Study on the growth mechanism of Bi-2212 ribbon-like thin films on flat Ag substrate by the atomization technique
The growth mechanism of Bi-2212 ribbon-like thin films on flat Ag substrate using an atomization technique was studied. The fine Bi-2212 powders were dispersed on the Ag substrate before the melting process, so as to avoid the change in the composition of the molten phase with distance, which would result in the formation of the impurity phases. Nearly reversible peritectic reaction on cooling causes the formation of well-defined Bi-2212 phase. Based on the results of in situ high temperature microscope observation, the wetting of the molten phase to the growing ribbons was identified as the essential condition for the growth of the ribbon-like thin films.
Formation processes of Bi-2212 films prepared on Ag(001) substrate by an atomization technique
Abstract We have studied in detail the growth of Bi-2212 ribbon-like thin film by melting Bi-2212 powders dispersed on flat, sputter-deposited Ag(0 0 1) films with order of tens of nm root-mean-square surface roughness. The formation processes of Bi-2212 ribbon-like thin films were studied by in situ high-temperature microscope observations. Because the powders melt incongruently, the liquid phase disperses with residual solid phases on the substrate. The residual solid phases act as the barrier for the melting phase to diffuse. Nearly monophasic Bi-2212 with excellent c -axis orientation in these thin films, proved by X-ray diffraction results, is the result of shortened diffusion length of the liquid phase. These techniques can be used especially to synthesize high quality Bi-based superconducting thin films for intrinsic Josephson junction devices.
Arc flash hazard assessment in the mining industry
When it comes to electrical safety in the workplace, arc flash has become the most prominent topic over the past decade. The Occupational Safety and Health Administration (OSHA, including state chapters) is the only government body that recognizes NFPA-70E, Standard for Electrical Safety in the Workplace. However, OSHA does not have jurisdiction in mining operations. Electrical safety for the metal and nonmetal surface mining industry is covered by the Code of Federal Regulations (CFR) Title 30, Part 56, Subpart K (Electricity). The Mine Safety and Health Administration (MSHA) is responsible for enforcing electrical safety in mining operations. CFR Title 30 does not reference personal protective equipment (PPE) to protect electrical workers against arc flash hazards. This paper provides maintenance and safety personnel in surface Metal/Nonmetal mining operations with a step by step guide to implementing an electrical safety program that meets the requirements of MSHA, CFR Title 30 and NFPA-70E.