ABSTRACT
An epoxy resin thermally conductive adhesive is a type of thermosetting polymer encapsulation material that exhibits comprehensive performance, and the thermomechanical properties of this adhesive vary significantly under different curing conditions. In this paper, spherical alumina was used as a filler for thermal conductivity to prepare an epoxy resin thermal conductivity adhesive using a multistage freezing mixing method. The effects of various curing conditions on the thermal-mechanical properties and fracture morphology of the epoxy resin thermal conductivity adhesive were studied. The results showed that the curing condition of 150 °C/2.5 h significantly improved the performance of the epoxy resin thermally conductive adhesive. Through the shear test of the composite material, the influence of the curing agent on the adhesion of the thermally conductive adhesive under fixed conditions was explored. It was found that the curing agent with a superbranched structure exhibited latent properties and greatly enhanced the toughness of the cured epoxy resin product. Altering the curing conditions increases the shear strength by up to 307%. With the increase in curing temperature and the extension of curing temperature, the glass transition temperature gradually increased from 103.9 to 159.8 °C. The initial decomposition temperature TIDT gradually increased from 295.4 to 310.1 °C, and the temperature at which the fastest decomposition rate occurs (Tmax) gradually increased from 312.48 to 330.33 °C. The thermal stability of the substance increased with both temperature and time. The curing time and curing temperature were increased, and the morphology of the fracture of the epoxy resin thermally conductive adhesive cured sample gradually showed a ductile fracture from a typical brittle fracture. The research results reveal the influence of curing conditions on the thermal conductivity and thermal stability of the epoxy resin thermally conductive adhesive, which has a specific reference value for improving the performance of the epoxy resin thermally conductive adhesive, optimizing its usage conditions, and improving production efficiency.
ABSTRACT
Persistent luminescence (PPL) materials have gained lots of attention and have been widely used in traffic signs, displays, medical diagnosis and architectural decoration. Single ion doped PPL materials with stable emission are excellent for practical applications, but it is difficult to cover the entire wavelength range. Here, a new cyan long-lasting phosphor CaSnO3:Lu3+ was successfully synthesized at 1200 °C by the conventional high temperature solid state method. From the X-ray photoelectron spectroscopy (XPS), it can be concluded that the Sn2+ ions exist in the crystal lattice because the doping of Lu3+ ions changes the valence state of the Sn ions. According to the thermally simulated luminescence (TSL), the continuous afterglow of CaSnO3:Lu3+ phosphors is produced by appropriate hole or electron traps, which are caused by doping the calcium stannate host with rare earth ions (Lu3+). The long-lasting phosphorescence (LLP) properties of the cyan phosphor were first discussed and the afterglow mechanism was expounded in detail. The excitation and the emission spectra of the phosphor revealed the characteristic broad peak of the Sn2+ ion. Typical afterglow behavior of the CaSnO3:Lu3+ phosphors was exhibited after power was turned off.
