Effect of Calcination Temperature on La-Modified Al2O3 Catalysts for Vapor Phase Hydrofluorination of Acetylene to Vinyl Fluoride

A La-modified Al₂O₃ catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH₃-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 oC exhibited the highest conversion of acetylene (94.6%) and highest selectivity to vinyl fluoride (83.4%) and lower coke deposition selectivity (0.72%). The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.     

Influence of Thermal Treatments on In-depth Compositional Uniformity of CuIn(S,Se)2 Thin Films

CuIn(S,Se)₂ thin films were prepared by thermal crystallization of co-sputtered Cu-In alloy precursors in S/Se atmosphere. In-depth compositional uniformity is an important prereq-uisite for obtaining device-quality CuIn(S,Se)₂ absorber thin films. In order to figure out the influence of heat treatments on in-depth composition uniformity of CuIn(S,Se)₂ thin films, two kinds of reaction temperature profiles were investigated. One process is "one step profile", referring to formation of CuIn(S,Se)₂ thin films just at elevated temperature (e.g. 500 oC). The other is "two step profile", which allows for slow diffusion of S and Se elements into the alloy precursors at a low temperature before the formation and re-crystallization of CuIn(S,Se)₂ thin films at higher temperature (e.g. first 250 oC then 500 oC). X-ray diffrac-tion studies reveal that there is a discrepancy in the shape of (112) peak. Samples annealed with "one step profile" have splits on (112) peaks, while samples annealed with "two step profile" have relatively symmetrical (112) peaks. Grazing incident X-ray diffraction and en-ergy dispersive spectrum measurements of samples successively etched in bromine methanol show that CuIn(S,Se)₂ thin films have better in-depth composition uniformity after "twostep profile" annealing. The reaction mechanism during the two thermal processing was also investigated by X-ray diffraction and Raman spectra.     

Synthesis and Characterization of ZrO2-CaSO4 Materials Prepared by the Sol–Gel Method

Mixtures of ZrO₂-CaSO₄ in different molar ratio were prepared by the sol–gel method. The precursors were anhydrous calcium sulfate (CaSO₄) and zirconium n-butoxide in ethanol. Sulfuric acid was used as a hydrolysis catalyst to carry out the reaction at pH 3. The samples were thermally annealed and characterized by X-ray powder diffraction (XRD). Crystalline structure for selected samples (100, 90, 80% molar ZrO₂), were refined by the Rietveld method. Tetragonal zirconia and anhydrite were obtained in all compositions ranges, from 400 up to 800°C, although baddeyelite appears in the zirconia rich end (98% molar) from 600°C. Towards high calcium content, different nanostructured calcium sulfates as gypsum, bassanite and anhydrite were obtained.     

Enhancement on the structural,functional, optical and morphological properties of temperature treated silver sulfide nanostructures

The Silver Sulfide (Ag₂S) nanostructures were synthesized via the facile co-precipitation method. Thorough study and analysis were carried out to reveal and compare the structural, optical, functional, and morphological characteristics of as-synthesized samples annealed at various temperatures. The XRD analysis characterized the structural properties of Ag₂S nanoparticles, which unveiled the excellent crystallinity and monoclinic structure. The as-synthesized samples show an average crystallite size of 52 nm–41.7 nm. The modes of vibration and peak position of metal sulfides in Ag₂S nanoparticles were investigated through the FTIR technique. The optical attributes of prepared samples were scrutinized using UV–Vis analysis, which portrays the cut-off wavelength in the range of 1192–1223 nm for non-annealed and annealed Ag₂S nanoparticles, alongside the optical band gap is about 0.86 eV–0.96 eV. This work elucidates a novel approach to synthesis and scrutinises the characteristics of Ag₂S nanoparticles by subjecting them to distinct annealing temperatures precisely, as-prepared, 200 °C and 400 °C.     

Influence of thermal annealing on the microstructure,hardness and corrosion behavior of TiAlSiCuN nanocomposite films

Nanocomposite TiAlSiCuN films were deposited on high speed steels by filtered magnetic arc ion plating. Detailed properties of the films annealed at various temperatures are studied. After thermal annealing at different temperatures ranging from 400 to 800 °C, changes in the film micro‐structure, chemical and phase composition, surface morphology, hardness and polarization curve properties were systematically characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, nano‐indenter and electrochemical workstation, respectively. It was found that the TiAlSiCuN films could be fully oxidized at 800 °C, Al and Ti atoms all diffused outwards and formed dense protective Al₂O₃ and TiO₂ layer. Simultaneously, the TiAlN phase gradually disappeared. The films annealed at 400 °C obtained the highest hardness because of the certain grain growth and little generated oxides. Besides, the certain formation of dense protective Al₂O₃ layer made the TiAlSiCuN film annealed at 600 °C present the least corrosion current density and the corrosion voltage. Copyright © 2016 John Wiley & Sons, Ltd.     

Sol-gel synthesis of mesoporous CaCu3Ti4O12 thin films and their gas sensing response

A new sol-gel synthesis procedure of stable calcium copper titanate (CaCu₃Ti₄O₁₂—CCTO) precursor sols for the fabrication of porous films was developed. The composition of the sol was selected in order to avoid the precipitation of undesired phases; ethanol was used as solvent, acetic acid as modifier and poly(ethyleneglycol) as a linker agent. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 °C. The main phase present in the samples, as detected by X-ray diffraction and Raman spectroscopy, was CaCu₃Ti₄O₁₂. Scanning electron microscopy analysis showed that mesoporous structures, with thicknesses between 200 and 400 nm, were developed as a result of the processing conditions. The films were tested regarding their sensibility towards oxygen and nitrogen at atmospheric pressure using working temperatures from 200 to 290 °C. The samples exhibited n-type conductivity, high sensitivity and short response times. These characteristics indicate that CCTO mesoporous structures obtained by sol-gel are suitable for application in gas sensing.     

以尿素为氮源制备氮改性二氧化钛及其改性机理

以钛酸丁酯为前驱体,以尿素为氮源,采用改进溶胶-凝胶法制备了不同N含量的改性TiO2光催化剂(N-TiO2).以重铬酸钾为目标污染物,以甲酸为空穴捕获剂,评价了可见光下该催化剂的催化还原活性.结果表明,N-TiO2催化剂活性明显高于未改性催化剂,当催化剂中N/Ti摩尔比为10%、焙烧温度为400℃时,其光催化还原活性最...     

Preparation and Characterization of Storage and Emission Functional Material of Cs2O-doped 12CaO·7Al2O3

We provides a novel approach to generate low-temperature atomic oxygen anions (O^-) emis-sion using the cesium oxide-doped 12CaO·7Al₂O₃ (Cs₂O-doped C12A7). The maximal emis-sion intensity of O^- from the Cs₂O-doped C12A7 at 700 oC and 800 V/cm reached about 0.54 μA/cm², which was about two times as strong as that from the un-doped C12A7(0.23 μA/cm²) under the same condition. The initiative temperature of the O^- emission from the Cs₂O-doped C12A7 was about 500 oC, which was also much lower than the initiative temperature from the un-doped C12A7 (570 oC) in the given field of 800 V/cm. High pure O^- emission close to 100% could be obtained from the Cs₂O-doped C12A7 under the lower temperature (<550oC). The emission features of the Cs₂-doped C12A7, including the emis-sion distribution, temperature effect, and emission branching ratio have been investigated in detail and compared with the un-doped C12A7. The structure and storage characteristics of the resulting material were also investigated via X-ray diffraction and electron paramag-netic resonance. It was found that doping Cs₂ to C12A7 will lower the initiative emission temperature and enhance the emission intensity.     

Analytical method for atmospheric tritium with a portable tritium sampling system

A portable tritium sampler was developed for the stepwise collections of water vapour (HTO), hydrogen (HT) and hydrocarbons (CH₃T) in the atmosphere. First, water vapour was collected in an electronic cooler and an HTO collection column containing 400 g of molecular sieve. Next, dried air was introduced into an HT collection column containing 150 g of palladium catalyst. Hydrogen was then converted to water by catalytic oxidation at room temperature and the resultant water was immediately adsorbed on the molecular sieve bed supporting the catalyst. The remaining gas was finally introduced into a CH₃T collection column containing 100 g of molecular sieve through a platinum catalyst column, in which hydrocarbons were burnt at 400°C. The resultant water was adsorbed in the CH₃T collection column. The collection efficiencies of water in the HTO, HT and CH₃T collection columns were all estimated to be nearly 100%. This newly developed method was found to be useful for the routine tritium monitoring by applying it to actual air samples.     

硝酸水热处理活性炭对其负载的Ba-Ru-K氨合成催化剂性能的影响

采用N2物理吸附、Boehm滴定、He-TPD-MS、CO化学吸附和透射电镜等手段考察了硝酸水热处理对活性炭(AC)及其负载的Ru基催化剂的孔结构、表面含氧基团、Ru分散度的影响,并评价了Ba-Ru-K/AC催化剂氨合成反应性能.结果表明,经硝酸水热处理后,AC表面含氧基团明显增多,但其孔结构变化不大.随着水热处理硝酸浓度的增加,AC表面含氧基团的数量增加,而相应催化剂的Ru分散度有所降低,Ru粒子尺寸增大.当硝酸浓度为2.0mol/L时,Ru分散度较高,且粒子尺寸(2.0nm)适宜,分散均匀,因此催化剂活性较高.在10MPa和10000h1条件下,400和375oC时,出口氨浓度分别达到17.80%和11.10%,较4.6mol/L硝酸回流处理AC负载的Ru基催化剂分别提高了16.8%和21.3%.水热处理AC的适宜条件为硝酸浓度2.0mol/L,150oC处理4h,填充度为70%.因此,通过调节水热处理时所用硝酸浓度可有效调控AC表面含氧基团的数量及其负载Ru的粒子尺寸.     

Photoluminescence of new Tb3+-intercalated octosilicates depending on phase transition caused by annealing

A new Tb³⁺-intercalated layered octosilicate (Tb-Oct) was prepared through protonation, exfoliation and intercalation processing. Photoluminescence of the Tb-Oct silicates dependant of phase transition has been investigated in detail. The emissions attributed to ⁵D₄-⁷F_J (J = 3, 4, 5, 6) transition of Tb³⁺were observed from the emission spectra of the as-prepared Tb-Oct silicates. After the as-prepared Tb-Oct silicates thermal treatment at 200 °C, all diffraction peaks disappeared, suggesting the collapse of layered structure. With the increase in the annealing temperature from 200 to 1000 °C, no diffraction peaks appeared in all the annealed samples. Photoluminescence spectra show that the green emission ascribed to ⁵D₄-⁷F₅ transition of Tb³⁺ markedly increased as the sample was annealed at 800 °C. However, this green emission disappeared while the sample was annealed at 400, 600, and 1000 °C, which may relate to actual surroundings of Tb³⁺ ions. That is, the amorphous phase formed at 800 °C is more favorable for the green emission of Tb³⁺.     

生物质焦油组分甲苯在镍/凹凸棒石上的二氧化碳催化重整

 以大比表面积的天然纳米矿物材料凹凸棒石 (PG) 为载体, 采用等体积浸渍法制备了 Ni/PG 催化剂. 运用 X 射线衍射、透射电镜和 CO₂ 程序升温脱附对 Ni/PG 催化剂进行了表征, 并用于以甲苯为生物质焦油模型化合物的 CO₂ 催化重整反应. 考察了反应温度、CO₂ 浓度以及催化剂中 Ni 负载量对甲苯与 CO₂ 重整性能的影响. 结果表明, 吸附在催化剂表面的 CO₂ 存在三个脱附峰, 其中高温脱附 CO₂ 与反应密切相关; 随着 CO₂ 浓度、Ni 负载量和反应温度的增加, 甲苯转化率和 H₂ 产率升高. 在 800 ^oC, CO₂/PhCH₃ 摩尔比为 0.2~0.26 时, 甲苯转化率达最高; 而在 CO₂/PhCH₃ 摩尔比为 0.2 时, H₂ 产率最高. 催化剂上积炭量随 CO₂ 浓度的增加和反应温度的升高而显著降低.     

Excess of nio loading - key for catalyst activity decline prevention

Summary The activity of co-precipitated NiO-Al₂O₃ catalyst for partial oxidation of methane in a steel flow reactor was investigated. The catalyst samples loaded with 5, 10 and 20 wt.% nickel before use were thermally treated at 400, 700 and 1100^oC. The feed gas for catalytic oxidation was prepared by dilution of natural gas with air, and had approximately the following volume composition: CH₄: O₂: N₂ = 5: 2: 8. The reaction was carried out over 100 mg unreduced NiO-Al₂O₃ catalyst at gas flow rate of 50 cm³/min at 650^oC and atmospheric pressure. The catalyst activity with 5 and 10 wt.% of nickel was very similar, decreasing with enhance of previous heat treatment. Further nickel loading did not increase significantly the catalyst activity compared to low level nickel samples. However, high nickel content has a levelling effect on catalyst activity, suppressing the undesired effect of previous heat treatment at high temperature     

Photocatalytic Activity for Water Decomposition to Hydrogen over Nitrogen‐doped TiO2 Nanoparticle

Nitrogen-doped TiO2 nanoparticle photocatalysts were obtained by an annealing method with gaseous ammonia and nitrogen. The influence of dopant N on the crystal structure was characterized by XRD, XPS, BET, TEM and UV-Vis spectra. The results of XRD indicate that, the crystal phase transforms from anatase to rutile structure gradually with increase of annealing temperature from 300 to 700 ℃. XPS studies indicate that the nitrogen atom enters the TiO2 lattice and occupies the position of oxygen atom. Agglomeration of particles is found in TEM images after annealing. BET results show that the specific surface areas of N-doped samples from 44.61 to 38.27 m2/g are smaller than that of Degussa TiO2. UV-Vis spectra indicate that the absorption threshold shifts gradually with increase of annealing temperature, which shows absorption in the visible region. The influence of annealing condition on the photocatalytic property has been researched over water decomposition to hydrogen, indicating that nitrogen raises the photocatalytic activity for hydrogen evolution, and the modified TiO2 annealed for 2 h at 400 ℃ under gas of NH3/N2 (V/V＝1/2) mixture shows better efficiency of hydrogen evolution. Furthermore, the N-doped TiO2 nanoparticle catalysts have obvious visible light activity, evidenced by hydrogen evolution under visible light (λ＞400 nm) irradiation. However, the catalytic activity under visible light irradiation is absent for Degussa as reference and the N-doped TiO2 annealed at 700 ℃.     

基于纤维素的固体酸催化剂的制备及其催化高酸值废油脂生产生物柴油

以廉价的纤维素为原料,经不完全炭化和磺化制得含高密度(1.69 mmol/g) SO3H基团的固体酸催化剂Cellulose-SO3H.结果表明,该催化剂适宜的制备条件为:在400℃炭化15h,再在150℃磺化15h.所得催化剂在油酸与甲醇的酯化反应中表现出明显高于其它几种典型固体酸催化剂(铌酸,Amberlyst- ...     

The effect of annealing temperatures on surface properties,hydroxyapatite growth and cell behaviors of TiO2 nanotubes

Well‐ordered TiO₂ nanotubes were prepared by the electrochemical anodization of titanium in an ethylene glycol electrolyte containing 1 wt% NH₄F and 10 wt% H₂O at 20 V for 20 min, followed by annealing. The surface morphology and crystal structure of the samples were examined as a function of the annealing temperature by field emission scanning electron microscopy (FE‐SEM) and X‐ray diffraction (XRD), respectively. Crystallization of the nanotubes to the anatase phase occurred at 450 °C, while rutile formation was observed at 600 °C. Disintegration of the nanotubes was observed at 600 °C and the structure vanished completely at 750 °C. Electrochemical corrosion studies showed that the annealed nanotubes exhibited higher corrosion resistance than the as‐formed nanotubes. The growth of hydroxyapatite on the different TiO₂ nanotubes was also investigated by soaking them in simulated body fluid (SBF). The results indicated that the tubes annealed to a mixture of anatase and rutile was clearly more efficient than that in their amorphous or plain anatase state. The in vitro cell response in terms of cell morphology and proliferation was evaluated using osteoblast cells. The highest cell activity was observed on the TiO₂ nanotubes annealed at 600 °C. Copyright © 2010 John Wiley & Sons, Ltd.     

Ag-catalyzed Synthesis of Tb(BO2)3 Nanorods

Well-crystallized with excellent luminescent properties, Tb(BO₂)₃ nanorods were first suc-cessfully synthesized by a simple solid-state method with Ag as catalyst. The result of X-ray diffraction showed that the Tb(BO₂)₃ nanorods could be well-crystallized at 700 oC. As-prepared straight nanorods of Tb(BO₂)₃ had the typical diameters in the range of 100-200 nm, the thickness of 30-50 nm and the lengths up to 3 μm by transmission elec-tron microscopy and the corresponding selected area electron diffraction indicated that the nanorod calcined at 700 oC was single-crystalline. Based on the fact that Ag nanoparti-cles attached to the tips and middles of the Tb(BO₂)₃ nanorods, a growth model of the Tb(BO₂)₃ nanorods was proposed. Photoluminescence spectra under excitation at 369 nm showed that these Tb(BO₂)₃ phosphors had a green emission at 546 nm, which is ascribed to ⁵D₄→⁷F₅ transition. The effect of calcining temperature on the structures, morphologies, and luminescent properties of Tb(BO₂)₃ phosphors were studied.     

Activity and selectivity of manganese oxides in alcohols Conversion as influenced by gamma-irradiation

Manganese oxide samples obtained from thermal decomposition of manganese carbonate at 400 and 600 °C were subjected to different doses of g-irradiation within the range 0.2 to 1.6 MGy. The surface and catalytic properties of the above samples were studied using nitrogen adsorption isotherms measured at -196 °C and catalytic conversion of ethanol and isopropanol at 300-400 °C using micropulse technique. The results obtained revealed that manganese oxides obtained at 400 °C consisted of a mixture of Mn₂O₃ and MnO₂ while the samples calcined at 600 °C composed entirely of Mn₂O₃. Gamma-irradiation resulted in a decrease in the particle size of manganese oxide phases with subsequent increase in their specific surface areas. Gamma-irradiation with 0.2 and 0.8 MGy effected a measurable progressive decrease in the catalytic activity in dehydration and dehydrogenation of both alcohols. However, the treated catalyst retained their initial activity upon exposure to a dose of 1.6 MGy. Also, g-irradiation increased the selectivities of the investigated solids towards dehydrogenation of both alcohols. The catalyst samples precalcined at 600 °C exhibited higher catalytic activities than those precalcined at 400 °C.     

Order-to-disorder phase transformation in ion irradiated uranium-bearing delta-phase oxides RE6U1O12 (RE=Y, Gd, Ho, Yb, and Lu)

Polycrystalline uranium-bearing compounds Y₆U₁O₁₂, Gd₆U₁O₁₂, Ho₆U₁O₁₂, Yb₆U₁O₁₂, and Lu₆U₁O₁₂ samples were irradiated with various ions species (300 keV Kr⁺⁺, 400 keV Ne⁺⁺, and 100 keV He⁺) at cryogenic temperature (∼100 K), and the microstructures were examined following irradiation using grazing incidence X-ray diffraction and transmission electron microscopy. The pristine samples are characterized by an ordered, fluorite derivative structure, known as the delta phase. This structure possesses rhombohedral symmetry. Amorphization was not observed in any of the irradiated samples, even at the highest dose ∼65 dpa (displacement per atom). On the other hand, some of these compounds experienced an order-to-disorder (O-D) phase transformation, from an ordered rhombohedral to a disordered fluorite structure, at ion doses between 2.5 and 65 dpa, depending on ion irradiation species. Factors influencing the irradiation-induced O-D transformation tendencies of these compounds are discussed in terms of density functional theory calculations of the O-D transformation energies.     

电沉积-退火工艺制备铜铟硒太阳能电池薄膜及表征

CuInSe₂ (CIS) films with good crystalline quality were synthesized by electrodeposition followed by annealing in Se vapor at 530 oC. The morphology, composition, crystal structure, optical and electrical properties of the CIS films were investigated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, UV-VIS-NIR spectroscopy, and admittance spectroscopy. The results revealed that the annealed CIS films had chalcopyrite structure and consisted of relatively large grains in the range of 500-1000 nm and single grain of films extend usually through the whole film thickness. The band gap of CIS films was 0.98 eV and carrier concentration was in the order of 10¹⁶ cm^-3 after etching the Cu-Se compounds on the film surface. Solar cells with the structure of AZO/i-ZnO/CdS/CIS/Mo/glass were fabricated. Current density vs. voltage test under standard reported condition showed the solar cells with an area of 0.2 cm² had a conversion efficiency of 0.96%. The underlying physics was also discussed.