Investigating the Microstructure and Mechanical Properties of Aluminum-Matrix Reinforced-Graphene Nanosheet Composites Fabricated by Mechanical Milling and Equal-Channel Angular Pressing

Bağcı

Journal of Composite Materials

et al. 2020

In the present study, graphene nanosheets were synthesised by liquid phase exfoliation process, and the obtained graphene was reinforced in the rates of 0.1, 0.2, 0.3 and 0.6 wt.%. After the composites were characterised, they were exposed to Equal Channel Angular Pressing (ECAP) process. While 0.1 wt.% and 0.2 wt.% graphene reinforced composite samples successfully completed the ECAP process, 0.1 wt.% and 0.2 wt.% graphene reinforced composite samples were broken during the ECAP process. Electrical, thermal, and mechanical properties of the composite increased with the increased amount of graphene. The mechanical properties of ECAP-processed samples showed significant increases compared to non-ECAP processed samples. To figure out the effect of the ECAP process, moulds with different channel angles were used, the ECAP temperature was changed, and different passes were performed and the angles of 120° and 90° were used. ECAP-processed samples in both mould angles showed similar mechanical properties. With the increasing ECAP temperature, the mechanical properties of the sample decreased, but its electrical conductivity increased. As the number of passes increased, mechanical properties increased and crack formation in material increased. In addition, it was not possible to successfully remove the matrix composites containing more than 0.3 wt.% graphene from the ECAP process. Especially in the sample containing 0.6 wt.% graphene, brittle fractures were seen during the ECAP process and the sample was divided into many parts. The results showed that the composite responded better to the ECAP process when low amounts of graphene were reinforced in the al matrix. Significant improvements were observed in the properties of these composites after the ECAP process. In this study, the properties of composites with and without ECAP process were extensively investigated. The results were compared in detail with the previous studies. The graphene was produced using a simple method and it was reinforced with the Al matrix with the easiest possible method.

Section: Resultsmentioning

confidence: 99%

“…These results are consistent with the literature. 60,[63][64][65][66] It was observed that there was a serious increase in the hardness of the ECAPprocessed samples. While microhardness value of the sample N0 in Figure 8(a) was 34.6 HV, an increase of 33% was observed when the same sample was subjected to ECAP process.…”

Section: Resultsmentioning

confidence: 99%

The effect of equal-channel angular pressing (ECAP) on the properties of graphene reinforced aluminium matrix composites

Bağcı

Journal of Composite Materials

et al. 2020

“…Apart from polymers, hybrid fillers can potentially escalate the effectivity of the fillers' role throughout the matrix, more than individual h-BN sheets. The combination of different thermal conductive fillers like CNT [35,71], Graphene [72][73][74], Graphite [27,75], ZnO [76], Al 2 O 3 [77], and so on, with h-BN, leads to a synergetic effect in the TC performances among counterparts [68]. As an example, a promising hybrid nanocomposite of in-situ grown CNT on BNNSs embedded in epoxy resin exhibited a 615% and 380% TC performance improvement for the cross-plane direction compared with pure epoxy and BNNSs/epoxy composite, respectively.…”

Section: H-bn Within Hybrid Filler Configurationsmentioning

confidence: 99%

Recent Progress in the Study of Thermal Properties and Tribological Behaviors of Hexagonal Boron Nitride-Reinforced Composites

et al. 2020

Ever-increasing significance of composite materials with high thermal conductivity, low thermal expansion coefficient and high optical bandgap over the last decade, have proved their indispensable roles in a wide range of applications. Hexagonal boron nitride (h-BN), a layered material having a high thermal conductivity along the planes and the band gap of 5.9 eV, has always been a promising candidate to provide superior heat transfer with minimal phonon scattering through the system. Hence, extensive researches have been devoted to improving the thermal conductivity of different matrices by using h-BN fillers. Apart from that, lubrication property of h-BN has also been extensively researched, demonstrating the effectivity of this layered structure in reduction of friction coefficient, increasing wear resistance and cost-effectivity of the process. Herein, an in-depth discussion of thermal and tribological properties of the reinforced composite by h-BN will be provided, focusing on the recent progress and future trends.

“…[46] Increased defect ratio of the 3% and 5% GNP samples can be attributed to higher disordering of the GNP sheets due to an increased number of collisions between stainless-steel balls and the GNP resulting from additional quantity of GNP. [47] Thus, it appears that the advancements of defects arise from increased quantity of GNP. However, despite the increment in I D /I G ratio for all three samples, the ratio less than 1 indicated the less defects and good quality of GNP deposition.…”

Section: Characterization Of Ball Milled þ Sintered Gnp-cu Coatingsmentioning

confidence: 99%

Effect of Ball Milled and Sintered Graphene Nanoplatelets–Copper Composite Coatings on Bubble Dynamics and Pool Boiling Heat Transfer

et al. 2020

In this work, we present the efficacy of graphene nanoplatelets-copper (GNP-Cu) composite coatings formed by ball milling and sintering methods in enhancing pool boiling i.e. phase change heat transfer tested for distilled water. The pool boiling performance was quantified by an increase in critical heat flux (CHF) and heat transfer coefficient (HTC) at the lower wall superheat temperature. The ball milling facilitated draping of highly thermally conductive GNP around individual copper particles and subsequent sintering resulted in morphological features that further promoted high wicking rates of the coatings. A variety of coatings were formed with varying GNP Introduction:The distinctive structure of a single layered sp 2 -hybridized carbon atoms endows the thinnest material known as graphene, which has gained an enormous attention in various industrial applications such as surface coatings [1][2][3][4] , electronics [5,6] , energy storage [7,8] , lithium-ion batteries [9][10][11][12] , automotive [13,14] , and aerospace sector [15][16][17] due to its exceptional electrical, thermal, and mechanical properties [18] . Owing to very high thermal conductivity, graphene has also been implemented in thermal interface materials [19,20] , nanofluids [21] , and composite coatings [22][23][24] for heat transfer applications that require high heat flux dissipation [25][26][27][28][29] . Pool boiling heat transfer is a phase change cooling technique which dissipates higher heat fluxes by absorbing a large amount of latent heat while converting a liquid into a vapor and is quantified by the maximum heat flux that a surface can dissipate, known as critical heat flux (CHF), the condition at which the vapor bubbles merge laterally due to excessive bubble generation and form a vapor layer on the boiling surface.The heat transfer coefficient (HTC), defined as the ratio of heat flux ( " ) to wall superheat temperature (ΔT �� = T �� -T �� ), determines how effectively the heat is being removed from the surface.Pool boiling performance primarily depends on heater surface properties along with thermal conductivity of the heater surface which allows the efficient extraction of heat by delaying the vapor layer formation over the entire heater surface. This CHF condition can result in serious thermal damage to the heater surface. Thus, to increase the operational range and safety of the instruments, enhancing the pool boiling performance is essential. Wickability is the ability of surface to absorb/wick the liquid and is crucial for achieving high pool boiling performance as high wickabiltiy ensures a continuous supply of liquid to bubble nucleation sites. Researchers have demonstrated that highly wickable graphene coatings [30][31][32] are able to inhibit the vapor layer formation, thereby, providing a better solution to improve the operational limits of the system. Our recent works have focused on exploring the surface-active properties and thermal characteristics for