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Purpose The purpose of this study is to determine the effects of post-annealing and post-tempering processes on the microstructure, mechanical properties and corrosion resistance of the AISI 304 stainless steel gas metal arc weldment. Design/methodology/approach Gas metal arc welding of AISI 304 stainless steel was carried out at an optimized processing condition. Thereafter, post-annealing and post-tempering processes were performed on the weldment. The microstructure, mechanical and electrochemical corrosion properties of the post-weld heat treated samples, as compared with the as-welded, were investigated. Findings The as-welded joint was characterized with sub-granular grain structure, martensite formation and Cr-rich carbides precipitates. This made it harder than the post-annealed and post-tempered joints. Because of slower cooling in the furnace, the post-annealed joint contained Cr-rich carbides precipitates. However, the microstructure of the post-tempered joint is more refined and significantly devoid of the carbide precipitates. Post-tempering process improved the elongation (∼23%), tensile (∼10%) and impact (∼31%) strengths of the gas metal arc AISI 304 stainless steel weldment, while post-annealing process improved the elongation (∼20%) and impact strength (∼72%). Owing to the refined grain structure and significant elimination of the Cr-rich carbide precipitates at the joint, the post-tempered joint exhibited better corrosion resistance in 3.5 Wt.% NaCl solution than the post-annealed and the as-welded joints. Originality/value The appropriate post-weld heat treatment that enhances microstructural homogeneity and quality of the AISI 304 gas metal arc welded joint was determined.

Abstract:The effect of five process parameters namely: reaction time, reaction temperature, stir speed, catalyst concentration and methanol-oil ratio on the transesterification process of waste frying oil to biodiesel were investigated. Optimization of the five process parameters and their quadratic cross effect was carried out using a four level-five factor central composite experimental design model and response surface methodology with each factor varied over four levels. Taking the biodiesel yield as the response of the designed experiment, the data obtained were statistically analysed to get a suitable model for optimization of biodiesel yield as a function of the five independent process parameters. The optimization produced 30 feasible solutions whose desirability equals to 1 and the selected (most desirable) condition was found to be: reaction time (3 hrs), reaction temperature (58°C), stir speed (305.5 rpm), catalyst concentration (1.4 wt%) and methanol to oil ratio (6:1), while the optimum yield of biodiesel for this condition was found to be 91.6%. The developed model was tested and validated for adequacy by substituting random experimental values as input parameters and the output parameters from the developed model were close to the experimental values. The biodiesel properties were characterized and the results obtained were found to satisfy the standard for both the ASTM D 6751 and EN 14214.

The need for quality control of biodiesel is important to ensure the development of a clean, trouble free and safe alternative fuel technology to fossil diesel. In this work, the gas chromatography analysis of the biodiesel produced from used frying oil was carried out using PerkinElmer Clarus 500 Gas Chromatograph (GC), fitted with a capillary split injector and Fourier Infrared Detector (FID). Also, the Fourier Transform Infrared Spectroscopy was used to determine and monitor the concentration of biodiesel produced from used and unused palm olein oil. The Fourier Transform Infrared (FTIR) analysis was carried out using the FTIR Spectroscopy (FTIR 1-S Shimadzu, Japan, Model 4100) and Microlab software as well as Attenuated Total Reflectance (ATR) sample interface system. 0.5 ml of samples of the unused palm olein oil and biodiesel were taken in at the interface at a resolution of 4 cm-1 within the region of 4000 cm-1 to 400 cm-1 . The GC-MS analysis did not indicate any soap-like material, indicating that the catalyst was able to handle transesterification reaction without transition to saponification reaction. The results of the interaction between the components of the fuel samples and the radiation as a function of wavelength indicates the functional groups and the type of vibration in the fuel samples. The results obtained indicate the presence of an intense band of C=O stretching of methyl ester and O-CH3 group. It also show concentration of the five main fatty acids that are present in most biodiesel; palmitic, stearic, oleic, linoleic, and linolenic acids indicating the successful transesterification of palm olein oil to biodiesel.

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The phytochemical and proximate composition of Aspillia Kotschyi belonging to Compositae family which is commonly used as medicinal plant in Nigeria was determined on both the Methanolic and Petroleum spirit extracts of the plant material The Methanolic extract of the plant revealed the presence of carbohydrates, cardiac glyscosides, flavonoids, triterpene, and alkaloids. The Petroleum sprit extract showed the presence of only carbohydrates and alkaloid. Proximate composition analysis shows moisture content of 5.7%, total ash of 4.03%, crude protein 10.39%, fibre 9.06%,Fat value 0.83%,and Nitrogen free extract of 70.19%. The results of this study suggest some merit in the popular use of Aspillia kotschi in herbal medicine.