Dielectric and Mechanical Properties of PDMS-La2Ba2XZn2Ti3O14 (X = Mg/Ca/Sr) Nanocomposites.

Flexible polydimethylsiloxane-La2Ba2XZn2Ti3O14 (X = Mg/Ca/Sr) [PDMS-LBT] nanocomposites with high permittivity (dielectric constant, k) are prepared through a room-temperature mixing process. The LBT nanoparticles used in this study are prepared through a high-temperature solid-state reaction. It is observed that LBT (X = Mg/Ca) nanoparticles are spherical in nature, with particle size ∼20 nm, as observed from the HRTEM images, whereas LBT (X = Sr) nanoparticles are cubical in nature with particle size ≥100 nm. These LBT (X = Mg/Ca/Sr) nanoparticles are crystalline in nature, as apparent from the XRD analysis and SAED patterns. The permittivity of LBT nanoparticles is higher when "Ca" is present in place of "X". These three oxides show a temperature-dependent dielectric behavior, where LBT nanoparticles with "Sr" show a sharp change in permittivity at a temperature of ∼105 °C. These kinds of oxide materials, especially LBT (X = Sr) nanoparticles/oxides, can be used in dielectric/resistive switching devices. The effect of LBT nanoparticle concentration on the dielectric and mechanical properties of PDMS-LBT nanocomposites is widely studied and found that there is a significant increase in dielectric constant with an increase in the concentration of LBT nanoparticles. There is a decrease in the volume resistivity with the increase in the LBT nanoparticle concentration. All the PDMS-LBT nanocomposites have low dielectric loss (ε″) compared to the dielectric constant value. It is found that both permittivity (ε') and AC conductivity (σac) of PDMS-LBT composites are increased with the temperature at a frequency of 1 Hz. The % elongation at break (% EB) and tensile strength (TS) decrease with the LBT nanoparticle concentration in the matrix PDMS, which is due to the non-reinforcing behavior of LBT nanoparticles. The distribution and dispersion of LBT nanoparticles in the matrix PDMS are observed through HRTEM and AFM/SPM.

Corrosion-Resistant Hydrophobic Thermal Barrier Composite Coating on Metal Strip: A New Dimension to Steel Strips for Roofing Segment.

This study demonstrates a cost-effective, thin, multifunctional composite coating system with outstanding thermal insulation for thermal management and heat shield applications, such as roofs, as well as outstanding resistance to corrosion. The hydrophobic multifunctional epoxy composite coating systems were designed with surface-modified fillers to impart both reduced heat conduction and high infrared reflectance in a thin coating with a 65-100 µm dry film thickness (DFT). With a judicial combination of hollow microspheres (HMS) activated and modified with silica (sHMS) and stearic acid-modified TiO2 (sMO), the developed composite coating attained the highest thermal insulation property with a temperature drop of 21-31 °C at different distances below the coated panel, which is superior to the values of temperature drop reported earlier. The high solar reflectance of the composite coating in the near-infrared (NIR) region exceeds 72% with a low thermal conductivity of 0.178 W m-1 K-1. After 720 h of exposure in a 3.5 wt % NaCl solution, the composite coating revealed a corrosion protection efficiency of 99%. The work demonstrates that high solar reflectivity and low thermal conductivity must be active simultaneously to achieve superior thermal shielding in a thin coating on a metal. A careful selection of fillers and appropriate surface modifications ensures hydrophobicity and proper distribution of the fillers in the coating for a high barrier effect to prevent environmental deterioration. With these superior performance parameters, the developed composite coatings make an essential contribution to energy sustainability and the protection against environmental degradation.

Functional Pyromellitic Diimide as a Corrosion Inhibitor for Galvanized Steel: An Atomic-Scale Engineering.

Corrosion of metal/steel is a major concern in terms of safety, durability, cost, and environment. We have studied a cost-effective, nontoxic, and environmentally friendly pyromellitic diimide (PMDI) compound as a corrosion inhibitor for galvanized steel through density functional theory. An atomic-scale engineering through the functionalization of PMDI is performed to showcase the enhancement in corrosion inhibition and strengthen the interaction between functionalized PMDI (F-PMDI) and zinc oxide (naturally existing on galvanized steel). PMDI is functionalized with methyl/diamine groups (inh1 (R = -CH3, R' = -CH3), inh2 (R = -CH3, R' = -CH2CH2NH2), and inh3 (R = -C6H3(NH2)2, R' = -CH2CH2NH2). The corrosion inhibition parameters (e.g., orbital energies, electronegativity, dipole moment, global hardness, and electron transfer) indicate the superior corrosion inhibition performance of inh3 (inh3 > inh2 > inh1). Inh3 (∼182.38 kJ/mol) strongly interacts with ZnO(101̅0) compared to inh2 (∼122.56 kJ/mol) and inh1 (∼119.66 kJ/mol). The superior performance of inh3 has been probed through charge density and density of states. Larger available states of N and H (of inh3) interact strongly with Zn and Osurf (of the surface), respectively, creating N-Zn and H-Osurf bonds. Interestingly, these bonds only appear in inh3. The charge accumulation on Osurf, and depletion on H(s), further strengthens the bonding between inh3 and ZnO(101̅0). The microscopic understanding obtained in this study will be useful to develop low-cost and efficient corrosion inhibitors for galvanized steel.