Al
3C
2B
48 crystals and Si doped Al
3C
2B
48 type crystals were prepared by the reaction between carbon, boron, aluminium and silicon powders as starting materials in an argon atmosphere. The experimental conditions for obtaining these crystals of relatively large size were determined. As-grown Al
3C
2B
48 crystals and Si doped Al
3C
2B
48 type crystals were subjected to chemical analysis and the study of oxidation in air at high temperatures, and also the measurements of crystal size, unit cell dimension, Vickers microhardness and electrical resistivity, respectively. The results obtained are as follows:
(1) The suitable conditions for growing Al
3C
2B
48 and Si doped Al
3C
2B
48 type crystals were the atomic ratios of starting materials (C/B=0.056, B/Al=0.10, Si/B=0-0.07), the soaking temperature (1450°C) and the soaking time (10hrs).
(2) Al
3C
2B
48 crystals made under the above conditions, were yellowish brown and semitransparent, having a nearly spherical polyhedral shape. The largest crystals prepared had the dimensions of about 1.8mm×1.8mm×1.8mm-2.5mm×2.5mm×2.5mm.
(3) The unit cell dimensions, Vickers microhardness (
Hv) and electrical resistivity (ρ) of the crystals were
a=12.302(1)Å,
b=12.621(1)Å,
c=10.161(1)Å,
V=1577.7(2)Å
3,
Hv=27GPa, ρ=2.58×10
-2Ω·
cm for Al
3C
2B
48 crystals (Si/B=0), and
a=12.291(2)Å,
b=12.620(4)Å,
c=10.161(1)Å,
V=1576.3(1)Å
3,
Hv=36GPa, ρ=90.52×10
-2Ω·
cm for Si doped Al
3C
2B
48 type crystals (Si/B=0.004), respectively.
(4) The oxidation reaction of Al
3C
2B
48 crystals and Si doped Al
3C
2B
48 type crystals began to proceed at about 710°C in air, and their oxidation products were found to be 9Al
2O
3·2B
2O
3 (orthorhombic system) and B
2O
3 (hexagonal system) phases.
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