Effects of surfactant/silica and silica/cerium ratios on the characteristics of mesoporous Ce-MCM-41

Using the surfactant CTMABr (cetyltrimethyl ammonium bromide) and cerium(IV) sulfate, mesoporous Ce-MCM-41 molecular sieves were produced under a hydrothermal condition with various surfactant/silica (surfactant/Si) and silica/cerium (Si/Ce) ratios. Changes to the structural traits caused by changing the molar ratios of both surfactant/Si and Si/Ce were investigated. XRD (X-ray diffraction), FT-IR (fourier transform infrared spectroscopy), and SEM (scanning electro microscopy) were used for the characterization of prepared mesoporous samples. Among the tested molar ratios, surfactant/Si ratio of 0.5 and 0.2 showed highest values of d_1 0 0 and intensity, respectively, for the Si-MCM-41. XRD analysis also identified a quintessential hexagonal structure of Ce-MCM-41 for the Si/Ce molar ratio higher than 40 (maintaining the surfactant/Si ratio at 0.2). When cerium content was increased to have the Si/Ce molar ratio of 20, the hexagonal structure of Ce-MCM-41 was collapsed due to the structural stress of substituted cerium. FT-IR results confirmed calcination of Ce-MCM-41 and the incorporation of Ce⁴⁺ ions of cerium sulfate into the silica surface with proper removal of the surfactant. Rod-like shape with rounded edges of the prepared Ce-MCM-41 samples was identified by SEM. These results suggest surfactant/Si ratio of 0.2 and Si/Ce ratio of 40 for the production of Ce-MCM-41 with the highest level of crystallinity.     

Characterization and synthesis of Ce-incorporated mesoporous molecular sieves under microwave irradiation condition

Ce-incorporated MCM-41 mesoporous molecular sieves (CeMCM-41) were synthesized by microwave irradiation method from sodium silicate and ammonium cerium (IV) nitrate precursors and using cetyltrimethyl ammonium bromide (CTAB) as template. The resulting samples were characterized by means of XRD, TEM, FT-IR, UV-Vis, XPS and N₂ physical adsorption, respectively. The effect of the Si/Ce molar ratio on the textural properties of CeMCM-41 was investigated. The results reveal that the CeMCM-41 was successfully synthesized. The resultant mesoporous materials have specific surface areas in the range of 602–1,216 m²/g and pore sizes in the range of ca. 2.6–2.9 nm. The structural properties are related to the amount of cerium incorporation. The surface area and pore volume of the resulting CeMCM-41 were gradually reduced as the cerium content in the sample increased, and the mesoporous ordering diminished.     

The effect of Al–O substitution for Si–N on the luminescence properties of YAG:Ce phosphor

The present paper describes the effect of various Si–N substitution degree on the crystal structure and optical properties of yellow YAG:Ce phosphor commonly used with combination of InGaN in white LEDs. It has been found that the course of silicon/nitrogen YAG:Ce garnet doping as well as formation of the liquid phase and its chemical composition controlled formation of the side phase besides YAG:Ce. Substitution of Al–O for Si–N chemical bonds according to the general formula Y_2.94Ce_0.06Al_(5?x)Si_xO_(12?x)N_x was confirmed by changes of the unit cell parameter and formation of the Si–N bonds as detected by FT-IR studies. Formation of the nitrogen ligand in cerium arrangement resulted in a red shift in emission spectrum of trivalent cerium if nominal x value was in the range of 0.2–0.3. Above x = 0.3 only decrease of emission intensity was observed because of the secondary phase precipitation but further solution of Si–N in YAG:Ce crystal lattice cannot be excluded.     

Pd/Ce-HMS介孔材料的结构和表面化学态

为了制备新型负载型Pd催化剂,采用合成后组装法和浸渍法室温合成了Pd/Ce-HMS介孔材料,产物用XRD、N2吸附、FTIR及XPS谱等手段进行表征。结果表明,Ce、Pd引入后六方介孔结构仍保持完好。产物的BET表面积为742.9 m2·g-1,孔容0.803 cm3·g-1,表面Pd、Ce物种主要以PdO2和CeO2形式存在。研究表明,Ce前驱体通过与孔表面富集的Si—OH基团作用而嵌入骨架或键合于孔表面,Pd担载时由于模板剂仍留在孔道中,因而没有造成孔道堵塞。     

Tailoring the properties of cerium doped zinc oxide/reduced graphene oxide composite: Characterization,photoluminescence study,antibacterial activity

Ce doped ZnO/rGO composite materials were prepared by a one-pot hydrothermal process without any surfactant. The size, crystallography and morphology of the composite were investigated in detail by X- ray diffraction (XRD) studies, Raman spectroscopy, scanning electron microscopic (SEM), transmission electron microscopic (TEM) studies, UV–Vis spectroscopic analysis and X-ray photoelectron spectroscopic (XPS) analysis. The XRD pattern substantiates the formation of Ce doped ZnO/rGO composite revealing the wurtzite structure of ZnO. The SEM micrograph illustrates flower-like morphology for ZnO/rGO composite which coalesced further after cerium incorporation. Additionally, TEM image illustrated that ZnO hexagons were disoriented from its flower structure in Ce/ZnO/rGO composite. The XPS spectra further reaffirm the formation of cerium doped ZnO/rGO composite. The photoluminescence (PL) spectra confirms that emission occurs in the UV and visible region and several active sub-levels were observed in visible region on deconvolution, due to the incorporation of cerium. Antibacterial activity towards B. subtills and V. harveyi affirmed that the incorporation of Ce in ZnO/rGO composite leads to an improved antibacterial activity.     

A mechanical and modelling study of magnetron sputtered cerium-titanium oxide film coatings on Si (100)

Ce/Ti mixed metal oxide thin films have well known optoelectrical properties amongst several other physio-chemical properties. Changes in the structural and mechanical properties of magnetron sputtered Ce/Ti oxide thin films on Si (100) wafers with different Ce:Ti ratios are investigated experimentally and by modelling. X-ray Photoemission Spectroscopy (XPS) and X-ray diffraction (XRD) confirm the primary phases as trigonal Ce₂O₃ and rutile form of TiO₂ with SiO₂ present in all prepared materials. FESEM imaging delivers information based on the variation of grain size, the mixed Ce/Ti oxides providing much smaller grain sizes in the thin film/substrate composite. Nanoindentation analysis concludes that the pure cerium oxide film has the highest hardness value (20.1?GPa), while the addition of excess titanium oxide decreases the hardness of the film coatings. High temperature in-situ XRD (up to 1000?°C) results indicate high thermal phase stability for all materials studied. The film with Ce:Ti?=?68%:32% has a new additional minor oxide phase above 800?°C. Contact angle experiments suggest that the chemical composition of the surface is insignificant affecting the water contact angle. Results show a narrow band of 87.7–95.7° contact angle. The finite element modelling (FEM) modelling of Ce/Ti thin film coatings based on Si(100); Si(110); silica and steel substrates shows a variation in stress concentration.     

Gold Catalysts Supported on Cerium–Gallium Mixed Oxide for the Carbon Monoxide Oxidation and Water Gas Shift Reaction

The synthesis, characterization and catalytic properties of gold supported on ceria, gallia and a cerium–gallium mixed oxide were investigated. The nanostructural characterization of the cerium–gallium support (nominal atomic composition Ce80Ga20) showed that gallium(III) cations are homogenously distributed into the ceria matrix by substituting cerium(IV) cations of the fluorite-type structure of ceria. Au was added to the supports by the deposition–precipitation method using urea. High Au dispersions were achieved for all the fresh materials (D > 60%). The CO oxidation and the water gas shift (WGS) reaction were tested on the whole set of catalysts. All the supported-gold catalysts showed high activity for the CO oxidation reaction. However, those containing gallium in their formulation deactivated due to gold particle sinterization. Au(2%)/CeO₂ was the most active material for the WGS reaction, and the Au(2%)/Ce80Ga20 was as active as a Au(3%)/Ce68Zr32 catalyst for CO oxidation, and even more active than the reference catalyst of the World Gold Council, Au(2%)/TiO₂.     

Direct synthesis of CeO2/SiO2 mesostructured composite materials via sol–gel process

A series of CeO₂/SiO₂ mesostructured composite materials was synthesized by sol–gel process using Pluronic P123 as template, tetraethylorthosilicate as silica source and hexahydrated cerium nitrate as precursor under acid condition. The as-synthesized materials with Ce/Si molar ratio ranging from 0.03 to 0.3 were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), laser Raman spectroscopy (LRS), and N₂ adsorption. Characterization revealed that all samples possess ordered hexagonal mesoporous structure similar to SBA-15 and possess high surface area, large pore volume and uniform pore size. The fact that cerium species are present as highly dispersed CeO₂ nanocrystals in hexagonal matrix was confirmed by XRD combined with high-resolution TEM and selected area electron diffraction (SAED) analysis. Introduction of ceria to silica matrix can cause a distortion of hexagonal ordering structure and decrease pore diameter and increase the wall thickness of mesopores. Moreover, it can be found that this sol–gel route is a feasible, effective and simple method for templating synthesis of CeO₂/SiO₂ composite materials.     

Influence of embedded ZnAlCe-NO3− layered double hydroxides on the anticorrosion properties of sol–gel coatings for aluminum alloy

A protective coating was designed by dispersing Ce-doped ZnAl layered double hydroxides (ZnAlCe-LDHs) nanoparticles in hybrid sol–gel (SiO_x/ZrO_x) layer on aluminum alloy AA2024. The concentration of cerium in synthesized LDHs was varied to ascertain the optimum condition for anticorrosion performance. The LDH nanoparticles were characterized in terms of structure, morphology and chemical composition. It was found that Ce (III) was inserted into the sheets of LDHs and two mixture phases of LDHs and CeO₂ were formed when the atomic ratio of Ce/(Al + Ce) was higher than 0.05. The sol–gel coating embedded with LDHs (Ce/(Al + Ce) = 0.1) exhibited high corrosion resistance, probably due to the synergistic inhibition of ZnAlCe-LDHs and CeO₂ nanoparticles.     

Modified supercritical CO2 extraction of amine template from hexagonal mesoporous silica (HMS) materials: Effects of template identity and matrix Al/Si molar ratio

In this work, the primary amine template has been extracted from freshly synthesized hexagonal mesoporous silica (HMS) materials by means of modified supercritical carbon dioxide at 60–85 °C under 10.0–20.0 MPa. The influences of amine identity and matrix Al/Si ratio on the extraction efficiencies and structural properties of HMS thus obtained are investigated in detail. The results show that the extraction efficiency is strongly dependent on the pore size of the HMS materials produced by five different templates. For aluminium-incorporated samples, the extraction efficiency is observed to decrease with the Al/Si molar ratio since as the Al/Si molar ratio increases, more amine will get protonated and the matrix/template interactions become stronger, subsequently rendering the extraction more difficult and the efficiency decrease. The formic acid modifier has resulted in better extraction performance than methanol, yielding higher extraction efficiencies. The SFE-treated materials exhibit better structural properties like higher pore volume and specific surface area as compared to those prepared by conventional calcinations. Besides, results of pyridine adsorption and conversion of 2-propanol to propylene suggest that the SFE-treated HMS materials may have higher acidity than the directly calcined samples.     

Synthesis and characterization of W-SBA-15 and W-HMS as supports for HDS

W-modified HMS and SBA-15 mesoporous materials (Si/W molar ratio equal to 40) were synthesized using sodium tungstate as tungsten source. In order to prepare NiW catalysts these mesoporous materials were impregnated with an aqueous solution of nickel salt of 12-tungstophosphoric acid Ni_3/2PW₁₂O₄₀. The synthesized W-HMS, W-SBA-15 materials and NiW catalysts have been characterized by S_BET, XRD, UV–Vis DRS, FT-IR, TPD of NH₃, ²⁹Si MAS NMR, SEM and HRTEM. The influence of these particular supports on catalytic activity of NiW catalysts was studied in the reaction of hydrodesulfurization (HDS) of thiophene. The results from the FT-IR and UV–Vis DR spectroscopy confirm incorporation of W into the HMS and SBA-15 structures. Additionally ²⁹Si MAS NMR measurements revealed relatively stronger effect of W ion incorporation in HMS structure on degree of silica cross-linking as compared to the effect of W ion incorporation in SBA-15 structure. The catalytic study showed that both W-HMS and W-SBA-15 materials modified with W are good supports for NiW catalysts in the HDS reaction of thiophene. The catalysts show lower selectivity for butanes than a reference NiW/γ-Al₂O₃ catalyst leveling of about 10% for chosen experimental conditions.     

Hydrothermal incorporation of Ce(La) ions into the framework of ZSM-5 by a multiple pH-adjusting co-hydrolysis

Ce and La incorporated ZSM-5 zeolitic materials with different metal loadings were synthesized via the multiple pH-adjusting procedures involving a co-hydrolysis of TEOS (tetraethyl-orthosilicate) with rare earth salts under a strong acidic condition, a further gelation under a weak acidic condition, and a final basic hydrothermal crystallization. Thus obtained Ce(La)-ZSM-5, as well as Ce or La ion-exchanged ZSM-5 samples, were characterized by XRD, SEM, TG, UV–vis, ²⁹Si MAS NMR, FT-IR, N₂-physisorption, and elemental analysis. The characterizations provide systematic and complementary evidences to demonstrate the incorporation of Ce(La) ions into the tetrahedral sites of ZSM-5 framework. The upper limits of the rare earth loadings in the synthesis gel and the final product are ca. 50 and 70 of the molar ratio of Si/Ce(La), respectively. It is observed that the synthesized Ce(La)-ZSM-5 zeolites possess an unusual morphology of microspheres that are assembled by numerous cubic prism-shaped nanocrystallines.     

镧系金属掺杂MCM-41的合成、表征及其脱硝性能研究

以正硅酸乙酯、硝酸镧、硝酸铈为原料,十六烷基三甲基溴化铵作模板剂,水热条件下合成镧、铈掺杂介孔分子筛。采用 XRD、FT-IR和氮气吸附脱附等对镧系金属掺杂MCM-41 进行表征,并以氨为还原剂研究其选择性催化还原一氧化氮活性以及反应条件（包括镧系掺量、反应温度、空速、氨氮比等）对催化性能的影响。本文旨在掺杂镧系金属提高分子筛的脱硝性能。镧系掺杂的分子筛改变了骨架增强了反应活性,稀土金属的高电荷密度使分子筛催化活性提高。结果表明,镧系金属镧、铈成功进入MCM-41 介孔材料的骨架内并保持有序的六方介孔结构,随着镧系掺杂量的增加,介孔有序性降低。当n（镧系金属）/n（硅）=0.04 、空速为4 000 h-1、n（氨气）/n（一氧化氮）为1 时 Ln-MCM-41催化剂在350 ℃反应时能保持较高活性。镧系掺杂的介孔分子筛能更有效地提高催化性能。     

Ce_(0.7)Zr_(0.3)/γ-Al_2O_3纳米固溶体的制备及其结构

以氯氧化锆、硝酸铈、硝酸铝为原料,按n(Ce)∶n(Zr)=0.7∶0.3的比例,采用化学共沉淀法与有机物共沸蒸馏法,将CeO2、ZrO2分散到γ-Al2O3表面上使其形成Ce0.7Zr0.3O2/γ-Al23固溶体。用XRD考察纳米固溶体在不同温度下焙烧后的相结构。结果表明:Ce0.7Zr0.3O2/γ-Al2O3纳米固溶体为立方晶型,且随着焙烧温度的升高,样品的衍射峰依次变强,峰宽变窄。     

A study on the growth mechanism and gas diffusion barrier property of homogeneously mixed silicon–tin oxide by atomic layer deposition

SiO₂ and SnO₂ films were deposited using plasma-enhanced atomic layer deposition (PEALD) at low temperature (100 °C), and homogeneously mixed structure (HMS) films consisting of Si, Sn, and O were deposited through a “1st precursor dose – 2nd precursor dose – oxidation”, a new ALD process method for mixing two elements. For a deep consideration of the growth mechanism during the HMS film deposition process, density functional theory (DFT) calculations of the adsorption reactions of the precursors on the surface were conducted. The properties of the thin films such as density, atomic composition, crystallinity, surface roughness, optical transmittance and the water vapor diffusion barrier property were analyzed by XRR, XPS, XRD, AFM, UV-VIS and the electrical Ca test.By changing the dose sequence of the two precursors in the HMS process, various physical/chemical characteristics of the films could be controlled. Also, by adjusting the appropriate amount of Sn in the HMS films, the shortcomings of SnO₂ were compensated by the mixed SiO₂; and through this process, excellent gas diffusion barrier properties of WVTR ∼ 1.33 × 10⁻⁴ g/m²day were secured.     

铈在介孔氧化锆中的液相移植

利用Ce(NO3) 3·6H2 O溶液与介孔氧化锆原粉在一定pH值的液相中反应 ,将Ce/CeO2 催化剂移植到多孔氧化锆材料中 .用XRD ,TEM ,N2 吸附 -脱附及UV -VIS吸收光谱等手段对产物进行表征 ,结果表明 :铈经Zr—O—Ce键成功地负载于多孔ZrO2 骨架中 ,并且分散于孔表面及孔道中 ,同时保持孔道的有序性及多孔氧化锆较高的比表面积 .     

Effect of Mn content on physical properties of CeOx–MnOy support and BaO–CeOx–MnOy catalysts for direct NO decomposition

A series of manganese–cerium mixed oxides were prepared by a glycothermal method, and the NO decomposition activities of the Ba-loaded Ce–Mn oxides were examined. Among the catalysts examined, the highest NO conversion was obtained on the BaO/Ce–Mn oxide catalyst with a Mn/(Ce+Mn) ratio of 0.25. The X-ray diffraction and Raman analyses indicated the formation of Ce–Mn oxide solid solutions with a cubic fluorite structure. The electron spin resonance analysis indicated the presence of paramagnetic Mn²⁺ species in the composite catalysts. Incorporation of Mn²⁺ in the fluorite structure of CeO₂ causes an increase in the concentration of oxygen vacancies, which play an important role in the NO decomposition activity of the catalysts. The catalysts were also characterized by X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Based on the results obtained, the relationship between the physical properties of the catalysts and their NO decomposition activities was discussed.     

Production of Iso-octanoic Acid Via Efficiently Synergetic Catalysis of Zn-Modified ZSM-5/HMS

Catalysis Letters - The composite structure ZSM-5/HMS was synthesized, and modified with zinc species by three methods. The effects of Si/Al ratio of ZSM-5, zinc contents in ZSM-5/HMS, and...     

The relationship between the electrochemical performance and the composition of Si–O–C materials prepared from a phenyl-substituted polysiloxane utilizing various processing methods

Si–O–C composite materials with various compositions are prepared from a phenyl-substituted polysiloxane. The pyrolyzing temperature and atmosphere is varied to determine the effect that these parameters have on the final composition. The compositional effect of using a divinylbenzene (DVB) as an alternative carbon source is also investigated. Materials prepared at either 800 or 1000 °C under a hydrogen atmosphere have a significantly larger reversible capacity than those prepared at the same temperature under an argon atmosphere. Utilizing DVB as the carbon source further increases the reversible capacity of the Si–O–C material. The specific capacity increases with an increase of the C/Si ratio and with a decrease of O/Si ratio of the source materials when the O/Si ratio is in the range of 1.0–2.0. A model based on the nanostructure of the Si–O–C material is employed to express the relationship between the specific reversible capacity and the structure of the Si–O–C phase. According to the utilized model, the reversible capacity of lithium in the Si–O–C phase is much greater than that in carbon, and the capacity increases with the increase of the p value in SiO_2(1?p)C_p. The “free carbon” in the synthesized materials was found to store twice as many lithium ions as the same amount of graphite.