MATERIALS LETTERS
·
2014
·
IF 2.269
Xiaozhu Shi,Junping Duan,Jianjun Lu,Miaoqing Liu,Lijuan Shi
A typical of network-like polyimide/silica composite microspheres with a high SiO 2 content was successfully prepared by a suspension polymerization method. The microstructure, morphology, surface composition and thermal property were characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analyzer (TGA), respectively. The results showed that the size of PI/SiO 2 composite microspheres with 20–25 μm presented rough surface and an interpenetrating network had formed inside the spheres. The temperature of 5% weight loss was at about 503 °C, having higher thermal stability than pure PI.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Reaction Kinetics Mechanisms and Catalysis
·
2015
·Vol. 116
·期 2
·451-466
·
IF 1.17
Jiang Dahao,Mao Jun,Fang Zheng,Ni Jun,Zhang Qunfeng,Li Xiaonian
In this paper, the deactivation causes of the Pd/SiO 2 catalyst for continuous liquid-phase selective hydrogenation of 6,10,14-trimethylpentadeca-13-en-2-one in 2000 h of pilot plant test were systematically investigated by N 2 adsorption–desorption, thermogravimetric and differential thermal analyses, scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray fluorescence, experiments of CO poisoning and regeneration, and laboratory retests of the deactivated catalyst samples. The pore textures of Pd/SiO 2 catalysts were not destructed during the pilot test, while there were no obvious carbonaceous deposits appearing on the deactivated catalyst samples. The sintering and crystallization of Pd metal nanoparticles were found, which could be partially accountable for the deactivation of Pd/SiO 2 catalysts. Though Pd leaching did not take place in the pilot test, the Pd active phase could be slightly poisoned by sulfur impurities from feedstock hydrogen. Combining the results of CO poisoning and regeneration experiments with those of compositional analyses of fresh and circulating hydrogen in the pilot test, it could be concluded that CO poisoning should be another important reason for the deactivation of the Pd/SiO 2 catalyst due to high concentration of CO in the reaction system of pilot test and relatively low reaction temperature in the middle and at the bottom of the catalyst bed. Fortunately, the CO poisoned Pd/SiO 2 catalyst in the pilot test could be in situ regenerated by installing a purifier for CO elimination from the circulating hydrogen and increasing the temperature of the whole catalyst bed to slightly higher than 383 K.
研究领域:
催化化学
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材料科学
·
工业化学
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL CROPS AND PRODUCTS
·
2019
·
IF 4.191
Gaofeng Chen,Tingzhou Lei,Zhiwei Wang,Shijie Liu,Xiaofeng He,Qian Guan,Xiaofei Xin,Haiyan Xu
A mesoporous composite CoCuK/ZrO 2 -SiO 2 catalyst with high activity and long life was prepared by vacuum impregnation and multisolvent self-assembly. The catalytic activity of the mesoporous catalyst was investigated for the synthesis of ethanol and higher alcohols from biomass syngas from wheat straw. The catalyst was characterized by small-angle X-ray diffraction, power XRD, N 2 adsorption and desorption experiments (BET), and transmission electron microscopy (TEM). The effects on the reaction activity and products from the addition of alkali metal promoter K, the modification of ZrO 2 and different copper/cobalt compositions were analyzed. The life of the catalyst was determined using a pressurized fixed-bed reactor. The results show that the catalyst possesses the high CO hydrogenation activity, high C 2+ OH selectivity and high life expectancy needed to meet industrial applications.
研究领域:
催化化学
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可再生能源
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS CHEMISTRY AND PHYSICS
·
2023
·
IF 4.6
Xia Zhao,Hong Hao,Haixia Pang,Min Jiang,Yanping Duan
Emulsifier-free polymerization was employed to prepare the submicron spherical PSA (the copolymer of styrene and acrylic acid), then SiO 2 was grown on the surface of the PSA by sol-gel method to form F–SiO 2 @PSA particles. It was found that when styrene: acrylic acid = 2.5:1 and tetraethyl orthosilicate : PSA was between 2.17:1 and 6.38:1, a perfect raspberry-like structure could be obtained. The coating based on F–SiO 2 @PSA particles exhibited contact angles of 167.3 ± 1.4°, 152.1 ± 1.5°,150.3 ± 1.6°, 150.9 ± 1.6°, 142.2 ± 1.7°, 143.7 ± 1.5° and 146.6 ± 1.9° to water, diiodomethane, soybean oil, rapeseed oil, hexadecane, kerosene, and waste engine oil , respectively. The F–SiO 2 @PSA coating could reduce the adsorption of protein by 90% compared with the control surface . It was observed that bacteria and platelets could hardly adhere to the coating surface after 24 h of E. coli culture and 3 h of platelet-rich plasma immersion. The anti-adhesion to proteins, platelets, and bacteria will give the coating a promising application in the medical field.
研究领域:
材料科学
·
生物医学工程
✓ 已验证
产品关联
DOI
高影响因子
Particuology
·
2023
·
IF 3.5
Zixu Shi,Chaoyun Shi,Huili Shi,Binfang He,Guoqiang Qin,Ao Li,Jing Zhu,Jingbo Chen
Silica-based anode material is the most concerned material at present, which has the advantages of good cycle stability, high theoretical specific capacity and abundant reserves. However, silica suffers from inherent low conductivity , severe volume expansion effect and low initial coulombic efficiency, which limits its application in lithium-ion batteries. Nanotubes structure can mitigate the volume expansion during lithiation/delithiation. In this article, silica nanotubes (SNTs) were prepared using carbon nanotubes (CNTs) as a template, and then the uniform carbon layer was coated on their surface by carbonization of citric acid . The hollow structure of nanotubes provides more sites for the insertion of Li + during lithiation and additional channels for Li + migration in the cycles, which improves the electrochemical performance. Conductivity can be enhanced by coating carbon layer. The specific capacity of the composite material is about 650 mAh g −1 at 0.1 A g −1 after 100 cycles. With a specific capacity of 400 mAh g −1 even at 1 A g −1 after 100 cycles. The silica-based material is a competitive anode material for lithium-ion batteries.
研究领域:
材料科学
·
电化学
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2022
·
IF 4.889
Jie Liu,Jianhao Cui,Lei Chen,Jingjing Chen,Huidong Zheng,S. Ted Oyama
The conversion of terpinolene epoxide to terpinen-4-ol is a desirable chemical transformation for the production of a valuable intermediate. This paper describes a one-pot, two-step system for the reaction that uses a bifunctional Ni/TiO 2 -SiO 2 catalyst with isomerization and hydrogenation capabilities. The TiO 2 -SiO 2 serves to isomerize the starting epoxide. The Ni component works to hydrogenate the allylic double bond. The tandem system achieves a high 64% yield of terpinen-4-ol. X-ray diffraction analysis showed that TiO 2 -SiO 2 was a mixed binary oxide, and Fourier transform infrared spectroscopy of adsorbed pyridine suggested that acid sites were mainly Lewis acid sites. Electron microscopy showed that the Ni/TiO 2 -SiO 2 catalyst consisted of spherical particles comprising a titanosilicate phase with highly dispersed zero-valent Ni or anatase on the surface. Additionally, there was strong interaction between Ni and the TiO 2 -SiO 2 mixed oxides. Control kinetic experiments demonstrated that the tandem use of the catalysts was more effective than simultaneous operation.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2014
·
IF 2.235
Lu Lin,Tong Zhang,Xiongfu Zhang,Haiou Liu,King Lun Yeung,Jieshan Qiu
In this work, we fabricated a new type of Pd/SiO2@ZIF-8 core–shell catalyst composed of a Pd/SiO2 microsphere as the core and a ZIF-8 membrane as the shell. The preparation procedure involves first loading Pd nanoparticles onto nonporous SiO2 microspheres to obtain the Pd/SiO2 core and then coating a perfect layer of ZIF-8 shell on the core by electrostatic induction to form a Pd/SiO2@ZIF-8 core–shell structure. It is crucial that the modification of the Pd/SiO2 core with polyelectrolyte was employed to improve the charge distribution of the core surface and preferably adsorb Zn2+ cations in the synthesis solution so as to assist the formation of a continuous ZIF-8 shell. The compactness and thickness of the shell were optimized by increasing the number of cycles of ZIF-8 growth. The hydrogenations of alkenes with different molecular sizes showed that the Pd/SiO2@ZIF-8 catalysts can provide excellent product selectivity and antipoisoning and antileaching properties for the hydrogenations of alkenes.
研究领域:
催化
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化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2017
·Vol. 7
·期 75
·47738-47745
·
IF 3.108
Kunquan Li,Xingrong Zeng,Xuejun Lai,Shengyong Chai
Fluorine-containing acrylates (FACs) with different glass transition temperature (Tg) were synthesized by solution copolymerization, and then the superhydrophobic coatings were fabricated based on the FAC, micro-SiO2 (M-SiO2) and nano-SiO2 (N-SiO2) particles through a two-step spray method. The prepared FAC was characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR) and differential scanning calorimetry (DSC). The wetting behavior and surface morphology of the superhydrophobic coating were studied. The resistance and mechanism of the superhydrophobic coating against abrasion were also investigated. FTIR and 1H-NMR showed that the fluorinated-containing monomer had copolymerized with the acrylate monomers, and FACs with different Tg of about 74.2 °C, 24.5 °C, −7.7 °C and −29.5 °C were prepared. After coating with FAC/M-SiO2/N-SiO2 composite coating, the surface showed hierarchical structures with a roughness (Sa) of 1.23 mm, and became superhydrophobic with a water contact angle higher than 150° and a low sliding angle lower than 5°. Abrasion testing showed that the superhydrophobic coating fabricated based on the FAC polymer with low Tg had better abrasion resistance in comparison with that of the FAC polymer with high Tg. Meanwhile, the M-SiO2 in the composite coating could weaken the abrasion force to the surface micro roughness damage and acted as connections for the adhesion of N-SiO2 particles during abrasion, which ensured the binary micro/nano structures required for good hydrophobicity after abrasion.
研究领域:
材料科学
·
表面化学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Xingjie Dong,Jianqin Wu,Qing Zhou,Wenqing Wang,Xueqin Zhang,Lu Zhang,Rujie He
Si 3 N 4 -SiO 2 ceramics are considered as the preferred high-performance wave-transmitting material in the aerospace field. However, traditional fabrication methods for Si 3 N 4 -SiO 2 ceramics have the disadvantages of high cost and complicated fabrication process. In this paper, Si 3 N 4 -SiO 2 ceramics with excellent mechanical and dielectric properties were fabricated by digital light processing-based 3D printing combined with oxidation sintering. Firstly, the curing thickness and viscosity of slurries with different solid loadings for vat photopolymerization-based 3D printing were studied. Then, the effects of the sintering temperature on the linear shrinkage, phase composition, microstructure, flexural strength , and dielectric properties of Si 3 N 4 -SiO 2 ceramics, and the influences of solid loading on them were explored. The curing thickness and viscosity of the slurry with a solid loading of 55 vol% were 30 μm and ∼1.5 Pa‧s, respectively. The open porosity and the flexural strength of Si 3 N 4 -SiO 2 ceramic with a solid loading of 55 vol% were 4.3 ± 0.61% and 76 ± 5.6 MPa, respectively. In the electromagnetic wave band of 8–18 GHz, the dielectric constant of Si 3 N 4 -SiO 2 ceramics was within the range of less than 4, and the dielectric loss remained below 0.09. The method of digital light processing-based 3D printing combined with oxidation sintering can be further extended in the preparation of Si 3 N 4 -based structure-function integrated ceramics.
研究领域:
材料科学
·
航空航天工程
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS CHEMISTRY AND PHYSICS
·
2022
·
IF 4.778
Zhang Tianwei,Liu Hao,Zhiyue Han,Du Zhiming,Zhang Cunwei,Shan Liya,Wang Yong,Zhang Guiyun,Wang Gaofeng
The seawater dry water extinguishing materials formed by coating seawater with nano-SiO 2 have greatly enlarged the application space of the seawater as a fire-extinguishing medium. Against the deficiencies in the evaluation of the size-fractionated and stability of dry water extinguishing materials, especially of the coating effect of nano-SiO 2 , this study designed an airflow size-fractionated system applicable to dry water materials and characterized the stability of dry water materials by electrochemical methods according to the pneumatic separation principle. The results showed that the grain size range of seawater@nano-SiO 2 dry water extinguishing materials was 0.2–400 μm, and that the dry water could be divided into three intervals by granule size by adjusting the turbo-dynamo frequency and draught fan frequency of the airflow size-fractionated system. The electrochemical methods are applicable to describe the stability of the dry water extinguishing materials, and the gelatinization of core material can significantly make up for the deficiency that the core material of dry water tends to separate out over storage time. However, the stability of dry water is subject to granule size more than the gelatinization of the core material, and the dry water with big-size granules has optimal stability. Graded dry water is less corrosive to aluminum sheets, and the corrosion resistance to big-grained gel-dry water is optimal. The research conclusion can provide a technical basis for size-fractionated and covering effect characterization of dry water extinguishing materials and for type selection of storage media.
研究领域:
材料科学
·
消防工程
·
电化学
✓ 已验证
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2022
·
IF 5.532
Xufeng Zhang,Huidan Zeng,Xin Wang,Weichang Li,Lili Hu,Shubin Chen
MgO–Al 2 O 3 –SiO 2 glass-ceramics have been widely used in military, industrial, and construction applications. The nucleating agent is one of the most important factors in the production of glass-ceramics as it can control the crystallization temperature or the grain size. In this study, we investigated the effect of replacing P 2 O 5 with different amounts of TiO 2 on the crystallization, structure, and mechanical properties of an MgO–Al 2 O 3 –SiO 2 system. The crystallization and microstructure were investigated by differential scanning calorimetry , Raman spectroscopy , X-ray diffraction, scanning electron microscopy, and transmission electron microscopy . The mechanical properties were investigated by measuring the Vickers hardness , Young's modulus , and fracture toughness. The results showed that adding TiO 2 favored the precipitation of fine grains and significantly increased the Vickers hardness, Young's modulus, and fracture toughness of the glasses. Introducing an appropriate amount of TiO 2 can make a glass structure more compact, promote crystallization, and improve the mechanical properties of MgO–Al 2 O 3 –SiO 2 glass-ceramics.
研究领域:
材料科学
·
陶瓷学
·
玻璃科学
✓ 已验证
DOI
高影响因子
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE
·
2019
·Vol. 645
·期 21
·1240-1246
·
IF 1.337
Lu Yuan,Ming Kang,Guanjun Chang,Xiangmeng Lv,Simin Shen,Rong Sun
Due to the unique size effects, nanomaterials in infrared absorption have attracted much attention for their strong absorption in the infrared region. To achieve the infrared multi-band absorption, we propose to synthesize a core-shell structure nanomaterial consisting of NaYF 4 :Yb 3+ , Er 3+ core and a layer of SiO 2 as shell. A series of NaYF 4 :Yb 3+ , Er 3+ nanocrystals were synthesized through hydrothermal method by adjusting the ratio of citric acid(CA)-to-NaOH, and the effects of CA concentration, and NaOH concentration were studied in detail. NaYF 4 :Yb 3+ , Er 3+ @SiO 2 nanoparticles were synthesized by sol-gel method using TEOS as silica source. The results show that the core-shell NaYF 4 :Yb 3+ , Er 3+ @SiO 2 nanoparticles were successfully synthesized. Up-conversion spectra of these nanoparticles were recorded with 980 nm laser excitation under room temperature. There are no changes of the emission centers of nanoparticles before or after silica coating, but the emission intensities of nanoparticles after silica coating are weakened. Furthermore, the property of infrared multi-band absorption was tested through ultraviolet-visible-near infrared spectrophotometer and infrared absorption spectra. The results illustrate that the multi-band infrared absorption nanomaterial was successfully synthesized.
研究领域:
材料科学
·
纳米技术
·
光学
✓ 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）