The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform

Leimin Deng - One of the best experts on this subject based on the ideXlab platform.

  • picosecond laser Seal Welding of perovskite films
    Optics and Laser Technology, 2021
    Co-Authors: Hang Chen, Jun Duan, Yulin Xie, Wei Xiong, Leimin Deng
    Abstract:

    Abstract Perovskite solar cells (PSCs) are a promising application industry, but its stability is not very ideal at present. The bottleneck of the PSCs industrialization is that perovskite material is very sensitive to humidity, and it is easy to produce hydrolysis and failure. Therefore, it is necessary to develop an effective encapsulation method to achieve a better long-term stability. Ultrashort pulse laser glass Welding technology is one of the effective encapsulation methods, but it is still difficult to be used in engineering due to the harsh conditions of optical contact. To solve these problems, a Sealing Welding method of perovskite films based on ultrashort pulse laser under the natural stacking conditions was proposed, the effectiveness of the Sealing weld was verified by experiments, which provides support for the engineering application of perovskite solar cells, and also provides a possible direction for the application of ultrashort pulse laser glass Welding technology.

  • Picosecond laser Seal Welding of glasses with a large gap.
    Optics Express, 2019
    Co-Authors: Chen Hang, Jun Duan, Yang Zeqi, Xiong Wei, Leimin Deng
    Abstract:

    Ultra-fast lasers can realize selective Welding of glasses through nonlinear effect and have the advantages of having high Welding accuracy, having small heat-affected zone, having high joint strength and not requiring intermediate absorption layer, which provides a new idea for chip packaging. However, this method is limited to the condition of optical contact, which is difficult to use in engineering applications. To solve this problem, an innovative Seal Welding method by picosecond laser is presented in this paper. In this method, a picosecond laser performs firstly rapid oscillating scan local Welding of the two natural overlap glasses with a large contact gap to form a closed area consisting of spot welds. The glass contact gap in the closed area can be reduced to about 1.5 μm through the solidification shrinkage effect of spot welds. Then a good Seal weld without plasma ablation, micro-hole, and micro-crack defects can be achieved by picosecond laser in this closed area to realize Seal Welding of glasses with a large contact gap. The Sealing test results show that the Seal Welding samples can keep good Sealing performance for more than one week.

Jianxun Zhang - One of the best experts on this subject based on the ideXlab platform.

  • laser Seal Welding of end plug to thin walled nanostructured high strength molybdenum alloy cladding with a zirconium interlayer
    Journal of Materials Processing Technology, 2019
    Co-Authors: Linjie Zhang, Junyu Pei, Liangliang Zhang, Jian Long, Jianxun Zhang
    Abstract:

    Abstract The effects of micro-alloying method on microstructure and properties of laser-welded molybdenum alloy joints were investigated, and zirconium was selected as the additive material. In the fusion zone of the joint without zirconium addition, the segregation of MoO2 on the grain boundary were observed, leading to the brittle fracture of the joint. When zirconium ring was added into the fusion zone, ZrO2 was preferentially formed in the grain interior which alleviated the segregation of MoO2. The grains at fusion zone were refined under the effect of heterogeneous nucleation particles of ZrO2, thus it changes the fracture mechanism of welded joint from intergranular fracture to cleavage fracture. When zirconium foil was pre-placed at the overlapped interface of cladding tube and the end plug, a parasitic brazing zone was generated due to the high melting point and high thermal conductivity of molybdenum. Tensile strength of the welded joints matched that of the base metal. These results highlight possibilities for achieving high strength joints when joining refractory materials with intrinsic brittleness in complex joint configurations.

  • effects of power modulation multipass remelting and zr addition upon porosity defects in laser Seal Welding of end plug to thin walled molybdenum alloy
    Journal of Manufacturing Processes, 2019
    Co-Authors: Linjie Zhang, Junyu Pei, Liangliang Zhang, Jian Long, Jiangzhe Liu, Jie Ning, Guifeng Zhang, Jianxun Zhang
    Abstract:

    Abstract Aiming to solve the serious porosity defects in laser welded girth joints of thin-walled tube and end plug made of nano-sized Ce2O3 doped Mo alloy (NC-Mo), the influences of laser power modulation, multipass remelting and zirconium (Zr) addition on the number, size and distribution of porosity defects were experimentally studied. By utilizing X-ray computed tomography (XCT), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, transmission electron microscope (TEM) and Raman spectrum (RS), the porosity feature of welded joints achieved under various conditions was analyzed. The results showed that Welding cycles had a significant influence on the porosity ratio of fusion zone (FZ) while the amplitude and frequency of laser power waveform slightly influenced the porosity. When the Welding cycles increased from 2 to 8, the porosity ratio of FZ decreased from about 1.00% to about 0.48% and the maximum and average pore diameters reduced by about 53% and 27%, respectively. Adding minor Zr in molten pool can further reduce the RP of FZ to about 0.35%. Through analysis, it can be seen that the pores in FZ can be divided into irregularly-shaped keyhole-induced pores and spherical metallurgy-induced pores. The latter was generated possibly because some impurity elements (including O and H) pre-existing in base metal (BM). Increasing Welding cycles can promote the gas in molten pool to float and outflow, thus significantly decreasing the porosity. Moreover, Zr added in molten pool can be preferentially reacted with O to generate ZrO2, which can inhibit the precipitation of volatile MoO2 to thus suppress the generation of metallurgy-induced pores.

Linjie Zhang - One of the best experts on this subject based on the ideXlab platform.

  • laser Seal Welding of end plug to thin walled nanostructured high strength molybdenum alloy cladding with a zirconium interlayer
    Journal of Materials Processing Technology, 2019
    Co-Authors: Linjie Zhang, Junyu Pei, Liangliang Zhang, Jian Long, Jianxun Zhang
    Abstract:

    Abstract The effects of micro-alloying method on microstructure and properties of laser-welded molybdenum alloy joints were investigated, and zirconium was selected as the additive material. In the fusion zone of the joint without zirconium addition, the segregation of MoO2 on the grain boundary were observed, leading to the brittle fracture of the joint. When zirconium ring was added into the fusion zone, ZrO2 was preferentially formed in the grain interior which alleviated the segregation of MoO2. The grains at fusion zone were refined under the effect of heterogeneous nucleation particles of ZrO2, thus it changes the fracture mechanism of welded joint from intergranular fracture to cleavage fracture. When zirconium foil was pre-placed at the overlapped interface of cladding tube and the end plug, a parasitic brazing zone was generated due to the high melting point and high thermal conductivity of molybdenum. Tensile strength of the welded joints matched that of the base metal. These results highlight possibilities for achieving high strength joints when joining refractory materials with intrinsic brittleness in complex joint configurations.

  • effects of power modulation multipass remelting and zr addition upon porosity defects in laser Seal Welding of end plug to thin walled molybdenum alloy
    Journal of Manufacturing Processes, 2019
    Co-Authors: Linjie Zhang, Junyu Pei, Liangliang Zhang, Jian Long, Jiangzhe Liu, Jie Ning, Guifeng Zhang, Jianxun Zhang
    Abstract:

    Abstract Aiming to solve the serious porosity defects in laser welded girth joints of thin-walled tube and end plug made of nano-sized Ce2O3 doped Mo alloy (NC-Mo), the influences of laser power modulation, multipass remelting and zirconium (Zr) addition on the number, size and distribution of porosity defects were experimentally studied. By utilizing X-ray computed tomography (XCT), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, transmission electron microscope (TEM) and Raman spectrum (RS), the porosity feature of welded joints achieved under various conditions was analyzed. The results showed that Welding cycles had a significant influence on the porosity ratio of fusion zone (FZ) while the amplitude and frequency of laser power waveform slightly influenced the porosity. When the Welding cycles increased from 2 to 8, the porosity ratio of FZ decreased from about 1.00% to about 0.48% and the maximum and average pore diameters reduced by about 53% and 27%, respectively. Adding minor Zr in molten pool can further reduce the RP of FZ to about 0.35%. Through analysis, it can be seen that the pores in FZ can be divided into irregularly-shaped keyhole-induced pores and spherical metallurgy-induced pores. The latter was generated possibly because some impurity elements (including O and H) pre-existing in base metal (BM). Increasing Welding cycles can promote the gas in molten pool to float and outflow, thus significantly decreasing the porosity. Moreover, Zr added in molten pool can be preferentially reacted with O to generate ZrO2, which can inhibit the precipitation of volatile MoO2 to thus suppress the generation of metallurgy-induced pores.

Chen Hang - One of the best experts on this subject based on the ideXlab platform.

  • Picosecond laser Seal Welding of glasses with a large gap.
    Optics Express, 2019
    Co-Authors: Chen Hang, Jun Duan, Yang Zeqi, Xiong Wei, Leimin Deng
    Abstract:

    Ultra-fast lasers can realize selective Welding of glasses through nonlinear effect and have the advantages of having high Welding accuracy, having small heat-affected zone, having high joint strength and not requiring intermediate absorption layer, which provides a new idea for chip packaging. However, this method is limited to the condition of optical contact, which is difficult to use in engineering applications. To solve this problem, an innovative Seal Welding method by picosecond laser is presented in this paper. In this method, a picosecond laser performs firstly rapid oscillating scan local Welding of the two natural overlap glasses with a large contact gap to form a closed area consisting of spot welds. The glass contact gap in the closed area can be reduced to about 1.5 μm through the solidification shrinkage effect of spot welds. Then a good Seal weld without plasma ablation, micro-hole, and micro-crack defects can be achieved by picosecond laser in this closed area to realize Seal Welding of glasses with a large contact gap. The Sealing test results show that the Seal Welding samples can keep good Sealing performance for more than one week.

Jun Duan - One of the best experts on this subject based on the ideXlab platform.

  • picosecond laser Seal Welding of perovskite films
    Optics and Laser Technology, 2021
    Co-Authors: Hang Chen, Jun Duan, Yulin Xie, Wei Xiong, Leimin Deng
    Abstract:

    Abstract Perovskite solar cells (PSCs) are a promising application industry, but its stability is not very ideal at present. The bottleneck of the PSCs industrialization is that perovskite material is very sensitive to humidity, and it is easy to produce hydrolysis and failure. Therefore, it is necessary to develop an effective encapsulation method to achieve a better long-term stability. Ultrashort pulse laser glass Welding technology is one of the effective encapsulation methods, but it is still difficult to be used in engineering due to the harsh conditions of optical contact. To solve these problems, a Sealing Welding method of perovskite films based on ultrashort pulse laser under the natural stacking conditions was proposed, the effectiveness of the Sealing weld was verified by experiments, which provides support for the engineering application of perovskite solar cells, and also provides a possible direction for the application of ultrashort pulse laser glass Welding technology.

  • Picosecond laser Seal Welding of glasses with a large gap.
    Optics Express, 2019
    Co-Authors: Chen Hang, Jun Duan, Yang Zeqi, Xiong Wei, Leimin Deng
    Abstract:

    Ultra-fast lasers can realize selective Welding of glasses through nonlinear effect and have the advantages of having high Welding accuracy, having small heat-affected zone, having high joint strength and not requiring intermediate absorption layer, which provides a new idea for chip packaging. However, this method is limited to the condition of optical contact, which is difficult to use in engineering applications. To solve this problem, an innovative Seal Welding method by picosecond laser is presented in this paper. In this method, a picosecond laser performs firstly rapid oscillating scan local Welding of the two natural overlap glasses with a large contact gap to form a closed area consisting of spot welds. The glass contact gap in the closed area can be reduced to about 1.5 μm through the solidification shrinkage effect of spot welds. Then a good Seal weld without plasma ablation, micro-hole, and micro-crack defects can be achieved by picosecond laser in this closed area to realize Seal Welding of glasses with a large contact gap. The Sealing test results show that the Seal Welding samples can keep good Sealing performance for more than one week.