Overview on Comparison of Four Preparation Methods and Physical Properties of Graphene

Nanometer sized particles formed by carbon atoms mainly arranged in a hexagonal atomic structure are called carbon nanostructures (CNS). In this chapter we focus exclusively on sp 2-bonded CNS that include graphene (Geim, 2009; Geim and Novoselov, 2007), single- and multi-walled carbon nanotubes (Iijima, 1991; Pantano et al., 2004), fullerenes (Kroto et al., 1985), and carbon onions (Banhart and Ajayan, 1996; Kroto, 1992; Ugarte, 1992, 1995). Especially graphene has drawn a lot of attention within the last years, because it possesses exceptional mechanical and electrical properties (Geim, 2009; Novoselov et al., 2004) and a high thermal conductivity (Lau et al., 2012). It is the main building block of all other CNS based on sp 2-bonded carbon, which therefore should inherit its exceptional properties making them promising candidates for applications in the field of structural mechanics and the electronics industry, as fillers in nanocomposites (Choi and Lee, 2012; Baughman et al., 2002; Stankovich et al., 2006) and as solid lubricants (Hirata et al., 2004). This chapter will focus on the amazing mechanical properties of CNS only. Information regarding the extraordinary electronic and thermal properties can be found elsewhere (Novoselov et al., 2004; Castro Neto et al., 2009; Balandin, 2011).

Atomically thin sheets of materials (2D materials) came to prominence in the early 2000s with the successful isolation of graphene. Since then, the interest in graphene has steadily increased thanks to its exceptional electronic, optical, mechanical and thermal properties. It also led to the isolation of other 2D materials such as black phosphorous, silicene, germanene and transition metal dichalcogenides (TMDs) such as MoS2. Due to their exceptional properties, these materials offer virtually endless opportunities for fundamental research as well as cutting edge applications.Most of these 2D materials can be stabilized by the covalent attachment of organic molecules. For instance, the chemisorption of organic units can promote the stabilization of dispersions of 2D materials in organic solvents improving their solution processability. Moreover, such chemisorption of organic molecules allows manipulation of their physicochemical properties by addition of desired functional groups in a tailor made fashion. However, controlling the spatial distribution of the covalently bound units remains a major challenge due to the highly reactive nature of the reagents used for the covalent modification process.In this talk, I will discuss the covalent modification of graphene, graphite and MoS2 using diazonium chemistry. The chemically activated decomposition of diazonium salts using mild conditions will be discussed in detail. The characterization of the modified materials using atomic force microscopy (AFM), scanning tunnelling microscopy (STM), and Raman spectroscopy will be presented. The micrometre-scale multicomponent patterning of surface-supported graphene achieved through a combination of e-beam lithography and diazonium chemistry will also be discussed. The impact of this functionalization on the surface potential will be evaluated through scanning probe microscopies. Lastly, I will also show how the chemical patterning can be extended to the lower end of the nanoscale by using physisorbed self-assembled monolayers of alkanes as sacrificial templates.

A state of art review on the graphene and carbon nanotube reinforced nanocomposites: A molecular dynamics approach

Since the development of graphene, a lot of other 2D materials have been discovered; they include hexagonal boron nitride (hBN), molybdenum disulphide (MoS2), tungsten diselenide (WSe2), etc. These 2D materials have exceptional properties, such as high conductivity, superb flexibilit,y and excellent properties of electronic transport; these properties make them ideal materials for use in several applications, including flexible electronics, energy storage devices, and industrial scale machines and structures. Various techniques and methods have been used for the design of 2D materials, but the development of these materials into desired shapes and sizes is still challenging. One of the techniques for the fabrication of materials that has emerged in the recent years is 3D printing. 3D printing provides ease of fabrication as well as high customizability, which makes it an ideal method of fabricing 2D materials-based structures. Recently, the use of 3D printing has increased, as well as its usage for fabricating 2D materials. This chapter sheds light on the use of 3D printing for the fabrication of 2D materials-based nanostructures. The basic properties and methods of preparation are discussed for 2D materials, with emphasis on the potential applications. The opportunities and challenges of the use of 3D printing for 2D materials is also discussed, along with the current trends and the future prospects of the use of this technology.

Atomically thin sheets of materials, the so-called two-dimensional (2D) materials arrived on the scene in early 2000s with the successful isolation of graphene as freestanding monolayer films. Graphene, a single atom thick sheet of sp2-hybridized carbon bonded in a honeycomb lattice, has exceptional electronic, optical, mechanical and thermal properties that outperform those of most of the existing materials. The research on graphene further fuelled emergence of related 2D materials such as black phosphorous, silicene, germanene and transition metal dichalcogenides (TMDs) such as MoS2. Due to their exotic properties, these materials offer virtually endless opportunities for fundamental research as well as cutting edge applications. Most of these 2D materials however exist as single layers only when supported by another solid surface or when stabilized by physisorbed or chemisorbed organic molecules. Given their layered nature, most 2D materials are extremely difficult to disperse in typical solvents. Chemisorption of organic molecules onto their basal plane allows dispersion of these materials in (organic) solvents thereby improving their solution processability. Such dispersions can be used in composite materials and as functional inks. Moreover, covalent functionalization allows modification of the intrinsic electrical, electronic and optical properties of these 2D materials. In this talk, I will discuss covalent modification graphene, graphite and MoS2 using diazonium chemistry. Two different routes for reductive decomposition of diazonium salts namely, chemical and electrochemical, will be discussed in detail. Special focus is on sub-nanometer characterization of modified materials using scanning tunneling and atomic force microscopy (STM and AFM). Initial results towards patterned covalent functionalization using physisorbed self-assembled templates will also be presented besides the discussion on the use of such surfaces as seed layers for atomic layer deposition (ALD).

Simple SummaryAmong animal facilities, compost-bedded pack (CBP) barns have attracted a lot of attention from milk producers and the scientific community. Systematic investigation of the main thermal, chemical, and physical properties of bedding materials in CBP barns is of environmental and economic relevance, helping dairy producers operate these beds properly. Here we assessed 42 CBPs in the state of Kentucky (USA), aiming to study the thermal, chemical, and physical properties of bedding materials. We found that thermal conductivity increased with increasing particle size. Regarding chemical features, the assessed CBPs were similar when considering the bedding materials. The particle weight fraction found in CBPs might result in excessive water retention and low aeration. Based on these main results, we concluded that many dairy producers could use the bedding compost to fertilize their crop fields and avoid over-applying nutrients, and reduce water pollution.The thermal, chemical, and physical properties of compost bedding materials play an important role in every phase of compost production. Based on this, we aimed to assess the thermal, chemical and physical properties of bedding materials for compost-bedded pack (CBP) barns. The database for this study was registered from 42 CBP barns, distributed throughout the state of Kentucky (USA). The thermal conductivity showed a linear relationship with moisture content and bulk density, while thermal resistivity decreased with increasing particle size. The bedding moisture average was 46.8% (±11.5). The average finer index (p < 0.05) was the highest weight percentage (30.1%) in the samples studied. Water-holding capacity (WHC) increased with increasingly fine particle size. The higher bulk density value was 3.6 times that of the lowest bulk density value. The chemical characterization of the bedding material provided the following results: 42.7% (±3.8%) C, 1.6% (±0.4%) N, and 28.2 (±8.0) C:N ratio. However, thermal properties are strongly dependent on particle size. Producers can use the bedding material as fertilizer in their crops, due to the chemical characteristics of the materials. Beds with good physical and chemical properties improve their moisture content.

Strain effects on thermoelectric properties of two-dimensional materials

Diamond PN junctions exhibit exceptional properties such as high electric breakdown field, the largest bandgap and the highest thermal conductivity compared to any known materials. These unique attributes make diamond highly suitable for high-power, high-frequency and harsh-environment applications. Currently, chemical vapor deposition (CVD) and high-pressure high-temperature (HPHT) methods can be used to synthesize diamond substrates. Among these, synthetic diamond produced by CVD has garnered significant interest due to its distinctive combination of exceptional electrical and thermal properties. However, its extremely high mechanical hardness and smaller substrate size pose substantial challenges for the implementation of device technology. This paper aims to explore the distinguished properties of diamond in electronics and the preparation process of diamond PN junctions, focusing on synthesis technologies, doping issues and terminal technologies. All of these are critical for maximizing the dependability and performance of electronic devices based on diamonds. By addressing these challenges, the research seeks to forward the application of diamond in various high-performance electronic devices, highlighting its capacity to improve device durability and effieciency in harsh operating conditions. The insights provided will contribute to a deeper understanding of the material’s capabilities and the technological advancements necessary to harness its full potential in electronic applications.

The isolation of graphene, now over decade ago, has given rise to the revitalization of an old full set of materials, two-dimensional materials (2DM), which have exceptional electrical, chemical and physical properties. Some of the materials under investigation in addition to graphene are hexagonal boron nitride (h-BN), semiconducting, metallic, and superconducting transition metal dichalcogenides (TMD) with a general chemical formula, MX2 where M is for example equal to Mo, W, Ta, Nb, Zr, Ti, and X = S, Se and Te, and others. While graphene is a material with many exceptional properties and h-BN is an excellent 2D insulator, TMD materials provide what neither graphene nor h-BN can, bandgap engineering that, in principle, can be used to create new devices that cannot be fabricated with h-BN and graphene alone. There is hope that 2DM can be integrated to fabricate numerous device types for many applications ranging from inkjet-printed circuits, photonic applications, flexible electronics, and high-performance electronics. However, to fully realize the benefits of these materials, the community will have to work together to define new device structures, device integration schemes, and materials growth processes to help the semiconductor industry make progress toward meeting the original goals of the International Technology Roadmap for Semiconductors (ITRS). A number of deposition/growth techniques have been used to prepare large area graphene, such as growth on SiC through the evaporation of Si at high temperatures, precipitation of carbon from metals, and catalytic chemical vapor deposition on Cu and Pt. Direct growth of good quality graphene on dielectrics/semiconductors other than SiC with reasonable properties has also been reported recently on Ge. Due to its insulating nature and compatibility with graphene and TMDs, the preparation of large area h-BN is also being developed on both metals and dielectrics. Transition metal dichalcogenides, however, present altogether different opportunities and difficulties in the preparation of low defect density large area single crystals. Vapor transport, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE) are being developed to produce these materials for initial studies of materials physics and device fabrication. In addition, there is some effort in performing simulations to guide growth for both CVD and MBE growers. Therefore, there is an opportunity here to have the crystal growers and the modeling community collaborate to develop high quality materials and processes. A number of devices structures are currently under evaluation to take advantage of the basic properties of graphene, bi-layer graphene, h-BN and TMDs. Some of the devices are based on tunneling phenomena while others are based on excitonic phenomena. In this presentation I will present the state of the art results of graphene, h-BN, and a few TMD materials and their prospects for future electronic device applications.

Chapter 9 - 2D materials in nonlinear optics

Since the successful exfoliation of graphene in 2004, many attentions have been paid to two-dimensional (2D) materials, which include graphene, h-BN, transition metal dichalcogenides (TMDCs), black phosphorus (BP) and so on. Although these materials have shown unique characteristics, there are numerous challenges in this emerging field. For example, charge trap between the substrate and the 2D materials seriously influences their excellent electrical properties; some 2D materials are unstable while exposed in air, which will lead to their degradation. To have an intensive study of the basic properties of 2D materials and broaden their field of application, researchers pay attentions to the heterostructures of these materials, which consist of vertically stacked or laterally pieced 2D materials, including graphene/h-BN, TMDCs/h-BN, TMDCs/graphene, and TMDCs/TMDCs heterostructures, et al. For vertical heterostructures, graphene/h- BN vertical heterostructures mainly take advantage of h-BN to decrease the charge trap between insulating layer and graphene, thus to increase the carrier mobility in graphene. TMDCs/graphene vertical heterostructures mainly combine the good photo responsivity of TMDCs with the high conductivity of graphene, which can be utilized for high performance optoelectronics. TMDCs/TMDCs vertical heterostructures mainly combine the band structures of two different materials to control the carrier transport behavior, thus realizing excellent carrier storage or high performance photo responsivity. Lateral heterostructures are only suitable for materials with low lattice mismatch, and they are usually used for studying the carrier transport behavior between the interfaces of materials. Along with the increasing requirements on integration and multifunction, 2D heterostructures-based electronic and optoelectronic devices are paid much more attention to. Controllable synthesis of 2D heterostructures is the precondition of constructions of high-performance and highly-integrated devices. This review first introduces the preparation methods of 2D materials, including exfoliation, molecular beam epitaxy (MBE) and chemical vapor deposition (CVD). Exfoliation method mainly pieces the exfoliated materials together to form heterostructures with the help of polymer. MBE can overcome the difficulties of the transfer process in exfoliation, however they are not suitable for large scale preparation. Compared with exfoliation and MBE, CVD has less restrictions on the substrate, as well as a simple preparation process with lower cost and higher quality of the as-prepared materials. 2D heterostructures can be prepared by the combination of exfoliation and CVD, or CVD process only. Then, considering the problem of the interface contamination in these preparation methods proposed at present, we put forward a liquid metal strategy in the controllable preparation of 2D heterostructures. Furthermore, we introduce the construction and performance of 2D-heterostructures-based electronic and optical devices. The opportunities and challenges in the preparation and application of 2D heterostructures are also discussed.

This thesis focuses on the development of conductive nanocomposite materials based on graphene and natural polymers such as cellulose and chitosan. Graphene, a single layer of carbon atoms arranged in a honeycomb lattice, exhibits exceptional electrical, mechanical, and thermal properties, making it an attractive filler for polymer composites. However, the challenge lies in effectively dispersing graphene sheets within polymer matrices. The work presented explores new strategies for grafting polysaccharide chains onto oxidized graphite (graphene oxide) to improve its compatibility and dispersion in cellulose and chitosan matrices. The resulting composites were doped with gold or nickel nanoparticles to further enhance their electrical and catalytic properties. Detailed characterization techniques, including spectroscopic and microscopic methods, were employed to analyze the structure, morphology, and properties of the developed nanocomposites. The thesis is organized into three main parts: 1) a literature review on graphene, polysaccharides, and their biocomposites; 2) a description of the experimental materials and methods; and 3) a scientific discussion of the results, presented in the form of three research publications. The findings demonstrate the successful synthesis of conductive nanocomposites with improved compatibility and performance, opening up new avenues for the application of these sustainable and multifunctional materials in areas such as electronics, catalysis, and electromagnetic shielding.

The construction of low cost, printable compatible, solution processed, of high performance, stable solar cells is one of the scientific milestones of the next ten years. The discovery of graphene launched a new era in the materials science, and the research implemented in the exceptional properties of the two-dimensional (2D) materials. The chemical, physical, electrical and mechanical properties of 2D materials match with the requirements that the various building blocks of the third-generation photovoltaics should have in order for these devices to deliver exceptional performance and become attractive alternatives to silicon-based solar cells. The 2D library of materials expands in a very high pace and nowadays includes 150 exotic layered materials. Among them are the transition metal dichalcogenides (2D-TMDs). Recent advances in atomically thin 2D-TMDs (e.g., MoS2, WS2, MoSe2 and WSe2) have introduced numerous promising technologies in nanotechnologies, photonics, sensing, energy storage and solar cells to name few. This chapter highlights the contributions of 2D-TMDs toward the construction of high efficiency and of long lifetime, solution-processed organic and perovskite solar cells.

Potassium sodium niobate (KNN)‐based piezoelectric ceramics have emerged as a promising alternative to lead‐based systems due to their exceptional properties. While extensive research has focused on improving the electrical properties of KNN‐based ceramics through doping and processing optimization, the concurrent investigation of their mechanical properties has been lacking. This study presents a comprehensive analysis of the mechanical and electrical properties of KNN‐based lead‐free piezoceramics doped with various transition metal oxides and rare earth oxides, based on substantial experimental data. Our findings reveal that the as‐sintered KNN‐based ceramics exhibit not only outstanding electrical properties but also remarkable mechanical robustness compared to conventional toughened lead zirconate titanate (PZT)‐based ceramics. These exceptional electrical and mechanical properties are attributed to the micro‐scale and atomic‐scale structure of the modified KNN‐based ceramics, characterized by a highly condensed structure, an inhomogeneous distribution of nano‐domain structure, and the presence of amorphous intergranular films at grain boundaries.

Science's gem: diamond science 2009