Woven silicon carbide ceramic fibers. Credit: Christian Heiss et al.; MaterialsViews/Wiley.

Textile structures made from silicon carbide fibers are very interesting for manufacturing of fiber reinforced high temperature resistant ceramic matrix composites materials. To produce such textile structures a one or multi-step manufacturing processes like braiding, weaving, warp, or weft knitting is necessary. Depending on the fiber packing density and orientation the fabric structure, the stiffness, deformation, and fracture behavior of the fabric structure vary in a wide range.

In contrast to woven fabrics, which exhibit a low drapability and stretchability in different directions, warp-knitted fabrics are formed by creating loops which give rise for high flexibility and deformability. However, a high Young’s modulus and low deformability of the carbide fibers makes loop formation during knitting difficult. Bending of fibers is also affected by the friction which is caused by ribbing between fibers and the machine parts and by the friction between the fibers inside the roving.

Recently, scientists from the Friedrich-Alexander-University Erlangen-Nuremberg, Germany, demonstrated the manufacturing of knitted fabrics made of silicon carbide ceramic fiber. In an article that appears in Advanced Engineering Materials, “Manufacturing of Silicon Carbide Knit Fabrics” (doi:10.1002/adem.201100192), they show how they derived the critical bending loads from fiber knot and loop testing in order to optimize yarn pretension, working speed, and take up speed during knitting processing. Subsequently, they tested and examined the mechanical behavior of the knit fabric under tensional load.

The investigations show that fiber fracture during knitting can be caused by torsion, bending, or tension. The German researchers considered fiber bending as the critical loading condition imposing boundary condition on the knitting process. Reduction of interfiber friction surface sizing was found to be a critical step in order to produce a continuous knit structure.

The scientists modified the processing conditions for knitting and reduced buckling and friction acting on the silicon carbide ceramic fiber rovings. Using penetrating oil the points of largest friction between fibers and critical knitting elements were lubricated which decreased fiber fracture. Compared to woven silicon carbide fabric structures the knitted fiber perform offers a superior flexibility, wider range of pore size and a higher degree of drapability.

Martin Grolms writes for MaterialsViews, where this post originally appeared.

A new research report titled, “Sol-Gel Processing of Ceramics and Glass” has been released by Reportlinker.com. The report is an update of the market report published in 2006, and it provides the most current information on the sol-gel industry.

Major objectives of the report are as follows:

To identify and profile companies involved in the development of sol-gel-derived products
To discover the technological and business issues associated with the development and manufacture of sol-gel-derived products
To provide a summary of a variety of commercial products produced with the sol-gel technology and their applications and
Others.
Sol-gel processing is a low-temperature processing methodology that uses chemical precursors and can produce ceramics and glass with better homogeneity and higher purity than conventional high-temperature methods. It can be used to produce materials with various compositions in different forms, including porous membranes, monoliths and composites, coatings and thin films, fibers and powders. The process is also ideal for producing organic or inorganic hybrids. One of the important benefits of the sol-gel technology is that it can create compositions that are impossible with conventional processes. In addition, the mixing molecular-scale mixing of the precursors which results in homogenous mixtures is maintained in the final product.

One of the major application fields of sol-gel-derived products is coatings and thin films that are used in optical, electronic and electro-optic devices and components. They are also utilized to produce antireflection coatings for architectural and automotive applications and protective and decorative coatings for use on metal, glass and other substrates. Composite powders made from sol-gel are ideal for use as herbicides or agrochemicals.

Additionally, the technology can be utilized to infiltrate fiber preforms to produce composites. Recently, sol-gel has been used in biotechnology applications, including drug delivery for medicine, environmental testing, biochemical process monitoring and food processing.

Source: http://www.reportlinker.com/

A new research report titled, “Sol-Gel Processing of Ceramics and Glass” has been released by Reportlinker.com. The report is an update of the market report published in 2006, and it provides the most current information on the sol-gel industry.

Major objectives of the report are as follows:

To identify and profile companies involved in the development of sol-gel-derived products
To discover the technological and business issues associated with the development and manufacture of sol-gel-derived products
To provide a summary of a variety of commercial products produced with the sol-gel technology and their applications and
Others.
Sol-gel processing is a low-temperature processing methodology that uses chemical precursors and can produce ceramics and glass with better homogeneity and higher purity than conventional high-temperature methods. It can be used to produce materials with various compositions in different forms, including porous membranes, monoliths and composites, coatings and thin films, fibers and powders. The process is also ideal for producing organic or inorganic hybrids. One of the important benefits of the sol-gel technology is that it can create compositions that are impossible with conventional processes. In addition, the mixing molecular-scale mixing of the precursors which results in homogenous mixtures is maintained in the final product.

One of the major application fields of sol-gel-derived products is coatings and thin films that are used in optical, electronic and electro-optic devices and components. They are also utilized to produce antireflection coatings for architectural and automotive applications and protective and decorative coatings for use on metal, glass and other substrates. Composite powders made from sol-gel are ideal for use as herbicides or agrochemicals.

Additionally, the technology can be utilized to infiltrate fiber preforms to produce composites. Recently, sol-gel has been used in biotechnology applications, including drug delivery for medicine, environmental testing, biochemical process monitoring and food processing.

Source: http://www.reportlinker.com/

KEMET, a provider of high performance capacitance solutions, has added C0G and Ultra-Stable X8R dielectric technologies to its flexible termination (FT-CAP) portfolio. These technologies are RoHS compliant and lead-free and are suitable for a wide range of applications that require effective and reliable performance.

Electronic parts are frequently subjected to severe vibration and flexing when they are utilized in different automotive and other harsh applications. In addition, mishandling during assembly of circuit boards may expose these parts to extreme flex and mechanical stresses. Under these conditions, the flexible termination technology from KEMET has proven to be a successful solution in reducing the damage risk to the multilayer ceramic capacitor (MLCC).

Dr. Abhijit Gurav, VP of Ceramic Technology at KEMET, stated that the C0G-type capacitors integrated with flexible termination technology deliver high performance and excellent capacitance stability of about 125ºC. They help meet the need for highly robust technologies in audio, power supply, mobile communications, telecom and automotive applications. Gurav added that the Ultra-Stable X8R-type capacitors from KEMET is ideal for high temperature applications and they decrease flex cracks that may be created under extreme board flex situations associated with handling, assembly and harsh environment up to 150°C.

The Ultra-Stable X8R delivers temperature capability similar to conventional X8R, but with no capacitance loss because of applied DC voltage. The device is an ideal alternative to higher capacitance and larger footprint solutions that do not offer capacitance stability.

Source: http://www.kemet.com/

KEMET, a provider of high performance capacitance solutions, has added C0G and Ultra-Stable X8R dielectric technologies to its flexible termination (FT-CAP) portfolio. These technologies are RoHS compliant and lead-free and are suitable for a wide range of applications that require effective and reliable performance.

Electronic parts are frequently subjected to severe vibration and flexing when they are utilized in different automotive and other harsh applications. In addition, mishandling during assembly of circuit boards may expose these parts to extreme flex and mechanical stresses. Under these conditions, the flexible termination technology from KEMET has proven to be a successful solution in reducing the damage risk to the multilayer ceramic capacitor (MLCC).

Dr. Abhijit Gurav, VP of Ceramic Technology at KEMET, stated that the C0G-type capacitors integrated with flexible termination technology deliver high performance and excellent capacitance stability of about 125ºC. They help meet the need for highly robust technologies in audio, power supply, mobile communications, telecom and automotive applications. Gurav added that the Ultra-Stable X8R-type capacitors from KEMET is ideal for high temperature applications and they decrease flex cracks that may be created under extreme board flex situations associated with handling, assembly and harsh environment up to 150°C.

The Ultra-Stable X8R delivers temperature capability similar to conventional X8R, but with no capacitance loss because of applied DC voltage. The device is an ideal alternative to higher capacitance and larger footprint solutions that do not offer capacitance stability.

Source: http://www.kemet.com/

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