Zheng Yang Li,Li Bo Wang,Guo Cai Zhong,Sai Sai Li,Ai Guo Zhou
Titanium tin carbide (Ti2SnC) is a member a MAX phases, which are ternary carbides or nitrides with layered structure. Ti powders are normally used as Ti source to synthesize Ti2SnC. In this paper, TiH2, a relative cheaper Ti source, was used to synthesize Ti2SnC. Ti2SnC was synthesized from TiH2/Sn/TiC or TiH2/Sn/graphite powders by a tube furnace at different temperatures under Ar atmosphere. From the analysis of X-ray diffraction results, the lowest temperature to synthesize Ti2SnC was 1000 °C. Ti2SnC content increased with temperature, and high purity Ti2SnC was fabricated at 1200 °C. From scanning electron microscopy, as-synthesized Ti2SnC from TiH2/Sn/TiC was with plate-like structure. However, for Ti2SnC from graphite as carbon source, there was some stripe microstructure. Some large pores existed between the Ti2SnC particles. The existence of the pores make the mechanical properties of Ti2SnC block significantly reduced, its compressive strength was only 0.483 MPa or 0.35 MPa respectively for samples synthesized from TiC or graphite as carbon source. The low mechanical properties make the porous sample easy to be broken as powders.
Titanium aluminum carbide (Ti 3 AlC 2 and Ti 2 AlC) powders were synthesized from TiH 2 powders instead of Ti powders as Ti source by a tube furnace under argon atmosphere without preliminary dehydrogenation. 95 wt% pure Ti 3 AlC 2 powders were synthesized from TiH 2 /1.1Al/2TiC at 1 450 °C for 120 min. High-purity Ti 2 AlC powders were also prepared from 3TiH 2 /1.5Al/C and 2TiH 2 /1.5Al/TiC powders at 1 400 °C for 120 min. The as-synthesized samples were porous and easy to be ground into powders. Sn or Si additives in starting materials increased the purity of synthesized Ti 3 AlC 2 obviously and expanded the temperature range for the synthesis of Ti 3 AlC 2 . With Si or Sn as additives, high pure Ti 3 AlC 2 was synthesized at 1 200 °C for 60 min from TiH 2 / x Si/Al/2TiC and TiH 2 / x Sn/Al/2TiC ( x = 0.1, 0.2), respectively.
Perfluoro copolymers (PFCPs) with PFD (long chain -(CF 2 ) 7 CF 3 moiety) have a wide range of applications, such as hydrophobic and oleophobic modification of dry chemicals suppressants. However, high fluorine contents may produce much HF in thermal environments. In this study, a newly designed perfluoro copolymer (DPFCP) was synthesized and its application, pyrolysis and HF production were investigated. The pyrolysis of DPFCP could be divided into three stages, whereas the gas mainly released at the second stage, including CH 2 O, CO 2 , H 2 O, C x H y , C x H y F z , NH 3 , HF. A tube furnace was used to heating DPFCP to collect residual products and HF. The results indicated that HF was mainly produced under 370 °C.
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