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排序方式: 共有143条查询结果,搜索用时 31 毫秒
1.
为提高AlN涂层的稳定性和阻氚性能,提出“Ti-AlN”复合结构涂层。采用磁控溅射法在316L不锈钢基体表面制备了结构致密、总厚度约500 nm的Ti/AlN/Ti/AlN复合涂层。对涂层样品进行不同的真空热处理后,采用SEM、XRD、AES等手段分析涂层样品在热处理前后的微观形貌和结构变化,并对样品在200-600 ℃的阻氘性能进行测试和分析。结果表明,仅热处理温度为760 ℃时,Ti-AlN界面反应生成少量的Al3Ti相。在所有涂层样品中,热处理温度为700 ℃、升温速率为1.5 ℃/min的复合涂层表现出最优的阻氘性能,其600 ℃的PRF(Permeation Reduction Factor)高达536。当热处理温度升高至760 ℃或升温速率达到2.5 ℃/min时,表层AlN层的开裂程度更为严重,并导致涂层的阻氘性能显著降低。另外,所有涂层样品的PRF(阻氘性能)均随渗透温度的降低而急剧减小,表明氘气渗透过程中的温度变化会导致复合涂层阻氘性能失效。  相似文献   
2.
Steel components are required in the infrastructure and the facilities of the hydrogen economy. The high hydrogen pressures in the hydrogen economy lead to embrittlement and surface corrosion of the steels. For the functionality of the facilities it is necessary to suppress the embrittlement and the surface corrosion of the steels by protective layers, e.g. ceramic thin films. With regard to fusion power plants ceramic thin films on the structural steel materials are also required. These thin films work as a tritium permeation barrier that is necessary to prevent the loss of the radioactive fuel inventory. Oxide thin films, e.g. Al2O3, Er2O3, and Y2O3, are promising candidates as tritium permeation barrier layers. In terms of the application in the first wall, this is especially true for yttrium due to its favorably short decay time after neutron activation compared to the other candidates. The Y2O3 layers with thicknesses of 0.5 μm–1 μm are deposited on both substrate sides by RF magnetron sputter deposition. Since the microstructure of the barrier layer plays an important role for the permeation reduction, layers with three different magnetron process modes and thus three different microstructures are prepared. After annealing the cubic crystal structure of all thin films is verified by X-ray diffraction and the different microstructures are investigated by scanning electron microscopy and transmission electron microscopy. The Y2O3 stoichiometry of all thin films and a chromium oxide material segregation at the interface are verified by analysis methods such as X-ray photoelectron spectroscopy. The permeation reduction factors of all thin films are determined in gas-driven deuterium permeation experiments. Corresponding to the three different microstructures, reduction factors of 25, 45, and 1100 are identified. Thus, the permeation reduction is strongly dependent on the Y2O3 microstructure. The measurement results suggest that a high density of grain boundaries leads to a high hydrogen permeation.  相似文献   
3.
Processes for separating hydrogen isotopes are important for future energy applications. Several separation methods are based on electrolytic process; however, electrolysis consumes large amounts of electric energy. In this study, we demonstrate deuterium isotope separation from a mixture of H2 and D2 gases using a polymer electrolyte fuel cell stack. To identify the most efficient process, we investigated two flow patterns for the fuel gas, namely, parallel and serial flow. The electrical power of the stacks depended on the flow pattern when a high current was generated. We attribute this dependence on membrane dehydration and water droplet formation in the serial flow, which passed through the single cells in a straight path. However, the stack with the serial path showed a high separation factor (α = 6.6) indicating enrichment of deuterium water during the operation. The long reaction path of the fuel gas contributed to effective separation. The fuel utilization in individual cells suggested the potential for even more effective separation processes by a serial flow path.  相似文献   
4.
This paper reports a study on the use of a polymer electrolyte fuel cell (PEFC) with a PtRu/C anode for isotopic separation of hydrogen (H) and deuterium (D). The performance of a PEFC, fed with pure hydrogen, deuterium or a their mix is depicted. In order to investigate the effect of the two isotopes, electrochemical impedance spectroscopy (EIS) tests have been carried out together with galvanostatic polarization and IR analysis. Results evidenced an isotope effect on the thermodynamics, conductivity, ionic mobility and cathode mass transfer. IR analysis at the cathode side indicated that the isotopic separation efficiency was dependent on the current density with a maximum at intermediate values.  相似文献   
5.
Experiments of deuterium absorption/desorption were performed on a foil of Pd77Ag23 (wt%) alloy in the 78–196 °C temperature and 1–4 bar pressure ranges under the neutron beam at ILL (Grenoble). Powder diffraction patterns were collected on the D1B diffractometer (λ = 1.2871 Å) on the Pd0.772Ag0.228Dν deuterated alloy, and the face-centred-cubic structure was Rietveld-refined locating the D atom in the octahedral site with a variable occupancy ν (=D/M ratio). The results of ν(T) curves at different p(D2) pressures are discussed in comparison with literature data on H and D absorption into PdAg alloys from thermodynamic measurements. A negative deviation from predictions of Sieverts' law is shown by the dependence of D occupancy on pressure. This effect relates the behaviour of the activity coefficient γD to D–D and D–M interactions in the solid solution phase.  相似文献   
6.
Hydrogen isotope selectivity of palladium membranes has long been known and studied, but the emergence of vanadium-based membranes as a low-cost alternative naturally inspires curiosity as to whether these membranes exhibit similar properties. Accordingly, experiments to calculate the permeability of hydrogen and deuterium through a palladium-coated vanadium membrane at 300 °C were undertaken, and they revealed that hydrogen permeates at a rate 1.5 × faster than deuterium. With hydrogen absorption experiments at the same temperature showing very little difference in the amount of each isotope absorbed over a wide pressure range, it can be concluded that atomic hydrogen diffuses through vanadium 1.5 × faster than atomic deuterium.In practice, this gives rise to a significant separation factor, with deuterium being depleted in the permeate stream, but enriched in the retentate stream. Creating a cascading series of membranes, with successive retentate streams combined, will allow the deuterium concentration to be enriched far beyond the natural value of 0.015%. This work suggests that further work is warranted to explore whether this separation factor can be enhanced (e.g., through alloying), and to demonstrate a cascading membrane system to deliver high purity deuterium from a natural hydrogen source.  相似文献   
7.
Beryllium intermetallic compounds (beryllides), such as Be12Ti and Be12V, are the most promising advanced neutron multipliers in demonstration (DEMO) fusion power reactors because of higher stability, lower retention, and swelling. The advanced neutron multipliers are being developed by Japan and the EU as a framework of Broader Approach (BA) activities, targeted at broadening the research fields to not only establish fabrication methods but also for their characterization. Our group has proposed a plasma sintering method for the synthesis of beryllides. When the mixed powder was plasma-sintered at the beginning of the experiment, consolidation of the target composition was so insufficient that single-phase beryllides could not be synthesized. In order to obtain single-phase beryllides, an additional homogenization treatment of the sintered beryllides at 1473 K was necessary, resulting in increased porosity. Using the homogenized powder as the starting material, single-phase Be12Ti and Be17Ti2 intermetallic compounds were successfully synthesized. As experimental results, the hardness of the compounds was relatively low owing to low sintering density. In addition, the oxidation behavior of the beryllides, when exposed to 15% H2O/Ar at high temperatures, were investigated and the results indicate the presence, gray colored Be oxide formed on the surface in Be12Ti tested at above 1073 K and Be oxide with a small fraction of white colored Ti oxide even tested at 873 K in Be17Ti2 phase resulting in the bigger increase of the weight gain than Be12Ti. In addition, this oxidation occurring at lower temperature can be reasoned by the assumption that the existence of BeO (=oxygen content) in Be12Ti (1.95%) and Be17Ti2 (2.95%) may facilitate increased reactivity. Furthermore, thermal expansion of Be17Ti2 was found out to be bigger than that of Be12Ti because Be17Ti2 has more complex crystal structure and higher melting temperature. In terms of deuterium desorption and retention properties, the maximum peaks are detected around 600 K in beryllides, while those in beryllium occur at 800 and 980 K. From the comparison of deuterium retention, it was obvious that Be17Ti2 has a lower retention than Be12Ti, while Be has the highest value.  相似文献   
8.
Absorption, diffusion, and desorption of hydrogen isotopes are expected to occur during operation in future fusion reactors and these processes will strongly depend on the irradiation conditions, neutron flux and purely ionizing radiation. The main aim of the work is to address the electron irradiation induced absorption of hydrogen isotopes in RB-SiC. Deuterium loading was carried out with both the sample and the surrounding deuterium gas exposed to 1.8 MeV electron irradiation in order to evaluate the radiation enhanced deuterium absorption. Thermo stimulated desorption (TSD) measurements were carried out for both electron irradiated and unirradiated samples in order to evaluate the possible radiation enhanced retention of the previously loaded deuterium. The materials subjected to the deuterium loading process were also studied by SIMS. Noticeable radiation enhanced deuterium absorption was observed. Most of the deuterium absorbed during irradiation was thermally released at about 600 °C.  相似文献   
9.
Effects of deuteron (D+) and electron donors on the oxidative stability in linoleic acid–water model systems were evaluated by analyzing headspace oxygen content and headspace volatiles. Acetic acid‐d and tetrakis(dimethylamino)ethylene (TDAE) were selected as a deuteron and an electron donor, respectively. Samples containing acetic acid‐d had significantly lower headspace oxygen content than controls while those containing TDAE had significantly higher headspace oxygen content (p < 0.05). Combination of acetic acid‐d and TDAE accelerated the consumption of headspace oxygen. Volatiles including t‐2‐heptenal, 2‐octenal, or 2,4‐octadienal had higher mass to charge ratio (m/z) of (molecular weight +1)/molecular weight in samples with deuterium oxide than in samples with deuterium free water. However, no significant difference was observed in the m/z ratio of (molecular weight +1)/molecular weight of those volatiles among samples with or without deuteron or electron donors. Also, lipid hydroperoxides with deuterium, were not found in samples containing deuterium oxide and acetic acid‐d. Therefore, added acetic acid‐d may not be involved on the formation of lipid hydroperoxides and volatiles directly.  相似文献   
10.
Deuterium recovery from water–isotopes mixture using thermal diffusion can be improved by employing the branch column device, instead of single column devices, with the same total column length. The remixing effect due to convection currents in a thermal diffusion column for heavy water enrichment is thus reduced and separation improvement increases when the flow rate or the total column length increases. The improvement in separation can reach about 50% for the numerical example given.  相似文献   
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