排序方式: 共有11条查询结果,搜索用时 15 毫秒
1.
Takatoshi Yamada Christoph E. Nebel Kumaragurubaran Somu Shin-ichi Shikata 《Applied Surface Science》2008,254(23):7921-7924
The relationship between field emission properties and C 1s core level shifts of heavily phosphorus-doped homoepitaxial (1 1 1) diamond is investigated as a function of annealing temperature in order to optimize surface carbon bonding configurations for device applications. A low field emission threshold voltage is observed from surfaces annealed at 800 °C for hydrogen-plasma treated surface, while a low field emission threshold voltage of wet-chemical oxidized surface is observed after annealing at 900 °C. The C 1s core level by X-ray photoelectron spectroscopy (XPS) showed a shoulder peak at 1 eV below the main peak over 800 and 900 °C annealing temperature for hydrogen-plasma treated and wet-chemical oxidized surfaces, respectively. When the shoulder peak intensity is less than 10% of the main peak intensity, lower threshold voltages are observed. This is due to the carbon-reconstruction which gives rise to a small positive electron affinity. By increasing annealing temperature, the shoulder peak ratios also increase, which indicates that a surface graphitization takes place. This leads to higher threshold voltages. 相似文献
2.
A series of 6.5.5 spiro bicyclic lactam scaffolds were synthesized from pipecolic acid in a sequence of reactions that was initiated with the alpha-allylation of tert-butoxycarbonyl pipecolic acid. Oxidative cleavage of the olefin to give an aldehyde followed by condensation with D-cysteine methyl ester gave a mixture of pipecolyl thiazolidines. Cyclization of the pipecolyl thiazolidines with Mukaiyama's reagent yielded the spiro bicyclic lactams 4a-d. Epimerization of the 7'a bridgehead carbon under acidic conditions was observed for those spiro bicyclic lactam scaffolds with an S stereochemistry at this position. The 6.5.5 spiro bicyclic lactam scaffold with the 3'S,6'R,7'aR stereochemistry mimicked a type II beta-turn, while the scaffold with the 3'S,6'S,7'aR stereochemistry mimicked a right-handed poly-d-proline II helix. 相似文献
3.
Dissimilar material joining using laser (aluminum to steel using zinc-based filler wire) 总被引:9,自引:0,他引:9
Alexandre Mathieu Rajashekar Shabadi Alexis Deschamps Michel Suery Simone Matteï Dominique Grevey Eugen Cicala 《Optics & Laser Technology》2007,39(3):652-661
Joining steel with aluminum involving the fusion of one or both materials is possible by laser beam welding technique. This paper describes a method, called laser braze welding, which is a suitable process to realize this structure. The main problem with thermal joining of steel/aluminum assembly with processes such as TIG or MIG is the formation of fragile intermetallic phases, which are detrimental to the mechanical performances of such joints. Braze welding permits a localized fusion of the materials resulting in a limitation on the growth of fragile phases. This article presents the results of a statistical approach for an overlap assembly configuration using a filler wire composed of 85% Zn and 15% Al. Tensile tests carried on these assemblies demonstrate a good performance of the joints. The fracture mechanisms of the joints are analyzed by a detailed characterization of the seams. 相似文献
4.
Ming Wei Zhenghong Tao Xugang Xiong Myunghwan Kim Jun Lee Sivasubramanian Somu Sandip Sengupta Ahmed Busnaina Carol Barry Joey Mead 《Macromolecular rapid communications》2006,27(21):1826-1832
Summary: The use of electrostatically addressable templates for the directed assembly of conducting polymers and pattern transfer to another polymer substrate is demonstrated. Doped conducting polyaniline was selectively assembled on the patterned template assisted by a DC electric field. Adding an insulated silicon dioxide layer onto the surface of the silicon wafer is critical to the formation of patterned PANi rather than a PANi film. After deposition, it was demonstrated that by compression molding or solution casting methods, patterned PANi can be completely transferred to a secondary polymer substrate, such as an NBR sheet or a polyurethane film. The conductivity of PANi lines on the PU film was found to be as high as 0.87 S · cm−1. The simple one‐step assembly process for patterning conductive polymers and transfer provides a promising nanomanufacturing approach for cost‐effective and high performance flexible nanoelectronics and biosensors.
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6.
A Catalyst‐free Green Protocol for the Synthesis of Pyranopyrazoles Using Room Temperature Ionic Liquid Choline Chloride‐urea 下载免费PDF全文
Toreshettahally R. Swaroop Kothanahally S. Sharath Kumar Mariyappan Palanivelu Somu Chaitanya Kanchugarakoppal S. Rangappa 《Journal of heterocyclic chemistry》2014,51(6):1866-1870
An efficient and rapid four component reaction of aldehydes, malanonitrile, β‐ketoesters and hydrazine hydrate (or phenyl hydrazine) in environmentally benign room temperature ionic liquid choline chloride‐urea has been developed for the synthesis of substituted 4H‐pyrano[2,3‐c]pyrazoles. 相似文献
7.
Laila Jaber-Ansari Myung Gwan Hahm Tae Hoon Kim Sivasubramanian Somu Ahmed Busnaina Yung Joon Jung 《Applied Physics A: Materials Science & Processing》2009,96(2):373-377
Large-scale room-temperature liquid-phase directed assembly of highly organized single-walled carbon nanotubes (SWNT) over
large areas is demonstrated. The presented process utilizes lithographically patterned template to guide the fluidic self-assembly
of SWNTs on a silicon-dioxide substrate. The width of these highly organized SWNT structures are in the micron range while
their heights are in orders of nanometers. Room temperature electrical I–V characterization of these fabricated high coverage SWNT wires show linear ohmic behavior. The resistivity of these assembled
SWNT network is in the order of 10−6 Ω m demonstrating their metallic characteristics during conductance. Scaling of the assembly processes on a wafer level with
high yield is demonstrated. Our developed assembly process is compatible with complimentary metal oxide semiconductor (CMOS)
processes and provides a simple and flexible way of building SWNT nanotube-based electronics in a large scale. 相似文献
8.
This paper presents the user defined nine-node piezoelectric shell element and its implementation within a user element subroutine for modeling and analysis of thin-walled active composite structures. The element has been implemented within commercial finite element software ABAQUS. Application of the element covers modeling of arbitrary thin-walled structures also with complex geometries, whereby the automated mesh generation has been accomplished by developing a Python based interface for meshing procedure. In order to be able to perform the post-processing, a special adaptation of the user element had to be performed for visualization purposes. The implemented element regards the piezoelectric thin layers polarized in the thickness direction and it is based on the \(e_{31}\) piezoelectric effect. It has been also shown that this biquadratic nine-node element based on degenerated shell approach is less prone to locking effects and more suitable for implementation with curved structures. Through several examples the accuracy of the implemented user defined shell element as well as of the Python-based mesh extension has been demonstrated, along with the possibilities for post-processing. Meshing the structures with the nine-node user element is not third party software dependent. 相似文献
9.
Gurjar MK Ravindranadh SV Sankar K Karmakar S Cherian J Chorghade MS 《Organic & biomolecular chemistry》2003,1(8):1366-1373
In the presence of allyl tri-n-butyltin--AIBN, cyclopropylmethyl bromides/xanthates undergo ring-opening reaction with concomitant formation of geminal diallyl derivatives in good yields. The ring closing metathesis reactions on geminal diallyl derivatives with Grubbs' catalyst provided spirocyclopentenyl products. Combination of these two methodologies has been applied to the synthesis of mono-, bis-cyclopentyl-carbohydrates as well as spirocyclopentylproline derivatives. 相似文献
10.
Ravindar Vadde Swamy S. Jagannatha Srihari Somu Lingaiah Puri 《Transition Metal Chemistry》1984,9(3):103-106
Summary Complexes of palladium(II) with 2-(acetylamino)benzoic acid, 2-(benzoylamino)benzoic acid, 2-[2-aminobenzoylamino]benzoic acid, 2-hydroxy benzanilide, 2-mercapto benzanilide, maleanilic acid, 2-(amino carbonyl)benzoic acid, 2-[(phenylamino)carbonyl]benzoic acid, 2-[(1-naphthalenylamino)carbonyl]benzoic acid, 2-[(2-aminophenylamino)carbonyl]benzoic acid, salicylanilide, 2-(aminobenzoyl)benzoic acid and 2-aminobenzamide have been prepared and characterized by chemical analyses, molar conductivity measurements, thermal data and i.r., electronic and n.m.r. spectra. 相似文献