查找使用阿拉丁产品的科研文献

Interface Optimization of Al2O3-Fe Composite Materials Prepared via Vacuum Sintering Method

Rui Hua Wang,Ai Xia Chen,Chao Yang,Fang Wang,Ming Han Xu,Shi Bin Li,Jie Guang Song,Lin Chen

In this paper, the effect of sintering temperature on the interfacial structure of the composite was investigated and three different formulation groups were used to compare the respective properties. To obtain a composite material with excellent interface, the law between reference number and performance is obtained. Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn: As the temperature increases, the density and hardness increase. The sample melts at 1500 °C, and there is no specific data. When the temperature reaches 1450 °C, the density and hardness reach the highest. When the formulation is Fe:Al2O3:SiO2=18:1:1 and the temperature reaches 1450 °C, the properties of the sample materials are optimized. The density is as high as 95% and the hardness reaches 42.9HBW.

Interface modulation of Pt/Al2O3 catalyst and their roles in thermal stability

Changjin Xu,Yinglei Liu,Baljeet Singh,Shiyuan Yi,Gaowu Qin,Song Li

Interfacial local environment of noble metal nanoparticles (NPs) and support is crucial for the development and design of thermally and chemically stable noble metal heterogeneous catalysts. The unique chemical environment can strengthen the NPs interaction with the support surface, which can effectively avoid the agglomeration of NPs . The strategy is developed to modulate the interfacial chemical environment of supported Pt NPs with the help of the unsaturated Al 3+ in Al 2 O 3 N (nanobelt) support, resulting in a sintering-resistant Pt/Al 2 O 3 N catalyst. Al solid-state MAS NMR characterization shows that Al 2 O 3 N support contains a large amount of unsaturated Al penta 3 + (about 22.6%). XAS confirms that Pt NPs deposited on the surface of Al 2 O 3 with rich unsaturated pentahedral coordinated Al 3+ sites have a unique coordination structure at the interface (more Pt-O coordination). When catalyzing the CO oxidation as a probe reaction, the catalytic activity and the particle sizes of Pt NPs do not change significantly even after the reaction at 400 °C for 15 days, and the complete CO conversion temperature increases only by 40 °C when the catalyst is screened at 600 °C for 5 days. This work demonstrates a new strategy to develop stable large-scale anti-sintering noble metal-based heterogeneous catalysts for many important high-temperature industrial applications.

Enhanced Oxidation of Xylene Using Plasma Activation of an Mn/Al2O3 Catalyst

Zuliang Wu,Weili Zhou,Zhoubin Zhu,Xiaodong Hao,Xuming Zhang

The heteroaggregation and deposition behavior of nanoplastics on Al2O3 in aquatic environments

Jiayan Wu,Jieyu Liu,Pingxiao Wu,Leiye Sun,Meiqing Chen,Zhongbo Shang,Quanyun Ye,Nengwu Zhu

The ubiquitous Al 2 O 3 is anticipated to interact with nanoplastics , affecting their fate and transport in aquatic environments. In this study, the heteroaggregation and deposition behaviors of polystyrene nanoplastics (PSNPs) on Al 2 O 3 were systematically investigated under different conditions (ionic strength, pH, and natural organic matter). The results showed that significant heteroaggregation occurred between PSNPs and Al 2 O 3 particles under acidic and neutral conditions. When the NaCl concentration was increased from 50 to 500 mM, the heteroaggregation ratio gradually increased. However, poly (acrylic acid) (PAA) inhibited the heteroaggregation of PSNPs-Al 2 O 3 due to steric repulsion. The deposition of PSNPs on Al 2 O 3 surfaces was inhibited as the NaCl concentration or pH values increased. Due to charge reversal and steric repulsion, humic acid (HA) and fulvic acid (FA) prevented the deposition of PSNPs onto Al 2 O 3 surfaces, and the former was more effective in reducing the deposition rate . The interaction mechanism between PSNPs and Al 2 O 3 was revealed by using various characterization techniques and density function theory (DFT) calculation. The results demonstrated that in addition to the dominant electrostatic interaction, there were also weak hydrogen bonds and van der Waals interactions. Our research is of great significance for predicting the migration and fate of PSNPs in aquatic environments.

Layered array Al2O3-LuAG: Ce composite ceramic phosphors for high-brightness display

Qi Zhang,Ruilin Zheng,Haiyang Wu,Guoyu Zhao,Jianyong Ding,Kehan Yu,Wei Wei

Thermally robust and efficient composite ceramic phosphors (CCPs) combined both the merits of matrix and phosphor have received growing interests. However, high matrix content (e.g., Al 2 O 3 >40 wt%) brings diluted activated ion concentration and dropped photoluminescence (PL) quantum yield (QY). Here, a novel layered array Al 2 O 3 -LuAG: Ce CCP, where Al 2 O 3 and LuAG: Ce thin layers (10–250 µm) are alternately arranged, was presented. Owing to the special structure, thermal phonons and photons are respectively routed into Al 2 O 3 layers and LuAG: Ce layers, which weakens the influence of Al 2 O 3 and heat accumulation on PL properties. Consequently, it exhibits high PLQY (84.1%) and good thermal conductivity (17.1 W·m −1 ·K −1 ). When it is irradiated under high-power density (27.2 W·mm −2 ) blue laser , the luminous efficiency and lumen-density are promoted to 220 lm·W −1 and 5994 lm·mm −2 , respectively. This work provides a promising new microstructure in developing novel phosphor converters for high-brightness laser phosphor display.

Weakly agglomerated α-Al2O3 nanopowders prepared by a novel spray precipitation method

Quanbin Li,Le Zhang,Shuai Wei,Yikun Zhang,Rong Sun,Tianyuan Zhou,Wei Bu,Qing Yao,Zhigang Jiang,Hao Chen

In this paper, weakly agglomerated and well dispersed α-Al 2 O 3 powders were synthesized by a novel spray precipitation method. It was demonstrated that the as-prepared powders exhibited better dispersity than powders from conventional precipitation due to the increased phase contact and reaction area during the precipitation process. The effects of different titration ways, calcination temperature and holding time on the morphology, phase composition and sintering behaviour of Al 2 O 3 powders were systematically investigated. Weakly agglomerated and well crystallized α-Al 2 O 3 powders were obtained when the as-prepared precursors were calcined at 1150 °C for 2 h in air. The average particle size of α-Al 2 O 3 powders with higher sintering activity was approximately 68.6 nm, and the specific surface area was above 22.4 m 2 g −1 .

Selenium-modulated Pt/Al2O3 electronic structure induces deactivation during catalytic CO oxidation

Tian Tang,Jianing Ma,Jingyu Xue,Xiaoqiang Shen,Jinfei Chen,Linhan Yu,Vladislav Rac,Vesna Rakić,Xinbao Li,Hao Song,Xuesen Du

Industrial sources, such as steel and power activities continue to emit substantial amounts of CO, but have not received the same level of attention as mobile sources due to a lack of relevant regulations. This work reports that a commercial Pt/Al 2 O 3 catalyst used in vehicle CO catalytic converters may face severe selenium (Se) poisoning deactivation from industrial sources. The turnover frequency (TOF) of the Pt/Al 2 O 3 catalyst (250 °C) decreased from 2.18 s −1 to 0.12 s −1 with only 0.49 wt% (ICP) Se deposition. Se deposition causes the Pt 5d orbital shift to a higher energy state, raising the oxidation state of platinum. As a result, the back-donation from the 5d electrons of Pt to the 2π* antibonding orbital of the adsorbed CO molecule is inhibited, weakening the bonding between Pt/Al 2 O 3 and the CO antibonding orbital, thereby significantly reducing CO activation ability. DRIFTS results, combined with apparent and microscopic kinetics, indicate that the surface of Se deposited Pt/Al 2 O 3 catalyst remains O* available (500 K, θ O* = 0.16), and the rate-controlling step changes from O 2  + 2* → 2O* to CO + * → CO*. The work suggests that the application of CO catalytic oxidation technology for industrial source should fully consider the toxic effect of Se, but is often neglected.

Fabrication of supported Pd–Ir/Al2O3 bimetallic catalysts for 2-ethylanthraquinone hydrogenation

Runrun Hong,Yufei He,Junting Feng,Dianqing Li

A series of χ wt % Pd-(1-χ) wt % Ir (χ = 0.75, 0.50, and 0.25) catalysts supported on γ-Al 2 O 3 have been prepared by co-impregnation and calcination-reduction, and subsequently employed in the hydrogenation of 2-ethylanthraquinone—a key step in the manufacture of hydrogen peroxide. Detailed studies showed that the size and structure of the bimetallic Pd–Ir particles vary as a function of Pd/Ir ratio. By virtue of its small metal particle size and the strong interaction between Pd and Ir, the 0.75 wt % Pd–0.25 wt % Ir/Al 2 O 3 catalyst afforded the highest yield of H 2 O 2 , some 25.4% higher than that obtained with the monometallic 1 wt % Pd catalyst. Moreover, the concentration of the undesired byproduct 2-ethyl-5,6,7,8-tetrahydroanthraquinone (H 4 eAQ) formed using the Pd–Ir bimetallic catalysts was much lower than that observed with the pure Pd catalyst, which can be assigned to the geometric and electronic effects caused by the introduction of Ir. © 2017 American Institute of Chemical Engineers AIChE J , 63: 3955–3965, 2017

High pyroelectric performance in Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3/Al2O3 composites by design

Jiaying Cao,Yuxin Yang,Yuying Liang,Yuxing Sha,Ling Li,Ji Zhang,Yaojin Wang

High pyroelectric performance around human body temperature is essential for ultra-sensitive infrared detectors of medical systems. Herein, toward human health monitoring, composite ceramics (1- x )Pb 0.99 Nb 0.02 [(Zr 0.57 Sn 0.43 ) 0.94 Ti 0.06 ] 0.98 O 3 / x Al 2 O 3 ( x = 0, 0.1, and 0.2) were designed. A metastable ferroelectric (FE) phase was induced in the anti-FE matrix by the Al 2 O 3 component-induced internal stress, and in turn FE-anti-FE phase boundary was constructed. The ceramics at x = 0.2 exhibit high pyroelectric coefficient with p = 10.9 × 10 −4 C·m −2 ·K −1 and figures of merit with current responsivity F i = 6.23 × 10 −10 m·V −1 , voltage responsivity F v = 12.71 × 10 −2 m 2 ·C −1 , and detectivity F d = 7.03 × 10 −5 Pa −1/2 around human body temperature. Moreover, the enhanced pyroelectric coefficients exist in a broad operation temperature range with a large full width at half maximums of 18.5°C and peak value of 29.2 × 10 −4 C·m −2 ·K −1 at 48.2°C. The designed composite ceramic is a promising candidate for infrared thermal imaging technology of noncontact human health monitoring system.

Thermally stable Ag/Al2O3 confined catalysts with high diffusion-induced oxidation activity

Houlin Wang,Shuting Luo,Xinghao Li,Wei Liu,Xiaodong Wu,Duan Weng,Shuang Liu

Developing catalysts with high cost-efficiency, good oxidation activities and strong thermal resistance is an ongoing task. Herein, we present the design and synthesis of confined catalysts with Ag protected by alumina. Thermal treatment at 800 °C for 10 h caused neither silver loss nor deactivation of this catalyst. Instead, nano-particles of Ag formed because of the heat/O 2 -derived ripening. These highly dispersed silver species and the catalyst’s mesoporous structure worked in tandem to achieve good catalytic performance for oxidation reactions, which made the aged sample a good candidate as CO elimination and gasoline particulate filter catalysts.

Compositional effects on the structure and properties of CaO-Al2O3-Ga2O3 glasses

Zhitao Shan,Hong Wang,Shujiang Liu,Yanfei Zhang,Cheng Zuo,Qiuju Zheng,Haizheng Tao,Yuanzheng Yue

In this work, we investigated the structural and physical property evolutions induced by the substitution of Al 2 O 3 by Ga 2 O 3 in two series of CaO-Al 2 O 3 -Ga 2 O 3 (CAG) glasses. To suppress crystallization, glasses with compositions of (I) 50CaO• (50- x )Al 2 O 3 • x Ga 2 O 3 ( x = 0–50 mol%) and (II) 63CaO• (37- x )Al 2 O 3 • x Ga 2 O 3 ( x = 0–37 mol%) were prepared via containerless aerodynamic levitation technique. It was found that with increasing substitution of Al 2 O 3 by Ga 2 O 3 (i.e., increasing x ), both glass series exhibited monotonic decreases in hardness, glass transition temperature and thermal expansion coefficient. High-resolution XPS analyses revealed that the two glass series exhibited distinct compositional dependences in their local structural evolution. Specifically, in series I ([CaO]:[Al 2 O 3 +Ga 2 O 3 ] = 1:1), the coordination environments of O, Ga, and Al remained largely unchanged upon substitution. In contrast, Series II ([CaO]:[Al 2 O 3 +Ga 2 O 3 ] = 12:7) exhibited significant shifts in O and Al coordination, while the Ga environment was only minimally affected. Furthermore, XPS indicated that trace OH - species preferentially interact with Al/Ga-O bonds by non-bridging oxygens within [AlO 4 ] or [GaO 4 ] tetrahedra. These findings elucidate the critical roles of both [CaO]/[Al 2 O 3 +Ga 2 O 3 ] and [Al 2 O 3 ]/[Al 2 O 3 +Ga 2 O 3 ] ratios in tailoring the structure - property relationships of CAG glasses.

Double Core–Shell BaTiO3@Al2O3@PDA-Based Nanocomposites for Energy Storage Applications

Li Xin,Zhou Sikai,Wu Lingyun,Li Haozhi,Lv Jiangyi,Ren Xinlei,Wang Zhuo

With their ultrahigh power density and excellent reliability, polymer-based dielectric capacitors are highly attractive for use in critical applications, such as DC-link capacitors in electric vehicles and power conditioning systems for renewable energy integration. Incorporating high-dielectric-constant inorganic fillers into polymers is the most common and direct strategy for enhancing energy storage. However, conventional composites suffer from poor compatibility and a large dielectric mismatch between the inorganic phase and the polymer matrix, which hinders simultaneous improvement of discharge energy density and energy storage efficiency. Herein, we report a BaTiO 3 @Al 2 O 3 @PDA double core–shell nanoparticle that significantly enhances the energy storage performance of PVDF-based composites at an ultralow filler loading. In this system, the Al 2 O 3 interlayer acts as a wide-bandgap-insulating barrier, mitigating local electric field concentration and suppressing leakage current, while the outer polydopamine (PDA) shell enhances both the dispersion of the fillers and their compatibility with the PVDF matrix. In this study, the 0.5 wt % BaTiO 3 @Al 2 O 3 @PDA/PVDF composite film exhibited significantly enhanced breakdown strength (437.02 kV/mm), a discharge energy density of up to 13.8 J/cm 3 , and an energy storage efficiency of 76.8%. These results indicate that this nanocomposite holds great potential for use in next-generation, high-performance film capacitors for electric vehicles and renewable energy systems.