Low Carrier Gas Flow Rate Research Articles

Adsorption of methylene blue from aqueous solution on biochar prepared from a K-rich biomass Alternanthera philoxeroides

ABSTRACT Alternanthera philoxeroides (AP) is a typical invasive plant. The quick spread of AP biomass may cause serious threat to ecological balance and biodiversity of the local area. However, AP has a high content of potassium, making it possible for preparing biochar through a self-activation process. In this study, AP biomass was employed to prepare porous carbon through a simple one-step pyrolysis. The effect of pyrolysis temperature (T) and carrier gas flow rate (v) onto the target carbon was intensively discussed. The obtained carbon were employed as adsorbents for methylene blue (MB) adsorption. Results showed that both of the T and v played great influence on the porous structure of the obtained biochar. Higher pyrolysis temperature and lower carrier gas flow rate were in favor of the formation of micropore and mesopore. The biochar obtained from 900°C pyrolysis temperature and 20 cm3 min−1 carrier gas flow rate (BC/900–20) possessed a satisfying specific surface area (825.6 m2 g−1) through the direct one-step pyrolysis, verifying the existence of pyrolysis gas self-activation and inorganic salt template self-activation effect. The maximum adsorption capacities calculated from Langmuir model were 424.9 mg g−1 for BC/900–20, which was comparable to that of the adsorbents reported recently.

Oil production from waste polyethylene and polystyrene co-pyrolysis: Interactions of temperature and carrier gas flow rate

This study investigated the co-pyrolysis of waste polyethylene (WPE) and polystyrene (WPS) for oil production under different operating conditions (temperature and carrier gas flow rate). The ratio of the real-life WPE and WPS is different in different regions. Therefore, the interactions of operating conditions were investigated under different WPE/WPS mixture compositions. A hybrid model of artificial neural network-genetic algorithm (ANN-GA) was adopted to predict and optimize the co-pyrolysis oil yield due to the complex interactions of the WPE/WPS mixture composition and operating conditions. Consequently, the highest oil yield was 82.33 wt% under 525°C, 10 wt% PS, and a non-sweeping atmosphere (0 mL/min). The results indicated that high temperature, low PS mass fraction, and low carrier gas flow rate led to a higher oil yield. The WPE/WPS co-pyrolysis oils were composed of alkanes, alkenes, and aromatics. Meanwhile, styrene accounted for the highest proportion of aromatics in oils. ANN-GA was also adopted to predict and optimize the oil components and fractions. The results revealed that low temperature, high PS mass fraction, and low carrier gas flow rate were conducive to a light WPE/WPS co-pyrolysis oil production. The findings could guide the industrial process of waste plastic pyrolysis in different regions. Moreover, ANN-GA coupled with central-composite design can be used to regulate different target products under more complex conditions due to its good robustness.

Sub- μ m features patterned with laser interference lithography for the epitaxial lateral overgrowth of α-Ga2O3 via mist chemical vapor deposition

The low growth rate of mist chemical vapor deposition normally requires a long growth time to achieve coalescence in the epitaxial lateral overgrowth of α-Ga2O3 thin films on sapphire substrates. To address this issue, sub-μm features were patterned using laser interference lithography. Periodical stripes with a ∼590-nm pitch allowed the overgrowth of crack-free, void-free, and continuous thin films, while typical growth conditions using a low carrier gas flow rate and a low Ga precursor concentration were maintained. Coalescence was achieved even with a short growth time of <30 min and a low film thickness of <500 nm. Transmittance and x-ray diffraction spectra show that the film was predominantly in α-phase. Transmission electron microscopy (TEM) images reveal cup-top-like α-Ga2O3 regions of low dislocation density on the SiOx mask. Selected area electron diffraction and high-resolution TEM analyses confirm that an α-Ga2O3 layer was formed even on the top of the SiOx mask. Interestingly, the dislocations formed on the window areas did not bend toward the center of the masks; rather, a dislocation bending outward from the center was observed. This suggests the occurrence of early coalescence and/or atomic rearrangement.

Effect of microgroove structures on the fluid dynamics and film conformality in spatial atomic layer deposition of Al2O3

With the development of semiconductors, efficient ultrathin coatings on large areas is of great significance to the commercial needs for the encapsulation of materials with micro- or nano-structures. Spatial Atomic Layer Deposition (ALD) is an emerging high throughput and economic technique which can deposit nano-scale films on substrates with different topographies. However, the complex fluid dynamics and diffusion kinetics in the spatial ALD system bring great challenge to the investigation and optimization of the film conformality. In this work, a two-dimensional model coupling Computational Fluid Dynamics (CFD) coupled with chemical kinetics details is built to investigate the hydrodynamics and film growth characteristics in spatial ALD system with different substrates. The effects of the microgroove structures and the microgroove heights on the velocity flow fields and the conformality of alumina films are studied, as shown in the Figure. With numerical simulations, our results show that higher aspect ratio of groove structure leads to more vortex flow at the corner of the microstructures. The motion of the substrates exacerbates the formation of vortex, which will definitely cause the precursor intermixing. Besides, the conformality of the alumina film decreases as the aspect ratio of microgroove structures increases. In order to ensure the self-limited ALD reaction and improve the film conformality, process parameters of total gap size, separate gas flow rate, the carrier gas flow rate as well as the motion velocity of the substrate are investigated. It is found that low carrier gas flow rate can not only reduce the chemical vapor deposition (CVD) growth, but also increase precursor utilization. This work is important for the packaging of micro structure devices and is rather instructive to the further design of spatial ALD system. Figure 1

Investigation of the conditions for selenium determination by photochemical vapor generation coupled to graphite furnace atomic absorption spectrometry

In this study instrumental parameters and sample preparation methods for Se determination using photochemical vapor generation (PVG) coupled to graphite furnace atomic absorption spectrometry (GF AAS) were investigated. Coconut water was selected as sample due to its nutritional importance and matrix complexity. The PVG was performed in a flow injection mode. The Se volatile species, generated in the UV reactor, were separated from the condensed phase in a gas-liquid separator and introduced automatically in the graphite furnace. These species were trapped on the integrated graphite platform surface coated with Ir as permanent modifier. The PVG conditions such as concentration of low molecular weight organic compound (LMWC), sample and carrier gas flow rate, effect of reagents frequently used in sample preparation (HNO3 and H2O2) were investigated. Formic acid 0.44 mol L−1 was selected as LMWC. The addition of HNO3 (14 mmol L−1) and H2O2 (145 mmol L−1) increased the sensitivity. Pre-reduction of Se (VI) to Se (IV) was performed on-line in a quartz spiral tube coated with a thin film of TiO2. The insertion of Ar flow rate (115 mL min−1) before the reactor inlet has improved the sensitivity, comparing with the introduction of Ar after the reactor. UV-assisted photo-oxidation of coconut water samples was employed as an alternative sample preparation to avoid the NO3−/NO2−, and H2O2 interference. The figures of merit were: sensitivity 0.0680 s ng−1, limits of detection and quantification 0.65 μg L−1 and 2.2 μg L−1, respectively, and characteristic mass of 62 pg. The PVG efficiency was estimated as 79% when comparing with conventional hydride generation. Furthermore, a mass balance study was accomplished in order to identify possible analyte losses in the PVG system, which the overall recovery was up to 85%. The results of recovery tests accomplished with real samples of coconut waters varied between 80 and 103% for Se (IV), Se (VI), and selenomethionine.

Application of response surface methodology in the design of functionally graded plasma sprayed hydroxyapatite coatings

The highly complex process-property-structure relationship poses a major challenge in the optimization of plasma sprayed hydroxyapatite coatings. In addition, contradictions in relation to the ideal coating properties exist; a dense, highly crystalline coating is required for long term coating stability, whereas coatings with lower crystallinity dissolve more rapidly but have an improved osteogenic response in vivo. In this study, response surface methodology (RSM) is utilized to investigate the influences and interaction effects of current, gas flow rate, powder feed rate, spray distance and carrier gas flow rate on the roughness, crystallinity, purity, porosity and thickness of plasma sprayed HA coatings. Roughness related to the particle velocity and particle melting, and was highest at low gas flow rates and, due to the quadratic effect of current, at the central current value. High crystallinity resulted at high current and low spray distance due to the presence of bulk crystalline material and recrystallization of amorphous material. Purity was highest at low carrier gas flow rate and high gas flow rate, where particle temperature was reduced. Porosity was dependent on the degree of particle melting and was highest at low gas flow rate and powder feed rate and at high current and spray distance. Coating thickness was determined by the number of particles and the degree of flattening on impact, and was highest at high current, low gas flow rate, high powder feed rate and low spray distance. From this in-depth analysis, predictive process equations were developed and optimized to produce two distinct coatings; a stable coating and a bioactive coating, designed to form the base and surface layers of a functionally graded coating respectively, to provide enhanced osteogenesis, while maintaining long-term stability. Culture of osteoblast-like cells on the coatings demonstrated an increased osteogenic response on the bioactive coating compared to the other groups. Overall, this study identifies parameter effects and interactions leading to the development of optimized coatings with the potential to enhance the functional life of HA coated implants in vivo.

Production of Syngas from Controlled Microwave-Assisted Pyrolysis of Crude Glycerol

Conversion of crude glycerol into synthesis gas was studied by using controlled microwave-assisted pyrolysis method. Pyrolysis of crude glycerol in the presence of carbonaceous catalyst was performed in a fixed bed reactor under oxygen-deficient environment using a domestic microwave. The effects of inert carrier gas flow rate and pyrolysis temperature on the product yield were investigated. Characterisation of the gaseous product showed that hydrogen, methane and carbon dioxide are the main components in the gaseous product. High temperature and low inert carrier gas flow rate are effective in pyrolysing crude glycerol due to sufficient energy and residence time for complete cracking of vapour into small gaseous molecules. Peak hydrogen yield of 35.2% by volume was obtained at the carrier gas flow rate of 100 mL/min and 600 °C.

Controlled vapour-phase deposition synthesis and growth mechanism of Bi2Te3 nanostructures

This work presents a study on the controlled growth and the growth mechanism of vapour-phase deposited two-dimensional Bi2Te3 nanostructures by investigating the influence of growth conditions on the morphology of Bi2Te3 nanostructures. The formation of a hexagonal plate geometry for Bi2Te3 nanostructures is a consequence of the large difference in growth rate between crystal facets along 〈0001〉 and 〈112¯0〉 directions. Under low Ar carrier gas flow rates (60–100 sccm), the growth of Bi2Te3 nanoplates occurs in the mass-transport limited regime, whereas under high carrier gas flow rates (130 sccm), the growth of Bi2Te3 nanoplates is in the surface-reaction limited regime. This leads to an increase in the lateral size of Bi2Te3 nanoplates with increasing the Ar carrier gas flow rate from 60 to 100 sccm, and a decrease in size for a flow rate of 130 sccm. In addition, the lateral size of Bi2Te3 nanoplates was found to increase with increasing growth time due to the kinetic characteristics of material growth. The proposed growth model provides an effective guide for achieving controlled growth of Bi2Te3 nanoplates, as well as other two dimensional nanomaterials.

Splat Morphology and Influence of Feeding Rate During Reactive Plasma Spray of Aluminum Powder

Fabrication of aluminum nitride (AlN) coatings using conventional plasma spraying processes directly has been deemed impossible. It is attributed to the thermal decomposition of the AlN feedstock particles during spraying without a stable melting phase. Using the reactivity of the plasma (reactive plasma spraying: RPS) showed a promising consideration for in situ formation of AlN thermally sprayed coatings. Several AlN-based coatings were fabricated through the RPS of aluminum powders in the N2/H2 plasma. The focus of this study is in discussing the morphology of splat deposition during the nitriding of Al particles. Furthermore, the influence of the feeding rate during the RPS and nitriding of Al powders will be investigated. The nitride content, as well as the unreacted molten Al phase, strongly influences splat deposition and morphology during the RPS of Al. The collected splats can be divided into reacted, partially reacted, and unreacted splats. The reacted splats tend to show a disk or egg-shell shape. The partially reacted mainly had outside nitride shells and an unreacted molten Al part in the center. The unreacted splats tended to show a splash shape. The main controlling factor is the time of the droplet impact on the substrate during the reaction sequence. The particle size and spray distance showed significant effects on the splat formation due to their effect on the nitriding conversion and the melting behavior of the particles during RPS nitriding. The powder feeding rate was investigated through increasing the injection rate and by using a low carrier gas flow rate. Increasing the powder feeding rate significantly improved the coating thickness. However, it suppressed the nitriding conversion of the large Al particles. Thus, with increasing the amount of the powder in the plasma, the Al molten particles are easily aggregated and agglomerate together upon colliding on the substrate with an AlN shell on the surface. This prevents the N2 from having access to all of the aggregated particles. Therefore, the fabricated coatings using large Al particles consist of surface AlN layers and the central parts of AlN and Al composite layers. On the other hand, it was possible to fabricate about 500-μm-thick AlN coatings using fine Al particles of 15 μm and increasing the feeding rate. Using the fine particles improved the nitriding reaction due to the improvement of the surface area (the reaction area). Moreover, the nitriding process of the Al particles with increasing the feeding rate was also investigated.

Plasma sprayed hydroxyapatite coatings: Understanding process relationships using design of experiment analysis

Abstract The biocompatibility and osteoconductivity of hydroxyapatite (HA) coatings have led to their use in a wide range of applications in dentistry and orthopaedics. One such application is for the uncemented fixation of implants, where coatings are commonly applied to titanium implants using a plasma thermal spraying process. The spraying process is affected by a large number of parameters leading to highly complex process–property–structure relationships. In a step forward from one-at-a-time analyses, this study used Design of Experiment (DOE) methodology to investigate the simultaneous effects of key plasma spray process parameters on hydroxyapatite coatings for biomedical applications. The effects of five plasma spray process parameters (current, gas flow rate, powder feed rate, spray distance and carrier gas flow rate) on the roughness, crystallinity and purity of hydroxyapatite coatings was determined using a fractional factorial design. The results of this study enabled identification of consistent and competing influences within the process and the identification of some first order interactions. In particular, the diffuse particle size of the HA feedstock powder was found to influence the responses observed within the parameter range investigated. The roughness of HA coatings was found to relate to the particle velocity and the degree of particle melting occurring, with higher coating roughness resulting when current was high, gas flow rate was low and powder feed rate was high. Highest coating crystallinity resulted at high current, low spray distance and low carrier gas flow rate. Under these conditions deposition of larger HA particles resulted leading to higher amounts of bulk crystalline material and the low spray distance increased the substrate temperature allowing amorphous material to recrystallise. Coating purity relates directly to thermal decomposition of the particles within the plasma jet with a high purity coating resulting at low particle temperatures i.e. at the lower ranges of powder feed rate, spray distance and carrier gas flow rate. This study thus brings greater clarity on the effects of plasma spray process parameters on the properties of resultant hydroxyapatite coatings.

Effects of GC temperature and carrier gas flow rate on on-line oxygen isotope measurement as studied by on-column CO injection.

Although deemed important to δ18 O measurement by on-line high-temperature conversion techniques, how the GC conditions affect δ18 O measurement is rarely examined adequately. We therefore directly injected different volumes of CO or CO-N2 mix onto the GC column by a six-port valve and examined the CO yield, CO peak shape, CO-N2 separation, and δ18 O value under different GC temperatures and carrier gas flow rates. The results show the CO peak area decreases when the carrier gas flow rate increases. The GC temperature has no effect on peak area. The peak width increases with the increase of CO injection volume but decreases with the increase of GC temperature and carrier gas flow rate. The peak intensity increases with the increase of GC temperature and CO injection volume but decreases with the increase of carrier gas flow rate. The peak separation time between N2 and CO decreases with an increase of GC temperature and carrier gas flow rate. δ18 O value decreases with the increase of CO injection volume (when half m/z 28 intensity is <3 V) and GC temperature but is insensitive to carrier gas flow rate. On average, the δ18 O value of the injected CO is about 1‰ higher than that of identical reference CO. The δ18 O distribution pattern of the injected CO is probably a combined result of ion source nonlinearity and preferential loss of C16 O or oxygen isotopic exchange between zeolite and CO. For practical application, a lower carrier gas flow rate is therefore recommended as it has the combined advantages of higher CO yield, better N2 -CO separation, lower He consumption, and insignificant effect on δ18 O value, while a higher-than-60 °C GC temperature and a larger-than-100 µl CO volume is also recommended. When no N2 peak is expected, a higher GC temperature is recommended, and vice versa. Copyright © 2015 John Wiley & Sons, Ltd.

Liquid Sampling–Atmospheric Pressure Glow Discharge as a Secondary Excitation Source for Laser Ablation-Generated Aerosols: Parametric Dependence and Robustness to Particle Loading

Liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma is being developed as a secondary vaporization-excitation source for the optical emission analysis of laser ablation (LA)-generated particle populations. The practicalities of this coupling are evaluated by determining the influence of source parameters on the emission response and the plasma's robustness upon LA introduction of easily ionized elements (EIEs). The influence of discharge current (45-70 mA), LA carrier gas flow rate (0.1-0.8 L min(-1)), and electrode separation distance (0.5-3.5 mm) was studied by measuring Cu emission lines after ablation of a brass sample. Best emission responses were observed for high-discharge currents, low He carrier gas flow rates, and relatively small (<1.5 mm) electrode gaps. Plasma robustness and spectroscopic matrix effects were studied by monitoring Mg(II) : Mg(I) intensity ratios and N2-derived plasma rotational temperatures after the ablation of Sr- and Ca-containing pellets. Plasma robustness investigations showed that the plasma is not appreciably affected by the particle loadings, with the microplasma being slightly more ionizing in the case of Ca introduction. In neither case did the concentration of the concomitant element change the robustness values, implying a high level of robustness. Introduction of the LA particles results in slight increases in the rotational temperatures (∼10% relative), with Ca-containing particles having a greater effect than Sr-containing particles. The observed variation of 9% in the plasma rotational temperature is in the same order of magnitude as the short-term reproducibility determined by the proposed LA-LS-APGD system. The determined rotational temperatures ranged from 1047 to 1212 K upon introducing various amounts of Ca and Sr. The relative immunity to LA particle-induced matrix effects is attributed to the relatively long residence times and high power densities (>10 W mm(-3)) of the LS-APGD microplasma.

Large-scale production of tungsten trioxide nanoparticles for electrochromic application

Large-scale, high yield production of tungsten trioxide (WO3) particles was successfully realized by using a facile, high-temperature, catalyst-free, solid evaporation route with ammonium paratungstate tetrahydrate as raw material. The crystalline structure, size, and morphology of the as-synthesized WO3 particles were systematically investigated by combined techniques of X-ray diffraction and electron microscopy, as a function of reaction temperature, deposition temperature, carrier gas flow rate, and size of the quartz tube. With low carrier gas flow rate (1–2 L min−1), the WO3 products collected from different deposition regions were found to exhibit a diversity of forms, such as thick rods, irregular, polyhedral, and octahedral particles, depending on the reaction temperature. At a reaction temperature of 1350 °C, increasing the carrier gas flow rate led to the formation of semi-spherical or quasi-spherical WO3 particles with decreased size and improved size distribution. A reaction temperature of 1350 °C and an Ar flow rate of 6 L min−1 yielded optimized quasi-spherical WO3 nanoparticles with high size uniformity, which have been found to exhibit stable electrochromic performance with high colour contrast and H+ insertion ability. The WO3 nanoparticles that can be effectively produced in high quantity are promising electrochromic candidates for potential applications in large-area smart windows.

CHROMATOGRAPHIC QUALIFICATIONS AND THEIR EFFECTS ON RELIABILITY OF LOW-LATITUDE TRACE LONG-CHAIN ALKENONE AS A TEMPERATURE INDICATOR

Two main chromatographic qualifications,programmed temperature mode and carrier gas flow rate,were investigated for the analysis of trace alkenone from low-latitude continental shelf samples.The separability,test precision and repeatability under various gas chromatographic(GC) analytical circumstances were discussed.Our results show that chromatographic qualifications have great impacts on the analysis of those trace alkenone.Traditional high GC programmed temperature ramps(PTR),which are adequate for ocean sediment samples,were confirmed no longer applicable for the analysis of the shelf samples highly diluted by terrigenous debris.Excellent separabilities for C37∶x(C37∶2 C37∶3) and the homolog compounds were obtained under Low PTR condition(1.3℃/min at high temperature stage),even for the samples in which the C37∶3 alkenone content is extremely low(1ng/g dry sediment,calculated sea surface temperature is near to 27 ℃).Furthermore,the test precision and repeatability are much better under low PTR.Our results also indicate that perfect separabilities and test precision are likely to be obtained under low carrier gas flow rate for those shelf sediment samples with low trace alkenone content.

Study on CO&lt;sub&gt;2&lt;/sub&gt; Adsorption on LiOH-Modified Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;

LiOH is known to be one of the most efficient CO2 adsorbent because it reacts with CO2 to form Li2CO3. However, LiOH still suffers from lack of enough hardness for practical use. In this study, various substrates, were modified with LiOH. Their X-ray diffraction patterns were investigated, and LiOH peak was observed from all prepared samples. CO2 adsorption capacity of each prepared sample was measured by monitoring CO2 concentration change during the adsorption process under constant CO2 gas inflow condition. LiOH-modified Al2O3 and zeolite 5A showed good CO2 adsorption performance, while LiOH-modified AC and SiO2 showed relatively poor CO2 adsorption. Al2O3 and zeolite 5A contains many basic functional groups of Al3+, which promote the neutralization reaction with acidic CO2. The effect of carrier gas, carrier gas flow rate, initial CO2 concentration, and amount of LiOH-modified Al2O3 loading was investigated. CO2 adsorption performance was better when the carrier gas was N2, because O2 competes with CO2 on LiOH. CO2 adsorption performance was better with lower carrier gas flow rate, lower initial CO2 concentration, and less loading of adsorbent due to the increase of contact time and contact points.

Accurate Measurements of Infinite Dilution Activity Coefficients Using Gas Chromatography with Static-Wall-Coated Open-Tubular Columns

Wall-coated open-tubular (WCOT) columns provide higher column efficiency and lower solute interfacial adsorption effect than packed columns. However, previous efforts used to measure the infinite dilution activity coefficient (γ(∞)) via a chromatographic technique have used packed columns, because the low carrier gas flow rate (U) and the small stationary phase amount (n(2)) in WCOT columns raise large errors. By rationally revising the γ(∞)-calculation equation for static-wall-coated open-tubular column, we observed that U and n(2) are not necessarily needed and the resulting error could be reduced, and WCOT column gas chromatography subsequently became a superior method for the accurate γ(∞) determination. In this study, we validate our revised γ(∞)-calculation equation by measuring γ(∞) in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate system, in which 55 organic compounds covering a wide range of functional groups were used as probe solutes and their γ(∞) values in the ionic liquid were determined at 40.0, 50.0, and 60.0 °C. Experimental error analysis shows that our revised equation remarkably reduces the error compared to the common γ(∞)-calculation equation. Our data is consistent with previously reported values obtained via other techniques, which further proves the credibility of our revised equation. The accurately determined γ(∞) values can be directly used to calculate the partial molar excess enthalpy, selectivity, and capacity, which will benefit for the rapid screening of solvents (especially ionic liquids) in separation approaches.

Research on the Relationship between the Spray Overlap Width and the Photoresist Film Thickness and Uniformity

Because of its small average droplet size, low carrier gas flow rate and the droplets not easy to splash etc, the ultrasonic atomizing spray technology is particularly suitable for making photoresist films. In order to get a reasonable spray scan interval, the parabolic deposition model was used to study the relationship between the spray overlap width and the photoresist film thickness and uniformity, and it can be concluded that the thickness of the film increases and the thickness variance of the film decreases oscillatorily along with the increasing of the spray overlap width.To obtain good uniformity of the photoresist film, the dimensionless overlap width should be at least greater than 0.15.

Hydrogen-free spray pyrolysis chemical vapor deposition method for the carbon nanotube growth: Parametric studies

Spray pyrolysis chemical vapor deposition (CVD) in the absence of hydrogen at low carrier gas flow rates has been used for the growth of carbon nanotubes (CNTs). A parametric study of the carbon nanotube growth has been conducted by optimizing various parameters such as temperature, injection speed, precursor volume, and catalyst concentration. Experimental observations and characterizations reveal that the growth rate, size and quality of the carbon nanotubes are significantly dependent on the reaction parameters. Scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy techniques were employed to characterize the morphology, structure and crystallinity of the carbon nanotubes. The synthesis process can be applied to both semiconducting silicon wafer and conducting substrates such as carbon microfibers and stainless steel plates. This approach promises great potential in building various nanodevices with different electron conducting requirements. In addition, the absence of hydrogen as a carrier gas and the relatively low synthesis temperature (typically 750 °C) qualify the spray pyrolysis CVD method as a safe and easy way to scale up the CNT growth, which is applicable in industrial production.

Influence of the operating parameters and of the sample introduction system on time correlation of line intensities using an axially viewed CCD-based ICP-AES system

The influence of the acquisition and operating parameters on time correlation between emission line intensities was investigated using axially viewed inductively coupled plasma-multichannel-based emission spectrometry and various sample introduction systems. It was found that to obtain flicker-noise limited signals, necessary to compensate for time-correlated signal fluctuations by internal standardization, the flicker-noise magnitude of the sample introduction system, the integration time and the emission line intensity had to be considered. The highest correlation between lines was observed for ultrasonic nebulization with desolvatation, the noisiest system among those considered, for which the contribution of the uncorrelated shot-noise was negligible. In contrast, for sample introduction systems characterized by lower flicker-noise levels, shot-noise led to high, non-correlated RSD values, making the internal standard method to be much less efficient. To minimize shot-noise, time correlation was improved by increasing the emission line intensities and the integration time. Improvement in repeatability did not depend only on time correlation, but also on the ratio between the relative standard deviations of the analytical and reference lines. The best signal compensation was obtained when RSD values of the reference and analytical lines were similar, which is usually obtained when the system is flicker-noise limited, while departure from similarity can lead to a degradation of repeatability when using the internal standard method. Moreover, the use of so-called robust plasma conditions, i.e. a high power (1500 W) along with a low carrier gas flow rate (0.8 L/min) improved also the compensation. Finally, high correlation and consequent improvement in repeatability by internal standardization was observed also in the presence of complex matrices (sediment and soil samples), although a matrix-induced degradation of the correlation between lines was generally observed when using ultrasonic nebulization.

Synthesis of Nanowires by Spray Pyrolysis

Nanowires of carbon as well as nickel‐carbon (Ni‐C) were synthesized by spray‐pyrolysis. The carbon nanowires were synthesized using methanol as a precursor while the Ni‐C nanowires were obtained by using nickel chloride methanol solution as feed. It was found that low argon carrier gas flow rates (&lt;100 cm3/min) and suitable reaction temperatures (∼700∘C) were found to be critical for the formation of wired structures. The formation of nanowires was quite sensitive to reaction temperature. Nanowires could not form at temperatures higher than 900∘C in the presence of hexane. Ruthenium chloride and nickel chloride dissolved in hexane and methanol resulted in carbon coated binary metallic nanoparticles. Morphological differences of carbon nanowires, Ni‐C wires and carbon coated binary nanoparticles were characterized by scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDS). The formation mechanism for the wired structures is proposed to explain the structural results obtained.