Bidirectional Reflectometry. Part I.: A High Resolution Laser Bidirectional Reflectometer With Results on Several Optical Coatings

A laser-source bidirectional reflectometer that is fully automated and has angular resolution on the order of one degree has been designed and built. The direction of incidence and viewing can be independently varied over an entire hemisphere except for directions more than 77.5° from the normal, and the two directions must be at least 2.5° apart. Bidirectional reflectances for 15 samples of black and white coatings are presented.     

Precipitation of barium sulphate in a hollow fiber membrane contactor: Part II The influence of process parameters

In this second of two papers, we investigated the influence of process parameters on BaSO₄ particle precipitation in a hollow fiber membrane device. The solution of barium chloride was passed tangentially over the membrane surface and reacted with a solution of K₂SO₄ introduced through the membrane pores. The resulting supersaturation induced nucleation and particle growth on the lumen side of the hollow fibers. A specific technique was developed to measure crystal size directly at the outlet of the hollow fiber device by using EDTA as a neutralizing agent of crystal nucleation and growth. Concentrations of barium chloride and potassium sulphate were shown to influence mainly the CSD, the effect of inlet flow rates on the lumen and shell sides being less pronounced. The chemical conversions measured were between 3.7% and 20.5%. We propose improvements in the design of hollow fiber devices in order to give higher chemical conversions.     

Influence of Barium Incorporation on the Electrochemical Performance of Ln0.58Sr0.4Fe0.8Co0.2O3–δ (Ln=La,Pr, Sm) Perovskites for Oxygen Activation at Intermediate Temperatures

Highly active perovskite‐based electrodes were obtained through partial substitution of lanthanides (La, Pr and Sm) by barium in the Ln_0.58Sr_0.4Fe_0.8Co_0.2O₃ system. These compositions were obtained as single phase crystalline compounds through a sol–gel synthetic route and tested by electrochemical impedance spectroscopy (EIS) as symmetrical cells on GDC‐electrolyte samples in the temperature range 450–650 °C. Cooperative effects arose through the incorporation of a large divalent active cation (Ba⁺²) in the perovskite lattice of lanthanide‐based strontium ferrites‐cobaltites. Reduction in the electrode polarisation resistance with respect to non‐substituted compositions is obtained irrespective of the amount of barium substitution and lanthanide nature. Barium addition also reduces the activation energy of these compositions, indicating changes in the oxygen activation processes. The specific effect of the barium incorporation on the electrode performance was dependent on the nature of the partially substituted lanthanide. Lanthanum–barium‐based compositions exhibited the lowest electrode polarisation resistance when the amount of the replaced barium was increased up to 50% molar. On the other hand, for praseodymium‐ or samarium–barium‐based compositions, the minimum in electrode polarisation resistance was achieved at barium substitutions close to 25% molar. The study of the effect of oxygen partial pressure on EIS data allowed in improving the understanding of the processes governing the electrode operation.     

同时添加Ba和Co对镍电极性能的影响

研究了Ba和Co同时添加对镍电极和MH/Ni电池电化学性能的影响,结果表明:Ba和Co同时添加与单添加Co相比更进一步提高了镍电极的析氧电位,从而提高了镍电极的充电效率和MH/Ni电池的放电容量和大电流放电能力。     

BST铁电薄膜的制备、应用及其研究进展

综述了钛酸锶钡（BST）铁电薄膜的4种制备工艺：磁控溅射（Magnetron sputtering）法、金属有机物化学气相沉积（MOCVD）法、脉冲激光淀积（PLD）法,以及溶胶-凝胶（Sol-Gel）法.并介绍了BST铁电薄膜在动态随机存储器、非致冷红外探测器热成像、移相器等方面的应用及其研究进展.     

Critical influence of different diamagnetic ions on electromagnetic properties of BaFe12O19

The correlation between the electromagnetic properties of BaFe_12-xD_xO₁₉ (0.1?x?1.2) solid solutions (D = Al³⁺, In³⁺ and Ga³⁺) and the concentration of diamagnetic ions was investigated. The changes of electromagnetic properties of the investigated samples were explained using neutron powder diffraction and Mossbauer spectroscopy data. The diamagnetic ions with different ionic radii and electronic configurations were chosen. The transmission spectra of all the samples demonstrated a deep minimum in the frequency range 20–65?GHz which was associated with the natural ferromagnetic resonance. The resonance frequency $f_{\mathit{res}}$ and amplitude were changed by the substitution type and level. With increasing the substitution concentration, the resonance frequency increases from 51?GHz to 61?GHz and decreases from 50.5?GHz to 27?GHz for Al- and In-substituted samples, respectively. More complicated concentration dependences of resonance characteristics were obtained for Ga-substituted samples in a narrow range of 49–50.5?GHz. The value of $f_{\mathit{res}}$ had a minimum around x?=?0.6 and further increased to 50.5?GHz for x?=?1.2. It was concluded that the intrasublattice interactions were responsible for tailoring the magneto crystalline anisotropy and resonance parameters. More detailed investigations would require the development of phenomenological model on the basis of the electronic structure using Goodenough-Kanamori approaches.     

Dielectric properties of Mn doped Bismuth Barium Titanate based ceramic thin films prepared by PLD technique

In this article, the effect of Mn doping on the permittivity and dielectric loss in 0.67BiFeO₃-0.33BaTiO₃ (BF-BT) based film bulk acoustic resonator test structures has been investigated. BF-BT thin films were deposited on the fused silica substrates with Pt/TiO₂/Ti as bottom electrode. During the study of the BF-BT based parallel-plate structures, it has been revealed that BF-BT is in the ferroelectric state at room temperature. Higher permittivity (ԑ) is observed at a growth temperature of 600 °C and lower dielectric loss is achieved at 0.3 wt% Mn doping contents. These results show that the proposed BF-BT based FBAR test structure has a great potential for applications in tunable thin Film Bulk Acoustic Resonator (FBAR) devices. Comparison of the measured and simulation results has been made by utilizing the Mason equivalent circuit.     

Influence of feedstock concentration on tetragonality and particle size of hydrothermally synthesized barium titanate powders

Barium titanate (BaTiO₃) powders were synthesized through hydrothermal process with Ba(OH)₂·8H₂O and TiO₂. By increasing the feedstock concentration (FC) from 0.25 to 1.50 M, BaTiO₃ powders maintain a stable average particle size (~180 nm and ~6.4441 m²/g) with an increasing tetragonality (c/a: 1.0065–1.0075). Johnson-Mehl-Avrami and standard reaction rate equations were adopted to analyze the kinetic process of BaTiO₃ formation. The reaction is governed by first-order and phase-boundary-controlled mechanism for 0.25 M and 1.50 M, respectively. Lower extent of reaction is believed to lead to the better tetragonality for BaTiO₃ powders fabricated with higher FC. On the other hand, the relative stable particle size is correlated with the unvaried nucleation frequency and grain growth rate with various FC. This work can provide a guideline to manipulate the properties of BaTiO₃ powders used in electronic industry.     

Fabrication and mechanical properties of carbon short fiber reinforced barium aluminosilicate glass–ceramic matrix composites

Dense BaSi₂Al₂O₈ (BAS) and Ba_0.75Sr_0.25Si₂Al₂O₈ (BSAS) glass–ceramic matrix composites reinforced with carbon short fibers (C_sf) were fabricated by hot pressing technique. The microstructure, mechanical properties and fracture behavior of the composites were investigated by X-ray diffraction, scanning and transmission electron microscopies, and three-point bend tests. The carbon fibers had a good chemical compatibility with the glass–ceramic matrices and can effectively reinforce the BAS (or BSAS) glass–ceramic because of associated toughening mechanisms such as crack deflection, fiber bridging and pullout effects. Doping of BAS with 25 mol% SrSi₂Al₂O₈ (SAS) can accelerate the hexacelsian to celsian transformation and result in the formation of pure monoclinic celsian in C_sf/BSAS composites, which can avoid the undesirable reversible hexacelsian to orthorhombic transformation at 300 °C and reduce the thermal expansion mismatch between the fiber and matrix.     

合成氨常解气在碳酸钡生产中的应用

阐述了碳酸钡的生产过程和控制及彩和合成氨常解气对生产过程的影响,并对解决这些问题提出相应的对策。