Evaluation of tribological behavior of silicon carbide and silicon nitride ceramics under different conditions

A comparative analysis of the tribological behavior of commercially available sintered silicon carbide (SiC) and three different types of silicon nitride (Si₃N₄) ceramics have been carried out using the ball-on-disk method in dry and lubrication (deionized [DI] water and ethanol) environment. Scanning electron microscopy (SEM) was used to understand the morphology and chemical composition of the tribo-surfaces. Sintered SiC (Hexoloy-SA) had the highest friction coefficient during dry sliding with an average of ∼0.34. Deionized water showed a minor improvement in friction (∼0.27) while ethanol reduced the friction greatly to ∼0.18 compared to dry sliding. During dry sliding, the presence of an abrasive third body was responsible for the high wear rates (WRs) in these compositions. Hexoloy-SA showed a lower WR during ethanol and DI water lubrication due to the formation of stable tribofilms as well as higher hardness which resisted the formation of third bodies. In comparison, Si₃N₄ samples showed a lower WR in DI water and ethanol. The samples also showed composition-dependent behavior which indicates that grain structure and grain boundary chemistry are playing a vital role in the tribological process.     

Design and Comparative Analysis of Heterogeneous Gate Dielectric Nanosheet TFET with Temperature Variance

Silicon - In this article, a Heterogeneous Gate-Dielectric Nanosheet Tunnel Field Effect Transistor (HD-NSH-TFET) with three channels is investigated using the 3-D Visual TCAD simulator. The HD...     

Binding of zinc to bovine and human milk proteins

Zn binding by whole bovine and human casein and by purified bovine caseins and whey proteins was investigated by equilibrium dialysis. Bovine alpha s1-casein had the greatest Zn-binding capacity (approximately 11 atoms Zn/mol). Protein aggregation was observed as Zn concentration was increased and the protein precipitated at a free Zn concentration of 1.7 mM. Zn binding increased with increasing pH in the range 5.4-7.0 and decreased with increasing ionic strength. Competition between Zn and Ca was observed for binding to alpha s1-casein indicating common binding sites for these two metals. Bovine beta-casein bound up to 8 atoms Zn/mol and precipitated at a free Zn concentration of approximately 2.5 mM, while kappa-casein bound 1-2 atoms Zn/mol. Whole bovine and human casein bound 5-8 atoms Zn/mol and precipitated at a free Zn concentration of approximately 2.0 mM. Scatchard plots for Zn binding to caseins showed upward convexity, possibly due to Zn-induced association of caseins. Apparent average association constants (Kapp) for all caseins were similar (log Kapp 3.0-3.2). Enzymic dephosphorylation of alpha s1- or whole bovine casein markedly reduced, but did not eliminate, Zn binding. Thus, phosphoserine residues appeared to be the primary Zn-binding sites in caseins. With the exception of bovine serum albumin, which bound over 8 atoms Zn/mol, the bovine whey proteins, beta-lactoglobulin, alpha-lactalbumin and lactotransferrin, had little capacity for Zn binding.     

Response of laying Japanese quails to graded levels of essential amino acids profile with reduced dietary protein

The effect on egg production of graded levels of ideal amino acids, combined with reduced protein in the diet, was investigated in 312 laying quails aged 6–18 weeks. The quails were offered six diets, each of which contained one of three levels of amino acids (85, 100 and 115% of essential amino acids (EAAs)) together with 5% or without fishmeal (FM) (3 × 2 factorial design). Each diet was offered to 26 replicated groups of two quails each. Hen‐day and hen‐housed egg production did not differ as a result of EAA level, protein type or their interaction during the overall period of egg production. Egg weight improved linearly (P < 0.01) with increased EAA levels, while egg mass output per bird per day remained similar at the 100 and 115% EAA levels. Quails fed higher (100 and 115%) EAA levels had an improved feed conversion ratio (P < 0.01) compared to birds fed 85% EAA. The gain in body weight during the laying period was higher (P < 0.01) at the 100 or 115% than at 85% EAA levels The ratio of egg mass or egg mass and live weight gain, together, to protein intake improved (P < 0.01) linearly with a decrease in EAA levels in the diets, while better (P < 0.01) energy efficiency (EE, energy intake: egg mass) and net EE (energy intake: egg mass plus gain) was obtained in higher EAA levels (100 or 115%). Protein and energy efficiencies remained similar due to protein type or interaction. Shape index, albumen index, yolk index, yolk colour and relative shell weight did not differ due to EAA levels, protein type or their interaction. Eggs laid from quails fed diets with 100% EAAs without FM and 115% EAAs with or without FM had higher shell thickness than those on 85% EAAs irrespective of protein type. The retention of nitrogen and calcium retention was higher (P < 0.01) at the 115% EAA level. The results indicated a dietary level of 100% EAA (185 g kg^?1 crude protein (CP)) with 12.13 MJ kg^?1 was suitable for laying quails of 6–18 weeks of age. Copyright © 2007 Society of Chemical Industry     

Status of dietary fiber contents in pigmented and non-pigmented rice varieties before and after parboiling

Five different varieties of paddy (four pigmented and one non-pigmented) were shelled and milled in pre and post parboiled form, their dietary fiber contents were estimated. Under similar conditions of milling, raw rice showed a high degree of polish (DOP), 9–12 g/100 g and parboiled rice showed low DOP, 4.6–6.6 g/100 g. Dietary fiber content was high in pigmented rice, 9–10 g/100 g compared to non-pigmented, ∼6 g/100 g. Soluble fiber content in pigmented head rice (dehusked) varied from 1 to 1.5 g/100 g and in its brokens varied from 0.45 to 1.45 g/100 g. Dietary fiber content was low by about 1% in parboiled rice. In the parboiled rice of pigmented varieties, the total fiber content varied from 7.95 ± 0.15 to 9.05 ± 0.25 g/100 g and the soluble fiber content varied from 0.7 to 0.9 g/100 g. In milled parboiled rice the respective values were 5 ± 0.4 to 6 ± 0.1 g/100 g and 0.85 ± 0.05 to 1.25 ± 0.05 g/100 g. However, the soluble fiber content in the non-pigmented brown rice, IR-64 remained same after parboiling, 0.75 ± 0.5 g/100 g. Milled parboiled rice showed higher soluble dietary fiber compared to milled raw rice. In conclusion, dietary fiber was high in pigmented rice varieties when compared with non-pigmented rice.     

Taguchi method to optimize the micron and submicron size cenosphere particulates filled E‐glass fiber‐reinforced vinylester composites

In this work, the mechanical and tribological characteristics of E‐glass fiber‐reinforced vinylester composites have been investigated experimentally under dry sliding conditions. The E‐glass fiber‐reinforced vinylester composites with uniform micron and submicron size cenosphere particulates of three different sizes (2 µm, 900 nm, and 400 nm) had been prepared in the laboratory. In this work the effect of parameters such as applied normal load, particulate size, sliding speed, sliding distance and roughness on friction and wear behavior have been carried. A plan of experiments, based on the Taguchi design, was performed to acquire data in a controlled way. An orthogonal array L₂₇ (3¹³) and Analysis of variance (ANOVA) have been applied to investigate the influence of process parameters on the coefficient of friction (COF) and sliding wear behavior of these composites. It was found that the submicron size particulates 400 nm as filler contributed significantly to improve the mechanical properties and wear resistance of the composites. The experimental results indicate that the specific wear rate is greatly influenced by applied normal load and particle size. ANOVA results showed that the applied normal load significantly influence the specific wear rate of cenosphere filled glass fiber‐reinforced vinylester composites. Regression analysis is carried to check the suitability of the prediction equation and modeling of the wear parameters and the typical R² values for COF and specific wear rate are 86.7 and 94.3%, respectively. The scanning electron microscopy are used clarify the experimental in the frictional and wear testing. POLYM. COMPOS., 35:775–787, 2014. © 2013 Society of Plastics Engineers     

Finite element modeling of orthogonal micromachining of anisotropic pyrolytic carbon via damaged plasticity

Engineered features on pyrolytic carbon (PyC) have been demonstrated as an approach to improve the flow hemodynamics of the cardiovascular implants such as bileaflet mechanical heart valve. PyC also finds application in thermonuclear and missile components due to its unique directional thermal properties. However, very little work has been reported on modeling of machining/micromachining of PyC. Note that PyC is a brittle anisotropic material and its machining characteristics differ from plastically deformable isotropic materials. Consequently, this study is aimed at developing a finite element model to understand the mechanics of material removal in the plane of transverse isotropy (horizontally stacked laminae) of PyC. A damaged plasticity model has been used to capture the effect of material degradation under machining. Uniaxial tension/compression tests have been carried out to calibrate the damaged plasticity model. A cohesive element layer has been used between the chip layer and the bulk material to simulate the delamination/peeling effect. The model predicts cutting force and thrust forces at different set of process parameters. The orthogonal cutting model has been validated against the experimental data for different cutting conditions for cutting and thrust forces. In addition, the chip geometry has also been compared. The prediction error in the model lies between 9% and 27%. Parametric studies have also been performed to understand the effect of the machining parameters on the process response. It is found that use of the positive rake angle decreases the cutting forces up to 75%.     

Improved Torque and Flux Performance of Type-2 Fuzzy-based Direct Torque Control Induction Motor Using Space Vector Pulse-width Modulation

The conventional proportional integral controlled direct torque control of an induction motor using the space vector pulse-width modulation technique may provide satisfactory dynamic response. However, the proportional integral controller (PIC) does not provide efficient dynamic performance in the induction motor drive during sudden changes in the load or speed. To improve dynamic performance of the induction motor drive, the PICs are replaced by type-2 fuzzy logic control. The type-2 fuzzy improves the starting transient performance as well as the steady-state response. In addition, the type-2 fuzzy direct torque control provides lesser current total harmonic distortion, flux distortion, and torque pulsation of the induction motor drive compared to conventional direct torque control. A MATLAB Simulink (The MathWorks, Natick, Massachusetts, USA) model for direct torque control with type-2 fuzzy logic control is developed to simulate the response of an induction motor drive with different operating conditions. The space vector pulse-width modulation technique is used to drive the inverter, as it produces lesser total harmonic distortion in inverter current and voltage waveforms for a given switching transition due to the single switching frequency for the movement of each state vector. A prototype type-2 fuzzy-based direct torque control induction motor with space vector pulse-width modulation is developed to validate the simulated response. The control signals for the inverter are generated by the DSPACE DS1104 (DSPACE GmbH, Germany) to drive a two-HP induction machine.     

Lateral trench oxide Schottky rectifier on SOI for power integrated circuits

In this paper, a Lateral Trench Oxide Schottky (LTOS) rectifier on silicon-on-insulator suitable for power integrated circuits is presented. The proposed structure utilizes a surface Schottky contact with vertical field-plate placed in a trench filled with oxide. The field-plate reduces the electric field on the Schottky contact and suppresses the barrier lowering effect leading to significant improvement in the device performance. Further, the proposed structure folds the drift region in vertical and horizontal directions resulting substantial reduction in pitch length of the device. Two-dimensional numerical simulations have been performed to analyse and optimize the performance of proposed device and results are compared with that of the conventional lateral Schottky rectifier. The LTOS rectifier provides 60 % improvement in breakdown voltage and 50 % reduction in pitch length as compared to the conventional device while maintaining low forward voltage drop and low reverse leakage current.     

Electrical characterization and parameter extraction of organic thin film transistors using two dimensional numerical simulations

In this paper a performance based comparison of top and bottom contact organic thin film transistor (OTFT) device structures, using two dimensional numerical simulations has been carried out. In addition to this, investigations pertaining to the estimation of contact resistance in these OTFTs were also performed. To estimate contact resistance the conventional transmission line method and modified transmission line method (M-TLM) were respectively invoked. Our simulation results clearly indicate that the latter is more accurate in the estimation of contact resistance compared to the conventional method. Furthermore, the M-TLM was used to estimate the gate voltage and film thickness dependence of the contact resistance for the two device structures. The observed results have been explained on the basis of the significantly lowered area of carrier injection and extraction regions, at the source/channel and channel/drain interface respectively, in bottom contact transistor that lead to its inferior performance over the top contact transistor.