Lingfei Ji

University of York

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i-10 index

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Co-Authors

Yijian Jiang

Beijing University of Technology

Yinzhou Yan

Beijing University of Technology

Zhenyuan Lin

Lanzhou University

Yijian Jiang

Beijing University of Technology

Bao Yong

China Electric Equipment Group (China)

Tianyang Yan

University of California, Los Angeles

Yan Wu

Nanjing Forestry University

Litian Zhang

Southern Medical University

Xinyu Du

Xi'an University of Architecture and Technology

David Whitehead

Geological Survey of Denmark and Greenland

Cooperative Institutions

Beijing University of Technology

Ministry of Education of the People's Republic of China

Chinese Academy of Sciences

Zhejiang University of Science and Technology

National University of Singapore

University of Chinese Academy of Sciences

University of Manchester

Northwestern Polytechnical University

Sun Yat-sen University

Fudan University

Author Statistics

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Research Field

A statistical model for research on the focal position effect on the taper of laser drilling

Pacific International Conference on Applications of Lasers and Optics (2008)

Yinzhou Yan Lingfei Ji Bao Yong Yijian Jiang

The relationships between focal position and diameter or taper of holes drilled by CO2 laser in ceramics were investigated by a new method named "equivalent stack plate method"(ESPM). The diameter of holes in different depth can be accurately measured by the new method. The present study reported a statistical analysis to study the effects of the focal position on the quality of the drilled holes and optimization of the processing parameter. The study was conducted based on the statistical experiments with the variable focal position from +1mm to −3mm. Then the relationship between focal position and diameter in different depth and corresponding mathematical model were ascertained by polynomial fitting analysis. The unique characteristics of ceramic during laser drilling were also discussed. The results indicate that the ideal focal position to achieve minimum taper in laser drilling holes should be set above the surface of workpiece.

Position (finance)

Laser drilling

10.2351/1.5057050

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Citations (0)

Laser sintering of (K0.5Na0.5NbO3)-LiTaO3 lead-free ceramics with novel piezoelectric properties

Pacific International Conference on Applications of Lasers and Optics (2008)

Lingfei Ji Yijian Jiang Xinyu Du

In this paper, by CO2 laser sintering technique, grain-oriented K0.5Na0.5NbO3-LiTaO3 ceramics with high dense of 92% theoretical density were prepared. The dielectric, piezoelectric and electromechanical properties were found to be ε ∼ 510, d33 ∼ 120 pC/N, and kp ∼ 36%, while with high Curie temperature of about 420 °C and low dielectric loss of about 0.03 ∼ 0.04. The high dense (92% theoretical density) structure with the texture character of grain-orientation is the factors to obtain good piezoelectric properties of the ceramics. The preparation of high dense ceramic is due to the suppression of O2 discharged by the coaxial gas injection systems on the volatilization of the K+, Na+ and Li+ during laser heating. An interesting change of grain shape from isometric to anisometric (needle-like) relating to the grain-orientation was observed obviously in the laser-sintered KNN-based. It was concluded that the enhanced Curie temperature associated with the high temperature phase transition was induced by the instant adjustment of laser power density from 0.07 kW/cm2 to 0.28 kW/cm2 just during 2 ∼ 5 s.

Texture (cosmology)

10.2351/1.5057070

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Citations (0)

Experimental and theoretical investigation of fibre laser crack-free cutting of thick-section alumina

International Journal of Machine Tools and Manufacture (2011)

Yinzhou Yan Lin Li Hüseyin Kürşad Sezer David Whitehead Lingfei Ji

Laser cutting

Stress field

10.1016/j.ijmachtools.2011.08.004

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Citations (46)

Correlation between fragility and eutectic instability and glass-forming ability in binary metallic glasses under growth controlled conditions

Journal of Applied Physics (2012)

Nan Wang Lingfei Ji Weigang Yao Yaping Zheng

We find that the fragility can be correlated to the eutectic instability and the glass forming ability in binary metallic glass formers under growth controlled conditions via a dimensionless parameter β defined as DfT0/2(Te − T0), where Df is fragility parameter, T0 is Vogel-Fulcher-Tammann temperature, and Te is eutectic temperature. It is shown that the large β value, which results from high Df and from that T0 is close to the eutectic temperature, can lead to small interface growth velocity and undercooling of eutectic structure, and good glass forming ability. This indicates that high β leads to small characteristic diffusion length resulting from sluggish material transport that governs the glass forming ability. The results might provide an in-depth insight into the glass formation mechanism and be helpful for searching new glasses in growth controlled process.

Supercooling

Dimensionless quantity

10.1063/1.4721405

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Citations (7)

Physical Properties and Structure Characteristics of Laser Prepared (Na_0.5K_0.5)NbO₃-LiNbO₃Ceramics

Ferroelectrics (2010)

Lingfei Ji Xinyu Du Yan Zhao Jie Liu Yijian Jiang

Fine ferroelectric properties with remnant polarization of 22.7 μC/cm2 and coercive field of 16.1 kV/cm of (1-x)K0.5Na0.5NbO3-xLiNbO3 ((1-x)KNN-xLN) ceramics were obtained by laser sintering method. The optimum piezoelectric properties of piezoelectric constant d33 ∼ 110 pC/N do not exist in the ceramics with the amount of LiNbO3 at x = 0.06 but lower to x = 0.04. The texture structure with the increase of (00l) orientation along the spontaneous polarization directions results in strong contribution to the ferroelectric response. High substitution effect of Li+ leads to the transformation from orthorhombic phase to tetragonal phases occurring at lower amount of LiNbO3.

Tetragonal crystal system

Orthorhombic crystal system

Natural bond orbital

Texture (cosmology)

10.1080/00150193.2010.505498

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Citations (1)

Parallel-axis positioning device for laser processing: Design and applications

Yinzhou Yan Lingfei Ji Bao Yong Yijian Jiang

A parallel-axis positioning device with ldquotwice positioningrdquo method is presented to exactly locate the laser spot at a special position on workpiece for laser macro-processing. Position accuracy of the laser spot on workpiece reaches 0.01 mm.

Position (finance)

10.1109/cleopr.2009.5292679

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Citations (1)

Influence of ambient gases on plasma dynamics of ultrafast laser-induced filamentation in sapphires

Optics Express (2020)

Rui Ma Lingfei Ji Tianyang Yan Litian Zhang Tong Zhang

The atmospheric influence on picosecond laser-induced filamentation in sapphires was investigated under Ar, N2 and O2 conditions provided by a coaxial nozzle. The spatial and temporal evolution of the whole plasma was analyzed on a nanosecond time scale by a time-resolved intensified charge-coupled device (ICCD). The regulation of the filamentation in sapphires by the atmosphere can be attributed to the modulation of the laser energy by surface ablation plasma. The thermal conductivity of the ambient gas is found to be the key factor affecting the surface plasma through a physical model. Ambient gas with higher thermal conductivity can effectively reduce the surface plasma temperature and expansion volume due to higher heat exchange efficiency. It is helpful for reducing the scattering and absorption of the laser energy. Therefore, the longest filamentary track and plasma lifetime were obtained in O2, which has higher thermal conductivity than Ar and N2. It is essential to understand the influence mechanism of ambient gas on filamentation, especially by providing a reliable method to regulate the filamentation induced in solid media.

Filamentation

Nanosecond

10.1364/oe.394765

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Citations (3)

Spatiotemporal evolution of high-aspect-ratio filamentary trace in sapphire of picosecond pulse burst-mode for laser lift-off

Journal of Central South University (2022)

Weigao Sun Tian-yang Yan Yuheng Wang Lingfei Ji

Picosecond

Nanosecond

Millisecond

Burst mode (computing)

Plasma channel

10.1007/s11771-022-5141-3

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Citations (3)

Influence of rising rate of power during laser sintering Ba<inf>0.5</inf>Sr<inf>1.5</inf>Na<inf>0.6</inf>K<inf>0.4</inf>Nb<inf>5</inf>O<inf>15</inf> ceramics

Xinyu Du Lingfei Ji Yijian Jiang

Tungsten bronze Ba _0.5 Sr _1.5 Na _0.6 K _0.4 Nb ₅ O ₁₅ ceramics with 97% theroetical density have been prepared successfully by CO ₂ laser sintering. The laser power rising rate of 1 W/s is the best technical parameter for obtaining dense ceramics. The temperature field analysis reveals that the lower rising rate of power can avoid the appearance of hollow structure in the sample.

10.1109/cleopr.2009.5292704

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Research on CO2 Laser-induced Nanocrystallization of Fe-based Amorphous Alloy Fe73.5Cu1Nb3Si13.5B9

Guorui Zhang Bao Yong Qianli Ma Limeng Yu Lingfei Ji

Fe-based amorphous alloy Fe73.5Cu1Nb3Si13.5B9 is irradiated by CO2 laser so that the homogeneous ultrafine grains are induced out, which are about 10 nm and have a bcc α-Fe(Si) structure. As a result, the samples of Fe-based nanocrystalline alloy have excellent soft magnetic properties. The results show that laser power of 71~99 W can realize the nanocrystallization even in short time of 5 seconds, but enough irradiation time of about 20~30 seconds is necessary to get optimum microstructure and soft magnetic properties.

Nanocrystalline material

10.1364/sumsession.2011.tu15

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