Shaohua Dong Weijian Han Yongming Luo Tong Zhao Caihong Xu
材料科学技术（英文）
Three new borazine derivatives, 2,4,6-tri(allylamino)borazine (CH2=CHCH2NHBNH)3 (1), 2,4,6-tri(3-ethynylanilino)borazine (CH´CC6H4NHBNH)3 (2), and 2,4,6-tri(4-propargyl oxyanilino)borazine (CH´CCH2OC6H4NHBNH)3 (3) were synthesized by reaction of 2,4,6-trichloro-borazine Cl3B3N3H3 (TCB) with corresponding primary amines, respectively. Their thermal behavior was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). These molecules were easily crosslinked via thermal
polymerization of reactive ethynyl or vinyl groups. The pyrolytic residues of borazines were investigated by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). The analytic results indicated that B-C-N ceramics were formed upon pyrolysis of the borazines under an inert atmosphere.
关键词:
Precursors
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Thermal properties
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B-C-N ceramic
Muhammad Iqbal
材料科学技术（英文）
Minor alloying plays an important role in the synthesis and improvement of thermal stability of bulk metallic glasses (BMGs). The present study was conducted to investigate the effect of minor additions of Y, Ti and Nb on crystallization behavior and thermal properties of Zr64.5Ni15.5Al11.5Cu8.5 base alloy. Thermal parameters and the activation energies for crystallization were calculated for four [Zr0.645Ni0.155Al0.115Cu0.085]100-xMx (M = Y, Ti and Nb while x = 0, 2 at. %) alloys. Parameters describing thermal stability in these systems, including the activation energies for crystallization, were determined. The present alloys have wide supercooled liquid region of ≥87 K. Maximum activation energy was found to be greater than 300 kJ/mol for the base alloy. Four crystalline phases were identified in the samples annealed at 823 K. Reduced glass transition temperature (Trg) and other thermal parameters like γ, δ and β improved by Y and Ti addition. Niobium addition resists crystallization below annealing temperature 713 K however its effect on thermal properties is not very promising.
关键词:
Activation energy
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