共查询到20条相似文献,搜索用时 531 毫秒
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本文对比研究了丁苯乳液改性混凝土、钢纤维改性混凝土以及丁苯乳液增强钢纤维混凝土的力学性能和韧性.试验结果表明:丁苯乳液能改善新拌混凝土的工作性能;混凝土的抗压强度随着丁苯乳液掺量的增加而显著降低,但其抗折强度随着丁苯乳液的增加而提高;丁苯乳液与钢纤维复掺,混凝土具有更高的抗折强度、以及弯曲韧性.丁苯乳液在混凝土中交织成膜,提高了界面过渡区的显微硬度;增加了浆体的致密性,增强了钢纤维与混凝土之间的界面粘结强度. 相似文献
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传统水泥混凝土由于存在抗拉强度低、脆性大、凝结硬化较缓慢、干缩量大等缺点,不能够满足当前实际工程对其力学性能的要求.当前,国内外研究者通过矿物添加剂、聚合物、纤维等材料,对普通混凝土进行改性研究,提高其综合性能,并取得了显著效果.论文从以上三个方面系统总结了国内外对混凝土改性研究的成果,全面分析改性混凝土的改性机理及其对混凝土性能的影响,认为改性材料的选择与材料的经济性、试验工艺、改性效果等有关,聚合物乳液和纤维材料是目前研究最为广泛的材料;对混凝土改性应当重视提高改性材料与骨料之间的粘结力及其在混凝土中的均匀分散度;现有聚合物改性机理模型虽然在不断完善,但还不能完全解释可溶性聚合物对混凝土的改性机理;目前具有巨大前景的石墨烯、石墨烯纤维以及纳米碳纤维材料对混凝土的改性性能有待进行进一步研究. 相似文献
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试验研究了不同聚合物胶粉掺量对改性混凝土的抗压强度、抗折强度、劈裂抗拉强度以及折压比和拉压比的影响,探讨了聚合物胶粉改性混凝土的力学性能.结果表明:聚合物胶粉的加入降低了混凝土的抗压、抗折强度,尤其是抗压强度的降低更加明显;当胶粉掺量在4.0% ~8.0%范围内增加时,混凝土的劈裂抗拉强度大幅度提高,且掺量为8.0%时的劈裂抗拉强度最大.同时,聚合物胶粉的加入能显著提高混凝土的折压比和拉压比,改善混凝土的韧性和抗裂性,且其掺量为8.0%时,综合增韧效果最佳. 相似文献
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聚硅氧烷改性苯丙乳液—II共聚改性 总被引:1,自引:0,他引:1
通过聚硅氧烷乳液与苯乙烯丙烯酸酯类单体接枝共聚,制得了具有互穿聚合物网络结构的聚硅氧苯丙复合乳液。本文研究了这种共聚、改性的苯丙橡胶膜的形态结构、力学性能及耐紫外性能。结果表明:共聚改性能有效的控制相分离和聚硅氧烷分子链向膜的表面迁移;橡胶膜的力学强度与乳液共混改性的橡胶膜相比大有提高;聚硅氧烷的改性明显了苯丙橡胶膜的耐紫外线性能。 相似文献
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基于参编的《聚合物水泥加固砂浆》指标要求,采用丙烯酸乳液对加固砂浆进行了改性,并且研究了丙烯酸乳液的加入对加固砂浆凝结时间、力学性能、黏接性能及干缩性能的影响.结果表明:随着乳液掺量的增加,加固砂浆的初凝和终凝时间延长,抗折和抗压强度下降,黏接强度变大,干缩率降低.当乳液掺量为16.2%时,其综合性能较好,初凝和终凝时间分别缩短为120 min和160 min;28 d龄期下的抗压强度达到55.3 MPa,抗折强度达到14.2 MPa,黏接强度达到3.01 MPa,干缩率达到0.08%,均满足正在参编的《聚合物水泥加固砂浆》标准指标.进一步对比观察不同乳液掺量下加固砂浆的扫描电镜图像,从微观的角度印证了上述结论. 相似文献
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《Ceramics International》2020,46(9):13695-13703
Manganese–copper ferrite (MCFO) and dysprosium (Dy)-doped manganese–copper ferrite nanocomposites (Mn0.5Cu0.5DyxFe2−xO4) (x = 0, 0.05, 0.10, and 0.15) were synthesized by sonochemical method. Crystal structure and the structural parameters of the MCFO were analyzed based on the doping concentration of Dy ion. It was observed that the average crystalline size of the synthesized nanocomposite decreases when the concentration of Dy increases. The existing spherical surface morphology of the MCFO and Dy-doped MCFO nanocomposites were obtained through scanning electron microscopy. In the UV spectrum, the pristine MCFO sample showed an absorbance peak at 743 nm whereas the absorbance values of Dy-doped ferrite nanocomposite considerably shifted (blue) toward a lower wavelength (231–222 nm). The dielectric parameters of all ferrite nanocomposites were studied in the frequency range of 100 Hz to 5 MHz. The dielectric spectrum revealed that dielectric constant and loss tangent decreased with increased doping concentration of Dy ion. The saturation magnetization also changed with Dy doping in MCFO. The impact of Dy on manganese–copper ferrite changed the optical, dielectric and magnetic properties of the prepared binary ferrite nanocomposite, which can be used for microwave-absorbing material applications. 相似文献
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E. S. Zainudin S. M. Sapuan K. Abdan M. T. M. Mohamad 《Polymer-Plastics Technology and Engineering》2013,52(1):97-101
Mechanical strengths of a banana pseudo-stem (BPS) fiber and unplasticized polyvinyl chloride (UPVC) composite were evaluated to assess the possibility of using it as a new material in engineering applications. Samples were fabricated by the compression molding process with reference to the effect of filler loading. The samples were submitted to mechanical tests to measure tensile, flexural, and impact properties of the composites. The nature of adhesion between the matrix and the reinforcement and information relating the structure of mechanical properties can be obtained by scanning electron microscopy (SEM) assessment of the composite fracture surface. The mechanical properties show that the composites did not have good adhesion between filler and matrix; on the other hand, the filler insertion improved the flexural modulus and the material rigidity. 相似文献
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核壳纳米粒子作为复合纳米粒子一个重要的分支,由于其光、磁和催化等方面的优异性能,近年来引起了人们广泛的关注.本文主要介绍了核壳纳米粒子的制备方法及诸多性能,并对核壳纳米粒子的发展进行了展望. 相似文献
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王丽 《合成材料老化与应用》2014,(4):15-17
分别以聚四氢呋喃醚二醇(PTMEG)、聚氧化丙烯二醇(PPG-1000)为软段,以二苯基甲烷二异氰酸酯(MDI-50、MDI-100LL),以及扩链剂1,4-丁二醇(BDO)、三羟甲基丙烷(TMP)为硬段,采用预聚体法制备了聚氨酯弹性体。并系统研究了聚氨酯体系中各组分的种类对材料机械性能和阻尼性能的影响。 相似文献
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《Ceramics International》2020,46(2):1974-1981
Nowadays, complicated preparation processes and harsh sintering conditions wave transparent ceramics limit its further development. To solve this problem, we explore a promising precursor by adopting a polymerization-pyrolysis method to prepare porous Si–Al–O–B ceramics at a mild sintering condition (1000 °C). The porous Si–Al–O–B ceramics exhibits enhanced wave transparency at 10–16 GHz with a low dielectric constant (<3), a low loss angle tangent value (<0.01), and simultaneously, a relative high flexible strength of 82 MPa. According to the results of the XRD and FTIR analysis, porous Al4B2O9 crystallization dispersed in the amorphous SiO2 matrix constructs the main phases of the products. The changes of Al and B elements are confirmed to have an effect on the phase compositions and micro structure of the composite ceramics, which obviously affect the mechanical and dielectric properties of the derived ceramics. The as-prepared porous Si–Al–O–B ceramics could be a potential candidate for next generation electronic window materials due to its low dielectric constant and loss angle tangent value, as well as high flexible strength. 相似文献
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Effects of support and additive on oxidation state and activity of Pt catalyst in propane combustion 总被引:1,自引:0,他引:1
The effects of support and additive on the oxidation state and catalytic activity of Pt catalyst in the low temperature propane combustion were systematically investigated on Pt/MgO, Pt/Al2O3 and Pt/SiO2–Al2O3. The catalytic activity varied much with both support materials and additives. The catalyst on the more acidic support showed higher activity, and the catalytic activity on every support materials increased as the electronegativity of additives increased, while some additives decreased the activity. The oxidation state of platinum, estimated by white line intensity of Pt LIII-edge XANES spectrum, also varied with the support and additives, and additives with higher electronegativity greatly prevented the platinum from its oxidation under oxidising atmosphere. Among almost all the catalysts with various supports and various additives, a clear relationship was observed between the oxidation state of platinum and the catalytic activity; the more metallic platinum showed higher activity. Thus, it was concluded that the total electrophilic/electrophobic property derived from those of the support and additive controls the oxidation state of platinum, which intensively affects the catalytic activity; i.e. higher electrophilic property provides less oxidised platinum, resulting in high catalytic activity. The mechanism of this effect was also discussed on the basis of thermochemical data, and it was proposed that the electrophobic materials promote the noble metal oxidation since the noble metal oxo-anion such as PtOδ− is more stabilised with electrophobic cation. 相似文献