Characterization of plasma processed ultra-fine Ni–Al powder

Thermal plasma processing utilizes the exotic properties of the plasma medium to effect physical, chemical or metallurgical changes/reactions in materials. Commercially available nickel and aluminium powders were mixed in the appropriate amount, ball milled and fed into a dc plasma jet produced by an atmospheric plasma torch. The particles are molten and leave the flame and falls through the atmospheric air inside a plasma reaction chamber. The particles are quenched, solidified and collected in a collection chamber. During in-flight if the particles are overheated, depending on the size, may be partially or fully vaporize. The smaller particles fly in all directions and get deposited on the walls of the reaction chamber. Vapors also condense on the cooled walls. The particles are collected. During in-flight the exothermic reaction to form nickel aluminide may also take place. The particles on the walls of the reaction chamber were collected and characterized using XRD, SEM with EDX and TG DTA analysis. The results are reported and discussed.     

Comparison of Multi Point Incremental Forming Tool with Single Point Incremental Forming Tool Using FLD,Fractography and 3D-Surface Roughness Analysis on Cr/Mn/Ni/Si Based Stainless Steel

Silicon - Manufacturing is a significant process for the engineering industries to convert raw materials into a complete product. Apart from other manufacturing processes, forming is one of the...     

Modelling and experimental investigation of process parameters in EDM of Si<Subscript>3</Subscript>N<Subscript>4</Subscript>-TiN composites using GRA-RSM

Electric discharge machining (EDM) is a highly promising machining process of ceramics. This research is an out of the paradigm investigation of EDM on Si₃N₄-TiN with Copper electrode. Ceramics are used for extrusion dies and bearing balls and they are more efficient, effective and even have longer life than conventional metal alloys. Owing to high hardness of ceramic composites, they are almost impossible to be machined by conventional machining as it entirely depends on relative hardness of tool with work piece. Whereas EDM offers easy machinability combined with exceptional surface finish. Input parameters of paramount significance such as current (I), pulse on (P_on) and off time (P_off), Dielectric pressure (DP) and gap voltage (SV) are studied using L₂₅ orthogonal array. With help of mean effective plots the relationship of output parameters like Material removal rate (MRR), Tool wear rate (TWR), Surface roughness (Ra), Radial overcut (ROC), Taper angle (α), Circularity (CIR), Cylindricity (CYL) and Perpendicularity (PER) with the considered input parameters and their individual influence were investigated. The significant machining parameters were obtained by Analysis of variance (ANOVA) based on Grey relational analysis (GRA) and value of regression coefficient was determined for each model. The results were further evaluated by using confirmatory experiment which illustrated that spark eroding process could effectively be improved.     

Physical properties of lauric acid crystals grown with KBr in aqueous solution

Lauric acid crystals were grown with potassium bromide (LAPB) in aqueous solution at room temperature by slow solvent evaporation technique. The monoclinic structure of grown single crystal was studied by single-crystal X-ray diffraction and powder X-ray diffraction analyses. The Fourier transform infrared spectrum incorporates signatures of functional groups. The optical absorbance study reveals the UV cut-off wavelength as 230 nm. The Kurtz powder technique ensures that LAPB crystal has 1.1 times greater second harmonic generation efficiency than that of KDP crystals. The thermo-gravimetric and differential thermal analyses ensure that the material has good thermal stability. A dielectric behaviour of the sample material is studied in the frequency range \(10^{1}\)–\(10^{6}\)  Hz.     

Experimental study of particle deposition characteristics of alumina using plasma spraying

Plasma spraying is one of the most versatile techniques used to form coatings for protection against oxidation, corrosion, and wear. The plasma spraying is ideally suited for refractory materials, but there are a number of variables that need to be controlled to obtain dense coatings. In spite of considerable progress made in the theoretical understanding of this complex process, there is a need for a simple method to evaluate the interaction between the plasma flame and powder particles that form the coatings. As reported in the literature, this involves metallographic observation of the powders collected from the plasma. In the present study, the structure and morphology of plasma-sprayed splats are experimentally investigated using different power levels and spray distances for alumina powder. The results show that the splashing occurs during splatting of a completely molten droplet. It is found that at higher power levels and shorter spray distances, spreading of molten droplets improves considerably.     

Characterization and comparison between APS coatings prepared from ball milled and plasma processed nickel–aluminium powders

Plasma spraying has wide range of applications which include corrosion, thermal and abrasion resistance coatings. In the present work, nickel and aluminium powders were ball milled and the same were thermal plasma processed to produce spherical nickel alumindes particles. Both ball milled and plasma processed powders were spray deposited on stainless steel (SS 304) substrate using atmospheric plasma spray technique (APS). The experiments were carried out for different plasma input power levels, torch to base distances and coating thicknesses. Microstructure, micro hardness, adhesive strength, and porosity of the coatings are reported and discussed. Effect of plasma processing parameters and plasma spheroidization of powders on coating properties has been evaluated and reported. High plasma power, low torch to base distance lead to high temperature supplied to in-flight particles which correspond to high hardness, low porosity and high adhesion. Spherical morphology and formation of nickel aluminide intermetallic were achieved by plasma spheroidization. Coatings prepared from plasma processed powders enhance the coating properties positively.     

Optimization of EDM Parameters on Machining Si3N4–TiN Composite for Improving Circularity,Cylindricity, and Perpendicularity

The dominance of the spark eroding process in complex ceramic components has promoted a significant growth analysis in the ceramic composites domain in modern manufacturing industries. The latest developments in ceramic components are concentrated on both the enhancement of the mechanical properties and the machinability of complex 3D parts while using spark EDM. The current (I), pulse on time (T_on), pulse off time (T_off), and dielectric flushing pressure (DP) are considered sparking parameters for the machining of a Si₃N₄–TiN ceramic composite. These composites find their application in high-temperature environments, viz. metal forming, extrusion dies, turbine blade, and non-ferrous molten metal handling components. Taguchi's orthogonal array (OA), L₁₈, has been used to design the experiments. The optimal machining inputs are determined by the grey relational grade (GRG), which is attained from the grey relation analysis (GRA) for various response characteristics, such as the material removal rate (MRR), tool wear rate (TWR), circularity (CIR), cylindricity (CYL), and perpendicularity (PER). The significant parameters are identified via an analysis of variance (ANOVA). Finally, the optimized process parameters resulting in a higher MRR, lower TWR, lower form tolerance, and decreased orientation tolerance are verified through a confirmation test demonstrating that sparking process responses can be effectively improved.     

Studies on (NaCl) x (KBr) y−x (KI)1−y solid solutions: 2. Electrical measurements

Ternary solid solutions were melt grown from NaCl, KBr and KI starting materials. D.C. and A.C. electrical measurements were done on the resulting ternary compositions at temperatures ranging from 50 to 150 °C. Activation energies and mean jump frequencies were also estimated. The bulk composition has complicated influences on the electrical parameters.     

Perpendicular magnetization in self-assembled films of citrate-capped gamma-Fe2O3 nanocrystals on Si(100) surfaces

gamma-Fe2O3 nanocrystals capped with citrate and octylamine have been chemically prepared. The octylamine-capped nanocrystals exhibit a tendency to form ordered lattices. Films of nanocrystals of varying thickness (454, 720, and 1400 microg/cm2 in the case of citrate-capped nanocrystals and 300 microg/cm2 in the case of octylamine-capped nanocrystals) have been prepared on Si(100) substrates by drop casting and have been characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Magnetic measurements have been carried out on the films as well as on nanocrystal powders. The films of citrate-capped gamma-Fe2O3 nanocrystals exhibit enhanced perpendicular magnetization, with the anisotropy depending on the film thickness.     

Studies on growth and characterization of an NLO crystal: L-alanine hydrogen chloride (LAHC)

A nonlinear optical (NLO) salt viz. L-alanine hydrogen chloride (LAHC) has been synthesized and solubility of the synthesized salt in de-ionized water was determined at different temperatures. Single crystals of L-alanine hydrogen chloride (LAHC) salt were grown by solution method with slow evaporation technique. The grown crystals were characterized by single crystal X-ray diffraction (XRD) and powder XRD analyses to study the crystal structure. The crystallinity of LAHC crystal was confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. FTIR study was used to confirm the presence of various functional groups in the grown crystals. UV–visible transmittance spectrum was recorded to study the optical transparency of LAHC crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz–Perry powder test. The density of LAHC crystal was determined by floatation method. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to TG/DTA analyses. The dielectric behavior of the sample was also studied.