Energy Technology
·
2016
·Vol. 4
·期 8
·943-949
·
IF 2.557
Dong Pi,Wen Zhi Li,Qi Zhao Lin,Qi Fu Huang,Hui Qing Hu,Chun Yu Shao
A series of Pd-based core–shell catalysts (Pd@SiO 2 , Pd@CeO 2 , and Pd@ZrO 2 ) supported on Si-modified Al 2 O 3 were prepared for the catalytic combustion of lean methane. Pd@SiO 2 exhibited slightly lower catalytic activity than Pd@CeO 2 and higher catalytic activity than Pd@ZrO 2 in dry conditions; however, Pd@SiO 2 had the highest catalytic activity among the three catalysts in the presence of high concentrations of water vapor. Furthermore, the Pd@SiO 2 catalyst showed good thermal stability and resistivity to water poisoning. CO chemisorption and TEM results demonstrated that the core–shell structure could help in the stabilization of the active phase compared to the uncoated Pd/Si-Al 2 O 3 catalyst. XRD and X-ray photoelectron spectroscopy results indicated that a balanced mixed phase of PdO x /Pd 0 is the main active phase of these Pd-based catalysts.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Nano Materials
·
2018
·
IF 0
Wuzhu Sun,Weiyi Yang,Zhengchao Xu,Qi Li
A novel and environmentally benign approach was developed to create a Fe3O4@SiO2 core–shell structure supported Pd catalyst consisting of a superparamagnetic Fe3O4 nanosphere core, a SiO2 shell with a rough surface, Pd nanoparticles deposited on a SiO2 shell, and a cross-linked polyvinylpyrrolidone (PVP) layer. It was found that both adsorbed PVP and SiO2 shell with a rough surface from the surface-protected etching process were critical to obtain the uniform PdO deposition, while the cross-linked PVP layer could effectively anchor and protect active Pd nanoparticles to enhance their stability to resist detachment from the catalyst support and improve the reusability of the catalyst. Because of its superparamagnetic behavior, it could disperse well in aqueous solution without external magnetic field and be separated easily from aqueous solution when an external magnetic field was present. It demonstrated a high catalytic activity, desirable N2 product selectivity over 99.7%, and good reusability for the catalytic nitrite reduction in aqueous solution.
研究领域:
材料科学
·
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
JOURNAL OF APPLIED POLYMER SCIENCE
·
2022
·Vol. 139
·期 19
·52115
·
IF 3.057
Chuying Zhang,Hang Zhao,Fan Yang,Na Zhang,Tongguang Zhu,Kunyue Leng,Jinbo Bai
The addition of inorganic particles can endow polymer matrices with different new features, thereby realizing an optimization to the structural and functional properties of composite. The overall properties of composites are greatly influenced by both fillers dispersion and fillers-polymer interfacial interaction. However, to simultaneously improve these mentioned two issues is still a critical challenge in the field of polymer-based nanocomposite. Herein, a typical core-shell structured mesoporous silica-coated silica (SiO 2 @mSiO 2 ) construction was successfully synthesized by using a bi-phase method. The SiO 2 @mSiO 2 filled polyethylene (PE) nanocomposite was fabricated through a precisely controlled melt-mixing approach. Benefiting from the additional mesoporous SiO 2 shell, both the dispersion of SiO 2 @mSiO 2 and the SiO 2 @mSiO 2 -PE matrix interfacial interaction are improved. Moreover, the stress–strain behavior, temperature-dependent mechanical property, thermal stability, and electrical insulating property of SiO 2 @mSiO 2 /PE composite were studied in detail. It is found that SiO 2 @mSiO 2 core-shell nanoparticles are capable of not only making a balance between the strength and toughness of the PE-based composite, but also improving the thermal stability of the composite. In addition, the SiO 2 @mSiO 2 /PE composite exhibited an enhanced breakdown strength (256.4 MV·m −1 ) when filled with as small as 1 wt% SiO 2 @mSiO 2 , which is 108% higher than neat PE. All these optimized features are attributed to the well-designed core-shell structure. These experimental results provide a promising way to design and fabricate future advanced composite with excellent structural and functional properties in the future.
研究领域:
材料科学
·
高分子科学
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2025
·
IF 5.6
Li Song,Zhiyao Fu,Zhi Ye,Junjia He
ZnO@SiO 2 core-shell structured powder, as the raw material for preparing ZnO varistor, is conducive to obtaining a fine and uniform microstructure, which is of positive significance for acquiring high-performance resistors. Currently, limited research has been conducted on the microstructural evolution of core-shell structures during the sintering process, and the mechanism of material migration remains inadequately understood. This study systematically investigated the sintering behavior of nanostructured ZnO@SiO 2 core-shell compacts by varying both the sintering profiles and Si 4+ /Zn 2+ molar ratios. XRD, SEM, and FTEM characterization techniques were employed to track the microstructural evolution across critical sintering stages and to analyze the effect of the shell layer thickness on the microstructure evolution. To more clearly elucidate the sintering characteristics of the core-shell structure, a control group comprising directly mixed ZnO-SiO 2 powders was included. The dominant mechanisms of material transport were elucidated by EPMA through elemental mapping at critical sintering stages, coupled with microstructural evolution analysis. The core-shell structure, acting as a heterogeneous unit, demonstrated distinct sintering behavior compared to directly mixed ZnO-SiO 2 powders. This disparity arises from the modified interfacial contact between ZnO and SiO 2 in the core-shell architecture. Specifically, the phase transition temperature was reduced, the onset sintering temperature was elevated, and the densification temperature was lowered. During microstructural evolution, Si from the shell layer initially diffuses into the sintered neck regions via surface transport. Notably, the mid-stage sintering is characterized by extensive formation of a glassy liquid phase, which significantly accelerates densification through viscous flow-mediated mass transfer. During the final densification stage of sintering, grain boundary diffusion mechanisms dominate the process. Throughout the sintering process, the network structure formed by Si migration promotes microstructural homogenization while effectively suppressing grain growth.
研究领域:
材料科学
·
纳米技术
·
陶瓷材料
·
固体物理
·
微观结构工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）