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Sökning: WFRF:(Zhang Feng) > Luleå tekniska universitet

  • Resultat 1-10 av 41
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1.
  • Zhang, Shuangshuang, et al. (författare)
  • Discovery of carbon-based strongest and hardest amorphous material
  • 2022
  • Ingår i: National Science Review. - : Oxford University Press. - 2095-5138 .- 2053-714X. ; 9:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Carbon is one of the most fascinating elements due to its structurally diverse allotropic forms stemming from its bonding varieties (sp, sp2, and sp3). Exploring new forms of carbon has always been the eternal theme of scientific research. Herein, we report the amorphous (AM) carbon materials with high fraction of sp3 bonding recovered from compression of fullerene C60 under high pressure and high temperature previously unexplored. Analysis of photoluminescence and absorption spectra demonstrates that they are semiconducting with a bandgap range of 1.5–2.2 eV, comparable to that of widely used amorphous silicon. Comprehensive mechanical tests demonstrate that the synthesized AM-III carbon is the hardest and strongest amorphous material known so far, which can scratch diamond crystal and approach its strength. The produced AM carbon materials combine outstanding mechanical and electronic properties, and may potentially be used in photovoltaic applications that require ultrahigh strength and wear resistance.
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2.
  • Shen, Gulou, et al. (författare)
  • Effect of surface roughness on partition of ionic liquids in nanopores by a perturbed-chain SAFT density functional theory
  • 2022
  • Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 157:1
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, the distribution and partition behavior of ionic liquids (ILs) in nanopores with rough surfaces are investigated by a two-dimensional (2D) classical density functional theory model. The model is consistent with the equation of state that combines the perturbed-chain statistical associating fluid theory and the mean spherical approximation theory for bulk fluids. Its performance is verified by comparing the theoretical predictions with the results from molecular simulations. The fast Fourier transform and a hybrid iteration method of Picard iteration and Anderson mixing are used to efficiently obtain the solution of density profile for the sizable 2D system. The molecular parameters for IL-ions are obtained by fitting model predictions to experimental densities of bulk ILs. The model is applied to study the structure and partition of the ILs in nanopores. The results show that the peak of the density profile of counterions near a rough surface is much higher than that near a smooth surface. The adsorption of counterions and removal of co-ions are enhanced by surface roughness. Thus, the nanopore with a rough surface can store more charge. At low absolute surface potential, the partition coefficient for ions on rough surfaces is lower than that on smooth surfaces. At high absolute surface potential, increasing surface roughness leads to an increase in the partition coefficient for counterions and a decrease in the partition coefficient for co-ions.
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3.
  • Wang, Zhang, et al. (författare)
  • Fabrication and properties of freeze-cast mullite foams derived from coal-series kaolin
  • 2016
  • Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 42:10, s. 12414-12421
  • Tidskriftsartikel (refereegranskat)abstract
    • Hierarchically porous mullite foams were fabricated from coal-series kaolin and Al2O3 slurries by freeze-casting using tert-butyl alcohol (TBA) and water as templates. TBA developed unidirectionally aligned pore channels along the freezing direction and water developed lamellar pores. The total porosity (60.2–83.4%), density (0.49–1.23 g/cm3) and macro-pore size (10–50 µm) of mullite foams were tailored by controlling the solid content of the slurries. The mullitization reaction was completed at the sintering temperature of 1500 °C. The compressive strength of mullite foams along the freezing direction was 3.8–49.4 MPa. Lower porosity and higher compressive strength of sintered mullite foams were obtained using TBA as solvent compared to water. The thermal conductivity of low density and mechanically stable TBA templated porous mullite with 80.2% porosity was 0.18 W/m K, indicting that the freeze-cast porous mullite was a promising refractory material for applications in thermal insulation
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4.
  • Yu, Qiangliang, et al. (författare)
  • Novel N, P-containing oil-soluble ionic liquids with excellent tribological and anti-corrosion performance
  • 2019
  • Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 132, s. 118-129
  • Tidskriftsartikel (refereegranskat)abstract
    • Two oil-soluble ionic liquids N, N-trimethyl-N-hexadecyl ammonium bis(2-ethylhexyl) phosphate (NP-16))and 1,2-bis-N, N-dimethyl-N-cetylammonium bis (2-ethylhexyl) phosphate (NP-16-2-16) have been synthesized and investigated as a potential friction reduction and anti-wear lubricant additive with anti-corrosion properties. The results indicate that the addition of 1.0 wt % NP-16 into PAO10 can significantly reduce friction coefficient and improve its anti-wear performance under RT and 100 °C. The performance is obviously better than that of traditional additives ZDDP and tricresyl phosphate. PAO10 + 1.0 wt % NP-16 even outperformed the PAO10 with about 40% lower friction and 2 orders of magnitude less wear. The analysis results of SEM, EDS and XPS show that an FePO4 or nitrogen-containing tribofilm is formed on the friction interface when NP-16 and NP-16-2-16 are selected as additives, which play a key role in reducing friction and wear.
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5.
  • Yu, Qiangliang, et al. (författare)
  • Physicochemical and tribological properties of gemini-type halogen-free dicationic ionic liquids
  • 2021
  • Ingår i: Friction. - : Springer. - 2223-7690 .- 2223-7704. ; 9:2, s. 344-355
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of new halogen-free dicationic ionic liquids (ILs) with different alkyl chain lengths were prepared, and the relationship between the alkyl chain length, physicochemical and tribological properties of ILs, and their role as neat lubricant for steel-steel friction pairs, was investigated. Evaluation of stability during hydrolysis and copper strip corrosion test results show that synthetic ILs are stable and not corrosive to metal contacts, due to the halogen-free anions. The friction and wear test results indicate that ILs with long alkyl chains have excellent friction-reducing and anti-wear properties, especially at high temperatures. Based on the surface three-dimensional (3D) profiles, electrical contact resistance, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and the X-ray photoelectron spectrometry (XPS) analysis of the worn surfaces of steel discs, we can conclude that the efficiency of ILs is due to the formation of high quality tribofilms that consist of both tribochemical reaction and ordered absorption films.
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6.
  • Zhang, Hanzhu, 1991- (författare)
  • High-entropy boron-carbide and its composites
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • High-entropy alloy (HEA) is a multicomponent alloy material that contains five or more principal elements in equi- or near equi-atomic ratios. The entropy stabilisation leads to the formation of a crystalline solid solution accommodating the principal elements. The HEA solid solution has characteristic features such as lattice distortion, sluggish diffusion and cocktail effect that contribute to the superior properties of HEA including high strength, high hardness, excellent thermal and chemical stability, etc. The concept of HEA has been extended to ceramic materials to process high-entropy ceramic (HEC) that consists of multiple ceramic compounds such as metallic oxides, nitrides or carbides. The HECs have shown entropy stabilisation and formed single-phase ceramic solid solutions. However, the formation mechanism of high-entropic phase in HECs remains unclear and unpredictable. Generally, in order to maximise the probability of forming a high-entropy solid solution in a ceramic system, ceramic compounds with least difference in the crystal structure, preferably with only one anionic constituent element, are favoured when designing HECs, which limits the potential of discovering and developing new HECs. In this project, a multicomponent ceramic system containing six ultra-high temperature ceramics (UHTCs), B4C, HfC, Mo2C, TaC, TiC and SiC, was used to investigate the formation of high-entropy ceramics, UHTC composites, as well as the microstructure evolution, properties and high temperature applications. A ceramic composite composed of SiC and a high-entropy boron-carbide with hexagonal crystal structure was successfully processed from the carbide system in spite of the difference in the crystal structures of precursors (face-centred cubic, hexagonal and rhombohedral). The hexagonal HEC solid solution exhibited a unique AlB2 structure with alternating layers of metal and non-metal C/B atoms according to the experimental and simulation investigations. The HEC/SiC composite showed superior mechanical properties such as ultra-high hardness, excellent wear and oxidation resistance. The addition of B4C was discovered to be the key factor in the formation of the hexagonal high-entropy boron-carbide solid solution, while the final phase composition was tailored by utilising precursors of different particle size. Additionally, SiC as the reinforcement component in the HEC/SiC composite was used to tailor the microstructure, phase evolution and mechanical properties of the high-entropy boron-carbide composite. Higher content of SiC resulted in enhanced mechanical properties such as hardness and fracture toughness, as well as promoted the formation of the hexagonal high-entropy boron-carbide solid solution. To extend the investigation on the high-entropy boron-carbide composite to application, B4C, HfC, Mo2C, TaC and TiC were consolidated into a target for magnetron sputtering. The target was used to deposit oxidation-resistant high-entropy coatings using magnetron sputtering on carbon-carbon composites. The coatings showed superior mechanical performance and high temperature oxidation resistance at 2000 °C on carbon-carbon composite, suggesting potential applications of high-entropy boron-carbide ceramics as a protective coating material against oxidation at elevated temperature. This work pointed out the possibilities of synthesising high-performance HECs with superior properties from components with vast elemental and structure diversity, and thereby advanced the design criteria of HECs and provided more potential research directions for the new high-performance ceramic materials.
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7.
  • Cao, Danyang, et al. (författare)
  • Biolubricant
  • 2023
  • Ingår i: Sustainable Production Innovations. - : John Wiley & Sons. ; , s. 1-56
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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8.
  • Chen, Feng, et al. (författare)
  • Data mining for the internet of things : Literature review and challenges
  • 2015
  • Ingår i: International Journal of Distributed Sensor Networks. - : SAGE Publications. - 1550-1329 .- 1550-1477. ; 2015
  • Tidskriftsartikel (refereegranskat)abstract
    • The massive data generated by the Internet of Things (IoT) are considered of high business value, and data mining algorithms can be applied to IoT to extract hidden information from data. In this paper, we give a systematic way to review data mining in knowledge view, technique view, and application view, including classification, clustering, association analysis, time series analysis and outlier analysis. And the latest application cases are also surveyed. As more and more devices connected to IoT, large volume of data should be analyzed, the latest algorithms should be modified to apply to big data. We reviewed these algorithms and discussed challenges and open research issues. At last a suggested big data mining system is proposed
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9.
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10.
  • Huang, Xianzhu, et al. (författare)
  • Flow-resistance analysis of nano-confined fluids inspired from liquid nano-lubrication : A Review
  • 2017
  • Ingår i: Chinese Journal of Chemical Engineering. - : Elsevier. - 1004-9541 .- 2210-321X. ; 25:11, s. 1552-1562
  • Tidskriftsartikel (refereegranskat)abstract
    •  How to reduce flow resistance of nano-confined fluids to achieve a high flux is a new challenge for modern chemical engineering applications, such as membrane separation and nanofluidic devices. Traditional models are inapplicable to explain the significant differences in the flow resistance of different liquid–solid systems. On the other hand, friction reduction in liquid nano-lubrication has received considerable attention during the past decades. Both fields are exposed to a common scientific issue regarding friction reduction during liquid–solid relative motion at nanoscale. A promising approach to control the flow resistance of nano-confined fluids is to reference the factors affecting liquid nano-lubrication. In this review, two concepts of the friction coefficient derived from fluid flow and tribology were discussed to reveal their intrinsic relations. Recent progress on low or ultra-low friction coefficients in liquid nano-lubrication was summarized based on two situations. Finally, a new strategy was introduced to study the friction coefficient based on analyzing the intermolecular interactions through an atomic force microscope (AFM), which is a cutting-point to build a new model to study flow-resistance at nanoscale.
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  • Resultat 1-10 av 41

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