Cu/TiO_(2) Photocatalysts for CO_(2) Reduction: Structure and Evolution of the Cocatalyst Active Form

Extensive work on a Cu-modified TiO_(2) photocatalyst for CO_(2) reduction under visible light irradiation was conducted. The structure of the copper cocatalyst was established using UV-vis diff use refl ectance spectroscopy, high-resolution transmis- sion electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. It was found that copper exists in different states (Cu 0 , Cu^(+) , and Cu^(2+) ), the content of which depends on the TiO_(2) calcination temperature and copper loading. The optimum composition of the cocatalyst has a photocatalyst based on TiO_(2) calcined at 700℃ and modified with 5 wt% copper, the activity of which is 22 μmol/(h·g cat ) (409 nm). Analysis of the photocatalysts after the photocatalytic reaction disclosed that the copper metal on the surface of the calcined TiO_(2) was gradually converted into Cu_(2) O during the photocatalytic reaction. Meanwhile, the metallic copper on the surface of the noncalcined TiO_(2) did not undergo any trans- formation during the reaction.

Synthesis of TiO_2/ZnSn(OH)_6 Hollow Nano-composite via a Simultaneous Crystallization-etching Route as Photocatalyst

We report the synthesis of TiO2/ZnSn（OH）6 as a novel nano-composite material via a simultaneous crystallization-etching route with cubic nano-ZnSn（OH）6 and TiF4 as the precursors. The structure, composition and morphology of the composite were characterized by XRD, EDS, FETEM and FESEM, which showed the prepared TiO2/ZnSn（OH）6 had a unique morphology of hollow cubic nano-ZnSn（OH）6 attached with rutile TiO2 nanoparticles. The results of photocatalytic activity measurement indicated the photocatalytic activity of the prepared composite was better than that of nano-ZnSn（OH）6. This study may be helpful for the design and fabrication of functional comoosite materials.

Mg-doped SrTaO_(2)N as a visible-light-driven H_(2)-evolution photocatalyst for accelerated Z-scheme overall water splitting

Perovskite SrTaO_(2)N is one of the most promising narrow-bandgap photocatalysts for Z-scheme overall water splitting.However,the formation of defect states during thermal nitridation severely hinders the separation of charges,resulting in poor photocatalytic activity.In the present study,we successfully synthesize SrTaO_(2)N photocatalyst with low density of defect states,uniform morphology and particle size by flux-assisted one-pot nitridation combined with Mg doping.Some important parameters,such as the size of unit cell,the content of nitrogen,and microstructure,prove the successful doping of Mg.The defect-related carrier recombination has been significantly reduced by Mg doping,which effectively promotes the charge separation.Moreover,Mg doping induces a change of the band edge,which makes proton reduction have a stronger driving force.After modifying with the core/shell-structured Pt/Cr_(2)O_(3)cocatalyst,the H_(2)evolution activity of the optimized SrTaO_(2)N:Mg is 10 times that of the undoped SrTaO_(2)N,with an impressive apparent quantum yield of 1.51%at 420 nm.By coupling with Au-FeCoO_(x)modified BiVO_(4)as an O_(2)-evolution photocatalyst and[Fe(CN)_(6)]_(3)−/[Fe(CN)_(6)]_(4)−as the redox couple,a redox-based Z-scheme overall water splitting system is successfully constructed with an apparent quantum yield of 1.36%at 420 nm.This work provides an alternative way to prepare oxynitride semiconductors with reduced defects to promote the conversion of solar energy.

TiO2-PES Fibrous Composite Material for Ammonia Removal Using UV-A Photocatalyst

This study focused on the development and characterization of TiO2-PES composite fibers with varying TiO2 loading amounts using a phase inversion process. The resulting composite fibers exhibited a sponge-like structure with embedded TiO2 nanoparticles within a polymer matrix. Their photocatalytic performance for ammonia removal from aqueous solutions under UV-A light exposure was thoroughly investigated. The findings revealed that PeTi8 composite fibers displayed superior adsorption capacity compared to other samples. Moreover, the study explored the impact of pH, light intensity, and catalyst dosage on the photocatalytic degradation of ammonia. Adsorption equilibrium isotherms closely followed the Langmuir model, with the results indicating a correlation between qm values of 2.49 mg/g and the porous structure of the adsorbents. The research underscored the efficacy of TiO2 composite fibers in the photocatalytic removal of aqueous under UV-A light. Notably, increasing the distance between the photocatalyst and the light source resulted in de-creased hydroxyl radical concentration, influencing photocatalytic efficiency. These findings contribute to our understanding of TiO2 composite fibers as promising photocatalysts for ammonia removal in water treatment applications.

Effects of rare earth on microstructures and properties of Ni-W-P-CeO_2-SiO_2 nano-composite coatings

Ni-W-P-CeO2-SiO2 nano-composite coatings were prepared on common carbon steel surface by pulse electrodeposition of nickel, tungsten, phosphorus, rare earth （nano-CeO2） and silicon carbide （nano-SiO2） particles. The effects of nano-CeO2 concentrations in electrolyte on microstructures and properties of nano-composite coatings were studied. The samples were characterized with chemical compositions, elements distributions, microhardness and microstructures. The results indicated that when nano-CeO2 concentration was controlled at 10 g/L, the nano-composite coatings possessed higher microhardness and compact microstmctures with clear outline of spherical matrix metal crystallites, fine crystallite sizes and uniform distribution of elements W, P, Ce and Si within the Ni-W-P matrix metal. Increasing the nano-CeO2 particles concentrations from 4 to 10 g/L led to refinement in grain structure and improvement of microstructures, while when increased to 14 g/L, the crystallite sizes began to increase again and there were a lot of small boss with nodulation shape appearing on the nano-composite coatings surface.

Wear and corrosion resistance and electroplating characteristics of electrodeposited Cr-SiC nano-composite coatings

Cr-SiC nanocomposite coatings with various contents of SiC nanoparticles were prepared by electrodeposition in optimized Cr plating bath containing different concentrations of SiC nanoparticles. Direct current electrocodeposition technique was used to deposit chromium layers with and without SiC nanoparticles on mild carbon steel. The effects of current density, stirring rate and concentration of nanoparticles in the plating bath were investigated. Scanning electron microscopy was used to study surface morphology. Energy dispersive analysis technique was used to verify the presence of SiC nanoparticles in the coated layers. The corrosion behaviors of coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy methods in 0.05 mol/L HCl, 1 mol/L NaOH and 3.5% NaCl （mass fraction）, respectively. Microhardness measurements and pin-on- disc tribometer technique were used to investigate the wear behavior of the coatings.

Synthesis and study of MPNS/SMA nano-composite tanning agent

The radical polymerization of maleic anhydride（MA）,styrene（ST）with the vinyl groups introduced onto the surface of the nano-sized silica via solution polymerization method was developed.The methacryloxypropyl nano-sized silica（MPNS）was used as macromonomer and polymerized with maleic anhydride and styrene by initiating with BPO in toluene.The structure and properties of MPNS/SMA nano-composite were characterized by FT-IR spectra and TEM.Meanwhile,it was applied as tanning agent compared with the traditional styrene-maleic anhydride copolymer in leather.It was found that the applied leather had better quality characteristics with the addition of the nano-sized silica.

Formations of AZ91/Al_(2)O_(3) nano-composite layer by friction stir processing

Composite layers containing~0.8%vol Al_(2)O_(3) nanoparticles were produced on AZ91 magnesium alloy by friction stir processing(FSP).The treated layers were characterized using optical and scanning electron microscopes,as well as microhardness and wear testing units.It was noticed that,by reducing the rotational speed and increasing the travel speed,the grain size of the treated layer reduces and its hardness increases.In addition,the presence of nano Al_(2)O_(3) reduces the grain sizes of the layers further and increases their hardness.Furthermore,FSP of AZ91 with Al_(2)O_(3) particles improved the wear resistance significantly and changed the wear mechanism from oxidation and adhesive mode in the as-received AZ91 to oxidation and abrasive in the FSPed specimens.Finally,the rotational speed of 800 rpm and the travel speed of 40 mm/min were the optimum parameters for achieving a suitable composite layer with the highest hardness and wear resistance among the treated layers.

Microstructure and mechanism of in-situ Al_2O_(3(p))/Al nano-composites synthesized by sonochemistry melt reaction

The Al2O3（p）/Al nano-composites were fabricated from Al-K2ZrF6-Na2B4O7 system by sonochemistry in situ reaction. The fabrication mechanisms, including high intensity ultrasonic influence on microstructures and reinforcement particles-aluminum matrix interface, were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The XRD results show that the component of the as-prepared composites is Al2O3 reinforcement. The SEM analysis results indicate that Al2O3 particles are uniformly distributed in the aluminum matrix. The TEM results show that the morphologies of Al2O3 particles present in nearly sphere-shape, the sizes are in the range of 20-100 nm, and the interfaces are net and no interfacial outgrowth is observed. Analysis with secondary development Image-J software shows that Al2O3 recoveries are firstly improved and then decreased with increasing ultrasonic power. When the power is 0.4 kW, the distribution is the best, and a maximum number of particles are obtained. The reaction mechanisms were investigated.

Effect of milling energy on preparation of Cu-Cr/CNT hybrid nano-composite by mechanical alloying

Production of Cu-Cr/carbon nanotube （CNT） hybrid nano-composite by wet and dry milling processes at three different levels of milling energy was investigated in order to study the effect of milling energy in two different media on dispersion of CNTs, and preparation of the nano-composite. The structural evolution and solid solution formation were evaluated by X-ray diffraction technique. The microstructure was characterized by scanning electron microscopy and transmission electron microscopy. Also, the mechanical properties were measured by microhardness test. The mean crystallite size was in the range of 20-63 nm depending on milling medium and energy. CNTs dispersion is a function of milling energy. According to FESEM images and microhardness results, it can be concluded that wet milling is more applicable in dispersing CNTs homogeneously in comparison to dry milling. It was also found that wet milling at higher milling energies can be a beneficial method of producing the homogeneous hybrid nano-composite with the least damages introducing on CNTs because of the higher microhardness which can be attributed to better dispersion of less damaged CNTs. Compared with crystallite size changes, CNTs dispersion and damages were considerably more effective on hardness.

Corrosion behavior of AZ31-WC nano-composites

In this study,the effects of WC nano-particles amount and surface roughness on corrosion behavior of magnesium metal matrix nanocomposites in 3.5%NaCl solution are examined with the help of electrochemical test.Varying wt%of WC nano-particles(0.5,1,1.5 and 2)are used to fabricate metal matrix nano-composites through ultrasonic vibration assisted stir casting method.Basic characterizations of fabricated composites are performed by using scanning electron microscopy(SEM)and energy dispersive x-ray analysis(EDAX).SEM images show that nano-particles are well distributed throughout the magnesium matrix while EDAX results confirm the presence of WC particles in nano-composites.Micro-hardness result shows increasing trend with increasing weight percentage of WC.Mg nano-composite containing 0.5 wt%WC nano-particles is found to be the most corrosion resistive one followed by base alloy,Mg-2 wt%WC,Mg-1.5 wt%WC and Mg-1 wt%WC.Additionally,corrosion behavior of Mg-2WC with different surface quality is examined and it is observed that sample with lowest surface roughness shows better corrosion resistance.In the end,corrosion mechanisms are assessed with the help of SEM and EDAX study of corroded surfaces.

Optical and Magnetic Properties of Fe_2O_3/SiO_2 Nano-composite Films

Fe2O3/SiO2 nano-composite films were prepared by sol-gel technique combining heat treatment in the range of 100-900 ℃. The particle size was observed by FE-SEM. Optical properties of the films were investigated by UV-visible spectra. Structural and magnetic characteristics were investigated through FT-IR and VSM. The transparency of the Fe2O3/SiO2 nano-composite films decreased with the content of the Fe2O3. Water and organic solvent in the films were evaporated with heat treatment, so the transparency of the films was enhanced under high temperature. It is also found that the saturation magnetization （Ms） of the films increases with the temperature. As the content of the Fe2O3 increases, when the content of the Fe2O3 is around 30wt%, the Ms of the films has a maximum value.

Nano-composite Particles Synthesized by a Hydrogen Arc Plasma

Nano-composite particles can be synthesized by a hydrogen arc plasma method, which possesses the advantages of high productivity, controllable size distribution and low electric energy consumption comparing with conventional gas condensation method. With this method, not only the nanoparticles of metals and alloys, but also the nano-composite particles with shell structure can be synthesized. The microstructures, compositions and the formation mechanism of the nano composite particles were studied

Novel Nano-composites SDC–LiNaSO_4 as Functional Layer for ITSOFC

As an ionic conductive functional layer of intermediate temperature solid oxide fuel cells(ITSOFC), samarium-doped ceria(SDC)–Li Na SO4nano-composites were synthesized by a sol–gel method and their properties were investigated. It was found that the content of Li Na SO4 strongly affected the crystal phase, defect concentration, and conductivity of the composites. When the content of Li Na SO4 was 20 wt%, the highest conductivity of the composite was found to be, respectively, 0.22, 0.26, and 0.35 S cm-1at temperatures of 550, 600, and 700 °C, which are much higher than those of SDC. The peak power density of the single cell using this composite as an interlayer was improved to, respectively, 0.23, 0.39, and 0.88 W cm-2at 500, 600, and 700 °C comparing with that of the SDC-based cell. Further, the SDC–Li Na SO4(20 wt%)-based cell also displayed better thermal stability according to the performance measurements at 560 °C for 50 h. These results reveal that SDC–Li Na SO4 composite may be a potential good candidate as interlayer for ITSOFC due to its high ionic conductivity and thermal stability.

Determination of A.C. Conductivity of Nano-Composite Perovskite Ba_{(1- x - y)}Sr_(x)TiFe_(y)O₃Prepared by the Sol-Gel Technique

Nano-composite, perovskite Ba(1- x - y)Sr(x)TiFe(y)O3, denoted as (BSTFe) in powder form was derived via sol-gel (SG) method followed by sintering at fixed temperature 750℃ for one hour. The chemical composition, morphology and structure of the powder samples were investigated by using X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The XRD characterization indicates formation of a cubic crystalline phase in the pure BST. A well defined perovskite phase with nano-crystallite sizes equal to about 34 nm was achieved from XRD for B10ST3F sample, while TEM study confirmed the obtained XRD results giving the following crystallite size value about 33.75 nm for the same sample. The dielectric A.C. conductivity was evaluated as a function of temperature and frequency ranging from 42 Hz up to 1 MHz.

Forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by CNTs based on MCST with temperature-variable material properties

In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.

A Metal-free Polyimide Photocatalyst for the Oxidation of Amines to Imines

Polyimide(PI) is an organic polymer material with good stability and diverse sources that has attracted widespread attention in the field of photocatalysis. In this study, a series of PI photocatalysts were synthesized by a thermal polymerization approach using pyromellitic dianhydride(PMDA) and various diamine monomers(melamine(MA), 4,4′-oxydianiline, and melem) as the precursors as well as different heating rates. The effects of the diamine precursor and heating rate on the structure, composition, morphology, and optical properties of the as-prepared PI materials were systematically investigated by various characterization techniques. The selective photo-oxidation of benzylamine was used as a model reaction to evaluate the photocatalytic activities of the resulting PI samples for the oxidation of amines to imines. The results revealed that the PI sample prepared using MA and PMDA as the precursors and a heating rate of 7 ℃/min(MA-PI-7) exhibited the best catalytic performance, with 98% benzylamine conversion and 98% selectivity for N-benzylidene benzylamine after 4 h of irradiation. Several benzylamine derivatives and heterocyclic amines also underwent the photo-oxidation reaction over the MA-PI-7 catalyst to afford the corresponding imines with good activity. In addition, MA-PI-7 exhibited good stability over four successive photocatalytic cycles.

Recent progress in research and design concepts for the characterization,testing,and photocatalysts for nitrogen reduction reaction

The reduction of molecular nitrogen(N_(2))to ammonia(NH_(3))under mild conditions is one of the most promising studies in the energy field due to the important role of NH_(3)in modern industry,production,and life.The photocatalytic reduction of N_(2)is expected to achieve clean and sustainable NH_(3)production by using clean solar energy.To date,the new photocatalysts for photocatalytic reduction of N_(2)to NH_(3)at room temperature and atmospheric pressure have not been fully developed.The major challenge is to achieve high light-absorption efficiency,conversion efficiency,and stability of photocatalysts.Herein,the methods for measuring produced NH_(3)are compared,and the problems related to possible NH_(3)pollution in photocatalytic systems are mentioned to provide accurate ideas for measuring photocatalytic efficiency.The recent progress of nitrogen reduction reaction(NRR)photocatalysts at ambient temperature and pressure is summarized by introducing charge transfer,migration,and separation in photocatalytic NRR,which provides a guidance for the selection of future photocatalyst.More importantly,we introduce the latest research strategies of photocatalysts in detail,which can guide the preparation and design of photocatalysts with high NRR activity.

Recent advances in bismuth-based photocatalysts:Environment and energy applications

Photocatalysis is an effective way to solve the problems of environmental pollution and energy shortage.Numerous photocatalysts have been developed and various strategies have been proposed to improve the photocatalytic performance.Among them,Bi-based photocatalysts have become one of the most popular research topics due to their suitable band gaps,unique layered structures,and physicochemical properties.In this review,Bi-based photocatalysts(BiOX,BiVO_(4),Bi_(2)S_(3),Bi_(2)MoO_(6),and other Bi-based photocatalysts)have been summarized in the field of photocatalysis,including their applications of the removal of organic pollutants,hydrogen production,oxygen production etc.The preparation strategies on how to improve the photocatalytic performance and the possible photocatalytic mechanism are also summarized,which could supply new insights for fabricating high-efficient Bi-based photocatalysts.Finally,we summarize the current challenges and make a reasonable outlook on the future development direction of Bi-based photocatalysts.

Influence of SiO_2 Particles on Microstructures and Properties of Ni-W-P-CeO_2-SiO_2 Nano-Composite Coatings

Ni-W-P-CeO2-SiO2 nano-composite coatings were prepared on the carbon steel surface by pulse co-deposition of nickel, tungsten, phosphorus, nano-CeO2 and nano-SiO2 particles. The influence of nano-SiO2 particles concentrations in electrolyte on microstructures and properties of the nano-composite coatings were researched, and the characteristics were assessed by chemical compositions, element distribution, deposition rate, microhardness and microstructures. The results indicate that when nano-SiO2 particles concentrations in electrolyte are controlled at 20 g·L-1, the deposition rate with 27.07 μm·h-1 and the microhardness with 666 Hv of the nano-composite coatings are highest, element line scanning and area scanning analyses show that the average contents of elements W, P, Si and Ce in the nano-composite coatings are close, displaying that the distribution of every element within the nano-composite coatings is even. An increase in nano-SiO2 particles concentrations in electrolyte (when lower than 20 g·L-1) leads to refinement in grain structure of nano-composite coatings, but when it improved to 30 g·L-1, the crystallite sizes increase again and in the meantime there are a lot of small boss with nodulation shape appearing on the surface of nano-composite coatings.