No abstract

The ultraviolet (UV)-C ageing behavior of silicone rubber (SiR) incorporated with titanium dioxide nanoparticles (nano-TiO 2 ) was studied under UV-C radiation. The SiR incorporated with nano-TiO 2 displayed excellent physical properties when exposed to UV-C radiation. With the increase of the ageing time, the SiR with nano-TiO 2 showed no significant change in crosslinking density and Shore A hardness. Moreover, compared with the SiR without nano-TiO 2 , the SiR incorporated with nano-TiO 2 also exhibited high retention ratio in tensile properties, especially elongation at break. It was found that nano-TiO 2 was a good ultraviolet light stabilizer during the UV ageing process of SiR and the optimum content of nano-TiO 2 was 2 phr. The results of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy showed the appearance of OAH and C@O and the decrease of the intensity of SiC 2 O 2 in SiR samples during the process of UV-C ageing. Based on these results, a possible UV ageing mechanism of SiR could be proposed.

No abstract

No abstract

Due to the small amount of transformation during the phase transformation process, it is difficult to determine the phase transition temperature of the proeutectoid cementite in the bearing steel by the expansion method. In this paper, the Gleeble3800 thermal simulator was used to study the phase transformation behavior of GCr15 bearing steel at different cooling rates. Firstly, the phase transformation temperature range of pearlite is about 550°C∼700°C measured by expansion method. Based on this, the transformation temperature range of proeutectoid cementite is about 700°C∼900°C studied by metallographic method; The precipitation curve of proeutectoid cementite was supplemented, and the complete continuous cooling phase transition curve (CCT curve) of bearing steel was drawn. On this basis, the scheme of inhibiting the formation of proeutectoid cementite by two-stage cooling process was proposed and discussed, and the finishing cooling temperature was studied, which provides a basis for controlling network carbide in field production.