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Volume 9, Number 3, September 2020

The microstructural evolution of different compositions of Mg-Sn alloys (30%Sn-70%Mg, 40%Sn-60%Mg and 50%Sn-50%Mg) is studied at first to understand the changes observed with change in tin content and deformation conditions. The Mg2Sn phase increases with increase in tin content and a significant substructure development is found in 50%Sn-50%Mg alloy. The above observation led to further deformation studies on Mg2Sn based thermoelectric materials with higher tin percentage. The microstructure in terms of Electron backscatter diffraction (EBSD) measurements is studied in detail followed by the determination of thermoelectric properties i.e., Seebeck coefficient and electrical conductivity for both as cast and extruded Mg(2+x)Sn-Ag alloys. The electrical conductivity of the extruded Mg(2+x)Sn-.3wt%Ag {x = 1} alloy was found to be more than its as cast counterpart while the Seebeck coefficient values remained almost the same.

Key Words
thermoelectric materials; magnesium tin alloys; microstructure; deformation; annealing

(1) Divija Pandel:
Department of Materials Research Centre, MNIT, Jaipur 302017, India;
(2) Malay K. Banerjee:
Department of Metallurgical and Material Engineering, MNIT, Jaipur 302017, India.

The objective of the present work is to investigate the effect of cutting parameters (Vc, fz and ap) on tool life and the level of vibrations velocity in the machined part during face milling operation of hardened AISI 52100 steel. Dry-face milling has been achieved in the annealed (28 HRc) and quenched (55 HRc) conditions using multi-layer coating micro-grain carbide inserts. Statistical analysis based on the Response surface methodology (RSM) and ANOVA analysis have been conducted through a plan of experiments methodology using a reduced Taguchi table (L9) in order to obtain engineering models for tool life and vibration velocity in the workpiece for both heat treatment conditions. The results show that the cutting speed has a dominant influence on tool life for both soft and hard part. Cutting speed and feed per tooth is the most significant parameters for vibration levels. Comparing the experimental values with those predicted by the developed engineering models of tool life and levels of vibrations velocity, a good correlation has been obtained (between 97% and 99%) in annealed and hard conditions.

Key Words
machinability; vibration; AISI52100 Steel; tool life; wear; modeling

Research Laboratory of Advanced Technologies in Mechanical Production (LRTAPM), BadjiMokhtar Annaba University, Annaba23000, Algeria.

This research paper presents the outcomes in terms of mechanical and microstructural characteristics of binary and ternary concrete when exposed to elevated temperature. Three parameter were taken into account, (a) elevated temperature (i.e., 200, 400, 600 and 800°C) (b) binary concrete with cementitious material sugarcane bagasse ash (SCBA) and ground granulated blast furnace slag (GGBFS) replacement percentage (i.e., 0, 15, 20, 25 and 30%) and (c) ternary concrete with cementitious material SCBA and GGBFS replacement percentage (i.e., 0, 15, 20, 25 and 30%). A total of 285 standard cube specimens (150 mm × 150 mm ×; 150 mm) containing Ordinary Portland Cement (OPC), SCBA, and GGBFS were made. These specimens then exposed to several elevated temperatures for 2 h, afterword is allowed to cool at room temperature. The following basic physical, mechanical, and microstructural characteristics were then determined and discussed. (a) mass loss ratio, (b) ultrasonic pulse velocity (UPV) (c) physical behavior, (d) compressive strength, and (e) field emission scanning electron microscope (FESEM). It was found that compressive strength increases up to 400°C; beyond this temperature, it decreases. UPV value and mass loss decrease with increase in temperature as well as the change in color and crack were observed at a higher temperature.

Key Words
concrete; sugarcane bagasse ash; ground granulated blast furnace slag; elevated temperature; residual strength; microstructural properties

Department of Civil Engineering, SVNIT, Surat, India.

The aim of this study is to investigate the durability of fly ash based geopolymer mortar with and without protective coatings in aggressive chemical environments. The source materials for geopolymer are Fly ash and Ground Granulated Blast furnace Slag (GGBS) and they are considered in the combination of 80% & 20% respectively. Two Molarities of NaOH solution were considered such as 8M and 10M. The ratio of binder to sand and Sodium silicate to Sodium hydroxide solution (Na2SiO3/NaOH) are taken as 1:2 and 2 respectively. The alkaline liquid to binder ratio is 0.4. Compressive strength tests were conducted at various ages of the mortar specimens. In order to evaluate the performance of coatings on geopolymer mortar under aggressive chemical environment, the mortar specimens were coated with two different types of coatings such as epoxy and Acrylic. They were then subjected to different chemical environments by immersing them in 10% standard solutions of each ammonium nitrate, sodium chloride and sulphuric acid. Drop in compressive strength as a result of chemical exposure was considered as a measure of chemical attack and the drop in compressive strength was measured after 30 and 60 days of chemical exposure. The compressive strength results following chemical exposure indicated that the specimens containing the acrylic coating proved to be more resistant to chemical attacks. The control specimen without coating showed a much greater degree of deterioration. Therefore, the application of acrylic coating was invariably much more effective in improving the compressive strength as well as the resistance of mortar against chemical attacks. The results also indicated that among all the aggressive attacks, the sulphate environment has the most adverse effect in terms of lowering the strength.

Key Words
durability; geopolymer mortar; fly ash; Ground Granulated Blast furnace Slag; epoxy; acrylic; compressive strength

(1) Kumutha Rathinam:
Department of Civil Engineering, Sri Venkateswara College of Engineering, Sriperumbudur, Tamilnadu, India;
(2) Vijai Kanagarajan:
Department of Civil Engineering, St. Joseph\'s College of Engineering, OMR, Chennai, Tamilnadu, India;
(3) Sara Banu:
Department of Civil Engineering, Sethu Institute of Technology, Kariapatti, Tamilnadu, India.

In this study, a chitosan based coating method was developed and applied on the shoe lining leather surface for evaluating its inhibition to bacterial and fungal attacks. At first, chitosan was prepared from raw prawn shells and then the prepared chitosan solution was applied onto the leather surface. Secondly, the characterization of the prepared chitosan and chitosan treated leather was performed by solubility test, ATR-FTIR, XRD pattern, SEM and TGA. Evaluation of antimicrobial efficacy of chitosan was assessed against two gram positive, two gram negative bacteria and a reputed fungi by agar diffusion test. The results of this study demonstrated that chitosan took place in both the surface of collagen fibres and inside the collagen matrix of crust leather. The chitosan showed strong antimicrobial activities against all the tested microorganisms and the inhibition increased with increasing percentage of chitosan. Therefore, the prepared chitosan in this study can be an environment friendly biocide, which functions simultaneously against different spoilage bacteria and fungi on the finished leather surface. Thus by using the prepared chitosan in shoe lining leather, the possibility of microbial attack during shoe wearing can be minimized which is one of the important hygienic requirements of footwear.

Key Words
chitosan; leather; antimicrobial property; leather coating; finishing

(1) Yead Mahmud, Md. Minhaz Uddin, Sayed Md. Shamsuddin:
Institute of Leather Engineering & Technology, University of Dhaka, Dhaka-1209, Bangladesh;
(2) Nizam Uddin, Ahmad Ismail Mustafa:
Nutrition and Food Engineering, Faculty of Allied Health Science, Daffodil International University, 102, Shukrabad, Mirpur Road, Dhanmondi, Dhaka-1207, Bangladesh;
(3) Thamina Acter:
Department of Mathematical and Physical Sciences, Faculty of Sciences and Engineering, East West University, A/2, Jahurul Islam Avenue Jahurul Islam City, Aftabnagar, Dhaka-1212, Bangladesh;
(4) A.M. Sarwaruddin Chowdhury, Sayed Md. Shamsuddin:
Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, University of Dhaka, Dhaka-1000, Bangladesh;
(5) Md. Latiful Bari:
Food Analysis and Research laboratory, Center for Advance Research in Sciences, University of Dhaka, Dhaka-1000, Bangladesh.

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