Effect of carbon fibre on properties of TiB2/C composite cathode coating for aluminum electrolysis

The tensile strength, compressive strength and electrical resistivity of TiB₂/C composite cathode coating were measured with a hydraulic pressure universal test machine and an electrical resistivity test device, and the effects of carbon fibre content and carbon fibre length on tensile strength, compressive strength and electrical resistivity were investigated. The results show that the tensile strength of coating increases at the beginning and then reduces with the increase of carbon fibre content when the carbon fibre (length of 3 mm) content ranges from 0 to 4.0%; at the carbon fibre content of 1.5%, the tensile strength of coating reaches the maximum, 25.6 MPa. For the coating with carbon fibre content of 1.5%, the carbon fibre length has a great influence on tensile strength and compressive strength of coating; when the carbon fibre length is 6 mm, the tensile strength and compressive strength of coating reach the maximum, 27.6 MPa and 39.2 MPa, respectively. The electrical resistivity of coating reduces with the rise of temperature and the length of carbon fibre, and the influence of carbon fibre length on electrical resistivity of coating at low temperature (30–200 °C) is more obvious than that at high temperature (960 °C). Foundation item: Project(2005CB623703) supported by the Major State Basic Research Development Program of China     

温度对聚丙烯纤维砂浆及测强曲线的影响

目的研究温度对聚丙烯纤维砂浆及测强曲线的影响,为以后工程防火加固选用砂胶比提供依据,从而达到降低成本的目的．方法通过测试不同胶砂质量比的聚丙烯纤维砂浆的初始流动度、终凝时间、抗压强度和抗折强度,研究不同温度下不同碳纤维掺量的聚丙烯纤维砂浆的耐高温性能．结果当碳纤维体积分数为0．3％、胶砂质量比为1．5时,聚丙烯纤维砂浆流动度大于320mm,终凝时间60min左右,28d抗压强度大于80MPa,1000℃高温燃烧后,残余50％以上强度,各龄期的测强曲线与实测强度有较好的拟合关系．结论采用普通硅酸盐水泥、铝酸盐水泥、石膏三元体系,通过添加碳纤维、偏高岭土掺合料及多种化学添加剂,可满足工程实际需要,并且具有良好的经济性．     

温度和湿态处理对酚醛/玻纤复合材料抗拉强度的影响

为确定新研制的酚醛/玻纤复合材料的抗拉强度是否满足设计及使用要求,研究了酚醛/玻纤复合材料在-55℃、20℃干态/湿态、71℃干态/湿态和93℃干态/湿态的经向拉伸性能,讨论了不同温度以及湿态处理对酚醛/玻纤复合材料拉伸强度的影响规律,利用扫描电子显微镜(SEM)考察了试件断口的显微结构和断裂形态.研究结果表明:随着温度的升高,酚醛/玻纤层合板的抗拉强度总体呈现下降的趋势.干态条件下,20℃状态的抗拉强度比-55℃状态下的降低了129.9MPa,即降低了24.26%;71℃状态下的抗拉强度比20℃状态下降低了50MPa,即降低了12.33%;93℃状态下的抗拉强度比71℃状态下降低了62MPa,即降低了20.33%.湿态条件下,71℃状态下的抗拉强度比20℃状态下降低了72.3MPa,即降低了29.19%;93℃状态下的抗拉强度比71℃状态下降低了72MPa,即降低了26.57%.在同一温度下,湿态状态下试样的抗拉强度比干态状态下的明显降低.20℃状态下,湿态比干态降低了69.67MPa,即降低了17.18%;71℃状态下,湿态比干态降低了117.7MPa,即降低了33.11%;93℃状态下,湿态比干态降低了111.6MPa,即降低了39.41%.     

水泥-粉煤灰复合胶凝体系的早期水化性能

为了研究粉煤灰掺量和温度对水泥水化的影响,测试了粉煤灰掺量0～60%的水泥-粉煤灰水化体系,在温度20、24和28 ℃下的凝结时间及2d内的电阻率发展及抗压强度,发现凝结时间与电阻率发展速率曲线的第一峰值点对应时间遵循线性关系. 在同一温度下,2d的抗压强度和电阻率值显示出良好的正相关线性关系——温度越高,斜率越小,表明电阻率比强度对温度变化更加敏感. 扫描电镜结果论证了粉煤灰在2d内尚未参与水化反应,主要起填充和稀释作用. 因此,可借助电测法估算和预测变温条件下水泥-粉煤灰水化体系的抗压强度及凝结时间.     

Preparation of eco-environmental protection bricks from lake sludge

Eco-environmental protection hollow bricks manufactured from lake sludge collected from North Lake in Wuhan of China were investigated. At first, the recipes of round sam- pies（diameter in 5 cm and thickness in 1 cm） prepared by pressing molding under a pressure of 8 MPa and firing system were optimized, and properties such as bending strength, compressive strength, total shrinkage rate, water adsorption rate, apparent porosity and bulk density of the fired samples were tested. The experimental results showed that water adsorption rate and apparent porosity decreased, while bulk density increased with firing temperature increasing. Addition of additive can result in the improvement of strength of fired samples. At the same time, fly ash and additive may also broaden the firing temperature range and reduce firing temperature. Toxic characteristic leaching procedure （TLCP） tests of samples also show that the metal leaching level is low. The conditions for manufacturing good quality sample include 80% sludge with 10% additive and 10% flyash fired at 1000 ℃ for 60 min. Bending strength and compressive strength of samples prepared under the conditions are 24.64 MPa, 131.95 MPa, respectively,which are far beyond the requirements of clay solid bricks of CNS. Finally, according to the optimized recipe,the eco-environmental protection hollow bricks with the sizes of 40 mm × 38 mm ×25 mm were made and tested by extrusion molding. Compared with the Chinese National Standards （CNS： GB 13545-2003）, compressive strength, water adsorption and bulk denstiy of the hollow bricks are 11.55 MPa ,14.5% and 986 kg/m^3 when they were fired at 1040 ℃, which are far beyond the require of of CNS. Especially, its water adsorption arrives to standard of high-class products（16.0%） and compressive strength is above the hightest class（MU 10.0）.     

Early age compressive strength of pastes by electrical resistivity method and maturity method

The compressive strength development of Portland cement pastes was investigated by the electrical resistivity method and the maturity method. The experiments were carried out on the cement pastes with different water-cement ratios at different curing temperatures. The results show that the application of the maturity method has limitation to obtain the strength. It is found that both of the compressive strength and the electrical resistivity follow hyperbolic trend for all the mixes. The hyperbolic equation of each mix is obtained to estimate the ultimate resistivity value which can probably be reached. The relationship between electrical resistivity and compressive strength of the cement pastes is established based on the test results and interpreted by the empirical Archie equation and a strength-porosity equation. The relationship between the electrical resistivity after temperature correction and the compressive strength was linear and independent of curing temperature and water-cement ratio.     

过共品铸造Al-Si—Cu—Mg—Fe合金组织性能研究

通过正交试验和单因素试验,考察了Cu、Mg、Zn、Ni和Fe对Al—18Si过共晶铝硅合金室温及高温（350℃）力学性能的影响规律,利用光学金相显微镜（OM）、扫描电镜（SEM）、能谱分析仪（EDX）对合金中富Cu相、富Fe相的组织组成进行了分析．结果表明：Cu、Mg是提高AI-18Si过共晶铝硅舍金室温及高温强度的主要因素;Zn含量增加明显降低合金350℃时的高温强度,改善合金的室温和高温延伸率;Fe降低合金的室温强度,显著提高合金的高温强度;当Cr：Fe=0．35：1,Mn：Cr=2：1,含铁0．8％～1．2％时,Al-18Si-4．0Cu-0．7Mg-0．2Zn-1.0Ni-（0．8～1．2）Fe合金力学性能σb（25℃））310MPa,延伸率受（25℃）≥0．75%,σb（350℃）〉130MPa,延伸率δs（35℃）〉1．5％;合金中富铜相主要以块状Al。Cu相和白灰色花卉状A15Si。cu2Mg8相存在,富铁相主要以三叶草状、树枝状和棒状Al5Si（Cr,Mn,Fe）相存在．     

再生粗骨料最大粒径对再生混凝土强度影响试验研究

为了研究再生粗骨料最大粒径对再生混凝土弯拉强度、抗压强度及折压比的影响程度，采用相同配合比下最大粒径为10、15、25和31 mm的再生粗骨料制备了4组再生混凝土棱柱体试件（100 mm×100 mm×400 mm）和4组立方体试件（100 mm×100 mm×100 mm），并通过试验获得了各组再生混凝土试块的弯拉强度和抗压强度。试验结果表明：相同水胶比下，再生混凝土弯拉强度及折压比均随再生粗骨料最大粒径的增大而减小，而抗压强度随再生粗骨料最大粒径的增大呈现出先增大而后减小的趋势。     

磷石膏/聚丙烯复合材料制备

为了将磷石膏资源化利用,将40℃下烘干处理的磷石膏与聚丙烯颗粒混合后,再添加少量液体石蜡,经过热压成型制备了磷石膏/聚丙烯复合材料.在所制备复合材料中磷石膏至少占50%以上,增大了磷石膏的消耗量;并且在材料制备工艺中磷石膏预处理方法简单易行,增加了整个制备工艺的可行性.结果表明,磷石膏/聚丙烯复合材料密度随原料中磷石膏掺量增加而增大,磷石膏掺量为50%时,视密度每立方厘米1.089克;磷石膏掺量为80%时,视密度每立方厘米1.405克.磷石膏/聚丙烯复合材料的弯曲强度随着磷石膏掺量增加而增大,磷石膏掺量为80%时弯曲强度可达14.3MPa.但所制备磷石膏/聚丙烯复合材料样品的脆性较大,拉伸强度较低,与磷石膏的掺量无明显的相关性,磷石膏掺量为70%时拉伸强度1.7MPa,适用于要求塑性变形小的场合.所制备复合材料还有另一显著特点是耐水性很好,无论原料配比如何其软化系数均在1.0以上,从而克服了一般石膏制品耐水性差的缺点.最佳成型制度为成型温度160℃,成型压力15MPa.     

高强石膏的制备工艺研究

以天然石膏为原料采用加压水热法制备高强石膏,考察了水热温度、水热时间、膏水质量比和干燥温度对高强石膏力学性能的影响. 利用X射线衍射对不同条件下制备得到的高强石膏进行物相和结晶度分析,得出了天然石膏制备高强石膏最佳工艺. 结果表明:在水热温度为120℃~150℃时,高强石膏抗压强度随着水热温度的升高而减小;在水热温度120℃条件下,膏水质量比的增加使高强石膏抗压强度呈先增加后减小的变化趋势;水热时间、干燥温度对高强石膏的抗压强度影响较小;水热温度120℃、水热时间1h、膏水质量比50%、干燥温度110℃的条件下制备出的高强石膏抗压强度达到42.41MPa,符合高强石膏JC/T 2038-2010 强度标准.     

聚丙烯纤维增强混凝土拉压比试验

针对聚丙烯纤维对混凝土强度和拉压比影响的问题,采用标准试验方法,对不同纤维掺量和不同纤维长度的混凝土进行立方体抗压强度试验和劈裂抗拉强度试验.结果表明,聚丙烯纤维混凝土立方体抗压强度和劈裂抗拉强度的预测模型与试验结果吻合程度较高;聚丙烯纤维混凝土拉压比在纤维掺量为0~0.1%之间递增,在纤维掺量为0.1%~0.25%之间递减;6 mm聚丙烯纤维混凝土拉压比与基准混凝土拉压比相比略有下降,12 mm聚丙烯纤维混凝土拉压比比基准混凝土提高了5.5%,聚丙烯纤维可以显著改善混凝土脆性破坏形态,提高混凝土韧性.     

梯度多孔镁的制备及压缩性能研究

以镁粉和造孔剂碳酸氢铵为主要原料,采用粉末冶金技术制备梯度多孔镁。研究了造孔剂梯度分布和烧结温度对梯度多孔镁孔隙特性、烧结收缩行为以及压缩性能的影响。研究结果表明,随着梯度结构中间层造孔剂含量的增加,梯度多孔镁样品的平均孔隙度升高,烧结收缩率、抗压强度以及杨氏模量均降低。此外,随着烧结温度的升高,梯度多孔镁样品的平均孔隙度降低,烧结收缩率、抗压强度和杨氏模量均增加。造孔剂分布为质量分数5％15％的多孔镁样品经620＂C烧结2h后,平均孔隙度为27．3％,烧结收缩率为11．7％,抗压强度为24．5MPa,杨氏模量为1．83GPa．     

铸态硅酸铝短纤维／ZL109复合材料性能的实验研究

比较了铸态硅酸铝短纤维／ＺＬ１０９复合材料与ＺＬ１０９合金的机械性能,磨损性能及摩擦性能．结果表明,由于硅酸铝短纤维的加入,使抗拉强度提高４５％到１倍以上,抗压强度提高５０％到１倍以上,磨损性能提高,摩擦系数下降,且随着纤维含量的增加,复合材料的性能也随着提高．     

耐热铸钢GX12的组织与力学性能分析

对耐热铸钢GX12的组织性能进行分析研究,为该材料的推广和应用提供一些基础参数。文中对耐热铸钢C-X12进行热处理、常温拉伸和高温托伸试验,常温下GX12钢的抗拉强度807MPa,在550℃、600℃、650℃、700℃下GX12钢抗托强度分别为565MPa、505MPa、410MPa、315MPa,研究结果表明：经正火＋高温回火获得的组织为吲火板条马氏体组织;通过与不锈钢（ZG0Cr13Ni4Mo）和碳素钢（ZG20MnSi）的对比,GX12耐热铸钢具有良好的高温力学性能,对高温断口扫描分析,GX12钢在高温下的断裂方式为韧性断裂,随温度升高其塑性提高。     

钛酸钾晶须改性偏高岭土基多孔地质聚合物的制备与性能

为提高多孔地质聚合物的力学强度和隔热性能,分别以双氧水（H2O2）和十二烷基硫酸钠（SDS）为发泡剂和稳泡剂,采用化学发泡法制备了由钛酸钾晶须改性的偏高岭土基多孔地质聚合物材料,对其进行了微观结构表征及性能测试。结果表明,当发泡剂和稳泡剂质量分数分别为2.0%和1.5%时,孔结构分布均匀,总孔隙率最高可达51.6%,平均孔径为0.87 mm,其抗压强度为3.63 MPa;随着钛酸钾晶须质量分数从0.0%增至10.0%时,其最高抗压强度可达4.11 MPa。在钛酸钾晶须质量分数为20%时,其最低导热系数可达0.048 W/（m?K）,相比于空白样,抗压强度提高了13.22%,导热系数降低了80.80%。钛酸钾晶须的引入可以明显提高多孔地质聚合物的抗压强度和隔热性能。     

转晶剂对脱硫石膏制备α-半水石膏形貌及强度的影响

目的探讨脱硫石膏浆体制备α-半水石膏时转晶剂对其形貌及强度的影响.方法采用高温蒸压法,在升温时间为75 m in、蒸压温度为120℃的条件下水热处理掺有转晶剂的脱硫石膏浆体制得α-半水石膏晶体,采用体视显微镜观测晶体的形貌特征、wΑ-Y300电子液压机测试抗压强度.结果脱硫石膏浆体采用单一转晶剂质量分数0.075%～1%硫酸铝钾效果较好,制得α-半水石膏晶体呈长柱状,抗压强度16.8 MPa;复合转晶剂硫酸铝钾掺量1.8%左右,柠檬酸钠掺量0.08%左右时效果最佳,α-半水石膏晶体呈短柱状,抗压强度30.2 MPa.结论单一转晶剂对α-半水石膏晶体抗压强度的影响并不显著,其中硫酸铝钾效果较为明显,而复合转晶剂对抗压强度提高影响显著,硫酸铝钾与柠檬酸钠作用下抗压强度最高.     

Mechanical Properties of Phenolic-Resin Composites Reinforced with CF/BF Interlayer Hybrid Fibers

Phenolic-resin composites reinforced with carbon fiber (CF) and basalt fiber (BF) interlayer hybrid fibers plain fabric were fabricated. The tensile strength, compressive strength and interlaminar shear strength of the prepared composites were studied. The results indicated that hybrid fibers reinforced composites possessed the advantages of both CF and BF. When resin content was 35% by volume fraction, the comprehensive mechanical performance of BF/CF reinforced phenolic resin composites reached the optimal values with the warp and weft direction tensile strength, compressive strength and interlayer shear strength being 252 MPa and 487 MPa, 105 MPa and 129 MPa, 21 MPa and 20 MPa, respectively. The scanning electron microscope (SEM) observations showed that the BF/CF hybrid fibers reinforced composites had better interfacial adhesion.     

Performance of RAP in the system of cold inplace recycling of asphalt pavement

The property of reclaimed asphalt pavement(RAP) mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials. It showed that if there was no soil in RAP, the unconfined compressive strength was only from 0.18 MPa to 1.07 MPa even if adding cement was from 2% to 6%, and RAP samples collapsed during conserving in water. The optimum water content rose from 6.5% to 11% with the declining of A/S from S=0 to A/S=1/5. Five RAP samples all got the maximum compressive strength when A/S=5/5, and the maximum compressive strength of the samples adding 6% cement was 3.17 MPa. It showed that the capacity of RAP was not only affected by A/S, but also by the content of cement. The dynamic modulus of RAP will increase with the rise of loading frequency and decrease with the temperature rising. SEM test showed that C-S-H interlacing formed the netted structure, and it enwrapped the aggregate and improved the strength of RAP.     

刺槐豆胶改良黏土强度抗压抗拉力学特性试验研究

为了研究刺槐豆胶改良黏土强度的效果,对不同养护龄期、刺槐豆胶掺量的改良黏土分别进行无侧限抗压强度试验以及抗拉试验研究。结果表明:刺槐豆胶的掺入可以显著改善黏土的抗压和抗拉性能。当养护龄期一定时,随着刺槐豆胶掺量的增加,改良黏土的抗压和抗拉强度均呈增长趋势,通过对比可知,刺槐豆胶的最优掺量为2%,试样的抗压和抗拉强度的最大值分别提升至425.74及234.61 kPa,与素土相比均提高约1.8倍;当刺槐豆胶掺量一定时,养护龄期对改良黏土的抗压、抗拉强度也有一定的影响。在刺槐豆胶掺量相同的条件下,养护龄期为7 d时,试样抗压、抗拉强度提升量最大,最大提升量分别为68.12 和34.39 kPa。刺槐豆胶在土体表层形成一层胶质薄膜,并利用自身延展性填充土颗粒间孔隙,改善了土体的粒间结构,增强土体的稳定性,从而提升黏土的强度特性。随着养护龄期的增加,胶质薄膜逐渐收缩,使土体颗粒排列更加紧密,进而提高改良黏土体的无侧限抗压强度及抗拉强度。     

聚丙烯纤维超高强石渣混凝土的力学性能研究

低碳聚丙烯纤维超高强石渣混凝土是利用地方原材料自主研发的强度高达134．9MPa、水泥消耗量低至350kgm-3且具有优异抗火性能的新型环境友好型混凝土。文章进行了11组立方体试件和8组棱柱体试件的抗压试验、9组劈拉试验和8组抗折试验,初步研究了聚丙烯纤维超高强石渣混凝土的力学性能。试验结果表明,在试验参数范围内,聚丙烯纤维超高强石渣混凝土与超高强石渣混凝土的力学特性有其相似之处,也有其自身的特点：在受压变形过程中,泊桑比几乎保持不变,由于聚丙烯纤维的阻裂效应,泊桑比小于超高强石渣混凝土,为0．244;拉压比在1／10．3—1／17．8之间;折压比为1／9．9—1／15．5;变形模量与超高强石渣混凝土相近,在14461MPa-16339MPa之间,小于超高强混凝土数值。