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Carbon nanotubes (CNTs) and graphene are nanocarbon materials with excellent mechanical and electrical properties. It is a great challenge to develop practical applications of these nanocarbons. One of the methods to make use of their excellent properties on the macroscopic scale is to assemble them into yarns, because the yarn can achieve higher orientation and higher content of nanocarbon. The establishment of the practical fabrication processes of the yarns of CNT and graphene (mainly reduced graphene oxide, rGO) is strongly demanded. The present review focuses on the fabrication processes of CNT and rGO yarns by analyzing respective procedures to contribute the development of practical applications of these yarns. The effectiveness of the fabrication processes is discussed based on the obtained mechanical properties and electrical conductivities.

Exfoliated graphite (EG) blocks are prepared from the ultra-large flakes of graphite by intercalation of H2SO4 using a large amount of H2O2 at 5 °C and following exfoliation at 30 °C. By the exfoliation in a closed container, EG blocks with the bulk densities of 0.008~0.024 g/cm3 are successfully prepared. The resultant EG blocks have high sorption capacities for a diesel oil, up to 45 g/g. The EG blocks after oil sorption can get certain resilience for compressive stress with high reproducibility by compression-release cycles, which allows us to apply the compression-releasing for the oil sorption-desorption of the EG blocks. The performance of cyclic oil sorption-desorption by compression-releasing of EG block is compared with those of filtration and distillation. Since the resultant EG blocks had sufficient mechanical strength, the continuous removal of oil floating on the water surface is possible, exporting oil through a catheter inserted into the block and connected to a peristaltic pump. By warming up by Joule heating, even a crude oil having high viscosity can be continuously removed from the water with sufficient rate. The high hydrophobicity and lipophilicity of EG make selective removal of oil from water possible.

Various carbon materials have been classified in two categories such as graphitizable and nongraphitizable carbons, or soft and hard carbons. For the characterization of the textures of the various carbon materials, high-resolution transmission electron microscopy, particularly dark-field technique, is efficient. Some disorganized carbon materials, such as turbostratic carbons, are known to give negative values of magnetoresistance. Since negative magnetoresistance is very characteristic for such carbon materials, much experimental work has been done. The magnetoresistance anisotropy on a specimen gives an information regarding the preferred orientation of the carbon layers along the main current direction in the specimen and in the plane perpendicular to this direction. Highly oriented graphites here mean graphite crystals with almost complete parallel alignment of graphite basal planes. The study for PAN/GC was first carried out by Hishiyama et al. by scanning electron microscopy, polarized light microscopy, and measurements of density, X-ray diffraction, and magnetoresistance.

Nano-sized pores in carbon materials are recently known to give certain constraints to the encapsulated materials by keeping them inside, accompanied with some changes in their structure, morphology, stability, etc. Consequently, nano-sized pores endow the constrained materials with improved performances in comparison with those prepared by conventional processes. These pores may be called “constraint spaces” in carbon materials. Here, we review the experimental results related to these constraint spaces by classifying as nanochannels in carbon nanotubes, nanopores and nanochannels in various porous carbons, and the spaces created by carbon coating.

Graphitic carbon nitride g-C3N4 was reviewed on its structure, synthesis, texture control, modification and applications, associating with the comparative discussion to carbon materials. Its basic structural unit is a layer of either triazine or heptazine cores consisting of C and N atoms, similar with a layer of hexagonal carbon rings of most of carbon materials. Fundamental synthesis process of g-C3N4 is pyrolysis of its precursors associated with different techniques, such as chemical vapor deposition, pressurizing, templating, doping, etc., as those applied for the synthesis of carbon materials. However, the properties of g-C3N4 are quite different from those of carbon materials; the former is hydrophilic but the latter is hydrophobic, and the former is photoactive for visible light but the latter is non-active. Here, g-C3N4 is reviewed on its structure, synthesis, texture control and modification, and application with comparative discussion to carbon materials.

The performance of the ultra-high-temperature furnace using graphite heater was examined to attain high temperatures above 2500 °C by using a system having the electric power supply with 30 kW maximum and in various atmospherics, vacuum, Ar, He, N2 and their mixtures. The atmospheric gas was shown to govern the performance of the furnace. On the bases of the present results, N2 gas is concluded to be the most preferable atmospheric gas for the steady heating up to 3000 °C.

Nitrogen-doped carbon materials are reviewed by focusing on their preparation and applications. Their preparation is described in the order of graphene, carbon nanotube and fibers, porous carbons and carbon blacks, because the investigations working on graphene have taught us many fundamental information on N-doping, though historically graphene has been developed the most recently. On their applications, fuel cells and lithium-sulfur batteries are emphasized because the applications of N-doped carbons in these devices are highly promising.

Temperature dependence of electrical resistivity of graphite materials at high temperatures up to 3000 °C was discussed on the bases of the published results on the measurements of resistivity of graphite rods and resistance of graphite heaters in high temperature furnace in inert atmospheres, Ar, N2 and He, and in vacuum. After passing through its minimum at around 1000 °C, resistance of graphite materials for most experimental conditions increases monotonically with increasing temperature up to 3000 °C. Due to extrinsic factors at certain experimental conditions in Ar atmosphere, however, a marked reduction in resistivity of the graphite rod above 2200 °C and also in resistance of the graphite heater above 2500 °C have been reported, no such resistance reduction having observed on the graphite heaters made from the same graphite material in N2 and He atmospheres, and under vacuum. The resistance reduction in Ar atmosphere at around 2000–2500 °C was supposed to be due to the formation of a short circuit by ionized Ar, which could be accelerated by the coexisted vaporized gases from the carbon materials loaded in the furnace to be heat-treated. The resistance reduction could be avoided by mixing more than 32% He in Ar.

The mechanical properties of graphene and reduced graphene oxide (rGO) and their applications are reviewed. Single-layer graphene has excellent mechanical properties, as Young’s modulus of 1 TPa. However, the practical applications of graphenes, mostly rGOs, are very limited; nano-sized additives for some lubricants, sensing component of mechanical sensors, and reinforcing fillers for plastics and metals, although they have the certain advantage as additives and fillers to need only a small amount, such as 0.5∼1 wt%. rGO fibers prepared by spinning of rGO suspension might be the way to use more effectively the excellent mechanical properties of graphene layers.

The thermal properties and related applications of graphene and reduced graphene oxide are reviewed. Thermal conductivity of single-layer graphene with high structural perfection is extremely high as 5000 W/mK. It decreases quickly with increasing the number of layers stacked and approaches to the value for graphite crystal, about 3000 W/mK. Different applications are explained, and thermal interface material, nanofluids, container of the phase-transition materials for thermal energy storage, and thermoelectric material are also discussed.

The procedures for preparing graphene and reduced graphene oxide (rGO) are reviewed in detail by classifying chemical vapor deposition, cleavage, and chemical synthesis for highly crystalline layers of graphene, and exfoliation and reduction via graphene oxide for highly defective layers of rGO. Formations in different morphologies (foams, ribbons, and horns) and doping of foreign atoms are also presented.

The blending of the matrix-forming polymer with the labile polymer (polymer blending) for designing carbon materials is reviewed. The organic template techniques are classified into three, on the basis of their purposes, pore structure control in the resultant carbons (membranes and fibers), preparation of hollow carbon nanofibers by spinning, and improvement in processability, particularly spinnability for carbon nanofiber fabrication. Data published are classified on the basis of the matrix-forming polymers by explaining each combination with a labile polymer.

Carbon materials for electrodes of capacitive deionization (CDI) process are reviewed. Electrochemical cells are briefly explained by classifying into conventional, membrane and flow-electrode CDI cells. CDI performance of carbon materials, porous carbons, including activated carbons (ACs), activated carbon fibers (ACFs), templated nanoporous carbons, carbon aerogels, carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphenes, have been reviewed in detail. The feasibility of CDI techniques is then discussed on the basis of the experimental results reported.

Templated mesoporous carbons are reviewed by focusing on their syntheses and applications by classifying with the template used because the resultant mesoporous carbon have their own characteristics in their pore structures depending on the template used. Carbon precursors employed, pore structure control, template performance and characteristics of the resultant carbons are discussed by comparing templating processes, and the applications reported on templated mesoporous carbons are briefly discussed.

Corannulene, a kind of bowl like polycyclic aromatic hydrocarbon (PAH), whose molecule is composed of a central pentagon and five closely adjacent hexagons on the pentagon's five sides, has received great scientific interest among research groups. In this review, the syntheses, characteristic molecule structure and properties of corannulene are clarified, as well as its derivatives with different substituted groups, fused derivatives, metal complex, and derivatives for host guest chemistry. On the basis of reviewing the applications and properties of corannulene together with its derivatives, the potential applications in hydrogen storage and lithium storage were highlighted and prospected.

Carbon foams are reviewed by focusing on their preparation and application. Their preparation processes are discussed by classifying them into five categories: blowing and carbonization, template carbonization, compression of exfoliated graphite, assembly of graphene nanosheets and others. Through these processes, density of the foam, sizes of cells and windows, as well as physical properties, are successfully controlled. Carbon foams are expected to give certain contributions to modern technology as containers for active materials for thermal energy storage, electrodes of electrochemical devices and electric energy storage, adsorbents for large molecules, and others including microwave absorption.

Mesoporous carbon (MPC) was synthesized via the thermal decomposition of magnesium citrate in a flow of Ar gas, followed by dissolution of MgO nanoparticles in the carbonaceous pyrolysis product. The MPC was then heated at 1800, 2000, 2200, 2400, 2500, 2700 and 3000 °C for 30 min. The MPC samples heated at 1800 and 2000 °C having a mesopore structure with graphitized carbon walls exhibited an enhanced rate capability as a composite anode for lithium ion batteries. Heat treatment of the MPC from 2200 to 2700 °C led to a partial collapse of micropores and mesopores, which decreased the charge/discharge capacity. The MPC samples heated at 2700 and 3000 °C having thick graphitized carbon layers and a mesopore structure with graphitized carbon walls showed charge/discharge curves with three lithium intercalation potential plateaus at approximately 0.2, 1.0, and 1.5 V vs. Li/Li+. The MPC sample heated at 3000 °C was the best anode material for lithium ion batteries among the MPC samples evaluated in this study because of its low irreversible capacity, high columbic efficiency, and high rate capability.

Graphite has pronounced anisotropy in its properties. Thermal conductivity of graphite crystal is extremely high along its layer plane, as high as 2000 Wm−1 K−1, much higher than metals, and very low across its layer plane, as low as 7 Wm−1 K−1. This anisotropy gives high possibility for graphite as thermal management materials. Here, graphite membranes with high thermal conductivity along the surface for heat dissipation and with low conductivity perpendicular to the surface for heat insulation, in addition to graphite foams as container of phase change materials for heat energy storage, are reviewed, particularly referring to the preparations of various graphite materials. Thermal conductivity of diamond crystal is also high, 2500 Wm−1 K−1, but it is very sensitive for structural defects, but that of graphitic materials is less sensitive for structural defects, suggesting that the latter is more practical for thermal management than the former.

New carbon materials have recently been derived from graphene theoretically and experimentally, hydrogenated graphene (graphane), fluorinated graphene (fluorographene), oxidized graphene (graphene oxide), and graphene introduced by acetylenic chains (graphyne and graphdiyne), which may be called graphene derivatives. Here, we review these graphene derivatives by emphasizing the experimental results.

Control of the crystalline structure in porous carbons by high temperature treatment and catalytic carbonization is reviewed, after a brief review of the control of pore structure. The development of crystallinity and the preservation of the porous structure in porous carbons by high temperature treatment depend predominantly on carbon precursors. The published experimental results are summarized, which suggest the necessity of more detailed and systematic investigations.

Aromatic polyimides are often employed as carbon precursors to prepare in various morphologies. After a brief explanation on carbonization behavior of aromatic polyimides, structure and functionalities of carbon materials prepared from polyimides are reviewed; highly-crystalline graphite membranes, nanoporous carbon membranes, carbon foams, carbon nanofibers and carbon nanoparticles. The advantages of polyimides as carbon precursors are discussed.

Corannulene, a kind of bowl like polycyclic aromatic hydrocarbon (PAH), whose molecule is composed of a central pentagon and five closely adjacent hexagons on the pentagon's five sides, has received great scientific interest among research groups. In this review, the syntheses, characteristic molecule structure and properties of corannulene are clarified, as well as its derivatives with different substituted groups, fused derivatives, metal complex, and derivatives for host guest chemistry. On the basis of reviewing the applications and properties of corannulene together with its derivatives, the potential applications in hydrogen storage and lithium storage were highlighted and prospected.

Carbon coating was reviewed by emphasizing its advantages on the recently developed photocatalyst particles and electrode materials for lithium-ion rechargeable batteries, in addition to various metals and metal oxides. Carbon coating on photocatalytic TiO2 and cathode material LiFePO4 can suppress their grain growth, which results in efficient utilization improvement of the active materials, and also increase electrical conductivity of the materials. It makes to be possible to prepare new functional materials, visible light active TinO2n-1 and W18O49, under a mild condition. It is also effective to improve the performance of ceramics and metals, such as anode material for lithium-ion batteries, roofing tiles, catalyst supports, heart valves, etc.

Carbon nanofibers prepared via electrospinning and following carbonization are summarized by focusing on the structure and properties in relation to their applications, after a brief review of electrospinning of some polymers. Carbon precursors, pore structure control, improvement in electrical conductivity,and metal loading into carbon nanofibers via electrospinning are discussed from the viewpoint of structure and texture control of carbon.