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increasingly sophisticated, more advanced finishing products and techniques are required to produce the desired results at the lowest possible cost. Precision cutting, minimal chipping and fractures, fast processing speeds, and smooth surface finishes with fewer production steps are just some of the requirements of today’s ceramic manufacturers.
Abrasives suppliers and others allied to the field are constantly developing new products and methods to meet those needs. Following are some of the most recent developments that are helping to secure a place for ceramics in the high-performance applications of the future (see sidebar for contact information).
New Abrasive ProductsPechiney Electrometallurgie, Abrasives & Refractories, recently developed a new abrasive grain (ABRAL) for snagging, fettling, cutting and grinding. The product is a solid solution of alumina and aluminium nitride characterized by high grinding performance and a long life. Used in the correct ratio with other abrasive materials and bonds, the abrasive is particularly suited for organic and vitrified grinding wheels when high stock removal rates are required.
Treibacher Schleifmittel offers a range of fused aluminum oxide abrasive products. Two of its most recent introductions include a monocrystalline aluminum oxide (SCTSK), used in precision grinding wheels, and a ceramic aluminum oxide (CCCSK), used in both bonded and coated abrasives.
A superhard boron carbide (TETRABOR) from Wacker Engineered Ceramics, Inc. (representing Electroshmelzwerk Kempten GmbH [ESK]) can be used for lapping, sawing and ultrasonic machining. The hardness of this material is 9.5+ on the mohs scale or 3000 knoops, making it ideal for machining sapphire, quartz, carbides and hard ceramics.
A 98.5% pure beta silicon carbide grain from Superior Graphite Co.’s Advanced Materials plant is used for lapping and polishing. Recently, alpha silicon carbide with the same purity has been milled at this plant to provide a harder alternative to complement the markets for beta. The average size currently ranges from 19 microns to 0.6 microns. The company has said that higher purity and finer particle size grades will soon be available to support additional requirements.
GE Superabrasives customizes diamond crystals to meet the needs of a variety of ceramic finishing processes. A nickel alloy applied to the abrasives improves the mechanical retention of the crystals in resin-bonded grinding wheels.
A variety of abrasives from Fujimi Corp. have gained popularity in the ceramic industry over the past several years. A platey white alumina abrasive features high quality platey crystals that provide flat surfaces and rapid stock removal rates. Additionally, an optical emery abrasive is widely used for lapping silicon wafers and other critical surfaces. Its uniform grain shape and the elimination of acute grain angles are said to help increase wafer flatness, reduce the depth of damage, and increase finish quality and yield. The product is especially suitable for double-sided lapping. Fujimi also offers a black silicon carbide for controlled cutting applications and a green silicon carbide for consistent stock removal and a fine surface finish.
Green silicon carbide powders from Electro Abrasives are 99.5% pure, making them suitable for use in high-purity applications. They have high thermal conductivity (100 W/m-k) and high strength at elevated temperatures—at 1000°C, green SiC is reportedly 7.5 times stronger than Al2O3. The company recently opened a new state-of-the-art powder facility that manufactures water-classified green SiC to ISO, FEPA and JIS standards.
C-E Minerals offers fused white alumina (MULGRIT™ White), brown fused alumina (MULGRIT™ Brown) and silicon carbide (MULGRIT™ SiC). The abrasives are offered in standard ANSI sizes and are used for blasting and polishing applications as well as raw material components that require tighter tolerances in size characteristics. The company recently completed a new state-of-the-art MULGRIT™ White sizing facility in Andersonville, Georgia.
New PublicationsFor those looking to implement better, more efficient processes, several publications are available to help. Norton Co. has released a new guide for coated abrasive users to help in the selection of backup pads for hand and machine tools. The guide includes a list of 40 pads used with applications including hand sanding, polishing, and corner and contour finishing.
The Handbook of Ceramic Grinding and Polishing, edited by Dr. Marinescu, has just been published by William Andrews/Noyes Publications. Priced at $145, the book is the first book dedicated to the machining of ceramic materials. Accompanying a description of ceramic materials and their mechanisms are chapters on experimental knowledge; advanced theories on stock removal mechanisms; and presentations of tools, machine tools, lubrications and fixtures for each machining operation. Other chapters cover the properties of ceramics; deformation and fracture of ceramic materials; abrasive processes; grinding, honing and superfinishing; and lapping and polishing.
Research & DevelopmentTo help ensure that technology is available to meet the demands of ceramic manufacturers and other abrasive users, researchers and scientists are conducting ongoing investigations into new materials and applications. For instance, researchers at the Nagaoka (Japan) University of Technology School of Mechanical Engineering have discovered that a laser can provide faster in-process dressing of diamond wheels. Working in cooperation with the Applied Laser Engineering Center and wheel supplier Nano-Tem Co. Ltd., the researchers found that a Nd:YAG (neodymium:yttrium aluminum garnet) laser removed bonding material but left diamond grains unaffected because they do not absorb the laser’s 532-nm wavelength light. Higher initial costs for laser dressing are offset by faster dressing (five times), better control of the amount bonding removed, and elimination of downtime for dressing cycles. Nano-Tem reports that the method is being patented and tested in production environments.
At the Iowa State University, Bruce Cook and other scientists have reported the discovery of a material harder than CBN. The researchers discovered that introducing a small amount of silicon and other additives into an alloy of aluminum-magnesium-boron creates the second-hardest bulk substance after diamond. In the initial round of tests on several different instruments, the material’s hardness was measured at 46 gigapascals (the equivalent of 6.7 million pounds per square inch). That’s slightly higher than cubic boron-nitride’s hardness of 45 GPa (6.5 million psi) and below diamond’s hardness of between 70 and 100 GPa (10.2 to 14.5 million psi). The new material is projected to sell for $700 per pound, in contrast to diamond at $2,000 per pound and CBN at $7,000 per pound.
Work at Shantou University in China has shown that grain pull out on CBN quills, which are used to grind deep grooves, can be eliminated by increasing the depth of cut and the length of the arc of cut. Additionally, work at Kumamoto University in Japan demonstrated that a 0.9 nm Ra finish on hot pressed silicon carbide ceramic is attainable using a #140 mesh metal bond diamond wheel and an oscillating infeed.
Advancing TechnologyAs ceramic technology advances, so, too, does the technology for finishing those ceramics. Abrasives manufacturers and researchers will continue to meet the needs of ceramic manufacturers both now and into the future.
Editor's NoteAll suppliers listed in this article submitted press releases to Ceramic Industry. Aside from special reports such as this article, press releases generally run in our “What’s New” department each issue in the order in which they are received. Press releases can be sent to: Susan Sutton, Editorial and Production Manager, Ceramic Industry, 6075 B Glick Road, Powell, OH 43065; (614) 789-1881; fax (614) 760-5922; email@example.com.
SIDEBAR: For More InformationPechiney Electrometallurgie, Abrasives & Refractories, (330) 673-4566, fax (330) 673-4561, Curtis_VAUGHT@PECHINEY.COM
Treibacher Schleifmittel, (716) 286-1234, fax (716) 286-1224
Wacker Engineered Ceramics, Inc., (800) 833-7608, fax (517) 264-8137, firstname.lastname@example.org
Superior Graphite Co., (312) 559-2999, fax (312) 559-9064
GE Superabrasives, (614) 438-2851, fax (614) 438-2829, email@example.com
Fujimi Corp., (630) 941-1400, fax (630) 941-7060, firstname.lastname@example.org
Electro Abrasives Corp., (800) 284-4748
C-E Minerals, (610) 265-6880, fax (610) 337-7163
Norton Co., (508) 795-5709, fax (508) 795-4130
William Andrews/Noyes Publications, (201) 505-4955, fax (201) 505-4965
Bruce Cook, Iowa State University, (515) 294-9673
Shantou University, (86) 754-2903279, fax (86) 754-2510505
Kumamoto University, fax (81) 96-342-3508