Polycrystalline AlN thin films were reactively deposited onto Al layers on negatively biased glass and Si substrates at temperatures < 80 oC by coherent magnetron sputtering. The target-to-substrate distance is 17 cm. The microstructures and morphology of the films grown at different bias voltages on the substrates were investigated. Typical thickness of the deposited film is 600 nm. The films were amorphous when no bias was applied to the substrates. Diffraction peak of AlN (002) direction was observed at bias voltages of -180 and -210 V. At a bias voltage of -210 V, the (002) granular crystal with the maximum diameter of 80 nm was obtained. In addition to the AlN (002) direction, AlN (100) direction was observed when the bias voltage was increased to -240 and -270 V. The peak of (002) plane vanished at a bias voltage of -320 V. Moreover, the deposited AlN films have specular reflectance owning to the large target-to-substrate distance. The maximum roughness of the films was 47.2¡Ó5.0 nm at a bias voltage of -210 V. The hardness and microstructure of aluminum nitride (AlN) thin films prepared by long-distance magnetron sputtering at room temperature has been investigated. The hardness and microstructure of the films were found to vary greatly with different substrate biases. At a bias voltage of ¡V210 V, the (002) polycrystalline AlN with the maximum hardness of 17.5 GPa was observed. The water droplet contact angle under this bias condition is larger than 90¢X indicating that hydrophobicity can be obtained at the film surface. In addition, hardness of (002) AlN films prepared by sputtering of AlN target at room temperature and by reactive sputtering of Al target at 400¢XC were discussed and compared with that of AlN films prepared by long-distance reactive sputtering.

The microstructure and residual stress of Ni thin film coating on Si influence the properties significantly, which play an important role in advanced applications of the electric and magnetic properties. The properties of Ni thin film deposited on Si at various temperatures and for different thickness have been studied in this work. Samples were characterized by nanoindentation, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), electrical measurement, grazing angle X-ray diffraction (XRD) and photo reflection spectroscopy of white light. The nanoindentation measurements reveal similar loading curves and young¡¦s modulus for Ni thin films on Si at different deposition temperatures. However, the higher the deposition temperature, the lower is the hardness of the Ni thin film on Si. A maximum stress occurs at deposition temperature of 88-122 ¢XC. From FTIR spectra an unusual IR oscillating absorption of the Ni/Si film was observed from the samples which was deposited at 230 ¢XC for 15 min (23 nm) and for 30 min (52 nm) compared to other deposition duration and deposition temperatures at room temperature, 88 ¢XC, and 122 ¢XC. Furthermore, annealing experiments of the samples were performed after deposited at room temperature, and then annealed at respective temperatures of 88, 122, 230 ¢XC for the durations of 15 min and 30 min for comparison. However, the unmoral IR oscillation doesn¡¦t occur else where. The phase change of Ni/Si was analyzed by grazing angle XRD. A single phase of NiSi (103) structure was observed only in the samples deposited at 230 ¢XC. Further study of the oscillation in the FTIR spectra shows its origin should be related to surface plasmon resonance (SPR) mode. The SPR absorption peaks at 471 nm and 616 nm are analyzed by a photo reflection experiment. The SPR absorption is due to the nano structure of nickel silicide on Ni/Si surface formed during deposition at 230 ¢XC.

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Abstract Cr-containing diamond-like carbon coatings (Cr-DLC) with gradient interlayers were studied to elucidate the effects of Cr content and substrate bias on the mechanical properties and microstructure of the deposited coatings. The coatings were deposited with a closed field unbalanced magnetron sputtering (CFUBMS) system. The Cr content and substrate bias were varied from 5 at.% to 30 at.% and -22 V to -60 V, respectively. Mechanical properties of the coatings were evaluated with nano-indenter, scratch tester, ball-on-disk tribo-tester and ball crater. Microstructures of the films were characterized by SEM, TEM, and Raman spectroscopy. Experimental results show that an increases in Cr content from 5 at.% to 30 at.% for the Cr-DLC coatings deposited at substrate bias of ¡V40V results in the increase of the hardness, Young¡¦s modulus, adhesion and friction coefficient, and the decrease of the deposition rate. A minimum abrasive wear rate was found at about 10 ~ 15 at.% Cr content. An increase in substrate bias from -22 V to -60 V for the Cr-DLC a of 10 at% Cr content results in a maximum hardness, Young¡¦s modulus and adhesion, and a minimum friction coefficient and abrasive wear rate at a substrate bias of -50 V, the although the deposition rate is decreased. TEM analysis revealed layered structure of about 35 nm period and fine CrC crystallite nanometer in size on the top layer of the Cr-DLC coatings.

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Cephalopods become one of the most important commercial marine resources worldwide. The knowledge of the basic biology and population dynamics of these resources is the way to ensure the resource to be utilized properly. In Taiwan, cephalopods are traditionally used and prized as foods with high market price. Sepioteuthis lessoniana is an important fishery species. Its distribution is concentrated around the northeastern and the southern coasts of Taiwan, and the Peng-Hu Island. Although there are some investigations on the statolith of the adults, studies on early stages are scarce. In this study, we use the known-age statoliths incubated in the different conditions to relate with those factors, i.e., temperature, salinity, and photoperiod, which influenced the ring formations during the embryonic and larval stages. From April to September, several clusters of bamboos, 3 ~ 4 m long, 1 ~ 2 m wide, were set on the sea bed at a depth of 16 to 20 m to attract their spawning, and the egg-strings were then transported to the laboratory. When the development of the embryo reached stage 24, iris of eyes being prominent as a colour circle and statolith being formed, they were transferred into different rearing conditions, i.e., 20, 25, 30, 35 o/oo and 15, 20, 25, 30 oC. The durations from stage 24 to hatching were different among all different rearing conditions. The statoliths were extracted and mounted in Crystal Bond thermoplastic cement for reading their growth rings. In the normal condition (25 oC and 35 o/oo), the duration from stage 24 to hatching is 9 ~ 16 days. Although the rings can be counted in each specimen, the numbers do not match between the embryonic rings and the developmental duration. Changes on the shape of the statolith were observed among different incubated conditions. The shape of the statolith at hatching had obvious differences among different embryonic developmental conditions. The statolith developed in the colder environment had smaller dorsal dome, thinner and shorter rostrum than that developed in the warmer condition. Using the shape of this embryonic ring was to be applied to measure the variation of the shape of the statolith. This is a useful tool to know the temperature factor during embryonic development by comparing with the shape of the hatchling¡¦s statolith. After hatching, squid hatchlings were separated to incubate in two different photoperiod regimes, 12 hr: 12 hr and 24 hr constant light conditions. Squid larvae were maintained as long as possible. Although the trend which older squids have more increments on the statolith than younger squids is consistent, the slope between the increments and survival days is less than one. The time required to form one ring on the statolith is needed for more than one day. Bell-shaped distributions can be found in several analyses in this study, especially with large sample size in 25 oC at 35 o/oo. If the sample size was small, the bell-shaped distribution would be obscure. This may result in oversimplification in interpretating the result. Sometimes this kind of problem could be inevitable because collecting large enough sample size was difficult or impossible. In any validation exercise, it would be difficult to obtain data for the whole life cycle. This study indicated that the hypothesis of daily-increment for the whole life history required further verification with larger sample size and wider size ranges of the tropical squids in future.

The way in which the myocardium responds to its mechanical environment must be understood in order to develop reasonable treatments for congestive heart failure. The first step toward this understanding is to characterize and quantify the cardiac microstructure in healthy and diseased hearts. Myocardium has a laminar architecture made up of myolaminae, which are sheets of myocytes surrounded by a collagen weave. By enhancing the contrast between the myocytes and the surrounding collagen, the myocardium can be investigated and its laminar structure can be quantified. Many of the techniques that have been used to view the microstructure of the heart require the use of toxic or caustic chemicals for fixation or staining. An efficient imaging method that uses polarization microscopy and enhances the contrast between the collagen and myocytes while minimizing the use of harmful chemicals was developed in this research. Collagen is birefringent; therefore its visibility should be enhanced through polarization microscopy and image processing. The sheet angles were viewed directly by cutting slices of a rat septum perpendicular to the fiber angle. Images of different polarization combinations were taken and a region of interest was selected on the sample. Image processing techniques were used to reduce the intensity variation on the images and account for the variable gain of the camera. The contrast between the collagen and myocytes was enhanced by comparing adjusted images to the background and looking at a single image this comparison produced. Although the contrast was enhanced, the embedding media reduced the collagen signal and the enhancement was not as striking as expected.

The focus of the research is to develop a consistent and repeatable method to evaluate the coefficient of thermal expansion (CTE) of carbon fibers at high temperatures. Accurate measurement of the CTE of carbon fibers is essential to understand and develop optimal processing procedures as well as computational simulations to predict properties and allowables for fiber-reinforced composites. The mismatch between the coefficient of thermal expansion of the fiber and the matrix has a profound impact on the development of residual stresses and the subsequent damage initiation and progression, potentially diminishing the performance of composite structures. In situ transmission electron microscopy (TEM) is selected to perform the experimental work on account of the high resolution and the capability of evaluating both the longitudinal and transverse CTE. The orthotropy in the CTE is tested by rotating the fibers through 45° about their axis. The method is validated by testing standard tungsten filaments of known CTE. Additionally, the microstructure of the fibers is studied in a field emission scanning electron microscope as well as through selected area diffraction patterns in a TEM to observe presence of any potential orthotropy. The pitch based P55 fiber revealed a cylindrically orthotropic microstructure, but the PAN based IM7 and T1000 fibers did not reveal any orthotropy. Finite element models of hexagonally arranged IM7 fibers in a 977 epoxy matrix are developed using PATRAN and analyzed using the commercial FEA code ABAQUS 6.4. The fiber properties were considered temperature independent where as the matrix properties were varied linearly with temperature. The lamina properties evaluated from the finite element modeling are in agreement with the experimental results in literature within 10% in the temperature range of room temperature to the stress free temperature of the epoxy, however at cryogenic temperatures the difference is greater. The residual stresses developed during processing of the composite indicated a potential location for fiber matrix debonding to be in the matrix dominant regions.

The objectives of this study were to examine the effect of strain and path change on the microstructural evolution of ultrafine grained interstitial free (IF) steel during equal channel angular extrusion (ECAE); to determine the mechanical properties; to observe the resulting texture; and to perform optical and electron microscopy of the resulting material. The effects of different routes of extrusion (A, B, C, C' and E), heat treatment and plastic strains from 1.15 to 18.4 were examined. Monotonous tensile testing was used to determine mechanical behavior of processed materials. X-ray diffraction and TEM analyses were performed to evaluate the effect of processing on texture and grain morphology. Hardness measurements were performed to determine recrystallization behavior of the processed material. Optical microscopy was conducted on heat treated samples to determine their grain size and refinement. Monotonous tensile testing of processed materials showed that there was significant strengthening after the first extrusion. Further processing resulted in increasing values of yield strength and ultimate tensile strength, with ductility at failure varying depending upon which processing route was used. The best tensile strength results were obtained after processing Routes 8C' and 16E, due to the significant grain refinement these routes produced. X-ray diffraction revealed increases in strength of preferred texture along the directions [111] and [001], perpendicular to the transverse plane, for all specimens that were processed using ECAE. TEM observations showed a consistent refinement of grain size as the amount of processing increased, especially within Routes C' and E. Hardness measurements of heat treated specimens showed that the onset of recrystallization occurred at approximately the same temperature of recrystallization as that of pure iron, 450°C. The recrystallization curves for all samples showed that grain growth begins at a temperature of around 700°C. The low carbon content of IF steel made optical microscopy challenging. The grain size of annealed materials becomes finer and more uniform, ranging between 60 and 90 μm2, at high strain levels under Routes C' and E, due to the many potential nucleation sites developed in highly worked material.

Thèse doctorat : Génie des Matériaux : Villeurbanne, INSA : 2000. / Titre provenant de l'écran-titre. Bibliogr. p. 129-142.