Photostriction of CH3NH3PbBr3 Perovskite Crystals

KAUST Repository

Wei, Tzu-Chiao

2017-07-17

Organic-inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light-matter interactions. The photoinduced strain of CH3 NH3 PbBr3 is investigated using high-resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH3 NH3 PbBr3 is calculated as 2.08 × 10-8 m2 W-1 at room temperature under visible light illumination. The significant photostriction of CH3 NH3 PbBr3 is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation-rotation coupling. Unlike CH3 NH3 PbI3 , it is noted that the photostriction of CH3 NH3 PbBr3 is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH3 NH3 PbBr3 for applications in next-generation optical micro-electromechanical devices.

Synthesis of Eu3+-doped calcium and strontium carbonate phosphors at room temperature

International Nuclear Information System (INIS)

Pan Yuexiao; Wu Mingmei; Su Qiang

2003-01-01

Red phosphors CaCO 3 :Eu 3+ and SrCO 3 :Eu 3+ have been prepared by co-precipitation with ammonium bicarbonate (NH 4 HCO 3 ) at room temperature. Pure calcite CaCO 3 can be obtained by prolonging the reaction time at 220 deg. C and it decomposes to cubic CaO at 1000 deg. C. Trivalent Eu 3+ acts as a luminescent probe to determine both the calcite and the mixed phase of calcite and vaterite phase of CaCO 3 host and to analyze its decomposition process. High temperature sintering improved both the crystallization and luminescence of SrCO 3 :Eu 3+ in aragonite phase

Temperature dependence of the effective mass of the hybrid organic-inorganic perovskites CH3NH3PbI3

Science.gov (United States)

Lu, Ying-Bo; Yang, Haozhi; Cong, Wei-Yan; Zhang, Peng; Guo, Hong

2017-12-01

The material of methylammonium lead iodide, CH3NH3PbI3 (MAPbI3), has shown significant promise in solar cell applications. A way to infer the microscopic scattering mechanism(s) in MAPbI3 is through the measured temperature dependence of carrier mobility. To this end, how does the carrier effective mass depend on temperature, m* = m*(T), is a useful information since the mobility is a function of m*. By atomistic first principles, we report the calculated m*(T) due to the thermal expansion of MAPbI3 materials, in the experimentally relevant range of 130 K to room temperature. The calculated results suggest m* = m*(T) to be linear in T. The increase of m* versus temperature is predominantly due to the expansion of the longitudinal atomic spacing that weakens the s/p hybridization between the I/Pb atoms.

Formation of simple nitrogen hydrides NH and NH2 at cryogenic temperatures through N + NH3→ NH + NH2 reaction: dark cloud chemistry of nitrogen.

Science.gov (United States)

Nourry, Sendres; Krim, Lahouari

2016-07-21

Although NH3 molecules interacting with ground state nitrogen atoms N((4)S) seem not to be a very reactive system without providing additional energy to initiate the chemical process, we show through this study that, in the solid phase, at very low temperature, NH3 + N((4)S) reaction leads to the formation of the amidogen radical NH2. Such a dissociation reaction previously thought to occur exclusively through UV photon or energetic particle irradiation is in this work readily occurring just by stimulating the mobility of N((4)S)-atoms in the 3-10 K temperature range in the solid sample. The N((4)S)-N((4)S) recombination may be the source of metastable molecular nitrogen N2(A), a reactive species which might trigger the NH3 dissociation or react with ground state nitrogen atoms N((4)S) to form excited nitrogen atoms N((4)P/(2)D) through energy transfer processes. Based on our obtained results, it is possible to propose reaction pathways to explain the NH2 radical formation which is the first step in the activation of stable species such as NH3, a chemical induction process that, in addition to playing an important role in the origin of molecular complexity in interstellar space, is known to require external energy supplies to occur in the gas phase.

Growth kinetics for temperature-controlled atomic layer deposition of GaN using trimethylgallium and remote-plasma-excited NH3

International Nuclear Information System (INIS)

Pansila, P.; Kanomata, K.; Miura, M.; Ahmmad, B.; Kubota, S.; Hirose, F.

2015-01-01

Highlights: • We discuss the reaction mechanism of the low temperature GaN ALD. • The plasma-excited NH 3 is effective in the nitridation of the TMG saturated GaN surface with surface temperatures in excess of 100 °C. • The temperature controlled ALD of GaN is examined using RT-TMG adsorption and plasma-excited NH 3 treatment with the temperature of 115 °C. - Abstract: Fundamental surface reactions in the atomic layer deposition of GaN with trimethylgallium (TMG) and plasma-excited NH 3 are investigated by multiple-internal-reflection infrared absorption spectroscopy (MIR-IRAS) at surface temperatures varying from room temperature (RT) to 400 °C. It is found that TMG is saturated at RT on GaN surfaces when the TMG exposure exceeds 8 × 10 4 Langmuir (L), where 1 L corresponds to 1.33 × 10 −4 Pa s (or 1.0 × 10 −6 Torr s), and its saturation density reaches the maximum value at RT. Nitridation with the plasma-excited NH 3 on the TMG-saturated GaN surface is investigated by X-ray photoelectron spectroscopy (XPS). The nitridation becomes effective at surface temperatures in excess of 100 °C. The reaction models of TMG adsorption and nitridation on the GaN surface are proposed in this paper. Based on the surface analysis, a temperature-controlled ALD process consisting of RT-TMG adsorption and nitridation at 115 °C is examined, where the growth per cycle of 0.045 nm/cycle is confirmed. XPS analysis indicates that all N atoms are bonded as GaN. Atomic force microscopy indicates an average roughness of 0.23 nm. We discuss the reaction mechanism of GaN ALD in the low-temperature region at around 115 °C with TMG and plasma-excited NH 3 .

Electron paramagnetic resonance of gamma irradiated (CH3)3NHClO4 and CH3NH3ClO4 single crystals

International Nuclear Information System (INIS)

Yavuz, Metin; Koeksal, Fevzi

1999-01-01

Gamma irradiation damage centers in (CH 3 ) 3 NHClO 4 and CH 3 NH 3 ClO 4 single crystals have been investigated at room temperature by the electron paramagnetic resonance (EPR) technique. It has been found that γ-irradiation produces the (CH 3 ) 3 N + radical in the first, and NH + 3 and ClO 3 radicals in the second compound. The EPR parameters of the observed radicals have been determined and discussed

Growth kinetics for temperature-controlled atomic layer deposition of GaN using trimethylgallium and remote-plasma-excited NH{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Pansila, P. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Kanomata, K. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Miura, M. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Ahmmad, B.; Kubota, S. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); CREST, Japan Science and Technology Agency, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Hirose, F., E-mail: fhirose@yz.yamagata-u.ac.jp [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); CREST, Japan Science and Technology Agency, 4-3-16 Jonan, Yonezawa 992-8510 (Japan)

2015-12-01

Highlights: • We discuss the reaction mechanism of the low temperature GaN ALD. • The plasma-excited NH{sub 3} is effective in the nitridation of the TMG saturated GaN surface with surface temperatures in excess of 100 °C. • The temperature controlled ALD of GaN is examined using RT-TMG adsorption and plasma-excited NH{sub 3} treatment with the temperature of 115 °C. - Abstract: Fundamental surface reactions in the atomic layer deposition of GaN with trimethylgallium (TMG) and plasma-excited NH{sub 3} are investigated by multiple-internal-reflection infrared absorption spectroscopy (MIR-IRAS) at surface temperatures varying from room temperature (RT) to 400 °C. It is found that TMG is saturated at RT on GaN surfaces when the TMG exposure exceeds 8 × 10{sup 4} Langmuir (L), where 1 L corresponds to 1.33 × 10{sup −4} Pa s (or 1.0 × 10{sup −6} Torr s), and its saturation density reaches the maximum value at RT. Nitridation with the plasma-excited NH{sub 3} on the TMG-saturated GaN surface is investigated by X-ray photoelectron spectroscopy (XPS). The nitridation becomes effective at surface temperatures in excess of 100 °C. The reaction models of TMG adsorption and nitridation on the GaN surface are proposed in this paper. Based on the surface analysis, a temperature-controlled ALD process consisting of RT-TMG adsorption and nitridation at 115 °C is examined, where the growth per cycle of 0.045 nm/cycle is confirmed. XPS analysis indicates that all N atoms are bonded as GaN. Atomic force microscopy indicates an average roughness of 0.23 nm. We discuss the reaction mechanism of GaN ALD in the low-temperature region at around 115 °C with TMG and plasma-excited NH{sub 3}.

A Low Temperature Infrared Study Of Deuterated NH4VO3

Science.gov (United States)

de Waal, D.; Heyns, A. M.

1989-12-01

The existence of (NH4)2V6016 as an intermediate in the thermal decomposition of NH4V03 to V205 has been confirmed by vibrational spectroscopy, resulting in the following reaction in an open systeml: NH4VO3 1 bar, air, 50-200°C/(1) (NH4)2v6o16 1 bar, air, ca.360°C/(2) V205 The kinetics of reaction (1) was studied by means of Raman spectroscopy, and structural information on NH4V03 and (N114)V60 16 was required to obtain an accurate description of the reaction mechanism2. Information on the site symmetry of an ammonium ion and hydrogen bonding in a crystal can be obtained by considering the infrared spectra of isotopically dilute NH3D+ ions in the lattice at liquid nitrogen temperatures3, especially as the position of hydrogen atoms in (NHO2V6016 could not be determined by X-ray methods.

Effect of layer number on recovery rate of WS{sub 2} nanosheets for ammonia detection at room temperature

Energy Technology Data Exchange (ETDEWEB)

Qin, Ziyu [State Key Laboratory of Materials Processing and Die Mould Technology, Huazhong University of Science and Technology (HUST), No. 1037, Luoyu Road, Wuhan 430074 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062 (China); Zeng, Dawen, E-mail: dwzeng@mail.hust.edu.cn [State Key Laboratory of Materials Processing and Die Mould Technology, Huazhong University of Science and Technology (HUST), No. 1037, Luoyu Road, Wuhan 430074 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062 (China); Zhang, Jia; Wu, Congyi; Wen, Yanwei; Shan, Bin; Xie, Changsheng [State Key Laboratory of Materials Processing and Die Mould Technology, Huazhong University of Science and Technology (HUST), No. 1037, Luoyu Road, Wuhan 430074 (China)

2017-08-31

Highlights: • Reasons for room-temperature difficult recovery of WS{sub 2} sensors for NH{sub 3} detection. • The excellent recovery within 271.9 s was observed for single-layer WS{sub 2} sensor. • The recovery time of WS{sub 2} sensor has a anti-linear relation with number of layer. - Abstract: Tungsten disulfide (WS{sub 2}), as a representative layered transition metal dichalcogenides (TMDs), is expected as a promising candidate for high-performance NH{sub 3} sensor at room temperature. Unfortunately, the common WS{sub 2} based NH{sub 3} sensors are difficult to recovery at room temperature, which severely limits its application. Hence, how to improve recovery has become an urgent problem to be solved. Herein, we prepare five types of WS{sub 2} nanosheets with different layer numbers from bulk to monolayer, and find that the recovery time of NH{sub 3} gas sensor is rapidly linear shorten as the number of layers decreasing. Through the first-principles calculation of the interaction between NH{sub 3} and WS{sub 2} substance, the different binding energy between ammonia and the surface (−0.179 eV) and interlayer (−0.356 eV) of layered WS{sub 2}, as well as the different electron transfer way, should be responsible for the difficult recovery rate of various WS{sub 2} samples. Therefore, reducing the number of layer of WS{sub 2} is a promising approach to speed up recovery. Based on this conclusion, we successfully prepare a fast recoverable ammonia gas sensor based on single layer WS{sub 2}, which exhibits exciting fast recovery within 271.9 s at room temperature without any condition. Moreover, our work also can act as a reference for other gas detection of TMDs based gas sensor to improve the gas performance at room-temperature.

Near room temperature approaches for the preparation of air-stable and crystalline CH{sub 3}NH{sub 3}PbI{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Gujarathi, Yogini D.; Haram, Santosh K., E-mail: haram@chem.unipune.ac.in

2016-04-15

This work demonstrates an exotic role of CH{sub 2}Cl{sub 2} in a formation of stable phase of highly crystalline CH{sub 3}NH{sub 3}PbI{sub 3} perovskite, on a bulk scale. In the first method, a partially-reacted product obtained after co-grinding of precursors viz. CH{sub 3}NH{sub 3}I and PbI{sub 2}was sonicated in CH{sub 2}Cl{sub 2} to form pure phase of CH{sub 3}NH{sub 3}PbI{sub 3}. In second method, the precursors in γ-Butyrolactone were treated with CH{sub 2}Cl{sub 2} to form crystalline and phase-pure CH{sub 3}NH{sub 3}PbI{sub 3}. X-ray Diffraction analysis confirmed the formation of stable and highly crystalline tetragonal phase of CH{sub 3}NH{sub 3}PbI{sub 3} perovskite having space group I4cm. Well-defined rhombo-hexagonal dodecahedron crystals were seen in SEM and TEM images. Exceptional air stability of CH{sub 3}NH{sub 3}PbI{sub 3} so forms are attributed to adsorption of CH{sub 2}Cl{sub 2}. Optical band gaps obtained from the diffused reflectance spectra (Kubelka–Munk analysis), matched very well with the one estimated from Cyclic Voltammetry (CV). Valence band and conduction band edge positions estimated from the CV analysis are in good agreement with the one reported from UV photoelectron spectroscopy. Both the samples gave steady state fluorescence at ca. 750 nm with quantum yields in the range 15–35.5%. - Highlights: • A role of CH{sub 2}Cl{sub 2} is brought out in formation of stable CH{sub 3}NH{sub 3}PbI{sub 3} perovskite. • Cyclic voltammetry has been used to estimate the band edge positions. • Excellent fluorescence quantum yield, underlines the minimal structural defects.

Growth kinetics for temperature-controlled atomic layer deposition of GaN using trimethylgallium and remote-plasma-excited NH3

Science.gov (United States)

Pansila, P.; Kanomata, K.; Miura, M.; Ahmmad, B.; Kubota, S.; Hirose, F.

2015-12-01

Fundamental surface reactions in the atomic layer deposition of GaN with trimethylgallium (TMG) and plasma-excited NH3 are investigated by multiple-internal-reflection infrared absorption spectroscopy (MIR-IRAS) at surface temperatures varying from room temperature (RT) to 400 °C. It is found that TMG is saturated at RT on GaN surfaces when the TMG exposure exceeds 8 × 104 Langmuir (L), where 1 L corresponds to 1.33 × 10-4 Pa s (or 1.0 × 10-6 Torr s), and its saturation density reaches the maximum value at RT. Nitridation with the plasma-excited NH3 on the TMG-saturated GaN surface is investigated by X-ray photoelectron spectroscopy (XPS). The nitridation becomes effective at surface temperatures in excess of 100 °C. The reaction models of TMG adsorption and nitridation on the GaN surface are proposed in this paper. Based on the surface analysis, a temperature-controlled ALD process consisting of RT-TMG adsorption and nitridation at 115 °C is examined, where the growth per cycle of 0.045 nm/cycle is confirmed. XPS analysis indicates that all N atoms are bonded as GaN. Atomic force microscopy indicates an average roughness of 0.23 nm. We discuss the reaction mechanism of GaN ALD in the low-temperature region at around 115 °C with TMG and plasma-excited NH3.

Mesoporous WN/WO3-Composite Nanosheets for the Chemiresistive Detection of NO2 at Room Temperature

Directory of Open Access Journals (Sweden)

Fengdong Qu

2016-07-01

Full Text Available Composite materials, which can optimally use the advantages of different materials, have been studied extensively. Herein, hybrid tungsten nitride and oxide (WN/WO3 composites were prepared through a simple aqueous solution route followed by nitriding in NH3, for application as novel sensing materials. We found that the introduction of WN can improve the electrical properties of the composites, thus improving the gas sensing properties of the composites when compared with bare WO3. The highest sensing response was up to 21.3 for 100 ppb NO2 with a fast response time of ~50 s at room temperature, and the low detection limit was 1.28 ppb, which is far below the level that is immediately dangerous to life or health (IDLH values (NO2: 20 ppm defined by the U.S. National Institute for Occupational Safety and Health (NIOSH. In addition, the composites successfully lower the optimum temperature of WO3 from 300 °C to room temperature, and the composites-based sensor presents good long-term stability for NO2 of 100 ppb. Furthermore, a possible sensing mechanism is proposed.

Optical modelling data for room temperature optical properties of organic–inorganic lead halide perovskites

Directory of Open Access Journals (Sweden)

Yajie Jiang

2015-06-01

Full Text Available The optical properties of perovskites at ambient temperatures are important both to the design of optimised solar cells as well as in other areas such as the refinement of electronic band structure calculations. Limited previous information on the optical modelling has been published. The experimental fitting parameters for optical constants of CH3NH3PbI3−xClx and CH3NH3PbI3 perovskite films are reported at 297 K as determined by detailed analysis of reflectance and transmittance data. The data in this study is related to the research article “Room temperature optical properties of organic–inorganic lead halide perovskites” in Solar Energy Materials & Solar Cells [1].

Room temperature superconductors

International Nuclear Information System (INIS)

Sleight, A.W.

1995-01-01

If the Holy Grail of room temperature superconductivity could be achieved, the impact on could be enormous. However, a useful room temperature superconductor for most applications must possess a T c somewhat above room temperature and must be capable of sustaining superconductivity in the presence of magnetic fields while carrying a significant current load. The authors will return to the subject of just what characteristics one might seek for a compound to be a room temperature superconductor. 30 refs., 3 figs., 1 tab

CH3NH3I treatment temperature of 70 °C in low-pressure vapor-assisted deposition for mesoscopic perovskite solar cells

Science.gov (United States)

Jin, Wenbin; Zou, Xiaoping; Bai, Xiao; Yang, Ying; Chen, Dan

2018-01-01

Herein, we report a modified vapor-assisted deposition method to fabricate CH3NH3PbI3 film at 70 °C in a vacuum drying oven. The modified method has excellent operability and expandability in preparing perovskite solar cells. The CH3NH3I treatment temperature is 130 °C or 150 °C in conventional method, but we reduced the temperature to 70 °C in the modified vapor-assisted method. Meanwhile, the quality of CH3NH3PbI3 films prepared via the modified method is superior to that of CH3NH3PbI3 films of solution-processed method.

Room temperature exchange bias in SmFeO_3 single crystal

International Nuclear Information System (INIS)

Wang, Xiaoxiong; Cheng, Xiangyi; Gao, Shang; Song, Junda; Ruan, Keqing; Li, Xiaoguang

2016-01-01

Exchange bias phenomenon is generally ascribed to the unidirectional magnetic shift along the field axes at interface of two magnetic materials. Room temperature exchange bias is found in SmFeO_3 single crystal. The behavior after different cooling procedure is regular, and the training behavior is attributed to the athermal training and its pinning origin is attributed to the antiferromagnetic clusters. Its being single phase and occurring at room temperature make it an appropriate candidate for application. - Graphical abstract: Room temperature exchange bias was found in oxide single crystal. Highlights: • Room temperature exchange bias has been discovered in single-crystalline SmFeO_3. • Its pinning origin is attributed to the antiferromagnetic clusters. • Its being single phase and occurring at room temperature make it an appropriate candidate for application.

O3 fast and simple treatment-enhanced p-doped in Spiro-MeOTAD for CH3NH3I vapor-assisted processed CH3NH3PbI3 perovskite solar cells

Institute of Scientific and Technical Information of China (English)

En-Dong Jia; Xi Lou; Chun-Lan Zhou; Wei-Chang Hao; Wen-Jing Wang

2017-01-01

We demonstrate a simple and fast post-deposition treatment with high process compatibility on the hole transport material (HTM) Spiro-MeOTAD in vapor-assisted solution processed methylammonium lead triiodide (CH3NH3PbI3)-based solar cells.The prepared Co-doped p-type Spiro-MeOTAD films are treated by O3 at room temperature for 5 min,10 min,and 20 min,respectively,prior to the deposition of the metal electrodes.Compared with the traditional oxidation of Spiro-MeOTAD films overnight in dry air,our fast O3 treatment of HTM at room temperature only needs just 10 min,and a relative 40.3％ increment in the power conversion efficiency is observed with respect to the result of without-treated perovskite solar cells.This improvement of efficiency is mainly attributed to the obvious increase of the fill factor and short-circuit current density,despite a slight decrease in the open-circuit voltage.Ultraviolet photoelectron spectroscopy (UPS) and Hall effect measurement method are employed in our study to determine the changes of properties after O3 treatment in HTM.It is found that after the HTM is exposed to O3,its p-type doping level is enhanced.The enhancement of conductivity and Hall mobility of the film,resulting from the improvement in p-doping level of HTM,leads to better performances of perovskite solar cells.Best power conversion efficiencies (PCEs) of 13.05％ and 16.39％ are achieved with most properly optimized HTM via CH3NH3I vapor-assisted method and traditional single-step method respectively.

Reconstructive phase transition in (NH4)3TiF7 accompanied by the ordering of TiF6 octahedra.

Science.gov (United States)

Molokeev, Maxim; Misjul, S V; Flerov, I N; Laptash, N M

2014-12-01

An unusual phase transition P4/mnc → Pa\\bar 3 has been detected after cooling the (NH4)3TiF7 compound. Some TiF6 octahedra, which are disordered in the room-temperature tetragonal structure, become ordered in the low-temperature cubic phase due to the disappearance of the fourfold axis. Other TiF6 octahedra undergo large rotations resulting in huge displacements of the F atoms by 1.5-1.8 Å that implies a reconstructive phase transition. It was supposed that phases P4/mbm and Pm\\bar 3m could be a high-temperature phase and a parent phase, respectively, in (NH4)3TiF7. Therefore, the sequence of phase transitions can be written as Pm\\bar 3m → P4/mbm → P4/mnc → Pa\\bar 3. The interrelation between (NH4)3TiF7, (NH4)3GeF7 and (NH4)3PbF7 is found, which allows us to suppose phase transitions in relative compounds.

Mechanical response of CH3NH3PbI3 nanowires

Science.gov (United States)

Ćirić, L.; Ashby, K.; Abadie, T.; Spina, M.; Duchamp, M.; Náfrádi, B.; Kollár, M.; Forró, L.; Horváth, E.

2018-03-01

We report a systematic study of the mechanical response of methylammonium lead triiodide CH3NH3PbI3 nanowires by employing bending measurements using atomic force microscope on suspended wires over photo-lithographically patterned channels. Force-deflection curves measured at room temperature give a Young's modulus between 2 and 14 GPa. This broad range of values is attributed to the variations in the microcrystalline texture of halide perovskite nanowires. The mechanical response of a highly crystalline nanowire is linear with force and has a brittle character. The braking modulus of 48 ± 20 MPa corresponds to 100 μm of radius of curvature of the nanowires, rendering them much better structures for flexible devices than spin coated films. The measured moduli decrease rapidly if the NW is exposed to water vapor.

Vapor Phase Synthesis of Organometal Halide Perovskite Nanowires for Tunable Room-Temperature Nanolasers.

Science.gov (United States)

Xing, Jun; Liu, Xin Feng; Zhang, Qing; Ha, Son Tung; Yuan, Yan Wen; Shen, Chao; Sum, Tze Chien; Xiong, Qihua

2015-07-08

Semiconductor nanowires have received considerable attention in the past decade driven by both unprecedented physics derived from the quantum size effect and strong isotropy and advanced applications as potential building blocks for nanoscale electronics and optoelectronic devices. Recently, organic-inorganic hybrid perovskites have been shown to exhibit high optical absorption coefficient, optimal direct band gap, and long electron/hole diffusion lengths, leading to high-performance photovoltaic devices. Herein, we present the vapor phase synthesis free-standing CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3PbIxCl3(-x) perovskite nanowires with high crystallinity. These rectangular cross-sectional perovskite nanowires have good optical properties and long electron hole diffusion length, which ensure adequate gain and efficient optical feedback. Indeed, we have demonstrated optical-pumped room-temperature CH3NH3PbI3 nanowire lasers with near-infrared wavelength of 777 nm, low threshold of 11 μJ/cm(2), and a quality factor as high as 405. Our research advocates the promise of optoelectronic devices based on organic-inorganic perovskite nanowires.

Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

Science.gov (United States)

Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

2016-07-01

Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

La0.7Sr0.3MnO3 Thin Films for Magnetic and Temperature Sensors at Room Temperature

Directory of Open Access Journals (Sweden)

Sheng Wu

2012-03-01

Full Text Available In this paper, the potentialities of the manganese oxide La0.7Sr0.3MnO3 (LSMO for the realization of sensitive room temperature thermometers and magnetic sensors are discussed. LSMO exhibits both a large change of the resistance versus temperature at its metal-to-insulator transition (about 330 K and low field magnetoresistive effects at room temperature. The sensor performances are described in terms of signal-to-noise ratio in the 1 Hz - 100 kHz frequency range. It is shown that due to the very low 1/f noise level, LSMO based sensors can exhibit competitive performances at room temperature.

Room temperature ammonia and VOC sensing properties of CuO nanorods

International Nuclear Information System (INIS)

Bhuvaneshwari, S.; Gopalakrishnan, N.

2016-01-01

Here, we report a NH 3 and Volatile Organic Compounds (VOCs) sensing prototype of CuO nanorods with peculiar sensing characteristics at room temperature. High quality polycrystalline nanorods were synthesized by a low temperature hydrothermal method. The rods are well oriented with an aspect ratio of 5.71. Luminescence spectrum of CuO nanorods exhibited a strong UV-emission around 415 nm (2.98 eV) which arises from the electron-hole recombination phenomenon. The absence of further deep level emissions establishes the lack of defects such as oxygen vacancies and Cu interstitials. At room temperature, the sensor response was recorded over a range of gas concentrations from 100-600 ppm of ammonia, ethanol and methanol. The sensor response showed power law dependence with the gas concentration. This low temperature sensing can be validated by the lower value of calculated activation energy of 1.65 eV observed from the temperature dependent conductivity measurement.

Room temperature ammonia and VOC sensing properties of CuO nanorods

Science.gov (United States)

Bhuvaneshwari, S.; Gopalakrishnan, N.

2016-05-01

Here, we report a NH3 and Volatile Organic Compounds (VOCs) sensing prototype of CuO nanorods with peculiar sensing characteristics at room temperature. High quality polycrystalline nanorods were synthesized by a low temperature hydrothermal method. The rods are well oriented with an aspect ratio of 5.71. Luminescence spectrum of CuO nanorods exhibited a strong UV-emission around 415 nm (2.98 eV) which arises from the electron-hole recombination phenomenon. The absence of further deep level emissions establishes the lack of defects such as oxygen vacancies and Cu interstitials. At room temperature, the sensor response was recorded over a range of gas concentrations from 100-600 ppm of ammonia, ethanol and methanol. The sensor response showed power law dependence with the gas concentration. This low temperature sensing can be validated by the lower value of calculated activation energy of 1.65 eV observed from the temperature dependent conductivity measurement.

Room temperature ammonia and VOC sensing properties of CuO nanorods

Energy Technology Data Exchange (ETDEWEB)

Bhuvaneshwari, S.; Gopalakrishnan, N., E-mail: ngk@nitt.edu [Thin film laboratory, National Institute of Technology, Tiruchirappalli-620015 (India)

2016-05-23

Here, we report a NH{sub 3} and Volatile Organic Compounds (VOCs) sensing prototype of CuO nanorods with peculiar sensing characteristics at room temperature. High quality polycrystalline nanorods were synthesized by a low temperature hydrothermal method. The rods are well oriented with an aspect ratio of 5.71. Luminescence spectrum of CuO nanorods exhibited a strong UV-emission around 415 nm (2.98 eV) which arises from the electron-hole recombination phenomenon. The absence of further deep level emissions establishes the lack of defects such as oxygen vacancies and Cu interstitials. At room temperature, the sensor response was recorded over a range of gas concentrations from 100-600 ppm of ammonia, ethanol and methanol. The sensor response showed power law dependence with the gas concentration. This low temperature sensing can be validated by the lower value of calculated activation energy of 1.65 eV observed from the temperature dependent conductivity measurement.

LPG and NH3 sensing characteristics of DC electrochemically deposited Co3O4 films

Science.gov (United States)

Shelke, P. N.; Khollam, Y. B.; Gunjal, S. D.; Koinkar, P. M.; Jadkar, S. R.; Mohite, K. C.

2015-03-01

Present communication reports the LPG and NH3 sensing properties of Co3O4 films prepared on throughly cleaned stainless steel (SS) and copper (CU) substrates by using DC electrochemical deposition method followed by air annealing at 350°C/2 h. The resultant films are characterized by using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The LPG and NH3 gas sensing properties of these films are measured at room temperature (RT) by using static gas sensing system at different concentrations of test gas ranging from 25 ppm to 350 ppm. The XRD and Raman spectroscopy studies clearly indicated the formation of pure cubic spinel Co3O4 in all films. The LPG and NH3 gas sensing properties of films showed (i) the increase in sensitivity factor (S.F.) with gas concentrations and (ii) more sensibility to LPG as compared to NH3 gas. In case of NH3 gas (conc. 150 ppm) and LPG gas (conc. 60 ppm) sensing, the maximum S.F. = 270 and 258 are found for the films deposited on CU substrates, respectively. For all films, the response time (3-5 min.) is found to be much higher than the recovery time (30-50 sec). For all films, the response and recovery time are found to be higher for LPG as compared to NH3 gas. Further, repeatability-reproducibility in gas sensing properties is clearly noted by analysis of data for number of cycles recorded for all films from different set of depositions.

Near-band-edge optical responses of solution-processed organic-inorganic hybrid perovskite CH3NH3PbI3 on mesoporous TiO2 electrodes

Science.gov (United States)

Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

2014-03-01

We studied the near-band-edge optical responses of solution-processed CH3NH3PbI3 on mesoporous TiO2 electrodes, which is utilized in mesoscopic heterojunction solar cells. Photoluminescence (PL) and PL excitation spectra peaks appear at 1.60 and 1.64 eV, respectively. The transient absorption spectrum shows a negative peak at 1.61 eV owing to photobleaching at the band-gap energy, indicating a direct band-gap semiconductor. On the basis of the temperature-dependent PL and diffuse reflectance spectra, we clarified that the absorption tail at room temperature is explained in terms of an Urbach tail and consistently determined the band-gap energy to be ˜1.61 eV at room temperature.

Transport, Optical, and Magnetic Properties of the Conducting Halide Perovskite CH 3NH 3SnI 3

Science.gov (United States)

Mitzi, D. B.; Feild, C. A.; Schlesinger, Z.; Laibowitz, R. B.

1995-01-01

A low-temperature ( T ≤ 100°C) solution technique is described for the preparation of polycrystalline and single crystal samples of the conducting halide perovskite, CH 3NH 3SnI 3. Transport, Hall effect, magnetic, and optical properties are examined over the temperature range 1.8-300 K, confirming that this unusual conducting halide perovskite is a low carrier density p-type metal with a Hall hole density, 1/ RHe ≃ 2 × 10 19 cm -3. The resistivity of pressed pellet samples decreases with decreasing temperature with resistivity ratio ρ(300 K)/ρ(2 K) ≃ 3 and room temperature resistivity ρ(300 K) ≃ 7 mΩ-cm. A free-carrier infrared reflectivity spectrum with a plasma edge observed at approximately 1600 cm -1 further attests to the metallic nature of this compound and suggests a small optical effective mass, m* ≃ 0.2.

Radio-Frequency-Based NH3-Selective Catalytic Reduction Catalyst Control: Studies on Temperature Dependency and Humidity Influences

Directory of Open Access Journals (Sweden)

Markus Dietrich

2017-07-01

Full Text Available The upcoming more stringent automotive emission legislations and current developments have promoted new technologies for more precise and reliable catalyst control. For this purpose, radio-frequency-based (RF catalyst state determination offers the only approach for directly measuring the NH3 loading on selective catalytic reduction (SCR catalysts and the state of other catalysts and filter systems. Recently, the ability of this technique to directly control the urea dosing on a current NH3 storing zeolite catalyst has been demonstrated on an engine dynamometer for the first time and this paper continues that work. Therefore, a well-known serial-type and zeolite-based SCR catalyst (Cu-SSZ-13 was investigated under deliberately chosen high space velocities. At first, the full functionality of the RF system with Cu-SSZ-13 as sample was tested successfully. By direct RF-based NH3 storage control, the influence of the storage degree on the catalyst performance, i.e., on NOx conversion and NH3 slip, was investigated in a temperature range between 250 and 400 °C. For each operation point, an ideal and a critical NH3 storage degree was found and analyzed in the whole temperature range. Based on the data of all experimental runs, temperature dependent calibration functions were developed as a basis for upcoming tests under transient conditions. Additionally, the influence of exhaust humidity was observed with special focus on cold start water and its effects to the RF signals.

Radio-Frequency-Based NH3-Selective Catalytic Reduction Catalyst Control: Studies on Temperature Dependency and Humidity Influences

Science.gov (United States)

Dietrich, Markus; Hagen, Gunter; Reitmeier, Willibald; Burger, Katharina; Hien, Markus; Grass, Philippe; Kubinski, David; Visser, Jaco; Moos, Ralf

2017-01-01

The upcoming more stringent automotive emission legislations and current developments have promoted new technologies for more precise and reliable catalyst control. For this purpose, radio-frequency-based (RF) catalyst state determination offers the only approach for directly measuring the NH3 loading on selective catalytic reduction (SCR) catalysts and the state of other catalysts and filter systems. Recently, the ability of this technique to directly control the urea dosing on a current NH3 storing zeolite catalyst has been demonstrated on an engine dynamometer for the first time and this paper continues that work. Therefore, a well-known serial-type and zeolite-based SCR catalyst (Cu-SSZ-13) was investigated under deliberately chosen high space velocities. At first, the full functionality of the RF system with Cu-SSZ-13 as sample was tested successfully. By direct RF-based NH3 storage control, the influence of the storage degree on the catalyst performance, i.e., on NOx conversion and NH3 slip, was investigated in a temperature range between 250 and 400 °C. For each operation point, an ideal and a critical NH3 storage degree was found and analyzed in the whole temperature range. Based on the data of all experimental runs, temperature dependent calibration functions were developed as a basis for upcoming tests under transient conditions. Additionally, the influence of exhaust humidity was observed with special focus on cold start water and its effects to the RF signals. PMID:28704929

Room temperature adsorption of NH3 on Zn-terminated ZnO(0 0 0 1)

International Nuclear Information System (INIS)

Hasegawa, T.; Shirotori, Y.; Ozawa, K.; Edamoto, K.; Takahashi, K.

2004-01-01

Adsorption process of ammonia on the Zn-terminated ZnO(0 0 0 1) surface at room temperature has been studied by photoelectron spectroscopy utilizing synchrotron radiation. Coverage-dependent measurements of the N 1s core-level peak and the work function change have been carried out. It is revealed that ammonia adsorbs molecularly in the initial stages of adsorption, whereas deprotonated species are formed after some amount of molecular ammonia is accumulated on the surface. The reactivity of the K-modified ZnO(0 0 0 1) surface towards ammonia adsorption has also been investigated and found to be significantly lowered by predeposited K

Flexible camphor sulfonic acid-doped PAni/α-Fe{sub 2}O{sub 3} nanocomposite films and their room temperature ammonia sensing activity

Energy Technology Data Exchange (ETDEWEB)

Bandgar, D.K. [Functional Materials Research Laboratory (FMRL), School of Physical Sciences, Solapur University, Solapur 413 255, M.S. (India); Navale, S.T. [College of Materials Science and Engineering, Shenzhen Key Laboratory of Polymer Science and Technology, Guangdong Research Center for Interfacial Engineering of Functional Materials, Nanshan District Key Lab for Biopolymers and Safety Evaluation, Shenzhen University, Shenzhen 518060 (China); Navale, Y.H.; Ingole, S.M. [Functional Materials Research Laboratory (FMRL), School of Physical Sciences, Solapur University, Solapur 413 255, M.S. (India); Stadler, F.J. [College of Materials Science and Engineering, Shenzhen Key Laboratory of Polymer Science and Technology, Guangdong Research Center for Interfacial Engineering of Functional Materials, Nanshan District Key Lab for Biopolymers and Safety Evaluation, Shenzhen University, Shenzhen 518060 (China); Ramgir, N.; Aswal, D.K.; Gupta, S.K. [Technical Physics Division, Babha Atomic Research Centre, Mumbai, M.S. (India); Mane, R.S. [School of Physical Sciences, SRTM University, Nanded 431606 (India); Patil, V.B., E-mail: drvbpatil@gmail.com [Functional Materials Research Laboratory (FMRL), School of Physical Sciences, Solapur University, Solapur 413 255, M.S. (India)

2017-03-01

Composite nanostructures play a crucial role in gas sensing applications owing to their tunable properties and sizes. The main goal of this article is to prepare camphor sulfonic acid (10–50 wt%)-doped PAni/α-Fe{sub 2}O{sub 3} (PFC) composite nanostructured films on flexible polyethylene terephthalate (PET) substrate through in-situ polymerization process and study their gas sensing activity towards various gases. Structural and morphological measurements along with gas sensing properties in terms of selectivity, response, stability, and response-recovery times are investigated and reported. The gas selectivity tests of flexible PFC nanostructured composite films are performed towards different gases such as NO{sub 2}, NH{sub 3}, LPG, CH{sub 3}OH, and C{sub 2}H{sub 5}OH etc., wherein all the flexible PFC (10–50%) films demonstrate a superior selectivity towards NH{sub 3} gas even in the presence of other test gases. Among the different compositions, 30% PFC flexible film exhibits highest response of 72% to 100 ppm NH{sub 3} with good response time of 65 s. The systematic study between PFC flexible nanocomposite films and NH{sub 3} gas is conducted and reported. In addition, the interfacial charge transfer kinetics across NH{sub 3} and PFC film interface was investigated by means of impendence spectroscopy study. - Highlights: • Novel route of preparation of camphor sulfonic acid doped PAni-Fe{sub 2}O{sub 3} (PFC) flexible films. • XRD, FTIR, and RAMAN analysis confirms the formation of PFC composites. • PFC films are highly selective towards NH{sub 3} gas at room temperature. • PFC films able to detect as low as 2.5 ppm concentration of NH{sub 3} gas. • 30% PFC flexible film exhibits highest response of 72%–100 ppm NH{sub 3} gas with good response time of 65 s.

Controllable Growth of Perovskite Films by Room-Temperature Air Exposure for Efficient Planar Heterojunction Photovoltaic Cells.

Science.gov (United States)

Yang, Bin; Dyck, Ondrej; Poplawsky, Jonathan; Keum, Jong; Das, Sanjib; Puretzky, Alexander; Aytug, Tolga; Joshi, Pooran C; Rouleau, Christopher M; Duscher, Gerd; Geohegan, David B; Xiao, Kai

2015-12-01

A two-step solution processing approach has been established to grow void-free perovskite films for low-cost high-performance planar heterojunction photovoltaic devices. A high-temperature thermal annealing treatment was applied to drive the diffusion of CH3NH3I precursor molecules into a compact PbI2 layer to form perovskite films. However, thermal annealing for extended periods led to degraded device performance owing to the defects generated by decomposition of perovskite into PbI2. A controllable layer-by-layer spin-coating method was used to grow "bilayer" CH3NH3I/PbI2 films, and then drive the interdiffusion between PbI2 and CH3NH3I layers by a simple air exposure at room temperature for making well-oriented, highly crystalline perovskite films without thermal annealing. This high degree of crystallinity resulted in a carrier diffusion length of ca. 800 nm and a high device efficiency of 15.6%, which is comparable to values reported for thermally annealed perovskite films. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gold catalysed synthesis of 3-alkoxyfurans at room temperature.

Science.gov (United States)

Pennell, Matthew N; Foster, Robert W; Turner, Peter G; Hailes, Helen C; Tame, Christopher J; Sheppard, Tom D

2014-02-09

Synthetically important 3-alkoxyfurans can be prepared efficiently via treatment of acetal-containing propargylic alcohols (obtained from the addition of 3,3-diethoxypropyne to aldehydes) with 2 mol% gold catalyst in an alcohol solvent at room temperature. The resulting furans show useful reactivity in a variety of subsequent transformations.

Room temperature synthesis of Si-MCM-41 using polymeric version of ethyl silicate as a source of silica

International Nuclear Information System (INIS)

Gaydhankar, T.R.; Samuel, V.; Jha, R.K.; Kumar, R.; Joshi, P.N.

2007-01-01

Synthesis of mesoporous MCM-41 materials at room temperature using less expensive polymeric version of ethyl silicate (40 wt% SiO 2 ) as a source of silica was established. The influence of crucial synthesis parameters such as molar ratios of H 2 O/NH 4 OH, NH 4 OH/SiO 2 and CTMABr/SiO 2 in gel on the quality of the phase formed was investigated. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and low temperature N 2 adsorption-desorption isotherms have been employed to characterize the products. The magnitude of orderness, textural properties and thermal stability of the Si-MCM-41 samples prepared under identical judiciously pre-controlled synthesis conditions using ethyl silicate and conventional tetraethyl orthosilicate (TEOS) were assessed. Even though, ethyl silicate has proved to be suitable source for the preparation of MCM-41 at room temperature, there exists an optimum value of H 2 O/NH 4 OH for different NH 4 OH/SiO 2 molar ratios in the gel. Changes in the morphology were observed when NH 4 OH/SiO 2 , H 2 O/NH 4 OH molar ratios in the gels were changed

Creation and annealing of metastable defect states in CH3NH3PbI3 at low temperatures

Science.gov (United States)

Lang, F.; Shargaieva, O.; Brus, V. V.; Rappich, J.; Nickel, N. H.

2018-02-01

Methylammonium lead iodide (CH3NH3PbI3), an organic-inorganic perovskite widely used for optoelectronic applications, is known to dissociate under illumination with light at photon energies around 2.7 eV and higher. Here, we show that photo-induced dissociation is not limited to ambient temperatures but can be observed even at 5 K. The photo-induced dissociation of N-H bonds results in the formation of metastable states. Photoluminescence (PL) measurements reveal the formation of defect states that are located 100 meV within the bandgap. This is accompanied by a quenching of the band-to-band PL by one order of magnitude. Defect generation is reversible and annealing at 30 K recovers the band-to-band PL, while the light-induced defect states disappear concurrently.

Crystal structure and characterization of the novel NH+⋯N hydrogen bonded polar crystal [NH2(CH2)4NH][BF4

Science.gov (United States)

Wojtaś, M.; Gaģor, A.; Czupiński, O.; Medycki, W.; Jakubas, R.

2012-03-01

Dielectric properties and phase transitions of the piperazinium tetrafluoroborate ([NH2(CH2)4NH][BF4], abbreviated as PFB) crystal are related to the one-dimensional arrangement of the cations linked by the bistable NH+⋯N hydrogen bonds and molecular motions of the [BF4]- units. The crystal structure of [NH2(CH2)4NH][BF4] is monoclinic at room temperature with the polar space group Pn. The polar/acentric properties of the room temperature phase IV have been confirmed by the piezoelectric and pyroelectric measurements. DSC measurements show that the compound undergoes three first-order structural phase transitions: at 421/411 K (heating/cooling), at 386/372 K and at 364/349 K. 1H and 19F NMR measurements indicate the reorientational motions of [BF4]- anions and piperazinium(+) cations as well as the proton motion in the hydrogen-bonded chains of piperazine along the [001] direction. Over the phase I the isotropic reorientational motions or even self-diffusion of the cations and anions are expected. The conductivity measurements in the vicinity of the II-I PT indicate a superionic phase over the phase I.

Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology.

Science.gov (United States)

Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping

2015-04-28

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.

Control of Emission Color of High Quantum Yield CH3NH3PbBr3 Perovskite Quantum Dots by Precipitation Temperature.

Science.gov (United States)

Huang, He; Susha, Andrei S; Kershaw, Stephen V; Hung, Tak Fu; Rogach, Andrey L

2015-09-01

Emission color controlled, high quantum yield CH 3 NH 3 PbBr 3 perovskite quantum dots are obtained by changing the temperature of a bad solvent during synthesis. The products for temperatures between 0 and 60 °C have good spectral purity with narrow emission line widths of 28-36 nm, high absolute emission quantum yields of 74% to 93%, and short radiative lifetimes of 13-27 ns.

CeBr3 as a room-temperature, high-resolution gamma-ray detector

International Nuclear Information System (INIS)

Guss, Paul; Reed, Michael; Yuan Ding; Reed, Alexis; Mukhopadhyay, Sanjoy

2009-01-01

Cerium bromide (CeBr 3 ) has become a material of interest in the race for high-resolution gamma-ray spectroscopy at room temperature. This investigation quantified the potential of CeBr 3 as a room-temperature, high-resolution gamma-ray detector. The performance of CeBr 3 crystals was compared to other scintillation crystals of similar dimensions and detection environments. Comparison of self-activity of CeBr 3 to cerium-doped lanthanum tribromide (LaBr 3 :Ce) was performed. Energy resolution and relative intrinsic efficiency were measured and are presented.

Carbon nitride films synthesized by NH3-ion-beam-assisted deposition

International Nuclear Information System (INIS)

Song, H.W.; Cui, F.Z.; He, X.M.; Li, W.Z.; Li, H.D.

1994-01-01

Carbon nitride thin film films have been prepared by NH 3 -ion-beam-assisted deposition with bombardment energies of 200-800 eV at room temperature. These films have been characterized by transmission electron microscopy. Auger electron spectroscopy and x-ray photoelectron spectroscopy for chemical analysis. It was found that the structure of the films varied with the bombardment energy. In the case of 400 eV bombardment, the tiny crystallites immersed on an amorphous matrix were identified to be β-C 3 N 4 . X-ray photoelectron spectroscopy indicated that some carbon atoms and nitrogen atoms form unpolarized covalent bonds in these films. (Author)

Study of the structural phase transitions of (CH 3NH 3) 3Sb 2Cl 9 (MACA) and (CH 3NH 3) 3Bi 2Cl 9 (MACB) by infrared spectroscopy

Science.gov (United States)

Bator, G.; Jakubas, R.; Malarski, Z.

1991-06-01

Infrared spectra of polycrystalline (CH 3NH 3) 3Sb 2Cl 9 and (CH 3NH 3) 3Bi 2Cl 9 have been studied in the temperature range 90-300 K. A systematic temperature dependence study of the internal modes has been carried out. We discuss the effects of the dynamic state of methylammonium (MA) cations on their vibrational spectra. The results show that the dynamics of MA cations in both compounds is similar in higher (about 300 K) and lower temperature (in the vicinity of 100 K) regions. Substantial differences are revealed in the intermediate temperature interval. The results are in good agreement with earlier dielectric, calorimetric and 1H NMR studies.

Effective identification of (NH4)2CO3 and NH4HCO3 concentrations in NaHCO3 regeneration process from desulfurized waste.

Science.gov (United States)

Govindan, Muthuraman; Karunakaran, Kannan; Nallasamy, Palanisami; Moon, Il Shik

2015-01-01

This work describes the quantitative analysis of (NH4)2CO3 and NH4HCO3 using a simple solution phase titration method. Back titration results at various (NH4)2CO3-NH4HCO3 ratios demonstrated that 6:4 ratio caused a 3% error in their differentiation, but very high errors were found at other ratios. A similar trend was observed for the double indicator method, especially when strong acid HCl was used as a titrant, where still less errors (2.5%) at a middle ratio of (NH4)2CO3-NH4HCO3 was found. Remaining ratios with low (NH4)2CO3 (2:8, 4:6) show high +ve error (found concentration is less) and high (NH4)2CO3 (7:3, 8:2, and 9:1) show high -ve error (found concentration is higher) and vice versa for NH4HCO3. In replacement titration using Na2SO4, at both higher end ratios of (NH4)2CO3-NH4HCO3 (2:8 and 9:1), both -ve and +ve errors were minimized to 75% by partial equilibrium arrest between (NH4)2CO3 and NH2COONH4, instead of more than 100% observed in back titration and only double indicator methods. In the presence of (NH4)2SO4 both -ve and +ve error% are completely reduced to 3±1 at ratios 2:8, 4:6, and 6:4 of (NH4)2CO3-NH4HCO3, which demonstrates that the equilibrium transformation between NH2COONH4 and (NH4)2CO3 is completely controlled. The titration conducted at lower temperature (5 °C) in the presence of (NH4)2SO4 at higher ratios of (NH4)2CO3-NH4HCO3 (7:3, 8:2,and 9:1) shows complete minimization of both -ve and +ve errors to 2±1%, which explains the complete arresting of equilibrium transformation. Finally, the developed method shows 2±1% error in differentiation of CO3(2-) and HCO3(-) in the regeneration process of NaHCO3 from crude desulfurized sample. The developed method is more promising to differentiate CO3(2-) and HCO3(-) in industrial applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Nanoscale charge localization induced by random orientations of organic molecules in hybrid perovskite CH3NH3PbI3

Science.gov (United States)

Ma, Jie; Wang, Lin-Wang

2015-03-01

Perovskite-based solar cells have achieved high solar-energy conversion efficiencies and attracted wide attentions nowadays. Despite the rapid progress in solar-cell devices, many fundamental issues of the hybrid perovskites have not been fully understood. Experimentally, it is well known that in CH3NH3PbI3, the organic molecules CH3NH3 are randomly orientated at the room temperature, but the impact of the random molecular orientation has not been investigated. Using linear-scaling ab-initiomethods, we have calculated the electronic structures of the tetragonal phase of CH3NH3PbI3 with randomly orientated organic molecules in large supercells up to ~20,000 atoms. Due to the dipole moment of the organic molecule, the random orientation creates a novel system with long-range potential fluctuations unlike alloys or other conventional disordered systems. We find that the charge densities of the conduction-band minimum and the valence-band maximum are localized separately in nanoscales due to the potential fluctuations. The charge localization causes electron-hole separation and reduces carrier recombination rates, which may contribute to the long carrier lifetime observed in experiments. We have also proposed a model to explain the charge localization.

Infrared spectra of the ammonium ion in ammonium metavanadate NH 4VO 3

Science.gov (United States)

de Waal, D.; Heyns, A. M.; Range, K.-J.; Eglmeier, C.

The ND stretching modes of isotopically dilute NH 3D + ions in NH 4VO 3 are in agreement with the predicted splitting into C s, C s and C1(2) components under C s site symmetry for the NH +4 ion. The three bands observed represent the three NH bonding distances in the crystal, and the position, shape and low temperature behaviour of each band confirms the existence of two types of hydrogen bonding in NH 4VO 3. The low temperature infrared modes of NH +4 and ND +4 in NH 4VO 3 and ND 4VO 3, respectively, can be assigned under space group Pbcm. Temperature dependence of these modes also reflects the presence of both normal and bifurcated hydrogen bonds in NH 4VO 3.

Rate-based modelling of combined SO2 removal and NH3 recycling integrated with an aqueous NH3-based CO2 capture process

International Nuclear Information System (INIS)

Li, Kangkang; Yu, Hai; Qi, Guojie; Feron, Paul; Tade, Moses; Yu, Jingwen; Wang, Shujuan

2015-01-01

Highlights: • A rigorous, rate-based model for an NH 3 –CO 2 –SO 2 –H 2 O system was developed. • Model predictions are in good agreement with pilot plant results. • >99.9% of SO 2 was captured and >99.9% of slipped ammonia was reused. • The process is highly adaptable to the variations of SO 2 /NH 3 level, temperatures. - Abstract: To reduce the costs of controlling emissions from coal-fired power stations, we propose an advanced and effective process of combined SO 2 removal and NH 3 recycling, which can be integrated with the aqueous NH 3 -based CO 2 capture process to simultaneously achieve SO 2 and CO 2 removal, NH 3 recycling and flue gas cooling in one process. A rigorous, rate-based model for an NH 3 –CO 2 –SO 2 –H 2 O system was developed and used to simulate the proposed process. The model was thermodynamically and kinetically validated by experimental results from the open literature and pilot-plant trials, respectively. Under typical flue gas conditions, the proposed process has SO 2 removal and NH 3 reuse efficiencies of >99.9%. The process is strongly adaptable to different scenarios such as high SO 2 levels in flue gas, high NH 3 levels from the CO 2 absorber and high flue gas temperatures, and has a low energy requirement. Because the process simplifies flue gas desulphurisation and resolves the problems of NH 3 loss and SO 2 removal, it could significantly reduce the cost of CO 2 and SO 2 capture by aqueous NH 3

Catalytic reduction of NH4NO3 by NO. Effects of solid acids and implications for low temperature DeNOx processes

International Nuclear Information System (INIS)

Savara, Aditya; Li, Mei-Jun; Sachtler, Wolfgang M.H.; Weitz, Eric

2008-01-01

Ammonium nitrate is thermally stable below 250 C and could potentially deactivate low temperature NO x reduction catalysts by blocking active sites. It is shown that NO reduces neat NH 4 NO 3 above its 170 C melting point, while acidic solids catalyze this reaction even at temperatures below 100 C. NO 2 , a product of the reduction, can dimerize and then dissociate in molten NH 4 NO 3 to NO + + NO 3 - , and may be stabilized within the melt as either an adduct or as HNO 2 formed from the hydrolysis of NO + or N 2 O 4 . The other product of reduction, NH 4 NO 2 , readily decomposes at ≤100 C to N 2 and H 2 O, the desired end products of DeNO x catalysis. A mechanism for the acid catalyzed reduction of NH 4 NO 3 by NO is proposed, with HNO 3 as an intermediate. These findings indicate that the use of acidic catalysts or promoters in DeNO x systems could help mitigate catalyst deactivation at low operating temperatures (<150 C). (author)

Heterolytic cleavage of ammonia N-H bond by bifunctional activation in silica-grafted single site Ta(V) imido amido surface complex. Importance of the outer sphere NH3 assistance

KAUST Repository

Gouré, Eric

2011-01-01

Ammonia N-H bond is cleaved at room temperature by the silica-supported tantalum imido amido complex [(≡SiO)2Ta(NH)(-NH2)], 2, if excess ammonia is present, but requires 150 °C to achieve the same reaction if only one equivalent NH3 is added to 2. MAS solid-state 15N NMR and in situ IR spectroscopic studies of the reaction of either 15N or 2H labeled ammonia with 2 show that initial coordination of the ammonia is followed by scrambling of either 15N or 2H among ammonia, amido and imido groups. Density functional theory (DFT) calculations with a cluster model [{(μ-O)[(H3SiO) 2SiO]2}Ta(NH)(-NH2)(NH3)], 2 q·NH3, show that the intramolecular H transfer from Ta-NH2 to TaNH is ruled out, but the H transfers from the coordinated ammonia to the amido and imido groups have accessible energy barriers. The energy barrier for the ammonia N-H activation by the Ta-amido group is energetically preferred relative to the Ta-imido group. The importance of excess NH3 for getting full isotope scrambling is rationalized by an outer sphere assistance of ammonia acting as proton transfer agent, which equalizes the energy barriers for H transfer from coordinated ammonia to the amido and imido groups. In contrast, additional coordinated ammonia does not favor significantly the H transfer. These results rationalize the experimental conditions used. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011.

Room Temperature Monoclinic Phase in BaTiO3 Single Crystals

Science.gov (United States)

Denev, Sava; Kumar, Amit; Barnes, Andrew; Vlahos, Eftihia; Shepard, Gabriella; Gopalan, Venkatraman

2010-03-01

BaTiO3 is a well studied ferroelectric material for the last half century. It is well known to show phase transitions to tetragonal, orthorhombic and rhombohedral phases upon cooling. Yet, some old and some recent studies have argued that all these phases co-exist with a second phase with monoclinic distortion. Using optical second harmonic generation (SHG) at room temperature we directly present evidence for such monoclininc phase co-existing with tetragonal phase at room temperature. We observe domains with the expected tetragonal symmetry exhibiting 90^o and 180^o domain walls. However, at points of higher stress at the tips of the interpenetrating tetragonal domains we observe a well pronounced metastable ``staircase pattern'' with a micron-scale fine structure. Polarization studies show that this phase can be explained only by monoclinic symmetry. This phase is very sensitive to external perturbations such as temperature and fields, hence stabilizing this phase at room temperature could lead to large properties' tunability.

A feasibility analysis of replacing the standard ammonia refrigeration device with the cascade NH3/CO2 refrigeration device in the food industry

Directory of Open Access Journals (Sweden)

Jankovich Dennis

2015-01-01

Full Text Available The thermodynamic analysis demonstrates the feasibility of replacing the standard ammonia refrigeration device with the cascade NH3/CO2 refrigeration device in the food industry. The main reason for replacement is to reduce the total amount of ammonia in spaces like deep-freezing chambers, daily chambers, working rooms and technical passageways. An ammonia-contaminated area is hazardous to human health and the safety of food products. Therefore the preferred reduced amount of ammonia is accumulated in the Central Refrigeration Engine Room, where the cascade NH3/CO2 device is installed as well. Furthermore, the analysis discusses and compares two left Carnot¢s refrigeration cycles, one for the standard ammonia device and the other for the cascade NH3/CO2 device. Both cycles are processes with two-stage compression and two-stage throttling. The thermodynamic analysis demonstrates that the selected refrigeration cycle is the most cost-effective process because it provides the best numerical values for the total refrigeration factor with respect to the observed refrigeration cycle. The chief analyzed influential parameters of the cascade device are: total refrigeration load, total reactive power, mean temperature of the heat exchanger, evaporating and condensing temperature of the low-temperature part.

Room-Temperature Atomic Layer Deposition of Al2 O3 : Impact on Efficiency, Stability and Surface Properties in Perovskite Solar Cells.

Science.gov (United States)

Kot, Malgorzata; Das, Chittaranjan; Wang, Zhiping; Henkel, Karsten; Rouissi, Zied; Wojciechowski, Konrad; Snaith, Henry J; Schmeisser, Dieter

2016-12-20

In this work, solar cells with a freshly made CH 3 NH 3 PbI 3 perovskite film showed a power conversion efficiency (PCE) of 15.4 % whereas the one with 50 days aged perovskite film only 6.1 %. However, when the aged perovskite was covered with a layer of Al 2 O 3 deposited by atomic layer deposition (ALD) at room temperature (RT), the PCE value was clearly enhanced. X-ray photoelectron spectroscopy study showed that the ALD precursors are chemically active only at the perovskite surface and passivate it. Moreover, the RT-ALD-Al 2 O 3 -covered perovskite films showed enhanced ambient air stability. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

CdO necklace like nanobeads decorated with PbS nanoparticles: Room temperature LPG sensor

Energy Technology Data Exchange (ETDEWEB)

Sonawane, N.B. [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon, 425001 M.S. (India); K.A.M.P. & N.K.P. Science College, Pimpalner, Sakri, Dhule, M.S. (India); Baviskar, P.K. [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon, 425001 M.S. (India); Ahire, R.R. [S.G. Patil Science, Sakri, Dhule, M.S. (India); Sankapal, B.R., E-mail: brsankapal@gmail.com [Nano Materials and Device Laboratory, Department of Applied Physics, Visvesvaraya National Institute of Technology, South Ambazari Road, Nagpur, 440010 M.S. (India)

2017-04-15

Simple chemical route has been employed to grow interconnected nanobeads of CdO having necklace like structure through air annealing of cadmium hydroxide nanowires. This nanobeads of n-CdO with high surface area has been decorated with p-PbS nanoparticles resulting in the formation of nano-heterojunction which has been utilized effectively as room temperature liquefied petroleum gas (LPG) sensor. The room temperature gas response towards C{sub 2}H{sub 5}OH, Cl{sub 2}, NH{sub 3}, CO{sub 2} and LPG was investigated, among which LPG exhibits significant response. The maximum gas response of 51.10% is achieved with 94.54% stability upon exposure of 1176 ppm concentration of LPG at room temperature (27 °C). The resulting parameters like gas response, response and recovery time along with stability studies has been studied and results are discussed herein. - Highlights: • Conversion of Cd(OH){sub 2} nanowires to CdO nanonecklace by air annealing at 290 °C. • Decoration of PbS nanoparticles over CdO nanobeads by SILAR method. • Formation of n-CdO/p-PbS nano-heterojunction as room temperature LPG sensor. • Maximum gas response of 51.10% with 94.54% stability.

Crystal structure and characterization of the novel NH+⋯N hydrogen bonded polar crystal [NH2(CH2)4NH][BF4

International Nuclear Information System (INIS)

Wojtaś, M.; Gagor, A.; Czupiński, O.; Medycki, W.; Jakubas, R.

2012-01-01

Dielectric properties and phase transitions of the piperazinium tetrafluoroborate ([NH 2 (CH 2 ) 4 NH][BF 4 ], abbreviated as PFB) crystal are related to the one-dimensional arrangement of the cations linked by the bistable NH + ⋯N hydrogen bonds and molecular motions of the [BF 4 ] − units. The crystal structure of [NH 2 (CH 2 ) 4 NH][BF 4 ] is monoclinic at room temperature with the polar space group Pn. The polar/acentric properties of the room temperature phase IV have been confirmed by the piezoelectric and pyroelectric measurements. DSC measurements show that the compound undergoes three first-order structural phase transitions: at 421/411 K (heating/cooling), at 386/372 K and at 364/349 K. 1 H and 19 F NMR measurements indicate the reorientational motions of [BF 4 ] − anions and piperazinium(+) cations as well as the proton motion in the hydrogen-bonded chains of piperazine along the [001] direction. Over the phase I the isotropic reorientational motions or even self-diffusion of the cations and anions are expected. The conductivity measurements in the vicinity of the II–I PT indicate a superionic phase over the phase I. - Graphical abstract: It must be emphasized that the titled compound represents the first organic–inorganic simple salt containing the single-protonated piperazinium cation which was studied by means of the wide variety of experimental techniques. A survey of Cambridge Structural Database (CSD version 5.32 (November 2010) and updates (May 2011)) for structure containing the piperazinium cations yields 248 compounds with the doubly protonated piperazinium(2+) cations and only eight compounds with the singly protonated piperazinium(+) cations. Among these structures only one is the hybrid organic–inorganic material. This is piperazinium nitrate characterized structurally. The crystal packing of [NH 2 (CH 2 ) 4 NH][BF 4 ], phase IV. The dashed lines stand for the hydrogen bonds. The hydrogen bonds to BF4 groups are not included for

THIN FILM-BASED SENSOR FOR MOTOR VEHICLE EXHAUST GAS, NH3, AND CO DETECTION

Directory of Open Access Journals (Sweden)

S. Sujarwata

2016-10-01

Full Text Available A copper phthalocyanine (CuPc thin film based gas sensor with FET structure and channel length 100 μm has been prepared by VE method and lithography technique to detect NH3, motor cycle exhaust gases and CO. CuPc material layer was deposited on SiO2 by the vacuum evaporator (VE method at room temperature and pressure of 8 x10-4 Pa. The stages of manufacturing gas sensor were Si/SiO2 substrate blenching with ethanol in an ultrasonic cleaner, source, and drain electrodes deposition on the substrate by using a vacuum evaporator, thin film deposition between the source/drain and gate deposition. The sensor response times to NH3, motorcycle exhaust gases and CO were 75 s, 135 s, and 150, respectively. The recovery times were 90 s, 150 s and 225, respectively. It is concluded that the CuPc thin film-based gas sensor with FET structure is the best sensor to detect the NH3 gas.Sensor gas berbasis film tipis copper phthalocyanine (CuPc berstruktur FET dengan panjang channel 100 μm telah dibuatdengan metode VE dan teknik lithography untuk mendeteksi NH3 gas buang kendaraan bermotor dan CO. Lapisan bahan CuPc dideposisikan pada permukaan silikon dioksida (SiO2 dengan metode vacuum evaporator (VE pada temperatur ruang dengan tekanan 8 x10-4 Pa. Tahapan pembuatan sensor gas adalah pencucian substrat Si/SiO2 dengan etanol dalam ultrasonic cleaner, deposisi elektroda source dan drain di atas substrat dengan metode vacuum evaporator, deposisi film tipis diantara source/drain dan deposisi gate. Waktu tanggap sensor terhadap NH3, gas buang kendaraan bermotor dan CO berturut-turut adalah 75 s, 135 s,dan 150 s. Waktu pemulihan berturut-turut adalah 90 s, 150 s,dan 225 s. Disimpulkan bahwa sensor gas berstruktur FET berbasis film tipis CuPc merupakan sensor paling baik untuk mendeteksi adanya gas NH3.

X-ray and neutron single crystal diffraction on (NH4)3H(SO4)2. II. Refinement of crystal structure of phase II at room temperature

International Nuclear Information System (INIS)

Reehuis, M.; Wozniak, K.; Dominiak, P.; Smirnov, L.S.; Natkaniec, I.; Baranov, A.I.; Dolbinina, V.V.

2006-01-01

The (NH 4 ) 3 H(SO 4 ) 2 is of special interest due to the possible influence of ammonium ions on a series of phase transitions: I => II => III => IV => V => VII. Earlier, the X-ray single crystal diffraction study of phase II of (NH 4 ) 3 H(SO 4 ) 2 showed that the crystal structure of this compound has two crystallographically independent groups of ammonium ions NH 4 (1) and NH 4 (2), but orientational positions of these ammonium ions were not determined exactly. The refinement of NH 4 (1) and NH 4 (2) orientational positions in phase II is carried out with the help of the X-ray and neutron single crystal diffraction study. The analyses of differential Fourier maps of electron charge density and nuclear density point out the possibility of disordering of NH 4 (2) ammonium ions

Solid-state thermal decomposition of the [Co(NH3)5CO3]NO3·0.5H2O complex: A simple, rapid and low-temperature synthetic route to Co3O4 nanoparticles

International Nuclear Information System (INIS)

Farhadi, Saeid; Safabakhsh, Jalil

2012-01-01

Highlights: ► [Co(NH 3 ) 5 CO 3 ]NO 3 ·0.5H 2 O complex was used for preparing pure Co 3 O 4 nanoparticles. ► Co 3 O 4 nanoparticles were prepared at low temperature of 175 °C. ► Co 3 O 4 nanoparticles show a weak ferromagnetic behaviour at room temperature. ► The method is simple, low-cost and suitable for the production of Co 3 O 4 . - Abstract: Co 3 O 4 nanoparticles were easily prepared via the decomposition of the pentammine(carbonato)cobalt(III) nitrate precursor complex [Co(NH 3 ) 5 CO 3 ]NO 3 ·0.5H 2 O at low temperature (175 °C). The product was characterized by thermal analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area measurements and magnetic measurements. The FT-IR, XRD, Raman and EDX results indicated that the synthesized Co 3 O 4 nanoparticles are highly pure and have a single phase. The TEM analysis revealed nearly uniform and quasi-spherical Co 3 O 4 nanoparticles with an average particle size of approximately 10 nm. The optical absorption spectrum of the Co 3 O 4 nanoparticles showed two direct band gaps of 2.18 and 3.52 eV with a red shift in comparison with previous reported values. The prepared Co 3 O 4 nanoparticles showed a weak ferromagnetic behaviour that could be attributed to uncompensated surface spins and/or finite-size effects. Using the present method, Co 3 O 4 nanoparticles can be produced without expensive organic solvents and complicated equipment. This simple, rapid, safe and low-cost synthetic route can be extended to the synthesis of other transition-metal oxides.

Neutron single crystal diffraction studies of orientational glass state in the [Rbx(NH4)1-x]3H(SO4)2 mixed crystals

International Nuclear Information System (INIS)

Smirnov, L.S.; Reehuis, M.; Loose, A.; Hohlwein, D.; Hoffmann, J.U.; Wozniak, K.; Dominiak, P.; Baranov, A.I.; Dolbinina, V.V.

2005-01-01

The [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystal with the concentration x=0.0 at room temperature crystallizes in a monoclinic C2/c with sp.gr. (space group), which is stabilized for x>0.09 down to low temperatures. This system is transformed in the orientational glass state below the freezing temperature T g =30 K. The differential Fourier maps for the [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals show that if for x=0.0 and 0.11 at 293 K the obtained maps reflect different orientational positions of crystallographically independent NH 4 (1) and NH 4 (2) groups, then the differential Fourier maps for x=0.20 at 9 K in the orientational glass state are similar for both ammonium groups reflecting their static disorder. The existence of the modulated structure in the [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals with x=0.11 at 2 K is discovered, while the modulated structure for x=0.20 at 2 K is absent. This observation supposes that there should be two different regions of the orientational glass state on x-T phase diagram of the [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals

Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3

Science.gov (United States)

Pourkhalil, Mahnaz; Moghaddam, Abdolsamad Zarringhalam; Rashidi, Alimorad; Towfighi, Jafar; Mortazavi, Yadollah

2013-08-01

Manganese oxide catalysts (MnOx) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O2 were prepared by the incipient wetness impregnation method. These catalysts were characterized by N2 adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H2-temperature programmed reduction (H2-TPR) methods. The effects of reaction temperature, MnOx loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NOx with NH3. Under the reaction conditions of 200 °C, 1 bar, NO = NH3 = 900 ppm, O2 = 5 vol%, GHSV = 30,000 h-1 and 12 wt% MnOx, NOx conversion and N2 selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO2 and 2.5 vol% H2O from 97% to 92% within 6 h at 200 °C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 °C due to thermal decomposition of ammonium sulphate salts.

Room temperature Q-band electron magnetic resonance study of radicals in X-ray-irradiated L-threonine single crystals

International Nuclear Information System (INIS)

Vanhaelewyn, Gauthier; Vrielinck, Henk; Callens, Freddy

2014-01-01

In the past, decennia radiation-induced radicals were successfully identified by electron magnetic resonance (EMR) in several solid-state amino acids and sugars. The authors present a room temperature (RT) EMR study of the stable radicals produced by X-ray-irradiation in the amino acid L-threonine (CH 3 CH(OH)CH(NH3 + )COO - ). Its chemical structure is similar to that of the well-known dosimetric material L-alanine (CH 3 CH(NH3 + )COO - ), and radiation defects in L-threonine may straightforwardly be compared with the extensively studied L-alanine radicals. The hyperfine coupling tensors of three different radicals were determined at RT using electron nuclear double resonance. These results indicate that the two most abundant radicals share the same basic structure CH 3 .C(OH)CH(NH3 + )COO - , obtained by H-abstraction, but are stabilised in slightly different conformations. The third radical is most probably obtained by deamination (CH 3 CH(OH).CHCOO - ), similar in structure to the stable alanine radical. (authors)

Preparation and characterization of magnetic nanoparticles (Fe_3O_4) coated with oleic acid at room temperature

International Nuclear Information System (INIS)

Souza, Marcio Nele de; Feuser, Paulo Emilio

2010-01-01

This work studied a method for preparation of Fe_3O_4 magnetic nanoparticles stabilized with acid oleic precipitating Fe"+"2 and Fe"+"3 (1:1) salts at room temperature. The method involved the coprecipitation of Fe_3O_4 in aqueous solution from FeCl_3·6H_2O and FeSO_4·7H_2O solutions using as NH_4OH (30%) precipitation agent. The final size of nanoparticles was 10nn with an initial pH of 0-1 and a final neutral pH, without addition of an acid and/ or hydroxide to adjust the pH of the material. The oleic acid coated nanoparticles were characterized by Ray-X of Diffraction (DRX), thermogravimetric analysis (TGA), scanning electron microscopy in field emission and dynamic light scattering (FEG-SEM). It is important to standardize the methods of preparation of Fe_3O_4 Magnetic Nanoparticles stabilized with oleic acid, to obtain a desired material for a given application it is in technology or Biomedical. (author)

Revealing the properties of defects formed by CH3NH2 molecules in organic-inorganic hybrid perovskite MAPbBr3

Science.gov (United States)

Wang, Ji; Zhang, Ao; Yan, Jun; Li, Dan; Chen, Yunlin

2017-03-01

The properties of defects in organic-inorganic hybrid perovskite are widely studied from the first-principles calculation. However, the defects of methylamine (methylamine = CH3NH2), which would be easily formed during the preparation of the organic-inorganic hybrid perovskite, are rarely investigated. Thermodynamic properties as well as defect states of methylamine embedded MAPbX3 (MA = methyl-ammonium = CH3NH3, X = Br, I) are studied based on first-principles calculations of density functional theory. It was found that there is a shallow defect level near the highest occupied molecular orbital, which induced by the interstitial methylamine defect in MAPbBr3, will lead to an increase of photoluminescence. The calculation results showed that interstitial defect states of methylamine may move deeper due to the interaction between methylamine molecules and methyl-ammonium cations. It was also showed that the interstitial methylamine defect is stable at room temperature, and the defect can be removed easily by annealing.

Highly selective room temperature NO2 gas sensor based on rGO-ZnO composite

Science.gov (United States)

Jyoti, Kanaujiya, Neha; Varma, G. D.

2018-05-01

Blending metal oxide nanoparticles with graphene or its derivatives can greatly enhance gas sensing characteristics. In the present work, ZnO nanoparticles have been synthesized via reflux method. Thin films of reduced graphene oxide (rGO) and composite of rGO-ZnO have been fabricated by drop casting method for gas sensing application. The samples have been characterized by X-ray diffraction (XRD) and Field-emission scanning electron microscope (FESEM) for the structural and morphological studies respectively. Sensing measurements have been carried out for the composite film of rGO-ZnO for different concentrations of NO2 ranging from 4 to 100 ppm. Effect of increasing temperature on the sensing performance has also been studied and the rGO-ZnO composite sensor shows maximum percentage response at room temperature. The limit of detection (LOD) for rGO-ZnO composite sensor is 4ppm and it exhibits a high response of 48.4% for 40 ppm NO2 at room temperature. To check the selectivity of the composite sensor, sensor film has been exposed to 40 ppm different gases like CO, NH3, H2S and Cl2 at room temperature and the sensor respond negligibly to these gases. The present work suggests that rGO-ZnO composite material can be a better candidate for fabrication of highly selective room temperature NO2 gas sensor.

Dechlorination of PCBs, CAHs, herbicides and pesticides neat and in soils at 25 degrees C using Na/NH3.

Science.gov (United States)

Pittman, Charles U; He, Jinbao

2002-05-03

Na/NH3 reductions have been used to dehalogenate polychlorinated biphenyls (PCBs), chlorinated aliphatic hydrocarbons (CAHs) and pesticides at diffusion controlled rates at room temperature in model compound studies in both dry NH3 and when water was added. The rate ratio of dechlorination (aliphatic and aromatic compounds) versus reaction of the solvated electron with water is very large, allowing wet soils or sludges to be remediated without an unreasonable consumption of sodium. Several soils, purposely contaminated with 1,1,1-trichloroethane, 1-chlorooctane and tetrachloroethylene, were remediated by slurring the soils in NH3 followed by addition of sodium. The consumption of sodium per mole of chlorine removed was examined as a function of both the hazardous substrate's concentration in the soil and the amount of water present. The Na consumption per Cl removed increases as the amount of water increases and as the substrate concentration in soil decreases. However, remediation was still readily accomplished from 5000 to 3000ppm to sub ppm levels of RCl in the presence of substantial amounts of water. PCB- and dioxin-contaminated oils were remediated with Na/NH3 as were PCB-contaminated soils and sludges from contaminated sites. Ca/NH3 treatments also successfully remediated PCB-contaminated clay, sandy and organic soils but laboratory studies demonstrated that Ca was less efficient than Na when substantial amounts of water were present. The advantages of solvated electron reductions using Na/NH3 include: (1) very rapid dehalogenation rates at ambient temperature, (2) soils (even clay soils) break down into particles and slurry nicely in NH3, (3) liquid ammonia handling technology is well known and (4) removal from soils, recovery and recycle of ammonia is easy due to its low boiling point. Finally, dechlorination is extremely fast even for the 'corner' chlorines in the substrate Mirex (structure in Eq. (5)).

In situ IR studies of Co and Ce doped Mn/TiO{sub 2} catalyst for low-temperature selective catalytic reduction of NO with NH{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Qiu, Lu; Pang, Dandan; Zhang, Changliang; Meng, Jiaojiao; Zhu, Rongshu; Ouyang, Feng, E-mail: ouyangfh@hit.edu.cn

2015-12-01

Highlights: • A SCR mechanistic pathway over Mn–Co–Ce/TiO{sub 2} is proposed. • The cobalt oxide produces lots of Brønsted acid sites, which favor to the adsorption of coordinated NH{sub 3} through NH{sub 3} migration. • Ce addition improves amide ions formation to reach best NO reduction selectivity. • At low-temperature coordinated NH{sub 3} reacts with NO{sub 2}{sup −}, or amide reacts with NO (ad) or NO (g) to form N{sub 2}. At high temperature, the reaction also occurs between coordinated NH{sub 3} and nitrate species. - Abstract: The Mn–Co–Ce/TiO{sub 2} catalyst was prepared by wet co-impregnation method for selective catalytic reduction of NO by NH{sub 3} in the presence of oxygen. The adsorption and co-adsorption of NH{sub 3}, NO and O{sub 2} on catalysts were investigated by in situ FTIR spectroscopy. The results suggested that addition of cobalt and cerium oxides increased the numbers of acid and redox sites. Especially, the cobalt oxide produced lots of Brønsted acid sites, which favor to the adsorption of coordinated NH{sub 3} through NH{sub 3} migration. Ce addition improved amide ions formation to reach best NO reduction selectivity. A mechanistic pathway over Mn–Co–Ce/TiO{sub 2} was proposed. At low-temperature SCR reaction, coordinated NH{sub 3} reacted with NO{sub 2}{sup −}, and amide reacted with NO (ad) or NO (g) to form N{sub 2}. NO{sub 2} was related to the formation of nitrite on Co-contained catalysts and the generation of −NH{sub 2}{sup −} on Ce-contained catalysts. At high temperature, the other branch reaction also occurred between the coordinated NH{sub 3} and nitrate species, resulting in N{sub 2}O yield increase.

Crystal structure and electrical conduction of the new organic-inorganic compound (CH2)2(NH3)2CdI4

Science.gov (United States)

Zhang, Liuqi; Wang, Jilin; Han, Feifei; Mo, Shuyi; Long, Fei; Gao, Yihua

2018-03-01

The new organic-inorganic compound (CH2)2(NH3)2CdI4 was prepared by slow evaporation method using a mixture solution of CdI2 and ethylenediamine iodide (EDAI) in the γ-butyrolactone (GBL). The synthesized compound was further characterized by single crystal diffraction, Infrared (IR) and Raman spectroscopy, energy dispersive spectrometer (EDS), X-Ray photoelectron spectroscopy (XPS) and thermogravimetric analysis. The relaxation behavior and conductivity mechanism of (CH2)2(NH3)2CdI4 was studied by the electrical impedance spectroscopy. The results indicated that (CH2)2(NH3)2CdI4 had a monoclinic structure with space group P21/c at room temperature. The complex impedance plotted as semicircle arcs and the proposed electrical equivalent circuit was to interpret the impedance behavior at different temperatures. The electrical equivalent circuit was made of a parallel combination of resistance (R) and fractal capacitance (CPE). Furthermore, the alternating current conductivity of the sample obeyed the Jonscher's law: σf =σdc + Afs and the conduction could be attributed to the correlated barrier hopping (CBH) model.

Increase in Ice Nucleation Efficiency of Feldspars, Kaolinite and Mica in Dilute NH3 and NH4+-containing Solutions

Science.gov (United States)

Kumar, A.; Marcolli, C.; Luo, B.; Krieger, U. K.; Peter, T.

2017-12-01

Semivolatile species present in the atmosphere are prone to adhere to mineral dust particle surfaces during long range transport, and could potentially change the particle surface properties and its ice nucleation (IN) efficiency. Immersion freezing experiments were performed with microcline (K-feldspar), known to be highly IN active, suspended in aqueous solutions of ammonia, (NH4)2SO4, NH4HSO4, NH4NO3, NH4Cl, Na2SO4, H2SO4, K2SO4 and KCl to investigate the effect of solutes on the IN efficiency. Freezing of emulsified droplets investigated with a differential scanning calorimeter (DSC) showed that the heterogeneous ice nucleation temperatures deviate from the water activity-based IN theory, describing heterogeneous ice nucleation temperatures as a function of solution water activity by a constant offset with respect to the ice melting point curve (Zobrist et al. 2008). IN temperatures enhanced up to 4.5 K were observed for very dilute NH3 and NH4+-containing solutions while a decrease was observed as the concentration was further increased. For all solutes with cations other than NH4+, the IN efficiency decreased. An increase of the IN efficiency in very dilute NH3 and NH4+-containing solutions followed by a decrease with increasing concentration was also observed for sanidine (K-feldspar) and andesine (Na/Ca-feldspar). This is an important indication towards specific chemical interactions between solutes and the feldspar surface which is not captured by the water activity-based IN theory. A similar trend is present but less pronounced in case of kaolinite and mica, while quartz is barely affected. We hypothesize that the hydrogen bonding of NH3 molecules with surface -OH groups could be the reason for the enhanced freezing temperatures in dilute ammonia and ammonium containing solutions as they could form an ice-like overlayer providing hydrogen bonding groups for ice to nucleate on top of it. This implies to possibilities of enhanced IN efficiency, especially

Using the Transient Response of WO3 Nanoneedles under Pulsed UV Light in the Detection of NH3 and NO2

Directory of Open Access Journals (Sweden)

Oriol Gonzalez

2018-04-01

Full Text Available Here we report on the use of pulsed UV light for activating the gas sensing response of metal oxides. Under pulsed UV light, the resistance of metal oxides presents a ripple due to light-induced transient adsorption and desorption phenomena. This methodology has been applied to tungsten oxide nanoneedle gas sensors operated either at room temperature or under mild heating (50 °C or 100 °C. It has been found that by analyzing the rate of resistance change caused by pulsed UV light, a fast determination of gas concentration is achieved (ten-fold improvement in response time. The technique is useful for detecting both oxidizing (NO2 and reducing (NH3 gases, even in the presence of different levels of ambient humidity. Room temperature operated sensors under pulsed UV light show good response towards ammonia and nitrogen dioxide at low power consumption levels. Increasing their operating temperature to 50 °C or 100 °C has the effect of further increasing sensitivity.

Shallow trapping vs. deep polarons in a hybrid lead halide perovskite, CH3NH3PbI3.

Science.gov (United States)

Kang, Byungkyun; Biswas, Koushik

2017-10-18

There has been considerable speculation over the nature of charge carriers in organic-inorganic hybrid perovskites, i.e., whether they are free and band-like, or they are prone to self-trapping via short range deformation potentials. Unusually long minority-carrier diffusion lengths and moderate-to-low mobilities, together with relatively few deep defects add to their intrigue. Here we implement density functional methods to investigate the room-temperature, tetragonal phase of CH 3 NH 3 PbI 3 . We compare charge localization behavior at shallow levels and associated lattice relaxation versus those at deep polaronic states. The shallow level originates from screened Coulomb interaction between the perturbed host and an excited electron or hole. The host lattice has a tendency towards forming these shallow traps where the electron or hole is localized not too far from the band edge. In contrast, there is a considerable potential barrier that must be overcome in order to initiate polaronic hole trapping. The formation of a hole polaron (I 2 - center) involves strong lattice relaxation, including large off-center displacement of the organic cation, CH 3 NH 3 + . This type of deep polaron is energetically unfavorable, and active shallow traps are expected to shape the carrier dynamics in this material.

Origin of Ferrimagnetism and Ferroelectricity in Room-Temperature Multiferroic ɛ -Fe2O3

Science.gov (United States)

Xu, K.; Feng, J. S.; Liu, Z. P.; Xiang, H. J.

2018-04-01

Exploring and identifying room-temperature multiferroics is critical for developing better nonvolatile random-access memory devices. Recently, ɛ -Fe2O3 was found to be a promising room-temperature multiferroic with a large polarization and magnetization. However, the origin of the multiferroicity in ɛ -Fe2O3 is still puzzling. In this work, we perform density-functional-theory calculations to reveal that the spin frustration between tetrahedral-site Fe3 + spins gives rise to the unexpected ferrimagnetism. For the ferroelectricity, we identify a low-energy polarization switching path with an energy barrier of 85 meV /f .u . by performing a stochastic surface walking simulation. The switching of the ferroelectric polarization is achieved by swapping the tetrahedral Fe ion with the octahedral Fe ion, different from the usual case (e.g., in BaTiO3 and BiFeO3 ) where the coordination number remains unchanged after the switching. Our results not only confirm that ɛ -Fe2O3 is a promising room-temperature multiferroic but also provide guiding principles to design high-performance multiferroics.

Morphological and luminescent characteristics of GaN dots deposited on AlN by alternate supply of TMG and NH3

International Nuclear Information System (INIS)

Tsai, Y.-L.; Gong, J.-R.; Lin, T.-Y.; Lin, H.-Y.; Chen, Yang-Fang; Lin, K.-M.

2006-01-01

GaN dots were deposited on AlN underlayers by alternate supply of trimethylgallium (TMG) and ammonia (NH 3 ) in an inductively heated quartz reactor operated at atmospheric pressure. Various growth parameters including deposition temperature, TMG admittance and pulse time between TMG and NH 3 exposures were proposed to investigate the influence of growth parameters on the size distribution of GaN dots. It appears that GaN dots with uniform size distribution can be achieved under certain growth conditions. Based on the study of atomic force microscopy (AFM), high deposition temperature was found to be in favor of forming large GaN dots with small dot density. Decrement of TMG flow rate or reduction in the number of growth cycle tends to enable the formation of GaN dots with small dot sizes. The results of room temperature (RT) cathodoluminescence (CL) measurements of the GaN dots exhibit an emission peak at 3.735 eV. A remarkable blue shift of GaN dot emission was observed by reduced temperature photoluminescence (PL) measurements

Effect of Thermal and Structural Disorder on the Electronic Structure of Hybrid Perovskite Semiconductor CH3NH3PbI3.

Science.gov (United States)

Singh, Shivam; Li, Cheng; Panzer, Fabian; Narasimhan, K L; Graeser, Anna; Gujar, Tanaji P; Köhler, Anna; Thelakkat, Mukundan; Huettner, Sven; Kabra, Dinesh

2016-08-04

In this Letter, we investigate the temperature dependence of the optical properties of methylammonium lead iodide (MAPbI3 = CH3NH3PbI3) from room temperature to 6 K. In both the tetragonal (T > 163 K) and the orthorhombic (T photoluminescence (PL) measurements) decreases with decrease in temperature, in contrast to what is normally seen for many inorganic semiconductors, such as Si, GaAs, GaN, etc. We show that in the perovskites reported here, the temperature coefficient of thermal expansion is large and accounts for the positive temperature coefficient of the band gap. A detailed analysis of the exciton line width allows us to distinguish between static and dynamic disorder. The low-energy tail of the exciton absorption is reminiscent of Urbach absorption. The Urbach energy is a measure of the disorder, which is modeled using thermal and static disorder for both the phases separately. The static disorder component, manifested in the exciton line width at low temperature, is small. Above 60 K, thermal disorder increases the line width. Both these features are a measure of the high crystal quality and low disorder of the perovskite films even though they are produced from solution.

Fiber-Amplifier-Enhanced QEPAS Sensor for Simultaneous Trace Gas Detection of NH3 and H2S

Directory of Open Access Journals (Sweden)

Hongpeng Wu

2015-10-01

Full Text Available A selective and sensitive quartz enhanced photoacoustic spectroscopy (QEPAS sensor, employing an erbium-doped fiber amplifier (EDFA, and a distributed feedback (DFB laser operating at 1582 nm was demonstrated for simultaneous detection of ammonia (NH3 and hydrogen sulfide (H2S. Two interference-free absorption lines located at 6322.45 cm−1 and 6328.88 cm−1 for NH3 and H2S detection, respectively, were identified. The sensor was optimized in terms of current modulation depth for both of the two target gases. An electrical modulation cancellation unit was equipped to suppress the background noise caused by the stray light. An Allan-Werle variance analysis was performed to investigate the long-term performance of the fiber-amplifier-enhanced QEPAS sensor. Benefitting from the high power boosted by the EDFA, a detection sensitivity (1σ of 52 parts per billion by volume (ppbv and 17 ppbv for NH3 and H2S, respectively, were achieved with a 132 s data acquisition time at atmospheric pressure and room temperature.

Fiber-Amplifier-Enhanced QEPAS Sensor for Simultaneous Trace Gas Detection of NH3 and H2S

Science.gov (United States)

Wu, Hongpeng; Dong, Lei; Liu, Xiaoli; Zheng, Huadan; Yin, Xukun; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Jia, Suotang

2015-01-01

A selective and sensitive quartz enhanced photoacoustic spectroscopy (QEPAS) sensor, employing an erbium-doped fiber amplifier (EDFA), and a distributed feedback (DFB) laser operating at 1582 nm was demonstrated for simultaneous detection of ammonia (NH3) and hydrogen sulfide (H2S). Two interference-free absorption lines located at 6322.45 cm−1 and 6328.88 cm−1 for NH3 and H2S detection, respectively, were identified. The sensor was optimized in terms of current modulation depth for both of the two target gases. An electrical modulation cancellation unit was equipped to suppress the background noise caused by the stray light. An Allan-Werle variance analysis was performed to investigate the long-term performance of the fiber-amplifier-enhanced QEPAS sensor. Benefitting from the high power boosted by the EDFA, a detection sensitivity (1σ) of 52 parts per billion by volume (ppbv) and 17 ppbv for NH3 and H2S, respectively, were achieved with a 132 s data acquisition time at atmospheric pressure and room temperature. PMID:26506351

Effect of etching current density on microstructure and NH3-sensing properties of porous silicon with intermediate-sized pores

International Nuclear Information System (INIS)

Li, Mingda; Hu, Ming; Zeng, Peng; Ma, Shuangyun; Yan, Wenjun; Qin, Yuxiang

2013-01-01

In this work, porous silicon with intermediate-sized pores (intermediate–PS) was prepared by using galvanostatic electrochemical etching method and the effect toward sensing response characteristics of NH 3 gas was also studied. The morphology and surface chemical bonds of intermediate–PS were characterized by using field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The results showed the intermediate–PS microstructure can be significantly modulated by the etching current density. Moreover, the freshly prepared intermediate–PS surface could achieve reliable passivation after storage in ethanol. Furthermore, the gas-sensing measurements of the intermediate–PS sensors were carried out versus different concentrations of NH 3 . The PS sensor exhibited good NH 3 -sensing performances at room temperature owing to its unique microstructure features, including large specific surface area and highly ordered pore channels. In addition, the conceivable pore formation mechanism as well as gas sensing mechanism was also discussed

Order-disorder phase transition in the peroxidovanadium complex NH4[VO(O2)2(NH3)].

Science.gov (United States)

Schwendt, Peter; Gyepes, Róbert; Chrappová, Jana; Němec, Ivan; Vaněk, Přemysl

2018-07-05

Complex NH 4 [VO(O 2 ) 2 (NH 3 )] (1) undergoes an order-disorder phase transition at T c ~258K. This transition is accompanied by change in the space group of the orthorhombic lattice and also by significant structural rearrangements of the constituent molecules, which are pertinent mostly to their NH 4 + ions and their ammonia ligands. The low-temperature solid state IR and Raman spectra of 1 were corroborated by solid-state computations that employed Gaussian functions as the basis set. Results of these computations yielded excellent agreement with experimental data. On the curves of temperature dependence of vibrational modes, the phase transition is expressed by an abrupt change of the slope above T c . Copyright © 2018 Elsevier B.V. All rights reserved.

Lithium Insertion in LiCr3O8, NaCr3O8, and KCr3O8 at Room Temperature and at 125°C

DEFF Research Database (Denmark)

Koksbang, R.; Fauteux, D.; Norby, P.

1989-01-01

Lithium insertion and deinsertion reactions have been carried out with LiCr3O8, NaCr3O8, and KCr3O8 chemically andelectrochemically at room temperature and at 125°C. The electrochemical experiments were performed with a nonaqueousliquid electrolyte at room temperature and with a polymer electroly...... is close to 4Li/NaCr3O8 and 1.3Li/KCr3O8.Lithium ion diffusion coefficients are similar for the two compounds in the comparable composition range.Thermally, the fully lithiated compounds appear to be as stable as the pristine materials.......Lithium insertion and deinsertion reactions have been carried out with LiCr3O8, NaCr3O8, and KCr3O8 chemically andelectrochemically at room temperature and at 125°C. The electrochemical experiments were performed with a nonaqueousliquid electrolyte at room temperature and with a polymer electrolyte....... At elevated temperatures, the isostructural compounds NaCr3O8 and KCr3O8 are able to accommodate morethan 4Li/MCr3O8. During this process, minor structural changes are observed. At room temperature, NaCr3O8 and KCr3O8also accommodate Li topotactically, but the maximum number of Li inserted per formula...

Fabry-Pérot Oscillation and Room Temperature Lasing in Perovskite Cube-Corner Pyramid Cavities

KAUST Repository

Mi, Yang; Liu, Zhixiong; Shang, Qiuyu; Niu, Xinxiang; Shi, Jia; Zhang, Shuai; Chen, Jie; Du, Wenna; Wu, Zhiyong; Wang, Rui; Qiu, Xiaohui; Hu, Xiaoyong; Zhang, Qing; Wu, Tao; Liu, Xinfeng

2018-01-01

Recently, organometal halide perovskite-based optoelectronics, particularly lasers, have attracted intensive attentions because of its outstanding spectral coherence, low threshold, and wideband tunability. In this work, high-quality CH3 NH3 PbBr3 single crystals with a unique shape of cube-corner pyramids are synthesized on mica substrates using chemical vapor deposition method. These micropyramids naturally form cube-corner cavities, which are eminent candidates for small-sized resonators and retroreflectors. The as-grown perovskites show strong emission ≈530 nm in the vertical direction at room temperature. A special Fabry-Pérot (F-P) mode is employed to interpret the light confinement in the cavity. Lasing from the perovskite pyramids is observed from 80 to 200 K, with threshold ranging from ≈92 µJ cm-2 to 2.2 mJ cm-2 , yielding a characteristic temperature of T0 = 35 K. By coating a thin layer of Ag film, the threshold is reduced from ≈92 to 26 µJ cm-2 , which is accompanied by room temperature lasing with a threshold of ≈75 µJ cm-2 . This work advocates the prospect of shape-engineered perovskite crystals toward developing micro-sized optoelectronic devices and potentially investigating light-matter coupling in quantum optics.

Fabry-Pérot Oscillation and Room Temperature Lasing in Perovskite Cube-Corner Pyramid Cavities

KAUST Repository

Mi, Yang

2018-01-10

Recently, organometal halide perovskite-based optoelectronics, particularly lasers, have attracted intensive attentions because of its outstanding spectral coherence, low threshold, and wideband tunability. In this work, high-quality CH3 NH3 PbBr3 single crystals with a unique shape of cube-corner pyramids are synthesized on mica substrates using chemical vapor deposition method. These micropyramids naturally form cube-corner cavities, which are eminent candidates for small-sized resonators and retroreflectors. The as-grown perovskites show strong emission ≈530 nm in the vertical direction at room temperature. A special Fabry-Pérot (F-P) mode is employed to interpret the light confinement in the cavity. Lasing from the perovskite pyramids is observed from 80 to 200 K, with threshold ranging from ≈92 µJ cm-2 to 2.2 mJ cm-2 , yielding a characteristic temperature of T0 = 35 K. By coating a thin layer of Ag film, the threshold is reduced from ≈92 to 26 µJ cm-2 , which is accompanied by room temperature lasing with a threshold of ≈75 µJ cm-2 . This work advocates the prospect of shape-engineered perovskite crystals toward developing micro-sized optoelectronic devices and potentially investigating light-matter coupling in quantum optics.

Morphological and luminescent characteristics of GaN dots deposited on AlN by alternate supply of TMG and NH{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Tsai, Y.-L. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Gong, J.-R. [Institute of Opto-Mechatronics, National Chung Cheng University, Chiayi 621, Taiwan (China); Lin, T.-Y. [Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 202, Taiwan (China); Lin, H.-Y. [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Chen, Yang-Fang [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Lin, K.-M. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China)

2006-03-15

GaN dots were deposited on AlN underlayers by alternate supply of trimethylgallium (TMG) and ammonia (NH{sub 3}) in an inductively heated quartz reactor operated at atmospheric pressure. Various growth parameters including deposition temperature, TMG admittance and pulse time between TMG and NH{sub 3} exposures were proposed to investigate the influence of growth parameters on the size distribution of GaN dots. It appears that GaN dots with uniform size distribution can be achieved under certain growth conditions. Based on the study of atomic force microscopy (AFM), high deposition temperature was found to be in favor of forming large GaN dots with small dot density. Decrement of TMG flow rate or reduction in the number of growth cycle tends to enable the formation of GaN dots with small dot sizes. The results of room temperature (RT) cathodoluminescence (CL) measurements of the GaN dots exhibit an emission peak at 3.735 eV. A remarkable blue shift of GaN dot emission was observed by reduced temperature photoluminescence (PL) measurements.

Enhanced NH3 gas sensing performance based on electrospun alkaline-earth metals composited SnO2 nanofibers

International Nuclear Information System (INIS)

Xu, Shuang; Kan, Kan; Yang, Ying; Jiang, Chao; Gao, Jun; Jing, Liqiang; Shen, Peikang; Li, Li

2015-01-01

Highlights: • The small-sized SnO 2 (5–7 nm) were obtained by adding the alkaline-earth. • Sr-composited SnO 2 nanofibers showed uniform nanotubes structure (Sr/SnO 2 ). • Sr/SnO 2 showed an excellent sensing performance to NH 3 at room temperature. - Abstract: One-dimensional alkaline-earth metals composited SnO 2 (Ae/SnO 2 ) nanofibres were fabricated via electrospinning technique, followed by thermal treatment at 600 °C for 5 h. Transmission electron microscopy (TEM) studies showed that the nanoparticles size of Ae/SnO 2 was 5–7 nm, which was smaller than the pristine SnO 2 nanorods attached by 20 nm nanoparticles. Moreover, Sr/SnO 2 nanocomposites showed uniform nanotubes structure with the wall thickness of about 30 nm, in which all the nanoparticles were connected to their neighbors by necks. The Sr/SnO 2 nanotubes exhibited an excellent sensing response toward NH 3 gas at room temperature, lower detection limit (10 ppm), faster response time (6 s towards 2000 ppm∼16 s towards 10 ppm) and better reversibility compared to the pristine SnO 2 nanorods. The enhanced sensor performances were attributed to the higher conductivity of the Sr/SnO 2 . Mott–Schottky plots (M–S) and electrochemical impedance spectroscopy (EIS) measurements indicated that the carrier density of Sr/SnO 2 nanotubes was 3 fold of that pristine SnO 2

Irradiated NH3 and ND3 - two new target materials for polarized targets

International Nuclear Information System (INIS)

Meyer, W.

1982-11-01

A study of dynamic nuclear polarization (DNP) in NH 3 and ND 3 was made at the Bonn 2.5 GeV electron synchrotron. The paramagnetic radicals in the polycristalline ammonia beads were created by irradiation in the high intensity 20 MeV electron beam (> 10 14 electrons/sec) of the injection linac. During irradiation the ammonia beads, produced by dropping into liquid nitrogen, were cooled in liquid argon at approx.= 90 K. DNP measurements were performed at 1 K, 0.5 K and 0.2 K in a 2.5 T magnetic field. Samples of NH 3 , prepared in this way, yielded a maximum proton polarization of 66% at a temperature of 0.5 K with a short polarization build-up time of 9 minutes. ND 3 could be polarized at a temperature of 0.2 K up to 31%. The radiation resistance of the polarization of NH 3 is better than that of butanol. (orig.)

High Efficient Reduction of Graphene Oxide via Nascent Hydrogen at Room Temperature

Directory of Open Access Journals (Sweden)

Qiqi Zhuo

2018-02-01

Full Text Available To develop a green and efficient method to synthesize graphene in relative milder conditions is prerequisite for graphene applications. A chemical reducing method has been developed to high efficiently reduce graphene oxide (GO using Fe2O3 and NH3BH3 as catalyst and reductants, respectively. During the process, environmental and strong reductive nascent hydrogen were generated surrounding the surface of GO sheets by catalyst hydrolysis reaction of NH3BH3 and were used for reduction of GO. The reduction process was studied by ultraviolet absorption spectroscopy, Raman spectroscopy, and Fourier transform infrared spectrum. The structure and morphology of the reduced GO were characterized with scanning electron microscopy and transmission electron microscopy. Compared to metal (Mg/Fe/Zn/Al particles and acid system which also use nascent hydrogen to reduce GO, this method exhibited higher reduction efficiency (43.6%. Also the reduction was carried out at room temperature condition, which is environmentally friendly. As a supercapacitor electrode, the reversible capacity of reduced graphene oxide was 113.8 F g−1 at 1 A g−1 and the capacitance retention still remained at 90% after 200 cycles. This approach provides a new method to reduce GO with high reduction efficiency by green reductant.

Large low-field magnetoresistance of Fe3O4 nanocrystal at room temperature

International Nuclear Information System (INIS)

Mi, Shu; Liu, Rui; Li, Yuanyuan; Xie, Yong; Chen, Ziyu

2017-01-01

Superparamagnetic magnetite (Fe 3 O 4 ) nanoparticles with an average size of 6.5 nm and good monodispersion were synthesized and investigated by X-ray diffraction, Raman spectrometer, transmission electron microscopy and vibrating sample magnetometer. Corresponding low-field magnetoresistance (LFMR) was tested by physical property measurement system. A quite high LFMR has been observed at room temperature. For examples, at a field of 3000 Oe, the LFMR is −3.5%, and when the field increases to 6000 Oe, the LFMR is up to −5.1%. The electron spin polarization was estimated at 25%. This result is superior to the previous reports showing the LFMR of no more than 2% at room temperature. The conduction mechanism is proposed to be the tunneling of conduction electrons between adjacent grains considering that the monodisperse nanocrystals may supply more grain boundaries increasing the tunneling probability, and consequently enhancing the overall magnetoresistance. - Highlights: • Superparamagnetic Fe3O4 nanoparticles with small size were synthesized. • A quite high LFMR has been observed at room temperature. • The more grain boundaries increase the tunneling probability and enlarge the MR. • The fast response of the sample increase the MR at a low field.

Ammonia gas sensors based on In2O3/PANI hetero-nanofibers operating at room temperature

Directory of Open Access Journals (Sweden)

Qingxin Nie

2016-09-01

Full Text Available Indium nitrate/polyvinyl pyrrolidone (In(NO33/PVP composite nanofibers were synthesized via electrospinning, and then hollow structure indium oxide (In2O3 nanofibers were obtained through calcination with PVP as template material. In situ polymerization was used to prepare indium oxide/polyaniline (In2O3/PANI composite nanofibers with different mass ratios of In2O3 to aniline. The structure and morphology of In(NO33/PVP, In2O3/PANI composite nanofibers and pure PANI were investigated by scanning electron microscopy (SEM, Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD, transmission electron microscopy (TEM and current–voltage (I–V measurements. The gas sensing properties of these materials towards NH3 vapor (100 to 1000 ppm were measured at room temperature. The results revealed that the gas sensing abilities of In2O3/PANI composite nanofibers were better than pure PANI. In addition, the mass ratio of In2O3 to aniline and the p–n heterostructure between In2O3 and PANI influences the sensing performance of the In2O3/PANI composite nanofibers. In this paper, In2O3/PANI composite nanofibers with a mass ratio of 1:2 exhibited the highest response values, excellent selectivity, good repeatability and reversibility.

Temperature-Dependent Electric Field Poling Effects in CH3NH3PbI3 Optoelectronic Devices.

Science.gov (United States)

Zhang, Chuang; Sun, Dali; Liu, Xiaojie; Sheng, Chuan-Xiang; Vardeny, Zeev Valy

2017-04-06

Organo-lead halide perovskites show excellent optoelectronic properties; however, the unexpected inconsistency in forward-backward I-V characteristics remains a problem for fabricating solar panels. Here we have investigated the reasons behind this "hysteresis" by following the changes in photocurrent and photoluminescence under electric field poling in transverse CH 3 NH 3 PbI 3 -based devices from 300 to 10 K. We found that the hysteresis disappears at cryogenic temperatures, indicating the "freeze-out" of the ionic diffusion contribution. When the same device is cooled under continuous poling, the built-in electric field from ion accumulation brings significant photovoltaic effect even at 10 K. From the change of photoluminescence upon polling, we found a second dipole-related mechanism which enhances radiative recombination upon the alignment of the organic cations. The ionic origin of hysteresis was also verified by applying a magnetic field to affect the ion diffusion. These findings reveal the coexistence of ionic and dipole-related mechanisms for the hysteresis in hybrid perovskites.

Shape-Evolution Control of hybrid perovskite CH3NH3PbI3 crystals via solvothermal synthesis

Science.gov (United States)

Zhang, Baohua; Guo, Fuqiang; Yang, Lianhong; Jia, Xiuling; Liu, Bin; Xie, Zili; Chen, Dunjun; Lu, Hai; Zhang, Rong; Zheng, Youdou

2017-02-01

We systematically synthesized CH3NH3PbI3 crystals using solvothermal process, and the reaction conditions such as concentration of the precursor, temperature, time, and lead source have been comprehensively investigated to obtain shape-controlled CH3NH3PbI3 crystals. The results showed that the CH3NH3PbI3 crystals exhibit tetragonal phase and the crystals change from nanoparticles to hopper-faced cuboids. Photoluminescence spectra of the crystals obtained with different lead sources show a blue shift due to the presence of defects in the crystals, and the peak intensity is very sensitive to the lead sources. Moreover, impurities (undesirable byproducts and excess components like HI or CH3NH2) presented during crystal growth can result in hopper growth.

Investigation on low room-temperature resistivity Cr/(Ba0.85Pb0.15)TiO3 positive temperature coefficient composites

DEFF Research Database (Denmark)

He, Zeming; Ma, J.; Qu, Yuanfang

2009-01-01

discussed. Using these special processes, the prepared composite with 20 wt% Cr possessed low room-temperature resistivity (2.96 Ω cm at 25 °C) and exhibited PTC effect (resistivity jump of 10), which is considered as a promising candidate for over-current protector when working at low voltage. The grain......Low room-temperature resistivity positive temperature coefficient (PTC) Cr/(Ba0.85Pb0.15)TiO3 composites were produced via a reducing sintering and a subsequent oxidation treatment. The effects of metallic content and processing conditions on materials resistivity–temperature properties were...

Above room-temperature ferromagnetism in La1-xCaxMnO3 epitaxial thin films on SrTiO3(001) substrates

Science.gov (United States)

Kou, Yunfang; Wang, Hui; Miao, Tian; Wang, Yanmei; Xie, Lin; Wang, Shasha; Liu, Hao; Lin, Hanxuan; Zhu, Yinyan; Wang, Wenbin; Du, Haifeng; Pan, Xiaoqing; Wu, Ruqian; Yin, Lifeng; Shen, Jian

The colossal magnetoresistive (CMR) manganites are popular materials for spintronics applications due to their high spin polarization. Only a couple of manganites like La1-xSrxMnO3 have a Curie temperature (Tc) that is higher than room temperature. Finding methods to raise the Tc of manganites over room temperature is useful but challenging. In this work, we use the most intensively studied La1-xCaxMnO3 (LCMO) as the prototype system to demonstrate that Tc can be greatly enhanced by carefully tuning the electronic structure using doping and strain. Specifically, we grow LCMO films on SrTiO3 (001) substrates using pulsed laser deposition. Magnetic and transport measurements indicate a great enhancement of Tc over room temperature at x =0.2 doping. Theoretical calculations indicate that the combined effects from doping and strain give rise to a new electronic structure favoring ferromagnetism in LCMO system. Furthermore, using the La0.8Ca0.2MnO3 as ferromagnetic electrodes, we achieve finite tunneling magnetoresistance (TMR) above room temperature.

[Effects of different NO3--N/NH4+-N ratios on cucumber seedlings growth, nitrogen absorption and metabolism under suboptimal temperature and light intensity].

Science.gov (United States)

Zhang, Xiao Cui; Liu, Yu Mei; Bai, Long Qiang; He, Chao Xing; Yu, Xian Chang; Li, Yan Su

2016-08-01

Cucumber (cv. Zhongnong 26) was used as material, the effects of NO 3 - -N/NH 4 + -N ratios on growth and physiological characteristics of cucumber seedlings under suboptimal temperature and light intensity (18 ℃/10 ℃,180 ± 20 μmol·m -2 ·s -1 ) were studied. Total nitrogen in the nutrient solution was equal and three NO 3 - -N/NH 4 + -N ratios, 26:2, 21:7 and 14:14, were applied as treatments. The results showed that cucumber treated by NO 3 - -N/NH 4 + -N=21:7 had the longest total root length, the biggest root volume and root surface area, and the maximum number of root tips. H + -ATPase activity and relative expression of genes encoding nitrate transporter (NRT) and ammonium transporter (AMT) in cucumber roots were increased significantly by the treatment of NO 3 - -N/NH 4 + -N=21:7. In addition, nitrate reductase (NR), glutamine synthetase (GS) and glutamate synthase (GOGAT) in cucumber leaves under the treatment of NO 3 - -N/NH 4 + -N=21:7 were higher. As a result, the nitrogen content and biomass of cucumber were significantly increased. Compared with the plants under the treatment of NO 3 - -N/NH 4 + -N=26:2 or 14:14, cucumber seedlings under the treatment of NO 3 - -N/NH 4 + -N=21:7 had the highest biomass and total dry mass (DM) which were increased by 14.0% and 19.3% respectively under suboptimal temperature and light intensity. In conclusion, under suboptimal environmental conditions, NO 3 - -N/NH 4 + -N ratio could be adjusted to increase nitrogen absorption and metabolism of cucumber and alleviate the de-trimental effects caused by suboptimal conditions and promoted the cucumber growth.

BF3/nano-γ-Al2O3 Promoted Knoevenagel Condensation at Room Temperature

Directory of Open Access Journals (Sweden)

B. F. Mirjalili

2015-10-01

Full Text Available The Knoevenagel condensation of aromatic aldehydes with barbituric acid, dimedone and malononitrile occurred in the presence of BF3/nano-γ-Al2O3 at room temperature in ethanol. This catalyst is characterized by powder X-ray diffraction (XRD, fourier transform infrared spectroscopy (FT-IR, thermal gravimetric analysis (TGA, field emission scanning electron microscopy (FESEM and energy-dispersive X-ray spectroscopy (EDS.

Growth of (CH$_3$)$_2$NH$_2$CuCl$_3$ single crystals using evaporation method with different temperatures and solvents

OpenAIRE

Chen, L. M.; Tao, W.; Zhao, Z. Y.; Li, Q. J.; Ke, W. P.; Wang, X. M.; Liu, X. G.; Fan, C.; Sun, X. F.

2013-01-01

The bulk single crystals of of low-dimensional magnet (CH$_3$)$_2$NH$_2$CuCl$_3$ (DMACuCl$_3$ or MCCL) are grown by a slow evaporation method with different kinds of solvents, different degrees of super-saturation of solution and different temperatures of solution, respectively. Among three kinds of solvent, methanol, alcohol and water, alcohol is found to be the best one for growing MCCL crystals because of its structural similarity to the raw materials and suitable evaporation rate. The bes...

Synthesis of 15N-enriched urea (CO(15NH22 from 15NH3, CO, and S in a discontinuous process

Directory of Open Access Journals (Sweden)

C. R. Sant Ana Filho

2012-12-01

Full Text Available CO(15NH22 enriched with the stable isotope 15N was synthesized based on a reaction involving CO, 15NH3, and S in the presence of CH3OH. The method differs from the industrial method; a stainless steel reactor internally lined with polytetrafluoroethylene (PTFE was used in a discontinuous process under low pressure and temperature. The yield of the synthesis was evaluated as a function of the parameters: the amount of reagents, reaction time, addition of H2S, liquid solution and reaction temperature. The results showed that under optimum conditions (1.36, 4.01, and 4.48 g of 15NH3, CO, and S, respectively, 40 ml CH3OH, 40 mg H2S, 100 ºC and 120 min of reaction 1.82 g (yield 76.5% of the compound was obtained per batch. The synthesized CO(15NH22 contained 46.2% N, 0.55% biuret, melting point of 132.55 ºC and did not exhibit isotopic fractionation. The production cost of CO(15NH22 with 90.0 at. % 15N was US$ 238.60 per gram.

Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 perovskites for solar cell applications.

Science.gov (United States)

Umari, Paolo; Mosconi, Edoardo; De Angelis, Filippo

2014-03-26

Hybrid AMX3 perovskites (A = Cs, CH3NH3; M = Sn, Pb; X = halide) have revolutionized the scenario of emerging photovoltaic technologies, with very recent results demonstrating 15% efficient solar cells. The CH3NH3PbI3/MAPb(I(1-x)Cl(x))3 perovskites have dominated the field, while the similar CH3NH3SnI3 has not been exploited for photovoltaic applications. Replacement of Pb by Sn would facilitate the large uptake of perovskite-based photovoltaics. Despite the extremely fast progress, the materials electronic properties which are key to the photovoltaic performance are relatively little understood. Density Functional Theory electronic structure methods have so far delivered an unbalanced description of Pb- and Sn-based perovskites. Here we develop an effective GW method incorporating spin-orbit coupling which allows us to accurately model the electronic, optical and transport properties of CH3NH3SnI3 and CH3NH3PbI3, opening the way to new materials design. The different CH3NH3SnI3 and CH3NH3PbI3 electronic properties are discussed in light of their exploitation for solar cells, and found to be dominantly due to relativistic effects. These effects stabilize the CH3NH3PbI3 material towards oxidation, by inducing a deeper valence band edge. Relativistic effects, however, also increase the material band-gap compared to CH3NH3SnI3, due to the valence band energy downshift (~0.7 eV) being only partly compensated by the conduction band downshift (~0.2 eV).

Electrochemically decorated ZnTe nanodots on single-walled carbon nanotubes for room-temperature NO2 sensor application.

Science.gov (United States)

Kim, Donguk; Park, Ki-Moon; Shanmugam, Rajakumar; Yoo, Bongyoung

2014-11-01

A gas sensor with ZnTe nanodot-modified single-walled carbon nanotubes (SWCNTs) is demonstrated for NO2 detection at room temperature. ZnTe nanodots are electrochemically deposited in an aqueous solution containing ZnSO4, TeO2 and citrate. A deposition potential range of ZnTe formation of -0.65 to -0.9 V is determined by cyclic voltammetry, and an intermetallic ZnTe compound is formed at above 50 degrees C bath. SWCNT-based sensors show the highly sensitive response down to 1 ppm NO2 gas at room temperature. In particular, the sensitivity of ZnTe nanodot-modified SWCNTs is increased by 6 times as compared to that of pristine SWCNT sensors. A selectivity test of SWCNT-ZnTe nanodots sensors is carried out with ammonia gas (NH3) and methanol vapor (MeOH), and the result confirms an excellent selectivity to NO2 gas.

Crystal structure and characterization of the novel NH{sup +} Midline-Horizontal-Ellipsis N hydrogen bonded polar crystal [NH{sub 2}(CH{sub 2}){sub 4}NH][BF{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Wojtas, M., E-mail: maciej.wojtas@chem.uni.wroc.pl [Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw (Poland); Gagor, A. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Science, PO Box 1410, 50-950 Wroclaw (Poland); Czupinski, O. [Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw (Poland); Medycki, W. [Institute of Molecular Physics, Polish Academy of Science, Smoluchowskiego 17, 60-179 Poznan (Poland); Jakubas, R. [Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw (Poland)

2012-03-15

Dielectric properties and phase transitions of the piperazinium tetrafluoroborate ([NH{sub 2}(CH{sub 2}){sub 4}NH][BF{sub 4}], abbreviated as PFB) crystal are related to the one-dimensional arrangement of the cations linked by the bistable NH{sup +} Midline-Horizontal-Ellipsis N hydrogen bonds and molecular motions of the [BF{sub 4}]{sup -} units. The crystal structure of [NH{sub 2}(CH{sub 2}){sub 4}NH][BF{sub 4}] is monoclinic at room temperature with the polar space group Pn. The polar/acentric properties of the room temperature phase IV have been confirmed by the piezoelectric and pyroelectric measurements. DSC measurements show that the compound undergoes three first-order structural phase transitions: at 421/411 K (heating/cooling), at 386/372 K and at 364/349 K. {sup 1}H and {sup 19}F NMR measurements indicate the reorientational motions of [BF{sub 4}]{sup -} anions and piperazinium(+) cations as well as the proton motion in the hydrogen-bonded chains of piperazine along the [001] direction. Over the phase I the isotropic reorientational motions or even self-diffusion of the cations and anions are expected. The conductivity measurements in the vicinity of the II-I PT indicate a superionic phase over the phase I. - Graphical abstract: It must be emphasized that the titled compound represents the first organic-inorganic simple salt containing the single-protonated piperazinium cation which was studied by means of the wide variety of experimental techniques. A survey of Cambridge Structural Database (CSD version 5.32 (November 2010) and updates (May 2011)) for structure containing the piperazinium cations yields 248 compounds with the doubly protonated piperazinium(2+) cations and only eight compounds with the singly protonated piperazinium(+) cations. Among these structures only one is the hybrid organic-inorganic material. This is piperazinium nitrate characterized structurally. The crystal packing of [NH{sub 2}(CH{sub 2}){sub 4}NH][BF{sub 4}], phase IV. The

Novel room temperature ferromagnetic semiconductors

Energy Technology Data Exchange (ETDEWEB)

Gupta, Amita [KTH Royal Inst. of Technology, Stockholm (Sweden)

2004-06-01

Today's information world, bits of data are processed by semiconductor chips, and stored in the magnetic disk drives. But tomorrow's information technology may see magnetism (spin) and semiconductivity (charge) combined in one 'spintronic' device that exploits both charge and 'spin' to carry data (the best of two worlds). Spintronic devices such as spin valve transistors, spin light emitting diodes, non-volatile memory, logic devices, optical isolators and ultra-fast optical switches are some of the areas of interest for introducing the ferromagnetic properties at room temperature in a semiconductor to make it multifunctional. The potential advantages of such spintronic devices will be higher speed, greater efficiency, and better stability at a reduced power consumption. This Thesis contains two main topics: In-depth understanding of magnetism in Mn doped ZnO, and our search and identification of at least six new above room temperature ferromagnetic semiconductors. Both complex doped ZnO based new materials, as well as a number of nonoxides like phosphides, and sulfides suitably doped with Mn or Cu are shown to give rise to ferromagnetism above room temperature. Some of the highlights of this work are discovery of room temperature ferromagnetism in: (1) ZnO:Mn (paper in Nature Materials, Oct issue, 2003); (2) ZnO doped with Cu (containing no magnetic elements in it); (3) GaP doped with Cu (again containing no magnetic elements in it); (4) Enhancement of Magnetization by Cu co-doping in ZnO:Mn; (5) CdS doped with Mn, and a few others not reported in this thesis. We discuss in detail the first observation of ferromagnetism above room temperature in the form of powder, bulk pellets, in 2-3 mu-m thick transparent pulsed laser deposited films of the Mn (<4 at. percent) doped ZnO. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) spectra recorded from 2 to 200nm areas showed homogeneous

Ultrasonic irradiation-promoted one-pot synthesis of CH3NH3PbBr3 quantum dots without using flammable CH3NH2 precursor

Science.gov (United States)

Jiang, Han; Wang, Chunlei; Lv, Changgui; Xu, Shuhong; Zhu, Li; Zhang, Ruohu; Cui, Yiping

2017-02-01

At present, the CH3NH3PbBr3 quantum dots (QDs) reported in the literature usually contain two synthesis steps: the initial preparation of CH3NH3Br via the reaction of flammable CH3NH2 and HBr, together with the subsequent formation of CH3NH3PbBr3 QDs. To avoid the use of dangerous CH3NH2, this work develops a novel one-pot method for synthesizing CH3NH3PbBr3 QDs using safe and commercially available reactants (CH3NH3Cl, KBr and PbCl2). It is found that ultrasonic treatment plays a key role during the synthesis of CH3NH3PbBr3 QDs. Without ultrasonic irradiation, it is not possible to synthesize CH3NH3PbBr3 QDs under heating or vigorous stirring. Aliquots of samples taken at different ultrasonic irradiation time intervals show a time-dependent redshift in the emission wavelength. This suggests the formation of CH3NH3PbCl3 QDs first, followed by the formation of CH3NH3PbBr3 QDs through ultrasonically promoted halide exchange. Moreover, mixed CH3NH3PbCl x Br3-x QDs with a tunable emission wavelength can also be prepared through this one-pot method by controlling the ultrasonic irradiation time. In comparison to the previous two-step method, the current one-pot method is simpler, less time-consuming and does not use flammable CH3NH2. The as-prepared CH3NH3PbBr3 QDs show a comparable photoluminescence (PL) quantum yield (QY) to that of the literature. What is more, the ultrasonic time-controlled emission wavelength of CH3NH3PbCl x Br3-x QDs also provides an alternative way of tuning QD emission to the traditional way of controlling the halide ratios.

Pressure and Temperature of the Room 1 for the Pipe Break Accidents of the 3-Pin Fuel Test Loop

Energy Technology Data Exchange (ETDEWEB)

Park, S. K.; Chi, D. Y.; Sim, B. S.; Park, K. N.; Ahn, S. H.; Lee, J. M.; Lee, C. Y.; Kim, H. R

2005-08-15

This report deals with the prediction of the pressure and temperature of the room 1 for the pipe break accidents of the 3-pin fuel test loop. The 3-pin fuel test loop is an experimental facility for nuclear fuel tests at the operation conditions similar to those of PWR and CANDU power plants. Because the most processing systems of the 3-pin fuel test loop are placed in the room 1. The structural integrity of the room 1 should be evaluated for the postulated accident conditions. Therefore the pressures and temperatures of the room 1 needed for the structural integrity evaluation have been calculated by using MARS code. The pressures and temperatures of the room 1 have been calculated in various conditions such as the thermal hydraulic operation parameters, the locations of pipe break, and the thermal properties of the room 1 wall. It is assumed that the pipe break accident occurs in the letdown operation without regeneration, because the mass and energy release to the room 1 is expected to be the largest. As a result of the calculations the maximum pressure and temperature are predicted to be 208kPa and 369.2K(96.0 .deg. C) in case the heat transfer is considered in the room 1 wall. However the pressure and temperature are asymptotically 243kPa and 378.1K(104.9 .deg. C) assuming that the heat transfer does not occur in the room 1 wall.

A new NH 3 orbital of the NH 3/Ni(110) surface observed by metastable quenching spectroscopy

Science.gov (United States)

Lee, Lihwa; Arias, Jose; Hanrahan, Ciaran; Martin, Richard M.; Metiu, Horia

1986-01-01

By using metastable quenching spectroscopy we have found a new NH 3 filled orbital (in the language of one electron theory) for NH 3/Ni(110), located at the Fermi level of the surface. The orbital is not observed when NH 3 is adsorbed on Ni(110), but it is detected for NH 3 adsorbed on polycrystalline Al.

High-resolution absorption measurements of NH₃ at high temperatures: 500–2100cm⁻¹

DEFF Research Database (Denmark)

Barton, Emma J.; Yurchenko, Sergei N.; Tennyson, Jonathan

2015-01-01

High-resolution absorption spectra of NH3 in the region 500–2100 cm -1 at temperatures up to1027 1C and approximately atmospheric pressure (1013±20 mbar) are measured. NH3 concentrations of 1000 ppm,0.5% and 1% in volume fraction were used in the measurements. Spectra are recorded in high tempera...... to a variational line list, BYTe, and experimental energy levels determined using the MARVEL procedure. Approximately 2000 lines have been assigned, of which 851are newly assigned to mainly hot bands involving vibrational states as high as v2=5....

Thermal properties and phase transition in the fluoride, (NH4)3SnF7

International Nuclear Information System (INIS)

Kartashev, A.V.; Gorev, M.V.; Bogdanov, E.V.; Flerov, I.N.; Laptash, N.M.

2016-01-01

Calorimetric, dilatometric and differential thermal analysis studies were performed on (NH 4 ) 3 SnF 7 for a wide range of temperatures and pressures. Large entropy (δS 0 =22 J/mol K) and elastic deformation (δ(ΔV/V) 0 =0.89%) jumps have proven that the Pa-3↔Pm-3m phase transition is a strong first order structural transformation. A total entropy change of ΔS 0 =32.5 J/mol K is characteristic for the order–disorder phase transition, and is equal to the sum of entropy changes in the related material, (NH 4 ) 3 TiF 7 , undergoing transformation between the two cubic phases through the intermediate phases. Hydrostatic pressure decreases the stability of the high temperature Pm-3m phase in (NH 4 ) 3 SnF 7 , contrary to (NH 4 ) 3 TiF 7 , characterised by a negative baric coefficient. The effect of experimental conditions on the chemical stability of (NH 4 ) 3 SnF 7 was observed. - Graphical abstract: Strong first order structural transformation Pa-3↔Pm-3m in (NH 4 ) 3 SnF 7 is associated with very large total entropy change of ΔS 0 =32.5 J/mol K characteristic for the ordering processes and equal to the sum of entropy changes in the related (NH 4 ) 3 TiF 7 undergoing transformation between the same two cubic phases through the intermediate phases. - Highlights: • (NH 4 ) 3 SnF 7 undergoes strong first order Pa-3↔Pm-3m phase transition. • Anomalous behaviour of ΔC p and ΔV/V exists far below phase transition temperature. • Structural distortions are accompanied by huge total entropy change ΔS≈Rln50. • High pressure strongly increases the stability of Pa-3 phase in (NH 4 ) 3 SnF 7 . • Entropy of the Pa-3↔Pm-3m phase transition does not depend on pressure.

NH3 and NH4+ permeability in aquaporin-expressing Xenopus oocytes

DEFF Research Database (Denmark)

Holm, Lars M.; Jahn, Thomas Paul; Møller, Anders Laurell Blom

2005-01-01

We have shown recently, in a yeast expression system, that some aquaporins are permeable to ammonia. In the present study, we expressed the mammalian aquaporins AQP8, AQQP9, AQP3, AQP1 and a plant aquaporin TIP2;1 in Xenopus oocytes to study the transport of ammonia (NH3) and ammonium (NH4+) under...... inwards currents carried by NH4+. This conductivity increased as a sigmoid function of external [NH3]: for AQP8 at a bath pH (pH(e)) of 6.5, the conductance was abolished, at pH(e) 7.4 it was half maximal and at pH(e) 7.8 it saturated. NY4+ influx was associated with oocyte swelling. In comparison, native...... oocytes as well as AQP1 and tip2;1-expressing oocytes showed small currents that were associated with small and even negative volume changes. We conclude that AQP8, AQP9, AQP3, and TIP2;1, apart from being water channels, also support significant fluxes of NH3. These aquaporins could support NH4...

Growth of (CH 3) 2NH 2CuCl 3 single crystals using evaporation method with different temperatures and solvents

Science.gov (United States)

Chen, L. M.; Tao, W.; Zhao, Z. Y.; Li, Q. J.; Ke, W. P.; Wang, X. M.; Liu, X. G.; Fan, C.; Sun, X. F.

2010-10-01

The bulk single crystals of low-dimensional magnet (CH 3) 2NH 2CuCl 3 (DMACuCl 3 or MCCL) are grown by a slow evaporation method with different kinds of solvents, different degrees of super-saturation of solution and different temperatures of solution, respectively. Among three kinds of solvent, methanol, alcohol and water, alcohol is found to be the best one for growing MCCL crystals because of its structural similarity to the raw materials and suitable evaporation rate. The best growth temperature is in the vicinity of 35 °C. The problem of the crystals deliquescing in air has been solved through recrystallization process. The crystals are characterized by means of X-ray diffraction, specific heat and magnetic susceptibility.

Crystal structure of [UO2(NH35]NO3·NH3

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Patrick Woidy

2016-12-01

Full Text Available Pentaammine dioxide uranium(V nitrate ammonia (1/1, [UO2(NH35]NO3·NH3, was obtained in the form of yellow crystals from the reaction of caesium uranyl nitrate, Cs[UO2(NO33], and uranium tetrafluoride, UF4, in dry liquid ammonia. The [UO2]+ cation is coordinated by five ammine ligands. The resulting [UO2(NH35] coordination polyhedron is best described as a pentagonal bipyramid with the O atoms forming the apices. In the crystal, numerous N—H...N and N—H...O hydrogen bonds are present between the cation, anion and solvent molecules, leading to a three-dimensional network.

Different transport behaviors of NH4 (+) and NH3 in transmembrane cyclic peptide nanotubes.

Science.gov (United States)

Zhang, Mingming; Fan, Jianfen; Xu, Jian; Weng, Peipei; Lin, Huifang

2016-10-01

Two water-filled transmembrane cyclic peptide nanotubes (CPNTs) of 8×cyclo-(WL)n=4,5/POPE were chosen to investigate the dependences of the transport properties of the positive NH4 (+) and neutral NH3 on the channel radius. Molecular dynamic simulations revealed that molecular charge, size, ability to form H-bonds and channel radius all significantly influence the behaviors of NH4 (+) and NH3 in a CPNT. Higher electrostatic interactions, more H-bonds, and water-bridges were found in the NH4 (+) system, resulting in NH4 (+) meeting higher energy barriers, while NH3 can enter, exit and permeate the channels effortlessly. This work sheds a first light on the differences between the mechanisms of NH4 (+) and NH3 moving in a CPNT at an atomic level. Graphical Abstract Snapshot of the simulation system of NH4 (+)_octa-CPNT with an NH4 (+) initially positioned at one mouth of the tube, PMF profiles for single NH4 (+) ion and NH3 molecule moving through water-filled transmembrane CPNTs of 8×cyclo-(WL)n=4,5/POPE and sketch graphs of the possible H-bond forms of NH3 and NH4 (+) with the neighboring water.

Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants.

Science.gov (United States)

Ariz, Idoia; Cruz, Cristina; Moran, Jose F; González-Moro, María B; García-Olaverri, Carmen; González-Murua, Carmen; Martins-Loução, Maria A; Aparicio-Tejo, Pedro M

2011-05-16

In plants, nitrate (NO3-) nutrition gives rise to a natural N isotopic signature (δ15N), which correlates with the δ15N of the N source. However, little is known about the relationship between the δ15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+) nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g) and NH4+ (aq) which drives to a different δ15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and δ15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4+ and NH3. Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. This article proposes that the negative values of δ15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ may have two components: one that transports N in the molecular form and is associated with

Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants

Science.gov (United States)

2011-01-01

Background In plants, nitrate (NO3-) nutrition gives rise to a natural N isotopic signature (δ15N), which correlates with the δ15N of the N source. However, little is known about the relationship between the δ15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+) nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g) and NH4+ (aq) which drives to a different δ15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and δ15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4+ and NH3. Results Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. Conclusions This article proposes that the negative values of δ15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ may have two components: one that transports N in the

A Layered Solution Crystal Growth Technique and the Crystal Structure of (C 6H 5C 2H 4NH 3) 2PbCl 4

Science.gov (United States)

Mitzi, D. B.

1999-07-01

Single crystals of the organic-inorganic perovskite (C6H5C2H4NH3)2PbCl4 have been grown at room temperature using a layered solution approach. The bottom solution layer, contained within a long straight tube, consists of PbCl2 dissolved in concentrated aqueous HCl. A less dense layer of methanol is carefully placed on top of the HCl/PbCl2 solution using a syringe. Finally, a stoichiometric quantity of C6H5C2H4NH2 (relative to the PbCl2) is added to the top of the column. As the layers slowly diffuse together, well-formed crystals of (C6H5C2H4NH3)2PbCl4 appear near the interface between the HCl/PbCl2 and C6H5C2H4NH2 solutions. The thick, plate-like crystals are well suited for X-ray crystallography studies. Room temperature intensity data were refined using a triclinic (Poverline1) cell (a=11.1463(3) Å, b=11.2181(3) Å, c=17.6966(5) Å, α= 99.173(1)°, β=104.634(1)°, γ=89.999(1)°, V=2111.8(1) Å3, Z=4, Rf/Rw=0.031/0.044). The organic-inorganic layered perovskite structure features well-ordered sheets of corner-sharing distorted PbCl6 octahedra separated by bilayers of phenethylammonium cations. Tilting and rotation of the PbCl6 octahedra within the perovskite sheets, coupled with organic cation ordering, leads to the unusual in-sheet 2ap×2ap superstructure, where ap is the lattice constant for the ideal cubic perovskite.

Structure of photosystem II and substrate binding at room temperature.

Science.gov (United States)

Young, Iris D; Ibrahim, Mohamed; Chatterjee, Ruchira; Gul, Sheraz; Fuller, Franklin; Koroidov, Sergey; Brewster, Aaron S; Tran, Rosalie; Alonso-Mori, Roberto; Kroll, Thomas; Michels-Clark, Tara; Laksmono, Hartawan; Sierra, Raymond G; Stan, Claudiu A; Hussein, Rana; Zhang, Miao; Douthit, Lacey; Kubin, Markus; de Lichtenberg, Casper; Long Vo, Pham; Nilsson, Håkan; Cheah, Mun Hon; Shevela, Dmitriy; Saracini, Claudio; Bean, Mackenzie A; Seuffert, Ina; Sokaras, Dimosthenis; Weng, Tsu-Chien; Pastor, Ernest; Weninger, Clemens; Fransson, Thomas; Lassalle, Louise; Bräuer, Philipp; Aller, Pierre; Docker, Peter T; Andi, Babak; Orville, Allen M; Glownia, James M; Nelson, Silke; Sikorski, Marcin; Zhu, Diling; Hunter, Mark S; Lane, Thomas J; Aquila, Andy; Koglin, Jason E; Robinson, Joseph; Liang, Mengning; Boutet, Sébastien; Lyubimov, Artem Y; Uervirojnangkoorn, Monarin; Moriarty, Nigel W; Liebschner, Dorothee; Afonine, Pavel V; Waterman, David G; Evans, Gwyndaf; Wernet, Philippe; Dobbek, Holger; Weis, William I; Brunger, Axel T; Zwart, Petrus H; Adams, Paul D; Zouni, Athina; Messinger, Johannes; Bergmann, Uwe; Sauter, Nicholas K; Kern, Jan; Yachandra, Vittal K; Yano, Junko

2016-12-15

Light-induced oxidation of water by photosystem II (PS II) in plants, algae and cyanobacteria has generated most of the dioxygen in the atmosphere. PS II, a membrane-bound multi-subunit pigment protein complex, couples the one-electron photochemistry at the reaction centre with the four-electron redox chemistry of water oxidation at the Mn 4 CaO 5 cluster in the oxygen-evolving complex (OEC). Under illumination, the OEC cycles through five intermediate S-states (S 0 to S 4 ), in which S 1 is the dark-stable state and S 3 is the last semi-stable state before O-O bond formation and O 2 evolution. A detailed understanding of the O-O bond formation mechanism remains a challenge, and will require elucidation of both the structures of the OEC in the different S-states and the binding of the two substrate waters to the catalytic site. Here we report the use of femtosecond pulses from an X-ray free electron laser (XFEL) to obtain damage-free, room temperature structures of dark-adapted (S 1 ), two-flash illuminated (2F; S 3 -enriched), and ammonia-bound two-flash illuminated (2F-NH 3 ; S 3 -enriched) PS II. Although the recent 1.95 Å resolution structure of PS II at cryogenic temperature using an XFEL provided a damage-free view of the S 1 state, measurements at room temperature are required to study the structural landscape of proteins under functional conditions, and also for in situ advancement of the S-states. To investigate the water-binding site(s), ammonia, a water analogue, has been used as a marker, as it binds to the Mn 4 CaO 5 cluster in the S 2 and S 3 states. Since the ammonia-bound OEC is active, the ammonia-binding Mn site is not a substrate water site. This approach, together with a comparison of the native dark and 2F states, is used to discriminate between proposed O-O bond formation mechanisms.

Room-Temperature Coherent Optical Phonon in 2D Electronic Spectra of CH₃NH₃PbI₃ Perovskite as a Possible Cooling Bottleneck

Energy Technology Data Exchange (ETDEWEB)

Monahan, Daniele M. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoSciences Inst. at Berkeley, Berkeley, CA (United States); Guo, Liang [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoSciences Inst. at Berkeley, Berkeley, CA (United States); Lin, Jia [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoSciences Inst. at Berkeley, Berkeley, CA (United States); Dou, Letian [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoSciences Inst. at Berkeley, Berkeley, CA (United States); Yang, Peidong [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoSciences Inst. at Berkeley, Berkeley, CA (United States); Fleming, Graham R. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoSciences Inst. at Berkeley, Berkeley, CA (United States)

2017-06-29

A hot phonon bottleneck may be responsible for slow hot carrier cooling in methylammonium lead iodide hybrid perovskite, creating the potential for more efficient hot carrier photovoltaics. In room-temperature 2D electronic spectra near the band edge, we observe in this paper amplitude oscillations due to a remarkably long lived 0.9 THz coherent phonon population at room temperature. This phonon (or set of phonons) is assigned to angular distortions of the Pb–I lattice, not coupled to cation rotations. The strong coupling between the electronic transition and the 0.9 THz mode(s), together with relative isolation from other phonon modes, makes it likely to cause a phonon bottleneck. Finally, the pump frequency resolution of the 2D spectra also enables independent observation of photoinduced absorptions and bleaches independently and confirms that features due to band gap renormalization are longer-lived than in transient absorption spectra.

UV-light-assisted ethanol sensing characteristics of g-C3N4/ZnO composites at room temperature

Science.gov (United States)

Zhai, Jiali; Wang, Tao; Wang, Chuang; Liu, Dechen

2018-05-01

A highly efficient UV-light-assisted room temperature sensor based on g-C3N4/ZnO composites were prepared by an in situ precipitation method. The thermostability, composition, structure, and morphology properties of the as-prepared g-C3N4/ZnO composites were characterized by TGA, XRD, FT-IR, TEM, and XPS, respectively. And then, we studied the ethanol (C2H5OH) sensing performance of the g-C3N4/ZnO composites at the room temperature. Compared with pure ZnO and g-C3N4, the gas sensing activity of g-C3N4/ZnO composites was greatly improved at room temperature, for example, the g-C3N4/ZnO-8% composites showed an obvious response of 121-40 ppm C2H5OH at room temperature, which was 60 times higher than the pure ZnO based on the sensors under the same condition. The great enhancement of the C2H5OH sensing properties of composites can be understood by the efficient separation of photogenerated charge carriers of g-C3N4/ZnO heterogeneous and the UV-light catalytic effect. Finally, a possible mechanism for the gas sensing activity was proposed.

Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants

Directory of Open Access Journals (Sweden)

Martins-Loução Maria A

2011-05-01

Full Text Available Abstract Background In plants, nitrate (NO3- nutrition gives rise to a natural N isotopic signature (δ15N, which correlates with the δ15N of the N source. However, little is known about the relationship between the δ15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+ nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g and NH4+ (aq which drives to a different δ15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and δ15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 form were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4+ and NH3. Results Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. Conclusions This article proposes that the negative values of δ15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ may have two components: one that

A facile synthesis of substituted 2-alkylquinolines through [3+3] annulation between 3-ethoxycyclobutanones and aromatic amines at room temperature.

Science.gov (United States)

Shan, Gang; Sun, Xiuyun; Xia, Qian; Rao, Yu

2011-11-04

An efficient single-step approach toward the synthesis of 2-alkylquinolines is described. Through a Lewis acid mediated [3+3] annulation reaction between 3-ethoxycyclobutanones and aromatic amines, a variety of multisubstituted 2-alkylquinoline derivatives were prepared regioselectively at room temperature. © 2011 American Chemical Society

Crystal structure and phase transition in (NH4)3WO2F5: from dynamic to static orientational disorder.

Science.gov (United States)

Udovenko, Anatoly; Laptash, Natalia

2015-08-01

Single crystals of tungsten double salt (NH4)3WO2F5 = (NH4)3[WO2F4]F have been synthesized by solid-state reaction or from fluoride solution and its crystal structures at 296 and 193 K were determined by X-ray diffraction. At room temperature, the crystal structure of the compound is dynamically disordered with the ligand atoms statistically distributed on two positions (6e and 24m) of the Pm3m unit cell [a = 6.0298 (1) Å], and the tungsten atom dynamically disordered on 12 orientations forming a spatial cuboctahedron [W12] that enables the real geometry of cis-WO2F4 octahedron to be determined with two short W-O distances. On cooling, the compound undergoes a first-order phase transition with the symmetry change Pm3m → Pa3 and a doubling of the unit-cell parameter [a = 11.9635 (7) Å]. The ligand F(O) atoms statistically occupy two general 24d sites and form W1X6 and W2X6 octahedra, in which the O and F atoms are not crystallographically different that means a static orientational disorder of (NH4)3WO2F5.

Fast-LPG Sensors at Room Temperature by α-Fe2O3/CNT Nanocomposite Thin Films

Directory of Open Access Journals (Sweden)

B. Chaitongrat

2018-01-01

Full Text Available We present performance of a room temperature LPG sensor based on α-Fe2O3/CNT (carbon nanotube nanocomposite films. The nanocomposite film was fabricated via the metallic Fe catalyst particle on CNTs in which both the catalyst particles and the CNT were simultaneously synthesized by chemical vapor deposition (CVD synthesis and were subsequently annealed in air to create α-Fe2O3. These methods are simple, inexpensive, and suitable for large-scale production. The structure, surface morphologies, and LPG response of nanocomposite films were investigated. Raman spectroscopy and XPS analysis showed the formation of α-Fe2O3 on small CNTs (SWNTs. Morphological analysis using FE-SEM and AFM revealed the formation of the porous surface along with roughness surface. Additionally, the sensing performance of α-Fe2O3/CNTs showed that it could detect LPG concentration at lower value than 25% of LEL with response/recovery time of less than 30 seconds at room temperature. These results suggest that the α-Fe2O3/CNTs films are challenging materials for monitoring LPG operating at room temperature.

Structural and electrical properties of room temperature pulsed laser deposited and post-annealed thin SrRuO3 films

International Nuclear Information System (INIS)

Gautreau, O.; Harnagea, C.; Normandin, F.; Veres, T.; Pignolet, A.

2007-01-01

Good quality strontium ruthenate (SrRuO 3 ) thin continuous films (15 to 125 nm thick) have been synthesized on silicon (100) substrates by room temperature pulsed laser deposition under vacuum followed by a post-deposition annealing, a route unexplored and yet not reported for SrRuO 3 film growth. The presence of an interfacial Sr 2 SiO 4 layer has been identified for films annealed at high temperature, and the properties of this interface layer as well as the properties of the SrRuO 3 film have been analyzed and characterized as a function of the annealing temperature. The room temperature resistivity of the SrRuO 3 films deposited by laser ablation at room temperature and post-annealed is 2000 μΩ.cm. A critical thickness of 120 nm has been determined above which the influence of the interface layer on the resistivity becomes negligible

Sensing of low concentration of ammonia at room temperature by decorated multi-walled carbon nanotube: fabrication and characteristics

Science.gov (United States)

Hasnahena, S. T.; Roy, M.

2018-01-01

A chemical sensor based on multi-walled carbon nanotube (MWCNT) decorated with densely populated thiol-capped gold nanoparticles (AuNPs) with sizes smaller than 3 nm for sensing low concentrations of ammonia gas is reported. The functionalized MWCNTs, subsequently decorated with AuNPs following an easy fabrication route were exposed to NH3 gas at the room temperature and the electrical resistance of the sensor changed upon exposure. The sensor also partially recovered the initial state after sensing in the normal air environment (without any dry air or N2 gas purge). The gold nanoparticles decoration is found to enhance the sensitivity and selectivity of MWCNT towards NH3 gas under ambient conditions with a reduced response and recovery time. The material was structurally characterized by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. Thermal stability of the sensor till 574 °C was demonstrated by TGA analysis. This papers describes how thiol-capped AuNPs are uniformly decorated on the outer walls of the MWCNTs with a separation of 2-3 nm making use of the ionic nature of Au and how this uniform distribution of AuNPs increases the active sites for absorption of NH3 gas molecules leading to sensing its low concentrations.

Room temperature ferromagnetism of nanocrystalline Nd1.90Ni0.10O3-δ

Science.gov (United States)

Sarkar, B. J.; Mandal, J.; Dalal, M.; Bandyopadhyay, A.; Chakrabarti, P. K.

2018-05-01

Nanocrystalline sample of Ni2+ doped neodymium oxide (Nd1.90Ni0.10O3-δ, NNO) is synthesized by co-precipitation method. Analysis of X-ray diffraction (XRD) pattern by Rietveld refinement method confirms the desired phase of NNO and complete substitution of Ni2+ ions in the Nd2O3 lattice. Analyses of transmission electron microscopy (TEM) and Raman spectroscopy of NNO recorded at room temperature (RT) also substantiate this fact. Besides, no traces of impurities are found in the analyses of XRD, TEM and Raman data. Room temperature hysteresis loop of NNO suggests the presence of weak ferromagnetism (FM) in low field region ( 600 mT), but in high field region paramagnetism of the host is more prominent. Magnetization vs. temperature ( M- T) curve in the entire temperature range (300-5 K) is analyzed successfully by a combined equation generated from three-dimensional (3D) spin wave model and Curie-Weiss law, which suggests the presence of mixed paramagnetic phase together with ferromagnetic phase in the doped sample. The onset of magnetic ordering is analyzed by oxygen vacancy mediated F-center exchange (FCE) coupling mechanism.

Crystal structure and dielectric measurements of mixed caesium-ammonium mercury chloride: Cs{sub 0.7}(NH{sub 4}){sub 0.3}HgCl{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Kabadou, A.; Hassen, R.B.; Salah, A.B. [Fac. des Sci., Sfax (Tunisia). Lab. de l`Etat Solide; Jouini, T.

1998-08-01

The title compound crystallises in the space group P3{sub 2} and has the unit cell dimensions a = 13.295(11) A, c = 9.419(8) A, V = 1441.82(2), Z = 9, D{sub exp} = 4.17, D{sub calc} = 4.153. The structure at room temperature is considered as distorted perovskite tentatively with R = 0.057 and WR{sub 2} = 0.153 for 700 observed reflections. The dielectric permittivity measured in the frequency and temperatures ranges 10{sup 3} to 10{sup 6} Hz and 307 to 613 K, respectively, reveals a transition at T = 449 K. Transport properties in this material appear to be due to the high mobility of NH{sub 4}{sup +} in the tunnels. (orig.) 13 refs.

X-ray and neutron single-crystal diffraction on [Rbx(NH4)1-x]3H(SO4)2. I. Refinement of crystal structure of phase II with x=0.11 at 300 K

International Nuclear Information System (INIS)

Loose, A.; Wozniak, K.; Dominiak, P.; Smirnov, L.S.; Natkaniec, I.; Frontas'eva, M.V.; Pomyakushina, E.V.; Baranov, A.I.; Dolbinina, V.V

2006-01-01

The study of [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals by X-ray single-crystal diffraction is known up to now only for x=0.57 at the temperatures 293 and 180 K. The crystal structures at these temperatures as was determined [1] belong to monoclinic phase II (C2/c sp. gr., Z=4). In accordance with this work, ammonium ions should be considered as deformed tetrahedra. Monoclinic phase II on the x-T phase diagram of [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals, which has earlier been determined by the dielectric spectroscopy, is stabilized below room temperature if Rb concentration exceeds 9%. The presented results of X-ray and neutron single-crystal diffraction of the [Rb 0.11 (NH 4 ) 0.89 ] 3 H(SO 4 ) 2 mixed crystal at T= 300 K show that ammonium ions could be considered as regular tetrahedra

A high performance hydrogen sulfide gas sensor based on porous α-Fe{sub 2}O{sub 3} operates at room-temperature

Energy Technology Data Exchange (ETDEWEB)

Huang, Yanwu; Chen, Weimei; Zhang, Shouchao; Kuang, Zhong; Ao, Dongyi [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Alkurd, Nooraldeen Rafat; Zhou, Weilie [Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Liu, Wei [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Shen, Wenzhong [Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, 030001 (China); Li, Zhijie, E-mail: zhijieli@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, 610054 (China)

2015-10-01

Highlights: • Novel porous α-Fe{sub 2}O{sub 3} nanoparticles were prepared by a facile hydrothermal method. • The sensor based on porous α-Fe{sub 2}O{sub 3} exhibits high sensitivity towards H{sub 2}S gas. • The detection limit towards H{sub 2}S gas was as low as 50 ppb at room temperature. • The sensor exhibits excellent selectivity against other toxic and noxious gases. - Abstract: Porous α-Fe{sub 2}O{sub 3} nanoparticles were synthesized by simple annealing of β-FeOOH precursor derived from a facile hydrothermal route, the structures and morphologies of the as-prepared product were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the average crystallite size of the obtained porous α-Fe{sub 2}O{sub 3} was 34 nm and exits numerous irregularly distributed pores with a diameter varying from 2 nm to 10 nm on the particle surface. The gas-sensing properties of the sensor based on porous α-Fe{sub 2}O{sub 3} nanoparticles were investigated, and the result showed that the sensor exhibited a high performance in hydrogen sulfide (H{sub 2}S) detection at room temperature. The highest sensitivity reached 38.4 for 100 ppm H{sub 2}S, and the detection limit was as low as 50 ppb. In addition, the response of the sensor towards other gases including C{sub 2}H{sub 5}OH, CO, H{sub 2} and NH{sub 3} indicates the sensor has an excellent selectivity to detection H{sub 2}S gas. Finally, the sensing mechanism of the sensor towards H{sub 2}S was also discussed.

Enhanced NH{sub 3} gas sensing performance based on electrospun alkaline-earth metals composited SnO{sub 2} nanofibers

Energy Technology Data Exchange (ETDEWEB)

Xu, Shuang [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Kan, Kan [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Daqing Branch, Heilongjiang Academy of Sciences, Daqing 163319 (China); Yang, Ying; Jiang, Chao [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Gao, Jun [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Department of Chemistry, Harbin Normal University, Harbin 150025 (China); Jing, Liqiang [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Shen, Peikang [Department of Physics and Engineering Sun Yat-sen University, Guangzhou 510275 (China); Li, Li, E-mail: llwjjhlju@sina.cn [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Key Laboratory of Chemical Engineering Process and Technology for High-efficiency Conversion, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); and others

2015-01-05

Highlights: • The small-sized SnO{sub 2} (5–7 nm) were obtained by adding the alkaline-earth. • Sr-composited SnO{sub 2} nanofibers showed uniform nanotubes structure (Sr/SnO{sub 2}). • Sr/SnO{sub 2} showed an excellent sensing performance to NH{sub 3} at room temperature. - Abstract: One-dimensional alkaline-earth metals composited SnO{sub 2} (Ae/SnO{sub 2}) nanofibres were fabricated via electrospinning technique, followed by thermal treatment at 600 °C for 5 h. Transmission electron microscopy (TEM) studies showed that the nanoparticles size of Ae/SnO{sub 2} was 5–7 nm, which was smaller than the pristine SnO{sub 2} nanorods attached by 20 nm nanoparticles. Moreover, Sr/SnO{sub 2} nanocomposites showed uniform nanotubes structure with the wall thickness of about 30 nm, in which all the nanoparticles were connected to their neighbors by necks. The Sr/SnO{sub 2} nanotubes exhibited an excellent sensing response toward NH{sub 3} gas at room temperature, lower detection limit (10 ppm), faster response time (6 s towards 2000 ppm∼16 s towards 10 ppm) and better reversibility compared to the pristine SnO{sub 2} nanorods. The enhanced sensor performances were attributed to the higher conductivity of the Sr/SnO{sub 2}. Mott–Schottky plots (M–S) and electrochemical impedance spectroscopy (EIS) measurements indicated that the carrier density of Sr/SnO{sub 2} nanotubes was 3 fold of that pristine SnO{sub 2}.

Forced volume magnetostriction in Mn3.3Sn0.7C compound at room temperature

International Nuclear Information System (INIS)

Wen Yongchun; Wang Cong; Sun Ying; Nie Man; Chu Lihua

2010-01-01

The negative volume magnetostriction in the external magnetic field for antiperovskite Mn 3.3 Sn 0.7 C compound is discovered. Its magnetic transition temperature from paramagnetism to ferrimagnetism is 348 K. The linear and volume magnetostrictions were investigated by measuring the change in length along the three-dimensional directions of the square samples at room temperature. Volume contraction was observed along all of the three directions throughout the whole magnetization. The value of volume magnetostriction is -44x10 -6 at 1.5 T. The magnetization saturates basically at 1.5 T, however the volume magnetostriction should be higher with further increase in magnetic field.

Molecular beam epitaxy of GaN(0001) utilizing NH3 and/or NH+x ions: Growth kinetics and defect structure

International Nuclear Information System (INIS)

Lee, N.; Powell, R.C.; Kim, Y.; Greene, J.E.

1995-01-01

Gas-source molecular beam epitaxy (GS-MBE), utilizing Ga and NH 3 , and reactive-ion MBE (RIMBE), incorporating both thermal NH 3 and low-energy NH + x ions, were used to grow single crystal GaN(0001) layers on Al 2 O 3 (0001) at temperatures T s between 700 and 850 degree C with deposition rates of 0.2--0.5 μm h -1 . The RIMBE experiments were carried out with incident NH + x /Ga flux ratios J NH + x /J Ga =1.9--3.2 and NH + x acceleration energies E NH + x =45--90 eV. Plan-view and cross-sectional transmission electron microscopy analyses showed that the primary defects in the GS-MBE films were threading dislocations having either pure edge or mixed edge/screw characteristics with Burgers vectors bar b=1/3 left-angle 2 bar 1 bar 10 right-angle, basal-plane stacking faults with displacement vectors bar R=1/6 left-angle 02 bar 23 right-angle, and prismatic stacking faults with bar R=1/2 left-angle bar 1101 right-angle. In the case of RIMBE films, no stacking faults or residual ion-induced defects were observed with E NH + x =45 eV and T s ≥800 degree C. However, increasing E NH + x to ≥60 eV at T s =800 degree C gave rise to the formation of residual ion-induced point-defect clusters observable by transmission electron microscopy (TEM). Increasing T s to 850 degree C with E NH + x ≥60 eV resulted in the ion-induced defects aggregating to form interstitial basal and prismatic dislocation loops, whose number densities depended upon the ion flux, with Burgers vectors 1/2 left-angle 0001 right-angle and 1/3 left-angle 2 bar 1 bar 10 right-angle, respectively. (Abstract Truncated)

Room temperature continuous wave mid-infrared VCSEL operating at 3.35 μm

Science.gov (United States)

Jayaraman, V.; Segal, S.; Lascola, K.; Burgner, C.; Towner, F.; Cazabat, A.; Cole, G. D.; Follman, D.; Heu, P.; Deutsch, C.

2018-02-01

Tunable vertical cavity surface emitting lasers (VCSELs) offer a potentially low cost tunable optical source in the 3-5 μm range that will enable commercial spectroscopic sensing of numerous environmentally and industrially important gases including methane, ethane, nitrous oxide, and carbon monoxide. Thus far, achieving room temperature continuous wave (RTCW) VCSEL operation at wavelengths beyond 3 μm has remained an elusive goal. In this paper, we introduce a new device structure that has enabled RTCW VCSEL operation near the methane absorption lines at 3.35 μm. This device structure employs two GaAs/AlGaAs mirrors wafer-bonded to an optically pumped active region comprising compressively strained type-I InGaAsSb quantum wells grown on a GaSb substrate. This substrate is removed in processing, as is one of the GaAs mirror substrates. The VCSEL structure is optically pumped at room temperature with a CW 1550 nm laser through the GaAs substrate, while the emitted 3.3 μm light is captured out of the top of the device. Power and spectrum shape measured as a function of pump power exhibit clear threshold behavior and robust singlemode spectra.

Efficient and stable CH3NH3PbI3-x(SCN)x planar perovskite solar cells fabricated in ambient air with low-temperature process

Science.gov (United States)

Zhang, Zongbao; Zhou, Yang; Cai, Yangyang; Liu, Hui; Qin, Qiqi; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

2018-02-01

Planar perovskite solar cells (PSCs) based on CH3NH3PbI3-x(SCN)x (SCN: thiocyanate) active layer and low-temperature processed TiO2 films are fabricated by a sequential two-step method in ambient air. Here, alkali thiocyanates (NaSCN, KSCN) are added into Pb(SCN)2 precursor to improve the microstructure of CH3NH3PbI3-x(SCN)x perovskite layers and performance of the as-prepared PSCs. At the optimum concentrations of alkali thiocyanates as additives, the as-prepared NaSCN-modified and KSCN-modified PSCs demonstrate the efficiencies of 16.59% and 15.63% respectively, being much higher than 12.73% of the reference PSCs without additives. This improvement is primarily ascribed to the enhanced electron transport, reduced recombination rates and much improved microstructures with large grain size and low defect density at grain boundaries. Importantly, it is revealed that the modified PSCs at the optimized concentrations of alkali thiocyanates additives exhibit remarkably improved stability than the reference PSCs against humid circumstance, and a continuous exposure to humid air without encapsulation over 45 days only records about 5% degradation of the efficiency. These findings provide a facile approach to fabricate efficient and stable PSCs by low processing temperature in ambient air, both of which are highly preferred for future practical applications of PSCs.

Large low-field magnetoresistance of Fe{sub 3}O{sub 4} nanocrystal at room temperature

Energy Technology Data Exchange (ETDEWEB)

Mi, Shu, E-mail: mishu@buaa.edu.cn; Liu, Rui, E-mail: liurui1987@buaa.edu.cn; Li, Yuanyuan, E-mail: buaaliyuan@163.com; Xie, Yong, E-mail: xiey@buaa.edu.cn; Chen, Ziyu, E-mail: chenzy@buaa.edu.cn

2017-04-15

Superparamagnetic magnetite (Fe{sub 3}O{sub 4}) nanoparticles with an average size of 6.5 nm and good monodispersion were synthesized and investigated by X-ray diffraction, Raman spectrometer, transmission electron microscopy and vibrating sample magnetometer. Corresponding low-field magnetoresistance (LFMR) was tested by physical property measurement system. A quite high LFMR has been observed at room temperature. For examples, at a field of 3000 Oe, the LFMR is −3.5%, and when the field increases to 6000 Oe, the LFMR is up to −5.1%. The electron spin polarization was estimated at 25%. This result is superior to the previous reports showing the LFMR of no more than 2% at room temperature. The conduction mechanism is proposed to be the tunneling of conduction electrons between adjacent grains considering that the monodisperse nanocrystals may supply more grain boundaries increasing the tunneling probability, and consequently enhancing the overall magnetoresistance. - Highlights: • Superparamagnetic Fe3O4 nanoparticles with small size were synthesized. • A quite high LFMR has been observed at room temperature. • The more grain boundaries increase the tunneling probability and enlarge the MR. • The fast response of the sample increase the MR at a low field.

CH3NH3PbCl3 Single Crystals: Inverse Temperature Crystallization and Visible-Blind UV-Photodetector

KAUST Repository

Maculan, Giacomo; Sheikh, Arif D.; Abdelhady, Ahmed L.; Saidaminov, Makhsud I.; Haque, Mohammed; Banavoth, Murali; Alarousu, Erkki; Mohammed, Omar F.; Wu, Tao; Bakr, Osman

2015-01-01

a new method of sizeable CH3NH3PbCl3 single crystal growth based on retrograde solubility behavior of hybrid perovskites. We show, for the first time, the energy band structure, charge-carrier recombination and transport properties of single crystal

Aquaporin 4 as a NH3 Channel

DEFF Research Database (Denmark)

Assentoft, Mette; Kaptan, Shreyas; Schneider, Hans-Peter

2016-01-01

-brain-interface, participate in the exchange of ammonia, which is required to sustain the glutamate-glutamine cycle. Here we observe that AQP4-expressing Xenopus oocytes display a reflection coefficient NH4Cl at pH 8.0, at which pH an increased amount of the ammonia occurs in the form of NH3 Taken together with an NH4......Cl-mediated intracellular alkalization (or lesser acidification) of AQP4-expressing oocytes, these data suggest that NH3 is able to permeate the pore of AQP4. Exposure to NH4Cl increased the membrane currents to a similar extent in uninjected oocytes and in oocytes expressing AQP4, indicating...... that the ionic NH4 (+) did not permeate AQP4. Molecular dynamics simulations revealed partial pore permeation events of NH3 but not of NH4 (+) and a reduced energy barrier for NH3 permeation through AQP4 compared with that of a cholesterol-containing lipid bilayer, suggesting AQP4 as a favored transmembrane...

CH3NH3PbCl3 Single Crystals: Inverse Temperature Crystallization and Visible-Blind UV-Photodetector

KAUST Repository

Maculan, Giacomo

2015-09-02

Single crystals of hybrid perovskites have shown remarkably improved physical properties compared to their polycrystalline film counterparts, underscoring their importance in the further development of advanced semiconductor devices. Here we present a new method of sizeable CH3NH3PbCl3 single crystal growth based on retrograde solubility behavior of hybrid perovskites. We show, for the first time, the energy band structure, charge-carrier recombination and transport properties of single crystal CH3NH3PbCl3. The chloride-based perovskite crystals exhibit trap-state density, charge carriers concentration, mobility and diffusion length comparable with the best quality crystals of methylammonium lead iodide or bromide perovskites reported so far. The high quality of the crystal along with its suitable optical bandgap enabled us to design and build an efficient visible-blind UV-photodetector, demonstrating the potential of this material to be employed in optoelectronic applications.

Engineering of Highly Susceptible Paramagnetic Nanostructures of Gd2S3:Eu3+: Potentially an Efficient Material for Room Temperature Gas Sensing Applications

Directory of Open Access Journals (Sweden)

Muhammed M. Radhi

2010-11-01

Full Text Available This research papers throws light into the compositional, morphological and structural properties of novel nanoparticles of Gd2S3:Eu3+ synthesized by a simple co-precipitation technique. Furthermore, we also prognosticate that this material could be useful for gas sensing applications at room temperature. Nanostructures formulation by this method resulted in the formation of orthorhombic crystal structure with primitive lattice having space group Pnma. The material characterizations are performed using X-ray diffraction (XRD, energy dispersive X-ray analysis (EDX, thermo-gravimetric analysis/differential thermal analysis (TGA/DTA and transmission electron microscope (TEM. The calculated crystallite sizes are ~ 2-5 nm and are in well accordance with the HRTEM results. EDX result confirms the presence and homogeneous distribution of Gd and Eu throughout the nanoparticle. The prepared nanoparticles exhibit strong paramagnetic nature with paramagnetic term, susceptibility c = 8.2 ´ 10-5 emg/g Gauss. TGA/DTA analysis shows 27 % weight loss with rise in temperature. The gas sensing capability of the prepared Gd2S3:Eu3+ magnetic nanoparticles are investigated using the amperometric method. These nanoparticles show good I-V characteristics with ideal semiconducting nature at room temperature with and without ammonia dose. The observed room temperature sensitivity with increasing dose of ammonia indicates applicability of Gd2S3 nanoparticles as room temperature ammonia sensors.

Real-time observation of formation and relaxation dynamics of NH4 in (CH3OH)m(NH3)n clusters.

Science.gov (United States)

Yamada, Yuji; Nishino, Yoko; Fujihara, Akimasa; Ishikawa, Haruki; Fuke, Kiyokazu

2009-03-26

The formation and relaxation dynamics of NH4(CH3OH)m(NH3)n clusters produced by photolysis of ammonia-methanol mixed clusters has been observed by a time-resolved pump-probe method with femtosecond pulse lasers. From the detailed analysis of the time evolutions of the protonated cluster ions, NH4(+)(CH3OH)m(NH3)n, the kinetic model has been constructed, which consists of sequential three-step reaction: ultrafast hydrogen-atom transfer producing the radical pair (NH4-NH2)*, the relaxation process of radical-pair clusters, and dissociation of the solvated NH4 clusters. The initial hydrogen transfer hardly occurs between ammonia and methanol, implying the unfavorable formation of radical pair, (CH3OH2-NH2)*. The remarkable dependence of the time constants in each step on the number and composition of solvents has been explained by the following factors: hydrogen delocalization within the clusters, the internal conversion of the excited-state radical pair, and the stabilization of NH4 by solvation. The dependence of the time profiles on the probe wavelength is attributed to the different ionization efficiency of the NH4(CH3OH)m(NH3)n clusters.

NMR Spectroscopic Characterization of Methylcobalt(III) Compounds with Classical Ligands. Crystal Structures of [Co(NH(3))(5)(CH(3))]S(2)O(6), trans-[Co(en)(2)(NH(3))(CH(3))]S(2)O(6) (en = 1,2-Ethanediamine), and [Co(NH(3))(6)]-mer,trans-[Co(NO(2))(3)(NH(

DEFF Research Database (Denmark)

Kofod, Pauli; Harris, Pernille; Larsen, Sine

1997-01-01

magnetic resonance spectroscopy and by absorption spectroscopy. Single-crystal X-ray structure determinations at 122.0(5) K were performed on [Co(NH(3))(5)(CH(3))]S(2)O(6) (1), trans-[Co(en)(2)(NH(3))(CH(3))]S(2)O(6) (2), and [Co(NH(3))(6)]-mer,trans-[Co(NO(2))(3)(NH(3))(2)(CH(3))](2)-trans-[Co(NO(2...

Structural study on cubic-tetragonal transition of CH3NH3PbI3

International Nuclear Information System (INIS)

Kawamura, Yukihiko; Mashiyama, Hiroyuki; Hasebe, Katsuhiko

2002-01-01

The cubic-tetragonal phase transition of CH 3 NH 3 PbI 3 was investigated by single crystal X-ray diffractometry. The crystal structure was refined at five temperatures in the tetragonal phase. The PbI 6 octahedron rotates around the c-axis alternatively to construct the SrTiO 3 -type tetragonal structure. A methylammonium ion is partially ordered; 24 disordered states in the cubic phase are reduced to 8. With decreasing temperature, the rotation angle of the octahedron increases monotonically, which indicates it is an order parameter of the cubic-tetragonal transition. (author)

First principles investigation of half-metallicity and spin gapless semiconductor in CH3NH3Cr x Pb1- x I3 mixed perovskites

Science.gov (United States)

Huang, H. M.; Zhu, Z. W.; Zhang, C. K.; He, Z. D.; Luo, S. J.

2018-04-01

The structural, electronic and magnetic properties of organic-inorganic hybrid mixed perovskites CH3NH3Cr x Pb1- x I3 ( x = 0.25, 0.50, 0.75, 1.00) in cubic, tetragonal and orthorhombic phases have been investigated by first-principles calculation. The results indicate that the tetragonal CH3NH3Cr0.75Pb0.25I3 is a spin gapless semiconductor with Curie temperature of 663 K estimated using mean field approximation. All other CH3NH3Cr x Pb1- x I3 mixed perovskites are half-metallic ferromagnets together with 100% spin polarization, and their total magnetic moment are 4.00, 8.00, 12.00 and 16.00 µB per unit cell for x = 0.25, 0.50, 0.75 and 1.00, respectively. The effect of , and orientation of organic cation CH3NH3 + on the electronic properties of CH3NH3Cr0.50Pb0.50I3 was investigated. The results show that the CH3NH3 + in different orientations have a slight effect on the lattice constants, the energy gap in minority-spin states, half-metallic gap, local magnetic moment, and Curie temperature.

Orthorhombic fulleride (CH3NH2)K3C60 close to Mott-Hubbard instability: Ab initio study

Science.gov (United States)

Potočnik, Anton; Manini, Nicola; Komelj, Matej; Tosatti, Erio; Arčon, Denis

2012-08-01

We study the electronic structure and magnetic interactions in methylamine-intercalated orthorhombic alkali-doped fullerene (CH3NH2)K3C60 within the density functional theory. As in the simpler ammonia intercalated compound (NH3)K3C60, the orthorhombic crystal-field anisotropy Δ lifts the t1u triple degeneracy at the Γ point and drives the system deep into the Mott-insulating phase. However, the computed Δ and conduction electron bandwidth W cannot alone account for the abnormally low experimental Néel temperature, TN=11 K, of the methylamine compound, compared to the much higher value TN=40 K of the ammonia one. Significant interactions between CH3NH2 and C603- are responsible for the stabilization of particular fullerene-cage distortions and the ensuing low-spin S=1/2 state. These interactions also seem to affect the magnetic properties, as interfullerene exchange interactions depend on the relative orientation of deformations of neighboring C603- molecules. For the ferro-orientational order of CH3NH2-K+ groups we find an apparent reduced dimensionality in magnetic exchange interactions, which may explain the suppressed Néel temperature. The disorder in exchange interactions caused by orientational disorder of CH3NH2-K+ groups could further contribute to this suppression.

Mesoporous Structure Control of Silica in Room-Temperature Synthesis under Basic Conditions

Directory of Open Access Journals (Sweden)

Jeong Wook Seo

2015-01-01

Full Text Available Various types of mesoporous silica, such as continuous cubic-phase MCM-48, hexagonal-phase MCM-41, and layer-phase spherical silica particles, have been synthesized at room temperature using cetyltrimethylammonium bromide as a surfactant, ethanol as a cosurfactant, tetraethyl orthosilicate as a silica precursor, and ammonia as a condensation agent. Special care must be taken both in the filtering of the resultant solid products and in the drying process. In the drying process, further condensation of the silica after filtering was induced. As the surfactant and cosurfactant concentrations in the reaction mixture increased and the NH3 concentration decreased, under given conditions, continuous cubic MCM-48 and layered silica became the dominant phases. A cooperative synthesis mechanism, in which both the surfactant and silica were involved in the formation of mesoporous structures, provided a good explanation of the experimental results.

Sequence of phase transitions in (NH4)3SiF7.

Science.gov (United States)

Mel'nikova, S V; Molokeev, M S; Laptash, N M; Pogoreltsev, E I; Misyul, S V; Flerov, I N

2017-02-21

Single crystals of silicon double salt (NH 4 ) 3 SiF 7 = (NH 4 ) 2 SiF 6 ·NH 4 F = (NH 4 ) 3 [SiF 6 ]F were grown and studied by the methods of polarization optics, X-ray diffraction and calorimetry. A sequence of symmetry transformations with the temperature change was established: P4/mbm (Z = 2) (G 1 ) ↔ Pbam (Z = 4) (G 2 ) ↔ P2 1 /c (Z = 4) (G 3 ) ↔ P1[combining macron] (Z = 4) (G 4 ) ↔ P2 1 /c (Z = 8) (G 5 ). Crystal structures of different phases were determined. The experimental data were also interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account critical and noncritical atomic displacements. Strengthening of the N-HF hydrogen bonds can be a driving force of the observed phase transitions.

Behavior of sheet-like crystalline ammonium trivanadate hemihydrate (NH4V3O8×0.5H2O) as a novel ammonia sensing material

International Nuclear Information System (INIS)

Leonardi, S.G.; Primerano, P.; Donato, N.; Neri, G.

2013-01-01

This work reports the use of ammonium trivanadate hemihydrate (NH 4 V 3 O 8 ×0.5H 2 O) as a novel sensing material for ammonia resistive sensors. It was prepared by a simple and fast hydrothermal method from V 2 O 5 as a precursor and characterized by SEM, FT-IR, XRD and TG techniques. The as-synthesized material showed a sheet-like morphology and was found thermally stable up to 250–280 °C. It reacted promptly and irreversibly when exposed to ammonia at room temperature. A full reversibility was instead registered undergoing the formed ammonia adduct at a temperature higher than 200 °C. A NH 4 V 3 O 8 ×0.5H 2 O-based resistive gas sensor was fabricated and its sensing properties were evaluated. Experimental results obtained have given a preliminary demonstration of the feasibility of using NH 4 V 3 O 8 ×0.5H 2 O as a novel ammonia sensing material since it yields several advantages including easy synthesis of the sensing layer, good sensitivity and reproducibility and fast response. - Graphical abstract: Sheet-like morphology of the synthesized trivanadate hemihydrate (NH 4 V 3 O 8 ×0.5H 2 O). Inset: Its electrical response to different ammonia concentrations in air. - Highlights: • A simple hydrothermal method for the fast synthesis of trivanadate hemihydrate (NH 4 V 3 O 8 ×0.5H 2 O) is reported. • Sheet particles could be obtained. • A preliminary demonstration of the feasibility of using NH 4 V 3 O 8 ×0.5H 2 O as a novel ammonia sensing material is presented

Investigation on thermal evaporated CH3NH3PbI3 thin films

Directory of Open Access Journals (Sweden)

Youzhen Li

2015-09-01

Full Text Available CH3NH3I, PbI2 and CH3NH3PbI3 films were fabricated by evaporation and characterized with X-ray Photoelectron Spectroscopy (XPS and X-ray diffraction (XRD. The XPS results indicate that the PbI2 and CH3NH3PbI3 films are more uniform and stable than the CH3NH3I film. The atomic ratio of the CH3NH3I, PbI2 and CH3NH3PbI3 films are C:N:I=1.00:1.01:0.70, Pb:I= 1.00:1.91 and C: N: Pb: I = 1.29:1.07:1.00:2.94, respectively. The atomic ratio of CH3NH3PbI3 is very close to that of the ideal perovskite. Small angle x-ray diffraction results demonstrate that the as evaporated CH3NH3PbI3 film is crystalline. The valence band maximum (VBM and work function (WF of the CH3NH3PbI3 film are about 0.85eV and 4.86eV, respectively.

Structural Studies of NH4-exchanged Natrolites at Ambient Conditions and High Temperature

Energy Technology Data Exchange (ETDEWEB)

Y Lee; D Seoung; Y Jang; J Bai; Y Lee

2011-12-31

We report here for the first time that fully and partially NH{sub 4}-exchanged natrolites can be prepared in hydrated states using the solution exchange method with potassium-natrolite. The structural models of the as-prepared hydrated phases and their dehydrated forms at elevated temperature were refined in space group Fdd2 using in situ synchrotron X-ray powder diffraction data and Rietveld methods. The unit-cell volumes of the hydrated NH{sub 4}-exchanged natrolites at ambient conditions, (NH{sub 4}){sub 16(2)}Al{sub 16}Si{sub 24}O{sub 80}{center_dot}14.1(9)H{sub 2}O and (NH{sub 4}){sub 5.1(1)}K{sub 10.9(1)}Al{sub 16}Si{sub 24}O{sub 80}{center_dot}15.7(3)H{sub 2}O, are found to be larger than that the original sodium-natrolite by ca. 15.6% and 12.8%, respectively. Upon temperature increase, the fully NH{sub 4}-exchanged natrolite undergoes dehydration at ca. 150 C with ca. 16.4% contraction in the unit-cell volume. The dehydrated phase of the fully NH{sub 4}-exchanged natrolite exhibits marginal volume expansion up to 425 C and then becomes amorphized during temperature decrease and exposure to atmospheric condition. In the case of the partially NH{sub 4}-exchanged natrolite, the dehydration starts from ca. 175 C with {approx}15.1% volume contraction and leads to a partial phase separation to show a phase related to the dehydrated K-natrolite. The degree of the phase separation decreases with temperature increase up to 475 C, concomitant to the gradual volume contraction occurring in the partially NH{sub 4}-exchanged natrolite in the dehydrared state. Upon temperature decrease and exposure to atmospheric condition, only the dehydrated K-natrolite is recovered as a crystalline phase from the partially NH{sub 4}-exchanged natrolite. In the hydrated model of the fully NH{sub 4}-exchanged natrolite, the ammonium cations and water molecules are statistically distributed along the elliptical channels, similar to the disordered pattern observed in natrolites exchanged

BF3.SiO2: an efficient catalyst for the synthesis of azo dyes at room temperature

Directory of Open Access Journals (Sweden)

Bi Bi Fatemeh Mirjalili

2012-07-01

Full Text Available A rapid one-pot method has been developed for the synthesis of azo dyes via ‎sequential diazotization–diazo coupling of aromatic amines with coupling agents at room ‎temperature in the presence of BF3.SiO2 as acidic catalyst. The obtained aryl diazonium salts bearing silica supported boron tri-flouride counter ion‎ was sufficiently stable to be kept at room ‎temperature in the dry state.‎

Accompanying growth and room-temperature ferromagnetism of η-Mn3N2 thin films by molecular beam epitaxy

International Nuclear Information System (INIS)

Yu, Fengmei; Liu, Yajing; Yang, Mei; Wu, Shuxiang; Zhou, Wenqi; Li, Shuwei

2013-01-01

η-phase manganese nitride films have been grown on LaAlO 3 (100) and LaSrAlO 4 (001) substrates by using plasma-assisted molecular beam epitaxy. On the basis of reflective high energy electron diffraction, X-ray diffraction, and X-ray photoemission spectroscopy, it is confirmed that two types of η-Mn 3 N 2 with different lattice constants coexist in the films due to the lattice mismatches between the Mn 3 N 2 films and the substrates. Magnetic properties of the films were characterized by a superconducting quantum interference device magnetometer at room temperature. The Mn 3 N 2 films on LaAlO 3 substrate were found to have room-temperature ferromagnetism. Two potential interaction mechanisms are proposed regarding the origin of the observed ferromagnetism. - Highlights: ► The films of two types of η-Mn 3 N 2 have been grown by molecular beam epitaxy. ► Mn 3 N 2 A and Mn 3 N 2 B coexisted in the films on LaAlO 3 and LaSrAlO 4 . ► The room-temperature ferromagnetism of the Mn 3 N 2 films on LaAlO 3 was obtained

NH3 Abatement in Fluidized Bed Co-Gasification of RDF and Coal

Science.gov (United States)

Gulyurtlu, I.; Pinto, Filomena; Dias, Mário; Lopes, Helena; André, Rui Neto; Cabrita, I.

Gasification of wastes may come out as an alternative technology to produce a gas with many potential applications, from direct burning in a boiler or motor to the production of synthetic chemicals and hydrogen. High tar production and high operational costs are preventing gasification wider dissemination. Besides these problems, the presence of NH3 in the syngas may have a negative impact as it can be converted into nitrogen oxides if the gas is further burnt. To reduce NH3 formation it is required a full understanding of how operational parameters contribute to the formation/reduction of this pollutant. A full studyon the effect of fuel composition, temperature and equivalence ratio on the formation of NH3 is given. Experimental results are compared to theoretical ones obtained with FactSage software. It is also analyzed the effect of feedstock mineral matterin NH3 release during gasification. Toaccomplish a significant decrease in the release of NH3, different catalysts and sorbents were tested with the aim of achieving high energy conversions and low environmental impact.

Isotopically decoupled vibrational spectra and proton exchange rates for crystalline NH3 and ammonia hydrate

Science.gov (United States)

Thornton, Cynthia; Khatkale, M. S.; Devlin, J. Paul

1981-12-01

Codeposits of NH3 with ND3 or D2O have been prepared at liquid nitrogen temperatures in the absence of proton exchange. Vibrational data for the anhydrous cubic crystalline ammonia, containing isolated NH3 or ND3, confirm that, relative to water ice, intermolecular coupling in ammonia ice exerts a relatively minor influence on the infrared and Raman spectra. Nevertheless, sizeable decoupling shifts, particularly for ν1, have been observed and attributed to a combination of factors including correlation field and Fermi resonance effects. The Raman polarization data has also affirmed long standing assignments of ν1 and ν3 for ammonia ice. Warming of the ammonia thin films resulted in limited isotopic scrambling at 130 K, apparently possible only through the agency of trace concentrations of water. The vibrational coupling pattern for the resultant NHD2 and NH2D molecules suggest that proton (deuteron) migration away from the exchange centers is impossible at temperatures up to 150 K. By contrast, isotopic scrambling was rapid and complete at 140 K for amorphous ammonia hydrate films (˜35% NH3, ˜65% D2O) which were also prepared without exchange at ˜90 K. The proton (deuteron) exchange rate is much greater for the amorphous ammonia hydrate at 140 K than for pure water ice. Such exchange requires both ion-pair defect formation and proton mobility. Since the NH3 suppresses the H3O+ concentration via formation of NH+4, a suppression the likes of which has been shown to stop proton exchange in water ice, the evidence strongly suggests that NH4+ in ammonia, like H3O+ in water, is an effective proton transfer agent, probably acting through a tunneling mechanism (i.e., H3N+-HṡṡṡNH3→H3NṡṡṡH-N+H3 etc.) to render the proton mobile in the ammonia hydrate. This mobility combined with the greater NH4+ concentration, relative to the H3O+ concentration in H2O ice Ic, results in isotopic scrambling at the reduced temperature.

Low-temperature SCR of NO with NH{sub 3} over activated semi-coke composite-supported rare earth oxides

Energy Technology Data Exchange (ETDEWEB)

Wang, Jinping; Yan, Zheng; Liu, Lili; Zhang, Yingyi; Zhang, Zuotai; Wang, Xidong, E-mail: xidong@pku.edu.cn

2014-08-01

The catalysts with different rare earth oxides (La, Ce, Pr and Nd) loaded onto activated semi-coke (ASC) via hydrothermal method are prepared for the selective catalytic reduction (SCR) of NO with NH{sub 3} at low temperature (150–300 °C). It is evidenced that CeO{sub 2} loaded catalysts present the best performance, and the optimum loading amount of CeO{sub 2} is about 10 wt%. Composite catalysts by doping La, Pr and Nd into CeO{sub 2} are prepared to obtain further improved catalytic properties. The SCR mechanism is investigated through various characterizations, including XRD, Raman, XPS and FT-IR, the results of which indicate that the oxygen defect plays an important role in SCR process and the doped rare earth elements effectively serve as promoters to increase the concentration of oxygen vacancies. It is also found that the oxygen vacancies in high concentration are favored for the adsorption of O{sub 2} and further oxidation of NO, which facilitates a rapid progressing of the following reduction reactions. The SCR process of NO with NH{sub 3} at low temperature over the catalysts of ASC composite-supported rare earth oxides mainly follows the Langmuir–Hinshlwood mechanism.

Role of NH3 and NH4+ transporters in renal acid-base transport.

Science.gov (United States)

Weiner, I David; Verlander, Jill W

2011-01-01

Renal ammonia excretion is the predominant component of renal net acid excretion. The majority of ammonia excretion is produced in the kidney and then undergoes regulated transport in a number of renal epithelial segments. Recent findings have substantially altered our understanding of renal ammonia transport. In particular, the classic model of passive, diffusive NH3 movement coupled with NH4+ "trapping" is being replaced by a model in which specific proteins mediate regulated transport of NH3 and NH4+ across plasma membranes. In the proximal tubule, the apical Na+/H+ exchanger, NHE-3, is a major mechanism of preferential NH4+ secretion. In the thick ascending limb of Henle's loop, the apical Na+-K+-2Cl- cotransporter, NKCC2, is a major contributor to ammonia reabsorption and the basolateral Na+/H+ exchanger, NHE-4, appears to be important for basolateral NH4+ exit. The collecting duct is a major site for renal ammonia secretion, involving parallel H+ secretion and NH3 secretion. The Rhesus glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), are recently recognized ammonia transporters in the distal tubule and collecting duct. Rhcg is present in both the apical and basolateral plasma membrane, is expressed in parallel with renal ammonia excretion, and mediates a critical role in renal ammonia excretion and collecting duct ammonia transport. Rhbg is expressed specifically in the basolateral plasma membrane, and its role in renal acid-base homeostasis is controversial. In the inner medullary collecting duct (IMCD), basolateral Na+-K+-ATPase enables active basolateral NH4+ uptake. In addition to these proteins, several other proteins also contribute to renal NH3/NH4+ transport. The role and mechanisms of these proteins are discussed in depth in this review.

Room temperature ferromagnetic and photoluminescence ...

Indian Academy of Sciences (India)

32

electrode, photo electronic devices, photo sensors, liquid crystal displays, electrochromic windows, solar panels and transparent coatings for solar-energy heat mirrors [11-13]. Here we report on magnetic properties of ITO nanoparticles at room temperature and at 100 K. 2. Experimental. The In1.9Sn0.1O3 powder samples ...

Generation of nanopores during desorption of NH3 from Mg(NH3)6Cl2

DEFF Research Database (Denmark)

Hummelshøj, Jens Strabo; Sørensen, Rasmus Zink; Kostova, M.Y.

2006-01-01

It is shown that nanopores are formed during desorption of NH3 from Mg(NH3)6Cl2, which has been proposed as a hydrogen storage material. The system of nanopores facilitates the transport of desorbed ammonia away from the interior of large volumes of compacted storage material. DFT calculations sh...

Low Temperature Growth of In2O3and InN Nanocrystals on Si(111 via Chemical Vapour Deposition Based on the Sublimation of NH4Cl in In

Directory of Open Access Journals (Sweden)

Tsokkou Demetra

2009-01-01

Full Text Available Abstract Indium oxide (In2O3 nanocrystals (NCs have been obtained via atmospheric pressure, chemical vapour deposition (APCVD on Si(111 via the direct oxidation of In with Ar:10% O2at 1000 °C but also at temperatures as low as 500 °C by the sublimation of ammonium chloride (NH4Cl which is incorporated into the In under a gas flow of nitrogen (N2. Similarly InN NCs have also been obtained using sublimation of NH4Cl in a gas flow of NH3. During oxidation of In under a flow of O2the transfer of In into the gas stream is inhibited by the formation of In2O3around the In powder which breaks up only at high temperatures, i.e.T > 900 °C, thereby releasing In into the gas stream which can then react with O2leading to a high yield formation of isolated 500 nm In2O3octahedrons but also chains of these nanostructures. No such NCs were obtained by direct oxidation forT G < 900 °C. The incorporation of NH4Cl in the In leads to the sublimation of NH4Cl into NH3and HCl at around 338 °C which in turn produces an efficient dispersion and transfer of the whole In into the gas stream of N2where it reacts with HCl forming primarily InCl. The latter adsorbs onto the Si(111 where it reacts with H2O and O2leading to the formation of In2O3nanopyramids on Si(111. The rest of the InCl is carried downstream, where it solidifies at lower temperatures, and rapidly breaks down into metallic In upon exposure to H2O in the air. Upon carrying out the reaction of In with NH4Cl at 600 °C under NH3as opposed to N2, we obtain InN nanoparticles on Si(111 with an average diameter of 300 nm.

Communication: Equivalence between symmetric and antisymmetric stretching modes of NH3 in promoting H + NH3 → H2 + NH2 reaction

Science.gov (United States)

Song, Hongwei; Yang, Minghui; Guo, Hua

2016-10-01

Vibrational excitations of reactants sometimes promote reactions more effectively than the same amount of translational energy. Such mode specificity provides insights into the transition-state modulation of reactivity and might be used to control chemical reactions. We report here a state-of-the-art full-dimensional quantum dynamical study of the hydrogen abstraction reaction H + NH3 → H2 + NH2 on an accurate ab initio based global potential energy surface. This reaction serves as an ideal candidate to study the relative efficacies of symmetric and degenerate antisymmetric stretching modes. Strong mode specificity, particularly for the NH3 stretching modes, is demonstrated. It is further shown that nearly identical efficacies of the symmetric and antisymmetric stretching modes of NH3 in promoting the reaction can be understood in terms of local-mode stretching vibrations of the reactant molecule.

Densities and apparent molar volumes of atmospherically important electrolyte solutions. 1. The solutes H2SO4, HNO3, HCl, Na2SO4, NaNO3, NaCl, (NH4)2SO4, NH4NO3, and NH4Cl from 0 to 50 °C, including extrapolations to very low temperature and to the pure liquid state, and NaHSO4, NaOH, and NH3 at 25 °C.

Science.gov (United States)

Clegg, S L; Wexler, A S

2011-04-21

Calculations of the size and density of atmospheric aerosols are complicated by the fact that they can exist at concentrations highly supersaturated with respect to dissolved salts and supercooled with respect to ice. Densities and apparent molar volumes of solutes in aqueous solutions containing the solutes H(2)SO(4), HNO(3), HCl, Na(2)SO(4), NaNO(3), NaCl, (NH(4))(2)SO(4), NH(4)NO(3), and NH(4)Cl have been critically evaluated and represented using fitted equations from 0 to 50 °C or greater and from infinite dilution to concentrations saturated or supersaturated with respect to the dissolved salts. Using extrapolated densities of high-temperature solutions and melts, the relationship between density and concentration is extended to the hypothetical pure liquid solutes. Above a given reference concentration of a few mol kg(-1), it is observed that density increases almost linearly with decreasing temperature, and comparisons with available data below 0 °C suggest that the fitted equations for density can be extrapolated to very low temperatures. As concentration is decreased below the reference concentration, the variation of density with temperature tends to that of water (which decreases as temperature is reduced below 3.98 °C). In this region below the reference concentration, and below 0 °C, densities are calculated using extrapolated apparent molar volumes which are constrained to agree at the reference concentrations with an equation for the directly fitted density. Calculated volume properties agree well with available data at low temperatures, for both concentrated and dilute solutions. Comparisons are made with literature data for temperatures of maximum density. Apparent molar volumes at infinite dilution are consistent, on a single ion basis, to better than ±0.1 cm(3) mol(-1) from 0 to 50 °C. Volume properties of aqueous NaHSO(4), NaOH, and NH(3) have also been evaluated, at 25 °C only. In part 2 of this work (ref 1 ) an ion interaction (Pitzer

Electrochemical Reduction of N2 under Ambient Conditions for Artificial N2 Fixation and Renewable Energy Storage Using N2 /NH3 Cycle.

Science.gov (United States)

Bao, Di; Zhang, Qi; Meng, Fan-Lu; Zhong, Hai-Xia; Shi, Miao-Miao; Zhang, Yu; Yan, Jun-Min; Jiang, Qing; Zhang, Xin-Bo

2017-01-01

Using tetrahexahedral gold nanorods as a heterogeneous electrocatalyst, an electrocatalytic N 2 reduction reaction is shown to be possible at room temperature and atmospheric pressure, with a high Faradic efficiency up to 4.02% at -0.2 V vs reversible hydrogen electrode (1.648 µg h -1 cm -2 and 0.102 µg h -1 cm -2 for NH 3 and N 2 H 4 ·H 2 O, respectively). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The recombination mechanisms leading to amplified spontaneous emission at the true-green wavelength in CH3NH3PbBr3 perovskites

KAUST Repository

Priante, Davide; Dursun, Ibrahim; Alias, M. S.; Shi, Dong; Melnikov, V. A.; Ng, Tien Khee; Mohammed, Omar F.; Bakr, Osman; Ooi, Boon S.

2015-01-01

We investigated the mechanisms of radiative recombination in a CH3NH3PbBr3 hybrid perovskite material using low-temperature, power-dependent (77K), and temperature-dependent photoluminescence (PL) measurements. Two bound-excitonic radiative

Experimental study of the aqueous CO2-NH3 rate of reaction for temperatures from 15 °C to 35 °C, NH3 concentrations from 5% to 15% and CO2 loadings from 0.2 to 0.6

DEFF Research Database (Denmark)

Lillia, Stefano; Bonalumi, Davide; Fosbøl, Philip L.

2018-01-01

, and lastly CO2 loadings from 0.2 to 0.6. The resulting overall mass transfer coefficient of absorption measured follows the trends described by the modelling of the reactor and the equations used to describe the rate of the absorption reactions. Moreover, the overall mass transfer coefficient of absorption...... loading conditions. The kinetic model intercept the values found in literature in every range of concentration. Consequently, the model is valid in every conditions and the rate of the reaction between NH3 and CO2 in liquid phase is described with an Arrhenius constant with a pre-exponential factor of 1......The absorption reaction between aqueous NH3 and CO2 was studied using the Wetted Wall Column. A total of 27 different cases are investigated in the region defined by temperatures from 15 °C to 35 °C, NH3 concentrations from 5% to 15%, which are the typical solvent conditions in absorption columns...

Investigation of Catalytic Effects and Compositional Variations in Desorption Characteristics of LiNH2-nanoMgH2

Directory of Open Access Journals (Sweden)

Sesha S. Srinivasan

2017-07-01

Full Text Available LiNH2 and a pre-processed nanoMgH2 with 1:1 and 2:1 molar ratios were mechano-chemically milled in a high-energy planetary ball mill under inert atmosphere, and at room temperature and atmospheric pressure. Based on the thermogravimetric analysis (TGA experiments, 2LiNH2-nanoMgH2 demonstrated superior desorption characteristics when compared to the LiNH2-nanoMgH2. The TGA studies also revealed that doping 2LiNH2-nanoMgH2 base material with 2 wt. % nanoNi catalyst enhances the sorption kinetics at lower temperatures. Additional investigation of different catalysts showed improved reaction kinetics (weight percentage of H2 released per minute of the order TiF3 > nanoNi > nanoTi > nanoCo > nanoFe > multiwall carbon nanotube (MWCNT, and reduction in the on-set decomposition temperatures of the order nanoCo > TiF3 > nanoTi > nanoFe > nanoNi > MWCNT for the base material 2LiNH2-nanoMgH2. Pristine and catalyst-doped 2LiNH2-nanoMgH2 samples were further probed by X-ray diffraction, Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, thermal programmed desorption and pressure-composition-temperature measurements to better understand the improved performance of the catalyst-doped samples, and the results are discussed.

Reversible flexible structural changes in multidimensional MOFs by guest molecules (I{sub 2}, NH{sub 3}) and thermal stimulation

Energy Technology Data Exchange (ETDEWEB)

Chen, Yang; Li, Libo; Yang, Jiangfeng; Wang, Shuang; Li, Jinping, E-mail: Jpli211@hotmail.com

2015-03-15

Three metal–organic frameworks (MOFs), [Cu(INA){sub 2}], [Cu(INA){sub 2}I{sub 2}] and [Cu(INA){sub 2}(H{sub 2}O){sub 2}(NH{sub 3}){sub 2}], were synthesized with 3D, 2D, and 0D structures, respectively. Reversible flexible structural changes of these MOFs were reported. Through high temperature (60–100 °C) stimulation of I{sub 2} or ambient temperature stimulation of NH{sub 3}, [Cu(INA){sub 2}] (3D) converted to [Cu(INA){sub 2}I{sub 2}] (2D) and [Cu(INA){sub 2}(H{sub 2}O){sub 2}(NH{sub 3}){sub 2}] (0D); as the temperature increased to 150 °C, the MOFs changed back to their original form. In this way, this 3D MOF has potential application in the capture of I{sub 2} and NH{sub 3} from polluted water and air. XRD, TGA, SEM, NH{sub 3}-TPD, and the measurement of gas adsorption were used to describe the changes in processes regarding the structure, morphology, and properties. - Graphical abstract: Through I{sub 2}, NH{sub 3} molecules and thermal stimulation, the three MOFs can achieve reversible flexible structural changes. Different methods were used to prove the flexible reversible changes. - Highlights: • [Cu(INA){sub 2}] can flexible transform to [Cu(INA){sub 2}I{sub 2}] and [Cu(INA){sub 2}(H{sub 2}O){sub 2}(NH{sub 3}){sub 2}] by adsorbing I{sub 2} or NH{sub 3}. • The reversible flexible transformation related to material source, temperature and concentration. • Potential applications for the capture of I{sub 2} and NH{sub 3} from polluted water or air.

Crystal structure and charge density analysis of Li2NH by synchrotron X-ray diffraction

International Nuclear Information System (INIS)

Noritake, T.; Nozaki, H.; Aoki, M.; Towata, S.; Kitahara, G.; Nakamori, Y.; Orimo, S.

2005-01-01

Complex hydrides, such as lithium amide (LiNH 2 ) and lithium imide (Li 2 NH), have recently been noticed as one of the most promising materials for reversible hydrogen storage. In this paper, we reveal the bonding nature of hydrogen in Li 2 NH crystal by synchrotron powder X-ray diffraction measurement at room temperature. The crystal structure was refined by Rietveld method and the charge density distribution was analyzed by maximum entropy method (MEM). The Li 2 NH crystal is anti-fluorite type structure (space group Fm3-bar m) consisting of Li and NH. Hydrogen atom occupies randomly the 48h (Wyckoff notation) sites around N atom. The refined lattice constant is a=5.0742(2)A. The charge density distribution around NH anion in Li 2 NH is almost spherical. The number of electrons within the sphere around the Li and NH is estimated from the obtained charge density distribution. As the result, the ionic charge is expressed as [Li 0.99+ ] 2 [NH] 1.21- . Therefore, it is confirmed experimentally that Li 2 NH is ionically bonded

Difference in chemical reactions in bulk plasma and sheath regions during surface modification of graphene oxide film using capacitively coupled NH{sub 3} plasma

Energy Technology Data Exchange (ETDEWEB)

Lee, Sung-Youp; Kim, Chan; Kim, Hong Tak, E-mail: zam89blue@gmail.com [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of)

2015-09-14

Reduced graphene oxide (r-GO) films were obtained from capacitively coupled NH{sub 3} plasma treatment of spin-coated graphene oxide (GO) films at room temperature. Variations were evaluated according to the two plasma treatment regions: the bulk plasma region (R{sub bulk}) and the sheath region (R{sub sheath}). Reduction and nitridation of the GO films began as soon as the NH{sub 3} plasma was exposed to both regions. However, with the increase in treatment time, the reduction and nitridation reactions differed in each region. In the R{sub bulk}, NH{sub 3} plasma ions reacted chemically with oxygen functional groups on the GO films, which was highly effective for reduction and nitridation. While in the R{sub sheath}, physical reactions by ion bombardment were dominant because plasma ions were accelerated by the strong electrical field. The accelerated plasma ions reacted not only with the oxygen functional groups but also with the broken carbon chains, which caused the removal of the GO films by the formation of hydrocarbon gas species. These results showed that reduction and nitridation in the R{sub bulk} using capacitively coupled NH{sub 3} plasma were very effective for modifying the properties of r-GO films for application as transparent conductive films.

Room temperature hydrogen generation from hydrolysis of ammonia-borane over an efficient NiAgPd/C catalyst

KAUST Repository

Hu, Lei

2014-12-01

NiAgPd nanoparticles are successfully synthesized by in-situ reduction of Ni, Ag and Pd salts on the surface of carbon. Their catalytic activity was examined in ammonia borane (NH3BH3) hydrolysis to generate hydrogen gas. This nanomaterial exhibits a higher catalytic activity than those of monometallic and bimetallic counterparts and a stoichiometric amount of hydrogen was produced at a high generation rate. Hydrogen production rates were investigated in different concentrations of NH3BH3 solutions, including in the borates saturated solution, showing little influence of the concentrations on the reaction rates. The hydrogen production rate can reach 3.6-3.8 mol H2 molcat -1 min-1 at room temperature (21 °C). The activation energy and TOF value are 38.36 kJ/mol and 93.8 mol H2 molcat -1 min-1, respectively, comparable to those of Pt based catalysts. This nanomaterial catalyst also exhibits excellent chemical stability, and no significant morphology change was observed from TEM after the reaction. Using this catalyst for continuously hydrogen generation, the hydrogen production rate can be kept after generating 6.2 L hydrogen with over 10,000 turnovers and a TOF value of 90.3 mol H2 molcat -1 min-1.

Solid-state thermal decomposition of the [Co(NH{sub 3}){sub 5}CO{sub 3}]NO{sub 3}{center_dot}0.5H{sub 2}O complex: A simple, rapid and low-temperature synthetic route to Co{sub 3}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Farhadi, Saeid, E-mail: sfarhad2001@yahoo.com [Department of Chemistry, Lorestan University, Khorramabad 68135-465 (Iran, Islamic Republic of); Safabakhsh, Jalil [Department of Chemistry, Lorestan University, Khorramabad 68135-465 (Iran, Islamic Republic of)

2012-02-25

Highlights: Black-Right-Pointing-Pointer [Co(NH{sub 3}){sub 5}CO{sub 3}]NO{sub 3}{center_dot}0.5H{sub 2}O complex was used for preparing pure Co{sub 3}O{sub 4} nanoparticles. Black-Right-Pointing-Pointer Co{sub 3}O{sub 4} nanoparticles were prepared at low temperature of 175 Degree-Sign C. Black-Right-Pointing-Pointer Co{sub 3}O{sub 4} nanoparticles show a weak ferromagnetic behaviour at room temperature. Black-Right-Pointing-Pointer The method is simple, low-cost and suitable for the production of Co{sub 3}O{sub 4}. - Abstract: Co{sub 3}O{sub 4} nanoparticles were easily prepared via the decomposition of the pentammine(carbonato)cobalt(III) nitrate precursor complex [Co(NH{sub 3}){sub 5}CO{sub 3}]NO{sub 3}{center_dot}0.5H{sub 2}O at low temperature (175 Degree-Sign C). The product was characterized by thermal analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Brunauer-Emmett-Teller (BET) specific surface area measurements and magnetic measurements. The FT-IR, XRD, Raman and EDX results indicated that the synthesized Co{sub 3}O{sub 4} nanoparticles are highly pure and have a single phase. The TEM analysis revealed nearly uniform and quasi-spherical Co{sub 3}O{sub 4} nanoparticles with an average particle size of approximately 10 nm. The optical absorption spectrum of the Co{sub 3}O{sub 4} nanoparticles showed two direct band gaps of 2.18 and 3.52 eV with a red shift in comparison with previous reported values. The prepared Co{sub 3}O{sub 4} nanoparticles showed a weak ferromagnetic behaviour that could be attributed to uncompensated surface spins and/or finite-size effects. Using the present method, Co{sub 3}O{sub 4} nanoparticles can be produced without expensive organic solvents and complicated equipment. This simple, rapid, safe and low-cost synthetic route can be extended to the synthesis of other

mer-Triammine trifluorido vanadium(III), mer-[VF{sub 3}(NH{sub 3}){sub 3}]. Synthesis and crystal structure

Energy Technology Data Exchange (ETDEWEB)

Woidy, Patrick [Technische Univ. Muenchen, Garching (Germany). Zentrale Technisch-Wissenschaftliche Betriebseinheit Radiochemie Muenchen RCM; Kraus, Florian [Marburg Univ. (Germany). Anorganische und Fluorchemie

2015-07-01

Vanadium trifluoride reacts with dry liquid ammonia under the formation of lilac plate-shaped crystals of mer-triammine trifluorido vanadium(III) (1), mer-[VF{sub 3}(NH{sub 3}){sub 3}]. Single-crystal X-ray analysis was carried out at low temperature to elucidate the structure. The compound crystallizes in the monoclinic space group P2{sup 1}/c with a = 5.7284(4), b = 9.2033(5), c = 10.5271(6) Aa, beta = 91.795(6)°, and V = 554.72(6) Aa{sup 3} at 123 K with Z = 4. The discrete [VF{sub 3}(NH{sub 3}){sub 3}] molecules are interconnected by hydrogen bonds.

Rapid ammonia gas transport accounts for futile transmembrane cycling under NH3/NH4+ toxicity in plant roots.

Science.gov (United States)

Coskun, Devrim; Britto, Dev T; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J

2013-12-01

Futile transmembrane NH3/NH4(+) cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4(+) toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4(+)) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope (13)N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4(+) ion. Influx of (13)NH3/(13)NH4(+), which exceeded 200 µmol g(-1) h(-1), was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4(+)), as a function of external concentration (Km = 152 µm, Vmax = 205 µmol g(-1) h(-1)). Efflux of (13)NH3/(13)NH4(+) responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions.

Biochar produced from oak sawdust by Lanthanum (La)-involved pyrolysis for adsorption of ammonium (NH4(+)), nitrate (NO3(-)), and phosphate (PO4(3-)).

Science.gov (United States)

Wang, Zhanghong; Guo, Haiyan; Shen, Fei; Yang, Gang; Zhang, Yanzong; Zeng, Yongmei; Wang, Lilin; Xiao, Hong; Deng, Shihuai

2015-01-01

A series of biochars were prepared by pyrolyzing oak sawdust with/without LaCl3 involvement at temperature of 300-600 °C, and approximate and ultimate analyses were carried out to check their basic characteristics. Meanwhile, the releases of readily soluble NH4(+), NO3(-) and PO4(3-) from biochars and the adsorption of NH4(+), NO3(-) and PO4(3-) by biochars were investigated. Results indicated that the involvement of LaCl3 in pyrolysis could advance the temperature of maximum mass loss by 10 °C compared with oak sawdust (CK), and potentially promoted biochar yield. Overall, the releases of readily soluble NH4(+), NO3(-) and PO4(3-) from biochars were negatively related to pyrolysis temperature, and the releases were greatly weakened by La-biochars. Additionally, the adsorption to NH4(+) can be promoted by the biochars produced at low temperature. On the contrary, the NO3(-) adsorption can be improved by increasing pyrolysis temperature. The highest PO4(3-) adsorption was achieved by the biochars produced at 500 °C. According to the results of adsorption isotherms, the maximum adsorption capacity of NH4(+), NO3(-) and PO4(3-) can be significantly promoted by 1.9, 11.2, and 4.5 folds using La-biochars. Based on the observations of FT-IR, SEM-EDS, and surface functional groups, the improvement of NH4(+) adsorption was potentially associated with the existing acidic function groups (phenolic-OH and carboxyl C=O). The increased basic functional groups on La-biochars were beneficial to improve NO3(-) and PO4(3-) adsorption. Besides, PO4(3-) adsorption was also potentially related to the formed La2O3. Copyright © 2014 Elsevier Ltd. All rights reserved.

Crystallographic Investigations into Properties of Acentric Hybrid Perovskite Single Crystals NH(CH3)3SnX3(X = Cl, Br)

KAUST Repository

Dang, Yangyang

2016-10-11

The hybrid perovskites with special optoelectronic properties have attracted more attention to the scientific and industrial applications. However, because of the toxicity and instability of lead complexes, there is interest in finding a nontoxic substitute for the lead in the halides perovskites and solving the ambiguous crystal structures and phase transition of NH(CH3)3SnX3 (X = Cl, Br). Here, we report the bulk crystal growths and different crystal morphologies of orthorhombic hybrid perovskites NH(CH3)3SnX3 (X = Cl, Br) in an ambient atmosphere by bottom-seeded solution growth (BSSG) method. More importantly, detailed structural determination and refinements, phase transition, band gap, band structure calculations, nonlinear optical (NLO) properties, XPS, thermal properties, and stability of NH(CH3)3SnX3 (X = Cl, Br) single crystals are demonstrated. NH(CH3)3SnCl3 single crystal undergoes reversible structural transformation from orthorhombic space group Cmc21 (no. 36) to monoclinic space group Cc (no. 9) and NH(CH3)3SnBr3 belongs to the orthorhombic space group Pna21 (no. 33) by DSC, single-crystal X-ray diffraction and temperature-dependent SHG measurements, which clarify the former results. These results should pave the way for further studies of these materials in optoelectronics.

Room temperature creep in metals and alloys

Energy Technology Data Exchange (ETDEWEB)

Deibler, Lisa Anne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Materials Characterization and Performance

2014-09-01

Time dependent deformation in the form of creep and stress relaxation is not often considered a factor when designing structural alloy parts for use at room temperature. However, creep and stress relaxation do occur at room temperature (0.09-0.21 T_m for alloys in this report) in structural alloys. This report will summarize the available literature on room temperature creep, present creep data collected on various structural alloys, and finally compare the acquired data to equations used in the literature to model creep behavior. Based on evidence from the literature and fitting of various equations, the mechanism which causes room temperature creep is found to include dislocation generation as well as exhaustion.

A study of proton polarization in ammonia (NH sub 3 ) under irradiation and annealing

Energy Technology Data Exchange (ETDEWEB)

Belyaev, A.A.; Get' man, V.A.; Dzyubak, A.P.; Karnaukhov, I.M.; Lukhanin, A.A.; Neffa, A.Yu.; Semisalov, I.L.; Sorokin, P.V.; Sporov, E.S.; Telegin, Yu.N.; Tolmachev, I.A.; Trotsenko, V.I. (Kharkov Institute of Physics and Technology, Ukrainian SSR, Academy of Sciences, 310108 Kharkov, USSR (UA))

1989-05-05

The proton polarization in irradiated NH{sub 3} has been measured as a function of the irradiation dose and annealing temperature. The analysis of the experimental data obtained shows that under low-temperature'' irradiation along with the NH{sup {minus}}{sub 2} the e{sub tr}-radical is likely to be formed which contributes to the polarization build-up and relaxation and influences the radiation damage resistance of the target.

Bluish-white-light-emitting diodes based on two-dimensional lead halide perovskite (C6H5C2H4NH3)2PbCl2Br2

Science.gov (United States)

Cai, Peiqing; Wang, Xiangfu; Seo, Hyo Jin; Yan, Xiaohong

2018-04-01

Bluish-white-light-emitting diodes (BWLEDs) are designed based on the two-dimensional mixed halide perovskite (C6H5C2H4NH3)2PbCl2Br2 at room temperature. Bluish-white electroluminescence devices were fabricated by a spin-coating method. The BWLEDs can be turned on at 4.9 V and depict a maximum luminance of ˜70 cd/m2 at 7 V. Low and room temperature photoluminescence spectra show the coexistence of free exciton and self-trapped exciton luminescence in a deformable lattice. The strategy of achieving white electroluminescence (EL) from mixed halide perovskite reported here can be applied to other two-dimensional perovskites to increase the optoelectronic efficiency of the device in the future.

Tunable bandgap in hybrid perovskite CH3NH3Pb(Br3−yXy single crystals and photodetector applications

Directory of Open Access Journals (Sweden)

L. Wang

2016-04-01

Full Text Available We report the synthesis of CH3NH3Pb(Br3−yXy (X=Cl and I single crystals via a stepwise temperature control approach. High-quality CH3NH3Pb(Br3−yXy crystals with a tunable bandgap from 1.92eV to 2.53eV have been prepared successfully in this way. And further experiments revealed the influence of halogen content and preparation temperature on the structural and optical properties of these crystals. It is observed that chlorine can lower the critical nucleation energy, which results in crystallizing at lower temperature with the chlorine content increasing, while the nucleation energy increases slowly with increasing iodine content. Moreover, in contrast to Frank–van der Merwe growth with low heating rate, high heating rate leads to a mass of small size single crystals and Stranski-Krastanov growth. The single crystals with tunable band gap and impressive characteristics enable us to fabricate high performance photodetectors for different wavelengths.

Highly sensitive room temperature ammonia gas sensor based on Ir-doped Pt porous ceramic electrodes

Energy Technology Data Exchange (ETDEWEB)

Liu, Wenlong [College of pharmacy and biological engineering, Chengdu University, Chengdu, 610106 (China); Department of chemical and materials engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan (China); Liu, Yen-Yu [Department of chemical and materials engineering, Tunghai University, Taichung 407, Taiwan (China); Do, Jing-Shan, E-mail: jsdo@ncut.edu.tw [Department of chemical and materials engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan (China); Li, Jing, E-mail: lijing@cdu.edu.cn [College of pharmacy and biological engineering, Chengdu University, Chengdu, 610106 (China)

2016-12-30

Highlights: • Water vapors seem to hugely improve the electrochemical activity of the Pt and Pt-Ir porous ceramic electrodes. • The gas sensors based on the Pt and Pt-Ir alloy electrodes possess good sensing performances. • The reaction path of the ammonia on platinum has been discussed. - Abstract: Room temperature NH{sub 3} gas sensors based on Pt and Pt-Ir (Ir doping Pt) porous ceramic electrodes have been fabricated by both electroplating and sputtering methods. The properties of the gaseous ammonia sensors have been examined by polarization and chronoamperometry techniques. The influence of humidity on the features of the resulting sensors in the system has also been discussed, and the working potential was optimized. Water vapors seem to hugely improve the electrochemical activity of the electrode. With increasing the relative humidity, the response of the Pt-Ir(E)/Pt(S)/PCP sensor to NH{sub 3} gas could be enhanced remarkably, and the sensitivity increases from 1.14 to 12.06 μA ppm{sup −1} cm{sup −2} .Then we have also discussed the sensing mechanism of the Pt-Ir sensor and the result has been confirmed by X-ray photoelectron spectroscopy of the electrode surface before and after reaction in the end.

Room-temperature antiferromagnetic memory resistor.

Science.gov (United States)

Marti, X; Fina, I; Frontera, C; Liu, Jian; Wadley, P; He, Q; Paull, R J; Clarkson, J D; Kudrnovský, J; Turek, I; Kuneš, J; Yi, D; Chu, J-H; Nelson, C T; You, L; Arenholz, E; Salahuddin, S; Fontcuberta, J; Jungwirth, T; Ramesh, R

2014-04-01

The bistability of ordered spin states in ferromagnets provides the basis for magnetic memory functionality. The latest generation of magnetic random access memories rely on an efficient approach in which magnetic fields are replaced by electrical means for writing and reading the information in ferromagnets. This concept may eventually reduce the sensitivity of ferromagnets to magnetic field perturbations to being a weakness for data retention and the ferromagnetic stray fields to an obstacle for high-density memory integration. Here we report a room-temperature bistable antiferromagnetic (AFM) memory that produces negligible stray fields and is insensitive to strong magnetic fields. We use a resistor made of a FeRh AFM, which orders ferromagnetically roughly 100 K above room temperature, and therefore allows us to set different collective directions for the Fe moments by applied magnetic field. On cooling to room temperature, AFM order sets in with the direction of the AFM moments predetermined by the field and moment direction in the high-temperature ferromagnetic state. For electrical reading, we use an AFM analogue of the anisotropic magnetoresistance. Our microscopic theory modelling confirms that this archetypical spintronic effect, discovered more than 150 years ago in ferromagnets, is also present in AFMs. Our work demonstrates the feasibility of fabricating room-temperature spintronic memories with AFMs, which in turn expands the base of available magnetic materials for devices with properties that cannot be achieved with ferromagnets.

A phase transition close to room temperature in BiFeO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Kreisel, J; Jadhav, P; Chaix-Pluchery, O [Laboratoire des Materiaux et du Genie Physique, Grenoble INP, CNRS, Minatec, 3, parvis Louis Neel, 38016 Grenoble (France); Varela, M [Departamento Fisica Aplicada i Optica, Universitat de Barcelona, Carrer MartI i Franques 1. 08028 Campus UAB, Bellaterra 08193 (Spain); Dix, N; Sanchez, F; Fontcuberta, J, E-mail: jens.kreisel@grenoble-inp.fr [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain)

2011-08-31

BiFeO{sub 3} (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 deg. C, and thus close to room temperature. (fast track communication)

A new sensor for ammonia based on cyanidin-sensitized titanium dioxide film operating at room temperature

Energy Technology Data Exchange (ETDEWEB)

Xiao-wei, Huang [School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, 212013 Zhenjiang, Jiangsu (China); Xiao-bo, Zou, E-mail: zou_xiaobo@ujs.edu.cn [School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, 212013 Zhenjiang, Jiangsu (China); Key Laboratory of Modern Agricultural Equipment and Technology, 301 Xuefu Road, 212013 Zhenjiang, Jiangsu (China); Ji-yong, Shi; Jie-wen, Zhao; Yanxiao, Li [School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, 212013 Zhenjiang, Jiangsu (China); Limin, Hao; Jianchun, Zhang [The Research Center of China Hemp Materials, Beijing (China)

2013-07-17

Graphical abstract: -- Highlights: •TiO{sub 2} was prepared by sol–gel method film and then functionalized with the cyanidin dye. •The morphology and the absorption spectra of films were examined. •The hybrid organic–inorganic formed film here can detect ammonia reversibly at room temperature. •The low humidity could promote the sensitivity of the sensors. -- Abstract: Design and fabrication of an ammonia sensor operating at room temperature based on pigment-sensitized TiO{sub 2} films was described. TiO{sub 2} was prepared by sol–gel method and deposited on glass slides containing gold electrodes. Then, the film immersed in a 2.5 × 10{sup −4} M ethanol solution of cyanidin to absorb the pigment. The hybrid organic–inorganic formed film here can detect ammonia reversibly at room temperature. The relative change resistance of the films at a potential difference of 1.5 V is determined when the films are exposed to atmospheres containing ammonia vapors with concentrations over the range 10–50 ppm. The relative change resistance, S, of the films increased almost linearly with increasing concentrations of ammonia (r = 0.92). The response time to increasing concentrations of the ammonia is about 180–220 s, and the corresponding values for decreasing concentrations 240–270 s. At low humidity, ammonia could be ionized by the cyanidin on the TiO{sub 2} film and thereby decrease in the proton concentration at the surface. Consequently, more positively charged holes at the surface of the TiO{sub 2} have to be extracted to neutralize the adsorbed cyanidin and water film. The resistance response to ammonia of the sensors was nearly independent on temperature from 10 to 50 °C. These results are not actually as good as those reported in the literature, but this preliminary work proposes simpler and cheaper processes to realize NH{sub 3} sensor for room temperature applications.

Thermodynamic modeling of NH_3-CO_2-SO_2-K_2SO_4-H_2O system for combined CO_2 and SO_2 capture using aqueous NH_3

International Nuclear Information System (INIS)

Qi, Guojie; Wang, Shujuan

2017-01-01

Highlights: • A new application of aqueous NH_3 based combined CO_2 and SO_2 process was proposed. • A thermodynamic model simulated the heat of absorption and the K_2SO_4 precipitation. • The CO_2 content can be regenerated in a stripper with lower heat of desorption. • The SO_2 content can be removed by K_2SO_4 precipitation from the lean NH_3 solvent. - Abstract: A new application of aqueous NH_3 based post-combustion CO_2 and SO_2 combined capture process was proposed to simultaneously capture CO_2 and SO_2, and remove sulfite by solid (K_2SO_4) precipitation method. The thermodynamic model of the NH_3-CO_2-SO_2-K_2SO_4-H_2O system for the combined CO_2 and SO_2 capture process was developed and validated in this work to analyze the heat of CO_2 and SO_2 absorption in the NH_3-CO_2-SO_2-H_2O system, and the K_2SO_4 precipitation characteristics in the NH_3-CO_2-SO_2-K_2SO_4-H_2O system. The average heat of CO_2 absorption in the NH_3-CO_2-H_2O system at 40 °C is around −73 kJ/mol CO_2 in 2.5 wt% NH_3 with CO_2 loading between 0.2 and 0.5 C/N. The average heat of SO_2 absorption in the NH_3-SO_2-H_2O system at 40 °C is around −120 kJ/mol SO_2 in 2.5 wt% NH_3 with SO_2 loading between 0 and 0.5 S/N. The average heat of CO_2 absorption in the NH_3-CO_2-SO_2-H_2O system at 40 °C is 77, 68, and 58 kJ/mol CO_2 in 2.5 wt% NH_3 with CO_2 loading between 0.2 and 0.5 C/N, when SO_2 loading is 0, 0.1, 0.2 S/N, respectively. The solubility of K_2SO_4 increases with temperature, CO_2 and SO_2 loadings, but decreases with NH_3 concentration in the CO_2 and SO_2 loaded aqueous NH_3. The thermodynamic evaluation indicates that the combined CO_2 and SO_2 capture process could employ the typical absorption/regeneration process to simultaneously capture CO_2 and SO_2 in an absorber, thermally desorb CO_2 in a stripper, and feasibly remove sulfite (oxidized to sulfate) content by precipitating K_2SO_4 from the lean NH_3 solvent after the lean/rich heat exchanger.

Thermal properties and phase transition in the fluoride, (NH{sub 4}){sub 3}SnF{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Kartashev, A.V. [Kirensky Institute of Physics, Siberian Department of the Russian Academy of Sciences, 660036 Krasnoyarsk (Russian Federation); Astafijev Krasnoyarsk State Pedagogical University, 660049 Krasnoyarsk (Russian Federation); Gorev, M.V. [Kirensky Institute of Physics, Siberian Department of the Russian Academy of Sciences, 660036 Krasnoyarsk (Russian Federation); Institute of Engineering Physics and Radio Electronics, Siberian State University, 660074 Krasnoyarsk (Russian Federation); Bogdanov, E.V. [Kirensky Institute of Physics, Siberian Department of the Russian Academy of Sciences, 660036 Krasnoyarsk (Russian Federation); Krasnoyarsk State Agrarian University, 660049 Krasnoyarsk (Russian Federation); Flerov, I.N. [Kirensky Institute of Physics, Siberian Department of the Russian Academy of Sciences, 660036 Krasnoyarsk (Russian Federation); Institute of Engineering Physics and Radio Electronics, Siberian State University, 660074 Krasnoyarsk (Russian Federation); Laptash, N.M. [Institute of Chemistry, Far Eastern Department of the Russian Academy of Sciences, 690022 Vladivostok (Russian Federation)

2016-05-15

Calorimetric, dilatometric and differential thermal analysis studies were performed on (NH{sub 4}){sub 3}SnF{sub 7} for a wide range of temperatures and pressures. Large entropy (δS{sub 0}=22 J/mol K) and elastic deformation (δ(ΔV/V){sub 0}=0.89%) jumps have proven that the Pa-3↔Pm-3m phase transition is a strong first order structural transformation. A total entropy change of ΔS{sub 0}=32.5 J/mol K is characteristic for the order–disorder phase transition, and is equal to the sum of entropy changes in the related material, (NH{sub 4}){sub 3}TiF{sub 7}, undergoing transformation between the two cubic phases through the intermediate phases. Hydrostatic pressure decreases the stability of the high temperature Pm-3m phase in (NH{sub 4}){sub 3}SnF{sub 7}, contrary to (NH{sub 4}){sub 3}TiF{sub 7}, characterised by a negative baric coefficient. The effect of experimental conditions on the chemical stability of (NH{sub 4}){sub 3}SnF{sub 7} was observed. - Graphical abstract: Strong first order structural transformation Pa-3↔Pm-3m in (NH{sub 4}){sub 3}SnF{sub 7} is associated with very large total entropy change of ΔS{sub 0}=32.5 J/mol K characteristic for the ordering processes and equal to the sum of entropy changes in the related (NH{sub 4}){sub 3}TiF{sub 7} undergoing transformation between the same two cubic phases through the intermediate phases. - Highlights: • (NH{sub 4}){sub 3}SnF{sub 7} undergoes strong first order Pa-3↔Pm-3m phase transition. • Anomalous behaviour of ΔC{sub p} and ΔV/V exists far below phase transition temperature. • Structural distortions are accompanied by huge total entropy change ΔS≈Rln50. • High pressure strongly increases the stability of Pa-3 phase in (NH{sub 4}){sub 3}SnF{sub 7}. • Entropy of the Pa-3↔Pm-3m phase transition does not depend on pressure.

Thin, Flexible Supercapacitors Made from Carbon Nanofiber Electrodes Decorated at Room Temperature with Manganese Oxide Nanosheets

OpenAIRE

Nataraj, S. K.; Song, Q.; Al-Muhtaseb, S. A.; Dutton, S. E.; Zhang, Q.; Sivaniah, E.

2013-01-01

We report the fabrication and electrochemical performance of a flexible thin film supercapacitor with a novel nanostructured composite electrode. The electrode was prepared by in situ coprecipitation of two-dimensional (2D) MnO2 nanosheets at room temperature in the presence of carbon nanofibers (CNFs). The highest specific capacitance of 142 F/g was achieved for CNFs-MnO2 electrodes in sandwiched assembly with PVA-H4SiW12O40nH2O polyelectrolyte separator. Peer Reviewed

Functionalized Ga2O3 nanowires as active material in room temperature capacitance-based gas sensors.

Science.gov (United States)

Mazeina, Lena; Perkins, F Keith; Bermudez, Victor M; Arnold, Stephen P; Prokes, S M

2010-08-17

We report the first evidence for functionalization of Ga(2)O(3) nanowires (NWs), which have been incorporated as the active material in room temperature capacitance gas-sensing devices. An adsorbed layer of pyruvic acid (PA) was successfully formed on Ga(2)O(3) NWs by simple room temperature vapor transport, which was confirmed by Fourier transform infrared spectroscopy. The effect of the adsorbed PA on the surface properties was demonstrated by the change in the response of the NW gas-sensing devices. Results indicate that the adsorption of PA reduced the sensitivity of the Ga(2)O(3) NW device to common hydrocarbons such as nitromethane and acetone while improving the response to triethylamine by an order of magnitude. Taking into account the simplicity of this functionalization together with the ease of producing these capacitance-based gas-sensing devices, this approach represents a viable technique for sensor development.

Room Temperature Ferromagnetic Mn:Ge(001

Directory of Open Access Journals (Sweden)

George Adrian Lungu

2013-12-01

Full Text Available We report the synthesis of a room temperature ferromagnetic Mn-Ge system obtained by simple deposition of manganese on Ge(001, heated at relatively high temperature (starting with 250 °C. The samples were characterized by low energy electron diffraction (LEED, scanning tunneling microscopy (STM, high resolution transmission electron microscopy (HRTEM, X-ray photoelectron spectroscopy (XPS, superconducting quantum interference device (SQUID, and magneto-optical Kerr effect (MOKE. Samples deposited at relatively elevated temperature (350 °C exhibited the formation of ~5–8 nm diameter Mn5Ge3 and Mn11Ge8 agglomerates by HRTEM, while XPS identified at least two Mn-containing phases: the agglomerates, together with a Ge-rich MnGe~2.5 phase, or manganese diluted into the Ge(001 crystal. LEED revealed the persistence of long range order after a relatively high amount of Mn (100 nm deposited on the single crystal substrate. STM probed the existence of dimer rows on the surface, slightly elongated as compared with Ge–Ge dimers on Ge(001. The films exhibited a clear ferromagnetism at room temperature, opening the possibility of forming a magnetic phase behind a nearly ideally terminated Ge surface, which could find applications in integration of magnetic functionalities on semiconductor bases. SQUID probed the co-existence of a superparamagnetic phase, with one phase which may be attributed to a diluted magnetic semiconductor. The hypothesis that the room temperature ferromagnetic phase might be the one with manganese diluted into the Ge crystal is formulated and discussed.

Direct Observation of Room-Temperature Stable Magnetism in LaAlO3/SrTiO3 Heterostructures.

Science.gov (United States)

Yang, Ming; Ariando; Zhou, Jun; Asmara, Teguh Citra; Krüger, Peter; Yu, Xiao Jiang; Wang, Xiao; Sanchez-Hanke, Cecilia; Feng, Yuan Ping; Venkatesan, T; Rusydi, Andrivo

2018-03-21

Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO 3 and SrTiO 3 (LaAlO 3 /SrTiO 3 ), striking interfacial magnetisms have been observed in LaAlO 3 /SrTiO 3 heterostructures. Interestingly, the strength of the interfacial magnetic moment is found to be dependent on oxygen partial pressures during the growth process. This raises an important, fundamental question on the origin of these remarkable interfacial magnetic orderings. Here, we report a direct evidence of room-temperature stable magnetism in a LaAlO 3 /SrTiO 3 heterostructure prepared at high oxygen partial pressure by using element-specific soft X-ray magnetic circular dichroism at both Ti L 3,2 and O K edges. By combining X-ray absorption spectroscopy at both Ti L 3,2 and O K edges and first-principles calculations, we qualitatively ascribe that this strong magnetic ordering with dominant interfacial Ti 3+ character is due to the coexistence of LaAlO 3 surface oxygen vacancies and interfacial (Ti Al -Al Ti ) antisite defects. On the basis of this new understanding, we revisit the origin of the weak magnetism in LaAlO 3 /SrTiO 3 heterostructures prepared at low oxygen partial pressures. Our calculations show that LaAlO 3 surface oxygen vacancies are responsible for the weak magnetism at the interface. Our result provides direct evidence on the presence of room-temperature stable magnetism and a novel perspective to understand magnetic and electronic reconstructions at such strategic oxide interfaces.

Investigation of Pristine Graphite Oxide as Room-Temperature Chemiresistive Ammonia Gas Sensing Material

Directory of Open Access Journals (Sweden)

Alexander G. Bannov

2017-02-01

Full Text Available Graphite oxide has been investigated as a possible room-temperature chemiresistive sensor of ammonia in a gas phase. Graphite oxide was synthesized from high purity graphite using the modified Hummers method. The graphite oxide sample was investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetry and differential scanning calorimetry. Sensing properties were tested in a wide range of ammonia concentrations in air (10–1000 ppm and under different relative humidity levels (3%–65%. It was concluded that the graphite oxide–based sensor possessed a good response to NH3 in dry synthetic air (ΔR/R0 ranged from 2.5% to 7.4% for concentrations of 100–500 ppm and 3% relative humidity with negligible cross-sensitivity towards H2 and CH4. It was determined that the sensor recovery rate was improved with ammonia concentration growth. Increasing the ambient relative humidity led to an increase of the sensor response. The highest response of 22.2% for 100 ppm of ammonia was achieved at a 65% relative humidity level.

Effect of cationic substitution on the double-well hydrogen-bond potential in [K1-x(NH4)x]3H(SO4)2 proton conductors: a single-crystal neutron diffraction study.

Science.gov (United States)

Choudhury, R R; Chitra, R; Selezneva, E V; Makarova, I P

2017-10-01

The structure of the mixed crystal [K 1-x (NH 4 ) x ] 3 H(SO 4 ) 2 as obtained from single-crystal neutron diffraction is compared with the previously reported room-temperature neutron structure of crystalline K 3 H(SO 4 ) 2 . The two structures are very similar, as indicated by the high value of their isostructurality index (94.8%). It was found that the replacement of even a small amount (3%) of K + with NH 4 + has a significant influence on the short strong hydrogen bond connecting the two SO 4 2- ions. Earlier optical measurements had revealed that the kinetics of the superionic transition in the solid solution [K 1-x (NH 4 ) x ] 3 H(SO 4 ) 2 are much faster than in K 3 H(SO 4 ) 2 ; this reported difference in the kinetics of the superionic phase transition in this class of crystal is explained on the basis of the difference in strength of the hydrogen-bond interactions in the two structures.

Ammonia Uptake and Release in the MnX2–NH3 (X = Cl, Br Systems and Structure of the Mn(NH3nX2 (n = 6, 2 Ammines

Directory of Open Access Journals (Sweden)

Duncan H. Gregory

2012-04-01

Full Text Available Hexa-ammine complexes, Mn(NH36X2 (X = Cl, Br, have been synthesized by ammoniation of the corresponding transition metal halide and characterized by Powder X-ray diffraction (PXRD and Raman spectroscopy. The hexa-ammine complexes are isostructural (Cubic, Fm-3m, Z = 4; a = 10.2742(6 Å and 10.527(1 Å for X = Cl, Br respectively. Temperature programmed desorption (TPD demonstrated that ammonia release from Mn(NH36X2 complexes occurred in three stages corresponding to the release of 4, 1 and 1 NH3 equivalents respectively. The chloride and bromide both exhibit a deammoniation onset temperature below 323 K. The di-ammoniates from the first desorption step were isolated during TPD measurements and their crystal structures determined by Rietveld refinement against PXRD data (X = Cl: orthorhombic Cmmm, a = 8.1991(9 Å, b = 8.2498(7 Å, c = 3.8212(4 Å, Z = 2; X = Br: orthorhombic Pbam, a = 6.0109(5 Å, b = 12.022(1 Å, c = 4.0230(2 Å, Z = 2.

Photoelectric characteristics of CH3NH3PbI3/p-Si heterojunction

Science.gov (United States)

Yamei, Wu; Ruixia, Yang; Hanmin, Tian; Shuai, Chen

2016-05-01

Organic-inorganic hybrid perovskite CH3NH3PbI3 film is prepared on p-type silicon substrate using the one-step solution method to form a CH3NH3PbI3/p-Si heterojunction. The film morphology and structure are characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The photoelectric properties of the CH3NH3PbI3/p-Si heterojunction are studied by testing the current-voltage (I-V) with and without illumination and capacitance-voltage (C-V) characteristics. It turns out from the I-V curve without illumination that the CH3NH3PbI3/p-Si heterojunction has a rectifier feature with the rectification ratio over 70 at the bias of ±5 V. Also, there appears a photoelectric conversion phenomenon on this heterojunction with a short circuit current (Isc) of 0.16 μA and an open circuit voltage (Voc) of about 10 mV The high frequency C-V characteristic of the Ag/CH3NH3PbI3/p-Si heterojunction turns out to be similar to that of the metal-insulator-semiconductor (MIS) structure, and a parallel translation of the C-V curve along the forward voltage axis is found. This parallel translation means the existence of defects at the CH3NH3PbI3/p-Si interface and positive fixed charges in the CH3NH3PbI3 layer. The defects at the interface of the CH3NH3PbI3/p-Si heterojunction result in the dramatic decline of the Voc. Besides, the C-V test of CH3NH3PbI3 film shows a non-linear dielectric property and the dielectric value is about 4.64 as calculated. Project supported by the Hebei Province Natural Science Foundation of China (No. F2014202184) and the Tianjin Natural Science Foundation of China (No. 15JCZDJC37800).

NH4+-NH3 removal from simulated wastewater using UV-TiO2 photocatalysis: effect of co-pollutants and pH.

Science.gov (United States)

Vohra, M S; Selimuzzaman, S M; Al-Suwaiyan, M S

2010-05-01

The main objective of the present study was to investigate the efficiency of titanium dioxide (TiO2) assisted photocatalytic degradation (PCD) process for the removal of ammonium-ammonia (NH4(+)-NH3) from the aqueous phase and in the presence of co-pollutants thiosulfate (S2O3(2-)) and p-cresol (C6H4CH3OH) under varying mixed conditions. For the NH4(+)-NH3 only PCD experiments, results showed higher NH4 -NH3 removal at pH 12 compared to pH 7 and 10. For the binary NH4(+)-NH3/S2O3(2-) studies the respective results indicated a significant lowering in NH4(+)-NH3 PCD in the presence of S2O32- at pH 7/12 whereas at pH 10 a marked increase in NH4(+)-NH3 removal transpired. A similar trend was noted for the p-cresol/NH4(+)-NH3 binary system. Comparing findings from the binary (NH4(+)-NH3/S2O3(2-) and p-cresol/NH4(+)-NH3) and tertiary (NH4(+)-NH3/S2O3(2-)/p-cresol) systems, at pH 10, showed fastest NH4(+)-NH3 removal transpiring for the tertiary system as compared to the binary systems, whereas both the binary systems indicated comparable NH4(+)-NH3 removal trends. The respective details have been discussed.

Comparative 4-E analysis of a bottoming pure NH3 and NH3-H2O mixture based power cycle for condenser waste heat recovery

Science.gov (United States)

Khankari, Goutam; Karmakar, Sujit

2017-06-01

This paper proposes a comparative performance analysis based on 4-E (Energy, Exergy, Environment, and Economic) of a bottoming pure Ammonia (NH3) based Organic Rankine Cycle (ORC) and Ammonia-water (NH3-H2O) based Kalina Cycle System 11(KCS 11) for additional power generation through condenser waste heat recovery integrated with a conventional 500MWe Subcritical coal-fired thermal power plant. A typical high-ash Indian coal is used for the analysis. The flow-sheet computer programme `Cycle Tempo' is used to simulate both the cycles for thermodynamic performance analysis at different plant operating conditions. Thermodynamic analysis is done by varying different NH3 mass fraction in KCS11 and at different turbine inlet pressure in both ORC and KCS11. Results show that the optimum operating pressure of ORC and KCS11 with NH3 mass fraction of 0.90 are about 15 bar and 11.70 bar, respectively and more than 14 bar of operating pressure, the plant performance of ORC integrated power plant is higher than the KCS11 integrated power plant and the result is observed reverse below this pressure. The energy and exergy efficiencies of ORC cycle are higher than the KCS11 by about 0.903 % point and 16.605 % points, respectively under similar saturation vapour temperature at turbine inlet for both the cycles. Similarly, plant energy and exergy efficiencies of ORC based combined cycle power plant are increased by 0.460 % point and 0.420 % point, respectively over KCS11 based combined cycle power plant. Moreover, the reduction of CO2 emission in ORC based combined cycle is about 3.23 t/hr which is about 1.5 times higher than the KCS11 based combined cycle power plant. Exergy destruction of the evaporator in ORC decreases with increase in operating pressure due to decrease in temperature difference of heat exchanging fluids. Exergy destruction rate in the evaporator of ORC is higher than KCS11 when the operating pressure of ORC reduces below 14 bar. This happens due to variable

Scintillation properties of (C sub 6 H sub 1 sub 3 NH sub 3) sub 2 PbI sub 4 Exciton luminescence of an organic/inorganic multiple quantum well structure compound induced by 2.0 MeV protons

CERN Document Server

Shibuya, K; Takeoka, Y; Asai, K

2002-01-01

We report a new type of scintillator especially suitable for pulse-radiation detection. Thin films of organic/inorganic perovskite compound (n-C sub 6 H sub 1 sub 3 NH sub 3) sub 2 PbI sub 4 , which is characterized by a multiple quantum well structure, were bombarded by 2.0 MeV protons, and their radiation-induced emission spectra were obtained. A single and sharp emission peak due to an exciton was observed at the wavelength of 524 nm. This emission was clearly detected even at room temperature, and its quantum efficiency was very high. The line shape of this emission did not change, retaining its sharpness, and no other emissions appeared throughout the irradiation. The optical response of (n-C sub 6 H sub 1 sub 3 NH sub 3) sub 2 PbI sub 4 is very fast. (n-C sub 6 H sub 1 sub 3 NH sub 3) sub 2 PbI sub 4 is a promising scintillator material, meeting requirements not satisfied by conventional scintillators.

Facile fabrication of CNT-based chemical sensor operating at room temperature

Science.gov (United States)

Sheng, Jiadong; Zeng, Xian; Zhu, Qi; Yang, Zhaohui; Zhang, Xiaohua

2017-12-01

This paper describes a simple, low cost and effective route to fabricate CNT-based chemical sensors, which operate at room temperature. Firstly, the incorporation of silk fibroin in vertically aligned CNT arrays (CNTA) obtained through a thermal chemical vapor deposition (CVD) method makes the direct removal of CNT arrays from substrates without any rigorous acid or sonication treatment feasible. Through a simple one-step in situ polymerization of anilines, the functionalization of CNT arrays with polyaniline (PANI) significantly improves the sensing performance of CNT-based chemical sensors in detecting ammonia (NH3) and hydrogen chloride (HCl) vapors. Chemically modified CNT arrays also show responses to organic vapors like menthol, ethyl acetate and acetone. Although the detection limits of chemically modified CNT-based chemical sensors are of the same orders of magnitudes reported in previous studies, these CNT-based chemical sensors show advantages of simplicity, low cost and energy efficiency in preparation and fabrication of devices. Additionally, a linear relationship between the relative sensitivity and concentration of analyte makes precise estimations on the concentrations of trace chemical vapors possible.

Solid-State Synthesis and Structure of the Enigmatic Ammonium Octaborate: (NH4)2[B7O9(OH)5]·3/4B(OH)3·5/4H2O.

Science.gov (United States)

Neiner, Doinita; Sevryugina, Yulia V; Schubert, David M

2016-09-06

The compound known since the 19th century as ammonium octaborate was structurally characterized revealing the ammonium salt of the ribbon isomer of the heptaborate anion, [B7O9(OH)5](2-), with boric acid and water molecules. Of composition (NH4)2B7.75O12.63·4.88H2O, it approximates the classical ammonium octaborate composition (NH4)2B8O13·6H2O and has the structural formula {(NH4)2[B7O9(OH)5]}4·3B(OH)3·5H2O. It spontaneously forms at room temperature in solid-state mixtures of ammonium tetraborate and ammonium pentaborate. It crystallizes in the monoclinic space group P21/c with a = 11.4137(2) Å, b = 11.8877(2) Å, c = 23.4459(3) Å, β = 90.092(1)°, V = 3181.19(8) Å(3), and Z = 2 and contains well-ordered ammonium cations and [B7O9(OH)5](2-) anions and disordered B(OH)3 and H2O molecules linked by extensive H bonding. Expeditious solid-state formation of the heptaborate anion under ambient conditions has important implications for development of practical syntheses of industrially useful borates.

Calculation of Vertical Temperature Gradients in Heated Rooms

DEFF Research Database (Denmark)

Overby, H.; Steen-Thøde, Mogens

This paper deals with a simple model which predicts the vertical temperature gradient in a heated room. The gradient is calculated from a dimensionless temperature profile which is determined by two room air temperatures only, the mean temperature in the occupied zone and the mean temperature...

VizieR Online Data Catalog: MSX high-contrast IRDCs with NH3 (Chira+,

Science.gov (United States)

Chira, R.-A.; Beuther, H.; Linz, H.; Walmsley, C. M.; Menten, K. M.; Bonfman, L.

2013-02-01

Based on MSX data, a catalogue of more than 10,000 candidate IRDCs was compiled. From this catalogue we selected a complete sample of northern hemisphere high-contrast IRDCs with Galactic longitudes >=19.27° (and nine exceptions with Galactic longitudes <19°). The sample was observed in ammonia (1,1) and (2,2) inversion transitions with the Effelsberg 100-m telescope. NH3 parameters are derived for 109 sample sources. For each source galactic coordinates, brightness temperatures, line width FWHMs and optical depths of (1,1) and (2,2) inversion lines and LSR velocity of (1,1) inversion line are given. Furthermore, we derived the rotation and kinetic temperatures, ammonia column densities, kinematic distances and virial masses using the NH3 data. In addition, notes about whether the sources being associated with Spitzer sources or not are given. Using ATLASGAL data, the 870 micron flux densities gas masses, virial parameters, H2 column densities and NH3 abundances are given. In addition, we listed the sample sources where no ammonia which did not fulfil our selection criteria. (4 data files).

The Green Bank Ammonia Survey: First Results of NH3 Mapping of the Gould Belt

Science.gov (United States)

Friesen, Rachel K.; Pineda, Jaime E.; co-PIs; Rosolowsky, Erik; Alves, Felipe; Chacón-Tanarro, Ana; How-Huan Chen, Hope; Chun-Yuan Chen, Michael; Di Francesco, James; Keown, Jared; Kirk, Helen; Punanova, Anna; Seo, Youngmin; Shirley, Yancy; Ginsburg, Adam; Hall, Christine; Offner, Stella S. R.; Singh, Ayushi; Arce, Héctor G.; Caselli, Paola; Goodman, Alyssa A.; Martin, Peter G.; Matzner, Christopher; Myers, Philip C.; Redaelli, Elena; The GAS Collaboration

2017-07-01

We present an overview of the first data release (DR1) and first-look science from the Green Bank Ammonia Survey (GAS). GAS is a Large Program at the Green Bank Telescope to map all Gould Belt star-forming regions with {A}{{V}}≳ 7 mag visible from the northern hemisphere in emission from NH3 and other key molecular tracers. This first release includes the data for four regions in the Gould Belt clouds: B18 in Taurus, NGC 1333 in Perseus, L1688 in Ophiuchus, and Orion A North in Orion. We compare the NH3 emission to dust continuum emission from Herschel and find that the two tracers correspond closely. We find that NH3 is present in over 60% of the lines of sight with {A}{{V}}≳ 7 mag in three of the four DR1 regions, in agreement with expectations from previous observations. The sole exception is B18, where NH3 is detected toward ∼40% of the lines of sight with {A}{{V}}≳ 7 mag. Moreover, we find that the NH3 emission is generally extended beyond the typical 0.1 pc length scales of dense cores. We produce maps of the gas kinematics, temperature, and NH3 column densities through forward modeling of the hyperfine structure of the NH3 (1, 1) and (2, 2) lines. We show that the NH3 velocity dispersion, {σ }v, and gas kinetic temperature, T K, vary systematically between the regions included in this release, with an increase in both the mean value and the spread of {σ }v and T K with increasing star formation activity. The data presented in this paper are publicly available (https://dataverse.harvard.edu/dataverse/GAS_DR1).

Improved Dehydrogenation Properties of 2LiNH2-MgH2 by Doping with Li3AlH6

Directory of Open Access Journals (Sweden)

Shujun Qiu

2017-01-01

Full Text Available Doping with additives in a Li-Mg-N-H system has been regarded as one of the most effective methods of improving hydrogen storage properties. In this paper, we prepared Li3AlH6 and evaluated its effect on the dehydrogenation properties of 2LiNH2-MgH2. Our studies show that doping with Li3AlH6 could effectively lower the dehydrogenation temperatures and increase the hydrogen content of 2LiNH2-MgH2. For example, 2LiNH2-MgH2-0.1Li3AlH6 can desorb 6.43 wt % of hydrogen upon heating to 300 °C, with the onset dehydrogenation temperature at 78 °C. Isothermal dehydrogenation testing indicated that 2LiNH2-MgH2-0.1Li3AlH6 had superior dehydrogenation kinetics at low temperature. Moreover, the release of byproduct NH3 was successfully suppressed. Measurement of the thermal diffusivity suggests that the enhanced dehydrogenation properties may be ascribed to the fact that doping with Li3AlH6 could improve the heat transfer for solid–solid reaction.

Organic titanates: a model for activating rapid room-temperature synthesis of shape-controlled CsPbBr3 nanocrystals and their derivatives.

Science.gov (United States)

Fang, Shaofan; Li, Guangshe; Li, Huixia; Lu, Yantong; Li, Liping

2018-04-12

The application of lead halide perovskite nanocrystals is challenged by the lack of strategies in rapid room-temperature synthesis with controlled morphologies. Here, we report on an initial study of adopting organic titanates as a model activator that promotes rapid room-temperature synthesis of shape-controlled, highly luminescent CsPbBr3 nanocrystals and their derivatives.

Imaging a multidimensional multichannel potential energy surface: Photodetachment of H(-)(NH3) and NH4 (.).

Science.gov (United States)

Hu, Qichi; Song, Hongwei; Johnson, Christopher J; Li, Jun; Guo, Hua; Continetti, Robert E

2016-06-28

Probes of the Born-Oppenheimer potential energy surfaces governing polyatomic molecules often rely on spectroscopy for the bound regions or collision experiments in the continuum. A combined spectroscopic and half-collision approach to image nuclear dynamics in a multidimensional and multichannel system is reported here. The Rydberg radical NH4 and the double Rydberg anion NH4 (-) represent a polyatomic system for benchmarking electronic structure and nine-dimensional quantum dynamics calculations. Photodetachment of the H(-)(NH3) ion-dipole complex and the NH4 (-) DRA probes different regions on the neutral NH4 PES. Photoelectron energy and angular distributions at photon energies of 1.17, 1.60, and 2.33 eV compare well with quantum dynamics. Photoelectron-photofragment coincidence experiments indicate dissociation of the nascent NH4 Rydberg radical occurs to H + NH3 with a peak kinetic energy of 0.13 eV, showing the ground state of NH4 to be unstable, decaying by tunneling-induced dissociation on a time scale beyond the present scope of multidimensional quantum dynamics.

Room-temperature synthesis of ultraviolet-emitting nanocrystalline GaN films using photochemical vapor deposition

International Nuclear Information System (INIS)

Yamazaki, Shunsuke; Yatsui, Takashi; Ohtsu, Motoichi; Kim, Taw-Won; Fujioka, Hiroshi

2004-01-01

We fabricated UV-emitting nanocrystalline gallium nitride (GaN) films at room temperature using photochemical vapor deposition (PCVD). For the samples synthesized at room temperature with V/III ratios exceeding 5.0x10 4 , strong photoluminescence peaks at 3.365 and 3.310 eV, which can be ascribed to transitions in a mixed phase of cubic and hexagonal GaN, were observed at 5 K. A UV emission spectrum with a full width at half-maximum of 100 meV was observed, even at room temperature. In addition, x-ray photoelectron spectroscopy measurement revealed that the film deposited by PCVD at room temperature was well nitridized

Charge carrier recombination channels in the low-temperature phase of organic-inorganic lead halide perovskite thin films

Science.gov (United States)

Wehrenfennig, Christian; Liu, Mingzhen; Snaith, Henry J.; Johnston, Michael B.; Herz, Laura M.

2014-08-01

The optoelectronic properties of the mixed hybrid lead halide perovskite CH3NH3PbI3-xClx have been subject to numerous recent studies related to its extraordinary capabilities as an absorber material in thin film solar cells. While the greatest part of the current research concentrates on the behavior of the perovskite at room temperature, the observed influence of phonon-coupling and excitonic effects on charge carrier dynamics suggests that low-temperature phenomena can give valuable additional insights into the underlying physics. Here, we present a temperature-dependent study of optical absorption and photoluminescence (PL) emission of vapor-deposited CH3NH3PbI3-xClx exploring the nature of recombination channels in the room- and the low-temperature phase of the material. On cooling, we identify an up-shift of the absorption onset by about 0.1 eV at about 100 K, which is likely to correspond to the known tetragonal-to-orthorhombic transition of the pure halide CH3NH3PbI3. With further decreasing temperature, a second PL emission peak emerges in addition to the peak from the room-temperature phase. The transition on heating is found to occur at about 140 K, i.e., revealing significant hysteresis in the system. While PL decay lifetimes are found to be independent of temperature above the transition, significantly accelerated recombination is observed in the low-temperature phase. Our data suggest that small inclusions of domains adopting the room-temperature phase are responsible for this behavior rather than a spontaneous increase in the intrinsic rate constants. These observations show that even sparse lower-energy sites can have a strong impact on material performance, acting as charge recombination centres that may detrimentally affect photovoltaic performance but that may also prove useful for optoelectronic applications such as lasing by enhancing population inversion.

On the room temperature multiferroic BiFeO3: magnetic, dielectric and thermal properties

Science.gov (United States)

Lu, J.; Günther, A.; Schrettle, F.; Mayr, F.; Krohns, S.; Lunkenheimer, P.; Pimenov, A.; Travkin, V. D.; Mukhin, A. A.; Loidl, A.

2010-06-01

Magnetic dc susceptibility between 1.5 and 800 K, ac susceptibility and magnetization, thermodynamic properties, temperature dependence of radio and audio-wave dielectric constants and conductivity, contact-free dielectric constants at mm-wavelengths, as well as ferroelectric polarization are reported for single crystalline BiFeO3. A well developed anomaly in the magnetic susceptibility signals the onset of antiferromagnetic order close to 635 K. Beside this anomaly no further indications of phase or glass transitions are indicated in the magnetic dc and ac susceptibilities down to the lowest temperatures. The heat capacity has been measured from 2 K up to room temperature and significant contributions from magnon excitations have been detected. From the low-temperature heat capacity an anisotropy gap of the magnon modes of the order of 6 meV has been determined. The dielectric constants measured in standard two-point configuration are dominated by Maxwell-Wagner like effects for temperatures T > 300 K and frequencies below 1 MHz. At lower temperatures the temperature dependence of the dielectric constant and loss reveals no anomalies outside the experimental errors, indicating neither phase transitions nor strong spin phonon coupling. The temperature dependence of the dielectric constant was measured contact free at microwave frequencies. At room temperature the dielectric constant has an intrinsic value of 53. The loss is substantial and strongly frequency dependent indicating the predominance of hopping conductivity. Finally, in small thin samples we were able to measure the ferroelectric polarization between 10 and 200 K. The saturation polarization is of the order of 40 μC/cm2, comparable to reports in literature.

Two-center three-electron bonding in ClNH{sub 3} revealed via helium droplet infrared laser Stark spectroscopy: Entrance channel complex along the Cl + NH{sub 3} → ClNH{sub 2} + H reaction

Energy Technology Data Exchange (ETDEWEB)

Moradi, Christopher P.; Douberly, Gary E., E-mail: douberly@uga.edu [Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556 (United States); Xie, Changjian; Guo, Hua [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Kaufmann, Matin [Department of Physical Chemistry II, Ruhr-University Bochum, D-44801 Bochum (Germany)

2016-04-28

Pyrolytic dissociation of Cl{sub 2} is employed to dope helium droplets with single Cl atoms. Sequential addition of NH{sub 3} to Cl-doped droplets leads to the formation of a complex residing in the entry valley to the substitution reaction Cl + NH{sub 3} → ClNH{sub 2} + H. Infrared Stark spectroscopy in the NH stretching region reveals symmetric and antisymmetric vibrations of a C{sub 3v} symmetric top. Frequency shifts from NH{sub 3} and dipole moment measurements are consistent with a ClNH{sub 3} complex containing a relatively strong two-center three-electron (2c–3e) bond. The nature of the 2c–3e bonding in ClNH{sub 3} is explored computationally and found to be consistent with the complexation-induced blue shifts observed experimentally. Computations of interconversion pathways reveal nearly barrierless routes to the formation of this complex, consistent with the absence in experimental spectra of two other complexes, NH{sub 3}Cl and Cl–HNH{sub 2}, which are predicted in the entry valley to the hydrogen abstraction reaction Cl + NH{sub 3} → HCl + NH{sub 2}.

Room temperature alcohol sensing by oxygen vacancy controlled TiO2 nanotube array

International Nuclear Information System (INIS)

Hazra, A.; Dutta, K.; Bhowmik, B.; Bhattacharyya, P.; Chattopadhyay, P. P.

2014-01-01

Oxygen vacancy (OV) controlled TiO 2 nanotubes, having diameters of 50–70 nm and lengths of 200–250 nm, were synthesized by electrochemical anodization in the mixed electrolyte comprising NH 4 F and ethylene glycol with selective H 2 O content. The structural evolution of TiO 2 nanoforms has been studied by field emission scanning electron microscopy. Variation in the formation of OVs with the variation of the structure of TiO 2 nanoforms has been evaluated by photoluminescence and X-ray photoelectron spectroscopy. The sensor characteristics were correlated to the variation of the amount of induced OVs in the nanotubes. The efficient room temperature sensing achieved by the control of OVs of TiO 2 nanotube array has paved the way for developing fast responding alcohol sensor with corresponding response magnitude of 60.2%, 45.3%, and 36.5% towards methanol, ethanol, and 2-propanol, respectively.

Effect of metal ions doping (M = Ti4+, Sn4+) on the catalytic performance of MnOx/CeO2 catalyst for low temperature selective catalytic reduction of NO with NH3

Science.gov (United States)

Xiong, Yan; Tang, Changjin; Dong, Lin

2015-04-01

Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China The abatement of nitrogen oxides (NOx) emission from exhaust gases of diesel and stationary sources is a significant challenge for economic and social development. Ceria-based solid solutions were synthesized and used as supports to prepare MnOx/Ce0.8Ti0.2O2 and MnOx/Ce0.8Sn0.2O2 catalysts (Mn/CeTi and Mn/CeSn) for low temperature selective catalytic reduction of NO by NH3 (NH3-SCR). The effects of Ti or Sn doping on the catalytic performance of MnOx/CeO2 catalyst were investigated. Experimental results show that doping of Ti or Sn increases the NO removal efficiency of MnOx/CeO2. The NO conversion of Mn/CeTi catalyst is more than 90 % at temperature window of 175 ~ 300 °C under a gas hour space velocity of 60,000 mL.g-1.h-1. Modified catalysts are also found to exhibit greatly improved resistance to sulfur-poisoning. NH3-TPD results suggest that NH3 desorption on the catalysts is observed over a wide temperature range, due to the variability of adsorbed NH3 species with different thermal stabilities. Doping of Ti and Sn into Mn/CeO2 greatly increased the NH3 adsorption ability of the composites which could promote the SCR reaction. Characterization results also indicate that doping of Ti or Sn brings about catalysts with higher BET surface area, enhanced oxygen storage capacity and increased surface acidity.

Comparative genomic and physiological analysis of nutrient response to NH4+, NH4+:NO3- and NO3- in barley seedlings.

Science.gov (United States)

Lopes, Marta S; Araus, José L

2008-09-01

Long-term differences in photosynthesis, respiration and growth of plants receiving distinct nitrogen (N) sources imply that N metabolism generates signals that regulate metabolism and development. The molecular basis of these signals remains unclear. Here we studied the gene expression profiles of barley (Hordeum vulgare L. cv. Graphic) seedlings fertilized either with ammonium (NH4+), with ammonium and nitrate (NH4+:NO3-), or with nitrate (NO3-) only. Our transcriptome analysis after 48 h of growth in these N sources showed major changes in the expression of genes involved in N metabolism (nitrate reductase), signalling (protein kinases and protein phosphatases), photosynthesis (chlorophyll a/b-binding protein and a PsbQ domain), where increases in NO3- as compared with NH4+ were observed. Moreover, NH4+ assimilation induced genes participating in C and sugars metabolism (phosphoglycerate kinase, glucosyltranferase and galactokinase), respiration (cytochrome c oxidase), protein fate (heat shock proteins) and development (MTN3-like protein). These changes in gene expression could well explain the long-term growth depression observed in NH4+ plants. Even if a few genes participating in protein fate (proteases) and development (OsNAC5) were upregulated in NH4+ as compared with NH4+:NO3-, the general pattern of expression was quite similar between these two N sources. Taken together, these results indicated that other downstream mechanisms should be involved in the synergetic long-term response of NH4+:NO3-.

Room temperature synthesis of ReS2 through aqueous perrhenate sulfidation

Science.gov (United States)

Borowiec, Joanna; Gillin, William P.; Willis, Maureen A. C.; Boi, Filippo S.; He, Y.; Wen, J. Q.; Wang, S. L.; Schulz, Leander

2018-02-01

In this study, a direct sulfidation reaction of ammonium perrhenate (NH4ReO4) leading to a synthesis of rhenium disulfide (ReS2) is demonstrated. These findings reveal the first example of a simplistic bottom-up approach to the chemical synthesis of crystalline ReS2. The reaction presented here takes place at room temperature, in an ambient and solvent-free environment and without the necessity of a catalyst. The atomic composition and structure of the as-synthesized product were characterized using several analysis techniques including energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The results indicated the formation of a lower symmetry (1Tʹ) ReS2 with a low degree of layer stacking.

Polarisation properties of irradiated ammonia (NH3 and ND3) at 1 K and 25 kG

International Nuclear Information System (INIS)

Riechert, H.

1982-11-01

Dynamic Nuclear Polarisation (DNP) of irradiated ammonia was examined in some detail at 1 K and 25 kG. In continuation of earlier studies conducted in Bonn, it was attempted to gain information about the prevailing mechanism of DNP in this material. Therefore the frequency dependence of DNP in NH 3 , of deuterons and unsubstituted protons in ND 3 , as well as the polarising time tau and the relaxation time T 1 in NH 3 were measured. Also the shape of the deuteron polarisation signal observed in ND 3 is discussed. The polarisation measurements in ND 3 rule out the equal spin temperature (EST) behaviour of proton and deuteron DNP that is observed in most of the currently used target materials. It is attempted to explain the observations with a differential solid state effect model. Results of calculations for NH 3 and ND 3 incorporating the measured EPR-spectra are presented. (orig.)

Immobilization of Ag(i) into a metal-organic framework with -SO3H sites for highly selective olefin-paraffin separation at room temperature.

Science.gov (United States)

Chang, Ganggang; Huang, Minhui; Su, Ye; Xing, Huabin; Su, Baogen; Zhang, Zhiguo; Yang, Qiwei; Yang, Yiwen; Ren, Qilong; Bao, Zongbi; Chen, Banglin

2015-02-18

Introduction of Ag(i) ions into a sulfonic acid functionalized MOF ((Cr)-MIL-101-SO3H) significantly enhances its interactions with olefin double bonds, leading to its much higher selectivities for the separation of C2H4-C2H6 and C3H6-C3H8 at room temperature over the original (Cr)-MIL-101-SO3H and other adsorbents at room temperature.

Synthesis, characterization, and application of Zn(NH 3)(CO3) for selective adsorptive separation of CO2

Science.gov (United States)

Khazeni, Naasser

This study explores the potential of Zn(NH3)(CO3) for selective CO2 separation. It develops a novel, highly controllable, single-pot synthesis approach based on urea hydrolysis and solvothermal aging to increase the feasibility of synthesizing Zn(NH3)(CO3), determines the structure of Zn(NH3)(CO3) in detail through single crystal X-ray diffraction and powder X-ray diffraction analyses, and performs adsorption analyses for the compound using CO2, N 2, H2, O2, and CH4 as adsorptives. Through adsorptive characterization, a systematic adsorbent selection screening is performed to assess the potential application of Zn(NH3)(CO 3) for adsorptive separation of CO2 from an upstream gas mixture of power generation, hydrogen production, and natural gas industries. Structural analysis shows Zn(NH3)(CO3) to have an inorganic helical framework that consists of a small helix of (ZnOCO) 2 and a large helix of (ZnOCO)4 with two ammines (NH 3) pendant from every other zinc. In terms of adsorption capacity and CO2 selectivity, Zn(NH3)(CO3) adsorbed 0.550 mmole/g CO2 at 293 K and 4500 mmHg, but only 0.047 mmole/g N 2, 0.084 mmole/g H2, 0.207 mmole/g 02, and 0.060 mmole/g CH4 at the same temperature and pressure. This behavior demonstrates considerable equilibrium selectivities - 36, 31, 63, and 11 - for separating CO2 from CH4, CO2 from H 2, CO2 from N2, and CO2 from 02, respectively. During adsorption, the pendant ammines act as the gates of check-valves: applied pressure opens the gates for adsorption; and during desorption, the gates are closed, trapping the adsorbates, until a reduction of pressure to near-atmospheric levels. Therefore, Zn(NH3)(CO3) exhibits low-pressure H3 or H4 hysteresis, indicating that the Zn(NH3)(CO3) framework can achieve gas storage at near-atmospheric pressures. Additionally, the compound proves structurally stable, with an adsorption decrease of 0.8% after 20 adsorption/desorption cycles - a factor that, considered with the other characteristics of Zn(NH

Photogeneration of metastable side-on N2 linkage isomers in [Ru(NH3)5N2]Cl2, [Ru(NH3)5N2]Br2 and [Os(NH3)5N2]Cl2.

Science.gov (United States)

Schaniel, Dominik; Woike, Theo; Delley, Bernard; Boskovic, Colette; Güdel, Hans-Ueli

2008-09-28

Photogeneration of side-on N2 linkage isomers in [Ru(NH3)5N2]2+ and [Os(NH3)5N2]2+ is achieved by irradiation with lambda = 325 nm of powder samples at T = 80 K and detected by the downshift of the nu(N-N) vibration and by the heat release at elevated temperature due to the back switching of the side-on configuration to the ground state. The concentration of the transferred molecules is evaluated by the decrease of the area of the nu(N-N) or 2nu(N-N) vibrational bands. All characteristic changes between the linear Ru-N-N and side-on configuration are predicted by DFT calculations: the structure of the anion, shifts of the vibrations, electronic excitation energy, energetic position and sequence of the electronic orbitals, the potentials of the ground and relaxed metastable state with the activation energy, saddle points and energetic position of the minimum.

Nanocrystalline CdSnO3 Based Room Temperature Methanol Sensor

Directory of Open Access Journals (Sweden)

Shanabhau BAGUL

2017-04-01

Full Text Available Synthesis of nanocrystalline CdSnO3 powder by ultrasonic atomizer assisted wet chemical method is reported in this paper. Synthesized CdSnO3 powder was characterized by X-Ray Diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM and Transmission Electron Microscopy (TEM to examine phase and microstructure. FESEM and TEM analysis reveals that the CdSnO3 powder prepared here is porous monodisperse nanocrystalline in nature, with average particle size of approximately 17 nm or smaller. The material is also characterized by UV-Visible and Photoluminescence (PL spectroscopy. Thick films of synthesized CdSnO3 powder fired at 850 0C are made by using screen printing method. The films surface is modified by using dipping method. CuCl2 (0.005 M dipped (for 2 min thick film shows high response (R= 477 to 100 ppm methanol at room temperature (35 0C. The sensor shows good selectivity and fast response recovery time to methanol. The excellent methanol sensing performance, particularly high response values is observed to be mainly due to porous CdSnO3 surface.

Electrochemical and SEM studies of tetra-ammine platinum (II) (Pt(NH3)4)(OH)2 solution

International Nuclear Information System (INIS)

Wan Jeffrey Basirun

2002-01-01

Electrochemical studies include cyclic voltammetry with microelectrodes were done on a solution of tetra-ammine platinum (II) (Pt(NH 3 ) 4 )(OH) 2 at pH 13 and showed that the electrochemical reduction of this compound was no different from the tetra-ammine platinum (II) (Pt(NH 3 ) 4 )(HPO 4 ) at pH 10.4. The solution was instable to high temperatures and results have shown that electroplating can be done at a limited temperature range for longer periods of time or at higher temperatures for short periods of time. Scanning electron microscopy was done on some of the constant current electrodeposited samples at high temperatures and result obtained was satisfactory. (Authors)

Alloyed Ni-Fe nanoparticles as catalysts for NH₃ decomposition

DEFF Research Database (Denmark)

Simonsen, Søren Bredmose; Chakraborty, Debasish; Chorkendorff, Ib

2012-01-01

A rational design approach was used to develop an alloyed Ni-Fe/Al2O3 catalyst for decomposition of ammonia. The dependence of the catalytic activity is tested as a function of the Ni-to-Fe ratio, the type of Ni-Fe alloy phase, the metal loading and the type of oxide support. In the tests with high...... temperatures and a low NH3-to-H2 ratio, the catalytic activity of the best Ni-Fe/Al2O3 catalyst was found to be comparable or even better to that of a more expensive Ru-based catalyst. Small Ni-Fe nanoparticle sizes are crucial for an optimal overall NH3 conversion because of a structural effect favoring...

Near-room temperature deposition of W and WO3 thin films by hydrogen atom assisted chemical vapor deposition

International Nuclear Information System (INIS)

Lee, W.W.; Reeves, R.R.

1992-01-01

A novel near-room temperatures CVD process has been developed using H-atoms reaction with WF 6 to produced tungsten and tungsten oxide films. The chemical, physical and electrical properties of these films were studied. Good adhesion and low resistivity of W films were measured. Conformal WO 3 films were obtained on columnar tungsten using a small amount of molecular oxygen in the gas stream. A reaction mechanism was evaluated on the basis of experimental results. The advantages of the method include deposition of adherent films in a plasma-free environment, near-room temperature, with a low level of impurity

The influence of room temperature on Mg isotope measurements by MC-ICP-MS.

Science.gov (United States)

Zhang, Xing-Chao; Zhang, An-Yu; Zhang, Zhao-Feng; Huang, Fang; Yu, Hui-Min

2018-03-24

We observed that the accuracy and precision of magnesium (Mg) isotope analyses could be affected if the room temperature oscillated during measurements. To achieve high quality Mg isotopic data, it is critical to evaluate how the unstable room temperature affects Mg isotope measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). We measured the Mg isotopes for the reference material DSM-3 using MC-ICP-MS under oscillating room temperatures in spring. For a comparison, we also measured the Mg isotopes under stable room temperatures, which was achieved by the installation of an improved temperature control system in the laboratory. The δ 26 Mg values measured under oscillating room temperatures have a larger deviation (δ 26 Mg from -0.09 to 0.08‰, with average δ 26 Mg = 0.00 ± 0.08 ‰) than those measured under a stable room temperature (δ 26 Mg from -0.03 to 0.03‰, with average δ 26 Mg = 0.00 ± 0.02 ‰) using the same MC-ICP-MS system. The room temperature variation can influence the stability of MC-ICP-MS. Therefore, it is critical to keep the room temperature stable to acquire high precise and accurate isotopic data when using MC-ICP-MS, especially when using the sample-standard bracketing (SSB) correction method. This article is protected by copyright. All rights reserved.

Optical Diode Effect at Spin-Wave Excitations of the Room-Temperature Multiferroic BiFeO_{3}.

Science.gov (United States)

Kézsmárki, I; Nagel, U; Bordács, S; Fishman, R S; Lee, J H; Yi, Hee Taek; Cheong, S-W; Rõõm, T

2015-09-18

Multiferroics permit the magnetic control of the electric polarization and the electric control of the magnetization. These static magnetoelectric (ME) effects are of enormous interest: The ability to read and write a magnetic state current-free by an electric voltage would provide a huge technological advantage. Dynamic or optical ME effects are equally interesting, because they give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. This phenomenon, if realized at room temperature, would allow the development of optical diodes which transmit unpolarized light in one, but not in the opposite, direction. Here, we report strong unidirectional transmission in the room-temperature multiferroic BiFeO_{3} over the gigahertz-terahertz frequency range. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. These findings are an important step toward the realization of optical diodes, supplemented by the ability to switch the transmission direction with a magnetic or electric field.

Promotion of redox and stability features of doped Ce–W–Ti for NH{sub 3}-SCR reaction over a wide temperature range

Energy Technology Data Exchange (ETDEWEB)

Zhao, Kun [State Key Laboratory for Oxo Synthesis and Selective Oxidation, National Engineering Research Center for Fine Petrochemical Intermediates, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Key laboratory of Oil & Gas Fine Chemical, Ministry of Education, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China); Han, Weiliang; Lu, Gongxuan [State Key Laboratory for Oxo Synthesis and Selective Oxidation, National Engineering Research Center for Fine Petrochemical Intermediates, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Lu, Jiangyin, E-mail: jiangyinlu6410@163.com [Key laboratory of Oil & Gas Fine Chemical, Ministry of Education, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China); Tang, Zhicheng, E-mail: tangzhicheng@licp.cas.cn [State Key Laboratory for Oxo Synthesis and Selective Oxidation, National Engineering Research Center for Fine Petrochemical Intermediates, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhen, Xinping [Key laboratory of Oil & Gas Fine Chemical, Ministry of Education, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China)

2016-08-30

Graphical abstract: In this study, different transition metals were introduced into Ce–W–Ti catalyst in order to promote the low temperature activity. The Cu/Ce–W–Ti catalyst prepared via a co-precipitation method displayed more excellent performance in the wide temperature range (260–400 °C). - Highlights: • Redox ability of Ce–W–Ti was enhanced by introduction of CuO. • The optimum catalyst provided high activity and broad operation window. • Cu/Ce–W–Ti presents an adequate tolerance to SO{sub 2} and hydrothermal aging. - Abstract: In this study, transition metals Co, Mn, and Cu were introduced into a Ce–W–Ti catalyst to promote low-temperature catalytic activity. Among these metal-modified M/Ce–W–Ti catalysts (M represents Co, Mn, or Cu), the Cu/Ce–W–Ti catalyst with an optimized Cu content of 5 wt.% exhibited more than 90% conversion of nitrogen oxide (NO{sub x}) in the selective catalytic reduction by NH{sub 3} over a wide temperature range (260–400 °C). This catalyst likewise exhibited higher resistance to SO{sub 2} gas and water vapor under severe test conditions. On the basis of the characterization results by powder X-ray diffraction and X-ray photoelectron spectroscopy, we concluded that the superior catalytic properties of the Cu/Ce–W–Ti catalyst could be attributed to the highly dispersed Cu species, which increased the contents of Ce{sup 3+} species and adsorbed oxygen species in the catalysts. In addition, the NH{sub 3} temperature-programmed desorption results demonstrated that the Cu species doped into the Ce–W–Ti catalysts optimized surface acid content.

Rapid Ammonia Gas Transport Accounts for Futile Transmembrane Cycling under NH3/NH4+ Toxicity in Plant Roots1[C][W

Science.gov (United States)

Coskun, Devrim; Britto, Dev T.; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J.

2013-01-01

Futile transmembrane NH3/NH4+ cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4+ toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4+) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope 13N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4+ ion. Influx of 13NH3/13NH4+, which exceeded 200 µmol g–1 h–1, was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4+), as a function of external concentration (Km = 152 µm, Vmax = 205 µmol g–1 h–1). Efflux of 13NH3/13NH4+ responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions. PMID:24134887

Study of NH3 Line Intensities in the THz and Far-IR Region

Science.gov (United States)

Yu, Shanshan

Ammonia (NH3) exists in the interstellar medium, late-type stars and giant planets of our solar system. Its temperature and abundance profiles in these environments, which are derived with its line parameters as fixed input , are commonly used to provide constraints on retrieving minor species. Therefore NH3 line parameters are essential for interpreting astrophysical and planetary spectra from Herschel, SOFIA, ALMA and JWST. However, our work under a predecessor grant with the APRA program revealed significant deficiencies in NH3 intensities in the terahertz and FIR region, including some weak Delta(K)=3 forbidden transitions predicted to be 100 times stronger. The Delta(K)=3 transitions are the ones connecting levels with different K values and therefore the only way other than collisions and l-doubled states to excite NH3 to K>0 levels. Their intensities have to be corrected to explain the observed high K excitation, such as the detection of NH3 (J,K) = (1,1), (2,2)&(14,14) and (18,18) transitions toward the galactic center star forming region Sgr B2, and to provide insights into the radiative- transfer vs. collision excitation mechanics of interstellar NH3. This proposal will remedy the serious deficiencies in the current databases involving NH3 line parameters in the terahertz and FIR region. We will target transitions with intensities greater than 10^{-23} cm-1/ (molecule/cm2) at 296 K, which will be among new astrophysical detections made by SOFIA, ALMA and JWST, and are 1000 times weaker than the strongest ground state transitions. We will retrieve new positions and intensities from existing laboratory spectra, use them to evaluate the current databases and ab initio calculations, and repair the line positions and intensities by replacing poorly calculated values with our new measurements. The proposed research will result in (1) a validated linelist containing the positions, intensities and lower state energies for the very important Delta(K)=3 NH3 FIR

Electron motion in high-pressure polar gases: NH3

International Nuclear Information System (INIS)

Christophorou, L.G.; Carter, J.G.; Maxey, D.V.

1982-01-01

Drift velocities w for slow electrons in NH 3 vapor have been measured and are reported as a function of the density-reduced electric field E/N ( -17 V cm 2 ), density N (2.43--292 x 10 18 molecule cm -3 ), and temperature T (300--650 K). The w decreases with increasing N considerably and this decrease varies with T; for a fixed N it is higher the lower the T. Use is made of the T- and N-dependence of w to assess the role of the various processes which delay the electron drift. The density range above approx.2.5 x 10 19 molecules cm -3 seems (anionic) electron state. The number density N/sub L/ at which complete electron localization occurs, has been estimated at various T. At T = 300 K, N/sub L/approx. =3.3 x 10 20 molecule cm -3 or approx.0.01 g cm 3 . Estimates have also been made of the binding energy of the electron to the trapping species (possibly NH 3 clusters) which, depending on T, range from 0.11 to 0.15 eV

Structural determinants of NH3 and NH4+ transport by mouse Rhbg, a renal Rh glycoprotein.

Science.gov (United States)

Abdulnour-Nakhoul, Solange; Le, Trang; Rabon, Edd; Hamm, L Lee; Nakhoul, Nazih L

2016-12-01

Renal Rhbg is localized to the basolateral membrane of intercalated cells and is involved in NH 3 /NH 4 + transport. The structure of Rhbg is not yet resolved; however, a high-resolution crystal structure of AmtB, a bacterial homolog of Rh, has been determined. We aligned the sequence of Rhbg to that of AmtB and identified important sites of Rhbg that may affect transport. Our analysis positioned three conserved amino acids, histidine 183 (H183), histidine 342 (H342), and tryptophan 230 (W230), within the hydrophobic pore where they presumably serve to control NH 3 transport. A fourth residue, phenylalanine 128 (F128) was positioned at the upper vestibule, presumably contributing to recruitment of NH 4 + We generated three mutations each of H183, H342, W230, and F128 and expressed them in frog oocytes. Immunolabeling showed that W230 and F128 mutants were localized to the cell membrane, whereas H183 and H342 staining was diffuse and mostly intracellular. To determine function, we compared measurements of NH 3 /NH 4 + and methyl amine (MA)/methyl ammonium (MA + )-induced currents, intracellular pH, and surface pH (pHs) among oocytes expressing the mutants, Rhbg, or injected with H 2 O. In H183 and W230 mutants, NH 4 + -induced current and intracellular acidification were inhibited compared with that of Rhbg, and MA-induced intracellular alkalinization was completely absent. Expression of H183A or W230A mutants inhibited NH 3 /NH 4 + - and MA/MA + -induced decrease in pHs to the level observed in H 2 O-injected oocytes. Mutations of F128 did not significantly affect transport of NH 3 or NH 4 + These data demonstrated that mutating H183 or W230 caused loss of function but not F128. H183 and H342 may affect membrane expression of the transporter.

The recombination mechanisms leading to amplified spontaneous emission at the true-green wavelength in CH3NH3PbBr3 perovskites

Science.gov (United States)

Priante, D.; Dursun, I.; Alias, M. S.; Shi, D.; Melnikov, V. A.; Ng, T. K.; Mohammed, O. F.; Bakr, O. M.; Ooi, B. S.

2015-02-01

We investigated the mechanisms of radiative recombination in a CH3NH3PbBr3 hybrid perovskite material using low-temperature, power-dependent (77 K), and temperature-dependent photoluminescence (PL) measurements. Two bound-excitonic radiative transitions related to grain size inhomogeneity were identified. Both transitions led to PL spectra broadening as a result of concurrent blue and red shifts of these excitonic peaks. The red-shifted bound-excitonic peak dominated at high PL excitation led to a true-green wavelength of 553 nm for CH3NH3PbBr3 powders that are encapsulated in polydimethylsiloxane. Amplified spontaneous emission was eventually achieved for an excitation threshold energy of approximately 350 μJ/cm2. Our results provide a platform for potential extension towards a true-green light-emitting device for solid-state lighting and display applications.

The recombination mechanisms leading to amplified spontaneous emission at the true-green wavelength in CH3NH3PbBr3 perovskites

KAUST Repository

Priante, Davide

2015-02-23

We investigated the mechanisms of radiative recombination in a CH3NH3PbBr3 hybrid perovskite material using low-temperature, power-dependent (77K), and temperature-dependent photoluminescence (PL) measurements. Two bound-excitonic radiative transitions related to grain size inhomogeneity were identified. Both transitions led to PL spectra broadening as a result of concurrent blue and red shifts of these excitonic peaks. The red-shifted bound-excitonic peak dominated at high PL excitation led to a true-green wavelength of 553nm for CH3NH3PbBr3 powders that are encapsulated in polydimethylsiloxane. Amplified spontaneous emission was eventually achieved for an excitation threshold energy of approximately 350μJ/cm2. Our results provide a platform for potential extension towards a true-green light-emitting device for solid-state lighting and display applications.

Room temperature d (0) ferromagnetism in hole doped Y2O3: widening the choice of host to tailor DMS.

Science.gov (United States)

Chakraborty, Brahmananda; Ramaniah, Lavanya M

2016-08-24

Transition metal-free-ferromagnetism in diluted magnetic semiconductors (DMS) is of much current interest in view of the search for more efficient DMS materials for spintronics applications. Our DFT results predict for the first time, that impurities from group1A (Li(+), Na(+), K(+)) doped on Y2O3 can induce a magnetic signature with a magnetic moment around 2.0 μ B per defect at hole concentrations around 1.63  ×  10(21) cm(-3), which is one order less than the critical hole density of ZnO with ferromagnetic coupling large enough to promote room temperature ferromagnetism. The induction of room temperature ferromagnetism by hole doping with an impurity atom from group 1A, which injects two holes per defect in the system, implies that the recommendation of three holes per defect given in the literature, which puts a restriction on the choice of host material and the impurity, is not a necessary criterion for hole induced room temperature ferromagnetism. DFT simulations with the generalized gradient approximation (GGA), confirmed by the more sophisticated hybrid functional, Heyd-Scuseria-Ernzerhof (HSE06), predict that the magnetic moment is mostly contributed by O atoms surrounding the impurity atom and the magnetic moment scale up with impurity concentration which is a positive indicator for practical applications. We quantitatively and extensively demonstrate through the analysis of the density of states and ferromagnetic coupling that the Stoner criterion is satisfied by pushing the Fermi level inside the valence band to activate room temperature ferromagnetism. The stability of the structure and the persistence of ferromagnetism at room temperature were demonstrated by ab initio MD simulations and computation of Curie temperature through the mean field approximation. This study widens the choice of host oxides to tailor DMS for spintronics applications.

Fracture Resistances of Y_2O_3 Particle Dispersion Strengthened 9Cr Steel at Room Temperature and High Temperatures

International Nuclear Information System (INIS)

Yoon, Ji Hyun; Kang, Suk Hoon; Lee, Yongbok; Kim, Sung Soo

2012-01-01

The fracture resistance and tensile properties of Y_2O_3 oxide dispersion strengthened steel containing 9 wt% Cr (9Cr-ODS) were measured at various temperatures up to 700°C. The fracture characteristics were compared with those of commercial E911 ferritic/martensitic steel. The strength of 9Cr-ODS was at least 30% higher than that of E911 steel at the test temperatures below 500°C. The strength difference between the two materials was almost diminished at 700°C. 9Cr-ODS showed cleavage fracture behavior at room temperature and unstable crack growth behaviors at 300°C and 500°C. The J-R fracture resistance of 9Cr-ODS was much lower than that of E911 steel at all temperatures. It was deduced that the coarse Cr_2O_3 particles that were formed during the alloying process provided the crack initiation sites of cleavage fracture in 9Cr-ODS.

Concurrent transition of ferroelectric and magnetic ordering near room temperature.

Science.gov (United States)

Ko, Kyung-Tae; Jung, Min Hwa; He, Qing; Lee, Jin Hong; Woo, Chang Su; Chu, Kanghyun; Seidel, Jan; Jeon, Byung-Gu; Oh, Yoon Seok; Kim, Kee Hoon; Liang, Wen-I; Chen, Hsiang-Jung; Chu, Ying-Hao; Jeong, Yoon Hee; Ramesh, Ramamoorthy; Park, Jae-Hoon; Yang, Chan-Ho

2011-11-29

Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

Effect of Different CH3NH3PbI3 Morphologies on Photovoltaic Properties of Perovskite Solar Cells

Science.gov (United States)

Chen, Lung-Chien; Lee, Kuan-Lin; Wu, Wen-Ti; Hsu, Chien-Feng; Tseng, Zong-Liang; Sun, Xiao Hong; Kao, Yu-Ting

2018-05-01

In this study, the perovskite layers were prepared by two-step wet process with different CH3NH3I (MAI) concentrations. The cell structure was glass/FTO/TiO2-mesoporous/CH3NH3PbI3 (MAPbI3)/spiro-OMeTAD/Ag. The MAPbI3 perovskite films were prepared using high and low MAI concentrations in a two-step process. The perovskite films were optimized at different spin coating speed and different annealing temperatures to enhance the power conversion efficiency (PCE) of perovskite solar cells. The PCE of the resulting device based on the different perovskite morphologies was discussed. The PCE of the best cell was up to 17.42%, open circuit voltage of 0.97 V, short current density of 24.06 mA/cm2, and fill factor of 0.747.

CH3NH3Pb1-xMgxI3 perovskites as environmentally friendly photovoltaic materials

Science.gov (United States)

Zhang, Y. D.; Feng, J.

2018-01-01

In an effort to reduce the toxicity of Pb in perovskite solar cells, the band structures, electron and hole effective masses, and electronic and optical properties of the novel perovskites CH3NH3Pb1-xMgxI3 were predicted using density functional theory with the scalar relativistic generalized gradient approximation. The calculation results indicated that the introduction of the Mg component caused the band gaps of the CH3NH3Pb1-xMgxI3 compounds to exceed that of CH3NH3PbI3. The calculated absorption coefficients of the CH3NH3PbI3 and CH3NH3Pb1-xMgxI3 perovskites revealed that substituting 12.5 mol % of the Pb in CH3NH3PbI3 with Mg had little effect on the absorption ability. Surprisingly, it was also found that CH3NH3Pb0.75Mg0.25I3 retained up to 83% of the absorption performance relative to CH3NH3PbI3. This indicates that the amount of toxic Pb used in perovskite solar cells could be reduced by a quarter while retaining over 80% of the light-absorbing ability. In general, these novel CH3NH3Pb1-xMgxI3 (x ≤ 0.25) perovskites represent promising candidates for environmentally friendly light-harvesting materials for use in solar cells.

X-ray and NQR studies of bromoindate(III) complexes. [C2H5NH3]4InBr7, [C(NH2)3]3InBr6, and [H3NCH2C(CH3)2CH2NH3]InBr5

International Nuclear Information System (INIS)

Iwakiri, Takeharu; Ishihara, Hideta; Terao, Hiromitsu; Lork, Enno; Gesing, Thorsten M.

2017-01-01

The crystal structures of [C 2 H 5 NH 3 ] 4 InBr 7 (1), [C(NH 2 ) 3 ] 3 InBr 6 (2), and [H 3 NCH 2 C(CH 3 ) 2 CH 2 NH 3 ]InBr 5 (3) were determined at 100(2) K: monoclinic, P2 1 /n, a=1061.94(3), b=1186.40(4), c=2007.88(7) pm, β= 104.575(1) , Z=4 for 1; monoclinic, C2/c, a=3128.81(12), b=878.42(3), c=2816.50(10) pm, β=92.1320(10) , Z=16 for 2; orthorhombic, P2 1 2 1 2 1 , a=1250.33(5), b=1391.46(6), c=2503.22(9) pm, Z=4 for 3. The structure of 1 contains an isolated octahedral [InBr 6 ] 3- ion and a Br - ion. The structure of 2 contains three different isolated octahedral [InBr 6 ] 3- ions. The structure of 3 has a corner-shared double-octahedral [In 2 Br 11 ] 5- ion and an isolated tetrahedral [InBr 4 ] - ion. The 81 Br nuclear quadrupole resonance (NQR) lines of the terminal Br atoms of the compounds are widely spread in frequency, and some of them show unusual positive temperature dependence. These observations manifest the N-H..Br-In hydrogen bond networks developed between the cations and anions to stabilize the crystal structures. The 81 Br NQR and differential thermal analysis (DTA) measurements have revealed the occurrence of unique phase transitions in 1 and 3. When the bond angles were estimated from the electric field gradient (EFG) directions calculated by the molecular orbital (MO) methods, accurate values were obtained for [InBr 6 ] 3- of 1 and for [In 2 Br 11 ] 5- and [InBr 4 ] - of 3, except for several exceptions in those for the latter two ions. On the other hand, the calculations of 81 Br NQR frequencies have produced up to 1.4 times higher values than the observed ones.

Room temperature inductively coupled plasma etching of InAs/InSb in BCl 3/Cl 2/Ar

KAUST Repository

Sun, Jian; Kosel, Jü rgen

2012-01-01

Inductively coupled plasma (ICP) etching of InAs and InSb at room temperature has been investigated using BCl 3/Cl 2/Ar plasma. Specifically, the etch rate and post-etching surface morphology were investigated as functions of the gas composition

Optical monitoring of CH3NH3PbI3 thin films upon atmospheric exposure

International Nuclear Information System (INIS)

Ghimire, Kiran; Zhao, Dewei; Cimaroli, Alex; Ke, Weijun; Yan, Yanfa; Podraza, Nikolas J

2016-01-01

CH 3 NH 3 PbI 3 perovskite films of interest for photovoltaic (PV) devices have been prepared by (i) vapor deposition and (ii) solution processing. Complex dielectric function ( ε   =   ε 1   +  i ε 2 ) spectra and structural parameters of the films have been extracted using near infrared to ultraviolet spectroscopic ellipsometry. In situ real time spectroscopic ellipsometry (RTSE) over a 48 h period has been performed on vapor deposited CH 3 NH 3 PbI 3 after the deposition in normal atmospheric laboratory ambient conditions. Analysis of RTSE data for vapor deposited CH 3 NH 3 PbI 3 film prepared under un-optimized conditions identifies phase segregated PbI 2 and CH 3 NH 3 I at the substrate/film interface and unreacted PbI 2 and CH 3 NH 3 I on the film surface. This analysis also provides the time dependence of the effective thicknesses of perovskite film, unreacted components, and phase segregated layers to track CH 3 NH 3 PbI 3 decomposition. (paper)

Room temperature giant and linear magnetoresistance in topological insulator Bi2Te3 nanosheets.

Science.gov (United States)

Wang, Xiaolin; Du, Yi; Dou, Shixue; Zhang, Chao

2012-06-29

Topological insulators, a new class of condensed matter having bulk insulating states and gapless metallic surface states, have demonstrated fascinating quantum effects. However, the potential practical applications of the topological insulators are still under exploration worldwide. We demonstrate that nanosheets of a Bi(2)Te(3) topological insulator several quintuple layers thick display giant and linear magnetoresistance. The giant and linear magnetoresistance achieved is as high as over 600% at room temperature, with a trend towards further increase at higher temperatures, as well as being weakly temperature-dependent and linear with the field, without any sign of saturation at measured fields up to 13 T. Furthermore, we observed a magnetic field induced gap below 10 K. The observation of giant and linear magnetoresistance paves the way for 3D topological insulators to be useful for practical applications in magnetoelectronic sensors such as disk reading heads, mechatronics, and other multifunctional electromagnetic applications.

Photovoltaic properties of Cu-doped CH3NH3PbI3 with perovskite structure

Science.gov (United States)

Shirahata, Yasuhiro; Oku, Takeo

2017-01-01

Photovoltaic properties of copper (Cu)-doped perovskite (CH3NH3PbCuxI3+x) photovoltaic devices with different Cu content were investigated. The CH3NH3PbCuxI3+x films were polycrystalline with a tetragonal system, and their lattice constants and crystallite size varied with Cu doping. Compared to conversion efficiencies of non-doped CH3NH3PbI3 photovoltaic device, those of CH3NH3PbCuxI3+x photovoltaic devises increased. The improvement of photovoltaic properties was attributed to partial substitution of Cu at the Pb sites.

Crystal structure, hydrogen bonding, and sup 8 sup 1 Br NQR of low-temperature phase of 4-aminopyridinium tetrabromoantimonate (3)

CERN Document Server

Hashimoto, M; Fuess, H; Svoboda, I; Ehrenberg, H

2003-01-01

The crystal structure of the low-temperature phase (LTP) of the title compound was determined at 220 K (monoclinic, P2 sub 1 sub / sub c). The 4-aminopyridinium cations (4-NH sub 2 C sub 5 H sub 4 NH sup +) were found to be ordered in LTP, while being severely disordered in the room-temperature phase (monoclinic, C2/c). The tetrabromoantimonate anions (SbBr sub 4 sup -) were incorporated into the infinite polyanion chains of irregular SbBr sub 6 octahedra with two-edges sharing. The trans-Br-Sb-Br moiety in the SbBr sub 4 sup - anion was approximately symmetric differing from the asymmetric Br-Sb centre dot centre dot centre dot Br moiety found in LTP of pyridinium tetrabromoantimonate (3). The N-H moieties in both of the pyridine ring and the amino (-NH sub 2) group participate in the formation of N-H centre dot centre dot centre dot Br hydrogen bonds. It was shown that the sup 8 sup 1 Br NQR spectrum of LTP is closely related to the anion structure and the hydrogen bonds. The distinctive anion structures, a...

Mechanochemical transformations in Li(Na)AlH4-Li(Na)NH2 systems

International Nuclear Information System (INIS)

Dolotko, Oleksandr; Zhang Haiqiao; Ugurlu, Ozan; Wiench, Jerzy W.; Pruski, Marek; Scott Chumbley, L.; Pecharsky, Vitalij

2007-01-01

Mechanochemical transformations of tetrahydroaluminates and amides of lithium and sodium have been investigated using gas volumetric analysis, X-ray powder diffraction, solid-state nuclear magnetic resonance (NMR) and transmission electron microscopy. In a transformation of LiAlH 4 and LiNH 2 taken in an 1:1 molar ratio, the amount of released hydrogen (6.6 wt.% after 30 min ball milling) was higher than in any known one pot mechanochemical process involving a hydrogen-containing solid. A total of 4.3 wt.% of hydrogen is released by the NaAlH 4 -NaNH 2 system after 60 min ball milling; and 5.2 wt.% H 2 is released when LiAlH 4 and NaNH 2 or NaAlH 4 and LiNH 2 are ball milled for 90 min and 120 min, respectively. All transformations proceed at room temperature. The mechanism of the overall transformation MAlH 4 (s) + MNH 2 (s) → 2MH(s) + AlN(s) + 2H 2 (g) was identified based on detailed spectroscopic analysis of the intermediate (M 3 AlH 6 ) and final products of the ball milling process

On the growth of CH3NH3PbI3-xClx single crystal and characterization

Science.gov (United States)

Su, J.; Wang, W. F.; Lei, Y.; Zhang, L.; Xu, L. H.; Wang, D.; Lu, D.; Bai, Y.

2018-05-01

In this paper, CH3NH3PbI3-xClx crystal was grown by solution cooling method with CH3NH3I and PbCl2 as raw materials. Lead compounds and CH3NH3PbI3-xClx crystal with size about 6 mm × 4 mm × 2 mm were obtained. The chemical reactions with different CH3NH3I/PbCl2 ratios were analyzed. XPS shows the content of chlorine in CH3NH3PbI3-xClx is about 0.91%. PXRD, FT-IR, Raman and absorbance spectra were used to study the structure and optical properties of CH3NH3PbI3-xClx by comparing with CH3NH3PbI3 crystal. The CH3NH3PbI3-xClx crystal grown is of tetragonal structure with the lattice constants a = b = 8.8165 Å, c = 12.7920 Å and the bandgap value of 1.57 eV.

The influence of the relative thermal expansion and electric permittivity on phase transitions in the perovskite-type bidimensional layered NH3(CH2)3NH3CdBr4 compound

Science.gov (United States)

Staśkiewicz, Beata; Staśkiewicz, Anna

2017-07-01

Hydrothermal method has been used to synthesized the layered hybrid compound NH3(CH2)3NH3CdBr4 of perovskite architecture. Structural, dielectric and dilatometric properties of the compound have been analyzed. Negative thermal expansion (NTE) effect in the direction perpendicular to the perovskite plane as well as an unusual phase sequence have been reported based on X-ray diffraction analysis. Electric permittivity measurements evidenced the phase transitions at Tc1=326/328 K and Tc2=368/369 K. Relative linear expansion measurements almost confirmed these temperatures of phase transitions. Anomalies of electric permittivity and expansion behavior connected with the phase transitions are detected at practically the same temperatures as those observed earlier in differential scanning calorimetry (DSC), infrared (IR), far infrared (FIR) and Raman spectroscopy studies. Mechanism of the phase transitions is explained. Relative linear expansion study was prototype to estimate critical exponent value β for continuous phase transition at Tc1. It has been inferred that there is a strong interplay between the distortion of the inorganic network, those hydrogen bonds and the intermolecular interactions of the organic component.

[UO2(NH3)5]Br2·NH3: synthesis, crystal structure, and speciation in liquid ammonia solution by first-principles molecular dynamics simulations.

Science.gov (United States)

Woidy, Patrick; Bühl, Michael; Kraus, Florian

2015-04-28

Pentaammine dioxido uranium(VI) dibromide ammonia (1/1), [UO2(NH3)5]Br2·NH3, was synthesized in the form of yellow crystals by the reaction of uranyl bromide, UO2Br2, with dry liquid ammonia. The compound crystallizes orthorhombic in space group Cmcm and is isotypic to [UO2(NH3)5]Cl2·NH3 with a = 13.2499(2), b = 10.5536(1), c = 8.9126(1) Å, V = 1246.29(3) Å(3) and Z = 4 at 123 K. The UO2(2+) cation is coordinated by five ammine ligands and the coordination polyhedron can be best described as pentagonal bipyramid. Car-Parrinello molecular dynamics simulations are reported for [UO2(NH3)5](2+) in the gas phase and in liquid NH3 solution (using the BLYP density functional). According to free-energy simulations, solvation by ammonia has only a small effect on the uranyl-NH3 bond strength.

Room temperature alcohol sensing by oxygen vacancy controlled TiO{sub 2} nanotube array

Energy Technology Data Exchange (ETDEWEB)

Hazra, A.; Dutta, K.; Bhowmik, B.; Bhattacharyya, P., E-mail: pb-etc-besu@yahoo.com [Nano-Thin Films and Solid State Gas Sensor Devices Laboratory, Department of Electronics and Telecommunication Engineering, Indian Institute of Engineering Science and Technology (IIEST), Shibpur, Howrah (India); Chattopadhyay, P. P. [Department of Metallurgy and Materials Engineering, Indian Institute of Engineering Science and Technology (IIEST), Shibpur, Howrah (India)

2014-08-25

Oxygen vacancy (OV) controlled TiO{sub 2} nanotubes, having diameters of 50–70 nm and lengths of 200–250 nm, were synthesized by electrochemical anodization in the mixed electrolyte comprising NH{sub 4}F and ethylene glycol with selective H{sub 2}O content. The structural evolution of TiO{sub 2} nanoforms has been studied by field emission scanning electron microscopy. Variation in the formation of OVs with the variation of the structure of TiO{sub 2} nanoforms has been evaluated by photoluminescence and X-ray photoelectron spectroscopy. The sensor characteristics were correlated to the variation of the amount of induced OVs in the nanotubes. The efficient room temperature sensing achieved by the control of OVs of TiO{sub 2} nanotube array has paved the way for developing fast responding alcohol sensor with corresponding response magnitude of 60.2%, 45.3%, and 36.5% towards methanol, ethanol, and 2-propanol, respectively.

A non-typical sequence of phase transitions in (NH4)3GeF7: optical and structural characterization.

Science.gov (United States)

Mel'nikova, S V; Molokeev, M S; Laptash, N M; Misyul, S V

2016-03-28

Single crystals of germanium double salt (NH4)3GeF7 = (NH4)2GeF6·NH4F = (NH4)3[GeF6]F were grown and studied by the methods of polarization optics and X-ray diffraction. The birefringence Δn = (no - ne), the rotation angle of the optical indicatrix ϕ(T) and unit cell parameters were measured in the temperature range 100-400 K. Three structural phase transitions were found at the temperatures: T1↓ = 279.2 K (T1↑ = 279.4 K), T2↑ = 270 K (T2↓ = 268.9 K), T3↓ = 218 K (T3↑ = 227 K). An unusual sequence of symmetry transformations with temperature change was established: P4/mbm (Z = 2) (G1) ↔ Pbam (Z = 4) (G2) ↔ P21/c (Z = 4) (G3) ↔ Pa3[combining macron] (Z = 8) (G4). The crystal structures of different phases were determined. The experimental data were additionally interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account the critical and noncritical atomic displacements. Strengthening of the N-HF hydrogen bonds can be a driving force of the observed phase transitions.

Room temperature large self-biased magnetoelectric effect in non-lead based piezoelectric and magnetostrictive (0−3) particulate composite system

International Nuclear Information System (INIS)

Kumari, Mukesh; Prakash, Chandra; Chatterjee, Ratnamala

2017-01-01

In this work, room temperature magnetoelectric properties of (0−3) particulate composites of non lead based piezoelectric BNTKNNLTS [0.97(Bi 0.5 Na 0.5 TiO 3 )–0.03(K 0.47 Na 0.47 Li 0.06 Nb 0.74 Sb 0.06 Ta 0.2 O 3 ) and magnetostrictive CZFMO (Co 0.6 Zn 0.4 Fe 1.7 Mn 0.3 O 4 ) are presented. Composite samples of (1-x)(BNTKNNLTS)-x(CZFMO) , with x=0.1 and 0.5, are synthesized by solid state reaction route. X-ray diffraction confirms the single phase formation of parent phases and the presence of two phases in the composites. Similar sintering conditions of the two individual components lead to optimal ferroelectric and ferromagnetic properties in the composites. A large self-biased magnetoelectric (ME) coupling ~74 mV/cm.Oe for the sample with x=0.1 (measured in longitudinally magnetized-transversely polarized configuration) is observed at room temperature. - Highlights: • Modified BNT-CFO based (0−3) particulate composites have been synthesized. • Similar sintering conditions of two components lead to optimal multiferroicity. • A large self-biased ME coupling ~74 mV/cm. Oe is obtained at room temperature.

Effect of He pressure on the superconducting transition temperatures of Na2CsC60 and (NH3)4Na2CsC60

International Nuclear Information System (INIS)

Schirber, J.E.; Bayless, W.R.; Rosseinsky, M.J.; Zhou, O.; Fleming, R.M.; Murphy, D.; Fischer, J.E.

1994-01-01

The Na based mixed alkali doped C 60 superconductors show anomalous behavior with respect to the ''universal'' superconducting transition temperature T c vs lattice constant a 0 relation followed by most of the fcc A 3 C 60 superconductors. We have measured dt c /dP for Na 2 CsC 60 and (NH 3 ) 4 Na 2 CsC 60 using solid He as the pressure medium to ∼ 6 kbar finding dT c /dP equal to -0.8±(0.01) K/kbar and -1.0(±0.1)K/kbar for Na 2 CsC 60 and Na 2 (NH 3 ) 4 C 60 respectively. Our value for Na 2 CsC 60 differs markedly from that obtained by Mizuki et al of about -1.3 K/kbar. However, using N 2 or Ar, we obtain values for dT c /dP in substantial agreement with Mizuki et al who used fluorinert to generate their pressure. This work emphasizes the need for compressibility measurements with the same pressure medium in the appropriate temperature range so that meaningful comparisons can be made between various pressure measurements and models which are based on lattic spacing

NH{sub 3} decomposition and simultaneous H{sub 2} separation with a commercial Pd-Cu-Ag/V membrane

Energy Technology Data Exchange (ETDEWEB)

Skodras, G.; Sakelleropoulos, G. [Centre for Research and Technology, Hellas, Ptolemaidas-Kozanis, Ptolemaida (Greece). Inst. for Solid Fuel Technolgy and Applications]|[Aristotle Univ. of Thessaloniki, Thessaloniki (Greece). Dept. of Chemical Engineering, Chemical Process Engineering Lab]|[Centre for Research and Technology, Hellas, Thermis, Thessaloniki (Greece). Chemical Process Research Inst.; Kaldis, S. [Centre for Research and Technology, Hellas, Thermis, Thessaloniki (Greece). Chemical Process Research Inst.; Topis, S. [Centre for Research and Technology, Hellas, Ptolemaidas-Kozanis, Ptolemaida (Greece). Inst. for Solid Fuel Technolgy and Applications]|[Aristotle Univ. of Thessaloniki, Thessaloniki (Greece). Dept. of Chemical Engineering, Chemical Process Engineering Lab; Koutsonikolas, D. [Aristotle Univ. of Thessaloniki, Thessaloniki (Greece). Dept. of Chemical Engineering, Chemical Process Engineering Lab; Grammelis, P. [Centre for Research and Technology, Hellas, Ptolemaidas-Kozanis, Ptolemaida (Greece). Inst. for Solid Fuel Technolgy and Applications

2006-07-01

The potential for integrated gasification combined cycle (IGCC) technology to emerge as an efficient and environmentally clean technology for power generation from coal gas was discussed. Ammonia (NH{sub 3}) is formed during gasification of coal. The concentration in coal gas depends on temperature, pressure, residence time and coal rank. In the gas turbine as much as 50 per cent of the NH{sub 3} in the fuel gas can be converted to NOx when the gas is combusted to produce power. A catalyst is required to bring NH{sub 3} levels down to acceptable levels for a gas turbine. This study examined the simultaneous ammonia (NH{sub 3}) decomposition and hydrogen (H{sub 2}) separation via a commercial Pd-Cu-Ag/V catalytic membrane reactor with 100 per cent H{sub 2} selectivity. A 16 per cent Ni/Al{sub 2}O{sub 3} catalyst was prepared and 88 per cent NH{sub 3} conversion was achieved with 20 per cent H{sub 2} in the feed stream. Increase of temperature and prolongation of residence time resulted in higher conversions. However, pressure increase lowered the decomposition due to the high H{sub 2} partial pressure. In order to develop kinetic equations, experiments at differential conversions were also performed. H{sub 2} diffusion was found to be the rate limiting step of H{sub 2} transport through the membrane. As such, H{sub 2} permeance increased exponentially with temperature. Mathematical model were then developed to describe the operation of the catalytic membrane reactor and to compare its performance with the conventional reactor. It was concluded that the conversion of NH{sub 3} can be increased significantly using the Pd-Cu-Ag/V membrane. 14 refs., 3 tabs., 7 figs.

Room-temperature ductile inorganic semiconductor

Science.gov (United States)

Shi, Xun; Chen, Hongyi; Hao, Feng; Liu, Ruiheng; Wang, Tuo; Qiu, Pengfei; Burkhardt, Ulrich; Grin, Yuri; Chen, Lidong

2018-05-01

Ductility is common in metals and metal-based alloys, but is rarely observed in inorganic semiconductors and ceramic insulators. In particular, room-temperature ductile inorganic semiconductors were not known until now. Here, we report an inorganic α-Ag2S semiconductor that exhibits extraordinary metal-like ductility with high plastic deformation strains at room temperature. Analysis of the chemical bonding reveals systems of planes with relatively weak atomic interactions in the crystal structure. In combination with irregularly distributed silver-silver and sulfur-silver bonds due to the silver diffusion, they suppress the cleavage of the material, and thus result in unprecedented ductility. This work opens up the possibility of searching for ductile inorganic semiconductors/ceramics for flexible electronic devices.

CH3NH3PbI3 based solar cell: Modified by antisolvent treatment

Science.gov (United States)

Nandi, Pronoy; Giri, Chandan; Bansode, Umesh; Topwal, D.

2017-05-01

Solar cells based on new class of organic inorganic hybrid perovskite CH3NH3PbI3 were prepared by Ethyl acetate (EA); antisolvent treatment for the first time. This treatment results in new morphology for CH3NH3PbI3 thin film. FESEM image shows microrod type structures of CH3NH3PbI3 after EA antisolvent treatment. Energy band diagram was constructed using photoluminescence and photoemission studies. A better power conversion efficiency was achieved in EA treated film compare to without EA treated film.

Glass Transitions and Low-Frequency Dynamics of Room-Temperature Ionic Liquids

International Nuclear Information System (INIS)

Yamamuro, O.; Inamura, Y.; Hayashi, S.; Hamaguchi, H.

2006-01-01

We have measured the heat capacity and neutrion quasi- and inelastic scattering spectra of some salts of 1-butyl-3-methylimidazolium ion bmim+, which is a typical cation of room-temperature ionic liquids, and its derivatives. The heat capacity measurements revealed that the room-temperature ionic liquids have glass transitions as molecular liquids. The temperature dependence of configurational entropy demonstrated that the room-temperature ionic liquids are 'fragile liquids'. Both heat capacity and inelastic neutron scattering data revealed that the glassy phases exhibit large low-energy excitations usually called 'boson peak'. The quasielastic neutron scattering data showed that so-called 'fast process' appears around Tg as in molecular and polymer glasses. The temperature dependence of the self-diffusion coefficient derived from the neutron scattering data indicated that the orientation of bmim+ ions and/or butyl-groups of bmim+ ions is highly disordered and very flexible in an ionic liquid phase

Room-temperature aqueous plasma electrolyzing Al2O3 nano-coating on carbon fiber

Science.gov (United States)

Zhang, Yuping; Meng, Yang; Shen, Yonghua; Chen, Weiwei; Cheng, Huanwu; Wang, Lu

2017-10-01

A novel room-temperature aqueous plasma electrolysis technique has been developed in order to prepared Al2O3 nano-coating on each fiber within a carbon fiber bundle. The microstructure and formation mechanism of the Al2O3 nano-coating were systematically investigated. The oxidation resistance and tensile strength of the Al2O3-coated carbon fiber was measured at elevated temperatures. It showed that the dense Al2O3 nano-coating was relatively uniformly deposited with 80-120 nm in thickness. The Al2O3 nano-coating effectively protected the carbon fiber, evidenced by the slower oxidation rate and significant increase of the burn-out temperature from 800 °C to 950 °C. Although the bare carbon fiber remained ∼25 wt.% after oxidation at 700 °C for 20 min, a full destruction was observed, evidenced by the ∼0 GPa of the tensile strength, compared to ∼1.3 GPa of the Al2O3-coated carbon fiber due to the effective protection from the Al2O3 nano-coating. The formation mechanism of the Al2O3 nano-coating on carbon fiber was schematically established mainly based on the physic-chemical effect in the cathodic plasma arc zone.

LPG and NH3 Sensing Properties of SnO2 Thick Film Resistors Prepared by Screen Printing Technique

Directory of Open Access Journals (Sweden)

A. S. GARDE

2010-11-01

Full Text Available The gas sensing behavior of SnO2 thick film resistors deposited on alumina substrates has been investigated for LPG and NH3 gas. The standard screen printing technology was used to prepare the thick films. The films were fired at optimized temperature of 780 0C for 30 minutes. The material characterization was performed by XRD, SEM, FTIR, UV and EDAX for elemental analysis. IR spectroscopy analysis at 2949.26 cm-1 showed the peak assigned to the –Sn-H vibration due to the effect of hybridization i.e. sp3 and the sharp peak at 3734.31 cm-1 assigned to –Sn-OH stretching vibration due to hydrogen bonding. The variation of D.C electrical resistance of SnO2 film samples was measured in air as well as in LPG and NH3 gas atmosphere as a function of temperature. The SnO2 film samples show negative temperature coefficient of résistance. The SnO2 film samples showed the highest sensitivity to 600 ppm of LPG at 230 0C and NH3 at 370 0C. The effect of microstructure on sensitivity, response time and recovery time of the sensor in the presence of LPG and NH3 gases were studied and discussed.

Room temperature photoinduced magnetism in [py.H]{sub 3}[FeCl{sub 4}]{sub 2}Cl

Energy Technology Data Exchange (ETDEWEB)

Baniasadi, F. [Physics Department, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Tehranchi, M.M., E-mail: teranchi@sbu.ac.ir [Physics Department, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Fathi, M.B. [Physics Department, Kharazmi University, Tehran (Iran, Islamic Republic of); Hamidi, S.M. [Laser and Plasma Research Institute, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Safari, N.; Amani, V. [Faculty of Chemistry, Shahid Beheshti University, Tehran (Iran, Islamic Republic of)

2015-11-15

Photoinduced magnetism in a homogeneous solution of [py.H]{sub 3}[FeCl{sub 4}]{sub 2}Cl is measured by Faraday rotation in visible light (λ∼450–750 nm) at room temperature. The physics of this phenomenon may be attributed to electronic transitions caused by absorption of light. X-ray diffraction and Debye function analysis are therefore applied to find the abundant unit of molecules dissolved in the solution which are being further utilized to investigate the electronic structure and molecular orbitals by means of hybrid density function theory (B3LYP). Faraday rotation is observed at certain wavelengths consistent with energy differences of HOMO-LUMO energy levels. Thus this work puts forward a new material with certain photomagnetic properties which may be used in fabrication of room temperature magneto-optical switches. - Highlights: • Photoinduced magnetism in (FeCl{sub 4}){sub 2}(py.H){sub 3}Cl is illustrated via Faraday rotation. • The abundant unit of molecule is characterized by Debye function analysis of XRD. • PIM in the molecule is attributed to the charge transfer between HOMO-LUMO.

H{sub 2} assisted NH{sub 3}-SCR over Ag/Al{sub 2}O{sub 3} for automotive applications

Energy Technology Data Exchange (ETDEWEB)

Fogel, S.

2013-05-15

The up-coming strict emission legislation demands new and improved catalysts for diesel vehicle deNO{sub x}. The demand for low-temperature activity is especially challenging. H{sub 2}-assisted NH{sub 3}-SCR over Ag/Al{sub 2}O{sub 3} has shown a very promising low-temperature activity and a combination of Ag/Al{sub 2}O{sub 3} and Fe-BEA can give a high NO{sub x} conversion in a broad temperature window without the need to dose H{sub 2} at higher temperatures. The aim of this study has been to investigate the combined Ag/Al{sub 2}O{sub 3} and Fe-BEA catalyst system both at laboratory-scale and in full-scale engine bench testing. The catalysts were combined both in a sequential dual-bed layout and a dual-layer layout where the catalysts were coated on top of each other. The Ag/Al{sub 2}O{sub 3} catalyst was also investigated with the aim of improving the sulphur tolerance and low-temperature activity by testing different alumina-supports. A large focus of this study has been the preparation of monolithic catalyst bricks for the catalyst testing. A high SBET and higher Ag loading gave a high sulphur tolerance and activity. It was believed that the high S{sub BET} is needed to give a higher NH{sub 3} adsorption capacity, necessary for the SCR reaction. A higher Ag loading gives more Ag sites and probably a favourable Ag dispersion. Testing with sulphur gave an increased activity of the catalysts. Testing of monolithic catalysts showed a similar activity enhancement after a few standard test cycles. A change in the dispersion or state of Ag can be possible reasons for the activation seen and the activation was believed to be related to Ag and not the alumina. Small-scale laboratory testing showed that it was preferred to have Ag/Al{sub 2}O{sub 3} either upstream or as the outer layer of Fe-BEA. This was attributed to complete NH{sub 3} oxidation over Fe-BEA giving a deficit of NH{sub 3} over the Ag/Al{sub 2}O{sub 3} if it was placed downstream or as the inner layer

Formation of doubly and triply bonded unsaturated compounds HCN, HNC, and CH2NH via N + CH4 low-temperature solid state reaction: from molecular clouds to solar system objects

Science.gov (United States)

Mencos, Alejandro; Krim, Lahouari

2018-06-01

We show in the current study carried out in solid phase at cryogenic temperatures that methane (CH4) ice exposed to nitrogen atoms is a source of two acids HCN, HNC, and their corresponding hydrogenated unsaturated species CH2NH, in addition to CH3, C2H6, CN-, and three nitrogen hydrides NH, NH2, and NH3. The solid state N + CH4 reaction taken in the ground state seems to be strongly temperature dependent. While at temperatures lower than 10 K only CH3, NH, NH2, and NH3 species formation is promoted due to CH bond dissociation and NH bond formation, stable compounds with CN bonds are formed at temperatures ranged between 10 and 40 K. Many of these reaction products, resulting from CH4 + N reaction, have already been observed in N2-rich regions such as the atmospheres of Titan, Kuiper belt objects, and molecular clouds of the interstellar medium. Our results show the power of the solid state N-atom chemistry in the transformation of simple astrochemical relevant species, such as CH4 molecules and N atoms into complex organic molecules which are also potentially prebiotic species.

Preparation of silver chloride nanoparticles by a mechanical treatment of the system NH4Cl−AgNO3−NH4NO3

Directory of Open Access Journals (Sweden)

Farit Urakaev

2014-08-01

Full Text Available Silver chloride nanoparticles dispersed within ammonium nitrate matrix have been prepared though displacement mechanochemical reaction NH4Cl + AgNO3 + z NH4NO3 = (z+1 NH4 NO3 + AgCl at various z coefficients z1 = 7.22 and z2 = 3.64. The intermediate compound of NH4Ag(NO32 were recorded after mechanochemical processing of studied system. By using simultaneous TG and DSC measurements possibilities to prepare silver chloride in its free form have been discussed by using thermal treatment.

Room temperature magnetic and dielectric properties of cobalt doped CaCu3Ti4O12 ceramics

Science.gov (United States)

Mu, Chunhong; Song, Yuanqiang; Wang, Haibin; Wang, Xiaoning

2015-05-01

CaCu3Ti4-xCoxO12 (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu3Ti4O12 (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu3Ti4O12 is well known for its colossal dielectric constant in a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (μ') as high as 5.5 and low magnetic loss (μ″ < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu3Ti4O12 was discussed.

Interplay between organic cations and inorganic framework and incommensurability in hybrid lead-halide perovskite CH3NH3PbBr3

Science.gov (United States)

Guo, Yinsheng; Yaffe, Omer; Paley, Daniel W.; Beecher, Alexander N.; Hull, Trevor D.; Szpak, Guilherme; Owen, Jonathan S.; Brus, Louis E.; Pimenta, Marcos A.

2017-09-01

Organic-inorganic coupling in the hybrid lead-halide perovskite is a central issue in rationalizing the outstanding photovoltaic performance of these emerging materials. Here, we compare and contrast the evolution of the structure and dynamics of hybrid CH3NH3PbBr3 and inorganic CsPbBr3 lead-halide perovskites with temperature, using Raman spectroscopy and single-crystal x-ray diffraction. Results reveal a stark contrast between their order-disorder transitions, which are abrupt for the hybrid whereas smooth for the inorganic perovskite. X-ray diffraction observes an intermediate incommensurate phase between the ordered and the disordered phases in CH3NH3PbBr3 . Low-frequency Raman scattering captures the appearance of a sharp soft mode in the incommensurate phase, ascribed to the theoretically predicted amplitudon mode. Our work highlights the interaction between the structural dynamics of organic cation CH3NH3+ and the lead-halide framework, and unravels the competition between tendencies for the organic and inorganic moieties to minimize energy in the incommensurate phase of the hybrid perovskite structure.

CH3NH3Pb1−xMgxI3 perovskites as environmentally friendly photovoltaic materials

Directory of Open Access Journals (Sweden)

Y. D. Zhang

2018-01-01

Full Text Available In an effort to reduce the toxicity of Pb in perovskite solar cells, the band structures, electron and hole effective masses, and electronic and optical properties of the novel perovskites CH3NH3Pb1−xMgxI3 were predicted using density functional theory with the scalar relativistic generalized gradient approximation. The calculation results indicated that the introduction of the Mg component caused the band gaps of the CH3NH3Pb1−xMgxI3 compounds to exceed that of CH3NH3PbI3. The calculated absorption coefficients of the CH3NH3PbI3 and CH3NH3Pb1−xMgxI3 perovskites revealed that substituting 12.5 mol % of the Pb in CH3NH3PbI3 with Mg had little effect on the absorption ability. Surprisingly, it was also found that CH3NH3Pb0.75Mg0.25I3 retained up to 83% of the absorption performance relative to CH3NH3PbI3. This indicates that the amount of toxic Pb used in perovskite solar cells could be reduced by a quarter while retaining over 80% of the light-absorbing ability. In general, these novel CH3NH3Pb1−xMgxI3 (x ≤ 0.25 perovskites represent promising candidates for environmentally friendly light-harvesting materials for use in solar cells.

Parallel Changes in Intracellular Water Volume and pH Induced by NH3/NH4+ Exposure in Single Neuroblastoma Cells

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Víctor M. Blanco

2013-12-01

Full Text Available Background: Increased blood levels of ammonia (NH3 and ammonium (NH4+, i.e. hyperammonemia, leads to cellular brain edema in humans with acute liver failure. The pathophysiology of this edema is poorly understood. This is partly due to incomplete understanding of the osmotic effects of the pair NH3/NH4+ at the cellular and molecular levels. Cell exposure to solutions containing NH3/NH4+ elicits changes in intracellular pH (pHi, which can in turn affect cell water volume (CWV by activating transport mechanisms that produce net gain or loss of solutes and water. The occurrence of CWV changes caused by NH3/NH4+ has long been suspected, but the mechanisms, magnitude and kinetics of these changes remain unknown. Methods: Using fluorescence imaging microscopy we measured, in real time, parallel changes in pHi and CWV caused by brief exposure to NH3/NH4+ of single cells (N1E-115 neuroblastoma or NG-108 neuroblastoma X glioma loaded with the fluorescent indicator BCECF. Changes in CWV were measured by exciting BCECF at its intracellular isosbestic wavelength (∼438 nm, and pHi was measured ratiometrically. Results: Brief exposure to isosmotic solutions (i.e. having the same osmolality as that of control solutions containing NH4Cl (0.5- 30 mM resulted in a rapid, dose-dependent swelling, followed by isosmotic regulatory volume decrease (iRVD. NH4Cl solutions in which either extracellular [NH3] or [NH4+] was kept constant while the other was changed by varying the pH of the solution, demonstrated that [NH3]o rather than [NH4+]o is the main determinant of the NH4Cl-induced swelling. The iRVD response was sensitive to the anion channel blocker NPPB, and partly dependent on external Ca2+. Upon removal of NH4Cl, cells shrank and displayed isosmotic regulatory volume increase (iRVI. Regulatory volume responses could not be activated by comparable CWV changes produced by anisosmotic solutions, suggesting that membrane stretch or contraction by themselves are

Conductivity of CH{sub 3}NH{sub 3}PbI{sub 3} thin film perovskite stored in ambient atmosphere

Energy Technology Data Exchange (ETDEWEB)

Gebremichael, Bizuneh, E-mail: bizunehme@gmail.com [Physics Department, Addis Ababa University, Addis Ababa, P.O. Box 1176 (Ethiopia); Alemu, Getachew [Physics Department, Addis Ababa University, Addis Ababa, P.O. Box 1176 (Ethiopia); Tessema Mola, Genene [School of Chemistry & Physics, University of KwaZulu-Nat al, Pietermaritzburg Campus, Private Bag X01, Scottsville 3209 (South Africa)

2017-06-01

Time dependent conductivity loss in CH{sub 3}NH{sub 3}PbI{sub 3} thin film perovskite stored in ambient atmosphere were studied based on electrical and optical measurements. Recent investigations on thin film perovskite solar cell suggest that in the steady state operation of the device, the V{sub oc} is unchanged by continuous illumination of light. Rather the reduction in the power conversion efficiency is caused by significant reduction of the short circuit current (J{sub sc}). In this paper, the effect of light on the optical absorption and electrical conductivity of the CH{sub 3}NH{sub 3}PbI{sub 3} thin film which is deposited on a glass substrate is investigated. The temperature dependent conductivity measurements indicated that the dominant conduction mechanism in the film perovskite is electronic rather than ionic.

Charge carrier recombination channels in the low-temperature phase of organic-inorganic lead halide perovskite thin films

Directory of Open Access Journals (Sweden)

Christian Wehrenfennig

2014-08-01

Full Text Available The optoelectronic properties of the mixed hybrid lead halide perovskite CH3NH3PbI3−xClx have been subject to numerous recent studies related to its extraordinary capabilities as an absorber material in thin film solar cells. While the greatest part of the current research concentrates on the behavior of the perovskite at room temperature, the observed influence of phonon-coupling and excitonic effects on charge carrier dynamics suggests that low-temperature phenomena can give valuable additional insights into the underlying physics. Here, we present a temperature-dependent study of optical absorption and photoluminescence (PL emission of vapor-deposited CH3NH3PbI3−xClx exploring the nature of recombination channels in the room- and the low-temperature phase of the material. On cooling, we identify an up-shift of the absorption onset by about 0.1 eV at about 100 K, which is likely to correspond to the known tetragonal-to-orthorhombic transition of the pure halide CH3NH3PbI3. With further decreasing temperature, a second PL emission peak emerges in addition to the peak from the room-temperature phase. The transition on heating is found to occur at about 140 K, i.e., revealing significant hysteresis in the system. While PL decay lifetimes are found to be independent of temperature above the transition, significantly accelerated recombination is observed in the low-temperature phase. Our data suggest that small inclusions of domains adopting the room-temperature phase are responsible for this behavior rather than a spontaneous increase in the intrinsic rate constants. These observations show that even sparse lower-energy sites can have a strong impact on material performance, acting as charge recombination centres that may detrimentally affect photovoltaic performance but that may also prove useful for optoelectronic applications such as lasing by enhancing population inversion.

Monitoring and understanding the paraelectric-ferroelectric phase transition in the metal-organic framework [NH4 ][M(HCOO)3 ] by solid-state NMR spectroscopy.

Science.gov (United States)

Xu, Jun; Lucier, Bryan E G; Sinelnikov, Regina; Terskikh, Victor V; Staroverov, Viktor N; Huang, Yining

2015-10-05

The paraelectric-ferroelectric phase transition in two isostructural metal-organic frameworks (MOFs) [NH4 ][M(HCOO)3 ] (M=Mg, Zn) was investigated by in situ variable-temperature (25) Mg, (67) Zn, (14) N, and (13) C solid-state NMR (SSNMR) spectroscopy. With decreasing temperature, a disorder-order transition of NH4 (+) cations causes a change in dielectric properties. It is thought that [NH4 ][Mg(HCOO)3 ] exhibits a higher transition temperature than [NH4 ][Zn(HCOO)3 ] due to stronger hydrogen-bonding interactions between NH4 (+) ions and framework oxygen atoms. (25) Mg and (67) Zn NMR parameters are very sensitive to temperature-induced changes in structure, dynamics, and dielectric behavior; stark spectral differences across the paraelectric-ferroelectric phase transition are intimately related to subtle changes in the local environment of the metal center. Although (25) Mg and (67) Zn are challenging nuclei for SSNMR experiments, the highly spherically symmetric metal-atom environments in [NH4 ][M(HCOO)3 ] give rise to relatively narrow spectra that can be acquired in 30-60 min at a low magnetic field of 9.4 T. Complementary (14) N and (13) C SSNMR experiments were performed to probe the role of NH4 (+) -framework hydrogen bonding in the paraelectric-ferroelectric phase transition. This multinuclear SSNMR approach yields new physical insights into the [NH4 ][M(HCOO)3 ] system and shows great potential for molecular-level studies on electric phenomena in a wide variety of MOFs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal structure and magnetoresistance of La0.7Ca0.3MnO3 perovskite at room temperature

International Nuclear Information System (INIS)

Engkir Sukirman; Wisnu Ari Adi; Yustinus Purwamargapratala

2012-01-01

A comparative study on crystal structure and magnetoresistance (MR) of La 0.7 Ca 0.3 MnO 3 (LCMO) perovskite toward LaMnO 3 (LMO) and CaMnO 3 (CMO) parent compounds have been carried out to study the change of LCMO due to magnetic fields variations at room temperature. The LCMO, LMO and CMO were synthesized using high energy milling (HEM) method. The precursors obtained were pressed into pellet and sintered at T s = 1350°C for 6 hours. The qualitative analysis were conducted by x-rays diffraction technique using Rietveld method. The MR effect on the samples were measured using four point probe (FPP) method and the surface structure of pellets were observed by scanning electron microscope (SEM). The samples have the same crystal structure, namely orthorhombic, space group: Pnma, No. 62. The lattice parameters of LCMO were successfully confirmed until four decimal precision, namely a = 5.4851(3) Å, b = 7.7601(4) Å, c = 5.5185(2) Å. The lattice parameters for LMO and CMO successively are a = 5.4405(9) Å, b = 7.717(1) Å, c = 5.537(1) Å and a = 5.2973(6) Å, b = 7.477(1) Å, c = 5.281 (1) Å. All samples have grain diameter of around 1,000 nm with a globule like form and every grain consists of 27 crystallites. The MR for LCMO, LMO and CMO samples at room temperature are -10.1; -7.3 dan -12.3%, respectively, and comparable with the one of multilayers based GMR [Cu/NiFeCo] x10 /Ta. The LCMO perovskite bulk can be used to detect the magnetic microbeads and ferrofluid. (author)

New insights into Cu/SSZ-13 SCR catalyst acidity. Part I: Nature of acidic sites probed by NH 3 titration

Energy Technology Data Exchange (ETDEWEB)

Luo, Jinyong; Gao, Feng; Kamasamudram, Krishna; Currier, Neal; Peden, Charles H. F.; Yezerets, Aleksey

2017-04-01

In this work we investigated an unusual acidity feature of a Cu/SSZ-13 catalyst used in selective catalytic reduction of NOx with NH3 (NH3-SCR). In particular, this catalyst showed two distinct NH3 desorption peaks in NH3-TPD measurements, in contrast to single, unresolved desorption peaks observed for other Cu-exchanged zeolites conventionally used in the SCR studies, including its isostructural but chemically different analogue Cu/SAPO-34. We further observed that the intensities of the two TPD peaks, which represented the amount of stored NH3, changed in opposite directions in response to progressive mild hydrothermal aging, while the total storage capacity was preserved. We proposed an explanation for this remarkable behavior, by using model reference samples and additional characterization techniques. At least three NH3 storage sites were identified: two distinct populations of Cu sites responsible for low-temperature NH3 storage, and Brønsted acid sites responsible for high-temperature NH3 storage. Contrary to the commonly accepted mechanism that Brønsted acid site loss during hydrothermal aging is driven by dealumination, we concluded that the decline in the number of Brønsted acid sites upon mild hydrothermal aging for Cu/SSZ-13 was not due to dealumination, but rather transformation of Cu sites, i.e., gradual conversion of ZCuOH (Cu2+ singly coordinated with Zeolite) to Z2Cu (Cu2+ doubly coordinated with Zeolite). This transformation was responsible for the increased low-temperature desorption peak in NH3-TPD since each ZCuOH adsorbed ~1 NH3 molecule while each Z2Cu adsorbed ~2 NH3 molecules under the conditions used here. These findings were used in Part II of this series of studies to develop a method for quantifying hydrothermal ageing of industrial Cu/SSZ-13 SCR catalysts. Authors would like to thank Randall Jines for his help with collecting the reactor data, Nancy W. Washton for measuring the NMR data and Tamas Varga for in-situ XRD measurements

Room temperature large self-biased magnetoelectric effect in non-lead based piezoelectric and magnetostrictive (0−3) particulate composite system

Energy Technology Data Exchange (ETDEWEB)

Kumari, Mukesh [Magnetics & Advanced Ceramics Laboratory, Indian Institute of Technology, Delhi-110016 India (India); Prakash, Chandra [Solid State Physics Laboratory Timarpur, Delhi-110054 India (India); Chatterjee, Ratnamala, E-mail: rmala@physics.iitd.ac.in [Magnetics & Advanced Ceramics Laboratory, Indian Institute of Technology, Delhi-110016 India (India)

2017-05-01

In this work, room temperature magnetoelectric properties of (0−3) particulate composites of non lead based piezoelectric BNTKNNLTS [0.97(Bi{sub 0.5}Na{sub 0.5}TiO{sub 3})–0.03(K{sub 0.47}Na{sub 0.47}Li{sub 0.06}Nb{sub 0.74}Sb{sub 0.06}Ta{sub 0.2}O{sub 3}) and magnetostrictive CZFMO (Co{sub 0.6}Zn{sub 0.4}Fe{sub 1.7}Mn{sub 0.3}O{sub 4}) are presented. Composite samples of (1-x)(BNTKNNLTS)-x(CZFMO){sub ,} with x=0.1 and 0.5, are synthesized by solid state reaction route. X-ray diffraction confirms the single phase formation of parent phases and the presence of two phases in the composites. Similar sintering conditions of the two individual components lead to optimal ferroelectric and ferromagnetic properties in the composites. A large self-biased magnetoelectric (ME) coupling ~74 mV/cm.Oe for the sample with x=0.1 (measured in longitudinally magnetized-transversely polarized configuration) is observed at room temperature. - Highlights: • Modified BNT-CFO based (0−3) particulate composites have been synthesized. • Similar sintering conditions of two components lead to optimal multiferroicity. • A large self-biased ME coupling ~74 mV/cm. Oe is obtained at room temperature.

CFD analysis of the temperature field in emergency pump room in Loviisa NPP

Energy Technology Data Exchange (ETDEWEB)

Rämä, Tommi, E-mail: tommi.rama@fortum.com [Fortum Power and Heat, P.O.B. 100, FI-00048 Fortum (Finland); Toppila, Timo, E-mail: timo.toppila@fortum.com [Fortum Power and Heat, P.O.B. 100, FI-00048 Fortum (Finland); Kelavirta, Teemu, E-mail: teemu.kelavirta@fortum.com [Fortum Power and Heat, Loviisa Power Plant, P.O.B. 23, FI-07901 Loviisa (Finland); Martin, Pasi, E-mail: pasi.martin@fortum.com [Fortum Power and Heat, Loviisa Power Plant, P.O.B. 23, FI-07901 Loviisa (Finland)

2014-11-15

Highlights: • Laser scanned room geometry from Loviisa NPP was utilized for CFD simulation. • Uncertainty of CFD simulation was estimated using the Grid Convergence Index. • Measured temperature field of pump room was reproduced with CFD simulation. - Abstract: In the Loviisa Nuclear Power Plant (NPP) six emergency pumps belonging to the same redundancy are located in the same room. During a postulated accident the cooling of the room is needed as the engines of the emergency pumps generate heat. Cooling is performed with fans blowing air to the upper part of the room. Temperature limits have been given to the operating conditions of the main components in order to ensure their reliable operation. Therefore the temperature field of the room is important to know. Temperature measurements were made close to the most important components of the pump room to get a better understanding of the temperature field. For these measurements emergency pumps and cooling fan units were activated. To simulate conditions during a postulated accident additional warm-air heaters were used. Computational fluid dynamic (CFD) simulations were made to support plant measurements. For the CFD study one of the pump rooms of Loviisa NPP was scanned with a laser and this data converted to detailed 3-D geometry. Tetrahedral computation grid was created inside the geometry. Grid sensitivity studies were made, and the model was then validated against the power plant tests. With CFD the detailed temperature and flow fields of the whole room were produced. The used CFD model was able to reproduce the temperature field of the measurements. Two postulated accident cases were simulated. In the cases the operating cooling units were varied. The temperature profile of the room changes significantly depending on which units are cooling and which only circulating the air. The room average temperature stays approximately the same. The simulation results were used to ensure the acceptable operating

The energy level alignment at the CH_3NH_3PbI_3/pentacene interface

International Nuclear Information System (INIS)

Ji, Gengwu; Zhao, Bin; Song, Fei; Zheng, Guanhaojie; Zhang, Xiaonan; Shen, Kongchao; Yang, Yingguo; Chen, Shi; Gao, Xingyu

2017-01-01

Highlights: • The Energy Level Alignment at the CH_3NH_3PbI_3/Pentacene Interface was resolved experimentally. • The downward band bending and the dipole found at the pentacene side would favorably drive holes away from the interface into pentacene. • A ∼0.7 eV offset between pentacene HOMO and CH_3NH_3PbI_3 VBM would be in favor of hole transfer whereas a ∼1.35 eV offset between pentacene LUMO and CH_3NH_3PbI_3 CBM should efficiently block the unwanted electron transfer from perovskite to pentacene. • Pentacene could be a viable hole transfer material candidate on perovskite to be explored in perovskite devices. - Abstract: Pentacene thin film on CH_3NH_3PbI_3 was studied by in-situ X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy to determine their interfacial energy level alignment. A 0.2 eV downward band bending together with a 0.1 eV interfacial dipole was found at the pentacene side, whereas there was no band bending found at the CH_3NH_3PbI_3 side. The offset between CH_3NH_3PbI_3 Valance Band Maximum (VBM) and pentacene Highest Occupied Molecular Orbital (HOMO) and that between CH_3NH_3PbI_3 Conduction Band Minimum (CBM) and pentacene Lowest Unoccupied Molecular Orbital (LUMO) was determined to be 0.7 and 1.35 eV, respectively. The band alignment at this interface is favor of efficient hole transfer, which suggests pentacene as a viable HTL candidate to be explored in perovskite solar cells.

Observation of room temperature saturated ferroelectric polarization in Dy substituted BiFeO3 ceramics

KAUST Repository

Zhang, Shuxia

2012-04-06

High quality Bi1− x Dy x FeO3 (0 ≤ x ≤ 0.15) ceramics have been fabricated by sintering Dy-doped BiFeO3 (BFO) precursor powders at a low temperature of 780 °C. The magnetic properties of BFO were improved by the introduction of Dy on the Bi-site. More importantly, well saturated ferroelectric hysteresis loops and polarization switching currents have been observed at room temperature. A large remnant polarization (2P r) value of 62 μC/cm2 is achieved, which is the highest value reported so far for rare-earth-doped BFO ceramics. Moreover, mechanisms for improved multiferroic properties depending on chemical doping-caused structure evolutions have also been discussed.

Observation of room temperature saturated ferroelectric polarization in Dy substituted BiFeO3 ceramics

KAUST Repository

Zhang, Shuxia; Wang, Lei; Chen, Yao; Wang, Dongliang; Yao, Yingbang; Ma, Yanwei

2012-01-01

High quality Bi1− x Dy x FeO3 (0 ≤ x ≤ 0.15) ceramics have been fabricated by sintering Dy-doped BiFeO3 (BFO) precursor powders at a low temperature of 780 °C. The magnetic properties of BFO were improved by the introduction of Dy on the Bi-site. More importantly, well saturated ferroelectric hysteresis loops and polarization switching currents have been observed at room temperature. A large remnant polarization (2P r) value of 62 μC/cm2 is achieved, which is the highest value reported so far for rare-earth-doped BFO ceramics. Moreover, mechanisms for improved multiferroic properties depending on chemical doping-caused structure evolutions have also been discussed.

Crystal structure and dynamics of K2-x(NH4)xSeO4 mixed crystals studied by x-ray and neutron scattering

International Nuclear Information System (INIS)

Smirnov, L.S.; Natkaniec, I.; Loose, A.

2006-01-01

The K 2-x (NH 4 ) x SeO 4 mixed crystals have been studied by powder X-ray and neutron diffraction and inelastic incoherent neutron scattering in a wide temperature range from 300 to 16 K. No phase transition is observed in (NH 4 ) 2 SeO 4 in the range from room temperature to 20 K. The reorientation potential barriers of ammonium ions in the K 2-x (NH 4 ) x SeO 4 mixed crystals increase with the increasing concentration of ammonium ions

Enhanced superconductivity and anisotropy of FeTe0.6Se0.4 single crystals with Li -NH3 intercalation

Science.gov (United States)

Li, Chenghe; Sun, Shanshan; Wang, Shaohua; Lei, Hechang

2017-10-01

We report a systematic study of anisotropy resistivity, magnetoresistance, and Hall effect of Li0.32(NH3)yFe2Te1.2Se0.8 single crystals. When compared to the parent compound FeTe0.6Se0.4 , the Li-NH3 intercalation not only increases the superconducting transition temperature but also enhances the electronic anisotropy in both normal and superconducting states. Moreover, in contrast to the parent compound, the Hall coefficient RH becomes negative at low temperature, indicating electron-type carriers are dominant due to Li doping. On the other hand, the sign reverse of RH at high temperature and the failure of scaling behavior of magnetoresistance imply that hole pockets may be still crossing or just below the Fermi energy level, leading to the multiband behavior in Li0.32(NH3)yFe2Te1.2Se0.8 .

Herschel/HIFI deepens the circumstellar NH3 enigma

NARCIS (Netherlands)

Menten, K. M.; Wyrowski, F.; Alcolea, J.; De Beck, E.; Decin, L.; Marston, A. P.; Bujarrabal, V.; Cernicharo, J.; Dominik, C.; Justtanont, K.; de Koter, A.; Melnick, G.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Schmidt, M.; Schoier, F. L.; Szczerba, R.; Teyssier, D.; Waters, L. B. F. M.; Edwards, K.; Olberg, M.; Phillips, T. G.; Morris, P.; Salez, M.; Caux, E.

2010-01-01

Context. Circumstellar envelopes (CSEs) of a variety of evolved stars have been found to contain ammonia (NH3) in amounts that exceed predictions from conventional chemical models by many orders of magnitude. Aims. The observations reported here were performed in order to better constrain the NH3

Electro-caloric effect in lead-free Sn doped BaTiO3 ceramics at room temperature and low applied fields

International Nuclear Information System (INIS)

Upadhyay, Sanjay Kumar; Reddy, V. Raghavendra; Bag, Pallab; Rawat, R.; Gupta, S. M.; Gupta, Ajay

2014-01-01

Structural, dielectric, ferroelectric (FE), 119 Sn Mössbauer, and specific heat measurements of polycrystalline BaTi 1–x Sn x O 3 (x = 0% to 15%) ceramics are reported. Phase purity and homogeneous phase formation with Sn doping is confirmed from x-ray diffraction and 119 Sn Mössbauer measurements. With Sn doping, the microstructure is found to change significantly. Better ferroelectric properties at room temperature, i.e., increased remnant polarization (38% more) and very low field switchability (225% less) are observed for x = 5% sample as compared to other samples and the results are explained in terms of grain size effects. With Sn doping, merging of all the phase transitions into a single one is observed for x ≥ 10% and for x = 5%, the tetragonal to orthorhombic transition temperature is found close to room temperature. As a consequence better electro-caloric effects are observed for x = 5% sample and therefore is expected to satisfy the requirements for non-toxic, low energy (field) and room temperature based applications.

Heavy atom enhanced room-temperature phosphorimetry for ultratrace determination of harmane

Directory of Open Access Journals (Sweden)

Flávia F. de Carvalho Marques

2008-01-01

Full Text Available Harmane has been proposed for the treatment of epilepsy, AIDS and leshmaniosis. Its room-temperature phosphorescence was induced using either AgNO3 or TlNO3, enabling absolute limits of detection of 0.12 and 2.4 ng respectively, with linear dynamic ranges extending up to 456 ng (AgNO3 and 911 ng (TlNO3. Relative standard deviations around 3% were observed for substrates containing 46 ng of harmane. Such sensitivity and precision are needed because harmane intake must be strictly controlled to achieve proper therapeutic response. Interference studies were performed using thalidomide, reserpine and yohimbine. Recovery of 104±6% was achieved using solid surface room-temperature phosphorimetry. The result was comparable to the one obtained by micellar electrokinetic chromatography.

Room temperature deposition of perpendicular magnetic anisotropic Co{sub 3}Pt thin films on glass substrate

Energy Technology Data Exchange (ETDEWEB)

Chen, Yu-Shen; Dai, Hong-Yu; Hsu, Yi-Wei [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China); Ou, Sin-Liang, E-mail: slo@mail.dyu.edu.tw [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Chen, Shi-Wei [National Synchrotron Radiation Research Center (NSRRC), Hsinchu 300, Taiwan (China); Lu, Hsi-Chuan; Wang, Sea-Fue [Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China); Sun, An-Cheng, E-mail: acsun@saturn.yzu.edu.tw [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China)

2017-03-01

Co{sub 3}Pt alloy thin films were deposited on the glass substrate at room temperature (RT) and 300 °C, which showed high perpendicular magnetic anisotropy (PMA) and isotropy magnetic behaviors, respectively. Co{sub 3}Pt HCP (0002) planes grew along the substrate plane for the films deposited at RT. The easy axis [0001] was consequently vertical to the substrate surface and obtained the predominant PMA. Large magnetic domains and sharp boundary also supported high PMA in RT-deposited samples. On the other hand, the PMA was significantly decreased with increasing the deposition temperature from RT to 300 °C. Hard HCP(0002) and soft A1(111) co-existed in the film and the magnetic exchanged coupling between these two phases induced isotropy magnetic behavior. In addition, the various thicknesses (t) of the RT-deposited Co{sub 3}Pt films were deposited with different base pressures prior to sputtering. The Kerr rotation loops showed high PMA and out-of-plane squareness (S{sub ⊥}) of ~0.9 were found in low base pressure chamber. Within high base pressure chamber, Co{sub 3}Pt films just show magnetic isotropy behaviors. This study provides a fabrication method for the preparation of high PMA HCP-type Co{sub 3}Pt films on the glass substrate without any underlayer at RT. The results could be the base for future development of RT-deposited magnetic alloy thin film with high PMA. - Highlights: • Fabricated high perpendicular magnetic anisotropy Co{sub 3}Pt thin film on glass substrate. • Prepared HCP Co{sub 3}Pt thin film at room temperature. • The key to enhance the PMA of the Co{sub 3}Pt films. • Thinner film is good to fabricate PMA Co{sub 3}Pt thin films.

Preparation and Performance of Modified Red Mud-Based Catalysts for Selective Catalytic Reduction of NOx with NH3

Directory of Open Access Journals (Sweden)

Jingkun Wu

2018-01-01

Full Text Available Bayer red mud was selected, and the NH3-SCR activity was tested in a fixed bed in which the typical flue gas atmosphere was simulated. Combined with XRF, XRD, BET, SEM, TG and NH3-Temperature Programmed Desorption (TPD characterization, the denitration characteristics of Ce-doped red mud catalysts were studied on the basis of alkali-removed red mud. The results showed that typical red mud was a feasible material for denitration catalyst. Acid washing and calcining comprised the best treatment process for raw red mud, which reduced the content of alkaline substances, cleared the catalyst pore and optimized the particle morphology with dispersion. In the temperature range of 300–400 °C, the denitrification efficiency of calcined acid washing of red mud catalyst (ARM was more than 70%. The doping of Ce significantly enhanced NH3 adsorption from weak, medium and strong acid sites, reduced the crystallinity of α-Fe2O3 in ARM, optimized the specific surface area and broadened the active temperature window, which increased the NOx conversion rate by an average of nearly 20% points from 250–350 °C. The denitration efficiency of Ce0.3/ARM at 300 °C was as high as 88%. The optimum conditions for the denitration reaction of the Ce0.3/ARM catalyst were controlled as follows: Gas Hourly Space Velocity (GHSV of 30,000 h−1, O2 volume fraction of 3.5–4% and the NH3/NO molar ratio ([NH3/NO] of 1.0. The presence of SO2 in the feed had an irreversible negative effect on the activity of the Ce0.3/ARM catalyst.

Room temperature ferromagnetism in Mn-doped NiO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Layek, Samar, E-mail: samarlayek@gmail.com; Verma, H.C.

2016-01-01

Mn-doped NiO nanoparticles of the series Ni{sub 1−x}Mn{sub x}O (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum. - Highlights: • Mn-doped NiO nanoparticles are prepared by a simple hydrothermal method. • Unit cell volume decreases with increasing doping concentration. • Mn-doping leads to room temperature ferromagnetism in NiO nanoparticles. • Magnetization is highest for 2% Mn-doping. • Above 2%, magnetization decreases with increasing doping.

Room temperature ferromagnetism in Mn-doped NiO nanoparticles

International Nuclear Information System (INIS)

Layek, Samar; Verma, H.C.

2016-01-01

Mn-doped NiO nanoparticles of the series Ni_1_−_xMn_xO (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum. - Highlights: • Mn-doped NiO nanoparticles are prepared by a simple hydrothermal method. • Unit cell volume decreases with increasing doping concentration. • Mn-doping leads to room temperature ferromagnetism in NiO nanoparticles. • Magnetization is highest for 2% Mn-doping. • Above 2%, magnetization decreases with increasing doping.

EPR investigation of gamma-irradiated L-citrulline, α-methyl-DL-serine, 3-fluoro-DL-valine and N-acetyl-L-cysteine

Science.gov (United States)

Osmanoğlu, Y. Emre; Sütçü, Kerem; Başkan, M. Halim

2017-02-01

The spectroscopic parameters of the paramagnetic species produced in gamma-irradiated L-citrulline, α-methyl-DL-serine, 3-fluoro-DL-valine and N-acetyl-L-cysteine were investigated at room temperature at a dose of 20 kGy by using EPR technique. The paramagnetic species were attributed to NH2CONH(CH2)3ĊNH2COOH, HOCH2ĊCH3COOH and HOĊHCCH3NH2COOH, CH3CH3ĊCHNH2COOH and SHCH2ĊNHCOCH3COOH radicals, respectively. EPR data of the unpaired electron with the environmental protons and 14N nucleus were used to characterize the contributing radicals produced in gamma irradiated compounds. In this paper, the stability of these compounds at room temperature after irradiation was also studied.

Characterization of nanostructured Mn3O4 thin films grown by SILAR method at room temperature

International Nuclear Information System (INIS)

Ubale, A.U.; Belkhedkar, M.R.; Sakhare, Y.S.; Singh, Arvind; Gurada, Chetan; Kothari, D.C.

2012-01-01

A novel successive ionic layer adsorption and reaction method has been successfully employed to grow nanostructured conducting nearly transparent thin films of Mn 3 O 4 on to glass substrates at room temperature using MnCl 2 and NaOH as cationic and anionic precursors. The structural and morphological characterizations of the as deposited Mn 3 O 4 films have been carried out by means of X-ray diffraction (XRD), Field Emission Scanning Electron Micrograph (FESEM), EDAX, Atomic Fore Microscopy (AFM) and Fourier Transform Infrared Spectrum (FTIR) analysis. The optical absorption and electrical resistivity measurements were carried out to investigate optical band gap and activation energy of Mn 3 O 4 films deposited by SILAR method. The optical band gap and activation energy of the as deposited film is found to be 2.70 and 0.14 eV respectively. The thermo-emf measurements of Mn 3 O 4 thin film confirm its p-type semiconducting nature. Highlights: ► Nanostructured Mn 3 O 4 thin film is prepared by SILAR method at room temperature. ► The film is nanocrystalline with orthorhombic structure of Mn 3 O 4 . ► The XRD, FTIR, FESEM, EDX and AFM characterization confirms nanocrystalline nature. ► Optical band gap, electrical resistivity and activation energy of film is reported. ► A thermo-emf measurement confirms p-type conductivity of Mn 3 O 4 films.

Effects of hot airflow during spin-coating process on CH3NH3PbI3-xClx perovskite solar cells

Science.gov (United States)

Tanaka, Hiroki; Ohishi, Yuya; Oku, Takeo

2018-01-01

CH3NH3PbI3-xClx photovoltaic devices were fabricated, and the effects of hot airflow during spin-coating were investigated. Cubic perovskite crystals that is a high temperature phase were obtained by the hot airflow method. The conversion efficiencies of the devices prepared by the hot airflow were remained even after 56 days.

Mechanical Resonators for Quantum Optomechanics Experiments at Room Temperature.

Science.gov (United States)

Norte, R A; Moura, J P; Gröblacher, S

2016-04-08

All quantum optomechanics experiments to date operate at cryogenic temperatures, imposing severe technical challenges and fundamental constraints. Here, we present a novel design of on-chip mechanical resonators which exhibit fundamental modes with frequencies f and mechanical quality factors Q_{m} sufficient to enter the optomechanical quantum regime at room temperature. We overcome previous limitations by designing ultrathin, high-stress silicon nitride (Si_{3}N_{4}) membranes, with tensile stress in the resonators' clamps close to the ultimate yield strength of the material. By patterning a photonic crystal on the SiN membranes, we observe reflectivities greater than 99%. These on-chip resonators have remarkably low mechanical dissipation, with Q_{m}∼10^{8}, while at the same time exhibiting large reflectivities. This makes them a unique platform for experiments towards the observation of massive quantum behavior at room temperature.

Fabrication of metallic Cd multifarious prismatic microcrystals (CMPMCs) under NH{sub 3} gas ambient

Energy Technology Data Exchange (ETDEWEB)

Khan, Waheed S. [Research Centre of Materials Science, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Cao, Chuanbao, E-mail: cbcao@bit.edu.cn [Research Centre of Materials Science, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Butt, Faheem K.; Ali, Zulfiqar [Research Centre of Materials Science, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Baig, Anisullah [Department of Engineering-Applied Sciences, University of California, Davis, CA 95616 (United States); Ain, Qurrat ul; Iqbal, M. Zubair [Department of Physics, School of Physics and Mathematics, University of Science and Technology Beijing, Beijing 100083 (China); Sadaf, Asma [Advance Photonics Center, Southeast University, Nanjing 210096 (China); Shah, Sajjad H. [Department of Physics, Beijing Institute of Technology, Beijing 100081 (China)