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81.
Effect of uniaxial compression on the nucleation of micro-damage in cement mortar under sulfate attack is investigated.Shape and size of micro-voids in cement mortar is detected using Micro Computed Tomography techniques.The formation of delayed ettringite crystal is analyzed using scanning electron microscope and energy disperse spectrum methods.Deformation of micro-voids and the distribution of stress at the surface of a micro-void are calculated.It is found that the nucleation of micro-cracks is caused by the tensile stress at the voids’ surface,and such damage nucleation will be speeded up by the remote uniaxial compressive load. 相似文献
82.
采用粉末冶金方法(机械合金化+真空热压烧结)制备了不同SrCO_3和Ag含量的NiCrW-Al_2O_3-SrCO_3-Ag金属陶瓷复合材料,利用UMT-3考察复合材料在室温至1000℃条件下的摩擦磨损性能,利用SEM、EDS、XRD等表征分析其显微组织、物相组成及其磨损机理.结果表明:热压烧结过程中,SrCO_3高温分解,并与Ti_3SiC_2反应生成SrAl_4O_7,同时生成了Cr_2O_3和NiCr_2O_4等新相.分别添加质量分数10%SrCO_3和Ag的复合材料在宽温域内的摩擦磨损性能最优,归因于在中高温阶段复合材料摩擦表面发生摩擦化学反应生成了SrCrO_4和NiO等润滑相,与复合材料中的Ag、NiCr_2O_4等润滑相形成协同润滑,使得复合材料在400~1000℃宽温域范围内具有优异的摩擦磨损性能. 相似文献
83.
V. I. Yakerson G. I. Frankfurt E. A. Boevskaya A. L. Lapidus E. Z. Golosman 《Russian Chemical Bulletin》1992,41(1):35-40
Using x-ray phase analysis, DTA, DTG, and temperature-programmed reduction, we have studied the phase composition and formation of cobalt-copper cement catalysts obtained by chemical mixing of hydroxocarbonates of cobalt (CoHC) and copper (CuHC) with the aluminocalcium cement talyum, consisting of CaAl2O4 and CaAl4O7, in an aqueous ammonia medium. We have shown that when the components are mixed, exchange reactions occur with development of new phases of cobalt and copper hydroxoaluminates, calcite, gibbsite, Cu(OH)2, CuO. We found that CaAl2O4 is more reactive than CaAl4O7. We have obtained data on the change in the phase composition upon thermolysis and reduction in H2.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 48–54, January, 1992. 相似文献
84.
Three novel adhesive oligomers having carboxylic acid and methacrylate groups were synthesized, characterized and used to formulate composite bone cements with newly synthesized zinc-calcium-silicate phosphate. The optimal formulation was determined based on types of oligomer, oligomer/diluent ratio, initiator concentration, and filler level using compressive strength (CS) and curing time (CT) as screening tools. Shrinkage, exotherm and aging of the formed composite cements were also evaluated. Results show that the experimental cement was 186% higher in CS, 16% higher in diametral tensile strength, similar in flexural strength, 56% less in exotherm and 64% less in shrinkage, as compared to conventional polymethylmethacrylate cement. The optimal concentrations for initiators were found to be 1.5% (by weight) for both benzoyl peroxide and N,N′-dimethyl-p-toluidine. With increasing initiator concentration, diluent content and zinc oxide content in the cement formulation, CS of the cement increased but curing time decreased. Shrinkage and exotherm of the cement decreased with increasing filler level. CS was not proportional to an increase of filler level and CT increased with an increase of filler level. During aging, the cement showed an increase of strength over 24 h and then no change for over nine months. It appears that this novel cement may be a potential candidate for orthopedic restoration if its biological performance is good and the formulation is optimized. 相似文献
85.
水泥砂浆在主动围压下的动态力学性能 总被引:1,自引:0,他引:1
水泥砂浆等脆性材料的力学性能与所受围压的大小密切相关。为了研究水泥砂浆在围压下的动态力学性能,研制了适于分立式Hopkinson压杆加载的主动围压装置,最大预加载主动围压大于30 MPa。实验得到了水泥砂浆在不同围压、不同应变率下的轴向应力应变曲线,发现材料在围压作用下抗压强度和韧性大大提高并且整体进入了伪塑性,而材料的应变率效应也是显著的。 相似文献
86.
电感耦合等离子体原子发射光谱(ICP-AES)法与内标法的结合扩展了ICP-AES的分析范围。采用氢氧化钠熔融样品,ICP-AES-内标法测定各类水泥标准物质样品中SiO2、Al2O3、TFe2O3、MgO、TiO2等氧化物的含量。实验结果表明,标准物质测定值与标准值吻合,6次平行样品测定相对标准偏差小于1.4%。方法一次熔样,纵向测定主常量元素,操作简单,快速,准确,为水泥标准物质的研制提供了另一种定值方式。 相似文献
87.
AbstractA new series of poly (AA-co-β-CD-A-co-TPEG) (PACDs) copolymers were prepared by the copolymerization of a novel monovinyl β-cyclodextrin monomer (β-CD-A), acrylic acid and isoprenyl oxy polyethylene glycol (TPEG-2400), which could be used as superplasticizers and shown excellent dispersion ability. Therefore, this work mainly investigated the adsorption behavior, dispersing properties as well as hydration behavior of cement pastes. Optical microscopy was employed to describe dispersing performance. X-ray diffraction (XRD) and TGA/DTG were utilized to account for the cement hydration process. We found that the PACDs with β-CD-A exhibited outstanding dispersion ability. In addition, the performances of the PACDs were monitored by evaluating the setting time and fluidity of the cement paste. The results clearly shown that the setting time was longer and slump loss was smaller than that of PACD0 that without β-CD-A. Therefore, PACDs with the proper content of β-CD pendants had excellent performances due to the steric hindrance of the CD moieties. 相似文献
88.
Gregory B. Kharas Gilbert Villaseñor Celeste A. Diener Matthew Baugh Kristen McColough Sarah Mikach 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):855-863
Unsaturated amorphous copolyesters of varied composition were prepared by transesterification copolymerization of diethyl fumarate, and two diols, 1,2‐propanediol and 2‐methyl‐1,3‐propanediol. The copolyesters were characterized by IR, 1H‐ and 13C‐NMR, GPC, DSC, and TGA. The glass transition is changing with composition from 0°C to 19°C as the content of 1,2‐propanediol residue in the copolyester increases. The copolyester structure and composition have an impact on the compressive strength and hydrolytic stability of the composites prepared by crosslinking the fumarate double bonds with N‐vinyl pyrrolidone in the presence of inorganic filler, calcium sulfate dihydrate, with the addition of a radical initiator, benzoyl peroxide, at ambient temperatures. 相似文献
89.
90.
The interaction between styrene-butadiene rubber (SBR) film and the ions from C2S and C3S hydration of Portland cement mortar composites has been evaluated by Fourier Transform Infrared Spectroscopy (FTIR), and the morphology of the composites characterized with scanning electron microscopy (SEM). The specimen used was cured for 28 days. FTIR spectrum supports the interaction of SBR with cement in the composite. Compressive strength, bulk density and water absorption properties of the cured composites were tested. Addition of SBR latex in Portland cement mortar increases the compressive strength and decreases the water absorption. Bulk density study revels interface formation in the composite. The role of the interface in relation to compressive strength of the composite has been discussed. A simple Matrix System model is shown to account composition dependence of bulk density. 相似文献