Ⅰ、The development of carbon nanotubes has undergone three main phases: from theoretical speculation, to experimental verification, and finally to technological application.

1. Theoretical Conception and Initial Discoveries (1952–1990).

As early as 1952, Soviet researchers Radushkevich and Lukyanovich observed hollow tubular carbon structures using electron microscopy, but failed to recognize their characteristics as a carbon allotrope. In the 1960s, Japanese scholar Akasaki Yasufumi produced carbon nanofibers under high-temperature and high-pressure conditions, providing an experimental foundation for subsequent research. The discovery of fullerenes in 1985 spurred theoretical exploration of carbon nanotube structures. By 1990, a German research team successfully synthesized multi-walled carbon nanotubes via the arc discharge method, though systematic characterization was not conducted.

2. Structural Confirmation and Fundamental Exploration (1991–2000).

In 1991, Japanese scholar Sumio Iijima first clearly revealed the crystal structure of multi-walled carbon nanotubes through high-resolution transmission electron microscopy, with his research findings published in Nature. In 1993, Donald Bethune and his team at IBM discovered single-walled carbon nanotubes, while Iijima and his collaborators achieved controlled synthesis of them in the same year. Between 1998 and 1999, researchers successively observed the quantum Hall effect and ballistic conduction behavior in carbon nanotubes, providing critical support for the development of nanoelectronics.

3. Process Advancement and Commercialization Progress (2000–present).

In 2002, the research group of Ajayan at Rice University in the United States developed the floating catalyst chemical vapor deposition (CVD) method, advancing the macroscale production of carbon nanotubes. The discovery of graphene in 2004 further stimulated research enthusiasm for carbon nanotubes. In 2008, South Korean research institutions developed transparent conductive films based on carbon nanotubes, and in 2013, Samsung首次 applied them in flexible display smartphones. Since the 2010s, the material has been gradually adopted in various fields such as aviation (e.g., Boeing 787), batteries (e.g., Tesla’s 4680 batteries), and composite materials (e.g., Porsche’s body structures). After 2020, new breakthroughs have continued to emerge in cutting-edge areas such as quantum computing and biomedicine.

Ⅱ、Major Milestones

1991: Sumio Iijima elucidated the structure of carbon nanotubes.

1996: China achieved large-area oriented growth of carbon nanotubes.

2000: Japan developed carbon nanotube-based field emission displays.

2023: Huawei applied carbon nanotubes to lithium batteries, significantly increasing capacity.

2025: Production costs of single-walled carbon nanotubes are projected to decrease substantially.

Ⅲ、Classification of Carbon Nanotubes

1. Single-Walled Carbon Nanotubes（SWCNT）.

Formed by rolling a single layer of graphene, with a diameter of approximately 0.4–2 nm, they exhibit metallic or semiconducting properties (e.g., armchair-type structures are metallic with extremely high electrical conductivity), making them suitable for microelectronics and sensing applications.

2. Multi-Walled Carbon Nanotubes（MWCNT）

Composed of multiple concentric layers of rolled graphene, with diameters ranging from 5–100 nm, they exhibit excellent mechanical properties and a high specific surface area, making them widely used in composite reinforcement and energy-related applications.

Ⅳ、Properties of Carbon Nanotubes

Mechanical Properties: Exceptionally high strength (theoretical value up to 300 GPa), outstanding toughness, and high fracture elongation, making them suitable for high-strength composites and flexible devices.

Electrical Properties: Tunable conductivity via structural design; metallic types exhibit higher conductivity than copper, while semiconducting types offer adjustable band gaps, ideal for high-frequency, low-power electronic devices.

Thermal Properties: Excellent axial thermal conductivity, applicable in high thermal conductivity materials.

Optical Properties: Exhibit near-infrared absorption and fluorescence emission characteristics, used in optoelectronic devices and bioimaging.

Ⅴ、Applications of Carbon Nanotubes

Aerospace: Used to reduce structural weight and enhance material strength; improve thermal management efficiency in components.

Electronics & Semiconductors: Fabrication of high-frequency transistors, flexible display electrodes, etc.

Energy Sector: Serve as conductive additives to boost battery performance; enable high-density hydrogen storage.

Composite Materials: Reinforce automotive parts, tires, and sports equipment for superior performance.

Biotechnology & Quantum Technology: Applied in neural interfaces, drug delivery systems, and extending qubit coherence time in quantum computing.