Graphene oxide for heavy metal pollution control

Heavy metals generally refer to more than 60 elements with a density of more than 4 or 45 elements with a density of more than 5. However, because the toxicity of different heavy metals in water and soil is very different, in the field of environmental science, people usually pay attention to vanadium, chromium and nickel. , cobalt, copper, zinc, cadmium, tin, mercury, lead and other metal ions. Heavy metal ions can accumulate in the human body and lead to poisoning, cancer and damage to the nervous system, so it is particularly important to do a good job of heavy metal pollution control.

Graphene oxide  is a carbon nano material prepared from natural graphite with a structure similar to carbon nanotubes. Compared with the adsorption capacity of activated carbon, carbon nanotubes and graphene materials for low-concentration lead-containing wastewater, the adsorption capacity of graphene oxide for lead is as high as 800 mg/g, which is much higher than that of activated carbon, which is 60 to 120 mg/g. It has extremely strong regeneration capacity, and the adsorption capacity drops only 5 to 10% after repeated adsorption/elution cycles.

Why does graphene oxide have such a strong heavy metal adsorption capacity? There are two reasons: one is that graphene oxide is a two-dimensional nano material with a thickness of one atomic layer, and its specific surface area can theoretically reach 2600 square meters/g, which is the largest among all carbon nano materials; During the preparation process, a large number of active groups such as carboxyl group, carbonyl group, hydroxyl group, epoxy group, etc. are formed on its surface. Therefore, graphene oxide has the most basic elements required for an excellent adsorbent: a sufficiently large specific surface area and a sufficiently high density of surface functional groups.

The use of graphene oxide material can reduce the discharge concentration of lead-containing wastewater in the lead-acid battery industry from the current 100-1000ppb to 1-10ppb, increase the lead recovery rate to 95%-99%, and reduce the total environmental discharge of lead by 90% compared with the existing technology. %. The achievement can be effectively extended to other heavy metal pollution systems such as cadmium, nickel, arsenic, copper, chromium, and radioactive elements, and has considerable economic and social benefits. https://www.hwnanomaterial.com/

Application of Nano-materials in Plastic Modification

Organic/inorganic nanocomposites formed by inorganic fillers dispersed in a general plastic matrix with nano size are called nanoplastics. In nanocomposites, nanoplastics have excellent properties such as high strength, heat resistance, high barrier properties, flame retardancy and excellent processability because of the nano size effect, large specific surface area and strong interfacial bonding of the dispersed phase, which is a new high-tech new material.

Application of nano materials in plastic modification:

(1) Anti-aging properties of reinforced plastics
The anti-aging performance of polymer directly affects its service life and working environment, especially for agricultural plastics and plastic building materials, which is an indicator that requires high attention. The ultraviolet wavelength in sunlight is 200~400nm, and the ultraviolet light in the 280~400nm band can break the polymer molecular chain, and never make the material age. Nano oxides powder, such as nano alumina(Al2O3), titanium dioxide(TiO2), silicon dioxide(SiO2), etc., have good absorption characteristics for infrared and microwave. Proper mixing of nano-SiO2 and TiO2 can absorb a large amount of ultraviolet rays, thereby making the material anti-aging.

(2) Improve the processing performance of plastics
Some high polymers, such as ultra-high molecular weight polyethylene with a viscosity average molecular weight of more than 150, have excellent comprehensive performance, but due to their extremely high viscosity, it is difficult to form and process, thus limiting their popularization and use. Taking advantage of the small friction coefficient between the layers of layered silicate sheets, the ultra-high molecular weight polyethylene and layered silicate are fully mixed to make nano rare earth / ultra-high molecular weight polyethylene composite material, which can effectively reduce the ultra-high molecular weight polyethylene. The entanglement of ethylene molecular chains reduces the viscosity and plays a good lubricating role, thus greatly improving its processing performance.

(3) Improve the toughness and strength of plastics
The emergence of nano materials provides a new method and approach for the enhancement and toughening of plastics. Small particle size dispersed phase has relatively few surface defects and more unpaired atoms. The ratio of the number of atoms on the surface to the total number of atoms increases sharply with the decrease of the particle size. The crystal field environment and binding energy of the surface atoms are different from those of the internal atoms, and they have great chemical activity. The micronization of the crystal field and the increase of active surface atoms greatly increase the surface energy, so it can be closely combined with the polymer substrate and has good compatibility. When subjected to external force, the ions are not easily separated from the substrate, and can better transmit the external stress. At the same time, under the interaction of the stress field, more micro-cracks and plastic deformation will be generated inside the material, which can cause the substrate to yield and consume a large amount of impact energy, thereby achieving the purpose of strengthening and toughening at the same time. Commonly used nanomaterials include nano silicon carbide(SiC), silicon carbide whiskers(SiC-W), nano aluminum oxide(Al2O3), multi-walled carbon nanotubes(MWCNTs), etc.

(4) The addition of nanomaterials enables the functionalization of metal nanoparticles have heterogeneous nucleation, which can induce the formation of certain crystal forms that impart toughness to the material. Polypropylene was filled with low melting point metal nanoparticles, and it was found that it can act as a conductive channel and strengthen and toughen the polypropylene. At the same time, its low melting point also improves the processing performance of the composite material.

Learn about Thermally Conductive Aluminum Nitride(ALN)

Introduction:
Aluminum nitride AlN is the only stable compound of Al and N, and is the semiconductor with the largest energy gap in the III-V group. Aluminum nitride atoms are combined by covalent bonds, which have good chemical stability and high melting point. At the same time, it has high mechanical strength and good electrical insulation properties. It is a piezoelectric material. It has good injection molding properties, can be used in composite materials, has good matching with semiconductor silicon, good interface compatibility, and can improve the mechanical properties and thermal conductivity and dielectric properties of composite materials.

Product advantages:
The particle size distribution is concentrated,
Good dispersion,
Low metal impurity content,
Low oxygen content,
Low coefficient of thermal expansion,
Strong hydrolysis resistance.

The particle size is complete (nano-level aluminum nitride 100-200nm, 300-500nm, 1-2um, 3-5um, 10um, etc.), and surface treatment can be done according to customer requirements.

Application direction of thermally conductive aluminum nitride powder:
Special for CPU thermal silica gel system;
Special for plastic system;
Special for epoxy resin system;
High thermal conductivity filler of thermal grease and thermal grease;
High thermal conductivity filler of thermal conductive glue, thermal conductive silicone sheet, epoxy resin thermal conductive potting glue;
High thermal conductivity filler of thermally conductive engineering plastics;
Packaging materials, high temperature lubricants, adhesives;
High thermal conductivity fillers for radiators, heat-dissipating paints, and heat-dissipating inks;
Manufacture of insulating and thermally conductive fillers for high thermal conductivity integrated circuit substrates (MCPCB, FCCL);
High thermal conductivity filler of thermal interface material (TIM);
Crucible metal smelting, evaporation boat, ceramic cutting tools, cutting tools, microwave dielectric materials;
Manufacturing high thermal conductivity aluminum nitride ceramic substrates and various ceramic products.

Aluminum nitride ALN powder should be sealed and stored in a dry and cool environment. It should not be exposed to the air for a long time to prevent agglomeration due to moisture, which will affect the dispersion performance and use effect. Surface treatment can be done according to user requirements.

If you need further inquiries about aluminum nitride powder, you can consult our sales staff online.

Comprehensively understand the heat conduction material hexagonal boron nitride HBN

1. What is boron nitride?
Boron nitride is a crystal (BN) composed of nitrogen atoms and boron atoms, and its chemical composition is 43.6% boron and 56.4% nitrogen.

2. What are the classifications of boron nitride?

According to the crystal type, boron nitride is divided into hexagonal boron nitride, cubic boron nitride, rhombohedral boron nitride and wurtzite boron nitride. However, the current research on boron nitride mainly focuses on the two crystal forms of hexagonal boron nitride and cubic boron nitride. Hongwu Nano mainly focuses on the production and supply of hexagonal boron nitride powder, which includes three categories: nanometer, submicron and micron.

3. What are the physical and chemical properties of hexagonal boron nitride?
The crystal structure of hexagonal boron nitride has a similar layered structure of graphite, which is a white powder that is loose, lubricating, easy to absorb, and light in weight. The theoretical density is 2.29g/cm3, the Mohs hardness is 2, and the chemical properties are extremely stable. The product has high humidity resistance, and the temperature can reach 2800℃ when used in nitrogen or argon. It not only has a low thermal expansion coefficient, but also a high thermal conductivity. It is not only a good conductor of heat, but also a typical electrical insulator. The thermal conductivity of BN measured at 300k using high-purity single crystal is 730w/mk.

4. How is hexagonal boron nitride prepared?
There are many synthetic methods for hexagonal boron nitride, but the basic principle is that the boron source and the nitrogen source are heated and refined together. Hexagonal boron nitride is the most commonly used form of boron nitride. Its preparation methods include borax-urea method, hydrothermal synthesis method, chemical vapor deposition method and precursor method.
Compared with the process flow of various methods, it is not difficult to produce boron nitride, but the process conditions of each process have a great impact on the quality and output of the product. In order to reduce costs and improve quality, Hongwu Nano believes that several issues that must be paid attention to through production practices are: the purity and proportion of raw materials, the influence of reaction temperature and time, the influence of washing methods and the influence of drying processes. Of course, production equipment, production environment, etc. will have an impact to a certain extent.

5. What are the main application areas of hexagonal boron nitride?
Evaporation boat ceramic products;
LED thermally conductive packaging materials;
Boron nitride ceramic parts;
Additives for plastics and refractory materials;
Metallurgical stripping machine;
Lubricant
Thermal shielding materials in the aerospace field;
Atomic reactor structural materials;
Cosmetic fillers;
Laser anti-counterfeiting aluminized trademark hot stamping material.

If you need further inquiries about hexagonal boron nitride product information, please contact us online.  https://www.hwnanomaterial.com

Application of Nano-silver Materials In The Field of Textile Functional Finishing Antibacterial, Antistatic, Anti-electromagnetic Radiation

The application of nano-silver materials to the field of textile functional finishing and the development of multi-functional, high-value-added fabrics will create huge economic and social benefits in the future textile industry. Nano-silver is a new type of nano-material that is under in-depth research and rapid development. It has broad application prospects in the textile industry due to its broad-spectrum and long-lasting anti-bacterial properties/anti-electromagnetic radiation properties/conductivity and absorption of some ultraviolet rays.

 

Application in natural fiber yarn and fabric

The fabrics made of natural fibers have good moisture absorption and are mostly porous fibers, which can provide enough water for the growth of bacteria. At the same time, the surrounding environment can also provide oxygen for the growth of bacteria and promote the reproduction of bacteria. Nano-silver has broad-spectrum and long-lasting antibacterial properties. At present, the antibacterial application of nano-silver in natural fibers is mainly for yarns and fabrics, and the antibacterial function is mainly obtained through finishing.

 

Nano-silver antibacterial finishing of yarn is generally aimed at cotton yarn or wool. For example, on the basis of puffing and pretreatment of cotton yarn with sodium hydroxide, tannic acid-reduced silver ammonia solution is used to load nano-scale silver particles in the micro gaps of the fiber to make The nano-silver particles and fibers are loaded on the yarn through coordination bonds, so that the silver-loaded cotton yarn has good antibacterial and washing resistance.

 

Under acidic conditions, using nano silver sol and acid dyes to dye wool yarns and antibacterial finishing at the same time, not only can improve the dye uptake, color fastness and flexibility of wool yarns, but also make wool yarns have good antibacterial properties.

 

 

According to reports, some scholars now use the reducibility and stability of the fabric itself to reduce the nano-silver particles in situ on the fabric, so that the fabric has good antibacterial and washing resistance. For example, Ma Tingfang uses the reducibility and dispersibility of cellulose macromolecules to reduce the silver nitrate solution in situ to prepare nano silver antibacterial cotton fabric, which has excellent antibacterial effect and washing resistance. After 20 cycles of washing, the antibacterial fabric will affect the large intestine. The inhibitory rates of Bacillus and Staphylococcus aureus are still as high as 98.5% and 94.3%, respectively. Majid Montazer and others also successfully used the reducibility and stability of cellulose to reduce Torrance reagent (silver ammonia solution) to synthesize nano silver. After the fabric treated with nano silver was washed for 30 times, the antibacterial performance was almost unchanged.

 

In addition, some scholars compound nano-silver with other substances, using inorganic-organic compounding method or inorganic-inorganic compounding method, to prepare compound such as nano-silver/polysaccharide quaternary ammonium salt (HACC), nano-silver/titanium dioxide, etc. Compound, and then padding and finishing the fabric to obtain functional textiles with multiple functions. Wang Haiyun prepared silver-loaded nano-TiO2 antibacterial agent in an inorganic-inorganic compounding method and used it for the finishing of cotton fabrics, so that the cotton fabric obtained the dual antibacterial functions of silver ion elution antibacterial and TiO2 photocatalytic antibacterial, and two kinds of antibacterial The effects promote each other, making the antibacterial effect far better than a single antibacterial agent with the same content.

 

Application in synthetic fibers and fabrics

Three types of synthetic fibers such as nylon, acrylic, and polyester are widely used. At present, the application research of nano-silver in synthetic fibers is mainly aimed at these three types of fibers and fabrics. The manufacturing of synthetic fiber functional fabrics mainly includes two methods: spinning functional fibers and finishing, specifically including blending spinning method, dipping (rolling) method and magnetron sputtering method. The direct-spun functional fiber has a long-lasting effect, but the technology is complex and the cost is high; the finishing agent is simple and convenient to use, and is suitable for most fiber textiles. The cost is low, but the washing resistance is relatively low.

 

(1) Blending spinning method

The blending spinning method is to add nano silver particles in the fiber manufacturing process to blend and spin the fiber to make the final fabric have corresponding functions. The blending spinning process has no pollution to the environment and is widely used. Zhang Hua uses ultra-fine hemp rod core powder to prepare nano silver particles and spun them into antibacterial multifunctional nylon. When the powder content is 2%, nylon fiber not only has excellent antibacterial properties, high strength, and good elasticity. , It also has the ability of far-infrared emission and negative oxygen ion release, and the spinnability also meets the requirements.

 

The antibacterial polyester masterbatch is prepared by blending the silver-loaded nano-zinc oxide antibacterial agent treated with T-aminopropyl triethoxysilane and polyester, which is added to the polyester skin layer, and the core-type antibacterial polyester is produced by spinning. This fiber has excellent antibacterial properties, and the sterilization rate of Escherichia coli and Staphylococcus aureus is above 99%.

 

(2) Dipping (rolling) method

Although the blending spinning method is environmentally friendly, it is difficult to prepare a spinnable spinning solution. In contrast, the dipping (rolling) process is relatively simple. Yu Qiaozhen treated the nano-silver particles to polyester fabrics by dipping, and studied its effect on the antistatic properties of the fabrics, and found that nano-silver treatment can effectively improve the antistatic capabilities of polyester fabrics; and different treatment methods have endless effects on the fabrics. Similarly, for example, the effect of the one-bath method in which nano-silver particle treatment and dyeing are performed at the same time is significantly better than the two-step method in which dyeing is followed by finishing.

 

Some researchers have explored a new type of finishing method that allows nano-silver particles to be bonded to the surface of the fiber through chemical bonding, so that the bond between nano-silver and the fiber is stronger. For example, the researchers amidoxim part of the acrylic fiber to make the fiber surface with chelating groups, which can be complexed with silver ions, and then use formaldehyde solution to reduce the silver ions to obtain nano-silver composite acrylic fiber. The killing rate of Staphylococcus aureus and Bacillus subtilis exceeds 99.99%, the antibacterial performance is good, and the original physical properties of the fiber have no obvious changes.

 

(3) Magnetron sputtering method

In order to avoid the waste liquid disposal problem of the dipping (rolling) method, some researchers used the radio frequency magnetron sputtering method to sputter nano-silver film on the surface of the fabric. The magnetron sputtering method is to charge a proper amount of argon in a high vacuum, and apply a DC voltage between the cathode (columnar target or flat target) and the anode (the wall of the coating chamber) to ionize the argon gas, and the argon ions are accelerated and bombarded by the cathode On the surface of the cathode target, the atoms on the surface of the target are sputtered and deposited on the surface of the substrate to form a thin film. This method has the advantages of strong bonding force between the coating layer and the substrate, and the coating layer is dense and uniform.

 

Application in industrial textiles

The application objects of nano-silver in industrial textiles are mainly non-woven fabrics, laminated composite fabrics and composite materials.

 

(1) Application in non-woven fabrics

The use of nano-silver to finish the non-woven fabric can obtain antibacterial properties and anti-electromagnetic radiation properties, which can be widely used in medical, sanitation, automotive interiors, electromagnetic shielding materials and other fields. Similar to synthetic fibers, the nano-silver finishing methods of non-woven fabrics also include blending spinning method, dipping (rolling) method and magnetron sputtering method, the principle of which is the same as described above. Hong Jianhan uses magnetron sputtering at room temperature to deposit nano-silver films on the surface of polyester spunbonded nonwovens to make the fabrics resistant to electromagnetic radiation. As the thickness of the nano-silver films increases, the shielding effect of electromagnetic waves is enhanced. This method expands the application field of nonwoven fabrics, and can be used to develop antistatic materials, conductive materials, electromagnetic shielding materials and fiber sensors.

 

The nano silver antibacterial agent is highly uniformly dispersed and implanted in the spinning solution to blend and spin, so that the fabric can obtain higher stability, antibacterial performance and washing resistance, and then obtain nano silver antibacterial spunlace nonwoven rolls and nano silver Antibacterial needle punched non-woven fabric rolls.

 

Its most extensive application field is the production of medical and sanitary products, such as nano-silver antibacterial masks, antibacterial wipes, medical bed sheets, medical wipes, etc. The latter’s market applications are also very broad, such as automobile compartment/indoor air conditioning antibacterial filter media, clothing linings, etc. , Antibacterial insoles, shoe materials, etc.

 

Application in laminated composite fabric

Laminated composite fabrics are ideal materials for civilian sportswear, cold-proof clothing, field work clothes, military combat uniforms, labor protective clothing and other products. The nano-silver finishing of composite laminated fabrics is mainly achieved by dipping or blending spinning. Researchers at Zhejiang Sci-Tech University used a cross-shaped cross-section polyester fiber material containing nano silver particles as an antibacterial modifier as the outer layer of the fabric, and combed cotton yarn with better moisture absorption as the inner layer of the fabric, using the changes in the fabric structure , Combined with advanced finishing technology, the fabric has multiple functions such as moisture absorption, perspiration, and antibacterial.

 

(3) Application in composite materials

 

The silver/polymer nanocomposite material not only has the excellent characteristics of nano silver and polymer, but also gives the material some new functions, so that it has broad application prospects in many fields such as textiles, electronics, and biomedicine.

 

Conclusion

As a new type of material, nano-silver is used in many fields, especially the textile industry is closely related to people’s lives, which has aroused the interest of many researchers. At present, the application of nano-silver in the textile industry is mainly to obtain antibacterial, antistatic, and anti-electromagnetic radiation functions. As people’s requirements for textile products increase, nano-silver will be increasingly used in functional fabrics, and its application prospects in the textile industry will become broader.

Semiconductor materials of three generations

Semiconductor materials are a class of electronic materials that have semiconductor properties and the conductivity at room temperature is between conductive materials and insulating materials, they can be used to make semiconductor devices and integrated circuits.

 

Common semiconductor material characteristics:

Conductivity between conductors and insulators

When stimulated by external light and heat, its electrical conductivity will change significantly.

In a pure semiconductor, adding a small amount of impurities will sharply enhance its conductivity.

 

First Generation Semiconductor Materials:

Silicon (Si) and Germanium (Ge). Mainly used in various discrete devices, integrated circuits, new energy and chip manufacturing.

 

Second-generation semiconductor materials:

Mainly refers to compound semiconductor materials, such as gallium arsenide (GaAs), indium antimonide (InSb); ternary compound semiconductors, such as GaAsAl, GaAsP; and some solid solution semiconductors, such as Ge-Si, GaAs-GaP; glass semiconductors ( Also known as amorphous semiconductors), such as amorphous silicon, glassy oxide semiconductors; organic semiconductors, such as phthalocyanine, copper phthalocyanine, polyacrylonitrile, etc. It is mainly used to make high-speed, high-frequency, high-power and light-emitting electronic devices, and is an excellent material for making high-performance microwave, millimeter-wave devices and light-emitting devices. Due to the rise of the information superhighway and the Internet, it is also widely used in satellite communications, mobile communications, optical communications and GPS navigation.

 

Third-generation semiconductor materials:

Wide bandgap (Eg>2.3eV) semiconductor materials mainly represented by silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), diamond, and aluminum nitride (AlN). The main applications are semiconductor lighting, power devices, microwave devices, lasers and detectors.

 

Components and integrated circuits made of semiconductor materials are important basic products of the electronics industry and have been widely used in various aspects of electronic technology. The production and scientific research of semiconductor materials, devices and integrated circuits have become an important part of the electronics industry. In terms of new product development and new technology development, the application areas are mainly Integrated Circuits, Microwave Devices and Optoelectronic Devices.

Nanographene is Getting Smarter in Agriculture Application

In the era of rapid development of Internet technology, the future direction of agriculture has become the focus of social attention. Using information technology to change future agricultural production scenarios, let agricultural production develop in the direction of intelligence and spatial three-dimensionality, thereby promoting a new round of agricultural science and technology revolution, promoting the transformation of agricultural production methods and the efficient use of resources.

The intelligent application of graphene in agriculture is mainly reflected in the following three aspects:

Application in greenhouse.

As a new heating method, nano-graphene heating is not only used in home life, but also has a wide range of applications in agriculture and rural areas, covering vegetable greenhouses, flower cultivation, agriculture and forestry nursery, soil insulation, chick hatching, special aquaculture and other industries. Greenhouse is the most popular production method in my country’s facility agriculture, which not only greatly improves the productivity of the land, but also solves the problem of off-season production. But the biggest trouble is that most of the greenhouse heat sources use hot blast stoves, heating stoves or electric heating wires. Not only high energy consumption, large pollution, but also poor stability and high cost. The graphene electrothermal film system has a high electrothermal conversion rate, which generally saves 30-50% of energy and will not cause pollution. After the graphene electrothermal film is covered with soil, far-infrared direct warming can significantly promote the development of seedlings and effectively enhance photosynthesis.

Smart farmland system

The farmland is covered with sensors to collect surrounding environmental parameters such as air temperature and humidity, soil temperature and humidity. If the land is short of water, the system will automatically give an early warning, and the manager can water it with one button on the mobile phone, which can be operated anytime, anywhere. It is no longer a fantasy that agricultural production becomes intelligent. Therefore, the smart farmland system not only makes agricultural production management more intelligent, but also makes the utilization of farmland resources more reasonable.

The main component of the smart farmland system is the sensor. Sensor technology is used worldwide for detecting and monitoring process parameters. Graphene sensors also work in the same way, it’s just a factor of the nanomaterials used in their fabrication. Sensors are a very important application field of graphene. Graphene sensors can convert environmental parameters into electrical signals processed and measured by computers. This feature meets the management needs of smart farmland. There are many advantages when people apply graphene sensors in smart farmland. Therefore, graphene sensors are the way to open the transformation and upgrading of smart agriculture. Graphene is known as the “king of new materials” because of its excellent properties, such as superconductivity, good flexibility, good transparency, and excellent mechanical properties. It is widely used in all walks of life.

Raising seedlings and adsorbing pollutants

Based on domestic and foreign research, appropriate addition of nano graphene powder to soil is beneficial to seed germination and seedling growth, and is beneficial to improve crop yield and quality. The addition of graphene nanomaterials to fertilizers can increase the clay content of the soil and improve the soil texture, and the nanocarbon has a large specific surface area, which can improve the adsorption force of the soil on nutrient elements, thereby effectively controlling the above-ground nutrient volatilization, surface runoff and Loss of deep seepage. At the same time, nano-carbon can improve the electrochemical properties of soil and promote the absorption of nutrients by the root system, thereby improving the utilization rate of fertilizers, reducing agricultural non-point source pollution, and ultimately saving fertilizers and increasing efficiency.

Graphene nanomaterials also play an excellent role in the adsorption and purification of agricultural pollutants, especially for pesticide and heavy metal pollution in water.

 

Graphene-hexagonal Boron Nitride Heterostructure Enables Ultra-fast Heat Transfer

Nano heat flow plays an important role in modern electronic and optoelectronic applications such as thermal management, photodetection, thermoelectricity, and data communication. Two-dimensional layered materials are beginning to consolidate their fundamental position in many applications. The van der Waals heterostructure is composed of different layered two-dimensional materials stacked. These stacks can be composed of materials with different physical properties, and the interface between the materials is super clean and has a clear outline.

 

Supported by the European Union’s “Graphene Flagship” program, the Spanish Institute of Photonics prepared a van der Waals heterostructure composed of hexagonal boron nitride encapsulated  gaphene nano powders, a two-dimensional dielectric material, and successfully observed and tracked the heat generated between the van der Waals heterostructures in real time. transmission. The researchers discovered a surprising phenomenon: the heat flow does not stay in the graphene layer, but flows to the surrounding hexagonal boron nitride layer. The heat transfer time is very fast, on the order of picoseconds. The research results were published in “Nature · Nanotechnology”.

 

The heat transfer process is realized by coupling the hot electrons excited by light irradiating graphene with the hyperbolic phonon-polarization excimer in the hexagonal boron nitride sheet. These phonon polaritons propagate in the hexagonal boron nitride sheet, just like light propagates in an optical fiber, but are limited to nano-scale infrared light. The results show that these bizarre hyperbolic modes are very effective heat dissipation methods.

 

The research results will have a profound impact on the application of graphene based on hexagonal boron nitride packaging (also the next-generation graphene application platform). In particular, this technology will provide direction for optoelectronic device design to make full use of heat flow, get more Carbon Material Nanopowders from https://www.hwnanomaterial.com quickly!.

 

Two common materials for ceramic toughening (silicon carbide whiskers and nano zirconia)

As new materials in the technological revolution, ceramic materials have attracted the attention of some developed countries as early as ten years ago. The fatal shortcomings of ceramic materials are its brittleness, low reliability and low repeatability, which seriously affect the application range of ceramic materials. Only by improving the fracture toughness of ceramics and providing its reliability and service life can ceramic materials truly become a new type of widely used material. Therefore, ceramic strengthening and toughening technology has always been a hot topic of discussion in the market.

Two commonly used ceramic toughening methods and materials include:

1) Beta Silicon Carbide Whisker(SiC-W) and Particle(SiC) Toughening

Silicon carbide(SiC) whiskers are added to the ceramic materials to improve the brittleness, enhance the toughness and strength of them, so that the ceramic matrix composite material can significantly improve the impact toughness and shock resistance, and reduce the brittleness of the ceramic material. At the same time, the ceramic has protective fibers. So that it will not be oxidized at high temperature, has high temperature strength and elastic modulus.

Ceramic silicon carbide whiskers are small ceramic single crystals with a certain aspect ratio and few defects, so they have high strength and are ideal toughening reinforcements for ceramic matrix composites. The macroscopic morphology of ceramic silicon carbide whiskers is flocculent powder. When preparing composite materials, the whiskers can be directly dispersed and then mixed with the matrix powder uniformly. The mixed powders are also hot-pressed and sintered to obtain dense whisker-toughened ceramic matrix composites.

2) Phase transformation toughening of ZrO2 Zirconia Nanopowder
The phase transformation toughening effect is remarkable, and it is mainly used in zirconia ceramics. Yttrium nano-zirconia(YSZ), phase-transformation toughened ZrO2 feldspar ceramics is a promising new type of structural ceramics. It mainly uses ZrO2 phase-transformation properties to improve the fracture toughness and flexural strength of ceramic materials, so that they have excellent mechanical properties, low high thermal conductivity and good thermal shock resistance. It can also be used to significantly improve the toughness and strength of brittle materials, and is an important toughening agent in composite materials and composite ceramics.

The outstanding properties of ZrO2 ceramics make it one of the most widely used oxide ceramics. Toughened ceramics based on ZrO2 materials have broad application prospects in machinery, electronics, petroleum, chemical industry, aerospace, textile, precision measuring instruments, precision machine tools, bioengineering and medical equipment and other industries. Because the partially stabilized zirconia has low thermal conductivity, good strength and toughness, low elastic modulus, thermal shock resistance and high working temperature (1100 ℃), it is used to manufacture diesel engine parts and internal combustion engine parts. It has the advantages of small size, light weight and high thermal efficiency, and is an effective energy-saving engine. The application of ZrO2 toughened ceramics in internal combustion engines is successful.

If you’re interested in further info or in need of SiC whisker, SiC particles, ZrO2 nanopowders, pls feel free to contact us now!

3 Types Of Nano Materials Used In Absorbing Materials

The so-called absorbing materials refer to a class of materials that can absorb or greatly weaken the electromagnetic wave energy received by its surface, thereby reducing the interference of electromagnetic waves.

In engineering applications, they require the absorbing material to have a high absorption rate of electromagnetic waves in a wide frequency band, they also require to have light weight, temperature resistance, moisture resistance, corrosion resistance and other properties.

Three commonly used nano materials for absorbing materials are as follows:
1. Carbon series nano materials: nano graphene, carbon nanotubes, etc.

Carbon nanotubes(CNTs) show excellent absorbing properties, and at the same time have the characteristics of light weight, good compatibility, and wide absorbing frequency band. They are the most potential absorbing materials of the new generation.

2. Iron series nanomaterials: nano iron(Fe) powder, nano iron oxide, etc.
Nano metals and alloys are mainly used as wave absorbers in a multi-phase composite way, mostly Fe, Co, Ni and other nano metals and alloy powders, and their wave-absorbing properties are better than single-phase nano metal powders.

3. Ceramic series nanomaterials. Such as silicon carbide whiskers, nano silicon carbide particles, nano silicon nitride, and so on.
Silicon carbide(SiC) has been studied a lot as an absorbent. Silicon carbide not only has certain wave absorbing properties, but also can weaken the infrared signal of the engine, and has the advantages of high temperature resistance, low relative density, good toughness, high strength and high resistivity. SiC is one of the rapidly developing absorbents abroad. The absorption band of nano silicon carbide is wider, and it has a good absorption effect on the millimeter and centimeter bands.

In the increasingly important stealth and electromagnetic compatibility (EMC) technology, the role and status of electromagnetic wave absorbing materials are very prominent. So far, nano-wave absorbing materials mainly work in two aspects: civil and military.

In civilian use, nano-wave absorbing materials are mainly used in human body protection. Due to the application of high-power radar, communication machine, microwave heating and other equipment, preventing electromagnetic radiation or leakage and protecting the health of operators is a new and complex topic, and absorbing materials can achieve this purpose. In addition, today’s household appliances generally have electromagnetic radiation problems, which can also be effectively suppressed by rational use of absorbing materials and their components. .

In the military, it is mainly used in radar shadow technology. Coating absorbing materials on various weapons equipment and military facilities such as aircraft, missiles, tanks, ships, warehouses, etc. can absorb reconnaissance radio waves and attenuate reflected signals, thereby breaking through the defense area of enemy radar. This is a kind of anti-radar reconnaissance, a powerful means of reducing the exposure of weapon systems to infrared-guided missiles and laser weapons.

Nano absorbing materials have the characteristics of light weight, wide frequency bandwidth and good performance, and have a wide range of applications. In the case of the same material, nano size materials are obviously better and can meet the requirements of the development of the times for absorbing materials. It is foreseeable that nano absorbing materials will play a huge role in thermal insulation and energy saving, environmental protection, human protection, and military stealth technology in the future.