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Introduction of gas sensing materials and application of nano tin oxide for gas sensors

A gas-sensitive material is a material that is very sensitive to a certain gas in a certain environment, generally a certain type of metal oxide, which is semiconductive by doping or non-stoichiometric changes, and its resistance changes with the changing atmosphere. Different types of gas-sensitive materials are particularly sensitive to one or several gases, and their resistance will change regularly with the concentration (partial pressure) of the gas, and their detection sensitivity is in the order of one millionth, while some individuals can reach the order of one billionth, far exceeding the olfactory perception of animals, so known as “electronic nose”.

 

A sensor is a detection device that can sense the measured information, and can transform the sensed information into electrical signals or other required forms of information output according to certain rules, so as to meet the requirements of information transmission, processing, storage, display, recorde and control requirements. A gas sensor is a sensor that senses the physicochemical properties of specific components contained in a gas and converts it into an appropriate electrical signal to detect the type and concentration of the gas. Semiconductor metal oxides such as SnO2, ZnO, Fe2O3 have been widely used as gas-sensing materials, and In2O3 as a new gas-sensing material has also attracted the attention of researchers.

 

With the continuous development of science and technology,  SnO2 Tin Oxide Nanopowder, as a special and important industrial raw material with various uses, has been continuously expanded in its use and dosage. The application of materials, etc. has shown the actual and potential huge market as gas sensitive, light, white conductive, nano composite photocatalytic materials, etc. Therefore, it is of great significance to find a preparation method with simple process equipment, low cost, high product yield and stable performance.

 

Nano tin dioxide SnO2 is the earliest and most widely used gas-sensing material. Because tin oxide nano has high gas-sensitivity to various combustible gases, it is widely used in the detection and alarm of combustible gases. The combustible gas sensor designed and manufactured with it has the characteristics of high sensitivity, large output signal, high impedance to toxic gas, long life and low cost. Taking nano tin oxide as the matrix material and incorporating appropriate catalysts or additives, a tin oxide gas sensor with selective sensitivity to alcohol, hydrogen, hydrogen sulfide, carbon monoxide and methane can also be prepared.

 

Since the gas-sensing mechanism of tin oxide is surface-controlled, the gas sensitivity is related to the specific surface area of ​​the material. Generally, the larger the specific surface area, the higher the gas sensitivity. Therefore, nanometerization and thin filmization of tin oxide gas-sensitive materials have become two ways to improve the sensitivity ratio of tin oxide gas.

 

In recent years, many materials science and electronics workers have joined this field one after another, dedicated to the research on the adsorption characteristics and detection mechanism of SnO2 gas-sensitive materials, and their products have also penetrated into various fields of petrochemical industry and household civil use. Used as a gas sensor, tin dioxide has many properties superior to other materials, such as higher sensitivity and lower operating temperature. In the past, there have been many studies on sintered and membrane sensors, which are currently widely used for the detection of toxic gases and flammable gases. However, this kind of gas sensor has poor stability and selectivity, long response time and recovery time, unsatisfactory repeatability of the device, and is not conducive to integration and multi-functionality. Nanotechnology can be used to make a large surface area thin-film and powder sensors are used to miniaturize and integrate components, improve sensitivity, and shorten response and recovery time. On the other hand, the development of highly selective sensors requires the use of silicon-based microelectronics technology, and thin-film technology is the most suitable method to achieve this goal. Another method to modify the traditional gas sensor is to dope pure tin oxide with various elements and compounds to reduce the working temperature and improve the sensitivity and selectivity.

 

Currently, Hongwu Nano has successfully produced more fine-grained nanometer tin dioxide, of which size reach to 10nm, in good shape, narrow distribution.https://www.hwnanomaterial.com

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Modification of Epoxy Resin by Silicon Carbide Whiskers (SiC-W)

Because of the small diameter, large aspect ratio, high strength, high modulus and excellent heat resistance, silicon carbide whiskers play a unique role in the modification of polymer materials. Epoxy resin has been widely used in various fields of the national economy because of its high strength, good adhesion, good thermal stability, high strength, and small shrinkage. SiC whisker modified epoxy resin can further improve its mechanical properties (strengthening and toughening), friction and wear resistance and antistatic properties.

 

Epoxy resin (EP) is one of the most widely used thermosetting polymer materials. It has excellent adhesion, thermal stability, electrical insulation, chemical resistance, high strength, small shrinkage, and low price and it’s widely used in various fields such as coatings, adhesives, light industry, construction, machinery, aerospace, electronic and electrical insulation materials, and advanced composite materials. However, due to the shortcomings of epoxy resin cured products such as high brittleness, low impact strength, easy cracking, and poor antistatic performance, its further applications are limited.

 

Epoxy resin glue is prepared by epoxy resin plus curing agent, filler and so on. It has the characteristics of high bonding strength, high hardness, good rigidity, acid, alkali, oil and organic solution resistance, and small curing shrinkage. At present, the bonding strength of epoxy adhesive is relatively high, but there are still some deficiencies in the bonding of some high-strength structures, and the bonding strength needs to be further improved.

 

Whiskers are fibers with extremely small diameters grown in the form of single crystals under special conditions. They have a highly ordered atomic arrangement structure, so they can approach the theoretical strength of valence bonds between atoms, and have great potential for strengthening epoxy adhesives. Many research results show that filling whiskers into epoxy resin matrix can effectively solve these shortcomings and greatly improve the comprehensive performance of epoxy resin.

 

Silicon carbide whisker is a cubic whisker whose crystal form is the same as that of diamond. It is currently the whisker with the highest hardness, the largest modulus, and the best heat resistance among whiskers. The crystal form is β-type, which has higher hardness, better comprehensive properties such as toughness and thermal conductivity, and is also one of the best reinforcing and toughening materials. It can significantly improve the toughness, flexural strength, hardness, wear resistance, and high temperature resistance, oxidation resistance, thermal conductivity, structural stability, thermal shock resistance, etc..

 

The silicon carbide whiskers treated with the coupling agent can be well and stably dispersed in the matrix, the whiskers are well infiltrated by the matrix, and the interface bonding strength is increased. Through this interface, the matrix and whiskers are connected as a whole. When the matrix is ​​subjected to external force, the stress can be uniformly transmitted through this interface and absorb a large amount of energy. On the one hand, when a crack appears in the matrix, the whiskers bridge the surface of the broken crack, which can hinder the further development of the crack; on the other hand, if the crack encounters silicon carbide powders, if it wants to develop further, the crystal must be destroyed or removed. Whiskers have high strength and high modulus, and it takes a lot of energy to destroy or pull out the whiskers, and when the crack bypasses the whiskers, it develops further and causes more microcracks. And because the whiskers have a relatively large L/D, more energy needs to be absorbed, thereby significantly increasing the strength and toughness of the EP matrix.

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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!

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Hongwu Nano is supplying high-tap density silver powder for solar photovoltaic cells in bulk

The basic structure of a crystalline silicon solar cell consists of a P-type silicon substrate, an n-type layer, an anti-reflection film (TiO2, SiO2 or Si3N4), a front silver electrode, a back aluminum electrode and a back silver electrode. The back-side silver electrode is an electrode formed by using silver conductive paste through screen printing and then sintering.

In the case of the same solid content, the different particle size, morphology, and ratio of silver powder would affect the viscosity performance. Tests show that the silver powder used in the back silver paste plays a key role in ensuring electrical performance, improving adhesion and welding power. In the case of low solid content, using a slurry prepared from micro-flaky silver powder, the resulting electrode film is dense and smooth, has excellent electrical properties, and good adhesion and welding properties.

The silver electrode paste on the light-receiving surface of solar cells uses high-performance metal conductive spherical silver powder.

The silver electronic paste used for the front electrode of silicon solar cell is mainly composed of three parts:
1. Superfine metallic silver powder with conductive effect. 70-80wt%. Ag powder has high photoelectric conversion efficiency.
2. Inorganic phase that plays a role of solidifying flux after heat treatment. 5-10wt%
3. The organic phase that acts as a binding agent at low temperatures. 15-20wt%

Ultra-fine silver powder is the main component of silver electronic paste, which ultimately forms the electrode of the conductive layer. Therefore, the particle size, shape, surface modification, specific surface area and tap density of silver powder have a greater impact on the performance of the slurry. The particle size of the silver powder used in the silver electronic paste is generally controlled within 0.2-3um, and the shape is spherical or quasi-spherical. If the particle size is too large, the viscosity and stability of the silver electronic paste will be significantly reduced, and because the gap between the particles is relatively large, the sintered electrode is not close enough, the contact resistance is significantly increased, and the mechanical properties of the electrode are also not ideal. If the particle size is too small, it is difficult to mix uniformly with other ingredients during the preparation of silver paste.

The silver coated copper powder materials prepared by Hongwu Nano’s technical engineers have relatively good sphericity, good dispersibility, uniform particle size, adjustable high tap density and superior electrical conductivity. The solar photovoltaic cell front electrode paste prepared by high-tap density silver powder has the characteristics of non-sticky rolls, easy printing, very small shrinkage, and dense sintered film, which fills the gap in the production of high-tap-density spherical silver powder in China.

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Carbon nanotubes are used in batteries

Lithium iron phosphate power cell is the most potential lithium-ion power battery for electric vehicles in the market, which has the advantages of good safety, long cycle life, and high energy density. However, lithium iron phosphate has poor electrical conductivity and conductive agent must be added to improve its conductivity. Most commonly used conductive agents are carbon black and graphite, which is cheap. However, in the process of multiple charging and discharging, the expansion and contraction of graphite materials reduces the contact between graphite particles, increases the gap, and even separates from the collector fluid and no longer participates in the electrode reaction. Therefore, the choice of conductive agent has an important role in improving battery performance.
At present, carbon nanotubes(CNTs) have gained wide attention in the application of conductive agents due to their excellent physical and chemical properties. The conductive mechanism of carbon nanotubes is that because they belong to one-dimensional nanomaterials, the length-diameter ratio is relatively large, which is good for the formation of conductive networks, and can improve the bonding between active materials and their collective flow, also it play the role as a physical adhesive. At the same time, it has excellent mechanical properties and chemical inertia, and it also has good thermal conductivity. It can improve the specific capacity and cycle life of the battery and improve the high temperature performance. It is an ideal new type of conductive material for lithium ion batteries.
In the experiment, multi-wall carbon nanotubes were applied to the positive and negative poles of lithium iron phosphate batteries respectively, and different tired batteries were prepared. The conventional performance and doubling rate were tested, and they were compared with the cores prepared by ordinary conductive carbon black. The test results show that, The electric core of high-conductive multi-wall carbon nanotubes added to the carburetor nanotubes has better conventional performance and double discharge performance than the conventional core, and the double discharge effect of both positive and negative poles is the best, followed by the addition of negative poles. The addition of MWCNTs to the negative electrode also shows the same situation. After the negative electrode capacity increases, it can embed more lithium ions when charging, which is conducive to the increase of discharge capacity, and because multi-walled carbon nanotubes have better electronic transport capabilities. In addition, more continuous conductive networks are formed in the click, which reduces the number of active substance particles encouraged. Also, the positive pole is added. The carbon nanotube, in high purity, is easy to disperse, has a low resistivity and can reach a resistivity of 650 μΩ. M, which is very suitable for battery use.
Multi-wall carbon nanotubes for lithium iron phosphate batteries
The addition of carbon nanotubes also has an important influence on the electrochemical performance of lead acid battery negative plates. After adding CNT, it can increase the amount of liquid absorption of the electrode, improve the transmission performance of the electrolyte in holes, and also improve the negative electrode conductivity, enhance the charging and discharging ability, improve the morphology and utilization rate of the active material, and slow down the salt of the negative electrode. In partial charge state, the rapid discharge cycle life of the plate can be extended. The negative electrode is added to the CNT battery prepared by 0.5 % CNT. When the SBAS0101 is rapidly charged and discharged under 50 % charge state, the battery discharge termination voltage is increased and the cycle life is extended.

Related Tags:Transparent Silver Colloid  Colloidal Gold

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Transparent flexible circuit based on silver nanowire conductive material

With the continuous development of technology, various transparent and flexible electronic devices have developed rapidly. However, compared with transparent flexible conductive materials, there are still many problems in the research of transparent flexible circuits. The research of many transparent flexible circuits only stays at the level of transparent substrate and opaque circuit. Recently, Professor Sun Jing of Dalian University has designed a transparent flexible circuit by using polydimethylsiloxane (PDMS) as a flexible substrate and silver nanowires (AgNWs) as a conductive material, which overcomes the previous transparent flexible circuit part. The drawback of transparency is the realization of a truly transparent transparent circuit. The related research work was published in Chemical Communications and was selected as the bottom article of the 5418, Volume 39, issue of 2018.

The researchers first performed experiments on PDMS, using the spin coating technique to spread the AgNWs solution evenly on the hydrophilically modified PDMS surface. The transmittance and resistance of the transparent flexible conductive material reached 90.86% and 3.22 Ω·sq-1, respectively. It is at the leading level in the field of transparent flexible conductive materials.

The research team used the mature microfluidic control technology to create holes with various complex patterns on the transparent flexible substrate PDMS surface, and the precision can reach micron level; then AgNWs are spread into these holes to make them high at the same time. Electrical conductivity. The transparent flexible circuit thus prepared has a strong wear resistance due to the protection of the channel to the AgNWs.

The transparent flexible circuit not only has good optical and electrical properties, but also has good mechanical properties. They used LEDs and ordinary dry batteries to test their electrical conductivity. The results showed that the conductivity was good. After the 180-degree inward and outward bending, 720-degree distortion and tensile test of the circuit, the brightness of the LEDs remained basically unchanged. change. The researchers further explored the application of the transparent flexible circuit, deposited Pd nanoparticles on the AgNWs of the circuit by electrodeposition, and used it to detect glucose. The results show that the sensor has high sensitivity to glucose detection.

The originality of this research is to solve two problems in the preparation of transparent flexible circuits: (1) to achieve a completely transparent flexible circuit; (2) to design circuit patterns as desired. The transparent flexible electrode prepared by the research is simple in preparation, controllable in quality and excellent in technical indicators, which can greatly promote the development of wearable electronic devices.

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Silver nanopowder for antibacterial

Antibacterial mechanism of nano silver powder

Nano-silver particles can enter inside the micro-organisms, interrupt RNA replication to stop it’s reproduction , meanwhile it attached to the microbial cell wall, the impact of microbial organisms transmission finally cause the cell’s rupture and death.

Advantage of nano silver powder in antibacterial application

1) Disinfection and sterilization effect is good, lasting and have no drug resistance problem.

2) small amount at ppm level nano-silver antimicrobial products means lower cost.

3) without shortcoming of allergies and excessive deposition as traditional silver salt antibacterial agent do.

4) non-toxic to human safety, environmentally friendly.

 

Speak of nano silver powder, it’s like a far away high-technology topic, but speaking of specific, detailed antibacterial applications, we know nano silver particle can be part of our daily life.

 

  1. Food

No doubt people consume food every day, and silver nano particle could take pat in our daily life in the way of antibacterial food container. Since nano silver have an inhibitory effect on the common food contamination bacteria (Gram-positive bacteria, Gram-negative bacteria, yeast, mold, etc.), it is applied to produce antibacterial food containers: nano silver food crisper, nano silver plastic wrap, antibacterial ceramic tableware, antibacterial refrigerator

 

  1. Clothing

Nano silver’s antibacterial works as well as on fabrics, try search nano silver antibacterial socks on your online purchasing platforms, there surly comes out lot of results. In fact, some researchers does experiments and proves that nano silver particle function more than merely antibacterial part, also fabrics’’ anti-static and far infrared performance is also improved by nano silver finishing.

 

  1. Living

Nano silver is also widely used in building materials: Nano silver antibacterial coatings, nano-silver antibacterial paint, etc., they are coated on the surface of the plate can kill the surface attached bacteria, and the antibacterial effect is lasting.

 

  1. Medicine

No doubt that antibacterial work is more critical when it comes to the matter of health. And yes nowadays nano silver particle is maturely applied into medicines. For example: nano silver antibacterial dressings, nano silver antibacterial gel, nano silver antibacterial catheter, nano silver antibacterial equipment, nano silver bone cement, etc. I cannot list them all.

 

Related reading:nano silver antimicrobial   antimicrobial silver nanoparticles

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Yttria stabilized zirconia powder Application

HW provide 3YSZ,5YSZ,8YSZ powder, size available from nano to micron size. Also can do customization. Below is the ,man application of Yttria stabilized zirconia powder.

 

  1. 1. Yttria stabilized zirconia powderas refractory material, widely used in Electronic ceramic bearing plate burning, glass, metallurgy molten metal.

 

  1. Due to yttrium stable nanometer zirconium oxide powder’s high oxygen ionic conductivity and ideal stabilityin REDOX atmosphere, it isa kind of ideal electrolyte has been widely applied in the field of solid oxide fuel cell, has the good market application prospect and commercial value.

 

  1. Yttrium stabilized zirconia powder has the characteristics of strong thermal shock resistance, high temperature resistance, good chemical stability and outstanding material composite. Yttrium stabilized zirconia powder and other materials (Al2O3, SiO2) composite, can greatly improve the performance parameters of the material and improve its fracture toughness, bending strength. Therefore, Yttrium stabilized zirconia powderis not only used in the field of structural ceramics and functional ceramics, but also in improving the surface properties of metal materials (thermal conductivity, thermal shock resistance, high temperature oxidation resistance, etc.).

 

  1. Yttrium stabilized zirconia with high hardness and wear resistance, has been widely usedin the field of grinding medium and grinding tool, such as ball mill and ball mill interior lining and wear parts, wire drawing die, etc.

 

  1. Used in functional ceramics, structural ceramics, especially electronic ceramics, bio-ceramics (such as: denture), we havea 3YSZ powder Specialized for dental use.

 

  1. Yttria stabilized zirconiapowder use in piezoelectric elements, oxygen-sensitive resistors, bulk capacitors, solid oxide fuel cells (SOFC) and oxygen sensors.

 

  1. Yttria stabilized zirconiapowder use as artificial gem materials, abrasive materials

 

  1. The additionof Yttria stabilized zirconia increase the ceramic structure toughness strength, the surface finish is good, and ceramic dense compact, resistant to beat.

 

Future information, pls feel free to contact us.

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nano-alumina Al2O3

By virtue of its special properties, nano-alumina is widely used in chemical and chemical industry, medicine, catalyst and its carrier, ceramics and other fields. In ceramic applications, precision ceramics made by nano alumina powder have the similar metal plasticity and toughness, light weight, in particular, greatly enhance the strength. By adding a small amount of micron or nano-alumina in the conventional ceramic matrix can make the mechanical properties of materials doubled improve the toughness of ceramics to reduce its sintering temperature.

 

As a new composite material and medical materials, nano-alumina Al2O3 can be used as dispersion strengthening and additives, such as cast iron with nano-Al2O3 grinding powder as a metamorphic nucleation, wear resistance can be improved several times. Nano-alumina as a new medical material, has been used to make the bearing force of artificial bone, dental root implants, drug delivery carrier, etc .; also successfully carried out alveolar ridge expansion, maxillofacial reconstruction, orthopedic and repair. As an optical material and surface protective layer of nano-alumina material can absorb ultraviolet light, and in some wavelengths of light excitation can be generated with the particle size of the wavelength of light. Αlpha-Al2O3 can be sintered into a transparent ceramic to use as a high-pressure sodium lamp material; as well as can be used as a compact fluorescent lamp in the protective layer of the phosphor layer; and mostly can made of fluorescent light-emitting materials rare earth phosphor composite to improve lamp life .

 

Hongwu International Group Ltd, with HWNANO brand, can supply nano-alumina powders with high purity and quality. Based on the existing scientific research as production-oriented, closely learning domestic and foreign advanced technology, and constantly improving and enhancing the production process to ensure that providing customers with good quality and stable products. We also can supply customized nano material according to your request. Shall you have any questions, please don’t hesitate to contact us at hwnano@xuzhounano.com.

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Nano Zirconia powder

Zirconia powder is also called Zirconium oxide powder. HW nano zirconia powder available in nano size and micron size(70-80nm,0.3-0.5um, 1-3um, YSZ), which has uniform particle size distribution, no hard reunion and good sphericity, size and purity are adjustable according to customer’s requirements.

 

The nano zirconia powder can be used for making metal zirconium and zirconium compounds, and the crucible refractory brick, high-frequency ceramic, ceramic pigment and zirconium salts are mainly used for piezoelectric ceramics, daily-use ceramics, refractory materials and precious metals smelting with brick of zirconium, zirconium tube, crucible, and so on. Also can be used in the production of steel and non-ferrous metals, optical glass and zirconium dioxide fiber.

 

Nano Zirconia powder using as Zirconia structural ceramics material:

1975 Australian R.G.Garvie use calcium oxide as stabilizer had get partially stabilized zirconia, and it’s the first time use zirconium oxide martensite phase transformation toughening effect to increase the toughness and strength, greatly extend the application of the zirconia in the field of structural ceramics.

 

Nano Zirconia powder using as thermal barrier coating material:

The application of Plasma spraying cubic zirconia thermal barrier coating in aerospace and industrial gas turbine has gain great progress, it has been used in gas turbine turbine parts. With this coating, the high temperature parts can reduce the temperature 50 ~ 200 ℃, thus can significantly improve the durability of the high temperature parts, or allow to improve gas temperature or reduce cooling gas, maintain the high temperature parts under constant temperature to improve the efficiency of the engine.

 

Nano zirconia powder using as polishing material:

It can be used as polishing material for soft lenses, camera lenses, precision optical glass material, soft water glass products, infrared filter, BK – 7 final polishing, asphalt, also can used as precision polishing material for Ceramics and silicon.

 

Nano zirconia powder using as Biomedical material:

Zirconium-containing compounds are used in many biomedical applications including dental implants and other restorative practices, knee and hip replacements, and middle-ear ossicular chain reconstruction.

Alisa