Open Access Short Research Article

Effects of Sb Addition on Microstructure and Mechanical Properties of Heat-Treated Recycled Al-Si-Mg Alloy

L. O. Mudashiru, I. A. Babatunde, O. I. Kolapo, S. O. Adetola

Journal of Materials Science Research and Reviews, Page 53-58

The uses of cast aluminum alloys in automotive and aerospace applications are growing rapidly because of the need to reduce weight and improve the efficiency of the engine as whole. The service life of aluminum cast component is determined by the size, form and distribution of microstructural features throughout the casting, especially in those regions that are critically stressed. The effects of antimony (Sb) additions on the microstructure and mechanical properties of recycled heat-treated Al−10.55Si-4.95Mg alloy were investigated. The results show that Sb can effectively modify the eutectic silicon platelets depending on its geometry. However, modification in the eutectic Si platelets were observed with increase addition of Sb. Improved mechanical properties in the as-cast Al-alloy on tensile strength (121 N/mm2) and yield strength (91.25 N/mm2) were obtained at 7.50 wt. % Sb addition.

Open Access Original Research Article

Numerical Simulation and Microstructural Correlation of Duplex Stainless Steel Solidification by Spray-Forming Process

Moises Meza Pariona, Luiz Gustavo Kobilacz

Journal of Materials Science Research and Reviews, Page 1-12

Duplex stainless steel are designed to provide better corrosion resistance, particularly chloride stress corrosion and chloride pitting corrosion, and higher strength than standard austenitic stainless steels. In Spray Forming processing, the gas atomizes a liquid metal stream and is generated a number of high velocity gas jets and is broken up into fine drops which solidify in flight and finally is captured the atomized metal spray of alloy onto a moving substrate into near net shape solid. In this research was be presented a thermal model for modeling the heat flow distribution during solidification process and the heat transfer analysis using finite element modeling was carried out, to study of solidification of droplet deposition in spray-forming process and its correlation with microstructure. For this purpose, was assumed a Gaussian distribution of droplet mass flux about the spray cone axis, boundary conditions non-linear of heat transfer coefficient and thermophysical properties dependent with temperature, the spray forming process parameters, such as, fluid pressure, geometrical parameter of the nozzle’s dimensionless characteristic, temperature of the saturation, workpiece height, thickness of the bottom’s sprayer were considerate too. As result were presented a solidification process analysis, study of thermal gradient, cooling curves analysis and correlation between numerical simulation and microstructural result. The microstructure analysis was used to establish the correlation with numerical simulation for has better performance of prevision. Duplex stainless steels are applied in various strategic areas, which are finding greater application in the chemical, oil and gas industries, petrochemical process plants, pollution control equipment, etc. Numerical simulation is a powerful tool to study the spray-forming process, whose parameters that involve this process can save runtime experimental and cost of equipment, besides, predict the result.

Open Access Original Research Article

Bio-Ethanol Production from Cocoyam Peels using Enzymatic Hydrolysis

Anthony Chukwuma Nnaji, Gordian Onyebuchukwu Mbah, Maxwell Ikechukwu Onoh, Onuora Okorie, Benson Chinwuba Udeh

Journal of Materials Science Research and Reviews, Page 13-28

This study investigated the great potential of cocoyam peels (non-edible waste material) as suitable substrate for bio-ethanol production using enzymatic hydrolysis process. The raw material was subjected to pretreatment prior to the hydrolysis and fermentation processes. Several experimental analyses to determine the suitability of this food waste as bioethanol feedstock -the proximate analyses, enzymatic hydrolysis, analysis of simple sugars, fermentation experiments, kinetics and optimization of the enzymatic hydrolysis and fermentation were done. Cellulase secreted from Aspergillus niger was used for the hydrolysis of the peels in a separate hydrolysis. Similarly, commercial saccharomyces cerevisiae was also used for the fermentation of the hydrolyzate. The kinetic studies revealed that Michaelis Menten model was suitable for the enzymatic hydrolysis and fermentation processes. The Seaman kinetic equation for the enzymatic hydrolysis was solved using Microsoft Excel Solver. The Box-Behnken of Response Surface Method (RSM) was employed to optimize the hydrolysis yield. From the numerical optimization solution, simple sugar yield from enzymatic hydrolysis was 57.5%. The result also showed that the highest ethanol yield of 7.15%v/v for 4 days with pH value of 7.3 was obtained.

Open Access Original Research Article

Investigating the Effects of Mono-Halogen-Substitutions on the Electronic, Non-Linear Optical and Thermodynamic Properties of Perylene Based on Density Functional Theory

Rabiu Nuhu Muhammad, A. S. Gidado

Journal of Materials Science Research and Reviews, Page 29-40

Perylene (C20 H12) is polycyclic aromatic hydrocarbons (PAHs) used in the production of organic field- effect transistors, organic photovoltaic cells, and biosensors. In this work, the molecular geometry, HOMO-LUMO energy gap, global indices, thermodynamic properties, non-linear optical properties, IR frequencies, and intensities of isolated perylene and its substituted molecules were calculated and reported. DFT/B3LYP using 6-311+G(d) basis sets was used for the work. All the computations were performed by using Gaussian 03 package and revealed that the substitutions affect the optimized parameters of the titled molecule. The results obtained for the bond lengths indicate that the strongest bond is C19-H12 with a value of 1.0757Å found in 1-fluoroperylene while the bond angles were found to be so close to 1200, revealing that the molecules are planar benzene in which the carbon atoms are  hybridized. The calculated value of the energy gap of 3.0572 eV shows that perylene has higher stability in a chemical reaction by substitution of fluorine. The value of the energy gap is closer to the reported value in the literature (2.9740 and 2.9935) eV. The molecule was found to be harder and less reactive in a chemical reaction by substitution of fluoride atom with a chemical hardness of 1.5286 eV. It was found that the specific heat capacity and entropy of the molecule increased while zero-point vibrational energy decreased due to the effect of the substitutions. From the results obtained for non-linear optical properties, it was found that substitution of bromine gives a higher value of the first-order hyperpolarizability with a value of 1.2748 x10-30 esu, which is at least 3 fold than that of prototype urea (0.3728 x10-30 esu) molecule. This suggests that 1-bromoperylene can be the best candidate for non-linear optical applications among the substituted molecules. The calculated frequencies and intensities results show that 1-bromoperylene with a value of 826.37 cm-1 at 96.9614  km/mol has the most intense frequency among the substituted molecules. The results of this work indicate that choosing a better halogen atom and basis sets can improve the electronic and nonlinear optical properties of the titled molecule for better applications.

Open Access Original Research Article

Study of Electronic and Molecular Properties of Poly (3-Octylthiophene-2,5 diyl) Polymer using Density Functional Theory (DFT) And Time-Dependant Density Functional Theory (TD-DFT)

Hassana Muhammad Shuwa, Mansur Said, A. S. Gidado

Journal of Materials Science Research and Reviews, Page 41-52

Poly(3-octylthiophene-2,5-diyl) denoted as P3OT with a chemical formula (C12H18S)n  is an alkylthiophene based conductive polymer with high electroluminescence that is soluble in most of the organic solvents. P3OT is a promising material for applications in solar cells, light-emitting diodes, displays, and other optoelectronic devices due to their processability, flexibility, and low production cost. In this work, DFT and TD-DFT methods were used to investigate the molecular and electronic properties of P3OT in a vacuum (gas phase). The effect of solvent was also investigated using different models such as Polarisable Continuum Model (PCM), Continuum polarisable continuum model (C-PCM), and Integral Equation Fourier Polarisable continuum model (IEFPCM) with Chloroform, Tetrahydrofuran (THF), and Toluene as solvents. Gaussian 09 program was used for all the calculations at the DFT/B3LYP/6-311+G(d) level of theory. The results obtained for the molecular geometry show that the lowest average value of bond length in the vacuum and the medium are 1.08311Å and 1.0830Å respectively. The HOMO, LUMO and Energy-gap calculated in the vacuum are obtained as -6.44eV,-3.63eV and 2.81eV respectively while the results obtained in medium show a little effect on the HOMO, LUMO and energy gap for all the solvents. The energy gap obtained is compared with the one in literature  (2.51eV).This indicates that the reported energy-gap leads by 0.3eV. From the UV-VIS spectrum, the excitation energy and oscillator strength were found to be 948.46nm and 0.0015 in the vacuum, while in the medium, the presence of solvents increase the excitation energy in the range 950.10-956.07nm and oscillator strength in the range 0.0020-0.0022. The open-circuit voltage was calculated theoretically. The result shows that the open-circuit voltage was found to be 2.711eV, this value is sufficient for possible electron injection from the molecule to the conduction band of ICBA(Indene-C60-bisadduct). Thus, it can be concluded that P3OT shows high stability and low reactivity in a chemical reaction, and due to its strong absorption properties in both a vacuum and a medium, it can be used for solar cell application.