Mechanical, chemical, metallurgical characteristics under HBSS solution and optimization of AZ91D-Ti functional graded composites using TOPSIS

ABSTRACT. Functional graded magnesium matrix composites (FGMMCs) are widely employed for biomedical, aerospace and thermal barrier applications because of their better mechanical properties, biocompatibility and bioactivity. In this study, AZ91D-wt. %Ti (x = 0, 4, 8, 12 and 16) composites are fabricated by ex-situ centrifugal casting method. The NaCl based solution is sprayed on all fabricated magnesium composites for 72 hours at the 1 kg/cm3 pressure spray and 6.9 pH value in salt spray chamber. The microhardness and flexural strength of fabricated composites are determined. The corrosion resistance of AZ91D-wt. %Ti fabricated composites is determined for 21 days immersion. The AZ91D -12wt. %Ti exhibits higher microhardness, flexural strength and corrosion resistance than other produced AZ91D-Ti composites. The optimization on micro machining process parameters is done on the AZ91D-12wt. %Ti with the help of Technique for order of preference by similarity to ideal solution (TOPSIS).The input process parameters are selected as cutting rate, feed rate, depth of cut and tool type and the response parameters are selected as feed force, normal force, tool wear rate, burr height and surface roughness. The computed optimal micro milling process parameters are at 120 m/min cutting speed, 0.5 µm feed rate, 0.15 mm depth of cut and the TiB2 coated tool.   KEY WORDS: AZ91D -Ti, TOPSIS, Surface roughness, Tool wear loss, Cutting force   Bull. Chem. Soc. Ethiop. 2023, 37(1), 77-89.                                                                    DOI: https://dx.doi.org/10.4314/bcse.v37i1.

Optimization of process parameters in micro milling of Ti4Al4Mo2Sn using nano Al2O3 additives based minimum quantity cooling lubrication

ABSTRACT. Aerospace and automotive industries employ Ti4Al4Mo2Sn material in many applications due to its properties of better strength to weight ratio and high corrosion resistance. Ti4Al4Mo2Sn finds itself difficult to cut materials due to its physical and chemical properties and is prone to more heat generation during machining. The more generation of heat affects the machined material surface quality and other related properties. In this investigation, the thermal conductivity and stability of Al2O3/Water based nanofluids are studied to select the best composition of nanofluid for transferring heat. The thermal conductivity and stability of the nanofluid for a duration of 30 days are computed by employing the KD2 thermal property meter and pH meter, respectively. Thermal conductivity and stability of the Water/4.5 vol.% Al2O3 nanofluid are found to be better than other combination of nanofluids. In the present study, optimizing the micro milling process parameters on Ti4Al4Mo2Sn material with Minimum quantity cooling lubrication (MQL) is focused. The input parameters selected for this micro milling process are spindle speed, feed rate, depth of cut and Water/4.5vol.% Al2O3 nanofluid and the output parameters selected are cutting forces in X(Fx) and Y(Fy) directions, tool wear rate (TWR) and surface roughness (SR). The optimization is done with the help of grey relational analysis (GRA) by using L9 Orthogonal Array (OA) Taguchi design. The obtained sequence of influencing parameters are feed rate per tooth, Al2O3nanofluid, spindle speed and depth of cut. The percentage of grey relational grade (GRG) for prediction and experimental is 0.721 and 0.957. The percentage of improvement of GRG is 12.46.   KEY WORDS: Ti4Al4Mo2Sn, Al2O3, Thermal conductivity, Grey relational analysis, Grey relational grade   Bull. Chem. Soc. Ethiop. 2022, 36(2), 339-351.                                                                DOI: https://dx.doi.org/10.4314/bcse.v36i2.

Electronic, reactivity and third order nonlinear optical properties of thermally-stable push-pull chalcones for optoelectronic interest: experimental and DFT assessments

The present work highlighted the integration of quantum chemical approach and experimental results in attempts to elucidate the structural-property characteristics and behaviour of the fused-aromatic chalcones on the impact of their nonlinear attribute at the molecular level. Two push-pull chalcones namely 1-(anthracen-9-yl)-3(9-ethyl-carbazol-3-yl)prop-2-en-1-one (1AECP) and 3(9-ethyl-carbazol-3-yl)-1(pyren-1-yl)prop-2-en-1-one (3ECPP) were successfully designed, synthesised and analysed through FT-IR, UV–Vis, 1D NMR, TGA, DSC and third-order optical nonlinearities were performed via Z-scan measurement. Concurrently, density functional theory (DFT) analysis with basis set of B3LYP/6-31G (d,p) was computed to optimize the most stable molecular geometry configuration, HOMO-LUMO energy gap, global chemical reactivity descriptors (GCRD), molecular electrostatic potentials (MEP), natural bond orbital (NBO) analysis and hyperpolarizability analyses. The experimental optical gap (Egopt) of both compounds has demonstrated good agreement with corresponding calculated result and fall in the range of organic semiconducting materials with low range of HOMO-LUMO energy gap values, 2.98 and 2.74 eV respectively. The DFT result revealed that fused-aromatic reinforce intramolecular charge transfer (ICT), electronic dipole moment and improve polarizabilities on NLO properties of the material. The thermal stability analysis pinpointed that both of these materials are able to withstand high temperature up to 300 °C which unintentionally unveil their encouraging performance potentially. Additionally, Z-scan analysis discovered that both of the targeted compounds are indeed nonlinear refraction (NLR) active, manifesting self-defocusing effect with n2 value of −1.75 x 10−9 esu (1AECP) and −1.75 x 10−8 esu (3ECPP). In short, the theoretical output complement the experimental results fundamentally in the evaluation and prediction of their electronic nature which hence proved their prospect essentially in the optoelectronic-manufacturing development