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The purpose of this research is to enhance the performance of self-compacting concrete (SCC) to make it a more sustainable alternative to traditional concrete. SCC serves the purpose in harsh environments, therefore, requires protection against de-icing agents and harmful saline environments. This paper reports the results from a laboratory study evaluating the efficacy of two impregnants; pure-silane and water-based silane. Both materials were applied on dry and wet SCC specimens manufactured with high and medium doses of superplasticizer. When treatment is applied on dry samples, a significant reduction in chloride penetration was noticed. However, the impregnants were less effective when applied on specimens subjected to intermediate and long-term exposure to water. In dry conditions, pure-silane performed better than the water-based silane, although they had a similar performance when applied on wet specimens. In addition, increasing the internal moisture content has shown an adverse effect on the efficacy of both materials. Key words: self-compacting concrete, protection, impregnation, moisture content, sorption. Cette recherche a pour but d'ameliorer le rendement du beton autocompactant (BAC) pour en faire une solution de rechange plus durable au beton traditionnel. Le BAC fait l'affaire dans des environnements difficiles et par consequent exige une protection contre les agents de deglacage et les environnements salins nuisibles. Cet article presente les resultats d'une etude de laboratoire evaluant l'efficacite de deux substances d'impregnation, soit le silane pur et le silane a base d'eau. Les deux materiaux ont ete appliques sur des specimens de BAC secs et humides fabriques avec des doses elevees et moyennes de superplastifiant. Lorsque le traitement est applique sur des echantillons secs, une reduction significative de la penetration de chlorure a ete remarquee. Toutefois, les substances d'impregnation etaient moins efficaces lorsqu'elles etaient appliquees sur des specimens soumis a une exposition intermediaire et a long terme a l'eau. Dans des conditions seches, le silane pur a donne de meilleurs resultats que le silane a base d'eau, bien qu'il ait eu un rendement similaire lorsqu'il a ete applique sur des specimens humides. En outre, l'augmentation de la teneur en humidite interne a montre un effet nefaste sur l'efficacite des deux materiaux. [Traduit par la Redaction] Mots-cles : beton autocompactant, protection, impregnation, teneur en humidite, sorption., 1. Introduction Self-compacting concrete (SCC) has been implemented in the construction industry for a long time since it was first introduced in Japan in the 1980s (Loukili 2011). Many countries, [...]

A low-temperature size-independent method for modifying the surface chemistry of the silicon nanocrystal (SiNC) surface is reported. Wilkinson's catalyst has been applied to accelerate the dehydrogenative coupling reaction between organosilane molecules and hydride-terminated SiNCs. Two strategies and multiple organosilanes were evaluated to study surface modification efficiency. During the investigations, it was determined that surface functionalization efficiency showed some dependence upon the organic modifier in question. The comparatively low reactivity of octadecyldimethyl silanes may result from the formation of 'Si-Rh-Si' intermediates hindered by the steric bulk of the silanes when reacted with activated SiNCs. Quenching of the SiNC-based photoluminescence is observed and the origin of this phenomenon has been attributed to the present of trace rhodium on SiNCs detected using X-ray photoelectron spectroscopy. Key words: silicon nanocrystals, size-independent functionalization, Wilkinson's catalyst, surface modification, dehydrocoupling. Une methode a basse temperature independante de la taille servant a modifier la chimie de surface de nanocristaux de silicium (NCSi) est decrite dans le present article. Le catalyseur de Wilkinson a ete employe pour accelerer la reaction de couplage deshydrogenant entre les molecules d'organosilane et les NCSi composes d'hydrures terminaux. Deux strategies et de nombreux organosilanes ont ete evalues pour etudier le rendement de modification de la surface. Au cours de cette etude, il a ete determine que le rendement de fonctionnalisation de la surface presentait une certaine dependance a l'agent modificateur en question. La reactivite relativement faible des octadecyldimethylsilanes peut resulter de la formation d'intermediaires << Si-Rh-Si >>, entravee par l'encombrement sterique des silanes lorsqu'ils reagissent avec les NCSi actives. L'extinction de la photoluminescence associee aux NCSi est observee et l'origine de ce phenomene est attribue a la presence de traces de rhodium sur les NCSi detectees a l'aide de la spectrometrie photoelectronique X. [Traduit par la Redaction] Mots-cles : nanocristaux de silicium, fonctionnalisation independante de la taille, catalyseur de Wilkinson, modification de la surface, deshydrocouplage., Introduction Since their discovery 30 years ago, semiconductor nanocrystals, or quantum dots (QDs), have received unprecedented attention because of their unique physical and chemical properties. (1-4) Our understanding and the [...]

Quantum chemical calculations were used for examining [S.sub.H]2 reaction between methyl radical and methylsilane. Findings reveal the favorable proceeding of the backside mechanism for the [S.sub.H]2 reaction in a wide range of C-Si-C angles.

A comprehensive study of interaction potentials of the prototype silane dimer in terms of HF, MP2 and DFT methods is presented. The studies provide better understanding effects of the repulsion exponent, the binding energy, the equilibrium bond length, and the asymptotic behavior of the intermolecular potentials.

The mechanism of excess electron and hole localizations in radical ions of poly(dimethylsilane) (PDMS) is investigated by means of molecular dynamics (MD) and extended Huckel methods. The geometry of PDMS with a regular all-trans form is fully optimized and the localization of the electron and hole is found after thermal activation.

A study was conducted to study the reaction paths of 73 reactions with well-defined transition states that take place during and after the decomposition of methyltrichlorosilane (MTS). The studies provided insight into reaction pathways, Gibbs free energy barriers and thermodynamic properties of the transition states.

A study was conducted to determine the structures and energies of the gas-phase species generated during and after the various unimolecular decomposition reactions of methyltrichlorosilane (MTS). The studies provided insight into reaction enthalpies, heat capacity and entropies, and Gibbs free energies of various species.

Interactions of DMF with hydrosilanes were studied by [sup.29]Si NMR. New resonance signals were observed in the [sup.29]Si NMR spectra of H[Me.sub.2]SiOSi[Me.sub.2]H and some (alkoxy)hydrosilanes for high ratios of concentrations [DMF]/[H-silane] at 25 [degrees]C. The intensities of new signals increased several times at -e0 [degrees]C. It seems that these new resonances correspond to molecular complexes of DMF with hydrosilanes. The role of DMF in the mechanism of dehydrocoupling of hydrosilanes with hydroxylic reagents in the presence of Zn(II) and Cd(II) halides (X = Cl, Br, I) is discussed. Some common features of the reaction mechanism with the mechanism of hydride transfer from the Si--H bond to the carbenium ion are discussed. Key words: hydrosilanes, hydroxylic reagents, reaction mechanism of dehydrocoupling in DMF, [sup.29]Si NMR. Resume : Faisant appel a la RMN du [sup.29]Si, on a etudie les interactions du DMF avec les hydrosilanes. A. 25 [degrees]C et a des rapports eleves des concentrations [DMF]/[H-silane], on a observe de nouveaux signaux de resonance dans les spectres RMN du [sup.29]Si du H[Me.sub.2]SiOSi[Me.sub.2]H et de quelques (alkoxy)hydrosilanes. Les intensites des nouveaux signaux ont augmente a quelques reprises a -60 [degrees]C. Il semble que ces nouvelles resonances correspondent a la formation de complexes moldculaires du DMF avec les hydrosilanes. On discute du role du DMF dans le mecanisme de deshydrocouplage des hydrosilanes avec les reactifs hydroxyles, en presence d'halogenures (X = C1, Br, I) de Zn(II) et de Cd(II). On discute aussi de caracteristiques communes du mecanisme reactionnel avec le mecanisme de transfert d'hydrure de la liaison Si--H a l'ion carbenium. Mots cles : hydrosilanes, reactifs hydroxyles, mecanisme de redaction du deshydrocouplage dans le DMF, RMN du [sup.29]Si. [Traduit par la Redaction]

The recent developments in the synthesis of organosilanols are discussed. The preparative and structural aspects of various types of silanols along with the emerging applications of silanols are reviewed.

Magnetic circular dichroism (MCD) of five peralkylated tetrasilanes (1-5) conformationally constrained to angles ranging from nearly 0[degrees] to 180[degrees] and of the open chain tetrasilane [Si.sub.4][Me.sub.10] (6) shows a clear conformational dependence and permits the detection of previously hidden transitions. In the tetrasilane C[H.sub.2][Si.sub.4][Me.sub.8] (1), with the smallest dihedral angle, comparison of MCD with absorption spectra reveals four low-energy electronic transitions. In the tetrasilanes 2-4, three distinct transitions are apparent. In tetrasilanes 5 and 6, MCD reveals the very weak transition that has been predicted to be buried under the first intense peak and to which the anomalous thermochromism of 6 and other short-chain oligosilanes has been attributed.

We propose a generalized model, based on a simple balance equation, explaining the temperature dependence of the agglomeration time of nanoclusters in Ar-Si[H.sub.4] plasmas. This model allows easy incorporation of specific mechanisms and verification of their effect on particle growth. We consider extra Silane consumption due to back diffusion, an important issue for the laboratory plasma experiments and modeling results interpretation. Index Terms--Complex plasmas, diagnostics, dust, harmonics, plasma CVD, plasma impedance, Silane, temperature dependence.

A one-dimensional fluid model was developed to study the formation of dust nanoparticles in a low-pressure capacitively coupled radio-frequency silane (Si[H.sub.4]) discharge. In this model, the particle balances, the electron energy balance, and the Poisson equation are solved self-consistently. A set of 66 species, including neutrals, radicals, ions, and electrons, are incorporated. A total of 111 reactions are described in the model, comprising electron impact reactions with silanes, neutral-neutral, and ion-neutral reactions. Plasma conditions are typically those used for the deposition of amorphous silicon (a-Si:H). The model includes the formation of silicon hydrides ([Si.sub.n],[H.sub.m]) containing up to 12 silicon atoms. Anion-induced chain reactions are considered to be the main pathway leading to cluster formation. Index Terms--Dusty silane plasma, nucleation.

Gas-phase reactions between silane (SiH4) and water (H2O) are investigated using ab initio calculations at the CCSD(T)/6-311++G//MP2/6-31+G level. It is concluded that providing more energy to the system, SiH4-H2Ocan dissociate atomically and the initial products can further eliminate H2 or H, producing smaller species of molecules SiH-OH, SiH2-O, Si-H2O, and SiO and radicals SiH2-OH, SiH-H2O, HSiO, and HOSi.

Gas-phase reactions between silane (SiH(sub 4)) and ammonia (NH(sub 3)) were investigated using ab initio calculations at the CCSD(T)/6-311++g(super **)//MP2/6-31+G(super *) level. The studies stated that within the energy range of 180 kcal/mol the investigation located 34 equilibrium and 23 transition states on the potential energy surfaces of the Si-N-H systems.

The friction of aromatic silane monolayers with surface forces apparatus (SFA) and friction force microscopy (FFM) in systems with low adhesion (gamma < 3 mN/m) is studied. The friction forces were lower in systems where both contacting surfaces were covered with a monolayer.

The first eight valence excited states of the three conformers of n-Si4Me10, transoid, ortho, and gauche, is described using the mutistate complete active space second-order pertubation theory (MS-CASPT2) method. The results show the dependence of the UV absorption spectrum of the tetrasilanechromophore on the skeletal dihedral angle in terms of avoided crossings of both B and A symmetry states.

The incomplete condensed monosilylated silesesquioxane were reacted with SiCi4 in the presence pf an amine, which yielded the dichloro compounds. These compounds could be hydrolyzed into the corresponding silesesquioxane containing geminal silanols and the acidities were compared with those of other silesesquioxane containing silanol groups.

The site-selective assembly of colloidal polymer particles onto laterally patterned silane layers was studied as a model system for the object assembly process at mesoscale dimensions. The structured silane monolayers on silicon oxide substrates were fabricated by a combination of liquid- and gas-phase deposition of different trialkoxysilanes with a photolithographic patterning technique. By using this method various types of surface functionalizations such as regions with amino functions next to areas of the bare silica surface or positively charged regions of a quaternary ammonium silane surrounded by a hydrophobic octadecylsilane film could be obtained. Furthermore, a triethoxysilane with a photoprotected amino group was synthesized, which allowed direct photopatterning after monolayer preparation, leading to free [NH.sub.2] groups at the irradiated regions. The different silane monolayer patterns were used to study the surface assembly behavior of carboxylated methacrylate particles by optical and scanning electron microscopy. In dependence of the assembly conditions (different surface functionalizations, pH, and drying conditions), a selective preference of the particles for a specific surface type versus others was found. Site-specific colloid adsorption could be observed also on the photosensitive silane layers after local deprotection with light. From the photosensitive silane and positively charged ammonium silane, molecularly mixed monolayers were prepared, which allowed particle adsorption and photoactivation within the same monolayer as shown by fluorescence labeling.

It has been possible to develop an unusual technique for the stereoselective synthesis of homoallylic amines based on addition of allyltrichlorosilanes to benzoylhydrazones. This work is the first to show high selectivities in the reaction of crotylmetals with imines or their analogues.

The homogeneous catalytic hydrosilation-hydrogenation of pyridines is observed in the presence of [Cp.sub.2]Ti[Me.sub.2] (Cp = [[eta].sup.5]-[C.sub.5][H.sub.5]) and CpCp*Ti[Me.sub.2] (Cp* = [[eta].sup.5]-[C.sub.5][Me.sub.5]) as catalysts and using PhSi[H.sub.3] or PhMeSi[H.sub.2] as the source of Si-H. Under appropriate conditions, and with appropriate ring-substitution, good yields of the N-silyldihydropyridine or N-silyltetrahydropyridine products are be obtained. Although complete saturation is not achieved with organosilane alone, carrying out the reaction under moderate [H.sub.2] pressures can give excellent yields of N-silylpiperidines. Under moderate pressures of [H.sub.2], [[[Cp.sub.2]TiH].sub.2] catalyzes rapid H-D exchange between [H.sub.2] and the 2- and 6-positions of [C.sub.5][D.sub.5]N. Under the same conditions, only traces of hydrogenation are observed. This, together with the regioselectivity of 3-picoline hydrosilation-hydrogenation, leads to the conclusion that the key step in the reaction is probably addition of Ti-Si to C=N. Key words: hydrosilation, hydrogenation, pyridines, dimethyltitanocene, catalysis.

Research is presented concerning the use of a microdischarge hollow cathode lamp and vacuum ultraviolet absorption spectroscopy technique to determine the behavior of the hydrogen atoms in 500 MHz, ultrahigh-frequency silane plasma.

Research is presented concerning the photochemistry of a number of o-phenol-containing alkoxyvinylsilanes which were prepared through the hydrosilylation of o-acetoxy arylacetylenes.