rus
Issue #1/2022
V.I.Lysenko
CERAMICS PREPARED FROM MOLYBDENUM OXIDE POWDER: PROPERTIES AND PRODUCTION BY SPS METHOD
CERAMICS PREPARED FROM MOLYBDENUM OXIDE POWDER: PROPERTIES AND PRODUCTION BY SPS METHOD
10.22184/1993-8578.2022.15.1.34.37
INTRODUCTION
The differences between nanocrystalline and coarse grained materials as regards elastic, damping, strength, thermal, electrical, magnetic and diffusion properties depend not only on the small grain size in nanocrystalline materials, but also on a special surface state or grain boundaries in it [1].
One of the nanotechnology trends is production of ceramics from nanoscale powders in which very small grain sizes can be retained. It is expected that nanoceramics will not only have the properties of ceramics obtained from coarse-grained materials, but also some unique ones (such as superplasticity [2]).
It is known that the smaller the ceramics grain size and the more developed the grain structure, the stronger and harder the ceramics are. At the same time, in the nanopowders used for production of ceramics, there are stable hard-to-break agglomerates of nanoparticles [3], which requires the use of non-standard methods of compaction (for example, hot pressing method).
The state of the art on nanoceramics prepared from various nanopowders is fairly well documented in papers [4–6] and others, including the author [7–13].
In this paper a ceramic produced from molybdenum oxide nanopowder has been studied.
Molybdenum oxide (VI) MoO3 is used in production of metallic molybdenum (which serves as an additive to in steel and corrosion resistant alloys). It is a co-catalyst for use in the industrial production of acrylonitrile, applied in electrochemical devices and displays, and used in glaze components and pigmentation dyes.
The aim of this work was to create dense and hard ceramics with a fine-grained (less than micron) structure from molybdenum oxide nanodisperse powder using the SPS method.
DESCRIPTION OF THE EXPERIMENT
In these studies, molybdenum oxide MoO3 nanopowder created by the Russian company Novosibirsk Nanomaterials (NskNano) was used (here powders are synthesized using an electrical conductor explosion (EVP)).
The average particle size of the initial powder was d = 90–110 nm.
The powder had the following properties: purity 98%, colour yellow, spherical particle shape, orthorhombic crystal structure.
For this powder sintering was carried out on Labox "Sinter Land" unit of IGiL SB RAS by the method of spark plasma sintering (hot pressing with the use of sintering spark plasma, SPS), when pulses of electric current pass through the pre-compressed powder (in these experiments the current strength reached 2 kA at a voltage of 3–4 V). The main difference of SPS from conventional pressing (successive pressing and sintering) is the pulse electric current directly applied to the sample, which results in rapid heating of the powder and largely preservation of its microstructural parameters in the consolidated material. The pressing was carried out at different maximum temperatures (670 and 750° C) and pressures of 40 MPa. The heating rate was, typically, 100˚/min and the holding time at the maximum temperature was 3 min.
The micro-hardness of all ceramic samples was studied using a PMT-3 micro-hardness tester.
The compressive strength and Young›s modulus were determined using a Zwick/Roell Z005 strength testing machine (Germany).
Chippings of ceramics were sputtered with gold and, afterwards, studied with the aid of a ZEISS EVO-50WDS-XVP-BU electron scanning microscope.
X-ray examination of the obtained ceramics was carried out using a HZG-4 diffractometer with monochromatic Cu-Kα radiation, a recording rate of 2 deg/min, a voltage of 35 kV and a current of 35 mA.
RESULTS AND DISCUSSION
The diameter and thickness of the obtained ceramic specimens were 10.4–10.5 mm and 1.8–1.9 mm, and the ceramic density was 4.57 g/cm3 (relative density (relative to the table density) was 0.974).
X-ray diffraction study of the ceramics showed that the sample is MoO3 (35–609) with an orthorhombic structure, space group Pbnm (No. 62) and lattice dimensions a = 3.963 Å, b = 13.856 Å and c = 3.6966 Å.
Fig.1 shows electron scanning microscopy of ceramic chippings at Tmax = 670 °C. It can be seen that the grain size of obtained ceramics is about 0.5–1 µm, i.e. using SPS method a fine-grained dense ceramic was created.
The micro-hardness of the ceramics obtained at Tmax = 750 °C turned out to be relatively high (Hv = 2.1 GPa).
The compressive strength of the ceramics obtained is σB = 0.1 GPa and the Young’s modulus is E = 60 GPa.
Thus, using the SPS method on the basis of nanosized molybdenum oxide powder, a fine-grained (about 0.5–1 µm), dense and strong ceramic with micro-hardness of 2.1 GPa was obtained.
ACKNOWLEDGEMENTS
The author thanks to A.G.Anisimov, V.I.Mali, V.A.Emelkin, G.V.Trubacheev, G.A.Pozdnyakov and A.A. Gusev for their help in this work.
Peer review info
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal's website and SELibrary eLIBRARY.RU.
Declaration of Competing Interest. The author declares that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
The differences between nanocrystalline and coarse grained materials as regards elastic, damping, strength, thermal, electrical, magnetic and diffusion properties depend not only on the small grain size in nanocrystalline materials, but also on a special surface state or grain boundaries in it [1].
One of the nanotechnology trends is production of ceramics from nanoscale powders in which very small grain sizes can be retained. It is expected that nanoceramics will not only have the properties of ceramics obtained from coarse-grained materials, but also some unique ones (such as superplasticity [2]).
It is known that the smaller the ceramics grain size and the more developed the grain structure, the stronger and harder the ceramics are. At the same time, in the nanopowders used for production of ceramics, there are stable hard-to-break agglomerates of nanoparticles [3], which requires the use of non-standard methods of compaction (for example, hot pressing method).
The state of the art on nanoceramics prepared from various nanopowders is fairly well documented in papers [4–6] and others, including the author [7–13].
In this paper a ceramic produced from molybdenum oxide nanopowder has been studied.
Molybdenum oxide (VI) MoO3 is used in production of metallic molybdenum (which serves as an additive to in steel and corrosion resistant alloys). It is a co-catalyst for use in the industrial production of acrylonitrile, applied in electrochemical devices and displays, and used in glaze components and pigmentation dyes.
The aim of this work was to create dense and hard ceramics with a fine-grained (less than micron) structure from molybdenum oxide nanodisperse powder using the SPS method.
DESCRIPTION OF THE EXPERIMENT
In these studies, molybdenum oxide MoO3 nanopowder created by the Russian company Novosibirsk Nanomaterials (NskNano) was used (here powders are synthesized using an electrical conductor explosion (EVP)).
The average particle size of the initial powder was d = 90–110 nm.
The powder had the following properties: purity 98%, colour yellow, spherical particle shape, orthorhombic crystal structure.
For this powder sintering was carried out on Labox "Sinter Land" unit of IGiL SB RAS by the method of spark plasma sintering (hot pressing with the use of sintering spark plasma, SPS), when pulses of electric current pass through the pre-compressed powder (in these experiments the current strength reached 2 kA at a voltage of 3–4 V). The main difference of SPS from conventional pressing (successive pressing and sintering) is the pulse electric current directly applied to the sample, which results in rapid heating of the powder and largely preservation of its microstructural parameters in the consolidated material. The pressing was carried out at different maximum temperatures (670 and 750° C) and pressures of 40 MPa. The heating rate was, typically, 100˚/min and the holding time at the maximum temperature was 3 min.
The micro-hardness of all ceramic samples was studied using a PMT-3 micro-hardness tester.
The compressive strength and Young›s modulus were determined using a Zwick/Roell Z005 strength testing machine (Germany).
Chippings of ceramics were sputtered with gold and, afterwards, studied with the aid of a ZEISS EVO-50WDS-XVP-BU electron scanning microscope.
X-ray examination of the obtained ceramics was carried out using a HZG-4 diffractometer with monochromatic Cu-Kα radiation, a recording rate of 2 deg/min, a voltage of 35 kV and a current of 35 mA.
RESULTS AND DISCUSSION
The diameter and thickness of the obtained ceramic specimens were 10.4–10.5 mm and 1.8–1.9 mm, and the ceramic density was 4.57 g/cm3 (relative density (relative to the table density) was 0.974).
X-ray diffraction study of the ceramics showed that the sample is MoO3 (35–609) with an orthorhombic structure, space group Pbnm (No. 62) and lattice dimensions a = 3.963 Å, b = 13.856 Å and c = 3.6966 Å.
Fig.1 shows electron scanning microscopy of ceramic chippings at Tmax = 670 °C. It can be seen that the grain size of obtained ceramics is about 0.5–1 µm, i.e. using SPS method a fine-grained dense ceramic was created.
The micro-hardness of the ceramics obtained at Tmax = 750 °C turned out to be relatively high (Hv = 2.1 GPa).
The compressive strength of the ceramics obtained is σB = 0.1 GPa and the Young’s modulus is E = 60 GPa.
Thus, using the SPS method on the basis of nanosized molybdenum oxide powder, a fine-grained (about 0.5–1 µm), dense and strong ceramic with micro-hardness of 2.1 GPa was obtained.
ACKNOWLEDGEMENTS
The author thanks to A.G.Anisimov, V.I.Mali, V.A.Emelkin, G.V.Trubacheev, G.A.Pozdnyakov and A.A. Gusev for their help in this work.
Peer review info
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal's website and SELibrary eLIBRARY.RU.
Declaration of Competing Interest. The author declares that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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