பொருள் அறிவியல் & பொறியியல் இதழ்

Rare earth elements, including neodymium, are in widespread use today. They serve, for example, as alloying elements in magnesium (WE 43, WE 54, AE44, AE42), in permanent magnets (neodymium-iron-boron) or as luminescent materials. In addition, they are amongst the most important commodities in Europe. The demand for their use is growing and the recycling of these elements is indispensable. Their recycling potential can be increased through detailed scientific studies and to this end this article presents a thermodynamic evaluation of equilibrium data in the system neodymium-chloride-hydrochloric acid (or sodium hydroxide)-water-di-(2-ethylhexyl) phosphoric acid (DEHPA)-kerosene. Considering the relationship between the activity coefficients 3 aq Nd + γ , Nd,org γ and ( )2 DEHPA γ , which arise from the law of mass action, the deviations of the experimental results from the ideal behaviour can be explained. From the calculation of 3 aq Nd + γ with the expanded Debye-Hückel equation and from literature data for ( )2 DEHPA γ , indications arise for the development of the functions of the activity coefficients of DEHPA and neodymium in the organic phase.

Low cycle fatigue (LCF) behaviors of pre-corroded Q345R steel under different corrosion environments were investigated where both concentration of H2S solution and pre-corrosion time served as two environmental factors. Low cycle fatigue tests were conducted at room temperature in air after the specimens were pre-corroded in H2S solution. The low cycle fatigue behaviours of pre-corrosion test material, such as strain-life relationships and cyclic stress-strain responses were investigated and compared. Results show that environmental factors had little effect on the cyclic stress response while it had much effect on the fatigue life. And pre-corrosion time had more significant effect on low cycle fatigue life of test material than the solution concentration of H2S. Furthermore, the fracture surfaces of the fatigue samples were characterized by scanning electron microscope (SEM) and the fracture mechanisms were discussed under different environmental conditions.

The purpose of this work was searching of the formation of grain boundaries in metal-ceramics composites at various metal concentrations and sintering temperatures, influence of these boundaries on elastic moduli, coefficient absorption ultrasonic waves (USW) and thermo-conductivity to find the coupling of these properties and to estimate the optimal value of the metal concentration for achieve high quality of ready composites “corundum-stainless steel”. These boundaries are formed in the sintering process. In this work, cermets sintered in a high vacuum at different temperatures are investigated. Сermets (metal-ceramic composites) are modern construction materials used in different branches of industry. Their toughness and heat resistance are determined by their elastic and thermo-physical properties. In addition, these properties are significantly dependent on the grain boundaries in the material. The elastic moduli and absorption coefficient were measured by the ultrasonic method at room temperature; measurement of the thermal conductivity coefficient was carried out at temperature 200°C. In addition the samples structure was investigated by optical and scanning electron microscopy (SEM), cermets composition was determined by energydispersive X-ray spectroscopy method (EDS). We found two extremes for the concentration dependence of the elastic moduli (E and G) on the stainless steel concentrations, the nature of which is unknown. Similar dependence is observed also for the thermal conductivity coefficient and coefficient absorption ultrasonic waves. A discussion of the results is based on the structure cermet model as multiphase micro heterogeneous media with isotropic physical properties is also presented.

The aim of this paper is to investigate the relationship between particle shape and radiation effects on Marangoni boundary layer flow and heat transfer of water, ethylene glycol and engine oil based Cu, Al2O3 and SWCNTs. There are three types of nanoparticle shapes are considered in this research such as sphere, cylinder and lamina. The governing nonlinear partial differential equations are reduced into a set of nonlinear ordinary differential equations by applying similarity transformation which is solved using shooting technique in conjunction with Newton’s method and Runge Kutta algorithm. Temperature profiles are graphically and tabularly provided for the effects of solid volume fraction parameter, radiation parameter and empirical shape factor. The result shows that solid volume fraction and radiation energy gives a good impact on thermal boundary layer. Sphere nanoparticle shape predicts a better result on heat transfer rather than other nanoparticle shapes.

Large area reduced graphene oxide (RGO) thin films have been grown using pulsed laser deposition (PLD) technique. A very large carrier mobility of 372 cm2 V-1s-1 has been observed in a PLD grown RGO thin film with a large sp2 carbon fraction of 87% along with narrow Raman 2D peak profile. The fraction of sp2 carbon and carbon/oxygen ratios are tuned through PLD growth parameters, and these are estimated from X-ray photoelectron spectroscopy (XPS) data. The electrical properties of the RGO thin films are comprehended by the intensity ratios between different optical phonon vibrational modes of Raman Spectra. The photoluminescence spectra also indicate a less intense and broader blue fluorescence spectrum detecting the presence of miniature sized sp2 domains in the near vicinity of π* electronic states which favor the variable range hopping transport phenomena. This study on large area RGO thin films with very large carrier mobility fabricated by PLD process will be very useful for high mobility electronic device applications and could open a roadmap for further extensive research in functionalized 2D materials.

The main purpose of this study is to investigate the current state of Additive Manufacturing of Fiber Reinforced Plastics technology. Recent advances in additive manufacturing, with the introduction of fused deposition modeling of continuous fiber-reinforced thermoplastics, have opened a door for further improvements in composite manufacturing. We explore in detail the different available methods of manufacturing structures with continuous fiber reinforced plastics using additive manufacturing. It was found that it's possible to print different types of fibers; Glass, Carbon, Kevlar and Yute (Bio Filaments), and there are two types of resins that are mainly used; thermosets and thermoplastics. Finally, we conclude by analyzing current challenges of this technology in the area of design and structural optimization.

This article proves the possibility of using amorphous aluminosilicate as a modifying additive for the adhesive dry mixes. The data is given on the microstructure and chemical composition of the amorphous aluminosilicates. This article described the character changes in the rheological properties of cement-sand mortar, depending on the percentage of additives. The model of cement stone strength using synthetic additives in the formulation is illustrated. The results of physical and mechanical properties of tile adhesive made on the basis of the developed adhesive dry mix formulations are described.

The electroplating method is a promising alternative to produce composite plating by using dispersed fine particles in the metal plating bath. The process can be either called electro-deposition or composite deposition. The particles are trapped in the deposit during the process. Internal stress is a common problem in plated deposits that affect the performance of the coatings and may even result in adhesion problems. Hence, the amount and type (compressive or tensile) of the internal stress must be controlled. MoS2 particle – nickel coatings can be referred as self-lubricating coatings that satisfy the demand for decreased friction in severe applications. The internal stress during MoS2 particle – nickel electro-deposition was measured by deposit stress analyzer. The effects of electroplating parameters that are MoS2 particle concentration, temperature and coating thickness on the internal stress values were investigated by Taguchi design. It is found that increasing MoS2 particle concentration and coating thickness led to decrease in the internal stress developed during MoS2-nickel composite coatings. Interaction effects of these parameters were also revealed.

The present work deals with the synthesis of nanostructured MgO from different organic precursors, by a facile precipitation method as catalysts for the decontamination of Malathion (stimulant of chemical warfare agents) (VX) and orange G as organic pollutants. The as-prepared nanoparticles were obtained by thermal decomposition of the oxalate, tartarate, citrate, succinate, malate, malonate and glycinate precursors at ≈650°C and were characterized by thermal analysis, FTIR, X-ray diffraction, high resolution transmission electron microscope (HRTEM) and absorption spectra. The morphology and crystal sizes were found to be highly affected by the starting organic precursors. The results revealed that the prepared inexpensive magnesium oxides have high potential as catalysts for photo degradation of both Malathion and orange G from water samples. Inhibitory activity against Breast Carcinoma MCF-7 cell line was detected using some selected nanosized MgO and compared to that of Vinblastine as a standard drug.

Fifty-eight years ago Fenman, during an American Physical Society meeting at the California Institute of Technology, anticipated the problem of modifying and governing the world of the infinitely small. He said: “What I want to talk about, is the problem of manipulating and controlling things on a small scale… What I have demonstrated is that there is room—that you can decrease the size of things in a practical way. I now want to show that there is plenty of room. I will not now discuss how we are going to do it, but only what is possible in principle… We are not doing it simply because we haven’t yet gotten around to it.” Useless to say how profound his sensibility for science was. We’ve just begun to walk in this enormous field, toward the assembly of devices atom by atom. What we did till now is still rudimentary. Anyhow we believe that Layered Double Hydroxides could play a role in manufacturing these nanometric equipments. Layered Double Hydroxides (LDHs) are 2D ionic lamellar nano-materials belonging to the group of anionic clays. Their structure consists of positively charged brucite-like layers and intercalated anions. The layered structure, together with the flexibility to intercept different anionic species in variable compositions, both inorganic and organic, has attracted increasing interest. In order to meet specific requirements in very distant fields, considerable efforts were made to tailor the physical/chemical properties of LDHs and to design engineered LDH for several applications, ranging from anticorrosion coatings, flame-retardants, catalysis, to water treatment/purification, and biomedical applications. Furthermore they have been applied in energy harvesting and conversion, thanks to the possibility of substituting the composing metals with transition metals. Within the framework of this contribution, we first briefly review the development of synthesis processes (§1). In Paragraph 2, examples of the LDHs applications are reported. We will than focus on our laboratory experimental activities, showing the growth of the structures either on printed circuit tracks for applications of LDHs as gas sensors and biosensors. One more application is in nanostructured-modified textiles.

This paper discuss the effect of processing details such as particle size, sintering temperature, preform preparation, aluminum alloy characteristics and melt temperature on the final mechanical properties of ceramic phase reinforced metal matrix composites. Since alloy composition was determined as 7075 and 7085 optimum solutionizing and ageing temperatures were studied to determine maximum hardness values. For only 7085 alloy best solutionizing temperature is 465°C and for 7075 alloy the maximum hardness achived as 178 BHN after heat treatment at 475°C. Alloys were heat treated for recystallization after hot rolling grain size were measured as 100-120 μm for 7085 alloy matrix. Various sintering temperatures were used for preform preparation such as 1300-1450°C. In 85% Al2O3 reinforced 7085 Alloy based MMCs preforms sintered at 1450°C high hardness values were achieved as 545 BHN. Intermetallic phase was determined in 7075 and 7085 alloys selected as alloy matrix. Al2Cu intermetallic pecipitate (θ phase) was determined as dominant second phase after T6 heat treatment but highly expected phase in 7000 series alloys MgZn2 (η phase) was not determined by XRD and SEM analysis techniques due to ultrafine precipitate size and homogeneous distribution.

A theoretical analysis of improving the separation power of size exclusion chromatography by decreasing flowrate is conveyed. The variance of the elution curves is larger than expected form estimated dispersity in molecular weight, Mw/Mn. The shape of the elution curves depends strongly on experimental conditions. When the experimental conditions are approaching those to the ideal separation, judged by statistical properties of the curves, both skew and excess kurtosis of the elution curves increase near the exclusion limit in accord with theoretical prediction. In analyses of polystyrene standards by size exclusion chromatography for polymers of molecular weight about thirty thousand and higher, the longitudinal diffusion is not important even at low flow-rates.

The patterns of stable quantum states in the Periodic Table are inverted and extended to infinity in both directions to accommodate spatial variation relative to the nucleus. The upper end leads to a cut off point for white matter. The lower end represents quantum states in plasma. At 10-15 m to 10-20 m the interaction between weak strong and gravity forces results in suitable boundary conditions for the production of elementary particles. Chemical classification of the elements requires convergence of chemical properties and quantum states. By defining GROUP NUMBER as the maximum number of electrons in any one shell, Hydrogen and Helium are moved to the first set of 2(1)2 states first proposed by Janet. The atomic numbers are adjusted and mass number removed as it is an average of isotopes of each element produced in every supernova. This produces the: Roberts Janet Nuclear Periodic Table which proposes two zero states, a cut off and start point, of the electric field in attractive then repulsive modes. By symmetry of these fields energy states emerge in plasma with the counter intuitive property that the nearer the nucleus the greater the number of energy states. Fusion results and the consequential recycling implies a more rapid collapse than supernovae given sufficient energy density that could create an as yet unobserved interaction at 10-50 m to 10-65 m between the strong and gravity forces. String theory and extra dimensions may be required to explain such mechanisms and multiverses.

Density functional theory and pseudopotentials were used to study reaction of the ferrite grains interface (doped with C, P, N, Ti, Ti+N and Ti+C) on deformations. It was shown that impurities could increase or decrease the tensile strength and the elongation limit. The best effect was demonstrated for cases when Ti presents simultaneous with C; the worst case is doping iron with P. As for the shift modulus, effect is not significant.

Olivine sand is used in steel plants operating with Electric Arc Furnaces as Eccentric Bottom Tap Hole. The free opening rate is mainly determined by the performance of the tap hole filler sand. A free opening occurs when steel flows freely from the tap hole to ladle once the tap hole is opened. Various parameters such as sintering behavior, particle size distribution, wettability, etc. affect the performance of the sand. One of the important factors affecting the performance of sand is wetting the sand by molten steel. Olivine sand is a type of sand that used in electric arc furnaces. Wetting of Olivine sand against FeO alloys were presented. The wetting characteristics of liquid FeO alloys in a matrix of the Olivine sand at air pressure and temperature of 1650°C were studied by determining the liquid metal- Olivine contact angles. The median wetting angle values from textually equilibrated samples were found 100°. These results suggest that the steel melt forms in isolated pockets at grain corners or on grain boundaries. This will Increase the permeability of sand And the performance of the tap hole filler sand.