Transport Tube Research Articles

Rapid nickel oxalate thermal decomposition for producing fine porous nickel metal powders

Precursor nickel oxalate powder was entrained in pure argon and a 5% hydrogen-in-argon carrier gas flow and carried through a heated transport tube reactor. The reactor wall temperature was maintained at 748–1018 K for residence times less than 4 s. Rapid reaction was possible because of high particle heating rates. A 5% addition of hydrogen to the carrier allowed for the synthesis of a high-purity elemental nickel powder with low residual oxygen content. Product particles consisted of nano-sized primary particles contained within an overall microcontainer matrix. Primary nickel particles nucleated within the precursor microcontainer matrix, followed by a coalescence period. The product powder was characterized as 2–40 μm diameter microcontainer particles comprised of nano-sized nickel primary particles with diameters of 20–70 nm. The production of porous elemental nickel powder via the aerosol flow thermal decomposition of nickel oxalate results in powder with acceptable electrical properties and is more benign and potentially cheaper than the current commercial process for nickel powder production.

Spinning wheel powder feeding device — fundamentals and applications

A spinning wheel powder feeding system has been developed as a conveying mechanism to feed fine particle aggregates on a laboratory scale. An example of a use of this conveying mechanism is with a transport tube reactor, since the reactor only provides a few seconds residence time to react the powder. Methods to shear the powder mechanically, as opposed to using a high gas velocity, are developed as to not reduce the available residence time in the reactor. The objective is to feed a powder at the smallest particle aggregate size possible rather than a large particle aggregate size generated by an upstream feeding device, and to achieve such dispersion using minimized gas flow. Statistical results show that the spinning wheel alone is able to reduce the mean aggregate size of the Particle Size Distribution (PSD) and when a minimal amount of gas is added to the system the PSD is reduced further. In addition, a fundamental model employing a discrete particle aggregate breakage equation combined with a Monte Carlo method has shown that the spinning wheel feeding system is able to consistently reduce particle aggregate size.

Computer simulations of laser ablation sample introduction for plasma-source elemental microanalysis

Elemental microanalysis, using laser ablation for sample introduction into plasma-source spectrometry, is based on the analytical information carried by the ablated particles that are delivered to the ICP. Numerical fluid-dynamical simulations allowed us to understand the flow characteristics of the carrier gas, which influence the sample introduction and signal intensity. The carrier gas flow in the transport tubing was found to be laminar, with nested velocity paraboloids, whose front profile is less sharp for heavier carrier gases. The gas velocity is also characterized by high-frequency fluctuations along the tube length due to molecular diffusion. The temporal signal profiles were modelled considering the aerosol filling and elution rates in the setup, the whole setup dimensions, the transport efficiency, and the particle sizes, combined with a condition of mass conservation. The simulated signal intensity showed a logarithmic dependence on the transport efficiency, which exacerbates signal structure. Finally, in passing from single shot to repeated shot analysis, the transient signals were modelled calculating the convolution of the single shot profile with the laser pulse sequence profile.

Orbit Transfer via Tube Jumping in Planar Restricted Problems of Four Bodies

In the circular-restricted three-body system, there exist bundles of solution orbits, involving a close encounter with the second primary, inside invariant manifolds of libration point orbits. Under the influence of perturbing forces, these trajectory bundles change their locations and distributions, but still exist as bundles, serving as low-energy passageways and forming a network of transportation tubes. Taking full advantage of these transportation mechanics, orbit transfers within planetary systems, achieved by considerably lowered fuel consumption, can be generated in a highly systematic manner. We present a design framework capable of methodologically producing sets of planar transfers between two circular orbits as well as two elliptic orbits. In particular, it is shown that orbit transfers, consistent with planar dynamical systems of four bodies modeling the Jovian system, can be directly identified without differential corrections, and provide solutions with a significantly lower propulsion cost than the conventional Hohmann transfer.

Optimization of ETV-ICP(TOF)MS and transient signal profiles for reducing isobaric interferences

One of the advantages of the ETV sample introduction is the ability to temporally separate analyte elements in complex mixtures by differences in their vaporization temperatures within the ETV for ICPMS. However, the broadening of the transient peaks in the transport tubing often obscures this temporal resolution. This study shows that decreasing the transport tubing diameter produces little broadening beyond that produced during aerosol production in the ETV. Maintaining such narrow peaks through the transport process to the ICP permits time resolution to circumvent atomic isobaric interferences. Differences in vaporization characteristics of the elements were used to resolve the isobaric overlaps among Zn, Ni, Se, Ge, Cd, In and Sn. A Monte Carlo simulation that focused on particle motion from the ETV to the plasma source was employed to evaluate the roles of diameter of transport tubing and heating rate of the ETV on signal broadening. It was shown that laminar flow broadening was reduced by decreasing the transport tubing diameter and thus more closely reflected the generation function of the ETV. However, for some elements there was as much as a 75% reduction in signal from use of the smaller, 1.5 mm i.d. tubing. There was also a trend to further improve the resolution using lower heating rates of the ETV, although the longitudinal non-isothermality of the graphite furnace broadened the peaks beyond the values expected if there was no gradient along the length of the ETV. This was more noticeable for lower heating rates, e.g., <400 °C s−1. Results are presented for Monte Carlo simulations and time resolved signals obtained on an ETV-ICP(TOF)MS system.

A pseudo-fluid representation of vertical liquid-coarse solids flow

The pseudo?fluid concept has been applied for the prediction of the pressure gradient and voidage in vertical liquid-coarse solids flow. Treating the flowing mixture as a single homogenous fluid, the correlation for the friction coefficient of the suspension?wall was developed, as was the correlation between the true voidage and the apparent (volumetric) voidage in the transport tube. Experiments were performed using water and spherical glass particles 1.20, 1.94 and 2.98 mm in diameter in a transport tube of 24 mm in diameter. The loading ratio (Gp/Gf) was varied between 0.05 and 1.05 and the fluid superficial velocity was between 0.4 Ut and 4.95 Ut where Ut represents the single particle terminal velocity. The voidage ranged from 0.648 to 0.951 for these ratios. Experimental data for the pressure gradient and voidage from the literature agree well with the proposed correlations.

F152 強制振動流型熱輸送管の総括熱コンダクタンス(一般セッション 熱交換器)

A numerical simulation was carried out to investigate the overall thermal conductance of a forced oscillating flow heat transport tube, which was cooled at the outer surface of the tube. In addition, the influence of oscillating frequency, inner diameter, length of the tube, and the heat transfer coefficient on the overall thermal conductance has been studied. The results indicated the thermal conductance of the heat transport tube was higher than that of a copper rod. Furthermore, it was revealed that the heat transport rate of the forced oscillating flow heat transport tube especially enhanced, in case of the length of the tube was 600mm.

Modelling the temporal intensity distribution of laser ablation inductively coupled plasma mass spectrometry in single shot mode

A transport model is proposed that describes the temporal intensity distribution observed in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in single-shot mode using quantitative signal equations. Calculations aim on the deduction of the dispersion function describing the time-dependent part of the signal equation. The dispersion function depends on transport time in the centre of the transport tube, as related to carrier gas flow rate and tube volume and on the relation between carrier gas flow rate and ablation chamber volume. The equations describing the signal shape standardize signals from different systems and allow quantitative optimization of the ablation chamber, the transport tube and the detector. Application of the model to ICP-MS shows that only a part of the area filled by the transported vaporization product and thus only a part of the transported vaporization product can be observed at the detector. The model is able to quantify both fractions. As was calculated, the observed fraction of analyte is always higher than the observed fraction of the sample containing cross section and depends on the chosen transport parameters characterising the dispersion function. Thus, the determination of the signal integrals in the usual way can lead to systematic errors if the parameters influencing the dispersion function are variable. Therefore, a different method of analysis based on signal equations is proposed and demonstrated. By this method of data treatment, all important system parameters influencing the dispersion function could be calculated and matched with theoretical ones. Furthermore, a complete integral of the transient signal including its statistical variation can be generated from a limited number of measurement points. For example, this can be applied to signals detected incompletely because of detector saturation and enables the use of high-abundance elements as internal standards. Furthermore, the method can be used to monitor system performance, to identify the flow regime inside the ablation chamber, to take into account the sample volume for quantitative analysis and finally, to detect anomalous signal distributions that would lead to systematic errors. The prospects and limitations of the model are discussed for LA-ICP-MS in single shot mode.

Improved solid-phase microextraction device for use in on-line immunoaffinity capillary electrophoresis.

A simple solid-phase microextraction device was fabricated for use in on-line immunoaffinity capillary electrophoresis (CE). The device, designed in the form of a four-part cross-shaped or cruciform configuration, includes a large-bore tube to transport samples and washing buffers and a small-bore fused-silica capillary for separation of analytes. At the intersection of the transport and separation tubes, a small cavity was fabricated, termed the analyte concentrator-microreactor, which contains four porous walls or semipermeable membranes (one for each inlet and outlet of the tubes) permitting the confinement of beads or suitable microstructures. The surface of the beads in the analyte concentrator carried a molecular recognition adsorbing chemical or affinity ligand material. The improved cruciform configuration of the analyte concentrator-microreactor device, designed for use in on-line immunoaffinity CE, enables it to specifically trap, enrich, and elute an analyte from any biological fluid or tissue sample extract without any sample pretreatment except filtration, centrifugation, and/or dilution allowing the separation and characterization of target analyte(s) with improved speed, sensitivity, and lower cost than existing techniques. As a model system, Fab' fragments derived from a purified immunoglobulin G (IgG) antibody were covalently bound to controlled-porosity glass and used as constituents of the analyte-microreactor device. The high-specificity polyclonal antibodies employed in these experiments were individually raised against the acidic nonsteroidal anti-inflammatory drugs ibuprofen and naproxen, and the neuropeptides angiotensin II, and neurotensin. These compounds, which were present in simple and complex matrices were captured by and eluted from the analyte concentrator-microreactor using a 50 mM sodium tetraborate buffer solution, pH 9.0, followed by a 100 nL plug of 300 mM glycine buffer, pH 3.4. Two analyte concentrators were tested independently: one containing Fab' fragments derived from antibodies raised against ibuprofen and naproxen; the other containing Fab' fragments derived from antibodies raised against angiotensin II and neurotensin. Each resulting electropherogram demonstrated the presence of two eluted materials in less than 20 min. Immunoaffinity CE performed in a cruciform structure was simpler and faster than previously reported in the literature using on-line microextraction devices designed in a linear format. The new concentration-separation system operated consistently for many runs, maintaining reproducible migration times and peak areas for every analyte studied.

The Na+/K+ ATPase is required for septate junction function and epithelial tube-size control in the Drosophila tracheal system.

Although the correct architecture of epithelial tubes is crucial for the function of organs such as the lung, kidney and vascular system, little is known about the molecular mechanisms that control tube size. We show that mutations in the ATPalpha alpha and nrv2 beta subunits of the Na+/K+ ATPase cause Drosophila tracheal tubes to have increased lengths and expanded diameters. ATPalpha and nrv2 mutations also disrupt stable formation of septate junctions, structures with some functional and molecular similarities to vertebrate tight junctions. The Nrv2 beta subunit isoforms have unique tube size and junctional functions because Nrv2, but not other Drosophila Na+/K+ ATPase beta subunits, can rescue nrv2 mutant phenotypes. Mutations in known septate junctions genes cause the same tracheal tube-size defects as ATPalpha and nrv2 mutations, indicating that septate junctions have a previously unidentified role in epithelial tube-size control. Double mutant analyses suggest that tube-size control by septate junctions is mediated by at least two discernable pathways, although the paracellular diffusion barrier function does not appear to involved because tube-size control and diffusion barrier function are genetically separable. Together, our results demonstrate that specific isoforms of the Na+/K+ ATPase play a crucial role in septate junction function and that septate junctions have multiple distinct functions that regulate paracellular transport and epithelial tube size.

Automated Transport and Sorting System in a Large Reference Laboratory: Part 1. Evaluation of Needs and Alternatives and Development of a Plan

Our laboratory, a large, commercial, esoteric reference laboratory, sought some form of total laboratory automation to keep pace with rapid growth of specimen volumes as well as to meet competitive demands for cost reduction and improved turnaround time. We conducted a systematic evaluation of our needs, which led to the development of a plan to implement an automated transport and sorting system. We systematically analyzed and studied our specimen containers, test submission requirements and temperatures, and the workflow and movement of people, specimens, and information throughout the laboratory. We performed an intricate timing study that identified bottlenecks in our manual handling processes. We also evaluated various automation options. The automation alternative viewed to best meet our needs was a transport and sorting system from MDS AutoLab. Our comprehensive plan also included a new standardized transport tube; a centralized automated core laboratory for higher volume tests; a new "automation-friendly" software system for order entry, tracking, and process control; a complete reengineering of our order-entry, handling, and tracking processes; and remodeling of our laboratory facility and specimen processing area. The scope of this project and its potential impact on overall laboratory operations and performance justified the extensive time we invested (nearly 4 years) in a systematic approach to the evaluation, design, and planning of this project.

Elemental composition of laser ablation aerosol particles deposited in the transport tube to an ICP

The element ratios in aerosol particles produced by laser ablation (λ=266 nm, pulse length: 5 ns) of brass and steel in Ar and He and deposited in different segments of the transport tube to an ICP have been measured by ICP-MS. The data are compared with the ratios obtained by a corresponding bulk analysis. For brass, the element compositions of the aerosol particles deposited in different parts of the tube deviated from the bulk and varied along the tube. For steel, moderate agreement of the element ratios in the aerosols and the bulk was found. It is also shown that elemental ratios measured on-line by laser ablation ICP-MS with the laser-produced aerosol should not be calibrated by elemental ratios obtained with wet aerosols from aqueous solutions of the bulk.

On the determination of nitrogen in carbon matrix by deuteron induced gamma-ray emission technique

The systematic study of the experimental conditions affecting the minimum detection limit attainable by the deuteron induced gamma-ray emission (DIGE) method in the case of nitrogen determination in carbon matrix is presented. An optimal experimental set-up has been realized with the use of plate glass linings of the transport tube and chamber close to the target and using copper diaphragms for shaping the beam. The necessity of the reduction of electronic pile-up and the cosmic background is also discussed. The best detection limit obtained was 130 μg/g. A comparison with other analytical methods has been made.

815 COSMOS Heat Pipe における振動流駆動動力

COSMOS Heat Pipe, which is a kind of oscillatory-controlled heat transport tubes, has strongly curved capillaries inside. The driving power of fluids in tube with strong curve was examined experimentally to estimate the operation coefficient (defined by a ratio of heat transport rate and added driving power) of COSMOS Heat Pipe. The result shows that the power to drive oscillatory flow in strongly curved capillary can be about twice larger than that of straight one under some conditions. Heat transport experiment was also carried out, and it was shown that the estimated operation condition of COSMOS Heat Pipe is fairly high.

Vertical pneumatic conveying in dilute and dense-phase flows: experimental study of the influence of particle density and diameter on fluid dynamic behavior

In this work, the effects of particle size and density on the fluid dynamic behavior of vertical gas-solid transport of Group D particles in a 53.4 mm diameter transport tube were studied. For the conditions tested, the experimental curves of pressure gradient versus air velocity presented a minimum pressure gradient point, which is associated with a change in the flow regime from dense to dilute phase. The increases in particle size from 1.00 to 3.68 mm and in density from 935 to 2500 kg/m3 caused an increase in pressure gradient for the dense-phase transport region, but were not relevant in dilute transport. The transition velocity between dense and dilute flow (Umin) also increased with increasing particle density and diameter. An empirical equation was fitted for predicting transition air velocity for the transport of glass spheres. Additional experiments, covering a wider range of conditions and particles properties, are still needed to allow the fitting of a generalized equation for prediction of Umin.

Peak broadening from an electrothermal vaporization sample introduction source into an inductively coupled plasma

Signal broadening using electrothermal vaporization with inductively coupled mass spectrometry (ETV-ICPMS) occurs at a rate much faster than would be predicted by simple longitudinal diffusion. A Monte Carlo simulation that focused on particle motion within the transport tubing was created to elucidate the causes of this dispersion within ETV-ICPMS. Several parameters, including the diffusion coefficient, tube diameter, transport tube length, and flow rate were varied to discern their role in signal broadening. Using typical instrumental parameters, the parabolic flow profile generated by laminar flow of the carrier gas was shown to be the primary cause of dispersion. Manipulating the aforementioned variables to lessen the effects of laminar flow led to a decrease in dispersion. Conversely, increasing the role of laminar flow promoted broadening. The broadening processes should be applicable to any transient introduction system where material must be transported to a detection system. Due to the difference in the rate of broadening expected for particles of different sizes, the simulation was used to calculate the average size of particles generated in the ETV using different mass amounts of sample. No change in particle size (∼1 nm) was seen for mass amounts ranging from 10–10 000 pg, which suggests that the particle number is increased with increasing sample mass rather than the average particle size. Using this method of determining particle size, it might be possible to further evaluate the mechanisms of physical ‘carrier’ action.

Triboelectric charging of polymer powders in fluidization and transport processes

In this paper, we investigated the role of tribocharging in fluidization, flowability, and q/m distribution as functions of particle size distribution (PSD), fluidization time, and transport tubes of different materials. A charge separator was used to determine mass fractions of powder that had positive, zero, and negative charges. For the two acrylic powders tested, one (Sample A) had volume median diameter d/sub 50/ 18.73 /spl mu/m while the other (Sample B) had d/sub 50/ 24.17-/spl mu/m diameter. During fluidization for 1 h at a relative humidity of 57%, powder B acquired positive charge with charge-to-mass ratio Q/M=0.3 /spl mu/C/g, and 25% of the powder mass had negative charge with Q/M=-0.36 /spl mu/C/g. About 35% of the powder mass had particles with nearly zero net charge. Tribocharging during fluidization and transport processes was attributed to particle-particle and particle-wall collisions. Of the total charged particles, about 60% were positively charged while 40% were negatively charged. Each particle may have had patches of charges on its surface, some positive and some negative. The sum total of all patches of charges may yield positive, negative, or essentially neutral polarities on a given particle. For a relatively narrow size distribution of powder, the PSD is often assumed to be conserved during fluidization. A shift in PSD toward larger diameter particles was anticipated because of the possible elutriation of the fine fraction of the powder, but the actual shift was only about 1 /spl mu/m after 1 h of fluidization. Under identical operational conditions using a fluidized bed, powder pump, transport hose, and corona gun, powder B had nearly twice the mass flow rate of Powder A. Such differences in flowability of powders influence charging and deposition efficiencies in powder coating applications.

Theoretical description and experimental observation of aerosol transport processes in laser ablation inductively coupled plasma mass spectrometry

The transport efficiency of laser-induced aerosols mainly influences the detection capabilities for high spatial resolution laser ablation microanalysis. Therefore, the volume of the ablation cell, the geometry, the gas flow pattern and the transfer tube to carry the aerosol into the ICP are important influences on the transport process and the signal structure. Four different ablation cell volumes, ranging from 0.25 to 63 cm3, in combination with various transfer tubes of different diameters and lengths were investigated. The signal structure was significantly modified by reducing the volume of the sample chamber by a factor of approximately 250. The peak height of single laser shot (aerosol density) was increased by a factor of 6, the signal width (aerosol dispersion) was reduced by a factor of 7 and the rinse time of the sample chamber was consequently shortened to approximately 1 s, thereby eliminating processes of sample recirculation within the cell. The gas flow pattern inside the cell was experimentally traced by introducing powder of different sizes (grain size <1 µm and <65 µm) inside the cell. An angle of 40° at the apex of the gas injection cone was observed at the tip of the inlet nozzle, for a 0.5 mm id nozzle and 1 L min−1 gas flow. The gas inlet nozzle ensured a steady, high efficiency flow, influencing the precision of the measurements. The amount of transported material was constant within the precision of the ablation process for optimized transport and ionization conditions in all ablation cells. The ablation in a sample cell of volume of 0.25 cm3 showed slightly reduced sample transport and a slightly longer rinse time than for a 1.5 cm3 cell, which could be an indication that with extremely reduced cell volumes aerosol–wall interaction might limit the transport efficiency. The variation of the transport tube diameter (4–7 mm) and length (1.5–6 m) showed an influence on the signal structure, but the total amount of sample transferred was not influenced. Nevertheless, the variation of the dispersion as a function of the total volume of the transport system (cell and tube) showed that cell volume more significantly influenced the signal structure. A mathematical model was developed to describe the structure of the signal in relation to the parameters of the ablation set-up and its scope is discussed.

Experiments and analyses of SiC thin film deposition from organo-silicon by a remote plasma method

The remote plasma enhanced chemical vapor depositions (RPECVD) using organo-silicon as source compounds have been examined in terms of the mechanism of the activation steps and film formation. The deposition experiments were performed for different configurations of the radical transportation tube (straight, with a light trap, and a radical trap) to prove how the source materials are effective for the film formation. In the SiC film formation, it is shown that hydrogen radicals act on the SiSi bonds or SiH bonds of the source materials, but SiC bonds in the source will not be broken by the hydrogen radicals because of its high binding energy. As a practical application, SiC film coatings on the plastic are examined using electron cyclotron resonance (ECR) plasma system. These SiC coatings provide many advantages for the development of scratch resistivity and UV degradation resistivity for plastic materials.

Characterization of pressure pulse and carrier gas flow changes resulting from pulsed heating in ETV-ICP-MS

A simplistic model was formulated to show the effects of pulsed heating upon a flow of gas through an ETV. Using this model, a significant change in flow was predicted with a profile that increased sharply during the initial stages of heating, but then tapered off. Experimentally, pressure and flow increases were shown to be coincident to the pulsed heating of an ETV, by using both a direct and an indirect method of determination. Direct measurement of both pressure and flow increases were acquired through the use of a probe that contained pressure, flow and temperature sensors. An indirect measurement of the pressure/flow pulse was obtained by monitoring the Ar2+, which is sensitive to the carrier gas flow rate. The pressure increase was determined to be minimal ( 100 ml min−1). The magnitudes of both pressure and flow increases were determined to be dependent upon the initial carrier gas flow rates. Due to the envisioned deleterious effects of the pressure/flow pulse, an attempt was made to separate the arrival of the pulse at the plasma from the analyte signal by lengthening the transport tubing. In this manner, it was determined that the analyte signal traveled at a velocity which was much less than that of the pressure pulse which propagates at the speed of sound in Ar. However, increased transport tubing lengths resulted in lower sensitivities and no significant gain in precision.