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Journal of The European Ceramic Society | 1989

Rheology of aqueous silicon nitride suspensions

Alwin Nagel; G. Petzow; Peter Greil

Abstract Highly concentrated silicon nitride slips with solid-volume concentrations φ of up to 0·475 were prepared from preoxidized, submicron powders in aqueous solutions at pH>8. Viscosity measurements reveal a pseudo-plastic flow behaviour at φ >0·35, which could not be described by existing flow equations. On the basis of the elastic-floc model for highly concentrated suspensions, a modified flow equation was derived, which is only determined by the initial floc-volume ratio and the particle-packing density. The calculated viscosity fits very well with the experimental values from low to high particle-volume concentrations φ from 0·2 to 0·475.


Key Engineering Materials | 2004

Processing, Microstructure and Mechanical and Tribological Properties of Rare Earth Containing Sialons

Stefan Holzer; Bernd Huchler; Alwin Nagel; Michael J. Hoffmann

Sialon ceramics with two types of additive elements and varying amounts of sintering aid have been studied with regard to their microstructural behaviour and their tribological performance. In this investigation, neodymium and ytterbium have been chosen as stabilising elements because of their different ionic radii. According to the general sialon formula MxSi12-m-nAlm+nOnN16-n (x = m / 3) the starting compositions have m values of 0.5 and 1.0, respectively, and n values of 1.0. With gas pressure sintering the sinterability strongly depends on the fraction of liquid phase and thus the amount of additive in the starting composition. Here, excess additive means a larger portion of rare earth oxide than calculated from the sialon formula. Excess additive contents change the microstructure in pure α-sialon ceramics from equiaxed to needle-like and increase the indentation fracture toughness up to 6.3 MPam 1/2 . Reciprocating sliding tests were performed with a cylinderon-disk apparatus and a Hertzian pressure of 180 MPa. Two neodymia containing sialon materials with different α:β-sialon ratios are compared with commercial alumina and silicon nitride materials. Isooctane is used as lubricant for simulating a fuel injection pump and shows the lowest friction coefficients of 0.3 for the sialon parts. With water as lubricating liquid the neodymium based α/βsialon reveals a friction coefficient of 0.08 compared to 0.4 for alumina and 0.95 for silicon nitride after a running-in distance of 250 m.


Journal of The European Ceramic Society | 2004

Preparation of interpenetrating ceramic–metal composites

A. Mattern; Bernd Huchler; D. Staudenecker; Rainer Oberacker; Alwin Nagel; Michael J. Hoffmann


Journal of the American Ceramic Society | 1989

Slip Casting of SiC‐Whisker‐Reinforced Si3N4

Michael J. Hoffmann; Alwin Nagel; Peter Greil; G. Petzow


Archive | 1989

PROCESS FOR PRODUCING SHAPED CERAMIC ARTICLES REINFORCED BY SHORT FIBRES

Claussen; Alwin Nagel; G. Petzow


Archive | 2004

Method for Manufacturing a Composite Component and Metal-Ceramic Component

Bernd Reinsch; Iris Postler; Klaus Czerwinski; Matthias Leonhardt; Alwin Nagel; Bernd Huchler; Dirk Staudenecker


Key Engineering Materials | 2005

Rare Earth Containing SiAlONS: Microstructure, Mechanical and Tribological Properties

Stefan Holzer; Jan Patrick Häntsche; Ulrich Spicher; Bernd Huchler; Alwin Nagel; Rainer Oberacker; Dirk Badenheim; Michael J. Hoffmann


Archive | 2007

COMPOSITE MATERIAL AND COMPOSITE COMPONENT, AND METHOD FOR PRODUCING SUCH

Dirk Staudenecker; Oliver Lott; Gert Lindemann; Matthias Leonhardt; Alwin Nagel


Silicon-Based Structural Ceramics for the New Millennium, Volume 142 | 2012

SiAION Ceramics: Processing, Microstructure and Properties

Stefan Holzer; Bernd Huchler; Alwin Nagel; Michael J. Hoffmann


Advanced Engineering Materials | 2012

Fabrication and High Temperature Creep Behaviour of Interpenetrated Nickel–Chromium/Alumina Composites

Andreas Haeger; Karl G. Schell; Alwin Nagel; Ethel C. Bucharsky; Rainer Oberacker; Michael J. Hoffmann

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Michael J. Hoffmann

Karlsruhe Institute of Technology

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Rainer Oberacker

Karlsruhe Institute of Technology

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Stefan Holzer

Karlsruhe Institute of Technology

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