Properties of polycarbonate containing BaTiO3 nanoparticles

Abstract

The real part of the relative permittivity, ε′, and dielectric loss, tan δ, have been determined at audio frequencies at temperatures from about 5 K to 350 K for nano-composites composed of BaTiO3 nanoparticles and polycarbonate. The room temperature breakdown strength was also measured and thermal analysis, nuclear magnetic resonance and scanning electron microscopy studies were carried out. For some films the nanoparticles were surface-treated (STNP) while for others they were not (UNP). For concentrations of UNP greater than about 3.4 vol. %, ε′ is much larger than expected on the basis of laws of mixing. On the other hand, ε′ for materials made using STNP is well-behaved. Correspondingly, increased loss (ε″ or tan δ) in the vicinity of room temperature is observed for the materials made from UNP. The anomalously large values of relative permittivity and increased loss are attributed to the presence of large aggregates in the materials made using the UNP. For both UNP-and STNP-based materials, the breakdown strength is found to decrease as nanoparticle concentration increases. The breakdown strength for the materials made using STNP is found to be larger for all concentrations than for those containing UNP despite the presence of large aggregates in some of the STNP-based materials. This shows that breakdown is strongly affected by the nanoparticle surfaces and/or the interface layer. It is also found that the breakdown strength for materials made using UNP increases as particle size increases. Finally, variable temperature and pressure proton nuclear magnetic resonance relaxation measurements were made to assess the effect of nanoparticle inclusion on polymer motion, and the effects were found to be very minor.

Surface‐modified MgO nanoparticle enhances the mechanical and direct‐current electrical characteristics of polypropylene/polyolefin elastomer nanodielectrics

“…The Figure 2, the weight loss of the surface-modified MgO nanoparticles was much bigger than that of the unmodified nanoparticles (ca. 27 In contrast, the TGA behavior of the surface-modified nanoparticles was more complex; this was attributed to the loss of organics grafted onto the surface of the nanoparticles during surface modification. The weight loss around 550 K of the unmodified nanoparticles was possibly associated with leaving lattice hydroxyls.…”

Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves

“…On the other hand, while ceramics such as BaTiO 3 are brittle and much less versatile with respect to processing, they have bulk permittivities at microwave frequencies that can be orders of magnitude larger than those of polymers [12,13]. Consequently, by dispersing micro-scale particles of BaTiO 3 in a polymer matrix, processable materials with ε up to 20 in the frequency range 12-18 GHz can be obtained [14][15][16][17][18].…”