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Ti3SiC2 ceramic bulk with a relative density greater than 99% was prepared by hot pressing sintering (HP) using Ti3SiC2 powder as raw material, and the hardness, flexural strength and fracture toughness of HP Ti3SiC2 bulk were 775HV, 520.46 MPa and 7.62 MPa·m1/2, respectively. To evaluate its oxidation-resistance and thermal shock resistance, ultra-high temperature ablation tests were conducted under oxyacetylene flame without cooling. The results show that the Ti3SiC2 ceramics remain flat within 10 s of the ablation, no macrocracks within 25 s.SEM and XRD analysis reveal that Ti3SiC2 samples are decomposed and oxidized during the ultra-high temperature ablation, elements Si and C are oxidized into gaseous Si-O and C-O compounds, TiO2 (rutile) with a loose structure remains on the surface of the sample. To analyze the internal oxide layer, a dense layer composed of rutile TiO2 and Al2TiO5 is observed, under which an Al2O3 particle-enriched layer is found covering the substrate. The dense internal oxide layer can effectively prevent O2 from diffusing inward, thereby reducing the oxidation rate of Ti3SiC2. The high melting point and high viscosity Al2O3 particle layer can absorb a large amount of heat and then reduce the transfer of heat flow to the Ti3SiC2 substrate, thus improving the anti-ablation of the Ti3SiC2 material.

Temperature-sensitive poly(N-isopropylacrylamide)/montmorillonite (PNIPAM/MMT) composite hydrogel was prepared by frontal polymerization. The effects of the MMT content and size of the reactor on the polymerization process and the properties of the products were investigated. The results indicated that the rapid thermal front propagation effectively suppressed the phase separation and caused a uniform distribution of MMT particles inside the PNIPAM matrix. The addition of MMT increased the compressive strength of composite hydrogel by 70% when compared to the one of the homopolymer but did not affect the lower critical solution temperature ) (LCST) of the hydrogel. The product containing 5 wt% MMT presented the quickest temperature response among all tested samples. As the diameter of the reactor increased, the front velocity and the front temperature increased but the compressive strength had a tendency to decrease. During the cycle uses, the performance of the composite gel prepared by frontal polymerization was almost maintained constant in contrast to the ones of the conventionally polymerized-product. [ABSTRACT FROM AUTHOR]