Microwave sintering of hardmetals

̈diger, K. Ro; Dreyer, K.; Gerdes, Thorsten; Willert‐Porada, Monika

doi:10.1016/s0263-4368(98)00050-x

Cited by 96 publications

(30 citation statements)

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“…1400-1600°C), and control of grain size and carbon content can further lengthen and complicate this process. [13,14] Previous studies have focused on the multimode MW sintering of WC and Co to produce cemented carbide composites, [15][16][17] while one report describes how such composites can be directly prepared via the reaction of W + C + Co. [18] Here, we show how these underlying principles can be significantly advanced to synthesize single-phase WC using electric field patterns supported in a TE 10n single-mode cavity. By comparison to multimode DMO methods, we demonstrate how the carbide can be produced with unprecedented reaction times.…”

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confidence: 88%

Ultrarapid Materials Processing: Synthesis of Tungsten Carbide on Subminute Timescales

2006

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In the twenty-first century, it is clear that manufacturing processes will need to be energy efficient and sustainable in addition to being economically viable. Such requirements are particularly important for materials processing, as advances in functional and structural materials continue to be made. Rapid processing and energy efficiency are only two of many attractions that microwave (MW) methods offer to the materials chemist. [1][2][3][4][5] At least as attractive are the opportunities to access new (metastable) materials and to understand the interaction of electric (and magnetic) fields with solids. MW heating has emerged as an exciting development in organic and solution-based synthesis, [6,7] but constraints preventing major advances in solid-state synthesis and materials processing remain in place. Without a polar solvent one is reliant on the coupling of one or more dielectric or conducting solid components, often restricting the range of reactions one can perform, creating problems of variable heating rate and sample inhomogeneity, or demanding the use of a MW susceptor (which may need to be separated from the products if intimately mixed to give a high degree of homogeneity). Furthermore, although cheap and readily accessible, domestic microwave ovens (DMOs) with multimode cavities and crude halfrectified power supplies lead to unpredictable mode patterns and poor synthesis reproducibility. Many of the above issues can be addressed if the sample can be positioned in a position of known (preferably high) electric field intensity. High electric field strength single-mode cavities consist of a metallic enclosure in which a microwave signal of the correct electromagnetic field polarization will undergo multiple reflections. The superposition of the reflected and incident waves gives rise to a standing wave pattern that is very well defined in space. The precise knowledge of electromagnetic field configurations enables the dielectric material to be placed in the position of maximum electric field strength, allowing maximum heating rates to be achieved at all times. Microwave power density (P) is proportional to the electric field strength inside the material squared (Eq. 1), [8] therefore such cavities offer extremely rapid heating rates and the opportunity to heat materials that appear transparent to microwaves in ordinary multimode cavities. The use of singlemode cavities for materials synthesis therefore promises not only to overcome issues of reproducibility, but should also lead to vastly reduced reaction times. The power density can be expressed aswhere f is the frequency, e 0 is the permittivity of free space, e″ is the dielectric loss, and E i represents the electric field.We report here how a TE 10n single-mode cavity can be exploited as a general method for the production of refractory carbides, with the synthesis of tungsten carbide as an example. The technique is well-suited to carbide processing, with carbon acting as both starting material and microwave susceptor. WC, with a high melting po...

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confidence: 88%

Ultrarapid Materials Processing: Synthesis of Tungsten Carbide on Subminute Timescales

2006

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“…Microwave sintering of cemented carbides like WC-Co also has been investigated since 1991 after the pioneering work of Cheng (Cheng J, 1991;Cheng JP et al, 1997;Breval E et al, 2005) and thereafter by Porada (Gerdes T & Porada MW, 1994;Rodinger K et al, 1998;Kolaska H et al, 2000). Breval et al (Breval E et al, 2005) investigated on the microwave sintering of 0.1-1 m sized WC particles with cobalt as the binder and compared the results with conventional sintering of the same powders.…”

Section: Microwave Sinteringmentioning

confidence: 99%

“…They found that the microwave sintered sample always showed improved mechanical properties when compared to the conventionally sintered one. Porada and her group showed that the microwave reaction sintering of W, C and Co powders yielded sintered WC-6Co compacts with fine and uniform microstructure (with an average grain size of 0.6 lm) which exhibited a 10% increase in hardness values in comparison to tools made by a conventional route (Gerdes T & Porada MW, 1994;Rodinger K et al, 1998;Kolaska H et al, 2000). Recently, microwave post-treatment of WC-Co cutting tools was also investigated by Ramkumar et al Ramkumar J et al, 2002& Aravindan S et al, 2005.…”

Section: Microwave Sinteringmentioning

confidence: 99%

Advanced Sintering of Nano-Ceramic Materials

Khalil¹

2012

Ceramic Materials - Progress in Modern Ceramics

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“…Entretanto, um outro foco de pesquisas, que vem ganhando destaque, está relacionado ao estudo da influência da componente magnética do campo eletromagnético no processamento de metais e cerâmicas, e ao processamento de metais e carbetos metálicos [38][39][40][41][42][43][44]. O processamento de materiais metálicos entrou em evidência após os estudos desenvolvidos no final da década de 90 [45,46], e apresenta interessantes perspectivas para o alargamento das aplicações da tecnologia de microondas.…”

Section: Processamento Por Microondasunclassified

Sinterização de cerâmicas em microondas. Parte I: aspectos fundamentais

2007

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ResumoO processamento de materiais baseado no aquecimento por meio de energia de microondas vem ganhado a cada dia mais destaque e importância em várias aplicações industriais, em virtude de uma série de vantagens em potenciais frente aos métodos convencionais de aquecimento. Na sinterização de materiais cerâmicos o uso de microondas permite redução no tempo de processamento, economia de energia e melhora na uniformidade microestrutural dos corpos cerâmicos. Como conseqüência das vantagens frente às técnicas de aquecimentos convencionais, a sinterização usando microondas vem sendo estudada por vários grupos de pesquisa em todo o mundo. Entretanto, os benefícios do uso das microondas só são obtidos quando a sinterização é realizada com o controle e entendimento científico de uma série de parâmetros e aspectos envolvidos no processo. Assim, esse trabalho tem por objetivo abordar aspectos científicos fundamentais do processo de sinterização de cerâmicas usando microondas, enfocando particularmente a interação matéria/microondas, aspectos peculiares do processo e a técnica de sinterização híbrida. Palavras-chave: microondas, sinterização, cerâmicas. Abstract Processing of materials based on heating by microwave energy has gained increasing importance in many industrial applications due to its potential advantages over conventional heating methods.In the sintering of ceramic materials, the use of microwave energy decreases the processing time, saves energy and improves the microstructural homogeneity of ceramic bodies. These advantages have motivated various research groups around the world to study microwave sintering. However, the benefits deriving from the use of microwaves depend on the control and scientific understanding of the parameters and aspects of the process. This paper offers a review of the fundamental scientific aspects of microwave sintering of ceramics, focusing on the interaction between materials and microwaves and highlighting particular points of the hybrid sintering process and methodology.

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Microwave sintering of hardmetals

Cited by 96 publications

References 2 publications

Ultrarapid Materials Processing: Synthesis of Tungsten Carbide on Subminute Timescales

Ultrarapid Materials Processing: Synthesis of Tungsten Carbide on Subminute Timescales

Advanced Sintering of Nano-Ceramic Materials

Sinterização de cerâmicas em microondas. Parte I: aspectos fundamentais

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