Formation and Stability of Nontoxic Perovskite Precursor

A novel highly dispersed calcium silicate hydrate nanosheets for efficient high-concentration Cu2+ adsorption

Currently, the low cost and effective purification toward heavy metal ions in wastewater has garnered global attention. Herein, we used hydrothermal method to prepare highly dispersed calcium silicate hydrate in fluorite tailings. And the stacking thickness of calcium silicate hydrate layered morphology was less than 5 nm. For high concentration Cu2+ purification investigation in wastewater, we found that the equilibrium adsorption capacity reached 797.92 mg/g via the CSH with 3:2 Ca/Si molar ratio, be 1.43-21.8 times than that of reported data. Therein, the metal-metal exchange and deposition are the primary pathways for Cu2+ adsorption, and electrostatic attraction is the secondary pathway. And the relative ∼100 % removal rate of high-concentration Ni2+ and Cr3+ ions were confirmed via CSH prepared from different tailings. This method offers a cost-effective way to utilize tailings for preparing highly efficient adsorbents toward HMIs removal in wastewater.

Increasing the Strain Resistance of Si/SiO2 Interfaces for Flexible Electronics

Understanding the changes that occur in the micro-mechanical properties of semiconductor materials is of utmost importance for the design of new flexible electronic devices, especially to control the properties of newly designed materials. In this work, we present the design, fabrication, and application of a novel tensile-testing device coupled to FTIR measurements that enables in situ atomic investigations of samples under uniaxial tensile load. The device allows for mechanical studies of rectangular samples with dimensions of 30 mm × 10 mm × 0.5 mm. By recording the alternation in dipole moments, the investigation of fracture mechanisms becomes feasible. Our results show that thermally treated SiO₂ on silicon wafers has a higher strain resistance and breaking force than the SiO₂ native oxide. The FTIR spectra of the samples during the unloading step indicate that for the native oxide sample, the fracture happened following the propagation of cracks from the surface into the silicon wafer. On the contrary, for the thermally treated samples, the crack growth starts from the deepest region of the oxide and propagates along the interface due to the change in the interface properties and redistribution of the applied stress. Finally, density functional theory calculations of model surfaces were conducted in order to unravel the differences in optic and electronic properties of the interfaces with and without applied stress.

Exchange Reactions at Mineral Interfaces

Exchange reactions are a family of chemical reactions that appear when mineral surfaces come into contact with protic solvents. Exchange reactions can also be understood as a unique interaction at mineral interfaces. Particularly significant interactions occurring at mineral surfaces are those with water and CO₂. The rather complex process occurring when minerals such as calcium silicate hydrate (C-S-H) phases come into contact with aqueous environments is referred to as a metal-proton exchange reaction (MPER). This process leads to the leaching of calcium ions from the near-surface region, the first step in the corrosion of cement-bound materials. Among the various corrosion reactions of C-S-H phases, the MPER appears to be the most important one. A promising approach to bridging certain problems caused by MPER and carbonation is the passivation of C-S-H surfaces. Today, such passivation is reached, for instance, by the functionalization of C-S-H surfaces with water-repelling organic films. Unfortunately, these organic films are weak against temperature and especially weak against abrasion. Exchange reactions at mineral interfaces allow the preparation of intrinsic, hydrophobic surfaces of C-S-H phases just at room temperature via a metal-metal exchange reaction.