Nanotechnology Research and Practice

109-131

Authors: Rajnish Kumar, Fauzia Raza, Jahan Akhtar

This paper deals with the numerical investigation of unsteady flow in a porous medium towards a stretching sheet. Twowater based nanofluids namely and are taken into consideration. With the auxiliary conditions the governing partial differentialequations are converted to ordinary differential equations with the pertinent corresponding conditions. MATLAB function “bvp4c” is applied to solve the resulting governing equations together with the boundary conditions. The effect of various parameters namely: solid volume fractions, Prandtl number, porosity parameter, thermal radiation and the unsteadiness parameter have been discussed. The numerical results obtained for different parameters are presented through plots. Comparison with known results is presented and it is found excellent.

98-105

Authors: K. Sujatha, T. Seethalakshmi, O.L. Shanmugasundaram

Pure SnO2 nano powders were synthesized by co-precipitation method. The structure, surface, optical, and functional groups were analyzed by X-ray diffraction, FESEM, UV-Vis spectroscopy, FTIR and fluorescence spectra, respectively. The results were compared with pure tin oxide nanoparticle. X-ray analysis shows that the obtained power has tetragonal rutile structure with average crystallite size of 34 nm. Band gap is observed from UV-Vis spectroscopy. Fluorescence spectrum of pure sample detected a strong emission peaks at 634nm due to surface defect and oxygen vacancies in SnO2 nanoparticles.

50-73

Authors: Ignat Ignatov, Oleg Mosin

In this review it is reported about new data on the structure of water cyclic associates (clusters) with general formula (Н2О)n and their charged ionic clusters [(Н2О)n]+ and [(Н2О)n]- by means of computer modelling and spectroscopy methods as 1Н-NMR, IR-spectroscopy, DNES, EXAFS-spectroscopy, X-Ray and neurons diffraction. The computer calculation of polyhedral nanoclusters (Н2О)n, where n = 3–20 are carried out. Based on this data the main structural mathematical models describing water structure (quasicrystalline, continious, fractal, fractal-clathrate) have been examined and some important physical characteristics were obtained.

4-11

Authors: Nguyen Thi Hong

One of the major mechanical and physical parameters for surface quality is hardness. In this paper was studied the electrochemical machining (ECM) to improve the surface micro-hardness and nano-hardness of stainless steel samples. The materials studied are used as samples of stainless steel Cr18Ni10Ti after electrochemical machining under different current density in a water solution of NaCl with various concentrations. The results showed that with increasing the current density from 0 to 28.3 A/cm2 the surface micro-hardness and nano-hardness of samples after the ECM increases and maximum value was 5.06 GPa.

29-46

Authors: Ignat Ignatov, Oleg Mosin, Enrico Bauer

Natural waters derived from various Bulgarian water springs as well as mountain water, melt water and water with varying deuterium content and the human blood serum of cancer patients were investigated by IR, NES and DNES methods to establish the structural mathematical models of water. As estimation factor was measured the values of the average energy of hydrogen bonds (∆EH...O) among H2O molecules, as well as local maxima in IR- and DNES-spectra of various samples of water and human blood serum at ∆EH...O = -0.1387 eV (the DNES-method) and λ = 8.95 μm (the IR-method). The increased content of deuterium in water leads to physiological, morphological and cytology alterations of the cell, and also renders negative influence on cellular metabolism, while deuterium depleted water with the residual 60–100 ppm deuterium content has beneficial effects on health. For a group of people in critical condition of life and patients with malignant tumors the greatest values of local maxima in DNES-spectra are shifted to lower energies relative to the control group. In frames of the research was carried out the computer calculation of elemental polyhedral nanoclusters with a formula (Н2О)n, where n = 3–20. Based on this data some important physical characteristics of water were obtained, e.g. the average energy of hydrogen bonding between Н2О molecules in the process of cluster formation measured by the DNES method was compiled -0.1067 ± 0.0011 eV.