Novel Carbon Materials and Composites

Synthesis, Properties and Applications

Xin Jiang, Zhenhui Kang, Xiaoning Guo, Hao Zhuang, Xin Jiang, Zhenhui Kang, Xiaoning Guo, Hao Zhuang

• Publisher: Wiley
• Year: 2019
• Print ISBN: 9781119313397
• eBook ISBN: 9781119313618
• Edition: 1
• Topic: Technik & Maschinenbau
• Subtopic: Nanotechnologie & MEMS

Connects knowledge about synthesis, properties, and applications of novel carbon materials and carbon-based composites

This book provides readers with new knowledge on the synthesis, properties, and applications of novel carbon materials and carbon-based composites, including thin films of silicon carbide, carbon nitrite, and their related composites. It examines the direct bottom-up synthesis of the carbon-based composite systems and their potential applications, and discusses the growth mechanism of the composite structures. It features applications that range from mechanical, electronic, chemical, biochemical, medical, and environmental to functional devices.

Novel Carbon Materials and Composites: Synthesis, Properties and Applications covers an overview of the synthesis, properties, and applications of novel carbon materials and composites. Especially, it covers everything from chemical vapor deposition of silicon carbide films and their electrochemical applications to applications of various novel carbon materials for the construction of supercapacitors to chemical vapor deposition of diamond/silicon carbide composite films to the covering and fabrication processes of nanodot composites.

• Looks at the recent progress and achievements in the fields of novel carbon materials and composites, including thin films of silicon carbide, carbon nitrite, and their related composites
• Discusses the many applications of carbon materials and composites
• Focuses on the hot topic of the fabrication of carbon-based composite materials and their abilities to extend the potential applications of carbon materials
• Published as a title in the new Wiley book series Nanocarbon Chemistry and Interfaces.

Novel Carbon Materials and Composites: Synthesis, Properties and Applications is an important book for academic researchers and industrial scientists working in the fabrication and application of carbon materials and carbon-based composite materials and related fields.

1
Cubic Silicon Carbide: Growth, Properties, and Electrochemical Applications

Nianjun Yang and Xin Jiang

Institute of Materials Engineering, University of Siegen, Paul‐Bonatz‐Str. 9‐11, , 57076 Siegen, Germany

1.1 General Overview of Silicon Carbide

It is well known that carbon and silicon atoms form similar, covalently bonded and giant structures, as shown schematically in Figure 1.1a. They are thus called carbon diamond and silicon diamond. In both diamond structures, each atom is covalently bonded to four other atoms located at the corner of a tetrahedron. Another diamond‐like compound is silicon carbide (SiC), building up with silicon and carbon atoms. In this crystal, each atom is sp³‐hybridized and forms four bonds to four other atoms of the opposite kind. The tetrahedral arrangement of atoms encountered in the pure carbon and silicon diamond structures is preserved in SiC (Figure 1.1a).

Figure 1.1 Chemical structures of carbon diamond, silicon diamond, SiC (a), 3C(β)‐SiC (b), 4H‐SiC (c), and 6H(α)‐SiC (d) using ball‐stick models.

The existence of a compound containing SiC bonds was proposed in 1824 for the first time by Jöns Jacob Berzelius, a Swedish chemist [1]. In 1905, Henri Moissan, a French chemist and the Nobel laureate, discovered SiC in nature [2]. In mineralogy, SiC is therefore known as moissanite [3]. In nature, moissanite SiC is very rare and only found in certain types of meteorite. The most commonly encountered SiC material is actually man‐made.

SiC exists in about 250 crystalline forms, as variations of the same chemical compound that are identical in two dimensions but differ in the third. They can be viewed as layers stacked in a certain sequence. Different stacking sequences of C‐Si double layers lead to different crystalline structures, or so‐called polytypes [4]. Therefore, more than 250 polytypes have been predicted [4,5]. Of these polytypes, only a few of them have been studied in detail. In principle, only three are of major importance: cubic (3C, or β)‐SiC, 4H‐SiC, and 6H(α)‐SiC, which are shown schematically in Figure 1.1b–d, respectively. The most commonly encountered polymorph is 6H(α)‐SiC, which forms at temperatures higher than 1700°C and has a hexagonal crystal structure (similar to wurtzite) (Figure 1.1c). Cubic 3C(β)‐SiC (Figure 1. 1b) is formed at temperatures below 1700°C and has a zincblende (ZnS) crystal structure, similar to diamond [6].

1.1.1 SiC Properties

SiC is a fascinating material, although it has quite complicated polytypes. This is because the type of SiC polytype implies a corresponding set of relevant physical properties. As examples, some important physical properties of 4H‐, 6H‐, and 3C‐SiC are listed in Table 1.1, compared with those of diamond and silicon.

Table 1.1 Basic properties of three kinds of SiC, Si, and diamond.

Property	4H‐SiC	6H‐SiC	3C‐SiC	Si	Diamond
Energy bandgap at 300 K (eV)	3.20	3.00	2.29	1.12	5.45
Intrinsic carrier concentration at 300 K (cm^−3)	5 × 10^−9	1.6 × 10^−6	1.5 × 10^−1	1 × 10^10	∼10^−27
Critical breakdown electric field (MV cm^−1)	2.2	2.5	2.12	0.25	1–10
Saturated electron drift velocity (×10^7 cm s^−1)	2.0	2.0	2.5	1.0	1.5
Electron mobility (cm^2 V^−1 s^−1)	1000	600	800	1450	480
Electron mobility (cm^2 V^−1 s^−1)	115	100	40	470	1600
Thermal conductivity at 300 K (W cm^−1 K^−1)	3.7	3.6	3.6	1.49	6–20
Coefficient of thermal expansion at 300 K (10^−6 K^−1)	4.3 4.7	4.3 4.7	3.2	3.0	1.0
Lattice coefficient (a, c in Å)	a = 3.073 c = 10.053	a = 3.081 c = 15.117	a = 4.360	a = 5.430	a = 3.567
Calculated elastic coefficient (GPa)	C44 = 600	C11 = 500 C12 = 92 C44 = 168	C11 = 352 C12 = 12 C44 = 233	C11 = 167 C12 = 65 C44 = 80	C11 = 1079 C12 = 124 C44 = 578

SiC has been known for decades to be a semiconductor, based on the very first electroluminescence (yellowish light) from SiC crystals when subjected to electricity in 1907 [7]. More interestingly, its indirect bandgap is tunable in the range of 2.36–3.23 eV, determined by the polytype of SiC films. For instance, the bandgaps for 3C‐, 4H‐, and 6H‐SiC are 2.36, 3.23, and 3.05 eV, respectively. However, SiC can be varied from insulating, semiconductive, to metallic‐like in its properties when the dopants (n‐ or p‐type) and the doping levels are altered. For example, SiC films can be doped with either n‐type dopants (e.g. nitrogen, phosphorus) or p‐type dopants (e.g. beryllium, boron, aluminum, gallium). Metallic conductivities of SiC films have been achieved by their heavy doping with boron, aluminum, or nitrogen. For example, at the same temperature of 1.5 K, superconductivity has been detected in 3C‐SiC films doped with aluminum and boron as well as in 6H‐SiC films doped with boron.

In comparison with Si, SiC has a higher thermal conductivity, electric field breakdown strength, and current density. It features a very low coefficient of thermal expansion (4.0 × 10⁻⁶ K⁻¹) and experiences no phase transitions that cause discontinuities in thermal expansion. The sublimation temperature of SiC is very high (approximately 2700°C), which makes it useful for bearings and furnace parts. SiC does not melt at any known temperature.

SiC is transparent to visible light. Pure SiC is colorless. The brown to black color of industrial SiC products results from iron impurities. The rainbow‐like lusters of SiC crystals are caused by the passivation layers of SiO₂ that form on the SiC surface.

SiC is a very hard material. Taking Mohs hardness scale as an example, the value of talc is given by 1 and diamond is given by 10: SiC has the value of 9.3 [8].

SiC is chemically inert. For example, it is resistive to radiation and many chemicals. This is because the electron bonds between the silicon and carbon atoms inside SiC are extremely strong. More importantly, SiC has shown superior biocompatibility and is non‐toxic in both in vitro and in vivo tests. In addition, SiC is multifunctional, originating from the possibility of adopting both silicon and carbon chemistry on its surface.

In conclusion, SiC is a material with exceptional physical properties (e.g. a low dens...

Table of contents

• Cover
• Table of Contents
• List of Contributors
• Series Preface
• Preface
• 1 Cubic Silicon Carbide: Growth, Properties, and Electrochemical Applications
• 2 Application of Silicon Carbide in Photocatalysis
• 3 Application of Silicon Carbide in Electrocatalysis
• 4 Carbon Nitride Fabrication and Its Water‐Splitting Applications
• 5 Carbon Materials for Supercapacitors
• 6 Diamond/β‐SiC Composite Films
• 7 Diamond/Graphite Nanostructured Film: Synthesis, Properties, and Applications
• 8 Carbon Nanodot Composites: Fabrication, Properties, and Environmental and Energy Applications
• Index
• End User License Agreement