Research on Preparation and Performance of Clay-Based Shield Tunnel Nonsintered Bricks

With the rapid development of rail transit in China, the number and scale of underground engineering construction have increased significantly, and a large amount of shield muck has been generated, which has brought great challenges to the urban environment. The reuse of shield muck has become an important research direction in underground engineering construction. In this paper, a nonsintered brick is prepared with shield muck soil as the matrix. The influence of different doping amounts of lime, fly ash, cement, and polyvinyl alcohol on porosity, density, water absorption, saturation coefficient, compressive strength, and other properties was explored to realize the resource utilization of shield dregs and at the same time obtain excellent performance nonsintered bricks. Through research, it is found that when the lime doping amount is 10% and the cement doping amount is 5%, with the increase of the fly ash doping amount, the overall compressive strength increases significantly, and the maximum compressive strength can reach 13.69 MPa. Although the doping of trace amounts of polyvinyl alcohol reduces the compressive strength, it can significantly reduce the compressive strength and mass loss rate after 15 freeze-thaw cycles.

Superconductivity in CuIr2-x Al x Te4 telluride chalcogenides

The relationship between charge-density-wave (CDW) and superconductivity (SC), two vital physical phases in condensed matter physics, has always been the focus of scientists' research over the past decades. Motivated by this research hotspot, we systematically studied the physical properties of the layered telluride chalcogenide superconductors CuIr2-x Al x Te4 (0 ≤ x ≤ 0.2). Through the resistance and magnetization measurements, we found that the CDW order was destroyed by a small amount of Al doping. Meanwhile, the superconducting transition temperature (T c ) kept changing with the change of doping amount and rose towards the maximum value of 2.75 K when x = 0.075. The value of normalized specific heat jump (ΔC/γT c ) for the highest T c sample CuIr1.925Al0.075Te4 was 1.53, which was larger than the BCS value of 1.43 and showed that bulk superconducting nature. In order to clearly show the relationship between SC and CDW states, we propose a phase diagram of T c vs. doping content.

The Odor Release Regularity of Livestock and Poultry Manure and the Screening of Deodorizing Strains

Human living environments and health are seriously affected by the odor produced from fermentation of livestock and poultry manure. In order to reduce the odor pollution caused by livestock and poultry manure, efficient strains were screened and two methods were tried in this study. The orthogonal test design was used to analyze the gas produced by pig manure under different conditions of temperature, time, wheat straw doping amount and calcium carbonate doping amount. Then, according to ammonia, hydrogen sulfide and comprehensive odor removal effects, the high efficiency of deodorizing strains were screened. The results showed that pig manure produced the least odor when the temperature was 20 °C, added 0% calcium carbonate, 20% wheat straw and waited for 48 h. Three strains were screened to inhibit the odor production of pig manure: Paracoccus denitrificans, Bacillus licheniformis and Saccharomyces cerevisiae, showed that their highest removal rate of ammonia and hydrogen sulfide gas could reach 96.58% and 99.74% among them; while for three strains of end-control pig manure stench: Pichia kudriavzevii, P. denitrificans and Bacillus subtilis, the highest removal rate of ammonia and hydrogen sulfide gas reached 85.91% and 90.80% among them. This research provides bacteria resources as the high-efficiency deodorizing function for the source suppression and the end treatment of the odor gas of pig manure, which has high application value for the control of odor pollution.

Study on the Preparation of Magnetic Mn–Co–Fe Spinel and Its Mercury Removal Performance

In this study, the manganese-doped manganese–cobalt–iron spinel was prepared by the sol–gel self-combustion method, and its physical and chemical properties were analyzed by XRD (X-ray diffraction analysis), SEM (scanning electron microscope), and VSM (vibrating sample magnetometer). The mercury removal performance of simulated flue gas was tested on a fixed bed experimental device, and the effects of Mn doping amount, fuel addition amount, reaction temperature, and flue gas composition on its mercury removal capacity were studied. The results showed that the best synthesized product was when the doping amount of Mn was the molar ratio of 0.5, and the average mercury removal efficiency was 87.5% within 120 min. Among the fuel rich, stoichiometric ratio, and fuel lean systems, the stoichiometric ratio system is most conductive to product synthesis, and the mercury removal performance of the obtained product was the best. Moreover, the removal ability of Hg0 was enhanced with the increase in temperature in the test temperature range, and both physical and chemical adsorption play key roles in the spinel adsorption of Hg0 in the medium temperature range. The addition of O2 can promote the removal of Hg0 by adsorbent, but the continuous increase after the volume fraction reached 10% had little effect on the removal efficiency of Hg0. While SO2 inhibited the removal of mercury by adsorbent, the higher the volume fraction, the more obvious the inhibition. In addition, in an oxygen-free environment, the addition of a small amount of HCl can promote the removal of mercury by adsorbent, but the addition of more HCl does not have a better promotion effect. Compared with other reported adsorbents, the adsorbent has better mercury removal performance and magnetic properties, and has a strong recycling performance. The removal efficiency of mercury can always be maintained above 85% in five cycles.

Fe-Doped Graphitic Carbon Nitride for Methylene Blue Degradation with Visible-Light

In the present work, degradation of methylene blue (MB) dye in aqueous solution through H2O 2and iron doped g-C3N4 (Fe-g-C3N4) was studied. The hybrid was fabricated by thermal polymerization with iron (III) nitrate nonahydrate and melamine, and it was characterized by X-ray diffraction, Fourier transform infrared, UV-Vis diffuse reflectance spectrum, X-ray photoelectron spectroscopy, transmission electron microscope and Brunner-Emmet-Teller. The various experimental conditions such as doping amount, a dose of the sample, solution pH, the addition of H2O2, and concentration of MB on the degradation of MB dye were optimized. The maximum extent of degradation of methylene blue was obtained at pH 5, doping amount of 2.7 wt% and dose of 0.07 g. The molar ratio of Fe:H2O2 is 1:1000 showed 99% of MB (30 mg/L) decolorization over 60 min. The hybrid showed good stability and recyclability after three cycles of use. Photo-Fenton reaction exhibited a higher synergetic effect than the combination of Fenton and photocatalytic process.

Effect of ZrO2 Doping on the Microstructure and Dielectric Properties of Ca0.97Y0.03Cu3Ti4-xZrxO12 Ceramics

Dielectric properties of CaCu3Ti4O12 (CCTO) ceramics were studied by doping amount of Zr4+ donor on the basis of doping Y3+ donor. Ca0.97Y0.03Cu3Ti4-xZrxO12 (x=0, 0.005, 0.010, 0.015, CYCTZO) ceramics were prepared by reaction sintering method, and the phase structure, microstructure and dielectric properties of the ceramics were studied. The single phase CCTO was detected in all ceramic samples. SEM images of samples showed a high density and uniform-sized microstructure, and the average grain sizes of the ceramics was reduced with increasing content of Zr4+ donor. Interestingly, the dielectric constant (εr) was increased significantly while the dielectric loss tangent (tanδ) was decreased with the suitable doping amount of Zr4+. CYCTZO ceramics with x=0.010 exhibited a relatively high εr value of 1.02×105 at 1kHz. Meanwhile, the improved grain boundaries response and dielectric properties were closely related to the strengthened grain boundaries resistance (Rgb). The present results indicate that the εr was improved and the tanδ was reduced by doping Zr4+ donors in Ca0.97Y0.03Cu3Ti4O12 (CYCTO) ceramics and explained that the electrical properties were closely related to the electrical heterogeneity of ceramic grains and grain boundaries.

An Ultrasound Application for TiO2 Photocatalytic Degradation of Methyl Orange

Nanometer TiO2 photocatalysts were prepared by the sol–gel method. The catalysts were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and other techniques. Methyl orange solution was used for the degradation of the organic material and ultrasonic technology was used to determine the photocatalytic performance of the catalysts. The results show that the photocatalytic performance of the Ni-N-TiO2 is clearly improved under ultrasonic conditions. The TiO2 photocatalytic degradation effect is optimal at a catalyst concentration of 0.3 g/L, an initial concentration of the organic matter of 0.03 mmol/L, a nickel-doping amount of 2 mol %, and a nitrogen-doping amount of 15 mol %. The use of ultrasound technology in combination with photocatalysis has a positive effect and results in a TiO2 degradation rate of methyl orange of 95 % after 3 h.

Enhanced Electrochemical Performance of LiNi0.5Mn1.5O4 Composite Cathodes for Lithium-Ion Batteries by Selective Doping of K+/Cl− and K+/F−

K+/Cl− and K+/F− co-doped LiNi0.5Mn1.5O4 (LNMO) materials were successfully synthesized via a solid-state method. Structural characterization revealed that both K+/Cl− and K+/F− co-doping reduced the LixNi1−xO impurities and enlarged the lattice parameters compared to those of pure LNMO. Besides this, the K+/F− co-doping decreased the Mn3+ ion content, which could inhibit the Jahn–Teller distortion and was beneficial to the cycling performance. Furthermore, both the K+/Cl− and the K+/F− co-doping reduced the particle size and made the particles more uniform. The K+/Cl− co-doped particles possessed a similar octahedral structure to that of pure LNMO. In contrast, as the K+/F− co-doping amount increased, the crystal structure became a truncated octahedral shape. The Li+ diffusion coefficient calculated from the CV tests showed that both K+/Cl− and K+/F− co-doping facilitated Li+ diffusion in the LNMO. The impedance tests showed that the charge transfer resistances were reduced by the co-doping. These results indicated that both the K+/Cl− and the K+/F− co-doping stabilized the crystal structures, facilitated Li+ diffusion, modified the particle morphologies, and increased the electrochemical kinetics. Benefiting from the unique advantages of the co-doping, the K+/Cl− and K+/F− co-doped samples exhibited improved rate and cycling performances. The K+/Cl− co-doped Li0.97K0.03Ni0.5Mn1.5O3.97Cl0.03 (LNMO-KCl0.03) exhibited the best rate capability with discharge capacities of 116.1, 109.3, and 93.9 mAh g−1 at high C-rates of 5C, 7C, and 10C, respectively. Moreover, the K+/F− co-doped Li0.98K0.02Ni0.5Mn1.5O3.98F0.02 (LNMO-KF0.02) delivered excellent cycling stability, maintaining 85.8% of its initial discharge capacity after circulation for 500 cycles at 5C. Therefore, the K+/Cl− or K+/F− co-doping strategy proposed herein will play a significant role in the further construction of other high-voltage cathodes for high-energy LIBs.