Synthesis and performance of itaconic acid/acrylamide/sodium styrene sulfonate as a self-adapting retarder for oil well cement

This journal is © The Royal Society of Chemistry. A novel self-adapting retarder itaconic acid/acrylamide/sodium styrene sulfonate (IA/AM/SSS, hereinafter referred to as PIAS) was synthesized by free-radical, aqueous-solution polymerization and characterized by FTIR and TG. The optimum reaction conditions of polymerization were obtained from orthogonal experiments (L3³) and subsequent data analysis. According to the evaluation as a retarder, the PIAS made it possible to obtain both a long thickening time and a swift compressive strength development for cement slurry, and therefore the applicable range of bottom hole circulation temperatures to the cement slurry has been widened to 60-180°C. Moreover, the working mechanism of the self-adapting retarder PIAS was found to rely on the change of spatial structure of the molecules to retard the hydration of the cement. This paper also expounds that the delayed coagulation of the cement slurry is attributed to adsorption, chelation and "poisoning" effects of the PIAS molecules on the surface of hydrated particles or ions through XRD and SEM analyses.

The facet selectivity of inorganic ions on silver nanocrystals in etching reactions

The facet selectivity of the halide ions and chlorauric acid for several shaped silver nanocrystals is presented in this paper. Two inorganic ions show different representations when they are used for etching silver nanocrystals in the self-sacrificial template reaction. The morphological changes of the silver nanocrystals indicate that the halide ions prefer to etch the (110) facets of silver nanocrystals, while in the chlorauric acid etching reaction, gold first modifies the (110) facets and then lets chlorauric acid etch the (111) facets instead. The selective facet etching on individual nanoparticles in the solution phase has crucial significance in the control-synthesis of nanocrystals and the facet asymmetric reaction.