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1.
Abstract This work attempts to discover, by experimentation, some of the parameters governing cutting efficiency in perspex of a continuous CO2 laser. The experimentation took the form of taking cuts in specimen pieces with the laser. While varying the parameters of speed of cut and position of the focal plane of the laser beam relative to the surface of the perspex, all other parameters were kept constant. These experiments produced conclusive ideas of the optimum position of the focal plane and the best speeds for cutting perspex at the same time producing the best cut quality obtainable. When the theoretically predicted minimum cut width is compared with the experimentally obtained results, the agreement is found to be almost exact. 相似文献
2.
Asghar Ali 《Fullerenes, Nanotubes and Carbon Nanostructures》2016,24(9):555-563
Photocatalytic reduction of CO2 over a Cu2Se–graphene nanocatalyst has been investigated. The nanocomposite material was successfully prepared via a modified hydrothermal method. The structure and properties of the prepared composite were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray microscopy, transmission electron microscopy, Raman spectroscopic analysis, and X-ray photoelectron spectroscopy. A synergetic effect of the combination of Cu2Se and graphene appeared in the form of excellent photocatalytic reduction capability of CO2. The photocatalytic efficiencies of the samples were characterized by testing for the photoreduction of CO2 to alcohol under visible light irradiation, which produced results such as to suggest that there is a significant potential for graphene-based semiconductor hybrid materials to be used as photocatalysts for reduction of CO2. 相似文献
3.
Abstract A uniform volumetric discharge was obtained by means of an auxiliary UV preionization in a home‐made TEA CO2 laser. The maximum output pulse energy of this laser system was about 12J per pulse with a pulse duration of 80 ns. The ratio of electric field to neutral particle density (E/N) in this laser was 7.6×10‐16 V cm2. The peak power and pulse shape of the laser were studied. The time delay between the predischarge and the maindischarge during the stable operation of this laser system has also been studied. It was observed that the laser was operating with uniform glow discharges when the time delayed between the predischarge and the maindischarge was in the range of 1.0 μs to 6.0 μs. The spark array used as a preionizer for producing the UV radiation in this system is new, simple, durable, and can be easily fabricated. 相似文献
4.
Asghar Ali 《Fullerenes, Nanotubes and Carbon Nanostructures》2017,25(8):449-458
The present work investigates the photocatalytic reduction of CO2 to CH3OH with a PbSe-G-TiO2 photocatalyst. A heterogeneous PbSe-G-TiO2 nanocomposite was prepared via ultra-sonication and was characterized via XRD, SEM, HRTEM, Raman, XPS, and DRS measurements. The photocatalytic efficiencies of the prepared sample were further characterized by GC for the photoreduction of CO2 to CH3OH under UV and visible light. The prepared PbSe-G-TiO2 ternary nanocomposites with an optimum GO loading of 6% exhibited outstanding photocatalytic activity (4.35 µmol g?1 h?1) after 48 hours of reaction. This indicated that the photocatalytic efficiency was mostly dependent on the weight ratio of graphene, sacrificial material Na2SO3/Na2S, and the type of reactant. This work provides an accessible way to improve the response of a graphene-based TiO2 photocatalyst to UV/visible light and to facilitate its application in environmental remediation. 相似文献
5.
AbstractA macro model for evaluating the steel flow in Japan is proposed. The steels are classified into four types; virgin steel for machinery and for construction and recycled steel for machinery and for construction. The steel is assumed to be discharged from the society in accordance with the lifetime distribution of each usage. The amount of recycled steel and the accumulation in society are calculated using a population balance model. The comparison with the calculated results and statistics ensures the validity of the model. Since the amount of recycled steel mainly supplied for construction will increase and be oversupplied, recycled steel will have to be used for machinery. The required amount and the available amount to supply recycled steel for machinery are considered from the point of allowable copper concentration for machinery use. Copper contaminates steel during the recycling process of steel used for machinery and the contamination ratio is evaluated with the model. The copper concentration in the recycled steel and the amount of CO2 emission are predicted for various scenarios. The relationship between recycling ratio and contamination ratio, which enables us to supply recycled steel for machinery, and the allowable CO2 emission to decrease the contamination ratio are discussed. © 2000 Published by Elsevier Science Ltd. 相似文献
6.
Ping Ouyang Yun-qing Kang Guang-fu Yin Zhong-bing Huang Ya-dong Yao Xiao-ming Liao 《Frontiers of Materials Science in China》2009,3(1):15-24
In this work, chemically bonded poly(D, L-lactide)-polyethylene glycol-poly(D, L-lactide) (PLA-PEG-PLA) triblock copolymers
with various PEG contents and PLA homopolymer were synthesized via melt polymerization, and were confirmed by FTIR and 1H-NMR results. The molecular weight and polydispersity of the synthesized PLA and PLA-PEG-PLA copolymers were investigated
by gel permeation chromatography. Hydrophilicity of the copolymers was identified by contact angle measurement. PLA-PEG-PLA
and PLA microparticles loaded with and without PTX were then produced via solution enhanced dispersion by supercritical CO2 (SEDS) process. The effect of the PEG content on the particle size distribution, morphology, drug load, and encapsulation
efficiency of the fabricated microparticles was also studied. Results indicate that PLA and PLA-PEG-PLA microparticles all
exhibit sphere-like shape with smooth surface, when PEG content is relatively low. The produced microparticles have narrow
particle size distributions and small particle sizes. The drug load and encapsulation efficiency of the produced microparticles
decreases with higher PEG content in the copolymer matrix. Moreover, high hydrophilicity is found when PEG is chemically attached
to originally hydrophobic PLA, providing the produced drug-loaded microparticles with high hydrophilicity, biocompatibility,
and prolonged circulation time, which are considered of vital importance for vessel-circulating drug delivery system. 相似文献
7.
Yan X Zhang Y Qiao K Li X Zhang Z Yan Z Komarneni S 《Journal of hazardous materials》2011,192(3):1505-1508
Amine-functionalized clover leaf-shaped Al2O3 extrudates (CA) were prepared for use as CO2 sorbent. The as-synthesized materials were characterized by N2 adsorption, XRD, SEM and elemental analysis followed by testing for CO2 capture using simulated flue gas containing 15.1% CO2. The results showed that a significant enhancement in CO2 uptake was achieved with the introduction of amines into CA materials. A remarkably high volume-based capacity of 70.1 mg/mL of sorbent of this hybrid material suggests that it can be potentially used for CO2 capture from flue gases and other stationary sources, especially those with low CO2 concentration. The novel adsorbent reported here performed well during prolonged cyclic operations of adsorption-desorption of CO2. 相似文献
8.
The transcritical CO2 process fits well to the air dehumidification process observed in a heat pump dryer. Gains (respectively avoided losses) in connection with heat transfer during the air heating phase and superior compressor performance make up for the higher throttling losses of the process, resulting in an equivalent or even better coefficient of performance than the comparative R134a process. 相似文献
9.
G. Di Nicola G. Giuliani G. Passerini F. Polonara R. Stryjek 《International Journal of Thermophysics》2004,25(5):1437-1447
PVTx measurements for the R116 + CO2 system for four isotherms (283, 304, 325 and 346 K) were performed. In total, 16 runs were performed in a pressure range from 5100 to 140 kPa. Seven runs along four isotherms in a pressure range from 3400 to 280 kPa were performed for pure hexafluoroethane (R116), and the second and third virial coefficients were derived. The values of the virial coefficients for CO2 were adopted from our previous measurements. The second and third virial coefficients along with the second and third cross-virial coefficients were derived from the mixture results. The Burnett apparatus was calibrated using helium. The experimental uncertainty in second and third virial coefficients was estimated to be within ±2 cm3· mol–1 and ±500 cm6 ·mol –2, respectively. 相似文献
10.
Cu2O cubes with average edge lengths of 640 nm were prepared by a chemical reduction approach. The as-synthesized Cu2O particles were deposited on carbon clothes for electrochemical characterizations in cyclic voltammetry (CV) and potentiostatic measurements. In 0.5 M NaOH electrolytes saturated with N2 or CO2, both the Cu2O and carbon clothes were stable at the potential range of 0 to − 1.7 V. Comparisons in the current responses from the CV and potentiostatic measurements suggested the Cu2O with notable catalytic abilities for the CO2 reduction. The mass activity was estimated at 0.94 mA/mg. Chemical analysis from gas chromatography confirmed the methanol to be the predominant product. 相似文献
11.
G. Di Nicola G. Giuliani F. Polonara R. Stryjek 《International Journal of Thermophysics》2003,24(3):651-665
Burnett PVT measurements were performed on trifluoromethane (R23) and mixtures of R23 with carbon dioxide (CO2). The Burnett apparatus was calibrated using helium. Fourteen expansions were performed for 5 isotherms and in a pressure range from 130 kPa to 6 MPa for R23. Second and third virial coefficients were derived from the collected data and compared with literature values; good agreement was found between them. PVTx measurements for the binary CO2+R23 system were carried out for five isotherms (303, 313, 323, 333, and 343 K). In all, 18 runs were performed in a pressure range from 150 kPa to 5.9 MPa. The composition of the mixtures was measured with a gas chromatograph after it had been calibrated using samples prepared gravimetrically. Second and third virial coefficients for the system were derived, together with the second and third cross virial coefficients, from experimental results using virial coefficients for CO2 from previous measurements (for the same sample as used in the present study). Samples for composition measurements were collected during the first Burnett expansion. Second virial coefficients for the system showed positive deviations from ideal values, while the third virials were negative. No previous experimental results were found for the PVTx properties of this binary system. 相似文献
12.
Inserting carbon dioxide (CO2) into ammonia molecules to produce urea is a traditional CO2 utilization method. An ionic liquid (IL), 1-butyl-3-methylimidazolium bromide ([Bmim]Br), was used as reaction medium and [Bmim]Br/KOH as catalyst. This study investigates CO2 carbonylation of cyclohexylamine and its reaction performance in a number of low- and high-pressure CO2/IL systems. The reaction yield was greatly increased as pressure ranges changed from 15–50 bar to 80–100 bar; the physiochemical properties of substrates and catalyst were greatly affected by CO2 in supercritical state. The yield was improved from 69% at 30 bar to 91.6% at 100 bar, much better than a previous study result of 53.5%, but as pressures further increased, a significant decrease was observed. The reaction activation energy was calculated to be 3.942 and 4.354 kcal/mol in mild and supercritical conditions. This process shows a low threshold reaction energy and great potential for industrial applications to store CO2 in amine molecular structures. 相似文献
13.
Shuhui Li Hongliang Zhang Guoxu Wang Lei Liu Yifeng Yu 《Fullerenes, Nanotubes and Carbon Nanostructures》2017,25(8):493-496
We prepare the hollow carbon nanospheres (HCNs) by employing SiO2 nanospheres as hard template, 5-Hydroxymethylfurfural (HMF) as carbon precursor under hydrothermal conditions. The HCNs show uniform spherical morphology copied from SiO2 nanospheres and exhibit large cavity, thin shell structure with the surface area of 790 m2 g?1 and pore volume of 2.23 cm3 g?1. Owing to their large internal voids and high surface area, the HCNs exhibit a promising prospect for CO2 capture with the capacity of 3.04 mmol g?1 at 1.0 bar and 298 K, as well as good recyclability for CO2 after ten adsorption-desorption cycles. 相似文献
14.
M. Bonetti F. Perrot D. Beysens Y. Garrabos 《International Journal of Thermophysics》1995,16(5):1059-1067
Heat transport in supercritical CO2 is studied under microgravity conditions. A large temperature and density region around the critical point is explored (CO2 cells were filled at critical density=
c and off-critical densities=
c±0.18
c). Local heating is obtained by using a small thermistor located in the bulk fluid. Through interferometric observations, a new mechanism of thermalization has been evidenced. Thermal expansion of a warm diffusing boundary layer around the heating thermistor is responsible for rapid adiabatic heating of the bulk fluid through the emission of pressure waves at the border. The scaled thickness of the thermal boundary layer follows a power law. When the heat flow stops, the bulk adiabatic heating instantaneously vanishes and the temperature relaxation inside the thermal boundary layer follows locally a diffusive process.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
15.
Jens Hetland 《Clean Technologies and Environmental Policy》2009,11(1):37-48
This article deals with emerging poly-generation schemes that employ pre-combustion decarbonisation of fossil fuels—eventually
with options for geological storage of the CO2. Inevitably, such schemes are highly complex, and may require new approaches and knowledge on interactions between key components
in large plants, as even new technologies and features are expected to occur in due course as the experience from polygeneration
matures. Reference is made to the European DYNAMIS project and the Sino-European project COACH—both conducted under the auspices
of the European Commission.
相似文献
Jens HetlandEmail: |
16.
D.G. Waugh J. Lawrence D.J. Morgan C.L. Thomas 《Materials science & engineering. C, Materials for biological applications》2009,29(8):2514-2524
It has been amply demonstrated previously that CO2 lasers hold the ability to surface modify various polymers. In addition, it has been observed that these surface enhancements can augment the biomimetic nature of the laser irradiated materials. This research has employed a CO2 laser marker to produce trench and hatch topographical patterns with peak heights of around 1 μm on the surface of nylon 6,6. The patterns generated have been analysed using white light interferometry, optical microscopy and X-ray photoelectron spectroscopy was employed to determine the surface oxygen content. Contact angle measurements were used to characterize each sample in terms of wettability. Generally, it was seen that as a result of laser processing the contact angle, surface roughness and surface oxygen content increased whilst the apparent polar and total surface energies decreased. The increase in contact angle and reduction in surface energy components was found to be on account of a mixed intermediate state wetting regime owing to the change in roughness due to the induced topographical patterns. To determine the biomimetic nature of the modified and as-received control samples each one was seeded with 2 × 104 cells/ml normal human osteoblast cells and observed after periods of 24 h and 4 days using optical microscopy and SEM to determine mean cell cover densities and variations in cell morphology. In addition, a haemocytometer was used to show that the cell count for the laser patterned samples had increased by up to a factor of 1.5 compared to the as-received control sample after 4 days of incubation. Significantly, it was determined that all laser-induced patterns gave rise to better cell response in comparison to the as-received control sample studied due to increased preferential cell growth on those surfaces with increased surface roughness. 相似文献
17.
Effect of leakage current and dielectric constant on single and double layer oxides in MOS structure
MOS structure of Al/Al2O3/n-Si, Al/TiO2/n-Si and Al/Al2O3/TiO2/n-Si was obtained by deposition of Al2O3 and TiO2 on silicon substrate by RF Magnetron Sputtering system. The total thickness of the oxide layer ~ 40 ± 5 nm in the MOS structure was kept constant. Samples were characterized by X-Ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), Impedance analyzer and Current-voltage (J-V) characteristics. The variations in the dielectric constant and tan δ of the MOS capacitor in the frequency range of 1000Hz-1MHz were measured by impedance analyzer. The variation in dielectric constant of the Al/Al2O3/TiO2/n-Si multilayer compared to single layer of Al/Al2O3/n-Si and Al/TiO2/n-Si is due to high probability of defects, lattice mismatch and interface interactions. The steep rise of Tan δ values in the Al/Al2O3/TiO2/n-Si structure is due to the resonance effect of both Al2O3 and TiO2 layers. The leakage current mechanisms of MOS structures were extracted from Schottky coefficient and Poole-Frenkel coefficient. Theoretical values of Schottky coefficients (βSC) and Poole-Frenkel coefficients (βPF) for each sample were estimated using the real part of the dielectric constant. The experimental values were calculated from J-V characteristics and compared with theoretical values. The appropriate model has been proposed. It was found that Schottky and Poole-Frenkel mechanisms are applicable at low and high field respectively for all MOS structures. The combination of Al/Al2O3/TiO2/n-Si is found to be a promising structure with high dielectric constant and low leakage current suitable for MOS devices. 相似文献
18.
We report here on the growth of large crystals of Gd-Ba-Cu-O superconductor by using the ‘K2CO3-method’ adopted earlier for preparing oriented ceramics and large crystals of Y-Ba-Cu-O superconductors. The temperature
favourable for the growth of GdBaCuO crystals is found to be higher than that required for YBaCuO crystals. Also, the crystal
perfection is better for these crystals and as a result, the oxygenation of the sample becomes more difficult. Resistivity
measurements on these samples show a sharp drop in resistivity at 90 K which then tails off at lower temperatures and attains
zero resistance around 35 K. Such behaviour is normally due to an inhomogeneous oxygen content in the sample. Chemical analysis
shows that the deviation from ‘123’ composition in GdBaCuO-samples is much less as compared to YBaCuO-samples obtained by
the same technique. 相似文献
19.
The increase of warm-room gas is thought to cause the rise of atmosphere temperature, which is called the warm-room effect. Therefore, the decomposition treatment of carbon dioxide (CO2) gas is an important research subject in order to solve the global environmental problem. In this study, a high-energy plasma process was used to decompose CO2 gas as a warm-room gas, and the decomposition mechanism was clarified by varying the plasma operation conditions. The possibility of transforming of the CO2 gas to various resources was also discussed. Firstly, the performance test of the gas tunnel-type plasma jet used for decomposition of CO2 was conducted, and decomposition characteristics of CO2 gas by the gas tunnel-type plasma jet was determined under various conditions. The decomposition ratio of CO2 was about 30%, when the power input was P=8 kW, and the CO2 content in argon was 10%. Secondly, the improvement of operating conditions of the plasma jet was discussed in order to enhance its performance. 相似文献
20.
《Materials at High Temperatures》2013,30(3):253-259
AbstractThe examination of high temperature (HT) oxide scale growth mechanisms was performed using secondary ion mass spectrometry (SIMS) and secondary neutral mass spectrometry (SNMS), in conjunction with 16O2/18O2 HT oxidation experiments. Cr2O3, NiO, ZrO2 and Al2O3 were studied because they constitute excellent representative thermally grown oxide scales: they grow by cationic diffusion (Cr2O3, NiO), anionic diffusion (ZrO2) or mixed anionic-cationic diffusion (Al2O3). The oxidation tests were performed first in 16O2 and subsequently in 18O2 at several temperatures (600–1000°C for NiO, 600°C for ZrO2, 1000°C for Cr2O3 and 1100°C for Al2O3). The oxygen isotope distribution observed by SIMS and SNMS profiles are discussed and related with the HT oxidation mechanisms proposed in the literature. 相似文献