Authors:Manoj Kumar Pal, Beena Singh, and Jaiswar Gautam
The influences of nanosized CaCO3 on the thermal and optical properties embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) were investigated. Calcium carbonate nanoparticles were synthesized by in situ deposition technique, and its nano size (32–35 nm) was confirmed by scanning electron microscope (SEM) and X-ray studies. Nanocomposites samples of PMMA/CaCO3 and PS/CaCO3 were prepared with different filler loading (0–4 wt%) of CaCO3 nanoparticles by solution mixing technique. The Fourier transform infrared analysis confirmed that CaCO3 nanoparticles were present in the polymers matrices. The morphology and elemental composition of nanocomposites were evaluated by SEM and energy dispersive X-ray spectroscopy. The thermal properties of nanocomposites were characterized by differential scanning calorimetric, thermogravimetric, and differential thermogravimetry analysis, and the results indicate that the incorporation of CaCO3 nanoparticles could significantly improve the thermal properties of PMMA/CaCO3 and PS/CaCO3 nanocomposites. The glass transition temperature (Tg) and decomposition temperature (Td) of nanocomposites with 4 wt% of CaCO3 nanoparticles were increased by 30 and 24 K in case of PMMA/CaCO3 and 32 and 15 K in the case of PS/CaCO3 nanocomposites, respectively. The obtained transparent nanocomposites films were characterized using UV–Vis spectrophotometer which shows the transparencies of nanocomposites are almost maintained in visible region while the intensity of absorption band in ultraviolet (UV) region is increased with CaCO3 nanoparticles contents and these composites particles could enhance the UV-shielding properties of polymers.
Authors:Daniel Koncz-Horvath, Aliz Molnar, Greta Gergely, Manoj Kumar Pal, and Zoltan Gacsi
In this paper, the effect of soldering technique and thermal shock test were investigated on SAC 305 solder joints, produced by 2 different solder methods, which are the most common solder materials used for through-hole reflow soldering (THRS) and multiwave soldering techniques. The solder joints were subjected to different cycle numbers up to 5000 thermal shock tests with 2 different thermal profiles of −30/+110 °C and −40/+125 °C. Microstructural properties of the tested joints were examined with the focus on intermetallic layer thickness and crack formation/propagation. The thickness of the scallop-shaped Cu6Sn5 intermetallic layer was increased with increasing cycle number for both THRS and multiwave joints, but the thickening was more effective for the THRS joints. Cracks typically formed at the solder alloy–plated-through-hole (PTH) barrel and the solder alloy–pin interfaces and propagated along grain boundaries and precipitations of an intermetallic compound.