Search results for: plasma kinetics

Authors: C. W. Kan, H. F. Cheung, Y. S. Lee

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This study examines the results of colour fading of cotton fabric by plasma-induced ozone treatment, with an aim to provide learning materials for fashion designers when designing colour fading effects in fashion products. Cotton knitted fabrics were dyed with red reactive dye with a colour depth of 1.5% and were subjected to ozone generated by a commercially available plasma machine for colour fading. The plasma-induced ozone treatment was conducted with different parameters: (i) air concentration = 10%, 30%, 50% and 70%; (ii) water content in fabric = 35% and 45%, and (iii) treatment time = 10 minutes, 20 minutes and 30 minutes. Finally, the colour properties of the plasma–induced ozone treated fabric were measured by spectrophotometer under illuminant D₆₅ to obtain the CIE L*, CIE a* and CIE b* values.

Keywords: learning materials, colour fading, colour properties, fashion products

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Authors: O. E. Okafor, L. U. S. Ezeanyika, C. G. Nkwonta, C. J. Okonkwo

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The effect of processing on plasma lipid profile and atherogenic indices of rats fed Artocarpus heterophyllus seed diets at different concentrations were investigated. Fifty five rats were used for this study, they were divided into eleven groups of five rats each (one control group and ten test groups), the test groups were fed raw, boiled, roasted, fermented, and soaked diets at 10 % and 40% concentrations. The study lasted for thirty five days. The diets led to significant decrease (p < 0.05) in plasma cholesterol and triacylglycerol of rats fed 10% and 40% concentrations of the diets, and a significant increase (p < 0.05) in high density lipoprotein (HDL) levels at 40% concentrations of the test diets. The diets also produced decrease in low density lipoprotein (LDL), very low density lipoprotein (VLDL), cardiac risk ratio (CRR), atherogenic index of plasma (AIP) and atherogenic coefficient (AC) at 40% concentrations except the soaked group that showed slight elevation of LDL, CRR, AC and AIP at 40% concentration. Artocarpus heterophyllus seeds could be beneficial to health because of its ability to increase plasma HDL and reduce plasma LDL, VLDL, cholesterol, triglycerides and atherogenic indices at higher diet concentration.

Keywords: artocarpus heterophyllus, atherogenic indices, concentrations, lipid profile

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Authors: S. Yakut, D. Deger, K. Ulutas, D. Bozoglu

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Plasma poly(ethylene oxide) (pPEO) thin films were deposited between Aluminum (Al) electrodes on glass substrates by plasma assisted physical vapor deposition (PAPVD). The deposition was operated inside Argon plasma under 10⁻³ Torr and the thicknesses of samples were determined as 20, 100, 250, 500 nm. The plasma was produced at 5 W by magnetron connected to RF power supply. The capacitance C and dielectric loss factor tan δ were measured by Novovontrol Alpha-A high frequency empedance analyzer at freqquency and temperature intervals of 0,1 Hz and 1MHz, 193-353K, respectively. AC conductivity was derived from these values. AC conductivity results exhibited three different conductivity regions except for 20 nm. These regions can be classified as low, mid and high frequency regions. Low frequency region is observed at around 10 Hz and 300 K while mid frequency region is observed at around 1 kHz and 300 K. The last one, high frequency region, is observed at around 1 kHz and 200 K. There are some coinciding definitions for conduction regions, because these regions shift depending on temperature. Low frequency region behaves as DC-like conductivity while mid and high frequency regions show conductivities corresponding to mechanisms such as classical hopping, tunneling, etc. which are observed for amorphous materials. Unlike other thicknesses, for 20 nm sample low frequency region can not be detected in the investigated freuency range. It is thought that this is arised because of the presence of dead layer behavior.

Keywords: plasma polymers, dead layer, dielectric spectroscopy, AC conductivity

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Authors: Muhammad Saiful Islam Khan, Yun Ji Kim

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Organophosphorus pesticides (OPPs) have been widely used to replace more persistent organochlorine pesticides because OPPs are more soluble in water and decompose rapidly in aquatic systems. Extensive uses of OPPs in modern agriculture are the major cause of the contamination of surface water. Regardless of the advantages gained by the application of pesticides in modern agriculture, they are a threat to the public health environment. With the aim of reducing possible health threats, several physical and chemical treatment processes have been studied to eliminate biological and chemical poisons from food stuff. In the present study, a micro-plasma device was used to reduce pesticides from the surface of food stuff. Pesticide free food items chosen in this study were perilla leaf, tomato, broccoli and blueberry. To evaluate the removal efficiency of pesticides, different washing methods were followed such as soaking with water, washing with bubbling water, washing with plasma-treated water and washing with chlorine water. 2 mL of 2000 ppm pesticide samples, namely, diazinone and chlorpyrifos were individuality inoculated on food surface and was air dried for 2 hours before treated with plasma. Plasma treated water was used in two different manners one is plasma treated water with bubbling the other one is aerosolized plasma treated water. The removal efficiency of pesticides from food surface was studied using HPLC. Washing with plasma treated water, aerosolized plasma treated water and chlorine water shows minimum 72% to maximum 87 % reduction for 4 min treatment irrespective to the types of food items and the types of pesticides sample, in case of soaking and bubbling the reduction is 8% to 48%. Washing with plasma treated water, aerosolized plasma treated water and chlorine water shows somewhat similar reduction ability which is significantly higher comparing to the soaking and bubbling washing system. The temperature effect of the washing systems was also evaluated; three different temperatures were set for the experiment, such as 22°C, 10°C and 4°C. Decreasing temperature from 22°C to 10°C shows a higher reduction in the case of washing with plasma and aerosolized plasma treated water, whereas an opposite trend was observed for the washing with chlorine water. Further temperature reduction from 10°C to 4°C does not show any significant reduction of pesticides, except for the washing with chlorine water. Chlorine water treatment shows lesser pesticide reduction with the decrease in temperature. The color changes of the treated sample were measured immediately and after one week to evaluate if there is any effect of washing with plasma treated water and with chlorine water. No significant color changes were observed for either of the washing systems, except for broccoli washing with chlorine water.

Keywords: chlorpyrifos, diazinone, pesticides, micro plasma

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Authors: Faisal Saleem, Kui Zhang, Adam Harvey

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The role of N₂ carrier gas towards the conversion of tar analogue was studied in a non-thermal plasma dielectric barrier discharge (DBD) reactor. The important parameters such as power (5-40W), residence time (1.41-4.23 s), concentration (20-82 g/Nm³), and temperature (Ambient-400°C) were explored. The present study demonstrated that plasma power and residence time played a key role in the decomposition of toluene, and almost complete removal of toluene was observed at 40w and 4.23 s. H₂ is obtained as a major gaseous product with a maximum selectivity of 40% along with some lighter hydrocarbons (5.5%). The removal efficiency of toluene slightly decreases with increasing the concentration of toluene from 20 g/Nm³ to 82 g/Nm³. The solid residue formation takes place inside the plasma reactor. The selectivity of LHC (lower hydrocarbons) increased up to 15% by increasing the temperature to 400°C. Introducing H₂ to the gas at elevated temperature opens up new reaction routes to raise the selectivity to lower hydrocarbons. The selectivity to methane reaches to 42% using 35% H₂ at 400°C and total selectivity of LHC increases to 57%.

Keywords: biomass gasification tar, non-thermal plasma, dielectric barrier discharge, residence time

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Authors: M. Fatmi, T. Chihi, M. A. Ghebouli, B. Ghebouli

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This work presents the experimental results of the differential scanning calorimetry (DSC), hardness measurements (Hv) and XRD analysis, for order to investigate the kinetics of precipitation phenomena in Al-7%wt. Mg alloy. In the XRD and DSC curves indicates the formation of the intermediate precipitation of β-(Al3Mg2) phase respectively. The activation energies associated with the processes have been determined according to the three models proposed by Kissinger, Ozawa, and Boswell. Consequently, the nucleation mechanism of the precipitates can be explained. These phases are confirmed by XRD analysis.

Keywords: discontinuous precipitation, hardening, Al–Mg alloys, mechanical and mechatronics engineering

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Authors: Dorina Rusu, Emil Ghiocel Ioanid, Marta Ursescu, Ana Maria Vlad, Mihaela Popescu

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During the last decades the cold plasma discharges made the subject of numerous studies concerning the applications in the cultural heritage field, especially concentrated on ecological and non-invasive aspect of these conservation procedures. The conservation treatment using cold plasma is based, on the one hand, on the well-known property of plasma discharges to inactivate the contaminant biological species and, on the other hand, on the surface cleaning effect. Moreover the plasma discharge produces the functionalization of the treated surface, allowing subsequent deposition of protective layers. The paper presents the behavior of printing inks on historical documents treated in cold RF plasma. Two types of printing inks were studied, namely red and black ink, used on a religious book published in 19 century. SEM-EDX analysis results in the identification of the two inks as carbon black ink (C presence in the EDX spectrum) and cinnabar based red ink (Hg and S lines in the spectrum), result confirmed by XRF analysis. The experiments have been performed on paper samples written with laboratory- made inks, of similar composition with the inks identified on historical documents. The samples were subjected to RF plasma discharge, operating in nitrogen gaseous medium, at 1.2 MHz frequency and low-pressure (0.5 mbar), performed in a self-designed equipment for the application of conservation treatments on naturally aged paper supports. The impact of plasma discharge on the inks has been evaluated by SEM, XRD and color analysis. The color analysis revealed a slight discoloration of cinnabar ink on the historical document. SEM and XRD analyses have been carried out in an attempt to elucidate the process responsable for color modification.

Keywords: RF plasma, printing inks, historical documents, surface cleaning effect

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Authors: Abderazak Guettaf

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The mathematical models of the physical phenomena interacting in inductive plasma were described by the physics equations of the continuous mediums. A 3D model based on magnetic potential vector and electric scalar potential (A, V) formulation is used. The finished volume method is applied to electromagnetic equation, to obtain the field distribution inside the plasma. The numerical results of the method developed on a basic model designed starting from a real three-dimensional model were exposed. From the mathematical model 3D spreading assumptions and boundary conditions, we evaluated the electric field in the load and we have developed a numerical code made under the MATLAB environment, all verifying the effectiveness and validity of this code.

Keywords: electric field, 3D magnetic potential vector and electric scalar potential (A, V) formulation, finished volumes, annular plasma

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Authors: Youjeong Hwang

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Purpose: Insulin-like growth factor-I (IGF-I) promotes B-cell development, immunoglobulin formation, and interleukin-6 (IL-6) production, then regulate the immune response and inflammation. As IGF-I and their receptor also exist in the periodontal tissue, they may affect the immune response caused by periodontal pathogens in aggressive periodontitis (AgP) patients. The function of IGF is regulated by IGF binding proteins (IGFBPs), and IGFBP-3 is known to most abundant in plasma. The aim of the present study was to assess the concentration of IGF-I and IGFBP-3 in plasma and gingival crevicular fluid (GCF) in AgP patients and to find out their association. Methods: Nine patients with AgP (test group) and nine healthy subjects (control group) were included in this study. None of the subjects had a history of systemic disease, smoking or steroids medication. GCF samples were collected by microcapillary pipettes and plasma samples were obtained by venipuncture. Probing pocket depth (PD), clinical attachment level (CAL) and bleeding on probing (BOP) were recorded. Samples were assayed for IGF-I and IGFBP-3 levels using ELISA. Results: Mean IGF-I level in GCF was higher in the test group than control. Mean IGF-I level in plasma and IGFBP-3 level in GCF and plasma in control group were higher than that of the test group. However, there was no statistical significance (p > 0.05). The mean level of IGF-I and IGFBP-3 in GCF was lower than those in plasma. Mean IGF-I level in plasma showed a negative correlation with PD and CAL (p < 0.05) in both groups. The levels of IGF-I and IGFBP-3 in GCF seemed to be negatively correlated with BOP in the test group (p < 0.05). Conclusions: The difference in the level of IGF-I and IGFBP-3 between AgP and healthy subjects was not significant. Further studies that explain the mechanism of the protective role of IGF-I with more samples are needed.

Keywords: aggressive periodontitis, pathogenesis, insulin-like growth factor, insulin-like growth factor binding protein

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Authors: K. Radha Krishnan, Mirajul Alom

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Dehydrated powder prepared from fresh radish (Raphanus sativus) leaves were investigated for the color stability by different drying methods (tray, sun and solar). The effect of blanching conditions, drying methods as well as drying temperatures (50 – 90°C) were considered for studying the color degradation kinetics of chlorophyll in the dehydrated powder. The hunter color parameters (L*, a*, b*) and total color difference (TCD) were determined in order to investigate the color degradation kinetics of chlorophyll. Blanching conditions, drying method and drying temperature influenced the changes in L*, a*, b* and TCD values. The changes in color values during processing were described by a first order kinetic model. The temperature dependence of chlorophyll degradation was adequately modeled by Arrhenius equation. To predict the losses in green color, a mathematical model was developed from the steady state kinetic parameters. The results from this study indicated the protective effect of blanching conditions on the color stability of dehydrated radish powder.

Keywords: chlorophyll, color stability, degradation kinetics, drying

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Authors: C. Ramamoorthy, R. Ranga Raj

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In olden days the Ramayana epic depicts the usage of invisible and fuel less aircraft named pushpavimana. The change of color in the reptile family chameleon paves way for the concept of color change phenomenon available in nature. In present scenario the aircrafts are visible so it is easily identified. So there are too many problems from the threatening. Research is still going on about this problem by using Liquid Crystal Display (LCD). Objective of this paper is to find much better to use the concept of invisible aircraft using plasma display through Couple Charged Device camera (CCD), which has a high resolution and can be used for many purposes like spying, defense, etc. Moreover it is cost wise cheap then, escaping the foe viewing.

Keywords: CCD camera, chameleon, invisible, plasma display

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Authors: Abdurraouf O. Gaja, Salah Y. A. Al-Dahash, Guru Solmon Raju, Chikara Kubota

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Corpus luteum cross sectional (by ultrasonography) and plasma progesterone (by DELFIA) were estimated in early pregnant and non pregnant cows on days 14th and 20th to 23rd post insemination. On day 14th, corpus luteum sectional area was 348.43 mm2 in pregnant and 387.84mm2 in non pregnant cows. Within days 20th to 23rd, corpus luteum sectional area ranged between 342.06 and 367.90 mm2 in pregnant and between 193.85 and 270.69 mm2 in non pregnant cows. Plasma progesterone level was 2.43 ng/ml in pregnant and 2.46 ng/ml in non pregnant cows on day 14th, while during days 20th to 23rd the level ranged between 2.47 and 2,84 ng/ml in pregnant and between 0.53 and 1.17 ng/ml in non pregnant cows. Results of both luteal tissue areas as well as plasma progesterone levels were highly significantly deferent (P<0.01) between pregnant and non pregnant cows during days 20th to 23rd, but there were no significant differences on day 14th. The correlation between CL cross-sectional area and plasma progesterone level was 0.4 in pregnant cows and 0.99 in non pregnant cow. It is clear, from this study, that ultrasonic assessment of corpora lutea is a viable alternative to determine plasma progesterone levels for early pregnancy diagnosis in cows.

Keywords: progesterone, ultrasonography, corpus luteum, pregnancy diagnosis, cow

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Authors: T. Zlámal, J. Petrů, M. Pagáč, P. Krajkovič

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For the required function of components with the thermal spray coating, it is necessary to perform additional machining of the coated surface. The paper deals with assessing the surface integrity of Metco 2042, a plasma sprayed coating, after its machining. The selected plasma sprayed coating serves as an abradable sealing coating in a jet engine. Therefore, the spray and its surface must meet high quality and functional requirements. Plasma sprayed coatings are characterized by lamellar structure, which requires a special approach to their machining. Therefore, the experimental part involves the set-up of special cutting tools and cutting parameters under which the applied coating was machined. For the assessment of suitably set machining parameters, selected parameters of surface integrity were measured and evaluated during the experiment. To determine the size of surface irregularities and the effect of the selected machining technology on the sprayed coating surface, the surface roughness parameters Ra and Rz were measured. Furthermore, the measurement of sprayed coating surface hardness by the HR 15 Y method before and after machining process was used to determine the surface strengthening. The changes of strengthening were detected after the machining. The impact of chosen cutting parameters on the surface roughness after the machining was not proven.

Keywords: machining, plasma sprayed coating, surface integrity, strengthening

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Authors: Prangya P. Sahoo, B. S. Murty

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The present study deals with phase evolution of oxide dispersed CoCrFeMnNi high entropy alloy as a function of amount of added Y2O3 during mechanical alloying and analysis of grain growth kinetics of CoCrFeMnNi high entropy alloy without and with oxide dispersion. Mechanical alloying of CoCrFeMnNi resulted in a single FCC phase. However, evolution of chromium carbide was observed after heat treatment between 1073 and 1473 K. Comparison of grain growth time exponents and activation energy barrier is also reported. Micro structural investigations, using electron microscopy and EBSD techniques, were carried out to confirm the enhanced grain growth resistance which is attributed to the presence oxide dispersoids.

Keywords: grain growth kinetics, mechanical alloying, oxide dispersion, phase evolution

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Authors: Z. Honarvar, M. Farhoodi, M. R. Khani, S. Shojaee-Aliabadi

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Recently, edible films and coating have attracted much attention in food industry due to their environmentally friendly nature and safety in direct contact with food. However edible films have relatively weak mechanical properties and high water vapor permeability. Therefore, the aim of the study was to develop bilayer carboxymethyl cellulose (CMC) coated polypropylene (PP) films to increase mechanical properties and water vapor resistance of each pure CMC or PP films. To modify the surface properties of PE for better attachment of CMC coating layer to PP the atmospheric cold plasma treatment was used. Then the PP surface changes were evaluated by contact angle, AFM, and ATR-FTIR. Furthermore, the physical, mechanical, optical and microstructure characteristics of plasma-treated and untreated films were analyzed. ATR-FTIR results showed that plasma treatment created oxygen-containing groups on PP surface leading to an increase in hydrophilic properties of PP surface. Moreover, a decrease in water contact angle (from 88.92° to 52.15°) and an increase of roughness were observed on PP film surface indicating good adhesion between hydrophilic CMC and hydrophobic PP. Furthermore, plasma pre-treatment improved the tensile strength of CMC coated-PP films from 58.19 to 61.82. Water vapor permeability of plasma treated bilayer film was lower in comparison with untreated film. Therefore, cold plasma treatment has potential to improve attachment of CMC coating to PP layer, leading to enhanced water barrier and mechanical properties of CMC coated polypropylene as food packaging in which also CMC is in contact with food.

Keywords: carboxymethyl cellulose film, cold plasma, Polypropylene, surface properties

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Authors: A. H. El-Shazly, A. El-Tayeb, M. F. Elkady, Mona G. E. Ibrahim, Abdelazim M. Negm

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In this paper, corona discharge plasma reactor was used for degradation of organic pollution in aqueous solutions in batch reactor. This work examines the possibility of increasing the organic pollution removal efficiency from wastewater using non-thermal plasma. Three types of organic pollution phenol, acid blue 25 and methylene blue are presented to investigate experimentally the amount of organic pollution removal efficiency from wastewater. Measurement results for phenol degradation percentage are 71% in 35 min and 96% when its residence time is 60 min. In addition, the degradation behavior of acid blue 25 utilizing dual pin-to-plate corona discharge plasma system displays a removal efficiency of 82% in 11 min. The complete decolorization was accomplished in 35 min for concentration of acid blue 25 up to 100 ppm. Furthermore, the methylene blue degradation touched up to 85% during 35 min treatment in corona discharge plasma a batch reactor system. The decolorization ratio, conductivity, corona current and discharge energy are considered at various concentration molarity for AlCl3, CaCl2, KCl and NaCl under different molar concentration. It was observed that the attendance of salts at the same concentration level considerably diminished the rate and the extent of decolorization. The research presented that the corona system could be positively utilized in a diversity of organically contaminated at diverse concentrations. Energy consumption requirements for decolorization was considered. The consequences will be valuable for designing the plasma treatment systems appropriate for industrial wastewaters.

Keywords: wastewater treatment, corona discharge, non-thermal plasma, organic pollution

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Authors: Chandrashekar, R. T. Radhika, B. M. Venkatesha, S. Ananda, Shivalingegowda, T. S. Shashikumar, H. Ramachandra

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The kinetics of the oxidation of amitriptyline (AT) by sodium N-bromotoluene sulphonamide (C₆H₅SO₂NBrNa) has been studied in an acidic buffer medium of pH 1.2 at 303 K. The oxidation reaction of AT was followed spectrophotometrically at maximum wavelength, 410 nm. The reaction rate shows a first order dependence each on concentration of AT and concentration of sodium N-bromotoluene sulphonamide. The reaction also shows an inverse fractional order dependence at low or high concentration of HCl. The dielectric constant of the solvent shows negative effect on the rate of reaction. The addition of halide ions and the reduction product of BAT have no significant effect on the rate. The rate is unchanged with the variation in the ionic strength (NaClO₄) of the medium. Addition of reaction mixtures to be aqueous acrylamide solution did not initiate polymerization, indicating the absence of free radical species. The stoichiometry of the reaction was found to be 1:1 and oxidation product of AT is identified. The Michaelis-Menton type of kinetics has been proposed. The CH₃C₆H₅SO₂NHBr has been assumed to be the reactive oxidizing species. Thermodynamical parameters were computed by studying the reactions at different temperatures. A mechanism consistent with observed kinetics is presented.

Keywords: amitriptyline, bromamine-T, kinetics, oxidation

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Authors: R. Ondarza-Rovira, T. J. M. Boyd

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Intense femtosecond laser light incident on over-critical density plasmas has shown to emit a prolific number of high-order harmonics of the driver frequency, with spectra characterized by power-law decays Pm ~ m-p, where m denotes the harmonic order and p the spectral decay index. When the laser pulse is p-polarized, plasma effects do modify the harmonic spectrum, weakening the so-called universal decay with p=8/3 to p=5/3, or below. In this work, appeal is made to a single particle radiation model in support of the predictions from particle-in-cell (PIC) simulations. Using this numerical technique we further show that the emission radiated by electrons -that are relativistically accelerated by the laser field inside the plasma, after being expelled into vacuum, the so-called Brunel electrons is characterized not only by the plasma line but also by ultraviolet harmonic orders described by the 5/3 decay index. Results obtained from these simulations suggest that for ultra-relativistic light intensities, the spectral decay index is further reduced, with p now in the range 2/3 ≤ p ≤ 4/3. This reduction is indicative of a transition from the regime where Brunel-induced plasma radiation influences the spectrum to one dominated by bremsstrahlung emission from the Brunel electrons.

Keywords: ultra-relativistic, laser-plasma interactions, high-order harmonic emission, radiation, spectrum

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Authors: Betül Özgenç, Soner Kuşlu, Sabri Çolak, Turan Çalban

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The aim of this study was investigate the leaching kinetics of ulexite in disodium hydrogen phosphate solutions in a mechanical agitation system. Reaction temperature, concentration of disodium hydrogen phosphate solutions, stirring speed, solid/liquid ratio and ulexite particle size were selected as parameters. The experimental results were successfully correlated by linear regression using Statistica program. Dissolution curves were evaluated shrinking core models for solid-fluid systems. It was observed that increase in the reaction temperature and decrease in the solid/liquid ratio causes an increase the dissolution rate of ulexite. The activation energy was found to be 63.4 kJ/mol. The leaching of ulexite was controlled by chemical reaction.

Keywords: ulexite, disodium hydrogen phosphate, leaching kinetics

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Authors: Azade Ghorbani-HasanSaraei, Seyed-Ahmad Shahidi, Sakineh Alizadeh, Adeleh Maghsoudlou

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Improvement of color, as a quality attribute of Plum Concentrate, has been made possible by the increase in knowledge of kinetic of color change. Three different heating/evaporation processes were employed for the production of pPlum juice concentrate. The Plum juice was concentrated to a final 55 °Bx from an initial °Bx of 15 by microwave heating, rotary vacuum evaporator and evaporating at atmospheric pressure. The final Plum juice concentration of 55 °Bx was achieved in 17, 24 and 57 min by using the microwave, rotary vacuum and atmospheric heating processes, respectively. The colour change during concentration processes was investigated. Total colour differences, Hunter L, a and b parameters were used to estimate the extent of colour loss. All Hunter colour parameters decreased with time. The zero-order, first-order and a combined kinetics model were applied to the changes in colour parameters. Results indicated that variation in TCD followed both first-order and combined kinetics models, and parameters L, a and b followed only combined model. This model implied that the colour formation and pigment destruction occurred during concentration processes of plum juice.

Keywords: colour, kinetics, concentration, plum juice

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Authors: Suresh Vidyasagar Chevuri, D. B. Karunakar Chevuri

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The main advantages of 'Metal Matrix Nano Composites (MMNCs)' include excellent mechanical performance, good wear resistance, low creep rate, etc. The method of fabrication of MMNCs is quite a challenge, which includes processing techniques like Spark Plasma Sintering (SPS), etc. The objective of the present work is to fabricate aluminum based MMNCs with the addition of small amounts of yttrium using Spark Plasma Sintering and to evaluate their mechanical and microstructure properties. Samples of 2024 AA with yttrium ranging from 0.1% to 0.5 wt% keeping 1 wt% TiB2 constant are fabricated by Spark Plasma Sintering (SPS). The mechanical property like hardness is determined using Vickers hardness testing machine. The metallurgical characterization of the samples is evaluated by Optical Microscopy (OM), Field Emission Scanning Electron Microscopy (FE-SEM) and X-Ray Diffraction (XRD). Unreinforced 2024 AA sample is also fabricated as a benchmark to compare its properties with that of the composite developed. It is found that the yttrium addition increases the above-mentioned properties to some extent and then decreases gradually when yttrium wt% increases beyond a point between 0.3 and 0.4 wt%. High density is achieved in the samples fabricated by spark plasma sintering when compared to any other fabrication route, and uniform distribution of yttrium is observed.

Keywords: spark plasma sintering, 2024 AA, yttrium addition, microstructure characterization, mechanical properties

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Authors: Alemayehu Mengesha, Solomon Belay

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We determine the general dispersion relation for the propagation of magnetohydrodynamic (MHD) waves in an astrophysical plasma by considering the effect of viscosity with an anisotropic pressure tensor. Basic MHD equations have been derived and linearized by the method of perturbation to develop the general form of the dispersion relation equation. Our result indicates that an astrophysical plasma with an anisotropic pressure tensor is stable in the presence of viscosity and a strong magnetic field at considerable wavelength. Currently, we are doing the numerical analysis of this work.

Keywords: astrophysical, magnetic field, instability, MHD, wavelength, viscosity

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Authors: Juan C. Domínguez, Belén Del Saz-Orozco, María V. Alonso, Mercedes Oliet, Francisco Rodríguez

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In the present study, the kinetics of thermal degradation of a phenolic and lignin reinforced phenolic foams, and the lignin used as reinforcement were studied and the activation energies of their degradation processes were obtained by a DAEM model. The average values for five heating rates of the mean activation energies obtained were: 99.1, 128.2, and 144.0 kJ.mol-1 for the phenolic foam, 109.5, 113.3, and 153.0 kJ.mol-1 for the lignin reinforcement, and 82.1, 106.9, and 124.4 kJ. mol-1 for the lignin reinforced phenolic foam. The standard deviation ranges calculated for each sample were 1.27-8.85, 2.22-12.82, and 3.17-8.11 kJ.mol-1 for the phenolic foam, lignin and the reinforced foam, respectively. The DAEM model showed low mean square errors (< 1x10-5), proving that is a suitable model to study the kinetics of thermal degradation of the foams and the reinforcement.

Keywords: kinetics, lignin, phenolic foam, thermal degradation

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Authors: Damian A. Mooney, Michael T. P. Mc Cann, J. M. Don MacElroy, Olli Antson, Denis P. Dowling

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Atmospheric pressure plasma liquid deposition (APPLD) is a novel technology used for the deposition of thin films via the injection of a reactive liquid precursor into a high-energy discharge plasma at ambient pressure. In this work, APPLD, utilising a TEOS precursor, was employed to produce asymmetric membranes consisting of a thin (100 nm) layer of deposited silica on a microporous silica support in order to assess their suitability for high temperature gas separation applications. He and N₂ gas permeability measurements were made for each of the fabricated membranes and a maximum ideal He/N₂ selectivity of 66 was observed at room temperature. He, N₂ and CO2 gas permeances were also measured at the elevated temperature of 673K and ideal He/N₂ and CO₂/N₂ selectivities of 300 and 7.4, respectively, were observed. The results suggest that this plasma-based deposition technique can be a viable method for the manufacture of membranes for the efficient separation of high temperature, post-combustion gases, including that of CO₂/N₂ where the constituent gases differ in size by fractions of an Ångstrom.

Keywords: asymmetric membrane, CO₂ separation, high temperature, plasma deposition, thin films

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Authors: H. E. Ferrari, R. Farengo, C. F. Clauser

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Tungsten (W) will be used in ITER as one of the plasma facing components (PFCs). The W could migrate to the plasma center. This could have a potentially deleterious effect on plasma confinement. Electron cyclotron resonance heating (ECRH) can be used to prevent W accumulation. We simulated a series of H mode discharges in ASDEX U with PFC containing W, where central ECRH was used to prevent W accumulation in the plasma center. The experiments showed that the W density profiles were flat after a sawtooth crash, and become hollow in between sawtooth crashes when ECRH has been applied. It was also observed that a saturated kink mode was active in these conditions. We studied the effect of saturated kink like instabilities on the redistribution of W impurities. The kink was modeled as the sum of a simple analytical equilibrium (large aspect ratio, circular cross section) plus the perturbation produced by the kink. A numerical code that follows the exact trajectories of the impurity ions in the total fields and includes collisions was employed. The code is written in Cuda C and runs in Graphical Processing Units (GPUs), allowing simulations with a large number of particles with modest resources. Our simulations show that when the W ions have a thermal velocity distribution, the kink has no effect on the W density. When we consider the plasma rotation, the kink can affect the W density. When the average passing frequency of the W particles is similar to the frequency of the kink mode, the expulsion of W ions from the plasma core is maximum, and the W density shows a hollow structure. This could have implications for the mitigation of W accumulation.

Keywords: impurity transport, kink instability, tungsten accumulation, tungsten dynamics

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Authors: Kalimi Trinadh, Corinne Nouveau, A. S. Khanna, Karanveer S. Aneja, K. Ram Mohan Rao

Abstract:

This study concerns improving the corrosion resistance of low alloy steel after plasma nitriding performed at variable time and temperature. Nitriding carried out in the temperature range of 450-550ᵒC for a various time period of 1-8 hrs. at 500Pa in a glow discharge plasma of H₂ and N₂ (80:20). The substrate was kept biased negatively at 250V. Following nitriding the X-ray diffraction studies shown that the phases formed were mainly γ′ (Fe₄N) and ε (Fe₂₋₃N). The ε (Fe₂₋₃N) phase found to be the dominating phase. Cross sections of the samples under scanning electron microscope point analyses revealed the presence of nitrogen in the surface region. For the assessment of corrosion resistance property, potentiodynamic polarization tests were performed in 3.5% NaCl solution. It has been shown that the plasma nitriding significantly improved the corrosion resistance when compared to the as-received steel. Furthermore, it has also been found that nitriding for 6h has more corrosion resistance than nitriding for the 8h duration. The hardness of the nitrided samples was measured by Vicker’s microhardness tester. The hardness of the nitrided steel was found to be improved much above the hardness of the steel in the as-received condition. It was found to be around two-fold of the initial hardness.

Keywords: corrosion, steel, plasma nitriding, X-ray diffraction

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Authors: Ibrahim Laro ABUBAKAR

Abstract:

The study examined the Availability and Utilization of E-Learning Technologies in Teaching of Human Kinetics and Health Education courses in Nigerian Universities, specifically, Universities in Kwara State. Two purposes were formulated to guide the study from which two research questions and two hypotheses were raised. The descriptive research design was used in the research. Three Hundred respondents (100 Lecturers and 200 Students) made up the population for the study. There was no sampling, as the population of the study was not much. A structured questionnaire tagged ‘Availability and Utilization of E-Learning Technologies in Teaching and Learning Questionnaire’ (AUETTLQ) was used for data collection. The questionnaire was subjected to face and content validation, and it was equally pilot tested. The validation yielded a reliability coefficient of 0.78. The data collected from the study were statistically analyzed using frequencies and percentage count for personal data of the respondents, mean and standard deviation to answer the research questions. The null hypotheses were tested at 0.05 level of significance using the independent t-test. One among other findings of this study showed that lecturers and Student are aware of synchronous e-learning technologies in teaching and learning of Human Kinetics and Health Education but often utilize the synchronous e-learning technologies. It was recommended among others that lecturers and Students should be sensitized through seminars and workshops on the need to maximally utilize available e-learning technologies in teaching and learning of Human Kinetics and Health Education courses in Universities.

Keywords: awareness, utilization, E-Learning, technologies, human kinetics synchronous

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Authors: M. Habibi

Abstract:

The time-resolved studies of soft and hard X-ray were carried out over a wide range of argon pressures by employing an array of eight filtered photo PIN diodes and a scintillation detector, simultaneously. In 50% of the discharges, the soft X-ray is seen to be emitted in short multiple pulses corresponding to different compression, whereas it is a single pulse for hard X-rays corresponding to only the first strong compression. It should be stated that multiple compressions dominantly occur at low pressures and high pressures are mostly in the single compression regime. In 43% of the discharges, at all pressures except for optimum pressure, the first period is characterized by two or more sharp peaks.The X–ray signal intensity during the second and subsequent compressions is much smaller than the first compression.

Keywords: plasma focus device, SXR, HXR, Pin-diode, argon plasma

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Authors: Abeer S. Elsherbiny, Ali H. Gemeay

Abstract:

In this study, graphene oxide (GO) nanosheets have been synthesized and characterized using different spectroscopic tools such as X-ray diffraction spectroscopy, infrared Fourier transform (FT-IR) spectroscopy, BET specific surface area and Transmission Electronic Microscope (TEM). The prepared GO was investigated for the removal of malachite green, a cationic dye from aqueous solution. The removal methods of malachite green has been proceeded via adsorption process. GO nanosheets can be predicted as a good adsorbent material for the adsorption of cationic species. The adsorption of the malachite green onto the GO nanosheets has been carried out at different experimental conditions such as adsorption kinetics, concentration of adsorbate, pH, and temperature. The kinetics of the adsorption data were analyzed using four kinetic models such as the pseudo first-order model, pseudo second-order model, intraparticle diffusion, and the Boyd model to understand the adsorption behavior of malachite green onto the GO nanosheets and the mechanism of adsorption. The adsorption isotherm of adsorption of the malachite green onto the GO nanosheets has been investigated at 25, 35 and 45 °C. The equilibrium data were fitted well to the Langmuir model. Various thermodynamic parameters such as the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) change were also evaluated. The interaction of malachite green onto the GO nanosheets has been investigated by infrared Fourier transform (FT-IR) spectroscopy.

Keywords: adsorption, graphene oxide, kinetics, malachite green

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Authors: Gela Gelashvili, David Gelenidze, Sulkhan Nanobashvili, Irakli Nanobashvili, George Tavkhelidze, Tsiuri Sitchinava

Abstract:

Development of new highly efficient plasma arc combustion system of pulverized coal is presented. As it is well-known, coal is one of the main energy carriers by means of which electric and heat energy is produced in thermal power stations. The quality of the extracted coal decreases very rapidly. Therefore, the difficulties associated with its firing and complete combustion arise and thermo-chemical preparation of pulverized coal becomes necessary. Usually, other organic fuels (mazut-fuel oil or natural gas) are added to low-quality coal for this purpose. The fraction of additional organic fuels varies within 35-40% range. This decreases dramatically the economic efficiency of such systems. At the same time, emission of noxious substances in the environment increases. Because of all these, intense development of plasma combustion systems of pulverized coal takes place in whole world. These systems are equipped with Non-Transferred Plasma Arc Torches. They allow practically complete combustion of pulverized coal (without organic additives) in boilers, increase of energetic and financial efficiency. At the same time, emission of noxious substances in the environment decreases dramatically. But, the non-transferred plasma torches have numerous drawbacks, e.g. complicated construction, low service life (especially in the case of high power), instability of plasma arc and most important – up to 30% of energy loss due to anode cooling. Due to these reasons, intense development of new plasma technologies that are free from these shortcomings takes place. In our proposed system, pulverized coal-air mixture passes through plasma arc area that burns between to carbon electrodes directly in pulverized coal muffler burner. Consumption of the carbon electrodes is low and does not need a cooling system, but the main advantage of this method is that radiation of plasma arc directly impacts on coal-air mixture that accelerates the process of thermo-chemical preparation of coal to burn. To ensure the stability of the plasma arc in such difficult conditions, we have developed a power source that provides fixed current during fluctuations in the arc resistance automatically compensated by the voltage change as well as regulation of plasma arc length over a wide range. Our combustion system where plasma arc acts directly on pulverized coal-air mixture is simple. This should allow a significant improvement of pulverized coal combustion (especially low-quality coal) and its economic efficiency. Preliminary experiments demonstrated the successful functioning of the system.

Keywords: coal combustion, plasma arc, plasma torches, pulverized coal

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