Temperature Stable Low Loss Ceramic Dielectrics in (1-x)ZnAI2O4-xTiO2 System for Microwave Substrate Applications

The microwave dielectric properties of ZnAl2O4 spinels were investigated and their properties were tailored by adding different mole fractions of Ti02. The samples were synthesized using the mixed oxide rout.e. The phase purity and crystal structure were identified using X-ray diffraction technique. The sintered specimens were characterized in the microwave frequency range (3-13 GHz). The ZnA12O4 ceramics exhibited interesting dielectric properties (dielectric constant (e,.) = 8.5, unloaded quality factor (Q.) = 4590 at 12.27 GHz and temperature coefficient of resonant frequency (Tf) = -79 ppm/°C). Addition of Ti02 into the spinel improved its properties and the Tf approached zero for 0.83ZnAl2O4- 0.17TiO2• This temperature compensated composition has excellent microwave dielectric properties (Cr _ 12.67, Q, = 9950 at 10.075 GHz) which can be exploited for microwave substrate applications

Nitrification in a packed bed bioreactor integrated into amarine recirculating maturation system under different substrate concentrations and flow rates

BACKGROUND: A packed bed bioreactor (PBBR) activated with an indigenous nitrifying bacterial consortia was developed and commercialized for rapid establishment of nitrification in brackish water and marine hatchery systems in the tropics. The present study evaluated nitrification in PBBR integrated into a Penaeus monodon recirculating maturation system under different substrate concentrations and flow rates. RESULTS:Instantnitrificationwasobservedafter integration ofPBBRinto thematuration system.TANandNO2-Nconcentrations were always maintained below0.5 mg L−1 during operation. The TANandNO2-N removalwas significant (P < 0.001) in all the six reactor compartments of the PBBR having the substrates at initial concentrations of 2, 5 and 10 mg L−1. The average volumetric TAN removal rates increased with flow rates from 43.51 (250 L h−1) to 130.44 (2500 L h−1) gTAN m−3 day−1 (P < 0.05). FISH analysis of the biofilms after 70 days of operation gave positive results with probes NSO 190 ((β ammonia oxidizers), NsV 443 (Nitrosospira spp.) NEU (halophilic Nitrosomonas), Ntspa 712 (Phylum Nitrospira) indicating stability of the consortia. CONCLUSION: The PBBR integrated into the P. monodon maturation system exhibited significant nitrification upon operation for 70 days as well as at different substrate concentrations and flow rates. This system can easily be integrated into marine and brackish water aquaculture systems, to establish instantaneous nitrification

Effect of Substrate Temperature on the Structural and Luminescent Characteristics of RF-Magnetron-Sputtered ZnGa2O4:Dy3+ Thin Films

ZnGa2O4:Dy3+ phosphor thin films were deposited on quartz substrates by radio frequency rf magnetron sputtering and the effect of substrate temperature on its structural and luminescent properties was investigated. Polycrystalline film could be deposited even at room temperature. The crystalline behavior, Zn/Ga ratio, and surface morphology of the films were found to be highly sensitive to substrate temperature. Under UV illumination, the as-deposited films at and above 300°C gave white luminescence even without any postdeposition treatments. The photoluminescent PL emission can be attributed to the combined effect of multicolor emissions from the single luminescence center Dy3+ via host-sensitization. Maximum PL emission intensity was observed for the film deposited at 600°C, and the CIE chromaticity coordinates of the emission were determined to be x,y = 0.34, 0.31 .

Engineering the Properties of Indium Sulfide for Thin Film Solar Cells by Doping

In the present work, structural, optical and electrical properties of indium sulfide are tuned by specific and controlled doping. Silver, tin, copper and chlorine were used as the doping elements. In2S3 thin films for the present study were prepared using a simple and low cost “Chemical Spray Pyrolysis (CSP)” technique. This technique is adaptable for large-area deposition of thin films in any required shape and facilitates easiness of doping and/or variation of atomic ratio. It involves spraying a solution, usually aqueous, containing soluble salts of the constituents of the desired compound onto a heated substrate. Doping process was optimized for different doping concentrations. On optimizing doping conditions, we tuned the structural, optical and electrical properties of indium sulfide thin films making them perform as an ideal buffer layer.

Characterization of Hydrothermally Annealed Low Temperature Bioactive Thin Film Coatings of Hydroxyapatite on TiAl6V4 Implant material

This thesis summarizes the results on the growth and characterisation of thin films of HA grown on TiAl6V4 (Ti) implant material at a lower substrate temperature by a combination of Pulsed laser deposition and a hydrothermal treatment to get sufficiently strong crystalline films suitable for orthopaedic applications. The comparison of the properties of the coated substrate has been made with other surface modification techniques like anodization and chemical etching. The in-vitro study has been conducted on the surface modified implants to assess its cell viability. A molecular level study has been conducted to analyze the adhesion mechanism of protein adhesion molecules on to HA coated implants.

Carbon/Nitrogen Ratio Optimization and Periphyton Development on the Production and Sustainability of Penaeus Monodon(Fabricius)in Extensive Culture System

Controlling the inorganic nitrogen by manipulating carbon / nitrogen ratio is a method gaining importance in aquaculture systems. Nitrogen control is induced by feeding bacteria with carbohydrates and through the subsequent uptake of nitrogen from the water for the synthesis of microbial proteins. The relationship between addition of carbohydrates, reduction of ammonium and the production of microbial protein depends on the microbial conversion coefficient. The carbon / nitrogen ratio in the microbial biomass is related to the carbon contents of the added material. The addition of carbonaceous substrate was found to reduce inorganic nitrogen in shrimp culture ponds and the resultant microbial proteins are taken up by shrimps. Thus, part of the feed protein is replaced and feeding costs are reduced in culture systems.The use of various locally available substrates for periphyton based aquaculture practices increases production and profitability .However, these techniques for extensive shrimp farming have not so far been evaluated. Moreover, an evaluation of artificial substrates together with carbohydrate source based farming system in reducing inorganic nitrogen production in culture systems has not yet been carried-out. Furthermore, variations in water and soil quality, periphyton production and shrimp production of the whole system have also not been determined so-far.This thesis starts with a general introduction , a brief review of the most relevant literature, results of various experiments and concludes with a summary (Chapter — 9). The chapters are organised conforming to the objectives of the present study. The major objectives of this thesis are, to improve the sustainability of shrimp farming by carbohydrate addition and periphyton substrate based shrimp production and to improve the nutrient utilisation in aquaculture systems.

Formation and characterisation of indium selenide thin films by elemental evaporation

This thesis deals with preparing stoichiometric crystalline thin films of InSe and In2Se3 by elemental evapouration and their property investigation.In the present study three temperature( or Elemental evapouration) method is utilized for the deposition of crystalline thin films . The deposition mechanism using three temperature method deals’ with condensation of solids on heated surfaces when the critical supersaturation of the vapour phase exceeds a certain limit. The critical values of the incident flux are related to substrate temperature and the interfacial energies of the involved vapours. At a favorable presence of component atoms in the vapour phase these can react and condense onto a substrate even at a elevated temperature. In the studies conducted the most significant factor is the formation of single compositional film namely indium mono selenide in the In –se system of compounds .Further this work shows the feasibility of thin film photovoltaic junctions of the schottky barrier type

Prospects of sprayed CZTS thin film solar cells from the perspective of material characterization and device performance

This thesis is devoted to the development of a relatively new, rapidly developing quaternary semiconducting material (viz., Cu2ZnSnS4) used for photovoltaic applications. This semiconductor, commonly known as CZTS, is closely related to a family of materials that have been used for solar cell applications. It is a compound semiconductor made of copper, zinc, tin and sulfur, which are sufficiently abundant elements; none of them is harmful to the environment even at large scale usage. Aim of this study is to fabricate CZTS solar cells through chemical spray pyrolysis (CSP) technique. At first the influence of various spray parameters like substrate temperature, spray rate, precursor ratio etc. on the opto-electronic properties of CZTS films will be studied in detail. Then the fabrication of CZTS/In2S3 hetero junctions and various ways to improve the performance parameters will be tried

Banana waste as substrate for a-amylase production by Bacillus subtilis (CBTK 106) under solid-state fermentation

Bacillus subtilis CBTK 106, isolated from banana wastes, produced high titres of a-amylase when banana fruit stalk was used as substrate in a solid-state fermentation system. The e¤ects of initial moisture content, particle size, cooking time and temperature, pH, incubation temperature, additional nutrients, inoculum size and incubation period on the production of a- amylase were characterised. A maximum yield of 5 345 000 U mg~1 min~1 was recorded when pretreated banana fruit stalk (autoclaved at 121 ¡C for 60 min) was used as substrate with 70% initial moisture content, 400 lm particle size, an initial pH of 7.0, a temperature of 35 ¡C, and additional nutrients (ammonium sulphate/sodium nitrate at 1.0%, beef extract/peptone at 0.5%, glucose/sucrose/starch/maltose at 0.1% and potassium chloride/sodium chloride at 1.0%) in the medium, with an inoculum-to-substrate ratio of 10% (v/w) for 24 h. The enzyme yield was 2.65-fold higher with banana fruit stalk medium compared to wheat bran

Influence of substrate topography on the growth and magnetic properties of obliquely deposited amorphous nanocolumns of Fe–Ni

We investigated the influence of substrate surface roughness on the structural and magnetic properties of obliquely deposited amorphous nanocolumns of Fe–Ni. Experiments showed that the surface roughness of the substrate greatly determines the morphology of the columnar structures and this in turn has a profound influence on the magnetic properties. Nucleation of Fe–Ni nanocolumns on a smooth silicon substrate was at random, while that on a rough glass substrate was defined by the irregularities on the substrate surface. It has been found that magnetic interaction between the nanocolumns prepared on a silicon substrate was due to their small inter-column separation. Well separated nanocolumns on a glass substrate resulted in exchange isolated magnetic domains. The size, shape and the distribution of nanocolumns can be tailored by appropriately choosing the surface roughness of the substrate. This will find potential applications in thin film magnetism.