FAST/SPS sintering of nanocrystalline zinc oxide—Part I: Enhanced densification and formation of hydrogen-related defects in presence of adsorbed water

Dargatz, Benjamin; González‐Julián, Jesús; Bram, Martin; Jakes, Peter; Besmehn, Astrid; Schade, Lisa; Röder, Robert; Ronning, Carsten; Guillon, Olivier

doi:10.1016/j.jeurceramsoc.2015.12.009

Cited by 65 publications

(59 citation statements)

References 87 publications

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“…In addition, the green densities increased with the applied pressure, achieving a maximal value of 59.5 % at 150 MPa. This effect, although not clearly investigated in detail and not modeled, is frequently observed and was already reported for lower pressures [14]. The second difference is clearly observed in the densification behaviour and the final density.…”

Section: Resultsmentioning

confidence: 63%

“…Figure 2 shows the onset temperature for the densification of ZnO/H2O and ZnO/Ac-H2O as a function of the applied pressure, including the value at 50 MPa under the same sintering conditions as reported by Dargatz et al [14]. This onset temperature was defined as the lowest temperature at which the axial displacement is larger than 60 µm in a period of 10 s.…”

Section: Resultsmentioning

confidence: 83%

“…Previous findings [14] showed that especially the grain boundary transport was affected by H 2 O loss during a heating experiment (cf. Tab.…”

Section: Analysis Of the Defect Formation By Kelvin Probe Force Micromentioning

confidence: 95%

“…Defect formation and interfacial energies dictate the sintering behaviour of ZnO, and their modification by the presence of water could be determinant to understand the observed better sinterability. In previous works, some of the authors have reported the modification of point defects when water was present during the FAST/SPS sintering by using photoluminescence at low temperature (5 K) and electron paramagnetic resonance [14] …”

Section: Analysis Of the Defect Formation By Kelvin Probe Force Micromentioning

confidence: 99%

“…Similarly, slow heating rates did not enable to achieve relative densities higher than ~ 65%. Dargatz et al [14][15] investigated further in great detail this phenomenon, so that highly dense ZnO (99,5 %) with a mean grain size of 200 nm was obtained at 400°C. A controlled, small amount of water (< 7.7 wt.%, optimized at 1.6 wt.%) was directly added into the green compact.…”

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confidence: 99%

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Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

et al. 2018

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The sintering behavior of nanocrystalline ZnO was investigated at only 250 °C. Densification was achieved by the combined effect of uniaxial pressure and the addition of water both in a Field Assisted Sintering Technology/Spark Plasma Sintering apparatus and a warm hand press with a heater holder. The final pure ZnO materials present high densities (> 90 % theoretical density) with nano-grain sizes. By measuring the shrinkage rate as a function of applied stress it was possible to identify the stress exponent related to the densification process. A value larger than one points to non-linear relationship going beyond single solid-state diffusion or liquid phase sintering. Only a low amount of water (1.7 wt.%) was needed since the process is dictated by the adsorption on the surface of the ZnO particles. Part of the adsorbed water dissociates into H + and OH -ions, which diffuse into the ZnO crystal structure, generating grain boundaries/interfaces with high defect chemistry. As characterized by Kelvin Probe Force Microscopy, and supported by impedance spectroscopy, this highly defective grain boundary area presents much higher surface energy than the bulk. This highly defective grain boundary area with high potential reduces the activation energy of the atomic diffusion, leading to sinter the compound at low temperature.

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Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 83%

“…Previous findings [14] showed that especially the grain boundary transport was affected by H 2 O loss during a heating experiment (cf. Tab.…”

Section: Analysis Of the Defect Formation By Kelvin Probe Force Micromentioning

confidence: 95%

Section: Analysis Of the Defect Formation By Kelvin Probe Force Micromentioning

confidence: 99%

mentioning

confidence: 99%

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Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

et al. 2018

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Application of Electric Current‐Assisted Sintering Techniques for the Processing of Advanced Materials

et al. 2020

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Highly efficient energy conversion and storage technologies such as high‐temperature solid oxide fuel and electrolysis cells, all‐solid‐state batteries, gas separation membranes, and thermal barrier coatings for advanced turbine systems depend on advanced materials. In all cases, processing of ceramics and metals starting from powders plays a key role and is often a challenging task. Depending on their composition, such powder materials often require high sintering temperatures and show an inherent risk of abnormal grain growth, evaporation, chemical reaction, or decomposition, especially in the case of long dwelling times. Electric current‐assisted sintering (ECAS) techniques are promising to overcome these restrictions, but a lot of fundamental and practical challenges must be solved properly to take full advantage of these techniques. A broad and long‐term expertise in the field of ECAS techniques and comprehensive facilities including conventional field‐assisted sintering technology/spark plasma sintering (FAST/SPS), hybrid FAST/SPS (with additional heater), sinter forging, and flash sintering (FS) devices are available at the Institute of Energy and Climate Research: Materials Synthesis and Processing (IEK‐1). Herein, main advantages and challenges of these techniques are discussed and the concept to overcome current limitations is introduced on selected examples.

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A Perspective on Emerging and Future Sintering Technologies of Ceramic Materials

2023

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Novel sintering methods have emerged in the recent past years, which have raised great interest in the scientific community. Relying on electric field effects, high heating rates, the use of mechanical pressure, or hydrothermal conditions, they offer fundamental advantages compared to conventional sintering routes like minimizing the energy consumption and enhancing the process efficiency. This perspective aims at explaining these effects in a general way and presenting the status quo of using them for the processing of high‐performing ceramic materials. In detail, this work focuses on flash sintering, ultrafast high‐temperature sintering, spark plasma sintering, cold sintering, and photonic sintering methods based on different light sources. The specificities, potentials, and limitations of each method are compared, especially in the light of a possible industrialization.

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FAST/SPS sintering of nanocrystalline zinc oxide—Part I: Enhanced densification and formation of hydrogen-related defects in presence of adsorbed water

Cited by 65 publications

References 87 publications

Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

Application of Electric Current‐Assisted Sintering Techniques for the Processing of Advanced Materials

A Perspective on Emerging and Future Sintering Technologies of Ceramic Materials

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