Showing papers on "Sintering published in 2020"
TL;DR: Spark plasma sintering (SPS) as discussed by the authors is a widely used powder metallurgy technique for high-dimensional materials, where the sample is simultaneously subjected to uniaxial pressure and electrical current in a vacuum or protective atmosphere.
248 citations
TL;DR: In this article, a new rapid ultra-high-temperature air ambient sintering method without mother powder (MP) is put forward for the preparation of high quality Ta-LLZO ceramic electrolyte.
141 citations
Qingdao University1, Nanjing University of Aeronautics and Astronautics2, Zhejiang University of Technology3, Shanghai University of Engineering Sciences4, Curtin University5, The University of Nottingham Ningbo China6, King Fahd University of Petroleum and Minerals7, Shandong University8, University of Sharjah9
TL;DR: In this article, a review of the optimization methods of ceramic corundum abrasive properties are introduced from three aspects: precursor synthesis, particle shaping, and sintering, and three methods of abrasive shaping are summarized.
119 citations
TL;DR: The intrinsic inhibition of interfacial reaction by using silica glass rather than multicomponent glasses as the matrix is reported, resulting in color-tunable phosphor-glass composites not only accessible to three-dimensional printing technique, but also highly efficient and stable.
Abstract: The development of high-power white light-emitting diodes demands highly efficient and stable all-inorganic color converters. In this respect, phosphor-glass/ceramic composites show great promise as they could combine the merits of high quantum efficiency of phosphors and high chemical and thermal stabilities of glass/ceramic matrices. However, strong interfacial reaction between phosphors and matrices at high temperature results in quantum efficiency loss of the embedded phosphors, and traditional solutions rely on high-pressure consolidation techniques. Here we report the intrinsic inhibition of interfacial reaction by using silica glass rather than multicomponent glasses as the matrix. The embedment of phosphors is achieved via a pressureless sintering method, rendering these color-tunable phosphor-glass composites not only accessible to three-dimensional printing technique, but also highly efficient (internal quantum efficiency >90.0%), thermally stable at 1200 °C and hydrothermally stable at 200 °C. Our results provide a facile and general strategy for developing all-inorganic functional composites. Phosphor-glass/ceramic composites are attractive for high-power white light-emitting diodes, but interfacial reaction leads to loss of quantum efficiency. Here the authors report a reduction sintering method for embedment of phosphors into silica glass with limited interfacial reaction.
107 citations
TL;DR: In this article, the microstructure, hardness and fracture toughness of the printed ZrO2-Al2O3 composite ceramics sintered at different maximum sintering temperature and holding time were investigated.
101 citations
TL;DR: The feature of this strategy is to allow the oriented three-dimensional skeleton to be strongly bonded by sintered ceramic phase instead of polymer-like adhesive to improve the intrinsic thermal conductivity of the skeleton to the greatest extent, which represents a new avenue to addressing the heat challenges in traditional electronic products.
Abstract: Conventional polymer composites normally suffer from undesired thermal conductivity enhancement which has hampered the development of modern electronics as they face a stricter heat dissipating requirement. It is still challenging to achieve satisfactory thermal conductivity enhancement with reasonable mechanical properties. Herein, we present a three-dimensional (3D), lightweight, and mechanically strong boron nitride (BN)-silicon carbide (SiC) skeleton with aligned thermal pathways via the combination of ice-templated assembly and high-temperature sintering. The sintering has introduced atomic-level coupling at the BN-SiC junction which contributes to efficient phonon transport via the newly formed borosilicate glass BCxN3-x (0 ≤ x ≤ 3) and SiCxN4-x (0 ≤ x ≤ 4) phases, leading to much lower interfacial thermal resistance. Thus, the obtained BN-SiC skeleton shows satisfactory thermal performance. The prepared 3D BN-SiC/polydimethylsiloxane (PDMS) composites exhibit a maximum through-plane thermal conductivity of 3.87 W·m-1·K-1 at a filler loading of only 8.35 vol %. The thermal conductivity enhancement efficiency reaches 220% per 1 vol % filler when compared to pure PDMS matrix, superior to other reported BN skeleton-based composites. The feature of our strategy is to allow the oriented three-dimensional skeleton to be strongly bonded by a sintered ceramic phase instead of polymer-like adhesive, namely, to improve the intrinsic thermal conductivity of the skeleton to the greatest extent. This strategy can be applied to develop novel thermal management materials that are lightweight and mechanically tough that rapidly transfer heat. It represents a new avenue to addressing the heat challenges in traditional electronic products.
99 citations
TL;DR: In this paper, Ni nanoparticles embedded in CeO2 and CeZrO2 were synthesized by sol-gel method and compared with a Ni/CeO2 prepared by support impregnation.
Abstract: Ni nanoparticles embedded in CeO2 (Ni@CeO2) and CeZrO2 (Ni@CeZrO2) were synthesized by sol-gel method and compared with a Ni/CeO2 prepared by support impregnation. The performance of the catalysts was investigated for dry reforming of methane reaction. In situ XRD, XANES and TEM showed that Ni embedded in CeO2 improved the resistance to sintering along the reduction at 800 °C. Doping ceria with zirconia inhibited the growth of Ni particles and increased the oxygen mobility. SEM, TEM, Raman spectroscopy and TGA of the used catalysts after dry reforming of methane showed that carbon formation rate was significantly reduced for the catalysts containing Ni nanoparticles embedded in ceria structure. Carbon deposits were not detected over Ni@CeZrO2 after 24 h of reaction. Therefore, the control of Ni particle size and the high oxygen mobility of Ni@CeZrO2 catalyst inhibited carbon deposition and favored the mechanism of carbon removal, promoting catalyst stability.
98 citations
TL;DR: This work provided a simple strategy to deposit small sized ceria on Ni@SiO2 catalyst surface for performance enhancement of low temperature CRM.
Abstract: Developing high performance catalysts for the low temperature CO2 reforming with methane (CRM) reaction is a challenge due to the occurrences of metal sintering and carbon deposition. In this study, we synthesized CeO2 modified Ni@SiO2 catalysts with excellent properties of sintering-resistance and low carbon deposition for high performance low temperature CRM. The Ni@SiO2-CeO2 catalysts displayed a size effect from tiny Ni nanoparticles to enhance CRM performance and a confinement effect from silica encapsulation to limit Ni sintering and exhibited oxygen storage capacity from ceria to reduce carbon deposition. Performance and characterization results revealed that the Ni@SiO2-CeO2-W catalyst with smaller ceria size exhibited higher performance and lower carbon deposition than the Ni@SiO2-CeO2-E catalyst with bigger ceria size, because the smaller ceria nanoparticles activated more CO2. This work provided a simple strategy to deposit small sized ceria on the Ni@SiO2 catalyst surface for the performance enhancement of low temperature CRM.
92 citations
TL;DR: In this paper, high-porosity Al2O3 ceramic foams called Al 2O3 PHM ceramics were fabricated through selective laser sintering (SLS) via Al 2 O3 poly-hollow microspheres (Al2O 3 PHMs).
88 citations
TL;DR: In this article, a high-entropy (Bi0.2Na 0.2K0.3TiO3 (BNKBCT) ceramic is successfully fabricated by using flash sintering technique.
85 citations
TL;DR: In this article, the authors used Fused Deposition Modeling and Sintering (FDMS) for fast 3D printing of metal parts at low energy consumption and low cost.
TL;DR: In this paper, W-Y2O3 alloys are prepared by freeze-drying and subsequent low temperature sintering, which results in a smaller grain size of 510 nm while maintaining a comparatively higher density of 97.8%.
TL;DR: The relationship between microstructures and mechanical properties, especially strength and toughness of high-entropy carbide based ceramics are reported in this paper, and the main toughening mechanism is considered to be crack deflection by SiC particles.
Abstract: The relationships between microstructures and mechanical properties especially strength and toughness of high-entropy carbide based ceramics are reported in this article. Dense (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C (HEC) and its composite containing 20 vol.% SiC (HEC-20SiC) were prepared by spark plasma sintering. The addition of SiC phase enhanced the densification process, resulting in the promotion of the formation of the single-phase high-entropy carbide during sintering. The high-entropy carbide phase demonstrated a fast grain coarsening but SiC particles remarkably inhibited this phenomena. Dense HEC and HEC-20SiC ceramics sintered at 1900 °C exhibits four-point bending strength of 332 ± 24 MPa and 554 ± 73 MPa, and fracture toughness of 4.51 ± 0.61 MPa·m1/2 and 5.24 ± 0.41 MPa·m1/2, respectively. The main toughening mechanism is considered to be crack deflection by the SiC particles.
TL;DR: The phase and microstructural investigations revealed that alongside the ZrB2, SiC, and TaC as the starting materials, two new phases of ZrC and TaSi2 were synthesized in-situ during the hot pressing as discussed by the authors.
TL;DR: In this article, the mechanical properties and wear behavior of AA6061/Silicon Carbide (SiC) composites fabricated through powder metallurgy routine were reported, which showed that increase in hardness and compressive strength of the composite was evidenced with increasing reinforcement level.
TL;DR: In this paper, the main source of heating in spark plasma sintering is perceived as the Joule heating effect, which is a result of electric current distribution in the setup.
TL;DR: In this paper, microstructural and phase analysis were carried out via scanning electron microscopy and X-ray diffraction spectroscopy, to illustrate the sintering and toughening mechanisms in the fabricated samples.
TL;DR: In this article, a few-layer graphene reinforced Ti6Al4V (TC4) alloy matrix nanocomposites with 3D network architecture were fabricated through spark plasma sintering (SPS) technique.
TL;DR: In this article, low-temperature fired CaMg1−xLi2xSi2O6 microwave dielectric ceramics were prepared via the traditional solid-state reaction method.
Abstract: In this study, low-temperature fired CaMg1−xLi2xSi2O6 microwave dielectric ceramics were prepared via the traditional solid-state reaction method. In this process, 0.4 wt% Li2CO3-B2O3-SiO2-CaCO3-Al2O3 (LBSCA) glass was added as a sintering aid. The results showed that ceramics consisted of CaMgSi2O6 as the main phase. The second phases were CaSiO3 always existing and Li2SiO3 occurring at substitution content x > 0.05. Li+ substitution effectively lowered sintering temperature due to 0.4 wt% LBSCA and contributed to grain densification, and the most homogeneous morphology could be observed at x = 0.05. The effects of relative density, the second phase, and ionic polarizability on dielectric constant (er) were investigated. The quality factor (Q × f) varied with packing fraction that concerned the second phase. Moreover, the temperature coefficient of the resonant frequency (τf) was influenced by MgO6 octahedral distortion and bond valence. Excellent dielectric properties of the CaMg1−xLi2xSi2O6 ceramic was exhibited at x = 0.05 with er = 7.44, Q × f = 41,017 GHz (f = 15.1638 GHz), and τf = −59.3 ppm/°C when sintered at 900 °C. It had a good application prospect in the field of low-temperature co-fired ceramic (LTCC) substrate and devices.
TL;DR: In this paper, the authors have rationalized the last ten years research in the field of sintering for the consolidation of ceramics and pointed out common features and differences among different techniques.
Abstract: Despite sintering has a history even longer than human civilization (its discovery dates back at least to 25,000 years ago), in the past decade, new exciting challenges have emerged in the field: reduction of environmental impact, densification of metastable phases, complete consolidation of ultra-refractory compounds, precise microstructural design to control properties of functional ceramics and integration between inorganic-organic compounds. In order to meet such challenges, new sintering routes employing electric fields/currents, water/solvents and external loads have been developed. The research also opened new questions about unexpected (and still not completely understood) interactions between electricity, presence of water/liquid, heating and diffusion processes. In this manuscript, we have rationalized the last-ten-years research in the field of sintering for the consolidation of ceramics. The processes are collected into three main groups: flash-like (sintering under relatively large electric fields and the material is internally heated by the Joule effect), spark plasma sintering-like (combination of pressure and limited electric field) and hydro-consolidation (sintering at temperature below ≈ 350 °C in the presence of a liquid under an applied pressure). This paper aims to point out common features and differences among different techniques. Finally, future research trends and new paradigm in material processing are anticipated.
TL;DR: A carbon atomization process that allows one not only to redisperse metal nanoparticles, but also to recover deactivated catalysts is reported, which opens up a window to preparation of sintering-resistant single atoms catalysts and regeneration of deactivated industrial catalysts.
Abstract: The sintering of supported metal nanoparticles is a major route to the deactivation of industrial heterogeneous catalysts, which largely increase the cost and decrease the productivity. Here, we discover that supported palladium/gold/platinum nanoparticles distributed at the interface of oxide supports and nitrogen-doped carbon shells would undergo an unexpected nitrogen-doped carbon atomization process against the sintering at high temperatures, during which the nanoparticles can be transformed into more active atomic species. The in situ transmission electron microscopy images reveal the abundant nitrogen defects in carbon shells provide atomic diffusion sites for the mobile atomistic palladium species detached from the palladium nanoparticles. More important, the catalytic activity of sintered and deactivated palladium catalyst can be recovered by this unique N-doped carbon atomization process. Our findings open up a window to preparation of sintering-resistant single atoms catalysts and regeneration of deactivated industrial catalysts.
TL;DR: In this article, a cylindrical sample consisting of a titanium carbide was investigated numerically and the governing equations of heat diffusion and electricity distribution in the whole device was solved using finite element method.
TL;DR: In this article, the effect of graphite nano-flakes addition on the microstructure, densification, and thermal characteristics of TiB2−25% SiC composite was investigated.
TL;DR: In this article, the effects of silicon carbide (SiC) as the most important reinforcement phase on the densification percentage and mechanical characteristics of zirconium diboride (ZrB2)-matrix composites were studied.
TL;DR: By introducing aliovalent cations and A-site vacancies, the relaxor characteristics are greatly enhanced in (Na1-2xBix)(Nb1-xZrx)O3 ceramics, leading to a high energy storage efficiency above 90% and a promising candidate for high power dielectric energy storage applications.
Abstract: Sodium niobate (NaNbO3)-based lead-free ceramics have
been actively studied for energy storage applications because of their
antiferroelectric and/or relaxor features achieved in modified systems
The P–E loops of NaNbO3-based ceramics are usually hysteretic because of the existence
of a metastable ferroelectric phase at room temperature In this study,
by introducing aliovalent cations and A-site vacancies, the relaxor
characteristics are greatly enhanced in (Na1–2xBix)(Nb1–xZrx)O3 ceramics,
leading to a high energy storage efficiency of above 90% In addition,
sintering aid CuO and a special ramp-to-spike sintering profile were
employed to decrease the sintering temperature and reduce the grain
size The modified ceramic exhibits improved insulating properties
and hence a higher breakdown strength, leading to a high recoverable
energy density of 49 J/cm3 and a high energy efficiency
of 88% at 430 kV/cm The ceramic also exhibits satisfactory temperature
stability over a wide temperature range from 25 to 125 °C and
charge–discharge performance, making it a promising candidate
for high-power dielectric energy storage applications
TL;DR: In this article, the effect of sintering temperature on the microstructural, calcium/phosphorus (Ca/P) ion ratios and mechanical properties of non-separated biowastes processed hydroxyapatite (HAp) prepared through a low cold compaction protocol was described.
TL;DR: In this article, the effects of sintering temperature on microstructure and physical and mechanical properties of alumina ceramics were investigated using stereolithography-based 3D printing.
Abstract: Alumina ceramics with different sintering temperatures in argon atmosphere were obtained using stereolithography-based 3D printing. The effects of sintering temperature on microstructure and physical and mechanical properties were investigated. The results show that the average particle size, shrinkage, bulk density, crystallite size, flexural strength, Vickers hardness, and nanoindentation hardness increased with the increase in sintering temperature, whereas the open porosity decreased with increasing sintering temperature. No change was observed in phase composition, chemical bond, atomic ratio, and surface roughness. For the sintered samples, the shrinkage in Z direction is much greater than that in X or Y direction. The optimum sintering temperature in argon atmosphere is 1350 °C with a shrinkage of 3.0%, 3.2%, and 5.5% in X, Y, and Z directions, respectively, flexural strength of 26.7 MPa, Vickers hardness of 198.5 HV, nanoindentation hardness of 33.1 GPa, bulk density of 2.5 g/cm3, and open porosity of 33.8%. The optimum sintering temperature was 70 °C higher than that sintering in air atmosphere when achieved the similar properties.
TL;DR: In this article, the authors proposed a reasonable way to deal with the large amount of iron ore tailings and coal gangue powder by making them as the sintered bricks with sewage sludge and shale as the binder, considering the advantages in both economic and environmental aspects.
TL;DR: ZrB2-SiC-graphite composites with 0-35vol% graphite flakes were densified via hot-pressing route at the temperature of 1800°C under the uniaxial pressure of 40MPa for 1h.
TL;DR: In this article, the effect of sintering temperature on the microstructure and mechanical properties of the alumina ceramics were investigated, which were sintered in vacuum.
Abstract: Stereolithography (SL) was used to form alumina ceramic cores. The effect of sintering temperature on the microstructure and mechanical properties of the alumina ceramics are investigated, which were sintered in vacuum. The results indicate that, as the sintering temperature increased the particle size of alumina slightly increased, and the interlayer spacing first decreased and then increased. The open porosity of alumina ceramics significantly decreased as the sintering temperature in vacuum increased. The flexural strength and hardness increased as the sintering temperature increased. When sintered at 1150 °C, the flexural strength was found to be 33.7 MPa, the shrinkage was 2.3 %, 2.4 %, and 5.3 % in the X, Y, and Z directions, respectively, and the open porosity was 37.9 %. These results are similar to those found from sintering at 1280 °C in air.