CCl4 Vapor Research Articles

Production of Mo+Beams Using an Arc Discharge Ion Source

A new method of Mo ion beam production is presented in the paper. The method bases on the chemical sputtering/etching of the molybdenum parts (e.g. anode) of the arc discharge ion source by the chloride containing plasma. A mixture of CCl4 (or CHCl3) vapor and air was used as the feeding substance. The separated Mo beam current of approximately 18 μA was achieved. The measurements of the ion current dependences on the discharge and lament currents as well as on the magnetic eld ux density from the electromagnet surrounding the discharge chamber were performed in order to nd the optimal working parameters of the ion source.

Formation of dispersed carbon in the course of chlorination with CCl4 vapor of γ-Al2O3 surface

Formation of dispersed carbon in the course of chlorination with CCl4 vapor of γ-Al2O3 surface

Emission characteristics of a barrier discharge in an argon-freon-water vapor mixture in the UV-VUV spectral range

Optical characteristics of an ArCl*-OH* lamp excited by a nanosecond barrier discharge are studied. This discharge is a source of the ArCl (B → X), (D’ → A’), and OH(A → X) molecular band emission with peaks at 175, 258, and 309 nm, respectively. The intensity of the barrier discharge plasma radiation is optimized as a function of the CCl4 vapor partial pressure at p(Ar) = 24 kPa and p(H2O) = 10–20 Pa.

Breakthrough behaviour of NBC canister against carbon tetrachloride: a simulant for chemical warfare agents

A nuclear, biological, chemical (NBC) canister was indigenously developed using active carbon impregnated with ammoniacal salts of copper (II), chromium (VI) and silver (I), and high efficiency particulate aerosol filter media. The NBC canister was evaluated against carbon tetra chloride (CCl4) vapours, which were used as a simulant for persistent chemical warfare agents under dynamic conditions for testing breakthrough times of canisters of gas masks in the National Approval Test of Respirators. The effects of CCl4 concentration, test flow rate, temperature, and relative humidity (RH) on the breakthrough time of the NBC canister against CCl4 vapour were also studied. The impregnated carbon that filled the NBC canister was characterized for surface area and pore volume by N2 adsorption-desorption isotherm at liquid nitrogen temperature. The study clearly indicated that the NBC canister provides adequate protection against CCl4 vapours. The breakthrough time decreased with the increase of the CCl4 concentration and flow rate. The variation in temperature and RH did not significantly affect the breakthrough behaviour of the NBC canister at high vapour concentration of CCl4, whereas the breakthrough time of the NBC canister was reduced by an increase of RH at low CCl4 vapour concentration.

Organic isocyanide-adsorbed gold nanostructure: a SERS sensory device for indirect peak-shift detection of volatile organic compounds

Organic isocyanide adsorbed on a noble metal nanostructure can be used as a platform for a volatile organic compound (VOC) sensor operating via surface-enhanced Raman scattering (SERS). This is possible since the NC stretching band of organic isocyanides such as 2,6-dimethylphenylisocyanide (2,6-DMPI) is very susceptible to the surface potential of Au onto which 2,6-DMPI is assembled. The surface potential of Au nanoparticles is even subject to change by VOCs, which can be easily monitored by the SERS of 2,6-DMPI. Thereby, under the flow of CCl(4) vapor at a partial pressure of 12.8 kPa, for instance, the NC stretching band is blue-shifted by up to 20 cm(-1) within 30 s, corresponding to a potential change of +0.56 V. Conversely, under the flow of butylamine at 12.8 kPa, the NC stretching band is red-shifted, instead of being blue-shifted, by as much as 12 cm(-1). At lower partial pressures, even a blue- or red-shift of 1 cm(-1) was reproducibly measured at a partial pressure of 125 mPa, corresponding to 6.5 ppm for CCl(4), suggesting that the present detection limit is superior to the results obtained via other techniques, especially those operating based on gold nanoparticles and aggregates.

Thirteen‐week Inhalation Toxicity of Carbon Tetrachloride in Rats and Mice

Subchronic toxicity of carbon tetrachloride (CCl4) was examined by inhalation exposure of F344 rats and BDF1 mice of both sexes to 0, 10, 30, 90, 270 or 810 ppm (v/v) CCl4 vapor for 13 wk (6 h/d and 5 d/wk). In the high exposure levels at 270 and 810 ppm, altered cell foci in the livers of both rats and mice, and fibrosis and cirrhosis in the rat liver were observed. Hematoxylin and eosin-stained altered cell foci of rats were recognized as glutathione-S-transferase placental form (GST-P) positive foci, which are preneoplastic lesions of hepatocarcinogenesis. The most sensitive endpoint of CCl4-induced toxicity was fatty change with large droplets in rats of both sexes and male mice, and cytoplasmic globules in male mice, as well as increased relative liver weight in male rats. Those endpoints were manifested at 10 ppm and the LOAEL was determined as 10 ppm for the hepatic endpoints in rats and mice. Enhanced cytolytic release of liver transaminases into plasma in rats and mice and its close association with hepatic collapse in mice were observed at medium and high levels of inhalation exposure. Both CCl4-induced hematotoxicity and nephrotoxicity were observed in both rats and mice, but those toxicities were manifested at higher exposure concentrations than hepatotoxicity. The LOAEL for the hepatic endpoint and the GST-P-stained altered cell foci provide relevant animal data for reconsidering the occupational exposure limit val1ue of 5 ppm for CCl4 and strengthen the evidence of CCl4-induced hepatocarcinogenicity which is used in its carcinogenicity classification.

Kinetics of low-temperature chlorination of vanadium pentoxide by carbon tetrachloride vapor

Low-temperature chlorination of vanadium pentoxide by carbon tetrachloride vapor in dilution with nitrogen has been carried out. The effect of time, particle size, partial pressure of CCl4 vapor (0.1 to 0.6 atm), and temperature (553 to 788 K) on the extent of chlorination of V2O5 has been investigated. The extent of chlorination of the oxide is found to increase with a decrease in its particle size. In all cases, the reaction followed a topochemical reaction model, obeying the following relationship: $$1 - (1 - \alpha )^{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}} = kt$$ where α is the fraction of V2O5 chlorinated in time t and k is the rate constant. The rate constant has been found to be directly proportional to the partial pressure of CCl4 (PCCl4). The activation energy values between 553 and 643 K and that between 683 and 788 K have been calculated and found to be 38.9 and 11.5 kJ/mole, respectively. Based on the kinetics results, mechanisms of reaction in the two temperature ranges have been suggested. It has been possible to chlorinate V2O5 at 753 K to about 87 pct in 30 minutes, using a very low partial pressure of CCl4 of 0.15 atm.

Evaluation of CCl4 and CS2 as carbon doping sources in MBE growth of GaN

GaN:C epilayers were grown by plasma-assisted molecular beam epitaxy on metalorganic vapor phase epitaxy-GaN/sapphire templates using CCl4 and CS2 vapors as carbon doping sources. The resulting epilayers were characterized by secondary ion mass spectrometry, photoluminescence, and electrical resistivity among other techniques. Both sources were found to controllably introduce carbon in the concentration range 1×1018–3×1019cm−3 with insignificant contamination by other impurities. The CCl4 source drastically reduced the effective Ga/N flux ratio due to a parasitic reaction, necessitating greatly increased Ga flux to maintain Ga-rich conditions. On the other hand GaN:C was successfully obtained with CS2 with no parasitic reaction. For both sources an anomalous concentration dependence of the carbon incorporation behavior was observed, leading to reduced concentrations of electrically active CN acceptors for higher total doping levels.

Effect of the Surface Pretreatment on the Electrokinetic Properties of Silicon and Silicon Oxide

The electrokinetic characteristics (the isoelectric point, electrokinetic potential, and surface conductivity) are studied as functions of pH against the background of NaCl solutions for the initial surfaces of silicon (covered with an oxide layer) and silicon oxide (a plane-parallel capillary of quartz glass and aerosil OX-50) and for the same surfaces after a preliminary thermal and chemical (CCl4 vapors at 400°C) treatment. The position of the isoelectric point for the systems in question is shown to be primarily affected by the preliminary annealing, which shifts this point toward higher pH. The electrokinetic behavior of silicon plates covered with an oxide film is compared to the electrode behavior of a similar board of an ion-selective field-effect transistor.

Adsorption of Carbon Tetrachloride on Pyridinium Montmorillonite

Effect of substitution of Na+ by pyridinium on the surface and pore structures of montmorillonite is studied by CCl4 vapor adsorption.

A New Method of Calculating Pore Size Distribution: Analysis of Adsorption Isotherms of N2 and CCl4 for a Series of MCM-41 Mesoporous Silicas

The adsorption isotherms of N2 gas at 77 K and CCl4 vapor at 283.15, 298.15, and 308.15 K were measured for six samples of the mesoporous silicas having uniform cylindrical pores (MCM-41). The pore radii of the six samples (rp), which were evaluated from the αs plots of the N2 isotherms, were 1.13, 1.29, 1.50, 1.65, 1.90, and 2.53 nm. The CCl4 adsorption isotherms show that the capillary condensation occurs at the very narrow P/P0 range. The core radii of the six adsorbents (rc), which were estimated from a comparison plot of the CCl4 isotherm, were 0.90, 1.01, 1.28, 1.37, 1.60, and 2.17 nm. In the comparison plot, the standard CCl4 isotherm for nonporous silica was used as the reference isotherm. It has been clarified that the Polanyi adsorption potential of capillary condensation is proportional to the reciprocal of the core radii: RT ln(P0/P)=5.37rc−1 nm−1, ln(P0/P)=2.17rc−1 nm−1 at 298.15 K, [A]. The statistical thickness of adsorbed CCl4 on the curved surface (t(pore)), which was estimated from the difference between the pore radii and the core radii, was given by Eq. [B]: t(pore)=0.188+0.336(P/P0)+0.382(P/P0)2 nm [B], (0.08<P/P0<0.60). The equations [A] and [B] give the fundamental information necessary to calculate the pore size distribution of mesoporous adsorbents in the range of rp=1.0–5 nm. Furthermore, it has been found that the pore size distribution up to rp=55 nm can be estimated from Eq. [A] and the adsorbed thickness of CCl4 up to P/P0=0.96 (cf. Table 5).

Cyclohexane as an alternative vapor of carbon tetrachloride for the assessment of gas removing capacities of gas masks.

An alternative vapor was explored to replace carbon tetrachloride (CCl4) for testing breakthrough times of cartridges and canisters of gas masks in the National Approval Test of Respirators. Cyclohexane was single out as a candidate for the alternative vapor out of six vapors: trichloroethylene, n-pentane, n-hexane, n-heptane, toluene and cyclohexane from the viewpoints of similarity of vapor pressure and water-solubility to CCl4, lower toxicity than CCl4, and technical feasibility in generating an airflow of 30 L/min containing the vapor ranging from 300 to 5000 ppm. Breakthrough times of cartridges and canisters were examined by generating cyclohexane vapor in a test airflow of 30 L/min in comparison with CCl4 vapor under various test conditions with different vapor concentrations and relative humidities (RH). As the results, the breakthrough times of the cartridges and canisters for cyclohexane were found to almost coincide with those for CCl4 under all examined range of concentrations and RH. By an increase of humidity from 50% RH to 80% RH, the cartridges showed significant shortening of breakthrough times for both of CCl4 and cyclohexane, but the susceptibility of the breakthrough time of cyclohexane to humidity was also similar to that of CCl4. It was, therefore, concluded that cyclohexane can be recommended as the alternative vapor of CCl4 for testing the breakthrough times of gas mask cartridges and canisters in the National Approval Test.

Attempts to exchange iron into H-Y and H-ZSM-5 zeolites by in situ formed chloride-containing mobile species

Three variants of solid-state ion exchange were studied. Iron exchange was found to proceed in the first case, in theFeCl2+NH4ZSM-5→ FeZSM-5 + NH4Cl↑ process, even at low exchange capacity (Si/Al = 25).The second, Fe2O3 (hematite) + HZ direct reaction does not result in any noticeable interaction for eitherZ = Y or ZSM-5. This process can significantly be promoted by introducing CCl4 vapor via forming chlorine-containingmobile species. However, the structure of the Y zeolite largely collapses during this treatment, whereas the crystalline state of ZSM-5is preserved.

Volumetric Properties and Interaction Parameters of Dissolved Gases in Poly(dimethylsiloxane) and Polyethylene

Henry's law coefficients and partial molar volumes of 34 penetrants (5 inert gases, 6 inorganic gases, 17 hydrocarbon gases, 5 fluorinated gases, and CCl4 vapor) dissolved in poly(dimethylsiloxane) and low-density polyethylene were determined at 25 °C by measuring sorption of the gases and the concomitant dilation of the polymers. From the Henry's law coefficients and the partial molar volumes, Flory−Huggins parameters for polymer/gas interactions were estimated. The partial molar volumes were correlated with critical molar volumes of gases, and the interaction parameters were found to depend on the partial molar volumes. These relationships for the fluorinated gases were clearly different from those of all other gases. For CO2 and CH4 in poly(dimethylsiloxane), partial molar volumes and interaction parameters were obtained as a function of temperature over a range −30 to 95 °C. Thermal expansivities of these dissolved molecules were estimated to be 2 × 10-3 °C-1 from the temperature dependence of partial...

Determination of erbium and neodymium dopants in bismuth tellurite optical crystals by graphite furnace atomic spectrometry techniques

Application of concentrated HCl as a solvent and triammonium citrate (TAC) as a chemical modifier is advantageous for the determination of Er and Nd dopants in bismuth tellurite (Bi2TeO5) single crystals by graphite furnace atomic absorption spectrometry (GFAAS). The use of mini-flow of the internal gas, instead of gas stop, results in better precision at a price of a relatively small decrease in sensitivity. By evaluating integrated absorbance (Aint) signals for the GFAAS measurements (in the presence of matrix and TAC additive), characteristic mass values of 42 and 320 pg, and a limit of detection (LOD) of 4.9 and 131 μg l−1 are found for Er and Nd, respectively. These LOD data correspond to 0.78 μg g−1 Er and 21 μg g−1 Nd in the solid samples. The calibration curves are linear up to 0.33 and 2.9 mg l−1 concentrations in the solutions of Er and Nd, respectively. The ratio of the Aint signals of Er and Nd under gas stop and mini-flow were found near constant (1.34) with and without the matrix plus TAC. According to the vaporisation studies by graphite furnace electrothermal vaporisation inductively coupled plasma atomic emission spectrometry (GF-ETV-ICP-AES), the vaporisation of Bi and Te components of the solid Bi2TeO5 can be completed at 1200°C in a relatively short time, ensuring a preconcentration for the Er and Nd dopants, which do not vaporise below 2200°C in an argon atmosphere. On the other hand, fast vaporisation can be performed for the analytes at 2200°C with the use of CCl4 vapour (∼0.5 v/v%) in the internal furnace gas (Ar). It was estimated for the Er analyte that by applying 10 mg of solid sample in the GF-ETV device (dispensed into a graphite sample boat) and using a two-step heating procedure (prevaporisation of the matrix in argon and vaporisation of the analyte in a chlorinating atmosphere), the lower limit of the quantitative determination with the ICP-AES method would be approximately one order of magnitude better than attainable with the GFAAS method based on dissolution.

On the Effects of TiO2 Additive on D.C. Conductivity and Morphology of Polyethylene

The effects of doping low density polyethylene (LDPE) with fine particles of TiO2 as an inorganic additive on the d.c. conductivity and morphology of LDPE were investigated using two temperature profiles: the first at constant temperature of 40°C and the second under thermal cycling between 40°C and 80°C in the presence of an electric field. Results indicate that the incorporation of TiO2 in the polymer has increased the charge carrier mobility and the d.c. conductivity of the doped LDPE. Morphological investigations using scanning electron microscopy (SEM) of CCl4 vapour etched surfaces of the undoped and doped materials show that the addition of the inorganic additive to LDPE has considerably changed the morphology of the polymer. It is also shown that the morphology of the doped LDPE has undergone considerable structural changes after thermal cycling in the presence of the d.c. electric field during d.c. conductivity measurements. The role of the additive in increasing the d.c. conductivity and changing the morphology of LDPE is discussed. An attempt is made to correlate between the recorded increase in the d.c. conductivity and the observed morphological changes in the investigated material.

Kinetics of chlorination of niobium pentoxide by carbon tetrachloride

Kinetics of the chlorination of Nb2O5 powder by CCl4 vapor in mixture with N2 in a static bed in the temperature range of 698 to 853 K were carried out at different partial pressures of CCl4 (p CCl 4), varying from 0.10 to 0.75 atm. The fraction of Nb2O5 chlorinated R at p CCl 4 of 0.6 atm in the temperature range of 698 to 773 K was found to be proportional to time t, and the activation energy E is calculated to be 112 kJ/mole. Results on the effect of p CCl 4 (0.4, 0.6, and 0.75 atm) at 723 K suggest that the rate v (R/min) is proportional to p CCl 4 1.5. However, at p CCl 4 of 0.2 atm, R is not linear with t, rather, R 1/2 is linear with t. Based on these results, two mechanisms, one at low p CCl 4 (0.2 atm) and another at higher p CCl 4 values, in the temperature range of 698 to 773 K have been suggested. Similar studies in the higher temperature range (793 to 853 K), where p CCl 4 used to decompose to elemental chlorine and carbon, were also carried out. At all temperatures and p CCl 4 values, R is found to be directly proportional to t. At two higher p CCl 4 (0.4 and 0.6 atm), v is proportional to p CCl 4 1.5, whereas at two lower p CCl 4 (0.1 and 0.2 atm) it is proportional to p CCl 4 1.5. The E values obtained in the temperature range of 793 to 853 K at p CCl 4 of 0.6 and 0.2 atm are found to be 57 and 115 kJ/mole, respectively. In this higher temperature range, two different reaction mechanisms have been proposed.

Effect of Chlorinated Hydrocarbons on the Fluorescence Emission Spectra of 1,3-Bis-(1-Pyrene)Propane in Solutions and Poly(Vinyl Alcohol) Films

This paper reports on our investigation of 1,3-bis-(1-pyrene)propane (bpp) as a potential probe for chlorinated hydrocarbons. Changes in the emission spectra of bpp in methanol solutions, upon addition of methylene chloride, chloroform, or carbon tetrachloride, are described. Dramatic changes in the emission spectrum were noted for CCl4, compared to the other additives. These effects are explained by the preferential solvation of bpp by CCl4 and the formation of an excited-state complex (exciplex), leading to quenching of the excimer emission and, ultimately, the monomer emission. When solutions of bpp in the neat chlorinated hydrocarbons were exposed over time to 350-nm light, changes in the emission spectrum were noted for all solvents. Changes in both the excitation and emission spectra of bpp in CCl4 are related to exciplex formation, leading to irreversible formation of photochemical products. Poly(vinyl alcohol) films containing bpp were exposed to CH2C12, CHC13, or CCl4 vapors, and trends consistent with the solution study were observed. A rapid decrease in bpp excimer emission, upon exposure to CCl4 vapors, was observed. The effects of CCl4 in air and argon atmospheres on the bpp/PVA films were also investigated, with oxygen quenching limiting the ability of this system to detect low concentrations of CCl4.

The nature of the lubricating films formed by carbon tetrachloride under conditions of extreme pressure

The temperature T between the lubricated surfaces in a pin and v-block apparatus is given, for any lubricant at an ambient temperature of T0, by the formula T = T0 + KrωμL where r is the radius of the pin, ω its rotational angular velocity, K a constant that depends on the thermal conductivity in the region of the contact between the pin and the v-block and L the applied load. The product Krω has been determined previously for the pin and v-block apparatus and the coefficient of friction μ can be measured from a plot of the torque required to rotate the pin versus applied load. The rate of material removal can also be measured from the width of the wear scar formed on the face of the v-block by the rubbing motion of the pin. Asymptotes in the plot of removal rate versus applied load have been shown to correspond to melting of the material that forms the anti-seizure film at the interface, so that measurement of the corresponding interfacial temperature yields its melting point, and therefore indicates the nature of the film. Using this strategy, it is shown that FeCl2 forms the lubricating layer at low loads when CCl4 is used as the lubricant additive. In addition, films grown by the thermal decomposition of CCl4 vapor on an iron foil also consist of iron chloride. Mössbauer analysis of films deposited from CCl4 vapor at higher temperatures (∼ 1050 K) show the formation of iron carbide (consisting of Fe3C). The tribological behavior is in accord with this observation since at higher loads, and therefore higher surface temperatures, asymptotes in the rate of film removal correspond to the melting of iron carbide (Fe3C) which is therefore proposed to form the anti-seizure film under these conditions. Ultimately, at the highest attainable loads, the asymptote in the removal rate curve suggests that a carbon film acts as the solid lubricant.

Iron overload facilitates hepatic fibrosis in the rat alcohol/low-dose carbon tetrachloride model

The role of iron deposition in initiating hepatic fibrosis in iron overload disorders is not clearly established, and it is becoming increasingly recognized that iron may be interacting with other potential liver-damaging agents. The authors therefore examined the interplay of iron and alcohol in rats administered subtoxic doses of carbon tetrachloride (CCl4) vapor at 20 ppm in customized chambers. At birth, the offspring of seven pregnant Porton rats were divided into two groups: one group was fed a normal rat chow diet and the other a diet supplemented with 3% (w/w) carbonyl iron for 10 weeks after weaning. In this latter group, the mothers were fed an iron supplement while breastfeeding. At 10 weeks, the animals from the first group (normal chow) were divided into two groups of six animals and fed a Lieber-DeCarli liquid diet with daily exposure to CCl4 vapor: group 1, liquid diet+CCl4; group 2, liquid diet+alcohol 150 kcal/l+CCl4. The animals from the second iron-supplemented group were divided into two groups of six animals and fed a liquid diet with 3% (w/v) carbonyl iron and exposed to CCl4 vapor for 10 weeks: group 3, liquid diet+iron+CCl4; group 4, liquid diet+iron+alcohol supplement+CCl4. Two animals from each group of six had a liver biopsy at 4, 6, and 8 weeks, and all animals were killed after 10 weeks of CCl4 exposure. After the first 10-week iron loading period, the rats fed the carbonyl iron-supplemented diet had a 10-fold elevation in hepatic iron concentration.(ABSTRACT TRUNCATED AT 250 WORDS)