Development Of Capacitive Composite Materials Using Alkaline Titanates And Kaolinite Clay

This research was designed to form a better dielectric composite material using one stable state dielectric matrix material and a good dielectric material as filler powder. The hypothesis is that the encapsulation of the filler powder by the matrix material, thus providing a bridge between the net polarizations of the composites. There are some limitations to the hypothesis, namely in the reactions and the limited control of the encapsulation process. Distinct dielectric composites were successfully produced using locally sourced kaolinite clay and chemically produced alkaline titanates for example, Barium Titanate (BT) and Strontium Titanate (ST). The samples were made using kaolinite as the base matrix and alkaline titanate added in varying ratios. The alkaline titanate were synthesized via solid-state reaction using a carbonate derivative of the alkaline cation and rutile titanium (IV) oxide sintered at 1200°C to 1300°C. White kaolinite was used to fuse the alkaline titanate material in varying weight ratios. The powders were dry-mixed and made into pellets for calcination at 1000°C. The XRD data of BT-kaolinite type composites revealed a chemical reaction between the matrix and the filler powder at various combinations. Thus, BT additives reacted with the mullite and silica components and produced celsian feldspar in the composite system. This suggests that the system polarization contains the sum of four interfacial polarization processes at different temperatures. ST-mullite composites showed distinct varying interfacial cladding and dipolar relaxation for all composites. SEM micrographs revealed fused and flaky parts formed in the BT composite samples whereby the powders were melted together. ST composite samples only showed inter-grain formation of the filler and matrix material. EDX, however, showed that there was some contamination in the matrix powder with potassium and carbon elements in the system. Dielectric properties for both BT and ST composites exhibited low dielectric constant values ranging from 10 to 20 in the frequency range 10 Hz to 1 MHz. Dielectric modelling showed that the BT composite samples displayed single relaxation processes for the sample series whereas the ST composite samples exhibited multiple thermally activated dielectric relaxations. The modelling of the dielectric data was done using the Havriliak-Negami equation to show two distinct dielectric processes occurring within the same framework. Impedance plots showed significant varied impedance based on the measured temperatures with both composite series exhibiting high resistance. DC conductivity measurements were carried out on the samples, yielding very high activation exothermic and endothermic activation of energy of reactions in the medium. Dielectric modulus plots, however showed varied dispersion due to deformations in dielectric stresses in the composite series. Microwave frequency measurements showed dielectric properties of the medium without the interfacial polarizatio

Dielectric properties of strontium titanate filled mullite composites in microwave region

This research was designed to form better dielectric composite material using one steady state dielectric with a good dielectric material. Distinct dielectric composite was successfully produced using locally sourced kaolinite clay. The samples were made using kaolinite as the base matrix and Strontium Titanate (ST) added in varying ratios. Strontium Titanate were synthesized via solid‐state reaction using Strontium Carbonate and rutile Titanium (IV) Oxide with sintering at 1300 °C. Local white kaolinite was used to fuse the barium titanate material in varying weight ratios. The powders were dry‐mixed and made into pellets for calcination at 1000 °C. The dielectric measurements were carried out using the HP 4291B Impedance Analyzer dielectric setup. Three samples were prepared, namely 10%ST, 20%ST and 30%ST. The dielectric measurements were carried out at room temperature. Microwave region measurements showed steady state and linear dielectric relaxation ranging from 7 in the control sample and dropping down to 5 in 30%ST. The responses indicate linear relation between ST addition and microwave region dielectric permittivity

Development of dielectric material with ceramic matrix composite (CMC) produced from kaolinite and CaCu3Ti4O12 (CCTO)

Ceramic matrix composites (CMC) combine reinforcing ceramic phases, CaCu3Ti4O12 (CCTO) with a ceramic matrix, kaolinite to create materials with new and superior properties. 10% and 20% CCTO were prepared by using a conventional solid state reaction method. CMC samples were pre‐sintered at 800 °C and sintered at 1000 °C. The dielectric properties of samples were measured using HP 4192A LF Impedance Analyzer. Microstructures of the samples were observed using an optical microscope. XRD was used to determine the crystalline structure of the samples. The AFM showed the morphology of the samples. The results showed that the dielectric constant and dielectric loss factor of both samples are frequency dependent. At 10 Hz, the dielectric constant is 1011 for both samples. The CMC samples were independent with temperature with low dielectric constant in the frequency range of 104–106 Hz. Since the CMC samples consist of different amount of kaolinite, so each sample exhibit different defect mechanism. Different reaction may occur for different composition of material. The effects of processing conditions on the microstructure and electrical properties of CMC are also discussed

The Little Hierarchy in Universal Extra Dimensions

In the standard model in universal extra dimensions (UED) the mass of the Higgs field is driven to the cutoff of the higher-dimensional theory. This re-introduces a small hierarchy since the compactification scale 1/R should not be smaller than the weak scale. In this paper we study possible solutions to this problem by considering five-dimensional theories where the Higgs field potential vanishes at tree level due to a global symmetry. We consider two avenues: a Little Higgs model and a Twin Higgs model. An obstacle for the embedding of these four-dimensional models in five dimensions is that their logarithmic sensitivity to the cutoff will result in linear divergences in the higher dimensional theory. We show that, despite the increased cutoff sensitivity of higher dimensional theories, it is possible to control the Higgs mass in these two scenarios. For the Little Higgs model studied, the phenomenology will be significantly different from the case of the standard model in UED. This is due to the fact that the compactification scale approximately coincides with the scale where the masses of the new states appear. For the case of the Twin Higgs model, the compactification scale may be considerably lower than the scale where the new states appear. If it is as low as allowed by current limits, it would be possible to experimentally observe the standard model Kaluza-Klein states as well as a new heavy quark. On the other hand, if the compactification scale is higher, then the phenomenology at colliders would coincide with the one for the standard model in UED.Comment: 25 pages, 2 figure

Data representation synthesis

We consider the problem of specifying combinations of data structures with complex sharing in a manner that is both declarative and results in provably correct code. In our approach, abstract data types are specified using relational algebra and functional dependencies. We describe a language of decompositions that permit the user to specify different concrete representations for relations, and show that operations on concrete representations soundly implement their relational specification. It is easy to incorporate data representations synthesized by our compiler into existing systems, leading to code that is simpler, correct by construction, and comparable in performance to the code it replaces

Development of dielectric material, CaCu3Ti4O12

CaCu3Ti4O12 (CCTO) was prepared by a conventional solid state reaction method. CCTO sample was pre-sintered at 900°C for 10 hours and sintered at 1075°C for 12 hours. The dielectric properties of the sample were measured using HP 4192A LF Impedance Analyzer. The complex permittivity was measured within the frequency range from 10 Hz to 106 Hz and the temperature ranging from 30°C to 400°C. The results showed that the dielectric constant and dielectric loss factor of the sample are frequency dependent and temperature dependent. CCTO sample exhibits a high dielectric constant which is around 105. Dielectric constant increases with decreasing frequency due to interfacial polarization. This could be explained by the Maxwell- Wagner effect

Dielectric behavior of β-SiC nanopowders in air between 30 and 400 °C

Silicon carbide (SiC) is regarded as a semiconductor and thus characterized mainly for its electrical conductivity. However, SiC does exhibit significant electrical resistance at low ambient temperatures and represents a possible dielectric insulator. In this paper, the dielectric properties of the β-SiC nanopowders were examined by X-ray diffraction and dielectric spectroscopy within the humid Malaysian environment. Research emphasis is placed on the stable dielectric behavior of the nanopowder itself as the nanopowder phase is susceptible to hydroxyl oxidization as mentioned by the nanopowder manufacturer. The XRD results identified the presence of β-SiC peaks whereas EDX detected minor oxygen presence in the nanopowder. Dielectric permittivity response of the nanopowder pellet indicated stable Quasi-DC dielectric behavior from 30 to 400 °C with minor increments of the initial relative dielectric permittivity at the lower temperatures. The relative dielectric permittivity of the SiC nanoparticles was determined to be 44 (30 °C) to 31 (400 °C) at 1 MHz. Arrhenius plot of the dielectric data resulted in a two linear energy activation plots due to possible hopping mechanisms within the SiC nanoparticles covalent structure. Overall, the β-SiC nanopowder exhibited a stable Quasi-DC behavior at the measured temperatures

Dielectric behavior of b-SiC nanopowders in air between 30 and 400˚C

Silicon carbide (SiC) is regarded as a semi-conductor and thus characterized mainly for its electrical conductivity. However, SiC does exhibit significant electrical resistance at low ambient temperatures and represents a possible dielectric insulator. In this paper, the dielectric properties of the b-SiC nanopowders were examined by X-ray diffraction and dielectric spectroscopy within the humid Malaysian environment. Research emphasis is placed on the stable dielectric behavior of the nanopowder itself as the nanopowder phase is susceptible to hydroxyloxidization as mentioned by the nanopowder manufacturer. The XRD results identified the presence of b-SiC peaks whereas EDX detected minor oxygen presence in the nanopowder. Dielectric permittivity response of the nanopowder pellet indicated stable Quasi-DC dielectric behavior from 30 to 400° C with minor increments of the initial relative dielectric permittivity at the lower temperatures. The relative dielectric permittivity of the SiC nanoparticles was determined to be 44 (30° C) to 31 (400° C) at 1MHz. Arrhenius plot of the dielectric data resulted in a two linear energy activation plots due to possible hopping mechanisms within the SiC nanoparticles covalent structure. Overall, the b-SiC nanopowder exhibited a stable Quasi-DC behavior at the measured temperatures