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91.
Takeshi Kondo 《Electrochimica acta》2003,48(19):2739-2748
The electrochemical properties of several types of diamond electrodes, including polycrystalline and homoepitaxial films, that underwent anodic treatment were examined with the electrochemical impedance spectroscopic (EIS) technique, as well as with capacitance-potential measurements. From an analysis of the impedance behavior, it was found that an additional capacitance element, which is apparent in the relatively high-frequency range (100-1000 Hz), was generated on the polycrystalline and (1 0 0) homoepitaxial diamond electrodes after anodic treatment. This capacitive element can be characterized as being non-Faradaic, because it has negligible dependence on the applied potential. Acceptor densities and depth profiles were calculated from the Mott-Schottky plots, and the acceptor densities in the near-surface region of the anodically treated surfaces were found to be extremely low. These results indicate that passive layers were generated on the diamond surfaces by the anodic treatment. The capacitance-potential behavior was also consistent with a model consisting of a semiconductor with a passive surface film. The passive film is proposed to arise as a result of the removal of hydrogen acting as an acceptor in the subsurface region, leaving hydrogen that is paired essentially quantitatively with the boron dopant, effectively neutralizing it. 相似文献
92.
Takuya Honma Ikue Sasaki Nobuhiro Tamura Junichi Tatami Shinichiro Fujichika Katsutoshi Komeya Takeshi Meguro 《International Journal of Applied Ceramic Technology》2013,10(2):348-353
To fabricate functionally graded materials, a highly concentrated slurry of SiO2‐Mo system was prepared and centrifugal force was applied in an attempt to achieve a graded composition. Subsequently, we formed a homogeneous green body with compositional gradation by floc‐casting at 80°C, which was then fired at 1750°C for 10 min in Ar. The sintered body had compositional ratios of SiO2 and Mo as well as electrical conductivities that changed gradually along the direction of centrifugal force. The results demonstrate that centrifugation and control of slurry characteristics such as flocculation are effective in fabricating functionally graded SiO2‐Mo materials. 相似文献
93.
Adduct formation of 2-thenoyltrifluoroacetonato(tta) lantha-num(III), europium(III), and ytterbium(I II) with α-pheny 1 1 actic, α-methoxy phenyl acetic, salicylic, and o-methoxy benzoic acids in chloroform has been studied by solvent extraction technique. It has been found that 1anthanoid(111) chelates form more stable adducts with these carboxylic acids in the sequence: Yb(tta)3 < Eu(tta) 3 < La(tta) 3. The adduct formation constants as well as the separation factors obtained as the ratio of the constants between a pair of metals are the largest for α-phenyl lactic acid among these acids. The characteristics with α-phenyl 1actic acid would be caused by the action as bidentate unlike benzoic acid derivatives which work as monodentates owing to the internal complexa-tion through hydrogen bonding. 相似文献
94.
In order to obtain thermoplastic (before curing) and thermosetting (after curing) polyimides with high Tg for adhesive film, we prepared novel polyimides having phenylethynyl group in the side chain (44% of concentration of curing group) from asymmetric 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA), 3,4′-oxydianiline (3,4′-ODA) or 1,3-bis(4-aminophenoxy)benzene (1,3,4-APB) or 1,3-bis(3-aminophenoxy)benzene (1,3,3-APB), and 2,4-diamino-1-(4-phenylethynylphenoxy)benzene (mPDAp). Among three kinds of polymer, uncured polyimide of a-BPDA/1,3,4-APB; mPDAp had rather high Tg (265 °C, DMA) and thermoplasticity (E′ drop>103 at Tg). After curing reaction of phenylethynyl group, the Tg of the polyimide was increased dramatically (364 °C, DMA). The polyimide derived from 1,3,4-APB having less concentration of curing group (20%) was also prepared to improve further film flexibility and toughness. 相似文献
95.
96.
Koji Matsui Nobukatsu Ohmichi Michiharu Ohgai Naoya Enomoto Junichi Hojo 《Journal of the American Ceramic Society》2005,88(12):3346-3352
The sinterabilities of fine zirconia powders including 5 mass% Y2 O3 were investigated, with emphasis on the effect of Al2 O3 at the initial sintering stage. The shrinkage of powder compact was measured under constant rates of heating (CRH). The powder compact including a small amount of Al2 O3 increased the densification rate with elevating temperature. The activation energies at the initial stage of sintering were determined by analyzing the densification curves. The activation energy of powder compact including Al2 O3 was lower than that of a powder compact without Al2 O3 . The diffusion mechanisms at the initial sintering stage were determined using the new analytical equation applied for CRH techniques. This analysis exhibited that Al2 O3 included in a powder compact changed the diffusion mechanism from grain boundary to volume diffusions (VD). Therefore, it is concluded that the effect of Al2 O3 enhanced the densification rate because of decrease in the activation energy of VD at the initial sintering stage. 相似文献
97.
Oxidation of SiC compositionally graded (SCGed) graphite coated with HfO2 derived from HfCl4 by a sol–gel process was performed at 1500° and 1600°C in a flowing gas mixture of Ar and O2 (80/20 kPa). SCGed graphite was produced by reaction of graphite with either molten Si or SiO gas at 1450°C. The sol–gel-derived HfO2 precursor was deposited on SCGed graphite by a dip-coating method. Isothermal and cyclic oxidation of uncoated- and HfO2 -coated SCGed graphite was studied by monitoring overall weight change using an electro-microbalance. Scanning electron microscopy with energy-dispersive X-ray analysis was used to observe the surfaces and cross-sections of the oxidized HfO2 -coated SCGed graphite. The formation of HfSiO4 was confirmed on the outer layer of the oxidized sample, beneath which a thin silica layer was formed. The improved oxidation resistance of SCGed graphite by coating with HfO2 is discussed on the basis of the formation of these two layers. 相似文献
98.
Abnormalities in the Metabolism of Fatty Acids and Triacylglycerols in the Liver of the Goto-Kakizaki Rat: A Model for Non-Obese Type 2 Diabetes 下载免费PDF全文
99.
Detecting when the process has changed is a classical problem in sequential analysis and is an important practical issue in statistical process control. This article is concerned about the binomial cumulative sum (CUSUM) control chart, which is extensively applied to industrial process control, health care, public health surveillance, and other fields. For the binomial CUSUM, a maximum likelihood estimator has been proposed to estimate the change point. In our article, following a decision theoretic approach, we develop a new estimator that aims to improve the existing methods. For interval estimation, we propose a parametric bootstrap procedure to construct the confidence set of the change point. We compare our proposed method with the maximum likelihood estimator and Page's last zero estimator in terms of mean squared error by simulations. We find that the proposed method gives more unbiased and robust results than the existing procedures under various parameter designs. We analyze jewelry manufacturing data for illustration. 相似文献
100.
Inside Cover: Onocerin Biosynthesis Requires Two Highly Dedicated Triterpene Cyclases in a Fern Lycopodium clavatum (ChemBioChem 4/2016) 下载免费PDF全文