JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2021
·
IF 5.302
Zhenxiao Tang,Maozhong Yi,Qiuling Xiang,Yuhui Du,Ke Peng
An improved high-solid-loading slurry impregnation process was developed to introduce HfB 2 particles into a low-density C/C preform efficiently, and precursor infiltration and pyrolysis process was used for densification to obtain a C/C-HfB 2 -SiC composite. The microstructure characterization revealed that HfB 2 particles uniformly filled the pores in the C/C preform, and SiC well densified the interstices between HfB 2 particles and the small pores in the carbon fiber bundles. After being tested, the C/C-HfB 2 -SiC composite had a density of 4.07 g/cm 3 and a bending strength of 344.8 MPa, and exhibited a non-brittle fracture behavior. After ablation with oxyacetylene flame at 2500 ℃ for 120 s, the mass ablation rate and linear ablation rate of the C/C-HfB 2 -SiC composite were 0.5 mg/s and 0.415 μm/s, respectively. The good ablation performance is attributed to the hindering effect of the HfO 2 scale on oxygen diffusion at high temperature.
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
JOURNAL OF MATERIALS SCIENCE
·
2023
·Vol. 58
·期 22
·9196-9209
·
IF 4.5
Tang Zhen-xiao,Yi Mao-zhong,Zhou Yuan-ming,Liu Rui-zhi,Peng Ke
A three-dimensional orthogonal woven C/C-SiC composite was successfully prepared by high-solid-loading slurry impregnation combined with precursor infiltration and pyrolysis. The microstructure, mechanical properties and ablation behavior of the C/C-SiC composite were investigated. The slurry impregnation and the precursor infiltration and pyrolysis acted as fast filling and supplementary densification, respectively. Based on a three-dimensional orthogonal woven C/C preform, the C/C-SiC composite had excellent mechanical properties with bending strength and fracture toughness of 364.46 and 22.86 MPa·m 1/2 . The mass and linear ablation rates of the C/C-SiC composite were 3.21 mg/s and 4.93 μm/s, respectively, after ablation under an oxyacetylene flame for 300 s. The good ablation performance was attributed to the passive oxidation of SiC at high temperature and high oxygen partial pressure, and the pitting caused by SiO 2 accelerated the failure of carbon fibers.
研究领域:
材料科学
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复合材料工程
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高温结构材料
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航天热防护材料
✓ 已验证
DOI
高影响因子
Applied Catalysis O: Open
·
2024
·
IF 0
Sijun Chen,Tingwei Zhang,Yongcan Jin,Huining Xiao
Fructose is a vital ketose in the production of 5-hydroxymethylfurfural platform molecules. Herein, Zr-doped hexagonal mesoporous silica was prepared over in situ co-assembly (Zr-x-HMS, x is the mole ratio of Si to Zr, x = 20, 50) and post-impregnation (Zr-Imx-HMS, x = 20, 50, 100) processes to regulate its catalytic performance against the isomerization of glucose to fructose in ethanol. The post-impregnation process did not significantly change the original pore structure and morphology of HMS, Zr-Im50-HMS with medium Zr loading possessed the most Lewis acid sites with medium strength among Zr-Imx-HMS catalysts. The in situ process changed the physical properties of HMS and enhanced the interaction of Zr sites and silica framework, facilitating the formation of Lewis acid sites with medium strength. Zr-Im50-HMS possessed the most suitable acidity for fructose production, and an optimal yield of 31.2% was achieved at 160 °C and 20 min. Moreover, the recyclability of Zr-Im50-HMS was acceptable.
研究领域:
催化
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化学工程
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材料科学
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绿色化学
✓ 已验证
DOI
JOURNAL OF SUPERCRITICAL FLUIDS
·
2025
·
IF 4.4
Wei Yang,Cong Cong Wang,Lingjun Wang,Li Bao,Fan Yang,Shengji Wu,Lei Che
The hydrolysis mechanism of ball milled bamboo impregnated with deionized water (B-ball), H 2 SO 4 (B-H 2 SO 4 ), HCl (B-HCl) and CH 3 COOH (B-CH 3 COOH) in subcritical water was investigated in the present study. Various mechanochemical reactions were induced during acid-associated mechanical milling and bamboo with improved solubility, reduced thermal stability and solubility was obtained. Acid-associated mechanical treatment also significantly affected the hydrolysis behavior of bamboo in subcritical water. The hydrolysis kinetics of pretreated bamboo could be well expressed by the Coats-Redfern method. The acid strength dominated the hydrolysis of bamboo during ball milling and subcritical water treatment. H 2 SO 4 and HCl possessed the highest ability to dissociate the glycosidic bond and holocellulose-lignin chemical linkages. The above ability, together with their catalytic effects resulted in the lower activation energies required to initiate the hydrolysis of B-H 2 SO 4 (38.87 kJ mol −1 ) and B-HCl (38.23 kJ mol −1 ) compared with those of raw bamboo (74.34 kJ mol −1 ), B-ball (104.42 kJ mol −1 ) and B-CH 3 COOH (90.65 kJ mol −1 ) in subcritical water. The cleavage of holocellulose-lignin chemical linkages liberated the polycondensation of monomer and hydrolysable oligomers from holocellulose for glucose char and aromatic-linked polymer char production, leading to the increase of solid residue yield at elevated reaction temperature. It also promoted the glycosidic bond cleavage and ring scission reactions during hydrolysis in subcritical water, resulting in the improved yields of carbohydrate, 5-hydroxymethylfurfural and furfural.
研究领域:
林业科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
Applied Sciences-Basel
·
2020
·Vol. 10
·期 21
·7607
·
IF 2.474
Yizhi Liu,Xu Liu,Ping Hu
A novel approach was proposed to increase the compactness, shorten the preparation period, and reduce the preparation cost by introducing acetone to optimize the polycarbosilane impregnation process. The porosity in internally derived SiC ceramics decreased and pore size was limited by using this new method, which led to higher compactness. Meanwhile, with the increase in acetone content, the viscosities of polycarbosilane and the wetting angles of polycarbosilane/graphite decreased appreciably, and the viscosity was 6.0 mPa·s with 40 wt.% acetone added—a factor of about 30 lower than that of original polycarbosilane. The wetting angle between polycarbosilane and graphite significantly decreased by 40%, which resulted in an enhancement in the impregnation efficiency of liquid polycarbosilane and a much shorter preparation period. This work provides a convenient and efficient method that is assistant during the practical production process of carbon fiber reinforced ceramic matrix composites (CMCs).Keywords:polycarbosilane;acetone;viscosity;wettability;impregnation efficiency
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
Sustainable Energy Technologies and Assessments
·
2021
·
IF 5.353
Aixia Chen,Zheng Tian,Rong Han,Xiao Wei,Ruirui Hu,Yang Chen
In this study, a nickel (Ni)-based catalyst was loaded onto steel slag that was rich in metal oxides using impregnation method. The effects of the catalyst on hydrogen-rich gas produced using sludge steam gasification were discussed. Under the conditions of 900 ℃, steam flowrate of 1.5 g min −1 and 20% Ni-based loading rate, the gas and H 2 yield reached 0.78 Nm 3 kg −1 and 15.72 mol kg −1 . At this time, the volume fraction of H 2 was as high as 45.096%. Compared with the raw sludge gasification without Ni-based catalyst, the gas and H 2 yield were increased by 39.22% and 60.15% respectively. However, excessive flowrate of steam (≥1.5 g min −1 ) and excessive rate of loading of Ni-based (≥25%) catalyst would lead to a decrease in the production of gas. In addition, the impregnation method could effectively disperse NiO particles on the surface of the support, increasing the ratio of active sites on the surface of catalyst and improving the catalytic activity. These characteristics indicated that the Ni-based steel slag catalysts prepared by the impregnation method had high application potential in the process of sludge steam gasification, and provided a novel idea for solid wastes recycling.
研究领域:
环境科学
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能源工程
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
Materials
·
2022
·Vol. 15
·期 24
·8971
·
IF 3.748
Yaohui Xu,Liangjuan Gao,Zhao Ding
Doping CeO2with Y cations was achieved in this study using three strategies: doping only during the hydrothermal process (H-Y-doped CeO2), doping only during the impregnation process (I-Y-doped CeO2), and doping during both the hydrothermal and impregnation processes (H/I-Y-doped CeO2). During the three synthesis strategies of Y-doped CeO2, these Y ions could be incorporated into the CeO2lattice in the +3 state while holding the cubic fluorite structure, and no impurity phases were detected. Pure CeO2crystal itself contained a certain number of intrinsicVOdefects, and Y-doping was beneficial for the creation of extrinsicVOdefects. The relative concentrations ofVOdefects were quantified by the values ofA592/A464obtained from Raman spectra, which were 1.47, 0.93, and 1.16 for the H-Y-, I-Y-, and H/I-Y-doped CeO2, respectively, and were higher than that of the undoped one (0.67). Moreover, the OSCs of the three Y-doped CeO2were enhanced, and the sequence of OSCs was: H-Y-doped CeO2(0.372 mmol/g) > H/I-Y-doped CeO2(0.353 mmol/g) > I-Y-doped CeO2(0.248 mmol/g) > Undoped CeO2(0.153 mmol/g); this result was in good agreement with the Raman spectroscopy results.Keywords:CeO2;rare-earth;doping;hydrothermal;impregnation;oxygen storage capability
研究领域:
材料科学
·
化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF RARE EARTHS
·
2017
·
IF 2.429
Junlian Wang,Meiying Xie,Juanjuan Ma,Huajun Wang,Shengming Xu
(2,3-Dimethylbutyl)(2,4,4′-trimethylpentyl)phosphinic acid (INET-3) was impregnated onto dry macroporous resins XAD-16 and pretreated XAD-16 with ethyl alcohol and HCl (Pre-XAD-16) to prepare the solvent impregnated resins SIRs-INET-3/XAD-16 and SIRs-INET-3/Pre-XAD-16. The molecular weight distribution of the low molecular weight (LMW) polymers washed off by ethyl alcohol during XAD-16 pretreatment was determined by gel permeation chromatography (GPC). The macroporous resins (XAD-16 & Pre-XAD-16), the corresponding solvent impregnated resins (SIRs-INET-3/XAD-16 & SIRs-INET-3/Pre-XAD-16) and the PVA coated SIRs-INET-3/Pre-XAD-16 with boric acid as cross-linking agent were characterized by FT-IR, SEM-EDS and TGA . The effects of XAD-16 pretreatment and PVA coating technology on RE(III) adsorption equilibrium time, INET-3 losses during extraction and adsorption capacity were investigated. The adsorption kinetics , selectivity and stripping behaviors of SIRs-INET-3/XAD-16 were further studied. The washed off LMW polymers had the Mn of 36,656, Mw of 40,310 and polydispersity coefficient of 1.10. The SIRs-INET-3/XAD-16 had shorter equilibrium time, less INET-3 loss and more Tm(III) adsorption capacity than the SIRs-INET-3/Pre-XAD-16. The PVA coated SIRs-INET-3/Pre-XAD-16 had less INET-3 loss and more Tm(III) adsorption capacity but longer equilibrium time than the uncoated SIRs-INET-3/Pre-XAD-16. The adsorption of RE(III) on the SIRs-INET-3/XAD-16 followed the pseudo-second-order kinetic model . The Tm(III) accumulative adsorption amounts onto SIRs-INET-3/XAD-16 after eight extraction stages was 23.6 mg/g. The separation factors of adjacent heavy RE(III) β Er/Ho , β Tm/Er , β Yb/Tm and β Lu/Yb values were 1.76, 2.59, 2.56 and 1.19, respectively. The adsorbed Lu(III) onto the SIRs-INET-3/XAD-16 can be stripped completely by 1.0 mol/L H 2 SO 4 .
研究领域:
化学工程
·
材料科学
✓ 已验证
DOI
高影响因子
TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA
·
2019
·
IF 2.338
Li-ping RAN,Fei RAO,Ke PENG,Huan YIN,Mao-zhong YI
Ultrahigh-temperature ceramics were added to C/C composites to meet their application requirement in a high-temperature oxidizing environment. C/C−ZrB 2 −SiC composites were fabricated by high-solid-loading slurry impregnation with polymer infiltration and pyrolysis. The dispersion and rheological behavior of ZrB 2 slurry and the microstructural, mechanical, and ablation properties of the C/C−ZrB 2 −SiC composites were investigated. Results indicated that a well-dispersed and low-viscosity ZrB 2 slurry was obtained using 0.40 wt.% polyethyleneimine as a dispersant at pH 5. Ceramics were uniformly distributed in the short-cut fiber layer and needle-punched area. The flexural strength of the C/C−ZrB 2 −SiC composites was 309.30 MPa. The composites exhibited satisfactory ablation resistance under the oxyacetylene flame of 2500 °C, and the mass and linear ablation rates were 0.40 mg/s and 0.91 μm/s, respectively. A continuous and compact ZrO 2 layer, which could effectively reduce the diffusion rate of oxygen and protect the composites from being ablated, was formed.
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
Journal of Materials Chemistry A
·
2015
·Vol. 3
·期 29
·15299-15306
·
IF 7.443
Jugong Zheng,Cancan Qin,Tongfu Wu,Shuangfei Xie,Liang Ni,Muyang Peng,Yuefeng Tang,Yanfeng Chen
Preparing high-performance LiMnPO4 is still a large obstacle due to its sluggish electrochemical kinetics. To overcome this problem, a novel method is developed for LiMnPO4/C nanoplates from nanoporous Mn2O3 precursors. There are two advantages. Firstly, through negative pressure immersion, lithium dihydrogen phosphate (LiH2PO4), lithium hydroxide (LiOH) and sucrose (C12H22O11) are deposited on the surface of porous Mn2O3 nanosheets. In the following solid-state reaction, three dimensional continuous conductive carbon is wrapped uniformly around the LiMnPO4/C nanoplates, which greatly improved the conductivity. Secondly, (010) exposed facets are obtained using the Mn2O3 hierarchical microspheres as precursors, which allows for a fast transmission of Li+ ions improving the rate capability. As a result, the as-synthesized L-Mn2O3-LMP/C samples exhibit a superior rate performance with discharge capacities of 157.3 mA h g−1 at C/20, 122.6 mA h g−1 at 1C, and 105.8 mA h g−1 at 2C. Meanwhile, they can retain 99.3% of the initial capacity after 100 cycles at 1C, revealing an excellent cycling stability. This method sheds more light on the fabrication of high-performance LiMnPO4/C cathode materials and is suitable for large scale productions.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
ENERGY & FUELS
·
2018
·
IF 3.024
Na Rao,Mei Wang,Ziming Shang,Yanwen Hou,Guozhi Fan,Jianfen Li
Modifications by impregnation and grafting are commonly used for the preparation of amine-functionalized MCM-41. A comprehensive evaluation of the advantages and disadvantages of the two methods was performed in this work. MCM-41 was synthesized by the hydrothermal method, setting the amine-loading mass fraction at 40, 50, and 60 wt %. Three amine-modified adsorbents were prepared by impregnating polyethylenimine (PEI), and the three other adsorbents were prepared by grafting 3-aminopropyltriethoxysilane (APTS) onto MCM-41. The as-prepared adsorbents were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and N2 adsorption–desorption techniques. CO2 adsorption capacities were measured, and the experimental data were fitted with adsorption kinetic models. The cyclic stability of the adsorbents prepared by the two kinds of amine-modified methods was compared using the cyclic adsorption–desorption experiments. The characterization results showed that the target adsorbents were prepared successfully. The thermal stability of the adsorbents modified by grafting was better than the thermal stability of the adsorbents modified by the impregnation. Maximum CO2 adsorption capacities of 3.53 mmol g–1 (50% PEI–MCM-41) and 2.41 mmol g–1 (50% APTS–MCM-41) could be reached at 25 °C and 1 atm, which were 4.7 and 3.2 times greater than that of MCM-41. The Avrami model fitted the experimental data well, indicating a variety of interactions between the adsorbents and CO2. CO2 adsorption capacity after 5 adsorption–desorption cycles decreased by 14.22 and 5.19% for the adsorbents prepared by impregnation and grafting, respectively. It was concluded that MCM-41 modified by impregnation and grafting followed the same kinetic model. The absorbents modified by impregnation showed higher CO2 adsorption capacity and amine-loading efficiency, while those prepared by grafting had better thermal and cyclic stabilities.
研究领域:
材料科学
·
环境科学
✓ 已验证
DOI
高影响因子
INDUSTRIAL CROPS AND PRODUCTS
·
2025
·
IF 6.2
Jing Li,Jia-Nan Tian,Zhao-Jun Liu,Shu-Hui Zhang,Xin-Yue Zhang,Han-Min Wang,Qing-Xi Hou
The structure of wood poses significant challenges for Chemi-thermomechanical pulp (CTMP) pulping process, particularly in achieving efficient chemical penetration and uniform distribution within woodchips. While alkali pre-impregnation is known to enhance pulp bleachability, this work advances prior work by systematically correlating lignin’s structural evolution under optimized pretreatment conditions with the bleaching performance of poplar woodchips (PWCs)-derived CTMP. The results show that the content of the main linkages, e.g. , β - O -4 and β - β , in lignin were significantly reduced 29.58 % and 21.00 %, respectively, after alkali pre-impregnation, and the number of aromatic regions including guaiacyl (G), syringyl (S) and para-coumaric acid ester (PCE) units reduced, confirming the partial depolymerization of lignin. The optimum pre-impregnation conditions, including 6 % alkali charge at 70 °C for 30 min, were beneficial to achieving a satisfied pulp brightness (74.73 % ISO). This work would highlight the critical role of alkali pre-impregnation techniques in CTMP pulping and bleaching processes.
研究领域:
林业工程
·
制浆造纸科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）