35 research outputs found
Effects of graphene sheet size on multi-functional properties of unidirectional graphene aerogel/epoxy nanocomposites
No full textGraphene aerogel (GA) has attracted vast interest in recent years due to its unique ability to feature the exceptional properties of graphene as a porous structure with large accessible surface area, presenting improved properties in chemical sensors, energy storage materials, thermal interface materials, and multifunctional nanocomposites. As a composite filler material, its 3D structure ensures consistent interconnections between graphene sheets, enabling the fabrication of high performance nanocomposites even at very low graphene content. However, it is important to have a comprehensive understanding in the assembly of graphene oxide (GO) sheets under freeze casting, which may be influenced by several factors including GO sheet size, in order to precisely control the GA microstructure. The purpose of this research is to elucidate the effects of GO sheet size on the morphology and properties of GA and its polymer composites. By varying the size of precursor graphene oxide (GO) sheets between 1.1 to 1595.8 μm2, unidirectional graphene aerogels (UGAs) with controllable densities, degree of alignment and electrical conductivities are prepared using the unidirectional freeze casting method. The UGAs prepared using ultralarge GO (UL-UGA) deliver the best properties compared with those made using small GO (S-UGA). UL-UGAs exhibit a low density of 0.27 mg cm-3, a high degree of alignment, and a high electrical conductivity of 0.178 S cm-1. The UL-UGA/epoxy composites prepared by infiltrating liquid epoxy resin into the porous UGA exhibit excellent electrical conductivities as high as 0.135 S cm-1, along with an ultralow percolation threshold of 0.0066 vol% which is one of the lowest values for all graphene-based composites. Owing to their 3D interconnection, high degree of alignment and effective reduction, the UL-UGAs are shown to significantly enhance the fracture toughness of epoxy by up to 69% at 0.11 vol% graphene content, through several toughening mechanisms such as crack pinning, crack deflection, interfacial debonding, and graphene rupture.</p
Effects of graphene sheet size on multi-functional properties of unidirectional graphene aerogel/epoxy nanocomposites
No full textThe future of two-dimensional semiconductors beyond Moore's law
No full textThe primary challenge facing silicon-based electronics, crucial for modern technological progress, is difficulty in dimensional scaling. This stems from a severe deterioration of transistor performance due to carrier scattering when silicon thickness is reduced below a few nanometres. Atomically thin two-dimensional (2D) semiconductors still maintain their electrical characteristics even at sub-nanometre scales and offer the potential for monolithic three-dimensional (3D) integration. Here we explore a strategic shift aimed at addressing the scaling bottleneck of silicon by adopting 2D semiconductors as new channel materials. Examining both academic and industrial viewpoints, we delve into the latest trends in channel materials, the integration of metal contacts and gate dielectrics, and offer insights into the emerging landscape of industrializing 2D semiconductor-based transistors for monolithic 3D integration.N
Effect of Porosity and Barrier Layer on Dielectric Properties of Highly Aligned rGO/PVA Composites
No full textFreeze-cast Graphene Aerogels and Their Epoxy Composites with Ultralow Percolation Threshold
No full textUltralight Graphene Composite Sandwich for Stretchable Light-emitting Display
No full textGraphene composite sandwiches with exceptional stretchability and electrical conductivities are fabricated using porous graphene honeycomb (GH)/polydimethylsiloxane (PDMS) composites as the core material and ultrahigh-density graphene foam (UDGF)/PDMS composites as the face sheets. The microscale GHs prepared by a 3D printing technique deliver a long-range ordered hexagonal porous structure, an excellent electrical conductivity as high as 72 S/m, along with an ultralow density of 3.25 mg/cm3 . To the best of authors’ knowledge, this is the lightest honeycomb structure ever reported in open literature. Taking advantage of the engineered porous structure of GHs, the graphene composite sandwich shows minimal resistance changes at large external deformations with excellent structural durability. A stretchable light-emitting display constructed using a graphene composite sandwich is demonstrated as the electric circuit, which delivers reliable electronic performance under different loading modes
Grounds of Difference
No full textBu çalismada Rogers Brubaker'in Farklilik Zeminleri kitabi incelenmistir. Bu kitap Gav Perspektif tarafindan 2020 yilinda basilmistir. Modern toplumda uygulanan güncel farklilik politikalari, küresellesme, dijital dünya esitsizlikleri daha görünür hale getirmistir. Irk ve etnisite biyolojiden ayrilip esitsizlik için nasil bir etkisi oldugu yazar tarafindan ele alinmistir. Esere göre günümüz dünyasinda kültürel farkliliklarin sosyal ve politik olarak farklilastigi en önemli alanlar dil ve dindir. Yazarin dilin ve dinin benzerligini sorgulamasi eserde tartisma çizgisizidir. Ele aldigimiz bu eserin birinci bölümünde yazar Charles Tilly’in esitsizlik teorisinden yola çikarak etnisitenin esitsizligini ele almaktadir. Bu bölümde esitsizligi yaratan unsurlar ele alinip, esitsizligin ne oldugunun kimin neye sahip oldugundan bagimsiz olacagi nedenleri içermektedir. Ikinci bölümde biyolojinin farklilik politikalarindaki belirleyiciligi sorgulanmistir. Üçüncü bölümde dil ve dinin kültürel farklilik noktasindaki yeri, kültürel sermayenin önemi ve Pierre Bourdieu’nun dil anlayisi tartisilmistir. Dördüncü bölümde din ve milliyetçilik arasindaki iliskiyi irdelenmektedir. Bu bölümde yazar, milliyetçiligi özünde seküler görür ve milliyetçiligin düsüsünü dine baglar. Besinci bölüm, diaspora kavrami ve dünyada kültürel farkliligin sosyal örgütlenmesi üzerindeki etkisi ele alinmistir. Altinci bölümde ise sinir-ötesi milliyetçilik biçimleri, ulus devlete üyelik ve aidiyet politikalari açiklanmistir. Son bölüm olan yedinci bölümde ise yazar, etnisite ve milliyetçilik üzerine modern bakis açisina odaklanmaktadir.This study analyzes Rogers Brubaker's book Grounds of Difference. This book was published by Gav Perspective in 2020. The current politics of difference in modern society, globalization and the digital world have made inequalities more visible. The author discusses how race and ethnicity are separated from biology and how they have an impact on inequality. According to the work, the most important areas where cultural differences are socially and politically differentiated in today's world are language and religion. The author's questioning of the similarity of language and religion is a line of discussion in the work. In the first chapter of this work, the author discusses the inequality of ethnicity based on Charles Tilly's theory of inequality. In this section, the elements that create inequality are discussed and the reasons for what inequality is will be independent of who owns what. In the second section, the determinant role of biology in the politics of difference is questioned. The third chapter discusses the place of language and religion in cultural difference, the importance of cultural capital and Pierre Bourdieu's understanding of language. The fourth chapter examines the relationship between religion and nationalism. In this chapter, the author sees nationalism as essentially secular and attributes the decline of nationalism to religion. The fifth chapter deals with the concept of diaspora and its impact on the social organization of cultural difference in the world. In the sixth chapter, cross-border forms of nationalism and the politics of membership and belonging to the nation-state are explained. In the last chapter, chapter seven, the author focuses on the modern perspective on ethnicity and nationalism
Graphene nanopattern as a universal epitaxy platform for single-crystal membrane production and defect reduction
No full textHeterogeneous integration of single-crystal materials offers great opportunities for advanced device platforms and functional systems'. Although substantial efforts have been made to co-integrate active device layers by heteroepitaxy, the mismatch in lattice polarity and lattice constants has been limiting the quality of the grown materials 2 . Layer transfer methods as an alternative approach, on the other hand, suffer from the limited availability of transferrable materials and transfer-process-related obstacles 3 . Here, we introduce graphene nanopatterns as an advanced heterointegration platform that allows the creation of a broad spectrum of freestanding single-crystalline membranes with substantially reduced defects, ranging from non-polar materials to polar materials and from low-bandgap to high-bandgap semiconductors. Additionally, we unveil unique mechanisms to substantially reduce crystallographic defects such as misfit dislocations, threading dislocations and antiphase boundaries in lattice- and polarity-mismatched heteroepitaxial systems, owing to the flexibility and chemical inertness of graphene nanopatterns. More importantly, we develop a comprehensive mechanics theory to precisely guide cracks through the graphene layer, and demonstrate the successful exfoliation of any epitaxial overlayers grown on the graphene nanopatterns. Thus, this approach has the potential to revolutionize the heterogeneous integration of dissimilar materials by widening the choice of materials and offering flexibility in designing heterointegrated systems.Y
Atomic lift-off of epitaxial membranes for cooling-free infrared detection
No full textRecent breakthroughs in ultrathin, single-crystalline, freestanding complex oxide systems have sparked industry interest in their potential for next-generation commercial devices1,2. However, the mass production of these ultrathin complex oxide membranes has been hindered by the challenging requirement of inserting an artificial release layer between the epilayers and substrates3,4. Here we introduce a technique that achieves atomic precision lift-off of ultrathin membranes without artificial release layers to facilitate the high-throughput production of scalable, ultrathin, freestanding perovskite systems. Leveraging both theoretical insights and empirical evidence, we have identified the pivotal role of lead in weakening the interface. This insight has led to the creation of a universal exfoliation strategy that enables the production of diverse ultrathin perovskite membranes less than 10 nm. Our pyroelectric membranes demonstrate a record-high pyroelectric coefficient of 1.76 x 10-2 C m-2 K-1, attributed to their exceptionally low thickness and freestanding nature. Moreover, this method offers an approach to manufacturing cooling-free detectors that can cover the full far-infrared spectrum, marking a notable advancement in detector technology5.N
Remote epitaxial interaction through graphene
No full textThe concept of remote epitaxy involves a two-dimensional van der Waals layer covering the substrate surface, which still enable adatoms to follow the atomic motif of the underlying substrate. The mode of growth must be carefully defined as defects, e.g., pinholes, in two-dimensional materials can allow direct epitaxy from the substrate, which, in combination with lateral epitaxial overgrowth, could also form an epilayer. Here, we show several unique cases that can only be observed for remote epitaxy, distinguishable from other two-dimensional material-based epitaxy mechanisms. We first grow BaTiO
3
on patterned graphene to establish a condition for minimizing epitaxial lateral overgrowth. By observing entire nanometer-scale nuclei grown aligned to the substrate on pinhole-free graphene confirmed by high-resolution scanning transmission electron microscopy, we visually confirm that remote epitaxy is operative at the atomic scale. Macroscopically, we also show variations in the density of GaN microcrystal arrays that depend on the ionicity of substrates and the number of graphene layers
