| 1. |
- Arne, B., et al.
(författare)
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Laser ablation breakdown spectroscopy technique for simultaneous analysis of steel and slags in metallurgical samples
- 2009
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Ingår i: Yejin Fenxi/Metallurgical Analysis. - 1000-7571. ; 29:2, s. s.8-13
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Tidskriftsartikel (refereegranskat)abstract
- The original purpose of this research was to develop a method for fast, simultaneous analysis of both the steel and slag content of heterogeneous metallurgical samples for process control. The method is based on Laser Induced Breakdown Spectroscopy (LIBS). The reason for choosing LIBS is that it can be employed for both conductive and non-conductive materials, and is relatively insensitive to sample shape and surface finish. The heterogeneous samples produced contain large numbers of sub-millimetre slag particles that cannot be completely separated from the surrounding steel in a LIBS analysis. A method has therefore been developed to perform a line scan analysis with approximately 0.5 mm resolution and 10 mm length along the sample. The laser pulse rate is 20 Hz and the scan speed is 1 mm/s. Slag particles appear in the line scan as "polluted areas" of the steel with very high concentrations of e. g. Ca, Al and Si. A mathematical model was developed to evaluate the data in steps, based on a single calibration. Firstly, "clean steel" areas are identified and the steel composition determined. In the second step, the average composition across the entire length of the scan is determined. In the final step, the average slag composition is determined by means of a difference calculation. The method was tested on several samples from the development of the heterogeneous sampler. It was found that the elements C, Si, Mn, P, S and Al can be determined in the steel with an RSD of a few percent. In the slag, the RSD's are higher, around10% for several important elements. It is expected that the method can be further developed for rapid analysis of smaller non-metallic inclusions.
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| 2. |
- Bengtson, Arne, et al.
(författare)
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Rapid inclusion characterisation by pulse distribution analysis optical emission spectroscopy-recent development
- 2013
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Ingår i: Yejin Fenxi/Metallurgical Analysis. - 1000-7571. ; 33:1, s. s.7-12
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the work is to further develop and validate the optical emission method pulse distribution analysis (PDA) for rapid inclusion characterisation in steel production. The experimental work was focused on investigation of several operational parameters: spark energy, spark frequency and time gating of signal acquisition. The results showed that a low spark energy improves the detection limit, but at the expense of measuring statistics due to a smaller sample volume. The measuring frequency proved to have no significant influence on the analytical results, but several existing instruments cannot handle the highest spark frequencies above about 300 Hz in PDA mode due to limitations in the electronics. Investigation of time gating (TRS) gave only a marginal improvement in the detection limit of Si outliers above the metallic content. The work also revealed that there is a risk to detect "false" outliers due to asymmetric intensity distributions. This has resulted in the development of more advanced algorithms for outlier detection, increasing the accuracy of the method. Another limitation found is that the particle number density must not exceed about 10 000 inclusions/mm3 for the method to effectively detect single inclusions. A method to overcome this limitation has been suggested, but not yet evaluated. The accuracy of quantitative determination of the Al content in inclusions has been verified by reference methods. In conclusion, it has been demonstrated that state-of-the-art PDA is a very powerful technique for rapid inclusion characterisation in steels. Furthermore, the speed of analysis is sufficiently high for process feedback and controllable.
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| 3. |
- Chen, Xiangrong, 1982, et al.
(författare)
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Study on conducting characteristics of electrical trees in cross-linked polyethylene cable insulation
- 2012
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Ingår i: Wuli Xuebao/Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 61:8, s. Art. no. 087701-
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Tidskriftsartikel (refereegranskat)abstract
- The conducting characteristics of two typical electrical trees in cross-linked polyethylene (XLPE) cable insulation are studied by a combination of optical microscopy observation, partial discharge measurement and con-focal Raman spectroscopy analysis. Although they are grown under similar conditions, these two trees display very different shapes. One is a typical branch-pine tree grown at 9 kV, and the other is a branch tree grown at 11 kV. The growth and the partial discharge regularities show obvious differences. The disordered graphitic carbon is condensed in the main tree channels of the branch-pine tree. From the relative intensity of the graphitic carbon G band to D band, the graphitic domain is estimated to be about 8 nm in size. The tree channel resistance per unit length is less than 10 Ω· μm-1, which is sufficient to prevent the partial discharge from developing within the tree structure. The branch-pine tree shows the features of the conducting tree. The fluorescence background is observed in the channels of branch tree, which shows the existence of the products of the material degradation, but no disordered graphitic carbon is observed in these tree channels. These tree channels display obvious non-conducting characteristics, which is not sufficient to prevent the continuous effect of the partial discharges. Finally, a single channel growth model is proposed for the conducting and non-conducting trees grown in XLPE cable insulation. Based on the equivalent circuit theory, the growth mechanisms of the two trees with different conducting characteristics in XLPE cable insulation are discussed.
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| 4. |
- Di, Jing, et al.
(författare)
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A novel composite electrolyte based on CeO2 for low temperature solid oxide fuel cells
- 2008
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Ingår i: Journal of Inorganic Materials. - 1000-324X. ; 23:3, s. 573-577
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Tidskriftsartikel (refereegranskat)abstract
- A novel composite material based on mixture of samarium-doped ceria (SDC)-carbonate was studied as electrolyte in low temperature solid oxide fuel cells. The phase and microstructures of composite electrolyte were examined by XRD and SEM. The electrical conductivity was investigated by AC impedance spectroscopy at 400-700 degrees C in different atmospheres. An abrupt change in the conductivity at about 500 degrees C indicates that different mechanisms affect transfer in different temperature ranges. The conductivity increases with the carbonate fraction above 500 degrees C. The conductivity in reduce atmosphere is higher than that in oxide atmosphere. An anode-supported fuel cell using SDC-carbonate as electrolyte was fabricated and tested. The result shows that all the composite electrolytes exhibit better performance than pure SDC electrolyte. The electrolyte with 20wt% carbonate can achieve the highest power density of 415mW center dot cm(-2) and an open circuit voltage of 1.00V at 500 degrees C.
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| 5. |
- Xihe, Liu, et al.
(författare)
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Influence of Carbon Nanotubes on Defects in AlSi10Mg Alloy Fabricated by Selective Laser Melting
- 2019
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Ingår i: Xiyou jinshu cailiao yu gongcheng. - 1002-185X. ; 48:5, s. 1637-1644
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Tidskriftsartikel (refereegranskat)abstract
- Pure AlSi10Mg alloy and carbon nanotubes (CNTs)-AlSi10Mg composite with different CNTs additions were fabricated by selective laser melting (SLM). The CNTs-AlSi10Mg composite is strengthened when the CNTs content is lower than 0.05 wt%. With the increasing CNTs content, however, the strength is decreased significantly because of the poor density. In order to understand the influence of CNTs on the defects in SLMed AlSi10Mg alloy, nano-CT technology was used to get the 3D information of the defects. The results indicate that the volume fraction of large defects (with diameter larger than 50 mu m) in the total volume of defects is increased from 12% to 46% in CNTs(0.5wt%)-AlSi10Mg composite. The number of gas pores in CNTs(0.5wt%)-AlSi10Mg composite are significantly increased. The diameter of gas pores in CNTs(0.5wt%)-AlSi10Mg composite are larger than that in pure AlSi10Mg alloy. The agglomeration of CNTs in the powder and gas adsorption are the fundamental reasons for the increase of the two types of defects.
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| 6. |
- Xin, Yan-Bo, et al.
(författare)
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Research progress of hydrogen tunneling in two-dimensional materials
- 2017
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Ingår i: Wuli xuebao. - : CHINESE PHYSICAL SOC. - 1000-3290. ; 66:5
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Forskningsöversikt (refereegranskat)abstract
- One-atom-thick material such as graphene, graphene derivatives and graphene-like materials, usually has a dense network lattice structure and therefore dense distribution of electronic clouds in the atomic plane. This unique structure makes it have great significance in both basic research and practical applications. Studies have shown that molecules, atoms and ions are very difficult to permeate through these above-mentioned two-dimensional materials. Theoretical investigations demonstrate that even hydrogen, the smallest in atoms, is expected to take billions of years to penetrate through the dense electronic cloud of graphene. Therefore, it is generally considered that one-atom-thin materialis impermeable for hydrogen. However, recent experimental results have shown that the hydrogen atoms can tunnel through graphene and monolayer hexagonal boron nitride at room temperature. The existence of defects in one-atomthin material can also effectively reduce the barrier height of the hydrogen tunneling through graphene. Controversy exists about whether hydrogen particles such as atoms, ions or hydrogen molecules can tunnel through two-dimensional materials, and it has been one of the popular topics in the fields of two-dimensional materials. In this paper, the recent research progressof hydrogen tunneling through two-dimensional materials is reviewed. The characteristics of hydrogen isotopes tunneling through different two-dimensional materials are introduced. Barrier heights of hydrogen tunneling through different graphene and graphene-like materials are discussed and the difficulties in its transition are compared. Hydrogen cannot tunnel through the monolayer molybdenum disulfide, only a little small number of hydrogen atoms can tunnel hrough graphene and hexagonal boron nitride, while hydrogen is relatively easy to tunnel through silicene and phosphorene. The introduction of atomic defects or some oxygen-containing functional groups into the two-dimensional material is discussed, which can effectively reduce the barrier height of the hydrogen tunneling barrier. By adding the catalyst and adjusting the temperature and humidity of the tunneling environment, the hydrogen tunneling ability can be enhanced and the hydrogen particles tunneling through the two-dimensional material can be realized. Finally, the applications of hydrogen tunneling through two-dimensional materials in ion-separation membranes, fuel cells and hydrogen storage materials are summarized. The potential applications of hydrogen permeable functional thin film materials, lithium ion battery electrode materials and nano-channel ions in low energy transmission are prospected. The exact mechanism of hydrogen tunneling through two-dimensional material is yet to be unravelled. In order to promote these applications and to realize large-scale production and precision machining of these two-dimensional materials, an in-depth understanding of the fundamental questions of the hydrogen tunneling mechanism is needed. Further studies are needed to predict the tunneling process quantitatively and to understand the effects of catalyst and the influences of chemical environments.
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| 7. |
- Fu, L., et al.
(författare)
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Wear mechanism of Cr 3 C 2 /Ni 3 Al composites showing excellent wear resistance
- 2019
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Ingår i: Gongcheng Kexue Xuebao/Chinese Journal of Engineering. - 2095-9389. ; 41:1, s. 117-123
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Tidskriftsartikel (refereegranskat)abstract
- The Ni 3 Al intermetallic compound is considered an excellent wear-resistant material. The addition of Cr 3 C 2 particles can further improve the wear resistance of Ni 3 Al-based alloys. In order to elucidate the wear mechanism of Cr 3 C 2 /Ni 3 Al composites improved by the Cr 3 C 2 strengthening phase, Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites were prepared by the hot isostatic pressing process in this study. The mechanical properties and wear resistance of each phase in the Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites were investigated using a nano-indentation instrument and a pin-on-disk friction and wear tester, respectively. The worn surface morphologies and the hardness of the subsurface layer under the worn surfaces of the Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites were determined by a scanning electron microscopy (SEM) and a nano-indentation instrument. The results indicate that the hardness of the matrix phase in the Cr 3 C 2 /Ni 3 Al composites is significantly improved by the addition of Cr 3 C 2 particles. The nano-hardness and the elastic modulus of each phase in the Cr 3 C 2 /Ni 3 Al composites gradually increase from matrix phase through diffusion phase to hard core phase. The mechanical properties between the matrix, diffusion, and hard core phases in the Cr 3 C 2 /Ni 3 Al composites present a gradient transition. This kind of structure distribution is good for enhancing the wear resistance of Cr 3 C 2 /Ni 3 Al composite materials. As for friction and wear conditions in this study, abrasive wear was the dominant wear mechanism, which occurred on the surfaces of the Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites. The Cr 3 C 2 /Ni 3 Al composites showed a good wear resistant property. The carbide-strengthening phase can block up the cutting action of the wear debris, reduce the interaction between the wear materials, and decrease the thickness of the subsurface layer and the size of the wear debris, resulting in improved wear resistance of Cr 3 C 2 /Ni 3 Al composites.
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| 8. |
- Fu, L. H., et al.
(författare)
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Influence of Cr3C2 content on the wear properties of Cr3C2/Ni3Al composites
- 2016
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Ingår i: Gongcheng Kexue Xuebao/Chinese Journal of Engineering. - 2095-9389. ; 38:8, s. 1145-1152
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Tidskriftsartikel (refereegranskat)abstract
- The Ni3Al-alloy and its composites with different Cr3C2 contents were fabricated by a hot isostatic pressing (HIP) technique. The influences of Cr3C2 content on the microstructure, hardness and wear properties of the Cr3C2/Ni3Al composites were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and wear tribometry. The results show that inter-diffusion occurs between the original Cr3C2 and the Ni3Al particles during the HIP process and the Cr3C2 particles partially transform into M7C3 (M=Cr, Fe, Ni) structures. Under specific friction and wear conditions, the wear resistance of the Cr3C2/Ni3Al composites is significantly improved due to the addition of Cr3C2 particles by about 4-10 times, compared to the Ni3Al alloy. In addition, the cutting and scraping effects of counter-part disks by the Cr3C2/Ni3Al composites decreases with increasing Cr3C2 addition, resulting in a reduction in wear rate of counter-part disks.
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| 9. |
- Fan, Y., et al.
(författare)
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Mechanical preparation of nano titanium dioxide powder and its optical properties
- 2007
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Ingår i: Journal of the Chinese Ceramic Society. - 0454-5648. ; 35:7, s. 832-837
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Tidskriftsartikel (refereegranskat)abstract
- mechanical preparation of the nano-sized particles of TiO2 powder by a stirred bead mill was investigated. The particle sizes of the ground products were determined by the acoustic particle sizer, the nitrogen gas adsorption method and a scanning electron microscopy. The diameter of the nano-sized particles, which were obtained after milling for 7 h, is about 50 nm and the specific surface area is up to 70 m2/g. The surface and structure of the samples have been investigated with X-ray diffraction. It is indicated that an intense comminution in the mill leads to a progressive loss in crystallinity of TiO2. The catalytic degradation of methyl orange in water was also studied by a photometer. The results show that the nano-sized particles of TiO2 powder prepared by milling possess photocatalysis effect and are capable of absorption of ultraviolet radiation
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| 10. |
- Fu, L. H., et al.
(författare)
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Microstructure and phases constitution of Cr3C2/Ni3Al composites prepared by hot isostatic pressing (HIP)
- 2016
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Ingår i: Journal of Iron and Steel Research. - 1001-0963. ; 28:12, s. 52-58
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Tidskriftsartikel (refereegranskat)abstract
- The Cr3Cj/Ni3Al composite materials were prepared by hot isostatic pressing (HIP) at 1160°C and 100MPa. Microstructure and phases constitution of the composite materials were investigated. The results indicate that the original Cr3C2 particle firstly dissolves into Cr and C atoms and then diffuses into the matrix. During the cooling process, the dissolved Cr and C atoms transformed into a stable Cr7C3 structure. Also, an uphill diffusion phenomenon is observed for Fe element from the matrix to the Cr7C3 carbide phase, which is attributed to the easy formation of stable carbides of Fe element in Ni3Al alloy with C element. And, the Fe atoms substitute a part of Cr atoms in Cr7C3 carbides and form a diffusion phase with M7 C3 (M for Cr, Fe) structure. When the original Cr3Q2 particles are large, it cannot be completely dissolved during the high temperature period. The undissolved core of Cr3C2 particles still remain the Cr3C2 structure after the cooling process. The Cr3C2/Ni3 Al composite materials are composed of Cr3C2 hard core phase, M7C3 diffusion phase and ?-Ni3Al matrix material phase. The Cr3C2 hard core phase and the ?'-Ni3Al matrix created a good diffusion bonding by the formed M7C3 diffusion phase. Therefore, the Cr3C2 particle on the worn surface does not peel off and the groove is interrupted around the chromium carbides during the wear test, resulting in significantly improved wear resistance of Cr3C2/Ni3Al composites.
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