Thermoresponsive materials, in particular those exhibiting switchable optical transmittance via temperature change, have been widely used in different applications. If the required temperature change is within seasonal temperature changes, the transmittance change would consume low energy or be autonomous. Here, a solid-state thermoresponsive phase-changing copolymer (TPCC) film has been demonstrated, with a large transmittance modulation between room and hot temperatures (>28 °C). The polymer film comprises a hydrophilic poly(hydroxyethyl acrylate) (HEA) cross-linked with a hydrophobic phase-changing poly(hexadecyl acrylate-co-tetradecyl acrylate) (HDA-TA). The TPCC was designed such that the HEA and HDA-TA moieties produce micrometer-scale phase separation, the HDA-TA moiety undergoes reversible crystalline-to-amorphous transition at 28–32 °C, and the refractive indices of the hydrophilic and hydrophobic phases are matched at ambient temperature but are mismatched when the temperature is above the transition. The TPCC film showed high modulations of transmittance in the visible (390–780 nm), solar (300–2500 nm), and infrared (780–2500 nm) spectrum of 68.8, 62.7, and 55.8%, respectively. The opacity switching was reversible without any decay after 1000 heating–cooling cycles. The TPCC film was investigated for autonomous and climate-adaptable solar modulation window application.
The mechanism of TiO 2 nanotubes has attracted increasing attention. However, relationships between the anodizing parameters and nanotube size (or oxide volume) have been rarely studied. The traditional field-assisted dissolution theory can only qualitatively explain the cause of the pore formation but cannot quantitatively explain the relationship between the growth height of nanotubes and the anodizing current. Here, the growing processes of TiO 2 nanotubes in four current at three different NH 4 F concentrations were carefully studied. Experimental results contradicting the traditional dissolution theory were found. Considering that the height of the nanotubes does not fully reflect oxide growth, the volume of growing oxide was studied for the first time. The results show that the oxide volume decreases while the pore volume increases with the increase of the concentration of NH 4 F in the process of constant current anodization. However, the sum of the two volumes was approximately a fixed value under the same current. The sum of the oxide volume and the pore volume increases with the increase of the anodizing current, regardless of the concentration of ammonium fluoride. It means that the growth height of nanotubes has nothing to do with the concentration of NH 4 F, which is against the field-assisted dissolution theory.
Nanoporous tin oxide layers were fabricated in NaOH during potentiostatic anodization at a low potential. With increasing potential, the nanochannel became fragmentized and a stacked morphology was formed. The total anodizing current was separated into ionic current and electronic current to explain the various morphologies of nanotubes. The ionic current determines ion migration and oxide growth. The electronic current determines oxygen evolution, porous structure formation, and oxide volume expansion. The continuous decline of the total current–time curve at 8 V was explained by a capacitor model. Through cyclic voltammetry, it was proposed that the stacked morphology exhibits a high specific capacitance (11.36 mF cm–2). Extending the annealing time can increase the crystallinity, thus improving the capacitive performance. The stacked morphology allows electrolytes to permeate the entire portion of the nanochannel more evenly, increasing the effective surface area of the electrode in the electrochemical process and thus improving the capacitive properties. The formation of a stacked morphology is related to the intense release of oxygen gas.
Various collectors were compared in the selective flotation of copper−zinc ore by using isopropyl ethylthionocarbamate (Z-200), buthl xanthate, ammonium dibutyl dithiophosphate, and mercapto benzothiazole (MBT). The latter showed effective selectivity in the flotation of chalcopyrite and marmatite and was selected for a detailed study by using cyclic voltammetry and Tafel. The results of microflotation pointed out that the flotation of marmatite was significantly affected by CuSO 4 activation. At weakly alkaline pH, marmatite activated by Cu 2+ is dependent on Cu 2+ concentration shown in electrochemical tests, and the activation products were Cu 2 S and CuS. The increasing addition of Cu 2+ may remove the hydroxides and S 0 , resulting in considerable activation. The corrosion of marmatite is accelerated with the addition of CuSO 4 . Mechanisms are suggested for the selectivity of chalcopyrite/marmatite by MBT: the hydrophilic hydroxides (Zn(OH) 2 and Fe(OH) 3 ) are formed on the marmatite surface, which renders the marmatite surface hydrophilic and hampers the reaction between MBT and marmatite-activated products, while the hydrophobic compounds (MBT) 2 and Cu(MBT) 2 formed on the chalcopyrite surface improve the flotability of chalcopyrite.
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