With the trend for green technology, the study focused on utilizing a forgotten herb to produce an eco-friendly coating. Andrographis paniculata or the kalmegh leaves extract (KLE) has been investigated for its abilities in retarding the corrosion process due to its excellent anti-oxidative and antimicrobial properties. Here, KLE was employed as a novel additive in coatings and formulations were made by varying its wt%: 0, 3, 6, 9, and 12. These were applied to stainless steel 316L immersed in seawater for up to 50 days. The samples were characterized and analyzed to measure effectiveness of inhibition of corrosion and microbial growth. The best concentration was revealed to be 6 wt% KLE; it exhibited the highest performance in improving the ionic resistance of the coating and reducing the growth of bacteria.

Zinc oxide (ZnO) varistors is a solid state electronic ceramic component whose function to protect electronic devices against over voltage surges due to their highly nonlinear electrical properties and ability in controlling the energy. In this study, ZnO varistor is prepared via solid state reaction method. The ZnO based varistor ceramics undergoes sintering temperature at 900 ℃, 1100 ℃ and 1300 ℃ for 45 minutes. The used of sintering temperature from 900 to 1300 ℃, has increased the grain size of ZnO and improved their crystallinity as shown from the peaks intensity of X-ray diffraction (XRD). Current-Voltage properties exhibit the value of nonlinear coefficient in the range of 1.44 to 1.76. Different sintering temperature is used to adjust the microstructure and improve the varistor ceramic characteristics where it shows a potential difference in various application of electronic devices. Increasing in sintering temperature would lead to improved grain growth for better electrical properties.

This paper investigated the effects of Pr₆O₁₁ and Co₃O₄ on the electrical properties of ZnO-BaTiO₃ varistor ceramics. The Pr₆O₁₁ doping has a notable influence on the characteristics of the nonlinear coefficient, varistor voltage, and leakage current where the values varied from 2.29 to 2.69, 12.36 to 68.36 V/mm and 599.33 to 548.16 µA/cm², respectively. The nonlinear varistor coefficient of 5.50 to 7.15 and the varistor voltage of 7.38 to 8.10 V/mm was also influenced by the use of Co₃O₄ as a dopant. When the amount of Co₃O₄ was above 0.5 wt.%, the leakage current increased from 202.41 to 302.71 μA/cm². The varistor ceramics with 1.5 wt.% Pr₆O₁₁ shows good nonlinear electrical performance at higher breakdown voltage and reduced the leakage current of the ceramic materials. Besides, the varistor sample that was doped with 0.5 wt.% Co₃O₄ was able to enhance the nonlinear electrical properties at low breakdown voltage with a smaller value of leakage current.

Conventional, free or pressure less sintering is the simplest technique which involves heating of a powder compact, previously prepared at ambient temperatures, without applying any external pressure. It can be conducted with various box furnaces or tube furnaces under different atmospheres (oxidizing, reducing, inert, and vacuum). Through the use of this method, a highly applicable varistor can be mass produced. Varistors are of a particular interest for modern surge protection of over-voltage. Nowadays, ZnO ceramic varistors are most favorable in electronic industry due to their excellent electrical characteristics and high energy handling capabilities. By optimizing the method during sintering process, the number of potential barriers formed can be controlled thus improving the capability of the low-voltage varistor.