Carrier Gas Concentration Research Articles

Microstructure and properties of YSZ-Al2O3 functional ceramic thermal barrier coatings for military applications

Current study renders its focus on the investigation of functionally graded Yttria Stabilized Zirconia (YSZ) and alumina (Al2O3) thermal barrier coatings (TBC) deposited on EN steel substrates used in gun barrel through atmospheric plasma spray (APS) process. A bond coat and the top coats was made with two distinct compositions using YSZ-Al2O3 in 75:25 and 50:50 weight ratio through APS process with two carrier gas concentrations of 3 and 4 standard cubic feet per hour (scfh). Coatings were characterized with thermal testing, X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscope examination (FESEM). Surface roughness test, wear and scratch test of the uncoated and coated steel specimens was also measured. YSZ-Al2O3 coated EN36C steel possessed greater insulation performance under a carrier gas flow rate of 3scfh compared to all other specimens. EN36C steel coated with YSZ-Al2O3 in the ratio of 75:25 has better wear and scratch resistance indicating lesser deformation compared to other materials.

Non-thermal dielectric barrier discharge plasma hydrogenation for production of margarine with low trans-fatty acid formation

A novel technique for palm oil hydrogenation with very low trans-fatty acid formation using non-thermal dielectric barrier discharge (DBD) plasma with parallel-plate configuration has been successfully demonstrated. This green technique does not require catalyst and is highly environmental-friendly. With 15% H2: 85% He mixed carrier gas concentration ratio and initial 31 °C (rising to 50 °C due to plasma), after 4 h of plasma hydrogenation, iodine value (IV) was reduced from 60.89 to 48.39 and detected trans-fat was 1.44%. This represents trans-fat generation rate of only 0.07% per % decrease in IV, which is about 6.12 times lower than a conventional method relying on high temperature, high pressure and catalyst. About 8 h was required to produce margarine with texture closest to commercial margarines. Acid value (AV) reduced from 0.47 to 0.27%, or 43% reduction, after 12–20 h of treatment, significantly indicating that plasma hydrogenation can also help extend shelf life of oil or margarine. Large portion of DBD plasma hydrogenated palm oil can, thus, be mixed with palm olein and interesterified palm oil to produce margarine with overall trans-fatty acid content no higher than regulatory requirement. Continuous production scheme was presented. This novel plasma hydrogenation technique offers promising possibility for commercial utilization by edible oils industry.

Effects of steam to enhance the production of light olefins from ex-situ catalytic fast pyrolysis of biomass

This study aims to report on the feasibility of enhancing light olefins production from ex-situ catalytic fast pyrolysis (CFP) of biomass by co-feeding with steam and determine the role of steam. Effects of steam on catalyst and pyrolysis/catalysis reactions in ex-situ CFP were investigated using a two-stage fluidized-bed/fixed-bed reactor. Carbon yield of olefins + monocyclic aromatic hydrocarbons (MAHs) increased by 23.80% after proper steam dealumination of HZSM-5 framework, which suggests that HZSM-5 can be activated at the initial exposure to steam. For activated HZSM-5, olefins carbon yield increased by 35.65% and olefins to MAHs (O/M) ratio boosted from 0.83 to 1.60 as steam concentration in carrier gas increased from 0% to 40%, while the total carbon yield of olefins and MAHs still kept at the same level. Steam enhanced olefins production by: (1) promoting the formation of light compounds in bio-oil, which are the main precursors of hydrocarbons, during pyrolysis; (2) inhibiting aromatization reactions during catalysis. It provides a possibility for the control of O/M ratio of hydrocarbon products and the enhancement of light olefins production from CFP of biomass.

Simulation Study on Urea Thermal Decomposition for SCR Process of Thermal Power Plant

Urea was used for SCR reducer in many power plants, but its pyrolysis process was very complex, and this process was showed by the TGA-DSC experimental results. An effective method for urea-water solution thermal decomposition was investigated in this paper. The factors of temperature, O2 concentration and catalyst had been mainly studied and analyzed. It can be concluded that in range of 200-650 °C, with temperature increasing, the NH3 conversion rate increased, HNCO could be hydrolyzed to produce NH3 and CO2 when temperature was higher than 400 °C, and the NH3 conversion rate was higher than 50%, and the maximal NH3 conversion rate was 85.1% when temperature was 650 °C; NH3 conversion rate decreased with O2 concentration in carrier gas increasing. More NH3 was produced by hydrolysis of HNCO on SCR catalyst below 400 °C, because the hydrolysis of HNCO took place at temperature lower than 400 °C mainly, however, the promotion of catalyst for hydrolysis of HNCO was not observed at higher temperature.

Physical properties of nanostructured ZnO thin films deposited by DC magnetron sputtering method with different volume of O2 in carrier gas

High-quality ZnO thin films with polycrystalline hexagonal structure and (101) preferentially oriented were deposited on Si and corning glass substrates by reactive direct current magnetron sputtering. The effects of different oxygen concentration in carrier gas on structural, morphological and optical properties have been investigated. The increase of O2 concentration resulted in the decrease of preferred orientation intensity and peak shifting to lower 2? values. Scanning electron microscopic images showed a porous tapered columnar structure similar to the zone 1 of Thornton?s structure zone model at lower O2 content and a smooth microstructure similar to the zone T structure at highest O2 content. AFM images showed that film morphology and surface roughness were influenced by O2 concentration. UV-Vis-NIR measurements indicated that the UV absorption intensity of samples was increased and shifted to shorter wavelength (blue shift) at higher O2 concentration. Moreover, the optical band gap increased from 3.91 to 4.41 eV as a function of the oxygen concentration.

Water nucleation in helium, methane, and argon: A molecular dynamics study.

Nucleation of highly supersaturated water vapor in helium, methane, and argon carrier gases at 350 K was investigated using molecular dynamics simulations. Nucleation rates obtained from the mean first passage time (MFPT) method are typically one order of magnitude lower than those from the Yasuoka and Matsumoto method, which can be attributed to the overestimation of the critical cluster size in the MFPT method. It was found that faster nucleation will occur in carrier gases that have better thermalization properties such that latent heat is removed more efficiently. These thermalization properties are shown to be strongly dependent on the molecular mass and Lennard-Jones (LJ) parameters. By varying the molecular mass, for unaltered LJ parameters, it was found that a heavier carrier gas removes less heat although it has a higher collision rate with water than a lighter carrier. Thus, it was shown that a clear distinction between water vapor-carrier gas collisions and water cluster-carrier gas collisions is indispensable for understanding the effect of collision rates on thermalization. It was also found that higher concentration of carrier gas leads to higher nucleation rate. The nucleation rates increased by a factor of 1.3 for a doubled concentration and by almost a factor of two for a tripled concentration.

Analysis of gasoline contaminated water samples by means of dopant-assisted atmospheric pressure photoionization differential ion mobility spectrometry

In this study the influence of aromatic dopant benzene on the sensitivity of GC-APPI-DMS to gasoline related aromatic compounds was investigated. This influence was investigated on example of four gasolin related fingerprints (toluene, ethylbenzene, o-xylene, and 1,2,4-trimethylbenzene), which were found in high relative abundance in the water-soluble gasoline fraction. The analysis of calibration curves slopes demonstrats that the GC-APPI-DMS sensitivity to gasoline fingerprints can be improved by up to seven times when benzene concentration in nitrogen carrier gas is less than 10 ppmv/v. The estimated detection limits (S/N = 3) for the analyzed in this study compounds were found to be within the range of 33–105 μg L−1 at benzene concentration in the carrier gas of 2.27 ppmv/v (10 μL injection volume). These limits of detection may be reduced (at the cost of lower resolution) using the larger injection volumes. For example, increase of injection volume to 100 μL at benzene concentration in the carrier gas of 2.27 ppmv/v leads to reduction of LOD values for toluene, ethylbenzene, and o-xylene to 11.1, 13.3, and 5.3 μg L−1, respectively.

Roles of Tobacco Fractions in the Formation of Polycyclic Aromatic Amines in Tobacco Pyrolysis

Abstract The aim of the present study was to gain further understanding of the precursors in tobacco of four polycyclic aromatic amines (PAAs) - 1- and 2-aminonaphthalene, 3- and 4-aminobiphenyl. We carried out non-isothermal pyrolysis of the residues, which were obtained after extraction of tobacco cut filler with methylene chloride followed by extraction with water, under three different pyrolysis conditions (target temperature 800 °C / 800 °C / 400 °C and O2 concentration in carrier gas 0% / 20% / 3%, resp.). The yields of the four PAAs obtained by the pyrolysis of each sample were evaluated. Several nitrogenous components in the sample were also analyzed. The results under all these pyrolysis conditions showed that 1) the methylene chloride-soluble fraction, in which 50-60% of nicotine was extracted, did NOT contribute significantly contribution to the yields of the four PAAs; 2) the watersoluble fraction, in which most of the nitrogenous inorganic ions and amino acids were extracted, contributed at an average of about 30% to total PAA yield; and 3) the insoluble residue, in which only protein was detected during the investigation of the nitrogenous components in the present study, showed the highest contribution, 50-60% of the four PAAs formed. Consequently, it is concluded that protein-like components in tobacco contribute highly to the formation of the four PAAs by tobacco pyrolysis.

Effect of Oxygen on the Microstructural Growth and Physical Properties of Transparent Conducting Fluorine-Doped Tin Oxide Thin Films Fabricated by the Spray Pyrolysis Method

We reported the fabrication of an FTO conducting thin film via a spray deposition method, which was used to investigate the effect of oxygen content in the carrier gas on deposited film morphology and properties. Using a carrier gas containing various O2/N2 concentrations (0%, 20%, 50%, 80%, and 100%) led to significant changes in the thickness, size, and shape of grain growth. The deposited films with 0–50% oxygen content yielded a low resistivity of ∼10−4 Ω-cm and a transmittance in the range of 76–96% at 550 nm. Furthermore, by changing the carrier gas concentration, the FTO films displayed different charge transport, recombination, and collection properties due to the surface and interfacial effects. These films with modified properties can be applied to dye-sensitized solar cells (DSSCs). Overall, the conversion efficiency of a solar cell based on a 0% O2 sample was increased by approximately 2% from that of a 100% O2 sample. The higher efficiency is mainly the result of the lower O2 content, which minimized the grain boundaries (spacing) and improved the electron transport on the FTO film surface.

Dependence of N-polar GaN rod morphology on growth parameters during selective area growth by MOVPE

Selective area growth of GaN rods by metalorganic vapor phase epitaxy has attracted great interest due to its novel applications in optoelectronic and photonics. In this work, we will present the dependence of GaN rod morphology on various growth parameters i.e. growth temperature, H2/N2 carrier gas concentration, V/III ratio, total carrier gas flow and reactor pressure. It is found that higher growth temperature helps to increase the aspect ratio of the rods, but reduces the height homogeneity. Furthermore, H2/N2 carrier gas concentration is found to be a critical factor to obtain vertical rod growth. Pure nitrogen carrier gas leads to irregular growth of GaN structure, while an increase of hydrogen carrier gas results in vertical GaN rod growth. Higher hydrogen carrier gas concentration also reduces the diameter and enhances the aspect of the GaN rods. Besides, increase of V/III ratio causes reduction of the aspect ratio of N-polar GaN rods, which could be explained by the relatively lower growth rate on (000-1) N-polar top surface when supplying more ammonia. In addition, an increase of the total carrier gas flow leads to a decrease in the diameter and the average volume of GaN rods. These phenomena are tentatively explained by the change of partial pressure of the source materials and boundary layer thickness in the reactor. Finally, it is shown that the average volume of the N-polar GaN rods keeps a similar value for a reactor pressure PR of 66 and 125mbar, while an incomplete filling of the pattern opening is observed with PR of 250mbar. Room temperature photoluminescence spectrum of the rods is also briefly discussed.

Synthesis and growth mechanism study of SnO2 micro/nanomaterials

Using Sn powders as source material, different SnO2 nanostructures, such as nanowires and nanorods, nanoflowers were synthesized successfully by simple chemical vapor deposition in a low temperature. SnO2 submicron rings were obtained by reducing the oxygen gas concentration in carrier gas and the effect of oxygen gas on controlling the morphology of products was demonstrated by adjusting the quantity of Sn powders and the rate of heating. The products were characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometry. The growth mechanism of the products was further discussed.

Growth of filamentous carbon by decomposition of ethanol on nickel foam: Influence of synthesis conditions and catalytic nanoparticles on growth yield and mechanism

This paper presents nano-sized carbon filaments grown by catalytic decomposition of ethanol on polycrystalline nickel foam. Our study is focused on the effects of synthesis conditions on the formation of filamentous carbon. The formation rate of filamentous carbon increased as the supply of liquid ethanol into the furnace and the synthesis time increased during growth process, whereas H 2 concentration in carrier gas had the opposite effect. The most favorable temperature for the highest formation rate was around 600 °C. We investigated the role of catalytic nanoparticles in the growth mechanism of filamentous carbon. Tip growth was the primary mechanism responsible for growth of the filamentous carbon; octopus-like carbon filaments were formed on large nanoparticles of about 100 nm in diameter. It was also discovered that surface break-up on the nickel foam precipitated the formation of filamentous carbon. We detected the presence of Ni 3C as synthesis conditions after a long exposure to ethanol.

海水中の二酸化炭素濃度（ｐＣＯ２）測定器の開発

Measuring system of carbon dioxide concentration (pCO2) in seawater is described. Newly developed instrument consists of an infrared gas analyzer (NDIR), an equilibrator, a carrier gas generator and a processing signal generator. The present instrument is designed to measure the carbon dioxide concentration of carrier gas which passed through the CO2 equilibrator. The gas circuit of the NDIR is opened to the atmosphere to maintain the carrier gas line at a barometric pressure. Sample seawater of 150ml is enough to determine pCO2. The present instrument can measure pCO2 every 20min. The measuring error in pCO2 is within 2ppmv (coefficient of variance: ca. 0.6%). This denotes that the present instrument is adequate to measure pCO2 under field conditions.

Electrostatic separation of powder mixtures based on the work functions of its constituents

The objective of this study was to investigate the feasibility of a dry electrostatic process to separate a powder mixture into its components based on their work functions. We studied the dry electrostatic beneficiation of high-sulfur, high-ash Illinois coals and relatively low carbon-containing oil shales, and separation of synthetic mixtures consisting of charcoal and silica to demonstrate the feasibility of such a separation. For nearly complete liberation of mineral inclusions from the organic matrix, both coal and shale need to be ground to a very fine particle size (below 5 μm). This is typically true for most of the mineral ores. The driving force in the electrostatic beneficiation of coal and shale is the observation that carbonaceous and non-carbonaceous matter can be imparted positive and negative surface charges, respectively, with a copper tribocharger. The polarity of surface charge is found to depend on the work function values of the particles and the tribocharger. Separation tests in a batch laboratory electrostatic separator showed that the efficacy of the electrostatic separation is strongly dependent on the hydrodynamic conditions such as gas velocity, electric field strength, and particle concentration in carrier gas. A dimensionless group called an ‘electrodiffusion number’ was identified which qualitatively described the separation process. Furthermore, the extent of separation was found to be limited by a strong cohesive force acting between the oppositely charged particles which resulted in the formation of agglomerates.

EFfect of the parameters of methylens chlorids carbonization on silica gel surface on the properties of an adsorbent (carbosil)

The properties of carbon-silica adsorbents (carbosils) prepared under dynamic conditions, using special apparatus, were investigated. On the surface of silica gel of Merck Si 100, methylene chloride was thermally decomposed. The influence of such factors as pyrolysis temperature, amount of CH 2Cl 2 used, its concentration in carrier gas and flow rate of carrier gas on the properties of carbosils has been defined. Adsorbents were characterized by: heats and isotherms of adsorption of n-hexane, benzene and chloroform, differential distribution of adsorption energy of n-hexane and specific surface area. Studies of the effect of the amount of carbon deposited on the silica surface area were carried out.

Shock wave study of benzyl UV absorption spectra: Revised toluene and benzyl decomposition rates

High temperature UV absorption spectra of benzyl radicals were recorded over the range 190–330 nm after shock wave induced thermal decomposition of three different precursor molecules, benzyliodide, benzylchloride, and methyl-benzyl-ketone. These spectra are consistent with “hot” and “cold” spectra of benzyl from laser flash photolysis studies. Benzyl radicals have an unexpectedly low stability; their “fragmentation” rates are characterized by the sum of two components k a +k b , with k a =10 15.3±0.3 exp (−349.6±12 kJmol −1 /RT) s −1 and k b =10 10±0.7 exp(−178±15 kJmol −1 /RT) s −1 measured between 1400 and 1900 K at carrier gas concentrations [Ar]=3±0.3·10 −5 mol cm −3 . Toluene and benzyl absorption profiles have been remeasured over the range 190–305 nm in the shock wave induced decomposition of toluene, and reinterpreted with the new benzyl spectra and “fragmentation” rates. The reaction mechanism is dominated by primary dissociation of toluene forming benzyl + H (rate coefficient k=10 15.3±0.1 exp(−369±6 kJmol −1 /RT) s −1 , 1500–1900 K, [Ar]=3±0.3·10 −5 mol cm −3 ) and by “fragmentation” of benzyl radicals which is about ten times faster. The recombination benzyl + H → toluene and toluene attack by H atoms play only a minor role for the concentrations employed (15≤[toluene]/[Ar]≤1000 ppm). An accurate representation of the observed toluene and benzyl concentration profiles over very wide ranges of conditions was possible using toluene and benzyl decomposition, H + benzyl and H + toluene reaction rates. The reason for the lower “stability” of benzyl radicals compared to toluene, as well as the anomalous properties of their apparent “fragmentation” rates remain to be elucidated. However, a revision of earlier mechanisms for toluene and ethylbenzene decomposition appears necessary.

Relation between flow, power, and presence of carrier gas during plasma deposition of thin films

Plasma deposition processes have become an integral part of the manufacturing of microelectronic devices. Control of proper deposition parameters and understanding their relation to the composition of the plasma, and therefore to the film properties, is essential for depositing films in a repeatable and a predictable way. Using mass spectrometry, we have studied the influence of input rf power, reactant gas flow, and the presence and concentration of carrier gas on the degree of decomposition of a wide range of starting materials used during plasma deposition. It is shown that all three parameters influence the decomposition of the starting material and therefore the composition and properties of the deposit. It is also shown that different degrees of decomposition for different materials cannot always be predicted from the bonding energy between species being dissociated by a plasma. Using silicon nitride as an example, it is shown that the N/Si atomic ratio in films deposited at various conditions corresponds to the relative degree of decomposition of the reactant gases NH3 and SiH4.

Homogeneous Condensation of Nitrogen in the Expansion Wave of a Cryogenic Shock Tube

AbstractCondensation of nitrogen carried in helium was studied in expansion waves of a cryogenic shock tube operated at 77.4 K. Condensation onset was detected by laser light scattering in conjunction with piezoelectric pressure measurements. In contrast to most of the previous studies employing supersonic nozzles or free jet expansions, the shock tube experiments showed condensation at supersaturated states close to phase equilibrium having temperatures from 66 K to 57 K and nitrogen partial pressures from 230 torr to 45 torr. The differences in condensation onset presumably caused by the different experimental conditions such as carrier gas concentrations, cooling rates and supply temperatures cannot be explained on the basis of conventional nucleation theories. It is instead possible to relate these differences qualitatively to the molecular kinetics of nitrogen microcluster formation.

Some remarks about nucleation theory

The due applicability of equilibrium thermodynamics to be the theory of supersaturated vapor nucleation depends on the ratio of the vapor and carrier gas concentrations. The contribution of cluster collective rotation and translation to its free energy of formation cannot be determined at present with certainty.