The in-vitro genotoxicity of nanosized TiO2 rutile and anatase was assessed in comparison with fine TiO2 rutile in human bronchial epithelial BEAS 2B cells using the single-cell gel electrophoresis ...(comet) assay and the cytokinesis-block micronucleus test. BEAS 2B cells were exposed to eight doses (1—100 μg/cm2) of titanium(IV) oxide nanosized rutile (>95%, <5% amorphous SiO2 coating; 10 × 40 nm), nanosized anatase (99.7%; <25 nm), or fine rutile (99.9%; <5 μm) for 24, 48, and 72 h. Fine rutile reduced cell viability at lower doses than nanosized anatase, which was more cytotoxic than nanosized rutile. In the comet assay, nanosized anatase and fine rutile induced DNA damage at several doses with all treatment times. Dose-dependent effects were seen after the 48- and 72-h treatments with nanosized anatase and after the 24-, 48- (in one out of two experiments), and 72-h treatments (one experiment) with fine rutile. The lowest doses inducing DNA damage were 1 μg/cm2 for fine rutile and 10 μg/cm 2 for nanosized anatase. Nanosized rutile showed a significant induction in DNA damage only at 80 μg/cm2 in the 24-h treatment and at 80 and 100 μg/ cm2 in the 72-h treatment (with a dose-dependent effect). Only nanosized anatase could elevate the frequency of micronucleated BEAS 2B cells, producing a significant increase at 10 and 60 μg/cm 2 after the 72-h treatment (no dose-dependency). At increasing doses of all the particles, MN analysis became difficult due to the presence of TiO2 on the microscopic slides. In conclusion, our studies in human bronchial epithelial BEAS 2B cells showed that uncoated nanosized anatase TiO2 and fine rutile TiO2 are more efficient than SiO 2-coated nanosized rutile TiO2 in inducing DNA damage, whereas only nanosized anatase is able to slightly induce micronuclei.
The manufacturing of thick wear-resistant steel plates commonly leads to a layered structure and non-uniform properties in the thickness direction which makes the processing and utilization of the ...plates problematic. The processing steps of thick plates include flame cutting, which generates a heat-affected zone and high residual stresses into the cut edge. In the worst case, the cutting causes cracking. However, the residual stress level alone is not high enough to break a wear-resistant steel plate that behaves normally. Therefore, high-tensile stress also requires a microstructurally weak factor for crack initiation. For this reason, the main objective of this study is to reveal the main microstructural reasons behind the cracking of plates in flame cutting. To achieve this, plate samples containing cracks are mechanically tested and analyzed by electron microscopy. The results show that cracks are commonly formed horizontally into the tempered region of the heat-affected zone. Cracks initiate in the segregations, which typically have a higher amount of impurity and alloying elements. Increased impurity and alloying content in the segregations decreases the cohesion of the prior austenite grain boundaries. These weakened grain boundaries combined with high-residual tensile stress generate the cracks in the flame-cutting process.
By using hybrid structures, attractive and advantageous combinations of material properties can be achieved. In addition to the combination of good mechanical properties and low weight, also ...dynamical properties can be enhanced by suitable materials selection. However, the hybrid structure properties depend on the properties of the constituent materials as well as on the interfacial properties.
In the present study, the damping properties of laminated structures consisting of steel, rubber or epoxy adhesive and glass fibre reinforced epoxy composite were studied. Damping properties of the structures were investigated through the loss factors. The loss factors of the hybrid structures and the constituent materials were determined by frequency and time domain test methods. By using the loss factor results of the constituent materials, the loss factor of the hybrid structures were estimated by the rule of mixtures and the results were compared with the experimental results. It was observed, that the use of weight fractions instead of volume fractions in the rule of mixtures provides a good average estimation of the damping behaviour of the hybrid structure and the results of rule of mixtures method can be used as rough estimates during the design phase of hybrids of this kind.
The significance of engineered nanomaterials (ENM) and nanotechnologies grows rapidly. Nanotechnology applications may have a positive marked impact on many aspects of on human every day life, for ...example by providing means for the production of clean energy and pure drinking water. Hundreds of consumer nano-based products are already on the market. However, very little is known of the risks of ENM to occupational safety and health (OSH), even though workers are likely to be at extra risk, as compared with other potentially exposed groups of people, because the levels of exposure are usually higher at workplaces than in other environments. However, knowledge of the exposure to, or effects of, ENM on human health and safety in occupational environments is limited and does not allow reliable assessment of risks of ENM on workers’ health. Several issues related to ENM in the workplaces require marked attention. The most topical issues include: (1) improved understanding of ENM metrics associated with ENM toxicity; (2) development of monitoring devices for ENM exposure assessment; (3) understanding the changes of ENM structure and state of agglomeration at different concentrations in aerosols; (4) understanding translocation of ENM in the human body; (5) identifying the key health effects of ENM including pulmonary toxicity, genotoxicity, carcinogenic effects, and effects on circulation; (6) development of tiered approaches for testing of safety of ENM; and (7) utilizing these data for health risk assessment, with a special emphasis on occupational environment. Available data on several ENM – ability to enter the body and reach almost any organ, to cause pulmonary inflammation and fibrosis, and even to cause increased risk of mesotheliomas in animal models, call for immediate action. It is crucial to identify those ENM that may cause occupational health and safety risks from those ENM which are innocent, hence allowing prioritization of regulatory and preventive actions at workplaces at national, regional and global levels.
One of the major challenges when preparing reliable hybrid structures is the adhesion between different components. Besides enduring the specific stress state, hybrid structures should maintain the ...required properties in the service environment without degradation. In this study, the environmental resistance of stainless steel/rubber/GFRP (glass fibre reinforced plastic) hybrid structures were tested by exposure to hot, moist and hot/moist environments and after the ageing by peel testing. Two different stainless steel surface finishes and two different rubber grades were investigated. The results were compared with the properties of a mild steel/rubber/GFRP structure. Both mild steel/rubber and composite/rubber structures are used in industrial applications, such as in vibration damping devices and in automotive components.
The peel tests showed that with right rubber compounds, stainless steel/rubber and GFRP/rubber interfaces can maintain their properties even in harsh hot/moist environments to such an extent that the interfacial strength of the joint is higher than the cohesive strength of the rubber. This enables the use of rubber's cohesive fracture properties instead of the substrate/rubber interfacial properties when estimating the strength of the steel/rubber/GFRP hybrid structure. In addition, based on the current study, time-consuming stainless steel pre-treatments are not needed but the stainless steel can be in the as-received stage. According to the chemical analysis even before and after the harsh hot/moist exposure used, none of the studied rubber grades had degraded. Thus, we conclude that it is possible to manufacture environmental resistant stainless steel/GFRP hybrid structures with the aid of EPDM rubbers.
Heavy steel plates are used in demanding applications that require both high strength and hardness. An important step in the production of such components is cutting the plates with a cost-effective ...thermal cutting method such as flame cutting. Flame cutting is performed with a controlled flame and oxygen jet, which burns the steel and forms a cutting edge. However, the thermal cutting of heavy steel plates causes several problems. A heat-affected zone (HAZ) is generated at the cut edge due to the steep temperature gradient. Consequently, volume changes, hardness variations, and microstructural changes occur in the HAZ. In addition, residual stresses are formed at the cut edge during the process. In the worst case, unsuitable flame cutting practices generate cracks at the cut edge. The flame cutting of thick steel plate was modeled using the commercial finite element software ABAQUS. The results of modeling were verified by X-ray diffraction-based residual stress measurements and microstructural analysis. The model provides several outcomes, such as obtaining more information related to the formation of residual stresses and the temperature history during the flame cutting process. In addition, an extensive series of flame cut samples was designed with the assistance of the model.
An investigation was made into the Barkhausen noise responses of three duplex grades: a lean alloy LDX 2101, a conventional duplex 2205 and a super duplex 2507, in welded conditions. The aim was to ...study the influence of alloy chemistry and microstructure on the Barkhausen noise response.
In addition, the residual stresses of the grades were measured by X-ray diffraction and the microstructure and hardness of the base materials and welds were determined. It was observed that the Barkhausen noise responses in the rolling direction and in the transverse direction were governed
by the phase morphology of the materials. Only the root mean square of the Barkhausen noise burst seemed to be additionally dependent on the alloy chemistry through the hardness of the materials. Furthermore, the relationships between various characteristics of the Barkhausen noise burst measured
in the rolling direction and the transverse direction and microstructural features are discussed.
The effect of sulphur and phosphorus on a Pt/SiO
2
–ZrO
2
catalyst was studied. The laboratory accelerated sulphur (SW) or phosphorus (PW), and their co-exposure (PSW) treatments were done in gas ...phase for 5 h at 400 °C. The fresh and treated catalysts were characterized by XPS, FESEM-EDS, TEM-EDS, BET and BJH. The catalyst activity was tested in lean diesel exhaust gas conditions by using a gas FTIR. The value of the light-off temperature of CO and C
3
H
6
over the studied catalysts was as follows: fresh ~ SW < PSW < PW. These results can be explained by XPS and EDS results that revealed that the amount of adsorbed sulphur was much lower than the amount of phosphorus. Based on the BET and BJH results, bigger changes in the catalyst structure were observed after the PSW and PW treatments. Therefore, the impact of sulphur was negligible in comparison with phosphorus, and the sulphur actually inhibited the deactivation effect of phosphorus.
In the present study, high velocity impact tests were carried out on stainless steel/rubber/composite hybrid plates. The projectile velocity, impact angle, number of impacts, sample temperature, and ...prior ageing were used as variables in order to investigate the effect of test parameters on the impact behaviour of the samples.
In general, the energy absorption and the damage behaviour of the studied hybrid structure were rather immune to the changes in the test parameters. Only the impact angle showed a stronger effect with increasing plastic deformation and dissipated energy with increasing impact angle. Similar but not as strong effect was found with increasing sample temperature. In addition, the effect of increasing impact angle on the damage size was found to be stronger than the effect of increasing impact energy at a constant impact angle. The repeated impact studies showed that the structure does not lose its ability to withstand dynamic loading even when there is a gradually progressive damage. The results support the potential of the studied steel/rubber/composite hybrid structure to be implemented in real life applications.
Hybrid structures are widely used since they enable unique combinations of properties for the final structure. Within polymer/metal hybrids, stainless steel instead of more regularly used mild steel ...or aluminium is a tempting choice but it is difficult to join adhesively. Thus improved solutions for the stainless steel joining with polymeric materials are needed. This study concentrates on the idea of utilisation of thin rubber layer as an adhesive between stainless steel and glass fibre reinforced epoxy composite (GFRP). Both mild steel and stainless steel with different surface finishes together with GFRP laminates were used as substrates for the ethylene propylene diene (EPDM) based rubber. The adhesion and microstructure of the interfaces were characterised. Transmission electron microscopical (TEM) studies indicated that a close contact between the components can be achieved and thus high quality interfaces are created by vulcanising the rubber to the steel or GFRP surface without pre-treatments. Stainless steel/rubber/GFRP hybrid structures where the strength of the steel/GFRP joint is defined by the cohesive strength of the rubber can be manufactured, as seen from the results of the peel tests. Since the fracture is located inside the rubber and not at the interface, the prediction of the structure's behaviour is also easier.
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