MATERIAL SIZE EFFECT ON THE MELTING POINT, CHEMICAL POTENTIAL, PHASE TRANSITION, AND ANTIBACTERIAL PROPERTIES OF TIO2

• Main Author: Olenka Margaretta, Desyana
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/49051
• Institution: Institut Teknologi Bandung

Various material properties are affected by their size. Basic understanding of changes in the intrinsic nature of a material is important to study in relation to the correlation with size. Such as the explanation of the dependence of melting point on size, the effect of size on chemical potential, and the size dependence of thermoelectric power factor. Necessary to support the experimental efforts to create new materials. Recent study, on the determination of new criteria for size dependence on melting point uses zipper model. The model originally used by Kittel to explain the changes in molecular phases. This zipper model is used to derive the equation of melting point dependence on size. In this dissertation we propose a new criterion as an alternative to Lindemann's criteria using the zipper model. This model generalized to all particle shapes with different geometries has produced adequate equation and is in accordance with previous experimental results. Melting process is assumed to start from the outermost layer to the center, and melting occurs when the logarithmic partition function per number of layers is zero. When deriving an equation to introduce a new criterion for the dependence of the melting point on size, there is a parameter of the atomic degree of freedom which seems to be universal for all metals. The degree of freedom of material is an interesting subject for further investigation. In the newly constructed criterion it is a summed that the atomic degree of freedom is proportional to the frequency of phonons. The parameters degrees of freedom used by us, based on previous research references. In nanostructures, chemical potential depends on the size. Size also affects the thermo-electric power factor. A general formula has been obtained to explain the chemical potential dependence on size. Using the basic configuration formulation as the basis for deriving the Fermi-Dirac distribution function. The general formula can explain all reports regarding the dependency of chemical potential measurements on size obtained experimentally or theoretically. Chemical potential generally increases with decreasing material dimensions. There are many advan-tages of a material being influenced by its chemical potential, hence this study is very important. General equations have also been derived to describe thermo-electric power factor depend on size. The equation are more general than equations introduced elsewhere. Then, this dissertation also investigates the phenomenon arising from the surrounding environment. The phenomenon also provides an intrinsic picture of material behavior related to the second order phase transition. Paying attention to natural phenomena we could find self-buckling occurs in the banana leaves, palm iv plants, pandanus and others because length increase. The effect of increasing length of macro conditions on the curvature that occurs in a material is experimented simply using paper. The simple numerical procedure introduced here has the potential for determining the bending profile of an in extensible column with arbitrary fixed angle. This procedure is used to explain the phenomenon of vertical self-buckling columns and to show that such self-buckling have a strong relationship with phase transition. The "critical temperature" for the phase transition corresponds precisely to the buckling height, 1/Lcr, and the deviation angle between the free end relative to the vertical direction comply a scaling relationship(1/???????????? ? 1/????)0,485. We also introduce a universal equation that is relevant to all thin columns having elastic homogeneous modulus, when the area and mass density are the same. Using the universal equation, we anew derive the famous buckling height ???????????? = (7,8373 ????????/ ????????????)1/3. Which has been derived two centuries ago using the Bessel function. Finally, in this study we introduce a new characteristic length that is 1/3 0 ) / ( ?gYIL? , and if the column length is a scale with this characteristic length, the bending profile of all columns positioned at the same fixed angle is appropriate. This scale unifies all types of in extensible and homogeneous columns. The application of material size effect is also related to its ability in bacterial degradation. This property is seen in order size below 20 nm. Through experiments it has been proven that material in micro size also have the ability to degrade bacteria under certain conditions. An additional topic, TiO2 coating has been investigated on textiles. The antibacterial activity is tested by coating TiO2 particles of 160 nm size on textiles cotton. Cotton is a type of textile that is widely used by people in tropical area. Data shows that bacterial growth is inhibited after irradiation and incubation. It is clearly observed that the technical grade of anatase TiO2 was effective in inhibiting bacterial growth. The ability not much different from TiO2 analyst grade which has a much smaller size. Differences in photocatalytic activity of different structures are closely related to the surface area and particle size of photocatalysts. Anatase particles of bulk structure are more reactive than rutile and brookite. Because, anatase has higher energy gap. Therefore, anatase has better photocatalytic activity. In this study we clearly found that the technical grade of anatase TiO2 has good potential for the process of bacterial degradation. The TiO2 can degrade bacteria under dark condition when incubation process.