Low-Temperature Fabrication of Mesoporous Solid Strong Bases by Using Multifunction of a Carbon Interlayer

Mesoporous solid strong bases are highly promising for applications as environmentally benign catalysts in various reactions. Their preparation attracts increasing attention for the demand of sustainable chemistry. In the present study, a new strategy was designed to fabricate strong basicity on mesoporous silica by using multifunction of a carbon interlayer. A typical mesoporous silica, SBA-15, was precoated with a layer of carbon prior to the introduction of base precursor LiNO₃. The carbon interlayer performs two functions by promoting the conversion of LiNO₃ at low temperatures and by improving the alkali-resistant ability of siliceous host. Only a tiny amount of LiNO₃ was decomposed on pristine SBA-15 at 400 °C; for the samples containing >8 wt % of carbon, however, LiNO₃ can be entirely converted to strongly basic sites Li₂O under the same conditions. The guest–host redox reaction was proven to be the answer for the conversion of LiNO₃, which breaks the tradition of thermally induced decomposition. More importantly, the residual carbon layer can prevent the siliceous frameworks from corroding by the newly formed strongly basic species, which is different from the complete destruction of mesostructure in the absence of carbon. Therefore, materials possessing both ordered mesostructure and strong basicity were successfully fabricated, which is extremely desirable for catalysis and impossible to realize by conventional methods. We also demonstrated that the resultant mesoporous basic materials are active in heterogeneous synthesis of dimethyl carbonate (DMC) and the yield of DMC can reach 32.4%, which is apparently higher than that over the catalysts without a carbon interlayer (<12.9%) despite the same lithium content. The strong basicity, in combination with the uniform mesopores, is believed to be responsible for such a high activity

Theoretical Study of Efficient Photon–Phonon Resonance Absorption in the Tungsten-Related Vibrational Mode of Scheelite

Tungsten (W) is an extremely rare and vital metal extensively used in metallurgy, the chemical industry, optoelectronic devices, and machinery manufacturing. In this work, an environmentally friendly and efficient physical method based on photon–phonon resonance absorption (PPRA) is proposed for separating W from scheelite. We calculated the vibrational spectrum of calcium tungstate (CaWO4) and assigned the infrared (IR) absorption and Raman scattering peaks through a dynamic analysis of the normal modes. We focused on the strong IR absorption peaks related to W and identified three high-intensity IR-active modes at around 830 cm–1, corresponding to the stretching of the W–O bonds. Therefore, we propose the use of high-power terahertz (∼25 THz) laser radiation to facilitate W extraction from compounds, leveraging the high efficiency of PPRA. Experimental testing is required to determine the precise absorption frequency under industrial production conditions

Multiscale Synergetic Bandgap/Structure Engineering in Semiconductor Nanofibrous Aerogels for Enhanced Solar Evaporation

Solar-driven interface evaporation has been identified as a sustainable seawater desalination and water purification technology. Nonetheless, the evaporation performance is still restricted by salt deposition and heat loss owing to weak solar spectrum absorption, tortuous channels, and limited plane area of conventional photothermal material. Herein, the semiconductor nanofibrous aerogels with a narrow bandgap, vertically aligned channels, and a conical architecture are constructed by the multiscale synergetic engineering strategy, encompassing bandgap engineering at the atomic scale and structure engineering at the nano–micro scale. As a proof-of-concept demonstration, a Co-doped MoS2 nanofibrous aerogel is synthesized, which exhibits the entire solar absorption, superhydrophilic, and excellent thermal insulation, achieving a net evaporation rate of 1.62 kg m–2 h–1 under 1 sun irradiation, as well as a synergistically efficient dye ion adsorption function. This work opens up new possibilities for the development of solar evaporators for practical applications in clean water production

Theoretical Study of Efficient Photon–Phonon Resonance Absorption in the Tungsten-Related Vibrational Mode of Scheelite

Tungsten (W) is an extremely rare and vital metal extensively used in metallurgy, the chemical industry, optoelectronic devices, and machinery manufacturing. In this work, an environmentally friendly and efficient physical method based on photon–phonon resonance absorption (PPRA) is proposed for separating W from scheelite. We calculated the vibrational spectrum of calcium tungstate (CaWO4) and assigned the infrared (IR) absorption and Raman scattering peaks through a dynamic analysis of the normal modes. We focused on the strong IR absorption peaks related to W and identified three high-intensity IR-active modes at around 830 cm–1, corresponding to the stretching of the W–O bonds. Therefore, we propose the use of high-power terahertz (∼25 THz) laser radiation to facilitate W extraction from compounds, leveraging the high efficiency of PPRA. Experimental testing is required to determine the precise absorption frequency under industrial production conditions

Scalable Fabrication of Electrospun True-Nanoscale Fiber Membranes for Effective Selective Separation

Electrospun fibers have received wide attention in various fields ranging from the environment and healthcare to energy. However, nearly all electrospun fibers suffer from a pseudonanoscale diameter, resulting in fabricated membranes with a large pore size and limited separation performance. Herein, we report a novel strategy based on manipulating the equilibrium of stretch deformation and phase separation of electrospun jets to develop true-nanoscale fibers for effective selective separation. The obtained fibers present true-nanoscale diameters (∼67 nm), 1 order of magnitude less than those of common electrospun fibers, which endows the resultant membranes with remarkable nanostructural characteristics and separation performances in areas of protective textiles (waterproofness of 113 kPa and breathability of 4.1 kg m–2 d–1), air filtration (efficiency of 99.3% and pressure drop of 127.4 Pa), and water purification (flux of 81.5 kg m–2 h–1 and salt rejection of 99.94%). This work may shed light on developing high-performance separation materials for various applications

Theoretical Study of Efficient Photon–Phonon Resonance Absorption in the Tungsten-Related Vibrational Mode of Scheelite

Tungsten (W) is an extremely rare and vital metal extensively used in metallurgy, the chemical industry, optoelectronic devices, and machinery manufacturing. In this work, an environmentally friendly and efficient physical method based on photon–phonon resonance absorption (PPRA) is proposed for separating W from scheelite. We calculated the vibrational spectrum of calcium tungstate (CaWO4) and assigned the infrared (IR) absorption and Raman scattering peaks through a dynamic analysis of the normal modes. We focused on the strong IR absorption peaks related to W and identified three high-intensity IR-active modes at around 830 cm–1, corresponding to the stretching of the W–O bonds. Therefore, we propose the use of high-power terahertz (∼25 THz) laser radiation to facilitate W extraction from compounds, leveraging the high efficiency of PPRA. Experimental testing is required to determine the precise absorption frequency under industrial production conditions

Computational Assignment of Tantalum-related Strong Absorption Peaks in the Infrared Spectrum of Potassium Heptafluorotantalate

Tantalum (Ta) is a valuable and rare metal that is extensively used in the production of implant materials and high-performance capacitors. However, a convenient and effective method for the separation of Ta from other compounds has yet to be developed. On the basis of first-principle density functional theory (DFT), we simulated the vibrational spectrum of potassium heptafluorotantalate (K2TaF7). By performing a dynamics analysis of vibrational modes, we assigned peaks in infrared (IR) absorption and Raman scattering spectra to their corresponding vibrations. We focused on the strong IR absorption peaks of Ta-related vibrational modes in K2TaF7 and concluded that three observed IR absorption peaks, at 285, 315, and 530 cm–1, are good candidates. Provided with high power radiation at these three frequencies (at about 8.55, 9.45, and 15.9 THz), the good efficiency of photon–phonon resonance absorption will facilitate Ta separation from a compound

Analysis of molecular variance (AMOVA) of the six <i>Spartina alterniflora</i> populations in Guangxi, China.

Analysis of molecular variance (AMOVA) of the six Spartina alterniflora populations in Guangxi, China.</p

The number of migrants among populations of <i>Spartina alterniflora</i> in Guangxi based on the inference of recent migration rates from Structure assignments.

The number of migrants among populations of Spartina alterniflora in Guangxi based on the inference of recent migration rates from Structure assignments.</p

DataSheet1_Pipeline Stress Test Simulation Under Freeze-Thaw Cycling via the XGBoost-Based Prediction Model.docx

This study conducted ten freeze-thaw cyclic tests to clarify the effect of freeze-thaw cycles on the forces acting on the buried oil pipeline. The stress evolution in the Q345 steel pipeline versus the number of freeze-thaw cycles was obtained. The test results were consistent with the COMSOL simulation of the effect of different moisture contents on the pipeline bottom stress. Besides the proposed XGBoost model, eleven machine-learning stress prediction models were also applied to 10–20 freeze-thaw cycling tests. The results showed that during the freeze-thaw process, the compressive stress at the pipeline bottom did not exceed −69.785 MPa. After eight freeze-thaw cycles, the extreme value of the principal stress of -252.437MPa, i.e., 73.17% of the yield stress, was reached. When the initial moisture content exceeded 20%, the eighth freeze-thaw cycle’s pipeline stress decreased remarkably. The XGBoost model effectively predicted the pipeline’s principal stress in each cycle of 10 freeze-thaw cyclic tests, with R2 = 0.978, MSE = 0.021, and MAE = 0.102. The above compressive stress fluctuated from −131.226 to −224.105 MPa. The predicted values well matched the experimental ones, being in concert with the “ratcheting effect” predicted by the freeze-thaw cycle theory. The results obtained provide references for the design, operation, and maintenance of buried oil pipelines.</p