Barium Nitrite Research Articles

Reactivity of Aluminum and Titanium Oxides under the Conditions of the Synthesis of Strontium and Barium Titanates in Water Fluid Media

Strontium and barium titanates deposited on a porous support (α-Al2O3) are synthesized by the treatment of previously deposited precursors (titanium oxide, strontium nitrate, or barium nitrite) in a water fluid medium at 400°C. The obtained samples are characterized by X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy. It is found that, in the presence of titanium oxide, α-Al2O3 is partially hydrated to form basic aluminum hydroxide AlO(OH) (boehmite), which is not detected by XRD after the treatment of α-Al2O3 in a water fluid. SEM with EDX spectroscopy demonstrates that strontium ions under the conditions of the treatment in a water fluid preferably interact with titanium oxide to form SrTiO3, although the aluminum oxide content in the samples is much higher. The conditions are determined for obtaining systems with different spatial distributions of the supported component inside the granules of the support by varying the procedure of its preliminary impregnation with the titanium oxide precursor.

Model sulfur-resistant NSR catalysts: An XPS study of the interaction of BaO/TiO2-ZrO2 and Pt-BaO/TiO2-ZrO2 with NO2

The interaction of NO2 with BaO/TiO2-ZrO2 and Pt-BaO/TiO2-ZrO2 model NO x storage-reduction (NSR) catalysts prepared on the surface of FeCrAl alloy substrates has been investigated by X-ray photoelectron spectroscopy. The action of nitrogen dioxide on these catalysts at room temperature causes the consecutive formation of surface barium nitrite and nitrate. Supposedly, NO2 reduction yielding barium nitrite at the early stages of the interaction is due to the oxidation of amorphous carbon impurities. The introduction of platinum into the catalyst accelerates nitrogen dioxide sorption. On being exposed to NO2 for a long time, platinum oxidizes to PtO2. This process is more pronounced in the sample containing freshly deposited platinum. Heat treatment of this sample in a vacuum, which coarsens the platinum particles, makes them more resistant to oxidation.

High-speed intravascular photoacoustic imaging of lipid-laden atherosclerotic plaque enabled by a 2-kHz barium nitrite raman laser.

Lipid deposition inside the arterial wall is a key indicator of plaque vulnerability. An intravascular photoacoustic (IVPA) catheter is considered a promising device for quantifying the amount of lipid inside the arterial wall. Thus far, IVPA systems suffered from slow imaging speed (~50 s per frame) due to the lack of a suitable laser source for high-speed excitation of molecular overtone vibrations. Here, we report an improvement in IVPA imaging speed by two orders of magnitude, to 1.0 s per frame, enabled by a custom-built, 2-kHz master oscillator power amplifier (MOPA)-pumped, barium nitrite [Ba(NO3)2] Raman laser. This advancement narrows the gap in translating the IVPA technology to the clinical setting.

AN XPS study of the interaction of model Ba/TiO2 AND Ba/ZrO2 NSR catalysts with NO2

X-ray photoelectron spectroscopy is used to study the interaction of model NO2 storage-reduction catalysts (NSR catalysts) Ba/TiO2 and Ba/ZrO2 with NO2. The catalysts are prepared on the surface of ultrathin Al2O3 film substrates obtained by the FeCrAl alloy oxidation. It is shown that at room temperature the model catalysts react with NO2 with the successive formation of surface barium nitrite and nitrate. The NO2 reduction with the formation of barium nitrite at the initial step of the interaction is assumed to be accompanied by the oxidation of residual metallic barium and amorphous carbon impurity. It is found that the formation of barium nitrate proceeds more efficiently on Ba/ZrO2 rather than on Ba/TiO2.

The first example of a molecule-based ferroelectric with barium cation: catena-(μ2-nitrito-O,O)-bi-aqua-(18-crown-6)-barium nitrite

The molecular crystal catena-(μ2-nitrito-O,O)-bi-aqua-(18-crown-6)-barium nitrite (1) undergoes a reversible ferroelectric phase (FP) transition at Tc (= 182 K, phase transition temperature) from a paraelectric phase (PP). The symmetry breaking is changed from a high temperature centrosymmetric space group (Pnma) to a low temperature noncentrosymmetric space group (Pca21) with an Aizu notation of mmmFmm2. Symmetry breaking analysis indicates that the FP space group is not a sub-group of the PP space group, suggesting it does not obey the Curie-symmetry principle. Some physical property anomalies near Tc, such as the temperature-dependences of Cp, dielectric constant, and second-harmonic generation effects, firmly confirm that this phase transition is reversible, and symmetry breaking really occurred during the temperature cooling down process from high- to low-temperature. Finally experimental fitting based on the Curie–Weiss constant and Cp gives a spontaneous polarization (Ps), reaching about 1.2 μC cm−2.

Cobalt Catalyst Doped with Cerium and Barium Obtained by Co-Precipitation Method for Ammonia Synthesis Process

Unsupported cobalt catalysts promoted with barium (symbol Co/Ba), cerium (Co/Ce) or both (Co/Ce/Ba) were synthesized and tested in ammonia synthesis at 6.3 MPa. The Ba-free Co and Co/Ce oxide forms of the catalysts were prepared by precipitation/co-precipitation and a subsequent calcination at 500 °C. The Co and Co/Ce powders were impregnated with an aqueous solution of barium nitrite. Nitrogen physisorption and H2 chemisorption measurements revealed that cerium and barium play the role of structural promoters, which hinder the sintering of cobalt oxide during calcination and stabilize the surface of cobalt under reduction conditions. It seems that barium also modifies the surface of the active phase, i.e., cobalt. The kinetic studies of NH3 synthesis have shown that the co-promoted material (Co/Ce/Ba) is about 2–3 times more active than the system doped with barium (Co/Ba) and more than ten times as active as that with Ce. At 400 °C and at low conversion (1% NH3), the ammonia synthesis rate (TOF) over Co/Ce/Ba proved to be almost 60% as high as that obtained for the commercial iron catalyst (KMI, H. Topsoe) commonly used in ammonia plants all over the world. Moreover, at the same temperature and a high ammonia concentration (8%) the co-promoted cobalt catalyst is over two times more active than the fused iron catalyst. Another asset of the cobalt catalyst is its high thermal stability. TG/DTG-MS studies of the cobalt catalysts. DTG curves of samples

Activated carbon as a template for creating catalyst precursors. Unsupported cobalt catalyst for ammonia synthesis

Abstract Unsupported cobalt catalysts promoted with barium (symbol Co + Ba), cerium (Co + Ce) or both (Co + Ce + Ba) were synthesized and tested in ammonia synthesis at 63 bar. The Ba-free Co and Co+Ce oxide forms of the catalysts were prepared by the templating route, using commercial activated carbon (GF45; Norit) preheated in hydrogen (800 °C) as the template and cobalt and cerium nitrates as the active phase precursor and the promoter precursor, respectively. Barium was introduced to the Co and Co + Ce powders by their impregnation with an aqueous solution of barium nitrite. The kinetic studies of NH3 synthesis have demonstrated that the doubly-promoted material (Co + Ce + Ba) is about 2.5 times more active than the system doped with barium and about 20 times as active as that with Ce. At 400 °C and at high conversion (8% NH3), the ammonia synthesis rate over Co + Ce + Ba proved to be almost twice as high as that obtained for the commercial iron catalyst (KM I, H. Topsoe) used commonly in ammonia plants all over the world.

Model NSR catalysts: Fabrication and reactivity of barium oxide layers on Cu(1 1 1)

The growth of barium oxide on a Cu(1 1 1) substrate, formed by the deposition of barium and its subsequent oxidation, yields stable BaO films which expose predominantly the BaO(1 0 0) surface. The interaction of the oxide films with common components of motor-vehicle exhaust gases (CO 2, H 2O, NO x ) has been studied using surface analytical techniques, including X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) and reflection IR spectroscopy (RAIRS). The spectroscopic identification of Ba(OH) 2, BaCO 3 and Ba(NO 2) 2 phases is discussed, and the relative stabilities and decomposition mechanisms of these materials when supported on Cu(1 1 1) is revealed by a combination of TPD and XPS. BaO is shown to be resistant to reaction with pure NO and NO/O 2 mixtures, but exposure to NO 2 leads to the rapid formation of barium nitrite. The formation of the nitrite is proposed to be the first-step in the production of barium nitrate, which has previously been shown to be the main phase involved in NO x storage and reduction (NSR) catalysis.

In situ FTIR studies of the mechanism of NO x storage and reduction on Pt/Ba/Al 2O 3 catalysts

The mechanism of NO x adsorption and reaction on a typical 1 wt.% Pt/20 wt.% BaO/Al 2O 3 NO x storage reduction (NSR) catalyst was studied by the use of in situ Fourier Transform InfraRed (FTIR) spectroscopy. Parallel studies were also conducted with the individual components of the NSR system (i.e., 1 wt.% Pt/Al 2O 3 and 20 wt.% BaO/Al 2O 3) in an effort to identify the role and importance of each component in the NSR process. Finally, the role of SO 2 was also investigated, since it has been reported that it represents a poison for the NSR process. The results indicate that at 350 °C NO x is stored on the NSR catalyst primarily in the form of barium nitrite and nitrate species. In the presence of Pt a conversion of the surface barium nitrite to bulk barium nitrate is taking place during the storage phase. This step is accelerated in the presence of gas phase oxygen and at elevated temperatures. Both barium nitrite and nitrate species are reduced in the presence of propylene, although at different rates. These reactions are catalyzed by Pt and do not proceed at any significant rate over the BaO/Al 2O 3 sample. Finally, the formation of surface and bulk barium sulfates was observed when SO 2 was introduced as a component of the NO-containing gas phase mixture. These species are stable on the catalyst surface under the reduction conditions studied and inhibit the NO x storage process.

Role of Support in Lean DeNOxCatalysis

FTIR and pulse thermal analysis were applied to investigate catalysts containing Pt (1 wt%)/Ba (17 wt%) supported on γ−Al2O3, SiO2 and ZrO2. The aim was to learn how the support material affects the thermal stability of barium carbonate and its activity in the reaction to bulk Ba(NO3)2. The lower thermal stability of BaCO3 in alumina supported samples was found to influence the formation of barium nitrate during the NOx storage process. Quantification of Ba(NO3)2 formed during NOx storage indicated that for alumina supported catalysts only ca. 30% of barium present in the sample is involved in the storage process. The low thermal stability found for alumina supported barium nitrite excludes its role in the formation of barium nitrate during interaction of NOx with the catalyst at 300 °C. The studies indicate that γ-Al2O3 plays a major role in influencing the thermal stability of BaCO3 and Ba(NO3)2. This finding seems to be relevant for the higher activity of γ-Al2O3-supported catalysts in NOx storage reduction reactions.

Characterization of the Surface of Ba(NO3) 2 Powder by XPS

This work reports survey and core level x-ray photoemission spectra obtained from the surface of a barium nitrate powder. The high purity (99.999%) barium nitrate specimen was commercially obtained from Alfa/AESARS. The XPS spectra were measured with a Kratos Axis 165 instrument using monochromatic Al Kα radiation. The survey spectrum was measured with an 80 eV pass energy and the core level spectra (Ba 3d, N 1s, O 1s, and C 1s) were acquired using a 20 eV pass energy corresponding to analyzer resolutions of 1.12 and 0.28 eV, respectively. The data are consistent with the surface being composed of primarily barium nitrate with a small contribution from barium nitrite. Carbon was the only contaminant species observed.

X-ray photoelectron spectroscopy/Fourier transform infrared spectroscopy study of the interaction of YBa2Cu3Ox with CO, NO, and H2+CO

The direct interaction of YBa2Cu3Ox (x=6–7) with CO, H2+CO, and NO is studied using x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and simultaneous thermal analysis. The CO interaction results in the release of CO2 at 400–800 K, and the formation of BaCO3, as well as the reduction of Cu(II) and Y(III), at temperatures above 800 K. The interaction between YBa2Cu3Ox and H2+CO results mainly in the formation of gaseous CO2 and H2O at temperatures below 830 K. At temperatures around 830 K, Cu(II) is reduced to Cu(I). In addition to barium carbonate, the methoxy group as well as the hydroxyl group can be identified on the YBa2Cu3Ox sample. At 1170 K carbides can be found on the sample surface. The NO interaction occurs at room temperature and above, leading to the release of N2, NO2, and N2O, as well as the formation of the nitride, nitrate, nitrite (NO−2), and nitrito (–ONO) groups. The nitride and nitrate species are mainly observed between 300 and 540 K, while at 830–920 K, barium nitrite is the predominant nitrogen-containing species on the surface. An active center (OBa⧠CuO) and mechanisms for the interaction between YBa2Cu3Ox and the gases are postulated and applied to explain the high catalytic activity of YBa2Cu3Ox.

XPS/FTIR study of the interaction between nitric oxide and yttrium barium copper oxide (YBa2Cu3O7)

The combination of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and simultaneous thermal analysis (STA) studies has shown that the interaction between NO and YBa[sub 2]Cu[sub 3]O[sub 7] occurs at room temperature and above, resulting in the formation of the nitride, nitrate, nitrite (NO[sub 2][sup [minus]]), and nitrito (-ONO) groups, as well as in the release of N[sub 2], NO[sub 2], and N[sub 2]O. The nitride species are observed at temperatures between 300 and 540 K but not at higher temperatures. The nitrate ion is the predominant nitrogen-containing species at temperatures below 540 K, and its concentration decays at elevated temperatures (>820 K). The nitrito group can be found at room temperature as well as elevated temperatures. The nitrite ion is observed with relatively low concentrations at lower temperatures but becomes the predominant nitrogen-containing species at high temperatures. The maximum increase in the sample weight ([approximately]7%) as measured by thermogravimetry (TG) corresponds to a net uptake of a NO[sub 2] group (or an NO molecule plus an O atom) per unit cell of YBa[sub 2]Cu[sub 3]O[sub 7]. The NO interaction also results in the oxidation of a small portion (<24%) of the lattice Cu(II) ions and, to amore » lesser extent, the oxidation of the lattice barium atoms. At 830-920 K the surface segregation of the barium atoms is evident and is thought to be indicative of the matrix degradation due to the formation of barium nitrite. A detailed mechanism of the interaction between YBa[sub 2]Cu[sub 3]O[sub 7] and NO is postulated and applied to explain the high catalytic activity for the selective reduction of NO on YBa[sub 2]Cu[sub 3]O[sub 7].« less

Phase relation and dehydration behavior of barium nitrite hydrates

The phase relation and the dehydration behavior of barium nitrite hydrates have been examined by DTA under various external pressures, and by TG-DTA in air. The equilibrium water vapor pressures of the mono-, hemi-, and 1 3 -hydrates have been measured. The temperatures of III-II and II-I phase transitions and melting point of the anhydrate are 469, 497 and 542 K, respectively. The dehydration in the atmosphere proceeds as follows ▪

Crystal structure of barium nitrite, Ba (NO2 )2

Crystal structure of barium nitrite, Ba (NO2 )2

Raman spectroscopic results for order–disorder transitions of K2Ba(NO2)4

AbstractThe temperature dependence of internal NO2 modes has been investigated by polarized Raman scattering from potassium barium nitrite single crystals. The frequencies of the symmetric stretching and bending modes are determined for the three non‐equivalent NO2 sites present at room temperature. The structural implications associated with the phase transition at about 200 K are derived from line splittings and relative intensities. The experimental results are consistent with an order–disorder transition and no soft lattice mode has been found.

Crystal structure of barium nitrite, Ba(NO2)2

Abstract Single crystals of slightly hygroscopic barium nitrite Ba(NO2)2 were prepared by thermal decomposition of barium nitrite monohydrate and subsequent recrystallization in a solution of methanol and p-xylene. The compound crystallizes in the orthorhombic space group P212121 with a = 7.6331(16) Å, b = 8.3671(36) Å, c = 6.7336(8) Å and Z = 4. The structure was determined from X-ray intensities measured on a four-circle diffractometer and refined to R = 0.035 and wR = 0.048. The barium atoms exhibit an elevenfold coordination made up by nine oxygen atoms within distances ranging from 2.776(6) Å to 3.010(6) Å and two nitrogen atoms within distances of 3.059(7) Å and 3.125(7) Å. Values for the O – Ba – O angles range from 41.5(2)° to 151.1(2)°. The N – O distances are in the range 1.236(9) to 1.265(8) Å.

Phase transition at 211 K in crystalline barium nitrite hemihydrate

A phase transition has been observed at 211 K in crystalline barium nitrite hemihydrate by DTA and dielectric measurements. A dielectric relaxation phenomenon was also found and the activation energies governing the relaxation were determined to be 23 kJ mol −1 and 41 kJ mol −1 below and above the transition temperature, respectively. Some discussions have been made on the nature of the phase transition.

Fluorescence and phosphorescence spectra of pure and doped single crystals of barium nitrite monohydrate

Fluorescence and phosphorescence spectra of single crystals of Ba(NO 2) 2·H 2O were studied at 4.2 K. The spectra are dominated by two series of narrow zero-phonon lines accompanied by a number of sub-series in the phonon sidebands, one of which has been assigned to Na +-induced singlet-exciton traps.

Polarized Raman spectra of an oriented single crystal of barium nitrite monohydrate

The symmetries of the observed Raman lines in the 4000–30 cm−1 region in different orientations of a single crystal of Ba(NO2)2•H2O have been determined and the spectra have been analysed in terms of the phonons originating from the internal modes of the NO2− and H2O groups and the external lattice modes. The longitudinal-optical and transverse-optical (LO–TO) splittings arising from the Coulomb forces in the crystal arc reported for the first time.