Dielectric response of nitrogen in soil amended with chicken litter biochar and urea under Oryza sativa L. cultivation

Unbalanced utilization of nitrogen (N) rice not economically viable neither is this practice environmental friendly. Co-application of biochar and urea could reduce the unbalanced use of this N fertilizer in rice cultivation. Thus, a field study was carried out to: (i) determine the effects of chicken litter biochar and urea fertilization on N concentration in soil solution of a cultivated rice (MR219) using dielectric measurement at a low frequency and (ii) correlate soil dielectric conductivity with rice grain yield at maturity. Dielectric response of the soil samples at 20, 40, 55, and 75 days after transplanting were determined using an inductance–capacitance–resistance meter HIOKI 3522-50 LCR HiTESTER. Selected soil chemical properties and yield were determined using standard procedures. The dielectric conductivity and permittivity of the soil samples measured before transplanting the rice seedlings were higher than those for the soil samples after transplanting. This was due to the inherent nitrogen of the chicken litter biochar and the low nitrogen uptake at the transplanting stage. The soil N response increased with increasing measurement frequency and N concentration. The permittivity of the soil samples was inversely proportional to frequency but directly proportional to N concentration in the soil solution. The estimated contents of N in the soil using the dielectric conductivity approach at 1000 Hz decreased with increasing days of fertilization and the results were similar to those of soil NH4+ determined using chemical analysis. The conductivity measured within 1000 Hz and 100,000 Hz correlated positively with the rice grain yield suggesting that nitrogen concentration of the soil can be used to estimate grain yield of the cultivated rice plants.

Influence of dielectric conductivity on corner error in wire electrical discharge machining of Al 7075 alloy

Comprehensive research has been carried out to investigate the effect of electrical conductivity (ĸ) of dielectric along with other process parameters in wire electrical discharge machining (WEDM) of Al 7075 alloy. Taguchi based design using L9 orthogonal array has been used to analyse the effect of open circuit voltage (VOC), pulse on time (TON), pulse frequency (fP) and servo sensitivity (SC) on corner accuracy including different other response criteria. The experimental result shows that dielectric conductivity plays a significant role in respect to corner error and surface finish in a single pass cutting operation. Surface topography and elemental analysis of the machined surface has been carried out for depth understanding of the influence of dielectric conductivity in WEDM. Experimental investigation and subsequent analysis of results showed that for a broad range of response variables (e.g. corner accuracy and surface finish) 12 mho conductivity setting gives the optimum result. However, to attain corner error (CE) and surface roughness (Ra) below a certain critical limit (i.e. CE = 0.101 mm & Ra = 2.671 µm), 4 mho conductivity setting is found to be the best setting for this alloy.

Thermally and electrically conducting polycarbonate/elastomer blends combined with multiwalled carbon nanotubes

In this article, we have studied thermal and dielectric conductivity and morphology of polycarbonate (PC)/ethylene–propylene copolymer (EPC)/multiwalled carbon nanotubes (MWCNTs) nanocomposites. Transmission electron microscopy has been used to investigate the localization and migration of MWCNTs within the matrix. The MWCNTs were located in the PC phase and at the interface of PC and EPC. The results showed that the thermal conductivity of the PC decreased with the increasing content of EPC elastomeric particles. However, at the same time, one could observe an increase of the thermal conductivity in the polymer blends along with an addition of MWCNT. The electrical conductivity of the PC/EPC blends containing 10 wt% of EPC increased with the incorporation of MWCNTs, and the conducting paths were formed at additive content less than 0.5 wt% of MWCNT.