Sol–Gel Fabrication of Epitaxial and Oriented TiO2 Thin Films

Thin films of titania have been prepared by spin coating on fused silica, Si(100), and rutile(110), starting with a sol–gel process. The alkoxide solution was chelated with diisopropanolamine, and the resulting precursor solution was hydrolyzed prior to coating. Oriented rutile films were obtained on fused silica and Si(100), while epitaxially oriented film was formed on rutile (110). X-ray diffraction results indicated that the as-deposited films transformed to rutile via anatase with increasing temperature. The phase transformation temperature was found to be dependent on the substrate, and it was in general higher on the substrates than that observed for the gel powder. Microstructural studies revealed that these films consisted of finely dispersed grains of 0.05 to 0.15 μm in size.     

Optimizing the Roadside Unit Deployment Mechanism in VANET with Efficient Protocol to Prevent Data Loss

Wireless Personal Communications - RTS/ CTS protocol serves multihop wireless networks poorly due to its single-hop design. TDMA protocol surpasses RTS/ CTS but unable to solve the dynamic needs of...     

Microwave Effects in Lead Zirconium Titanate Synthesis: Enhanced Kinetics and Changed Mechanisms

A novel, simple, and fast solid-state procedure has been demonstrated for the synthesis of Pb(Zr,Ti)O₃ (PZT), using microwave radiation. The process consists of starting with the respective oxides mixed in the required proportions and exposing the charge to the microwaves. By making one or more of the constituent oxides slightly nonstoichiometric, enormous enhancement in reaction rates has been achieved, and single-phase PZT can be synthesized at temperatures as low as 600°C. Moreover, it has been shown that the combined use of nonstoichiometric precursors and microwave irradiation leads to different reaction pathways for the formation of PZT. Further, the microwave method diminishes PbO loss.     

Sintering of Zirconia Nanopowder by Microwave-Laser Hybrid Process

A new hybrid sintering process has been developed by replacing all but one laser by microwaves in the existing simultaneous multiple laser process (SIMPLE). Microwave energy has been used to preheat the material before laser radiation, and the synergism between microwave and laser energies could effectively heat the material to temperatures of 1700°C and beyond in just a few minutes. Using this process, rapid sintering of 3Y–ZrO₂ (3Y–TZP) pellets has been achieved in a few minutes. Microstructural investigations reveal that the microwave–laser hybrid sintered pellets of 3Y–ZrO₂ have nanograins averaging about 20 nm. The microwave–laser hybrid sintering process can clearly be a new approach for fabrication of nanoceramics and nanocomposites.     

Modified mixed oxide perovskites 0.7Sr(Al1/2B1/2) O3·0.3LaAlO3 and 0.7Sr(Al1/2B1/2) O3·0.3NdGaO3 (B=Ta5+ or Nb5+) for high-T c superconductor substrate applications

Single-crystal fibres of modified strontium aluminium tantalum oxide (1-x)Sr(Al_1/2Ta_1/2) O₃·xLaAlO₃(SAT-LA) and (1-x)Sr(Al_1/2Ta_1/2)O₃·xNdGaO₃ (SAT·NG), and modified strontium aluminum niobium oxide (1-x)Sr(Al_1/2Nb_1/2)O₃·xNdGaO₃(SAT·NG) and (1-x)Sr (Al_1/2Nb_1/2)O₃·xLaAlO₃ (SAN·LA) were grown using a laser-heated pedestal growth technique. 0.7SAT·0.3LA grows congruently and retains a twin free simple cubic perovskite structure (as the SAT) when cooled down to room temperature. 0.7SAT·0.3LA crystals have a moderate dielectric constant ( = 21.7) and low dielectric loss (tan = 7.5 × 10^–5) at 10 kHz and 90 K. The reduction problem of Ta⁵⁺ is eliminated (which is common in the case of SAT growth). 0.7SAT·0.3NG and 0.7SAN·0.3NG have lower melting temperatures and crystal growth is easier. NdGaO₃ addition to the SAT and SAN enhances the potential of SAT and SAN as large-area substrates for high-T _c superconductor growth. However, the dielectric constants increased from -12 to -16(0.7SAT·0.3NG) and from 18 to 23 (0.7SAN·0.3NG) as a result of NdGaO₃ incorporation.     

[NZP], a new radiophase for ceramic nuclear waste forms

The NZP structure is a candidate for immobilization of certain types of nuclear waste. It will incorporate ¹³⁷Cs, ⁹⁰Sr, and a range of other nuclides. The leach resistance of CsZr₂(PO₄)₃ appears to be comparable with that of other phases under consideration for radio-Cs immobilization. This phase can be formed by sintering at ～850°C; it is reasonably refractory, and it is compatible with monazite, a favored immobilizing agent for waste actinides.     

Irradiated and metamict materials: relevance to radioactive waste science

The relation of the structures of metamict mineral phases and non-crystalline solids is discussed; the question of radiation effects in solidified nuclear waste forms is considered in this regard. In ceramics, if the actinides can be concentrated in radiation-resistant phases such as uraninite or monazite, the overall radiation effects on the ceramics should be quite small.     

Synthesis and Dielectric Properties of Solution Sol-Gel-Derived 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 Ceramics

A solution sol-gel method has been developed to prepare 0.9Pb(Mg_1/3Nb_2/3)O₃-0.1PbTiO₃ (0.9PMN-0.1PT) ceramics. During the processing the gel first converted to cubic pyrochlore phase at a calcination temperature of 600°C followed by the formation of pure perovskite phase at 775°C. The ceramics sintered at 1250°C for 4 h showed ≈98% of the theoretical density. The room-temperature dielectric constant of the pellets sintered at 1250°C showed a maximum value of 25035 at 1 kHz. Sintering studies at different temperatures revealed that the dielectric constant increased with increasing grain size in these ceramics.