| 1. |
- Ratko, A., et al.
(författare)
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Sorption and gas sensitive properties of In2O3 based ceramics doped with Ga2O3
- 1998
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 18:14, s. 2227-2232
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Tidskriftsartikel (refereegranskat)abstract
- The process of structure formation in In2O3 based ceramics doped with Ga2O3 was investigated. The data obtained demonstrated the profound influence of Ga-dopands both on the crystallization path of solids produced by coprecipitation and on their final physical and electrical properties. The limited solubility of Ga2O3 dopands in cubic In2O3 lattice which lies within the 11-12 wt% was also noted. Ga2O3-dopands caused the formation of a porous structure in the In2O3-based ceramics, providing an active interaction surface in the semiconductor for reducing gases. Ga-doped ceramics demonstrated better gas sensor properties then pure In2O3.
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| 2. |
- Ashkin, A., et al.
(författare)
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At-temperature observation of phase development in yttrium α-Sialon
- 1995
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 15:11, s. 1101-1109
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Tidskriftsartikel (refereegranskat)abstract
- A powder mixture of α-Si3N4, AlN and Y2O3 corresponding to an yttrium α-sialon composition, Y0.4Si10.2Al1.8O0.6N15.4, was sintered both in a high temperature X-ray diffraction unit and in a regular sintering furnace. X-ray analysis was performed and it was shown that high temperature X-ray diffraction can be used to monitor the kinetics of the α-sialon phase formation during sintering at temperatures between 1450 and 1580 °C as the reactions take place. A variety of yttrium-rich intermediate and secondary phases are formed during sintering; those formed in the HT-XRD unit were not the same as those formed in the regular sintering furnace, but they do not significantly influence the overall reaction sequence or the amount of α-sialon formed. Quantitative analysis of the acquired data was used to evaluate the kinetics of the α-sialon phase formation; the estimated activation energy of the initial stage α-sialon formation was 330kJ/mol. After this initial stage of relatively rapid α-sialon formation the process became inhibited
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| 3. |
- Ashkin, A., et al.
(författare)
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Investigation of α-sialon formation by high temperature X-ray diffraction
- 1994
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Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 89-91, s. 373-380
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Tidskriftsartikel (refereegranskat)abstract
- A technique for following sialon formation in situ by high temperature x-ray diffraction (HT-XRD) was developed. The composition chosen for study was an yttrium α-sialon with x = 0.4. Powder compacts containing silicon nitride, aluminum nitride and yttria powders were pre-sintered at 1350 °C and then studied by HT-XRD at temperatures between 1450 and 1580 °C and nitrogen pressures of 0.11 MPa. The furnace was made from graphite coated with porous silicon nitride/silicon carbide. The coating prevented silicon carbide formation in the sample up to 1600 °C. X-ray diffraction results show the formation of a Y10Al2Si3O18N4 phase at 1350 °C, which dissolved to form α-sialon and other phases at higher temperatures. The amounts of α-sialon formed are similar to the amounts reported by other authors. An empirical method was used for the calculation of activation energy for the silicon nitride to α-sialon transformation and resulted in a value of 330 kJ mol-1.
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| 4. |
- Noël, Maxime, et al.
(författare)
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Effects of non-hydrostatic pressure on electrical resistance of bundled single-wall carbon nanotubes
- 2013
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Ingår i: 7th EEIGM International Conference on Advanced Materials Research. - : IOP Publishing Ltd.
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Konferensbidrag (refereegranskat)abstract
- Recent studies have shown that single wall carbon nanotubes (SWCNT) exhibit a sequence of phase transitions and demonstrate a high structural stability up to 35 GPa of quasi-hydrostatic pressure [1] beyond which an irreversible structural transformation occurs. Here we report on the study of electrical resistance of SWCNTs at pressures up to 34 GPa in the temperature range of 293 – 395 K. In the pressure range 10–25 GPathe rate of resistance change decreases considerably. We associate such behavior of the resistance with a structural modification of the SWCNTs or/and change of the conductivity character at high pressure. Raman spectra of the samples recovered after 30 GPa exhibit a large increase of defect concentration in the CNTs. Isobaric temperature dependences of the CNT resistance R(T) measured in the temperature range 300–400 K reveal some changes with pressure whereas the semiconducting character of the R(T) remains unaltered.
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| 5. |
- Noël, Maxime, et al.
(författare)
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Electrical transport in bundled single-wall carbon nanotubes under high pressure
- 2013
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Konferensbidrag (refereegranskat)abstract
- According to recent experimental data single wall carbon nanotubes (SWCNT) exhibit a sequence of phase transitions and demonstrate a high structural stability up to 35 GPa of non-hydrostatic pressure beyond which an irreversible transformation occurs. Here we report a study of electrical transport in SWCNTs at pressures up to 45 GPa in the temperature range of 300 - 400K. High pressure was generated in diamond anvil cell. The anvils are made of electrically conducting "carbonado"-type synthetic diamond. In the pressure range 10-25 GPa the CNT electrical resistance decreases considerably, whereas above 25 GPa it remains essentially unchanged. Such behaviour of the resistance can be connected to a structural modification of the SWCNTs accompanied by change of the conductivity character at high pressure. Raman spectra of the samples recovered after 30 GPa exhibit a large increase of D/G band intensity ratio. The Radial Breathing Mode part of the spectra remains essentially unaltered which testifies for structural integrity of the nanotubes after exposure to high non-hydrostatic pressure and lack of covalent interlinking between the tubes. Pressure dependences of resistance, activation energy for conductivity and charge carriers mobility were determined and discussed.
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| 6. |
- Osso, D., et al.
(författare)
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Mechanical-thermal synthesis of Al2O3-Cr composite powders
- 1995
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 15:12, s. 1207-1212
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Tidskriftsartikel (refereegranskat)abstract
- Three different approaches have been investigated to synthesize alumina-chromium composites by displacement reactions between aluminium and chromia. The reactions have been performed either by pure mechanosynthesis or pure thermal ignition or also by a combined mechanical and thermal activation process. Differential thermal analysis, dilatometry and high temperature X-ray diffraction have been used to show the various reaction mechanisms and chemical transformations. High-energy milling of the powder modifies the reactivity of the system. A partial pre-milling treatment not only reduces the reaction temperature but can also induce a different reaction path. It has been shown that an appropriate mechanical-thermal treatment leads to the synthesis of an alumina-chromia composite by a pure solid-state process: intermediate reaction stages exhibit little if any liquid phases.
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| 7. |
- Rotili, Dante, et al.
(författare)
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Exploring the role of 2-chloro-6-fluoro substitution in 2-alkylthio-6-benzyl-5-alkylpyrimidin-4(3H)-ones : effects in HIV-1-infected cells and in HIV-1 reverse transcriptase enzymes.
- 2014
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 57:12, s. 5212-25
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Tidskriftsartikel (refereegranskat)abstract
- A comparison of the effects of the 6-(2-chloro-6-fluorobenzyl)-2-(alkylthio)pyrimidin-4(3H)-ones (2-Cl-6-F-S-DABOs) 7-12 and the related 6-(2,6-difluorobenzyl) counterparts 13-15 in HIV-1 infected cells and in the HIV-1 reverse transcriptase (RT) assays is here described. The new 2-Cl-6-F-S-DABOs showed up to picomolar activity against wt HIV-1. Against clinically relevant HIV-1 mutants and in enzyme assays, the simultaneous C5(methyl)/C6(methyl/ethyl) substitution in the 2-Cl-6-F- and 2,6-F2-benzyl series furnished compounds with the highest, wide-spectrum inhibitory activity against HIV-1. Three representative 2-Cl-6-F-S-DABOs carrying two (9c, 10c) or one (10a) stereogenic centers were resolved into their individual stereoisomers and showed a significant diastereo- and enantioselectivity in HIV-1 inhibition, the highest antiviral activity well correlating with the R absolute configuration to the stereogenic center of the C6-benzylic position in both cellular and enzymatic tests. Application of previously reported COMBINEr protocol on 9c and 10c confirmed the influence of the stereogenic centers on their binding modes in the HIV-1 RT.
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