Mechanical activation-assisted autoclave processing and sintering of HfB2-HfO2 ceramic powders

Akçamlı, Nazlı; Ağaoğulları, Duygu; Balcı, Özge; Öveçoğlu, M. Lütfi; Duman, İsmail

doi:10.1016/j.ceramint.2016.06.087

Cited by 21 publications

(8 citation statements)

References 46 publications

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“…The weak absorption bands in the region between 3900 and 3650 cm −1 have been assigned to stretching vibration of isolated O–H groups bound to single cations Hf 4+ 45 and to bridging O–H coordinate to more than one cation 46 . The broad peak at ~3400 cm −1 is ascribed to the stretching vibrations of ‐OH associated with the hydroxyl groups of trapped ethanol or physically absorbed water 47 in acidic conditions, as well as resulted from the formation of hafnium oxychloride compounds with different hydration levels (HfOCl 2 .xH 2 O) 48 or the Hf(OH) 4 precipitation due to partial hydrolysis of polymeric precursor in neutral conditions 42 . The absorption peaks at the wavenumbers of 2918 and 1490 cm −1 are attributed to C‐H stretching vibrations of the PVP 49 .…”

Section: Resultsmentioning

confidence: 99%

A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

Ghelich

Abdizadeh

Jahannama³

et al. 2020

Int J Applied Ceramic Tech

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This study reports on the synthesis of hafnium diboride (HfB2)‐based nanofibers via electrospinning of polyhafnoxanesal (PHO)‐based solution followed by pyrolyzing hafnium‐boron containing polyvinylpyrrolidone precursor fibers by a moderate heat treatment at 1500°C under argon atmosphere. The influence of the molar ratios of C/Hf and B/Hf in preceramic polymer method is investigated on the final phase of HfB2‐based nanofibers. Structural, thermal, microstructural, and physical properties of the hafnium‐based fibers are evaluated using Fourier transform infrared spectra (FTIR), thermogravimetry and differential scanning calorimetry (TG/DSC), X‐ray diffractometer (XRD), high‐temperature X‐ray diffraction (HT‐XRD), field‐emission scanning electron microscope/energy‐dispersive spectrometer (FE‐SEM/EDS), and Brunauer‐Emmett‐Teller (BET). The results unveiled that the acidic pH was the optimal condition needed for obtaining the single phase of HfB2 nanofibers. The precursor fibers with the stoichiometric ratio of 1:4:5 of Hf:B:C prepared under the acidic conditions converted into pure HfB2 nanofibers having rough and porous surface after pyrolysis at 1500°C for 2 hour in argon, whereas HfB2‐HfC composite nanofibers with smooth surface were produced in the neutral conditions. The HfB2 nanofibers with a mean diameter of ~100 nm prepared under the acidic conditions showed a higher specific surface area compared to HfB2‐HfC composite nanofibers with a diameter of ~121 nm derived in the neutral conditions.

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Section: Resultsmentioning

confidence: 99%

A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

Ghelich

Abdizadeh

Jahannama³

et al. 2020

Int J Applied Ceramic Tech

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“…The stretching vibration of TM-O-C (TM = Hf, Ti, Mo, Ta, and Nb) bond (1070-852 cm −1 ) was confirmed and ascribed to the reaction between ethanol, CTAB, and transition metal chlorides. 33 The weak absorption peak of TM-O-TM at 700 cm −1 was assigned to the condensation of transition metal alkoxides during the hydrothermal polymerization. 34,35 The absorption peaks of C-H at 2854-2922 cm −1 , H-OH at 2344-2371 cm −1 and 1645 cm −1 , C=C at 1570 cm −1 , C-C at 1461 cm −1 , and C-O at 1360 cm −1 can be attributed to organic groups and absorbed water on surfaces of the precursors.…”

Section: Synthesis and Structural Characterization Of Heb-hftimotanbmentioning

confidence: 99%

Low‐temperature synthesis of high‐entropy (Hf_0.2Ti_0.2Mo_0.2Ta_0.2Nb_0.2)B₂ powders combined with theoretical forecast of its elastic and thermal properties

et al. 2022

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A theoretical calculation combined with experiment was used to study highentropy (Hf 0.2 Ti 0.2 Mo 0.2 Ta 0.2 Nb 0.2 )B 2 (HEB-HfTiMoTaNb). The theoretical calculation suggested HEB-HfTiMoTaNb could be stable over a wide temperature range. Then, a novel solvothermal/molten salt-assisted borothermal reduction method was proposed to efficiently pre-disperse transitional metal atoms in a precursor and synthesize (Hf 0.2 Ti 0.2 Mo 0.2 Ta 0.2 Nb 0.2 )B 2 nanoscale powders at 1573 K for 6 h, which is nearly 300 K lower than previous reports. The characterization results indicated that the as-synthesized nanoscale HEB-HfTiMoTaNb powder was hexagonal single-phase with homogeneous elements distribution and uniform size, and the oxygen content of the particles is 0.97 wt%. Simultaneously, the mechanical properties, anisotropic nature, and thermal properties of HEB-HfTiMoTaNb were investigated by density functional theory (DFT) calculations. The Cannikin's law was adopted to explain the improvement of comprehensive mechanical properties. In addition, a significant reduction of thermal conductivity was observed for HEB-HfTiMoTaNb and it only was 1/15 of the value of HfB 2 . This work suggests a reliable technique for synthesis of nanosized HEB powders and discovery of high-entropy materials under the guidance of first-principle theory.

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“…The pack cementation technique with Graphite (20-40 wt.%) and Si (60-80 wt.%) as raw materials were used for fabricating the inner SiC coating [21]. While the raw materials of B2O3 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) wt.%), graphite (3-15 wt.%), HfO2 (25- were weighed by an analytical balance whose sensitivity is ± 0.1 mg. The samples were taken out of the oxidation furnace at set intervals during oxidation.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, introducing transition-metal borides into the SiC coatings is promising to broaden their application prospect. 3 Among the transition metal borides ceramic, hafnium diboride (HfB 2 ) [18][19][20] as one of promising candidates has attracted much attention in recent years, which has a series of unexceptionable performances, for instance, excellent resistance to oxidation and thermal shock. The method of in-situ synthesis is easy to fabricate the UHTCs borides at the lower temperature [21].…”

Section: Introductionmentioning

confidence: 99%

HfB2-SiC-MoSi2 oxidation resistance coating fabricated through in-situ synthesis for SiC coated C/C composites

Wang

Ren

et al. 2017

Journal of Alloys and Compounds

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A brand new HfB 2 -SiC-MoSi 2 coating was fabricated to protect carbon/carbon (C/C) composites with inner SiC coating from oxidation, which was prepared by in-situ synthesis. In this paper, the C/C substrate with the protection of the HfB 2 -SiC-MoSi 2 /SiC coating could resist oxidation in 1773 K air for 408 h. The double coating also presented expected oxidation protection performance at dynamic oxidation environment. In the test process, the surface coating was oxidized to form a self-sealing silicate glass layer containing HfO 2 and HfSiO 4 , which could hinder crack propagation in coating.

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Mechanical activation-assisted autoclave processing and sintering of HfB2-HfO2 ceramic powders

Cited by 21 publications

References 46 publications

A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

Low‐temperature synthesis of high‐entropy (Hf_0.2Ti_0.2Mo_0.2Ta_0.2Nb_0.2)B₂ powders combined with theoretical forecast of its elastic and thermal properties

HfB2-SiC-MoSi2 oxidation resistance coating fabricated through in-situ synthesis for SiC coated C/C composites

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Mechanical activation-assisted autoclave processing and sintering of HfB2-HfO2 ceramic powders

Cited by 21 publications

References 46 publications

A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

Low‐temperature synthesis of high‐entropy (Hf0.2Ti0.2Mo0.2Ta0.2Nb0.2)B2 powders combined with theoretical forecast of its elastic and thermal properties

HfB2-SiC-MoSi2 oxidation resistance coating fabricated through in-situ synthesis for SiC coated C/C composites

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Low‐temperature synthesis of high‐entropy (Hf_0.2Ti_0.2Mo_0.2Ta_0.2Nb_0.2)B₂ powders combined with theoretical forecast of its elastic and thermal properties