Transparent conductive graphene films prepared by hydroiodic acid and thermal reduction

Transparent conductive graphene films are fabricated by the transfer printing of graphene aqueous dispersion followed by hydrohalic acids and thermal reduction. Results indicate that the graphene film reduced by hydroiodic acid （HI） reduction combined with thermal treatment shows a higher electrical conductivity than that reduced only by thermal treatment at the same transparency. A film with a sheet resistance of - 2400 D./sq at a transparency over 72% is obtained at a typical wavelength of 550 nm.

Research on Development of Dolomite-Ferrosilicon Thermal Reduction Process of Magnesium Production

Up to now, the Pedgion magnesium reduction process is the dominating magnesium production process. In 2004, about 98% of raw magnesium is produced by Pedgion magnesium reduction process in China which equals to 60% of the global output. It shows that the dolomite-ferrosilicon thermal reduction process is the most important method to produce magnesium in the world. Limited by the disadvantage of dolomite-ferrosilicon thermal reduction process, the magnesium producing process always followed by relatively severe pollution, while the resource utilizing efficiency keeps very low. With the rapid development of dolomite-ferrosilicon thermal reduction process in China, many research works have been done aiming at the process technology and the reduction theory, and the magnesium producing process has got great evolution. The history of dolomite-ferrosilicon thermal reduction process was introduced; the process character, the merits and which defects were also discussed. Defects in dolomite-ferrosilicon thermal reduction process were expatiated, and feasible method and idea to upgrade the process was put forward. The main problems and the potential troubles hindering the development of magnesium industry were analyzed. Finally, the probability to further improve the thermal reduction process and the effective approaches to develop Chinese magnesium industry were discussed.

Metal Fe,Ni and Fe-Ni Fine Fibers Derived from the Organic Gel-Thermal Reduction Process

The organic gel-thermal reduction process was successfully used for the preparation of magnetic metal Ni, Fe, Fe-Ni fine fibers from raw materials of citric acid or lactic acid and metal salts. Ni, Fe and Fe-Ni fine fibers synthesized were featured with diameters of around 1 μm and lengths of as long as 2 m for Ni fibers, 0.5 m for iron fibers, 1 m for Fe-Ni fibers. The structure, thermal decomposition process and morphologies of the gel precursors and fibers derived from thermal reduction of these gel precursors were characterized by FTIR, XRD,TG/DSC and SEM, respectively. The gel spinnability largely depends on molecular structures of metal-carboxylate complexes formed in the gel. It is reasoned that these gels consist of linear-type structural molecules [（C6H6O7）Ni]n or [（C6H5O7）2Ni3] for the nickel citrate gel, [（C3H5O3）3Fe] for the ferric lactate gel, [（C6H5O7）5（NiFe）3] for the iron-nickel citrate gel respectively and the gels obtain showed a good spinning performance.

Preparation of ferromagnetic metal fine fibers by organic gel-thermal reduction process

The organic gel-thermal reduction process was used for the preparation of ferromagnetic metal Ni, Co and Fe fine fibers from the raw materials of citric acid, lactic acid and metal salts. The structure, thermal decomposition process and morphologies of the gel precursors and fibers derived from thermal reduction of these gel precursors were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermo-gravimetric/differential scanning calorimetry and scanning electron microscopy. The results show that spinnability of gel largely depends on molecular structure of metal-carboxylate complex that is a linear-type structure formed in the gel. As a result, the gels exhibit a good spinnability. Metal Ni, Co and Fe fine fibers are featured with diameters of around 1 μm and a high aspect ratio up to 1×106.

Synthesis of(HfZrTiNbTa)N powders via nitride thermal reduction with soft mechano-chemical assistance

High-entropy nitride powders are one of prerequisite materials for the preparation of high-performance high-entropy nitride ceramics.In this paper,high-entropy(HfZrTiNbTa)N powders were synthesized via nitride(i.e.,silicon nitride(Si_(3)N_(4)))thermal reduction with soft mechanochemical assistance.The results show that metal oxides like hafnium dioxide(HfO_(2)),zirconium dioxide(ZrO_(2)),titanium dioxide(TiO_(2)),niobium pentoxide(Nb_(2)O_(5)),and tantalum pentoxide(Ta_(2)O_(5))can all be transformed into the corresponding metal nitrides in the presence of Si_(3)N_(4)at 1700℃,and solid solution of the metal nitrides can be formed as the temperature increases to 2100℃.The high-entropy(HfZrTiNbTa)N powders with submicron-sized particles,a narrower size distribution,and a single face-centered cubic(fcc)structure are obtained from raw material mixtures ground for 10 h and subsequently sintered at 1800℃.In addition,the high-entropy bulk nitride ceramics with relative density(Rw)of 94.31%±0.76%,Vickers hardness of 21.00±0.94 GPa,and fracture toughness(KIC)of 3.18±0.16 MPa·m1/2 are obtained with submicron-sized powders,which are superior to those obtained with micron-sized powders.

Preparation and electromagnetic shielding properties of PET/rGO/SWCNT composite fabric

Graphene oxide(GO)with excellent dispersion ability can assist the dispersion of single-walled carbon nanotube(SWCNT)and promote the formation of uniform and stable GO/SWCNT coating liquid.The highly conductive polyethylene terephthalate/reduced graphene oxide/SWCNT(PET/rGO/SWCNT)electromagnetic shielding composite fabric was successfully prepared by anchoring rGO/SWCNT on PET fabric via dip-coating piror to low-temperature thermal reduction.The results showed that the carboxyl groups and hydroxyl groups formed of hydrophilic-treated PET were conducive to the formation of hydrogen bonds with that of GO,which enhanced the interaction between PET fabric and GO/SWCNT coating;the loading of GO/SWCNT increased with the number of dip-coating,the unit area loading of rGO/SWCNT in the final composite fabric was 2.7 mg/cm^(2) after 10 dip-coating cycles and thermal reduction;the PET/rGO/SWCNT composite fabric had a continuous and dense conductive network,with a conductivity of up to 41.6 S/m and the average electromagnetic interference shielding effectiveness in X-band was 22 dB;the flexible PET/rGO/SWCNT composite fabric was not only easy to process,but also exhibited excellent conductivity and shielding efficiency,showing great potential in the application of electromagnetic shielding fabrics.

Isothermal kinetics of mechanochemically and thermally synthesized Ag from Ag_2O

The kinetics of isothermal reduction of Ag2O with graphite under argon atmosphere for a non-activated sample and mechanically activated sample was investigated.It is found that Johnson-Mehl-Avrami model appropriately explained the thermal and mechanochemical synthesis of Ag from Ag2O＋ghraphite mixture.The process kinetics was investigated using the same approach for milled and unmilled samples.The results show that the Avrami exponent of mechanochemical reduction is higher than that of high temperature thermal reduction.Also,the mechanisms of nuclei growth in thermal and mechanochemical reduction are diffusion controlled and interface controlled,respectively.

Langmuir-Blodgett assembly of ultra-large graphene oxide films for transparent electrodes

Monolayer ultra-large graphene oxide （UL-GO） sheets with diameter up to about 100 μm were synthesized based on a chemical method. Transparent conductive films were produced using the UL-GO sheets that were deposited layer-by-layer on a substrate by the Langmuir-Blodgett （L-B） assembly technique. The films produced from UL-GO sheets with a close-packed flat structure exhibit exceptionally high electrical conductivity and transparency after thermal reduction. A remarkable sheet resistance of 605 -/sq at 86% transparency is obtained, which outperforms the graphene films grown on a Ni substrate by chemical vapor deposition. The technique used to produce transparent conductive films is facile, inexpensive and tunable for mass production.

Structure evolution of oxygen removal from porous carbon for optimizing supercapacitor performance

The presence of oxygen functional groups is detrimental to the capacitive performance of porous carbon electrode in organic electrolyte. In this regards, hydrogen thermal reduction has been demonstrated effective approach in removing the unstable surface oxygen while maintaining the high porosity of carbon matrix. However, the exact evolution mechanism of various oxygen species during this process, as well as the correlation with electrochemical properties, is still under development. Herein, biomass-based porous carbon is adopted as the model material to trace its structure evolution of oxygen removal under hydrogen thermal reduction process with the temperature range of 400–800 °C. The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700°C. XPS, TPRMS and Boehm titration results indicate that the oxygen elimination undergoes three distinctive stages(intermolecular dehydration, hydrogenation and decomposition reactions). The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700 °C. Benefiting from the stable electrochemical interface and the optimized porous structure, the as-obtained HAC-700 exhibit significantly suppressed self-discharge and leak current, with improved cycling stability, which is attributable to the stabilization of electrochemical interface between carbon surface and electrolyte. The result provides insights for rational design of surface chemistry for high-performance carbon electrode towards advanced energy storage.

Temperature-Dependent Formation of Redox Sites in Molybdenum Trioxide Studied by Electron Paramagnetic Resonance Spectroscopy

The formation and qualification of redox sites in transition metal oxides are always the active fields related to electronics, catalysis, sensors, and energy-storage units. In the present study, the temperature dependence of thermal reduction of MoO3 was surveyed at the range of 350℃ to 750℃. Upon reduction, the formed redox species characterized by EPR spectroscopy are the MoVion and superoxide anion radical (O2-) when the reduction was induced at the optimal temperature of 300-350℃. When heating-up from 350℃, the EPR signals started to decline in amplitude. The signals in the range of 400-450℃ decreased to half of that at 350℃, and then to zero at ~600℃. Further treatment at even higher temperature or prolonged heating time at 500℃ caused more reduction and more free electrons were released to the MoO3 bulk, which results in a delocalized means similar to the antiferromagnetic coupling. These data herein are helpful to prepare and study the metal-oxide catalysts.

Comparison and integration of final electromagnetic stirring and thermal soft reduction on continuous casting billet

Final electromagnetic stirring(F-EMS)and thermal soft reduction(TSR)are techniques that improve the inner quality of continuous casting billets,but they have rarely been applied simultaneously.The application effects of F-EMS and TSR were compared,and a process integrating F-EMS and TSR was adopted for a billet continuous caster.A heat transfer model was established to calculate the thermal behavior of 82A tire cord steel billet.The locations of F-EMS and TSR were determined,followed by conducting a series of plant trials,involving F-EMS alone,TSR alone,and the integrated process of F-EMS and TSR.The results showed that F-EMS or TSR could effectively improve the inner quality of the billet under their respective suitable working conditions.Moreover,F-EMS was found to be more helpful in terms of improving central segregation,while TSR tended to improve V-segregation,central porosity,and pipe.The integration of F-EMS and TSR allowed the advantages of each technique to be utilized,thereby better improving the inner quality.Among all the working conditions,82A steel billet showed optimum inner quality when the current of F-EMS was 240 A and the cooling intensity of TSR was 2.2 m^(3) h^(−1).These findings demonstrate that the integration of F-EMS and TSR is promising for application on continuous casting billets.

Process of producing magnesium by thermal vacuum reduction using silicocalcium as reductant

A new process of producing magnesium by thermal vacuum reduction using dolomite and magnesite as materials and silicocalcium as reductant was studied in this study. The reduction process of MgO by silicocalcium was analyzed by phases analysis of reduction slag through X-ray diffraction （XRD） and the factors influencing the reduction ratio of MgO were investigated. The experi- mental results show that when using silicocalcium as reductant, the reduction ratio of MgO can be over 93 %. In the reduction process, calcium in silicocalcium takes part in the reduction reaction of MgO firstly below 1,000 ℃ and it makes CaSi2 decompose. It also releases elemental silicon which has more reactive activity and improves the reduction reaction of MgO. That is the main cause that the reduction ratio of MgO using silicocalcium as reductant is 8 %-10 % higher than that by Pidgeon process using fer- rosilicon as reductant under the same conditions.

Recovery of iron from lead-zinc metallurgical slags by bath smelting

The recovery of iron from iron sinking slag and lead smelter slag was investigated by desulfurization-reduction bath smelting. The effects of lead smelter slag(LSS) to iron sinking slag(ISS) mass ratio and temperature were investigated in desulfurization experiments. The X-ray diffraction(XRD) and X-ray fluorescence(XRF) analyses show that the optimum conditions are LSS:ISS of 3:7 and temperature of 1350°C. The composition of desulfurization products is mainly Zn Fe2O4, and the desulfurization rate of 99.66% is obtained under optimum conditions. The thermogravimetric(TG) and differential scanning calorimeter(DSC) analyses demonstrate that reductant is necessary for decomposition and reduction of zinc ferrite in desulfurization product. The effects of reductant, temperature and feeding modes on iron enrichment were investigated in reduction experiments. The scanning electron microscope(SEM) and energy dispersive spectrometer(EDS) determination show that the iron content of reduction product is up to 99.36% under optimum conditions of coke as reductant, reduction temperature of 1450°C and the feeding mode of premixing.

Oxygen vacancy engineering for tuning the catalytic activity of LaCoO_(3) perovskite

Herein, we attempted to engineer oxygen vacancies on the surface of LaCoO_(3) perovskite through simple post-treatments(acid or reductive thermal treatments). Acid treatment induces oxygen vacancies through the selective etching of the La cations, whereas thermal treatment in a reducing atmosphere generates oxygen vacancies by directly removing lattice oxygen. The characterization results confirm that the number of surface oxygen vacancies, which are crucial in various catalytic oxidation reactions,considerably increases in the LaCoO_(3) catalysts treated with acid or reducing gas. Acid treatment enriches the oxygen vacancies while maintaining the structure of the LaCoO_(3) catalysts, which can not be achieved through reductive thermal treatment. Therefore, the acid treatment is considered a promising technique for oxygen vacancy engineering of perovskite catalysts for tuning their catalytic activities. Furthermore,the catalytic activities of the posttreated LaCoO_(3) catalysts for CO oxidation were evaluated and are noted to be considerably better than those of the pristine LaCoO_(3) catalyst due to their abundant oxygen vacancies. Consequently, we conclude that the oxygen vacancies of perovskite catalysts can be effectively engineered via two simple methods and play a significant role in CO oxidation.

Enhancement in boiling heat transfer performance using reduced graphene oxide coating with controllable components and porous structures

Enhancement in boiling heat transfer performance is significant for addressing thermal management bottlenecks of advanced electronic systems.Reduced graphene oxides(rGO)are regarded as promising candidates for thermal management due to their excellent thermal properties,chemical stability and adjustable wettability.In this study,rGO coatings with micron pores and controllable oxygen contents are prepared on Al substrate via cathodic electrophoretic deposition and subsequent thermal annealing,leading to enhanced pool boiling performance.The heat transfer coefficient for Al/rGO450is 37.2 kW m-2K-1,which is increased by 112.6%compared with bare Al,also outperformed previously reported Al based substrates.It is assumed that the hydrophilic and aerophobic r GO coatings effectively promote the liquid infiltration and bubble departure during pool boiling process.Importantly,repeatability tests indicate the durable stability of vertically oriented rGO nanosheets.Reverse nonequilibrium molecular dynamics simulation indicates that the interfacial transmission coefficients of Al/rGO increase after thermal annealing,indicative of the enhanced heat transfer performance of heterogeneous interface.Our study opens a new avenue for endowing metal substrates with high pool boiling performance using porous carbon coating nanoengineering strategy with controllable morphology and components.

Preparation and lithium storage performances of g-C_(3)N_(4)/Si nanocomposites as anode materials for lithium-ion battery

As the anode material of lithium-ion battery,silicon-based materials have a high theoretical capacity,but their volume changes greatly in the charging and discharging process.To ameliorate the volume expansion issue of silicobased anode materials,g-C_(3)N_(4)/Si nanocomposites are prepared by using the magnesium thermal reduction technique.It is well known that g-C_(3)N_(4)/Si nanocomposites can not only improve the electronic transmission ability,but also ameliorate the physical properties of the material for adapting the stress and strain caused by the volume expansion of silicon in the lithiation and delithiation process.When g-C_(3)N_(4)/Si electrode is evaluated,the initial discharge capacity of g-C_(3)N_(4)/Si nanocomposites is as high as 1033.3 mAh/g at 0.1 A/g,and its reversible capacity is maintained at 548 mAh/g after 400 cycles.Meanwhile,the improved rate capability is achieved with a relatively high reversible specific capacity of 218 mAh/g at 2.0 A/g.The superior lithium storage performances benefit from the unique g-C_(3)N_(4)/Si nanostructure,which improves electroconductivity,reduces volume expansion,and accelerates lithiumion transmission compared to pure silicon.

Temperature-induced resistance transition behaviors of melamine sponge composites wrapped with different graphene oxide derivatives

Temperature-re s ponsive resistance transition behaviors of the melamine sponges wrapped with different graphene oxide derivatives(i.e.nanoribbon,wide-ribbon and sheet)were investigated.Melamine sponge composites coated by three types of GO derivatives were prepared by a simple dip-coating approach.All these composites show good mechanical flexibility and reliability(almost unchanged compressive stress at 70%strain after 100 cycles),high hydrophobicity(water contact angle>120°),excellent flame resistance(self-extinguishing)and structural stability even after burning,which was used to construct the resistance-based fire alarm/warning sensor.Notably,the different resistance response behaviors of such sensors are strongly dependent on the GO size and network formed on the MF skeleton surface.Typically,at a fixed high temperature of~350℃,the three fire alarm sensors show different response time(to trigger the alarm light)of 6.3,8.4 and 11.1 s for nanoribbon,wide-ribbon and sheet at the same concentration,respectively.The structural observation and chemical analysis demonstrated that the discrepancy of temperature-responsive resistance transition behaviors of various GO derivatives was strongly determined by their different thermal reduction degrees during the high-tempe rature or flame treating process.This work offers a design and development for construction of smart fire alarm device for potential fire prevention and safety applications.

Theoretical energy consumption analytical method for metal separation process

The theoretical energy consumption(TEC)analytical methods and the calculated models for the electrolytic and thermal reduction metal separation processes have been put forward based on thermodynamics and physical chemistry principles,providing theoretical foundation for choosing the optimum metal separation methods.Based on the models,the TECs of the Mg separation processes are taken as an example,and have been calculated and analyzed contrastively,including the MgCl_2 electrolytic method,the MgO electrolytic method with inert electrode and with carbon anode,and the silicothermic method.It is shown that the thermal method is more reasonable than the electrolytic methods to separate Mg under low efficiency of coal power generation.

Highly Sensitive and Portable Gas Sensing System Based on Reduced Graphene Oxide

Graphene has been widely used in gas-sensing applications due to its large specific surface area and strong adsorption ability. Among different forms of graphene used as gas-sensing materials, reduced graphene oxide is one of the most convenient and economical materials to integrate with Si-based electronics, which is very important to graphene-based gas sensors. In addition, the stacking structure of graphene oxide flakes facilitates absorption and detection of gas molecules. Based on reduced graphene oxide, a highly sensitive and portable gas-sensing system was demonstrated here. Solution-based graphene oxide was cast on a chip like a TF memory card and then reduced thermally. A signal acquisition system was designed to monitor resistance variation as a sign of gas concentration. This miniature graphene-based gas sensor array demonstrates a new path for the use of graphene in gas-detection technologies. And the creation of a sensitive and portable graphene gas sensor also shows great potential in fields such as medicine and environmental science.