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Solder and Automated Soldering Processes
Published in Jack Arabian, Computer Integrated Electronics Manufacturing and Testing, 2020
Even before soldering a PWB, the manufacturing engineer should recognize those methods for preserving board solderability during storage and handling. One method to protect the exposed copper on a PWB is a protective organic coating which is compatible with rosin fluxes and which prevents copper oxidation. If such a coating is used, the following precautions should be taken: Avoidance of excessive heating during curingProtection from any sulfur-rich environmentIn the storing and packaging of components, contamination may spread between parts in bins and on shelves. Packaging, for example, must be specified as being sulfur-free. Common packaging materials such as cardboard boxes, rubber bands and paper bags normally contain large amounts of sulfur. This sulfur will react with the tin and lead to create tin sulfate and lead sulfate which are difficult to remove with flux from critical soldering surfaces of component leads and PWBs. Also, in the case of most manufactured solder pastes, they can be produced with oxide-free alloys, but sulfur, a strong oxidizing agent, is a common contaminant depending on the country of origin.Elimination of high humidity during storage
Biology of Joints
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
The swelling pressure of cartilage comes from its proteoglycan content. In these large aggregates, glycosaminoglycan polymers (predominantly chondroi-tin sulfate) branch away from central protein cores that themselves branch off from even larger hyaluronic acid chains (19). The sulfate and carboxylic acid moieties of the glycosaminoglycans are negatively charged. The consequence of these electrostatic forces is that each branch repels its neighbor, leading the isolated molecules to assume a configuration that has been likened to that of a bottlebrush. In situ, however, these molecules are restrained within the arching framework of type II collagen. The repellent electrostatic and osmotic forces of the proteoglycans are thus balanced by the mechanical restraint of collagen to produce the firmness and resilience that characterize this tissue.
Esterification of high acidity vegetable oil catalyzed by tin-based catalysts with different sulfate contents: contribution of homogeneous catalysis
Published in Chemical Engineering Communications, 2019
Camila O. P. Teixeira, Kelly C. N. R. Pedro, Thais L. A. P. Fernandes, Cristiane A. Henriques, Fatima M. Z. Zotin
Specific surface areas of the precursor SnSO4 and the calcined catalysts are also presented in Table 1. Area increased significantly for samples calcined at temperatures higher than 300 °C. This behavior is attributed to the transition of SnSO4 to SnO2. The BET area values go through a maximum as the calcination temperature increases. The SnSO4(500) has the largest area BET as compared to SnSO4. This behavior was also observed by Zhou et al. (2008) that have studied SnSO4 calcined between 150 and 600 °C for the alkylation of hydroquinone with tert-butanol but the highest BET surface area was obtained for a calcination temperature of 350 °C. Dabbawala et al. (2013) also verified this tendency for sulfated tin oxides (STO) with different sulfur content (1–8 wt %). In this case, tin sulfate samples were calcined for a longer time (4 h) in flowing air. These authors confirmed the transformation of SnSO4 to SnO2 by desulfation. According to Moreno et al. (2011), this tendency is due to the stabilization of the mesoporous structure, increasing thermal stability of the catalysts. Thus, the solid undergoes a restructuring that causes an increase in the specific surface area of the catalyst and changes several physical properties. This behavior is observed up to 600 °C. At this temperature, practically only SnO2 is present, and therefore, calcination at higher temperatures causes a decrease in the specific surface area, now associated with the sintering of SnO2.
Effect of wastewater quality parameters on coliform inactivation by tin oxide anodes
Published in Journal of Environmental Science and Health, Part A, 2018
Sodium bicarbonate, sodium sulfate, ammonium chloride, sodium nitrite, sodium nitrate, isopropanol, tin chloride pentahydrate, antimony chloride, and tin sulfate were purchased from Sigma-Aldrich. M-Endo broth, potassium dichromate, sodium thiosulfate, hydrochloric acid, and sulfuric acid were purchased from J.T. Baker. M9 medium was prepared as described in Standard Methods for the Examination of Water and Wastewater.[16] Chemical oxygen demand (COD) analysis reagents were purchased from Hach Chemical. Titanium rods (2 mm diameter) were purchased from GoodFellow Metals.