With the support of the Chinese Academy of Sciences, the Ministry of Science and Technology and the National Natural Science Foundation of China, in response to these scientific issues, the relevant researchers of the Institute of Organic Solids of the Institute of Chemistry of the Chinese Academy of Sciences have been able to control the preparation of graphene on the basis of existing work. Significant progress has been made in performance studies, and the results are published in Adv. Mater., NPG Asia Mater., J. Am. Chem. Soc. and Nat. Commun.
Graphene is directly grown on the dielectric layer.
Chemical vapor deposition (CVD) has become one of the most important methods for graphene preparation because of its combination of high quality and macro quantity. However, graphene prepared by this method generally needs to be transferred to other dielectric layers to prepare graphene devices and circuits, and the transfer process will cause problems such as graphene damage, wrinkles, contamination, and material waste. Therefore, the ability to directly grow graphene on the dielectric layer has important scientific significance and huge technical requirements. The direct growth of graphene on the dielectric layer is compatible with current silicon electronics processing and can be directly used for device fabrication and assembly.
In the preliminary work, the researchers of the Key Laboratory of the Organic Solids Institute invented the oxygen-assisted method to directly prepare graphene films on silica insulating materials (J. Am. Chem. Soc. 2011, 133, 17548), and then It was found that the nucleation point and crystallite size of graphene can be controlled by two-stage chemical vapor deposition method, and the direct growth of high-quality graphene film on the silicon nitride surface is realized. The size of the graphene domain crystal in the prepared graphene film was 1 m. The film has high electrical properties, and its mobility can reach 1510 cm2V-1s-1 in air and 1518 cm2V-1s-1 in nitrogen. These properties are twice as high as those of graphene films grown directly on silica substrates, which are already higher than those of partially metal-catalyzed graphene. The research was published in Advanced Materials (Adv. Mater., 2013, 25, 992) and was selected as the inner cover (Figure 1).
Morphology regulation and etching of single crystal graphene.
The realization of the preparation of single crystal graphene and the regulation of its boundary structure are the frontier topics widely recognized in the research of graphene control preparation. The latter goal is especially faced with the dual challenge of lack of theoretical guidance and specific solutions. Researchers at the Chemical Solid State Laboratory have previously prepared hexagonal single crystal graphene using isotropic CVD on a liquid copper surface (Proc. Natl. Acad. Sci. USA, 2012, 109, 7992). A series of new thermodynamic graphene metastable structures were obtained for the first time through the regulation of the microscopic kinetics of graphene nucleation growth (continuous regulation of the ratio of Ar and H2) (Fig. 2).
The morphology of a series of graphites with a high degree of six-fold symmetry follows a defined pattern: the boundary changes of graphene contain a complete range from positive to negative curvature. This graphene pattern system is strikingly similar to the collection of snowflake structures in nature, and represents the only example of a known material that reproduces a collection of snowflake structures in a two-dimensional manner that is much simpler (snowflakes are three-dimensional crystals). Based on the above facts, the general growth mechanism of diffusion control is further proposed and is consistent with the theoretical simulation. For the first time, this work links the growth and morphology control of graphene with the kinetic regulation of non-equilibrium systems, revealing a fundamental rule in the growth of graphene that has never been discovered but is ubiquitous. A wider range of two-dimensional atomic crystal materials. Related work was published in the Natural Materials Group's Asia Materials (NPG Asia Mater., 2013, 5, e36).
Based on this work, the researchers applied this control method to the study of graphene etching behavior. Traditional experimental results and beliefs suggest that due to the regular arrangement of the building elements, the etching of the perfect crystal is characterized by anisotropic etching, and the etching pattern is characterized by a simple Euclidean geometry. Previous experimental results have also shown that graphene follows This law. By adjusting the ratio of etching gas H2 to inert gas Ar, the researchers revealed for the first time that the etching mode of graphene can be greatly deviated from the ideal anisotropic etching mode, so that the etching pattern of graphene is from simple Euclid. The structure evolved into a complex fractal structure (Fig. 3). The simple Euclidean etch pattern of graphene observed in previous studies is only a special case in this general evolution. Related work is published in the American Chemical Society (J. Am. Chem. Soc. 2013, 135, 6431). The British Royal Chemical Society's "Chemistry World" reported the results on the headline of its homepage with "Carving graphene snowflakes with gases", saying that "the beautiful snowflakes are not made of ice, but are etched by graphene sheets. to".
Single-walled carbon nanotubes/graphenes have intramolecular junctions. Dr. Wei Dacheng and Professor ATSWee from the National University of Singapore collaborated with relevant personnel from the Organic Solids Laboratory to prepare a single-walled carbon nanotube/graphene band intramolecular junction (Fig. 4), which shows a typical asymmetric rectification curve (Fig. 4) Switching ratio: ~160, at ±1.5 V), its photocurrent and photovoltage are linear and exponential, respectively. Under the condition of light intensity of 98.6 kW/cm2, high photocurrent (11.6 nA) and highlight are obtained respectively. The voltage (270 mV) and the external photoelectric sensitivity of 3 mA/W are higher than the pn junction of two-dimensional graphene or carbon nanotubes, indicating that the intramolecular junction can be expected as a high-performance photodetector. The results were published on Nat. Commun. (2013, 4, 1374).
This series of work reveals the rich connotation of graphene growth process under non-equilibrium conditions, and provides a broad research space for further control of high quality, large area, pollution-free graphene. These findings also have a general reference to the understanding of material growth processes in non-equilibrium systems. They also introduce some basic physical concepts and natural phenomena in graphene and science (such as disorder and order, certainty and randomness, and simplicity). Close to the complex, liquid, snow, etc.).
The title of the Circular Pipe Fan
The circular Pipe Fan is an ideal ventilator with the perfect combination of performance and appearance. The clever cooperation between the newly designed chassis and the centrifugal impeller makes the gas hydromechanics reach the extreme, and its shape is small and very practical. With easy installation, light weight, low noise and so on. For the air, exhaust, return air and air purification to provide the source of power, high pressure can take tens of meters of pipe, a fan control multi-zone centralized ventilation, commonly used in real estate buildings, indoor ventilation Or pipe pressure. Circular duct fans can be the same size on both sides of the pipe, while the other side into the wind out of the wind
working principle
Circular duct blower with wing-shaped backward impeller, high-speed operation of gas hydrodynamics to the extreme, so the energy efficiency is very high, up to 70%, which means that with the smallest motor power delivery maximum wind power, which is normal Forward Centrifugal Fan can not achieve the effect. Therefore, both the fan duct energy-saving and strong winds. Ultra-high pressure can take tens of meters of pipe concentrate ventilation, the main characteristic of the pipeline fan is the pressure. Replace the traditional ventilation equipment. Fan vibration-free, dynamic balance of less than 0.17g, only the standard value to ensure the superior quality fan, imported metal impeller or PP plastic perforated in accordance with the wing, which is characterized by strong rigidity, high temperature, environmental protection, air volume Large, but also to a certain extent reduce the noise.
Round tube fan core with an external rotor motor, its life depends on the bearing, the motor uses imported single deep groove ball bearings, external rotor motor compact structure, small size, energy efficient, pure imported bearings, 120 ℃ automatic parking hot Protection, high-quality copper winding and so on. 24h continuous operation can be more than 30,000 hours.
About noise
Motor does not make any sound, the fan is mainly air flow sound, because the impeller speed is high 2500 rpm, resulting in high pressure air volume is high, so you can take a long pipe with the same and to ensure that does not affect the air flow. If you use it when you sleep at night, it is certainly noisy. However, you can reduce the speed to reduce the noise, it is to ensure that there is sufficient air volume to reduce the speed.
if you want to customize product, please contact us.
Circular Pipe Fan
Circular Pipe Fan,Pipe Type Exhaust Fan,Circular Pipe Centrifugal Fan,Variable Frequency Pipe Fan
Shenzhen Fu Sheng Electric Co., LTD. , http://www.fushengfan.com