temperature phase change materials (PCMs), expanded graphite (EG) /NaNO₃-LiNO₃ composite was prepared by the method of eutectic aqueous solution infiltration porous structure of EG. The composites with an EG amount of 10%, 20% and 30% were prepared in the similar way. The results proved that the eutectic was an excellent PCM, for its melting (solidification) temperature was 193.7 (191.7) °C, and its latent heat was 272.6(262.6) kJ/kg. With the increasing in graphite amount, the thermal conductivity of the composite was found to progressively increase with intensifications up to 10. We can conclude that the saturated water solution method was a simple and effective way to strengthen the thermal conductivity of the eutectic.

Abstract: This paper deals with the aggregate-cement ratio and the influence of flue gas desulphurization(FGD) gypsum, fly ash and ground slag on the properties of EPS thermal insulation mortar. Results show that with the increase of aggregate-cement ratio, dry density and compressive strength of EPS thermal insulation mortar decreases, water absorption increases, softening coefficient decreases, meanwhile the performance of mortar becomes worse. When aggregate-cement ratio is 6% , the mortar shows the best performance. When aggregate-cement ratio reaches 7%, the mixture is loose in structure and difficult to shape. Fly ash and slag powder improves the performance of EPS thermal insulation mortar significantly, reduces the dry density, increases the comprehensive strength, water absorption and softening coefficient is improved. FGD gypsum makes insulation mortar strengthful, it plays excitation role for the activity in composite cementitious material admixture.

Abstract: The paper studies the influences of mineral mixtures on the performance of self-leveling mortar through orthogonal experiments. Morphology by Scanning electron microscopy was used to examine the morphology of mortar. The experiments studied the law of strength as well as the influence by three kinds of additives (fly ash, slag and gypsum). Orthogonal experimental results show that, when the content of Fly ash, gypsum, slag were 5%, 2%, 5%, respectively they work best, and for fluidity results show that the best results were when they take up 7.5%, 2% and 10%, respectively.

Abstract: Hydroxyl zinc mono-methacrylate/carbon black/hydrogenated nitrile rubber composites were prepared by using HZMMA as a partial substitution for carbon black. The morphology and properties of the composites during the vulcanization process were investigated. The results showed that during early stage of the curing process, the tensile strength and modulus at 100% of the composites increased slightly, the tear strength and elongation at break decreased. The favorable mechanical properties for composites could be achieved after post-curing. FTIR, XRD, and TEM results showed that the polymerization of HZMMA completes at the beginning stage of curing process. Grafting and crosslinking reaction between HZMMA and HNBR may occur during the curing process and metallic bridge bond between them forms. The phase state of homopolymer transformed from disperse phase to continuous phase and has a good compatibility with HNBR.

Abstract: Mn, Co, and Ni-doped La_0.5Sr_0.5FeO₃ thin films were prepared by the sol-gel technique with different annesling atmosphere. The structure and dielectric properties of the films were researched by XRD, SEM and Agilent. The study found that LSF-Mn (Co, Ni) films under the argon annealing atmosphere were have optimal dielectric properties. And Mn, Co, Ni elements are integrated into La_0.5Sr_0.5FeO₃ lattices with the single perovskite phase. And uniform grain was distribution on the film surface.

Abstract: The effect of grain size on erosion wear of B₄C/TiC/Al₂O₃ (BT) ceramic nozzles was studied. XRD analysis showed that B₄C/TiC/Al₂O₃ ceramic nozzle was composed of B₄C, TiB₂, Al₂O₃ and C. The erosion experimental results showed that grain size affected the erosion behaviours of BT nozzles significantly. The volume erosion rate of BT2 nozzle was enlarged by 0.88 times than that of BT1 nozzle. Analysis of experimental data and observations on the worn surface revealed that the enhancement in the erosion resistance for BT1 nozzle was mainly owing to the finer grains in nozzle, which resulted in improved fracture toughness.

Abstract: The effect of destabilization at (960°C,1000°C,1050°C) followed by sub-critical heat treatment (SCHT) at (260°C, 450°C, 550°C) on microstructure and mechanical properties of a hypereutectic chromium cast iron containing 31 wt.% Cr was investigated. The response of the microstructure of the specimens differed significantly to heat treatment. With increasing destabilization temperature, the amount of retained austenite increased and it became more stable during following SCHT. The peak values of bulk hardness deceased with increasing destabilization temperature, while higher SCHT was needed to reach the hardness maximum. The hardness and erosion wear property of the specimens destabilization at 960°C or 1000°C deteriorated after SCHT at 550°C due to the formation of ferrite/carbide product, which was not found in the specimens destabilization at 1050°C followed by SCHT at 550°C. The specimen destabilization at 960°C + SCHT at 260°C performed best erosion wear resistance with matrix of martensite containing little austenite.