Papers by Keyword: Nanocrystalline

Abstract: This study examines the mechanical and microstructural characteristics of magnesium nanocrystalline (nc) AZ61 alloy, which is produced using the SPS and mechanical milling processes. The results are presented and discussed. Using optical microscopy, it has been shown that the powders underwent twining, and after eight hours of milling, the subgrain boundaries developed, defining the grains with a nanometer size of 60 nm. The AZ61 alloy was sintered by spark plasma sintering at temperatures between 465⁰ to 565⁰ degrees Celsius. It has been noted that the grains in pure magnesium magnesium AZ61 alloys are uniformly dispersed, have few pores, and have particle boundaries throughout the SPS process. The mechanical parameters of the AZ61 alloy, namely hardness, compressive strength, and corrosion resistance, increase with increasing sintering temperature by approximately 725MPa, 298 MPa, and 0.18 mm.y-1.

Abstract: The photocatalytic activity of NiZnFe₂O₄/TiO₂ core-shell gg nanocrystalline was carried out. The NiZnFe₂O₄/TiO₂ core-shell was synthesized using co-precipitation method with various concentrations 1:0, 1:1, 1:2, 1:3, 1:4, and 1:5. X-ray diffraction spectra pattern showed crystallite size at various concentrations 1:0, 1:1, and 1:3, which of 5.00 nm, 4.90 nm, and 10.81 nm, respectively. The morphology of NiZnFe₂O₄ nanocrystalline was characterized by transmission electron microscopy which confirmed that the sample undergoes agglomeration with not uniform particle shape. The average particle size of the nanocrystalline was 10.26 nm. Fourier transform infra-red showed functional groups such as Ti-O-Ti, M-O_tetra, and M-O_octa at 1473.62, 563 - 586, and 401- 424 cm^-1. In addition, the presence of Ti-O-Ti and M-O functional groups indicates NiZnFe₂O₄/TiO₂ core-shell has been formed. The absorbance spectrum of the NiZnFe₂O₄/TiO₂ core-shell has an energy band gap in the range of 2.1 – 3.3 eV. The results of the Vibrating sample magnetometer showed saturation magnetization and coercivity values ​​in the range of 12.4 – 22.9 emu/gr and 47 - 55 Oe, which were correlated as soft magnetic properties. NiZnFe₂O₄/TiO₂ was successfully degraded Methylene Blue that reach 99.8% under UV light irradiation. The addition of TiO₂ increases degradation, TiO₂ acts as a trapping state that inhibits electron-hole recombination which can prolong the reaction time between free electrons and MB solution molecules. This study revealed the high potential of NiZnFe₂O₄/TiO₂ core-shell nanocrystalline in photocatalytic application.

Abstract: Renewable energy source is a clean energy production source and can overcome climatic challenges caused by the excessive use of fossil fuels. The nanocrystalline material of composition Cu_0.2Fe_0.2(Ce_0.6Gd_0.4-xNd_x)_0.6O_2-x has been synthesized by WOWS sol-gel process by varying Neodymium as such x= 0.0, 0.05. These samples were calcined at 500°C for 2 hours and the pellets were sintered at 750°C for 5 hours. X-Ray Diffraction technique confirms the cubic fluorite structure of the material. The doped material has showed high dielectric constant value and low dissipation factor and increased AC conductivity. AC conductivity obeys the Universal Dielectric Response. The material shows the potential for applications such as an electrode/electrolyte for fuel cells or also as a dielectric resonator.

Abstract: In this paper, a theoretical model based on multi-gene genetic programming (MGGP) approach has been applied to predict the structural and magnetic properties in nanocrystalline Fe–Ni powders prepared by mechanical alloying (MA) using a planetary ball mill. The MGGP model was used to correlate the input parameters (milling speed, chemical composition, and milling time), to output parameters (crystallite size and coercivity) of nanocrystalline Fe–Ni powders. The model obtained was tested with additional data to demonstrate its performance and prediction ability. The MGGP model is a robust and efficient method to find an accurate mathematical relationship between input and output data. A sensitivity analysis study was applied to determine the most influential milling parameters on the crystallite size and coercivity.

Abstract: This work examine the potential of ZrB₂ in the presence of Ni-P-Zn sulphate rich bath coating on mild steel under change in time from 10-25 min. The coating pH of 5, current density of 1 A/cm², and stirring rate of 250 rpm was considered in the fabrication process. The microstructure evolution and properties of the deposited coating was analysed using a scanning electron microscope enhanced with energy dispersive spectroscopy (SEM/EDS). All deposited composite coating was investigated in 0.5 M H₂SO₄ and 3.5% NaCl with the help of linear polarization and open circuit potential. From the result, a solid crystal formation containing zirconium boride was seen from the SEM study. At 25 min a remarkable dispersed and even thin film was noticeable at the interface. From all indication, coating produced with Ni-P-Zn-10ZrB₂ at 25 min provides a passive response against corrosion damage. Keywords: Electrodeposition, interface, nanocrystalline, structure, coating

Abstract: In photovoltaic system the major challenge is the cost reduction of the solar cell module to compete with those of conventional energy sources. Evolution of solar photovoltaic comprises of several generations through the last sixty years. The first generation solar cells were based on single crystal silicon and bulk polycrystalline Si wafers. The single crystal silicon solar cell has high material cost and the fabrication also requires very high energy. The second generation solar cells were based on thin film fabrication technology. Due to low temperature manufacturing process and less material requirement, remarkable cost reduction was achieved in these solar cells. Among all the thin film technologies amorphous silicon thin film solar cell is in most advanced stage of development and is commercially available. However, an inherent problem of light induced degradation in amorphous silicon hinders the higher efficiency in this kind of cell. The third generation silicon solar cells are based on nano-crystalline and nano-porous materials. Hydrogenated nanocrystalline silicon (nc-Si:H) is becoming a promising material as an absorber layer of solar cell due to its high stability with high V_oc. It is also suggested that the cause of high stability and less degradation of certain nc-Si:H films may be due to the improvement of medium range order (MRO) of the films. During the last ten years, organic, polymer, dye sensitized and perovskites materials are also attract much attention of the photovoltaic researchers as the low budget next generation PV material worldwide. Although most important challenge for those organic solar cells in practical applications is the stability issue. In this work nc-Si:H films are successfully deposited at a high deposition rate using a high pressure and a high power by Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF PECVD) technique. The transmission electron microscopy (TEM) studies show the formations of distinct nano-sized grains in the amorphous tissue with sharp crystalline orientations. Light induced degradation of photoconductivity of nc-Si:H materials have been studied. Single junction solar cells and solar module were successfully fabricated using nanocrystalline silicon as absorber layer. The optimum cell is 7.1 % efficient initially. Improvement in efficiency can be achieved by optimizing the doped layer/interface and using Ag back contact.

Abstract: In aluminate alkaline electrolyte the effect of aluminate on the microstructure and properties and the MAO(micro-arc oxidation) behavior of micro-arc oxide film of AZ91 magnesium alloy was studied. Transmission electron microscope(TEM), energy dispersive spectrum (EDS), X-ray diffraction(XRD), salt spray test and scanning electron microscope(SEM)were used to analyze and characterize the structure and properties of the film. The results show that the concentration of aluminate has an important effect on the tank voltage, corrosion resistance, surface morphology and phase structure of micro-arc oxidation film. The corrosion resistance and film quality of the film were increased first and then decreased, but the surface roughness decreased first and then increased with the increase of aluminate concentration from 5g/L to 30g/L. At our work, the concentration of 10g/L aluminate electrolyte is most favorable to the formation of micro-arc oxide film.

Abstract: The present work is aimed at the synthesis of fluorine substituted and carbonate substituted hydroxyapatites (FHA, CHA) by the mechanochemical method. The shortest milling time required for the synthesis of FHA and CHA using calcium hydroxide and diammonium hydrogen phosphate as precursors was estimated. In addition to the Ca and P precursors, ammonium carbonate and ammonium fluoride were used for carbonate and fluorine substitutions, respectively. Thermal stability of the synthesized FHA and CHA was evaluated. The phase composition and crystallite size were evaluated by the X-Ray Diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR) technique was employed to confirm the functional groups corresponding to the FHA and CHA. Thermal stability of the FHA and CHA was determined by the XRD and FTIR studies on the FHA and CHA powders annealed at 900 ^°C. From the XRD and FTIR results, it is observed that the 30 min milling time is the shortest time for the complete formation of FHA and CHA. The powders synthesized with a minimum milling time of 30 min exhibited better thermal stability.

Abstract: In this present study, molecular dynamics simulation of creep for ultrafine grain NC Ni specimens with different grain sizes have been carried out under a constant 1 GPa applied load for various creep temperatures to study the dependence of grain growth on creep temperature and grain size during creep process and its influence on creep properties. It is observed that the extent of grain growth in ultrafine grain NC Ni during creep deformation process is more if creep in creep temperature is higher. A noteworthy anomaly, that is NC Ni with smaller grain exhibits better creep property compared to NC Ni with larger grain, is observed in case of higher creep temperatures (i.e. around or greater than 1400K).

Abstract: In the modern formation of the architecture of the market economy, which determines the vectors of movement for decades in the conditions of global changes, in any production an important role is played by the presence of information systems of integration, which can combine activities from the supply of raw materials to the analysis of quality in the manufacture of products. Its place in this environment and find the availability of information technology organization of product quality control based on the identification system, as a set of different elements, using information, regulatory, methodological and laboratory resources [3].