Enrichment of fine mica originating from rock aggregate production and its influence on the mechanical properties of bituminous mixtures

Analyses of mica-bearing, crushed granitoid rocks revealed a significant enrichment of free mica in the fine fraction. Qualitative tests of bituminous mixtures with an increasing content of free mica in the fine fraction suggested a considerable deterioration of the mechanical properties of the asphalt mass. The negative influence of fine mica on the mechanical properties of the asphalt mixtures was most likely caused by the ability of mica to adsorb bitumen and to create zones of weakness. This phenomenon seemed to be linked to a preferred orientation (foliation) of the mica particles that was connected to the compaction of asphalt masses during the construction of the surface course. The threshold content at which the fine mica negatively influenced the quality of the bituminous mixtures was estimated to be 30–35 vol.%.     

不同加载速率和围压作用下沥青混凝土三轴压缩力学特性数值模拟研究

为研究加载机制下路面沥青混凝土的力学特性,利用颗粒流数值模拟软件PFC3D建立满足实际沥青混凝土粒径级配的数值模型,并对其进行三轴压缩试验,分析不同围压及加载速率下沥青混凝土的力学特性.结果表明:同一围压下,随着加载速率的逐渐增大,试样的峰值应力、峰值应变和弹性模量均呈逐渐递增的趋势,以围压0.5 MPa为例,加载速率...     

NL-2型粘结力试验仪

乳化沥青稀浆封层是一种经济可靠的路面处治方法，以先进可靠的配合比设计和试验检测手段为基础，介绍NL－2型粘结力试验仪的工作原理和结构特点，以及对路面乳化沥青稀浆封层混合料粘结程度的测试方法等，有助于我国乳化沥青稀浆封层技术的应用和发展。     

The formation,structure, and properties of the Au–Co alloys produced by severe plastic deformation under pressure

The mechanical alloying of Au–Co mixtures, which are systems with high positive mixing enthalpy, is studied following high-pressure torsion deformation at room and cryogenic temperatures. X-ray diffractometry in synchrotron radiation and scanning microscopy are used to investigate the sequence of structural changes in the course of deforming the mixtures up to the end state of the fcc substitutional solid solution based on gold. The mechanical properties of the alloys are measured both during mixture processing and after mechanical alloying. Microfractographic studies are performed. Factors that facilitate the solubility of Co in Au, namely, increased processing pressure, cobalt concentration in a charge mixture, true strain, and temperature decreased to cryogenic level have been identified.     

水性UV聚氨酯丙烯酸酯/二氧化硅复合材料的制备及涂膜性能

目的 制备光固化水性聚氨酯改性丙烯酸酯/二氧化硅（WPUA/SiO2）复合材料,提高水性光固化聚合物材料的涂膜性能。方法 制备含双键官能化的二氧化硅纳米粒子,将其引入到制备的可光固化聚氨酯改性丙烯酸酯乳液体系中,制备水性UV固化WPUA/SiO2复合乳液,研究复合材料制备方法,分析体系中官能化二氧化硅纳米粒子的分散稳定性及其对涂膜形貌、透光性、硬度等性能的影响。结果 由于WPUA和官能化二氧化硅纳米粒子均含有C==C,所制备的WPUA/SiO2复合材料可以用UV光进行固化,官能化二氧化硅纳米颗粒由于表面存在有机分子链,与水性聚氨酯改性丙烯酸酯相容性提高,使得二氧化硅纳米颗粒掺杂量达到10％（质量分数）时可存储稳定性达30天以上。固化后涂层的透光性和力学性能明显提升,涂层铅笔硬度达到3H,粘附性为1级,抗冲击强度大于50 kg?cm。结论 制备的WPUA/SiO2复合体系具有良好的稳定性,改性纳米粒子的掺杂对水性UV固化聚氨酯改性丙烯酸酯的力学性能有明显改善,且可提高复合涂层的透光性。     

Elastic properties of the main species present in Portland cement pastes

The elastic properties of the most important phases present in cement pastes have been studied by force field atomistic methods. Calculations reproduce the mechanical properties of crystalline species alite, belite and portlandite fairly well. The elastic properties of amorphous calcium–silicate–hydrate (C–S–H) gel are also explained in terms of the commonly used structural models 1.4 nm tobermorite and jennite, once the intrinsic porosity and the silicate chain length are concurrently considered through the appropriate micromechanical models. The findings conclude that bringing the atomic structure into contact with the mechanical properties of C–S–H gel may modify the actual view of the gel.     

Fabrication of Co−Ni−P film with excellent wear and corrosion resistance by electroplating with supercritical CO2 emulsion

To avoid the defects caused by the hydrogen evolution and improve the corrosion and wear properties of the electroplated films in the traditional aqueous bath electrodeposition, a supercritical carbon dioxide (Sc-CO₂) emulsion was proposed to electrodeposite ternary nanocrystalline Co?Ni?P alloy films. Microstructure, corrosive and tribological properties of the Co?Ni?P films were investigated and compared with the ones electroplated by conventional method. The results show that the Co?Ni?P films produced with Sc-CO₂ assisted electrodeposition exhibit a more compact microstructure. The preferred orientation plane of hcp (110) for the Co?Ni?P films produced in conventional aqueous bath is changed to be hcp (100) for the one prepared in emulsified Sc-CO₂ bath. The microhardness, corrosion resistance and tribological properties of the Co?Ni?P films are substantially improved with the assistance of Sc-CO₂ in the electrodeposition bath.     

碳纳米管改性无机-有机水性富锌涂料的制备及其性能

在常见的水性无机硅酸盐富锌涂料中添加适量的硅丙乳液及碳纳米管,制成了无机-有机复合水性富锌涂料。对几种不同配比涂层的主要力学性能、电化学性能、耐盐雾性能及耐空蚀性能进行了测试分析,结果表明当硅丙乳液和碳纳米管分别占基料的20%和1%,颜基比为2:1时,涂料的基料稳定,喷涂粘度适中;同时涂层在保持了无机富锌涂料优异耐腐蚀性能的基础上,其耐空蚀性能也得到了很大提高。     

EXPLORATION OF Nb-BASED ADVANCED INTERMETALLIC MATERIAL

ＥＸＰＬＯＲＡＴＩＯＮＯＦＮｂ－ＢＡＳＥＤＡＤＶＡＮＣＥＤＩＮＴＥＲＭＥＴＡＬＬＩＣＭＡＴＥＲＩＡＬＳＤＭＤＩＭＩＤＵＫ（Ｗｒｉｇｈｔ－Ｌａｂｏｒａｔｏｒｙ，ＭａｔｅｒｉａｌｓＤｉｒｅｃｔｏｒａｔｅ，ＷＬ／ＭＬＬＭ，Ｗｒｉｇｈｔ－ＰａｔｔｅｒｓｏｎＡ...     

铈对硬质合金性能与粘结相结构稳定性的影响

采用动态热模拟技术,研究铈对硬质合金性能与粘结相结构稳定性的影响。发现铈可改善合金性能,其主要作用是抑制粘结相Ｃｏ向六方结构转变,且在长期热循环效应下保持稳定。     

Applications of Rapid Solidification

The attributes of rapid solidification have been sufficiently developed for both crystalline and amorphous materials that commercial products are now available. The constitutional and microstructural advantages to be gained using rapid solidification have been used to develop improved structural alloys form crystalline materials and enhanced mechanical, chemical, electrical and magnetic properties in amorphous alloys. Some predictions are made on which segments of the array of rapidly solidified materials will prove to be of significant commercial value in the future.     

Dynamic modulus of asphalt mixture by ultrasonic direct test

This paper describes the experimental procedure followed for direct determination of dynamic modulus of asphalt mixtures by ultrasonic direct test at a specified temperature. Tests were performed on ten cylindrical samples of dense and porous asphalt mixtures manufactured with dolerite and limestone aggregates. Dynamic moduli obtained by ultrasonic transmission, calculated at a frequency of 65 kHz, were compared with values directly determined by standard dynamic tests applied in Spain at frequencies of 2, 5, 8 and 10 Hz. The obtained results demonstrate that the magnitudes for moduli calculated by ultrasonics are higher than those obtained by standard dynamic tests. It is concluded that for asphalt mixtures tested ultrasonically the increase of moduli magnitude can be associated with an increase in the frequency used but may also be due to the different testing methods. Nevertheless, these values can be used as a reference value for dynamic modulus of asphalt pavements at low strain, being necessary to apply a correction factor to replace the low frequency standard dynamic test, which is more expensive, difficult and time consuming.     

大跨径钢箱梁桥面铺装层下喷锌涂层腐蚀行为

本工作研究大跨径钢箱梁桥面锌涂层腐蚀规律。采用电化学工作站研究粘结层在完好状态、嵌入刻划破损和电化学剥离破损时锌涂层腐蚀阻抗、极化曲线和腐蚀电位变化,用扫描电镜观察界面腐蚀形貌,用X射线衍射仪分析腐蚀产物等腐蚀规律,采用伺服试验机对铺装层体系进行剪切试验。试验结果表明,腐蚀介质通过沥青混凝土铺装层-沥青粘结层-防腐蚀涂层体系腐蚀锌涂层,沥青粘结层嵌入刻划破损下锌涂层腐蚀明显高于粘结层剥离破损。粘结层-锌涂层之间存在界面腐蚀,使沥青混凝土铺装的抗剪切结合力下降50%以上,界面锌涂层腐蚀产物主要有ZnO、Zn_5(CO_3)_2(OH)_6、Zn_5(OH)_8Cl_2H_2O等,锌的腐蚀速度受电荷传递和离子扩散控制,界面锌涂层腐蚀为车载下的桥面沥青混凝土铺装局部位移和开裂创造了条件。     

Vanadium alloys for fusion reactor applications

Fusion reactors will produce a severe operating environment for structural materials. The material should have good mechanical strength and ductility to high temperature, be corrosion resistant to the local environment, have attractive thermophysical properties to accommodate high heat loads, and be resistant to neutron damage. Vanadium alloys are being developed for such applications, and they exhibit desirable properties in many areas. Recent progress in vanadium alloy development indicates good strength and ductility to 700°C, minimal degradation by neutron irradiation, and reduced radioactivity compared with other candidate alloy systems.     

Polypyrrole-bearing conductive composite prepared by an inverted emulsion pathway involving nonionic surfactants

Polypyrrole-rubber composites were prepared in two steps using an inverted emulsion pathway. In the first step, an inverted emulsion was generated by dispersing an aqueous solution of FeCl₃ (as oxidant and dopant) in an organic solution (six different solvents have been employed) of a host polymer (styrene-butadiene-styrene (SBS), styrene-ethylenebutylene-styrene (SES) or styrene-isoprene-styrene (SIS) and nonionic surfactant (six different surfactants have been employed) with stirring. In the second step, a solution of pyrrole in toluene was introduced dropwise in the emulsion generated in the first step and polypyrrole was thus formed rapidly (10–15 min). Methanol was introduced to precipitate the composite after polymerization was completed. The ratio of pyrrole/host polymer, the surfactant and the organic solvent employed in the inverted emulsion, the ratio of aqueous phase/organic phase in the inverted emulsion, the nature of the host polymer and even the organic solvent used to wash the composite are important factors that affect the conductive and mechanical properties of the composites. When a small amount (0.007 g/ml organic phase of the emulsion) of Span 80 and isooctane/toluene (1:1 vol./vol.) were employed as surfactant and solvent for the continuous phase, respectively, of the inverted emulsion and the volume ratio of aqueous phase/organic phase in the inverted emulsion was 0.4, the composites consisting of polypyrrole and SBS washed finally with petroleum ether had good conductivities, as well as good mechanical properties. The conductivities were in the range 2.4-3.5 S/cm with tensile strengths 10.9-7.8 MPa and elongations 166-38% at break point. The morphology of the composites was investigated by scanning electron microscopy (SEM), and their compositions determined by energy-dispersive spectroscopy (EDS) and elemental analyses.     

铜表面透明防蚀封护剂的研究

采用纳米TiO2、缓蚀剂BTA及助剂等对水性丙烯酸 乳液改性，制成铜和铜合金防蚀封护剂.用电化学交流阻抗法(EIS)，紫外吸收光谱法、盐雾实验、耐化学品、耐水性测试和力学性能测试等，研究其性能的结果表明，该封护剂综合性能优异，对铜合金具有较强的保护能力.纳米TiO2的紫外线特性，有效提高了涂层抗紫外光老化能力.      

The effects of induction heating rate on properties of Ni–Al based intermetallic compound layer coated on ductile cast iron by combustion synthesis

Applying brittle intermetallic compound coating on metals can enlarge the range of their use. In this instance, the properties of the coating layer are influenced by the constituent phases of intermetallic compound coating layer.In this study, the mixtures of Ni and Al powder have been reacted at different heating rates in an induction furnace in order to obtain the intermetallic compound coating layer with a single phase structure on a ductile cast iron. The microstructures and mechanical properties of the coating layer are investigated and the effects of heating rate in the induction furnace on the properties of intermetallic compound coating layers are evaluated.It was found that the ignition temperature and the maximum temperature increase significantly with increasing heating rate. It was also found that the coating layer is composed of single phase NiAl corresponding to the initial composition of mixed powder and adhesion qualities with substrate are improved with increasing heating rate.     

Real-Time Debonding Monitoring of Composite Repaired Materials via Electrical, Acoustic, and Thermographic Methods

The electrical properties of composite materials have been thoroughly investigated recently for the detection and monitoring of damage in carbon fiber-reinforced polymers (CFRPs) under mechanical loading. Carbon nanotubes are incorporated in the polymer matrix of CFRPs for the enhancement of their electrical properties. The electrical properties have shown to be sensitive to the damage state of the material and hence their monitoring provides the profile of their structural deterioration. The aim of the paper is the cross-validation and benchmarking of an electrical potential change monitoring (EPCM) technique against acoustic emission (AE) and lock-in thermography (LT). All techniques successfully identified damage and its propagation. Thermography was more efficient in quantifying damage and describing dynamically the debond topology, as it provided full 2D imaging of the debond in real time. EPCM was successful in providing quantitative information on debond propagation and its directionality. AE provided consistent information on damage propagation. All techniques identified three stages in the fatigue life of the interrogated coupons. The representation of the fatigue behavior as a function of life fraction, the correlation of AE data with EPCM and LT data, and most importantly the consistent behavior of all tested coupons allowed for both the direct and indirect cross-correlation of all employed methodologies, which consistently identified all aforementioned fatigue life stages.     

改性硅溶胶-苯丙乳液复合涂层的制备及性能

目的 以硅溶胶、苯丙乳液为主要原材料,制备高性能有机-无机复合涂层,并为其应用提供一定价值的参考.方法 采用KH550、KH560以及KH570等3种硅烷偶联剂依次对硅溶胶进行接枝改性,选用改性效果较好的硅溶胶,制备改性硅溶胶添加量为0％、35％、70％、105％(相对于苯丙乳液的质量百分比)的4种涂层.用傅里叶变换红外光谱仪、马尔文Zeta电位仪以及扫描电子显微镜对硅溶胶的改性效果进行表征,用多功能材料表面性能试验仪等涂层力学测试仪、紫外/可见/近红外分光光度计、扫描电子显微镜分别对4种涂层的力学性能、隔热节能性能及微观形貌进行表征.结果 KH560对碱性硅溶胶的接枝改性效果最优.向苯丙乳液中添加一定量的改性硅溶胶可以显著提升涂层性能.当改性硅溶胶添加量为苯丙乳液质量的70％时,涂层综合性能提升最高,此时涂层太阳光反射比为0.683,近红外反射比为0.624,附着力为3.85 MPa,1000圈磨损后的质量损失率为53％,抗拉强度为5.4 MPa,但断裂伸长率降低较为明显,仅为49.8％.结论 KH560更适合对碱性硅溶胶进行接枝改性.添加KH560改性硅溶胶后,苯丙乳液涂层的力学性能、隔热节能性能得到了显著提升.实际使用时,建议改性硅溶胶添加量为苯丙乳液质量的70％.     

Mechanical behavior of nanocrystalline metals and alloys

Nanocrystalline metals and alloys, with average and range of grain sizes typically smaller than 100 nm, have been the subject of considerable research in recent years. Such interest has been spurred by progress in the processing of materials and by advances in computational materials science. It has also been kindled by the recognition that these materials possess some appealing mechanical properties, such as high strength, increased resistance to tribological and environmentally-assisted damage, increasing strength and/or ductility with increasing strain rate, and potential for enhanced superplastic deformation at lower temperatures and faster strain rates. From a scientific standpoint, advances in nanomechanical probes capable of measuring forces and displacements at resolutions of fractions of a picoNewton and nanometer, respectively, and developments in structural characterization have provided unprecedented opportunities to probe the mechanisms underlying mechanical response. In this paper, we present an overview of the mechanical properties of nanocrystalline metals and alloys with the objective of assessing recent advances in the experimental and computational studies of deformation, damage evolution, fracture and fatigue, and highlighting opportunities for further research.