SiC nanoparticles reinforced magnesium matrix composites fabricated by ultrasonic method

SiC nanoparticles reinforced magnesium matrix composites were fabricated by ultrasonic method.The AZ91 alloy and SiC nanoparticles with the average diameter of 50 nm were used as the matrix alloy and the reinforcement,respectively.The addition of nanoparticles was 0.1%,0.3%,and 0.5%(mass fraction) of the composites.The results of microstructural evaluation and mechanical properties indicate that the nanoparticles can be dispersed into magnesium alloys efficiently and uniformly with the aid of ultrasonic vibration.As compared with the matrix alloys,the grains of composites were refined and the mechanical properties of composites were improved significantly.The SEM and DSC analyses show that the SiC nanoparticles can act as the heterogeneous nucleation of α-Mg.Also,the strengthening mechanism responsible for the composites reinforced with SiC nanoparticles was discussed.

Damping performance of SiC nanoparticles reinforced magnesium matrix composites processed by cyclic extrusion and compression

This work dealt with the damping performance and its underlying mechanism in SiC nanoparticles reinforced AZ91D composite(SiC_(np)/AZ91D)processed by cyclic extrusion and compression(CEC).It was found that the CEC process significantly affects the damping performance of the composite due to alterations in the density of dislocations and grain boundaries in the matrix alloy.Although there would be dynamic precipitation of the Mg17Al12 phase during processing which increases the phase interface and limits the mobility of dislocations and grain boundaries.The results also showed that the damping capacity of 1%SiC_(np)/AZ91D composite continuously decreases with adding CEC pass number and it consistently increases with rising the applied temperature.Considering the first derivative of the tanδ-T curve,the dominant damping mechanism based on test temperature can be divided into three regions.These three regions are as follows(i)dislocation vibration of the weak pinning points(≤T_(cr)),(ii)dislocation vibration of the strong pinning points(T_(cr)∼T_(V)),and(iii)grain boundary/interface sliding(≥T_(V))

Effect of Fe_(3)O_(4) nanoparticles on magnetic xerogel composites for enhanced removal of fluoride and arsenic from aqueous solution

Fe_(3)O_(4)magnetic xerogel composites were prepared by polycondensation of resorcinol(R)-formaldehyde reaction via a sol-gel process in an aqueous solution through varying the molar ratio of Fe_(3)O_(4)nanoparticles(MNPs),catalyst(C),and water(W)content.MNPs were obtained by co-precipitation(MC),oxidation of iron salts(MO),or solvothermal synthesis(MS).Both MNPs and magnetic xerogels were examined regarding the performance of arsenic and fluoride removal in a batch system.The MC-based MNPs had higher adsorption capacities for both fluoride(202.9 mg/g)and arsenic(3.2 mg/g)than other MNPs in optimum conditions.The X-ray diffraction,Fourier transform infrared spectroscopy,and energy-dispersive X-ray spectroscopy confirmed that Fe was composed into the polymeric matrix of magnetic xerogels that contained 0.59%-4.42%of Fe with a molar ratio of MNPs(M)to R between 0.01 and 0.10.With low R/C and optimum M/R ratios,an increase in the surface area of magnetic xerogels affected the fluoride and arsenic adsorption capacities.The magnetic xerogel composites with the MC-based MNPs prepared at a fixed R/C ratio(100)and at different R/W(0.05-0.06)and M/R(0.07-0.10)ratios had a high arsenic removal efficiency of 100%at an As(V)concentration of 0.1 mg/L and pH of 3.0.The maximum adsorption capacities of magnetic xerogels were approximately five times higher than those of the xerogels without MNP composites.Therefore,Fe_(3)O_(4)nanoparticles enhanced the adsorption of arsenate and fluoride.The variations of alkaline catalyst and water content significantly affected the resulting properties of textural and surface chemistry of magnetic xerogel composites.

Synthesis and Enhanced Electrochemical Activity of Ag-Pt Bimetallic Nanoparticles Decorated MWCNTs/PANI Nanocomposites

Ag-Pt bimetallic nanoparticles decorated on MWCNTs/PANI nanocomposites have been synthesized by in-situ chemical oxidative polymerization and chemical co-reduction method. The Fourier transform infrared（FT-IR） spectroscopy, X-ray diffraction（XRD）, ultraviolet-visible（UV-vis） absorption spectroscopy, scanning electron microscopy（SEM） and transmission electron microscopy（TEM） were used to characterize the morphology and structure of the nanocomposites. It can be observed that the PANI was uniformly grown along the MWCNTs to form MWCNsT/PANI fiber-like nanocomposites with diameter about 60 nm, and the Ag-Pt binary nanoparticles were decorated onto MWCNTs/PANI with particle sizes around 6.8 nm. Cyclic voltammetry（CV） and electrochemical impedance spectroscopy（EIS） were used to characterize the electrochemical performance of the prepared electrode. The results demonstrated that the obtained MWCNTs/PANI/Ag-Pt electrode displayed a good electrochemical activity and fast electron transport, which has potential applications in biosensors and supercapacitors.

Yolk-shell Si/C composites with multiple Si nanoparticles encapsulated into double carbon shells as lithium-ion battery anodes

The conceptual design of yolk-shell structured Si/C composites is considered to be an effective way to improve the recyclability and conductivity of Si-based anode materials. Herein, a new type of yolk-shell structured Si/C composite (denoted as TSC-PDA-B) has been intelligently designed by rational engineering and precise control. In the novel structure, the multiple Si nanoparticles with small size are successfully encapsulated into the porous carbon shells with double layers benefiting from the strong etching effect of HF. The TSC-PDA-B product prepared is evaluated as anode materials for lithium-ion batteries (LIBs). The TSC-PDA-B product exhibits an excellent lithium storage performance with a high initial capacity of 2108 mAh g^-1 at a current density of 100 mA g^-1 and superior cycling performance of 1113 mAh g^-1 over 200 cycles. The enhancement of lithium storage performance may be attributed to the construction of hybrid structure including small Si nanoparticles, high surface area, and double carbon shells, which can not only increase electrical conductiv让y and intimate electrical contact with Si nanoparticles, but also provide built-in buffer voids for Si nanoparticles to expand freely without damaging the carbon layer. The present findings can provide some scientific insights into the design and the application of advanced Si-based anode materials in energy storage fields.

Formation of Copolymer-Ag Nanoparticles Composite Micelles in Three-dimensional Co-flow Focusing Microfluidic Device

A novel method was presented to create composite micelles of amphiphilic copolymers and Ag nanoparticles(NPs) in a three-dimensional co-flow focusing microfluidic device(3D CFMD). Self-assembly of the copolymers was initiated by the fast mixing of water and a blend dispersion of hydrophobic Ag NPs and amphiphilic copolymers. At the same time, the hydrophobic Ag NPs enter the core of copolymer micelles, based on the hydrophobic interaction. The copolymer-Ag NPs composite micelles have a core-shell structure with copolymer shell and Ag NPs core. COMSOL Multiphysics is used to simulate the concentration distribution of copolymers and Ag NPs under different flow rates. Co-assembly microfluidic conditions are determined based on simulation results. Under suitable microfluidic conditions, both block copolymers and gradient copolymers can co-assemble with hydrophobic Ag NPs to form composite micelles, respectively. This microfluidic coassembly method will have a good prospect in the preparation of composite micelles of amphiphilic copolymers and metal nanoparticles.

Composite magnetic nanoparticles:Synthesis and cancer-related applications

Recent advances in the preparation and applications of composite magnetic nanoparticles are reviewed and summa- rized, with a focus on cancer-related applications.

Synthesis and Characterization of Superparamagnetic Fe₃O₄@SiO₂Core-Shell Composite Nanoparticles

The Fe3O4@SiO2 composite nanoparticles were obtained from as-synthesized magnetite (Fe3O4) nanoparticles through the modified St?ber method. Then, the Fe3O4 nanoparticles and Fe3O4@SiO2 composite nanoparticles were characterized by means of X-ray diffraction (XRD), Raman spectra, scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). Recently, the studies focus on how to improve the dispersion of composite particle and achieve good magnetic performance. Hence effects of the volume ratio of tetraethyl orthosilicate (TEOS) and magnetite colloid on the structural, morphological and magnetic properties of the composite nanoparticles were systematically investi-gated. The results revealed that the Fe3O4@SiO2 had better thermal stability and dispersion than the magnetite nanoparticles. Furthermore, the particle size and magnetic property of the Fe3O4@SiO2 composite nanoparticles can be adjusted by changing the volume ratio of TEOS and magnetite colloid.

Synthesis and characterization of Fe_3O_4@SiO_2 magnetic composite nanoparticles by a one-pot process

Fe3O4@SiO2 core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe3O4@SiO2 core–shell structures from prepared Fe3O4 nanoparticles. The properties of the Fe3O4 and Fe3O4@SiO2 composite nanoparticles were studied by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The prepared Fe3O4 particles were approximately 12 nm in size, and the thickness of the SiO2 coating was approximately 4 nm. The magnetic properties were studied by vibrating sample magnetometry. The results show that the maximum saturation magnetization of the Fe3O4@SiO2 powder（34.85 A·m^2·kg^–1） was markedly lower than that of the Fe3O4 powder（79.55 A·m^2·kg^–1）, which demonstrates that Fe3O4 was successfully wrapped by SiO2. The Fe3O4@SiO2 composite nanoparticles have broad prospects in biomedical applications; thus, our next study will apply them in magnetic resonance imaging.

Nanoparticles Transport in Ceramic Matriсes: A Novel Approach for Ceramic Matrix Composites Fabrication

The results of practical implementation of a new method for porous piezoceramics, and ceramic matrix piezocomposites fabrication were presented. The method was based on nanoparticles transport in ceramic matrices using a polymer nanogranules coated or filled with a various chemicals, with successive porous ceramics fabrication processes. Different types of polymer microgranules filled and coated by metal-containing nanoparticles were used for a pilot samples fabrication. Polymer microgranules were examined using transmission and scanning electron microscopy as well as by EXAFS and X-ray emission spectroscopy. Pilot samples of nano- and microporous ceramics and composites were fabricated using different piezoceramics compositions (PZT, lead potassium niobate and lead titanate) as a ceramic matrix bases. Resulting ceramic matrix piezocomposites were composed by super lattices of closed or open pores filled or coated by nanoparticles of metals, oxides, ferromagnetics etc. embedded in piezoceramic matrix. Dielectric and piezoelectric parameters of pilot samples were measured using piezoelectric resonance analysis method. New family of nano- and microporous piezoceramics and ceramic matrix piezocomposites are characterized by a unique spectrum of the electrophysical properties unachievable for standard PZT ceramic compositions and fabrication methods.

Thermal and Structural Analyses of PMMA/TiO₂Nanoparticles Composites

In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to their importance broad practical and medical applications. Thermal properties as well as X-ray diffraction analyses were employed to characterize the structure properties of such composite. The obtained results showed variations in the glass transition temperature (Tg), the melting temperature (Tm), shape and area of thermal peaks which were attributed to the different degrees of crystallinity and the existence of interactions between PMMA and TiO2 nanoparticle molecules. The XRD patterns showed sharpening of peaks at different concentrations of nano-TiO2 powder with PMMA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo- polymers PMMA and nano-TiO2 powder is possible.The results showed that nano-TiO2 powder mix with PMMA can improve the thermal stability of the homo-polymer under investigation, lead- ing to interesting technological applications.

Decorating MXene with tiny ZIF-8 nanoparticles:An effective approach to construct composites for water pollutant removal

MXenes have attracted increasing research enthusiasm owing to their unique physical and chemical properties.Although MXenes exhibit exciting potential in cations adsorption due to their unique surface groups,the adsorption capacity is limited by the low specific surface area and undeveloped porosity.Our work aims at enhancing the adsorption performance of a well-known MXene,Ti3C2Tx,for methylene blue(MB)by decorating tiny ZIF-8 nanoparticles in the interlayer.After the incorporation of ZIF-8,suitable interspace in the layers resulting from the distribution of tiny ZIF-8 appears.When employing in MB,the adsorption capacity of composites can reach up to 107 mg·g^(-1) while both ZIF-8(3 mg·g^(-1))and Ti_(3)C_(2)Tx(9mg·g^(-1))show nearly no adsorption capacity.The adsorption mechanism was explored,and the good adsorption capacity is caused by the synergistic effect of ZIF-8 and Ti_(3)C_(2)Tx,for neither of them is of suitable interspace or surface groups for MB adsorption.Our work might pave the way for constructing functional materials based on the introduction of nanoparticles into layered materials for various adsorption applications.

Synthesis and Characterization of Polymeric Composites Embeded with Silver Nanoparticles

Silver nanoparticles were synthesized by chemical reduction method. The Ag nanoparticles (AgNP) were characterized using UV-Vis spectroscopy which shows an absorption band at 420 nm confirming the formation of nanoparticles. For any practical application of the silver nanoparticles it is necessary to stabilize it which can be done by making a composite. In the present studies three polymers were chosen such that AgNP could be put to some practical use. Polyvinyl Alcohol (PVA), Polypyrrole (Ppy) and Carboxymethyl cellulose (CMC) are important for use in textiles, electronics and food/drug technologies respectively. Polymeric composites of PVA, PPy, and CMC were prepared by mixing the aqueous solutions of the respective polymers and the colloidal suspension of preformed silver nanoparticles. Various compositions containing 1% to 5% of Ag nanoparticles were prepared. Thin films of these composites were characterized by UV-Vis spectroscopy, X-ray diffraction and Scanning electron microscopy. X-ray diffraction showed the presence of the peaks at 2θ values of 38.1°, 44.2°, 64.4 and 78.2° corresponding to cubic phase of silver metal. SEM photographs revealed the presence of Ag nanoparticles of sizes varying from 40 to 80 nm. The electrical conductivity of these materials was studied using the four probe method. The conductivity was found to increase from 10–6 for control samples to 10–3 S/cm after the formation of the nanocomposites.

Compositionally Graded Microstructure for Ag-Fe Nanoparticles

Ag-Fe nanoparticles with a highly Ag rich average composition were synthesized by the sonochemical route.Silver-iron system exhibits a wide miscibility gap in the bulk materials.Interestingly,a graded compositional profile along the nanoparticle radius was observed.Regions at and near the surface of the nanoparticle contained both Ag and Fe atoms.The composition got relatively deficient Fe towards the center of the particle with particle core made up of pure Ag.Alloying of Ag and Fe is confirmed by the absence of diffraction signal corresponding to pure Fe phase and presence of a paramagnetic phase in nanoparticles containing a diamagnetic(Ag)and ferromagnetic(Fe)elements.

The Impact Compression Behaviors of Silica Nanoparticles—Epoxy Composites

The compressive properties of epoxy with different silica nanoparticles (SiO2 nanoparticles) contents at quasi-static and high strain rates loading were investigated via experiment. This article evaluates the compressive failure behaviors and modes at different SiO2 nanoparticles contents and different strain rates. The results indicated that the stress strain curves were sensitive to strain rate, and the compressive failure stress of composites with various SiO2 nanoparticles contents increased with the strain rates, and it increased along with SiO2 nanoparticles contents and then declined. The compressive failure stress and the compressive failure modes of the composites were apparently different from the change of SiO2 nanoparticles contents.

The Role of Bamboo Nanoparticles in Kenaf Fiber Reinforced Unsaturated Polyester Composites

In this study,bamboo nanoparticles in concentration ranges from 0-5%were incorporated along with woven/nonwoven kenaf fiber mat into unsaturated polyester and the developed composites were further characterized.Bamboo chips were subjected to ball milling process for the synthesis of nanoparticles with a particle size of 52.92 nm.The effect that the incorporation of nanoparticles had on various properties of reinforced composites was further observed.Due to the high surface area of nanoparticles,incorporation of 3%of nanofillers contributed towards strong bonding and better wettability with matrix,thus resulting in excellent mechanical properties and thermal characteristics in reinforced unsaturated polyester composites.Furthermore,mechanical characteristics of reinforced composites were deteriorated by the addition of a higher percentage of nanoparticles(>3%)due to agglomeration,as confirmed by scanning electron microscopy.Moreover,ordered structural arrangement of woven kenaf textile fiber showed enhancement in interfacial adhesion and promoted superior mechanical strength in reinforced composites as compared with nonwoven composites.

The Development and Characterization of Zirconia-Silica Sand Nanoparticles Composites

The present study aims to develop zirconia-Silica sand nanoparticles composites through powder processing route and to study the physical properties, mechanical properties and microstructure of the composites. Zirconia based silica sand nanoparticles composite with 5, 10, 15 and 20 wt.% were developed through powder processing technique and sintered at 1500 ℃ for two hours. A decreasing trend of green density however an improvement in sintered density was observed. Also the addition of silica sand nanoparticles with 20 wt.% increased the hardness up to 12.45 GPa and microstructures indicated the diffusion mechanism of silica sand nanoparticles into pore sites of the composites.

Ternary Ag/AgCl/BiOIO_3 composites for enhanced visible-light-driven photocatalysis

Ternary Ag/AgC l/BiO IO3 composite photocatalysts are prepared by a facile method. Enhanced visible-light absorption and charge carrier separation are achieved after the introduction of Ag/AgC l particles into BiO IO3 systems,as revealed by ultraviolet-visible diffuse-reflectance spectrometry,photocurrent response and electrochemical impedance spectroscopy. The Ag/AgC l/BiO IO3 composites are applied to the visible-light photocatalytic oxidization of NO in air and exhibit an enhanced activity for NO removal in comparison with Ag/AgC l and pure BiO IO3. A possible photocatalytic mechanism for Ag/AgC l/BiO IO3 is proposed,which is related to the surface plasmon resonance effects of Ag metal and the effective carrier separation ability of BiO IO3. This work provides insight into the design and preparation of BiO IO3-based materials with enhanced visible-light photocatalysis ability.

Microstructure evolution and nitrides precipitation in in-situ Ti_2 AlN/TiAl composites during isothermal aging at 900°C

Microstructures of Ti2AlN/TiAl composites prepared by in-situ method were characterized in in-situ and aging treatment conditions and the nitride precipitation was investigated in Ti2AlN/TiAl composites aged at 900 ℃ for 24 h after being heat treated at 1400 ℃ for 0.5 h. The in-situ composites consist of γ＋α2 lamellar colonies, equiaxed y grains and Ti2AlN reinforcements. Matrix with nearly fully lamellar structure formed after solution and subsequently aging treatment. With the increase of Ti2AlN content, the nearly fully lamellar structure becomes instable for the aged composites. According to TEM study, fine Ti2AlN precipitates are found to distribute at the grain boundaries of lamellar colony. Needle-like Ti3AlN precipitates arrange in line with growing axis parallel to [001] direction of the γ-TiAl matrix and another needle-like Ti3AlN precipitates with lager size distribute at the dislocations. Key words：

Size control and its mechanism of SnAg nanoparticles

Sn3.5Ag （mass fraction, %） nanoparticles were synthesized by an improved chemical reduction method at room temperature. 1,10-phenanthroline and sodium borohydride were selected as the surfactant and reducing agent, respectively. It was found that no obvious oxidation of the synthesized nanoparticles was traced by X-ray diffraction. In addition, the results show that the density of primary particles decreases with decreasing the addition rate of the reducing agent. Moreover, the slight particle agglomeration and slow secondary particle growth can result in small-sized nanoparticles. Meanwhile, the effect of surfactant concentration on the particle size can effectively be controlled when the reducing agent is added into the precursor at an appropriate rate. In summary, the capping effect caused by the surfactant molecules coordinating with the nanoclusters will restrict the growth of the nanoparticles. The larger the mass ratio of the surfactant to the precursor is, the smaller the particle size is.