Synthesis of dental resins using diatomite and nano-sized SiO2 and TiO2

The mechanical properties of dental composites were improved by porous diatomite and nano-sized silica (OX-50) used as co-fillers.The resin composites,filled with silanized OX-50 and silanized diatomit...     

Growth, structural, optical, thermal and dielectric properties of a novel semi-organic nonline ar optical crystal: Dichloro-diglycine zinc II

Dichloro-diglycine zinc II(DCDGZ II),a semi-organic nonlinear optical material has been synthesized and single crystals were grown from the aqueous solution up to dimensions 20×10×3 mm3.The title compound,DCDGZ II(C4H10Cl2N2O4Zn H2O) crystallizes into monoclinic structure with the space group of C2/c.The unit-cell parameters were found to be a=14.4191(7),b=6.9180(2),c=12.9452(6) and Z=4.In the crystal structure,DCDGZ II layer is building up alternatingly with layers of water in which the zinc ions lie on a twofold axis.Theoretical calculations for polarizability,which are useful for device fabrication were made using Clausius–Mosotti equation and Penn analysis and the results were compared.Fourier transform infrared(FTIR) spectroscopic studies were performed for the identification of the different functional groups presented in the compound.The UV–vis–NIR absorption spectrum reveals that the lower UV cut-off wavelength is 240 nm.The optical band gap of the crystal was estimated as 2.2 eV.The surface morphology,thermal behaviour,dielectric properties have been studied using SEM,TG/DTA and LCR HITESTER analyzer.The nonlinear optical property of the crystal was also confirmed using Kurtz powder technique.     

Effect of Co addition on crystallization and magnetic properties of FeSiBPCu alloy

The effects of Co addition on the microstructure,crystallization processes and soft magnetic properties of(Fe1 xCox)83Si4B8P4Cu1(x?0.35,0.5,0.65)alloys were investigated.The experimental results demonstrated that the addition of Co decreased the thermal stability against crystallization of the amorphous phase,and thus improved the heat treatment temperature of this alloy.Fe Co Si BPCu nanocrystalline alloys with a dispersedα0-Fe Co phase were obtained by appropriately annealing the as-quenched ribbons at 763 K for 10 min.Theα0-Fe Co with grains size ranging from 9 to 28 nm was identified in primary crystallization.The coercivity(Hc)markedly increased with increasing x and exhibited a minimum value at x0.35,while the saturation magnetic flux density(Bs)shows a slight decrease.The(Fe0.65Co0.35)83Si4B8P4Cu1nanocrystalline alloy exhibited a high saturation magnetic flux density Bsof 1.68 T,a low coercivity,Hcof 5.4 A/m and a high effective permeability meof 29,000 at 1 k Hz.     

Zr-pillared montmoril lonite supported cobalt nanoparticles for Fischer – Tropsch synthesis

In this article Fischer–Tropsch(FT) synthesis was studied over cobalt nanoparticles supported on modifed Montmorillonite(Zr-PILC).Co-loaded/Zr-PILC catalysts were synthesized by hydrothermal methods and were characterized by XRD,XRF,BET,H2-TPR,TGA and SEM techniques.FT reactions were carried out in fxed bed microreactor(T 225 1C,260 1C and 275 1C,P 1,5 and 10 bars).The FT-products obtained over Co-loaded/Zr-PILC catalysts showed increased selectivity of C2–C12hydrocarbons and decreased selectivity towards CH4and higher molecular weight hydrocarbons(C21) at a TOS of 2–30 h as compared to the Co-loaded/NaMMT catalysts.With increase in reaction temperature from225 1C to 275 1C,CO-conversion and CH4selectivity increases while that of C5+hydrocarbons decreases.Decrease in CH4selectivity while increase in C5+hydrocarbons and CO-conversion were observed on increasing the pressure of reaction.     

Facile synthesis of nanosized sodium magnesium hydride, NaMgH3

The ternary magnesium hydride NaMgH 3 has been synthesised via reactive milling techniques.The method employed neither a reactive H2 atmosphere nor high pressure sintering or other post-treatment processes.The formation of the ternary hydride was studied as a function of milling time and ball:powder ratio.High purity NaMgH 3 powder(orthorhombic space group Pnma,a 5.437(2),b 7.705(5),c 5.477(2) ;Z 4) was prepared in 5 h at high ball:powder ratios and characterised by powder X-ray diffraction(PXD),Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDX).The products formed sub-micron scale(typically 200-400 nm in size) crystallites that were approximately isotropic in shape.The dehydrogenation behaviour of the ternary hydride was investigated by temperature programmed desorption(TPD).The nanostructured hydride releases hydrogen in two steps with an onset temperature for the first step of 513 K.     

Activated carbon derived from rice husk by NaOH activation and its application in supercapacitor

Four activated carbon(AC) samples prepared from rice husk under different activation temperatures have been characterized by N2adsorption–desorption isotherms, thermogravimetric analysis(TGA–DTA), Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). The specific surface area of AC sample reached 2681 m2 g 1under activation temperature of 800 1C. The AC samples were then tested as electrode material; the specific capacitance of the as-prepared activated carbon electrode was found to be 172.3 F g 1using cyclic voltammetry at a scan rate of 5 mV s 1and 198.4 F g 1at current density 1000 mA g 1in the charge/discharge mode.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

The enhanced corrosion resistance of UMAO coatings on Mg by silane treatment

The surface silanization was carried out on ultrasonic micro-arc oxidation(UMAO) coatings on pure magnesium using KH550 as silane coupling agent(SCA). The surface morphology, chemical bonds and corrosion resistance of the silane films were investigated by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FTIR) and electrochemical workstation, respectively. The results showed that hybrid coatings were successfully prepared on pure magnesium by UMAO-Na OH(1 mol/L, 2 mol/L, 3 mol/L)-SCA processing. The organic films with Si–O–Mg bonds are helpful for the reduction of the pores in UMAO coatings. The pores decreased with increasing Na OH concentration. Compared with single UMAO treatment, the corrosion potentials(Ecorr) of magnesium plates with UMAO-Na OH(1 mol/L,2 mol/L, 3 mol/L)-SCA treatment increased by 29 m V, 53 m V and 75 m V, respectively, meanwhile the corrosion current density(Icorr) reduced one to two orders of magnitude. It indicated that the corrosion resistance of the coatings was improved by silane treatment.     

Microstructure and mechanical properties of Nb–Si alloys fabricated by spark plasma sintering

This paper deals with microstructural evolutions and mechanical properties of Nb-Si binaries containing dual-phase Nb/Nb5Si3 with Nb to Nb5Si3 fraction ratios of 90:10,80:20,70:30 and 50:50,prepared by spark plasma sintering(SPS).Dense Nb/Nb5Si3 samples with a relative density larger than 99.5% were obtained by SPS processing.The SPS samples consist of the Nb and Nb5Si3 phases with less than 3% fraction of NbO oxide.Hv at room temperature,and compressive strength at 1150℃ and 1250 1C of the bulk SPS alloys increase monolithically by enhancing fraction of the stiffening Nb5Si3 phase.For example,0.2% yield strength,σ0.2,increases from 175 MPa to 420 MPa at 1150℃ and from 110 MPa to 280 MPa at 1250℃,when the Nb5Si3 fraction increases from 10% to 50%.It is interesting that the fracture toughness,KQ,of the bulk SPS samples seems not to be sensitive to phase fraction.Heat treatment,however,plays a key role on the KQ as compared with that of the as-sintered state,at the corresponding Nb5Si3 fraction and considerably improves the KQ by about 100% for samples with the Nb5Si3 fractions of 10%-30%,and by about 50% for the sample with 50% Nb5Si3 fraction.     

Hydrogen absorption properties of amorphous (Ni0.6Nb0.4−yTay)100−xZrx membranes

Ni based amorphous materials have great potential as hydrogen purification membranes. In the present work the melt spun(Ni_(0.6)Nb_(0.4-y)Ta_y)_(100-x)Zr_x with y=0, 0.1 and x=20, 30 was studied. The result of X-ray diffraction spectra of the ribbons showed an amorphous nature of the alloys. Heating these ribbons below T 400 °C, even in a hydrogen atmosphere(1-10 bar), the amorphous structure was retained. The crystallization process was characterized by differential thermal analysis and the activation energy of such process was obtained. The hydrogen absorption properties of the samples in their amorphous state were studied by the volumetric method,and the results showed that the addition of Ta did not significantly influence the absorption properties, a clear change of the hydrogen solubility was observed with the variation of the Zr content. The values of the hydrogenation enthalpy changed from ~37 k J/mol for x=30 to ~9 k J/mol for x=20. The analysis of the volumetric data provides the indications about the hydrogen occupation sites during hydrogenation, suggesting that at the beginning of the absorption process the deepest energy levels are occupied, while only shallower energy levels are available at higher hydrogen content, with the available interstitial sites forming a continuum of energy levels.     

Phase analysis of AlFe2B2 by synchrotron X-ray diffraction, magnetic and Mössbauer studies

The structural and magnetic properties of essentially phase pure AlFe_2B_2 prepared by arc melting were compared with a sample containing impurities. Analysis was carried out by means of synchrotron X-ray diffraction, magnetic measurements and M?ssbauer spectroscopy. The analysis of synchrotron X-ray diffraction data confirmed the orthorhombic structure of space group Cmmm for AlFe_2B_2 with Al_(13)Fe_4 as main impurity phase. The magnetic measurements revealed an unsaturated ferromagnetic state in AlFe_2B_2 with a transition temperature(T_c) of 286 K. Isothermal magnetization measurment at 5 K gave a saturation magnetization of 0.7 μB per Fe atom while Arrott plots establish the second order nature of ferromagnetic transition. The thermal evolution of M?ssbauer spectra confirmed the ferromagnetic nature of this material revealing an hyperfine field of 73 kOe and an isomer shift of 0.46 mm/s at 100 K. The M?ssbauer spectra of a phase pure sample was compared with the one containing impurity phases. It is suggested that the low temperature paramagnetic contribution in M?ssbauer spectra of phase pure material may have its origin in some intrinsic phenomena arising from defects or inhomogeneities in crystal structure.     

Solvother mal synthesis of Co1-xNixFe2O4 nanoparticles and its application in ammonia vapors detection

Magnetic Co1-xNixFe2O4 nanoparticles (NPs) were successfully synthesized via a solvothermal method using ethylene glycol as solvent.The samples were characterized by X-ray diffraction (XRD),field emiss...     

Band structur e design of semiconduc tors for enhanced photocatalytic activity: The case of TiO2

General strategies are proposed by passivated co-doping in present paper to improve the photocatalytic activity of semiconductors for degradation of environmental pollutants.The ideal band gap of semiconductors for enhancement of photocatalytic activity can be lowered to match with visible light absorption and the location of the Conduction Band(CB) should be raised to meet the reducing capacity.Then we apply the strategy to anatase TiO2.It is predicted that nonmetal–metal co-doping TiO2can modify the catalyst band edges by raising the valence band(VB) edge signifcantly and making the CB edge increased 0.24 eV.Therefore,the band gap for co-doping system should be narrowed to about2.72 eV.(N,Ta) is predicted to be the target donor–acceptor combination with the band gap of 2.71 eV,which red-shifts the TiO2absorption edge to 457.6 nm in visible range.The band engineering principle will be ft to other wide-band-gap semiconductors for enhanced photocatalytic activity.     

Thermal behavior of zirconia-dop ed mullite gel fibers

The zirconia-doped mullite gel fibers were prepared via a sol-gel method.The thermal behaviors of the gel fibers during pyrolysis were investigated by means of thermal gravitydifferential scanning calo...     

Minor-alloyed Cu-Ni-Si alloys with high hardness and electric conductivity designed by a cluster formula approach

Cu-Ni-Si alloys are widely used due to their good electrical conductivities in combination with high strength and hardness. In the present work, minor-alloying with M =(Cr, Fe, Mo, Zr) was conducted for the objective of further improving their hardness while maintaining their conductivity level. A cluster-plus-glue-atom model was introduced to design the compositions of M-alloyed Cu-Ni-Si alloys, in which an ideal composition formula[(Ni,Si,M)-Cu_(12)]Cu_3(molar proportion) was proposed. To guarantee the complete precipitation of solute elements in fine δ-Ni_2 Si precipitates, the atomic ratio of(Ni,M)/Si was set as 2/1. Thus the designed alloy series of Cu_(93.75)(Ni/Zr)_(3.75)Si_(2.08)(Cr/Fe/Mo)_(0.42)(at%) were arc-melted into ingots under argon atmosphere, and solidsolutioned at 950 ℃ for 1 h plus water quenching and then aged at 450 ℃ for different hours. The experimental results showed that these designed alloys exhibit high hardness(HV 1.7 GPa) and good electrical conductivities(≥ 35% IACS). Specifically, the quinary Cu_(93.75)Ni_(3.54)Si_(2.08)(Cr/Fe)_(0.42)Zr_(0.21) alloys(Cu-3.32 Ni-0.93 Si-0.37(Cr/Fe)-0.30 Zr wt%) possess both a high hardness with HV = 2.5-2.7 GPa, comparable to the highstrength KLFA85 alloy(Cu-3.2 Ni-0.7 Si-1.1 Zn wt%,HV= 2.548 GPa),and a good electrical conductivity(35-36% IACS).     

Effect of Sr on microstructure and aging behavior of Mg–14Li alloys

The as-cast and as-extruded Mg–14 wt%Li–x Sr ( x=0.14, 0.19, 0.39 wt%) alloys were,respectively, prepared through a simple alloying process and hot extrusion. The effects of Sr addition on microstructure and aging behavior of the Mg–14 wt%Li–xSr alloys were studied. The results indicated that β(Li) and Mg2Sr were the two primary phases in the microstructures of both as-cast and as-extruded Mg–14 wt%Li–xSr alloys. Interestingly, with the increase of Sr content from 0.14 wt% to 0.39 wt%, the grain sizes of the as-cast and as-extruded Mg–14 wt%Li–xSr alloys markedly decreased from 5000mm and 38mm to 330 mm and 22mm respectively, while no obvious changes of the micro-hardness and microstructure of the as-extruded alloys were observed during the aging treatment.     

Core loss analysis of Finemet type nanocrystalline alloy ribbon with different thickness

Nanocrystalline soft magnetic materials are widely used in power electronic applications due to their high permeability,magnetization and low core loss.In this paper,Fe_(73.5)Cu_1Nb_3Si_(15.5)B_7(at%)nanocrystalline alloy ribbons,with ultra-thin thickness of 14μm,and also 18 and 22μm,were prepared by a planar flow casting method with a single roller device.Soft magnetic properties of these ribbons were analyzed after nanocrystallization annealing.The experiments were conducted on toroidal samples using IWATSU B-H Analyzer over a frequency range of 10–100 kHz,at induction amplitudes of 100–500 m T,at room temperature.It was found that the excess eddy current loss P_(ex)was the dominant factor in the overall core loss above 10 k Hz.The toroidal samples made of the 14μm thickness ribbon exhibit very low total core loss of 48 W/kg at a frequency of100 kHz and magnetic flux density of 300 mT.The ratio of the P_(ex)was up to 89%at 100 kHz.The ribbon with lower thickness exhibits lower P_(ex)and therefore lower total core loss.The domain structure evidences were found.It indicates that the ribbons with small thickness are preferable for application in high frequency condition.     

Effect of CuO addition on the sintering temperature and microwave dielectric properties of CaSiO3– Al2O3 ceramics

CuO-doped CaSiO3–1 wt% Al2O3 ceramics were synthesized via a traditional solid-state reaction method, and their sintering behavior,microstructure and microwave dielectric properties were investigated. The results showed that appropriate CuO addition could accelerate the sintering process and assist the densification of CaSiO3–1 wt% Al2O3 ceramics, which could effectively lower the densification temperature from1250 1C to 1050 1C. However, the addition of CuO undermined the microwave dielectric properties. The optimal amount of CuO addition was found to be 0.8 wt%, and the derived CaSiO3–Al2O3ceramic sintered at 1100 1C presented good microwave dielectric properties of εr?7.27,Q f?16,850 GHz and τf? 39.53 ppm/1C, which is much better than those of pure CaSiO3 ceramic sintered at 1340oC(Q f?13,109 GHz).The chemical compatibility of the above ceramic with 30 Pd/70 Ag during the cofiring process has also been investigated, and the result showed that there was no chemical reaction between palladium–silver alloys and ceramics.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

Mn0.8Zn0.2Fe2O4 nanoparticulates spinel ferrites:An approach to enhance the antenna field strength for improved magnitude versus offset（MVO）

Electromagnetic signals in deep reservoir are very weak so that it is difficult to predict about the presence of hydrocarbon in seabed logging(SBL) environment.In the present work,Mn0.8Zn0.2Fe2O4 nanoferrites were prepared by a sol–gel technique at different sintering temperatures of450 °C,650 °C and 850 °C to increase the strength of electromagnetic(EM) antenna.XRD,FESEM,Raman spectroscopy and HRTEM were used to analyze the phase,surface morphology and size of the nanoferrites.Magnetic properties of the nanoferrites were also measured using an impedance network analyzer.However,nanoferrites sintered at 850 °C with initial permeability of 200 and Q factor of 50 were used as magnetic feeders with the EM antenna.Lab scale experiments were performed to investigate the effect of magnetic field strength in scale tank.SPSS and MATLAB softwares were also used to confirm the oil presence in scale tank.It was observed that the magnitude of the EM waves for the antenna was increased up to 233%.Finally,the correlation values also show 208% increase in the magnetic field strength with the presence of the oil.Therefore,antenna with Mn0.8Zn0.2Fe2O4 nanoferrites based magnetic feeders can be used for deep water and deep target hydrocarbon exploration.     

Electroch emical properties and interfacial reactions of LiNi0.5Mn1.5O4-δ nanorods

LiNi0.5Mn1.5O4-δ which possesses a high voltage of 4.7 V vs.Li+/Li and stable structure has been considered as a promising cathode material for high energy Li-ion batteries.In this study,well-crystalli...     

Size-manipulat ion, compacti on and electrical properties of barium manganite nanorods synthesized via the CHM method

A composite-hydroxide mediated method was employed to synthesize barium manganite nanorods.Diameter,surface smoothness and uniformity of these nanorods were optimized by varying reaction temperature and reaction time.The rods with an average diameter of 200 nm and length of1–1.5 μm were obtained at optimum conditions of 200 1C/48 h.The dielectric study of these rods reveals that they have higher value of dielectric constant at lower frequencies which was attributed to the interfacial and rotational type polarizations.Similarly,the increase in dielectric constant with temperature was attributed to the thermal activation of such polarizations.Furthermore,the analysis of ln(J) vs.E1/2characteristics in the temperature range of 300–400 K shows that possible operative conduction mechanism was of Poole–Frenkel type.The value of βexp was found to be 4.85 times greater than the expected theoretical value of feld lowering coeffcient with an internal feld enhancement factor ofα2 23.5.This high value of βexp may be due to some localized electric felds existing inside the sample.