Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures.
This study investigated the dry and aqueous erosion of mild steel using electrochemical and dry sand impact techniques. In dry sand impact experiments, mild steel was eroded with 45 μm and 150 μm sand particles. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness techniques were used to elaborate the surface morphology of the eroded samples. The results revealed significant change in morphology of the eroded samples. In-depth analysis showed that although the metal erosion due to larger particles was significantly higher, the fines also notably damaged the metal surface. The surface damages were appreciably reduced with decrease in impact angle of the accelerated particles. The maximum damages were observed at an impact angle of 90°. The hardness of the samples treated with 45 μm and 150 μm sand remained in the range of 88.34 to 102.31 VHN and 87.7 to 97.55 VHN, respectively. In electrochemical experiments, a triple electrode probe was added into the metal treatment process. The linear polarization resistance (LPR) measurements were performed in slurries having 5% (by weight) of sand particles. LPR of the samples treated with 45 μm and 150 μm sand slurries was calculated about 949 Ω.cm(2) and 809 Ω.cm(2), respectively.
The world does not have too much time to ensure that the fast-growing population has enough land, food, water and energy. The rising food demand has brought a positive surge in fertilizers' demand and agriculture-based economy. The world is using 170 million tons of fertilizer every year for food, fuel, fiber, and feed. The nitrogenous fertilizers are being used to meet 48% of the total food demand of the world. High fertilizer inputs augment the reactive nitrogen levels in soil, air, and water. The unassimilated reactive nitrogen changes into a pollutant and harms the natural resources. The use of controlled-release fertilizers for slowing down the nutrients' leaching has recently been practiced by farmers. However, to date, monitoring of the complete discharge time and discharge rate of controlled released fertilizers is not completely understood by the researchers. In this work, corn starch was thermally processed into a week gel-like coating material by reacting with urea and borate. The granular urea was coated with native and processed starch in a fluidized bed reactor having bottom-up fluid delivery system. The processed starch exhibited better thermal and mechanical stability as compared to the native starch. Unlike the pure starch, the storage modulus of the processed starch dominated the loss modulus. The release time of urea, coated with processed starch, remained remarkably larger than the uncoated urea.