scholarly journals The Influence of Thermal Properties Anisotropy on Subtractive Laser Processing of B4C/h-BN Composites

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5191
Author(s):  
Paweł Rutkowski ◽  
Karol Gala ◽  
Kamila Misiura ◽  
Jan Huebner
Keyword(s):  
Thermal Properties ◽  
Laser Processing ◽  
Hexagonal Boron Nitride ◽  
Laser Flash ◽  
Travel Speed ◽  
Uniaxial Pressure ◽  
Perpendicular Direction ◽  
Material Surface ◽  
Laser Ablation Process ◽  
Continuous Work

This work concerns boron carbide matrix composites with the addition of hexagonal boron nitride particles (h-BN) as a solid lubricate. The composite materials were hot-pressed and analysed in terms of phase, structure, and microstructure changes in relation to the h-BN content. The uniaxial pressure applied during the manufacturing process allowed the orientation of single h-BN particles and its agglomerates in perpendicular direction to the pressing axis. The anisotropy of heat transfer and thermal expansion coefficient (CTE) and density changes in relation to temperature are discussed. Thermal diffusivity and conductivity were measured in relation to the material direction by the laser flash analysis method (LFA). In this paper, understanding the heat flow and CTE changes allowed explaining the results of investigated subtractive laser processes of the manufactured composites. The laser ablation process was conducted on B4C/h-BN composites in parallel and perpendicular direction to each other. It was done in a continuous work (CW) mode at 50 W with a 40 µm spot and 3 mm/s beam travel speed. The influence of h-BN particles and their orientation on thermal properties is discussed. The effect of laser processing on B4C/h-BN composites was also discussed in relation to the material surface roughness measured with a confocal microscope, microstructure observations, density, and thermal properties changes in relation to the material direction.

scholarly journals Causes and Measures of Fume in Directed Energy Deposition: A Review

2020 ◽  
Vol 58 (6) ◽  
pp. 383-396
Author(s):  
Kang-Hyung Kim ◽  
Chan-Hyun Jung ◽  
Dae-Yong Jeong ◽  
Soong-Keun Hyun
Keyword(s):  
Laser Processing ◽  
Energy Deposition ◽  
Laser Flash ◽  
Travel Speed ◽  
Trial And Error ◽  
Directed Energy Deposition ◽  
Directed Energy ◽  
Harmful Effects ◽  
Gas Supply ◽  
Metal Additive

Pores and cracks are known as the main defects in metal additive manufacturing (MAM), including directed energy deposition(DED). A gaseous fume is often produced by laser flash (instantaneous high temperature) during laser processing, which may cause various defects such as porosity, lack of fusion, inhomogeneity, low flowability and composition change, either. However the cause and harmful effects of fume generation in DED are known little. In laser processing, especially laser welding, many studies have been conducted on the prevention of fume because it generates defects that hinder uniform reactions between the laser beam and the materials. Generally, the fume occurs with easily vaporizing low melting point components or sensitive oxidizing elements. Unsuitable conditions are also known to have an effect, including laser power, travel speed, powder feed rate and shielding gas supply. Practically, there are many more fume generating factors in the DED process, and the lack of understanding requires a lot of trial and error. In this article the laser-related and weld metallurgy literatures were reviewed, focusing on the prevention of fume in powder DED. The causes of the fume, were explained to result from the stages of cavitation bubbles generated by the laser induced plasma and the nanoparticles released. Additionally, the effects of alloying components and environmental conditions for fume generation in the DED process were investigated, and suggestions are proposed to prevent fume.

scholarly journals Scanning Thermal Microscopy of Ultrathin Films: Numerical Studies Regarding Cantilever Displacement, Thermal Contact Areas, Heat Fluxes, and Heat Distribution

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 491
Author(s):  
Christoph Metzke ◽  
Fabian Kühnel ◽  
Jonas Weber ◽  
Günther Benstetter
Keyword(s):  
Thermal Properties ◽  
Ultrathin Films ◽  
Hexagonal Boron Nitride ◽  
Thermal Contact ◽  
Heat Transfer Process ◽  
Heat Propagation ◽  
Heat Fluxes ◽  
Detailed Knowledge ◽  
Scanning Thermal Microscopy ◽  
Thermal Microscopy

New micro- and nanoscale devices require electrically isolating materials with specific thermal properties. One option to characterize these thermal properties is the atomic force microscopy (AFM)-based scanning thermal microscopy (SThM) technique. It enables qualitative mapping of local thermal conductivities of ultrathin films. To fully understand and correctly interpret the results of practical SThM measurements, it is essential to have detailed knowledge about the heat transfer process between the probe and the sample. However, little can be found in the literature so far. Therefore, this work focuses on theoretical SThM studies of ultrathin films with anisotropic thermal properties such as hexagonal boron nitride (h-BN) and compares the results with a bulk silicon (Si) sample. Energy fluxes from the probe to the sample between 0.6 µW and 126.8 µW are found for different cases with a tip radius of approximately 300 nm. A present thermal interface resistance (TIR) between bulk Si and ultrathin h-BN on top can fully suppress a further heat penetration. The time until heat propagation within the sample is stationary is found to be below 1 µs, which may justify higher tip velocities in practical SThM investigations of up to 20 µms−1. It is also demonstrated that there is almost no influence of convection and radiation, whereas a possible TIR between probe and sample must be considered.

scholarly journals Experimental Study of Plasma Plume Analysis of Long Pulse Laser Irradiates CFRP and GFRP Composite Materials

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 545
Author(s):  
Yao Ma ◽  
Chao Xin ◽  
Wei Zhang ◽  
Guangyong Jin
Keyword(s):  
Composite Materials ◽  
Laser Processing ◽  
Plasma Plume ◽  
Material Surface ◽  
Laser Fabrication ◽  
Breakdown Time ◽  
Reinforced Polymer ◽  
Gfrp Composite ◽  
Damage Process ◽  
Long Pulse

The application of laser fabrication of fiber-reinforced polymer (FRP) has an irreplaceable advantage. However, the effect of the plasma generated in laser fabrication on the damage process is rarely mentioned. In order to further study the law and mechanism of laser processing, the laser process was measured. CFRP and GFRP materials were damaged by a 1064 nm millisecond pulsed laser. Moreover, the propagation velocity and breakdown time of plasma plume were compared. The results show that GFRP is more vulnerable to breakdown than CFRP under the same conditions. In addition, the variation of plasma plume and material surface temperature with the number of pulses was also studied. The results show that the variation trend is correlated, that is, the singularities occur at the second pulse. Based on the analysis of experimental phenomena, this paper provides guidance for plasma phenomena in laser processing of composite materials.

Study on Thermal Conductivity of Polyetheretherketone/Thermally Conductive Filler Composites

2007 ◽  
Vol 124-126 ◽  
pp. 1079-1082 ◽  
Author(s):  
Sung Ryong Kim ◽  
Dae Hoon Kim ◽  
Dong Ju Kim ◽  
Min Hyung Kim ◽  
Joung Man Park
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Carbon Fiber ◽  
Conductive Filler ◽  
Laser Flash ◽  
Flash Method ◽  
Phase System ◽  
Two Phase ◽  
Nielsen Theory ◽  
Thermally Conductive

Thermal properties of PEEK/silicon carbide(SiC) and PEEK/carbon fiber(CF) were investigated from ambient temperature up to 200°C measured by laser flash method. Thermal conductivity was increased from 0.29W/m-K without filler up to 2.4 W/m-K with at 50 volume % SiC and 3.1W/m-K with 40 volume % carbon fiber. Values from Nielsen theory that predicts thermal conductivity of two-phase system were compared to those obtained from experiment.

scholarly journals Thermal properties and laser processing of hot-pressed materials from Ti–Al–C system

2019 ◽  
Vol 137 (6) ◽  
pp. 1891-1902 ◽  
Author(s):  
Paweł Rutkowski ◽  
Jan Huebner ◽  
Dariusz Kata ◽  
Leszek Chlubny ◽  
Jerzy Lis ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Laser Processing

Mechanical and thermal properties of wood-plastic composites reinforced with hexagonal boron nitride

2013 ◽  
Vol 35 (1) ◽  
pp. 194-200 ◽  
Author(s):  
Nadir Ayrilmis ◽  
Turker Dundar ◽  
Alperen Kaymakci ◽  
Ferhat Ozdemir ◽  
Jin Heon Kwon
Keyword(s):  
Thermal Properties ◽  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Mechanical And Thermal Properties ◽  
Wood Plastic Composites ◽  
Plastic Composites

Thermal Property Measurements of Reactive Materials: The Macroscopic Behavior of a Nanocomposite

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Amanda Gordon ◽  
Keerti Kappagantula ◽  
Michelle L. Pantoya
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Initial Temperature ◽  
Weighted Average ◽  
Laser Flash ◽  
Fuel Particle ◽  
Experimental Measurements ◽  
Weighted Averages ◽  
Reactive Materials ◽  
The Matrix

This study experimentally examined the thermal properties of reactive materials that are a composite of fuel and oxidizer particles. Three reactive materials were selected: aluminum (Al) with iron (III) oxide (Fe2O3); Al with Teflon (C2F4); and Al with titanium (IV) oxide (TiO2). The experimental measurements were performed using a laser flash analyzer (LFA) and then compared with calculations based on weighted averages of each component in the composite. The effects of fuel particle size, oxidizer, and initial temperature on thermal properties were studied. Nanometric Al composites are more insulative than their micron-scale counterparts, exhibiting three times lower thermal conductivity in some cases. Increased overall contact resistance may be a key contributor to the reduction in thermal conductivity. The measured values deviated as high as 69% from weighted average estimates of thermal properties. These results suggest that factors not accounted for in weighted average estimates significantly influence the thermal properties of the matrix.

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