Luminescence in Porous Silicon—Surface vs. Bulk

The mechanism of luminescence in porous silicon still remains poorly understood. The main point of controversy is whether the luminescence is due to recombination in the quantum size structures that constitute porous silicon or whether it is dominated by surface recombination. In this paper, we present evidence that emphasises the role that surface recombination plays in the luminescence of porous silicon. In this framework, we also attempt to reconcile the resonant luminescence data (which argues for bulk recombination) with our results.     

Synthesis,NMR Spectral and DFT Studies of Styryl Imidazole Derivatives—Nano-SiO2 as an Efficient Catalyst

A series of novel styryl imidazole derivatives has been designed and synthesized using nano-SiO₂ as an efficient catalyst. Synthesized compounds have been characterized by ¹H and ¹³C-NMR spectral studies. The significant features of this nanocatalyst are high product yield, short reaction times and a vast range of substrates usage. Proton and ¹³C chemical shifts of the synthesized compounds were calculated. Single crystal XRD analysis has been carried out to confirm the structure of MDPI (1-(3-methoxyphenyl)-4, 5-dimethyl-2-phenyl-1H-imidazole) and it shows the imidazole ring is essentially planar and triclinic crystal. Optimization of compound MDPI was performed by DFT at B3LYP/6-31G (d, p) using Gaussian-03. Imidazole derivatives were used to construct highly sensitive fluorescent chemosensors for sensing of metal ions.

     

Laplacian Growth Models for Porous Silicon Formation—Stability Analysis

We develop a Laplacian model of interface growth which includes basic features of the anodisation of silicon in hydrofluoric acid. Our aim is to find mechanisms for the characteristic properties of porous silicon formation, such as the transition from electropolishing to pore formation and the typical pore distance. The local etching rate of the interface between the semiconductor and the electrolyte is determined by the local current density. We model the diffusive transport of charge carriers in the semiconductor and of reactants in the electrolyte including the basic features of the electrochemical reaction at the interface. A linear stability analysis of a flat and planar interface is performed in order to study the initial state of pore formation.     

The Mechanism of Silicon and Silicon Carbide Making Carbon—containing Materials Antioxidize

The paper analyses redox reactions of an-tioxidants Si and SiC ete at different positions in the course of oxidation of carbon-containing materials,It is pointed out that redox reaction of antioxidants in oxidized-zone plays a very important part in antioxidation of carbon-con-taining materials,The reason why SiC can make carbon-containing material antioxide at thermodynamic temperature has been ex-plained,Experiment proves that antioxidants in oxidized zone can make carbon-containing materils antioxidize.     

Structure of Coreless, Long Silicon Carbide Fibres and Aluminum—SiC Composites

Using electron microscopic, x-ray, and sorption methods, the internal structure, surface, and porosity of coreless silicon carbide fibres and composites were investigated. A model of the interaction at the aluminum melt —SiC fibre interface was proposed. The effect of low-temperature annealing on the structure and properties of domestic and Japanese coreless silicon carbide fibres was observed. The reaction rate in composites reinforced with domestic annealed fibres decreased.     

Historical Background of the Interface—Studies and Theories

This paper is a historical review of the many theories of the interface which were proposed during the period 1947 up to 1964. The evidence for and against these theories are discussed.     

Study on the Si–Si Vibrational States of the Near Surface Region of Porous Silicon

The Si–Si vibrational states near the surface region of porous silicon has been characterized using Fourier Transform Infrared Spectroscopy (FTIR) due to its enlarged surface area. By means of anodic etch and oxidization experiments, two Si–Si vibration modes of porous silicon have been identified as near the surface regions and in the bulk, respectively. The intensity of absorption peak at 620 cm^–1, which originates from the Si–Si bonds vibrations on the surface and near surface regions of porous silicon, is found to vary depending on the length of etch and degree of oxidation of porous silicon, which exists before etching and is recovered again after fully oxidation. The peak of 610 cm^–1 doesn't change throughout the oxidation experiment, and to be assigned for Si–Si bond vibrations in the bulk. With an extra irradiation of Nd:Yag laser on the PS sample the Raman and FTIR spectra reveal a red shift. These results can give an interpretation to explain the different phenomenon of Si–Si vibrations of Raman and FTIR spectroscopy.     

Synthesis and Thermal Decomposition Studies of Silicon (IV) Compounds with N,N’-Bis(Salicylidene)Ethylenediimine

The silicon (IV) compounds possessing SiN₄O₂ (6), SiN₂O₂C₂ (7, 8), SiN₂O₂CCl (9) and SiN₄O₄ (10) coordinating frameworks have been synthesized in high yield by the reaction of the O,N,N,O- donor salen-type ligand N,N’-bis(salicylidene)ethylenediimine L with different silanes i.e. diethoxydiisocyanatosilane-(C₂H₅O)₂Si(NCO)₂ 1, dichlorodiphenylsilane-Ph₂SiCl₂ 2, dichloromethyl- phenylsilane-MePhSiCl₂ 3, trichlorophenylsilane-PhSiCl₃ 4 and silicon tetrachloride-SiCl₄ 5. The compounds 6–10 have been characterized by elemental analysis, IR, ¹H, ¹³C and ²⁹Si NMR and mass spectrometry. The decomposition reactivity of these compounds has been studied using a Thermal Gravimetric Analyzer (TGA) at a heating rate of 10°C/minute in an inert atmosphere.     

Nitridation Behaviour,Microstructure and Proerties of Si—SiC Compostites Seeded with Morphologically Regulated β—Silicon Nitride Crystals

Nitridation of Si-SiC compacts ,containing β-Si3N4 single crystals as seed ,showed a higher yield of nitride with increase of the seed content,Samples containing seed with the largest aspect-ratio gave the best nitridation results.The evolution of the large epitaxially-grown grains,from the seed( as nucleus),during the subsequent liquid phase sintering process,gave ,rise to a bi-modal microstructure,The population of large grains was found to inrease with the volume of added seed.Samples containing 3 volume % exhibited the best mechanical properties,Fracture toughness of the sintered reaction bonded silicon nitride showed improvement in excess of 35% compared to the baselince Si3N4.     

Are Nanosilica,Potassium Silicate and New Soluble Sources of Silicon Effective for Silicon Foliar Application to Soybean and Rice Plants?

Silicon - Foliar application of silicon (Si) is an effective way of supplying this beneficial element to plants. The emergence of new potential liquid sources for foliar application requires...     

Design,Synthesis, and Self-Assembly Studies of a Suite of Monodisperse,Facially Amphiphilic,Protein–Dendron Conjugates

The custom design of protein–dendron amphiphilic macromolecules is at the forefront of macromolecular engineering. Macromolecules with this architecture are very interesting because of their ability to self-assemble into various biomimetic nanoscopic structures. However, to date, there are no reports on this concept due to technical challenges associated with the chemical synthesis. Towards that end, herein, a new chemical methodology for the modular synthesis of a suite of monodisperse, facially amphiphilic, protein–dendron bioconjugates is reported. Benzyl ether dendrons of different generations (G1–G4) are coupled to monodisperse cetyl ethylene glycol to form macromolecular amphiphilic activity-based probes (AABPs) with a single protein reactive functionality. Micelle-assisted protein labeling technology is utilized for site-specific conjugation of macromolecular AABPs to globular proteins to make monodisperse, facially amphiphilic, protein–dendron bioconjugates. These biohybrid conjugates have the ability to self-assemble into supramolecular protein nanoassemblies. Self-assembly is primarily mediated by strong hydrophobic interactions of the benzyl ether dendron domain. The size, surface charge, and oligomeric state of protein nanoassemblies could be systematically tuned by choosing an appropriate dendron or protein of interest. This chemical method discloses a new way to custom-make monodisperse, facially amphiphilic, protein–dendron bioconjugates.     

Development of Semi—Graphite Carbon—Silicon Carbide Brick and Its Application in Slag Forming Zone of Large—sized Blast Furnace

Based on the damage mechanism of the lining at the slag forming zone of the blast furnace and the charactieristics of various refractory ma-terials,the methods to increase the service life of the lining at the slag forming zone have been found:(1) to improve the capacity of the blast furnace brick lining subjet to heat impact;(2) to reduce the working side temperature of the brick lining.On this basis,the semi-graphitized ,high temperature electrically calcined anthracite and silicon carbide etc ,were used as the main raw materials,Through a lot of experiments the proper raw material mix and grain size compo-sition were determined,In addition ,a suitable amount of additives and binders was added.After high pressur forming,high temperature firing and grinding ,the semi-graphitic carbon-silicon carbide bricks with close dimension tler-ances and ideal physical and chemical properties have been made.They have been applied in some blast furnaces,such as No.11(2580 m^3) and No.6(1050 m^3) blast furnaces etc.at Anshan Iron and Steel Company,and the problem of short service life at slag forming zone of blast furnace has been solved.     

Complexation of Tolane by Fluorinated Organomercurials—Structures and Luminescence Properties of an Unusual Class of Supramolecular π-Coordination Polymers

The interaction of the Hg(II) derivatives bis(pentafluoro)phenyl mercury (1), (pentafluoro)phenyl mercury chloride (2) and trimeric perfluoro-ortho-phenylene mercury (3) with tolane (diphenylacetylene) in CH₂Cl₂ leads to the formation of [1·tolane], [2 ₂·tolane], and [3·tolane·CH₂Cl₂]. These adducts have been characterized by elemental analysis, X-ray crystallography, and luminescence spectroscopy. In the solid state of these adducts, the tolane molecules interact with the molecules of 1, 2 and 3 via secondary Hg–π interactions and arene–fluoroarene interactions. As a result of an external mercury heavy atom effect, adducts [1·tolane] and [2 ₂·tolane] are phosphorescent at room temperature.     

Synthesis and Spectroscopic Studies of DGEBA–Grafted Polyaniline

N-grafted polyaniline with diglycidyl ether bisphenol A (DGEBA) was synthesized via anionic copolymerization technique. Metalation reaction was performed to cause grafting to occur between DGEBA with emeraldine salt polyaniline (PANI-ES) and leucoemeraldine base polyaniline (PANI-LEB), respectively. Fourier transform infrared (FTIR), ¹³C-nuclear magnetic resonance (NMR), and ¹H-NMR spectroscopies and gel permeation chromatography (GPC) were performed to characterize the PANI-EB-g-DGEBA and PANI-ES-g-DGEBA copolymers. The gel content of the resultant copolymers was determined by Soxhlet extraction. Results of spectroscopic studies showed that grafting took place together with the side reaction, cross-linking, and DGEBA homopolymerization. Oxidation states of PANI were found to influence the gel content and molecular weight distribution of copolymers produced.     

Synthesis and Spectral Studies of CdTe–Dendrimer Conjugates

In order to couple high cellular uptake and target specificity of dendrimer molecule with excellent optical properties of semiconductor nanoparticles, the interaction of cysteine-capped CdTe quantum dots with dendrimer was investigated through spectroscopic techniques. NH₂-terminated dendrimer molecule quenched the photoluminescence of CdTe quantum dots. The binding constants and binding capacity were calculated, and the nature of binding was found to be noncovalent. Significant decrease in luminescence intensity of CdTe quantum dots owing to noncovalent binding with dendrimer limits further utilization of these nanoassemblies. Hence, an attempt is made, for the first time, to synthesize stable, highly luminescent, covalently linked CdTe–Dendrimer conjugate in aqueous medium using glutaric dialdehyde (G) linker. Conjugate has been characterized through Fourier transform infrared spectroscopy and transmission electron microscopy. In this strategy, photoluminescence quantum efficiency of CdTe quantum dots with narrow emission bandwidths remained unaffected after formation of the conjugate.     

Studies on Mechanical and Thermal Properties of Ternary Blends of Polyethylenes Having Fixed Percentage of High-Density Polyethylene—II

Six film samples of varying compositions of low-density polyethylene (LDPE); (20–45 wt%) and linear low-density polyethylene (LLDPE); (25–45 wt%) having a fixed percentage of high-density polyethylene (HDPE) at 30 wt% have been extruded by melt blending in a single screw extruder (L/D ratio = 20:1) of uniform thickness of 2 mil. The tensile strength and elongation at break have been found to increase up to 40 wt% with LLDPE addition, starting from 25 wt% LLDPE, in the blends and then decreased. The blend sample containing 30 wt% LDPE, 40 wt% LLDPE, and 30 wt% HDPE (sample C-300) was found to be more thermally stable blend amongst all the prepared blends. In most of the blends, two exothermic peaks appeared that showed the formation of immiscible blend systems; this was further confirmed by scanning electron microscopic (SEM) analysis.     

Studies of surface chemistry — physico-chemical aspects of porous silicate surfaces

A series of porous silicates are prepared by destabilization (precipitation) of an alkaline silicate with a polyvalent metal salt in aqueous medium. The experimental conditions are optimised in such a manner as to obtain almost all particles with precise control on their size. On an average 98 – 99% of the product is in the particle size range −300 +350 BSS mesh. For the source of silica and alumina, several starting materials of both chemical and natural sources have been used in the synthesis. The porous silicates thus developed are exhaustively characterised for bulk density, oil absorption, specific gravity, pore volume, surface area and particle size distribution. The results obtained show that the surface properties of porous silicates vary over a wide range, although the chemical composition of the products remains practically the same. It is discussed that mode of preparation, the reactants employed and the key process variables ultimately decide the surface properties and the end-use applications.     

Chemical Analysis Method for Magnesia and Magnesia-Alumina Refractories——Gravimetric-Molybdenum Blue Photometric Method for Determination of Silicon Dioxide Content

GB/T 5069.3-2001 1 Scope This standard specifies the gravimetric-molybdenum blue photometric method for determination of silicon dioyide content.This standard is used for the determination of silicon dioxide content of magnesia and magnesia-alumina refractory materials. Determination range: >5.00%.     

Dissolved Silicon and Its Origin in Belgian Beers—A Multivariate Analysis

Beer is a quintessential part of Belgian heritage. We performed a detailed analysis of factors controlling Si content in Belgian beers as a case study to coincide with the 2011 IBiS meeting in Antwerp (Belgium). Beer is one of the richest dietary sources of Si. Three decades of research have yielded evidence of a role for Si in human physiology: it plays an essential role in bone mineral density and reduces the biological availability of aluminium. We analysed 119 Belgian beers: highest dissolved Si concentrations were found in high fermentation, traditionally brewed ales. Concentrations ranged between 214 and 2,071 μmol L^???1. This is probably due to the complexity and length of the brewing procedure: longer, more complicated processing and presence of brewing sediment in the bottle allows more Si to dissolve out of the base products like hop, barley or even rice. As a side effect of fermentation, alcohol content was related to Si content.