Effects of In-situ Generated Coinage Nanometals on Crystallization and Microstructure of Fluorophlogopite Mica Containing Glass-Ceramics

The effects of in-situ generated coinage nanometals（Cu,Ag and Au） on crystallization behavior,microstructure,thermal and mechanical properties of SiO2-MgO-Al2O3-B2O3-K2O-MgF2（BMAPS） glassceramics were systematically studied.On addition of coinage nanometai,the glass transition temperature（Tg） is increased by 20-30 ℃,crystallization temperature（Tc） by 30-50 ℃ and dilatometric softening temperature（Td） by 10-25 ℃.It was found that the density of Cu-containing glass was 2.59 g cm-3and for other glasses it was in the range of 2.56-2.57 g cm-3.From the non-isothermal differential scanning calorimetry study,the activation energy of crystallization for BMAPS base glass was calculated as 344 kJ/mol,and changed to 406,334 and 274 kJ/mol on addition of Cu,Ag and Au-nanometals,respectively.Crystals evolved in the opaque BMAPS glass-ceramics derived by controlled heat treatment,were identified as fluorophlogopite mica(KMg3(AlSi3O10)F2) by X-ray diffraction（XRD） technique and confirmed by Fourier transformed infrared spectroscopy.Presences of copper,silver and gold nanometals were also identified by XRD technique.It is found from field emission scanning electron microscopy that the interlocked grain like microstructure developed in BMAPS glass-ceramics（being heat-treated at 1050 ℃ for 4 h） changed to denser house-of-cards like microstructure（containing smaller sized mica crystals） on addition of coinage nanometals.Density of BMAPS base glass-ceramic was 2.60 g cm-3and marginally changed to 2.61-2.62 g cm-3on addition of Cu,Ag and Au-nanometals.The change in microstructure resulted in the decrease of Vickers micro hardness value from 5.37 to 4.12,4.20 and 4.58 GPa on addition of Cu,Ag and Au,respectively.Coinage nanometai doped mica glass-ceramics containing interlocked microstructure with higher thermal expansion coefficient,hence,is suitable for high temperature sealing application（like solid oxide fuel cell）.

Studies on Synthesis and Characterization of Magnesia Based Refractory Aggregates Developed from Indian Magnesite

The present work intends to study the properties of magnesia based refractory aggregates developed from Indian magnesite by changing lime/silica ratio. The material has been sintered in the temperature range of 1550C - 1700C. The sintered samples are characterized in terms of bulk density, apparent porosity, true density, percentage densification, mechanical, thermo-mechanical properties like cold modulus of rupture, hot modulus of rupture and thermal shock resistance and structural properties by XRD. The developed microstructures at different temperatures are studied through FESEM study and compositional analysis of the developed phases is done by EDX study.

Effect of Seed Size, Suspension Recycling and Substrate Pre-Treatment on the CVD Growth of Diamond Coatings

CVD growth of uniform conformal polycrystalline diamond (PCD) coatings over complex three dimensional structures is very important material processing technique. It has been found that the nucleation and subsequent growth period is very critical for successful development of CVD diamond based technologies. There are many methods of enhancing diamond nucleation on foreign substrates-ultrasonic treatment with diamond seed suspension being the best among them. A combination of ultrasonic seeding (US) technique with prior treatment (PT) of the substrate under CVD diamond growth conditions for brief period of time, has found to be very effective in enhancing the diamond nucleation during CVD growth—together they are known as NNP. But successive usage of the same seeding suspension up to ten cycles deteriorates the seeding efficiency. 6th seeding cycle onwards the silicon substrates are barely get covered by diamond crystallites. Five different diamond micron grits were used for seeding the silicon substrates and it is observed that US with the sub-micron particles (0.25 μm) is very effective in efficient nucleation of PCD on Si substrates. PT of the substrate somewhat negates the effect of successive use of the same seeding slurry but it is best to avoid recycling of the same seeding suspension using micron size diamond grits.

Layered double hydroxide using hydrothermal treatment： morphology evolution, intercalation and release kinetics of diclofenac sodium

The present work demonstrates the possibilities of hydrothermal trans- formation of Zn-AI layered double hydroxide （LDH） nanostructure by varying the synthetic conditions. The manipulation in washing step before hydrothermal treatment allows control over crystal morphologies, size and stability of their aqueous solutions. We examined the crystal growth process in the presence and the absence of extra ions during hydrothermal treatment and its dependence on the drug （diclofenac sodium （Dic- Na）） loading and release processes. Hexagonal plate-like crystals show sustained release with -90% of the drug from the matrix in a week, suggesting the applicability of LDH nanohybrids in sustained drug delivery systems. The fits to the release kinetics data indicated the drug release as a diffusion-controlled release process. LDH with rod-like morphology shows excellent colloidal stability in aqueous suspension, as studied by photon correlation spectroscopy.

Spectroscopic investigation confirms retaining the pristine nature of single-walled carbon nanotubes on dissolution in aniline

Carbon nanotubes in all forms are very much insoluble in both organic and inorganic solvents due to its high agglomeration and entangled morphology. General methods for dissolution of single-walled carbon nanotubes （SWNTs） are mostly associated with complexation or polymerization or addition of macromolecules which change the physical or chemical properties of SWNTs and the pristine nature of SWNTs is lost. Dissolution of SWNTs in a solvent like aniline is practiced here which is a very simple reaction method. Here aniline is capable to form a SWNT-aniline charge transfer complex without attachment of macromolecules or polymer which is also soluble in other organic solvents. Solvation of SWNTs by this method is also capable of maintaining the similarity between the structure of SWNTs before and after the dissolution, which means that the pristine nature of SWNTs is preserved. Formation of charge transfer complex in this reaction has been proven by UV-Vis/NIR absorption and photoluminescence spectroscopy. Raman spectroscopy and electron microscopy （FESEM and TEM） are the evidences for protection of the pristine nature of SWNTs even after high-temperature complexation reaction with aniline and also after solubilization in organic solvents.