Temperature characterization of dielectric permittivity and AC conductivity of nano copper oxide-doped polyaniline composite

The polyaniline/copper oxide(PANI/CuO)nanocomposite was prepared by mixing solutions of polyaniline and copper oxide nanoparticles in dimethyl sulfoxide(DMSO).The synthesized polymer nanocomposites were characterized by X-ray powder diffraction(XRD),scanning electron microscope(SEM)and UV-visible spectroscopy.The characteristic peaks in XRD and UV-visible spectra confirmed the presence of CuO in the polymer structure.SEM images indicated morphological changes in the composite matrix as compared to the pristine PANI.The DC conductivity measurements were performed using two-probe method for various temperatures.AC conductivity and dielectric response of the composites were investigated in the frequency range of 10^(2)-10^(6)Hz using LCR meter.Dielectric permittivity
ε′(w)and dielectric loss factor
ε″(w)were investigated.It was observed thatε′(w)and
ε″(w)decrease with increase in frequency at all temperatures.At a particular frequency it is observed that bothε′(w)andε″(w)increase with increase in temperature.It was also observed that AC conductivity increased with increase in frequency and temperature.

Dielectric properties of edible fungi powder related to radio-frequency and microwave drying

Edible fungi are rich in nutrition,but they are susceptible to spoilage,and often prolonged by drying.RF and microwave energy drying have the advantages of short drying time,high energy efficiency and good process control.However,to develop an effective dielectric drying method,it is important to understand dielectric properties,the major factor characterizing the interaction between the electromagnetic energy and the food.At present,there is a lack of research on dielectric properties of edible fungi.In this study,a vector network analyzer and an open-ended coaxial-line probe were employed to measure the dielectric parameters.The dielectric parameters were observed at different temperatures(25–85°C)for edible fungi powder with moisture content ranging from 5 to 30%wet basis over a frequency range of 1–3000 MHz.The relationship between the dielectric properties and frequency,temperature,and moisture content were obtained via regression analysis.Further,the dielectric penetration depth was calculated,and the effects of frequency,moisture content,and temperature on the penetration depth were also analyzed.The results showed that the dielectric properties of edible fungi powder increased with an increase in moisture content and temperature,while they decreased with increasing frequency.At high moisture content and temperature,the increase in dielectric properties was slightly larger than that at low moisture content and temperature.The dielectric properties changed more evidently at lower radio frequencies than at higher radio frequencies.The penetration depth decreased with an increase in temperature,moisture content,and frequency.It can be concluded that a large penetration depth at radio frequencies below 100 MHz could be used to dry edible fungi on a large scale,whereas microwave energy could be employed for drying edible fungi on a small scale.