Smaller Number Of Carbon Atoms Research Articles

Effects of the addition of multi-walled carbon nanotubes on the microstructure and properties of Ti(C,N)-based cermets prepared by spark plasma sintering

To improve the toughness of Ti(C,N)-based cermets, multi-walled carbon nanotubes (MWCNTs) and nano-WC were added, and spark plasma sintering (SPS) technology was applied. The effects of the addition of MWCNTs on the phase composition, microstructure, and the comprehensive properties of Ti(C,N)-based cermets were investigated. The results show that the cermet (0.4 wt% MWCNTs) prepared by SPS (1350 °C, 16 min, and 35 MPa) has uniform microstructure and excellent comprehensive properties. The hardness and fracture toughness of this sample reach maximum values of HV 3050.29 and 10.90 MPa·m1/2, respectively. Compared with the sample without MWCNTs, the values are increased by 82.57% and 105.66%, respectively. A small number of carbon atoms from the MWCNTs enter the lattice of Ti (C,N) solid solution, which is conducive to improving the bonding ability and high-temperature wettability between MWCNTs and the matrix, thus enhancing the strength and toughness of the matrix materials. The addition of MWCNTs plays a bridging and toughening role at different interfaces. Moreover, the addition of nano-WC is conducive to the plastic flow and particle rearrangement of hard particles at high temperature.

Volumetric and sound speed study of aqueous 1-butanol liquid mixtures at different temperatures

Simultaneous measurements of density and sound speed, at five temperatures, T = (283.15–303.15) K and pressure, P = 0.1 MPa within the miscible composition range were performed in 24 aqueous liquid mixtures of 1-butanol. Composition and temperature effects on different excess molar, and excess partial molar properties such as volume, isobaric expansion and isentropic compression are analysed, in terms of different changes in the hydration and association patterns, across the composition ranges studied. Comparison of the different thermodynamic properties, derived for this system, with those for two aqueous system of smaller number of carbon atoms is made. Limiting excess partial molar volumes, isobaric expansions and isentropic compressions at both ends of the composition range are presented. Limiting partial molar isentropic compression values for 1-butanol, infinitely diluted in water, compare very well with values calculated by the group contribution scheme previously presented by some of us.

Interaction of Humic Acids with Organic Toxicants

Interaction of humic acids with polyaromatic hydrocarbons (PAH) (naphthalene and anthracene) and triazole series fungicides (cyproconazole (CC) and tebuconazole (TC)) is investigated by the method of fluorescence quenching depending on the concentration of substances in solutions and their structural features. Humic acids were modified by mechanochemical activation in a planetary mill. The complex character of intermolecular interactions between PAH and fungicides with humic acids, including donor-acceptor and hydrophobic binding, is established. Thermodynamically stable conformations of biocide molecules were estimated using ChemOffice CS Chem3D 8.0 by methods of molecular mechanics (MM2) and molecular dynamics. Biocide molecules with pH 7 are in energetically favorable position when the benzene and triazole rings are almost parallel to each other. After acidification of solutions to pH 4.5, the CC molecule retains the geometry for which donor-acceptor interactions are possible: the benzene ring in the molecule represents the electron donor, and triazole is the acceptor. In this case, the electron density in CC is redistributed easier, which is explained by a smaller number of carbon atoms between the triazole and benzene rings, unlike TC. As a result, the TC triazole ring is protonated to a greater degree, acquiring a positive charge, and enters into donoracceptor interactions with humic acid (HA) samples. The above-indicated bond types allow HA to participate actively in sorption processes and to provide their interaction with biocides and PAH and hence, to act as detoxifying agents for recultivation of the polluted environment.

A theoretical investigation of the mechanical stability of single-walled carbon nanotube 3-D junctions

The deformation behavior of five types of X-junctions made from ultrathin single-walled carbon nanotubes (SWCNTs) was investigated using molecular dynamics (MD) simulation. Three deformation modes were observed in the X-junctions under uni-axial or bi-axial tensile stresses. If the junction is strong, as is the case with certain (3,3)-(3,3) junctions, then the bonds break at individual nanotubes, rather than at the junction region, and the original bonding structures around the junctions remain. However, for some (3,3)–(3,3) junctions and X-junctions formed by (5,0)–(5,0) nanotubes, the bonds at the junction region break and are reconstructed, which results in the transformation of a 3-D junction into a 2-D type. Either one neck or two necks may be nucleated near the junction. The use of random seed numbers in MD simulations plays an important role in the outcome of the deformation process due to the small number of carbon atoms involved in the junction regions.

Microstructure characterization of nanocrystalline Fe 3C synthesized by high-energy ball milling

Carbide preparation in a conventional route requires a huge instrumentation regarding melting the metal and graphite under vacuum at a very high temperature. However, mechanical milling of powder ingredients at room temperature can easily produce nanocrystalline metal carbides. This article reports the preparation of nanocrystalline Fe 3C by mechanical milling of α-Fe and graphite powders under inert atmosphere at room temperature. Mössbauer spectra of ball-milled powder clearly reveal that the Fe 3C phase is initiated at 3 h of milling and the stoichiometric Fe 3C is formed after 5 h of milling. Further milling up to 8 h results in peak-broadening of X-ray diffraction pattern of Fe 3C phase. Microstructure in terms of different lattice imperfections is characterized employing Rietveld's method of structure refinement. The phase transformation kinetics studied through Rietveld method reveals that a small number of carbon atoms diffuse into α-Fe matrix and Fe 3C phase is formed through the solid-state reaction of nanocrystalline graphite and α-Fe powders during ball milling.

Phenomenological characteristics of cool-flame oxidation of cyclohexane

The phenomenological characteristics of cool flames of cyclohexane are studied. It is shown that cyclohexane flames arise at lower temperatures (beginning at T ≈ 230°C) and lower pressures (lower than 10 torr at T = 290°C) than alkane and alkene flames. The temperature dependence of the lower pressure limit of the cool flame is determined. It is established that, depending on the conditions (p, T, and C6H12/O2 ratio), cool-flame ignition is characterized by a rise and drop of the temperature ΔT or by several peaks imposed on each other. The dependence of the cool-flame structure (for ΔT) on the oxygen content in the reaction mixture is studied. It is shown that the cool flame resulting from cyclohexane oxidation is accompanied by ring opening and formation of products with a smaller number of carbon atoms. It is established that cool flames of cyclohexane are characterized by a negative temperature coefficient.

Precursor biostructures in kerogen matrix revealed by oxidative degradation: oxidation of kerogen from Estonian kukersite

The products of stepwise alkaline permanganate degradation of kerogen from Estonian kukersite are considered as possible derivatives of preserved biostructures of the microfossil G. prisca. The aliphatic component, constituting ca. 25% of the matrix, was oxidized giving n-α,ω-alkyldicarboxylic (C 4–C 15), α-methyldicarboxylic (C 7–C 12, C 14, C 15), branched dicarboxylic (C 5–C 10), and n-alkylmonocarboxylic (C 14–C 18, C 22) acids. When compared with previously studied kerogens, the oxidation products of kukersite differ (short carbon chains <C 20, dicarboxylic acids' maximum shifted towards smaller number of carbon atoms, and a much higher degradation “loss”) indicating that the aliphatic moieties in the kukersite kerogen correspond to unusually short carbon chains with significant alkylsubstitution. The occurrence of such moieties is in agreement with the supposed feature of the aliphatic components of the resistant biopolymer comprising G. prisca cell walls. Hetero- and alicyclic structures constituting ca. 10% of the matrix yielded C 6–C 18 alkyltri- and C 8–C 14 alkyltetracarboxylic acids. The similarities in the distributions of alkyltri- and tetracarboxylic acids (C n tri vs. C n−3 tetra) suggested that the precursor moieties of those acids had the same source. Furthermore, similarities in the distribution of n-α,ω-alkyldicarboxylic and alkyltetracarboxylic acids (C n di vs. C n+1 tetra) may mean that some, at least, of these structures were produced diagenetically from terminally bifunctional alkyl-chains in preserved biopolymers. Alkylsuccinic acids (C 10, C 11 and C 15) and alkylsuccinic acids containing an O-functional group in the alkyl chain (C 11–C 20), were obtained in appreciable yield (ca. 4% w/w of the matrix). Their precursor moieties, although still unknown, were most probably structural building blocks of the microfossil. Benzenediol derivatives, characteristic of kukersites, were not observed as they are not amenable to analysis using the methods employed in this study.

Effect of fatty acid Esters on permeation of ketoprofen through hairless rat skin

Twelve medium to long chain fatty acid Esters (Esters), the total number of carbon atoms of which ranged from 17 to 34, were used to study the effect of the vehicle on the permeation of ketoprofen, and the effect was compared with the case of indomethacin. The solubility of ketoprofen was higher in Esters with a smaller number of carbon atoms. The permeation rate of ketoprofen from the Ester suspension through excised hairless rat skin was proportional to its solubility in the suspension, which was the same in the case of indomethacin. The diffusion constant and partition coefficient were calculated using the computer program MULTI(FILT). The diffusion constant decreased with increasing number of carbon atoms, and the partition coefficient was increased with increasing number of carbon atoms, in both cases of ketoprofen and indomethacin. Esters also penetrated the skin with the concentration of about 10 mg/g, independent of the number of carbon atoms. The Esters in the skin increase the diffusion rate of the drugs, especially in the case of Esters with a small number of carbon atoms. Also the drug solubility in the skin was improved, although the effect was similar for the range of Esters investigated in the present study. Then the permeation rate of ketoprofen and indomethacin increased.

Cladospirones B to I from Sphaeropsidales sp. F‐24′707 by Variation of Culture Conditions

Variation of the culture conditions − static surface cultures in particular − of the fungus Sphaeropsidales sp. (strain F-24′707), which produces cladospirone bisepoxide (1), led to the isolation of eight new spirobisnaphthalenes − the cladospirones B to I (8−15) − together with seven known representatives of this class of secondary metabolites. Cladospirones C (9) and D (11) show antibiotic activity against bacteria and algae. The structures of cladospirone B (8) and E (12) were confirmed by X-ray structure analysis. Cladospirones C (9) and G to I (10, 14−15) represent new members of the spirobisnaphthalene family, thanks to their hydroxylation patterns. Moreover, they underline the extraordinary status of this interesting class of compounds as the most diverse secondary metabolites, allowing for their small number of carbon atoms, described to date. Almost all possible permutations of stereochemistry and oxygen substitution pattern on the C10 skeleton are produced by different fungi.

Excitability and multistability in the electrochemical oxidation of primary alcohols

Results are presented from experiments on the electrocatalyzed oxidation of 1-butanol at a Pt electrode conducted under conditions of constant current in both acid and NaOH solutions. Several nonlinear behaviors are characterized. In acid solution, the oxidation of 1-butanol exhibits excitability, i.e. a small perturbation induces a large amplitude excursion with mixed time scales before the system returns to stationary behavior. It is argued that excitability reveals that oxides directly partake in the oxidation process. Butanol oxidation also exhibits a tristable response in acid solution in which three different stationary states exist under the same conditions. A different tristability also occurs in which an oscillatory state coexists with two stationary states. Instead of a tristable response, the oxidation of 1-butanol displays a bistable response in NaOH solution. Results are compared with those obtained for alcohols with a smaller number of carbon atoms, ethanol and methanol. In view of results from potential controlled experiments, the results of the current controlled experiments reveal what can be considered nonintuitive current-potential relations. Relations among the observed nonlinear behaviors, current-potential relations, and mechanisms, as well as the differences between results obtained in NaOH solution and those obtained in acid solution are discussed.

Sensitive determination of quaternary ammonium salts by extraction-spectrophotometry of ion associates with bromophenol blue anion and coextraction

The chloroform extraction behaviour of the ion-associates of a Bromophenol Blue anion (BPB 2− :blue) with quaternary ammonium cations (Q +) was examined. During extraction using Q + with a small number of carbon atoms (Nc) or using Q + with a large Nc and high concentrations of BPB 2−, the addition of a proton to BPB 2− gives HBPB − (yellow), which can be extracted as the 1:1 ion-associate Q + ·HBPB − ( ϵ = 2.5 × 10 4 1 mol −1 cm −1 at λ max = 416 nm) with Q + into chloroform. At high BPB 2− concentrations, the extraction level of the 1:2 ion-associate of one Q +, (Q +) 2 ·BPB 2− ( ϵ = 9.4 × 10 4 1 mol −1 cm −1 at λ max = 608 nm) was elevated by the presence of other Q + and the sensitivity and the selectivity for Q + determination was increased by using co-extraction and a wavelength of 608 nm.

Electrooxidation and reduction of propylenecarbonate, ethylene carbonate and 1,2-propanediol in aqueous acid solution—A comparative study using on-line MS and isotope labelled electrolytes

The electrooxidation and reduction of propylenecarbonate, ethylenecarbonate and 1,2-propanediol is investigated at porous platinum electrodes in aqueous acid electrolytes by a combination of potentiodynamic and potential step techniques with on-line MS (DEMS) for detection of volatile products. Propylenecarbonate forms (oxidatively) only CO 2 above 0.5 V vs. rhe, without the contribution of a bulk reaction being evidenced by transient experiments. In addition, CO 2 is also produced around 0.3 V vs. rhe during anodic and cathodic scans of cyclic voltammograms. In order to investigate the origin of these signals, a H 2O 18 containing electrolyte was used. The electrooxidation of ethylenecarbonate to CO 2 also starts at 0.5 V vs. rhe, showing a small contribution of a bulk reaction in addition to the oxidation of the adsorbate. At 0.3 V vs. rhe, CO 2 production is significantly decreased in comparison to propylenecarbonate. In contrast to the behaviour of the carbonates, the electrooxidation of 1,2-propanediol is dominated by two independent bulk reactions. One reaction pathway forms CO 2, while the other produces aldehydes. The three compounds studied show fewer differences during electroreduction, forming hydrocarbons via adsorbates below 0.15 V vs. rhe. Hydrocarbons are produced having the same as or a smaller number of carbon atoms than the original compounds with the exception of 1,2-propanediol, which additionally forms butane. Ethanes and propanes with a high number of deuterium atoms are formed during electroreduction of propylenecarbonate as well as 1,2-propanediol in D 2SO 4/D 2O containing solutions. Under these conditions, 1,2-propanediol produces butanes with only a small number of deuterium atoms.

Annealing graphite-like structures. A Monte Carlo-quantum chemical study

A standard Monte Carlo procedure, known as simulated annealing, and a simple and very popular all-valence electron quantum chemical Hamiltonian, namely the extended Hückel Hamiltonian, have been combined. To test this combination of two very simple procedures, we study systems containing a small number of carbon atoms. The test is thought to be of particular interest because of the nature of the carbon atom which can yield a number of different bonds.

Hydrogen Peroxide Oxidation. I. A New Selenium Dioxide-Catalyzed Synthesis of Carboxylic Acids from Aliphatic Ketones Accompanied by Rearrangement of Alkyl Groups

Abstract 1) Selenium dioxide catalyzed oxidation of aliphatic ketones with hydrogen peroxide gave carboxylic acids which were produced by the rearrangement of the alkyl group as shown by equation 5. 2) Acetone, methyl ethyl ketone, methyl n-propyl ketone and diethyl ketone were selected as starting materials. The main rearrangement observed is due to the migration of the alkyl group having a smaller number of carbon atoms to the α-carbon atom of the larger alkyl group, and the migration of the alkyl group with a larger number of carbon atoms to the smaller one also occurs in some degree. 3) The yield of the generated acids were about 30∼40% of the theoretical amounts based on the ketones used. Small amounts of cleavage products were obtained as the by-products in all cases. Both of the cleavaged groups from a ketone were oxidized to acids in these reaction systems. 4) The most probable catalytic form seems to be peroxyselenious acid which may be produced by the oxidation of selenium dioxide with hydrogen peroxide (equation 6). Inferential reaction mechanism was discussed.

界面活性剤の製剤への応用研究 (第1報)

Drug preparations containing non-ionic surface active agents as a solubilizer is apt to become molded and the addition of an antifungal agents in such preparations at times do not exhibit the anticipated effect. This was assumed to be due to the fact that the solubilized antifungal agent is enveloped inside the micelle formed by the surface active agent. Using Tween 20 as the surface active agent and four kinds of p-hydroxybenzoic acid esters as the antifungal agent, solubility of the antifungal agent in the presence of surfactant and effect on Aspeyillus niger were tested and the relationship between the degree of hydrophilic or lipophilic properties of the antifungal agents and micelle formation of surfactants was considered. Addition of Tween 20 solution increases the solubility of the esters (Fig. 1) but the antifungal activity decreases (Fig. 2). Since the rate of decrease is different in each ester, antifungal activity of each ester differs in magnitude above a certain concentration of Tween 20. The ratio of solubility to antifungal concentration is approximately constant in each ester and this value is smaller in the esters with smaller number of carbon atoms (Fig. 3). It was thereby concluded that the antifungal agents easily soluble in aqueous phase outside the micelle possessed greater antifungal activity.