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Dental and Maxillofacial Surgery Applications of Polymers
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
These materials are supplied as two pastes. The “base” paste contains a polysulfide, the formula of which is given in Figure 23.40. This molecule contains three –SH groups; two of these groups are terminal, one is pendant. The base paste also contains a filler, between 11% and 54% for different materials, for example, TiO2. This paste is usually colored white, because of the color of the filler. The reactor paste (sometimes called “accelerator” or “catalyst” paste) contains lead dioxide (PbO2) that causes polymerization and cross-linking, by oxidation of –SH groups (Figure 23.40). Sulfur is also present. An oil (an ester or chlorinated paraffin) is included to form a paste of the correct consistency. This paste is brown colored due to the lead dioxide. On mixing the pastes, the –SH groups can be oxidized by PbO2, giving S-S linkages, resulting in both chain lengthening and cross-linking.
Modular Systems for Energy and Fuel Storage
Published in Yatish T. Shah, Modular Systems for Energy Usage Management, 2020
Invented in the 19th century, lead–acid batteries are the most fully developed and commercially mature type of rechargeable battery. They are widely used in both mobile applications like cars and boats and stationary consumer applications like uninterruptible power supply (UPS) units and off-grid PV. However, several issues have prevented widespread adoption for utility-scale grid applications. These include short cycle life, slow charging rates and high maintenance at power rating ≫1 MW. These perform a variety of services including peak shaving, on- site power, ancillary services, ramping, and renewables capacity firming. Lead–acid batteries rely on a positive, lead-dioxide electrode reacting with a negative, metallic lead electrode through a sulfuric acid electrolyte. Ongoing research and development have produced several proprietary technologies in two categories: advanced lead–acid and lead acid–carbon batteries [1–12].
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Published in D. Yogi Goswami, Frank Kreith, Energy Conversion, 2017
Jeffrey P. Chamberlain, Roel Hammerschlag, Christopher P. Schaber
Lead-acid is one of the oldest and most mature battery technologies. In its basic form, the lead-acid battery consists of a lead (Pb) negative electrode, a lead dioxide (PbO2) positive electrode, and a separator to electrically isolate them. The electrolyte is dilute sulfuric acid (H2SO4), which provides the sulfate ions for the discharge reactions. The chemistry is represented by
Modern developments in electrodes for electrochemical technology and the role of surface finishing
Published in Transactions of the IMF, 2019
Recio et al. have described nanostructured, three-dimensional-like β-PbO2 coatings by galvanostatic anodic deposition from electrolytes containing 1.0 mol dm−3 lead (II) methanesulfonate and 0.2 mol dm−3 methanesulfonic acid at 60°C and 20 mA cm−2.36 The deposits were adherent to the carbon substrate and XRD analysis revealed that the crystallite size was in the range 20–30 nm; AFM imaging showed very uniform deposits with high surface roughness (255–275 nm). The authors studied several porous, 3D supports for the lead dioxide. Promising results were obtained with 275 cm3 of 0.25 mmol dm−3 methyl orange in 0.05 mol dm−3 Na2SO4, at pH 3.0 and 22.5°C. An anodic Fenton oxidation (involving oxidation catalysed by soluble ferric ions to produce hydroxyl radicals) at a large area carbon-felt cathode, in the presence of 0.2 mmol dm−3 Fe2+ catalyst in the electrolyte, performed better than a direct anodic oxidation in the absence of the Fe2+. Substantial decolourisation was achieved in 60 min.
Potentiostatic studies of the influence of temperature on lead-silver anodes during electrowinning and decay period
Published in Canadian Metallurgical Quarterly, 2019
Wei Zhang, Georges Houlachi, Edward Ghali
Figures 9 and 10 show the evolution of potential during 1 h decay in sulphuric acid solution with and without ZnSO4 addition at 35°C, 40°C and 45°C around an average of 1100 mV, respectively. It can be observed that the potential of the Pb-0.7% Ag anode drops slowly at 35°C in sulphuric acid solution with and without ZnSO4, and shows the longest potential plateaus among the Pb-0.7% Ag anode at 35°C, 40°C, and 45°C. This plateaus period corresponds to the theoretical potential value of the PbO2/Pb2+ equilibrium. Since thermodynamically lead dioxide is unstable on the surface of lead in the sulphuric acid solution, lead dioxide was transformed spontaneously into lead sulphate [20].
Effect of temperature on the residual stress of a β-PbO2 coating
Published in Surface Engineering, 2018
Bingqian Du, Zhen Chen, Qiang Yu, Wei Zhu, Wen Yan, Zhongcheng Guo
The samples were anode materials named #1–5 that were plated at temperatures of 30°C, 40°C, 50°C, 60°C, and 70°C, respectively. Lead dioxide was plated on a titanium (UNS GR1) substrate. The bath contained the following components: Pb(NO3)2 (210 g L−1), Cu(NO3)2 (20 g L−1), NaF (0.5 g L−1), and additive (fatty alcohol polyoxyethylene ether, 0.5 g L−1). The chemicals were of analytical grade, and the solutions were prepared using deionised water. The samples were plated for 60 min at a current density of 20 mA cm−2 and a plating temperature of 30–70°C.