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The deuterium–tritium (D–T) reaction has been identified as the most efficient reaction for fusion devices. Deuterium can be obtained by heavy water electrolysis. Heavy water (D 2 O) with a high purity level is necessary for nuclear fusion application. A D 2 O isotopic analysis is thus very important. A system for a heavy water analysis was built and a newly designed isotopic analysis experiment was carried out. We tried to analyze the D 2 O purity using Fourier Transform infrared (FT-IR) spectroscopy and newly introduced off-axis integrated cavity output spectroscopy (OA-ICOS). We found that the OA-ICOS based on measurement via laser absorption spectroscopy shows very high sensitivity. We ameliorated the sensitivity by an order of magnitude of more than 10 3 –10 5 . We could make the apparatus smaller by employing very tiny diode laser and fiber optics elements of a DFB (Distributed Feedback) type. Consequently, our device has advantages in terms of maintainability and mobility even in a radioactive environment. This new method could be used for an accurate isotopic analysis in the future.

Scaling factors have been applied to the estimation of the spectroscopic constants of pure isotopologues of two polyatomic molecules: ammonia (NH 3 ) and formaldehyde (HCHO). Vibrational frequencies and rotational constants of four isotopologues of each molecule have been calculated using the resolution-of-the-identity second-order coupled cluster (RICC2) and coupled cluster singles and doubles (CCSD) methods with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. It has been observed that the scaling factors for the vibrational frequencies and rotational constants of the isotopologues are dependent on the isotopic mass. With the given scaling factors calculated at the CCSD/aug-cc-pVTZ level of theory, the experimental spectroscopic data are reproduced with an error range of 0.6% for the D 13 CD 16 O isotopologue. In addition, the spectrum of H 13 CH 16 O is accurately predicted with the scaling factors calculated from the other isotopologues. The estimated spectrum is in good agreement with the experimental spectrum.

A micro-beam scanning X-ray photoelectron spectroscopy (XPS) has been utilized to obtain information about the attachment of ligand to nanoparticles in solution by measuring the ligand components relative to nanoparticle components. CdSe/ZnS core/shell nanoparticles capped with three different kinds of ligand molecules are drop-casted on a substrate and led to dry into self-agglomerated micropatterns. Those specimens are mapped out by element-sensitive XPS imaging. The spatial correlation between surface ligand molecules and core nanoparticle atoms is statistically analysed using Pearson correlation function, which provides with a useful assessment of the ligand binding to nanoparticle surfaces. Copyright © 2014 John Wiley & Sons, Ltd.

We have used X-ray diffraction and photoluminescence measurements to investigate the effects of helium annealing of ZnO single crystals grown by using the hydrothermal method. The crystal structure of the grown ZnO single crystal was hexagonal with cell parameters a = 0.3249 and c = 0.5206 nm. The crystal structure did not change after helium annealing. The full width at half-maximum (FWHM) of the (002) diffraction peak following the helium annealing treatment decreases to 0.048° from 0.093° for the as-grown sample, indicating improved crystalline quality. The PL spectra of the crystals showed near-band-edge and visible (green and yellow) emission bands. The PL intensity of the near-band edge emissions of helium-annealed sample was increased while that of the yellow emission band was decreased. From the temperature dependence of the PL spectra, the peak positions of the free exciton (FE) and the donor-bound exciton (BE) shifted to lower energy whereas the visible emission bands show an anomalous temperature-dependent behavior.

Gold nanoparticles (AuNPs) and poly(ethylene glycol) (PEG) are known to be safe, biocompatible materials. In this study, AuNPs were conjugated with PEG ligands, and the suspensions of AuNPs with and without free PEG ligands were characterized using UV-visible spectroscopy, hydrodynamic size measurement, and time-of-flight SIMS (ToF-SIMS) imaging analysis. The two AuNPs solutions were each dropped onto a hydrophilic surface (bare Si wafer) and a hydrophobic surface (a plasma-polymerized cyclohexane-coated Si wafer), then dried to produce self-aggregated micropatterns, from which ToF-SIMS images were obtained. From these ToF-SIMS images, we calculated the Pearson product–moment correlation coefficient (PMCC) of the AuNPs and PEG intensities to quantitatively measure the coexistence of both materials in the solution. Good coexistence between AuNPs and PEG ligands was obtained only from the sample film prepared by dropping the suspension of PEG-conjugated AuNPs without free ligands onto a hydrophobic surface. The degrees of coexistence (i.e. PMCC value) seem to correlate with the amount of free PEG ligands in suspension to affect the stability of organic conjugated nanoparticles in solution. In addition, it was found that minimal interaction between the conjugated ligands and the substrate used for the sample film preparation led to an optimum PMCC statistical analysis. Our results lead us to believe that this new approach could simplify the method by which to quantitatively study the degrees of coexistence between nanoparticles and ligands, the amount of free ligands, and the stability of ligand-conjugated nanoparticles in suspension. Copyright © 2012 John Wiley & Sons, Ltd.

Gold nanoparticles (AuNPs) and poly(ethylene glycol) (PEG) are known safe materials to be used in vivo, and so, are becoming increasingly important in biomedical applications. Here, the stability of PEG-conjugated AuNPs in an aqueous solution was monitored as a function of time using several techniques, namely dynamic light scattering (DLS)-size analysis, UV-visible absorption spectrometry and ToF-SIMS. Roughly 15-nm-sized AuNPs were synthesized and pegylated with mPEG (MW = 5 kDa). Four different samples were synthesized, depending on whether or not a dialysis procedure was performed right after synthesis of the AuNPs or pegylation of the AuNPs. The DLS results show that size of mPEG-conjugated AuNPs and standard deviation increased in cases where a dialysis procedure was performed after pegylation of the AuNPs, indicating aggregation of the AuNPs due to the detachment of mPEG ligands from the surface of the AuNPs. Also, results from UV-visible absorption spectra and ToF-SIMS images point to the likelihood that free mPEG ligands in solution help prevent aggregation by maintaining a dynamic equilibrium between the conjugated ligands on the surface of the AuNPs and the free ligands in the aqueous solution. Conversely, once free, mPEG ligands were eliminated from the solution by dialysis and conjugated mPEG ligands detached from the surface of AuNPs into the solution, suspension stability lowered and the AuNPs showed signs of aggregation. We believe that the ToF-SIMS imaging analysis with DLS and UV-visible absorption analyses would be useful to study the stability of PEG-conjugated AuNPs in different environmental conditions.

This study examines the effect of calcium oxide (CaO) addition to Ce 0.9 Gd 0.1 O 1.95 (gadolinia-doped ceria, GDC) containing 500 ppm SiO 2 on grain-interior and grain-boundary conduction. The GDC can be used as a solid electrolyte for intermediate and low-temperature solid oxide fuel cells. Doping with ≥2 mol% CaO results in a decrease in apparent grain-boundary resistivity at 300 °C from 746.7 kΩ cm to 2.8–3.5 kΩ cm. The total resistivity exhibits a minimum at 2 mol% CaO. Further increase in CaO concentration to 10 mol% results in an increase in grain-interior resistivity from 3.1 to 40 kΩ cm. Although most of the CaO is incorporated into the GDC lattice, a small amount of CaO scavenges the intergranular siliceous phase, which leads to a significant increase in grain-boundary conduction. The increase in grain-interior resistivity at high CaO concentration is attributed to defect association between V O and Ca Ce ″.

We have developed a laser isotope separation technology for the production of the 168Yb and 176Yb isotopes. 168Yb is very useful for the generation of a non destructive testing source, 169Yb. 176Yb can be used to produce 177Lu which is known to be a promising radioisotope for a medical application. For these applications, the abundances of 168Yb and 176Yb isotopes should be enriched to more than 15% and 97%, respectively. Our developed system consists of three dye lasers pumped by a diode-pumped solid-state laser, a Yb evaporator, and a photo-ion extractor. Up to now, we could enrich 168Yb to more than 31% with a productivity of 0.5 mg/h. Also, we succeeded in enriching 176Yb to more than 97% with a productivity of 27 mg/h.

We investigate the ferroelectric properties of Pb(Zn1/3Nb2/3)O3–PbTiO3(PZN–PT)-based ceramics, which are stabilized by adding a small amount of NaNbO3 (NN) and KNbO3 (KN). As the content of alkali niobate increased, the ferroelectric properties of Pb(Zn1/3Nb2/3)O3–PbTiO3–RNbO3 (PZN–PT–RN; R=Na, K) became softer, which was more pronounced in PZN–PT–KN. The difference in the piezoelectric properties between PZN–PT–KN and PZN–PT–NN was explained by the cation size effect. Because the ionic size of Na is smaller than that of K, the Na ion can retain the ferroelectricity of the solid solution more effectively. The field-induced strain of 85PZN–5PT–10NN under 10 kV/cm was as high as 0.1%. Also, the addition of NN increased the tunability of dielectric constant significantly. At a composition of 85PZN–5PT–20NN, the tunability was 90% and no hysteresis was observed. In contrast to RN, the increase in the content of PT caused the transition from relaxor to normal ferroelectrics, which were accompanied by the structural change from the rhombohedral to tetragonal phase.

LiFePO 4 is one of the promising materials for cathode of secondary lithium batteries due to its high energy density, low cost, environmental friendliness and safety. However, LiFePO 4 has very poor electronic conductivity (∼10 −9 S cm −1 ) and Li-ion diffusion coefficient (∼1.8 × 10 −14 cm 2 s −1 ) at room temperature. In an attempt to improve electrochemical properties, Li X FePO 4 with various amounts of Li contents were investigated in this study. Li X FePO 4 ( X = 0.7–1.1) samples were synthesized by solid-state reaction. High resolution X-ray diffraction, Rietveld analysis, BET, scanning electron microscopy, and hall effect measurement system were used to characterize these samples. Electronic conductivities of the samples with Li-deficient and Li-excess in Li x FePO 4 were 10 −3 to 10 −1 S cm −1 . Discharge capacities and rate capabilities of the samples with Li-deficient and Li-excess in Li X FePO 4 were higher than those of stoichiometric LiFePO 4 sample. Li 0.9 FePO 4 samples fired at 700 °C had discharge capacity of 156 and 140 mAh g −1 at 0.1 C- and 2 C-rate, respectively.

Al substituted Li 1 + x Al x Hf 2 − x (PO 4 ) 3 ( x = 0.0∼0.5) solid electrolytes were prepared by conventional sintering (CS) and spark plasma sintering (SPS), and the Li + ion conductivity of the sintered pellets was examined using an impedance analyzer. All the samples exhibited a rhombohedral NASICON-type structure. SPS improved the densification compared to CS, and Al substitution further increased the sample density resulting in a maximum density of ∼90%. The Li + ion conductivity increased in proportion to the sample density and the highest conductivity of 1.1 × 10 − 4 Scm − 1 was found in the Li 1.5 Al 0.5 Hf 1.5 (PO 4 ) 3 SPS specimen, which is comparable to the best value reported elsewhere. The activation energy of the total conductivity (bulk + grain boundary) reduced from 0.39 to 0.28 eV with Al substitution. The enhanced conductivity was discussed in terms of the densification, bottleneck size, and lithium ion content.

Solid electrolytes, LiTi2(PO4)3 (LTP), Li1.3Al0.3Ti1.7(PO4)3 (LATP), and Li1.3Al0.3Ti1.7(PO4)2.9(VO4)0.1 (LATPV), were prepared by conventional sintering (CS) and spark plasma sintering (SPS) methods, and the Li+ ion conductivity of the sintered pellets was examined using an impedance analyzer. SPS remarkably improved the densification compared to CS and resulted in dense ceramics (95–97% of theoretical density) irrespective of the substituted ions. The highest conductivity of 2.6 × 10−4 S/cm was found for the LATPV specimen sintered by spark plasma at 1100°C. LATP and LATPV exhibited an order of magnitude higher ionic conductivity than LTP in the specimens of similar densities. The results demonstrated that the enhanced conductivity in substituted LTP is not due to the enhanced densification alone. The other possible explanations are discussed in terms of bottleneck size, lithium content, and grain boundary characteristics.

The dielectric properties and their related microstructural characteristics in solid solutions of (1 - x)Ba(Mg 1/3 Nb 2/3 )O 3 (BMN)-xLa(Mg 2/3 Nb 1/3 ))O 3 (LMN) (BLMN) were investigated by measuring the relative permittivity (e r ), Q value, and temperature coefficient of resonator frequency (τ f ), and by observing the microstructure using transmission electron microscopy. The trend of variation of the temperature coefficient of the dielectric permittivity (τ e ) was the same for our solid solutions as that reported by Reaney et al. When the tolerance factor (t) was >1.01 in BLMN with composition x = 0 to 1.0, where the tilting of oxygen octahedra was not involved, the components of the microstructure included a disordered and transition phase as well 1:1 and 1:2 ordered phases. In the region where 1.01 < t < 0.96 with x = 0.2 to 0.7, the 1:1 order, the disorder, and the phase due to the antiphase tilting of oxygen octahedra were present. Finally, in the region where t < 0.96 with x = 0.7 to 1.0, the microstructure of BLMN was the same as that of the pure LMN, including the 1:1 order and the antiphase, inphase tilting of oxygen octahedra, and the antiparallel shift of A-site cations.

Dielectric properties and their related microstructural characteristics in solid solutions of (1 –x)Ba(Mg1/3Nb2/3)O3–xSr(Mg1/3Nb2/3)O3 (BMN–SMN, or BSMN) were investigated by measuring the relative permittivity (ɛr), Q values, and temperature coefficient of resonator frequency (τf), and by observing microstructure using transmission electron microscopy. When the tolerance factor (t) was >0.99 in BSMN with composition 0 t > 0.97 with 0.7 < x < 1.0, the phase due to the antiphase tilting of oxygen octahedral, the disordered phase, and the 1:2 ordered phase were also present. In a few of the grains, core–shell-type structures, whose main components were dislocations and stacking faults, were found in the solid solution of BSMN.

The effect of ZrO2 on crystallographic order, microstructure, and microwave dielectric properties of Ba(Zn1/3Ta2/3)O3 (BZT) ceramics was investigated. A small amount of ZrO2 disturbed the 1:2 cation ordering. The average grain size of the BZT significantly increased with the addition of ZrO2, which was attributed to liquid-phase formation. The relative density increased with the addition of a small amount of ZrO2, but it decreased when the ZrO2 content was increased. Variation of the dielectric constant with ZrO2 addition ranged between 27 and 30, and the temperature coefficient of resonant frequency increased abruptly as the ZrO2 amount exceeded 2.0 mol%. The Q value of the BZT significantly improved with the addition of ZrO2, which could be explained by the increased relative density and grain size. The maximum Q×f value achieved in this investigation was ∼164 000 GHz for the BZT with 2.0 mol% ZrO2 sintered at 1550°C for 10 h.

Based on laser absorption spectroscopy (LAS), we developed a vapor density monitor for controlling the vaporization rate of Yb using a tunable diode laser. The laser source consisted of an extended cavity violet diode laser which has an emission wavelength of 398.8 nm coincident with the Yb absorption transition line, 6s(2) 1S(0)-6s6p 1P(1). The light emitted from the diode laser was transmitted across an atomic vapor column generated by heating the Yb metal, while the laser frequency was scanned across the atomic transition line. By comparing the amount of incident light to the amount of light transmitted after the light passed through the vapor column, the vapor density was determined using the Beer's law. From the experimental results, we demonstrated that the diode-laser-based LAS operated successfully for the real-time monitoring of the Yb vapor density.

Ba(Zn1/3Ta2/3)O3 (BZT) ceramic has 1:2 ordered hexagonal structure, but was destroyed with the addition of ZrO2. The 1:1 ordered cubic structure was developed when a large amount of ZrO2 was added. BZT has a porous and inhomogeneous microstructure with a Ba5Ta4O15 second phase. When ZrO2 was added, a new Ba0.5TaO3 second phase formed and grain growth occurred. Presence of liquid phase which is related to the Ba0.5TaO3 second phase could be responsible for the grain growth. Q value of BZT was greatly enhanced with the addition of ZrO2. The improvement of Q value can be explained by the increase of relative density and grain size. Especially, grain size is considered to be one of the crucial factors for the improvement of Q value of BZT ceramic.

The microstructure and microwave dielectric properties of (1-x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 [(1-x)BCN–xBZN] ceramics with 0.0≤x≤1.0 were investigated. When the sintering temperature was 1400°C, a homogeneous phase with a 1:2 ordered structure was found in the specimens with x≤0.3 but for the specimens with x≥0.6, a disordered structure and BaNb6O16 second phase were found. The grain growth related to the BaNb6O16 second phase occurred in the specimens with x≥0.5. The temperature coefficient of the resonant frequency (τf) increased with increasing x, and the specimens with 0.3≤x≤0.4 have zero τf. Dielectric constant (er) increased with the increase in x and was about 34.5 when x=0.3. For the specimens with x≤0.3, the Q×f value was high but decreased as x exceeded 0.3. The maximum Q×f value, 97,000 GHz, was obtained for 0.7BCN–0.3BZN ceramics sintered at 1400°C for 20 h.

Zn and/or Fe substituted alinite cement was synthesized using reagent grade chemicals, and its formation and hydration behavior were investigated. Mg, which is known to be essential for alinite formation, was completely replaced by Zn. XRD, FT-IR, and 29Si MAS NMR results indicated that a Zn substituted alinite was a nearly single phase and was easy to grind compared to Mg-alinite. In addition, partially or fully Zn substituted alinite had superior hydration characteristics, and NMR results showed that most of the alinite was hydrated after 100 days. Fe substitution of Al was not effective for alinite formation and its hydration properties were similar to Mg-alinite. Cl− ions leached out during alinite hydration, but the exsolution of Zn and Fe was below the detection limit.

Ba(Co1/3Nb2/3)O3(BCN) has a 1:2 ordered hexagonal structure. A large amount of the liquid phase, which contains high concentrations of Ba and Nb ions was found in the BCN ceramics. Q-values of BCN increased with increasing sintering temperature; however, it significantly decreased when the sintering temperature exceeded 1400 °C. The presence of a large amount of liquid phase could be responsible for the decrease of the Q-value. For (1−x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 [(1−x)BCN–xBZN] ceramics, the 1:2 ordered hexagonal structure was observed in the specimens with x⩽0.3 and the BaNb6O16 second phase was found in the specimens with x⩾0.6. Grain growth, which is related to the BaNb6O16 second phase occurred in the specimens with x⩾0.5. In this work, the excellent microwave dielectric properties of τf=0.0 ppm/°C, er=34.5 and Q×f=97,000 GHz were obtained for the 0.7BCN–0.3BZN ceramics sintered at 1400 °C for 20 h.

Ba(Co1/3Nb2/3)O3 (BCN) ceramics has a 1:2 ordered hexagonal structure and the degree of the 1:2 ordering slightly decreased when the sintering temperature exceeded 1400°C. A large amount of the liquid phase was found in the BCN ceramics sintered above 1400°C the formation of which is related to the evaporation of CoO. The liquid phase contains high concentrations of Ba and Nb ions. The grain size increased for the specimens sintered above 1400°C due to the presence of the liquid phase during the sintering. The Q-value of BCN increased with increasing sintering temperature and the specimen sintered at 1400°C had the maximum Q-value. When the sintering temperature exceeded 1400°C, however, the Q-value significantly decreased. The presence of a large amount of liquid phase could be responsible for the decrease of the Q-value. BCN ceramics were also sintered for various times at 1400°C and 1450°C and the variations of the microwave dielectric properties were explained in terms of the grain size and the relative density.

Crystal structure and microwave dielectric properties of (1− x )NdAlO 3 – x CaTiO 3 ceramics have been investigated. Crystal structure of the specimens changed with the composition. Rhombohedral structure was found for the specimens with x ≤0.1. When 0.3≤ x ≤0.7, the specimens had the tetragonal structure and it changed to the orthorhombic structure as x exceeded 0.7. Two types of the second phases were observed in (1− x )NdAlO 3 – x CaTiO 3 ceramics. For the specimens with x ≤0.5, Nd 4 Al 2 O 9 phase was observed and Al-rich phase was found in the specimens with x ≥0.7. The dielectric constant ( e r ) and the temperature coefficient of the resonant frequency ( τ f ) increased with the increase of x . The Q × f value of the specimen increased with x and exhibited the maximum value when x =0.5. The microwave dielectric properties of Q × f =45,000 GHz, e r =45 and τ f =−1.5 ppm/°C were obtained for 0.3NdAlO 3 –0.7CaTiO 3 ceramics.

The effect of Ga2O3 on the microstructure and microwave dielectric properties of Ba(Zn1/3Ta2/3)O3 (BZT) ceramics was investigated. The 1:2 ordered hexagonal structure disappeared with the addition of Ga2O3. The average grain size of BZT increased with the addition of Ga2O3, which was attributed to the liquid phase formation. The liquid phase contains high concentrations of Ba and Ga ions. The relative density of the specimen increased with the addition of a small amount of Ga2O3 but it decreased when the Ga2O3 content was increased. Variation of the dielectric constant with Ga2O3 addition was similar to that of the relative density and ranged between 27 and 29. The temperature coefficient of resonant frequency decreased with increasing Ga2O3. The Q×f value of BZT was about 88,000 GHz and it significantly improved with the addition of Ga2O3. The maximum Q×f value achieved in this investigation was about 161,000 GHz for the BZT with 1.0 mol% Ga2O3 sintered at 1550°C for 10 h.

Microstructure and microwave dielectric properties of (1-x)NdGaO3–xCaTiO3 ceramics have been investigated. Crystal structure of all the specimens was orthorhombic and the lattice parameters decreased with an increase of x. For specimens with x ≤0.5, a Nd3Ga5O12 phase was observed. The Q value of Nd3Ga5O12 ceramics was about 10,000 at 12 GHz and the dielectric constant (er) was about 12. A liquid phase was found in the specimens with x ≥0.5, containing a high concentration of Ca and Ga ions. The dielectric constant and the temperature coefficient of resonant frequency (τf) of the specimens increased with an increase of x. The Q ×f value of the NdGaO3 specimen was about 85,000 GHz and it decreased inversely with x. Excellent microwave dielectric properties of Q ×f=46,000 GHz, er=45 and τf=-2.0 ppm/°C were obtained for (1-x)NdGaO3–xCaTiO3 ceramics.

Microstructure and microwave dielectric properties of (1 m x)NdGaO 3 -xCaTiO 3 ceramics have been investigated. For specimens with x h 0.5, a Nd 3 Ga 5 O 12 phase was observed. A liquid phase was found in the specimens with x S 0.5, containing a high concentration of Ca and Ga ions. The dielectric constant ( l r ) and the temperature coefficient of the resonant frequency ( ‰ f ) of the specimens increased with an increase of x. The Q 2 f value of the NdGaO 3 ceramics was about 85,000 GHz, and decreased inversely with x. Excellent microwave dielectric properties of Q 2 f=46,000 GHz, l r =45 and ‰ f = m; 2 ppm/°C were obtained for 0.35NdGaO 3 -0.65CaTiO 3 ceramics.

(Mg0.22Mn0.07Fe0.71)3–δO4 ferrites with different oxygen nonstoichiometry (δ) were prepared in the range of −0.006 ≤ δ ≤ 0.0050 by a solid-state electrochemical technique, and their lattice parameter–nonstoichiometry correlation was examined. It was found that the lattice parameter decreases with increasing deviation (|δ|) from the stoichiometric composition (δ = 0). The electrochemical technique is detailed, and the correlation is discussed in light of defect structure of the ferrite.

We have grown (Mn 0.7 Cr 0.3 ) 2 As and (Fe 0.7 Mn 0.3 ) 2 As thin films directly on Si (1 0 0) substrate by molecular beam epitaxy at the substrate temperature, T S =300 °C. We found that the crystal structure of (Mn 0.7 Cr 0.3 ) 2 As and (Fe 0.7 Mn 0.3 ) 2 As thin films was the tetragonal Mn 2 As type with the lattice constants of a= 3.745 and 3.70A, respectively. (Mn 0.7 Cr 0.3 ) 2 As thin film shows spin-glass behaviour below 130 K, while (Fe 0.7 Mn 0.3 ) 2 As alloy has ferrimagnetic ordering at above room temperature.

Silicon carbide has specific advantages over other structural ceramics, such as high temperature capability and excellent chemical stability. So silicon carbide is a promising candidate for high temperature structural materials as well as for corrosion resistance applications. Like brittle materials, however, strength of silicon carbide is closely related to the size and distribution of surface flaws such as machining-induced cracks, because of their inherent low toughness. Thus, a smooth polishing procedure after grinding is often needed in order to reduce the size of surface flaws, leading to an increase in cost of ceramic components. Moreover, the allowable flaws in ceramics are so small that it is almost impossible to detect the flaws and also difficult to remove them completely using machining techniques. As a result, the structural integrity of a ceramic component is seriously affected. A method, to heal a crack, could be considered to overcome this problem. Studies on crack healing have been reported for alumina [1–3], silicon nitride [4–6], silicon nitride/silicon carbide composite [7], Mullite/silicon carbide composite [8] and silicon carbide [9–12]. Our research group recently proposed a mechanism of crack healing and strengthening by pre-oxidation procedure in silicon carbide [11, 12]. The major observation is that the residual stress produced by the thermal expansion mismatch between silica (within cracks) and surrounding silicon carbide played a significant role in the strength increase. As the crack healing technique can be adopted in practical strength applications, considerable advantages can be expected either in the reliability or in the machining and inspection costs of ceramic components. In the above perspectives, the effect of pre-oxidation on strength of silicon carbide with grinding-induced surface cracks was investigated and reported in the present communication. SiC material (Hexoloy, Carborandom, Inc., USA) was received in a plate form. The microstructure of the material consisted of SiC grains smaller than 10 lm and average grain size is about 5 lm (see Fig. 1). The material was machined into flexure specimens of 3 mm · 4 mm · 40 mm. The specimen surface was ground using diamond wheels with girt sizes of 127 lm, 64 lm, 42 lm and 32 lm. Grinding conditions were: 3,300 rpm, 35 m/s peripheral wheel speed and 10 lm depth of cut. The specimens were mounted on a holder in such a manner that grinding was oriented along the width of the specimens (perpendicular to the tensile stresses applied during the strength measurement). The ground specimens were then heat-treated at 1,500 C for 50 h in air. The heating rate was 10 C/min and cooling was done by turning off the electric power of the furnace. For comparison, some heat treatment experiments were also conducted in vacuum under similar conditions. The microstructure was characterized by field-emission scanning electron microscopy (FESEM), Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD). The strength of specimens was measured using a four-point bending fixture with outer and inner spans of 30 mm and 10 mm, respectively at a crosshead speed of 0.5 mm/min, as per the standard procedure [13]. Specimens were placed in the fixture such that the surface containing grinding-induced cracks was in M. C. Chu (&) AE S. J. Cho AE G. J. Yoon AE H. M. Park Division of Chemical Metrology and Materials Evaluation, Korea Research Institute of Standard and Science, 1 Doryong-dong, Yuseong, Deajeon 305-600, Korea e-mail: chumin@kriss.re.kr

Organic photovoltaic devices are difficult to commercialize because of their vulnerability to chemical degradation related with oxygen and water and to physical degradation with aging at high temperatures. We investigated the photophysical degradation behaviors of a series of poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl C61-butyric acid methyl ester (PC60BM) bulk heterojunctions (BHJs) as a model system according to the donor–acceptor ratio. We found that the optimum P3HT:PC60BM ratio in terms of long-term stability differs from that in terms of initial cell efficiency. On the basis of cell performance decays and time-resolved photoluminescence measurements, we investigated the effects of oxygen and material self-aggregation on the stability of an organic photovoltaic device. We also observed the changes in morphological geometry and analyzed the surface elements to verify the mechanisms of degradation.

We synthesized various hollow oxide nanoparticles from as-prepared MnO and iron oxide nanocrystals. Heating metal oxide nanocrystals dispersed in technical grade trioctylphosphine oxide (TOPO) at 300 degrees C for hours yielded hollow nanoparticles retaining the size and shape uniformity of the original nanocrystals. The method was highly reproducible and could be generalized to synthesize hollow oxide nanoparticles of various sizes, shapes, and compositions. Control experiments revealed that the impurities in technical grade TOPO, especially alkylphosphonic acid, were responsible for the etching of metal oxide nanocrystals to the hollow structures. Elemental mapping analysis revealed that the inward diffusion of phosphorus and the outward diffusion of metal took place in the intermediate stages during the etching process. The elemental analysis using XPS, EELS, and EDX showed that the hollow nanoparticles were amorphous metal oxides containing significant amount of phosphorus. The hollow nanoparticles synthesized from MnO and iron oxide nanocrystals were paramagnetic at room temperature and when dispersed in water showed spin relaxation enhancement effect for magnetic resonance imaging (MRI). Because of their morphology and magnetic property, the hollow nanoparticles would be utilized for multifunctional biomedical applications such as the drug delivery vehicles and the MRI contrast agents.

The isotope-selective-optical-pumping is investigated by the linear absorption experiment of the metastable thallium atoms. The optical-pumping-intensity dependence of the absorption spectrum is investigated by the experimental and numerical methods. In addition, the isotope selectivity depending on the optical pumping in a cell has been discussed.

The authors report the formation of a new manganese silicide phase, MnSi2, using an intermixing method that involves evaporating a manganese thin film on a silicon substrate at a high temperature of 600 °C. The crystal structure of MnSi2 is tetragonal with lattice constants of a = 5.518 A and c = 17.449 A, identical to that of Mn4Si7. Analysis of the film using high-angle annular dark-field imaging confirmed that the composition ratio of Mn and Si was 1:2. The electric resistivity and Seebeck coefficient of the film were 2.08 × 10−3 Ω cm and 107.84 μV/K at 410 K, respectively, which resulted in a maximum power factor of 5.60 × 10−4 W/K2m.

The present paper reports more extensive and precise experimental results about the isotope shifts of Sm I in the 635 nm — 690 nm range by Doppler-free saturation absorption spectroscopy using a single-mode diode laser with a small linewidth. We measured newly the isotope shifts and hyperfine structures of 20 transition lines, which are mostly originating from the [4f 66s 2] 7 F J to [4f 66s6p] 9 D o 9 F o and 7 G o levels, with a resolution better than 8 MHz. The measured isotope shifts were resolved into mass shifts and field shifts by King plot analysis. Finally, we could obtain the changes in mean-square nuclear charge radii from field shifts, and they were compared with the previous results.

Three-photon ionization of gadolinium (Gd) atom was investigated. The ions were detected by time-of-flight mass spectrometer. The amount of residual atoms in the excited state after the laser illumination in the interaction region was estimated by measuring the variation of the fluorescence signal. This method was used to estimate the ionization efficiency.

This study examined the effect of adding SrO on the grain-boundary conduction of Ce0.9Gd0.1O1.95 gadolinia-doped ceria containing 500 ppm SiO2. The apparent grain-boundary resistivity at 300°C decreased drastically from 746.7 to 0.90–1.97 k cm upon doping with 1 mol % SrO, while the grain-interior resistivity increased gradually from 3.1 to 11.6 k cm as the SrO concentration was increased up to 5 mol %. Therefore, doping with 1 mol % SrO resulted in the minimum total resistivity. The electron probe X-ray microanalysis and the analysis of the lattice parameters suggest that the 140–500-fold enhancement in the grain-boundary conduction is attributed to the scavenging of the highly resistive siliceous phase by the SrO-containing phase.

Also, we performed the experiment with the same parameters in a heat oven. The numerical results, such as the widths and the shifts of the absorption signals of the thallium metastable atoms in the optical pumping, are compared with the experimental results. We also discussed the collision eect in the heat oven.

This study examined the effect of CaO addition on grain-boundary conductivity in 10 mol % Gd 2 O 3 -doped CeO 2 containing 500 ppm SiO 2 as an impurity. The addition of CaO increased the grain-boundary conductivity ∼ 50 times without affecting the grain-interior conductivity significantly. CaO was incorporated into the CeO 2 lattice completely, which means that a scavenging reaction between a large CaO-related second phase and siliceous impurity was not the reason for the increased conductivity. After adding CaO, grain boundary structure changed from random to faceted. Configuration change in the grain-boundary segregation in relation to the boundary-structure variation is suggested as a possible reason.

6392 Cerium dioxide (CeO2) with a cubic fluorite structure has long been considered as one of the most important oxide materials because of its chemical stability and close lattice match with silicon. Therefore CeO2 thin films have been utilized as stable buffer layers for high-temperature superconducting materials 1) and ferroelectric gate materials on silicon. 2, 3) Recently, Morshed et al. 4) reported violet/blue luminescence from annealed CeO2 thin films on Si substrates. We observed similar luminescence but its origin is entirely different. In this letter, we report on our observation of stable UVB photoluminescence (PL) from annealed CeOx thin films on Si and discuss the origin of the luminescence. CeOx thin films were prepared by using radio-frequency (rf) sputtering of cerium (Ce) single target (` D 10 cm, purityD 99:99%) in a reactive argon-oxygen gas mixture on p-type silicon (100) at room temperature. During the deposition, the working gas pressure and rf-power density were maintained at 3:0£ 10 i3 Torr and 1.3 W/cm 2 , respectively. The as-prepared CeOx films were then annealed at temperatures in the range of 800‐1100 ‐ C in a nitrogen ambient using a rapid lamp heating (RLH) method. PL, Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements of the prepared samples before and after the thermal treatment were then carried out. The PL of the samples was measured at both room temperature and at 16 K in a variable temperature cryogenic system. Samples were excited by a 325 nm line from a He‐Cd laser. No luminescence was observed for as-deposited samples or