苯甲酸钡的热分解机理

碱土金属苯甲酸盐是一类比较稳定的化合物,对其已有的报道主要涉及含结晶水碱土金属苯甲酸盐的红外光谱和热分解过程,这些热分解仅涉及失水过程和固体残留物的分析［１～３］。我们首次用半固相法合成了苯甲酸钡,并对无水苯甲酸钡在氮气中热分解的气相凝聚物进行了分析...     

Thermal,structural and optical properties of Al2CoO4-Crocoite composite nanoparticles used as pigments

Novel zinc(II) complex compounds of general formula Zn(C₆H₅COO)₂·L₂ (where L=caffeine (caf) and urea (u)) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied during heating in air by thermogravimetry. It was found that the thermal decomposition of the anhydrous Zn(II) benzoate compounds with bioactive ligands was initiated by the release of organic ligands at various temperatures. On further heating of the compounds up to 400°C the thermal degradation of the benzoate anions took place. Zinc oxide was found as the final product of the thermal decomposition of all zinc(II) benzoate complex compounds heated to 600°C. Results of elemental analysis, infrared spectroscopy, mass spectroscopy and thermogravimetry are presented.     

Characterization and Activity of MnO/γ‐Al2O3 for Hydrogenation of Methyl Benzoate to Benzaldehyde

The activities of a MnO/γ‐Al₂O₃ catalyst for the selective reduction of methyl benzoate to benzaldehyde have been studied in a continuous flow reactor. Characterization of the catalyst has been conducted by XRD, XPS, NH₃‐TPD and TPD‐IR. XRD and XPS results revealed that the steady state catalyst is mainly MnO₂/γ‐AlO₃ before reduction and MnO/γ‐Al₂O₃ after reduction. Monolayer dispersion capacity obtained by XPS method is about w (Mn)11.3% TPD‐IR results revealed that there are only L acidic centers on the catalytic surface. NH₃‐TPD determinations have verified that the catalyst with a certain number of moderate strength acidic sites is advantageous to hydrogenation of methyl benzoate to benzaldehyde.     

Variable denticity in carboxylate binding to the uranyl coordination complexes

Tris-carboxylate complexes of uranyl [UO₂]²⁺ with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transform ion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetato uranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of symmetric and antisymmetric −CO₂ stretches of the monodentate and bidentate acetate, CH₃ bending and umbrella vibrations, and a uranyl O—U—O asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the predominant conformer of the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate and two bidentate benzoate ligands.     

A thermal analysis evaluation of the low temperature synthesis of BaBiO3

Thermal decomposition of metal-organic precursors for the mixed oxide BaBiO₃ was studied using TG and EGA. Precursors produced by polyesterification of bifunctional acids with ethylene glycol (Pechini process) decomposed about 100°C higher than those without the diol. BaCO₃ was identified by IR and XRD as a reaction intermediate. EGA proved that the amount of BaCO₃ was below 10% of the total barium, and that the barium exists mainly as a nitro-compound up to 650°C. Phase-pure BaBiO₃ with a moderately high surface area (1.4 m²/g) could be synthesised from a citrate precursor by the Pechini process at around 850°C.     

Synthesis and study of compounds of the general formula MIITh(VO4)2 (MII = Mn, Cd, Ca, Sr, Pb, or Ba)

Double vanadates of thorium and bivalent metals with r(M^II) ?? 0.96 ? were prepared by high-temperature solid-phase reactions. Manganese and barium derivatives were obtained for the first time. The compounds crystallize in three structural types: zircon for manganese, cadmium, calcium, strontium, and lead derivatives; scheelite for the lead phase; and monazite for the compounds containing lead and barium. Thus, two morphotropic transitions are observed in the series of the compounds studied; and for double thorium vanadates of lead, strontium, and barium, phase transitions are observed. The bands in the IR spectra were assigned. The incongruent melting points of the compounds were determined by differential scanning calorimetry. Compounds ??-PbTh(VO₄)₂ and BaTh(VO₄)₂ were studied by high-temperature X-ray diffraction.     

Synthesis and investigation of barium titanate nanoparticles covered with silica shell

Matrix isolation of ferroelectric BaTiO₃ nanoparticles was executed by formation of protective silica shell (via hydrolysis and polycondensation of tetraethyl orthosilicate) on particles of precursor—barium titanyl oxalate. Synthesized BaTiO₃–SiO₂ composites have been characterized by IR spectroscopy, XRD, TEM, DTA/DTG methods.     

Role of Tin Difluoride and Gallium Trifluoride in Glass Formation in SnF2–GaF3–BaF2

The structure of glasses in SnF₂–GaF₃ and SnF₂–GaF₃–BaF₂ systems was investigated by IR spectroscopy. It is shown that the glass structure in systems of this type is formed by two glass-forming agents: gallium trifluoride and tin difluoride. The introduction of 5 mole % barium difluoride shifts the edge of the absorption band to the low-frequency region.     

2，4，6-三硝基间苯二酚钡一水化合物的热分解动力学(英)

0IntroductionBarium2,4,6鄄trinitroresorecinatemonohydrate,Ba(TNR)·H2O,hasgooddetonatingpropertiesandissensitivetoflame.Itcanbeusedasinitiatingagent,igniterpowderordelaypowder.Itspreparation[1],pro鄄perties[1],crystalstructure[1]andthermalbehavior[2]haveb…     

Synthesis and properties of molybdenum tellurite glasses of the BaCl<Subscript>2</Subscript>-MoO<Subscript>3</Subscript>-TeO<Subscript>2</Subscript> system

Molybdenum tellurite glasses of the BaCl₂-MoO₃-TeO₂ system have been synthesized. The effect of barium chloride on the density and spectral properties of the glasses has been studied using the pycnometer method and IR spectroscopy, respectively.     

Synthesis and study of Li<Subscript>3</Subscript>BaSrR<Subscript>3</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>8</Subscript> compounds (R = La-Lu,Y) with stratified sheelite structure

Possibility of substituting barium ions with strontium ions in the stratified sheelite structure of Li₃Ba₂R₃(MoO₄)₈ (sp. gr. C2/c) was examined. The molybdates Li₃BaSrR₃(MoO₄)₈ were synthesized and studied by X-ray diffraction analysis, differential-thermal analysis, and IR spectroscopy.     

A Zn(II)-Coordination Polymer Formed by Benzoate and 3-Pyridinemethanol Ligands: Synthesis,Spectroscopic Properties,Crystal Structure and Kinetics of Thermal Decomposition

The complex catena-poly[bis(benzoato-O)-bis(3-pyridinemethanol-N,O)-zinc(II)], [Zn(benz)₂(3-pymeth)₂] _n was prepared and characterised by elemental analysis, IR spectroscopy, thermal analysis and an X-ray structure determination. Zinc is octahedrally coordinated. Two coordination sites are occupied by oxygen atoms of two monodentate benzoate groups, two by the nitrogen atoms of 3-pyridinemethanol, and two by methanolic oxygen atoms of 3-pyridinemethanol from neighbouring structural units. Due to the bridging 3-pyridinemethanol ligand, molecules of the complex are connected into infinite chains along the c axis. The bridging function is reflected in the IR spectrum by a very sharp absorption band due to the stretching vibration of the methanolic O–H group. Non-isothermal kinetics of the thermal decomposition were studied using the model-free isoconversional method. Based on isoconversional dependencies, a multi-step mechanism with parallel reactions was recognised for the decomposition of the complex.     

Regioselective tritiation of benzoic acid and its alkali metal salts. The action of benzoate ions

Benzoic acid, lithium benzoate, and sodium benzoate were tritiated with virtually 100% regioselectivity in the ortho-positions by the T-for-H exchange reaction with HTO in the presence of RhCl₃.3H₂O. The labeling of both alkali metal salts was favored by a factor of about 3 over that of benzoic acid. Methyl benzoate was essentially inactive in the present reaction.     

苯甲酸钐的水热合成和热分解反应机理

用水热法合成了无水苯甲酸钐配合物,经元素分析、IR和X射线粉末衍射表征了该配合物,系层状结构,属单斜晶系。用TG、DTA、IR、色谱-质谱联用仪研究了它的热分解机理。在氮气氛下,热分解分两步进行:第一步分解生成钐的二碳酸一氧盐和有机化合物。生成的有机化合物成分比较复杂,主要成分为苯甲酸、二苯甲酮、9,10-蒽醌和1,3-二苯基异苯并呋喃等。第二步二碳酸一氧盐进一步分解生成氧化钐和二氧化碳。     

State of various stereoregulating electron-donating compounds in titanium-magnesium catalysts for propylene polymerization: A diffuse reflectance IR spectroscopic study

Propylene polymerization on TiCl₄/donor/MgCl₂ (donor = ethyl benzoate, dibutyl phthalate, diisobutyl phthalate, diethyl 2,3-diisopropylsuccinate) supported catalysts is considered. The states of the donors in the catalysts have been investigated by diffuse reflectance IR spectroscopy. Data characterizing the distribution of the donors and the active component (TiCl₄) on the support surface have been obtained. Molecular weight distribution data for polypropylene are presented. The molecular weight distribution of polypropylene depends on the location of the donor and TiCl₄ molecules.     

Thermal Decomposition of Barium Dioxodiaquaperoxyoxalato Uranate(VI) Hydrate

Barium dioxodiaquaperoxyoxalatouranate was obtained by reaction of uranyl nitrate with oxalic acid and then hydrogen peroxide in the presence of barium ion. The complex was subjected to chemical analysis. The thermal decomposition behaviour of the complex was studied using TG, DTG and DTA techniques. The solid complex salt and the intermediate product of its thermal decomposition were characterized using IR absorption and X-ray diffraction spectra. Based on data from these physico-chemical investigations the structural formula of the complex was proposed as Ba[UO₂(O₂)(C₂O₄)(H₂O)₂]⋅H₂O. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of barium source on the characteristics of sol-precipitated BaTiO<Subscript>3</Subscript> powders and related ceramics

In order to obtain pure and fine BaTiO₃ powders with controlled morphology, sol-precipitation methods involving the use of titanium iso-propoxide and of two different barium sources, i.e. barium nitrate and barium acetate, were proposed in this work. The thermal behaviour of the synthesized gels and the X-ray diffraction data obtained for the oxide powders pointed out that, by using Ba(NO₃)₂ as barium source, the decomposition process was completed at lower temperature (750°C) and was accompanied by a more pronounced tendency to obtain a single phase BaTiO₃ composition, by comparison with the synthesis where barium acetate was used as raw material (1100°C). Scanning electron microscopy investigations emphasized the effect of the nature of barium source and synthesis conditions on the morphology of the oxide powders, as well as on the microstructure of the related ceramics.     

Darstellung,Kristallstruktur und schwingungsspektroskopische Untersuchung von Cs2Ba2(CO3)3

Preparation, Crystal Structure Determination, and Vibrational Spectroscopy on Cs₂Ba₂(CO₃)₃ A new alkali metal alkaline earth metal double carbonate, Cs₂Ba₂(CO₃)₃, was obtained by the reaction of cesium carbonate and barium oxalate in the solid state using elevated pressure (2.026GPa). It has been characterized by single X-ray diffraction: 1162 diffractometer data, space group I2₁3, a = 10.349(2) Å; Z = 4; R_w = 0.026. The internal vibrations of the carbonate group exhibit unusually pronounced splittings caused by crystal field effects. All vibrational absorptions in the IR spectrum as to be expected at the level of the factor group approximation have been observed at recording the IR spectrum at low temperatures (?196°C).     

Preparation of Barium Titanate Nanopowder through Thermal Decomposition of Peroxide Precursor and Its Formation Mechanism

H₂TiO₃ was dissolved in the mixture of hydrogen formed peroxide and ammonia under the pH range of 8–10 with a transparent yellow solution formed. When an equivalent mole of Ba²⁺ solution was added into the yellow solution, the precipitate produced was the peroxide precursor of barium titanate. The cubic nanopowder of barium titanate was obtained when the precipitate was washed, stoved, and then calcined at 600°C for 1 h. The peroxide precursor of barium titanate and barium titanate nanopowder prepared were characterized to be BaTi(H₂O₂)₂O₃ by TGA‐DTA, XRD, TEM, SEM, and XREDS. The peroxide precursor of barium titanate was determined to be BaTi(H₂O₂)₂O₃. The particle size of the barium titanate nanopowder, the calcined product of BaTi(H₂O₂)₂O₃, was in the range of 20–40 nm. A formation mechanism of the barium titanate nanopowder through thermal decomposition of its peroxide precursor was proposed and then validated.     

Synthesis and Characterization of Barium Amidoborane

Barium amidoborane was synthesized for the first time by the reaction of metal barium with ammonia borane. The compound was characterized by the methods of the solid-phase ¹¹B NMR and IR spectroscopy and elemental analysis. It was shown by simultaneous thermal analysis that hydrogen is the only volatile product of barium amidoborane decomposition in the temperature range 50–240°C.