Activated tungsten inert gas (ATIG) welding has a good depth of penetration (DOP) as compared to the conventional tungsten inert gas (TIG) welding. This paper is mainly focused on ATIG characterization and mechanical behavior of aluminum alloy (AA) 6063-T6 using SiO2 flux. The characterization of the base material (BM), fusion zone (FZ), heat affected zone (HAZ) and, partially melted zone is carried out using the suitable characterization methods. The weld quality is characterized using ultrasonic-assisted non-destructive evaluation. A-scan result confirms that the ATIG welded samples have more DOP and less bead width as compared to conventional TIG. The recorded tensile strength of ATIG with SiO2 is better than the conventional TIG welding. The failure mode is ductile for ATIG welding with larger fracture edges and is brittle in the case of conventional TIG welding.
The process of historical building conservation includes the repair of mortars eroded due to material and environmental factors. Identification of old mortar constituents is necessary to enable duplicating the material. Information on the binder and aggregate types and contents can be obtained from microscopic observation used in combination with instrumental methods. This paper presents the results of microstructure and mineral composition tests of mortars collected from the walls of thirteenth century buildings. A combination of techniques was used, which included X-ray diffraction, transmitted light optical microscopy and scanning electron microscopy with micro-area elemental composition analysis. The test results revealed porous lime and sand mortars with a binder-aggregate ratio often beyond the commonly adopted values. The mortars contained sand grains of up to 0.5 mm and larger pieces of limestone, flint, feldspar and brick. Transmitted light optical microscopy and scanning microscopy were found to be essential techniques for mortar characterization in existing buildings and structures.
Numerical analysis of the dark current (Jd) in the type-II superlattice (T2SL) barrier (nBn) detector operated at high temperatures was presented. Theoretical calculations were compared with the experimental results for the nBn detector with the absorber and contact layers in an InAs/InAsSb superlattice separated AlAsSb barrier. Detector structure was grown using MBE technique on a GaAs substrate. The k p model was used to determine the first electron band and the first heavy and light hole bands in T2SL, as well as to calculate the absorption coefficient. The paper presents the effect of the additional hole barrier on electrical and optical parameters of the nBn structure. According to the principle of the nBn detector operation, the electrons barrier is to prevent the current flow from the contact layer to the absorber, while the holes barrier should be low enough to ensure the flow of optically generated carriers. The barrier height in the valence band (VB) was adjusted by changing the electron affinity of a ternary AlAsSb material. Results of numerical calculations similar to the experimental data were obtained, assuming the presence of a high barrier in VB which, at the same time, lowered the detector current responsivity.