Effect of compaction pressure on the sinterability of submicron powders of tetragonal zirconium dioxide

Галахов, А. В.; Kutsev, S. V.; Kryuchkov, V. A.; Prokof’ev, A. V.; Литвинов, И. А.

doi:10.1007/bf01281300

Cited by 12 publications

(9 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Graphite powder heated to 300 C comes from chamber (2) to reactor (7) where it is continuously intermixed with concentrated hydrochloric acid coming from reservoir (8).…”

Section: The Methods Of Chemical Purification Of Graphitesmentioning

confidence: 99%

See 1 more Smart Citation

Process development: Low cost, continuous nano-scale purification technology of powered carbonaceous materials for applications in electrochemical energy storage systems ELECTROCONSOLIDATON® process technology (Final CRADA Report)

Raptis¹,

Ehst²,

Gopalsami³

2010

View full text Add to dashboard Cite

show abstract

“…Graphite powder heated to 300 C comes from chamber (2) to reactor (7) where it is continuously intermixed with concentrated hydrochloric acid coming from reservoir (8).…”

Section: The Methods Of Chemical Purification Of Graphitesmentioning

confidence: 99%

“…Neutralization of filtrate with acid reaction is performed in storage tank (9) by lime milk from tank with Ca(OH) 2 (8). Both vessels ( 8) and ( 9) are fed with compressed air from compressor (16) for agitation of the solutions.…”

Section: I-31 Knutd Laboratory Demo Line For Chemical Purification Of...mentioning

confidence: 99%

Process development: Low cost, continuous nano-scale purification technology of powered carbonaceous materials for applications in electrochemical energy storage systems ELECTROCONSOLIDATON® process technology (Final CRADA Report)

Raptis¹,

Ehst²,

Gopalsami³

2010

View full text Add to dashboard Cite

show abstract

“…The effect of hydrostatic compaction pressure is shown in Fig. 8 on the content of inter-agglomerate pores in powder compacts of nanopowders of tetragonal ZrO 2 + 3 mol.% Y 2 O 3 [7]. In compacts formed at low pressure (1 kbar) with an overall porosity of 58 vol.% the overwhelming volume of pores (70%) is comprised of coarse inter-agglomerate pores.…”

Section: Agglomerates In Nanopowders and Ceramic Technology 349mentioning

confidence: 98%

Agglomerates in nanopowders and ceramic technology

Галахов

2009

Refract Ind Ceram

Self Cite

View full text Add to dashboard Cite

Questions are considered connected with use in ceramic technology of ultrafine powder raw material with agglomerated particles. It is shown that presence of agglomerates in nanopowders unavoidably leads to formation in sintered material of structural defects in the form of residual porosity and microcracks. Data are provided for a quantitative dependence of pore structure characteristics for a powder compact on the content of agglomerated particles and the connection of pore structure characteristics with sintering kinetics and the properties of the sintered material obtained.One of the main tendencies in the development of contemporary ceramic material technology is the extensive use of powders with a submicron particle size. Use of powder with particles of this size makes it possible to intensify sintering considerably, to promote preparation of material with a fine grain structure and improved physicomechanical properties.Recently quite productive technology has been developed for preparing ultrafine powders, however, attempts to use them in mass production often does not lead to the expected effect. In spite of the predicted theory, compacts of submicron powders after sintering do not reach an acceptable density, they have coarse unsintered pores and other defects within them, thus worsening material properties [1, 2]. A powder system of nanoparticles should not be considered as a simple collection of individual particles. As a result of the high specific surface in these powder systems the finest individual particles are collected into well-formed, sometimes strongly sintered groups of particles, that have been given the name agglomerates. An example is shown in Fig. 1 of an electron microscope picture of agglomerates in submicron powders of transformation-strengthened structural ceramic of the composition ZrO 2 + 3 mol.% Y 2 O 3 . With an average size of individual particles of 0.036 mm the average size of agglomerates is 5.8 mm, i.e. it exceeds the size of individual particles by more than two orders of magnitude. The pore structure of a compact of agglomerated powder is extremely nonuniform. Apart from the finest pores between individual submicron powder particles (intra-agglomerate) they contain a significant number of coarse high-coordination 2 inter-agglomerate pores. These pores in size exceed the intra-agglomerate sizes by a factor of several tens or hundreds. Presence of two types of pores is confirmed by the nature of the distribution of pores in a compact. This distribution of the pore volume within a compact is shown in Fig. 2, compacted from ultrafine agglomerated ZrO 2 (Y 2 O 3 ) powder with an avFig. 1. Agglomerates in submicron powders of the composition ZrO 2 + 3 mol.% Y 2 O 3 : a) collection of agglomerates in powder at low magnification; b ) structure of an individual agglomerate. * The coordination number of a pore equals the number of particles surrounding it.

show abstract

“…In cold pressing of ultradisperse powders a high pressure is required to increase the density of powder compacts, which often causes pressing cracks and rejection of the articles. The use of isostatic pressing in the production of articles from ultradisperse powders is most effective [9] and is often the only possible method. However, it is used in industrial production much more rarely than cold pressing because of its comparatively low productivity and expensiveness.…”

mentioning

confidence: 99%

Sinterability of monodisperse TiO2 powders

et al. 1996

Self Cite

View full text Add to dashboard Cite

Sintering of monodisperse titania powders with a relatively large grain size (0.84 -+ 0.24 l.tm) is investigated. It is established that the use of nonagglomerated monodisperse powders makes it possible to fabricate ceramics with a density of 99.5% of the theoretical value and a narrow distribution of pore sizes without preliminary milling and by relatively simple technological means, namely, cold pressing and casting into gypsum molds followed by sintering at a relatively low temperature. In combination with a high density such a structure makes the developed ceramic material applicable for the production of porous membranes for microbiology and medicine.The wide use of ultradisperse powders in modem ceramic technology is explainable by the desire to intensify the sintering process, decrease the sintering temperature, and improve the properties of the materials produced. However, the advantages of ultradisperse powders are often achieved incompletely in actual practice due to a tendency to form cluster agglomerates. The presence of the latter causes formation of inhomogeneous particle packings in the powder compacts. Such compacts contain coarse interagglomerate pores between dense intraagglomerate regions. In sintering, the compaction rates differ in microvolumes with different densities and cause the growth of interagglomerate pores [1] and the formation ofmicrocracks [2] and other defects. These defects worsen considerably the properties of the sintered material [3]. In order to eliminate the effects caused by the presence of agglomerates the sintering temperature is often increased, causing grain growth in the material and decreasing its mechanical characteristics.The structure of a powder compact can be optimized, the sintering kinetics improved, and the defects removed by using nonagglomerated powders with a narrow size distribution of the particles or monodisperse powders. An analysis of packing in monodisperse powders [4] showed, that they give compacts with a high density and uniform packing of the particles. They exhibit a tendency toward improvement of the factors that promote more rapid and better sintering compared to the packing in powders with a wide size distribution of the particles and powders from agglomerated particles [5].

show abstract

Effect of compaction pressure on the sinterability of submicron powders of tetragonal zirconium dioxide

Cited by 12 publications

References 13 publications

Process development: Low cost, continuous nano-scale purification technology of powered carbonaceous materials for applications in electrochemical energy storage systems ELECTROCONSOLIDATON® process technology (Final CRADA Report)

Process development: Low cost, continuous nano-scale purification technology of powered carbonaceous materials for applications in electrochemical energy storage systems ELECTROCONSOLIDATON® process technology (Final CRADA Report)

Agglomerates in nanopowders and ceramic technology

Sinterability of monodisperse TiO2 powders

Contact Info

Product

Resources

About