Preparation and Thermoelectric Properties of SiO_2/β-Zn_4Sb_3 Nanocomposite Materials

A series of SiO2/β-Zn4Sb3 core-shell composite particles with 3, 6, 9, and 12 nm of SiO2 shell in thickness were prepared by coatingβ-Zn4Sb3 microparticles with SiO2 nanoparticles formed by hydrolyzing the tetraethoxysilane in alcohol-alkali-water solution. SiO2/β-Zn4Sb3 nanocomposite thermoelectric materials were fabricated with these core-shell composite particles by spark plasma sintering （SPS） method. Microstructure, phase composition, and thermoelectric properties of SiO2/β-Zn4Sb3 nanocomposite thermoelectric materials were systemically investigated. The results show thatβ-Zn4Sb3 microparticles are uniformly coated by SiO2 nanoparticles, and no any phase transformation reaction takes place during SPS process. The electrical and thermal conductivity gradually decreases, and the Seebeck coefficient increases compared to that ofβ-Zn4Sb3 bulk material, but the increment of Seebeck coefficient in high temperature range remarkably increases. The thermal conductivity of SiO2/β-Zn4Sb3 nanocomposite material with 12 nm of SiO2 shell is the lowest and only 0.56 W·m^-1·K^-1 at 460 K. As a result, the ZT value of the SiO2/β-Zn4Sb3 nanocomposite material reaches 0.87 at 700 K and increases by 30%.

Modeling and Simulation of ΔH in Solid State Synthesis of Nanocomposites Al-Cu-Zr

Amorphous structure generated by high-energy ball miller(BM)is often used as a precursor for generating nanocomposites through controlled devitrification.The amorphous forming composition range of ternary Al-Cu-Zr system was calculated using the extended Miedema’s semiempirical model.Eleven compositions of Al-Cu-Zr system showed a wide range of negative enthalpy of mixing(-ΔH^(mix))and amorphization(-ΔH^(amor))among the constituent elements was selected for synthesis by BM.They yielded either nanocomposites of partial amorphous and crystalline structure or no amorphous phase at all in the as-milled condition.The Al_(88)Cu_(6)Zr_(6) alloy with relatively small negativeΔH^(mix)(-0.4 kJ/mol)andΔH^(amor)(-14.8 kJ/mol)became completely amorphous after 120 h of milling.

Solution combustion synthesis of Fe-Ni-Y_2O_3 nanocomposites for magnetic application

Fe-Ni-Y2O3 nanocomposites with uniform distribution of fine oxide particles in the gamma Fe Ni matrix were successfully fabricated via solution combustion followed by hydrogen reduction. The morphological characteristics and phase transformation of the combusted powder and the Fe-Ni-Y2O3 nanocomposites were characterized by XRD, FESEM and TEM.Porous Fe-Ni-Y2O3 nanocomposites with crystallite size below 100 nm were obtained after reduction. The morphology, phases and magnetic property of Fe-Ni-Y2O3 nanocomposites reduced at different temperatures were investigated. The Fe-Ni-Y2O3 nanocomposite reduced at 900 °C has the maximum saturation magnetization and the minimum coercivity values of 167.41 A/(m2·kg)and 3.11 k A/m, respectively.

Preparation, Characterization and Optical Properties of Host-guest Nanocomposite Material Mordenite-silver Iodide

Silver iodide nanoclusters were successfully prepared in the channels of mordenite by a heat diffusion method. Powder X ray diffraction, adsorption technique and infrared spectroscopy were used to characterize the prepared materials, which showed that the guest silver iodide had been encapsulated in the channels of mordenite. The optical properties of the solid phase diffuse reflectance absorption of nanocomposite material NaM AgI were studied, showing that the absorption bands of the diffuse reflectance absorption of the prepared material moved to the region of high energy. The absorption peak of the material prepared shifted to the region of high energy. Namely, blue shift was caused. This has demonstrated the incorporation of silver iodide into the channels of the zeolite. We observed the luminescence and surface photovoltage spectra of NaM AgI sample, proposing the mechanisms of the photoluminescence and photovoltaic responses.

Mn3O4/carbon nanotube nanocomposites recycled from waste alkaline Zn–MnO2 batteries as high-performance energy materials

Alkaline zinc manganese dioxide（Zn–MnO2）batteries are widely used in everyday life. Recycling of waste alkaline Zn–MnO2 batteries has always been a hot environmental concern. In this study, a simple and costeffective process for synthesizing Mn3O4/carbon nanotube（CNT） nanocomposites from recycled alkaline Zn–MnO2 batteries is presented. Manganese oxide was recovered from spent Zn–MnO2 battery cathodes. The Mn3O4/CNT nanocomposites were produced by ball milling the recovered manganese oxide in a commercial multi-wall carbon nanotubes（MWCNTs） solution. Scanning electron microscopy（SEM） analysis demonstrates that the nanocomposite has a unique three-dimensional（3D） bird nest structure. Mn3O4 nanoparticles are homogeneously distributed on MWCNT framework. Mn3O4/CNT nanocomposites were evaluated as an anode material for lithium-ion batteries, exhibiting a highly reversible specific capacitance of -580 mA h·g^-1 after 100 cycles. Moreover, Mn3O4/CNT nanocomposite also shows a fairly positive onset potential of -0.15 V and quite high oxygen reducibility when considered as an electrocatalyst for oxygen reduction reaction.

Synergistic effect of chitin nanofibers and polyacrylamide on electrochemical performance of their ternary composite with polypyrrole

Development of simple methods for preparation of polymeric electrode materials with nanofibrous network structure is a perspective way toward cheap supercapacitors with high specific capacitance and energy density. In this work one-pot synthesis of electroactive ternary composite based on polypyrrole, polyacrylamide and chitin nanofibers with beneficial morphology was elaborated. Ternary system demonstrates better electrochemical performance in comparison with both polypyrrole–polyacrylamide and polypyrrole–chitin binary composites. Possible mechanism of synergistic effect of simultaneous influence of polyacrylamide and chitin nanofibers on the formation of composite＇s structure is discussed.The highest attained specific capacitance of electroactive polypyrrole in ternary composite reached 249 F/g at 0.5 A/g and 150 F/g at 32 A/g. Symmetrical supercapacitor was assembled using the elaborated electrode material. High specific capacitance 89 F/g and good cycling stability with capacitance retention of 90% after 3000 cycles at 2 A/g were measured.

On the higher-order thermal vibrations of FG saturated porous cylindrical micro-shells integrated with nanocomposite skins in viscoelastic medium

Since the multi-layered structures are widely used nowadays, and due to interesting applications of cylindrical shells, this study is dedicated to analyzing free vibrational behaviors of functionally graded saturated porous micro cylindrical shells with two nanocomposite skins. Based on Biot's assumptions, constitutive relations for the core are presented and effective properties of the skins are determined via the rule of mixture. A sinusoidal theory is used to capture the shear deformation effects, and to account for the scale effects, the modified couple stress theory is employed which suggests a material length-scale parameter for predicting the results in small-dimension. With the aid of extended form of Hamilton's principle for dynamic systems, differential equations of motion are extracted. Fourier series functions are used to obtain natural frequencies and after validating them, a set of parametric studies are carried out. The results show the significant effects of porosity and Skempton coefficient, pores placement patterns, CNTs addition and distribution patterns, temperature variations, material length-scale parameter and viscoelastic medium on the natural frequencies of the microstructure. The outcomes of this work could be used to design and manufacture more reliable micro cylindrical structures in thermo-dynamical environments.

Effects of Rare Earth Elements on Preparation of TiO_2-Pillared Bentonite

Layered nanocomposite materials containing rare earth elements, titanium dioxide and bentonite (RE/TiO_2/Bent) were prepared by ion exchange technique with titanium tetrachloride and cerium nitrate as main precursors, and ethanol absolute as solvent. Their preparation, technical parameters, and mechanism of rare earth elements were studied. The results show that the interplanar distance d_ 100 of bentonite increases from 0.96781 nm of original bentonite to 1.88655 nm when ethanol absolute acts as solvent. The interaction between rare earth ions and titanium ions has an effect on titanium ions exchange. When Ce/Ti (in molar ratio)=0.1, rare earth elements are advantageous to the transfer of titanium ions to the interlayers of bentonite; when Ce/Ti=0.2, the action of rare earth elements is not evident; when Ce/Ti=0.4, the rare earth elements are disadvantageous to the preparation of nanocomposite materials.

Synthesis and Characterization of the Host-Guest NanocompositeMaterial Zeolite Y-Iron Bipyridine

This paper reports the synthesis of host-guest nanocomposite material [Fe(bpy)(3)]Y2+ (where bpy=2,2'-bipyridine) using the flexible ligand method. X-ray diffraction analysis. adsorption technique, and cyclic voltammetry were used to characterize the material. The results show that [Fe(bpy)(3)](2+) has been entrapped in the supercage of zeolite, its electron transfer is realized by electron hopping of [Fe(bpy)(3)](2+) within the supercage of zeolite.

LiMn_2O_4/CNTs and LiNi_(0.5)Mn_(1.5)O_4/CNTs Nanocomposites as High-Performance Cathode Materials for Lithium-Ion Batteries

The demand of higher energy density and higher power capacity of lithium（Li）-ion secondary batteries has led to the search for electrode materials whose capacities and performance are better than those available today. Carbon nanotubes（CNTs）, with their unique properties such as 1D tubular structure, high electrical and thermal conductivities, and extremely large surface area, have been used as materials to prepare cathodes for Li-ion batteries. The structure and morphology of CNTs were analyzed by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and transmission electron microscopy（TEM）. The functional groups on the purified CNT surface such as –COOH, –OH were characterized by Fourier Transform infrared spectroscopy. The electrode materials were fabricated from LiMn2O4（LMO）, doped spinel LiNi0.5Mn1.5O4, and purified CNTs via solid-state reaction. The structure and morphology of the electrode were characterized using XRD, SEM, and TEM. Finally, the efficiency of the electrode materials using CNTs was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy.

Preparation and characterization of nano-rare earth composite materials:application in selectivity catalytic oxidation of ammonia and its cytotoxicity study

The manufacture,physical characterization,environmental applications and cytotoxicity properties of nanocomposites consisting of CuO/CeO2 nano-rare earth composite materials prepared using the coprecipitation method at molar ratio of 6:4 with aqueous solutions of copper nitrate and cerium nitrate were reported.The performance of the selective catalytic oxidation of ammonia to N2(NH3-SCO) over a CuO/CeO2 nano-rare earth composite materials in a tubular fixed-bed reactor(TFBR) at temperatures from 423 to 673 K in the presence of oxygen was elucidated.The catalytic redox behavior was determined by cyclic voltammetry(CV).The nanocomposite particles were characterized by TEM,with a tiny particle size around 10 nm with high dispersion phenomena.Further,cell cytotoxicity and the percentage cell survival were determined by using 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetra-zolium(MTS) assay on human lung MRC-5 cell line.Experimental results showed that no apparent cytotoxicity was observed when the MRC-5 was exposed to the CuO/CeO2 nanocomposite materials.

Infusing High-density Polyethylene with Graphene-Zinc Oxide to Produce Antibacterial Nanocomposites with Improved Properties

Nanocomposites of high-density polyethylene(HDPE)modified with 0.2 phr graphene-zinc oxide(GN-ZnO)exhibited optimal mechanical properties and thermal stability.Two other nano-materials—GN and nano-ZnO—were also used to compare them with GN-ZnO.increasing the content of GN-ZnO gradually enhanced the antibacterial and barrier properties,but the addition of 0.3 phr GN-ZnO led to agglomeration that caused defects in the nanocomposites.Herein,we investigated the antibacterial and barrier properties of HDPE nanocomposites infused with different nanoparticles(GN,ZnO,GN-ZnO)of varying concentrations.HDPE and the nanoparticles were meltblended together in a Haake-Buchler Rheomixer to produce a new environment-friendly nano-material with improved physical and chemical properties.The following characterizations were conducted:tensile test,thermogravimetric analysis,morphology,differential scanning calorimetry,X-ray diffraction,antibacterial test,and oxygen and water vapor permeation test.The results showed that the crystallinity of HDPE was affected with the addition of GN-ZnO,and the nanocomposites had effective antibacterial capacity,strong mechanical properties,high thermal stability,and excellent barrier performance.This type of HDPE nanocomposites reinforced with GN-ZnO would be attractive for packaging industries.

Performance of rolling piston type rotary compressor using fullerenes(C70)and NiFe204 nanocomposites as lubricants additives

A novel way for a compressor to improve its coefficient of performance was proposed in this paper.Fullerenes(C70)and NiFe2O4 nanocomposites were modified by span 80 and dispersed in refrigeration oil by solid grinding(SG).Besides,the tribological properties of the nanocomposites were investigated using a four ball friction tester.The results show that when the mass concentration of fullerenes nanocomposite is higher than 60 ppm and the concentration of nano-oil is 2 g/L,the friction coefficient decreases from 0.13 to 0.06 which means the wear is reduced.The coefficient of performance of the compressor under the air conditioning test condition can be raised by 1.23%.

Boron Oxide Glasses and Nanocomposites: Synthetic, Structural and Statistical Approach

Three different precursors of boron-aqua and glycerol solutions of boric acid and ethanol solution of trimethyl borate were used for the preparation of organic–inorganic advanced materials. The films and bulk materials samples were heat treated at 100, 400, 800？C for 2 h. The hybrid samples were stable and transparent until 100？C. The further increase of temperature to 400？C led to destruction of samples, and at 800？C they were molten. The structural changes during the pyrolysis were studied by Fourier transform infrared spectroscopy, differential thermal analysis, and X-ray diffraction. Details of surface morphology were observed by scanning electron microscopy. The obtained BO_3 and BO_4 groups were identified in the molten materials after pyrolysis. The quantities and order of borate structural units as well as residual carbon in the networks depended on boron precursor type. PVA/PEG/B_2O_3 hybrid materials were proved to be appropriate precursors for synthesizing borate and carboborate glass and carbon/borate glass nanocomposites. To access the impact of the experimental conditions on the structural changes of the nanocomposites, cluster analysis of the IR-spectral data was used as a classification method.

Soft template PEG-assisted synthesis of Fe_3O_4@C nanocomposite as superior anode materials for lithium-ion batteries

Carbon-encapsulated Fe3O4 composites were successfully fabricated via hydrothermal method and ex- amined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The Fe3O4@C nanocomposite as an anode material with novel structure demonstrated excellent electrochemical performance, with enhanced specific reversible current density of 50 mA/g capacity （950 mAh/g at the after 50 cycles）, remarkable rate capability （more than 650 mAh/g even at the current density of 1,000 mAJg） and good cycle ability with less capacity fading （2.4 % after 50 cycles）. Two factors have been attributed to the ultrahigh electrochemical perfor- mance： Firstly, the 30- to 50-nm spherical structure with a short diffusion pathway and the amorphous carbon layer could not only provide extra space for buffering the volumetric change during the continuous charging-dis- charging but also improve the whole conductivity of the Fe3O4@C nanocomposite electrode; secondly, the syner- gistic effects of Fe304 and carbon could avoid Fe304 direct exposure to the electrolyte and maintain the structural stabilization of Fe3O4@C nanocomposite. It was suggested that the Fe3O4@C nanocomposite could be suitable as analternative anode for lithium-ion batteries with a high ap- plication potential.

Interface interaction and inter-osmosis effect of Fe_x (SiO_2)_(1-x) nanocomposite materials on magnetic properties

Fe_x(SiC_2 )_(1 - x) nanocomposites prepared by using mechanical alloying method were reported. The mi-crostructure character and magnetic properties of Fex (SiO_2) 1 - x nanocomposite samples with different Fe content and different ball milling time were studied by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Mossbauer spectroscopy, and Faraday magnetic balance in a wide temperature range. The results indicate that the mi-crostructure and magnetic properties are closely related to ball milling time and Fe content. When Fe content is less than 20 wt% , the sample after 80-h ball milling has very complex microstructure. Small α-Fe grains and Fe cluster are implanted in SiO2 matrix. And there are not only isolated α-Fe granular and Fe cluster, but also nanometer scaled sandwich network-like structure. Fex (SiO_2) 1 - x nanocomposite samples display a rich variety of physical and chemical properties as a result of their unique nanostructure, strong interface interaction and inter-osmosis effect in Fe-SiO_2 boundaries, and the grain size effect.

Preparation of Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite films and its performance of photoelectrochemical cathodic protection

A Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite film with high performance of photogenerated cathodic protection was prepared by hydrothermal and photoreduction methods.The results showed that when the CuFe_(2)O_(4) hydrothermal reaction time was 6 h and the AgNO_(3) concentration was 0.1 M,the Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite material performed the best cathodic protection capability for 304 stainless steel(304SS).In this case,the protective potential achieved-930 mV(versus SCE)associated with the photocurrent density of 475μA/cm^(2),which was 14.8 times that of pure TiO_(2) nanowires.In the dark,the nanocomposite provided cathodic protection of up to 485 mV for 304SS.Due to the heterogeneous junctions at the two interfaces among the three kinds of nanocomposite materials,the build-in electric field was fabricated,which promoted the separation efficiency of photogenerated electrons and holes and effectively improved the photochemical cathodic protection of 304SS.

Enhancement in ballistic performance of composite hard armor through carbon nanotubes

The use of carbon nanotubes in composite hard armor is discussed in this study.The processing techniques to make various armor composite panels consisting of Kevlar■29 woven fabric in an epoxy matrix and the subsequent V50 test results for both 44 caliber soft-point rounds and 30 caliber FSP(fragment simulated projectile)threats are presented.A 6.5%improvement in the V50 test results was found for a combination of 1.65 wt%loading of carbon nanotubes and 1.65 wt%loading of milled fibers.The failure mechanism of carbon nanotubes during the ballistic event is discussed through scanning electron microscope images of the panels after the failure.Raman Spectroscopy was also utilized to evaluate the residual strain in the Kevlar■29 fibers post shoot.The Raman Spectroscopy shows a Raman shift of 25 cm^(−1) for the Kevlar■29 fiber utilized in the composite panel that had an enhancement in the V50 performance by using milled fiber and multi-walled carbon nanotubes.Evaluating both scenarios where an improvement was made and other panels without any improvement allows for understanding of how loading levels and synergistic effects between carbon nanotubes and milled fibers can further enhance ballistic performance.

Scalable gas-phase processes to create nanostructured particles

The properties of nanoparticles are often different from those of larger grains of the same solid material because of their very large specific surface area. This enables many novel applications, but properties such as agglomeration can also hinder their potential use. By creating nanostructured particles one can take optimum benefit from the desired properties while minimizing the adverse effects. We aim at developing high-precision routes for scalable production of nanostructured particles. Two gas-phase synthesis routes are explored. The first one - covering nanoparticles with a continuous layer - is carried out using atomic layer deposition in a fluidized bed. Through fluidization, the full surface area of the nanoparticles becomes available. With this process, particles can be coated with an ultra-thin film of constant and well-tunable thickness. For the second route - attaching nanoparticles to larger particles - a novel approach using electrostatic forces is demonstrated. The micron-sized particles are charged with one polarity using tribocharging. Using electrospraying, a spray of charged nanoparticles with opposite polarity is generated. Their charge prevents agglomeration, while it enhances efficient deposition at the surface of the host particle. While the proposed processes offer good potential for scale-up, further work is needed to realize large-scale processes.

Titanate Nanorods Modified with Nanocrystalline ZnS Particles and Their Photocatalytic Activity on Pollutant Removal

Aiming to produce materials with enhanced photocatalytic properties, the synthesis of new crystalline nanocomposites by combining titanate nanorods（TNR） with ZnS nanocrystallites is described in this work.The TNR modification was accomplished by an in situ nucleation and growth process of ZnS nanoparticles.Zinc diethyldithiocarbamate was used as the metal chalcogenide precursor. The prepared materials were structural, morphological and optical characterized by X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy, energy dispersive spectroscopy and powder diffuse reflectance spectra. Crystalline Zn S nanoparticles were obtained as a homogeneous and continuous layer, covering completely the TNR surface. The application of these new nanocomposite materials on photocatalytic degradation of pollutants was investigated. First, the evaluation of hydroxyl radical formation, using the terephthalic acid as probe, was studied. Afterwards, the adsorption and photodegradation of safranine-T, used here as a model pollutant molecule, was investigated. The obtained data indicate that the prepared nanocomposites have potential to be used as photocatalysts for organic pollutant removal.The best removal results（97% removal） were obtained using the 0.01 Zn S/HTNR sample as catalyst（0.2 g/L; 10 ppm safranin-T solution） with a combination of a low dye adsorption（20%） and a high dye photocatalytic degradation（77%）.