People often use uncanny workmanship to describe the beauty of nature and the power of their natural power. They use ingenuity to describe the ingenuity of artificial things and the resulting praise and praise. It is generally considered that metamaterials are artificial composite structures or composites with extraordinary physical properties that are not possessed by natural materials. They are characterized by ultrafast light modulation, negative refractive index, evanescent wave propagation, anomalous Doppler effect, subwavelength imaging, and stealth. , All-optical communication, chiral recognition, photonic crystals and other fields have great application value.

However, the issue of preparation of metamaterials has plagued many researchers. At present, common preparation techniques include electron beam lithography, laser direct writing, focused ion beam etching, and template-assisted electrochemical deposition. These methods have the following deficiencies: difficulty in large-area preparation, high preparation cost, cumbersome and lengthy process flow, and difficult control Wait. In particular, template-assisted electrochemical deposition is used as an example. Due to the limitations of the size of the mold body, the microstructure of the metamaterial is difficult to enter into the 10 nm range, and a conductive substrate is required. The resulting material also has chemical defects.

Recently, Gao Junhua and researcher Cao Hongtao, an associate researcher at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, proposed a new method for the preparation of metal-ceramic metamaterial films. A conventional RF co-sputter deposition process was used, supplemented with substrate bias to fabricate directional rows. Fabricated Ag metal nanowire/aluminum oxide ceramic composite metamaterial films, the nanowire spacing (axis to axis) enters the sub-5 nm region, the average diameter of the nanowires in the array is about 3 nm; the aspect ratio of the nanowires can be deposited Time to flexibly adjust; using PVD coating with good expandability, not only can realize the preparation of large-area metamaterial films, but also can easily construct a multi-layer metamaterial film structure in a “cover building” manner, in which different layers can have The same geometrical characteristics (diameter, spacing, length-to-diameter ratio) can also "personalize" the structural characteristics of individual layers; in addition, because they are prepared at approximately room temperature, no single crystal or conductive substrate is required, and even Prepared on flexible substrates such as PET, it provides physical support for the emerging concept of flexible metamaterials, as shown in the figure below. The researchers used classical thermodynamics (metal silver and alumina composites are phase separation systems), interfacial bonding forces, and sputtered particle dynamics analysis of the deposition area after substrate bias was applied, supplemented by comparative experiments (applied substrate bias With or without) and high-resolution microstructure observation, the physical and chemical mechanism of the direct growth of the Ag metal nanowire/alumina ceramic composite metamaterial film was clarified.

The structurally anisotropic metamaterials described above exhibit singular steady-state and transient optical properties. Due to the strong coupling between the nanowires caused by the smaller nanowire spacing, the axial plasmon resonance absorption peaks can be easily adjusted from the visible region to the near infrared region; in addition, the material exhibits an ultrafast non-visible region in the visible region. Linear optical properties, plasmon bleaching process relaxation time is about 1.5 picoseconds.

Related preparation techniques applied for national invention patents. Academic results were published in Advanced Materials (Adv. Mater., 2017, DOI: 10.1002) under the title Template-free growth of well-ordered silver nano forest/ceramic metamaterial films with tunable optical responses. /adma.201605324) This work not only embodies cooperation within the institute, that is, cooperation with researchers Huang Feng and Du Shiyi in terms of growth mechanism and first-principles calculations, but also with Professor Song Xiaolin of the Physics Department of Harbin Institute of Technology in the optical field. Deep inter-unit cooperation was conducted. This work was funded by the National Natural Science Foundation of China, the Natural Science Foundation of Zhejiang Province, the Key Laboratory of Zhejiang Province, and the Ningbo Science and Technology Innovation Team.

Graphite Powder soft, dark gray; greasy feeling, can contaminate the paper. Hardness of 1 to 2, along the vertical direction with the increase in the hardness of the hardness can be increased to 3 to 5. Specific gravity of 1.9 to 2.3. In the isolated oxygen conditions, the melting point of more than 3000 ℃, is one of the most resistant minerals. At room temperature, the chemical properties of Graphite powder is relatively stable, insoluble in water, dilute acid, dilute alkali and organic solvents; materials with high temperature conductive properties, do refractory materials, conductive materials, wear-resistant lubricating materials.

Graphite powder is widely used, according to its different use, we can be divided into the following categories of graphite powder

1. Scale graphite powder

Flake Graphite powder is the most widely used, but also processed into other graphite powder of the original material, scaly graphite powder specifications from 32 to -12000 mesh range, scaly graphite powder toughness is good, with good thermal conductivity and corrosion resistance, can be used as refractory Materials, wear-resistant lubricating materials, conductive materials, casting, Fansha, die and high temperature metallurgical materials

2. Colloidal Graphite powder

Colloidal graphite is formed by the average dispersion of graphite particles below 2u meters in an organic solvent. Colloidal graphite is a viscous suspension of black filaments. Colloidal graphite powder with high quality Natural Flake Graphite performance, in high temperature conditions with special oxidation resistance, self-lubricating and plasticity, at the same time with good conductivity, thermal conductivity and adhesion, mainly used in sealing, metallurgical stripping and other industries

3. Ultrafine graphite powder

Ultrafine graphite powder specifications are generally between 8000 mesh -10000 mesh, mainly used in powder metallurgy release agent, the production of graphite crucible, the battery anode and make conductive materials additives

4, Nano-Graphite Powder

Nano-graphite powder main specifications for the D30 50 100 400 nm, nano-graphite powder process is more complex, low production rate, so relatively high prices, mainly used in anti-corrosion coatings, lubricants additives, grease additives, precision graphite seal And other industries, in addition, nano-graphite powder in scientific research institutions also has a high application value

5, High Purity Graphite powder

Graphite Powder

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