Advanced Materials Research Vols. 690-693

Abstract: Using alumina-rich MgAl₂O₄ spinel AR78 and 97 fused magnesite as raw materials, brine as the binder, magnesia alumina spinel bricks close to theoretical composition and spinel bricks with zirconia have been prepared. Then the influences of zirconia on the properties of MgAl₂O₄ spinel bricks are researched. The results show that: (1) After the addition of zirconia, the direct bonding structure formed between spinel and zirconia can strengthen matrix structure and promote sintering, so the structural properties, the alkali resistance performance and the creep property of MgAl₂O₄ spinel bricks are all improved. (2) The optimal addition of zirconia is 6%, with which the spinel bricks have well alkali resistance performance and creep property of which the final creep rate is -1.46% after creep experiment for 50h.

Abstract: Ti/Al/TiC mixed powders were used as the raw materials for the fabrication of functionally graded material (FGM) by hot pressing sintering. The sample was analyzed by SEM combined with Metallographic microscope and Energy Disperse Spectroscopy,The results show that each layer is composed of TiC and Ti₂AlC, without containing other phases. The size of TiC grains are about 3-6 μm. With TiC content in the layers increasing, Ti₂AlC grains gradually decrease. The lathy Ti₂AlC grains of the FGM have a length of about 10 μm and a width of about 4 μm. The interface of each layer has a good combination with a certain thickness transition layer.Microhardness tester is used to analyse the hardness of material.The results show that the Vickers hardness of every layer increases with TiC content increasing. The thermal shock performance test found that material has good thermal shock performance.

Abstract: The La1-xSrxMnO3 materials have potential applications in thermal control systems of microsatellites. The microstructure of La1-xSrxMnO3 materials is very sensitive to the compound of Sr incorporated into it. In this paper, preparation process of La1-xSrxMnO3 compounds was explored. Ceramic sintering process combined with a conventional solid state reaction method was used to prepare various components of La1-xSrxMnO3。 Annealing temperature, time and doped ratio were controlled in the experiment. X-ray diffraction and Raman spectroscopy were used to analyze phase structure and crystalline. Thermal radiative properties were measured on a Calorimetric Emissometer at 175K～375K. These investigations reveal that microstructure of La1-xSrxMnO3 compounds are affected by Sr2+doping level(x).Thermal emissivity of La0.825Sr0.175MnO3 materials vary widely from 0.68 to 0.37, which can meet requirement of future space thermal design.

Abstract: Using alumina-rich MgAl₂O₄ spinel AR78 and 97 fused magnesite as raw materials, brine as the binder, magnesia alumina spinel bricks close to theoretical composition have been prepared. Then the high temperature creep experiments are carried on. The creep property is analyzed by microstructure and creep curve. The results show that: (1) The magnesia alumina spinel bricks close to theoretical composition prepared have well sintering performance and compact structure.(2) The specimen 1# has the best creep property, of which the final creep rate was -1.45% after creep experiment for 50h. (3) Under high temperature and pressure for a long time in creep experiment, the internal of spinel is further sintered, the pores of the specimens are rearranged.

Abstract: In order to improve the hydration resistance of MgO-Al-C bricks, Fe₂O₃ was chosen as an additive according to thermodynamic calculations. MgO-Al-C refractories were prepared by using Si, Fe₂O₃ or both as additives. The effects of additives on the hydration resistance of specimens were investigated. XRD was conducted to determine the phase composition. The results showed that the hydration resistance of MgO-Al-C bricks would be slightly bettered with addition of only Si. However, it was helpful when Fe₂O₃ was added along with Si. The mechanism is that Fe₂O₃ could decompose to give off oxygen during heating, which could promote the oxidation of Al powder and inhibit the formation of Al₄C₃ and AlN.

Abstract: The effects of addition of silicon powder (1 wt. %) and Na₂CO₃ (converting to additional 0.5%, 1% Na₂O) on the hot modulus of rupture (HMOR) of MgO-Al-C bricks were investigated. MgO-Al-C refractories were prepared by using fused magnesia and graphite flake as main starting materials, and Si, Na₂CO₃ or both as additives. Its phase composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results showed that the HMOR of MgO-Al-C bricks increased slightly with addition of Si powder. However, the HMOR decreased when adding Na₂CO₃ and Si powder together. Moreover, the HMOR deduced with the increase of Na₂CO₃ content. The mechanism is that Al powder reacted to form fibrous Al₄C₃ and AlN, which could improve the HMOR. When silicon was added, β-SiC and M₂S were formed, which could fill the passages and pores. So the densification and strength were improved. The addition of Na₂CO₃ could promote the oxidation of Al powder to form Al₂O₃, and inhibit the formation of Al₄C₃ and AlN. Hence the strength of MgO-Al-C deduced.

Abstract: Effect of waste tire rubber particles (WTRP) and glazed hollow beads as an aggregate on mechanical properties and thermal conductivity of thermal insulting mortar was studied. Several mortar mixtures were prepared by keeping the accumulated volume of both WTRP and glazed hollow beads equal to 1 m³ and by using WTRP contents of 0, 125, 250, 375 and 500 (its accumulated density) kg/m³ respectively. Results indicate that dry bulk densities of the mortars containing WTRP are all less than 900 kg/m³. The mortars or the WTRP have a certain hydrophobic property. The 28 d compressive strengths of the mortars are 1.4~2.0 MPa. And the thermal conductivity values are 0.095~0.139 W/(m.K) increased with the WTRP content increasing. The results suggest that the mortars containing WTRP as a part of an aggregate can be used as thermal insulating material.

Abstract: With the continuous development of social economy, of residents’living consumption structure upgrade, building energy consumption quantity huge, the increasing focus on research and application of building energy-saving technology. Based on low carbon concept, this paper expounds the necessity of building energy-saving, introducing building envelopes structure energy-saving technology, HVAC systems energy saving technology and new energy utilization technology, analyses the application of building energy-saving about the "Bird's Nest" and the "Water Cube", draw the urgency and the reality of building energy saving technology promotion and application.

Abstract: For the problem of square concrete-filled steel tube (CFST) under the action of axial pressure, concrete received local compression and buckling occurred in the application of thin-walled steel pipe.Using built-in spiral reinforcement to strengthen the constraints of thin-walled square steel tube to core concrete. And by using ANSYS program established the built-in spiral reinforcement of thin-walled square steel tube concrete composite column 3 d finite element model, and the results show that spiral reinforcement strengthen the constraint effect, increase the ultimate bearing capacity of the composite columns of square steel tube by 7.41%; And with stiffening rib and rod measures were compared, built-in spiral ripe construction is convenient, easily applied.

Abstract: Polycarboxylate superplasticizer (PCE) was usually sensitive to clay in mortar or concrete. The flow properties of cement pastes and mortars for PCEs with either kaolin or bentonite were studied systematically. The results showed that bentonite had a stronger influence on PCEs performance than kaolin, even no fluidity when bentonite dosage was more than 2%. The adsorption amount of bentonite on PCE was about 5-10 times more than that of kaolin, and PCEs adsorption on clay was proportional to its sensitivity to clay. The influencing mechanism of clay on PCE was analyzed from the structures of kaolin and bentonite and their adsorption characteristics between interlayer. The result of exploring control measure showed that adding the synthesized pre-adsorbent can effectively inhibit the effect of clay on PCE and ensure its workability.