R.Pielaszek1,2, B.Palosz1, S.Gierlotka1, S.Stel'makh1, E.Grzanka1,2 and G.Goerigk3
1High
Pressure Research Center, Polish Academy of Sciences, Sokolowska 29, 01-142
Warsaw, Poland
2Institute of Experimental Physics, Warsaw University, Hoza
69, 00-681 Warsaw, Poland
3Hasylab, DESY, Notkestr. 85, D-22603 Hamburg, Germany
There is an increasing interest
in the nanocrystalline materials with respect to their fundamental properties
as well as potential applications for fabrication of high-tech construction
and electronic ceramics [1]. Knowledge of microstructure, understood as
morphology of crystallites, their size, shape and spatial arrangements
during sintering is essential for technology of such materials. For us
it's also basis (that has to be defined) for further strain analysis in
high-pressure investigations [2,3].
Ten samples of nanometric SiC
and three samples of their ceramics obtained during high-pressure, high-temperature
sintering experiments [4] were examined (see Tab.1.). Four samples
of nanocrystalline SiC powder were formed in pills (c.a. 2mm in diameter,
1mm thick) using hand press; increasing forces were applied ("F1", "F2",
"F3", "F4"). However precisely undefined, the pressures were lower than
0.5GPa.
Analysis of the Small Angle X-Ray
Scattering (SAXS) data gave microstructure characteristics of the materials.In
most cases we were able to derive surface fractal dimension Ds.
In eight cases shape of lowest-angle part of the scattering curve was clear
sufficiently to derive mass fractal dimension Dm.
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157k family | SiC | 3.9 nm | powder synthesized from organic precursors | ||
157k | SiC | 3.9 nm | powder manually pressed during sample preparation | 0.685(9) | 2.04(1) |
157kbis | SiC | 3.9 nm | powder manually pressed during sample preparation | 0.63(1) | 1.98(1) |
157k-F1 | SiC | 3.9 nm | powder not pressed ("F"=1) | 1.80(1) | 2.04(1) |
157k-F2 | SiC | 3.9 nm | powder pressed "a little" ("F"=2) | 1.23(1) | 1.984(9) |
157k-F3 | SiC | 3.9 nm | powder pressed heavily ("F"=3) | 0.42(1) | 1.96(1) |
157k-F4 | SiC | 3.9 nm | powder pressed heavily ("F"=4) | 0.73(1) | 1.920(8) |
h1k | SiC | 2.0 nm | powder synthesized from organic precursors, manually pressed during sample preparation | 0.41(4) | 2.12(1) |
w3k | SiC | 2.7 nm | powder synthesized from organic precursors, manually pressed during sample preparation | 0.75(2) | 2.14(1) |
98-g1 | SiC | nm | powder synthesized from organic precursors | ||
max-9711 family | SiC | microns | nano-SiC sintered in MAX80 6-anvill press (Hasylab/DESY) | ||
max-9711-01SI | SiC | 2.43(1) | |||
max-9711-02SI | SiC | 2.164(8) | |||
max-9711-03KI | SiC | 2.33(1) |
Table 1: Mass and surface fractal dimensions of nanocrystalline SiC powders and (max-9711-...) sintered powders
We found that:
Figure 1: Pressure decreases slope of smallest-angle part of the scattering curve (thus pores mass fractal dimension Dm) for SiC nanocrystalline powder
References