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1.
Donghong Zhu Xin Weng Yuqiong Tang Jingya Sun Shourong Zheng Zhaoyi Xu 《RSC advances》2020,10(24):14208
Selective catalytic hydrogenation of p-chloronitrobenzene on Pt-based catalysts is a green and high-efficient way for p-chloroaniline production. However, supported monometallic Pt catalysts often exhibit undesirable p-chloroaniline selectivity. We herein reported supported Pt catalysts with N-doped carbon (NC) as an overcoating (Pt/Al2O3@NC) to overcome the disadvantage. Three Pt/Al2O3@NC catalysts with different NC coating amounts were prepared by in situ carbonization of an ionic liquid. For comparison, Al2O3 coated by NC and Pt/Al2O3 coated by SiO2 were also prepared. A combination characterization confirmed that the NC overcoating was successfully formed on Pt/Al2O3 surface and Pt particles were completely coated by NC layers when ion liquid amount increased to 25 μl per g catalyst. Due to the intimate contact of NC layers and Pt particles Pt-NC heterojunctions were effectively formed on the catalyst surface. For the catalytic hydrogenation of p-chloronitrobenzene, Pt/Al2O3@NC with 25 μl ionic liquid as the NC precursor exhibited 100% selectivity to p-chloroaniline at 100% conversion of p-chloronitrobenzene. A lower ionic liquid amount led to decreased selectivity to p-chloroaniline. Furthermore, no deactivation was observed on Pt/Al2O3@NC during 5 catalytic cycles. The findings in the study demonstrate that coating noble metal catalysts by N-doped carbon is a promising method to enhance the selectivity and stability for catalytic hydrogenation of p-chloronitrobenzene.Pt/Al2O3 with N-doped carbon overcoating exhibited 100% selectivity to p-chloroaniline for catalytic hydrogenation of p-chloronitrobenzene. 相似文献
2.
Asif Jan Jisu Shin Junsung Ahn Sungeun Yang Kyung Joong Yoon Ji-Won Son Hyoungchul Kim Jong-Ho Lee Ho-Il Ji 《RSC advances》2019,9(46):27002
Low temperature CO oxidation reaction is known to be facilitated over platinum supported on a reducible cerium oxide. Pt species act as binding sites for reactant CO molecules, and oxygen vacancies on surface of cerium oxide atomically activate the reactant O2 molecules. However, the impacts of size of Pt species and concentration of oxygen vacancy at the surface of cerium oxide on the CO oxidation reaction have not been clearly distinguished, thereby various diverse approaches have been suggested to date. Here using the co-precipitation method we have prepared pure ceria support and infiltrated it with Pt solution to obtain 0.5 atomic% Pt supported on cerium oxide catalyst, and then systematically varied the size of Pt from single atom to ∼1.7 nm sized nanoparticles and oxygen vacancy concentration at surface of cerium oxide by controlling the heat-treatment conditions, which are temperature and oxygen partial pressure. It is found that Pt nanoparticles in range of 1–1.7 nm achieve 100% of CO oxidation reaction at ∼100 °C lower temperature compared to Pt single atom owing to the facile adsorption of CO but weaker binding strength between Pt and CO molecules, and the oxygen vacancy in the vicinity of Pt accelerates CO oxidation below 150 °C. Based on this understanding, we show that a simple hydrogen reduction at 550 °C for the single atom Pt supported on CeO2 catalyst induces the formation of highly dispersed Pt nanoparticles with size of 1.7 ± 0.2 nm and the higher concentration of surface oxygen vacancies simultaneously, enabling 100% conversion from CO to CO2 at 200 °C as well as 16% conversion even at 150 °C owing to the synergistic effects of Pt nanoparticles and oxygen vacancies.Understanding on effects of Pt size and oxygen vacancy at CeO2 surface in Pt/CeO2 catalyst for CO oxidation reaction enables to boost catalytic activity. 相似文献
3.
The widely studied Pt/C catalyst for direct methanol fuel cells (DMFCs) suffers severe carbon corrosion under operation, which undermines the catalytic activity and durability. It is of great importance to develop a carbon-free support with co-catalytic functionality for improving both the activity and durability of Pt-based catalysts. The direct loading of Pt on the smooth surface of oxides may be difficult. Herein, the Cu assisted loading of Pt on CeO2 is developed. Cu pre-coated CeO2 was facilely synthesized and Pt was electrochemically deposited to fabricate the carbon-free PtCu/CeO2 catalyst. The PtCu/CeO2 catalyst has a mass activity up to 1.84 and 1.57 times higher than Pt/C towards methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), respectively. Better durability is also confirmed by chronoamperometry and accelerated degradation tests. The strategy in this work would be greatly helpful for developing an efficient carbon-free support of Pt-based catalysts for applications in DMFCs.TEM images of the PtCu/CeO2-21 catalyst. The scale bar in image (B) is 5 nm. Image (C) shows the area chosen for elemental mapping; image (D, E, and F) show the mapping of Ce, Cu, and Pt, respectively. 相似文献
4.
In this paper, CuO and CeO2 were screened as co-catalyst components for Fe2O3/attapulgite (ATP) catalyst, and three new catalysts (CuO–Fe2O3/ATP, CeO2–Fe2O3/ATP and CuO–CeO2–Fe2O3/ATP) were prepared for degradation of methylene blue (MB). The three catalysts'' characteristics were determined by BET, XRD, FT-IR, SEM and XPS. MB degradation in different systems and at different pH values was also studied. Under the conditions of H2O2 concentration of 4.9 mmol L−1, catalyst dosage of 5 g L−1, pH of 5, reaction temperature of 60 °C and MB initial concentration of 100 mg L−1, the as-synthesized catalysts showed much greater reaction rate and degradation efficiency of MB than Fe2O3/ATP catalyst. In addition, the reusability of the as-prepared composites was evaluated. The intermediate products of MB degradation were identified by LC-MS and the possible degradation process of MB was put forward.A novel heterogeneous catalyst CuO–CeO2–Fe2O3/ATP was synthesized for MB degradation and the catalytic mechanism was put forward. 相似文献
5.
Jianghui Lin Caiping Ma Jing Luo Xianghui Kong Yanfei Xu Guangyuan Ma Jie Wang Chenghua Zhang Zhengfeng Li Mingyue Ding 《RSC advances》2019,9(15):8684
A Ni based mesoporous γ-Al2O3 (MA) catalyst was prepared via partial hydrolysis without organic surfactants and employed in the carbon dioxide methanation reaction. The obtained catalysts were characterized by N2 adsorption–desorption, H2-TPR, XRD, XPS, TG, SEM and TEM-EDS techniques. CO2 methanation was performed in a fixed-bed reactor. A high surface area of MA with excellent hydrothermal stability was obtained, which promoted the dispersion of nickel species, producing a better catalytic performance. Incorporation of more NiO species into the Ni/MA catalyst increased the amount of active metallic Ni sties, further improving the catalytic activity and CH4 selectivity. Moreover, the monolithic skeleton of MA with fabric-like walls suppressed the aggregation of active metallic Ni sites and carbon deposition, enhancing the catalyst''s stability, which provides a new insight for potential industrial applications.A Ni based mesoporous γ-Al2O3 (MA) catalyst was prepared via partial hydrolysis without organic surfactants and employed in the carbon dioxide methanation reaction. 相似文献
6.
High-temperature arsenic resistance catalysts of CeLa0.5Fex/Ti (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) series were prepared and measured under a simulation condition of arsenic poisoning. The as-prepared catalysts were characterized by XRD, SEM, TEM, and XPS. The specific surface area and pore size of the catalysts were measured. At x = 0.2, the catalyst shows the best arsenic resistance and catalytic performance. The active temperature range of the CeLa0.5Fe0.2/Ti catalyst is 345–520 °C when the gas hourly space velocity is up to 225 000 mL g−1 h−1. Compared with commercial vanadium-based catalysts, CeLa0.5Fe0.2/Ti shows much better catalytic performance. The introduction of Fe will improve the dispersion of CeO2 and increase the concentration of Ce3+ and unsaturated active oxygen on the surface. The NH3-TPD and H2-TPR results show that the CeLa0.5Fe0.2/Ti catalyst has more acidic sites and more excellent redox performance than CeLa0.5Fe0/Ti. The CeLa0.5Fe0.2/Ti catalyst might have application prospects in the field of selective catalytic reduction of NOx with NH3.The NO conversion of the CeLa0.5Fe0.2/Ti is obviously better than that of the commercial vanadium-based catalyst with regard to arsenic resistance and it has good N2 selectivity, and good SO2 resistance. 相似文献
7.
Selective catalytic conversion of carbohydrates to 5-ethoxymethylfurfural (EMF) is a critical approach to the biorefinery. In this work, solid acid catalysts of γ-AlOOH and CeO2@B2O3 were used to convert carbohydrates to EMF in a one-pot process, performed in an ethanol/DMSO solvent system. The synergistic effect of γ-AlOOH and CeO2@B2O3 was studied. Furthermore, the morpho-structural properties of the catalysts were characterized, and the effects of reaction time, reaction temperature, catalyst load, and the amount of cosolvent on the conversion of glucose to EMF were examined and optimized. Under the reaction conditions of 170 °C for 20 h, glucose, sucrose, cellobiose, inulin and starch were used as raw materials, and the EMF yield range was 9.2–27.7%. The results showed that the synergistic effect of γ-AlOOH and CeO2@B2O3 further causes the combination of multiple acid sites with different types and strength distributions. Particularly, the collaboration between weak, medium-strong, and strong acid, as well as between Lewis and Brønsted acidity, is of great significance for EMF generation. The reusability experiments showed that the combined catalytic system was easily separated and maintained catalytic activity for five successive reactions without further intermediate regeneration steps. This work provides a promising route for the catalytic conversion of biomass-derived carbohydrates into EMF.γ-AlOOH and CeO2@B2O3 solid acid catalysts were synthesized for the one-pot selective conversion of carbohydrates into 5-ethoxymethylfurfural under their synergistic catalysis. 相似文献
8.
Yushan Wu Jianghui Lin Guangyuan Ma Yanfei Xu Jianli Zhang Chanatip Samart Mingyue Ding 《RSC advances》2020,10(4):2067
The selectivity and activity of a nickel catalyst for the hydrogenation of carbon dioxide to form methane at low temperatures could be enhanced by mesoporous Al2O3–CeO2 synthesized through a one-pot sol–gel method. The performances of the as-prepared Ni/Al2O3–CeO2 catalysts exceeded those of their single Al2O3 counterpart giving a conversion of 78% carbon dioxide with 100% selectivity for methane during 100 h testing, without any deactivation, at the low temperature of 320 °C. The influence of CeO2 doping on the structure of the catalysts, the interactions between the mesoporous support and nickel species, and the reduction behaviors of Ni2+ ions were investigated in detail. In this work, the addition of CeO2 to the composites increased the oxygen vacancies and active metallic nickel sites, and also decreased the size of the nickel particles, thus improving the low temperature catalytic activity and selectivity significantly.The addition of CeO2 to form Ni composite catalysts increased the oxygen vacancies and active metallic nickel sites thus improving the low temperature CO2 methanation performance. 相似文献
9.
The dehydrocyclization–cracking of methyl oleate was performed by ZnZSM-5–Al2O3 hierarchical composite-supported Pt catalysts in the range of 450–550 °C under 0.5 MPa hydrogen pressure. Most catalysts converted methyl oleate completely and produced aromatics with more than 10 wt% yield as well as valuable fuels even at 450 °C. The reactivity of catalysts changed remarkably depending on the addition method of Pt, while supporting Pt of 0–0.16 wt% did not affect the pore structure of each catalyst. When Pt was introduced into the composite support by the conventional impregnation method, remarkable hydrocracking proceeded through the decarboxylation and decarbonylation of methyl oleate and the successive conversion of C17 fragments and gave the significant amounts of gaseous products. Nevertheless, the selectivity for the aromatics of the gasoline fraction was relatively high and the yields of aromatics reached maximum 19% at 500 °C under 0.5 MPa, suggesting that gaseous olefins would be cyclized through the Diels–Alder reaction on ZnZSM-5 in the composite support. In contrast, when Pt was introduced into catalysts by ion-exchange with ZnZSM-5, the significant conversion of methyl oleate was inhibited and produced liquid fuels in a wide range.The ideal reaction route in the dehydrocyclization–cracking of methyl oleate catalyzed by Pt/ZnZSM-5–Al2O3 is to produce xylene, toluene, and hydrogen through decarboxylation. 相似文献
10.
Dehydrogenative cross-coupling (DCC) is a clean methodology to make C–C bonds by using abundant C–H bonds. The blended catalyst, developed in this study, consists of a TiO2 photocatalyst and an Al2O3 supported Pd–Au bimetallic catalyst and shows superior activity to the conventional TiO2 photocatalyst loaded with the corresponding metal co-catalyst for the direct DCC between various arenes and tetrahydrofuran, with concomitant evolution of hydrogen gas. The reactions were done under mild conditions without consuming any oxidising agent or other additional chemicals. This new approach of separating the photocatalyst and the metal catalyst parts allows their independent modification to improve the overall catalytic performance.A TiO2 photocatalyst physically mixed with a supported Pd–Au bimetallic catalyst is more efficient than Pd loaded TiO2 sample for the photocatalytic DCC between arene and THF. 相似文献
11.
Kyriakos N. Papageridis Nikolaos D. Charisiou Savvas Douvartzides Victor Sebastian Steven J. Hinder Mark A. Baker Ayesha A. AlKhoori Sara I. AlKhoori Kyriaki Polychronopoulou Maria A. Goula 《RSC advances》2021,11(15):8569
The present study provides, for the first time in the literature, a comparative assessment of the catalytic performance of Ni catalysts supported on γ-Al2O3 and γ-Al2O3 modified with La2O3, in a continuous flow trickle bed reactor, for the selective deoxygenation of palm oil. The catalysts were prepared via the wet impregnation method and were characterized, after calcination and/or reduction, by N2 adsorption/desorption, XRD, NH3-TPD, CO2-TPD, H2-TPR, H2-TPD, XPS and TEM, and after the time-on-stream tests, by TGA, TPO, Raman and TEM. Catalytic experiments were performed between 300–400 °C, at a constant pressure (30 bar) and different LHSV (1.2–3.6 h−1). The results show that the incorporation of La2O3 in the Al2O3 support increased the Ni surface atomic concentration (XPS), affected the nature and abundance of surface basicity (CO2-TPD), and despite leading to a drop in surface acidity (NH3-TPD), the Ni/LaAl catalyst presented a larger population of medium-strength acid sites. These characteristics helped promote the SDO process and prevented extended cracking and the formation of coke. Thus, higher triglyceride conversions and n-C15 to n-C18 hydrocarbon yields were achieved with the Ni/LaAl at lower reaction temperatures. Moreover, the Ni/LaAl catalyst was considerably more stable during 20 h of time-on-stream. Examination of the spent catalysts revealed that both carbon deposition and degree of graphitization of the surface coke, as well as, the extent of sintering were lower on the Ni/LaAl catalyst, explaining its excellent performance during time-on-stream.Highly selective and stable Ni supported on La2O3–Al2O3 catalyst on the deCO/deCO2 reaction paths for the production of renewable diesel. 相似文献
12.
Titanium and alumina are very well suited as constituents of dental metal/ceramic implants because of their excellent biocompatibility and their special chemical and mechanical properties which can be exploited to tailor composite implant structures. However, prior attempts to join pure titanium without any intermediate layer to alumina ceramic led to unsatisfactory results mainly due to thermal expansion mismatch between both materials. Therefore we used recently developed Ti alloys containing 30%wt Ta or 40%wt Nb for manufacturing dental implants. Moreover, we studied two alternative methods to join pure titanium with alumina using intermediate layers to reduce internal stresses within the joint caused by thermal expansion mismatch. We examined the interface region of these joints by metallographic, mechanical, analytical, and electron microscopy methods. Additionally, a comparison of the properties of the hitherto investigated types of joints with a view of their applicability in dental implants is given. Promising results were obtained for Ti/alumina joints with Nb interlayers. The studies are continuing. 相似文献
13.
Ye Jiang Mingyuan Lu Shaojun Liu Changzhong Bao Guitao Liang Chengzhen Lai Weiyun Shi Shiyuan Ma 《RSC advances》2018,8(32):17677
The effect of HCl on a CeO2–MoO3/TiO2 catalyst for the selective catalytic reduction of NO with NH3 was investigated with BET, XRD, NH3-TPD, H2-TPR, XPS and catalytic activity measurements. The results showed that HCl had an inhibiting effect on the activity of the CeO2–MoO3/TiO2 catalyst. The deactivation by HCl of the CeO2–MoO3/TiO2 catalyst could be attributed to pore blockage, weakened interaction among ceria, molybdenum and titania, reduction in surface acidity and degradation of redox ability. The Ce3+/Ce4+ redox cycle was damaged because unreactive Ce3+ in the form of CeCl3 lost the ability to be converted to active Ce4+ in the SCR reaction. In addition, a decrease in the amount of chemisorbed oxygen and the concentrations of surface Ce and Mo was also responsible for the deactivation by HCl of the CeO2–MoO3/TiO2 catalyst.The effect of HCl on a CeO2–MoO3/TiO2 catalyst for the selective catalytic reduction of NO with NH3. 相似文献
14.
Jia-qi Huang Kunming Liu Xinlong Song Guocheng Zheng Qing Chen Jiadi Sun Haozhe Jin Lanlan Jiang Yusheng Jiang Yi Zhang Peng Jiang Wangping Wu 《RSC advances》2022,12(38):24804
Nano-Al2O3 particles and graphene oxide (GO) nanosheets were modified by 3-aminopropyltriethoxysilane (KH550), and then dispersed in epoxy resin, and finally modified-Al2O3/epoxy, modified-GO/epoxy and modified-Al2O3@GO/epoxy composite coatings were prepared on steel sheets by the scraping stick method. The microstructure, phase identification, surface bonding and composition of the nanoparticles were characterized by SEM, XRD, FT-IR, and Raman spectroscopy, respectively. The hardness of the coating was assessed by the pencil hardness method. The abrasion resistance of the coating was tested by a sand washing machine. The corrosion resistance of the coating was assessed using salt spray, a long-period immersion test, potentiodynamic polarization curves and electrochemical impedance spectra. With the addition of a small amount of nanoparticles, the dispersion of nanoparticles in the epoxy resin was good. When the content of nano-Al2O3 particles was equal to 1.5 wt%, the particles in the epoxy exhibited the best dispersion and stability. However, the GO and Al2O3@GO nanofillers in the epoxy resin exhibited poor dispersion and stability. The hardness, abrasion and corrosion resistance of the composite coatings were improved with the addition of a small amount of nanoparticles, but the performance began to decline after exceeding a certain content range of the nanoparticles. A relatively good abrasion resistance for the coatings was obtained when the content of Al2O3, GO and Al2O3@GO after modification was 1.5 wt%, 0.2 wt% and 0.4 wt%, respectively. The corrosion resistance of the coatings doped with nano-Al2O3 particles was better than that of the coatings incorporating GO nanosheets and Al2O3@GO hybrids. The corrosion mechanism of the composite coatings in 3.5 wt% NaCl solution was addressed and studied.Nano-Al2O3 particles and graphene oxide (GO) nanosheets were modified by 3-aminopropyltriethoxysilane (KH550), and then dispersed in epoxy resin, and finally modified-Al2O3/epoxy, modified-GO/epoxy and modified-Al2O3@GO/epoxy composite coatings were prepared on steel sheets by the scraping stick method. 相似文献
15.
Suleiman Sabo Bello Chao Wang Mengjuan Zhang Zhennan Han Lei Shi Kangjun Wang Ziyi Zhong Fabing Su Guangwen Xu 《RSC advances》2020,10(61):37287
Hydrotreatment is an effective upgrading technology for removing contaminants and saturating double bonds. Still, few studies have reported the hydro-upgrading of shale oil, with unusually high sulfur (13200 ppm) content, using the CoMo/Al2O3 catalyst. Here we report an extensive study on the upgrading of shale oil by hydrotreatment in a stirred batch autoclave reactor (500 ml) for sulfur removal and viscosity reduction. From a preliminary optimization of the reaction factors, the best-operating conditions were 400 °C, an initial H2-pressure of 5 MPa, and an agitation rate of 800 rpm, a catalyst-to-oil ratio of 0.1, and a reaction time of 1 h. We could achieve a sulfur removal efficiency of 87.1% and 88.2% viscosity reduction under the optimal conditions. After that, the spent CoMo/Al2O3 was repeatedly used for subsequent upgrading tests without any form of pre-treatment. The results showed an increase in the sulfur removal efficiency with an increase in the number of catalyst runs. Ultimately, 99.5–99.9% sulfur removal from the shale oil was achieved by recycling the spent material. Both the fresh and the spent CoMo/Al2O3 were characterized and analyzed to ascertain their transformation levels by XRD, TEM, TG, XPS, TPD and N2 adsorption analysis. The increasing HDS efficiency is attributed to the continuing rise in the sulfidation degree of the catalyst in the sulfur-rich shale oil. The light fraction component in the liquid products (IBP–180 °C) was 30–37 vol% higher than in the fresh shale oil. The product oil can meet the sulfur content requirement of the national standard marine fuel (GB17411-2015/XG1-2018) of China.The CoMo/Al2O3 catalyst was used to upgrade shale oil. Sulfur removal was increased on the spent catalyst. The transition of oxidic Mo-species into active phase MoS2 was observed with recycling. The high sulfidation degree of the CoMo/Al2O3 suppressed deactivation by coking. 相似文献
16.
Herein, the wet-chemical process (co-precipitation) was used to prepare nanosheets (NSs) of Co3O4/Al2O3 in an alkaline medium (pH ∼ 10.5). The synthesized NSs were totally characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV/vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). The synthesized NSs were deposited onto a glassy carbon electrode (GCE) to prepare a very thin layer with a conducting binder for detecting 2-nitrophenol (2-NP) selectively by a reliable electrochemical method. The proposed chemical sensor exhibits good sensitivity (54.9842 μA μM−1 cm−2), long-term stability, and enhanced chemical response by electrochemical approaches. The resultant current is found to be linear over the concentration range (LDR) from 0.01 nM to 0.01 mM. The estimated detection limit (DL) is equal to 1.73 ± 0.02 pM. This study introduces a potential route for future sensitive sensor development with Co3O4/Al2O3 NSs by an electrochemical approach for the selective detection of hazardous and carcinogenic chemicals in environmental and health care fields.This potential research work introduces a route of future sensitive sensor development with Co3O4/Al2O3 NSs by electrochemical approach to selective detection of hazardous and carcinogenic chemicals in environmental and health care fields. 相似文献
17.
Chunliu Li Linchao Zhang Junfeng Yang Zhuoming Xie Tao Zhang Jianxin Wang Qianfeng Fang Xianping Wang 《RSC advances》2019,9(6):3436
In this work, to improve the cyclability and high-temperature performance of cubic spinel LiMn2O4 (LMO) as cathode materials, Nb5+-doped LiMn2O4 powders coated and uncoated with Al2O3 and/or B2O3 were synthesized via the modified solid-state reaction method. It was found that Nb5+-doped and B2O3 + Al2O3-coated LMO powders comprising 5 μm granular agglomerated fine primary particles smaller than 350 nm in diameter exhibited superior electrochemical properties with initial discharge capacity of 101.68 mA h g−1; we also observed capacity retention of 96.31% after 300 cycles at room temperature (RT) and that of 98% after 50 cycles at 55 °C and 1C rate.Nb-doped and Al2O3 + B2O3-coated granular secondary LMO particles enabling superior cycling performance at 25 and 55 °C. 相似文献
18.
Jiyou Zhong Weiren Zhao Lunwei Yang Peng Shi Zifeng Liao Menglong Xia Wenhua Pu Wei Xiao Ligen Wang 《RSC advances》2018,8(24):13054
A series of red-emitting Ca3ZrSi2O9:Eu3+,xBi3+ phosphors was synthesized using a conventional high temperature solid-state reaction method, for the purpose of promoting the emission efficiency of Eu3+ in a Ca3ZrSi2O9 host. The site preference of Bi3+ and Eu3+ in the Ca3ZrSi2O9 host was evaluated by formation energy. The effects of Bi3+ on electronic structure, luminescent properties, and related mechanisms were investigated. The inner quantum yield of the optimized sample increased to 72.9% (x = 0.08) from 34.6% (x = 0) at 300 nm ultraviolet light excitation. The optimized sample (x = 0.08) also showed excellent thermal stability, and typically, 84.2% of the initial emission intensity was maintained when the temperature increased to 150 °C from 25 °C, which is much higher than that without Bi3+ doping (70.1%). The mechanisms of emission properties and thermal stability enhancement, as well as the redshift of the charge transfer band (CTB) induced by Bi3+ doping in the Ca3ZrSi2O9:Eu3+ phosphor, were discussed. This study elucidates the photoluminescence properties of Bi3+-doped Ca3ZrSi2O9:Eu3+ phosphor, and indicates that it is a promising luminescent material that can be used in ultraviolet light-emitting diodes.A red-emitting phosphor Ca3ZrSi2O9:Eu3+,Bi3+ with high quantum yield and thermal stability was developed by introducing Bi3+ as an efficient sensitizer. 相似文献
19.
Ruifeng Wang Lungang Chen Xinghua Zhang Qi Zhang Yuping Li Chenguang Wang Longlong Ma 《RSC advances》2018,8(71):40989
Novel catalytic material with high catalytic activity and hydrothermal stability plays a key role in the efficient conversion of levulinic acid (LA) to γ-valerolactone (GVL) in water. In this study, mixed oxides Al2O3–TiO2, Al2O3–MoO3 and Al2O3–Co3O4 were synthesized by co-precipitation using aqueous solution of NaOH as precipitant. Ru catalysts supported on mixed oxides were prepared by impregnation method and their catalytic performances were tested in the hydrogenation of LA to GVL on a fixed bed reactor. The physicochemical properties of the catalysts were characterized by XRD, H2-TPR, NH3-TPD, and BET techniques. The TiO2 component significantly affected the acidity of the catalyst, and thus its catalytic activity for the GVL yield was affected. The desired product GVL with a yield of about 97% was obtained over the Ru/Al2O3–TiO2 catalyst under mild conditions (WHSV = 1.8 h−1, T = 80 °C). Moreover, the catalyst Ru/Al2O3–TiO2 exhibited excellent thermal stability in the test period of time.Novel catalytic material with high catalytic activity and hydrothermal stability plays a key role in the efficient conversion of levulinic acid (LA) to γ-valerolactone (GVL) in water. 相似文献
20.
Fused deposition modelling (3D) printing is used extensively in modern fabrication processes. Although the technique was designed for polymer printing, it can now be applied in advanced ceramic research. An alumina/aluminum (Al2O3/Al) composite refractory can be fabricated by mixing metallic aluminum in a polymer to form an Al/polymer composite filament. The filament can be printed via a regular thermoplastic material extrusion printer with no machine modification. In this study, Al/polymer composite samples were printed in a crucible shape and sintered at different temperatures to form Al2O3/Al composite refractory specimens. The sintered samples were examined via several analytical techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, compressive testing, hardness testing, XPS, and Hall measurement. Unlike other ceramic printing techniques that require expensive 3D printing machines and a very high temperature furnace (above 1500 °C) for post processing, this study demonstrates the viability of fabricating refractory items using a cost-effective fused deposition modelling 3D printer and a low temperature furnace (900 °C). The samples did not disintegrate at 1400 °C and were still sufficiently electrically conductive for advanced refractory applications.An Al2O3/Al composite is fabricated by the 3D printing, sintering, and calcination processes that can be used in refractory applications. 相似文献