查找使用阿拉丁产品的科研文献

Boosting hydrogen production from steam reforming of glycerol via constructing moderate metal-support interaction in Ni@Al2O3 catalyst

Yunzhu Wang,Songshan Zhu,Jichang Lu,Jiangping Liu,Yi Zhao,Sufang He,Yuhui Zhao,Huihui Lu,Yongming Luo

In this manuscript, the relationship between metal-support interaction and the catalytic performance for hydrogen production from steam reforming of glycerol (GSR) over Ni-Al 2 O 3 based catalysts was studied. Pure core–shell structured Ni@Al 2 O 3 and supported Ni/Al 2 O 3 with a fixed medium-sized nickel particle were synthesized without the other additional components to eliminate the influence of other factors. And then the nickel-alumina interaction of Ni@Al 2 O 3 was tuned precisely and the regulatory mechanism of nickel-alumina interaction on catalytic activity was elaborated. The strong nickel-alumina interaction over Ni/Al 2 O 3 and Ni@Al 2 O 3 with high calcination temperature resulted in the formation of NiAl 2 O 4 , which was unfavorable to the reduction of nickel species to obtain the more active nickel. Consequently, the poor catalytic performance was caused. The moderate nickel-alumina interaction of Ni@Al 2 O 3 promoted the exposure of the maximum area of active nickel and obtained higher turnover frequency (TOF). Thus, Ni@Al 2 O 3 showed the high catalytic performance in GSR. Additionally, metal-support interaction affected the morphology and growth mechanism of coke deposition. For Ni@Al 2 O 3 with moderate nickel-alumina interaction, the formation of carbon deposition followed the ‘tip-growth’ pattern, and the filamentous coke was mainly formed on catalysts. Conversely, ‘base-growth’ pattern was followed on Ni/Al 2 O 3 with strong nickel-alumina interaction to form mainly encapsulated coke. The research findings of the regulatory role of interaction between nickel and alumina on catalytic performance will provide valuable guidelines for designing effective GSR catalysts.

Oxidation resistance and heat transfer simulation of MoSi2-based coatings on carbon fiber reinforced C-Al2O3 aerogel composite

Dai Tao,Wu Zhanwu,Wang Zihan,Cui Sheng,Wu Xiaodong,Zhu Xiaofei

Fiber-reinforced aerogels with excellent properties such as low density and low thermal conductivity are potential thermal insulation materials. The slurry method and the embedding sintering method were used to fabricate MoSi 2 -aluminoborosilicate glass coatings on the surface of a carbon fiber-reinforced C-Al 2 O 3 aerogel composite under a low-oxygen atmosphere. The microstructure and phase composition of the coatings with different MoSi 2 contents before and after static oxidation were investigated. The resulting composite exhibited excellent radiating properties and outstanding oxidation resistance. The total emissivity of the as-prepared coatings was above 0.8185 in the wavelength range of 300–2500 nm. The sample with 40 wt% MoSi 2 in the outer coating had superior thermal endurance with a weight loss of only 0.54% after isothermal oxidation at 1200 °C for 180 min. This can be attributed to the optimum viscosity of the binder, which would relieve thermal stress defects and block oxygen diffusion. To further evaluate the thermal protection performance of the coatings, the heat transfer characteristics were simulated using the Fluent software package. Graphical abstract

The critical role of aggregate microstructure in thermal shock resistance and slag resistance of Al2O3–SiC–C castable

Jiuhong Ma,Huizhong Zhao,Jun Yu,Han Zhang,Yichong Li,Lida Shi,Yi Zhao,Jian He

In this study, four types of commercial tabular corundum were selected as aggregates, and four Al 2 O 3 –SiC–C castables were prepared under same conditions. The microstructure characteristics of the aggregates were observed. The thermal shock resistance and slag resistance mechanism were evaluated. Dendritic pores were proven to be beneficial for relieving and guiding thermal stress. According to the Lobe method, the dendritic pores provided the aggregates with a higher thermal conductivity and better thermal stability than the circular pores. The role of the aggregate microstructure in resisting slag erosion was discussed through thermodynamic and kinetic analyses. The presence of dendritic pores and a small neck size led to a faster dissolution rate during the slag erosion process. At the same time, the dissolution rate and dissolution amount increased, resulting in the faster supersaturation of the slag. Based on Ostwald's supersaturation theory, a thicker spinel isolation layer would be precipitated on the inner walls of the slag erosion path, thereby preventing the further erosion of the slag.

High-Performance Thin-Film Transistors and Inverters Based on ALD-Derived Ultrathin Al2O3-Passivated CeO2 Bilayer Gate Dielectrics

Leini Wang,Gang He,Wenhao Wang,Xiaofen Xu,Bo He,Xiaoyu Wu,Yongchun Zhang

Flexible thermal conductive Al2O3@siloxane composite with rapid self-healing property based on carboxyl-amine dynamic reversible bonds

Ziyue Hu,Weijian Wu,Xiang Chen,Yuanzhou Chen,Junlin Chen,Zhifeng Hao

Thermal interface materials (TIMs) are one of the efficacious ways to alleviate the heat accumulation problem of microelectronics devices. However, conventional TIMs based on polydimethylsiloxane (PDMS) always suffer from mechanical damage, leading to shortened service life or loss of thermal conductivity. In this work, we fabricated a high-thermal conductivity and fast self-healable Al2O3@siloxane composite by hydrosilylation reaction. The siloxane matrix consisted of thermosetting silicone rubber matrix (SR) and heat reversibility matrix (SCNR); the SR was synthesized via hydrosilylation between silicon hydrogen bond and vinyl, the SCNR was fabricated by thermal-curing between amino and carboxyl functionalized PDMS. Different sized spherical Al2O3 fillers were introduced into the SR/SCNR matrix system to construct the Al2O3@SR/SCNR composites. By adjusting the ratio of SR/SCNR, the obtained composites can achieve flexibility, self-healing and high filling simultaneously. It is notable that the self-healing efficiency of the composite is high, up to 95.6% within 3 minutes with 6.7 wt% mass ratio of SCNR/SR; these fast self-healing behaviors benefit from the assistance of thermal diffusion by 3D heat conduction pathways on the rearrangement of the dynamic cross-linked network. The resultant composites also exhibited the optimal thermal conductivity of 5.85 W mK−1. This work provides a novel approach for constructing longer service life and high thermal conductivity multifunctional TIM based PDMS.

Influence of Micro@Nano-Al2O3 Structure on Mechanical Properties, Thermal Conductivity, and Electrical Properties of Epoxy Resin Composites

Mai Yuxiang,Du Bin,Liu Qian,Zhao Yushun,Yang Wei,Yan Bingyue

Abstract The interfacial structure between the inorganic filler and epoxy resin matrix in epoxy resin (EP) composites has a great influence on the mechanical properties, thermal conductivity, and electrical properties. In this paper, two micro@nanostructured Al 2 O 3 fillers and their epoxy resin composites were prepared, and their morphology, interfacial bond strength, mechanical properties, thermal conductivity, and electrical properties systematically tested and analyzed. The experimental results show that modification by a nano-Al 2 O 3 coating on the surface of micro-Al 2 O 3 can effectively improve the infiltration of Al 2 O 3 filler and epoxy resin, reduce the interfacial defects caused by weak bonding of Al 2 O 3 filler and epoxy resin, and thus synergistically improve the mechanical properties, thermal conductivity, and electrical properties of epoxy resin composites. The thermal conductivity was improved by 22.5% compared with 22.65% when using micro-Al 2 O 3 /EP, the tensile and flexural strength were improved by 36.67% and 20.82%, and the alternating-current breakdown strength was improved by 12.88%. In addition, thermally stimulated current experiments were carried out to study the electron transport properties of micro@nano-Al 2 O 3 epoxy resin composites, revealing that filler nanomodification could improve the trap depth, suppress the carrier transport, and improve the dielectric properties of the composites. Graphic Abstract

Fabrication and characterization of ZrO2(3Y)/Al2O3 micro-ceramic gears with high performance by vat photopolymerization 3D printing

Lizheng Zhang,Yong Zeng,Haihua Yao,Zhaoyao Shi,Jimin Chen

To date, overcoming the trade-off between high solid loading and print accuracy and strength , achieving high-performance and fine ZrO 2 micro-ceramic components through vat photopolymerization 3D printing remains challenging. In this study, the effects of dispersant, particle size and solid content on the dispersion, rheological behavior and stability of ZrO 2 ceramic slurry were systematically studied, and complex, fine and high-performance ZrO 2 micro-ceramic gears were successfully prepared. Then, the microstructure, mechanical properties, tribological properties and surface quality were evaluated. The results show that the rheological behavior of the slurry is the best when the optimal dispersant content is 3.5 wt%. With the increase of solid content, the sintering shrinkage of ZrO 2 (3Y)/Al 2 O 3 ceramics decreased, while the relative density, compressive strength , flexural strength , fracture toughness and hardness increased. The prepared micro-ceramic gears not only have fine structure, but also have dense microstructure and good mechanical properties. The relative density, compressive strength, flexural strength, fracture toughness and hardness strength of ZrO 2 (3Y)/Al 2 O 3 ceramics can reach 98.53 %, 1900 MPa, 648 MPa, 6.4 MPa × m 1/2 and 13.40 GPa, respectively. In particular, this study couples the printing accuracy and strength with the solid load. By adjusting the relationship between the fixed load and the shrinkage rate, the printing of samples with different sizes is realized, which breaks through the accuracy limit of the printing equipment and provides a new idea for the preparation of micro-ceramic gears.

Preparation and enhanced mechanical properties of novel Al2O3-C ceramic filter reinforced by microporous powder and SiC whiskers

Wen Yan,Zhe Chen,Guangqiang Li,Shaosong Hong,Nan Li

In present work, the novel Al 2 O 3 -C ceramic filter fabricated by using microporous corundum-spinel powder instead of dense Al 2 O 3 powder and reinforced by SiC whiskers is proposed. The effects of Si powder content (0, 3, 6, and 9 wt. %) on the microstructures and mechanical properties of the filters were studied. After replacing the α-Al 2 O 3 micro-powder with microporous corundum-spinel powder, the in situ spinel whiskers were formed inside the filter skeleton under the reducing atmosphere. The rough surface structure of the microporous powder increased the interface contact area with the small-sized carbon particles, resulting in a compact interface bonding in the filter skeleton and a higher cold compressive strength of the filter. When the Si powder content increased to 6–9 wt. %, the in-situ SiC whiskers were formed not only between the microporous powder, but also inside the pores near the surface of it by vapor-solid reaction mechanism in the filter skeleton. The SiC whiskers synergized with the microporous powder to form a more compact interface structure, thus remarkably enhancing their cold compressive strength and thermal shock resistance. Overall, the mechanical properties of the filters were significantly improved by the addition of 9 wt. % Si powder. The filter skeleton had an apparent porosity of 36.2% and a bulk density of 1.93 g/cm 3 . The filter also exhibited a high cold compressive strength of 1.59 MPa and a superior thermal shock resistance. It has the potential for better purification efficiency on molten steel in the future due to a rougher skeleton surface structure compared to existing Al 2 O 3 -C filters.

The novel ternary phase CaAl2±xCr2±xO7 in the Al2O3–CaO–Cr2O3 system: What is the chromium solubility?

Hang Liu,Shengqiang Song,Rundong Jing,Mithun Nath

Recently, in the Al 2 O 3 –CaO–Cr 2 O 3 system, a Cr 3+ ternary phase named wuboraite (CaAl 2 Cr 2 O 7 ) was synthesized for the first time in an air atmosphere, which later showed an undetermined hint of solid solubility between Cr 3+ and Al 3+ in different atmosphere. In the present investigation, the solubility limits (or x values) of the CaAl 2± x Cr 2± x O 7 were determined by conducting high-temperature equilibrium experiments in both air and N 2 atmospheres with the various proportionate mixtures of CaO, Al 2 O 3 , and Cr 2 O 3 , and subsequently using powder X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis. In the air atmosphere, the Cr richest end-member of the Wuboraite solid solution phase is CaAl 1.77 Cr 2.23 O 7 (or x  = 0.23), while that of Al richest end-member is CaAl 2.18 Cr 1.82 O 7 (or x  = 0.18). Whereas, in the N 2 atmosphere, the Cr richest end-member of the wuboraite solid solution phase is CaAl 1.77 Cr 2.23 O 7 (or x  = 0.23), while that of Al richest end-member is CaAl 2.15 Cr 1.85 O 7 (or x  = 0.15).

Improved mechanical performance and electrochemical corrosion of WC-Al2O3 composite in NaCl solution by adding the TiC additives

Bin Han,Shigen Zhu,Weiwei Dong,Yunfeng Bai,Hao Ding,Yilan Luo,Ping Di

In this study, 85-xWC-xTiC-15wt%Al 2 O 3 (x = 0, 5, 10 and 20 wt%) composites were fabricated via hot pressing sintering technology. The influences of TiC additives on the mechanical performance and electrochemical behavior of WC-Al 2 O 3 composite in NaCl solution were investigated. The mean size of WC grain showed a downward trend with the increase of TiC content. The relative density, hardness and fracture toughness of WC-based composites were improved by TiC additives. The maximum values of mechanical performance were obtained when TiC content was 10 wt%. Moreover, the research results indicated that TiC additives significantly increase the corrosion potential and decrease the corrosion current density in NaCl solution. When TiC content increased, the charge-change resistance (R ct ) value presented an uptrend, and then decreased obviously when the TiC content reached 20 wt%. The XPS spectrum and SEM images proved that TiO 2 passivation film was formed on the surface of WA15-10TiC composite. Therefore, it could be concluded that TiO 2 passive film could inhibit further corrosion of the composite.

Hydrogenolysis of glycerol to 1,3-propanediol over a Al2O3-supported platinum tungsten catalyst with two-dimensional open structure

Xu Wenfeng,Niu Pengyu,Guo Heqin,Jia Litao,Li Debao

This work investigated the effect of texture properties of the Al 2 O 3 -based catalysts on the catalytic performance for glycerol hydrogenolysis to 1,3-propanediol (1,3-PDO) in fixed bed reactor. Three kinds of Al 2 O 3 supports with different pore structures, namely rod-like (Al 2 O 3 -R), flake-like (Al 2 O 3 -F) and spindle-like (Al 2 O 3 -SP) were synthesized by hydrothermal crystallization method, and correspondingly catalysts were prepared by the incipient-wetness impregnation method. The properties of active components, Pt and WO x species, loaded on different Al 2 O 3 supports were similar, which was confirmed by N 2 adsorption–desorption isotherms, XRD, Raman spectroscopy, UV–Vis DRS spectroscopy, 27 Al MAS NMR, SEM, HR-TEM, NH 3 -TPD, Py-FTIR, H 2 -TPR and XPS. Considering the similar active sites, the distinct reaction performance of the catalysts mainly results from the texture properties. Flake-like catalyst containing the two-dimensional nanosheets with open pore structure significantly enhances the accessibility of active sites to the glycerol molecules, which contributes to increasing the efficiency of catalysts. The high glycerol conversion of 80.5% and the 1,3-PDO yield of 38.2% were achieved under low Pt loading and high space velocity.

Mechanical and Friction Properties of Al2O3-ZrO2-TiC Composite with Varying TiC Contents Fabricated by Spark Plasma Sintering

Zhu Yabin,Chai Jianlong,Shen Tielong,Wang Zhiguang

Al 2 O 3 -ZrO 2 -TiC composites with different proportions of TiC were prepared by ball milling and spark plasma sintering. Structural characterization revealed that the composites exhibited fine and homogeneous microstructures. No other phases except α-Al 2 O 3 , t-ZrO 2 and c-TiC were detected by XRD in all Al 2 O 3 -ZrO 2 -TiC composites. The internal stress induced by the mismatch of the thermal expansion coefficients result in a shift of t-ZrO 2 diffraction peak. SEM and TEM observations showed that the Al 2 O 3 grain size was inversely proportional to the TiC content, while the grain sizes of ZrO 2 and TiC stayed nearly constant. HRTEM micrograph presented that there are glassy phase boundaries with thickness of several nanometers around the TiC grains. As the TiC content increases, the relative density and hardness decreased from 99.2 to 97.7 pct and from 21.0 to 15.8 GPa, respectively. Compared with Al 2 O 3 -ZrO 2 matrix, composites with TiC exhibited lower flexural strength but enhanced fracture toughness. Composite with TiC of 10 vol pct possessed the best friction property. The increased porosity was mainly responsible for the deterioration of mechanical and friction properties except for the fracture toughness. The improvement in fracture toughness with increasing TiC content was attribute to the crack deflection and pinning effects induced by the TiC particles.