This work falls within the general framework of the valorization of the clays of Ivory Coast in order to propose innovative solutions in the resolution of certain problems related to development such as the depollutio...This work falls within the general framework of the valorization of the clays of Ivory Coast in order to propose innovative solutions in the resolution of certain problems related to development such as the depollution of water. Its main objective is therefore to study the physico-chemical properties of two Dabou clays with a view to using them in chemical processes for the treatment of dyeing wastewater. The results of the chemical analysis and the ray diffraction showed that the DAB 1 and DAB 2 samples are clays of the kaolinitic type consisting mainly of kaolinite with 51.17% for DAB 1 against 65.81% for DAB 2 and quartz with respectively 41.76% and 25.8% for DAB 1 and DAB 2. They also contain relatively large amounts of goethite with 9.96% for DAB 1 and 12.8% for DAB 2. The specific surfaces measured in both samples are greater than 25 m<sup>2</sup>/g. All the results of the physico-chemical characterization, in particular the presence in significant quantity of clay minerals, the presence of iron compounds and the large specific surface area of both samples, allow the conclusion that they can be used in adsorption studies and in the heterogeneous Fenton process for water treatment.展开更多
Silicon and Silicon carbide particles have been investigated by the mean of infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) to establish their surface states. The results of this research are bas...Silicon and Silicon carbide particles have been investigated by the mean of infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) to establish their surface states. The results of this research are based on the estimation of the area under the high resolution peaks by isosceles triangles. This approach leads to the repartition of the particles surfaces in term of atomic percentage and of type of bonds. The surface of silicon particles is divided up into 54.85% of Si-O bonds and 36.85% of Si-Si bonds. The remaining surface is constituted of zeolite, the raw material used to produce the silicon particles. The surface of silicon carbide particles consists of 50.44% of Si-C bonds, 24.01% of Si-O bonds and 25.55% of graphite. 10.01% of the graphite is derived from the oxidation of Si-C bonds while 11.48% is due to contamination. The zeta potential evolution versus pH confirms the distribution of chemical groups found.展开更多
This work aims at the suitability of electroslag process on production of high technological steels such as Maraging steel, modified high speed tool steel (niobium, high nitrogen, and free nitrogen) has been investiga...This work aims at the suitability of electroslag process on production of high technological steels such as Maraging steel, modified high speed tool steel (niobium, high nitrogen, and free nitrogen) has been investigated. The experimental results show that high recovery of alloying elements during electroslag remelting of such steels especially high nitrogen tool steel. The previous results are attributed to the slag used in electroslag protect the molten metal from atmospheric oxygen. Also higher recovery of alloying elements during remelting high nitrogen high speed tool steel are due to partial dissolution of nitrides during remelting of such steel which increase nitrogen content above the molten slag which decrease the partial pressure of oxygen leads to protection of molten metal from further oxidation. Also, the results show that, produced ingots are free from internal pipes, porosity and other surface defects. Microstructure obtained for remelted steels is very fine and well distributed for all steel under investigation. In the case of electroslag remelted Maraging steels lower non-metallic inclusions with very fine inclusions and redistribution retained austenite with very fine structure leads to increasing all tensile properties of investigated steels. In the case of high speed tool steels, also the structure is very fine, well distributed, densely and short carbides with lower non-metallic inclusions contents. High cooling rate accompanying with electroslag process has a great effect on type, morphology and content of carbides precipitated in both nitrogen and niobium modified tool steels.展开更多
The present work reveals the study of mechanical properties of Al2024-Tungsten carbide MMCs containing tungsten carbide (WC) particulates. The reinforcing particulates in the Al2024 alloy were varied from 0% to 5% by ...The present work reveals the study of mechanical properties of Al2024-Tungsten carbide MMCs containing tungsten carbide (WC) particulates. The reinforcing particulates in the Al2024 alloy were varied from 0% to 5% by weight. The vortex method of cast production was employed to fabricate the MMCs, in which the reinforcement was poured into the vortex created by stirring the molten metal by means of a mechanical agitator. The composite so produced was subjected to a series of mechanical tests. The results of this study revealed that as the tungsten carbide particle content was increased, there were significant increases in the ultimate tensile strength, hardness and young’s modulus, compressive strength, accompanied by a reduction in its ductility. An attempt is made in the paper to provide explanations for these phenomena.展开更多
In this investigation, an attempt has been made to develop Al6061-Frit particulate metal matrix composites through stir casting technique using metal molds and to study the corrosion behaviour. Pre heated frit particl...In this investigation, an attempt has been made to develop Al6061-Frit particulate metal matrix composites through stir casting technique using metal molds and to study the corrosion behaviour. Pre heated frit particles were added to matrix as reinforcement. Al6061 containing 2 wt% to 8 wt % in steps of 2 wt % of frit particulate composites were prepared. Corrosion tests were conducted by using Potentiostat model SEP238C where 3.5% NaCl solution was used as corrodent. The corrosion rate of metal matrix composites was lower than that of matrix material Al6061 under the corrosive atmosphere for both un-heat treated and heat treated conditions.展开更多
A transparent polymer based solar cell was designed and fabricated to utilize the solar energy when exposed to sunlight. The transparent solar cell for window module was composed of a polymeric material PPV (Polypheny...A transparent polymer based solar cell was designed and fabricated to utilize the solar energy when exposed to sunlight. The transparent solar cell for window module was composed of a polymeric material PPV (Polyphenylene vinylene), ITO (Indium Tin Oxide) and electrode (Al, Mg, Ca). The polymeric sheet of this cell is by casting process, and electrode is applied on it by CVD (Chemical Vapor Deposition) process. The solar energy collected by this window can be used to power up small household electrical appliances. Recently, polymeric solar cell is made by a roll-to-roll process without using indium-tin oxide (ITO). A commercially available kapton (Polyimide) foil with an over layer of copper was used as the substrate. Sputtering of titanium metal on to the kapton/copper in a vacuum metalizing process gave the monolithic substrate and back electrode for the devices. The active layer was slot-die coated on to the kapton/Cu/Ti foil followed by slot-die coating of a layer of PET, PC or PEN.展开更多
Blending of polymer with organic/inorganic material has given a new direction for developing novel materials. This is an easy and inexpensive method of modifying various properties of the individual materials and comp...Blending of polymer with organic/inorganic material has given a new direction for developing novel materials. This is an easy and inexpensive method of modifying various properties of the individual materials and composites. The aim of the present work is an attempt to incorporate crystals in polymer host and investigate the effect, on optical properties of the of polymer- crystal combine. In this paper a novel technique of incorporating inorganic/organic crystal in a host polymer matrix is reported. Crystals of acetoacetanilide (AA) are grown in the host Poly Methyl Methacrelate (PMMA) by simple evaporation technique. The scanning electron micrograph (SEM) studies reveal the growth of Acetoacetanilide crystals of varying sizes and shapes (flakes) in prepared samples. The results are confirmed by various spectroscopic characterization studies such as X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and the UV-Vis spectroscopy. The investigations carried out, show a change in optical absorption band edge which is attributed due to change in band gap because of crystal sizes.展开更多
This study determined mineral value and antioxidant activity of Senegal fruits for contributing to improving healthy diet and preventing some chronic diseases. Mineral element contents of Dialium guineense, Landolphia...This study determined mineral value and antioxidant activity of Senegal fruits for contributing to improving healthy diet and preventing some chronic diseases. Mineral element contents of Dialium guineense, Landolphia heudelotti, Mangifera indica, Cyperus esculentus and Saba senegalensis, which are widely available and consumed, were studied. The results by ICP-OES spectrophotometry after acid mineralization showed highest levels of (per 100 g fruits), calcium (158 mg), potassium (1018 mg), magnesium (532 mg), zinc (26 mg) with juice of Landolphia heudelotti fruit pulp. Mangifera indica pulp is richer in sodium (89 mg), phosphorus (556 mg), sulphur (384 mg) and silicon (110 mg). Dialium senegalensis pulp is richer in iron (23 mg) and manganese (19 mg). Lyophilized Cyperus esculentus rhizomes analyzed by atomic absorption spectrophotometry gave highest concentrations of (per 100 g fruits), calcium (2550 mg), potassium (11,843 mg) and magnesium (7669 mg) but sodium content (22 mg) is lower. In vitro antioxidant activity evaluation with the DPPH radical showed for 10 mg/ml concentration, highest inhibition percentage for Saba senegalensis 4.03%, followed by Landolphia heudelotti and Dialium guineense, which were significantly similar 2.29% and 2.20% respectively, Mangifera indica 1.7% and finally Cyperus esculentus 0.5%, but much lower compared to the ascorbic acid equal to 96.32% used as a reference.展开更多
The problem of void growth and interaction is of importance to understanding the mechanics of failure in metals exhibiting ductility. In this work, the growth and interaction of voids in 6061-T6 aluminum were studied ...The problem of void growth and interaction is of importance to understanding the mechanics of failure in metals exhibiting ductility. In this work, the growth and interaction of voids in 6061-T6 aluminum were studied experimentally. Specifically, holes of varying numbers and relative placement were investigated for their normalized area growth with applied displacement. Flat dog-bone specimens were carefully drilled in their gauge area with no (zero) holes, one hole, and two holes (arranged vertically or horizontally) for experimentation after polishing. The growth of holes, captured by video recordings, exhibited exponential behavior and was influenced greatly by the number and arrangement of holes with the horizontal voids growing the fastest and the vertical ones growing the slowest. Also, the ensuring deformation of the sample was studied using load-displacement curves, pictography and videography, SEM imaging and Atomic Force Microscopy (AFM). The methods revealed that although the major part failure is due to large crack formation, it was preceded by intense dislocation slip activity and the formation of micro cavities. Also, the AFM quantified the three-dimensional nature of crystal or grain deformation and how it is greatly influenced by distance and location from the hole. Lastly, theoretical understanding of hole growth was offered.展开更多
A technological clayey sandstone sample from Wadi Qena locality, Eastern Desert of Egypt, was directed to processing. Fine kaolin and clean silica sand were produced after intensive attrition scrubbing of the sample. ...A technological clayey sandstone sample from Wadi Qena locality, Eastern Desert of Egypt, was directed to processing. Fine kaolin and clean silica sand were produced after intensive attrition scrubbing of the sample. To increase the quality of the produced silica, it was subjected to reverse anionic flotation to minimize its iron content. In this respect, conventional flotation tests using three anionic oxyhydryl surfactants namely: sodium dodecyl benzene sulphonate, sodium naphtha sulphonate, and sodium dodecyl sulphate, were tried. Results showed a privilege action for sodium dodecyl sulphate to remove most of the iron oxide content of the sample. A statistical Box-Behnken design was constructed to optimize the process efficiency. It was shown that from a flotation feed contained 360 ppm Fe<sub>2</sub>O<sub>3</sub> and 1190 ppm Al<sub>2</sub>O<sub>3</sub>, sand concentrate contained 29 ppm Fe<sub>2</sub>O<sub>3</sub> and 564 ppm Al<sub>2</sub>O<sub>3</sub>, was produced. The optimum flotation conditions were 3.86 kg/t sodium dodecyl sulphate dose, 3.22 flotation pulp pH, 1226 rpm impeller speed, and 22.24 L/min airflow rate. Variables interaction effects results showed that flotation separation efficiency was significantly influenced by air flow rate and cell impeller speed of the process.展开更多
The use of waste materials to produce engineering components is currently attracting so much interest due to their low cost, availability and environmental impact. In this study, coconut shell ash (CSA) and kyanite pa...The use of waste materials to produce engineering components is currently attracting so much interest due to their low cost, availability and environmental impact. In this study, coconut shell ash (CSA) and kyanite particles (KP) produced from coconut shells and kyanite mineral respectively were characterized. X-ray Florence (XRF), X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to analyze the oxide compositions, crystalline phases and microstructures of CSA and KP. The XRF analysis revealed major oxides in CSA and KP as SiO2 and Fe2O3;and Al2O3 and SiO2 respectively. The XRD analysis revealed the presence of Quartz, Hematite, Andradite and Gaultite phases at major peaks in diffractogram of CSA;and Quartz and Beryl phases at major peaks in the diffractogram of KP. The crystallite sizes of the quartz phases in CSA and KP at diffraction angle of 26.72°C and 20.91°C were determined as 638.28 Åand 789.38 Årespectively. From the SEM image of CSA, it was observed that particles of different sizes are present in the microstructure of CSA. The average size of the particles in the microstructure of CSA is 26.24 μm. A similar result was observed in the SEM image of KP and average size of the particles is 3.074 μm. Also, the energy dispersive X-ray (EDX) spectrums of CSA and KP revealed the presence of many elements with calcium as the major element in CSA and Aluminium as major element in KP. The presence of the crystalline phases in CSA (SiO2, Al2O3, andradite, gaultite and hematite) and KP (SiO2 and Al2O3) will make them good strengthening materials for the production of Aluminium based composites that can be used in applications where a good combination of strength and wear characteristics is a basic requirement like brake disc.展开更多
This paper focuses on the study of the physical, biochemical, structural, and thermal properties of plant fibres of <i>Rhecktophyllum camerunense</i> (RC), <i>Neuropeltis acuminatas</i> (NA) an...This paper focuses on the study of the physical, biochemical, structural, and thermal properties of plant fibres of <i>Rhecktophyllum camerunense</i> (RC), <i>Neuropeltis acuminatas</i> (NA) and <i>Ananas</i> <i>comosus</i> (AC) from the equatorial region of Cameroon. The traditional use of these fibres inspired researchers to investigated their properties. This study aims at improving the state of knowledge with a view to diversifying applications. The fibres are extracted by retting. Then, their apparent density was measured following the ASTM D792 standard and their water moisture absorption and moisture content were also evaluated. Their molecular structure was studied by ATR-FTIR spectroscopy. A quantitative analysis of the biochemical composition was performed according to the analytical technique for the pulp and paper industry (TAPPI). A TGA/DSC analysis was also performed. The results reveal that the AC, NA and RC fibres have densities of 1.26 ± 1.06, 0.846 ± 0.13 and 0.757 ± 0.08 g·cm<sup>-3</sup> respectively. They are also hydrophilic with a water absorption rate of 188.64 ± 11.94%, 276.16% ± 8.07% and 198.17% ± 20%. They have a moisture content of 12.21%, 10.36% and 9.37%. The studied fibres exhibit functional groups that are related to the presence of hemicellulose, pectin, lignin and cellulose. The cellulose crystallinity index was found to be 67.99%, 46.5% and 59.72% respectively. The fibres under study have the following chemical composition: an extractive content of 3.07%, 14.77% and 8.74%;a pectin content of 4.15%, 7.69% and 3.45%;a hemicellulose content of 4.90%, 15.33% and 7.42%;a cellulose content of 68.11%, 36.08% and 65.15%;a lignin content of 12.01%, 25.15% and 16.2%;and an ash content of 0.27%, 1.53% and 0.47% respectively. The thermal transitions observed on the thermograms correlate with the TAPPI chemical composition. It is observed that these fibres are thermally stable up to temperatures of 200°C, 220°C and 285°C. These results make it possible to envisage uses similar to those of sisal, hemp and flax fibres.展开更多
This study focuses on mineralogical and chemical characterization of clay of Sitakunda anticline, Bangladesh and potential suitability of this shale as raw materials in ceramic industries. The shale which is clay in t...This study focuses on mineralogical and chemical characterization of clay of Sitakunda anticline, Bangladesh and potential suitability of this shale as raw materials in ceramic industries. The shale which is clay in texture is composed of chlorite and kaolinite with common illite, smectite, quartz, mica and feldspar. There are two types of samples in color, grey and red. Chemical compositions of clay samples are analyzed by XRF and mineralogical composition of sample analyzed by XRD. Clay samples contain significant amount SiO2, Al2O3 and Fe2O3 with other minor compounds. The plasticity index (12.08 and 16.37) indicates medium ranges of the plasticity of clay. To determine the suitability of ceramic materials, samples were made in a rectangular shape for firing 850°C to 1100°C temperature. The samples were tested for different physical properties such as compressive strength, linear shrinkage, water absorption, porosity and bulk density. Low linear firing shrinkage (0.7% to 2.69%) and water absorption (1.5% to 11%) of the developed ceramic bodies were observed. Scanning Electron Microscope photographs confirm the vitrification of the ceramic bodies. The chemical, physical and ceramic properties of these clays indicate their suitability as raw materials for the production of a wide range of ceramic materials.展开更多
The major objective of this experimental study is to investigate and compare the corrosion resistance of medium Carbon steel (MCS) and KS7 stainless steel in saline and sodium carbonate environments. The MCS and KS7 S...The major objective of this experimental study is to investigate and compare the corrosion resistance of medium Carbon steel (MCS) and KS7 stainless steel in saline and sodium carbonate environments. The MCS and KS7 SS were exposed to 0.5 M each of NaCl and Na2CO3 solutions for a period of 36 days. The weight loss was taken every 3 days in order to evaluate CPR. The results obtained showed that KS7 SS generally offers a better corrosion resistance than the MCS in the selected media. While MCS is found to be inappropriate alloy in saline and sodium carbonate environments, KS7 SS is an unfailing choice material for manufacturing machines and other engineering amenities in which their service lives are predominant in Na2CO3 medium and fairly pleasing in NaCl environment.展开更多
Single crystals of the NLO material L-Prolinium tartrate (LPT) have been grown in the presence and absence of picric acid, by slow evaporation technique. Good quality crystals were harvested within 30 days. The grown ...Single crystals of the NLO material L-Prolinium tartrate (LPT) have been grown in the presence and absence of picric acid, by slow evaporation technique. Good quality crystals were harvested within 30 days. The grown crystals were characterized by single crystal X-ray diffraction. The quality of the crystals grown in the presence and absence of picric acid was examined by high resolution X-ray diffractometry (HRXRD). Fourier transform infrared spectroscopy (FTIR) and Fourier transform Raman spectroscopy were used to confirm the presence of the functional groups of L-Prolinium tartrate and the absence of picric acid in the crystals. The thermal stability and the trend of decomposition of the grown crystals were analyzed by thermo gravimetric analysis (TGA). The influence of picric acid on the second harmonic generation efficiency was studied by Kurtz and Perry method. It was observed that the SHG efficiency increased by about 2.3 times compared to that of normal LPT crystals. The results are discussed in detail.展开更多
This article contributes to the development of the new class of fully biodegradable “green” composites by combining fibers (natural/bio) with biodegradable resin. The vegetable fibers (Triumfetta cordifolia and suga...This article contributes to the development of the new class of fully biodegradable “green” composites by combining fibers (natural/bio) with biodegradable resin. The vegetable fibers (Triumfetta cordifolia and sugarcane bagasse) treated with NaOH and bleached were incorporated into a natural rubber matrix. The influence of the fiber ratio on the physical properties, tensile strength and surface hardness of the hybrid composites was analyzed. The results show that the addition of fibers in the natural rubber matrix increases the water absorption capacity but gradually reduces it with increasing fiber ratio. The hybrid composites of the NRT50-50B proportions show the best tensile strengths at 20 phr and a shore A hardness of 43.7 at 30 phr. The combination of two fibers has improved the physical and mechanical properties of the hybrid composites which can be used in engineering applications.展开更多
Enhancement of productivity optimization is steadily gaining the priority in mining companies especially in the underground coal mining industry which faces a daunting task to balance marginal profit generation with a...Enhancement of productivity optimization is steadily gaining the priority in mining companies especially in the underground coal mining industry which faces a daunting task to balance marginal profit generation with a comparatively high cost of production, volatile market price and rapid grade variation. This paper is aimed to analyze some of the causal factors both technical and site specific which are directly or indirectly impacting the productivity of the longwall coal mining system such as downtime of equipment system in longwall panel, overloading of conveyors and bin, preventive maintenance, gas management practices and injury severity rate. Structured Equation Modelling (SEM) was used to study the causal relationships between the above-mentioned factors and mine productivity. The equipment considered for analysis included shearer, armored face conveyor, crusher, bridge stage loader, chock supports, main gate drive, gate conveyor, hydraulic pumps and crusher. SEM was applied to relate the correlations existing among these causal variables in order to assess their direct or indirect impact on mining productivity. Based on the data extracted over a period of 10 months which included the extraction of 2 longwall panels, the study revealed a significant negative causal relationship between injury severity rate (p < 0.01) and equipment downtime (p = 0.001), with mine productivity. However, preventive maintenance delay time, gas management delay time and conveyor overloading delay time were found to have an insignificant direct influence on mine productivity but indirectly modify it through a significant mediator relationship with equipment downtime. This information would assist mine management to take proper preventive measures.展开更多
The organizations used quality tools to develop their processes and gain satisfaction from the customers. The main objective of this study is to develop levels of quality in the construction industry through the use o...The organizations used quality tools to develop their processes and gain satisfaction from the customers. The main objective of this study is to develop levels of quality in the construction industry through the use of the seven basic quality control tools. Such tools are extremely crucial tools which are used worldwide in the industries for continual improvement. The seven basic quality tools are Check Sheet, Histogram, Pareto Chart, Fishbone Diagram, Control Chart, Flowchart and Scatter Diagram. They were implemented in various steps of the process in order to define the problems, measure its impacts, find out its root causes and solve these problems to ensure the production of non-defective items. The study shows how the seven basic tools of quality are very useful and effective in identifying and removal of defects from the manufacturing process. These tools are helpful in every stage of the defect removal process. This study was conducted on Cleopatra Group Company. This company succeeded to serve the public and private projects in the Egyptian construction sectors.展开更多
The quality assessment and prediction becomes one of the most critical requirements for improving reliability, efficiency and safety of laser welding. Accurate and efficient model to perform non-destructive quality es...The quality assessment and prediction becomes one of the most critical requirements for improving reliability, efficiency and safety of laser welding. Accurate and efficient model to perform non-destructive quality estimation is an essential part of this assessment. This paper presents a structured and comprehensive approach developed to design an effective artificial neural network based model for weld bead geometry prediction and control in laser welding of galvanized steel in butt joint configurations. The proposed approach examines laser welding parameters and conditions known to have an influence on geometric characteristics of the welds and builds a weld quality prediction model step by step. The modelling procedure begins by examining, through structured experimental investigations and exhaustive 3D modelling and simulation efforts, the direct and the interaction effects of laser welding parameters such as laser power, welding speed, fibre diameter and gap, on the weld bead geometry (i.e. depth of penetration and bead width). Using these results and various statistical tools, various neural network based prediction models are developed and evaluated. The results demonstrate that the proposed approach can effectively lead to a consistent model able to accurately and reliably provide an appropriate prediction of weld bead geometry under variable welding conditions.展开更多
In this paper, Okhuen wood sawdust and recycled polyethylene (RLDPE) were blended and then hot-pressed to produce sawdust/recycled polyethylene composite board. The optimum processing parameters for preparing the comp...In this paper, Okhuen wood sawdust and recycled polyethylene (RLDPE) were blended and then hot-pressed to produce sawdust/recycled polyethylene composite board. The optimum processing parameters for preparing the composite such as temperature, pressing time, sawdust/RLDPE content and pressure were investigated and optimized using L<sub>9</sub> (3<sup>4</sup>) Taguchi experimental design orthogonal array. The tensile strength of the various formulations was determined. The results show that those factors made different effects on the tensile strength of the composites. The optimized process conditions obtained are as follows: press time 7 min, press temperature 180°C, saw-dust/RLDPE 60:40%, press pressure 40kg/cm<sup>2</sup>. The average tensile strength of the optimized composite board was 13.991 MPa. The composite board met the standard for general purpose applications.展开更多
文摘This work falls within the general framework of the valorization of the clays of Ivory Coast in order to propose innovative solutions in the resolution of certain problems related to development such as the depollution of water. Its main objective is therefore to study the physico-chemical properties of two Dabou clays with a view to using them in chemical processes for the treatment of dyeing wastewater. The results of the chemical analysis and the ray diffraction showed that the DAB 1 and DAB 2 samples are clays of the kaolinitic type consisting mainly of kaolinite with 51.17% for DAB 1 against 65.81% for DAB 2 and quartz with respectively 41.76% and 25.8% for DAB 1 and DAB 2. They also contain relatively large amounts of goethite with 9.96% for DAB 1 and 12.8% for DAB 2. The specific surfaces measured in both samples are greater than 25 m<sup>2</sup>/g. All the results of the physico-chemical characterization, in particular the presence in significant quantity of clay minerals, the presence of iron compounds and the large specific surface area of both samples, allow the conclusion that they can be used in adsorption studies and in the heterogeneous Fenton process for water treatment.
文摘Silicon and Silicon carbide particles have been investigated by the mean of infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) to establish their surface states. The results of this research are based on the estimation of the area under the high resolution peaks by isosceles triangles. This approach leads to the repartition of the particles surfaces in term of atomic percentage and of type of bonds. The surface of silicon particles is divided up into 54.85% of Si-O bonds and 36.85% of Si-Si bonds. The remaining surface is constituted of zeolite, the raw material used to produce the silicon particles. The surface of silicon carbide particles consists of 50.44% of Si-C bonds, 24.01% of Si-O bonds and 25.55% of graphite. 10.01% of the graphite is derived from the oxidation of Si-C bonds while 11.48% is due to contamination. The zeta potential evolution versus pH confirms the distribution of chemical groups found.
文摘This work aims at the suitability of electroslag process on production of high technological steels such as Maraging steel, modified high speed tool steel (niobium, high nitrogen, and free nitrogen) has been investigated. The experimental results show that high recovery of alloying elements during electroslag remelting of such steels especially high nitrogen tool steel. The previous results are attributed to the slag used in electroslag protect the molten metal from atmospheric oxygen. Also higher recovery of alloying elements during remelting high nitrogen high speed tool steel are due to partial dissolution of nitrides during remelting of such steel which increase nitrogen content above the molten slag which decrease the partial pressure of oxygen leads to protection of molten metal from further oxidation. Also, the results show that, produced ingots are free from internal pipes, porosity and other surface defects. Microstructure obtained for remelted steels is very fine and well distributed for all steel under investigation. In the case of electroslag remelted Maraging steels lower non-metallic inclusions with very fine inclusions and redistribution retained austenite with very fine structure leads to increasing all tensile properties of investigated steels. In the case of high speed tool steels, also the structure is very fine, well distributed, densely and short carbides with lower non-metallic inclusions contents. High cooling rate accompanying with electroslag process has a great effect on type, morphology and content of carbides precipitated in both nitrogen and niobium modified tool steels.
文摘The present work reveals the study of mechanical properties of Al2024-Tungsten carbide MMCs containing tungsten carbide (WC) particulates. The reinforcing particulates in the Al2024 alloy were varied from 0% to 5% by weight. The vortex method of cast production was employed to fabricate the MMCs, in which the reinforcement was poured into the vortex created by stirring the molten metal by means of a mechanical agitator. The composite so produced was subjected to a series of mechanical tests. The results of this study revealed that as the tungsten carbide particle content was increased, there were significant increases in the ultimate tensile strength, hardness and young’s modulus, compressive strength, accompanied by a reduction in its ductility. An attempt is made in the paper to provide explanations for these phenomena.
文摘In this investigation, an attempt has been made to develop Al6061-Frit particulate metal matrix composites through stir casting technique using metal molds and to study the corrosion behaviour. Pre heated frit particles were added to matrix as reinforcement. Al6061 containing 2 wt% to 8 wt % in steps of 2 wt % of frit particulate composites were prepared. Corrosion tests were conducted by using Potentiostat model SEP238C where 3.5% NaCl solution was used as corrodent. The corrosion rate of metal matrix composites was lower than that of matrix material Al6061 under the corrosive atmosphere for both un-heat treated and heat treated conditions.
文摘A transparent polymer based solar cell was designed and fabricated to utilize the solar energy when exposed to sunlight. The transparent solar cell for window module was composed of a polymeric material PPV (Polyphenylene vinylene), ITO (Indium Tin Oxide) and electrode (Al, Mg, Ca). The polymeric sheet of this cell is by casting process, and electrode is applied on it by CVD (Chemical Vapor Deposition) process. The solar energy collected by this window can be used to power up small household electrical appliances. Recently, polymeric solar cell is made by a roll-to-roll process without using indium-tin oxide (ITO). A commercially available kapton (Polyimide) foil with an over layer of copper was used as the substrate. Sputtering of titanium metal on to the kapton/copper in a vacuum metalizing process gave the monolithic substrate and back electrode for the devices. The active layer was slot-die coated on to the kapton/Cu/Ti foil followed by slot-die coating of a layer of PET, PC or PEN.
文摘Blending of polymer with organic/inorganic material has given a new direction for developing novel materials. This is an easy and inexpensive method of modifying various properties of the individual materials and composites. The aim of the present work is an attempt to incorporate crystals in polymer host and investigate the effect, on optical properties of the of polymer- crystal combine. In this paper a novel technique of incorporating inorganic/organic crystal in a host polymer matrix is reported. Crystals of acetoacetanilide (AA) are grown in the host Poly Methyl Methacrelate (PMMA) by simple evaporation technique. The scanning electron micrograph (SEM) studies reveal the growth of Acetoacetanilide crystals of varying sizes and shapes (flakes) in prepared samples. The results are confirmed by various spectroscopic characterization studies such as X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and the UV-Vis spectroscopy. The investigations carried out, show a change in optical absorption band edge which is attributed due to change in band gap because of crystal sizes.
文摘This study determined mineral value and antioxidant activity of Senegal fruits for contributing to improving healthy diet and preventing some chronic diseases. Mineral element contents of Dialium guineense, Landolphia heudelotti, Mangifera indica, Cyperus esculentus and Saba senegalensis, which are widely available and consumed, were studied. The results by ICP-OES spectrophotometry after acid mineralization showed highest levels of (per 100 g fruits), calcium (158 mg), potassium (1018 mg), magnesium (532 mg), zinc (26 mg) with juice of Landolphia heudelotti fruit pulp. Mangifera indica pulp is richer in sodium (89 mg), phosphorus (556 mg), sulphur (384 mg) and silicon (110 mg). Dialium senegalensis pulp is richer in iron (23 mg) and manganese (19 mg). Lyophilized Cyperus esculentus rhizomes analyzed by atomic absorption spectrophotometry gave highest concentrations of (per 100 g fruits), calcium (2550 mg), potassium (11,843 mg) and magnesium (7669 mg) but sodium content (22 mg) is lower. In vitro antioxidant activity evaluation with the DPPH radical showed for 10 mg/ml concentration, highest inhibition percentage for Saba senegalensis 4.03%, followed by Landolphia heudelotti and Dialium guineense, which were significantly similar 2.29% and 2.20% respectively, Mangifera indica 1.7% and finally Cyperus esculentus 0.5%, but much lower compared to the ascorbic acid equal to 96.32% used as a reference.
文摘The problem of void growth and interaction is of importance to understanding the mechanics of failure in metals exhibiting ductility. In this work, the growth and interaction of voids in 6061-T6 aluminum were studied experimentally. Specifically, holes of varying numbers and relative placement were investigated for their normalized area growth with applied displacement. Flat dog-bone specimens were carefully drilled in their gauge area with no (zero) holes, one hole, and two holes (arranged vertically or horizontally) for experimentation after polishing. The growth of holes, captured by video recordings, exhibited exponential behavior and was influenced greatly by the number and arrangement of holes with the horizontal voids growing the fastest and the vertical ones growing the slowest. Also, the ensuring deformation of the sample was studied using load-displacement curves, pictography and videography, SEM imaging and Atomic Force Microscopy (AFM). The methods revealed that although the major part failure is due to large crack formation, it was preceded by intense dislocation slip activity and the formation of micro cavities. Also, the AFM quantified the three-dimensional nature of crystal or grain deformation and how it is greatly influenced by distance and location from the hole. Lastly, theoretical understanding of hole growth was offered.
文摘A technological clayey sandstone sample from Wadi Qena locality, Eastern Desert of Egypt, was directed to processing. Fine kaolin and clean silica sand were produced after intensive attrition scrubbing of the sample. To increase the quality of the produced silica, it was subjected to reverse anionic flotation to minimize its iron content. In this respect, conventional flotation tests using three anionic oxyhydryl surfactants namely: sodium dodecyl benzene sulphonate, sodium naphtha sulphonate, and sodium dodecyl sulphate, were tried. Results showed a privilege action for sodium dodecyl sulphate to remove most of the iron oxide content of the sample. A statistical Box-Behnken design was constructed to optimize the process efficiency. It was shown that from a flotation feed contained 360 ppm Fe<sub>2</sub>O<sub>3</sub> and 1190 ppm Al<sub>2</sub>O<sub>3</sub>, sand concentrate contained 29 ppm Fe<sub>2</sub>O<sub>3</sub> and 564 ppm Al<sub>2</sub>O<sub>3</sub>, was produced. The optimum flotation conditions were 3.86 kg/t sodium dodecyl sulphate dose, 3.22 flotation pulp pH, 1226 rpm impeller speed, and 22.24 L/min airflow rate. Variables interaction effects results showed that flotation separation efficiency was significantly influenced by air flow rate and cell impeller speed of the process.
文摘The use of waste materials to produce engineering components is currently attracting so much interest due to their low cost, availability and environmental impact. In this study, coconut shell ash (CSA) and kyanite particles (KP) produced from coconut shells and kyanite mineral respectively were characterized. X-ray Florence (XRF), X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to analyze the oxide compositions, crystalline phases and microstructures of CSA and KP. The XRF analysis revealed major oxides in CSA and KP as SiO2 and Fe2O3;and Al2O3 and SiO2 respectively. The XRD analysis revealed the presence of Quartz, Hematite, Andradite and Gaultite phases at major peaks in diffractogram of CSA;and Quartz and Beryl phases at major peaks in the diffractogram of KP. The crystallite sizes of the quartz phases in CSA and KP at diffraction angle of 26.72°C and 20.91°C were determined as 638.28 Åand 789.38 Årespectively. From the SEM image of CSA, it was observed that particles of different sizes are present in the microstructure of CSA. The average size of the particles in the microstructure of CSA is 26.24 μm. A similar result was observed in the SEM image of KP and average size of the particles is 3.074 μm. Also, the energy dispersive X-ray (EDX) spectrums of CSA and KP revealed the presence of many elements with calcium as the major element in CSA and Aluminium as major element in KP. The presence of the crystalline phases in CSA (SiO2, Al2O3, andradite, gaultite and hematite) and KP (SiO2 and Al2O3) will make them good strengthening materials for the production of Aluminium based composites that can be used in applications where a good combination of strength and wear characteristics is a basic requirement like brake disc.
文摘This paper focuses on the study of the physical, biochemical, structural, and thermal properties of plant fibres of <i>Rhecktophyllum camerunense</i> (RC), <i>Neuropeltis acuminatas</i> (NA) and <i>Ananas</i> <i>comosus</i> (AC) from the equatorial region of Cameroon. The traditional use of these fibres inspired researchers to investigated their properties. This study aims at improving the state of knowledge with a view to diversifying applications. The fibres are extracted by retting. Then, their apparent density was measured following the ASTM D792 standard and their water moisture absorption and moisture content were also evaluated. Their molecular structure was studied by ATR-FTIR spectroscopy. A quantitative analysis of the biochemical composition was performed according to the analytical technique for the pulp and paper industry (TAPPI). A TGA/DSC analysis was also performed. The results reveal that the AC, NA and RC fibres have densities of 1.26 ± 1.06, 0.846 ± 0.13 and 0.757 ± 0.08 g·cm<sup>-3</sup> respectively. They are also hydrophilic with a water absorption rate of 188.64 ± 11.94%, 276.16% ± 8.07% and 198.17% ± 20%. They have a moisture content of 12.21%, 10.36% and 9.37%. The studied fibres exhibit functional groups that are related to the presence of hemicellulose, pectin, lignin and cellulose. The cellulose crystallinity index was found to be 67.99%, 46.5% and 59.72% respectively. The fibres under study have the following chemical composition: an extractive content of 3.07%, 14.77% and 8.74%;a pectin content of 4.15%, 7.69% and 3.45%;a hemicellulose content of 4.90%, 15.33% and 7.42%;a cellulose content of 68.11%, 36.08% and 65.15%;a lignin content of 12.01%, 25.15% and 16.2%;and an ash content of 0.27%, 1.53% and 0.47% respectively. The thermal transitions observed on the thermograms correlate with the TAPPI chemical composition. It is observed that these fibres are thermally stable up to temperatures of 200°C, 220°C and 285°C. These results make it possible to envisage uses similar to those of sisal, hemp and flax fibres.
文摘This study focuses on mineralogical and chemical characterization of clay of Sitakunda anticline, Bangladesh and potential suitability of this shale as raw materials in ceramic industries. The shale which is clay in texture is composed of chlorite and kaolinite with common illite, smectite, quartz, mica and feldspar. There are two types of samples in color, grey and red. Chemical compositions of clay samples are analyzed by XRF and mineralogical composition of sample analyzed by XRD. Clay samples contain significant amount SiO2, Al2O3 and Fe2O3 with other minor compounds. The plasticity index (12.08 and 16.37) indicates medium ranges of the plasticity of clay. To determine the suitability of ceramic materials, samples were made in a rectangular shape for firing 850°C to 1100°C temperature. The samples were tested for different physical properties such as compressive strength, linear shrinkage, water absorption, porosity and bulk density. Low linear firing shrinkage (0.7% to 2.69%) and water absorption (1.5% to 11%) of the developed ceramic bodies were observed. Scanning Electron Microscope photographs confirm the vitrification of the ceramic bodies. The chemical, physical and ceramic properties of these clays indicate their suitability as raw materials for the production of a wide range of ceramic materials.
文摘The major objective of this experimental study is to investigate and compare the corrosion resistance of medium Carbon steel (MCS) and KS7 stainless steel in saline and sodium carbonate environments. The MCS and KS7 SS were exposed to 0.5 M each of NaCl and Na2CO3 solutions for a period of 36 days. The weight loss was taken every 3 days in order to evaluate CPR. The results obtained showed that KS7 SS generally offers a better corrosion resistance than the MCS in the selected media. While MCS is found to be inappropriate alloy in saline and sodium carbonate environments, KS7 SS is an unfailing choice material for manufacturing machines and other engineering amenities in which their service lives are predominant in Na2CO3 medium and fairly pleasing in NaCl environment.
文摘Single crystals of the NLO material L-Prolinium tartrate (LPT) have been grown in the presence and absence of picric acid, by slow evaporation technique. Good quality crystals were harvested within 30 days. The grown crystals were characterized by single crystal X-ray diffraction. The quality of the crystals grown in the presence and absence of picric acid was examined by high resolution X-ray diffractometry (HRXRD). Fourier transform infrared spectroscopy (FTIR) and Fourier transform Raman spectroscopy were used to confirm the presence of the functional groups of L-Prolinium tartrate and the absence of picric acid in the crystals. The thermal stability and the trend of decomposition of the grown crystals were analyzed by thermo gravimetric analysis (TGA). The influence of picric acid on the second harmonic generation efficiency was studied by Kurtz and Perry method. It was observed that the SHG efficiency increased by about 2.3 times compared to that of normal LPT crystals. The results are discussed in detail.
文摘This article contributes to the development of the new class of fully biodegradable “green” composites by combining fibers (natural/bio) with biodegradable resin. The vegetable fibers (Triumfetta cordifolia and sugarcane bagasse) treated with NaOH and bleached were incorporated into a natural rubber matrix. The influence of the fiber ratio on the physical properties, tensile strength and surface hardness of the hybrid composites was analyzed. The results show that the addition of fibers in the natural rubber matrix increases the water absorption capacity but gradually reduces it with increasing fiber ratio. The hybrid composites of the NRT50-50B proportions show the best tensile strengths at 20 phr and a shore A hardness of 43.7 at 30 phr. The combination of two fibers has improved the physical and mechanical properties of the hybrid composites which can be used in engineering applications.
文摘Enhancement of productivity optimization is steadily gaining the priority in mining companies especially in the underground coal mining industry which faces a daunting task to balance marginal profit generation with a comparatively high cost of production, volatile market price and rapid grade variation. This paper is aimed to analyze some of the causal factors both technical and site specific which are directly or indirectly impacting the productivity of the longwall coal mining system such as downtime of equipment system in longwall panel, overloading of conveyors and bin, preventive maintenance, gas management practices and injury severity rate. Structured Equation Modelling (SEM) was used to study the causal relationships between the above-mentioned factors and mine productivity. The equipment considered for analysis included shearer, armored face conveyor, crusher, bridge stage loader, chock supports, main gate drive, gate conveyor, hydraulic pumps and crusher. SEM was applied to relate the correlations existing among these causal variables in order to assess their direct or indirect impact on mining productivity. Based on the data extracted over a period of 10 months which included the extraction of 2 longwall panels, the study revealed a significant negative causal relationship between injury severity rate (p < 0.01) and equipment downtime (p = 0.001), with mine productivity. However, preventive maintenance delay time, gas management delay time and conveyor overloading delay time were found to have an insignificant direct influence on mine productivity but indirectly modify it through a significant mediator relationship with equipment downtime. This information would assist mine management to take proper preventive measures.
文摘The organizations used quality tools to develop their processes and gain satisfaction from the customers. The main objective of this study is to develop levels of quality in the construction industry through the use of the seven basic quality control tools. Such tools are extremely crucial tools which are used worldwide in the industries for continual improvement. The seven basic quality tools are Check Sheet, Histogram, Pareto Chart, Fishbone Diagram, Control Chart, Flowchart and Scatter Diagram. They were implemented in various steps of the process in order to define the problems, measure its impacts, find out its root causes and solve these problems to ensure the production of non-defective items. The study shows how the seven basic tools of quality are very useful and effective in identifying and removal of defects from the manufacturing process. These tools are helpful in every stage of the defect removal process. This study was conducted on Cleopatra Group Company. This company succeeded to serve the public and private projects in the Egyptian construction sectors.
文摘The quality assessment and prediction becomes one of the most critical requirements for improving reliability, efficiency and safety of laser welding. Accurate and efficient model to perform non-destructive quality estimation is an essential part of this assessment. This paper presents a structured and comprehensive approach developed to design an effective artificial neural network based model for weld bead geometry prediction and control in laser welding of galvanized steel in butt joint configurations. The proposed approach examines laser welding parameters and conditions known to have an influence on geometric characteristics of the welds and builds a weld quality prediction model step by step. The modelling procedure begins by examining, through structured experimental investigations and exhaustive 3D modelling and simulation efforts, the direct and the interaction effects of laser welding parameters such as laser power, welding speed, fibre diameter and gap, on the weld bead geometry (i.e. depth of penetration and bead width). Using these results and various statistical tools, various neural network based prediction models are developed and evaluated. The results demonstrate that the proposed approach can effectively lead to a consistent model able to accurately and reliably provide an appropriate prediction of weld bead geometry under variable welding conditions.
文摘In this paper, Okhuen wood sawdust and recycled polyethylene (RLDPE) were blended and then hot-pressed to produce sawdust/recycled polyethylene composite board. The optimum processing parameters for preparing the composite such as temperature, pressing time, sawdust/RLDPE content and pressure were investigated and optimized using L<sub>9</sub> (3<sup>4</sup>) Taguchi experimental design orthogonal array. The tensile strength of the various formulations was determined. The results show that those factors made different effects on the tensile strength of the composites. The optimized process conditions obtained are as follows: press time 7 min, press temperature 180°C, saw-dust/RLDPE 60:40%, press pressure 40kg/cm<sup>2</sup>. The average tensile strength of the optimized composite board was 13.991 MPa. The composite board met the standard for general purpose applications.
