1H NMR study of proton dynamics in (NH4)3H(SO4)2

Proton dynamics in (NH₄)₃H(SO₄)₂ has been studied by means of ¹H solid-state NMR. The ¹H magic-angle-spinning (MAS) NMR spectra were traced at room temperature (RT) and at Larmor frequency of 400.13 MHz. ¹H static NMR spectra were measured at 200.13 MHz in the range of 135–490 K. ¹H spin-lattice relaxation times, T₁, were measured at 200.13 and 19.65 MHz in the ranges of 135–490 and 153–456 K, respectively. The ¹H chemical shift for the acidic proton (14.7 ppm) indicates strong hydrogen bonds. In phase III, NH₄⁺ reorientation takes place; one type of NH₄⁺ ions reorients with an activation energy (E_a) of 14 kJ mol^− 1 and the inverse of a frequency factor (τ₀) of 0.85 × 10^− 14 s. In phase II, a very fast local and anisotropic motion of the acidic protons takes place. NH₄⁺ ions start to diffuse translationally, and no proton exchange is observed between NH₄⁺ ions and the acidic protons. In phase I, both NH₄⁺ ions and the acidic protons diffuse translationally. The acidic protons diffuse with parameters of E_a = 27 kJ mol^− 1 and τ₀ = 4.2 × 10^− 13 s. The translational diffusion of the acidic protons is responsible for the macroscopic proton conductivity, as the NH₄⁺ translational diffusion is slow and proton exchange between NH₄⁺ ions and the acidic protons is negligible.     

Microfabrication of solenoid-type RF SMD chip inductors with an Al2O3 core

We investigated micron size, high-performance, and solenoid-type radio-frequency surface-mounted device (SMD) chip inductors with a low-loss Al₂O₃ core for a GHz drive microwave circuit application. Copper coils with a diameter of 27 μm were used and the chip inductors fabricated in this study are 0.86 × 0.46 × 0.45 mm³. The high-frequency characteristics of the inductance (L), quality factor (Q), and impedance (Z) of the developed inductors were measured using a RF impedance/material analyzer (HP4291B with HP16193A test fixture). The developed inductors have a self-resonant frequency of 3.7–5.2 GHz and exhibit L of 15–34 nH. The inductors have Q of 38–49 over the frequency ranges of 900 MHz–1.7 GHz. The calculated data obtained from the equivalent circuit and the derived equation of Q described the high-frequency data of L, Q, and Z of the inductors developed quite well.     

Stark and Frequency Measurements in the FIR Spectrum of H2O2

The submillimeter-wave spectrum of H₂O₂has been recorded by means of a tunable FIR spectrometer. Stark measurements have been performed on three selected transitions in then= 0 state, namely, the 2₂₀–1₁₀(τ = 4 ← 2) at 1 272 297 MHz, the 8₂₆–7₁₆(τ = 1 ← 3) at 882 451 MHz, and the 9₂₈–8₁₈(τ = 1 ← 3) at 962 933 MHz. Accurate values of the transition dipole moments of the molecule have been derived by considering the interaction between the levels involved in the transition and the close near-resonant levels. About 40 new lines, belonging to the^rQ₄and^rQ₅subbranches of the rotational transitions between the lowest torsional states (τ = 1, 2, 3, 4n= 0), have been measured in the 2.8 and 3.4 THz spectral regions and analyzed together with the previously measured millimeter- and submillimeter-wave, as well as IR, transitions.     

Flux pinning and superconducting properties of melt-textured NEG-123 superconductor with TiO2 addition

We studied the effect of TiO₂ doping on flux pinning and superconducting properties of a melt-grown (Nd_0.33Eu_0.33Gd_0.33) Ba₂Cu₃O_y + 35 mol% Gd₂BaCuO₅ (70 nm in size) composite (NEG-123) processed in Ar–1% O₂ atmosphere. As indicated by similar, sharp superconducting transitions, the small quantities of TiO₂ used in our experiments did not deteriorate superconducting properties of the NEG material. Transmission electron microscopy (TEM) analysis found 20–50 nm Ti-based particles in the NEG-123 matrix. However, we have not observed the clouds of <10 nm sized particles in the NEG-123 matrix, as in the case of recently reported NEG-123 composites doped by Mo and Nb nanoparticles. Nevertheless, quite a good J_c–B performance in the 0.1 mol% Ti-doped sample, namely 550 kA/cm² at the self-field and at the secondary peak field (4.5 T) was achieved at 65 K, while 320 kA/cm² was obtained at zero-field at 77 K, and 50 kA/cm² at 90.2 K. The pinning effectiveness decreased with increasing Ti content above 0.2 mol%. The analysis of the pinning force showed that higher concentration of Ti (>0.2 mol%) increased the amount of normal pins (δl pinning), indicated by the Fp(h) peak shift from h = 0.42–0.36. The maximum pinning effect in a broad field range could be achieved by optimizing Ti content and adding sub-micron Gd-211 particles.     

Microscopic magnetic properties of (V1−xTix)2O3 near the phase boundary of the metal–insulator transition

Magnetic susceptibility (χ) and ⁵¹V NMR have been measured in (V_1−xTi_x)₂O₃ near the phase boundary of the metal–insulator transition. It is established that the transition from antiferromagnetic insulating (AFI) to antiferromagnetic metallic phases near x_c≈0.05 is not quantum critical, but is discontinuous with a jump of the transition temperature. In the AFI phase at 4.2 K, we observed the satellite in the zero-field ⁵¹V NMR spectrum around 181 MHz in addition to the ‘host’ resonance around 203 MHz. The satellite is also observable in the paramagnetic metallic phase of the x=0.055 sample. We associated the satellite with the V sites near Ti, which are in the V³⁺-like oxidation state, but has different temperature dependence of the NMR shift from that of the host V site. The host d-spin susceptibility for x=0.055 decreases below ∼60 K, but remains finite in the low-temperature limit.     

Universal dynamics behavior in superionic conducting glasses

The inelastic neutron scattering experiment on superionic glass system AgI-AgPO₃ have been performed in the energy and momentum transfer range from ? 5 to 15 meV and 0 to 8 Å^? 1, respectively by using a time of flight MARI instrument at Rutherford Appleton Laboratory, ISIS, UK. The E-dependence of the inelastic data show an excess intensity at low energy around 3 meV, the so-called Boson peak, which increased with the dopant salt. The Q-dependence of the elastic scattering reveals a prepeak at anomalously low Q value around 0.8 Å^? 1, which is not observed in the undoped AgPO₃ glass. The Q-dependence in the energy region from 1 to 3 meV shows clearly an excess intensity at Q ~ 2.2 Å ^? 1compared with the undoped AgPO₃. All these features correlate with the increasing mobility of Ag⁺ ions due to the expansion of the network structure caused by salt doping, which leads to the increase of ionic conductivity. Similar results have also been observed in the corresponding superionic glass system AgI-Ag₂S-AgPO₃ that was observed by both MARI and NEAT instrument at HMI, Berlin. The results show a universal dynamic behavior in silver phosphate glasses.     

Submillimeter-wave measurements of N2 and O2 pressure broadening for HO2 radical generated by Hg-photosensitized reaction

The N₂ and O₂ pressure broadening coefficients of the pure rotational transitions at 625.66 GHz (N_KaKc=10_1?9–10_0?10, J=10.5–10.5) and 649.70 GHz (N_KaKc=10_2?9–9_2?8, J=9.5–8.5) in the vibronic ground state X²A′ of the perhydroxyl (HO₂) radical have been determined by precise laboratory measurements. For the production of HO₂, the mercury-photosensitized reaction of the H₂ and O₂ precursors was used to provide an optimum condition for measurement of the pressure broadening coefficient. The Superconducting Submillimeter-wave Limb Emission Sounder (SMILES) was designed to monitor the volume mixing ratio of trace gases including HO₂ in the Earth's upper atmosphere using these transitions. The precise measurement of pressure broadening coefficient γ in terms of the half width at half maximum is required in order to retrieve the atmospheric volume mixing ratio. In this work, γ coefficients of the 625.66 GHz transition were determined for N₂ and O₂ at room temperature as γ(N₂)=4.085±0.049 MHz/Torr and γ(O₂)=2.578±0.047 MHz/Torr with 3σ uncertainty. Similarly, the coefficients of the 649.70 GHz transition were determined as γ(N₂)=3.489±0.094 MHz/Torr and γ(O₂)=2.615±0.099 MHz/Torr. The air broadening coefficients for the 625.66 GHz and 649.70 GHz lines were estimated at γ(air)=3.769±0.067 MHz and 3.298±0.099 MHz respectively, where the uncertainty includes possible systematic errors. The newly determined coefficients are compared with previous results and we discuss the advantage of the mercury-photosensitized reaction for HO₂ generation. In comparison with those of other singlet molecules, the pressure broadening coefficients of the HO₂ radical are not much affected by the existence of an unpaired electron.     

Lithium superionic conductors Li3InBr6 and LiInBr4 studied by 7Li, 115In NMR

Li₃InBr₆ undergoes a phase transition to a superionic phase at 314 K associated with a steep increase of the conductivity (σ = 4 × 10^− 3 Scm^− 1 at 330 K). This superionic phase is isomorphous with Li₃InCl₆ in which a positional disorder at the In³⁺ site is introduced. A pseudo cubic-close-packing of the bromide ions is formed in this phase. On the other hand, a new superionic phase of LiInBr₄ was found above ca 315 K and its structure was confirmed to be a defect spinel. The dynamic properties of the cations in these two superionic phases were investigated by ⁷Li and ¹¹⁵In NMR spectroscopy.     

Nuclear polarization by optical pumping in InP:Fe above liquid nitrogen temperature

Hyperpolarized nuclear spins are observed in optically pumped iron-doped InP from 70 K to 140 K. ³¹P NMR was carried out at 9.28 T (159.8 MHz) during optical excitation with circularly polarized light, using a laser diode (λ∼830 nm) as a source. The enhancement of the nuclear spin polarization by optical pumping at 70 K is estimated to be about 34 for those nuclei in the region of the sample absorbing light. This enhancement decreases with increasing temperature. As the direction of the enhanced nuclear spin polarization is found parallel or antiparallel to the travelling direction of the σ⁺ or σ⁻, the contact hyperfine interaction is dominant compared to the dipolar hyperfine interaction.     

Proton diffusion in the superprotonic phase of [(NH4)1 − xRbx]3H(SO4)2 as studied by 1H spin-lattice relaxation

Proton diffusion in [(NH₄)_1 ? xRb_x]₃H(SO₄)₂ (0 < x < 1) has been studied by means of ¹H spin-lattice relaxation times, T₁. The relaxation times were measured at 200.13 MHz in the range of 296–490 K and at 19.65 MHz in the range of 300–470 K. In the high-temperature phase (phase I), translational diffusion of the acidic protons relaxes both the acidic protons and the ammonium protons. Spin diffusion averages the relaxation rate of the two kinds of protons, whereas proton exchange between them are slow. The spin-lattice relaxation times in phase I were analyzed theoretically, and parameters of proton diffusion were obtained. The mean residence time of the acidic protons increases with increase in x for [(NH₄)_1 ? xRb_x]₃H(SO₄)₂ (0 ≤ x ≤ 0.54). Rb₃H(SO₄)₂ does not obey this trend. The results of NMR well explain the macroscopic proton conductivity.     

Synthesis of nanocomposites of iron oxide/gold (Fe3O4/Au) loaded on activated carbon and their application in water treatment by using sonochemistry: Optimization study

This paper focuses on the finding best operational conditions using response surface methodology (RSM) for Rhodamine123 (R123) and Disulfine blue (DSB) dyes removal by ultrasound assisted adsorption onto Au-Fe₃O₄ nanoparticles loaded on activated carbon (Au-Fe₃O₄ NPs-AC). The influences of variables such as initial R123 (X₁) and DSB concentration (X₂), pH (X₃), adsorbent mass (X₄) and sonication time (X₅) on their removal were investigated by small central composite design (CCD) under response surface methodology. The significant variables and the possible interactions among variables were investigated and estimated accordingly. The best conditions were set as: 4 min, 4.0, 0.025 g, 13.5 and 26.5 mg L⁻¹ for sonication time, pH, adsorbent weight, initial R123 and DSB concentration, respectively. At above conditions, the adsorption equilibrium and kinetic follow the Langmuir isotherm and pseudo-second-order kinetic model, respectively. The maximum monolayer capacity (Q_max) of 71.46 and 76.38 mg g⁻¹ for R123 and DSB show sufficiency of model for well presentation of experimental data.     

Structural and permeability sensitivity of cells to low intensity ultrasound: Infrared and fluorescence evidence in vitro

This work is focused on the in vitro study of the effects induced by medical ultrasound (US) in murine fibroblast cells (NIH-3T3) at a low-intensity of exposure (spatial peak temporal average intensity I_ta < 0.1 W cm⁻²). Conventional 1 MHz and 3 MHz US devices of therapeutic relevance were employed with varying intensity and exposure time parameters. In this framework, upon cells exposure to US, structural changes at the molecular level were evaluated by infrared spectroscopy; alterations in plasma membrane permeability were monitored in terms of uptake efficiency of small cell-impermeable model drug molecules, as measured by fluorescence microscopy and flow cytometry. The results were related to the cell viability and combined with the statistical PCA analysis, confirming that NIH-3T3 cells are sensitive to therapeutic US, mainly at 1 MHz, with time-dependent increases in both efficiency of uptake, recovery of wild-type membrane permeability, and the size of molecules entering 3T3. On the contrary, the exposures from US equipment at 3 MHz show uptakes comparable with untreated samples.     

High performance batch production of LREBa2Cu3Oy using novel thin film Nd-123 seed

A batch production for fabrication of LREBa₂Cu₃O_y (LRE: Sm, Gd, NEG) “LRE-123” pellets are developed in air and Ar-1% O₂ using a novel thin film Nd-123 seeds grown on MgO crystals. The SEM and XRD results conformed that the quality and orientation of the seed crystals are excellent. On the other hand, new seeds can withstand temperatures >1100 °C, as a result, the cold seeding process was applied even to grow Sm-123 material in Air. The trapped field observed in the best 45 mm single-grain puck of Gd-123 was in the range of 1.35 T and 0.35 T at 77.3 K and 87.3 K, respectively. The average trapped field at 77.3 K in the 24 mm diameter NEG-123 samples batch lies between 0.9 and 1 T. The maximum trapped field of 1.2 T was recorded at the sample surface. Further, the maximum trapped field of 0.23 T at 77 K was recorded in a sample with 16 mm diameter of Sm-123 with 3 mol% BaO₂ addition. As a result we made more then 130 single grain pucks within a couple of months. Taking advantage of the single grain batch processed material, we constructed self-made chilled levitation disk, which was used on the open day of railway technical research Institute. More then 150 children stood on the levitation disk and revel the experience of levitation. The present results prove that a high-performance good-quality class of LREBa₂Cu₃O_y material can be made by using a novel thin film Nd-123 seeds.     

Hyperfine interactions in magnetoelectric hexaferrite system

Nuclear magnetic resonance (NMR) in Y-hexaferrite system (Ba_1?xSr_x)₂Zn₂Fe₁₂O₂₂ was measured on both monocrystalline and polycrystalline samples at liquid helium temperature. Corresponding ab-initio calculation of the hyperfine parameters was also performed. The signal from ⁵⁷Fe was detected in the frequency interval 65–76 MHz, while NMR spectrum of ⁶⁷Zn nuclei occurs between 15 and 30 MHz. Due to the disorder in two tetrahedral sublattices occupied partly by Zn and partly by Fe, the NMR lines are broad and the spectra are poorly resolved. Comparison between the experimentally observed ⁶⁷Zn spectra and the spectra modelled using the calculated hyperfine parameters was made. It indicates that the spectra of ⁶⁷Zn can be used to determine the distribution of Zn and Fe between the two tetrahedral sublattices.     

Sonochemical preparation of SbS1−xSexI nanowires

A sonochemical method for direct preparation of nanowires of SbS_1?xSe_xI solid solution has been established. The SbS_1?xSe_xI gel was synthesized using elemental Sb, S, Se and I in the presence of ethanol under ultrasonic irradiation (35 kHz, 2 W/cm²) at 50 °C for 2 h. The product was characterized by using techniques such as powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray analysis, selected area electron diffraction, and optical diffuse reflection spectroscopy. The SEM and HRTEM investigations exhibit that the as-prepared samples are made up of large quantity nanowires with lateral dimensions of about 10–50 nm and lengths reaching up to several micrometers and single-crystalline in nature. The increase of molar composition of Se affects linear decrease of the indirect forbidden optical energy gap as well as the distance between (121) planes of the SbS_1?xSe_xI nanowires.     

Development and characteristics of solenoid-type SMD RF chip inductors

Simple, solenoid-type surface-mounted device (SMD) chip inductors utilizing low-loss Al₂O₃ core materials for a radio-frequency (RF) drive microwave circuit application were developed. The SMD chip inductors were fabricated with five different specifications, namely, 0.86 × 0.46 × 0.45, 1.0 × 0.5 × 0.5, 1.5 × 1.0 × 0.7, 2.1 × 1.5 × 1.0, and 2.4 × 2.0 × 1.4 mm³. Copper coils with diameters in the range of 27–40 μm were used. The frequency characteristics of the inductance (L), quality factor (Q), and impedance of the developed inductors were measured using a RF impedance/material analyzer (HP4291B with HP16193A test fixture). It was observed that the developed inductors with the number of turns of 12 have L of 34–270 nH, exhibit a self-resonant frequency (SRF) of 3.7–0.75 GHz, and have Q of 40–70 over the frequency ranges of 200 MHz–1.2 GHz. The L of inductors increases and the SRF decreases with increasing the size of inductors. From the experimental results, it was concluded that the high-frequency data calculated from the equivalent circuit and the derived equation of Q described quite well the experimental data of the developed inductors.     

Long RE123 coated conductors with high critical current over 500 A/cm by IBAD/PLD technique

We have developed long RE₁Ba₂Cu₃O_7?X (RE123) coated conductors with large current capacity by the ion beam assisted deposition (IBAD) and the pulsed laser deposition using hot wall heating (HW-PLD) technique. As a result, we could fabricate an 8 m-long Gd₁Ba₂Cu₃O_7?X (Gd123) coated wire with the minimum and maximum critical current (I_c) of 951 A/cm-w and 1003 A/cm-w at 77 K, 0 T, respectively, measured in 0.7 m-long sections by the standard 4-probe technique. Furthermore, we succeeded in preparation of over 600 m-long Gd123 coated wire with the uniform I_c distribution over 600 A/cm-w. It had average, maximum and minimum I_c of 665, 698, 609 A/cm-w, respectively. The n-values of the sample showed the maximum I_c and minimum I_c were 40 and 36, respectively. As a result, we set the new world record of I_c × L value as 374535 A m (= 609 A × 615 m). The in-field performance of this long wire was quite high as well; the minimum I_c exceeded 50 A/cm-w at 77 K, 3 T.     

Sensor application-related defect chemistry and electromechanical properties of langasite

The operation of langasite (La₃Ga₅SiO₁₄) resonators as sensors at elevated temperature and controlled atmospheres is examined. This paper focuses on mapping the regimes of gas-insensitive operation of uncoated langasite resonators and the correlation to langasite's defect chemistry for temperatures up to 1000 °C. As a measure of sensitivity, the fundamental resonant mode at 5 MHz is estimated to be determined to within ± 4 Hz by network analysis for resonators operated in air at temperatures below 1000 °C. The calculated frequency shift induced by redox-related reactions in langasite only exceeds the limit of ± 4 Hz below p_O2 ≈ 10^− 17 bar at 1000 °C, below 10^− 24 bar at 800 °C and below 10^− 36 bar at 600 °C. Water vapor is found to shift the resonance frequency at higher oxygen partial pressures. In the hydrogen-containing atmospheres applied here, langasite can be regarded as a stable resonator material above oxygen partial pressures of about 10^− 13 and 10^− 20 bar at 800 and 600 °C, respectively.     

Proton dynamics in Cs3(HSO4)2(HPO4) studied by 1H NMR

Proton dynamics in Cs₃(HSO₄)₂(H₂PO₄) has been studied by means of ¹H solid-state NMR as well as thermal analyses. The thermal analysis shows an endothermic peak at 408 K, which corresponds to a superprotonic transition. Above the transition temperature a mass loss is observed in a dry atmosphere, which is easily recovered in a conventional dry atmosphere below the transition temperature. The ¹H magic-angle-spinning NMR spectra at room temperature show two peaks at 13.5 and 15.8 ppm, and a shoulder at 11.3 ppm from tetramethylsilane, demonstrating a presence of several inequivalent proton sites. Translational diffusion of protons takes place in both a room-temperature phase (RT) and a high-temperature phase (HT). In both phases reorientation of the SO₄/PO₄ tetrahedron limits the rate of the proton transport. The ¹H mean residence times are estimated as E_a = 33 kJ mol^− 1 and τ₀ = 0.97 × 10^− 9 s for phase RT from the second moment analysis and as E_a = 20 kJ mol^− 1 and τ₀ = 5.0 × 10^− 12 s for phase HT from the analysis of the ¹H T₁ results.     

Empirical expression for the composition and temperature dependence of the energy gap in InAlSb

An empirical expression for the energy bandgap as a function of alloy composition x and temperature for In_1−xAl_xSb was reported. The In_1−xAl_xSb epitaxial layers were grown by molecular beam epitaxy (MBE) on InSb(1 0 0) substrate, utilizing a p⁺–p⁺–n–n⁺ structure. High resolution X-ray diffraction was used to characterize the epitaxial layers. The Al composition of 2.8% was obtained by assuming the Bragg’s formula and Vegard’s law. Spectral response measurement of the diodes has been employed to investigate the temperature dependence of the band gap of In_1−xAl_xSb alloys in the range between 77 K and 260 K. The calculated results for energy gap of InAlSb were in good agreement with the available data and our experimental observation.