Addition Of Fine Powder Research Articles

Optimization of process parameters in magnetic field assisted powder mixed EDM of aluminium 6061 alloy

Magnetic field assisted powder mixed electrical discharge machining (MFAPM-EDM) is a variant of EDM process where magnetic field coupled with electric field is used with addition of fine powder in dielectric to improve the surface quality, machining rate and stability of the process. Aluminium 6061 alloy as workpiece was selected due to growing use in aviation, automotive, naval industries. In this present work, parametric study and optimization was carried out on MFAPM-EDM machined Aluminium 6061 alloy. In this study, process parameters such as discharge current (IP), spark duration (PON), pause duration (POFF), concentration of powder (CP) and magnetic field (MF) were considered to analyze the effect on material erosion rate (MER) and electrode wear rate (EWR). Box Behnken design approach based on response surface methodology (RSM) was utilized for performing the experiments. Quadratic model to predict the MER and EWR were developed using response surface methodology. Discharge current has most significant effect of 50.176% and 36.36% on MER and EWR, respectively among all others process parameters. Teacher-learning-based optimization (TLBO) was employed for determining the optimal process parameters for maximum MER and minimal EWR. The results obtained with TLBO was compared with well-known optimization methods such as genetic algorithm (GA) and desirability function of RSM. Minimum EWR (0.1021 mm3/min) and maximum MER (30.4687 mm3/min) obtained using TLBO algorithm for optimized process parameters was found to better as compared to GA and desirability function.

The Raman Spectra and Molecular Relaxation Properties of Heterophase Glasses and Melts of K,Ca/CH3COO and Li,K,Cs/CH3COO

The Raman spectra and conductivity of KCH3COO–Ca(CH3COO)2 and LiCH3COO–KCH3COO–CsCH3COO vitrified acetate systems doped with fine Al2O3 and SiO2 powders at various concentrations were investigated. It was established that at temperatures below the glass formation temperature the addition of fine powders of Al2O3 and SiO2 increases the conductivity of heterophase glasses. It is shown that in the heterogeneous system there are two types of acetate ions differing in relaxation time.

Influence of Rubber Fine Powder on the Characteristics of the Bitumens in Algeria

The presented research aims to develop the rubber fine powder in wearing course. It is interested particularly in the behaviour of two types of bitumen 40/50 modified by addition of two varieties of fine powders of rubber of different granularities. In addition to the objective of study and the evaluation of the influence of polymer added on the physical properties of the road bitumens, this work aims at following the influence of the granularity and proportioning in fine powders on the rheological performances of the bitumen by the intermediary of the tests of softening and Ring and of the tests of penetrability to the needle according to various contents. Except the environmental advantage, the tests carried out showed that the addition of fine powders, in a certain interval, has a significant influence on the mechanical properties and rheological of the analyzed bitumen and leads on a whole of interesting correlations.

Magnetic Properties of Nanocrystalline Powder Cores Fabricated by Mechanically Crushed Powders

Fe73.5Cu1Nb3Si15.5B7 nanocrystalline powder cores with different particle sizes ranging from 10 to 125 μm were fabricated by cold-pressing techniques. The cores exhibited increased core loss Pcv and decreased initial permeability μi with addition of fine powders below 50 μm in size, and the content should be less than 40 mass%. It was thought to be closely related to the high coercive force Hc due to the stresses generated during the crushing process and high demagnetization fields of small powders. Furthermore, modifying the alloy compositions by adding defined amount of Ni could improve the soft magnetic properties, including superior characteristics of permeability under high direct current (DC) bias field and comparable low core loss at high frequency.

Development of Compound for Anisotropic Bonded Nd Magnets Using d-HDDR Magnet Powder

Bonded anisotropic Nd magnets with high-energy product (BH) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 20MGOe and freedom of shape design are effective in realizing motor size and weight reductions. The anisotropic powders were produced by d-HDDR treatment, grain boundary diffusion treatment with NdCuAl, and powder surface coating treatment. However, during the compression molding process, the molding pressure can induce the magnet powder grains to crack, which leads to degradation in magnetic performance, in particular the squareness ratio. A compound made of d-HDDR magnet powder coated with resin, fine SmFeN powder, and lubricant can produce molded blocks with a high density of 6.0 g/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at a low molding pressure of 1 t/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In addition, by enabling molding at a low pressure, the loss of squareness of the magnet powder was reduced to 0.5%. From the above, through kneading and the addition of fine powder and lubricant, the surface treatment of d-HDDR magnet powder achieved high-density magnets at a low molding pressure and a compound capable of controlling the reduction in loss of squareness.

Effect of powder mixing on thermoelectric properties in Bi 2Te 3-based sintered compounds

The effect of powder mixing on thermoelectric properties was studied in n-type Bi 2Te 2.85Se 0.15 compounds and p-type Bi 0.5Sb 1.5Te 3 compounds. The figure-of-merit of the n- and p-type sintered compounds was strongly affected by carrier mobility. The use of coarse powders (200–300 μm) was beneficial to improve the crystallographic orientation of sintered compound. However, voids in the compound decreased the carrier mobility. As the fine powders (below 45 μm) were blended with coarse powders up to about 30%, the carrier mobility was increased due to the reduction of the voids. The addition of fine powders over 30% degraded the carrier mobility due to the decrease of crystallographic orientation and the increase of particle boundary. When the fine powder content was 20%, the n- and p-type compounds exhibited the maximum figure-of-merit of 2.31 × 10 −3 K −1 and 2.89 × 10 −3 K −1, respectively.

Conduction Mechanisms in Concentrated LiI‐Polyethylene Oxide‐ Al2 O 3‐Based Solid Electrolytes

The ionic conductivity of concentrated LiI‐polyethylene oxide high surface area oxide composite polymer electrolytes has been investigated. Two different Arrhenius dependences for concentrated composite polymer electrolytes (CPEs) have been identified. The first one is characterized by an inflection point at about 80°C, and the second, by a conductivity jump. We have suggested that in CPEs, where 3 < n < 9, the solid phase is major contributor to the overall ionic conductivity at temperatures above, but close to the melting point of the eutectic (Tm < T < Tk), where Tk is the knee temperature. It is important to note that at T < Tk the apparent activation energy of conduction (Ea) for composite solid electrolytes (CSEs, n ⩽ 3), is about 40% of that for CPEs. We believe that the preferred conduction path in even more concentrated CPEs, which are defined as CSEs, is interfacial conduction. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and x‐ray data, presented in this communication, are evidence supporting our view The effects of several parameters including type and content of oxide matrix, Li salt to ethylene oxide (EO) ratio, copolymers, and solvents on polymer electrolyte conductivity (especially at T > Tk or Tjump) and on Ea have been studied (Tjump is a temperature of the conductivity jump). The addition of small quantities of ethylene carbonate (EC), poly(methyl methacrylate), and polyacrylonitrile were found to be beneficial while poly(methyl acrylate), poly(butyl acrylate), and poly(vinylidene fluoride) additions made the polymer electrolyte stiffer and less conductive. MgO, , and potassium aluminosilicate muscovite mica based CSEs have similar conductivity. DSC and SEM results clearly demonstrated the depression of CPE crystallinity by addition of fine powder, ethylene carbonate, and poly(ethylene glycol) dimethyl ether. This is in agreement with the conductivity enhancement of the CPE.

The Porosity Change Based upon Mixing of Fine Powders Having Different Sizes

The packing models such as those devised by Hudson and Horsfield and ordinarily used for mixed powders of different sizes are not applicable to fine powders in which the force of interaction between the powder particles can not be neglected.The change of porosity based upon mixing of fine powders having different particle size, was measured. The porosity increased rapidly by addition of small amount of fine powders. However, the porosity seemed to remain constant within certain range of further addition of fine powders. But it increased again when more amount of fine powders were added beyond this range.The mechanism of this process can be explained by a simple assumption that cohesion of small particles to larger ones increased their points of contact. And the relation between the weight fraction of the small particles added and the increase ratio of porosity of powder bed in every mixed powder was obtained asWs/f(e)×(W0-Ws)=α+βWs/W0where Ws is the weight of added powder, W0 is that of total powder mixed and e is the porosity. The constant β was related to the equilibrium porosity, but the meaning of the constant α was not yet known.