| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Li, L, et al.
(författare)
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Damage coupled thermo-mechanical model for rock failure process and applications
- 2006
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Ingår i: CHINESE JOURNAL OF THEORETICAL AND APPLIED MECHANICS. - 0459-1879. ; 38:4, s. 505-513
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Tidskriftsartikel (refereegranskat)abstract
- Based on the heterogeneous characteristics of rock at mesoscopic level, the thermo-mechanical (TM) coupled behavior during the failure process of rock subjected to thermal stress is analyzed with elastic damage mechanics and thermo-elastic theory. A mesoscopic TM coupling model, implemented in rock fracture process analysis (RFPA), is proposed, which can be used to study the damage and failure process, as well as elastic stress for the coupled TM rock problem. With the numerical model, the damage and associated mechanical properties evolution of mesoscopic structure in rocks subjected to TM loading can be analyzed. Numerical simulation is carried out to investigate the stability of the rock pillar in a hard rock laboratory. The numerically obtained stress field, failure pattern of pillar rock and associated acoustic emission (AE) events all agree well with the in-situ data, which shows that the proposed model is reasonable and effective, and may provide guides for the experiment design and associated applications
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| 5. |
- Li, Z. L., et al.
(författare)
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Effect of the electronic dimensionality of electrodes on the current-voltage characteristics of single molecular devices
- 2004
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 53:5, s. 1490-1495
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Tidskriftsartikel (refereegranskat)abstract
- The electrodes can be constructed by different dimensionality of electronic systems in energy representation when the current through the molecular junction is measured. Basing on the elastic scattering Green function theory, we have developed the theoretical methods for studying the electronic transport properties of molecular junctions and paid attention to the influence of the dimensionality of electrodes. The alpha, alpha'-xylyl dithiol molecule is taken as an example and its current-voltage characteristics have been investigated for electrodes with different-dimension electronic systems. The numerical results show that dimensionality of metal contacts has strong effect on the current-voltage characteristics of molecular junction, in particular the shape of the conductance curves.
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| 6. |
- Ma, Y., et al.
(författare)
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Theoretical studies on electronic transport properties of six-membered heterocyclic molecules
- 2006
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 55:4, s. 1974-1978
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Tidskriftsartikel (refereegranskat)abstract
- By applying the elastic scattering Green's function theory in combination with the hybrid density function theory, the electronic transport properties of molecular junctions constructed by the six-membered heterocyclic molecules, pyridazine-2, 5-dithiol, pyrazine-2, 5-dithiol, and pyrimidine-2, 5-dithiol, have been studied. For the heterocyclic molecule pyridine, the influence of the terminal atoms on the current-voltage characteristics has also been obtained. We have accurately determined the coupling constant between the molecule and electrodes by using the frontier molecular orbital theory and the perturbation method. The numerical results show that pyridazine-2,5-dithiol has higher current and conductance, while the conductance of pyrimidine-2, 5-dithiol is very small when the bias voltage is lower than 4V. The conductivity of the molecule pyridine with selenium atom as the terminal atom is higher than that with oxygen atom or sulfur atom.
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| 7. |
- Shi, F., et al.
(författare)
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Synthesis and properties of a new donor model compound for PSII
- 2004
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Ingår i: Gaodeng xuéxiào huàxué xuébào. - 0251-0790. ; 25:9, s. 1666-1672
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Tidskriftsartikel (refereegranskat)abstract
- As a model compound for redox components on the donor side of photosystem II (PS II) in green plants, a supramolecular complex 2 was synthesized and characterized. In this complex, two {[(2-hydroxy-3-(morpholin-4-ylmethyl)-5-tert-butyl-benzyl)(pyridyl-2-methyl)amino]methyl} arms are linked to the ortho-positions of a phenol which is expected covalently to be linked to Ru(II) tris-bipyridine through an amide bond. The arms on the substituted-phenol can coordinate two Mn(III) ions. The structure of complex 2 was confirmed by electrospray ionization mass spectrometry (ESI-MS) and 2D-NMR (gCOSY, HSQC and HMBC). Its photochemical and electrochemical properties were studied. The results showed that the MLCT band of the compound was red-shifted compared to that of [Ru(byp)(3)](2+) and the luminescence quantum yield was enhanced. In addition, the oxidation potential of ruthenium was higher than the phenol(+)/phenol and Mn(III, IV)/Mn(III) which was consisted with the electron transfer sequence of the donor side of PS II in nature. All these showed that this compound was a good model to mimic the donor side of PS II.
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