Electron localization in CdS nanocrystals studied by time-resolved terahertz spectroscopy
Measurement and Monte-Carlo simulations of THz photoconductivity spectra of CdS nanocrystalline films revealed a strong coupling between adjacent nanocrystals. Investigation of ultrafast dynamics provides information about initial sub-picosecond carrier cooling and subsequent carrier recombination.
Ammonia-free method for preparation of CdS nanocrystalline films by chemical bath deposition technique
The preparation of thin films of CdS by chemical bath deposition is mostly based on the utilisation of ammonia as a complexing agent for cadmium ions. Here we report on a new method based on potassium nitrilotriacetate that eliminates the problems of ammonia volatility and toxicity. We prepared high quality films of closely packed nanocrystals with a thickness of up to 300 nm. The radius of the nanocrystals can be tuned from 2.6 to more than 10 nm by post-preparation heat treatment of the as-prepared films.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.