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A series of ZrO2-SiO2 composite aerogels have been synthesized by adjusting the volume of tetraethoxysilane (TEOS) during supercritical fluid drying process. ZrO2 aerogels have been prepared via the sol-gel reaction using ZrOCl2ꞏ8H2O and the gel initiator malic acid as raw materials. Then the ZrO2-SiO2 composite aerogels have been obtained by supercritical fluid deposition (SCFD). The samples have been characterized applying XRD, FTIR, SEM, TEM, TGA and Nitrogen adsorption-desorption. The introduction of SiO2 can effectively restrain the growth of the nanoparticles and the transformation of crystalline phase, and reduce the linear shrinkage of the aerogels. It indicates the improvement of the thermostability of the ZrO2-SiO2 composite aerogels. [ABSTRACT FROM AUTHOR]

A small-volume hot-wall batch reactor with excess precursor loading was proposed for supercritical fluid deposition of Cu during the fabrication of sub-millimeter-scale, metal-coated terahertz (THz) wave devices. Conformal film formation was experimentally demonstrated, validating our method. Our method enables a much higher precursor concentration (at least 20 mol mâˆ'3) than the conventional method (below 2 mol mâˆ'3), facilitating conformal film formation on sub-millimeter structures. Kinetic analysis revealed that our proposed method was applicable for fabricating rectangular metal-coated THz waveguides; furthermore, it was promising for monolithically integrated THz wave devices. [ABSTRACT FROM AUTHOR]

Highly dispersed palladium nanoparticles (NPs) supported on UiO-66 as catalyst for CO2 methanation were prepared by supercritical fluid deposition (SFD). As a result, the most suitable Pd precursor salt and co-solvent are Na2PdCl4 and ethanol/DMF, respectively. The best SFD process condition to deposit the Pd precursor on UiO-66 is 40 °C, 10 MPa and 2 h. Under the above condition, 4% Pd/UiO-66 exhibits the highest activity with 53% of CO2 conversion and 95% of CH4 selectivity while the turnover frequency (TOF) value is 3669.4 h−1. The catalysts were characterized by XRD, BET, TEM, XPS, TGA, CO-DRIFTS and ICP-OES to investigate the structure–activity relationship. The 4% Pd/UiO-66 with the average size of 2.2 nm of Pd prepared in assistance of supercritical fluid behaved the similar activity as the 6%Pd/UiO-66 with average size of 9.7 nm of Pd prepared by sol–gel method. It is showed prospect of technique for reducing noble metal loading resulting from high dispersion effect. [ABSTRACT FROM AUTHOR]

We studied the temperature dependence of the emission and absorption of PbS quantum dots deposited on glass by a supercritical CO2 fluid process. The results show that the emission is ruled by different transitions than the absorption, particularly at cryogenic temperatures. We found indications that these observations can be linked to the PbS concentration used to form the films in conjunction with the capability of the supercritical CO2 method to form dense homogeneous films. [ABSTRACT FROM AUTHOR]

Deposition of ibuprofen (IBU) into ordered mesoporous silica SBA-15 was carried out to prepare controlled release nanodrug using supercritical carbon dioxide (scCO2) as solvent at 17 MPa and 310.15 K. The maximum drug loading of IBU/SBA-15 was as high as 41.96%. The characterization of the obtained materials was performed using x-ray diffractometry (XRD), scanning electron microscopy (SEM), and nitrogen (N2) adsorption-desorption isotherms; the results indicate that most adsorbed drugs were inside the nanoscale channels. The in vitro study shows that the time of complete (100%) release significantly decreases as drug-loading decreases. The interesting aspect is that the samples with similar drug loading display different release rates, which may be due to differences in the drug quantity adsorbed inside the pores. In addition, the modified Noyes-Whitney equation was used to model the release kinetics for all the samples and a good agreement was obtained between the model representation and experimental data. In addition, the solubility of IBU in scCO2was tested through a high-pressure view cell at the temperature range of 298.15–320.15 K and pressure range of 7–17 MPa. The experimental solubility data were well correlated using Chrastil’s equation as well as Mendez-Santiago and Teja’s equation. [ABSTRACT FROM PUBLISHER]

Copper nanoparticles and nanorods were prepared in the one-dimensional channels of SBA-15 supported by a modified supercritical fluid deposition (SCFD) method. In this approach, cheap and widely available copper nitrate, which is insoluble in supercritical CO2 (scCO2), was used as the copper source and ethanol as the co-solvent, thus avoiding the employment of expensive and less available scCO2-soluble precursors. The deposition was carried out at the pressure of 21-25 MPa and temperature of 50°C, followed by calcinations at 500°C and H2 reduction at 500°C. The results showed that highly dispersed Cu nanoparticles or nanorods were obtained controllably just by varying the deposition time, as characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). On the other hand, when Cu(acac)2 was used as the precursor and without any co-solvent, only nanoparticles were formed in the channels of SBA-15 no matter how long the deposition time. [ABSTRACT FROM AUTHOR]