Strength degradation of polymer concrete in acidic environments

This paper presents an assessment of the chemical resistance of eight different compositions of polymeric mortars using four different concentrations of filler, fly ash, and two types of unsaturated polyester resins, namely isophtalic polyester and orthophtalic polyester. The samples were exposed to seven different acid environments that represent those that often account for corrosive processes in industrial environments. None of the compositions in the study showed evidence of physical surface changes nor weight loss. There was a decrease in the flexural strength of the samples exposed to corrosive agents and this effect was more pronounced in the compositions with lower filler concentrations. However, even in those samples, the remaining flexural strength values remained far higher than those found in mortars prepared with Portland cement, an inorganic binder. Statistical analysis showed that the type of resin, the concentration of filler and the type of corrosive solution used have a significant effect on the chemical resistance of the polymeric mortars investigated in this study. SEM analyses also showed that the chemical attack occurred in the polymer matrix–aggregate interface.     

Flexible ceramic-reinforced polyurethane composite coatings on synthetic fibres: Process of continuous liquid film coating and its influence on the coating thickness

A concept for the realisation of composite layers on the surface of synthetic fibres by continuous liquid film coating of spread roving or monofilaments with a slurry containing ceramic particles and a polymeric binder is successfully demonstrated. Polyamide 6 monofilaments were coated with alumina particles and a polyurethane elastomer based binder system to achieve higher abrasion resistance. Under frictional load, the coating is abraded in small units consisting of some particles and the surrounding polyurethane matrix, which predetermines it to be used as sacrificial layer. The slurries showed shear thinning behaviour. Increasing the content of the rheological agent (carboxymethylcellulose [CMC]) led to an exponential increase of the viscosity, which therefore can be tailored by varying the CMC content. An increase of fibre radius, slurry viscosity or withdrawal speed led to an increase of the coating thickness, which is in accordance to published results of Newtonian or non-Newtonian coating fluids.     

Non-Temperature-Sensitive and Large Low-Field Magnetoresistance in Bonded Perovskite Manganite Composites

Perovskite manganite composites containing polymer binder (epoxy resin) and additional metal (Sn) were prepared using a novel bonded method. The magnetoresistance (MR) for the sample containing 4 % polymer binder and 10 % metal was as high as 20 % and nonsensitive to temperature in the temperature range of 50–300 K under applied field of 3 kOe. The nontemperature-sensitive and large MR could be ascribed to the contribution of polymer and metal, respectively. When temperature was higher than 300 K, intrinsic colossal magnetoresistance effect was observed.     

高能复合固体推进剂的研究进展

高能化始终是复合固体推进剂的研究热点.介绍了当今复合固体推进剂高能化研究进程中国内外在氧化剂、金属燃烧剂和含能粘合剂体系方面的主要研究成果.借助先进的技术途径改善氧化剂和金属燃烧剂的燃烧性能是目前国内复合固体推进剂的研究重点.超高能量密度材料(氮原子簇化合物和多异氰基立方烷类化合物)和贮氢类金属燃烧剂三氢化铝以及一些新型的含能粘合剂等新型含能材料的出现,为下一代高能复合固体推进剂的研究指明了方向.     

Influence of rolling direction on strength and ductility of aluminium and aluminium alloys produced by accumulative roll bonding

Sheets from commercial purity aluminium AA1050 and aluminium alloy AA6016 were processed by accumulative roll bonding to obtain an ultrafine-grained microstructure. The accumulative roll bonded samples showed a significant increase in specific strength paired with high ductility. Despite a strongly elongated grain structure, tensile testing of samples oriented 45° to the rolling direction revealed considerable improvement in elongation to failure compared to the samples oriented parallel to the rolling direction. From hydraulic bulge tests, it was observed that the accumulative roll bonded samples reached higher burst pressures and slightly lower equivalent strains in comparison to the as-received conventionally grain-sized samples. This behaviour reflects the extraordinary mechanical properties of the ultrafine-grained materials and indicates promising metal sheet formability.     

Hochreflektierende Beschichtungen auf Kunststoffoptiken

Metallized polymer substrates offering highest reflectance are not yet state of the art. Coating organic substrate materials is still a task that is connected with multiple problems. Insufficient adhesion of coatings on polymer substrates represents one of the main difficulties. We could show by experiment that aluminium and silver layers indicate good coating adhesion on many different polymers if they are deposited by vacuum evaporation considering certain process parameters. High reflectance values and a good climatic stability of the metal coated polymer parts are other important challenges to plastic mirrors. By performing roughness measurements on the different polymer samples and by comparing reflection values obtained after coating these samples the impact of the polymers surface quality on the reflectance after metal coating has been investigated. Particularly high reflectance above 97% was realized with a protected silver mirror as well as with dielectric enhanced aluminium. Applying these layer systems excellent reflection properties has been obtained on several plastic substrates comparable to those on glass mirrors. Furthermore the dielectric layers used for reflection enhancement showed the ability to protect the aluminium coating against climatic influences.     

Aluminization of nickel-formation of intermetallic phases and Ni2Al3 coatings

The occurrence and growth mechanisms of the various intermetallic phases of the Al-Ni system formed during pack aluminization of unalloyed nickel have been investigated with respect to the aluminium activity in the pack. Several types of coatings were obtained: (1) a Ni₂Al₃ coating formed by inward aluminium diffusion in a high activity cement of pure aluminium; (2) a Ni-rich NiAl coating formed by outward nickel diffusion in a low activity pack constituted by an Al-Ni alloy; (3) a mixed type of coating exhibiting the phases Ni₂Al₃, Al-rich NiAl, Ni-rich NiAl and Ni₃Al in four superposed layers, formed in a pack containing an Al-Cr alloy; (4) a high temperature, high activity type of coating formed above 950° C with an outer layer exhibiting a hypereutectic structure of NiAl₃ grains in a eutectic matrix due to precipitation from the liquid state. The optimum cementation conditions, for the production of maximum thickness and quality Ni₂Al₃ coatings were determined. The influence of surface reactivity and pack activity on the coating quality parameters was investigated.     

Conditions for the routine preparation of tantalum/aluminium films

Tantalum/aluminium alloy films of certain compositions have been found to have desirable properties for use in the fabrication of reliable micro-miniature resistors and capacitors¹. This paper covers the critical stages in the evolution of satisfactory process arrangements for the more stable of these films, and includes some results of accelerated life tests and structural analyses, to illustrate the choice of preferred composition. This film composition was found to result when the aluminium part of the target area was approximately 21% of the total, under sputtering conditions such that roughly equal numbers of tantalum and aluminium atoms were being removed from the whole of the bombarded surface. A maximum numerical value of -195 ppm/°C for the temperature coefficient of resistance (t.c.r.) is achieved under these conditions and the specific resistivity is higher than for films containing either slightly more or slightly less aluminium. Also the t.c.r. is practically independent of film thickness at this composition, whereas deviations in aluminium content, in either direction, result in films with less negative t.c.r. values as the thickness of deposit is increased.The type of sputtering used was not changed over the period of the work, but significant improvements in deposition rate and reproducibility were achieved by paying close attention to the provision of a stable environment in which to perform the process, and by careful substrate preparation and handling. The availability of higher purity sputtering targets led to further improvements in film quality.Although the work has been directed towards the production of a specific alloy film, the method is applicable to the controlled deposition of alternative binary alloy films of pure metals.     

Self-assembled monolayer of 3-aminopropyltrimethoxysilane for improved adhesion between aluminum alloy substrate and polyurethane coating

A good adhesion between a polymer coating and a metal or metal alloy substrate such as Al 2024-T3 plays a critical role in corrosion protection of metal substrates. In our study, a self-assembled monolayer film of 3-aminopropyltrimethoxysilane was formed on Al 2024-T3 substrate by covalent bonding. The adhesion property of a self-priming polyurethane coating was evaluated by pull-off adhesion test, wet tape test and thermal cycling test. All the testing results indicate that both dry and wet adhesion properties of the polyurethane coating were improved significantly after APS treatment of Al 2024-T3 in polar solvents such as methanol and acetone. In nonpolar solvents such as hexane, the APS treatment led to inconsistent improvement or sometime decreased adhesion of polyurethane coating. X-ray photoelectron spectroscopic study revealed that while a monolayer film was formed on the aluminum alloy surface after treating the substrate with APS in methanol and acetone, a multilayer film was formed on the substrate surface when the treatment was conducted in hexane. The APS monolayer film served as a covalent bond linkage between polymer coating and aluminum alloy substrates, which led to the increased adhesion property of polymer coating and corrosion resistance of the metal alloy substrate.     

Characterisation of surface preparation of 2024 aluminium alloy for conversion coating

Abstract

X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and electrochemical potentiodynamic experiments have been used to study the pretreatment of 2024–T3 aluminium alloy before conversion coating. The pretreatment process included vapour degreasing, alkaline cleaning and Cr based acidic deoxidising steps. This type of pretreatment is appropriate for conversion coatings which meet aerospace standards for corrosion resistance and paint adhesion. During alkaline cleaning an oxide containing Mg, Zn, Si, and Fe developed on the surface of the alloy. During deoxidation there was dissolution and etching of both the intermetallics and the basic oxide scale left after the alkaline cleaning. Characterisation by XPS indicated that the surface was coated with a thin Cr containing coating after deoxidation which provided a degree of passivation to the surface as determined by electrochemical measurements.

MST/3372     

The effect of electron beam sterilization on the physical properties of the bioresorbable polymer coatings on the titanium 6-aluminum 4-vanadium substrate

The aim of the work is to determine the physical properties of titanium 6-aluminum 4-vanadium alloy with poly (glycolide-ϵ-caprolactone) coating after electron beam sterilization. First, the metal substrate is machined with grade 120 and 320 grinding papers. Some of the samples are subjected to anodic oxidation. Then, the samples are coated with a biodegradable polymer layer of poly (glycolide-ϵ-caprolactone). Samples with polymer coatings are subjected to electron beam sterilization. To evaluate the effect of sterilization on physical properties of modified titanium alloy the scanning electron microscopy and atomic force microscopy, adhesion studies of the polymer coating to the metal substrate and wettability tests are applied. On the basis of the obtained results, an increase of the contact angle value is found both after applying the polymer coating to the surface of the tested titanium 6-aluminium 4-vanadium alloy as well as after electron beam sterilization. In addition, a slight increase of the adhesion in sterilized samples comparted to non-sterilized is observed. In scanning electron microscopic observations, traces of machining on the surface of the metal substrate and the continuity of the polymer coatings before and after sterilization are found. In the atomic force microscopic studies in relation to the initial state, a very good mapping of the surface topography of the samples with a homogeneous coating is found.     

Korrosionsverhalten von SiC-partikelverstärkten Aluminiumlegierungen

Corrosion Behavior of SiC Particle Reinforced Aluminium Alloys Since two decades Metal Matrix Composites (MMC'S) are a major topic in research and development. They show features, which are superior to those of conventional materials. As in any other composite material the interface metal matrix/reinforcing material is the weak point of these materials. Therefore information on their corrosion behavior is necessary before estimating their possible range of application. The purpose of this project is to gather information on the corrosion behavior of SiC particle reinforced aluminium alloys. The materials examined were alloys of the series 6XXX and 2XXX with varying amounts of SiC particle in comparison to the widely used aluminium alloy 2024. Experiments were performed with uncoated specimens and with specimens protected by a typical aircraft coating. Looking at the uncoated specimens the high copper MMC-alloy has a greater corrosion susceptibility than its matrix alloy. The coating on the MMC's examined has a better corrosion protection effectiveness than the same coating on the matrix alloy AA 2024.     

Mechanical Properties,Morphologies, and Microstructures of Novel Electrospun Metallized Nanofibers

We report that the metal‐deposited single nanofibers can be successfully prepared by electrospinning and metallization. The tensile strength of the metal‐deposited single nanofibers as well as various non‐metallized polymeric nanofibers was investigated by recently developed tensile test machine. The tensile strength of 50 nm metal‐deposited single nanofibers was dramatically improved, which was much higher than that of pure polymer single nanofiber. The result is attributed to the formation of metallic hard‐coating layers onto the surface of single nanofibers. The tensile strength of the metal‐deposited single nanofibers was also depended on the types of metals (for instance, Cu, Ni, Sn, and Al) used for metallization. In addition, we investigated various annealing conditions, such as annealing temperature and time, and composition ratio of two metals (Cu and Ni), in order to find out optimum annealing process for the formation of metal alloy nanofibers. The characterization of the metallized nanofibers was conducted by field emission scanning electron microscope (FE‐SEM) and X‐ray diffraction (XRD).     

Effect of Polymer Loading on Drug Release from Film-Coated Ibuprofen Pellets Prepared by Extrusion-Spheronization

Many factors are capable of influencing the mechanism of drug release from pellets prepared by extrusion-spheronization. This study was designed to elucidate the effect of polymer type and loading and the effect of processing variables on the rate and mechanism of drug release from ibuprofen pellets coated using aqueous polymeric dispersions. Qualitative and quantitative assessment of the success of the film coating process and the quality of the resultant films is made using scanning electron microscopy and in-vitro dissolution testing. The importance of plasticizer in polymeric film formation is also discussed. Uncoated pellets containing 60, 70 and 80% ibuprofen were coated with aqueous polymeric dispersions of polymethacrylates, ethylcellulose and silicone elastomer films. The high drug loading of these pellets adds special interest to this study. Drug release from uncoated pellets appears to follow first-order kinetics. The application of a polymeric membrane to uncoated cores has the effect of retarding drug release. There appears to be a critical coating level below which core coverage by the polymer is incomplete, drug release is diffusion controlled and first-order release kinetics are observed. Above a defined polymer level, drug release appears to be membrane controlled and zero-order kinetics are observed. The presence of plasticizer in the polymeric film imparts a hydrophilic component to an otherwise hydrophobic membrane. This enhances the penetration of aqueous solvent into the pellet core during in-vitro dissolution testing, increasing the rate of drug release. Scanning electron micrographs reveal the nature of these hydrophilic pores, beneath which a fine tortuous skeletal network of drug-depleted core is exposed.     

用Sol-Gel法在PC上制备有机-无机复合耐磨涂层

用ｓｏｌ－ｇｅｌ法在聚碳酸酯ＰＣ上制备一层耐磨涂层。该涂层为有机－无机复合网络,由γ—缩水甘油醚氧丙基三甲氧基硅烷（γ—ＧＰＴＭＳ）和金属醇盐Ｔｉ（ＯＣ２Ｈ５）４合成。采用浸涂工艺,热固化后可得到几微米厚的透明涂层。用３—氨丙基三乙氧基硅烷（３—ＡＰＳ）对ＰＣ表面进行处理,可使涂层与基体的结合力大大提高。涂层的基本骨架由Ｓｉ－Ｏ－Ｔｉ组成,能显著改善ＰＣ材料的耐磨性能。     

Effect of a commercial hard anodizing on the fatigue property of a 2014-T6 aluminium alloy

The effect of a commercial hard anodizing on the fatigue property of 2014 Al alloy which has been solution heat treated and age hardened prior to the hard anodizing of approximately 10 μm in thickness have been investigated. The results indicated that fatigue life in high stress region for aluminium alloy samples hard anodized was shorter than that of the other material condition which has been solution heat treated and then age hardened (T6 heat treated), while the life in low stress region was longer than that of the material (T6 heat treated). However, such a coating to the aluminium substrate gives rise to a significant increase in fatigue strength of 10⁷ cycle in comparison with the as cast condition, but a much less increase in comparison with T6 heat treated samples. From the microscopic point of view, it has been observed that fatigue fracture of samples hard anodized initiated in the coating in high stress region in opposition to low stress region in which fatigue fracture initiation started on the interface between coating and substrate.     

Effect of Polymer Loading on Drug Release from Film-Coated Ibuprofen Pellets Prepared by Extrusion-Spheronization

Abstract

Many factors are capable of influencing the mechanism of drug release from pellets prepared by extrusion-spheronization. This study was designed to elucidate the effect of polymer type and loading and the effect of processing variables on the rate and mechanism of drug release from ibuprofen pellets coated using aqueous polymeric dispersions. Qualitative and quantitative assessment of the success of the film coating process and the quality of the resultant films is made using scanning electron microscopy and in-vitro dissolution testing. The importance of plasticizer in polymeric film formation is also discussed. Uncoated pellets containing 60, 70 and 80% ibuprofen were coated with aqueous polymeric dispersions of polymethacrylates, ethylcellulose and silicone elastomer films. The high drug loading of these pellets adds special interest to this study. Drug release from uncoated pellets appears to follow first-order kinetics. The application of a polymeric membrane to uncoated cores has the effect of retarding drug release. There appears to be a critical coating level below which core coverage by the polymer is incomplete, drug release is diffusion controlled and first-order release kinetics are observed. Above a defined polymer level, drug release appears to be membrane controlled and zero-order kinetics are observed. The presence of plasticizer in the polymeric film imparts a hydrophilic component to an otherwise hydrophobic membrane. This enhances the penetration of aqueous solvent into the pellet core during in-vitro dissolution testing, increasing the rate of drug release. Scanning electron micrographs reveal the nature of these hydrophilic pores, beneath which a fine tortuous skeletal network of drug-depleted core is exposed.     

Fabrication of gradient distribution alumina short fibre reinforced aluminium alloy

Gradient distribution alumina short fibre reinforced 6061 aluminium alloy have been fabricated by taking advantage of preform compressive deformation during squeeze casting. Pressure was applied mechanically by a punch. Velocity of the punch, pre-heat temperature of the preforms and pouring temperature were controlled during the infiltration of molten 6061 alloy into alumina short fibre preforms. The distribution of hardness along the infiltration direction in the composites was measured and the distribution of volume fraction along the infiltration direction was calculated by the hardness. Velocity of the inflow, pre-heat temperature of the preform, pouring temperature of the molten metal, binder content of the preform and volume fraction of fibres, all have a very great effect on the gradient distribution of alumina short fibres in the aluminium alloy composites.     

Al-Cu双金属复合结构的扩散连接试验研究

应用扩散连方法进行了Al-Cu双金属复合结构的试验研究，比较了不同的焊接工艺，材料组合以及母材状态情况Al合金与Cu的连接性，观察了接头区域的微观组织结构，研究表明，固相扩散连接是一种适用于异种材料连接的有效方法，通过在连接区域形成Al-Cu金属间化合物，达到Al和Cu的有效连接，材料组合，母材原始状态以及连接工艺参数对Al合金与Cu的扩散连接存在着明显的影响。表面镀Ni工艺不但能够有效阻止Al和Cu之间形成脆性相，而且Al和Ni之间形成了良好的扩散连接，改善了接头性能。     

Mechanical behaviour of polymer–metal hybrid joints produced by clinching using different tools

In the present study, the mechanical behaviour of polymer–metal hybrid connections produced by clinching is investigated. Thin sheets were joined using different tools including grooved, split and flat dies as well as rectangular tools. The effect of the joining force on joinability was also analysed. Polycarbonate was used as the polymer partner because of its high strength and toughness, while aluminium alloy AA6082-T6, which is characterized by a high yield stress but low ductility, was used as the metal sheet. Mechanical characterization involved single lap shear tests and peeling tests. According to the achieved results, grooved dies are not suitable for joining polymers. Rectangular clinching tools required lower joining forces and produced the highest peeling performances; however, because of the low ductility of the aluminium alloy, the joints were partially damaged resulting in the weakest shear strength. Round clinching tools required higher joining force compared to rectangular ones. The joints produced by flat dies were characterized by higher shear strength; however, because of the small interlock produced, they were characterized by small values of peeling strength. Round split dies allowed producing the joints with the highest performances in shear and peeling tests.