Abstract: In this work a new method of Ti-void composites (foam, scaffold) preparation is shown. In this process as a space holder particles we have applied a saccharose crystals (table sugar) with size up to 1.3 mm. After Ti and saccharose particles mixing and pressing, a green compacts composed of sugar and Ti grains were produced. Then, the sugar crystals were removed by its dissolution in water, which lead to open spaces (pores) formation in the green compacts. Then the compacts were sintered at 1250 °C. Alternatively, a sugar was evaporated during sintering without water dissolution. The foams were investigated by SEM, XRD and computed tomography. Such prepared void metal composites have porosity of about 72% and average pore size of about 0.7 mm. The pores have cubical shape corresponding to sugar crystals shape. The method is very promising in foams preparation and the made Ti-void composites can be applied for hard tissue implants, for example.
Abstract: Two types of graphene/MnO2 composites were synthesized by different reaction procedures. R-GO/MnO2 was synthesized as follows: first, nanoneedle MnO2 was formed on the GO sheets using various functional groups (GO/MnO2). In the second stage, GO/MnO2 was reduced to graphene/MnO2 (R-GO/MnO2) via the dipping method. rGO/MnO2 was synthesized using a different reaction order: first, graphene oxide was reduced to graphene and nanoneedle MnO2 was formed on graphene sheets. Characterization indicated that the nanoneedle MnO2 structures in the R-GO/MnO2 composite were homogeneously dispersed on graphene sheets, whereas MnO2 in the rGO/MnO2 composite formed aggregates due to absence of functional groups. The R-GO/MnO2 electrode exhibited a specific capacitance as high as 327.5 Fg-1at 10 mVs-1, which was higher than that of the rGO/MnO2 electrode (229.9 Fg-1). It is anticipated that the formation of nanoneedle MnO2 on the GO surface following the reduction procedure could be a promising fabrication method for supercapacitor electrodes.
Abstract: This study is aimed to evaluate the effect of sugarcane bagasse ash fineness on the properties of cement-based composites. Three sugarcane bagasse ash contents (10, 20 and 30% by weight of cement) and three particle sizes of bagasse ash (particles less than 45, 75 and 150 μm) were used as a partial replacement for cement in mortar specimens with a constant water/cementitious ratio of 0.55. The pozzolanic strength activity test, compressive strength test and scanning electron microscope observations were conducted and compared. Test results indicated that the compressive strength decreased with the addition of sugarcane bagasse ash content increased. Addition of sugarcane bagasse ash to replace cement in cementitious composites could provide hydration and pozzolanic reaction, but it would still keep more rugged and some larger pores observed from the paste surface and resulted in the weaker microstructures and poorer properties in cementitious composites. In conclusion, the critical usage of sugarcane bagasse ash is 10 % with 45μm particles.
Abstract: Based on the comparison of several types of core formwork for large span hollow box girder, their structural characters, and assemble and disassemble in application is analysed to find that steel-wood core formwork is a better choice. Then the installation technique of steel-wood core formwork is discussed, including assemble, disassemble and anti-floating counter measures. The practice in some large span prestressed hollow box girder construction prove that steel-wood core formwork is a simple but effective core formwork construction technique with technological economic advantages because of its low cost, high working efficiency and better accuracy..
Abstract: Aluminium silicon carbide particulate composites have wide ranging applications in automobile, aerospace and military industries because of their attractive properties such as high strength-to weight ratio, high wear resistance, high temperature stability etc. From the machining point of view, these are one of the most difficult-to-machine materials, primarily due to the presence of SiC reinforcements causing an excessive wear of cutting tools during machining. On the other hand aluminium-graphite composites are widely used in tribological applications because of their excellent antifriction properties, wear resistance and antiseizure characteristics. Investigations have been carried out in this work to assess the machinability of aluminium matrix composites containing both SiC and graphite particulates as reinforcements. Turning experiments have been conducted on Aluminium-Graphite-Silicon Carbide hybrid composites using Carbide and PCD tool inserts to determine the flank wear. Experiments have been carried out based on Central Composite Design approach.
Abstract: Aluminium metal matrix composites due to their excellent properties like high strength to weight ratio and high wear resistant are becoming new generation of materials useful for various engineering applications. A continuing problem with these composites is that they are difficult to machine. Machining of these composites depends on the relative content of the reinforcement and the matrix material as well as on its response to the machining process. Experimental investigations have been carried out on the machinability aspects of Aluminium hybrid composites reinforced with Graphite and Silicon Carbide particulates. Experiments have been carried out by Design of Experiments approach. Mathematical models which correlate the interactive and higher order influences of cutting parameters on the resultant force have been developed.
Abstract: This work reports on a study of thermal degradation of flax fibres to gain an improved understanding of the use and limitations of flax fibres as reinforcement for thermoplastic composites manufactured by the vacuum forming process. The effect of heating on chemical decomposition and thermal stability was performed, using fourier transform infrared spectrometry (FTIR) and thermogravimetry (TG) techniques. In addition, the characterisation of micro structures of failure surface following tensile testing of the composites was conducted. The results show that the hemicelluloses decomposition of flax fibres during thermal degradation is a factor to have the detrimental effect on the thermal stability of fibres, particularly with low heating rate. The present investigation, A decrease of hemicellulose and pectin content of the fibres, a decrease of consolidation temperature and an increase of heating rate during the manufacturing of flax fibre thermoplastic composites should improve their mechanical performance.
Abstract: This research aimed to apply the Blown Film Extrusion technique to synthesize the titanium dioxide (TiO2) bio-composite films incorporated on a thin film as a photocatalyst. The biopolymer materials have great recognition via their renewable and biodegradable characteristic and the green composite has been a new challenge path to replace traditional polymer composite. In this work, TiO2/Polybutylene succinate (PBS) bio-composite film was developed to be used as a supporter for determining the photocatalytic oxidation activity of the TiO2 on the chlorinated volatile organic compounds degradation. PBS is a synthetic biopolymer which has a reasonable mechanical strength. The modified-TiO2/PBS bio-composite films were studied to evaluate the degradation of dichloromethane. In order to improve the distribution of the developed photocatalyst, the TiO2 powders were modified by 0.05% mole of ethyl triethoxysilane (ETES) and stearic acid (SA), respectively. The 10% wt. TiO2/PBS bio-composite films with thickness of 30 μm were prepared by blown film technique. To evaluate the dispersion efficacy, the modified-TiO2/PBS bio-composite films were characterized by Scanning Electron microscopy (SEM). Photocatalytic degradation of dichloromethane in gas phase was determined using an annular closed system photoreactor. The obtained result which was corresponding to the absorption of TiO2/PBS bio composites film was investigated in a range of 300-400 nm via UV/VIS spectrophotometry. The energy band gap of TiO2, ethyl triethoxysilane-TiO2 and stearic acid-TiO2 bio-composite film was found to be 3.18, 3.21, and 3.26 eV, respectively. The SEM shows that the modified-TiO2 with both ETES and SA exhibit uniform dispersion, while the only TiO2 shows an evidence of agglomeration in the PBS matrix. For photocatalyst efficiency, the photocatalytic activity of modified-TiO2/PBS bio-composite film increased comparing to the TiO2/PBS bio-composite film. Moreover, the photocatalytic degradation of dichloromethane by ETES-TiO2/PBS bio-composite film yielded degradation efficiency of 47.0%, whereas SA-TiO2/PBS bio-composite film yielded the removal efficiency of 41.0% for detention time at 350 min.
Abstract: In this paper an experimental program has been carried out in order to compare compressive strength fc and elastic static modulus Ec of recycled concrete with ultrasonic waves velocity Vp, to establish the possibility of employing nondestructive ultrasonic tests to qualify recycled concrete. 9 mix of concrete with different substitution percentage of recycled aggregates instead of natural ones and 27 cylindrical samples have been made.
At first ultrasonic tests have been carried out on cylindrical samples, later elastic static modulus Ec and compressive strength fc have been experimentally evaluated.
The dynamic elastic modulus Ed has been determined in function of ultrasonic wave velocity Vp; furthermore the correlations among Ed, Ec, fc e Vp have been determined.
It has been demonstrated that ultrasonic tests are suitable for evaluating different deformative and resisting concrete performances even when variations are small.