Because of the contradiction between the safe thickening time of cement slurry and over-retarding at the top in the cementing of a long sealing section with large temperature difference, we synthesized a quaternary copolymerization retarder with 2-acrylamide-2-methyl propane sulfonic acid (AMPS), acrylic acid (AA), diallyl dimethyl ammonium chloride (DMDAAC) and allyl polyoxyethylene ether (APEG). The structure of the retarder was characterized by FTIR and 1H NMR and its thermal stability was tested by TG-DSC. The results showed that the molecule contained the designed functional groups, the initial pyrolysis temperature was 364 °C, and its performance was stable in the temperature range of 90–150 °C. There was no “bulge” or “step” on the thickening curve, and the thickening time could meet the safety requirements of pumping at high temperatures. It can also ensure the development of compressive strength of cement in the low-temperature section and has excellent temperature adaptability. Through the study of its retardation mechanism, it was found that the retarder molecules formed an adsorption layer of a certain thickness on the surface of cement particles by adsorption, and the concentration of Ca2+ in the solution was reduced by complexation, so as to prevent cement hydration and prolong the thickening time. Generally speaking, the large temperature difference adaptability of retarders was mainly manifested in the decrease of molecular adsorption capacity and performance at low-temperature and the improvement of molecular adsorption capacity and performance at high-temperature.
Ling Liu,Jia Fu,Xueyan Hu,Dengsen Yuan,Jin Wang,Qingwen Li
A large number of areas on earth is suffered from large-temperature fluctuation (LTF) during the days or over the seasons. However, current strategies for adaptive thermal management in the LTF environment are limited. In this study, we developed a simple and cost-effective strategy to synthesize ultrafine and nearly monodispersed silica aerogel microspheres (SAM) with an average diameter of 1.9 μm. The aerogels possess low thermal conductivity of 0.039 W·m −1 ·K −1 and can preserve heat by reducing heat dissipation in cold environments. Meanwhile, IR emissivities range from 0.13 to 0.98 and a relatively high solar reflectance of 0.65, leading to an impressive sub-ambient cooling of 9.1 °C in a hot daytime. Additionally, a theoretical carbon emission analysis of the aerogels' daytime cooling and night warming suggests a carbon emission reduction of 13.6 tCO 2 eq. This study develops a strategy to synthesize ultrafine SAM and provides a strategy for passive cooling and passive warming by SAM with the combination of passive cooling and thermal insulation, which could help to achieve global carbon neutrality and sustainability, and solve the problems of thermal management with large temperature-fluctuation.
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