Structure evolution of Y2O3 nanoparticle/Fe composite during mechanical milling and annealing

Fe-25 wt% Y2O3composite powders have been fabricated by mechanical milling(MM) Fe powders of 100 μm in diameter and Y2O3nanoparticles in an argon atmosphere for the milling periods of4,8,12,24,36,and 48 h,respectively.The features of these powders were characterized by using X-ray diffraction(XRD),scanning electron microscopy(SEM),electron probe micro analyzer(EPMA) and transmission electron microscopy(TEM).The experimental results showed that the mean particle size and crystalline size of MM powders decreased with the milling time increasing.All the elements distributed homogenously inside the powders after 48 h of MM.The lattice constant of the matrix α-Fe kept constant with the milling time,and no solid solution took place during MM process.After 8 h of MM,the α-Fe in each powder became nanocrystalline.After 48 h of MM,Y2O3changes from nanostructure into amorphous structure,and the crystalline size of α-Fe further decreased to 10 nm.The Y2O3in the powders mechanically milled for 48 h kept the amorphous structure after being annealed at 400 1C,and starts to crystallize when the powders are annealed at 600 1C.The amorphous Y2O3contains a small amount of Fe,and crystalline FeYO3appears at 800 1C.     

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.     

An in vitro evaluation of novel NHA/zircon plasma coating on 316L stainless steel dental implant

The surface characteristics of an implant that influence the speed and strength of osseointegration include crystal structure and bioactivity. The aim of this study was to evaluate the bioactivity of a novel natural hydroxyapatite/zircon(NHA/zircon) nanobiocomposite coating on 316L stainless steel(SS) dental implants soaking in simulated body fluid. A novel NHA/zircon nanobiocomposite was fabricated with 0(control),5, 10, and 15 wt% of zircon in NHA using ball mill for 1 h. The composite mixture was coated on SS implants using a plasma spray method.Scanning electron microscopy(SEM) was used to evaluate surface morphology, and X-ray diffraction(XRD) was used to analyze phase composition and crystallinity(Xc). Further, calcium ion release was measured to evaluate the coated nanobiocomposite samples. The prepared NHA/zircon coating had a nanoscale morphological structure with a mean crystallite size of 30–40 nm in diameter and a bone-like composition,which is similar to that of the biological apatite of a bone. For the prepared NHA powder, high bioactivity was observed owing to the formation of apatite crystals on its surface. Both minimum crystallinity(Xc=41.1%) and maximum bioactivity occurred in the sample containing 10 wt% of zircon because of minimum Xcand maximum biodegradation of the coating sample.     

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...     

Corrosion study of resorbable Ca60Mg15Zn25 bulk metallic glasses in physiological fluids

The corrosion activity of amorphous plates of Ca_(60)Mg_(15)Zn_(25)alloy was investigated.The biocompatible elements were selected for the alloy composition.The electrochemical corrosion and immersion tests were carried out in a multi-electrolyte fluid and Ringer's solution.Better corrosion behavior was observed for the samples tested in a multi-electrolyte fluid despite the active dissolution of Ca and Mg in Ringer's solution.The experimental results indicated that reducing concentration of NaCl from 8.6 g/dm~3for Ringer's solution to 5.75 g/dm~3caused the decrease of the corrosion rate.The volume of the hydrogen evolved after 480 min in Ringer's solution(40.1 ml/cm~2)was higher in comparison with that obtained in a multi-electrolyte fluid(24.4 ml/cm~2).The values of opencircuit potential(E_(OCP))for the Ca_(60)Mg_(15)Zn_(25)glass after 1 h incubation in Ringer's solution and a multielectrolyte fluid were determined to be-1553 and-1536 m V vs.a saturated calomel electrode(SCE).The electrochemical measurements indicated a shift of the corrosion current density(j_(corr))from 1062μA/cm~2for the sample tested in Ringer's solution to 788μA/cm~2for the specimen immersed in a multi-electrolyte fluid.The corrosion products analysis was conducted by using the X-ray photoelectron spectroscopy(XPS).The corrosion products were identified to be CaCO_3,Mg(OH)_2,CaO,MgO and Zn O.The mechanism of corrosion process was proposed and described based on the microscopic observations.The X-ray diffraction and Fourier transform infrared spectroscopy(FTIR)also indicated that Ca(OH)_2,CaCO_3,Zn(OH)_2and Ca(Zn(OH)_3)_2·2H_2O mainly formed on the surface of the studied alloy.     

Bilirubin sensor based on CuO-CdO composites deposited in a nafion/glassy carbon electrode matrixes

Copper oxide-cadmium oxide nanocomposites(CuO-CdO NCs) were synthesized by solvothermal technique in a basic medium. CuO-CdO NCs were characterized using conventional techniques, such as Fourier Transform Infrared Spectroscopy(FTIR), UV–Visible Spectroscopy(UV/Vis), Field-Emission Scanning Electron Microscopy(FESEM), X-ray electron dispersive spectroscopy(XEDS), X-ray photoelectron spectroscopy(XPS), and powder X-ray diffraction(XRD). A selective and enzyme-less Bilirubin(BLR) sensor was developed with a thin-layer of NCs onto a glassy carbon electrode(GCE, surface area = 0.0316 cm~2) using 5% nafion binders at room conditions. Improved electrochemical performances of higher sensitivity, lower detection limit,linear dynamic range(LDR), and long-term stability of preferred BLR were achieved by a reliable currentvoltage(I-V) approach. The calibration curve was found linear(R~2= 0.9347) in a wide range of BLR concentration(10.0 pM ~ 10.0 mM). Based on the signal to noise ratio value of 3, the sensitivity and limit of detection(LOD) of the sensor were calculated as 95.0 pA μM~(-1) cm~(-2) and 1.0 ± 0.1 pM respectively.Solvothermally synthesized CuO-CdO NCs/GCE is an excellent advancement of developing a selective and sensitive BLR sensor by electrochemical approach and practically implemented in real sample applications.     

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.     

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.     

Synthesis, structure, and optical properties of manganese phthalocyanine thin films and nanostructures

Manganese phthalocyanine(MnPc) nanostructures with different morphologies were prepared on porous anodic alumina oxide(AAO) at different substrate temperature(T_S=50 ℃,80 ℃,120 ℃,180 ℃,240 ℃) in an organic molecular beam deposition(OMBD) system.The nanostructures morphologies were studied using scanning electron microscopy(SEM) and the results showed that the nanostructures morphologies could be modulated by the control of T_S,as a result,the continuous film was obtained at 50 ℃,whereas the nanorods(NRs),nanoribbons(NBs),nanowires(NWs),nanosheets(NSs) and nanoparticles(NPs) were facilely generated as T_S increased.At the same time,the density and the uniformity of the nanostructures decreased.The results of X-ray diffraction(XRD) indicated that only the(3-phase polymorph formed throughout the growth process irrelevant to the T_S.Additionally,the ultraviolet visible(UV-Vis) absorption spectra demonstrated that the main absorption bands of MnPc nanostructures showed a remarkable band broadening as the T_S was increased.     

Structural,elemental, optical and magnetic study of Fe doped ZnO and impurity phase formation

We have prepared a series of(ZnO)1-x(Fe2O3)x≤0.10bulk samples with various concentrations of Fe dopant by ball milling and investigated their structural, compositional, optical and magnetic properties by means of X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS),Raman spectrometer and vibrating sample magnetometer(VSM), respectively. Information about different impurity phases was obtained through Rietveld refinements of XRD data analysis. XPS results showed different valence states(Fe2+ tand Fe3+) supported by shaking satellite peaks in samples. With increasing Fe doping percentage, the crystal quality deteriorated and a shift of E2 low band(characteristic of ZnO) has been observed in Raman spectra. Energy band gap estimated from reflectance UV–vis spectroscopy showed shift for all bulk samples. The magnetic behavior was examined using a vibrating sample magnetometer(VSM), indicating ferromagnetic behavior at room temperature(300 K). The effective magnetic moment per Fe atom decreases with increase in doping percentage which indicates that ferromagnetic behavior arises from the substitution of Fe ions in the ZnO lattice.     

MgCo2-D2 and MgCoNi-D2 systems synthesized at high pressures and interaction mechanism during the HDDR processing

MgCo_2 and MgNiCo crystallize with hexagonal Laves type intermetallic structures of the C14 type and do not form hydrides at ambient hydrogen pressures. However, applying high hydrogen pressures in the GPa range forces the hydrogen absorption and leads to the formation of multi-phase compositions, which contain approximately 2.5 atoms H per formula unit of MgCo_2 or MgNiCo and remain thermally stable under normal conditions.The hydrogenation of MgCo_2 resulted in its decomposition to a ternary Mg_2CoD_5 deuteride and metallic cobalt. Phase-structural transformations accompanying the vacuum desorption of deuterium in the temperature range of 27–500 °C were studied using in situ neutron powder diffraction. The investigation showed a complete recovery of the initial MgCo_2 intermetallic via a Hydrogenation-Disproportionation-Desorption-Recombination process. At 300°C, the Mg_2CoD_5 deuteride first decomposed to elementary Mg and hexagonal Co. At 400°C, a MgCo phase was formed by interaction between Mg and Co. At the highest processing temperature of 500°C, a solid-state interaction of MgCo and Co resulted in the recovery of the initial MgCo_2.The interaction of MgNiCo with deuterium under the synthesis conditions of 2.8 GPa and 200 °C proceeded in a more complex way. A very stable ternary deuteride MgNi_2D_3 was leached away while Co was separated in the form of Mg_2CoD_5 and the remaining nickel formed a solid solution with Co with the approximate composition Ni_(0.7)Co_(0.3).The thermal desorption of deuterium from MgCo_2D_(2.5) and from MgNiCoD_(2.5) has been studied by Thermal Desorption Spectroscopy with deuterium released into a closed volume. The observed effects nicely correlate with changes in the phase structural composition of the hydrides formed.MgCo_2 is a new example of the hydrogen storage alloy, in which a successful HDDR processing results in the reversible formation of the initial intermetallic at much lower temperatures than in the equilibrium phase diagram of the Mg-Co system.     

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...     

Densification behavior of mechanically milled Cu–8 at% Cr alloy and its mechanical and electrical properties

Synthesis and consolidation behavior of Cu–8 at%Cr alloy powders made by mechanical alloying with elemental Cu and Cr powders,and subsequently,compressive and electrical properties of the consolidated alloys were studied.Solid solubility of Cr in Cu during milling,and subsequent phase transformations during sintering and heat treatment of sintered components were analyzed using X-ray diffraction,scanning electron microscopy and transmission electron microscopy.The milled powders were compacted applying three different pressures(200 MPa,400 MPa and 600 MPa)and sintered in H2atmosphere at 900 1C for 30 min and at 1000 1C for 1 h and 2 h.The maximum densification(92.8%)was achieved for the sample compacted at 600 MPa and sintered for 1000 1C for 2 h.Hardness and densification behavior further increased for the compacts sintered at 900 1C for 30 min after rolling and annealing process.TEM investigation of the sintered compacts revealed the bimodal distribution of Cu grains with nano-sized Cr and Cr2O3precipitation along the grain boundary as well as in grain interior.Pinning of grain boundaries by the precipitates stabilized the fine grain structure in bimodal distribution.     

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.     

La2O3–Al2O3 –SiO2 glass-infiltrated 3Y-TZP all-ceramic composite for the dental restora tive application

The 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) powder had three particle size distributions, while the fine one was lower than 100 nm. The 3Y-TZP compact was prepared by dry-pressing under pressures ranged from 10 to 30 MPa and then presintered at 1250°C for 2 h. The matrix dry-pressed under the pressure of 20 MPa had a porosity of 16.7% and could be easily processed by computer aided design and computer aided manufacturing (CAD/CAM), and which had been infiltrated by the La2O3–Al2O3–SiO2 glass at 1200°C for 4 h. The flexural strength and fracture toughness of the composite were 710.7 MPa and 6.51 MPa m^1/2, respectively. The low shrinkage (0.3%) of the composite can satisfy the net-shape fabrication standard. XRD results illustrated that zirconia in the La2O3–Al2O3–SiO2 glass-infiltrated 3Y-TZP all-ceramic composite was mainly in the tetragonal phase. SEM and EDS results indicated that the pores of the matrix were almost filled by the La2O3–Al2O3 –SiO2 glass     

Microstructure and oxidation resistance of SiC–MoSi2 multi-phase coating for SiC coated C/C composites

In order to improve the anti-oxidation of C/C composites, a SiC–MoSi2multi-phase coating for SiC coated carbon/carbon composites(C/C)was prepared by low pressure chemical vapor deposition(LPCVD) using methyltrichlorosilane(MTS) as precursor, combined with slurry painting from MoSi2 powder. The phase composition and morphology were analyzed by scanning electron microscope(SEM) and X-ray diffraction(XRD) methods, and the deposition mechanism was discussed. The isothermal oxidation and thermal shock resistance were investigated in a furnace containing air environment at 1500 1C. The results show that the as-prepared SiC–MoSi2coating consists of MoSi2 particles as a dispersing phase and CVD–SiC as a continuous phase. The weight loss of the coated samples is 1.51% after oxidation at 1500 1C for 90 h, and 4.79% after 30 thermal cycles between 1500 1C and room temperature. The penetrable cracks and cavities in the coating served as the diffusion channel of oxygen, resulted in the oxidation of C/C composites, and led to the weight loss in oxidation.     

Effect of B2O3 on the aqueous tape casting and microwave properties of Li2O–Nb2O5–TiO2 ceramics

The effect of B2O3 addition on the aqueous tape casting, sintering, microstructure and microwave dielectric properties of Li2O-Nb2O5-TiO2 ceramics has been investigated. The tape casting slurries exhibit a typical shear-thinning behavior without thixotropy, but the addition of B2O3 increases the viscosity of the slurries significantly. It was found that doping of B2O3 can decrease the tensile strength, strain to failure and density of the green tapes. The sintering temperature could be lowed down to 900℃ with the addition of 2 wt% B2O3 due to the liquid phase effect. No secondary phase is observed. The addition of B2O3 does not induce much degradation on the microwave dielectric properties. Optimum microwave dielectric properties of εr 67, Q×f 6560 GHz are obtained for Li2O-Nb2O5-TiO2 ceramics containing 2 wt% B2O3 sintered at 900 1C. It represents that the ceramics could be promising for multilayer low-temperature co-fired ceramics (LTCC) application.     

Integrated Bi2O3 nanostructure modified with Au nanoparticles for enhanced photocatalytic activity under visible light irradiation

An integrated Bi_2O_3(i-Bi_2O_3) nanostructure with a particle size 10 nm inducing agglomerated structure were synthesized by dissolving bismuth nitrate pentahydrate in diethylene glycol at 180 ℃ with post heat treatment.The prepared i-Bi_2O_3 nanostructures were employed for the construction of Au/i-Bi_2O_3 composite system and characterized by X-ray diffraction pattern,UV-visible diffuse reflectance spectroscopy(DRS),and transmission electron microscopy,X-ray photoemission spectroscopy(XPS) and Energy dispersive X-ray spectroscopy(EDS).The i-Bi_2O_3 nanostructure and Au/i-Bi_2O_3 composite system were found to exhibit high photocatalytic activity than commercial Bi_2O_3 in decomposing salicylic acid under visible light irradiation.The high catalytic activity of i-Bi_2O_3 nanostructure was deduced to be caused by charge separation facilitated by electron hopping between the particles within the integrated structure and space-charge separation between i-Bi_2O_3 and Au.The charge separation behavior in i-Bi_2O_3 nanostructure was further bolstered by comparing the measured.OH radical produced in the solution with i-Bi_2O_3 nanostructure,commercial Bi_2O_3 and Au/i-Bi_2O_3 composite which readily react with 1,4-terephthalic acid(TA) inducing 2-hydroxy terephthalic acid(TAOH) that shows unique fluorescence peak at 426 nm.The space-charge separation between i-Bi_2O_3 and An was confirmed by measuring the electron spin resonance(ESR) spectra.     

Competing crystallite size and zinc concentration in silica coated cobalt ferrite nanoparticles

Silica coated(30 wt%) cobalt zinc ferrite(Co1 xZnxFe2O4, x?0, 0.2, 0.3, 0.4, 0.5 and 1) nanoparticles were synthesized by using sol–gel method. Silica acts as a spacer among the nanoparticles to avoid the agglomeration. X-ray diffraction(XRD) reveals the cubic spinel ferrite structure of nanoparticles with crystallite size in the range 37–45 nm. Fourier transform infrared(FTIR) spectroscopy confirmed the formation of spinel ferrite and SiO2. Scanning electron microscopy(SEM) images show that the nanoparticles are nearly spherical and non-agglomerated due to presence of non-magnetic SiO2 surface coating. All these measurements signify that the structural and magnetic properties of Co1 xZnxFe2O4 ferrite nanoparticles strongly depend on Zn concentration and nanoparticle average crystallite size in different Zn concentration regimes.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

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.