Current Search:  dielectric properties (x)

View All Items

  • CSV Spreadsheet
(1 - 2 of 2)
ALUMINA-ALUMINUM TITANATE-TITANIA NANOCOMPOSITE: SYNTHESIS, SINTERING STUDIES, ASSESSMENT OF BIOACTIVITY AND ITS MECHANICAL AND ELECTRICAL PROPERTIES
Title
ALUMINA-ALUMINUM TITANATE-TITANIA NANOCOMPOSITE: SYNTHESIS, SINTERING STUDIES, ASSESSMENT OF BIOACTIVITY AND ITS MECHANICAL AND ELECTRICAL PROPERTIES.
Creator
Somani, Vikas, Kalita, Samar, University of Central Florida
Abstract / Description
This thesis reports the development, synthesis and characterization of a ceramic-ceramic nanocomposite system for its possible application as structural and electronic biomaterial in the biomedical industry. The study selected and synthesized alumina-aluminum titanate-titania (Al2O3-Al2TiO5-TiO2) nanoceramic composite using a simple Sol-Gel technique, which can be easily reproduced. Aluminum propoxide and titanium propoxide were used as precursor chemicals. Propanol and 2- methoxy ethanol...
Show moreThis thesis reports the development, synthesis and characterization of a ceramic-ceramic nanocomposite system for its possible application as structural and electronic biomaterial in the biomedical industry. The study selected and synthesized alumina-aluminum titanate-titania (Al2O3-Al2TiO5-TiO2) nanoceramic composite using a simple Sol-Gel technique, which can be easily reproduced. Aluminum propoxide and titanium propoxide were used as precursor chemicals. Propanol and 2- methoxy ethanol were used as solvent and stabilizer, respectively. Thermal analyses were performed for a systematic understanding of phase evolution from the synthesized gel. X-Ray diffraction technique was used to confirm the phase evolution, phase purity, crystallite size and crystal structure(s) of the phase(s). Calcination of the powder at low temperatures (700°C) leads to formation of Al2O3-TiO2 nanocomposite and at higher temperatures into Al2O3-Al2TiO5-TiO2 nanocomposite confirmed by XRD analysis. Electron microscopic techniques were used to investigate powder morphology, crystallite size and inter-planner spacing. High Resolution Transmission Electron Microscopy images of the calcined powder showed agglomerates of powder particles with particle size in 15-20 nm range. As-synthesized powder was uniaxially pressed into cylindrical pellets and sintered at elevated temperatures (1000-1400oC) to study the sintering behavior, densification characteristics, and measurement of mechanical and electrical properties and assessment of bioactivity. Phase transformation induced by the sintering process was analyzed by X-ray powder diffraction technique. The effects of nanosize of powder particles and multi-phases on densification, and mechanical and electrical properties were investigated. Vickers hardness and biaxial flexural strength tests were used to determine mechanical properties. Bioactivity of the nanocomposite was assessed in Simulated Body Fluid (SBF), which has the same ionic concentration as that of human plasma. Effects of biodegradation and change in mechanical properties of the composite when kept in SBF and maintained in a static condition were studied in terms of weight loss, change in the pH of the acellular solution and change in mechanical properties (hardness and biaxial strength). Scanning Electron Microscopy was used to observe the formation of apatite crystals on the surface of the nanocomposite specimens soaked in SBF. The results obtained throw light on biocompatibility and bioactivity of Al2TiO5 phase, which has not been reported so far in the literature to the best of our knowledge. Dielectric constant and dissipation factor of the sintered nanocomposite pellets were measured using HP 4284A impedance-capacitance-resistance meter and 16451 B dielectric test fixture at 1 MHz frequency. The effects of sintering time, temperature and phases present on the electrical properties were studied and are reported in the thesis.
Show less
Date Issued
2006
Identifier
CFE0001092, ucf:46775
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001092
Structure and Properties of Polymer-Derived SiBCN Ceramics
Title
Structure and Properties of Polymer-Derived SiBCN Ceramics.
Creator
Chen, Yaohan, An, Linan, Fang, Jiyu, Xu, Chengying, Zhai, Lei, Huo, Qun, Gong, Xun, University of Central Florida
Abstract / Description
Polymer-derived ceramics (PDCs) are a unique class of multifunctional materials synthesized by thermal decomposition of polymeric precursors. Due to their unique and excellent properties and flexible manufacturing capability, PDC is a promising technology to prepare ceramic fibers, coatings, composites and micro-sensors for high-temperature applications. However, the structure-property relationships of PDCs have not been well understood. The lack of such understandings drastically limited the...
Show morePolymer-derived ceramics (PDCs) are a unique class of multifunctional materials synthesized by thermal decomposition of polymeric precursors. Due to their unique and excellent properties and flexible manufacturing capability, PDC is a promising technology to prepare ceramic fibers, coatings, composites and micro-sensors for high-temperature applications. However, the structure-property relationships of PDCs have not been well understood. The lack of such understandings drastically limited the further developments and applications of the materials.In this dissertation, the structure and properties of amorphous polymer-derived silicon carbonitride (SiCN) and silicoboron carbonitride (SiBCN) have been studied. The SiCN was obtained using commercially available polysilazane as pre-ceramic precursor, and the SiBCN ceramics with varied Si-to-B ratio were obtained from polyborosilazanes, which were synthesized by the hydroboration and dehydrocoupling reaction of borane and polysilazane. The structural evolution of polymer-derived SiCN and SiBCN ceramics from polymer to ceramics was investigated by NMR, FTIR, Raman, EPR, TG/DTA, and XRD. The results show a phase-separation of amorphous matrix and a graphitization of (")free(") carbon phase, and suggest that the boron doping has a great influence on the structural evolution. The electric and dielectric properties of the SiCN and SiBCNs were studied by I-V curves, LCR Meter, and network analyzer. A new electronic conduction mechanism and structure model has been proposed to account for the relationships between the observed properties and microstructure of the materials. Furthermore, the SiBCN ceramics showed the improved dielectric properties at characterization temperature up to 1300 (&)#186;C, which allows the fabrication of ultrahigh-temperature wireless microsensors for extreme environments.
Show less
Date Issued
2012
Identifier
CFE0004195, ucf:49014
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004195