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Property mapping of polycrystalline diamond coatings over large area

Journal of Advanced Ceramics 2014年第1期3卷 56-70页

作者： awadesh kumar mallik Sandip BYSAKH Monjoy SREEMANY Sudakshina ROY Jiten GHOSH Soumyendu ROY Joana Catarina MENDES Jose GRACIO Someswar DATTA CSIR-Central Glass&Ceramic Research Institute Kolkata 700032West BengalIndia Department of Physics Indian Institute of Technology BombayPowaiMumbai 400076MaharashtraIndia Instituto de Telecomunicações Campus Universitário de Santiago3810-193Portugal Nanotechnology Research Division Centre for Mechanical Technology and AutomationUniversity of Aveiro3810-193Portugal

Large-area polycrystalline diamond(PCD)coatings are important for fields such as thermal management,optical windows,tribological moving mechanical assemblies,harsh chemical environments,biological sensors,*** plasma chemical vapor deposition(MPCVD)is a standard technique to grow high-quality PCD films over large area due to the absence of contact between the reactive species and the filament or the chamber ***,the existence of temperature gradients during growth may compromise the desired uniformity of the final diamond *** the present work,a thick PCD coating was deposited on a 100-mm silicon substrate inside a 915-MHz reactor;the temperature gradient resulted in a non-uniform diamond *** attempt was made to relate the local temperature variation during deposition and the different properties of the final *** was found that there was large instability inside the system,in terms of substrate temperature(as high asΔT=212℃),that resulted in a large dispersion of the diamond coating’s final properties:residual stress(-15.8 GPa to+6.2 GPa),surface morphology(octahedral pyramids with(111)planes to cubo-octahedrals with(100)flat top surfaces),thickness(190μm to 245μm),columnar growth of diamond(with appearance of variety of nanostructures),nucleation side hardness(17 GPa to 48 GPa),quality(Raman peak FWHM varying from 5.1 cm^(-1) to 12.4 cm^(-1) with occasional splitting).This random variation in properties over large-area PCD coating may hamper reproducible diamond growth for any meaningful technological application.

关键词： plasma-enhanced chemical vapor deposition(CVD) diamond film mechanical properties nanostructures

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Cobalt Incorporated Pyramidal Shaped α-Fe₂O₃ Nanoparticles from Poly-vinyl Alcohol Based Precursor

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Advances in Nanoparticles 2016年第1期5卷 9-17页

作者： Atanu Naskar Susanta Bera awadesh kumar mallik Sunirmal Jana Sol-Gel Division CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI) P.O. Jadavpur University Kolkata India Bioceramic and Coating Division CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI) P.O. Jadavpur University Kolkata India

Precursor foam based Co incorporated α-Fe2O3 (AFC) was successfully synthesized at 600℃ calcination temperature by simple solution method using PVA. The formation of α-Fe2O3 nanoparticles was confirmed by X-ray diffraction measurement and reduction in crystallite size was found after cobalt incorporation. Field emission scanning electron microscopy revealed the existence of pyramidal shaped iron oxide in AFC. FTIR and Raman spectra also confirmed the presence of α-Fe2O3. Photocatalytic activity study showed that the cobalt incorporated α-Fe2O3 was better photocatalyst than pure α-Fe2O3. The cobalt incorporated iron oxide nanoparticles could be used for drug delivery application and this simple preparation method could be adopted for the synthesis of other transition metal oxides.

关键词： Sol-Gel Based Foam α-Fe2O3 Nanoparticles Polyvinyl Alcohol Catalytic Activity

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

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Open Journal of Applied Sciences 2015年第12期5卷 747-763页

作者： awadesh kumar mallik Sandip Bysakh Radhaballabh Bhar Shlomo Z. Rotter Joana Catarina Mendes CSIR-Central Glass & Ceramic Research Institute Kolkata India Department of Instrumentation Science Jadavpur University Kolkata India Instituto de Telecomunicaç õ es Campus Universitário de Santiago Aveiro Portugal

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.

关键词： Microwave Plasma CVD Seeding Diamond Micron Grits Novel Nucleation Process (NNP) Polycrystalline Diamond

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