Compatibility relationship among reaction equilibria, equivalence principle of reaction approaches, and silicon contamination in semiconductors

This paper discovers some shortcomings in the algorithm for the incorporation of Si into GaAs in the GaAs VPE process. These faults arise from neglecting a link, the compatibility relationship, in chemical thermodynamics. The meaning of said relationship is as follows: In an equilibrium complex system, each species can only contribute one and the same quantity (its equilibrium quantity) to the different equilibria of the various reactions involving it; yet even under this restriction, every equilibrium constant is satisfied, and all the reaction equilibria coexist compatibly in the system. Only by adding the relationship can the equilibrium theory for the complex system be complete. This paper also tells its position in chemical thermodynamics. Such a compatibility concept directly leads to an equivalence principle: In a complex system, a certain species can usually be simultaneously formed by many chemical reactions; when the system has reached equilibrium under fixed environmental conditions, the equilibrium quantity of said species calculated according to each chemical equation of these reactions will be equal and the various reaction approaches will be equivalent, provided that for all the reactants and all the other products of these reactions their equilibrium quantities in the system are respectively taken as corresponding knowns for the calculations, which is extremely useful for seeking a functional relation among the species' equilibrium quantities in a system (Si contamination is one of the examples). Under the guidance of those arguments, the various schools' algorithms for the Si contamination can be uniformized and simplified, and the contamination quantity relation between Si and O, two very important impurities, is found.

On the acid-base stability of Keggin Al-13 and Al-30 polymers in polyaluminum coagulants

The acid-base stabilities of Al-13 and Al-30 in polyaluminum coagulants during aging and after dosing into water were studied systematically using batch and flow-through acid-base titration experiments. The acid decomposition rates of both Al-13 and Al-30 increase rapidly with the decrease in solution pH. The acid decompositions of Al-13 and Al-30 with respect to H+ concentration are composed of two parallel first-order and second-order reactions, and the reaction orders are 1.169 and 1.005, respectively. The acid decomposition rates of Al-13 and Al-30 increase slightly when the temperature increases from 20 to ca. 35 A degrees C, but decrease when the temperature increases further. Al-30 is more stable than Al-13 in acidic solution, and the stability difference increases as the pH decreases. Al-30 is more possible to become the dominant species in polyaluminum coagulants than Al-13. The acid catalyzed decomposition and followed by recrystallization to form bayerite is one of the main processes that are responsible for the decrease of Al-13 and Al-30 in polyaluminum coagulants during storage. The deprotonation and polymerization of Al-13 and Al-30 depend on solution pH. The hydrolysis products are positively charged, and consist mainly of repeated Al-13 and Al-30 units rather than amorphous Al(OH)(3) precipitates. Al-30 is less stable than Al-13 upon alkaline hydrolysis. Al-13 is stable at pH < 5.9, while Al-30 lose one proton at the pH 4.6-5.75. Al-13 and Al-30 lose respective 5 and 10 protons and form [Al-13] (n) and [Al-30] (n) clusters within the pH region of 5.9-6.25 and 5.75-6.65, respectively. This indicates that Al-30 is easier to aggregate than Al-13 at the acidic side, but [Al-13] (n) is much easier to convert to Alsol-gel than [Al-30] (n) . Al-30 possesses better characteristics than Al-13 when used as coagulant because the hydrolysis products of Al-30 possess higher charges than that of Al-13, and [Al-30] (n) clusters exist within a wider pH range.

Construction of 2-D directional filter bank by cascading checkerboard-shaped filter pair and CMFB

In this paper, we propose a new approach to construct a 2-dimensional (2-D) directional filter bank (DFB) by cascading a 2-D nonseparable checkerboard-shaped filter pair and 2-D separable cosine modulated filter bank (CMFB). Similar to diagonal subbands in 2-D separable wavelets, most of the subbands in 2-D separable CMFBs, tensor products of two 1-D CMFBs, are poor in directional selectivity due to the fact that the frequency supports of most of the subband filters are concentrated along two different directions. To improve the directional selectivity, we propose a new DFB to realize the subband decomposition. First, a checkerboard-shaped filter pair is used to decompose an input image into two images containing different directional information of the original image. Next, a 2-D separable CMFB is applied to each of the two images for directional decomposition. The new DFB is easy in design and has merits: low redundancy ratio and fine directional-frequency tiling. As its application, the BLS-GSM algorithm for image denoising is extended to use the new DFBs. Experimental results show that the proposed DFB achieves better denoising performance than the methods using other DFBs for images of abundant textures. (C) 2008 Elsevier B.V. All rights reserved.

Influence of zinc phthalocyanines on photoelectrical properties of hydrogenated amorphous silicon

Composites consisting of hydrogenated amorphous silicon (a-Si: H, inorganic) and zinc phthalocyanine (ZnPc, organic) were prepared by vacuum evaporation of ZnPc and sequential deposition amorphous silicon via plasma enhanced chemical vapor deposition (PECVD). The optical and electrical properties of the composite film have been investigated. The results demonstrate that ZnPc can endure the temperature and bombardment of the PECVD plasma and photoconductivity of the composite film was improved by 89.9% compared to pure a-Si: H film. Electron mobility-lifetime products μτ of the composite film were increased by nearly one order of magnitude from 6.96 × 10~(-7) to 5.08 × 10~(-6) cm~2/V. Combined with photoconductivity spectra of the composites and pure a-Si: H, we tentatively elucidate the improvement in photoconductivity of the composite film.

Concentrations of alkyphenol polyethoxylates entering UK estuaries

Concentrations of the weakly oestrogenic degradation products of alkylphenol polyethoxylate (APE) surfactants (nonylphenol, octylphenol, nonylphenol monoethoxylate and nonylphenol diethoxylate) were measured in water and sediments from British rivers and estuaries collected during 1994 and 1995. In addition, a series of samples of tissues of wild fish from the River Aire, and from a laboratory dosing experiment were analysed for alkylphenols, to assess the degree of bioaccumulation of these compounds. Measurable concentrations of APE residues were recorded in the River Aire (15–76 μg/l total extractable alkylphenols), the River Mersey (6–11 μg/l) and the Tees estuary (up to 76 μg/l). These levels exceed, or are close to, the no observed effect concentration for the induction of vitellogenesis in caged trout (5–20 μg/l total extractable alkylphenols), and may be sufficient to exert an oestrogenic effect on fish populations in these areas. A sediment sample from Bingley on the River Aire contained 15 μg/g (dry weight) nonylphenol, and concentrations in sediments from the Tees and Mersey estuaries exceeded 1 μg/g. These rivers receive a variety of trade waters via sewage treatment works (STW) effluents containing significant concentrations of APE. Elsewhere, concentrations in water and sediments were near or below limits of detection and biological effects are unlikely, suggesting that any oestrogenic effects observed in sewage outfalls and rivers not directly impacted by APE-containing trade-waters may be caused by other chemicals. Analysis of samples of trout muscle taken from a tank dosed at 65 μg/l nonylphenol indicated a bioaccumulation factor of between 90 and 125 after 3 weeks exposure. Samples of wild fish from the River Aire contained up to 0.8 μg/g nonylphenol in the muscle, a tissue bioaccumulation factor of approximately 50 relative to measured concentrations in water samples. A series of fish samples taken from offshore for food quality assurance purposes contained no detectable levels of APE residues (0.05–0.1 μg/g nonylphenol).

Strengthening carbon deposition of polyolefin using combined catalyst as a general method for improving fire retardancy

Combination of Ni2O3 and solid acid with Bronsted acid sites and Lewis acid sites (such as HZSM-5 and H-beta) could dramatically improve fire retardancy of polyolefin, including polypropylene and linear low-density polyethylene. This is mainly attributed to the formation of a large amount of residual char from degradation products of polyolefin in the intermediate stage of combustion. Thus, the amount of flammable components diffusing into the flame zone was small.

Studies on the stability of diester-diterpenoid alkaloids from the genus Aconitum L. by high performance liquid chromatography combined with electrospray ionisation tandem mass spectrometry (HPLC/ESI/MSn)

The stability of diester-diterpenoid alkaloids (DDA) from plants of the genus Aconitum L. has been studied in different solvents and pH buffers. The HPLC/ESIMS method for analysing the concentration of DDA was established and DDA's decomposition products were elucidated by HPLC/ESI-MS/MSn. In different solvents, e.g. dichloromethane, ether, methanol and distilled water, the decomposition pathways of DDA are quite different and their difference in stabilities depends on the difference of their structures, in which substituents at the N atom and substituents at C-3 are different. The pyrolytic products of DDA, such as deacetoxy aconitine-type alkaloids, have been observed in the above solvents, whereas 8-methoxy-14-benzoyl aconitine-type alkaloids have been obtained only in methanol.

Promoting carbonization of polypropylene during combustion through synergistic catalysis of a trace of halogenated compounds and Ni2O3 for improving flame retardancy

The effect of combination between a trace of halogenated compounds (such as ferric chloride and ammonium bromide) and Ni2O3 particles on the carbonization of polypropylene (PP) was investigated during combustion. The results showed a synergistic catalysis of combined halogenated compounds with Ni2O3 in promoting the formation of the residual char during combustion. The investigation on the promotion mechanism showed that halide radical releasing from halogen-containing additives worked as a catalyst to accelerate dehydrogenation-aromatization of degradation products of PR which promote the degradation products to form the residual char catalyzed by nickel catalyst.

Combination of Carbon Nanotubes with Ni2O3 for Simultaneously Improving the Flame Retardancy and Mechanical Properties of Polyethylene

Effects of multiwalled carbon nanotubes (MWCNTs) and Ni2O3 on the flame retardancy of linear low density polyethylene (LLDPE) have been studied. A combination of MWCNTs and Ni2O3 showed a synergistic effect in improving the flame retardancy of LLDPE compared with LLDPE composites containing MWCNTs or Ni2O3 alone. As a result, the peak value of heat release rate measured by cone calorimeter was obviously decreased in the LLDPE/MWCNTs/Ni2O3 Composites. According to the results from rheological tests, carbonization experiments, and structural characterization of residual char, the improved flame retardancy was partially attributed to the formation of a networklike structure due to the good dispersion of MWCNTs in LLDPE matrix, and partially to the carbonization of degradation products of LLDPE catalyzed by Ni catalyst originated from Ni2O3, More importantly, both viscoelastic characteristics and catalytic carbonization behavior of LLDPE/MWCNTs/Ni2O3 composites acted in concert to result in a synergistic effect in improving the flame retardancy.

The combined catalytic action of solid acids with nickel for the transformation of polypropylene into carbon nanotubes by pyrolysis

The effects of both organically modified montmorillonite (OMMT) and Ni2O3 on the carbonization of polypropylene (PP) during pyrolysis were investigated. The results from TEM and Raman spectroscopy showed that the carbonized products of PP were mainly multiwalled carbon nanotubes (MWNTs). Surprisingly, a combination of OMMT and Ni2O3 led to high-yield formation of MWNTs. X-ray powder diffraction (XRD) and GC-MS were used to investigate the mechanism of this combination for the high-yield formation of MWNTs from PP. Bronsted acid sites were created in degraded OMMT layers by thermal decomposition of the modifiers. The resultant carbenium ions play an important role in the carbonization of PP and the formation of MWNTs. The degradation of PP was induced by the presence of carbenium ions to form predominantly products with lower carbon numbers that could be easily catalyzed by the nickel catalyst for the growth of MWNTs. Furthermore, carbenium ions are active intermediates that promote the growth of MWNTs from the degradation products with higher carbon numbers through hydride-transfer reactions. The XRD measurements showed that Ni2O3 was reduced into metallic nickel (Ni) in situ to afford the active sites for the growth of MWNTs.

Polypropylene as a carbon source for the synthesis of multi-walled carbon nanotubes via catalytic combustion

Multi-walled carbon nanotubes (MWCNTs) were efficiently synthesized by catalytic combustion of polypropylene (PP) using nickel compounds (such as Ni2O3, NiO, Ni(OH)(2) and NiCO3 (.) 2Ni(OH)(2)) as catalysts in the presence of organic-modified montmorillonite (OMMT) at 630-830 degrees C. Morphologies of the sample undergoing different combustion times were observed to investigate actual process producing MWCNTs by this method. The obtained MWCNTs were characterized by X-ray diffraction (XRD), transmission electron microscope and Raman spectroscopy. The yield of MWCNTs was affected by the composition of PP mixtures with OMMT and nickel compounds and the combustion temperature. The proton acidic sites from the degraded OMMT layers due to the Hoffman reaction of the modifiers at high temperature played an important role in the catalytic degradation of PP to supply carbon sources that are easy to be catalyzed by nickel catalyst for the growth of MWCNTs. The XRD measurements demonstrated that the nickel compounds were in situ reduced into the Ni(0) state with the aid of hydrogen gas and/or hydrocarbons in the degradation products of PP, and the Ni(O) was really the active site for the growth of MWCNTs. The combination of nickel compounds with OMMT was a key factor to efficiently synthesize MWCNTs via catalytic combustion of PP.

Hydrogel of biodegradable cellulose derivatives. I. Radiation-induced crosslinking of CMC

Radiation crosslinking of carboxymethylcellulose (CMC) with a degree of substitution (DS) from 0.7 to 2.2 was the subject of the current investigation. CMC was irradiated in solid-state and aqueous solutions at various irradiation doses. The DS and the concentration of the aqueous solution had a remarkable affect on the crosslinking of CMC. Irradiation of CMC, even with a high DS, 2.2 in solid state, and a low DS, 0.7 in 10% aqueous solution, resulted in degradation. However, it was found that irradiation of CMC with a relatively high DS, 1.32, led to crosslinking in a 5% aqueous solution, and 20% CMC gave the highest gel fraction. CMC with a DS of 2.2 induced higher crosslinking than that with a DS of 1.32 at lower doses with the same concentration. Hence, it was apparent that a high DS and a high concentration in an aqueous solution were favorable for high crosslinking of CMC. It is assumed that; high radiation crosslinking of CMC was induced by the increased mobility of its molecules in water and by the formation of CMC radicals from the abstraction of H atoms from macromolecules in the intermediate products of water radiolysis. A preliminary biodegradation study confirmed that crosslinked CMC hydrogel can be digested by a cellulase enzyme. (C) 2000 John Wiley & Sons, Inc.

Gas-phase ion - Molecule reactions of neutral C-60 with the plasmas of alkyl methyl ethers and primary alcohols

The gas-phase ion-molecule reactions of C-60 with the methoxymethyl ion [CH3O=CH2](+) and the 1-hydroxyethyl ion [CH3CH=OH](+) generated under the self-chemical-ionization (self-CI) conditions of alkyl methyl ethers and primary alcohols were studied in the ion source of a mass spectrometer. The adduct ions [C60C2H5O](+) and protonated molecules [C60H](+) were observed as the major products of C-60 with the plasma of alkyl methyl ethers. On the contrary, the reactions of C-60 With the plasmas of primary alcohols produced few corresponding adduct ions. The AM1 semiempirical molecular orbital calculations were carried out on 14 possible structures. The calculated results showed that the most stable structure among the possible isomers of [C60C2H5O](+) is the [3+2] cycloadduct. According to experimental and theoretical results, the pathway for the formation of the adduct was presented.

Electrocatalytic mechanism for formaldehyde oxidation on the highly dispersed gold microparticles and the surface characteristics of the electrode

Electrocatalytic mechanism for the electrochemical oxidation of formaldehyde (HCHO) on the highly dispersed Au microparticles electrodeposited on the surface of the glass carbon (GC) electrode in the alkaline Na2CO3/NaHCO3 solution and the surface characteristics of the Au microparticle-modified glass carbon (Au/GC) electrode were studied with in situ FTIR spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the final products of HCHO oxidation is HCOO- at the Au/GC electrode and CO2 at the bulk Au electrode. The difference may be ascribed to the different surface characteristics between the Au/GC electrode and the bulk Au electrode. (C) 1999 Elsevier Science B.V. All rights reserved.

Cleavage of nucleotides by lanthanide metal complexes

The present work revealed that the praseodymium( II ) complex of 2-carboxyethylgermanium sesquioxide (Ge-132) promotes the hydrolysis of the phosphodiester linkages of 3',5'-cyclic adenosine monophosphate (cAMP), 3' , 5'-cyclic deoxyadenosine monophosphate (dcAMP), 5'-adenosine monophosphate(5'-AMP) and 5'-deoxyadenosine monophosphate (5'-dAMP) under mild conditions. Both cAMP and dcAMP were hydrolyzed site-specifically, yielding predominantly 3'-monophosphates, the main products of the cleavage of 5'-AMP and 5'-dAMP included adenosine (Ado). deoxyadenosine (dAdo) and free phosphates respectively. A hydrolytic mechanism was proposed for cAMP, dcAMP, 5'-AMP and 5'-dAMP.