Showing papers in "Advanced Materials Research in 2019"

Comparative Study of the Second Generation a-Si:H, CdTe, and CIGS Thin-Film Solar Cells

Abstract: In this article, simulation results of novel and facilitated heterostructures of the Second Generation (2G) Thin-film Solar Cells (TFSCs): hydrogenated amorphous Silicon (a-Si:H), Cadmium Telluride (CdTe), and Copper Indium Gallium di-Selenide (Cu(In,Ga)Se2 or CIGS) have been presented to compare their performances. The solar cells have been modeled and analyzed for investigating optimized structure with higher stabilized efficiency. Entire simulations have been accomplished using Analysis of Microelectronic and Photonic Structures – 1 Dimensional (AMPS-1D) device simulator. The thickness of the absorber layer was varied from 50 nm to 1400 nm for a-Si:H and from 50 nm to 3 μm for both CdTe and CIGS cells to realize its impact on cell performance. The utmost efficiency, η of 9.134%, 20.776%, and 23.03% were achieved at AM 1.5 (1000 W/m2) for a-Si:H, CdTe, and CIGS material cells, respectively. Lastly, the operating temperature of the three cells was varied from 280°K to 328°K to realize its effect on the cell PV performances.

Electrochemical Frequency Modulation and Reactivation Investigation of Thioglycolurils in Strong Acid Medium

Abstract: The Electrochemical frequency modulation and Reactivation investigation results have shown that the anticorrosion inhibitors of 3a,6a- bistolylthioglycoluril, 4,5-dihydroxy-4,5-bistolylimidazolidine-2-thione and 5,5-bistolyl-2-thione-4-imidazolidone maximally reduced H+ impacts on metal surface so these inhibitors have decreased the degree of sensitization to intergranular stress corrosion cracking on N80 steel surface.

Thermal Buckling of Functionally Graded Sandwich Beams

Abstract: Thermal buckling of new model of functionally graded (FG) sandwich beams is presented in this study. Material properties and thermal expansion coefficient of FG sheets are assumed to vary continuously along the thickness according to either power-law (P-FGM) or sigmoid function (S-FGM) in terms of the volume fractions of the constituents. Equations of stability are derived based on the generalized higher-order shear deformation beam theory. Thermal loads are supposed to be constant, linear or nonlinear distribution along the thickness direction. An accurate form solution for nonlinear temperature variation through the thickness of S-FGM and P-FGM sandwich beams is presented. Numerical examples are presented to examine the influence of thickness ratio, the inhomogeneity parameter and the thermal loading kinds on the thermal buckling response of various types of FG sandwich beams.

Early Hydration of Activated Belite-Rich Cement

Abstract: Implementation of high belite cement in cement production would have strong environmental impact in reduction CO2 emissions and saving of pure limestone deposits. The goal of the study is to describe the role of alkali and C-S-H activators on hydration of high belite cement. Analytical approach for early hydration is based on combination of isothermal calorimetry, X-ray powder diffraction in-situ, DTA-TG, FT-IR.

PVA and PVP Hydrogel Blends for Wound Dressing: Synthesis and Characterisation

Abstract: The purpose of this study is the development and characterizations of novel polyvinyl alcohol (PVA)/polyvinyl pyrolidone (PVP) hydrogel blends. Different mixtures of the two polymeric solutions leaded to several hydrogels that were further characterized using X-ray difraction (XRD), differential thermal and thermogravimetric analysis (DTA/TGA) and Fourier transform infrared spectroscopy (FTIR). The influence of the polymer type on hydrogel hydration was also studied, by observing and comparing the samples after drying and rehydration in bidistilled water. The results revealed the maintenance of the amorphous character of the hydrogels after rehydration as well as a higher softening and decomposition temperature in direct relation with the increase of PVA content. The best wetting and swelling results were also given by the hydrogel with the highest PVA content prepared at pH 6.

Utilization of XSYTIN-1 Tool in Electrically-Assisted Friction Stir Welding of Dissimilar Metals - Al 6061-T651 to Mild Steel

Abstract: Friction stir welding (FSW) is a solid-state metal fusion process that is characterized by several benefits over comparable processes such as a reduction in energy input and low part distortion. This process has been shown to hold great potential in the fusion of dissimilar metals, a technology highly sought after in the aerospace and automotive industries for its promising weight-reduction capabilities. Furthermore, electrically-assisted FSW (EAFSW) is the supplementation of the FSW process with an electrical current. This modification has been shown to improve many parameters; however, the current literature related to this subject is scarce. Herein, the fusion of Al 6061-T651 to mild steel is performed using EAFSW methods. A novel tool constructed a proprietary ceramic, XSYTIN-1, is also tested in this application. It was found that EAFSW improved material flow between the constituent materials; however, was unable to increase the joint strength of the weld. Additionally, it was found that the XSYTIN-1 tool did not exhibit any significant differences when compared to a conventional steel tool.

Retracted: Development of Bulk Metallic Glass Matrix Composites (BMGMC) by Additive Manufacturing: Modelling and Simulation – A Review: Part A

Abstract: Bulk metallic glasses (BMGs) and their composites (BMGMC) have emerged as competitive materials for structural engineering applications exhibiting superior tensile strength, hardness along with very high elastic strain limit. However, they suffer from a lack of ductility and subsequent low toughness due to the inherent brittleness of the glassy structure which render them to failure without appreciable yielding owing to mechanisms of rapid movement of shear bands all throughout the volume of the material. This severely limits their use in the manufacture of structural engineering parts. Various theories and mechanisms have been proposed to counter this effect. Introduction of secondary ductile phase in the form of in-situ nucleating and growing dendrites from melt during solidification have proved out to be best solution of this problem. Nucleation and growth of these ductile phases have been extensively studied over the last 16 years since their introduction for the first time in Zr-based BMGMC by Prof. Johnson at Caltech. Data about almost all types of phases appearing in different systems have been successfully reported. However, there is very little information available about the precise mechanism underlying their nucleation and growth during solidification in a copper mould during conventional vacuum casting and melt pool of additively manufactured parts. Various routes have been proposed to study this including experiments in microgravity, levitation in synchrotron light and modelling and simulation. In this report, which is Part B of two parts comprehensive overview, state of the art of development, manufacturing, characterisation and modelling and simulation of BMGMCs is described in detail. Evolution of microstructure in BMGMC during additive manufacturing have been presented with the aim to address fundamental problem of lack in ductility along with prediction of grain size and phase evolution with the help of advanced modelling and simulation techniques. It has been systematically proposed that 2 and 3 dimensional cellular automaton method combined with finite element (CAFE) tools programmed on MATLAB® and simulated on Ansys® would best be able to describe this phenomenon in most efficient way. Present part B focuses on methodology by which modelling and simulation can be adopted and applied to describe evolution of microstructure in this complex class of materials.

Investigation of Workability and Compressive Strength of Wood Ash Cement Concrete Containing Nanosilica

Abstract: Studies have revealed that wood ash cement concrete just like other pozzolanic cement concrete has lower early strength compared to plain cement concrete. Nanoparticles have been found to improve the early strength of concrete due to its small size and large surface area. This paper reports the findings on influence of nanosilica on the workability and compressive strength of wood ash cement concrete. Wood ash was obtained as a waste product from Ladoke Akintola University of Technology (LAUTECH) bread bakery, Ogbomoso. Biological synthesis of nanosilica using kola pod extract and silica precursor (1:5) was conducted at Nanotechnology research group laboratory at LAUTECH. The chemical composition, specific gravity and grading of wood ash, fine and coarse aggregate used were determined. Concrete with 10% wood ash replacement for cement was produced using 1:2:4 mix proportion and water to binder ratio of 0.5. Nanosilica was added at 0.5, 1.0, 1.5 and 2.0% levels. Concrete with no wood ash and nanosilica served as the control. Workability and compressive strength of the plain and composite concrete were determined. The results showed that concrete workability was enhanced with introduction of nanosilica. The compressive strength also increased with the addition of nanosilica. Maximum compressive strength of 27.53MPa was achieved at 90 days with 1.5% nanosilica addition. It was concluded that nanosilica enhanced workability and improved both early and later strength development in wood ash concrete with 1.5% as the optimum addition.

Synthesis of Biodegradable Mixing-Polymer as Coating Material for Controlled-Release Urea Fertilizer

Abstract: The biodegradable mixing-polymer as low cost, environmentally friendly coating material for controlled-release urea fertilizer was synthesized by borax crosslinked phosphated distarch phosphate (PDSP)/polyvinyl alcohol (PVA) and polyacrylic acid (PAA) via pan coating method. The physico-chemical characteristics of biodegradable mixing-polymer were confirmed by FTIR, TGA and SEM techniques. The kinetics of urea release were also carefully investigated in water and soil. It’s been found that a uniform layer with better bonding structure was created on surface of the mixing-polymer PDSP/PVA-PAA and the time released 70% urea reached 6 hours in water and more than 27 days in soil.

Effect of Electrode Coating on Austenitic Stainless Steel Weld Metal Properties

Abstract: The effect of electrode coating on austenitic stainless steel weld metal properties was studied. Manual metal arc welding method was used to produce the joints with the tungsten inert gas welding serving as the control. Metallographic and chemical analyses of the fusion zones of the joints were conducted. Results indicate that the weldment produced from E 308-16/12 lime-titania electrode has a higher ductility and strength of about 36% in terms of percentage elongation and 517 N/mm2 respectively, compared to 26% and 18% and 475 N/mm2 and 425 N/mm2 respectively, obtained from weldments produced from E 308-16/10 rutile and E 308-16/12 rutile electrodes respectively. The presence of lime which is a slag former in E 308-16/12 lime-titania electrode was relevant in slowing down the cooling rate of both the weld pool and the just solidified weld metal resulting in the overall improvement of the resultant weld metal properties. It was found that the values of the strain hardening exponent were 0.379 for E 308-16 gauge 10, rutile electrode, 0.406 for E 308-16 gauge 12 rutile electrode, 0.382 for TIG welding, 0.353 for E 308–16 gauge 12, lime-titania electrode, 0.435 for E 310-16 gauge 10, rutile electrode. E 310 – 16 gauge 10, rutile electrode had the greatest strength and strain hardening coefficients of 1180 N/mm2 and 0.435 respectively, and will be more amenable to cold working. Keywords: Austenitic stainless steel, microstructure, electrode coating, welding, joints.

Comparative Study of Jute, Okra and Pineapple Leaf Fiber Reinforced Polypropylene Based Composite

Abstract: In this experimental studies, three types of fabric such as Jute, Okra and Pineapple Leaf Fiber (PALF) were selected and matrix material such as polypropylene (PP) was selected to manufacture composites. Jute/PP, Okra/PP, and PALF/PP based composites were prepared successfully by a conventional compression molding technique. The objective of this study is to compare the mechanical such as tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM), elongation at break (Eb%) and interfacial properties of the composites. Jute fiber (hessian cloth)-reinforced polypropylene matrix composites (45wt% fiber) were fabricated by compression molding. TS, TM, BS, BM, and IS of the composites were found to be 45 MPa, 2.2 GPa, 54 MPa, 4.1 GPa, and 16 kJ/m2, respectively. Then Okra and PALF fiber reinforced polypropylene-based composites (45 wt% fiber) were fabricated and the mechanical properties were compared with those of the jute-based composites. The result revealed that mechanical properties of PALF composite higher than jute and Okra fiber reinforced composites. Water absorption and elongation percentage at break showed different scenario and it was noticed from the experimental study that water absorption and elongation at break (%) of jute fabric was higher than other composites. Fracture sides of the composites were studied by scanning electron microscope (SEM), and the results revealed poor fiber-matrix adhesion for jute fiber-based composites compared to that of the other fiber-based composites (OF/PP and PALF/PP). KEY WORDS: Polypropylene, Jute Fiber, Okra Fiber, Pineapple Fiber, Mechanical Properties, Interfacial Properties, Composites. *Corresponding Address: dr.ruhul_khan@yahoo.com

Development of Bulk Metallic Glasses and their Composites by Additive Manufacturing - Evolution, Challenges and a Proposed Novel Solution

Abstract: Bulk metallic glasses (BMGs) and their composites (BMGMCs) have emerged as competitive materials for structural engineering applications exhibiting superior tensile strength, hardness along with very large elastic strain limit. However, they suffer from lack of ductility and subsequent low toughness due to the inherent brittleness of the glassy structure which makes them amenable to failure without appreciable yielding. Various mechanisms and methods have been proposed to counter this effect out of which, recently Additive Manufacturing has gained widespread attention. It is proposed that additive manufacturing can overcome these difficulties in single step due to inherent existence of very high cooling rate in the process which is essential for glass formation. This, when coupled with careful selection of alloy chemistry is proposed to be the best solution to fabricate near net shape parts in a single step with excellent properties. In this report, an effort has been made to describe one possible route to achieve this. Solidification processing employing carefully selected inoculants based on edge to edge matching technique along with the carefuly controlled inoculation procedure is proposed to reflect upon enhanced mechanical properties. It is hypothesized that number density, size and distribution of ductile crystalline phase would best be able to improve microstructure and hence properties. This is meant to be controlled by manipulating type, size and the amount of inoculants. The proposed methodology is claimed to bear maximum potential.

Regeneration of Waste Diatomite from Palm Oil Production Process as a Support Material for PCMs in Thermal Energy Storage in Buildings

Abstract: In this study, the use of spent diatomite, an industrial waste in the palm oil production process, was evaluated as a support material for phase change materials (PCMs). Calcination tests of the diatomite were carried out at different temperatures (400, 550 and 700 °C) and times (1 and 2 h). For the PCMs preparation, the organic phase, mixtures of palm oil and commercial stearic acid esters, were impregnated on calcined diatomite under vacuum. Differential scanning calorimetry (DSC) analyses were performed in order to select the PCM with the highest latent heat of fusion and a range of phase change temperature corresponding to the thermal comfort range. DSC, TGA and FT-IR analyses were performed before and after the application of 360 thermal cycles to establish the thermal and chemical reliability of the PCM. It was found that 700 °C and 1 h are the best conditions of the calcination process, and the PCM consisting in 100 % methyl esters of commercial stearic acid presented the highest value of latent heat of fusion (34.67 J/g) and a phase change temperature range of 16.4 to 33.5 °C. After the thermal cycles, the results show that the prepared PCMs has thermal and chemical stability.

The Effect of Electropolishing Time Variation at Room Temperature and Low Voltage on the Surface Quality of Cardiovascular Stent

Abstract: Electropolishing is an attractive method for surface smoothing of cardiovascular stent. This study investigated the effect of times of electropolishing on the surface characteristics both are upper surface and surface of the strut of cardiovascular stent after the by die sinking electrical discharge machining (EDM). The observed surface characteristics of the strut were recast layer, surface roughness and brightness. The weight analysis, and the reduction of the width strut were conducted. The recast layer was analyzed by optical microscope qualitatively, the surface roughness was measured by surface texture measuring instrument, the weight analysis and the reduction of width strut were calculated. The stent was made from steel AISI 316 L. The times which were used in the electropolishing were 3 minutes, 7 minutes, and 11 minutes. The experimental results show that the time for smoothing and brightening of stent at room temperature and low voltage 5 V is 7 minutes. The times affect the upper and EDM surface roughness, the weight of stent and the width of strut. The results show that increasing of times, than the value of surface roughness, the weight of stent and the width of strut will decrease, and vice versa. The average surface roughness of EDM surface after electropolishing is in the range of 3.49 – 1.62 µm. The average surface roughness of upper surface after electropolishing is in the range of 0.55-0.22 µm. The weight analysis show that the loss of weight is in the range of 0.12-1.12 %, and the reduction of width strut is in the range of 11.02 – 69.3 %.

Development of Methodology for Determining the Physical Properties of Natural and Innovative Materials

Abstract: The high energy consumption of buildings in the various sectors of society, the exploitation of natural resources and the use of fossil fuels make it necessary to research constructive alternatives that can reduce the impact on the planet. The use of thermal insulation in buildings is important for the reduction of energy consumption, however, most of the materials developed are manufactured generating high rates of pollution. This study starts with the use of natural elements (corn cob / soybean straw / pine bark) and innovative elements (vacuum / slimstone plate), in order to improve energy efficiency of buildings. The methodological development of the work began in the selection of materials and development of facade cladding boards. The determination of the thermal conductivity was analyzed using a heating plate and PT100 temperature sensors, determination of the apparent and actual density, and analysis of the material composition using Scanning Electron Microscopy (SEM). After the development of the analyzes, the natural slabs and recycled slimstone showed significant results, with thermal conductivity lower than 0.07 W / m.k.

Effect of Mo Addition on Room and High Temperature Tensile Behavior of Al-Si-Cu-Mg Alloy in As-Cast and Heat-Treated Conditions

Abstract: This study focuses on the role of Mo addition on the mechanical properties of an Al-Si-Cu-Mg alloy in as-cast and heat-treated condition at ambient and elevated temperature. Addition of 0.4 to 0.6 wt.% Mo forms Mo-bearing dispersoid particles which have a relatively high melting point and improve high temperature tensile strength. Ductility suffered in the presence of Mo-bearing particles. Trace addition of Mo up to 0.6 wt.% has a negligible influence on the yield strength and hardness of Al-Si-Cu-Mg alloy in as-cast and heat-treated conditions at ambient temperature and 250 °C.

Preparation and Characterization of Polypropylene and Unsaturated Polyester Resin Filled with Jute Fiber

Abstract: Jute fabrics reinforced Polypropylene (PP) matrix composite was fabricated by compression molding and Unsaturated Polyester Resin (UPR) matrix composites were also fabricated by hand lay-up technique. The fiber content of the composites was 40% by weight. Mechanical properties between two types of composites were compared. Tensile Strength (TS), Tensile Modulus (TM), Elongation at break (Eb%) , and Impact Strength (IS) of the jute fabrics/PP composites were found to be 47 MPa, 1.2 GPa, 13% and 8 kg/cm, respectively. On the other hand, TS, TM, Eb%, and IS of the jute fabrics/UPR composite were found to be 43 MPa, 1.3 GPa, 10% and 6 kg/cm, respectively. It was found that both composites showed almost similar mechanical properties. After tensile testing, fracture sides of both types of the composites were studied by Scanning Electron Microscope (SEM) and the results revealed poor fiber matrix adhesion for jute fabrics with PP and UPR. The fabricated composites became partly biodegradable because of jute (natural fiber) and mechanical properties of both types of composites showed promising results for commercial applications.

Powder Bed Fusion of Biomedical Co-Cr-Mo and Ti-6Al-4V Alloys: Microstructure and Mechanical Properties

Abstract: Powder bed fusion (PBF) is an additive manufacturing technique, which allows to build complex functional mechanical parts layer-by-layer, starting from a computer-aided design (CAD) model. PBF is particularly attractive for biomedical applications, where a high degree of individualization is required. In this work, the microstructure of two biomedical alloys, namely Co-Cr-Mo and Ti-6Al-4V, were studied by X-ray diffraction and electron microscopy techniques. Hardness and tensile tests were performed on the sintered parts.

Effect of Temperature, Strain and Strain Rate on Efficiency of Power Dissipation during Hot Deformation of Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B (at. %) Shape Memory Alloy Using Taguchi Method

Abstract: Recently a ferrous-based Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B (at.%) shape memory alloy (abbreviated NCATB) has attracted attention because of its huge superelasticity (～13%). In order to manufacture this alloy on a large scale, a deeper knowledge of the plastic deformation behaviour of the alloy is required. During hot deformation, temperature and strain rate exert significant effect on the mechanical properties. The main objective of the work, therefore, is to investigate the influence of deformation parameters, such as temperature, strain rate and strain, on flow behaviour of an NCATB shape memory alloy. Flow behaviour tests on an NCATB alloy were performed on a Gleeble-3800 thermomechanical simulator at deformation temperatures of 1100, 1150 and 1200°C and strain rates of 0.1, 1.0 and 10s-1 with the strains maintained at 0.2, 0.4 and 0.6, respectively. The workpiece is considered asa dissipater of power, and the features of power dissipation will,therfore, be seen as changes in the microstructure. These features of power dissipation are measured by a parameter called efficiency of power dissipation (η). It is directly related to the strain rate sensitivity parameter(m). Taguchi method is used to evaluate the influence of deformation temperature, strain rate and strain on efficiency of power dissipation. Based on the results, optimum parameters for higher efficiency of power dissipation are: 1150°C (temperature), 0.1 s-1 (strain rate) and 0.2 (strain). An analysis of experimental results in terms of percentage contribution reveals that strain rate plays a more predominant role (39.73%) compared to temperature (24.03%) and strain (32.73%) on NCATB alloy.

Performance of Rice Husk Ash - Calcium Carbide Waste in Concrete

Abstract: This paper examines and present the findings of the physical and mechanical properties of concrete containing rice husk ash (RHA), and the blend of rice husk ash with calcium carbide waste (RHA-CCW). Concrete cubes, cylindrical and beam specimens containing different percentages of RHA and RHA-CCW by weight of cement (5, 10, 15 and 20 %) were cast. Compressive strength test was carried out after the specimens were cured in water for 7, 14, 28 and 56 days. Test for tensile and flexural strength was carried out after 28 days curing. Initial and final setting time test was carried out on mortar specimens with the same percentage of RHA and RHA-CCW. Bogues model was used to determine the elemental and compound composition of cement when blended with the RHA and RHA-CCW. From the results obtained, the compressive strength of RHA-CCW concrete increases as cement is partially replaced with RHA-CCW content, with the maximum strength attained at 5 % replacement. RHA concrete attains it maximum strength at 10 % replacement. The maximum compressive strength results obtained for both RHA and RHA-CCW concrete were higher than the strength of plain concrete (0 % replacement) by 1.1 % and 14.7 % respectively. Interestingly, results obtained for the tensile strength also shows a similar pattern of strength development with that of compressive strength. The flexural strength properties of concrete was improved upon when RHA-CCW was used in concrete compared to RHA. The results of setting time test for RHA mortar showed a decrease in setting time, while the reverse was the case for RHA-CCW mortar. In conclusion, provided adequate curing is maintained, the used of RHA-CCW gives a better performance in concrete than RHA. However, they both perform better in concrete than the plain, and can be used as additives in concrete production.

A Scenario on Dry-WEDM and WEDM for Industrial Applications

Abstract: In present day manufacturing industries playing the major role in the machining of new materials with complex shapes, intricate structure and difficult profiles. The improvement of industries and machines is accountable for product quality and accuracy, which are not satisfied in conventional machining techniques. The WEDM is advanced machining process, they are capable to machining the components which are difficult to machine, whereas Dry-WEDM is another method, it utilizes the gas instead of dielectric liquid, it exhibits lower corrosion, fine finish, decrease dielectrics and environment friendly. Development of WEDM is suitable machining option for meeting the demands of modern tool room application and metal cutting industries. The purpose of the article attempts is to highlights the application, improvement and future scope of Dry-WEDM and WEDM in industrial areas.

Investigations of Corrosion Behavior on Combined Fast Laser Texturing and HVOF TiO2 Powder Deposition Surface Engineering Treatment

Abstract: The paper presents the characteristics of TiO2 coatings realized by HVOF spraying process by two different processing paths, i.e. using the classical method of preparing the substrate by sandblasting and by applying a fast laser texturing of the substrate (instead of sandblasting) before the actual HVOF spraying respectively (a duplex treatment). The obtained coatings’ morphology were characterized by SEM before and after electrochemical measurements in NaCl solution. The textured sample presented better resistance to corrosion compared with classical processing path. Keywords: coatings, fast laser texturing, HVOF spraying, duplex surface treatment, anticorrosive.

Research on the Welding Behavior for Alloy EN AW 5754 when Using FSW-US Hybrid Process

Abstract: We approached a new hybrid technology that integrates ultrasonic energy with FSW welding. By integrating ultrasound in the FSW process, a number of benefits are expected in terms of welding quality, forces and tool life. Our research aimed at developing a new technique of friction stir welding assisted by ultrasonic energy, namely FSW-US, which can improve the process, it can contribute to the decrease of forces that develop during the welding process and can increase the quality of welded joints. Metal welding and processing technologies that use ultrasonic vibrations, either as a primary source to achieve prescribed performance, or as a source of assistance to improve the efficiency of the operation and product quality, are currently being researched or discussed in the international scientific environment. The present paper analyzes the effects of overlapping ultrasonic vibrations with heat generation, temperature distribution and material flow generated by applying the FSW process. Mechanical effect plays a dominant role in the welding process assisted by ultrasonic vibrations, while thermal effects are insignificant. Overlapping ultrasonic vibrations on the friction stir welding process can produce a stream of improved plasticized material, increases the welding speed and efficiency, it can also improve weld quality by increasing the flow / volume of plastic material around the tool. [1]

Chemical Activation of Dicalcium Silicate and its Use for Cement Production

Abstract: In this work, it was found out that dicalcium silicate doped with SO3 shows higher hydraulic activity compared to pure dicalcium silicate. This finding was used to prepare and optimize high-belite cement from SO3 doped clinkers. The belite cement exhibited the same technological parameters, including short-term strengths, as ordinary Portland cement with a high content of tricalcium silicate. The clinker for belite cement is environmentally and economically advantageous. It is possible to burn the clinker at a temperature of 100 °C lower than conventional clinker and with lower consumption of calcium carbonate. In particular, methods of optical and electron microscopy were used for the research.

Method and Technologies for Cutting and Sealing Composite Polymeric Materials

Abstract: Existing equipment units in specialized industry market, used to process composite polymeric materials, are made with constructive solutions dedicated to specific applications, actual cutting operation are being achieved by thermal effect often resulting in burns of the material on the working area, the version proposed in this paper, a hybrid technology using ultrasonic energy assisted thermic energy, proved to be an excellent solution.The technical problem solved by solution presented by our technology is represented by real market necessity of providing clean processing – in this case cutting and sealing, of composite polymeric materials, in the form of strips, which must correspond in dimensional and qualitative terms to specifications in product documentation, textile tape, used in the textile, food, medical and army industries.

The Effects of Sintering Atmosphere on the Fabrication of Transparent Polycrystalline YAG Ceramics

Abstract: In this paper, a mixture of commercial Al2O3 and Y2O3 nanopowders was prepared according to the stoichiometric ratios of YAG (Y3Al5O12) with 0.5 wt% tetraethyl orthosilicate (TEOS) as a sintering aid. The effects of air and vacuum sintering atmosphere were examined on the phase transformation, densification, in-line transmission, microstructure evolution, grain size distribution, sintering trajectories, and grain growth map of the YAG ceramics. The results showed that all samples were pure YAG phase. Nearly pore-free microstructure (99.8%) and narrow grain size distribution (4-10 μm) with an average grain size of 7 μm was obtained for the sample sintered in the vacuum atmosphere, while both inner and inter pores with abnormal grain growth, wider grain size distribution (9-27 μm) with the average grain size of 12 μm were detected in air atmosphere. Also, the results showed that the specimens sintered in vacuum atmosphere had higher relative densities and smaller grain sizes at all sintering temperatures for 6 h. The maximum transmittance at 1064 nm of the YAG ceramics sintered at air and vacuum atmosphere was 26% and 68%, respectively.

Temper Bead Welding, a Possible Solution to Possible Removal of Heat Treatments

Abstract: The papers aim is to detail temper bead realization, as a possible solution to the removal of heat treatments. Applying temper beads could be a solution for repair, in case surface heat treatments are required, provided they are correctly applied. The paper presents the main ways of applying temper beads, presenting in the same time what the outcomes could be in case of not respecting the prescribed work sequence.

Experimental Study of the Mechanical Properties Concrete Reinforced with Steel Fibers

Abstract: Before and after the completion of a project we often encounter unforeseen events that affect the sustainability of the project. We understand that engineers and practitioners need to look for the best average or process in terms of quality and cost, to ensure project maintenance. Among the possible methods; we can quote the concrete reinforced by the metallic fibers between the pavement and asphalt concrete pavement, the latter will ensure the continuity between two materials (flexible-rigid). This work consists of studying the formulation of a metal fiber concrete based on local materials (cement, gravel and sand) and studying the effect of fibers. The results of this study highlighted the improvement of both the mechanical properties of concrete and the problem of cracking between the pavement and pavement concrete joints.

Research on Metallurgic Active Precursors

Abstract: The paper presents the current state of researches carried out in order to improve homogeneity of mixtures for metallic powders; our priority is those with different participation in the mixture, by mechanical alloying. Mixtures of this type are used in the production of welding and related materials.Recently, research has been done to improve deposited metal properties by welding with coated electrodes, by depositing nanostructures, with uncertain results due to the low degree of homogeneity of blends involved in the electrode coating.The performance enhancement method for coated rods, developed by introducing in their coat activating precursors, used for brazing, is well known. The solution to improve the degree of homogeneity of alloying systems by mechanical alloying has been successfully applied for the manufacture of coated electrodes and those tubular with a composite core which are deposited by manual welding or TIG welding, type Fe25% Cr-4% W-V-Ti-La. The grouping of powder components for mechanical alloying was done in such a way that, finally, we have groups with the granulation, respectively specific weight, close and a low potential of segregation.The method of mechanical alloying of the components was used in the manufacture of coated rods in order to improve the fluidity of silver-rich buffer layers deposited in order to favor the diffusion phenomena of brazing alloys in the base materials.Testing the homogeneity of the alloying systems was performed indirectly by metallographic analysis and sclerometric tests.

Technical Characteristics of the Equipment for Friction Stir Welding (FSW), Depending on the Base Metals

Abstract: There are various base metals that might be subjected to friction stir welding (FSW). They have different yield strength, ultimate tensile strength and other mechanical characteristics that influence the complex phenomena of the FSW process. The nature, mechanical characteristic and other properties of the base metals introduce also certain requirements for the FSW equipment, because FSW is a mechanical process.Experimental data of the FSW of the following materials are presented and compared:- similar overlapped sheets of aluminium alloy EN AW 5754, having the thickness 1.0 mm; - dissimilar overlapped sheets of 3 - 6 mm thickness of the base metal couples: aluminium alloy EN AW 1200 / copper Cu 99 ET, aluminium alloy EN AW 5754 / copper Cu 99, aluminium alloy EN AW 6082 / copper Cu 99 ET;- sheets of nickel alloy, inconel 718, thickness 8 - 10 mm, by friction stir processing. The characteristics of the FSW tool are described and the main technology parameters are mentioned: overlap, rotational speed of the FSW tool, rotational direction, travel speed, thrust force, as well as electric current of the motor for the rotating motion of the tool.Other important factors are also taken into account: sizes and positioning of the sheets (up or down), rolling direction of the sheets, room temperature, temperature of the sheets, material and temperature of the support plate.The linear energy of the FSW process is the main parameter. This is an indirect parameter, because it must be calculated, based on the previous mentioned parameters. According to the definition, the linear energy depends directly on the mechanical power developed during the stirring process, respectively it depends indirectly on the travel speed.On the other hand, the heat input is directly proportional to the linear energy and the thermal efficiency of the transfer of the heat produced by the friction of the shoulder and pin, to the nugget zone, where the weld metal is produced. These quantities are also analysed.For these materials the power developed by the motor for the rotational movement is determined, as well as the mechanical torque applied to the FSW tool. All these data are important for the design of the FSW equipment, in order to realize its main technical characteristics, depending on the base metals.Conclusions on the results are exposed, with important consequences for the industrial applications of the FSW process.