| 1. |
- Andersson, Odd E., et al.
(författare)
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A study of temperature and pressure induced structural and electronic changes in SbCl5 intercalated graphite : Part II. Experimental data for c-axis resistivity
- 1992
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Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 7:11, s. 2989-3000
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental data for the c-axis resistivity ?c of stage s = 2, 3, 4, 5, and 8, SbCl5 intercalated graphite, over the temperature range 40 to 300 K and the pressure range 0 to 0.8 GPa (0–8 kbar). For most specimens studied, resistance anomalies are observed below 230 K at atmospheric pressure and at pressures up to 0.5 GPa at 293 K. These anomalies are explained in terms of structural changes from a disordered or partly crystallized in-plane intercalate structure at atmospheric pressure and T > 230 K to an almost completely crystallized structure below this temperature, or at elevated pressures, as discussed in a companion paper. In the crystallized phases ?c is approximately linear in T except for stage 8, for which a nonlinear behavior, with a negative temperature coefficient of resistivity below 200 K, is observed. The results are compared with previously available literature data, and the p-T phase diagram is briefly discussed.
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| 2. |
- Cheng, Y.F., et al.
(författare)
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TEM study of the early stages of the precipitation process in strip-cast Al3003 alloys
- 1992
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Ingår i: Journal of Materials Research. - 0884-2914. ; 7, s. 3235-3241
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Tidskriftsartikel (refereegranskat)abstract
- The precipitation behavior, especially the early nucleation stages, of the industrial strip-cast Al3003 alloys was investigated by using transmission electron microscopy (TEM). An icosahedral quasicrystalline phase was found as secondary particles in these strip-cast alloys after heat treatment for a few seconds. Three different nucleation paths are proposed based on the TEM observations. They have the same origin, viz. (Mn, Fe)-containing Mackay icosahedra, and are governed by the composition of alloys, especially the Mn and Si content.
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| 3. |
- Lelaurain, Michelle, et al.
(författare)
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A study of temperature and pressure induced structural and electronic changes in SbCl5 intercalated graphite : Part I: Structural aspects
- 1992
-
Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 7:11, s. 2978-2988
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effects of temperature (10 = T = 295 K) and pressure (0 = p = 0.8 GPa) on the state of intercalate layer crystallization in SbCl5 graphite intercalation compounds of stages 2, 4, and 8. At room temperature (RT), the intercalate layer may in some second stage compounds be fully crystallized and lowering the temperature creates no further modifications. In all other cases, i.e., those in which the intercalate layer has only partial crystallization at RT, lowering T leads to the formation of new in-plane unit cells, the final state depending on the kinetics. Applying pressure to above 0.3–0.5 GPa results in crystallization in all cases, different from that induced simply by lowering of the temperature. We discuss the unit cells observed and the relationships they bear to each other in the light of other works on similar compounds.
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| 4. |
- Otamiri, JC, et al.
(författare)
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Preparation of YBa2Cu3O6 + x by a Formic Acid Method
- 1990
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Ingår i: Journal of Materials Research. - 0884-2914. ; 5:7, s. 1388-1391
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of YBa2Cu3O6+x from formic acid solutions of stoichiometric amounts of the initial materials has been investigated in the temperature range 750–950°C. The reaction is strongly influenced by the concentration of formic acid. Dilute solutions favor synthesis of purer samples under moderate conditions of temperature and sintering time. At lower temperature the same effect can be achieved if sintering time is longer, while at higher temperature, multiple grinding and heating at very short intervals are necessary to avoid formation of Y2BaCuO5. The observed effect of HCOOH concentration is explained by the different mechanisms involved in the decomposition of the formates obtained.
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