High-temperature Reduction Method Research Articles

Reduction and reconstruction of vanadium-containing steel slag at high temperature

The effective recovery of metallic iron and vanadium from steel slag and ensuring the gelling properties of the residual slag after metal separation are crucial for their high-value-added utilisation. In this study, we established suitable process conditions for high-temperature reduction and reconstruction using the Si/Al ratio as an adjustment parameter and employing rice husk ash, SiO2, and Al2O3 as the adjustment materials. The influence of the reconstructed steel slag composition and structure on the iron reduction rate and vanadium migration was investigated. Additionally, we tested the compressive strength of the cement slurry at different times to compare the gelling performance of the tailings after iron reduction from the Vanadium-containing steel slag.The results showed that the high-temperature reduction method effectively reduced metallic iron and vanadium in the steel slag. The iron reduction rate reached as high as 98.53%, and inert components such as the CaO-FeO-MgO-MnO solid solution (RO) phase, C2F, and Fe3O4 in the original steel slag could be effectively reconstructed to form a glass-phase structure with certain gelling properties. Moreover, the content of the glass phase remained stable above 90%. For the same temperature, the liquid viscosity of the reconstructed steel slag increased, and after cooling, the glass-phase content decreased with decreasing Si/Al ratio. This resulted in an increase in the amount of crystalline-phase minerals such as Ca3Mg(SiO4)2, Ca2Al2SiO7, and C2S. The iron reduction rate generally exhibited a downward trend, and the change in the vanadium content was consistent with the iron reduction rate. Following the reduction and reconstruction of iron separation, the gelling properties of the vanadium-containing steel slag improved, with a 28-day strength that was 64.26% higher than that of the original steel slag.

Reduced graphene oxide aerogel for supercapacitor electrode

In this study, the rGO aerogel material was successfully fabricated by freeze-drying combined with high-temperature reduction method. The characteristics of rGO aerogel were investigated by modern techniques such as SEM-EDX, XRD, Raman, N2 adsorption and desorption. Electrochemical properties were studied through cyclic potential scanning (CV), charge-discharge (GCD) and electrochemical Imdependance Spectroscopy (EIS) methods in 6M KOH electrolyte solution. Research results show that rGO aerogel has a large specific surface area and pore volume of 162.4 m2/g and 0.237 cm3/g, respectively, and a large specific capacitance of 90 F/g at a current density of 0.1. A/g and long charge-discharge life with specific capacitance reaching 87.5% after 500 charge-discharge cycles.

Pyrolyzed Silk Carbon Fabric-Enabled Wearable Functional Actuators With Heating and Sound-Emitting Capabilities

Textile-based wearable electronics are widely favored by researchers due to their superior comfort. However, there are few studies on textile-based flexible actuators with multiple uses. In this article, a highly flexible actuator with heating and sound-emitting capabilities enabled by pyrolyzed silk carbon fabrics is developed. The functionalized fabrics with ideal physical properties are prepared by a high-temperature reduction method, which is simple and efficient. Its electrothermal and photothermal effects endow the device with heating function. The steady-state temperature can reach 188 °C and 280 °C under 0.80-W/cm2 electricity power density and 1.46-W/cm2 laser power density with high stability, respectively. By taking advantage of thermoacoustic effect, it can also produce intuitive sound messages. Test results show that acoustic properties are in good agreement with theoretical model. The output sound pressure level can be stabilized at about 55 dB in the range of 8–20 kHz under 101-mW power. The actuator carries great potentials in wearable thermal and acoustic applications.

Enhanced the combustion performance of DAP-4 with assembled Cu2O nanoclusters

In this work, the catalytic combustion performance of molecular perovskite energetic material DAP-4 with assembled Cu2O nanoclusters added was studied. Results showed that aggregated spherical Cu2O clusters with the size of ∼1 μm were assembled by nano particles with ∼50 nm diameter by the high-temperature reduction method. Assembled Cu2O nanoclusters have intrinsic catalysis combustion characteristics on DAP-4. With 5 wt% Cu2O added, the combustion time of DAP-4 had reduced by ∼70 ms from raw DAP-4 (∼90 ms) to DAP-4/Cu2O (20 ms). The combustion pressurization rate of DAP-4/Cu2O is ∼4 times of DAP-4. The catalysis combustion mechanism of DAP-4 with assembled Cu2O nanoclusters as an additive was proposed. The work offered a new idea to utilize novel catalysts for enhancing the combustion performance of DAP-4.

Tuning surface composition of multiwalled carbon nanotubes supported Pt-Co bimetallic nanoparticles for boosting methanol oxidation catalysis

Developing catalysts with high performance and low cost for methanol oxidation reaction (MOR) is the key to promoting the industrialization of direct methanol fuel cells (DMFCs). In this work, multiwalled carbon nanotubes (MWCNTs) supported PtCo alloys catalysts with improved MOR properties and anti-CO poisoning ability are successfully prepared by integrating low temperature adsorption and high temperature reduction method. The Pt1Co3@NC/MWCNTs sample with moderate Co2+ feeding content (0.81 mA/ugPt) achieves a factor of 1.93 enhancement in MOR mass activity compared to the commercial Pt/C catalyst (0.42 mA/ugPt). In addition, the Pt1Co3@NC/MWCNTs sample displays a lower CO oxidation onset potential respect to pristine Pt/C catalyst (0.74 V vs. 0.82 V). Scuh improvement of MOR activity, durability and anti-CO poisoning ability of the Pt1Co3@NC/MWCNTs catalyst is ascribed to the moderate surface compositions, optimal electronic interaction between PtCo alloys and MWCNTs, and the protection of N-doped carbon (NC) shells. This study provides a new direction to decrease the utilization of platinum and improve the MOR activity, stability and anti-CO poisoning ability of electrocatalysts which will be potential in design and fabrication of the highly efficient electrocatalysts for DMFCs applications.

In situ growth of Co nanoparticles in Ketjen Black for enhanced electrochemical performances of lithium-sulfur battery cathode

Lithium–sulfur (Li−S) batteries have the advantages of ultra-high theoretical energy density, low cost, and being environmentally friendly. However, the low S loading “shuttling” effect of intermediate lithium polysulfides in redox reactions and short cycle life limit their commercial applications. In this study, a facile, low-cost high-temperature reduction method was used to synthesize nano metallic Co particles in situ in Ketjen Black (KB) pores with excellent physical properties for nano Co/KB composites formation. In these composites, the particle size of Co is 5–30 nm, which is helpful to promote the transfer of electronic and ionic charges. Moreover, the catalytic effect of nano Co/KB composites and the strong chemical interactions of the Co–S bond were demonstrated, which significantly prohibits soluble polysulfides from migrating out of the KB skeleton because of the strong adsorption, enhancing the electrochemical performances of Li−S batteries. With a high S areal loading of 3 mg cm−2, the initial discharge specific capacity of the Co/KB/S cathode reached 1249.0 mAh g−1 at 0.05 C, while at 0.5 C the initial specific capacity of 785.5 mAh g−1 was achieved, and after 500 cycles the specific capacity maintained at 352.3 mAh g−1 with a fade rate of only 0.09% per cycle.

SnS2 Nanocrystalline-Anchored Three-Dimensional Graphene for Sodium Batteries with Improved Rate Performance.

Tin disulfide (SnS2) is regarded as one of the most suitable candidates as the electrode material for sodium-ion batteries (SIBs). However, the easy restacking and volume expansion properties of SnS2 during the charge/discharge process lead to the destruction of the electrode structure and a decrease in capacity. We successfully synthesized a SnS2 nanocrystalline-anchored three-dimensional porous graphene composite (SnS2/3DG) by combining hydrothermal and high-temperature reduction methods. The SnS2 nanocrystalline was uniformly dispersed within the connected reduced graphene oxide matrix. The SnS2/3DG battery showed a high reversible capacity of 430 mAh/g after 50 cycles at 100 mA/g. The SnS2/3DG composite showed an excellent rate capability with the current density increasing from 100 mA/g to 2 A/g. The excellent performance of the novel SnS2/3DG composite is attributed to the porous structure, which not only promoted the infiltration of electrolytes and hindered volume expansion for the porous structure, but also improved the conductivity of the whole electrode, demonstrating that the SnS2/3DG composite is a prospective anode for the next generation of sodium-ion batteries.

Preparation and properties of hierarchical Al–Mg layered double hydroxides as UV resistant hydrotalcite

Anti-ultraviolet Mg–Al hydrotalcite samples (MgAl–P-LDH) with 4-metoxybenzoic acid (PMOBA) ion intercalation were prepared by high temperature reduction method. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Visible absorption spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and thermogravimetry. SEM images indicate that the UV-resistant MgAl–P-LDH had a layered structure. The results of X-ray diffraction analysis showed that the purity of MgAl–P-LDH sample was higher. Compared to MgAl-LDH, the characteristic peak for MgAl–P-LDH shifted towards small angle of 2θ, and it was found that the PMOBA ions have been inserted into the interlayer of MgAl hydrotalcite. The infrared spectra also showed that PMOBA ions were successfully intercalated within Mg–Al hydrotalcite layer. The ultraviolet absorption of MgAl–P-LDH was better than that of PMOBA and MgAl-LDH with the wavelength range of 225–325 nm, and the maximum absorption over 80% was observed.

Preparation and properties of black Ti-doped zirconia ceramics

Black zirconia ceramics has many problems, such as uneven color and poor phase stability. The reason for this phenomenon is that the colorant uses a colorant with a complex black spinel structure, and also the application of a dyeing method. To improve the color uniformity and phase stability of black ceramics, TiO2 was introduced to replace the traditional complex black spinel, a high-temperature reduction method (HTR) was employed to prepare a black Ti-doped zirconia ceramic, stead of the conventional dyeing method. After the HTR at 1400 °C, the concentration of Ti3+ and oxygen vacancies increased, and the lightness of the ceramic samples decreased from 93.48 to 44.17. The black ceramic is uniform in color and stable in phase, avoiding the disordered phase of the spinel doped multiphase zirconia ceramic. The results indicate that the overall color of the samples depends on the development mechanism of the color center. The formation of color centers (F+ centers) in this work was related to the electronic transition of Ti 3d states and oxygen vacancies generated during the HTR. F+ centers cause a strong light absorbance over the entire visible light range (400–750 nm), so that the color of the ceramics is black. Based on their good color attributes, black ceramics have great potential in industry, for example as the back plate of mobile phones.

Synthesis of high-quality graphene with enhanced electrochemical properties by two-step reduction method

In this study, we reported a facile two-step reduction method to prepare a high-quality graphene with intact structure. Hydroxyl group is acquired by utilizing LiAlH4 to reduce the oxygen-containing functional groups in GO. Then it is further reduced by ethanethiol/aluminum trichloride (Et-SH/AlCl3) to obtain graphene. The results of Infrared and XPS showed that the prepared graphene material (rGO2) has been reduced completely and had structural integrity. Besides, the conductivity of rGO2 obtained can reach 2.632 * 103 S m−1, which is higher than that obtained by general chemical reduction method and high temperature reduction method. Investigated as a potential material for supercapacitors, the as-prepared graphene reveals excellent electrochemical properties, including good rate capability and cycling stability, which mainly benefits from its intact structural characteristics.

Development mechanism of Ce-doped red zirconia ceramics prepared by a high-temperature reduction method

Red zirconia ceramics is unstable at high temperature and the saturate degree of color is very poor. To broaden the application especially in colorful backsheet of mobile phone, a red zirconia ceramics based on Ce-doped yttria stabilized zirconia (YSZ) was sintered at 1450 °C. Then, the red zirconia ceramics were prepared by a high-temperature reduction method. As the reduction temperature and the doping of CeO2 increased, the value of a* (a<0 indicates green, and a>0 indicates red) first increased and then decreased. The redness of the ceramic sample reached the highest value of 32.5. The maximum fracture toughness reached was 9.6 MPa m1/2. According to first principle calculations, it is shown that the Ce 4f state appears near the Fermi level after Ce2O3 doping. During the electronic transition from 4f states of Ce atoms to 4d states of Zr and Y atoms, it combines with the oxygen vacancies generated during the reduction to form a color center. The appearance of the color centers causes a band gap of about 2.0 eV in the crystal. The corresponding absorption wavelength is 480–500 nm, and thus the observed color is red. This work provides a way to prepare stable high-temperature red zirconia ceramic with high saturate degree of color. The color centers development mechanism was considered to be the formation of red.

One-Step Laser Patterned Highly Uniform Reduced Graphene Oxide Thin Films for Circuit-Enabled Tattoo and Flexible Humidity Sensor Application.

The conversion of graphene oxide (GO) into reduced graphene oxide (rGO) is imperative for the electronic device applications of graphene-based materials. Efficient and cost-effective fabrication of highly uniform GO films and the successive reduction into rGO on a large area is still a cumbersome task through conventional protocols. Improved film casting of GO sheets on a polymeric substrate with quick and green reduction processes has a potential that may establish a path to the practical flexible electronics. Herein, we report a facile deposition process of GO on flexible polymer substrates to create highly uniform thin films over a large area by a flow-enabled self-assembly approach. The self-assembly of GO sheets was successfully performed by dragging the trapped solution of GO in confined geometry, which consisted of an upper stationary blade and a lower moving substrate on a motorized translational stage. The prepared GO thin films could be selectively reduced and facilitated from the simple laser direct writing process for programmable circuit printing with the desired configuration and less sample damage due to the non-contact mode operation without the use of photolithography, toxic chemistry, or high-temperature reduction methods. Furthermore, two different modes of the laser operating system for the reduction of GO films turned out to be valuable for the construction of novel graphene-based high-throughput electrical circuit boards compatible with integrating electronic module chips and flexible humidity sensors.

Evolution of deposited carbon during multi-stage fluidized-bed reduction of iron ore fines

The influence of reduction conditions on carbon deposition during fluidized-bed pre-reduction of iron ore fines was investigated experimentally. The results showed that reduction temperature and the composition of reducing gases had a significant effect on the rate of carbon deposition and the type of carbon deposits (graphite and Fe3C). Low reduction temperature, high CO content, and addition of H2 favored the deposition of carbon, especially graphite. The reduction conditions also significantly affected the surface morphology of the as-reduced iron ore fines. As the amount of deposited graphite increased, the formation of fibrous iron disappeared and graphite filaments were observed. The pre-reduced iron ore fines were further fluidized in pure CO at 850°C for final reduction. The results showed that graphite could suppress the formation of fibrous iron and decrease the surface viscosity, thereby inhibiting agglomeration during the final high-temperature reduction stage. Reactions that consume the deposited carbon during the final high-temperature reduction were identified and graphite was shown to be more reactive than Fe3C. To enhance the application of fluidization technology in producing sponge iron, a novel solid-state high-temperature reduction method via deposited carbon was proposed and demonstrated to be feasible.

TiO2 nanotubes wrapped with reduced graphene oxide as a high-performance anode material for lithium-ion batteries.

Through electrostatic interaction and high-temperature reduction methods, rGO was closely coated onto the surface of TiO2 nanotubes. Even at a high temperature of 700 °C, the nanotube morphology of TiO2 (anatase) was preserved because of the assistance of rGO, which provides a framework that prevents the tubes from breaking into particles and undergoing a phase transformation. The rGO/TiO2 nanotubes deliver a high capacity (263 mAh g−1 at the end of 100 cycles at 0.1 A g−1), excellent rate performance (151 mAh g−1 at 2 A g−1 and 102 mAh g−1 at 5 A g−1), and good cycle stability (206 mAh g−1 after 500 cycles at 0.5 A g−1). These characteristics arise from the GO/TiO2 nanotubes’ advanced structure. First, the closely coated rGO and Ti3+ in the tubes give rise to a high electro-conductivity of the nanotubes. Additionally, the Li+ ions can rapidly transfer into the electrode via the nanotubes’ empty inner diameter and short tube wall.

Synthesis of Hafnium Oxide-Gold Core–Shell Nanoparticles

Developing cheap composite nanoparticle systems that combines a high dielectric constant with good conductivity is important for the future of the electronic industry. In this study, two different sizes, 7.3 ± 2.2 and 5.6 ± 1.9 nm, of HfO(2)@Au core-shell nanoparticles are prepared by using a high-temperature reduction method. The core-shell nanoparticles are characterized by powder X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), and UV-visible absorption spectroscopy. HfO(2) exhibits no absorption in the visible region, but the HfO(2)@Au core-shell nanoparticles show a plasmon absorption band at 555 nm that is 25 nm red-shifted as compared to pure gold nanoparticles. According to transmission electron microscopy and energy dispersive X-ray analysis, the HfO(2) particles are coated with approximately three atomic layers of gold.

Phase-Controlled Synthesis of Iron Silicide (Fe3Si and FeSi2) Nanoparticles in Solution

In this study, a high-temperature reduction method is developed to prepare iron silicide nanoparticles in solution phase. The synthesis applies a reaction of silicon tetrachloride with iron pentacarbonyl in the presence of 1,2-hexadecanediol to form iron silicide nanoparticles. Under iron-rich synthetic conditions, superparamagnetic Fe3Si nanoparticles form. The saturation magnetization of Fe3Si nanoparticles has been found to be 60 emu/g by superconducting quantum interference device (SQUID) magnetometry technique. The value is close to that of iron oxide (Fe3O4) nanoparticles but less than that of iron nanoparticles. When silicon-rich conditions are used, mainly β-FeSi2 nanoparticles form. The nanoparticle size, size distribution, and crystallinity are characterized by transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffraction (XRD), and atomic force microscopy (AFM).

Systematics of the Electronic Transport Properties in the Metallic State of Pr2− xCexCuO4+ δ single crystals

Using an improved high temperature reduction method we found that in the n-type high- T c -system Pr 2− x Ce x CuO 4+ δ bulk superconductivity can be established between x ≤ 0.09 and x ≈ 0.17 i.e. over a much broader range than previously reported. The T 2-contribution to the resistivity increases with the Ce-concentration. In the evolution of the Hall-coefficient with the Ce-concentration we find clear indications for a coexisting hole-type and electron-type of orbit at the Fermi surface.

Electrochemical reduction of the high Tc superconductor YBa 2Cu 3O y0 by lithium via new compound formation

We report on the electrochemical reduction of polycrystalline YBa 2Cu 3O y0 (YBCO) pellets by lithium at room temperature in organic electrolyte galvanic cells at low current densities and its effect on superconductivity. The reaction is found to occur by irreversible new compound formation, which removes oxygen and copper from YBCO to form Li 6CuO 4 and a reduced YBCO phase, rather than by insertion as previously thought. This conclusion is based on various types of analyses of electrochemically lithium-reacted samples which include, for the first time to be reported, their electronic transport and magnetic susceptibility behavior at superconducting temperatures, determination of their oxygen content, peak assignment of the additional phase in their powder X-ray diffraction pattern, and lithium analysis of samples reacted and after cell charging. The removal of oxygen and copper does not alter the orthorhombic symmetry of the YBCO phase nor its T c onset but progressively destroys superconductivity. Annealing at 150°C in argon causes structural rearrangement to tetragonal symmetry, restores superconductivity and the T c now depends on the reduction level. The significance of the lithium reaction technique as compared to high temperature reduction methods is that it provides an accurate means, via coulometric control, to separate changes in YBCO stoichiometry from structural rearrangements thus enabling electronic and structural contributions to superconductivity to be evaluated individually.

Diffusion of gold in Cu 3Au

Using an improved high temperature reduction method we found that in the n-type high-Tc-system Pr2−xCexCuO4+δ bulk superconductivity can be established between x ≤ 0.09 and x ≈ 0.17 i.e. over a much broader range than previously reported. The T2-contribution to the resistivity increases with the Ce-concentration. In the evolution of the Hall-coefficient with the Ce-concentration we find clear indications for a coexisting hole-type and electron-type of orbit at the Fermi surface.