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•Proper activation of the catalyst gives a 9-fold increase in the yield.•Carbon nanotube length and defectiveness can be preserved when activation tuned.•Optimal activation comprises ...efficient delivery and flow dynamics.•Carbon nanotube diameter distribution is not affected by the injection flowrate.•Supply of carbon intermediates is rate-limiting step for nanotube nucleation.
In this work, we evaluate the effect of ferrocene delivery in the reactor on the growth of single-walled carbon nanotubes (SWCNTs) in an aerosol CVD utilizing carbon monoxide as a feedstock. For this purpose, we assess the reactor output parameters varying a gas flow rate through a ferrocene vapor injector in the hot zone with other conditions (temperature, total flow rate, and reactant concentration) being fixed. Our experimental results reveal the adjustment of the ferrocene injection strategy (injector flow rate) to cause a 9-fold improvement in the synthesis yield while preserving the SWCNT properties. We show the catalyst injection optimization to enhance catalyst activation degree as a result of a streamline catalyst delivery, preventing particle over-growth; the experimental data are supported by the computational fluid dynamics. We believe our work to highlight the importance of appropriate aerosol CVD reactor engineering and to facilitate the optimization of reactor productivity, which is one of the fundamental milestones towards SWCNT-based technology.
New type of Ag-containing nanostructured catalyst for high-temperature alcohol oxidation was developed on the basis of mesoporous SiO2 support. Active component (silver clusters/nanoparticles) ...stabilized by support surface and polyphosphate inside the pores. It was shown that Ag/P2O5/SiO2 catalyst provides high activity in the course of ethylene glycol oxidation to glyoxal at 500-600 °C. Formation of stable structure of catalyst during thermal treatment includes self-organization of mesoporous structure and chemical bonding of phosphate with silica. The catalyst treatment in red-ox conditions leads to reversible oxidation-reduction of silver and its redistribution from bulk to surface of the catalyst. Silver nanoparticles stabilized with silica-phosphate support are active species in the ethylene glycol oxidation into glyoxal.
This article addresses temporary labour migration - known in Russian as otkhodnichestvo (going away on foot) - from the Russian republic of Dagestan. The discussion is situated within reviews of ...current work on migration in the former Soviet Union, push-pull factors determining migration behaviour in the North Caucasus, and the historical importance of otkhodnichestvo in imperial Russia and the USSR. The paper then turns to the results of a census conducted in summer 2006, which found that most migrants come from Dagestan's mountainous southwest, frequently obtain work at locations characterized by economic growth and high pay, and rely on ethnic or communal networks as a basis for choosing employment sector and destination when searching for work.
We investigate the aerosol doping method for a thermoelectric performance enhancement of single-walled carbon nanotube (SWCNT) films. A study of doping behavior by depositing an aerosolized dopant ...solution and real-time optimization of thin film properties focuses on thermoelectric characteristics. Achieving precise control over doping results, we demonstrated the thermoelectric power factor of 657 and 708 μW/mK2 for, respectively, p-type and n-type doped SWCNT films. The proposed doping strategy offers superior flexibility for device design and comparable performance to solution-based doping, paving the way to efficient and scalable thermoelectric generator production based on carbon nanotube materials.
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•New method for doping of nanotube-based thermoelectric generators.•The aerosol doping of thermoelectrics is tunable and provides a real-time control.•The method is suitable for both p- and n-type dopants.•State-of-the-art combination of power factors: 657 (p-) and 708 μW/mK2 (n-doping).
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•Residence time in aerosol CVD was tuned while nanotube nucleation maintained.•Carbon nanotube length and IG/ID ratio increase with a higher residence time.•The increase in length and ...defectiveness drops equivalent sheet resistance.•Effect of vortices, diffusion, and thermophoresis on nanotube yield was shown.•SWCNT/HAuCl4 thin films with equivalent sheet resistance of 51 Ω/□ were obtained.
We examine an effect of residence time on the growth of single-walled carbon nanotubes (SWCNTs) in an aerosol (floating catalyst) chemical vapor deposition (CVD) process using CO as a carbon source and ferrocene as a catalyst precursor. The key feature of aerosol CVD reactors, namely stabilization of fine nanoparticles by an extreme dilution, limits the method for catalyst evolution studies. We show an approach to examine the role of the residence time while maintaining all the processes preceding the nanotube growth (catalyst formation, nanotube nucleation). Using the diameter distribution of nanotubes as a fingerprint of the SWCNT nucleation stage, we have proven the latter to be unaffected by changes in the residence time. Using SEM observations, we have revealed a quite intuitive but inspiring correlation between the carbon nanotube length and residence time. We have also found a decrease in the SWCNT yield caused by the drop in the aerosol concentration, which could be attributed to the gas-phase losses as well as the shift in the catalyst activation degree. Nevertheless, the trends observed allowed us to reach a tenfold decrease in an equivalent sheet resistance (sheet resistance of a film with 90% transmittance at 550 nm) by a threefold increase in the residence time at optimal CO2 concentration. SWCNT films with the equivalent sheet resistance as low as 245 Ω/□ and 51 Ω/□ (for pristine and doped carbon nanotubes, correspondingly) ensure the promising future of the proposed strategy for optimization of both aerosol CVD reactors and SWCNT-based films for optoelectronic applications.
The gas and chemical flooding for reservoir stimulation with residual hydrocarbons reserves are highly relevant problem of current oil and gas recovery strategy. The objective of this paper is ...laboratory study and field implementation of new gas-EOR technology—in situ carbon dioxide generation technique for CO
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-liquid slug formation under oil displacement, increasing the reservoir sweep efficiency and residual oil recovery. This paper presents a summary of a wide range of laboratory tests conducted on different core samples and chemical compositions. Several physical and hydrodynamic phenomena of in situ CO
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generation in highly permeable zones of a porous medium have been investigated as a part of complex study, which involved laboratory tests on the field-scale industrial technology applications, determination of optimal concentrations of foaming agents and inhibiting additives in gas-releasing solutions, etc. The results of laboratory experiments showed that the incremental recovery ranged between 30 and 35% oil original in place. The unique results of the field implementation provide developing an optimal technological scheme of reservoir stimulation with residual oil reserves both onshore and offshore oil fields. Technology of in situ CO
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generation was applied on the group of wells on Penglai offshore oil field (Bohai Bay). Incremental oil production for field operation was 37,740 bbl of crude oil. Theoretical and laboratory studies, as well as the outcomes of industrial implementation of a new method of residual oil recovery, using a CO
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-slug confirm technology and economic profitability of the proposed solution.
To evaluate the prognostic value of some pathological variables in rectal cancer survival.
247 patients who underwent curative resection of rectal cancer were included in the study. The influence on ...survival of five pathological variables (histopathological tumor type, histopathological tumor grade differentiation, blood vessel invasion, perineural invasion and lymphatic invasion) was assessed using statistical analyses.
Overall 5-year survival was 71.2%. Univariate analysis of all tested variables showed an effect on survival but only the effect of lymphatic invasion was statistically significant. At stages three and four it had a negative effect on survival (P = 0.0212). Lymphatic invasion also significantly affected cancer related survival in multivariate analysis at stages three and four. At lower stages (stage 0, stage 1 and stage 2) multivariate analysis showed a negative effect of perineural invasion on cancer related survival.
Patients with lymphatic and perineural invasion have a higher risk for rectal cancer related death after curative resection. Examination of these variables should be an important step in detecting patients with a poorer prognosis.
This work is devoted to the strategy towards the optimal development of multiparametric process of single-walled carbon nanotube (SWCNT) synthesis. Here, we examine the implementation of machine ...learning techniques and discuss features of the optimal dataset size and density for aerosol chemical vapor deposition method with a complex carbon source. We employ the dataset of 369 points, comprising synthesis parameters (catalyst amount, temperature, feed of carbon sources) and corresponding carbon nanotube characteristics (yield, quality, structure, optoelectrical figure of merit). Assessing the performance of six machine learning methods on the dataset, we demonstrate Artificial Neural Network to be the most suitable approach to predict the outcome of synthesis processes. We show that even a dataset of 250 points with the inhomogeneous distribution of input parameters is enough to reach an acceptable performance of the Artificial Neural Network, wherein the error is most likely to arise from experimental inaccuracy and hidden uncontrolled variables. We believe our work will contribute to the selection of an appropriate regression algorithm for the controlled carbon nanotube synthesis and further development of an autonomous synthesis system for an “on-demand” SWCNT production.
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•Machine learning applied to semi-industrial aerosol reactor for nanotube synthesis.•Six methods applied to dataset of 369 points with 3 input and 4 output features.•Neural networks outperform other tested algorithms including decision-tree methods.•Prediction errors comparable to experimental inaccuracy achieved for all features.•The dataset of as low as 250 points found to be sufficient for moderate performance.
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