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    A comprehensive experimental study on the effects of hexagonal boron nitride particle size and loading ratio on thermal and mechanical performance in epoxy composites
    (Sage Publications Ltd, 2024) Ozyigit, Samet; Mehdipour, Mostafa; Al-Nadhari, Abdulrahman; Tabrizi, Arvin T.; Dogan, Semih; Dericiler, Kuray; Beylergil, Bertan
    Harnessing the potential of hexagonal boron nitride (h-BN) in epoxy composites for tailoring thermal conductivity is a promising avenue in materials science. However, achieving balanced enhancements in both in-plane and through-plane directions remains a challenge that requires innovative solutions. The primary objective of this research is to evaluate how thermal and mechanical characteristics of an epoxy matrix are affected by the size and amount of h-BN particles. To achieve this goal, h-BN particles with varying sizes (micro and nano) are incorporated into the epoxy matrix at different weight ratios spanning from 0.5 wt % to 20 wt % using a pre-dispersion technique. The epoxy composites reinforced with h-BN through a molding process exhibits enhanced mechanical and thermal performance in contrast to the pristine epoxy material. During the flexural test, acoustic emission data is collected to identify the initiation and progression of damage within the specimens under testing conditions. The most notable enhancement in thermal conductivity is observed when incorporating 20 wt% of micron-sized h-BN particles. This leads to a remarkable 107% increase in the in-plane direction and an impressive 112% increase in the through-plane direction. These results can be attributed to the formation of a three-dimensional thermally conductive network by the larger h-BN particles, which extends the path of phonon scattering. Furthermore, there are significant improvements in both flexural modulus and tensile modulus. Epoxy composites containing 10 wt% of micron-sized h-BN experiences an approximate 42% increase, while those with 20 wt% of the same particles displays a substantial 47% rise in these properties. This study effectively addresses the challenges associated with tailoring the thermal properties of epoxy composites, opening up new opportunities for applications in various industries, including electronics, aerospace and thermal management systems. Graphical Abstract
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    Engineering interfacial thermal transport through comparative analysis of electrospraying and dip coating of silanized h-BN for thermo-mechanical enhancement of CF/Epoxy composites
    (Elsevier Sci Ltd, 2025) Mehdipour, Mostafa; Dogan, Semih; Tabrizi, Arvin Taghizadeh; Bafqi, Mohammad Sajad Sorayani; Beylergil, Bertan; Yildiz, Mehmet; Okan, Burcu Saner
    The inherently low thermal conductivity of carbon fiber (CF) reinforced epoxy composites is mainly due to porosity and fabrication defects that interrupt thermal pathways. This study demonstrated a pathway to control heat in both out-of-plane and in-plane directions by incorporating hexagonal boron nitride (h-BN) as a thermally conductive agent and by configuring interface interactions on the CF and within the epoxy resin while evaluating physical and chemical interactions. Two integration techniques of dip coating and electrospraying were employed to apply h-BN, effectively creating robust h-BN layers on CF and dispersing neat or silane-modified hBN within the epoxy matrix by combining vacuum bag and hot compression processes to reduce void content. Electrospraying silane-modified h-BN onto carbon fiber, together with incorporating 20 wt% silane-modified hBN into the matrix, resulting in a total loading of 11 wt% in the composite-led to the highest out-of-plane thermal conductivity of 1.3 W/mK, representing a 166 % increase compared to CF reinforced into epoxy composite (CF+/ EP) with the out-of-plane thermal conductivity of 0.49 W/mK. Mechanically, the configuration using neat h-BN in both the matrix and dip-coated CF achieved a 127 % increase in flexural modulus and a 49 % improvement in Charpy impact strength versus unfilled CF/epoxy composites. Resizing the CF improved directional thermal conductivity in CF/epoxy composites by controlling porosity, achieving approximately an 81 % reduction in porosity when using silanized h-BN.
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    Enhancing directional thermal conductivity in hexagonal boron nitride reinforced epoxy composites through robust interfacial bonding
    (Wiley, 2025) Mehdipour, Mostafa; Dogan, Semih; Hezarkhani, Marjan; Dericiler, Kuray; Arik, Muhammet Nasuh; Yildirim, Cennet; Beylergil, Bertan
    Establishing a robust interfacial bond between hexagonal boron nitride (h-BN) plates and the epoxy matrix is essential for enhancing heat transfer, which is difficult because of h-BN's low-surface energy, tendency to clump together, and the chemical inertness of the epoxy matrix. This research shows different techniques for treating the surface of h-BN fillers by applying acids and thermal processes to activate the surface. The silanization process was used to increase the silane content on the surface of activated h-BN in order to make it more compatible with the epoxy matrix. X-ray photoelectron spectroscopy analysis revealed silicon peaks (Si2s peak at 150.1 eV and Si2p peak at 100.3 eV) in the spectrum of silane-treated samples. Heat treatment resulted in the production of more oxygen molecules on the shell of h-BN compared to the acid treatment. Here, the primary focus was on examining how surface treatment affects thermal conductivity (TC) performance in both in-plane and through-thickness paths. There was an increase in the epoxy's TC perpendicular to the plane, going from 0.21 to 0.47 (W/mK), showing a remarkable 123.8% enhancement by adding 10 wt% of silane-modified-thermal treated h-BN particles. The improvement resulted from effectively silanizing the exterior boundary of h-BN particles, enhancing connection and distribution in the epoxy matrix. Surface modification of h-BN-epoxy composites improves TC, leading to better heat conduction in thermal management systems, benefiting industries like aerospace, automotive, and energy systems.Highlights Silanization of h-BN for better filler-matrix bonding leading to improved heat transfer Boosting thermal conductivity in the through-thickness direction with surface-modified h-BN Significant improvement in through-thickness thermal conductivity with treated h-BN. Thermal treatment of h-BN produced better oxygenation than acid treatment. Application in aerospace and automotive through improved heat transfer. h-BN functionalization route for higher thermal conductivity. image
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    Influence of functionalized h-BN particle interphase and interface regulation with structural design on the directional thermal conductivity and mechanical performance of carbon fiber/epoxy composites
    (Elsevier Sci Ltd, 2025) Mehdipour, Mostafa; Dogan, Semih; Al-Nadhari, Abdulrahman; Bafqi, Mohammad Sajad Sorayani; Beylergil, Bertan; Yildiz, Mehmet; Okan, Burcu Saner
    This study highlights the importance of interfacial adhesion between carbon fiber (CF) and the epoxy matrix by adopting a novel approach that combines untreated and silane-treated h-BN in a multilayered structure. The interface was engineered by electrospraying h-BN particles, while the interphase was modified by incorporating up to 20 % h-BN into the epoxy matrix. The highest out-of-plane thermal conductivity of 2.31 W/mK, a 116 % increase compared to the reference value of 1.07 W/mK, was achieved by sizing CF with silanized h-BN through electrospraying, in conjunction with the 20 % h-BN-loaded epoxy matrix. Conversely, the incorporation of h-BN in the epoxy alone resulted in the best mechanical performance, with approximately a 46.4 % increase in elastic modulus, a 105 % improvement in flexural modulus, and a nearly 5 % increase in Charpy impact strength. Based on CT scan results, the resizing of CF fabrics improved directional thermal conductivity in CF/epoxy composites with controlled porosity.