56 results
Search Results
2. Influence of source parameters on the longitudinal phase-space distribution of a pulsed cryogenic beam of barium fluoride molecules.
- Author
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Mooij, M C, Bethlem, H L, Boeschoten, A, Borschevsky, A, Esajas, K, Fikkers, T H, Hoekstra, S, van Hofslot, J W F, Jungmann, K, Marshall, V R, Meijknecht, T B, Timmermans, R G E, Touwen, A, Ubachs, W, Willmann, L, and Yin, Y
- Subjects
BARIUM fluoride ,GAS dynamics ,MOLECULAR beams ,PHASE space ,DUST ,MOLECULES ,ELECTRIC dipole moments - Abstract
Recently, we have demonstrated a method to record the longitudinal phase-space distribution of a pulsed cryogenic buffer gas cooled beam of barium fluoride molecules with high resolution. In this paper, we use this method to determine the influence of various source parameters. Besides the expected dependence on temperature and pressure, the forward velocity of the molecules is strongly correlated with the time they exit the cell, revealing the dynamics of the gas inside the cell. Three observations are particularly noteworthy: (1) The velocity of the barium fluoride molecules increases rapidly as a function of time, reaches a maximum 50–200 µ s after the ablation pulse and then decreases exponentially. We attribute this to the buffer gas being heated up by the plume of hot atoms released from the target by the ablation pulse and subsequently being cooled down via conduction to the cell walls. (2) The time constant associated with the exponentially decreasing temperature increases when the source is used for a longer period of time, which we attribute to the formation of a layer of isolating dust on the walls of the cell. By thoroughly cleaning the cell, the time constant is reset to its initial value. (3) The velocity of the molecules at the trailing end of the molecular pulse depends on the length of the cell. For short cells, the velocity is significantly higher than expected from the sudden freeze model. We attribute this to the target remaining warm over the duration of the molecular pulse giving rise to a temperature gradient within the cell. Our observations will help to optimize the source parameters for producing the most intense molecular beam at the target velocity. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Design, analysis and validation of pinnacles impedance FSS absorber based on La-doped mullite ceramic.
- Author
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Yang, Xianzhao, Gong, Guan, and Li, Xiangcheng
- Subjects
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BARIUM fluoride , *DOPING agents (Chemistry) , *MULLITE , *FREQUENCY selective surfaces , *IMPEDANCE matching , *CERAMICS - Abstract
The bandwidth adaptation factor (BAF), which is calculated as BW • (λ L - λ H): (d • f r), is a crucial evaluation parameter for designing ultrathin broadband absorbers. In this paper, a high BAF absorber is designed by utilizing an impedance frequency selective surface (FSS), which includes a six pinnacles FSS, a La-doped mullite ceramic dielectric layer and a metal backplane. The optimal numbers of pinnacled FSS is determined through comparison and optimization, and the power monitor results indicate that the main loss modes are electrical and ohmic loss. Subsequently, the impedance analysis reveals that the favourable absorption performance is attributed to good impedance matching and high loss coefficient. Furthermore, the observation of the current distribution on the surface confirms that the primary loss appears at the pinnacles. The proposed absorber has below −10 dB reflectivity in 12.26–18.00 GHz. Meanwhile, the BAF is 3.36 and the thickness is only 0.061 λ L (1.5 mm). The measured results are in good agreement with the simulation results, demonstrating an excellent BAF characteristic. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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- View/download PDF
4. Spectroscopic properties and numerical analysis of novel erbium doped multi-component tellurite glasses.
- Author
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Wan, Rui, Guo, Chen, Li, Xianda, and Wang, Pengfei
- Subjects
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BARIUM fluoride , *MID-infrared lasers , *ACTIVE medium , *NUMERICAL analysis , *INFRARED lasers , *FIBER lasers , *ABSORPTION cross sections , *ERBIUM - Abstract
In this paper, Er3+ doped TeO 2 -ZnF 2 -BaF 2 -KF-Ta 2 O 5 tellurite glasses with low hydroxyl content (∼0.03 × 10−19 cm−3) were investigated employing both glass composition and glass melting process optimization. The Raman spectra and physical properties were characterized to analyze the structure of the glasses. Under the pumping of 980 nm LD laser, intense up-conversion fluorescence at 1.5 and 2.7 μm of samples and their lifetimes were detected and analyzed, and the related transition mechanisms with gradient-varying Er3+ doping concentrations were discussed. The maximum absorption and emission cross section at 2.7 μm was calculated to be 6.4 × 10−21 cm2 and 6.8 × 10−21 cm2, correspondingly, which were higher than those of traditional tellurite glasses. Using the calculated and measured spectroscopic parameters of bulk tellurite glass, a dual-wavelength pumping model was established to verify the feasibility of mid-infrared laser output in similar tellurite glass fiber. Experimental results support the assertion that the Er3+ doped tellurite glasses hold promise as a candidate laser gain medium for mid-infrared fiber laser systems. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
5. Compact NEXAFS System Based on Laser-Plasma Soft X-ray Light Source for the Analysis of Barium Edges in a B+BaF2 Optical Filter.
- Author
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FOK, T., WACHULAK, P., WARDZINSKA, M., BARTNIK, A., NYGA, P., NOWAK, M. P., and FIEDOROWICZ, H.
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BARIUM fluoride ,X-ray absorption near edge structure ,SOFT X rays ,LIGHT filters ,LIGHT sources ,BARIUM ,DIFFRACTION gratings ,RADIATION absorption - Abstract
In this work, we present the results of the analysis performed with near edge absorption fine structure spectroscopy of barium edges in a B+BaF2 optical filter. The radiation was generated by a laser-plasma soft X-ray source based on a double-stream gas puff target. The use of a flat-field spectrometer based on a diffraction grating allowed us to collect the absorption spectra of the radiation transmitted by the analyzed optical filter. The results demonstrate the appearance of clear M-edges of barium (M4 and M5). [ABSTRACT FROM AUTHOR]
- Published
- 2024
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6. Kerr-Lens Mode-Locked Yb:BaF 2 Laser.
- Author
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Li, Zhi-Qiang, Lin, Zhang-Lang, Loiko, Pavel, Zeng, Huang-Jun, Zhang, Ge, Nie, Hai-Yu, Normani, Simone, Benayad, Abdelmjid, Camy, Patrice, Mateos, Xavier, Petrov, Valentin, and Chen, Weidong
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MODE-locked lasers ,BARIUM fluoride ,LASERS ,SEMICONDUCTOR lasers ,SOLID-state lasers ,LASER pulses ,INDIUM gallium arsenide - Abstract
We present sub-50 fs soliton pulse generation from a diode-pumped Kerr-lens mode-locked laser based on an Yb
3+ -doped BaF2 crystal. Utilizing a spatially single-mode, fiber-coupled InGaAs laser diode at 976 nm as a pump source, the Yb:BaF2 laser generates pulses as short as 46 fs at 1060.1 nm with an average output power of 45 mW at a pulse repetition rate of ~65.6 MHz via soft-aperture Kerr-lens mode locking. To the best of our knowledge, this represents the first demonstration of Kerr-lens mode-locked operation of the Yb:BaF2 crystal, as well as the shortest pulse duration ever achieved from any diode-pumped mode-locked laser based on an Yb3+ -doped alkaline-earth fluoride crystal. [ABSTRACT FROM AUTHOR]- Published
- 2024
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7. The Microstructure and Mechanical Properties of High Entropy Alloy CoCrFeNiMn Matrix with Cr 3 C 2 Reinforcement and Ag, BaF 2 /CaF 2 Solid Lubrication.
- Author
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Guo, Zhiming, Li, Jingdan, and Ren, Xiaoyan
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BARIUM fluoride ,FACE centered cubic structure ,MICROSTRUCTURE ,ALLOYS ,ENTROPY ,BRITTLE fractures - Abstract
A series of CoCrFeNiMn high-entropy alloy matrix self-lubricating composites were prepared by spark plasma sintering. The composites are composed of an FCC phase, Cr
7 C3 , Ag, and eutectic fluoride BaF2 /CaF2 phases. The microstructure of the composites is uniform. The additional phases distribute along the boundary of equiaxed grains of the FCC phase. The compressive yield strength and fracture toughness decrease with the increase of eutectic fluoride BaF2 /CaF2 . The composites are susceptible to brittle cleavage fracture. [ABSTRACT FROM AUTHOR]- Published
- 2023
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8. Microstructure and scintillation characteristics of BaF ceramics.
- Author
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Fedorov, P., Kuznetsov, S., Smirnov, A., Garibin, E., Gusev, P., Krutov, M., Chernenko, K., and Khanin, V.
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METAL microstructure ,SCINTILLATORS ,BARIUM fluoride ,CERAMIC metals ,PHASE transitions ,SINGLE crystals - Abstract
This paper examines how the transformation of BaF from a single-crystalline to polycrystalline state as a result of uniaxial hot-forming influences its properties. With increasing strain, the microstructure of the material changes from a nonuniform polycrystalline one, with a block size of about 1 mm, to a classic ceramic structure made up of grains in which dislocations form walls, resulting in a subgrain structure. The best mechanical characteristics are offered by the ceramic produced at a strain on the order of 700%. The intensity of the fast X-ray luminescence component (band at 220 nm) is independent of strain, whereas that of the slow component (band at 310 nm) decreases with increasing strain. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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9. Microwave-hydrothermal synthesis of nano-sized Sn2+-doped BaTiO3 powders and dielectric properties of corresponding ceramics obtained by spark plasma sintering method.
- Author
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Xie, Yahong, Yin, Shu, Hashimoto, Takatoshi, Kimura, Hisamichi, and Sato, Tsugio
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MICROWAVES ,ELECTRIC waves ,TIN ,METALS ,BARIUM compounds ,BARIUM fluoride - Abstract
Ternary oxides containing Sn
2+ are rare and difficult to prepare using solid state reaction due to disproportionation of Sn2+ at high temperature. In this paper, nanoparticles of barium titanate doped with different amounts of Sn2+ consisting of single phase perovskite structure were successfully synthesized for the first time by using a microwave-assisted solvothermal reaction. The particle sizes were about 20–40 nm in diameter and increased with increasing the amount of doped tin. Solidified ceramic bodies were obtained using a spark plasma sintering method under argon atmosphere avoiding the disproportionation and oxidation of Sn2+ in the air. The grain size and dielectric constant of the sintered body decreased with increasing the amount of doped tin. [ABSTRACT FROM AUTHOR]- Published
- 2009
- Full Text
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10. Nucleation of YBa2Cu3O7 From Precursor Films Using the Barium Fluoride Process.
- Author
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Solovyov, Vyacheslav F., Wiesmann, Harold J., and Suenaga, Masaki
- Subjects
NUCLEATION ,BARIUM fluoride ,OPTICAL polarization ,BARIUM compounds ,OPTICS ,FLUORIDES - Abstract
Coated-conductor applications of YBCO require YBCO layers with high J
c and a thickness of several micrometers. The barium fluoride process offers a convenient way of depositing crack-free fluorinated precursor layers up to 5 microns thick. However, converting thick precursor layers into c-axis-oriented YBCO flints is challenging due to extensive nucleation of random grains. In this paper we address this problem with both a theoretical and experimental analysis of YBCO nucleation. We utilized optical polarization contrast to observe YBCO nuclei imbedded in the precursor matrix. We observed that the nuclei density strongly depends on processing parameters, with the oxygen partial pressure being one of the strongest factors. During ex-situ processing the nuclei merge and form grains and the nuclei density is, therefore, directly related to the grain size of YBCO film. It is desirable to have a small grain structure, since large grains do not connect well and the Jc of such a film is low. However, attempts to increase the nuclei density also generates more randomly oriented grains. Therefore the optimization of ex-situ processing is essentially finding a balance between c-axis grain density and random grain content. [ABSTRACT FROM AUTHOR]- Published
- 2005
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11. Spectral and Cathodoluminescence Decay Characteristics of the Ba 1−x Ce x F 2+x (x = 0.3–0.4) Solid Solution Synthesized by Precipitation from Aqueous Solutions and Fusion.
- Author
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Kuznetsov, Sergey V., Yasyrkina, Darya S., Valiev, Damir T., Stepanov, Sergey A., Alexandrov, Alexander A., Batygov, Sergey Kh., Voronov, Valeriy V., Konyushkin, Vasilii A., Nakladov, Andrey N., Ermakova, Julia A., and Fedorov, Pavel P.
- Subjects
SOLID solutions ,AQUEOUS solutions ,CATHODOLUMINESCENCE ,POTASSIUM fluoride ,ELECTRONIC excitation ,SINGLE crystals ,SCINTILLATORS ,EMBEDDING theorems - Abstract
Single-phase samples of the Ba
1−x Cex F2+x solid solution (x = 0.3–0.4) were synthesized by directional crystallization in the form of single crystals and by co-precipitation from aqueous nitrate solutions using potassium fluoride as a fluorinating agent in the form of nanopowders. The cathodoluminescence of the pressed powder samples was studied in comparison with the BaF2 : Ce single crystals in 250–460 nm (2.7–5 eV) spectral range upon excitation by an electron accelerator. The cathodoluminescence spectra of the samples revealed a wide band in the range of 3.0–4.0 eV, which consists of two typical components of Ce3+ with decay time 23 ns in the case of single crystals and three decay times 27 ns, 140–170 ns, and ~600 ns in the case of pressed powders. The decay time of the short-wavelength component (27 ns) in the case of pressed powders is close to the lifetime of the excited state of the Ce3+ ion. The developed X-ray phosphors can be applied for embedding in diamonds for diamond–nanoparticle composite preparation. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
12. Bulk Polystyrene-BaF 2 Composite Scintillators for Highly Efficient Radiation Detection.
- Author
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Li, Xiang, Deng, Mingxue, Shi, Yun, Qi, Xuejun, Wang, Shaohan, Lu, Yugui, Du, Yong, and Chen, Junfeng
- Subjects
SCINTILLATORS ,GAMMA rays ,RADIATION ,LUMINESCENCE ,BARIUM fluoride ,EMULSION polymerization - Abstract
Organic–inorganic composite scintillators, demonstrating advantages of easy large-area preparation and a high detection efficiency, have shown enormous potential application prospects in radiation detection and imaging. In this study, bulk polystyrene (PS) composite scintillators were successfully prepared by embedding inorganic BaF
2 particles with a loading amount of up to 80 wt% during the polymerization process of the plastic scintillator. The inorganic BaF2 particles were uniformly dispersed in the organic matrix. With the increase of the loading amounts of BaF2 particles, the X-ray-excited luminescence intensity of the PS-BaF2 composite scintillators was about eight times higher than that of the commercial pure plastic scintillator. The scintillation counts under the gamma ray (59.5 KeV) irradiation also showed that the detection efficiency was obviously enhanced by BaF2 particle loading. More importantly, their scintillation pulse retains the decay kinetics of the organic matrix without loading the slow-decay component of BaF2 . This work provides a promising solution for the application of the PS-BaF2 composite scintillator in high-efficiency radiation detection and large-area imaging. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
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13. Elimination of the contaminant fluoride ions from plant zinc sulfate electrolytes by aluminum sulfate.
- Author
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Hodjaoglu, Gyunver, Hodzhaoglu, Feyzim, Dobrev, Tsvetan, Mincheva, Irina, Kyurkchiev, Alexander, and Krastev, Ivan
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ALUMINUM sulfate ,ZINC sulfate ,SODIUM fluoride ,CHEMICAL elements ,IONS ,FLUORIDES ,BARIUM fluoride - Abstract
Based on the literature data, the most used chemical element for the removal of the contaminant fluoride ions from different water systems was the Al followed by the Zr, Mg, Fe, C, and several others elements that form stable Me–F complexes. The application of mixed composite adsorbents is a modern tendency, but in this study, the dry aluminum sulfate was tested for direct chemical elimination of the fluoride ions from real industrial zinc sulfate electrolytes. The behavior of the used fluorine ion-selective electrode (FISE) was tested in the presence of sodium fluoride and aluminum sulfate. For suppression of the negative role of the aluminum ions on the FISE potential citrate total ionic strength adjustment buffer (TISAB) was used for appropriate ex situ analytical measurements of the fluoride ions in the real zinc electrolytes from the different hydrometallurgical purification stages. The elimination of the free fluorine ions was tested at room temperature (18–27 °C) and by heating up to 40 °C. The obtained results show that at room temperature, the efficiency of the reaction between F
− and Al3+ ions was not very satisfied. Maximum 13% from the initial fluoride concentration was reduced at real conditions. By heating the process was intensified up to 75–95%, but in excess of non-reacted aluminum ions that additionally contaminated the electrolyte for zinc electrowining. The experimentally proven advantages and disadvantages revealed that the elimination reaction needs further optimizations before any applications at plant conditions. Factors as temperature was beneficial, whereas pH was hard for operation since the dry aluminum sulfate acidified the plant electrolytes and the zinc sulfate matrix precipitated easy by titration from acid to neutral conditions. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
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14. Thermal Conductivity of Single Crystals of CaF2–SrF2–BaF2–YbF3 Solid Solutions
- Author
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Popov, P. A., Krugovykh, A. A., Konyushkin, V. A., Nakladov, A. N., Ushakov, S. N., Uslamina, M. A., Nishchev, K. N., Kuznetsov, S. V., and Fedorov, P. P.
- Published
- 2023
- Full Text
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15. Low-Temperature Phase Formation in the BaF2–LaF3 System.
- Author
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Alexandrov, A. A., Bragina, A. G., Sorokin, N. I., Voronov, V. V., Luginina, A. A., Kuznetsov, S. V., Ivanov, V. K., and Fedorov, P. P.
- Subjects
SODIUM nitrate ,IONIC conductivity ,BARIUM fluoride ,FLUORITE ,LANTHANUM ,ENTHALPY ,POLYELECTROLYTES ,SODIUM fluoride - Abstract
Barium lanthanum fluoride powders have been prepared by reacting barium nitrate and lanthanum nitrate in molten sodium nitrate at 350 and 450°C, using a sodium fluoride as a fluorinating agent. A fivefold excess of sodium fluoride has been shown to prevent pyrohydrolysis. We have identified a phase of variable composition with the fluorite structure, Ba
1–x Lax F2+x (0.3 < x < 0.5), which has high ionic conductivity (2.3 × 10–4 S/cm at 500 K) and an activation enthalpy for ionic transport of 0.50 ± 0.01 eV. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
16. Low-Temperature Phase Formation in the BaF2–LaF3 System
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Alexandrov, A. A., Bragina, A. G., Sorokin, N. I., Voronov, V. V., Luginina, A. A., Kuznetsov, S. V., Ivanov, V. K., and Fedorov, P. P.
- Published
- 2023
- Full Text
- View/download PDF
17. Nonlinear chirped interferometry for frequency-shift measurement and χ(3) spectroscopy.
- Author
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Neradovskaia, E., Maingot, B., Chériaux, G., Claudet, C., Forget, N., and Jullien, A.
- Subjects
INTERFEROMETRY ,HETERODYNE detection ,FOUR-wave mixing ,SPECTROMETRY ,NONLINEAR optical spectroscopy ,OPTICS ,BARIUM fluoride - Abstract
Four-wave mixing processes are ubiquitous in ultrafast optics and the determination of the coefficients of the χ
(3) tensor is thus essential. We introduce a novel time-resolved ultrafast spectroscopic method to characterize the third-order nonlinearity on the femtosecond time-scale. This approach, coined as "nonlinear chirped interferometry," makes use of the variation of the optical group delay of a transmitted probe under the effect of an intense pump pulse in the nonlinear medium of interest. The observable is the spectral interference between the probe and a reference pulse sampled upstream and the metric is the transient swing of the probe group delay. We show that the detected signal is enhanced when the pulses are weakly chirped, and that, although interferometric, the method is intrinsically less sensitive to environmental phase fluctuations and drifts. By chirping adequately the reference pulse, the transient frequency shift of the probe pulses is also detected in the time domain and the detected nonlinear signal is enhanced. Nonlinear phase shifts as low as 10 mrad, corresponding to a frequency shift of 30 GHz, i.e., 0.01% of the carrier frequency, are detected without heterodyne detection or active phase-stabilization. The diagonal and/or non-diagonal terms of reference glasses (SiO2 ) and crystals (Al2 O3 , BaF2 , CaF2 ) are characterized. The method is finally applied to measure the soft vibration mode of KTiOAsO4 (KTA). [ABSTRACT FROM AUTHOR]- Published
- 2022
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18. The Effect of Fluorides (BaF 2 , MgF 2 , AlF 3) on Structural and Luminescent Properties of Er 3+ -Doped Gallo-Germanate Glass.
- Author
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Leśniak, Magdalena, Mach, Gabriela, Starzyk, Bartłomiej, Sadowska, Karolina, Ragiń, Tomasz, Żmojda, Jacek, Kochanowicz, Marcin, Kuwik, Marta, Miluski, Piotr, Jimenez, Gloria Lesly, Baranowska, Agata, Dorosz, Jan, Pisarski, Wojciech, Pisarska, Joanna, Olejniczak, Zbigniew, and Dorosz, Dominik
- Subjects
BARIUM fluoride ,ERBIUM ,GLASS ,RAMAN spectroscopy ,FLUORIDES ,INFRARED spectra ,GLASS construction - Abstract
The effect of BaF
2 , MgF2 , and AlF3 on the structural and luminescent properties of gallo-germanate glass (BGG) doped with erbium ions was investigated. A detailed analysis of infrared and Raman spectra shows that the local environment of erbium ions in the glass was influenced mainly by [GeO]4 and [GeO]6 units. Moreover, the highest number of non-bridging oxygens was found in the network of the BGG glass modified by MgF2 . The27 Al MAS NMR spectrum of BGG glass with AlF3 suggests the presence of aluminum in tetra-, penta-, and octahedral coordination geometry. Therefore, the probability of the4 I13/2 →4 I15/2 transition of Er3+ ions increases in the BGG + MgF2 glass system. On the other hand, the luminescence spectra showed that the fluoride modifiers lead to an enhancement in the emission of each analyzed transition when different excitation sources are employed (808 nm and 980 nm). The analysis of energy transfer mechanisms shows that the fluoride compounds promote the emission intensity in different channels. These results represent a strong base for designing glasses with unique luminescent properties. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
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19. Improved cross polarized wave generation with an aperture.
- Author
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Zhao, Baozhen, Zhang, Xiaohua, Lv, Chong, Liu, Qiushi, Zhang, Ji, Ma, Mingjiang, and Yang, Guoqing
- Subjects
CRYSTALS ,BARIUM fluoride - Abstract
A cross polarized wave (XPW) generation experiment with double BaF
2 crystals in air was demonstrated with 120 µJ input pulse. A circular aperture was used to truncate the near field profile of the input beam and remove the outer part of the beam, and circularly symmetric beam profiles were generated at the BaF2 crystal positions. The measured focal spot size was close to the diffraction limit, and the energy stability of XPW was improved from ∼1.89% (without the aperture) to ∼0.67% (with the aperture). [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
20. Thermal Conductivity of Single Crystals of CaF2–BaF2 Solid Solutions.
- Author
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Popov, P. A., Krugovykh, A. A., Zentsova, A. A., Konyushkin, V. A., Nakladov, A. N., Kuznetsov, S. V., and Fedorov, P. P.
- Subjects
SOLID solutions ,SINGLE crystals ,AXIAL flow ,CALCIUM fluoride ,BARIUM fluoride - Abstract
Single crystals of Ca
1 – х Baх F2 (x = 0.001–0.05 and 0.85–0.99) solid solutions have been grown by the Bridgman method, and their thermal conductivity has been measured in the range 50–300 K by an absolute steady-state axial heat flow technique. The thermal conductivity of all samples has been shown to decrease with increasing temperature. At 300 K, the lowest thermal conductivity of the samples with x ≤ 0.05 exceeds 6 W/(m K), and that of the samples with x ≥ 0.85 is a factor of 2 lower. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
21. Characterizing the Grating-like Nanostructures Formed on BaF 2 Surfaces Exposed to Extreme Ultraviolet Laser Radiation.
- Author
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Cui, Huaiyu, Frolov, Alexandr, Schmidt, Jiri, Straus, Jaroslav, Burian, Tomas, Hajkova, Vera, Chalupsky, Jaromir, Zhao, Yongpeng, Kolacek, Karel, and Juha, Libor
- Subjects
ULTRAVIOLET lasers ,LASER beams ,NANOSTRUCTURES ,BARIUM fluoride ,SINGLE crystals - Abstract
Featured Application: laser surface-processing. Monocrystalline barium fluoride (BaF
2 ) slab targets were irradiated by focused 46.9-nm laser radiation at various fluence levels above the ablation threshold. Well-developed ablation patterns with sharp edges were studied by AFM (atomic force microscopy). Their inner surfaces were uniformly covered by periodic structures. The spatial period of the ripples depends on the laser fluence. When the sample is rotated by 45°, the orientation of the grating-like structure changes accordingly. Thus, the grating vector of the periodic structure seems to be coupled to the crystallographic planes of the single crystal. This means that the XUV-laser induced ripples reported here differ from LIPSS (laser-induced periodic surface structures) associated with interference phenomena occurring on illuminated surfaces. Therefore, other mechanisms are discussed to explain the formation of the periodic nanostructures reported in this article. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
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22. Thermal Conductivity of Single Crystals of CaF2–BaF2 Solid Solutions
- Author
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Popov, P. A., Krugovykh, A. A., Zentsova, A. A., Konyushkin, V. A., Nakladov, A. N., Kuznetsov, S. V., and Fedorov, P. P.
- Published
- 2022
- Full Text
- View/download PDF
23. The effects of the solution reactant concentration and temperature on the preparation of Pr3+:BaF2 transparent ceramics.
- Author
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Liu, Xinwen, Zhou, Zhiwei, Li, Weiwei, Yang, Yu, and Mei, Bingchu
- Subjects
TRANSPARENT ceramics ,SCINTILLATORS ,RARE earth ions ,BARIUM fluoride ,BIOCHEMICAL substrates ,LIGHT sources - Abstract
Barium fluoride (BaF2) crystals are attracting much attention as efficient inorganic scintillator promising for high‐energy physics, industrial inspection, and other fields because of the fast component of the decay time (0.6 ns) and high radiation resistance. However, two major drawbacks limit its practical application: (i) a slow decay time of ~600 ns is derived from self‐trapping excitons; (ii) the absolute light yield from the fast luminescence component is not competitive. The introducing of rare earth ions and preparation of BaF2 polycrystalline ceramics is considered to be effective measures to solve these bottlenecks. Pr3+ is extremely suitable as the activated ion of scintillation materials, which possess emission peaks located in visible band and the faster 5d–4f transition. In this work, highly sinterable Pr3+:BaF2 precursor powder was synthesized via the coprecipitation method by adjusting the reactant concentration and temperature. The morphology and microstructure of as‐synthesized powders were characterized using scanning electron microscopy (SEM) and transmittance electron microscopy analysis. The 5 at.% Pr3+:BaF2 transparent ceramic with a transmittance of 50.7% at the wavelength of 500 nm was fabricated by hot pressing the as‐prepared powders at 900°C for 4 h under the axial pressure of 50 MPa. The SEM images of ceramic cross‐section show that the residual pore is the main light scattering source. The absorption and emission spectrum of ceramic samples were discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
24. Thermal Conductivity of Sr1 –xBaxF2 Single Crystals
- Author
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Popov, P. A., Krugovykh, A. A., Konyushkin, V. A., Nakladov, A. N., Kuznetsov, S. V., and Fedorov, P. P.
- Published
- 2021
- Full Text
- View/download PDF
25. The performance of simultaneous denitrification and biogas desulfurization system for the treatment of domestic sewage.
- Author
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Xu, Xi-Jun, Li, Hui-Juan, Wang, Wei, Zhang, Ruo-Chen, Zhou, Xu, Xing, De-Feng, Ren, Nan-Qi, Lee, Duu-Jong, Yuan, Yi-Xing, Liu, Li-Hong, and Chen, Chuan
- Subjects
- *
BARIUM fluoride , *SEWAGE , *SEWAGE purification , *SEWAGE disposal plants , *DENITRIFICATION , *DESULFURIZATION , *SEQUENCING batch reactor process , *NITROGEN removal (Water purification) , *NITROGEN removal (Sewage purification) - Abstract
• A simultaneous denitrification and biogas desulfurization process (SDBD) was proposed. • 0.9%–1.5% hydrogen sulfide in biogas was completely removed. • More than 85% COD, 98% NH 4 +-N and 81.65% TN was removed from real domestic sewage. • Hydrogen sulfide introduction altered the pathway of nitrate removal. • Economic assessment enables SDBD system to be a promising way in biological N removal. This paper proposed a novel simultaneous denitrification and biogas desulfurization (SDBD) process for domestic sewage treatment and biogas upgrading. The process consisted of an expanded granular sludge bed (EGSB) for integrated autotrophic and heterotrophic denitrification (IAHD) and a biological aerated filter (BAF) for nitrification. The experiments were firstly conducted to investigate the performance of the lab-scale SDBD system with real domestic sewage at various hydraulic retention times (HRT). The system successfully achieved 83.0 ± 1.8% chemical oxygen demand (COD), 96.2 ± 1.8% ammonia (NH 4 +-N) and 67.3 ± 4.1% total nitrogen (TN) removal efficiency without biogas introduction, and the optimal HRT of EGSB and BAF was determined to be 6 h and 4 h, respectively. Then, biogas with three different hydrogen sulfide concentrations (1.5%, 1.2% and 0.9%) was introduced into the system. Almost complete removal of hydrogen sulfide in biogas was achieved in all the tested scenarios and the removal efficiency of COD, NH 4 +-N and TN maintained at around 86.8%, 98.4% and 83.4%, respectively. Microbial community analysis results showed that biogas introduction notably increased the bacterial diversity and particularly enriched the nitrate-reducing, sulfide-oxidizing bacteria, which forms the major contribution to the hydrogen sulfide removal in the system. Finally, we put the SDBD system in the whole treatment system of domestic sewage and discussed its economics. The results indicated that the total operating cost of sewage treatment plant could be saved to 0.59 RMB/m3, which proved SDBD system to be a promising alternative way in biological nitrogen removal and biogas desulfurization. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
26. Mechanisms of Upconversion Luminescence in BaF2–HoF3 Crystals under Excitation to the 5I5 Level of Ho3+ Ions.
- Author
-
Lyapin, A. A., Ryabochkina, P. A., Ermakov, A. S., Gushchin, S. V., and Fedorov, P. P.
- Subjects
BARIUM fluoride ,PHOTON upconversion ,LASER beams ,CRYSTALS ,IONS ,INFRARED lasers - Abstract
We report a study of upconversion luminescence in BaF
2 –HoF3 crystals in the visible spectral region under excitation to the5 I5 level of Ho3+ ions by laser radiation with a wavelength of 890 nm. For these excitation conditions, we propose mechanisms responsible for upconversion luminescence from the5 F3 ,5 S2 (5 F4 ) and5 F5 levels of Ho3+ ions. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
27. Crystallization Behavior of Glasses in the ZrF4–BaF2–LaF3–AlF3–NaF and HfF4–BaF2–LaF3–AlF3–NaF Systems Modified with Chlorine and Bromine Ions
- Author
-
Brekhovskikh, M. N., Moiseeva, L. V., Shukshin, V. E., Zhidkova, I. A., Egorysheva, A. V., and Fedorov, V. A.
- Subjects
BARIUM fluoride ,BROMINE ,DIFFERENTIAL thermal analysis ,GLASS transition temperature ,CHLORINE ,HEAT treatment ,GLASS-ceramics - Abstract
We have prepared glasses in the ZrF
4 –BaF2 –LaF3 –AlF3 –NaF (ZBLAN) and HfF4 –BaF2 –LaF3 –AlF3 –NaF (HBLAN) systems in which fluorine anions are partially replaced by chlorine and bromine anions. Structural changes in the chlorine-substituted glasses have been investigated by Raman spectroscopy and their crystallization behavior has been studied by differential thermal analysis and X-ray diffraction. The results demonstrate a characteristic decrease in glass transition temperature (Tg ) and the precipitation of fine-particle crystalline chloride and bromide phases in a temperature range well below the crystallization temperature (Tx ) of the fluoride analogues. We have identified phases that crystallize during heat treatment of the glasses at various temperatures. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
28. Growth Kinetics and Microstructure of PbTe Films Produced on Si and BaF2 Substrates by a Modified Hot-Wall Method.
- Author
-
Samoylov, A. M., Kuzminykh, O. G., Synorov, Yu. V., Belonogov, E. K., Belenko, S. V., and Agapov, B. L.
- Subjects
MICROSTRUCTURE ,LEAD telluride crystals ,MICROCHEMISTRY ,X-ray diffraction ,SCANNING electron microscopy - Abstract
Lead telluride films have been grown on Si (100) and BaF
2 (100) substrates by a modified hot-wall method using a graphite reaction chamber. According to X-ray diffraction, X-ray microanalysis, and scanning electron microscopy characterization results, the average growth rate of PbTe films having compositions within the homogeneity range of lead telluride increases with increasing lead vapor partial pressure and decreases with increasing tellurium vapor partial pressure, independent of the nature of the substrate. The rate of PbTe film growth has been shown to be maximal in the initial stage of the process and decrease monotonically over time, independent of the nature of the substrate. Independent of the growth time, the average growth rate of the PbTe films on the Si (100) substrates is considerably higher than that on the BaF2 (100) substrates. Reflection high-energy electron diffraction data indicate that the texture of the PbTe films on Si (100) corresponds to the substrate orientation and that the misorientation angle of the mosaic blocks does not exceed 20°. On the BaF2 (100) substrates, we observe epitaxial PbTe film growth with the orientation relationship (100), [011] PbTe ║ (100), [011] BaF2 . [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
29. Readout concepts for the suppression of the slow component of BaF2for the upgrade of the TAPS spectrometer at ELSA
- Author
-
Reinhard Beck, Stefan Diehl, R. W. Novotny, and Benjamin Wohlfahrt
- Subjects
History ,Engineering ,Spectrometer ,business.industry ,Barium fluoride ,Scintillator ,Computer Science Applications ,Education ,Nuclear physics ,chemistry.chemical_compound ,Optics ,Upgrade ,Band-pass filter ,chemistry ,Orders of magnitude (time) ,Component (UML) ,business ,Energy (signal processing) - Abstract
For the measurement at extremely high interaction rates with fast scintillators, pile-up of consecutive events is a limiting factor. With a decay time of 600 ps of the fast crossluminescence component, Barium Fluoride (BaF2) is one of the fastest inorganic scintillators known today. However, the dominating slow component with a 3 orders of magnitude longer decay time of 630 ns limits the rate capability. To circumvent this limit, different approaches have been made in the past. The slow component can be suppressed for example by doping the crystals with rare earth ions like La3+. The paper will give an overview over the various concepts investigated in the past and present the suppression via optical band pass filters. This method has been chosen for the upgrade of the BaF2 crystals in the most forward region of the TAPS-spectrometer at ELSA in Bonn. It allows to reuse the existing crystals and to achieve a high degree of suppression of the slow component. The focus of the paper will be on the selection of the filters, the achievable rate capability and the energy resolution of the fast component.
- Published
- 2015
30. BaLaF, BaLaF:Eu, BaLaF:Eu/Tb and BaLaF:Eu@BaLaF:Gd core/shell nanoplates: hydrothermal synthesis, luminescence and magnetic properties.
- Author
-
Ladol, Jigmet, Khajuria, Heena, and Sheikh, Haq
- Subjects
LANTHANUM compounds ,LUMINESCENCE ,BARIUM fluoride ,HYDROTHERMAL synthesis ,SYNTHESIS of Nanocomposite materials ,QUENCHING (Chemistry) ,MAGNETIC properties ,EUROPIUM - Abstract
Well defined and photoluminescent BaLaF:Eu, BaLaF:Eu/Tb and BaLaF:Eu@BaLaF:Gd core/shell nanoplates were synthesized via facile hydrothermal method. X-ray powder diffraction, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, Fourier transform infrared spectrum, photoluminescence, kinetics of luminescence decay and magnetic studies were used to characterize the structural, optical and magnetic properties of these nanoplates. TEM images show that these nanoplates have pseudo spherical shape with the average crystallite size of 14-21 nm. Down-conversion luminescent properties of doped BaLaF nanoplates were investigated and impact of core/shell formation and co-doping has been explored. The luminescent intensity and lifetime of Eu in Eu/Tb co-doped BaLaF nanoplates and BaLaF:Eu@BaLaF:Gd core/shell nanoplates are enhanced with respect to the bare BaLaF:Eu nanoplates. Coating BaLaF:Eu core with BaLaF:Gd shell on the surface reduces defects on the surface of core and so the surface quenching is suppressed, thus reducing the efficiency of nonradiative decay pathways. In the case of Eu/Tb co-doped BaLaF nanoplates, energy transfer process from Tb to Eu enhanced the luminescent intensity of Eu ion. Also the Gd doped BaLaF core/shell nanoplates exhibit weakly ferromagnetic interactions with coercivity value of 418.96 G at room temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
31. Ho-Doped ZrF-BaF-BiF Ceramic 2-µm laser beam visualizer.
- Author
-
Savikin, A., Egorov, A., Budruev, A., and Grishin, I.
- Subjects
LASER beams ,BARIUM fluoride ,LUMINESCENCE ,ZIRCONIUM ,POWER density - Abstract
A ceramic 2-µm laser beam visualizer based on Ho-doped β-BaZrF is proposed. The ceramic has been prepared by crystallizing 60ZrF-35BaF-5BiF glass doped with 3 wt % HoF. Exciting the Ho I level by a Tm:LiYF (Tm:YLF) laser at λ = 1910 nm, we observed a strong red luminescence, due to the F → I transition, and a weaker, green luminescence, corresponding to the ( F, S) → I transition. The threshold power density of the Tm:YLF laser at which a red spot was observed on a ceramic sample was 1.1 W/cm. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
32. Development of Yttrium-Doped BaF2 Crystals for Future HEP Experiments
- Author
-
Liyuan Zhang, Ren-Yuan Zhu, Qinghui Zhang, Chao Xu, and Chen Hu
- Subjects
Nuclear and High Energy Physics ,Scintillation ,Materials science ,Barium fluoride ,Doping ,Analytical chemistry ,chemistry.chemical_element ,Yttrium ,Calorimeter ,Crystal ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Nuclear Energy and Engineering ,chemistry ,Electrical and Electronic Engineering ,Ingot ,Absorption (electromagnetic radiation) - Abstract
Because of their ultrafast scintillation with subnanosecond decay time, barium fluoride (BaF2) crystals have attracted broad interest in the high energy physics and nuclear physics communities. One crucial issue, however, is its slow scintillation component with 600-ns decay time, which causes pile-up in a high rate environment. Previous studies show that the slow component can be suppressed effectively by rare earth doping. In this paper, we report investigations on a set of $\Phi \,\,18\times21$ mm3 BaF2 cylinders doped with different yttrium levels grown at Beijing Glass Research Institute (BGRI), from which the optimized yttrium doping level was determined. $\text{A}\Phi \,\,40\times160$ mm3 BaF2 ingot with 5 atomic % (at.%) yttrium doping was consequently grown at BGRI and was used to cut one $25\times 25\times100$ mm3 crystal and several thin slices. Their optical and scintillation properties were measured at Caltech. The results show that yttrium doping effectively suppresses the slow component while maintaining its ultrafast light unchanged. Research and development will continue to develop large-size BaF2:Y crystals with improved optical quality for a fast BaF2:Y crystal calorimeter for Mu2e-II.
- Published
- 2019
33. Slow Scintillation Suppression in Yttrium Doped BaF2 Crystals
- Author
-
Ren-Yuan Zhu, Shiyun Sun, Fan Yang, Liyuan Zhang, Xiang Li, Shaohua Wang, Chen Junfeng, and Yong Du
- Subjects
010302 applied physics ,Nuclear and High Energy Physics ,Scintillation ,Materials science ,010308 nuclear & particles physics ,business.industry ,Doping ,Barium fluoride ,chemistry.chemical_element ,Yttrium ,Radioluminescence ,01 natural sciences ,Light scattering ,Crystal ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Nuclear Energy and Engineering ,chemistry ,Condensed Matter::Superconductivity ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Ultrashort pulse - Abstract
Barium fluoride (BaF2) crystal has a fast scintillation light peaked at 195 and 220 nm with a sub-ns decay time. This ultrafast scintillation promises a wide application in an area where extreme fast timing is important, such as future high-energy physics experiments, gigahertz hard X-ray imaging, and time-of-flight positron emission tomography. BaF2 crystal, however, has also a slow scintillation component peaked at 310 nm with a decay time of about 600 ns, which causes pileup. Suppression of the slow scintillation component by selective doping, such as Ce, La, Tm, and Y, was discussed 20 years ago. In this paper, we report suppression of the slow component in BaF2 crystals by yttrium doping. Single crystals with 1 at% Y doping were grown by vacuum Bridgman technique at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China. Their radioluminescence, optical transmittance, light output, fast/slow ratio, decay kinetics, and light response uniformity were measured. The results show that 1 at% Y doping suppresses the slow scintillation component in BaF2 crystals by a factor of 6, while the fast component remains unaffected.
- Published
- 2018
34. Preparation of ZrF-NaF-BaF-LaF-YbF glasses with YbF substitution for BaF (LaF).
- Author
-
Ivanenko, A., Kompanichenko, N., Omel'chuk, A., Savchuk, R., and Zinchenko, V.
- Subjects
CHEMICAL preparations industry ,ZIRCONIUM compounds ,METALLIC glasses ,SUBSTITUTION reactions ,BARIUM fluoride ,THERMAL analysis ,GLASS transition temperature - Abstract
We have prepared glasses and semicrystalline phases with a green color in the systems ZrF(53.5)-NaF(20)-BaF(20)-LaF(6.5 − x)-YbF( x) (0 ≤ x ≤ 6.5 mol %) (I) and ZrF(53.5)-NaF(20)-BaF(20 − x)-LaF(6.5)-YbF( x) (0 ≤ x ≤ 20 mol %) (II). Thermal analysis results demonstrate that, in both systems, the glass transition temperature of the samples containing ≤3 mol % YbF lies in the range 200-250°C, their heating curves show two or three crystallization events (at 320-340, 380-460, and 415-490°C), and their melting points range from 460 to 490°C. Increasing the YbF content of the glasses to 4 mol % and above (system I) has no effect on their glass transition temperature, reduces the temperature of the first crystallization event from 340 to 305°C, and produces extra peaks in the range 545-600°C, above the major melting peak, which can be accounted for by a nonequilibrium state of the glasses. Ytterbium difluoride substitution for barium difluoride (10 to 20 mol %) (system II) leads to the formation of semicrystalline phases and increases the glass-transition (305°C), crystallization (470-515°C), and melting (570-690°C) temperatures. The IR spectra of such samples show, in addition to a so-called 'featureless continuum' (∼500 cm), absorption bands characteristic of the Yb-F bond. Electronic spectra also confirm that the glasses contain both divalent and trivalent ytterbium. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
35. Edge-Emitting Lead Salt Mid-Infrared Laser Structure on BaF2 (110) Substrate.
- Author
-
D. Li, S. Mukherjee, J. Ma, G. Bi, Ray, D., F. Zhao, Elizondo, S. L., G. Yu, and Z. Shi
- Subjects
MOLECULAR beam epitaxy ,LASERS ,INFRARED radiation ,ENERGY dissipation ,PHOTOLUMINESCENCE ,BARIUM fluoride - Abstract
A lead salt mid-infrared laser sample grown by molecular-beam epitaxy (MBE) on a polished BaF
2 (110) substrate is studied. For improving the laser performance at higher operating temperature, a method of substrate transfer from a BaF2 substrate to a copper heat sink is developed. The cleaved facet along the {100} plane, which is helpful for the formation of a Fabry-Pérot resonant cavity on the laser sample, is observed. Pulsed photoluminescence measurements are conducted on the laser sample step by step during processing in order to trace the effect of each process step. [ABSTRACT FROM AUTHOR]- Published
- 2009
- Full Text
- View/download PDF
36. Luminescence of SiO 2 -BaF 2 :Tb 3+ , Eu 3+ Nano-Glass-Ceramics Made from Sol–Gel Method at Low Temperature.
- Author
-
Pawlik, Natalia, Szpikowska-Sroka, Barbara, Goryczka, Tomasz, Pietrasik, Ewa, and Pisarski, Wojciech A.
- Subjects
BARIUM fluoride ,GLASS-ceramics ,ATTENUATED total reflectance ,SOL-gel processes ,LOW temperatures ,SOL-gel materials ,DIFFERENTIAL scanning calorimetry ,LUMINESCENCE - Abstract
The synthesis and characterization of multicolor light-emitting nanomaterials based on rare earths (RE
3+ ) are of great importance due to their possible use in optoelectronic devices, such as LEDs or displays. In the present work, oxyfluoride glass-ceramics containing BaF2 nanocrystals co-doped with Tb3+ , Eu3+ ions were fabricated from amorphous xerogels at 350 °C. The analysis of the thermal behavior of fabricated xerogels was performed using TG/DSC measurements (thermogravimetry (TG), differential scanning calorimetry (DSC)). The crystallization of BaF2 phase at the nanoscale was confirmed by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM), and the changes in silicate sol–gel host were determined by attenuated total reflectance infrared (ATR-IR) spectroscopy. The luminescent characterization of prepared sol–gel materials was carried out by excitation and emission spectra along with decay analysis from the5 D4 level of Tb3+ . As a result, the visible light according to the electronic transitions of Tb3+ (5 D4 →7 FJ (J = 6–3)) and Eu3+ (5 D0 →7 FJ (J = 0–4)) was recorded. It was also observed that co-doping with Eu3+ caused the shortening in decay times of the5 D4 state from 1.11 ms to 0.88 ms (for xerogels) and from 6.56 ms to 4.06 ms (for glass-ceramics). Thus, based on lifetime values, the Tb3+ /Eu3+ energy transfer (ET) efficiencies were estimated to be almost 21% for xerogels and 38% for nano-glass-ceramics. Therefore, such materials could be successfully predisposed for laser technologies, spectral converters, and three-dimensional displays. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
37. BaF(p -BDC) 0.5 as the Catalyst Precursor for the Catalytic Dehydrochlorination of 1-Chloro-1,1-Difluoroethane to Vinylidene Fluoride.
- Author
-
Wang, Shucheng, Wang, Chuanzhao, Yu, Houlin, Yu, Wei, Liu, Yongnan, Liu, Wucan, Zhou, Feixiang, Yu, Wanjin, Wang, Jiuju, Zhang, Jianjun, and Han, Wenfeng
- Subjects
DIFLUOROETHYLENE ,CATALYSTS ,LOW temperatures ,HIGH temperatures ,BARIUM fluoride ,PYROLYSIS - Abstract
A BaF(p-BDC)
0.5 catalyst was prepared by solid state reaction at room temperature with Ba(OH)2 as precursor, NH4 F as F source, and H2 (p-BDC) as organic ligand. The calcined samples were used as catalysts for dehydrochlorination of 1-chloro-1,1-difluoroethane to generate vinylidene fluoride (VDF) at 350 °C. Commercial production of VDF is carried out at 600–700 °C. Clearly, pyrolysis of the BaF(p-BDC)0.5 catalyst provided a promising way to prepare VDF at low temperatures. Prior to calcination, the activity of the BaF(p-BDC)0.5 catalyst was low. Following calcination at high temperatures, BaF(p-BDC)0.5 decomposed to BaF2 and BaCO3 , and then the catalyst was chlorinated and fluorinated to BaClF, which showed high activity and stable VDF selectivity for dehydrochlorination of 1-Chloro-1,1-Difluoroethane to VDF. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
38. Microstructures of YBa[sub 2]Cu[sub 3]O[sub 7-X] Films Prepared by Low-Pressure Oxygen Atmosphere Post-Annealing of Precursor Films Using Y, BaF[sub 2] and Cu.
- Author
-
Ichinose, Ataru, Kikuchi, Akihiro, Tachikawa, Kyoji, Akita, Shirabe, and Inoue, Kiyoshi
- Subjects
SUPERCONDUCTORS ,BARIUM fluoride ,THIN films - Abstract
Transmission electron microscopy (TEM), reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) are used to characterize the microstructure and surface topography of YBa[sub 2]Cu[sub 3]O[sub 7-x] (YBCO) films. The YBCO films of approximately 0.2 and 0.8 µm thickness are prepared by a postannealing of precursor films of co-evaporated Y, BaF[sub 2] and Cu. The annealing conditions are the same for all cases except for the temperature elevation rate. RHEED patterns corresponding to the YBCO structure are observed in both the samples after annealing at 700°C for 30 minutes. The XRD patterns show that both YBCO films have primarily c-axis orientation. According to TEM observation results, the YBCO film of 0.2 µm thickness is epitaxially grown from a substrate surface. In the case of thicker films of 0.8 µm, the bottom region of the film is epitaxial YBCO, while the top region is a mixture of a-axis orientation, other orientations and impurities. [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
39. Optimization method of manufacturing for diamond turning soft-brittle materials’ harmonic diffractive optical elements
- Author
-
Yue Liu, Yang Chao, Changxi Xue, and Xiang Gao
- Subjects
Materials science ,business.industry ,Barium fluoride ,Surface finish ,Diamond turning ,Diffraction efficiency ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,chemistry.chemical_compound ,Brittleness ,Optics ,chemistry ,0103 physical sciences ,Range (statistics) ,Harmonic ,Surface roughness ,Electrical and Electronic Engineering ,business ,Engineering (miscellaneous) - Abstract
Single-point diamond turning is a high-efficiency, low-cost method for manufacturing harmonic diffractive optical elements (HDOEs). Generally, in order to ensure high diffraction efficiency of HDOEs, a half-round tool is used to reduce surface-relief profile errors and a super small feed rate is selected to control surface roughness when hard-brittle materials are turning. However, this method is no longer suitable for soft-brittle materials, which have a strict requirement for the range of the feed rate. It limits the types of materials available for HDOEs. Therefore, according to the range of the feed rate and the cutting depth for soft-brittle materials, an optimized turning model is proposed in this paper. It overcomes the high surface roughness caused by the half-round tool; meanwhile, the advantage of the half-round tool is kept in terms of surface-relief profile errors. On this basis, a mathematical model is proposed to reveal the relationship among diffraction efficiency, period widths, tool radius, and feed rate with different soft-brittle optical materials. As a typical soft-brittle material, barium fluoride ( B a F 2 ) was selected to be the material for manufacturing HDOEs. By using the optimized model, the turning experiment of B a F 2 HDOEs was completed, and then the B a F 2 HDOEs with R a = 2.75 n m were obtained. The optimized model is verified to be effective and further provides theory guidance and engineering application in the optical manufactory field of soft-brittle materials for HDOEs. The range of application materials for HDOEs is enriched, and the freedom of advanced optical design is broadened.
- Published
- 2020
40. BaF2:Y and ZnO:Ga crystal scintillators for GHz hard X-ray imaging
- Author
-
Zongfu Yu, Liyuan Zhang, Lei Ying, Chen Hu, Aiping Chen, Zhehui Wang, and Ren-Yuan Zhu
- Subjects
Nuclear and High Energy Physics ,Barium fluoride ,Physics::Optics ,chemistry.chemical_element ,02 engineering and technology ,Scintillator ,01 natural sciences ,Crystal ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Condensed Matter::Superconductivity ,0103 physical sciences ,Gallium ,Instrumentation ,Radiation hardening ,Physics ,Scintillation ,010308 nuclear & particles physics ,business.industry ,Doping ,Yttrium ,021001 nanoscience & nanotechnology ,chemistry ,Optoelectronics ,0210 nano-technology ,business - Abstract
Gigahertz (GHz) hard X-ray imaging for the proposed MaRIE project presents an unprecedented challenge for the front imager in both speed and radiation hardness. We proposed two ultrafast inorganic-scintillator-based front imager concepts: a total absorption one and a multilayer one, and investigated optical and scintillation properties for a set of inorganic scintillators at the Caltech HEP crystal laboratory. The results show that yttrium doped barium fluoride crystals and gallium doped ZnO nano-particle-based films are promising for these two concepts, respectively. In this paper, we report their optical and scintillation property as well recent progresses on slow component suppressing in barium fluoride crystals by yttrium doping, and its radiation hardness.
- Published
- 2020
41. Thermal expansion of solid solutions based on calcium and barium fluorides.
- Author
-
Sidorov, A., Popov, P., Aksenov, S., Begunov, A., and Fedorov, P.
- Subjects
THERMAL expansion ,SOLID solutions ,CALCIUM fluoride ,BARIUM fluoride ,DOPING agents (Chemistry) ,CRYSTAL structure ,TEMPERATURE effect - Abstract
The thermal expansion of the CaYF, CaYbF, CaCoF, BaLaF, and BaNdF solid solutions has been studied experimentally from below liquid-nitrogen temperature to room temperature. The results demonstrate that both the iso- and heterovalent dopants have a weak effect on the linear thermal expansion coefficient of the fluorite-structure crystals. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
42. Novel Perspective Coatings for the Optoelectronic Elements: Features of the Carbon Nanotubes to Modify the Surface Relief of BaF2 Materials.
- Author
-
Kamanina, Natalia, Kuzhakov, Pavel, and Kvashnin, Dmitry
- Subjects
BARIUM fluoride ,CARBON nanotubes ,MULTIWALLED carbon nanotubes ,COVALENT bonds ,SURFACE coatings ,MATERIALS ,MECHANICAL properties of condensed matter - Abstract
It is well known that the optimization of the basic properties of materials is related not only to changes of the substance of the material itself, but can also predict the change of their surface. In this regards, the search for, and study of, new nanostructured coatings based on the laser deposition method becomes extremely promising. Here, we used a laser-oriented deposition technique in order to place carbon nanotubes in a vertical position on the BaF
2 surface to modify it. Such modification affected the increasing material transparency, connected with a decrease of the reflection via change the Fresnel losses; hydrophobicity and microhardness as well. Characteristics of the obtained material were studied via spectral analysis, AFM-method, wetting-angle measurements, microhardness estimations to support the possible covalent bonding between the carbon atoms and the interface materials atoms. Moreover, the quantum–chemical calculations completely confirmed the experimental results of the changes of electronic properties of BaF2 substrate after deposition of the CNTs. As the results novel optimized structure based on BaF2 is presented to be used in general optoelectronics, cosmos and laser technique as well. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
43. A Method for Improving Nucleation of Thick YBCO Films in the Ex-Situ Process.
- Author
-
Solovyov, Vyacheslav F., Wiesmann, Harold J., Li-Jun Wu, Yimei Zhu, Suenaga, Masaki, Norton, D., and Marken, K.R.
- Subjects
BARIUM fluoride ,SUPERCONDUCTORS - Abstract
Some coated conductor applications require a YBCO layer at least 5 µm thick with high J[sub c]. The growth of thick c-axis oriented epitaxial layers using the barium fluoride ex-situ technology is not always possible. Films over 3 µm thick have more undesirable a-oriented and random grains than thinner ones. We present an analysis of thick film nucleation and conclude that thick precursor layers impede out-diffusion of the ex-situ reaction product, HF. High impedance for HF diffusion results in large variations of the chemical potential of the growth reaction and disruption of the nucleation process. We conclude that a solution for c-axis growth is control of the precursor permeability. A method is described for controlling the permeability of precursor layers. Using this technique we were able to grow c-axis oriented 5-µm thick films on oxide-buffered Ni tape with J[sub c](0 T) = 4 × 10[sup 5] A/cm² and J[sub c](1 T) = 8 × 10[sup 4] A/cm². [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
44. LAMBDA: Large Area Modular Detector Array for the measurement of high energy rays
- Author
-
C. Bhattacharya, K. Banerjee, S. Kundu, Srijit Bhattacharya, Soumik Bhattacharya, S. Mukhopadhyay, S.R. Banerjee, A. Ray, T. K. Rana, A. De, Surajit Pal, and Deepak Pandit
- Subjects
Physics ,Nuclear and High Energy Physics ,Physics::Instrumentation and Detectors ,business.industry ,Barium fluoride ,Monte Carlo method ,Detector ,Gamma ray ,Photon energy ,Nuclear physics ,chemistry.chemical_compound ,Optics ,Data acquisition ,chemistry ,Cascade ,business ,Instrumentation ,Computer Automated Measurement and Control - Abstract
A large BaF 2 detector array along with its dedicated CAMAC electronics and VME based data acquisition system has been designed, constructed and installed successfully at VECC, Kolkata for studying high energy γ rays ( > 8 MeV ). The array consists of 162 detector elements. The detectors were fabricated from bare barium fluoride crystals (each measuring 35 cm in length and having cross-sectional area of 3.5 × 3.5 cm 2 ). The basic properties of the detectors (energy resolution, time resolution, efficiency, uniformity, fast to slow ratio, etc.) were studied exhaustively. Complete GEANT3 Monte Carlo simulations were performed to optimize the detector design and also to generate the response function. The detector system has been used successfully to measure high energy photons from 113 Sb, formed by bombarding 145 and 160 MeV 20 Ne beams on a 93 Nb target. The measured experimental spectra are in good agreement with those from a modified version of the statistical model code CASCADE. In this paper, we present the complete description of this detector array along with its in-beam performance.
- Published
- 2007
45. Nucleation of<tex>$rm YBa_2rm Cu_3rm O_7$</tex>From Precursor Films Using the Barium Fluoride Process
- Author
-
Harold J. Wiesmann, Masaki Suenaga, and Vyacheslav F. Solovyov
- Subjects
Materials science ,High-temperature superconductivity ,Condensed matter physics ,Barium fluoride ,Nucleation ,Optical polarization ,Yttrium barium copper oxide ,Partial pressure ,Condensed Matter Physics ,Grain size ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Particle-size distribution ,Electrical and Electronic Engineering - Abstract
Coated-conductor applications of YBCO require YBCO layers with high J/sub c/ and a thickness of several micrometers. The barium fluoride process offers a convenient way of depositing crack-free fluorinated precursor layers up to 5 microns thick. However, converting thick precursor layers into c-axis-oriented YBCO films is challenging due to extensive nucleation of random grains. In this paper we address this problem with both a theoretical and experimental analysis of YBCO nucleation. We utilized optical polarization contrast to observe YBCO nuclei imbedded in the precursor matrix. We observed that the nuclei density strongly depends on processing parameters, with the oxygen partial pressure being one of the strongest factors. During ex-situ processing the nuclei merge and form grains and the nuclei density is, therefore, directly related to the grain size of YBCO film. It is desirable to have a small grain structure, since large grains do not connect well and the J/sub c/ of such a film is low. However, attempts to increase the nuclei density also generates more randomly oriented grains. Therefore the optimization of ex-situ processing is essentially finding a balance between c-axis grain density and random grain content.
- Published
- 2005
46. The Effect of Compositional Tailoring on the Thermal Expansion and Tribological Properties of PS300: A Solid Lubricant Composite Coating
- Author
-
Christopher DellaCorte and J. A. Fellenstein
- Subjects
Materials science ,Mechanical Engineering ,Composite number ,Barium fluoride ,Mineralogy ,Surfaces and Interfaces ,engineering.material ,Thermal expansion ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Coating ,chemistry ,Mechanics of Materials ,engineering ,Dilatometer ,Lubricant ,Composite material ,Dry lubricant ,Eutectic system - Abstract
This paper describes a research program in which the goal is to alter the thermal expansion coefficient of a composite solid lubricant coating, PS300, by compositional tailoring. PS300 is a plasma sprayed coating consisting of chrome oxide, silver and barium fluoride/calcium fluoride eutectic in NiCr binder. By adjusting the composition, the thermal expansion coefficient can be altered, and hence chosen, to more closely match a selected substrate preventing coating spallation at extreme temperatures. Thermal expansion coefficients (CTE) for a variety of compositions were measured from 25 to 800 C using a commercial dilatometer. The CTE's ranged from 7.0 to 13 x lO(exp -6)/deg C depending on the binder content. Subsequent tribological testing of a modified composition indicated that friction and wear properties were relatively insensitive to compositional tailoring.
- Published
- 1997
47. Precision Machining And Polishing Of Scintillating Crystals For Large Calorimeters And Hodoscopes
- Author
-
Joaquim L. Heck, Fred R. Holdener, Baruch A. Fuchs, and Craig R. Wuest
- Subjects
Materials science ,business.industry ,Barium fluoride ,Detector ,Polishing ,Calorimeter ,Crystal ,chemistry.chemical_compound ,Optics ,Machining ,chemistry ,Surface roughness ,PHENIX detector ,business - Abstract
New machining and polishing techniques have been developed for large scintillating crystal arrays such as the Barium Fluoride Electromagnetic Calorimeter for the GEM Detector at SSCL, the Crystal Clear Collaboration's cerium fluoride or lead tungstenate calorimeter at the proposed LHC at CERN, the PHENIX Detector at RHIC (barium fluoride), and the cesium iodide Calorimeter for the BaBar Detector at PEP-I B Factory at SLAC. The machining and polishing methods to be presented in this paper provide crystalline surfaces without sub-surface damage or deformation as verified by Rutherford Back-scattering (RBS) analysis. Surface roughness of about 10-20 angstroms and sub-micron mechanical tolerances have been demonstrated on large barium fluoride crystal samples. Mass production techniques have also been developed for machining the proper angled surfaces and polishing up to five 50 cm long crystals at one time. These techniques utilize kinematic mount technology developed at LLNL to allow precision machining and polishing of complex surfaces. We will present this technology along with detailed surface studies of barium fluoride and cerium fluoride crystals polished with this technique.
- Published
- 1994
48. Effects of light exposure on irradiated barium fluoride crystals
- Author
-
C.R. Wuest and G.J. Mauger
- Subjects
chemistry.chemical_compound ,Materials science ,genetic structures ,chemistry ,Barium fluoride ,Radiochemistry ,Gamma ray ,sense organs ,Irradiation ,Visible radiation ,Nuclear chemistry ,Light exposure - Abstract
Small barium fluoride crystals have been irradiated using cobalt-60 gamma rays under various illumination conditions to establish the effect of photo-bleaching of the radiation-induced color centers. This paper describes results of a few different experiments conducted at LLNL over the past few weeks.
- Published
- 1993
49. Temperature variation of the Debye-Waller factors of Ba++ and F− ions in BaF2 powder by x-ray diffraction
- Author
-
Srinivasan, R and Girirajan, K S
- Published
- 1982
- Full Text
- View/download PDF
50. Different Mapping Algorithms for the Analysis of Exfoliated Cervical Cells by Infrared Microscopy
- Author
-
S.R. Lowry, M.J. Smith, and B.A. Leimer
- Subjects
Cervical cancer ,Microscope ,Materials science ,Near-infrared spectroscopy ,Barium fluoride ,Papanicolaou stain ,Cervical cells ,medicine.disease ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Mapping algorithm ,medicine ,Infrared microscopy ,Instrumentation ,Biomedical engineering - Abstract
The Papanicolaou (Pap) smear is the technique used to screen for abnormalities in cervical cells that may be related to cervical cancer and other problems. A number of research groups have reported results that indicate the infrared or NIR spectroscopy can be used to differentiate between samples of normal cervical cells and abnormal cells.In this paper we will describe studies performed on cervical cell samples with an infrared microscope and a motorized x-y stage. This configuration allowed us to “Map” the sample in 100 micron increments, where an infrared spectrum is acquired at each point. This integrated system also allowed chemometric algorithms developed with the Nicolet TQ Analyst software to be automatically applied to the spectral data. Samples of cervical cells were obtained from patients using the standard procedure. Part of the sample was used to prepare the Pap smear slide and the remainder was placed in a saline solution and centrifuged for several minutes. The cell suspension was then applied to a Barium Fluoride 5mm X 5mm window and dried.
- Published
- 1997
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