Papers by Keyword: Surface

Abstract: A new method on examining the micro cracks of monocrystalline silicon during nano indentation is proposed. It is established based on a study of the increasing rate of absorbed energy in nano indentation. This method provides a simple approach in understanding whether cracks on the silicon surfaces occur, while it is tedious in conventional method.

Abstract: The protein adsorption behavior was investigated for highly (001) oriented hydroxypatatite coatings (HACs). Highly (001) oriented (HO-) HACs and HAC with low orientation (LO-HAC) were prepared on titanium (Ti) substrates through a radio-frequency thermal plasma spraying method. Sintered HA pellets (S-HA) was also prepared as a control. The solution of 22 'g/100 'l PBS of the fluorescein-isothiocyanate (FITC) labeled bovine serum albumin (FITC-BSA), immunoglobulin G (FITC-IgG) and cytochrom c (FITC-CCC) was separately dropped on the surface of HACs and was incubated for 30 min. After the incubation, such HACs were washed with the PBS additionally supplemented with 125mM NaCl and observed using a fluorescence microscope. Fluorescence microscopic examination indicates that FITC labeled proteins somewhat adsorbed on the HACs, while proteins adsorbed little on S-HA surface. In particular, it can be seen that FITC-CCC adsorbed more prominently on the HO-HAC.

Abstract: It is shown using aluminum single crystals with kink bands like a plate through the depth that the nucleation and growth of recrystallized grains (RGs) on/in the surface precede those in the interior.

Abstract: Ti-Cr-V alloys with body-centered cubic (BCC) structure were investigated on hydrogen absorbing-desorbing cyclic durability by using H2 without and with several concentrations of CO (Hereafter, they are described as pure H2 and n ppm CO, respectively.). The alloy which offers the excellent durability except the early stages of cyclic absorption-desorption under pure H2 atmosphere gave good durability also in a flow of low concentration of CO. However, capacities’ degradation curves under high CO concentration reflected that duration and concentration effects competed with each other. The results suggests to be able to express each degradation by intrinsic and extrinsic factors as an aggregation of several prime functions.

Abstract: The surface of Ti-29Nb-13Ta-4.6Zr (TNTZ) subjected to gas nitriding at 1023–1223 K was investigated in comparison with the conventional biomedical titanium alloy, Ti-6Al-4V ELI (Ti64). After gas nitriding, the microstructures near the surface of these alloys were observed by optical microscopy, X-ray diffraction, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. In both alloys, two titanium nitrides (TiN and Ti2N) are formed and the α phase precipitated by gas nitriding. Furthermore, oxygen impurity in the gas nitriding atmosphere reacts with the titanium nitrides; thus, TiO2 is formed at the outermost titanium nitride layer. The surface hardening was also evaluated by Vickers hardness measurement. The Vickers hardness near the surface of TNTZ and Ti64 increases significantly by gas nitriding.

Abstract: Vjg"rwtrqug"qh"vjg"rtgugpv"uvwf{"ku"vq"enctkh{"vjg"tqqo"vgorgtcvwtg"oketq/dqpfkpi"dg/ jcxkqt"dgvyggp"yktgu"cpf"hqknu."dcugf"qp"vjg"cfjgukqp"vjgqt{"cpf"gzrgtkogpvu0""Vjg"cvoqurjgtke" eqpfkvkqp"*xcewwo"fgitgg+"hqt"dqpfkpi"ycu"cdqwv"307z32/:"Rc0"Vjg"dqpfkpi"uwthcegu"ygtg"engcpgf" d{"ctiqp"kqp"kttcfkcvkqp"dghqtg"dqpfkpi0"Cfjgukqp"*eqpvcev+"ykfvj"nctign{"fgrgpfgf"qp"vjg"{kgnf" uvtguu"qh"vjg"uqhvgt"ogvcn0"Vjg"eqpvcev"ykfvj"ejcpigf"d{"tgrncekpi"vjg"ocvgtkcnu"qh"yktg"cpf"hqkn0"Hqt" gzcorng."vjg"eqpvcev"ykfvj"dgvyggp"Cn/yktg"cpf"Cw/hqkn"ycu"nguu"vjcp"vjcv"qh"Cw/yktg"cpf"Cn/hqkn."k0g0." vjg"eqpvcev"ykfvj"dgeqogu"nctigt"yjgp"uqhvgt"ogvcn"ku"wugf"cu"c"hqkn0""Vjg"cfjgukqp"dgvyggp"Cn"yktg" cpf"jctf"hqknu"vgpfu"vq"dg"hqtogf"kp"vjg"rgtkrjgt{0"Qp"vjg"qvjgt"jcpf."vjg"cfjgukqp"dgvyggp"Cn"hqkn" cpf"jctf"yktgu"ku"gcukn{"hqtogf"kp"vjg"egpvtcn"ctgc0"

Abstract: We have investigated the influence of surface modification on the electrical properties of SiC diodes. Schottky diodes (SBDs) as well as PiN diodes were fabricated on n-type SiC substrate with an epilayer, and electrically characterized before and after high temperature annealing, and after removing the surface modified layer, respectively. The devices annealed without graphite cap layer showed ohmic behavior. The surface layer was modified to a conductive layer possibly due to the preferred sublimation of Si species. In order to confirm the existence of modified surface conductive layer, diode was fabricated on the same substrate and electrically characterized after removing 30nm-thick damaged layer by ICP-RIE. The leakage current reduced dramatically, as much as 7 orders of magnitude. The PiN diodes fabricated on the damaged surface layer showed the reverse leakage current and the breakdown voltage of 50mA and 1250V, respectively. While those of the diode fabricated after removing the damaged surface layer were 200nA at the breakdown voltage of 2100V, respectively.

Abstract: Atomic structure and morphology of 6H-SiC(0001) and 3C-SiC(100) surfaces are studied by scanning tunneling microscopy (STM), synchrotron radiation-based !-spot x-ray photoemission spectroscopy (!-spot XPS) and low energy electron microscopy (LEEM). STM shows very high quality Si-rich 6H-SiC(0001) 3x3 surfaces with less than 2% of atomic defects. Si removal upon annealing leads to atomic crack defects formation with a novel 2"3x2"3-R30° reconstruction coexisting with few 3x3 domains having no crack, suggesting important stress relief during the phase transition. LEEM also shows cracks formation on cubic 3C-SiC(100) surfaces and gives insights about surface morphology with large faceting and mesa (!m) formation. These defect fractures developing upon Si removal are likely to be also generated during initial oxidation since the initial oxygen interaction tends to relieve surface strain on SiC in contrast to Si surfaces. These atomic crack defects could be related to the interface electronic states recurrent at SiO2/SiC interfaces.

Abstract: The surface layer of binary Al-Zn alloy specimen, ever after a long time aging, remains softer than the interior when the specimens are age-hardened at around room temperature after quenching from high temperature. In this study, effects of the soft surface layer on the fatigue strength of Al-Zn alloys were studied under repeated tensile loading. Vickers microharhness test revealed that there existed less hardened region in the vicinity of grain boundary and specimens surface, and that the region extends 50 to 100μm from the surface inward. From the plot of the stress amplitude against the number of cycles to failure, it is concluded that the presence of less hardened surface layer increases fatigue resistance of age-hardened Al-Zn alloys containing 8 to 16 mass%Zn under the repeated tensile loading.