Effects of milling and particle size distribution on the sintering behavior and the evolution of the microstructure in sintering powder compacts

Shiau, Fuh-Shan; Fang, Te‐Hua; Leu, Tsung-Hsing

doi:10.1016/s0254-0584(98)00195-3

Cited by 39 publications

(14 citation statements)

References 29 publications

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“…The state of agglomeration of the powders has been significantly improved by attrition milling but 10% of the particles (in volume) are still above 100nm -this will still affect the green body homogeneity. Perhaps smaller milling media can help bring us towards a particle size distribution with all particles below 100nm giving us the narrow size distribution known to help reduce final grain sizes in alpha alumina ceramics [17]. The use of a finer alpha alumina as a seed source should enhance the effects of densification and hopefully reduce the grain size if the "one seed leading to one grain" approximation can be assumed, similar to the early work on boehmites [18].…”

Section: Sinteringmentioning

confidence: 97%

“…The use of a finer alpha alumina as a seed source should enhance the effects of densification and hopefully reduce the grain size if the "one seed leading to one grain" approximation can be assumed, similar to the early work on boehmites [18]. Zirconia impurities from milling have also been shown to have an adverse effect on alpha alumina sintering [17,19]. Reduction of this effect by using suitable alumina milling media should also help us to reach a better control of the sintering process.…”

Section: Sinteringmentioning

confidence: 98%

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Colloidal processing and sintering of nanosized transition aluminas

et al. 2005

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Abstract. The dispersion of nanosized gamma aluminas with high specific surfaces areas (100 m 2 /g) and primary particle sizes around 20 nm, using polyacrylic acid has been investigated. The effect of pH and polymer concentration showed that the highest density green bodies were produced using high polymer concentrations (6% wt) and pH of 6. Interparticle potential calculations have been made and help explain the underlying dispersion mechanism at least on a qualitative level. The dispersions were then used to slip cast green bodies followed by drying and sintering. The types of gamma alumina powder have been investigated, the pure gamma alumina, doped with MgO and also with the addition of alpha alumina seeds. The high degree of agglomeration of the gamma alumina powders led to very low densities (60%) even the alpha seeded alumina reached only 85 % theoretical density. Attrition milling with zirconia media improves both green density and sintered densities significantly with all powders showing sintered densities > 97%. Mictrostructural analysis on polished and etched surfaces show, however, that the grain sizes are well above 1 micron over 50 times greater than the initial gamma alumina primary particles. A two step sintering cycle was investigated with the Mg doped powder and average grain sizes around 580 nm were achieved.

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Section: Sinteringmentioning

confidence: 97%

Section: Sinteringmentioning

confidence: 98%

Colloidal processing and sintering of nanosized transition aluminas

et al. 2005

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“…This allows the pores to close as late as possible during the sintering cycle, reduces the sintering temperature 5,11 and retards the occurrence of grain growth. 12,13 As well as processing, the quality of the starting powder also plays a key role. Due to the very limited solubility of ions in Al 2 O 3 (in the ppm range), the grain boundary composition can be affected by segregated dopants or impurities, the powder should thus be of very high purity.…”

Section: Introductionmentioning

confidence: 99%

Transparent polycrystalline alumina using spark plasma sintering: Effect of Mg, Y and La doping

Stuer

Zhao

Aschauer

et al. 2010

Journal of the European Ceramic Society

110

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Transparent polycrystalline alumina (PCA) is a promising replacement for sapphire. Its optical properties however are highly dependent on the grain size and residual porosity which need to be controlled for real inline transmittances (RIT), that are high enough for possible applications.To achieve high RITs, doping as well as pressure assisted sintering is often used. In this study spark plasma sintering (SPS) and doping are investigated. A systematic experimental design is used to study the influence of Mg, Y and La single or co-doping (75-450 ppm) as well as the SPS sintering pressure and temperature on the RIT and grain size of PCA.Using optimized sintering parameters, RITs of >50% were attained in the visible wavelength (640 nm) for 0.8 mm thick samples for almost all doping strategies. The best RIT of 57% was for triple-doped samples at a total dopant level of 450 ppm. These results are significantly better than previously published SPS studies and illustrate that SPS sintered alumina can attain high and reproducible optical transmittances under various doping and sintering conditions.

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“…As such, the evolution of the powder microstructures upon sintering is a function of the concerted effects of differences in the powder particle size distributions and surface chemistries. Typically, fine powders with uniform size distributions display less rapid grain growth during intermediate stage sintering [49]. It is therefore reasonable that the relatively uniform particle size distributions of NiO powders milled in Vertrel and methanol result in smaller grain sizes after sintering to 1100 ℃ in comparison to unmilled NiO or NiO milled with carbon.…”

Section: Scanning Electron Microscopy and Thermal Analyses Of Sintementioning

confidence: 99%

The effect of milling additives on powder properties and sintered body microstructure of NiO

2015

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The evolution of powder particle size, crystal structure, and surface chemistry was evaluated for micron scale NiO powders subjected to impact milling with commonly employed milling additives: methanol, Vertrel XF, and amorphous carbon. The effect of the different comminution protocols on sintered body microstructure was evaluated for high temperature sintering in inert atmosphere (N 2 ). X-ray photoelectron spectroscopy showed that NiO powder surface chemistry is surprisingly sensitive to milling additive choice. In particular, the proportion of powder surface defect sites varied with additive, and methanol left an alcohol or alkoxy residue even after drying. Upon sintering to intermediate temperatures (1100 ℃), scanning electron microscopy (SEM) showed that slurry milled NiO powders exhibit hindered sintering behaviors. This effect was amplified for NiO milled with methanol, in which sub-500 nm grain sizes dominated even after sintering to 1100 ℃. Upon heating to high temperatures (1500 ℃), simultaneous differential scanning calorimetry/thermogravimetric analysis (DSC/TGA) showed that the powders containing carbon residues undergo carbothermal reduction, resulting in a melting transition between 1425 and 1454 ℃. Taken together, the results demonstrated that when processing metal oxide powders for advanced ceramics, the choice of milling additive is crucial as it exerts significant control over sintered body microstructure.

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Effects of milling and particle size distribution on the sintering behavior and the evolution of the microstructure in sintering powder compacts

Cited by 39 publications

References 29 publications

Colloidal processing and sintering of nanosized transition aluminas

Colloidal processing and sintering of nanosized transition aluminas

Transparent polycrystalline alumina using spark plasma sintering: Effect of Mg, Y and La doping

The effect of milling additives on powder properties and sintered body microstructure of NiO

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