What are the Properties of Highly Porous Cordierite Ceramic?

Cordierite was discovered by French geologist Louis. A. Cordier in the year 1815. Cordierite is basically magnesium aluminium silicate in its natural form. In the 19th century, a polish mineralogist obtained synthetic cordierite. Synthetic cordierite had excellent properties, such as it hardly deforms when exposed to heat and cold, making it highly resistant to temperature changes. 

The researchers then advanced this mineral experimentation using a modified manufacturing process, which allows the formation of a honeycomb-like structure. The cordierite substrates so formed could withstand the tough conditions in car exhaust. The cordierite ceramics substrates were used in the core of the catalytic converter, which helped the automakers to meet the emission regulations in the clean air act 1970. 

The English mineralogist G.A. Rankin and H.E. Merwin suggested the name “Cordierite” for the mineral. It is one of the most researched minerals because of its low coefficient of thermal expansion, which varies depending upon the material composition, pores volume fraction and other phases presence. 

Cordierite ceramics contains more than 80% crystalline phase and other phases that include aluminium, magnesium and silica. They have high heat resistance and low thermal expansion, which keeps them stable in challenging situations. Corundum electrical components used today have been replaced by cordierite components due to their electrical properties.

Synthetic cordierite is used in several applications. Some of them are below: 

• Heat conductors and spark protection. 
• Electric heating systems and gas engineering. 
• Electric resistors and electric heat accumulators 
• Used of making components in cartridge heaters. 
• Porous ceramics 

Some extraordinary properties of cordierite:- 

• Excellent thermal shock resistance 
• High mechanical strength 
• Low dielectric constant 
• Good chemical durability 

Porous ceramics exhibit properties that their denser counterparts can't achieve. Researchers are showing interest in porous ceramics because of its wide applications in thermal structural materials, thermal gas separation and lightweight structural components. Different fabrication methods are used to manufacture highly porous ceramics. 

In addition, high-porous ceramics used at high temperatures require a high melting point, low thermal conductivity, good mechanical strength, and an open pore structure. As in spaceflight, active cooling is used for thermal protection against high loads. Often the coolant is injected into the porous ceramic to reduce the core temperature for thermal protection. And as various components in the active coolant must withstand very high temperatures and pressures, the porous ceramic must have a high melting point and strength. 

Porous ceramics properties can be modified for a specific application by changing its microstructure and composition. Changes in pores size distribution and pore morphology can significantly affect the material properties. Structure parameters such as pore size are used to determine the mechanical properties of porous materials. 

Like mechanical properties, the thermal conductivity of ceramic is determined by the pore size and porosity. According to a study, the thermal conductivity of ceramics decreases with the increase in porosity. Also, with the increase in the size of the pores, the water-retaining capacity of the material increase. Due to this, porous ceramics are used in applications that range from filtration and absorption to catalyst. 

Characteristics of Porous Ceramics 

• It has good chemical stability: Choosing different materials and techniques make the porous material suitable for working in corrosive conditions. 
• Has good specific strength and hardness: When the gas pressure, liquid pressure and other loads change, the shape and size of the pores will not change. 
• Has excellent thermal stability: Some heat-resistant ceramics filter high-temperature molten steel and gas. These three properties of a porous material make it useful for a wide range of applications. And adaptable for use in chemical engineering, metallurgy, energy source, etc.

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Overview of the Ceramic Fuel Cells and How the New Discovery could Revolutionize it?

Ceramic fuel cells, also known as solid oxide fuel cells provide an eco-friendly conversion system to produce electric energy (from chemical energy). They offer several advantages over the traditional power generation system, such as high conversion efficiency, low emissions of gases such as carbon dioxide, carbon monoxide, sulphur dioxide and a lot more. 

Most fuel cells are composed of an anode and cathode, an electrolyte (generally liquid). In ceramic fuel cells, this liquid electrolyte is replaced with ceramic membrane/ solid oxide material. The absence of liquid electrolyte in the solid oxide fuel permits the free shape of the geometry. Due to this, they are manufactured in different shapes and sizes. Moreover, the high-temperature resistance of ceramic cells allows its use in the gas turbines coupled with electro generators. The most commonly used ceramic membrane is Zirconia that has high thermal stability with a high-temperature range. 

Working 

CFC contains four or three layers of ceramics( hence called ceramic fuel cells) Single-cell comprising these layers are then connected in series to form a stack. These ceramic layers don’t get electrically active until they reach a very high temperature. In the ceramic fuel cell cathode, oxygen reduces to oxygen ions. These ions then diffuse through the electrolyte to the anode to electrochemically oxidize the fuel in the cell. In response to this, two electrons and a byproduct of water are given. These electrons then flow into the external circuit to do the remaining work. This cycle then repeats. 

Ceramic fuel cell

Cathode 

In the cathode, the reduction of oxygen takes place. The cathode must have good compatibility with the connecting components, high electron conductivity, good porosity to allow diffusion for electrochemical reduction. Cathode materials are divided into two groups- a) Pure electronic conductors b) MIEC materials. 

In pure electronic conductors, the oxygen reduction process occurs at the three-phase boundary of the cathode. MIEC cathodes, on the other hand, reduce oxygen all over the surface of the cathode and transport oxygen in bulk to the electrolyte. Using MIEC, the cathode performance can improve significantly. 

Electrolyte 

The electrolyte in a fuel cell is responsible for conducting oxygen ions, without which no current can flow through the cell. There are broadly three types of electrolytes: Anionic, Protonic, mixed ionic. Most of the high-temperature fuel cells such as SOFC/CFC employ oxygen ion conduction. 

The oxygen ions in ceramic fuel cells move in the direction of the electric field throughout the crystal lattice structure. Therefore the conduction takes place due to the presence of vacancies. In other words, the crystal lattice must have unoccupied sites for oxygen ion conduction. The most popular ceramic material electrolyte used in high-temperature fuel cells are Zirconia. This most investigated electrolyte exhibits three polymorphs in different temperature ranges: Mono-clinic( room temperature), tetragonal( at 1170°C) cubic phases (Above 2370 °C). 

Both the tetragonal and cubic phase structures are not stable at low temperatures. Therefore, doping is required to stabilize them at room temperature. The dopants mainly added to Zirconia are Mgo, Cao, Y2O3 and SC2O3. All of these exhibit high solubility with Zr crystal lattice, but the most widely used are Y2O3 and SC2O3. 

The dopant concentration also plays an important role in the conductivity of the doped Zirconia. Several studies suggested that adding Y2O3 to 8 molecules per cent significantly increases the conductivity of the Zirconia. (Y2O3)0.08(ZrO2)0.92 has higher ionic conductivity and stability due to which it is widely used as an electrolyte material in the CFC/SOFC. Moreover, the components used in this are inexpensive and found in abundance. 

The scandia doped Zr has high ionic conductivity but faces thermal ageing at extreme temperatures. The high conductivity might allow its usage at an intermediate temperature range. However, its limiting factors must be taken into consideration. The electrolyte characteristics, such as conductivity and width determine the operating temperature range of CFC/SOFC. The yttrium based Zirconia performs well at temperatures above 850°C. But for intermediate temperature( between 600-800°C) doped LaGaO3 and CeO2 have shown better results.

The ceria has a large iconic radius which makes its magnitude approximately one order greater than YSZ (for a small temperature range). Moreover, ceria possesses a fluorite structure at room temperature up to its melting point, unlike its counterpart. Therefore the only function of doping is to increase the conductivity of the electrolyte through the formation of vacancies. 

Doped lanthanum gallate has also been studied to use as an electrolyte in CFC/SOFC. The lanthanum was partially replaced by Ca, Ba, Sm and Sr and gallate by Mg, In and Al. These compositions especially, Mg and Sr offer high conductivity both in reduction and oxidation environments. However, there are some limitations to these compositions. They reduce the stability of the ceramic and sometimes leads to the formation of new phases. 

Anode

At the anode, the electrochemical oxidation of the fuel takes place. For satisfactory performance, it must have- high electrical conductivity, compatibility with interconnects ( like electrolyte), high porosity and good conductive phases. The Ni/YSZ cermet (Yttria stabilized zirconia) is the most common anode material employed in developing ceramic fuel cells. Their widespread use is due to their chemical stability and low cost. The Ni( Nickel) has high catalytic activity and relatively low cost as compared to other catalysts such as Cu and Co. The volume ratio of Ni to YSZ varies from 35:65 to 55:45 and the selected ratio determines the conductivity of the material. 

There are two mechanisms through which cermet conductivity occurs: iconic and electronic. The conductivity is iconic if the ni concentration is below 30% and electronic if above 30%. The anode performance mainly depends upon the thickness, Ni particles connectivity, grain size distribution, the initial particle size of Ni and YSZ particles. 

The Ni/YSZ has a few disadvantages that limit its long term stability such as, carbon deposition and sulphur poisoning. However, research has been going on to decrease/ replace the use of Ni in the anode to improve the performance of the cermet. The modified Ni/YSZ use materials such as CeO2, Y2O3, La2O3, Mgo that resists sulphur poisoning and provide solutions for carbon deposition. 

Conclusion: 

At last, ceramic fuel cells are offering clean power generation options to businesses and technologies. And deep research has been going on in this technology to take it to another level. Several new materials have been tested to increase the stability and cost-effectiveness of ceramic fuel cells and older components are being replaced. In short, it is a fuel cell technology that is both advanced and cost-effective.

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Quartz Glass Handling Instructions

Quartz glass products are mainly usable in the processes where high purity is needed. That's why it is vital to handle quartz glass products in a clean environment to prevent devitrification.

Handling- It is recommended to keep it in a plastic bag to protect it from dirt and dust and increase the service life.

Cleaning- Quartz glass might be cleaned by drenching it in 5% to 10% hydrofluoric acid (HF) for not more than 10 minutes. Subsequent to cleaning, it should be entirely washed by deionized.

Storage- Quartz glass should be put in an closed container when not being used to shield it from surface flaws and dampness that could influence the quality and performance of the quartz glass.

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Types of Ceramics for Industrial Applications

The word ceramic refers to the world of ceramics, clay pots, and more which are found in various households. Appreciated by both the user and the creator, these items are made from simply occurring clay and sand. Due to the improvement of technology, ceramic elements are now being produced in a laboratory under the keen eye of experts. Created with a variety of ingredients and many processing methods, ceramics are used in a broad range of industrial commodities. Ceramics obtained through the above-mentioned technique are recognised as advanced ceramics or industrial ceramics. The thermal stability of industrial ceramics, wear protection and resistance to corrosion of ceramic elements make the use of ceramics the perfect choice for several industrial uses. There are several types of ceramics available for industrial application, the following are some of them. Take a look: 

Alumina Ceramic: Alumina ceramic offers excellent insulation features for electricity along with high wear and tear protection and high hardness but has relatively lower energy and rupture toughness. It is the most developed form of construction ceramics. Most of the alumina ceramics is usually white. Some of these ceramics might also be dawn-tinted which has nearly 80 per cent of alumina or brown that has about 90 per cent of alumina. The colour of the ceramic comes from the contaminants in the raw elements or the sintering additives. Alumina ceramics have excellent cleanliness and are most suitable for the environment wherein protection from corrosive substances or wear and tear is needed. These ceramics are also employed in fields where the temperatures are very high and stability to it is needed as this ceramic is identified to have elevated thermal resistance. For the alumina wear braces, the alumina ceramic is the most desirable material because of the capacity to maintain heat and wear and tear makes the ceramic ideal for making wear-resistant components. 

Steatite Ceramic: Steatite ceramic is an advanced ceramic made from magnesium silicate and is a traditional choice of metal for insulations for electrical elements. Other features of steatite include superior dielectric intensity, low emission factor, and high production intensity. Moreover, due to steatite’s great insulating properties, it is used in thermostats and several other electrical household items. 

Zirconium Ceramic: Zirconium dioxide which is also recognised as zirconia is a white crystalline oxide of the element zirconium. Zirconia can be supposed to have the most powerful toughness and durability at any place temperature and this is said in association with most of the superior ceramic elements. Its excellent texture size enables extremely fine edges and even surfaces. It has many uses as it is used in blades, shears, metal forming machines, slitters, pump handles, tweezers, bearing sleeves, cable drawing circles and valves. The main application of zirconia is that it is used in the production and creation of ceramics. There are some other applications such as the protective coating on the particles of titanium dioxide orpiments. It is used as a stiff material, grinders, enamels and surrounding as well. The sustained zirconia is used in the oxygen sensors and the layers of fuel containers because of its unique capability to provide the oxygen ions to flow very smoothly through the construction of the crystal at very high heat. 

Silicon Carbide Ceramic: When the fragments of silicon carbide are bonded collectively through a process which is called sintering, they create a very strong ceramic. Because of its hardness, it is used in applications demanding high endurance like car clutches, ceramic plates, car brakes, and bulletproof vests. 

Mullite Ceramic: Mullite is a very unique silicate material, produced at high temperatures and in low-pressure situations. Its features include low thermal extension, low thermic conductivity, superior creep stability, suitable high-temperature durability and leading resistance under severe chemical environments. 

Besides these ceramics, machinable glass ceramics like Macor is also a type of industrial ceramic.

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What is Frac Sand

Fracking is a general or slang term used for hydraulic fracturing. Hydraulic fracturing requires digging into the ground to get energy-rich natural gases from under the shale rock. Frac sand is a unique form of sand because it is much rounder, tougher and permeable. The rounded form of the sand granules enables the water and gases to move through. It limits the clogging of the hole and lets the cracks keep open while still allowing the gases to move around. This feature of the frac sand makes it unique from other materials. This material is important to ensure the pure and natural gas result in the extraction process and there will be no contaminants or foreign figures that could be hiding. 

More developed sand that is almost quartz is the ideal kind of frac sand and this should be properly rounded. More fresh sand usually has a more visible or angular appearance and they often bring several minerals and rock particles. Excellent attribute frac sand is effortless to clean and separate from other elements, making it more comfortable to eliminate the particles and mud. The sand experiences various processes to eliminate any contaminants, to separate the sand by the measurement of all units and the quality of the textures. It must hold a form that is similar to brown sugar. 

Frac sand drilling is a really effective application. With the aid of sand mining, there can be more projects and it could help enhance the economy of the areas. By using high-quality sand, it is likely to satisfy the requirements for natural gas as a kind of fresh fuel and it can better support the industry. 

Uses of Frac Sand

High-quality Frac Sands need to pass a crush examination because of the high volumes of force it has to endure. The quartz sand is remarkably pure and reliable. The more powerful the crush circumstance, the more reliable the sand. Also, the more powerful the cleanliness and crush factor, the more valuable the product. There are many different things that industries look for in the high standard and high crush frac sand. 

Take a look:

• It should be a high-quality quartz silica sand.
• It needs to be the proper texture size for a hydraulic fracturing work.
• It should be round in shape.
• It is ready to withstand the crushing capabilities of the neighbouring shale rock. 

Since the fracking industry has evolved, so demand for nearby sourced frac sand is also increasing. Hence, alternative ceramic and alloy particles have started to replace expensive, high-end sands.

Originally Published on - https://anchor.fm/multi-lab/episodes/What-is-Frac-Sand-e17g0qc

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