Effect of solution pH value changes on fluorescence intensity of magnetic-luminescent Fe3O4@Gd2O3:Eu3+ nanoparticles

In this paper, bifunctional Fe3O4@Gd2O3:Eu3+ core-shell nanoparticles with both magnetic and fluorescent properties were synthesized through a urea homogeneous precipitation(UHP) method. Particular emphasis was placed on investigating the influence of the solution p H value on the photoluminescence of the core-shell nanocomposites. It showed that the samples treated at the solution of p H=3.0 had the highest luminescence due to the enhanced crystallinity and size uniformity of nanoparticles. The Fe3O4@Gd2O3:Eu3+ nanocomposites exhibited an almost spherical shape with a mean diameter of 60 nm, and had strong red emissions of Eu3+ at 612 nm as well as good magnetization with the saturation magnetization of 1.29 emu/g. It thus indicated that the core-shell nanocomposites investigated has great potential in biomedical applications.     

Study on Preparation and Properties of La2O3/MC Nylon Nanocomposites

MC nylon,monomer casting nylon,is a newtypeof engineering plastics,whichis synthesized by anion-ic polymerization with caprolactam as the major rawmaterial,under normal pressure,pouring directlyto amould preheatedto a certaintemperature.It has manyadvantages,such as low polymerized temperature,si mple technology,high crystallinity,low-cost,highequipment efficiency as well as good mechanical prop-erties,shock decrease but wear proof,corrosion-resis-ting,self-ubricant,chemicals-resisting,wide us…     

Magnetic and thermosensitive luminescent nanocomposites based on Fe3O4/SiO2/poly (N-isopropylacrylamide)/lanthanide-polyoxometalates and their controllable luminescence properties

Magnetic and temperature-responsive luminescent composites based on poly(N-isopropylacrylamide),magnetic nanoparticles and Na_9[EuW_(10)O_(36)] were fabricated. The composites were investigated by IR, UV,XRD, TGA, SEM and TEM. The prepared nanocomposites exhibit good superparamagnetic property and thermo-responsive switchable luminescence properties. The multifunctional nanocomposites can be separated by external magnetic field. Moreover, the nanocomposites exhibit an appreciable temperature response, and the red luminescence of the nanocomposites in solution can be controlled by the temperature stimuli. The hydrogel emits strong redluminescence in solution at 25 ℃,which can be seen by naked eyes. When the external temperature is 40 ℃, the red luminescence almost disappears in solution.It is expected that the multifunctional nanoparticles have potential applications in the field of biomedicine.     

Ordering transformations and mechanical properties of Ti3Ai and Ti3Al-Nb alloys

Phase transformations and the kinetics of domain growth were studied in near stoichiometric Ti₃Al and in a similar alloy containing about 5 at. pct Nb (Cb). The alloys were quenched from the β and from the α+ β fields and were subsequently annealed in the α₂ field to study the ordering transformation. The critical temperature (T _c) for ordering was found to be between 1125 and 1150° for both alloys. When quenched from aboveT _c the microstructure of the stoichiometric compound contained massive martensite with small antiphase domains of average size 8 × 10^— μm. On annealing the quenched structures in the range 700 to 1000°, domain coalescence occurred, the domains growing approximately as the square root of the annealing time. The activation energy for the domain growth process was found to be 64.6 ± 6 Kcal/mole (2.68 ± 0.25 × 10⁵ J/mole). On quenching the alloy containing Nb the β transforms to a fine acicular martensite. On annealing, antiphase domain coalescence within the martensite plates and the simultaneous recrystallization of the martensite resulted in a fine subgrain structure even after annealing at 900° for up to 3 h. The mechanical properties and the fracture modes of the two alloys tested at 700° were correlated with the observed microstructural changes. The effects of Nb in this alloy are to slow the domain growth kinetics, to reduce the planarity of slip, and to increase nonbasal slip activity. Formerly NRC Research Associate in the Air Force Materials Laboratory, Wright-Patterson Air Force Base, OH     

Unidirectionally solidified Ti−TiB and Ti−Ti5Si3 eutectic composites

Induction melting and electron beam melting techniques were employed in the production of unidirectionally solidified eutectic composites of Ti-1.7 wt pct B and Ti-8.5 wt pct Si. The grown eutectics were reinforced by 7.7 volume pct of TiB fibers and 31 volume pct of Ti₅Si₃ fibers respectively. Controlled dendritic solidification of a hypereutectic composition of Ti-12 wt pct Si was also accomplished. Tensile, compressive, creep, and stress rupture specimens were cut from the eutectic composites and tested with reinforcing fibers parallel to the load axis. Ti?TiB eutectic was found to have less than the critical volume fraction of fibers necessary for reinforcement, while Ti?Ti₅Si₃ composite attained a compressive yield strength of 275,000 psi and a compressive Young's modulus of 30×10⁸ psi after heat treatment. The 500 and 4000 hr stress rupture properties of Ti?Si eutectic were superior to commercial titanium alloys at 1000° and 1200°F. The minimum creep rate of Ti?Ti₅Si₃ eutectic composite was lower than all other titanium alloys at 1000°F. Tensile, compressive, and creep properties of the Ti-8.5 wt pct Si eutectic are discussed in terms of the current theories of composite behavior.     

Electrosynthesis of Ti5Si3, Ti5Si3/TiC,and Ti5Si3/Ti3SiC2 from Ti-Bearing Blast Furnace Slag in Molten CaCl2

Metallurgical and Materials Transactions B - Ti5Si3, Ti5Si3/TiC, and Ti5Si3/Ti3SiC2 have been electrochemically synthesized from the Ti-bearing blast furnace slag/TiO2 and/or C mixture precursors...     

Eco-friendly green synthesis of novel magnetic Fe_3O_4/SiO_2/ZnO-Pr_6O_(11) nanocomposites for photocatalytic degradation of organic pollutant

This study reports the successful so nochemical synthesis of novel Fe_3O_4/SiO_2/ZnO-Pr_6O_(11)(Fe/Si/Zn-Pr_6O_(11)) nanocomposites using fructose as a green capping agent.The influence of various parameters containing capping agent,power and time of ultrasound irradiation was investigated to reach optimum morphology and size conditions.The products obtained were characterized by transmission electron microscopy(TEM),UV/Vis diffuse reflectance spectroscopy(DRS),Fourier transform infrared spectra(FT-IR),vibration sample magnetometer(VSM),scanning electron microscopy(SEM),energy dispersive X-ray microanalysis(EDS) and X-ray diffraction(XRD).The Fe_3O_4/SiO_2/ZnO-Pr_6O_(11) nanocomposites display remarkably enhanced photocatalytic activity towards rhodamine b degradation(89.6%)and Congo red(84.7%) under UV irradiation compared with the other products.The results illustrate that the photocatalytic efficiency of magnetic nanocomposites is very much higher than pure Pr_6O_(11)nanostructures.Magnetic photocatalyst still has good stability after five successive runs.So,these recyclable nanocomposites can play a role in the treatment of both industrial and domestic contaminated water.     

Alloying behavior of Co3Ti

The alloying (substitution) behavior of Ll₂-type Co₃Ti({fx1433-01}) compound was investigated at an isothermal section of 1323 K by the observation of the direction of solubility lobe of Ll₂ phase. The solubility lobes of additions of V, Ta, Cr, W, and Al indicated that they substitute for Ti site, those of Ni and Cu for Co site, and that of Fe for both sites. However, the preferable substitution natures for additions of Zr, Hf, Nb, Mn, and Si, and of Mo and Ge were not determined because of the small solubility limit, and because of no preferable solubility lobe, respectively. The substitution behavior and solubility limit obtained in the ternary Co₃Ti compound were evaluated with the thermo-dynamic concept. The Research Institute for Iron, Steel and Other Metals The Research Institute for Iron, Steel and Other Metals     

Characterization of Ti4AlN3

Bulk samples of Ti₄AIN₃ were fabricated by reactive hot isostatic pressing (hipping) of TiH₂, AlN, and TiN powders at 1275 °C for 24 hours under 70 MPa. Further annealing at 1325 °C for 168 hours under Ar resulted in dense, predominantly single-phase samples, with <1 vol pct of TiN as a secondary phase. This ternary nitride, with a grain size of ≈20 μm on average, is relatively soft (Vickers hardness 2.5 GPa), lightweight (4.6 g/cm³), and machinable. Its Young’s and shear moduli are 310 and 127 GPa, respectively. The compressive and flexural strengths at room temperature are 475 and 350 MPa, respectively. At 1000 °C, the deformation is plastic, with a maximum compressive stress of ≈450 MPa. Ti₄AlN₃ thermal shocks gradually, whereby the largest strength loss (50 pct) is seen at a ΔT of 1000 °C. Further increases in quench temperature, however, increase the retained strength before it ultimately decreases once again. This material is also damage tolerant; a 100 N-load diamond indentation, which produced an ≈0.4 mm defect, reduces the flexural strength by only ≈12 pct. The thermal-expansion coefficient in the 25 °C to 1100 °C temperature range is 9.7±0.2 × 10⁻⁶ °C⁻¹. The room-temperature electrical conductivity is 0.5 × 10⁶ (Θ · m)⁻¹. The resistivity increases linearly with increasing temperature. Ti₄AlN₃ is stable up to 1500 °C in Ar, but decomposes in air to form TiN at ≈1400 °C. graduated from the Department in June of 1999 with an MS thesis.     

Ti3A1基合金研究

介绍了西北有色金属研究院(NIN)在“七五”、“八五”期间有关Ti3A1化合物基合金材料的研制情况，包括冶金制备、热加工、热处理、显微组织与力学性能等。并简要介绍了当前Ti3A1基合金国内外研究状况。     

Microstructure Investigation of Cu-Ni Base Al2O3 Nanocomposites: From Nanoparticles Synthesis to Consolidation

Metallurgical and Materials Transactions A - Different compositions of Cu-Ni/Al2O3 nanocomposites were prepared by a chemical-based synthesis of co-formed oxides (CuO-NiO-Al2O3) nanoparticles...     

Effects of Thermal and Cryogenic Conditionings on Flexural Behavior of Thermally Shocked Cu-Al2O3 Micro and NanoComposites

This investigation has used flexural test to explore the effects of thermal treatments, i.e., high-temperature and cryogenic environments on the mechanical property of Al₂O₃ particulate-reinforced Cu metal matrix micro and nanocomposites in ex-situ and in-situ conditions. Cu-5 vol. pct Al₂O₃ micro (10 μm)- and nanocomposites (<50 nm) fabricated by powder metallurgy route were subjected to up-thermal shock cycle [193 K to 353 K (?80 °C to 80 °C)] and down-thermal shock cycle [353 K to 193 K (from 80 °C to ?80 °C)] for different time periods followed by 3-point bend test. One batch of specimens (micro and nanocomposites) was conditioned at 353 K and 193 K (80 °C and ?80 °C) separately followed by 3-point flexural test. High-temperature flexural test was performed at 373 K and 523 K (80 °C and 250 °C) on the micro and nanocomposites. All the fractured samples obtained after various thermal treatments were studied under scanning electron microscope (SEM). The development of thermal stresses quite often results in concentration of residual stresses at the particle/matrix interface eventually weakening it. Enhancement of flexural strength was recorded for down- as well as for up-thermal shock in microcomposites. The high-temperature flexural strengths of micro and nanocomposites are lower than those at ambient temperature. The amelioration and declination in mechanical properties as a consequence of thermal shock, thermal conditioning, and high-temperature flexural testing have been discussed in the light of fractography.     

Combination of Mechanical and Electromagnetic Stirring to Distribute Nano-Sized Al2O3 Particles in Magnesium Matrix Composite

Powder Metallurgy and Metal Ceramics - In this article, a novel stirring method has been developed for producing metal matrix nanocomposites, in which two different stirring methods, i.e....     

Atomic ordering in Ni3Mn-Ni3Ti microcrystalline alloys

Neutron diffraction is used to determine the concentration dependences of the long-and short-range order parameters and the antiphase-domain size in Ni₃Mn-Ni₃Ti microcrystalline alloys produced by melt quenching and the initial bulk alloys quenched from 1433 K. The dependences of the order parameters on the order-disorder transition temperatures are determined. Microcrystals of the γ’ phase are found to have a high long-range order parameter as compared to this parameter in the bulk alloys. This fact is explained by the high degree of supersaturation of a solid solution with excess vacancies formed during melt quenching and, hence, a sharp increase in the atomic diffusion mobility.     

Concentration and annealing effect on PL properties of sol-gel derived SiO2-Y2O3:Eu3+ nanocomposites

An improved sol-gel method was employed to prepare Eu3+ ions doped SiO2-Y2O3 nanocomposites.Systematic study was carried out on the effect of post-annealing treatment on photoluminescence(PL) properties of the samples under various europium ions doping concentrations.X-ray diffraction(XRD) patterns indicated that the samples showed an amorphous matrix structure,and the scanning electron microscopy(SEM) pictures showed that the samples presented a nano size(from 21 to 42 nm) granular-stack structure after high-temperature annealing treatment(from 600 to 900 °C,respectively) for 3 h.Raman spectra demonstrated that Y3+ and Eu3+ ions were incorporated into the composites through the sol-gel and post-annealing process.Under the excitation of 394 nm(7F0→5L6) light,red emission was observed around 613 nm(5D0→7F2).Without annealing treatment,the optimized doping amount of Eu ions was about 6.5 mol.%,which was much higher than that single doped in SiO2 glass matrix with Eu ions concentration of 3%,and it raised to 9.0% when the samples were annealed at high-temperature(900 °C) annealing.     

纳米高强度复合材料的发展现状

本文介绍了纳米高强度复合材料所用的纳米材料制备方法、纳米复合材料制备工艺和强度改善进展。目前陶瓷纳米复合材料是人们开发的热点。碳纳米管与其它材料的复合材料的开发也是热点。最后介绍了应用前景。     

Ti3Ga and αTi interdiffusion between 660° and 860°C

Diffusion experiments were conducted in vacuum with bimetallic couples of the Ti₃Ga (α₂) composition and unalloyed α titanium. The gallium-composition profiles after various timetemperature exposures were determined by microprobe analyzer transverses and evaluated by established techniques. Results from this evaluation include the definition of the α to α +α₂ and the α + α₂ to α₂ phase boundaries for the Ti?Ga system and the determination of the interdiffusion coefficients for gallium in the α Ti and Ti₃Ga (α₂) phases. The interdiffusion coefficients were found to conform to the relationships: $$\tilde D_{\alpha Ti} = 4.4 \times 10^{ - 4} \exp [ - (43.4 \pm 4.7)10^3 /RT]cm^2 /\sec $$ $$\tilde D_{\alpha Ti_3 Ga} = 7.4 \times 10^{ - 5} \exp [ - (43.8 \pm 10.7)10^3 /RT]cm^2 /\sec $$