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991.
Costas A. Charitidis 《Applied Surface Science》2010,256(24):7583-8727
In this study, we report on the mechanical properties, failure and fracture modes in two cases of engineering materials; that is transparent silicon oxide thin films onto poly(ethylene terephthalate) (PET) membranes and glass-ceramic materials. The first system was studied by the quazi-static indentation technique at the nano-scale and the second by the static indentation technique at the micro-scale. Nanocomposite laminates of silicon oxide thin films onto PET were found to sustain higher scratch induced stresses and were effective as protective coating material for PET membranes. Glass-ceramic materials with separated crystallites of different morphologies sustained a mixed crack propagation pattern in brittle fracture mode. 相似文献
992.
Optical and Electrical Properties of Ferroelectric SBN Thin Films Prepared by Sol-Gel Process 总被引:1,自引:0,他引:1
Junmo Koo Jae Hyeok Jang Byeong-Soo Bae 《Journal of Sol-Gel Science and Technology》2000,19(1-3):611-614
Strontium barium niobate thin films were prepared by sol-gel method on various substrates using an improved process, two-step heating process. The two-step heating process applies an additive heat-treatment before crystallization for enhancement of the densification and the nucleation of films. Also, highly c-axis oriented SBN thin films with various compositions were obtained on MgO(100) and Pt(100)/MgO(100) substrates. Their optical and electrical properties such as optical propagation loss, refractive index, P-E hysteresis, and dielectric constant, were characterized as a function of the film composition. 相似文献
993.
V. Pedroni P. C. Schulz M. E. Gschaider de Ferreira M. A. Morini 《Colloid and polymer science》2000,278(10):964-971
We synthesised a porous siliceous material via hydrothermal hydrolysis of sodium silicate, using chitosan as a template.
As far as we know, this is the first synthesis of siliceous porous material using chitosan as a template in a hydrothermal
way. A fibrous material was obtained, whose macroscopic fibres were formed by a spongelike siliceous network with pores having
a radius of 0.57 μm. The siliceous walls of the pores were, in turn, of the form of a microporous–mesoporous material; the
pore radius distribution was polymodal with maxima at 0.84, 1.0, 1.2 and 1.5 nm and a broad band between 3 and 10 nm. This
structure may be due to the aggregation of the hydrated chitosan helices in bundles of parallel fibres with different size
and the gelation of the system. The aggregation process might be induced by the addition of silicate.
Received: 12 January 2000/Accepted: 7 March 2000 相似文献
994.
995.
Through the reaction between the hydroxyl groups of 2-hydroxyl-3-methylbenzoic acid (HMBA), the glycol (G), the diglycol (DG) or the polyethylene glycol (PEG) and the isocyanate groups of 3-(triethoxysilyl)-propyl isocyanate (TEPIC), the hybrid precursors HMBA-Si, G-Si, DG-Si and PEG-Si were obtained. And then the precursors HMBA-Si and G-Si (DG-Si, PEG-Si) have coordinated to the rare earth ions with the carbonyl group of G-Si (DG-Si, PEG-Si) and the carboxyl group of HMBA-Si to form the hybrid materials HMBA-G-RE-Si (HMBA-DG-RE-Si, HMBA-PEG-RE-Si) through hydrolysis and copolycondensation with the tetraethoxysilane (TEOS) via sol–gel process. Subsequently, the NMR, FT-IR and ultraviolet absorption spectra have indicated that the effective precursors have been obtained successfully and the obtained materials possess the characteristic fluorescent properties, thermal stabilities and regular trunk with hole-like microstructures. 相似文献
996.
我们利用稀土直接掺杂工艺 ,通过向带隙宽为 4~ 5eV的ⅡA ⅥA族化合物中掺入稀土离子Eu、Sm ,合成了电子俘获材料 (ETM ElectronTrap pingMaterial)CaS :Eu ,Sm。该材料具有红外上转换和光存储特性 ,其红外响应光谱宽 ( 0 .8~ 1 .6μm)、量子转换效率高达 76% [1 ,2 ] 、热稳定性好、使用方便 (室温下工作 ,不需制冷 )、造价低 ,并且具有“常光充能”特性 ,即不需紫外线预激发就能在室温下将红外光 ( 0 .8~ 1 .6μm)直接转换为醒目的可见红光 ,是一种优良的红外探测材料 ,利用该材料制作的… 相似文献
997.
998.
999.
Ying Li 《Journal of solid state chemistry》2008,181(5):1032-1039
Novel organic-inorganic mesoporous hybrid materials were synthesized by linking lanthanide (Tb3+, Eu3+) complexes to the mesoporous MCM-41 through the modified meta-methylbenzoic acid (MMBA-Si) using co-condensation method in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as template. The luminescence properties of these resulting materials (denoted as Ln-MMBA-MCM-41, Ln=Tb, Eu) were characterized in detail, and the results reveal that luminescent mesoporous materials have high surface area, uniformity in the ordered mesoporous structure. Moreover, the mesoporous material covalently bonded Tb3+ complex (Tb-MMBA-MCM-41) exhibits the stronger characteristic emission of Tb3+ and longer lifetime than Eu-MMBA-MCM-41 due to the triplet state energy of organic legend MMBA-Si matches with the emissive energy level of Tb3+ very well. 相似文献
1000.
Low‐temperature sol–gel transformation of methyl silicon precursors to silica‐based hybrid materials
Veena Dhayal Rakesh Bohra Meena Nagar Ajay Kaushik Sanjay Mathur Sven Barth 《应用有机金属化学》2008,22(11):629-636
Six new methyl silicon (IV) precursors of the type [MeSi{ON?C(R)Ar}3] [when R = Me, Ar = 2‐C5H4N ( 1 ), 2‐C4H3O ( 2 ) or 2‐C4H3S ( 3 ); and when R = H, Ar = 2‐C5H4N ( 4 ), 2‐C4H3O ( 5 ) or 2‐C4H3S ( 6 )] were prepared and structurally characterized by various spectroscopic techniques. Molecular weight measurements and FAB (Fast Atomic Bombardment) mass spectral studies indicated their monomeric nature. 1H and 13C{1H} NMR spectral studies suggested the oximate ligands to be monodentate in solution, which was confirmed by 29Si{1H} NMR signals in the region expected for tetra‐coordinated methylsilicon (IV) derivatives. Thermogravimetric analysis of 1 revealed the complex to be thermally labile, decomposing to a hybrid material of definite composition. Two representative compounds ( 2 and 4 ) were studied as single source molecular precursor for low‐temperature transformation to silica‐based hybrid materials using sol–gel technique. Formation of homogenous methyl‐bonded silica materials (MeSiO3/2) at low sintering temperature was observed. The thermogravimetric analysis of the methylsilica material indicated that silicon‐methyl bond is thermally stable up to a temperature of 400 °C. Reaction of 2 and Al(OPri)3 in equimolar ratio in anhydrous toluene yielded a brown‐colored viscous liquid of the composition [MeSi{ON?C(CH3)C4H3O}3.Al(OPri)3]. Spectroscopic techniques 1H, 13C{1H}, 27Al{1H} and 29Si{1H} NMR spectra of the viscous product indicated the presence of tetracoordination around both silicon and aluminum atoms. On hydrolysis it yielded methylated aluminosilicate material with high specific surface area (464 m2/g). Scanning electron micrography confirmed a regular porous structure with porosity in the nanometric range. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献