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81.
《能源学会志》2020,93(6):2511-2525
Oxy-fuel combustion of heavy oil can be applied to oil field steam injection boilers, allowing the utilization of both heavy oil and CO2 resources. This paper studied the local distribution characteristics of OH on oxy-fuel combustion of heavy oil during the ignition and stable combustion processes. During the ignition process, we observed the generation and evolution of fire kernel, and got the flame propagation velocity. During the stable combustion process, the results showed that the OH distribution and its relative signal intensity were influenced by the oxygen concentration, excess air coefficient, gas flow, reaction atmosphere, oil mist scattering, incident laser energy and laser sheet position. In the same reaction atmosphere, the ranges of OH dense distribution and the high temperature area increased as O2 concentration increased. In the same O2 concentration, both the ranges of OH dense distribution and the high temperature area in O2/N2 were larger than that in O2/CO2. In 29% O2/71% CO2, the flame shape was similar to combust in air, while the OH relative signal intensity and its volatility were much larger than that in air. In the same combustion condition, the location of high concentration of OH relative concentration field lagged behind the high temperature area. The results further reveal the differences between the conventional and oxy-fuel combustion. 相似文献
82.
《Carbon》2015
Based on comparative studies of pressure–temperature-induced transformations of naphthalene, octafluoronaphthalene, and their binary mixtures, the nature of formation of nano- and micron-size diamond fractions in the products of transformations of hydrocarbons and fluorocarbons has been revealed. It was found that the main reason for the massive formation of nano-size diamonds is the specifics of carbonization of fluorocarbon compounds under pressure. In this particular process, micron-size particles of graphite are formed simultaneously with a significant amount of closed two- to five-layered carbon nanoparticles of 5–15-nm size, acting as precursors for the formation of nano-size diamond fractions. The obtained results open up a new avenue for the metal catalyst-free synthesis of nano/micron-size fractions of pure and doped diamonds. 相似文献
83.
《Ceramics International》2020,46(3):3113-3118
Currently, phosphor-converted white light-emitting diodes offer low energy consumption, good environmental stability, and a long lifetime. Hence, they are widely utilized in high-power light-emitting diode (LED) applications such as those in the automotive headlamp industries. However, obtaining high luminous efficiency of such diodes is challenging because of their internal structural properties such as micropores. Herein, we developed phosphor-in-glass (PiG) plates by mixing a blue LED chip and yellow phosphor to create high-power white LEDs (w-LEDs). In addition, the influence of post-annealing on the prepared PiG plates at different temperatures (350°C-550 °C) was investigated. Post-annealing, a treatment that facilitates the mobility of the ceramic matrix encapsulating the phosphor powder, decreases an LED's porosity, thereby enhancing its overall luminous efficiency. Results show that PiG plates post-annealed at 450 °C exhibit superior optical performance and effective color properties than PiG plates that were non-annealed or post-annealed at 350 °C, 400 °C, 500 °C, and 550 °C. Therefore, post-annealed PiG plates are more suitable potential materials for application in the high-power LED industry. 相似文献
84.
《材料与设计》2015
Scanning electron microscope (SEM) observation shows that the cuticle of Dorcus titanus is a kind of natural sandwich structure consisting of upper and lower panels and middle pillars. The observation also shows that the material of the sandwich structure is a biocomposite consisting of chitin-fiber layers and sclerous-protein matrix. More careful observation shows that the fiber layers in the sandwich structure continuously join the panels and the pillars to form a fiber-continuous panel–pillar sandwich structure. The strength of the fiber-continuous panel–pillar structure is investigated and compared with that of the non-fiber-continuous panel–pillar structure based on their representative models. It is shown that the fiber-continuous panel–pillar structure has higher ultimate strength compared to that of the non-fiber-continuous panel–pillar structure. Based on the observations and analyses, the fiber-continuous panel–pillar structure is biomimetically fabricated with a special mould and process. The ultimate strength of the structure is tested and compared with that of the non-fiber-continuous panel–pillar structure. It is indicated that the ultimate strength of the fiber-continuous panel–pillar structure is distinctly larger than that of the non-fiber-continuous panel–pillar structure. 相似文献
85.
《Journal of the European Ceramic Society》2020,40(4):1522-1531
Predicting the in-line transmittance of transparent ceramics via model calculations is a useful guide for materials design and optimization of preparation process. However, the absence of reliable input information (volume fractions and size) usually precludes the direct verification of these calculations. On the other hand, suspensions, which can be prepared with well controlled volume fractions of the solids selected, may serve as model systems that are amenable to verification. This paper describes the procedure to perform these calculations, and compares calculated data for suspensions of monodisperse spheres of amorphous silica with spectrophotometric measurements of silica monosphere suspensions with four different concentrations. Moreover, completely analogous model calculations are performed for bubbles in silica glass and pores in spinel ceramics. The results are discussed on the basis on 3D graphs, the use of which is highly recommended. The results may be considered as a benchmark for future model calculations for polydisperse systems. 相似文献
86.
《International Journal of Hydrogen Energy》2020,45(51):27202-27209
The catalytic mechanism and activity of transition metal atom doped C2N (M-C2N, M = Fe, Co, Ni, and Cu) for the oxygen reduction reaction (ORR) are investigated in detail by density functional theory method. All the screened M-C2N are thermodynamically stable based on the binding energy calculations. The adsorption energy results indicate that the adsorption strength of O2 and ORR intermediates are decreased in the order of Fe-C2N ˃ Co-C2N ˃ Ni-C2N ˃ Cu-C2N, in which the adsorption energy values on Cu-C2N are most close to those on the Pt(111). Based on the relative energy diagram of ORR, the energetically favorable pathway on Fe-C2N and Co-C2N is direct 4e− mechanism, in which the O–O bond is directly dissociated after the second electron transfer. While for Ni-C2N and Cu-C2N, the most favorable pathway is indirect 4e− mechanism, in which the H2O2 is formed as the intermediate product. For all studied M-C2N, the Ni-C2N and Cu-C2N hold better catalytic activity, which could attribute to the contribution of metal atom and part of its activated nitrogen atoms. 相似文献
87.
《Ceramics International》2022,48(21):31587-31597
The effects of the incorporation of a Bi3+ sensitizer on the phosphorescence properties and oxygen partial pressure sensitivity of the Eu3+ doped yttria stabilized zirconia (YSZ) phosphors were studied using a lifetime-based optical measurement system. Two series of YSZ: Eu phosphors were investigated in this work: Eu0.01BixY0.07-xZr0.92O1.96 substitutional series and Eu0.01BixY0.07Zr0.92-xO1.96-0.5x additive series. The phosphorescence intensity of the additive-series phosphors was enhanced by 47% excited at 405 nm with a Bi3+ concentration of 2 mol% due to the energy transfer between Bi3+ and Eu3+. In contrast, the phosphorescence intensity of the substitutional-series phosphors decreased as the Bi3+ concentration increased. The phosphorescence lifetimes for both series phosphors were highly sensitive to oxygen partial pressure at elevated temperatures. With increasing Bi3+ concentration, the oxygen sensitivities of both series were enhanced initially, which was related to the increment of concentration dependent non-radiative decay via cross-relaxation between Bi3+ and Eu3+. With 1 mol% Bi3+ doping, the oxygen sensitivity was enhanced by 28% and 12% for substitutional-series and additive-series phosphors, respectively. As the Bi3+ concentration further increased, the oxygen sensitivities of both series declined, which was attributed to the energy transfer between Bi3+, the formation of Bi3+ aggregates as well as the increase of the Eu3+ site symmetry. The results of this study not only provided valuable references for phosphor thermometry, but also offered new ideas for developing high-temperature non-contact pressure sensors. 相似文献
88.
In this study, a highly efficient method for chemical mechanical polishing (CMP) of silicon carbide (SiC) substrates using enhanced slurry was proposed and developed. The enhanced slurry contains bubbles of ozone gas generated by ozone gas generator in pure water mixed with a conventional commercially available slurry. Therefore, the enhanced slurry has an oxidizing effect on the Si-face of SiC substrates. To confirm the effectiveness of bubbles enclosing ozone gas, both nano-indentation test and X-ray photoelectron spectroscopy (XPS) analysis were conducted. As a result, the hardness decrease of the Si-face of the SiC substrate was confirmed through the nano-indentation test, and the generation of reaction products was confirmed on Si-face of SiC substrate in the XPS analysis. According to a series of experimental results of our proposed highly efficient CMP method for SiC substrates, the removal rate can be increased when the enhanced slurry was applied, comparing with that for the not only conventional commercially available slurry but also commercially available dedicated slurry. 相似文献
89.
《中国有色金属学会会刊》2022,32(10):3312-3320
The effects of trace addition of Al2O3 nanoparticles (NPs) on thermal reliabilities of Sn-0.5Ag-0.7Cu/Cu solder joints were investigated. Experimental results showed that trace addition of Al2O3 NPs could increase the isotheraml aging (IA) and thermal cyclic (TC) lifetimes of Sn-0.5Ag-0.7Cu/Cu joint from 662 to 787 h, and from 1597 to 1824 cycles, respectively. Also, trace addition of Al2O3 NPs could slow down the shear force reduction of solder joint during thermal services, which was attributed to the pinning effect of Al2O3 NPs on hindering the growth of grains and interfacial intermetallic compounds (IMCs). Theoretically, the growth coefficients of interfacial IMCs in IA process were calculated to be decreased from 1.61×10-10 to 0.79×10-10 cm2/h in IA process, and from 0.92×10-10 to 0.53×10-10 cm2/h in TC process. This indicated that trace addition of Al2O3 NPs can improve both IA and TC reliabilities of Sn-0.5Ag- 0.7Cu/Cu joint, and a little more obvious in IA reliability. 相似文献
90.
《Carbon》2015
A simple wet chemical method involving only sonication in aqueous GdCl3 solution was used for surface functionalization of iron-filled multiwalled carbon nanotubes with gadolinium. Functional groups on the sidewalls produced by the sonication provide active nucleation sites for the loading of Gd3+ ions. Characterization by EPR, EELS, and HRTEM confirmed the presence of Gd3+ ions on the sidewall surface. The room temperature ferromagnetic properties of the encapsulated iron nanowire, saturation magnetization of 40 emu/g and coercivity 600 Oe, were maintained after surface functionalization. Heating functionality in an alternating applied magnetic field was quantified through the measurement of specific absorption rate: 50 W/gFe at magnetic field strength 8 kA/m and frequency of 696 kHz. These results point to candidacy for dual-functioning MRI imaging and magnetic hyperthermia structures for cancer therapy. 相似文献