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11.
To synthesize diamond films by microwave plasma enhanced chemical vapor deposition (MPECVD), the methane concentration (CH4/H2)plays a crucial role. It is well-known that there always exists a critical methane concentration (≤0.6%) only below which
a good quality diamond film can be obtained. In this study, however, the phenomena of diamond synthesis resulting from high
carbon concentration conditions were observed. The molten metals, e.g., Ag, Cu, were used as the deposition substrates on
which crystalline diamonds can be achieved from a methane content of CH4/H2≥6% or even from solid carbon sources. These results suggest that there may exist a low methane content boundary layer (<0.6%)
in the proximity of molten metal surface on which suitable species, CH, CH+, Hα and Hβ are composed for the diamond nucleation and growth similar to the condition as in the conventional low methane contents.
The molten metal inclines to dissolve other forms of carbonaceous materials other than diamond, and thus keeps a much higher
steady supply of carbon atoms that enhances the quality as well as the growth rate of the forming diamonds.
Received: 23 June 2001 / Accepted: 23 July 2001 相似文献
12.
We report here the identification of a new precipitate phase in thin-film Al-4wt.%Cu metallization used for interconnects
on integrated circuits. The phase is based on a trigonal distortion of a face centered cubic lattice. Computer simulation
of electron diffraction intensities suggests that the basis structure is isomorphous with Al2Ca but with a large and ordered population of vacancies on Cu sites. The reason for the formation of the new phase and its
implications for electromigration reliability are discussed. 相似文献
13.
The microstructure and thermal behavior of the Sn-Zn-Ag solder were investigated for 8.73–9% Zn and 0–3.0% Ag. The scanning
electron microscopy (SEM) analysis shows the Ag-Zn compound when the solder contains 0.1% Ag. X-ray diffraction (XRD) analysis
results indicate that Ag5Zn8 and AgZn3 become prominent when the Ag content is 0.3% and above. Meanwhile, the Zn-rich phase is refined, and the Zn orientations
gradually diminish upon increase in Ag content. The morphology of the Ag-Zn compound varies from nodular to dendrite structure
when the Ag content increases. The growth of the Ag-Zn compounds is accompanied by the diminishing of the eutectic structure
of the Sn-9Zn solder. Differential scanning calorimetry (DSC) investigation reveals that the solidus temperature of these
solders exists at around 198°C. A single, sharp exothermic peak was found for the solders with Ag content less than 0.5%.
Liquidus temperatures were identified with the DSC analysis to vary from 206°C to 215°C when the Ag content ranges from 1.0%
to 3.0% 相似文献
14.
A facile method was developed to quantify unreacted ketene acetals during polymerization of poly(ortho ester)s. The method was based on isotopic (deuterium) labeling of the unreacted ketene acetal groups arising from the diketene acetal monomer, 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5,5]undecane (DETOSU). In deuterium oxide, free ketene acetals are hydrolyzed to an α-deuterated ester; ortho ester bonds are hydrolyzed to the nondeuterated analog. The relative abundance of the deuterated ester side chain can be quantified by gas chromatography-mass spectrometry (GC-MS). In the current method, aliquots of a diketene acetal/polyol(s) reaction mixture were dissolved (crosslinked polymers swollen) in methylene chloride and excess D2O. The diketene acetal/polyol(s) reaction mixture was hydrolyzed under mildly acidic conditions to yield pentaerythritol dipropionate (PDP; hydrolysis product of DETOSU). PDP was extracted into an organic phase, silylated, and analyzed by GC-MS. Fragments corresponding to the C2H5C?O+ ion (57 a.m.u.) and C2H4DC?O+ ion (58 a. m. u.) were monitored and the quantity of free ketene acetal groups were calculated from the peak areas of the chromatograms. The precision of the method was ±0.1%. The accuracy, as compared to a parallel 1H-NMR study, was within 5%. This method permits determination of the cure end-point of a poly(ortho ester) polymerization reaction to within ±0.25%. The curing kinetics agreed well with DSC branching/crosslinking measurements. © 1994 John Wiley & Sons, Inc. 相似文献
15.
This study analyzed the effects of polyurethane (PU) resin treatments on surface homogeneity, dimensional stability, and finishing performances of medium‐ and small‐diameter softwoods produced in Taiwan. Two‐pack PU resins were prepared by combing short castor oil‐modified alkyd resin serving as a polyol with polymeric 4,4′‐diphenymethane diisocyanate (PMDI) serving as a hardener, by the molar ratio of NCO/OH+COOH of 1.2. Four types of short oil‐modified alkyd resins with different polyhydric alcohols (glycerin and pentaerythritol) and polybasic acids (phthalic anhydride and isophthalic acid) were synthesized. Three kinds of medium‐ and small‐diameter softwoods, including China fir, Taiwanina, and Japanese fir with a diameter of 10–15 cm were obtained from Hui‐Sun Forest Station, Taiwan. The wood coating of nitrocellulose (NC) lacquer including sanding sealer and top clear was used. Results show that the surface hardness, homogeneity, moisture excluding efficiency, and antiswelling efficiency of woods were enhanced by PU resin treatments. Among all the PU resins, the isophthalic acid and pentaerythritol‐containing PU resin (IPA‐P‐MDI) achieved the best improved efficiency on dimensional stability of woods. Results of two types of finishing procedure, i.e. NC lacquer sanding sealer plus top clear and top clear only, applied onto the PU‐treated woods revealed that the hardness, adhesion, and durability of NC lacquer films on the PU‐treated wood were superior to those of untreated one, especially for top clear finishing alone. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
16.
Kuo‐Hsiung Wang Tzong‐Ming Wu Yeng‐Fong Shih Chien‐Ming Huang 《Polymer Engineering and Science》2008,48(9):1833-1839
The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the Tg of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
17.
Heloisa Martins Shih Mitchell M Tseng 《International Journal of Project Management》1996,14(6):373-378
In this paper the application of workflow technology to monitor, control and coordinate business processes and projects is proposed. The conceptual characteristics of processes and projects as well as their management needs in the functions of planning, execution, monitoring and control are compared. The general design of the proposed system is then developed, with an application example. The proposed monitoring and control system provides proactive tracking of the flow of work and information, and of the utilization and commitment of resources. The design supports hierarchical management of the project and/or business process, allowing concerned persons to visualize and to utilize it in different levels of abstraction, as necessary. The application of workflow technology also provides additional benefits in facilitating communication, documentation and re-utilization. 相似文献
18.
McKeon J.B. Chindalore G. Hareland S.A. Shih W.-K. Wang C. Tasch A.F. Jr. Maziar C.M. 《Electron Device Letters, IEEE》1997,18(5):200-202
This letter presents for the first time, the experimentally determined majority carrier mobilities in the accumulation layer of a MOSFET for both p-type and n-type channel doping for a wide range of doping concentrations. The measured carrier mobility is observed to follow a universal behavior at high transverse fields, similar to that observed for minority carriers in MOS inversion layers. At the higher doping levels, the effective mobility for majority carriers at low to moderate transverse fields is found to be very close to the bulk mobility. This is believed to be due to carrier screening of the ionized impurity scattering which dominates at the higher doping concentrations 相似文献
19.
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