The Experts below are selected from a list of 13044 Experts worldwide ranked by ideXlab platform

Jonathan Lawrence - One of the best experts on this subject based on the ideXlab platform.

  • The influence of brightness during laser surface treatment of Si3N4 Engineering Ceramics
    Optics and Lasers in Engineering, 2012
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    A comparative study between the fiber and an Nd:YAG laser during the surface treatment of a Si 3N 4 Engineering Ceramic was conducted to investigate the contribution of the laser-beam brightness. A fiber and an Nd:YAG laser with identical process parameters were employed. The effects of the laser-beam brightness were investigated with respect to modification in the dimensional size and the microstructure of the laser irradiated Si 3N 4 Engineering Ceramic. The results showed a change in the dimensional size and the microstructure of the surfaces treated by the two lasers despite using identical laser processing parameters. This was due to the difference between the laser-beam brightness of the two lasers as the fiber laser produced larger power per unit area in Steradians when compared to the Nd:YAG laser. Owing to this, high interaction temperature, larger fibre laserCeramic interaction zone and melt-pool at the laserSi 3N 4 interface were found, which further led to changes in the physical attributes of the Si 3N 4 Engineering Ceramic. This shows that laser surface treatment using high brightness would be cost effective as the brighter laser utilises lower power for the same surface treatment in comparison with that of a low brightness laser. Therefore, processing Ceramics and other materials by employing high brightness lasers could aid in gaining an economical benefit. © 2012 Elsevier Ltd.

  • A comparative study on the processing parameters during fibre and CO2 laser surface treatments of silicon nitride Engineering Ceramic
    The International Journal of Advanced Manufacturing Technology, 2012
    Co-Authors: P P Shukla, Jonathan Lawrence
    Abstract:

    This paper demonstrates a comparative study of a relatively novel fibre laser and a conventional CO2 laser to surface-process silicon nitride (Si3N4) Engineering Ceramic. The objective of the research is to investigate the threshold of the novel fibre laser and compare it to the conventionally used CO2 laser to process Si3N4 Engineering Ceramic and to produce a laser surface treatment free from major surface cracking without using any of the pre- or post heating techniques as this would increase the cost of the process and add more expense to the product when considering a bigger view point. The results showed that the fibre laser surface processing of the Si3N4 Engineering Ceramic differed to that of the CO2 laser as the Gaussian beam modes, the beam quality factors, wavelength and the beam delivery systems were different between the two lasers. This consequently had a different effect on the surface of the Si3N4 Engineering Ceramic. The CO2 laser wavelength when surface treating the Si3N4 Engineering Ceramic was being absorbed more than that of the fibre laser as higher power density and same traverse speed was used to reach the threshold for the Si3N4 Engineering Ceramic.

  • characterization and compositional study of a zro2 Engineering Ceramic irradiated with a fibre laser beam
    Optics and Laser Technology, 2011
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    Laser surface Engineering of Zirconia Technical Ceramics, covering issues relating to a compositional, chemical, topographical, microstructural investigation. Fibre laser surface treatment (FLST) of a cold isostatic pressed (CIP) ZrO 2 Engineering Ceramic (ZEC) was performed using various processing gas compositions. This is the first time that a surface treatment of ZEC has been employed hitherto by using the fibre laser (FL) radiation to observe the changes on and within the surface of the Engineering Ceramic; in particular, material removal, surface topography, chemical composition, changes in the surface hardness and distribution of the heat affected zone (HAZ). Bonding of the grain boundaries was found through surface melting with all FL irradiated samples to some extent, but the effect was more marked on the sample FL irradiated with an Ar assist gas and proved to be the most effective combination for modifying the surface morphology. The surface finish and the material removal were varied with the changes in the gas composition. Maximum material removal was observed when an O 2 assist gas was employed on account of the O 2 generating an exothermic reaction. This in turn, produced excessive heating. The compositional analysis revealed a chemical change occurring within the FL irradiated surfaces, regardless of the assist gas used, with the ZEC transforming to zirconia carbide (ZrC)

  • mathematical modelling of the fibre laser surface processing of a zirconia Engineering Ceramic by means of three dimensional finite element analysis
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    The thermal effects of fibre laser surface treatment on a ZrO2 Engineering Ceramic were studied using a computational finite element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the fibre laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5% with the surface and 18% within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed; power density; time; depth and the temperature during various stages of the fibre laser surface treatment of the ZrO2. By utilizing data obtained from a thermo, gravimetry- differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser surface treatment of the ZrO2. The mapping revealed that the fibre laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the paper.

  • mathematical modelling of the fibre laser surface processing of a zirconia Engineering Ceramic by means of three dimensional finite element analysis
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    The thermal effects of fibre laser surface treatment on a ZrO2 Engineering Ceramic were studied using a computational finite-element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the fibre laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5 per cent with the surface and 18 per cent within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed, power density, time, depth, and the temperature during various stages of the fibre laser surface treatment of the ZrO2. By utilizing data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser surface treatment of the ZrO2. The mapping revealed that the fibre laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the article.

Pratik Shukla - One of the best experts on this subject based on the ideXlab platform.

  • The influence of brightness during laser surface treatment of Si3N4 Engineering Ceramics
    Optics and Lasers in Engineering, 2012
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    A comparative study between the fiber and an Nd:YAG laser during the surface treatment of a Si 3N 4 Engineering Ceramic was conducted to investigate the contribution of the laser-beam brightness. A fiber and an Nd:YAG laser with identical process parameters were employed. The effects of the laser-beam brightness were investigated with respect to modification in the dimensional size and the microstructure of the laser irradiated Si 3N 4 Engineering Ceramic. The results showed a change in the dimensional size and the microstructure of the surfaces treated by the two lasers despite using identical laser processing parameters. This was due to the difference between the laser-beam brightness of the two lasers as the fiber laser produced larger power per unit area in Steradians when compared to the Nd:YAG laser. Owing to this, high interaction temperature, larger fibre laserCeramic interaction zone and melt-pool at the laserSi 3N 4 interface were found, which further led to changes in the physical attributes of the Si 3N 4 Engineering Ceramic. This shows that laser surface treatment using high brightness would be cost effective as the brighter laser utilises lower power for the same surface treatment in comparison with that of a low brightness laser. Therefore, processing Ceramics and other materials by employing high brightness lasers could aid in gaining an economical benefit. © 2012 Elsevier Ltd.

  • characterization and compositional study of a zro2 Engineering Ceramic irradiated with a fibre laser beam
    Optics and Laser Technology, 2011
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    Laser surface Engineering of Zirconia Technical Ceramics, covering issues relating to a compositional, chemical, topographical, microstructural investigation. Fibre laser surface treatment (FLST) of a cold isostatic pressed (CIP) ZrO 2 Engineering Ceramic (ZEC) was performed using various processing gas compositions. This is the first time that a surface treatment of ZEC has been employed hitherto by using the fibre laser (FL) radiation to observe the changes on and within the surface of the Engineering Ceramic; in particular, material removal, surface topography, chemical composition, changes in the surface hardness and distribution of the heat affected zone (HAZ). Bonding of the grain boundaries was found through surface melting with all FL irradiated samples to some extent, but the effect was more marked on the sample FL irradiated with an Ar assist gas and proved to be the most effective combination for modifying the surface morphology. The surface finish and the material removal were varied with the changes in the gas composition. Maximum material removal was observed when an O 2 assist gas was employed on account of the O 2 generating an exothermic reaction. This in turn, produced excessive heating. The compositional analysis revealed a chemical change occurring within the FL irradiated surfaces, regardless of the assist gas used, with the ZEC transforming to zirconia carbide (ZrC)

  • mathematical modelling of the fibre laser surface processing of a zirconia Engineering Ceramic by means of three dimensional finite element analysis
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    The thermal effects of fibre laser surface treatment on a ZrO2 Engineering Ceramic were studied using a computational finite element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the fibre laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5% with the surface and 18% within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed; power density; time; depth and the temperature during various stages of the fibre laser surface treatment of the ZrO2. By utilizing data obtained from a thermo, gravimetry- differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser surface treatment of the ZrO2. The mapping revealed that the fibre laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the paper.

  • mathematical modelling of the fibre laser surface processing of a zirconia Engineering Ceramic by means of three dimensional finite element analysis
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    The thermal effects of fibre laser surface treatment on a ZrO2 Engineering Ceramic were studied using a computational finite-element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the fibre laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5 per cent with the surface and 18 per cent within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed, power density, time, depth, and the temperature during various stages of the fibre laser surface treatment of the ZrO2. By utilizing data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser surface treatment of the ZrO2. The mapping revealed that the fibre laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the article.

  • distribution of temperature during fibre laser radiation and effects thereon phase transformation of zro2 Engineering Ceramic
    Surface Engineering, 2011
    Co-Authors: Pratik Shukla, Jonathan Lawrence
    Abstract:

    Distribution of surface and the bulk temperature was recorded during fibre laser surface treatment of ZrO2 Engineering Ceramic. The experimental readings were then compared with a finite element model which showed the flow and distribution of the laser induced heat as a result of the fibre laser surface treatment. Moreover, thermogravimetry–differential scanning calorimetry was used to collect data with respect to physical changes during heating and cooling of the ZrO2 Engineering Ceramic. The thermogravimetry–differential scanning calorimetry data and the finite element model predictions were then used to map the phase transitions within the ZrO2 Engineering Ceramic resulting from fibre laser surface treatment. The mapping revealed that the fibre laser surface treatment had generally resulted in a phase transformation of the ZrO2 Engineering Ceramic from the monoclinic (M) state to a mixture of tetragonal and cubic (T+C) followed by partially formed liquid (L) phase during fibre laser surface treatment a...

P P Shukla - One of the best experts on this subject based on the ideXlab platform.

  • A comparative study on the processing parameters during fibre and CO2 laser surface treatments of silicon nitride Engineering Ceramic
    The International Journal of Advanced Manufacturing Technology, 2012
    Co-Authors: P P Shukla, Jonathan Lawrence
    Abstract:

    This paper demonstrates a comparative study of a relatively novel fibre laser and a conventional CO2 laser to surface-process silicon nitride (Si3N4) Engineering Ceramic. The objective of the research is to investigate the threshold of the novel fibre laser and compare it to the conventionally used CO2 laser to process Si3N4 Engineering Ceramic and to produce a laser surface treatment free from major surface cracking without using any of the pre- or post heating techniques as this would increase the cost of the process and add more expense to the product when considering a bigger view point. The results showed that the fibre laser surface processing of the Si3N4 Engineering Ceramic differed to that of the CO2 laser as the Gaussian beam modes, the beam quality factors, wavelength and the beam delivery systems were different between the two lasers. This consequently had a different effect on the surface of the Si3N4 Engineering Ceramic. The CO2 laser wavelength when surface treating the Si3N4 Engineering Ceramic was being absorbed more than that of the fibre laser as higher power density and same traverse speed was used to reach the threshold for the Si3N4 Engineering Ceramic.

  • Examination of temperature distribution and the thermal effects on Si3N4 Engineering Ceramics during fibre laser surface treatment
    Optics and Lasers in Engineering, 2011
    Co-Authors: P P Shukla, Jonathan Lawrence
    Abstract:

    The thermal effects of fibre laser surface treatment on a Si3N4 Engineering Ceramic were studied using a computational finite element analysis (FEA). Temperature increases on the surface of the Si3N4 during fibre laser processing were measured using an infra-red thermometer; temperature distributions in the bulk were measured with specifically located thermocouples. A computational model by using FEA was then developed to model the flow and the distribution of the radiated heat resulting from the fibre laser treatment of the Si3N4 Ceramic. By utilising data obtained from a TG-DSC analysis the FEA model predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser surface treatment of the Si3N4. The TG-DSC analysis also indicated that the fibre laser surface treatment generally resulted in a phase transformation of the Si3N4 from α-phase to β-phase modification as elongated rod-like grains were found.

  • Analysis of temperature distribution during fibre laser surface treatment of a zirconia Engineering Ceramic
    Proceedings of the 36th International MATADOR Conference, 2010
    Co-Authors: P P Shukla, Jonathan Lawrence
    Abstract:

    The thermal effects of fibre laser surface treatment of a ZrO2 Engineering Ceramic were studied using finite element analysis (FEA). Temperature increases on the surface and in the bulk of the ZrO2 during fibre laser processing were measured. FEA was then used to model the flow and distribution of the radiated heat resulting from the fibre laser surface treatment. Data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC) analysis and the FEA model predictions was used to map the phase transformations in the ZrO2 resulting from fibre laser surface treatment. The mapping revealed that the fibre laser surface treatment generally resulted in a phase transformation of the ZrO2 from the M state to a mixture of T+C during fibre laser irradiation and from T+C to T followed by the M state during solidification.

  • Fracture toughness of a zirconia Engineering Ceramic and the effects thereon of surface processing with fibre laser radiation
    Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2010
    Co-Authors: H. Wu, P P Shukla, Jonathan Lawrence
    Abstract:

    Vickers hardness indentation tests were employed to investigate the near-surface changes in the hardness of a fibre laser-treated and an as-received ZrO2 Engineering Ceramic. Indents were created using 5, 20, and 30 kg loads to obtain the hardness. Optical microscopy, white-light interferometry, and a coordinate measuring machine were then used to observe the crack lengths and crack geometry. Palmqvist and half-penny median crack profiles were found, which dictated the selection of the group of equations used herein. Computational and analytical approaches were then adapted to determine the K1c of ZrO2. It was found that the best applicable equation was: K1c = 0.016 (E/H)1/2 (P/c3/2), which was confirmed to be 42 per cent accurate in producing K1c values within the range of 8 to 12 MPa m1/2 for ZrO2. Fibre laser surface treatment reduced the surface hardness and produced smaller crack lengths in comparison with the as-received surface. The surface crack lengths, hardness, and indentation loads were found to be important, particularly the crack length, which significantly influenced the end K1c value when K1c = 0.016 (E/H)1/2 (P/c3/2) was used. This is because, the longer the crack lengths, the lower the Ceramic's resistance to indentation. This, in turn, increased the end K1c value. Also, the hardness influences the K1c, and a softer surface was produced by the fibre laser treatment; this resulted in higher resistance to crack propagation and enhanced the Ceramic's K1c. Increasing the indentation load also varied the end K1c value, as higher indentation loads resulted in a bigger diamond footprint, and the Ceramic exhibited longer crack lengths.

Mingchao Wang - One of the best experts on this subject based on the ideXlab platform.

  • an Engineering Ceramic used high temperature resistant inorganic phosphate based adhesive self reinforced by in situ growth of mullite whiskers
    Journal of The European Ceramic Society, 2019
    Co-Authors: Mingchao Wang, Xiaomeng Zhou, Mingrun Du, Xue Dong, Qingjun Zhou, Zhaojie Feng, Yunlong Liao, Yuqing Gu
    Abstract:

    Abstract Mullite whiskers were successfully in-situ synthesized in phosphate-based adhesive by taking Si and Al(OH)3 as reaction sources and AlF3 as the catalytic initiator. After calcination at 1300 °C, both strength and toughness of whisker-growth adhesive got greatly improved, which were increased by 75% and 156%, respectively. The bonding strength was enhanced to 23.8 MPa, which was close to some hot preCeramic polymer-based adhesives. An approximate yield stage appeared on its corresponding loading-curve, showing unprecedented toughness and high damage capacity. In addition, the residual rate of bonding strength still maintained 63% after 20 thermal cycles (room temperature-1300 °C).

  • multiple high temperature resistant phases modified phosphate based adhesive for Engineering Ceramic connection in extreme environment
    Ceramics International, 2019
    Co-Authors: Mingchao Wang, Qinggong Song, Yuqing Gu, Chongrui Wu, Xiaomeng Zhou, Mingrun Du
    Abstract:

    Abstract The lower-strength defect of inorganic phosphate adhesive had been definitely improved by self-generating multiple high-temperature resistant phases. Compared to our previous product, the best bonding performance of this novel adhesive for mullite was increased by 270%, which was close to some popular preCeramic polymer-based adhesives. The apparent shear strength at room temperature was up to 33.1 MPa after calcination at 900 °C, while the high-temperature strength researched 23.3 MPa at 900 °C and maintained above 17 MPa from 700° to 1200 °C. The reinforced effect of adhesive owed to the introduction of various Cu-based intermetallics, the premature generation of Al4B2O18 at 900 °C, and the structure optimizing through the oxidization of Si and B4C. Besides, the novel adhesive displayed good resistance to thermal-shock, especially for air-cooling test. After 15 thermal cycles in air, the residual strength of 1300 °C-calcined joints was still above 13 MPa (~40%).

Yuqing Gu - One of the best experts on this subject based on the ideXlab platform.

  • an Engineering Ceramic used high temperature resistant inorganic phosphate based adhesive self reinforced by in situ growth of mullite whiskers
    Journal of The European Ceramic Society, 2019
    Co-Authors: Mingchao Wang, Xiaomeng Zhou, Mingrun Du, Xue Dong, Qingjun Zhou, Zhaojie Feng, Yunlong Liao, Yuqing Gu
    Abstract:

    Abstract Mullite whiskers were successfully in-situ synthesized in phosphate-based adhesive by taking Si and Al(OH)3 as reaction sources and AlF3 as the catalytic initiator. After calcination at 1300 °C, both strength and toughness of whisker-growth adhesive got greatly improved, which were increased by 75% and 156%, respectively. The bonding strength was enhanced to 23.8 MPa, which was close to some hot preCeramic polymer-based adhesives. An approximate yield stage appeared on its corresponding loading-curve, showing unprecedented toughness and high damage capacity. In addition, the residual rate of bonding strength still maintained 63% after 20 thermal cycles (room temperature-1300 °C).

  • multiple high temperature resistant phases modified phosphate based adhesive for Engineering Ceramic connection in extreme environment
    Ceramics International, 2019
    Co-Authors: Mingchao Wang, Qinggong Song, Yuqing Gu, Chongrui Wu, Xiaomeng Zhou, Mingrun Du
    Abstract:

    Abstract The lower-strength defect of inorganic phosphate adhesive had been definitely improved by self-generating multiple high-temperature resistant phases. Compared to our previous product, the best bonding performance of this novel adhesive for mullite was increased by 270%, which was close to some popular preCeramic polymer-based adhesives. The apparent shear strength at room temperature was up to 33.1 MPa after calcination at 900 °C, while the high-temperature strength researched 23.3 MPa at 900 °C and maintained above 17 MPa from 700° to 1200 °C. The reinforced effect of adhesive owed to the introduction of various Cu-based intermetallics, the premature generation of Al4B2O18 at 900 °C, and the structure optimizing through the oxidization of Si and B4C. Besides, the novel adhesive displayed good resistance to thermal-shock, especially for air-cooling test. After 15 thermal cycles in air, the residual strength of 1300 °C-calcined joints was still above 13 MPa (~40%).