High-temperature tensile-hold crack-growth behavior of HASTELLOY<Superscript>®</Superscript> X alloy compared to HAYNES<Superscript>®</Superscript> 188 and HAYNES<Superscript>®</Superscript> 230<Superscript>®</Superscript> alloys

The creep–fatigue crack-growth tests of HASTELLOY^® X alloy were carried out at the temperatures of 649°C, 816°C, and 927°C in laboratory air. The experiments were conducted under a constant stress-intensity-factor-range (ΔK) control mode with a R-ratio of 0.05. In the constant ΔK tests, a ΔK of 27.5 MPa\(\sqrt{\mathrm{m}}\) and a triangular waveform with a frequency of 0.333 Hz were used. Various tensile hold times at the maximum load were imposed to study fatigue and creep–fatigue interactions. Crack lengths were measured by a direct current potential drop method. In this paper, effects of hold time and temperature on the crack-growth rates are discussed. Furthermore, the crack-growth rates of the HASTELLOY^® X alloy are compared to those of the HAYNES^® 188 and HAYNES^® 230^® superalloys.     

Spectroscopic properties of Nd<Superscript>3+</Superscript>, Yb<Superscript>3+</Superscript>-doped and Nd<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript>-codoped high silica glass

The Nd³⁺, Yb³⁺-doped and Nd³⁺–Yb³⁺-codoped high silica glasses (HSGs) were fabricated by sintering porous glasses impregnated with Nd³⁺ and Yb³⁺ ions solutions. The Judd–Ofelt theory was used to study the spectroscopic properties of Nd³⁺-doped HSGs. Large parameter Ω₂ of Nd³⁺-doped HSGs suggests a lower centrosymmetric coordination environment around the Nd³⁺ in HSG. The spontaneous emission probability and emission cross-section (σ_em) of Yb³⁺-doped HSGs are obtained. A broad emission band from 950 to 1,100 nm was detected when the Nd³⁺–Yb³⁺-codoped HSG was excited by 808 nm LD. The energy transfer process from Nd³⁺ to Yb³⁺ in HSG was described in this paper.     

Structure,electrical, and optical properties of ZnO-substituted PbO for the Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript> co-doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–GeO<Subscript>2</Subscript>–Na<Subscript>2</Subscript>O glass system

Glasses of the 0.5Er³⁺/2.5Yb³⁺ co-doped (40Bi₂O₃–20GeO₂–(30 − x)PbO–xZnO–10Na₂O system where x = 0.0, 5, 10, 15, 20, 25, and 30 mol%) have been characterized by FT-IR spectroscopy measurements to obtain information about the influence of ZnO-substituted PbO on the local structure of the glass matrix. The density and the molar volume have been determined. The influences of the ZnO-substituted PbO on the structure of glasses have been discussed. The dc conductivity measured in the temperature range 475–700 K obeys Arrhenius law. The conductivity decreases while the activation energy for conduction increases with increase ZnO content. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 400–1100 nm. The values of the optical band gap E _opt for all types of electronic transitions and refractive index have been determined and discussed. The real and imaginary parts ε₁ and ε₂ of dielectric constant have been determined.     

Effect of Zn<Superscript>2+</Superscript>, Ti<Superscript>2+</Superscript> dopants on structural,optical and electrochemical properties of V<Subscript>2</Subscript>O<Subscript>5</Subscript> nanoparticles synthesized via non-aqueous sol–gel route

Transition divalent metal cations (Zn²⁺, Ti²⁺) doped V₂O₅ nanoparticles were synthesized via non-aqueous sol–gel route. The influence of dopant materials on the characteristics of V₂O₅ nanoparticles was studied. XRD studies ensure that all the prepared samples possess phase pure orthorhombic structure. From the FESEM images, it was noted that the products possess uniform particle size around 20–30 nm. The presence of functional groups and dopants was confirmed by FTIR, Raman, and elemental analysis respectively. From UV–Vis spectra, the significant blue shift was observed for doped samples compared to pure V₂O₅ nanoparticles, which is attributed to the quantum confinement effect. The high capacity retention of the intercalation compound was measured by using C–V study and implies that the prepared samples are very promising electrode materials for supercapacitor.     

Role of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, and F<Superscript>–</Superscript> ions in octacalcium phosphate crystallization

We have synthesized octacalcium phosphate (OCP) in the presence of inorganic additives (magnesium, strontium, and fluoride ions) and studied the composition, morphology, thermal stability, and dynamic dissolution of the samples thus obtained. It has been shown that, in addition to OCP, magnesium and strontium ions favor the formation of brushite and hydroxyapatite (HA), whereas fluoride ions favor the formation of HA and fluorohydroxyapatite (FHA). We have proposed a process for the preparation of powder materials whose resorption kinetics in corrosive liquid media are corrected by adding dopants capable of activating the dissolution process.     

Refinement of the energy characteristics of <Superscript>213</Superscript>Bi α-radiation

Results of experiments on determination of the energy of ²¹³Bi α-particles for the existing lines with the intensities of 1.94 and 0.15% per decay are reported. The results were obtained by semiconductor α-ray spectrometry by comparison with the α-particle energies for the major lines of ²²¹Fr and ²¹³Po, known with a lower uncertainty. The experiments were designed so as to minimize and, at the same time, take into account factors affecting the deviations of the peak maxima from the true values. Special emphasis is made on the decay of recoil nuclei on the detector surface. To eliminate this effect, samples containing highly nonequilibrium systems ²¹³Bi + ²²¹Fr and ²¹³Bi + ²²⁵Ac were prepared. For the measurement conditions used, the equilibrium spectra of ²²⁵Ac with daughter decay products were found to be unsuitable for accurate determination of the energy of the ²¹³Bi major peak and can be used only for tentative estimations. The actual energies of ²¹³Bi α-radiation do not coincide with the assessed reference data used today and are in the region of the upper limit of the uncertainty range for these data. The results show that the presently used energy characteristics of ²¹³Bi α-radiation require refinement.     

Structural and dielectric properties of nanocrystalline Nd<Superscript>3+</Superscript> substituted nickel–zinc ferrites

Ferrite samples with general formula Ni_1−xZn_xNd_yFe_2−yO₄ (x = 0, 0.2, 0.4, 0.6, 0.8 and 1; y = 0.01, 0.02 and 0.03) were synthesized by oxalate co-precipitation technique. The X-ray diffraction study confirms the formation of single-phase cubic spinel structure. The lattice constant of the samples increases with increase in zinc content and obeys Vegard’s law. On Nd³⁺ substitution lattice constant of the samples slightly increases except zinc ferrite. The frequency dependence of the dielectric constant, dielectric loss and AC conductivity of the samples were determined in the frequency range from 20 Hz to 1 MHz at room temperature. The experimental results reveal that the dielectric constant and dielectric loss decreases where as AC electrical conductivity increases with increase in frequency. The dielectric loss increases with increase in zinc content whereas it decreases with increase in Nd³⁺ content. There is no appreciable change in permittivity of the samples with increase in Nd³⁺ content. Permeability of all the samples increases with increase in Nd³⁺ content. Because of lower dielectric loss, Nd³⁺ substituted Ni–Zn ferrites are useful in electronic devices.     

Synthesis,characterization and temperature studies on the conductivity of AlCl<Superscript>−</Superscript><Subscript>4</Subscript> ion doped polypyrrole

Synthesis of free standing conducting polypyrrole film using room temperature melt as the electrolyte is reported. We also report variation in the contribution of ionic conductance with temperature of the polymer film by four probe method and electrochemical properties like diffusion coefficient and ionic mobility of AlCl⁻₄ doped polypyrrole film. An attempt has been made to arrive at the stability of charge carrier concentration over a temperature range of 295 to 350 K under vacuum. The film was characterized by optical techniques and scanning electron micrography.     

Comparison of an experimental bone cement with surgical Simplex<Superscript>®</Superscript> P,Spineplex<Superscript>®</Superscript> and Cortoss<Superscript>®</Superscript>

Conventional polymethylmethacrylate (PMMA) cements and more recently Bisphenol-a-glycidyl dimethacrylate (BIS-GMA) composite cements are employed in procedures such as vertebroplasty. Unfortunately, such materials have inherent drawbacks including, a high curing exotherm, the incorporation of toxic components in their formulations, and critically, exhibit a modulus mismatch between cement and bone. The literature suggests that aluminium free, zinc based glass polyalkenoate cements (Zn-GPC) may be suitable alternative materials for consideration in such applications as vertebroplasty. This paper, examines one formulation of Zn-GPC and compares its strengths, modulus, and biocompatibility with three commercially available bone cements, Spineplex, Simplex P and Cortoss. The setting times indicate that the current formulation of Zn-GPC sets in a time unsuitable for clinical deployment. However during setting, the peak exotherm was recorded to be 33 degrees C, the lowest of all cements examined, and well below the threshold level for tissue necrosis to occur. The data obtained from mechanical testing shows the Zn-GPC has strengths of 63 MPa in compression and 30 MPa in biaxial flexure. Importantly these strengths remain stable with maturation; similar long term stability was exhibited by both Spineplex and Simplex P. Conversely, the strengths of Cortoss were observed to rapidly diminish with time, a cause for clinical concern. In addition to strengths, the modulus of each material was determined. Only the Zn-GPC exhibited a modulus similar to vertebral trabecular bone, with all commercial materials exhibiting excessively high moduli. Such data indicates that the use of Zn-GPC may reduce adjacent fractures. The final investigation used the well established simulated body fluid (SBF) method to examine the ability of each material to bond with bone. The results indicate that the Zn-GPC is capable of producing a bone like apatite layer at its surface within 24 h which increased in coverage and density up to 7 days. Conversely, Spineplex, and Simplex P exhibit no apatite layer formation, while Cortoss exhibits only minimal formation of an apatite layer after 7 days incubation in SBF. This paper shows that Zn-GPC, with optimised setting times, are suitable candidate materials for further development as bone cements.     

Characterization of <Superscript>4</Superscript>I<Subscript>9/2</Subscript> ↔ <Superscript>4</Superscript>F<Subscript>3/2</Subscript> optical transitions in trivalent Nd<Superscript>3+</Superscript> ions in GaLaS glass

The positions of Stark levels have been determined, using a step-by-step procedure, in the ⁴I_9/2 and ⁴F_3/2 manifolds of Nd³⁺ ions from absorption and photoluminescence measurements in the 12–293 K temperature range. This data has been used to calculate the emission cross-section for which the maximum value turns out to be ～2.3 × 10^?20 cm². The radiative recombination time, calculated using Judd–Ofelt analysis, of the ⁴F_3/2 manifold is in close vicinity to the experimentally determined times that were measured by the conventional decay of PL after interruption of excitation and by QFRS. Moreover, the peak time defined by QFRS is independent of temperature. Therefore, the dominant relaxation mechanism from the ⁴F_3/2 excited manifold of Nd³⁺ ions in GaLaS glass is believed to be by radiative emission.     

Synthesis of Yb<Superscript>3+</Superscript>, Ho<Superscript>3+</Superscript> and Tm<Superscript>3+</Superscript> co-doped β-NaYF<Subscript>4</Subscript> nanoparticles by sol–gel method and the multi-color upconversion luminescence properties

Well-crystalline β-NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles were synthesized by sol–gel method using isopropyl alcohol [(CH₃)₂CHOH] as a complexing agent. The samples were characterized by X-ray diffraction, scanning electron microscopic analysis and fluorescence spectrum analysis methods. Under the excitation of 980 nm laser diode (LD), the samples displayed bright upconversion luminescence (UCL), which was generated from the energy level transition of Ho³⁺ and Tm³⁺ ions. With the increase of Tm³⁺, Ho³⁺ and Yb³⁺-doping concentration, the UCL intensity of blue, green and red light emission of the samples varied. Calculation of the CIE color coordinate of the β-NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles revealed that with the adjustment of Tm³⁺, Ho³⁺ and Yb³⁺ doping concentration and the excitation power of 980 nm LD, the multi-color UCL can be realized. Approximately single red light output with the CIE color coordinate of x?=?0.545, y?=?0.306 and white light output with the CIE color coordinate of x?=?0.325, y?=?0.320 can be obtained in the synthesized β-NaYF₄: Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles.     

Photoluminescence of Eu<Superscript>3+</Superscript> ion in SnO<Subscript>2</Subscript> obtained by sol–gel

Photoluminescence data of Eu-doped SnO₂ xerogels are presented, yielding information on the symmetry of Eu³⁺ luminescent centers, which can be related to their location in the matrix: at lattice sites, substituting to Sn⁴⁺, or segregated at particles surface. Influence of doping concentration and/or particle size on the photoluminescence spectra obtained by energy transfer from the matrix to Eu³⁺ sites is investigated. Results show that a better efficiency in the energy transfer processes is obtained for high symmetry Eu³⁺ sites and low doping levels. Emission intensity from ⁵D₀→⁷F₁ transition increases as the temperature is raised from 10 to 240 K, under excitation at 266 nm laser line, because in this transition the multiphonon emission becomes significant only above 240 K. As an extension of this result, we predict high effectiveness for room temperature operation of Eu-based optical communication devices. X-ray diffraction data show that the impurity excess inhibits particle growth, which may influence the asymmetry ratio of luminescence spectra.     

Use of a nanostructured material for separation of <Superscript>238</Superscript>U and <Superscript>237</Superscript>U produced by the photonuclear reaction <Superscript>238</Superscript>U(γ, <Emphasis Type="Italic">n</Emphasis>)<Superscript>237</Superscript>U

²³⁷U was produced by the reaction ²³⁸U(γ, n) on an electron accelerator, MT-25 microtron, at the Flerov Laboratory of Nuclear Reactions. For the separation of ²³⁷U and [²³⁸U, the recoil nuclei were collected by a nanostructured material, hydrated manganese dioxide (of the cryptomelane type), in the solid-solid system. From fission products, ²³⁷U was separated by ion exchange. The specific activity of the resulting ²³⁷U was 4.5 × 10⁹ Bq (mg ²³⁸U)^-1, with the content of radioactive impurities of ≤10^-6 Bq Bq^-1. The chemical yield of ²³⁷U was 80%.     

Synthesis,electronic state,and particle size stabilization of nanoparticulate [Co(OH)<Subscript>2</Subscript>(H<Subscript>3</Subscript>O)<Stack><Subscript>δ</Subscript><Superscript>+</Superscript></Stack>]<Superscript>δ+</Superscript>

We have synthesized nanoparticulate cobalt(II) hydroxide containing Co²⁺ in tetrahedral oxygen coordination (Co _Td ²⁺ ), atypical of such systems: nano- [Co(OH)₂(H₃O) _δ ⁺ ]^δ+. The (Co _Td ²⁺ ) coordination in the hydroxide is inferred from its electronic diffuse reflectance spectrum, which shows a multiplet of strong absorption bands at 14500, 15000, and 16000 cm^?1 (⁴ A ₂(F)-⁴ T ₁(P) transition). Nanoparticulate cobalt(II) hydroxide forms in a weakly acidic medium under essentially nonequilibrium conditions due to supersaturation (by three to four orders of magnitude) with the starting reagents (CoCl₂ and LiOH) at the instant of the formation of the poorly soluble phase Co(OH)₂. Presumably, colloidal particles of nanoparticulate cobalt(II) hydroxide in a weakly acidic aqueous medium have a positive surface charge, compensated by a counter-ion (Cl^?) layer: nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ · δCl^?. The XRD patterns of pastes (gels) containing this hydroxide show three broad-ened lines with d = 5.31 (2θ = 16.7°), 2.77 (2θ = 32.3°), and 2.32 Å (2θ = 38.8°). According to small-angle X-ray scattering data, nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ has a narrow particle size distribution (1.0–2.0 nm). Synthesis and storage conditions are identified which ensure stabilization of the electronic state and particle size of nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ for a long time.     

Cathodoluminescence properties of SiO<Subscript>2</Subscript>:Pr<Superscript>3+</Superscript>and ZnO·SiO<Subscript>2</Subscript>:Pr<Superscript>3+</Superscript> phosphor nanopowders

The successful incorporation of ZnO nanoparticles in Pr³⁺-doped SiO₂ using a sol–gel process is reported. SiO₂:Pr³⁺ gels, with or without ZnO nanoparticles, were dried at room temperature and annealed at 600 °C. On the basis of the X-ray Diffraction (XRD) results, the SiO₂ was amorphous regardless of the incorporation of Pr³⁺ and nanocrystalline ZnO or annealing at 600 °C. The particles were mostly spherical and agglomerated as confirmed by Field Emission Scanning Electron Microscopy. Thermogravimetric analysis of dried gels performed in an N₂ atmosphere indicated that stable phases were formed at ≥900 °C. Absorption bands ascribed to ³H₄-³P_{(J = 0,1,2)}, ¹I₆ and ¹D₂ in the UV–VIS region were observed from SiO₂:Pr³⁺ colloids. The red cathodoluminescent (CL) emission corresponding to the ³P₀ → ³H₆ transition of Pr³⁺ was observed at 614 nm from dried and annealed SiO₂:Pr³⁺ powder samples. This emission was increased considerably when ZnO nanoparticles were incorporated. The CL intensity was measured at an accelerating voltage of 1-5 keV and a fixed beam current of 8.5 μA. The effects of accelerating voltage on the CL intensity and the CL degradation of SiO₂:Pr³⁺ and ZnO·SiO₂:Pr³⁺ were also investigated using Auger electron spectroscopy coupled with an Ocean Optics S2000 spectrometer.     

Density,Surface Tension,and Viscosity of CMSX-4<Superscript>®</Superscript> Superalloy

The surface tension, density, and viscosity of the Ni-based superalloy CMSX-4^® have been determined in the temperature ranges of 1,650–1,850 K, 1,650–1,950 K, and 1,623–1,800 K, respectively. Each property has been measured in parallel by different techniques at different participating laboratories, and the results are compared with the aim to improve the reliability of data and to identify recommended values. The following relationships have been proposed: density-ρ (T) [kg· m^?3] = 7,876 ? 1.23(T ? 1,654 K); surface tension-γ (T) [mN·m^?1] = 1,773 ? 0.56 (T ? 1, 654 K); viscosity-η (T) [mPa·s] = 8.36 ? 1.82 × 10^?2(T ? 1,654 K). For a comparison, surface-tension measurements on the Al-88.6 at% Ni liquid alloy with the same Al-content as the CMSX-4^® alloy were also performed. In addition, the surface tension and density have been theoretically evaluated by different models, and subsequently compared with new experimental data as well as with those reported in the literature. The surface-tension experimental data for the liquid CMSX-4^® alloy were found to be close to that of the Al-88.6 at% Ni alloy which is consistent with results from the compound formation model (CFM).     

Mechanochemical synthesis of γ-LiAlO<Subscript>2</Subscript> studied by <Superscript>6</Superscript>Li and <Superscript>27</Superscript>Al NMR and synchrotron X-Ray diffraction

The structural transformations accompanying the mechanochemical synthesis of fine-particle γ-LiAlO₂ have been studied by ⁶Li and ²⁷Al NMR and in situ X-ray diffraction. Mechanical activation of a mixture of aluminum hydroxide and lithium carbonate in an AGO-2 planetary mill results not only in size reduction, intermixing, and partial amorphization of the starting materials but also in the mechanochemical synthesis of a carbonate form of aluminum lithium hydroxide. Subsequent heat treatment of the mechanically activated mixture leads to the release of water and carbon dioxide molecules and the formation of an X-ray amorphous phase containing aluminum in octahedral and tetrahedral oxygen coordination. The X-ray amorphous material converts to gamma lithium aluminate through an intermediate phase.     

Intense 2.0 µm emission from Ho<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript> co-doped Na<Subscript>5</Subscript>Lu<Subscript>9</Subscript>F<Subscript>32</Subscript> single crystal excited by 980 nm

This paper reported on optical spectra of Na₅Lu₉F₃₂ single crystals co-doped with ~?0.91 mol% Ho³⁺ and various Yb³⁺ concentrations by using an improved Bridgman method. The emission spectra and fluorescence decay curves were measured to investigate the luminescent properties of the Ho³⁺/Yb³⁺ co-doped Na₅Lu₉F₃₂ and the energy transfer process from Yb³⁺ to Ho³⁺ ion. Compared with the Ho³⁺ singly doped Na₅Lu₉F₃₂ crystal, the Ho³⁺/Yb³⁺ co-doped crystal had an obviously enhanced emission at 2.0 µm via the 980 nm laser diode excitation because of the efficient energy transfer from Yb³⁺ to Ho³⁺ ion. The maximum emission intensity at 2.0 µm was obtained at about 6.99 mol% Yb³⁺ concentration when the concentration of Ho³⁺ ions is fixed at ~?0.91 mol% in the current research. The maximum emission cross section of the above sample at 2.0 µm was calculated to be 1.23?×?10^?20 cm² according to the measured emission spectrum. The energy transfer efficiency from Yb³⁺:²F_5/2 to Ho³⁺:⁵I₆ for the crystal was estimated up to 90.8% indicating that Yb³⁺ ions can efficiently sensitize the Ho³⁺ ions.     

Stability of the LaCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> and LuCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> Ions Studied by Mass Spectrometry

The enthalpy stability of the LaCl ₄ ^? and LuCl ₄ ^? ions is assessed using high-temperature mass spectrometry. The enthalpy of Cl^? detachment is determined to be Δ_rH⁰(298.15 K) = 332 ± 10 kJ/mol for LaCl ₄ ^? and 359 ± 10 kJ/mol for LuCl ₄ ^? .     

Estimating the effect of C<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> and C<Stack><Subscript>3</Subscript><Superscript>+</Superscript></Stack> radicals and neutral clusters on the fullerene formation

The mass spectrum of the products of arc discharge in helium between graphite electrodes has been studied for various values of the gas flow rate. As the gas flow rate increases, the intensity of C₆₀^±, C₇₀^±, C₈₄^± and C₉₀^± fullerene peaks increases and that of the C₂⁻ and C₃⁺ cluster radicals decreases, but the total decay in radicals amounts to only 21% of the total growth of fullerenes. From this it follows that a contribution to the formation of fullerenes from the neutral clusters (which are taken into account for the first time) significantly exceeds the contribution due to small radical species.