Showing papers on "Sintering published in 2021"
TL;DR: Li et al. as mentioned in this paper proposed a novel (Ni/CeO2)@SiO2 catalyst for MDR by photothermal catalysis, which was characterized by BET, XRD, TEM and UV-vis diffuse reflectance spectrum to analyze structural and optical properties.
83 citations
TL;DR: In this article, the effects of adding fine grains and sintering additives on the stereolithography additive manufactured Al2O3 ceramic lattice structures with high precise and high compressive strength were investigated.
74 citations
TL;DR: In this paper, a strategy of designing small grain sizes and abundant amorphous grain boundaries is proposed to improve the energy storage properties under the guidance of phase field theory, and the results show that the grain size and grain boundaries are carefully controlled by the high-energy ball milling method and two-step sintering strategy.
65 citations
TL;DR: The role of sintering temperature on the relative density, microstructure and mechanical characteristics of as-sintered specimens were studied in this paper, and the role of produced in-situ phases on the grain growth also studied using SEM fractographs.
Abstract: Ti–10 wt% Mo–1 wt% B4C composite samples were SPSed under the circumstances of 5 min dwell time, 50 MPa external pressure and sintering temperatures of 1150 °C, 1300 °C and 1450 °C. The role of sintering temperature on the relative density, microstructure and mechanical characteristics of as-sintered specimens were studied. Near fully dense relative density was obtained for the samples sintered at 1450 °C. The best mechanical properties including UTS, elongation, bending strength and micro/macro hardness were achieved for the composites SPSed at the highest temperature. The XRD results and also microscopic photographs disclosed the formation of TiB + TiC in-situ phases. However, there was not any evidence for chemical reaction between Mo and other phases. The role of produced in-situ phases on the grain growth also studied using SEM fractographs.
62 citations
TL;DR: In this paper, the impacts of methane and oxygen injection concentrations on sintering performance were numerically examined, and the recommended operating conditions were determined based on parametric studies to achieve a tradeoff between the sinter quality and productivity.
58 citations
01 Mar 2021
TL;DR: In this paper, a review of powder bed selective laser processing is presented, focusing on the process description, feedstock criteria and process parameters and strategy, and technical aspects and challenges about how to address these issues are presented.
Abstract: This review offers an overview on the latest advances in the powder bed selective laser processing, known as selective laser sintering/melting, of calcium phosphate, silicon carbide, zirconia, alumina, and some of their composites. A number of published studies between 1991 and August 2020 was collected, analyzed and an inclusive state of the art was created for this review. The paper focuses on the process description, feedstock criteria and process parameters and strategy. A comparison is made between direct and indirect powder bed selective laser processing of each ceramic, regarding the present achievements, limitations and solutions. In addition, technical aspects and challenges about how to address these issues are presented.
56 citations
TL;DR: In this paper, high-strength ceramsite was prepared from red mud, fly ash, and bentonite without any other chemical additives by a two-stage sintering process.
54 citations
TL;DR: In this paper, the authors outline the basics of microwave dielectric ceramics alongside the mechanism of cold sintering and discuss future prospects and critical issues for advancing cold-sintered materials and devices, such as unclear mechanism, low Q'×'f values and poor mechanical properties.
Abstract: Microwave (MW) dielectric ceramics are used in numerous electronic components for modern wireless communication systems, including antennas, resonators, capacitors and filters. However, to date, MW ceramics are manufactured by an energy-intensive, conventional high-temperature (> 1000 °C) sintering technology and thus cannot be co-sintered with low melting point and base electrodes (Ag, Al, etc., < 1000 °C), nor directly integrated with polymers (< 200 °C). Cold sintering is able to densify ceramics at < 200 °C via a combination of external pressure and a transient liquid phase, reducing the energy consumed and facilitating greater integration with dissimilar materials. This review outlines the basics of MW ceramics alongside the mechanism of cold sintering. Recent developments in cold sintering of MW ceramics, composites and devices are described, emphasizing new materials and progress towards component/device fabrication. Future prospects and critical issues for advancing cold-sintered MW materials and devices, such as unclear mechanism, low Q × f values and poor mechanical properties, are discussed.
52 citations
TL;DR: In this paper, a unique in-house synthesized oxide@W core-shell nanopowder was used as a precursor to prepare W-based oxide dispersion strengthened (ODS) alloy, which achieved a great enhancement of strength and ductility at room temperature.
Abstract: With excellent creep resistance, good high-temperature microstructural stability and good irradiation resistance, oxide dispersion strengthened (ODS) alloys are a class of important alloys that are promising for high-temperature applications. However, plagued by a nerve-wracking fact that the oxide particles tend to aggregate at grain boundary of metal matrix, their improvement effect on the mechanical properties of metal matrix tends to be limited. In this work, we employ a unique in-house synthesized oxide@W core-shell nanopowder as precursor to prepare W-based ODS alloy. After low-temperature sintering and high-energy-rate forging, high-density oxide nanoparticles are dispersed homogeneously within W grains in the prepared alloy, accompanying with the intergranular oxide particles completely disappearing. As a result, our prepared alloy achieves a great enhancement of strength and ductility at room temperature. Our strategy using core-shell powder as precursor to prepare high-performance ODS alloy has potential to be applied to other dispersion-strengthened alloy systems.
52 citations
TL;DR: In this article, a methodology of powder sintering and in-situ press forging was used to manipulate a new bimorphic microstructure in Ti-6Al-4V alloy.
51 citations
TL;DR: In this paper, the fabrication of the AA7075/B4C micro composite subjected to different sintering techniques was investigated, and the results showed that conventional sintered composite showed inadequate mechanical responses because of their high-temperature processing and time, intermetallic compound formation, high porosity levels, and high strain to fracture values.
TL;DR: In this article, a cold sintering process (150 °C, 250 MPa, 60 min) was employed to pre-densify LiF ceramics to 78 % relative density.
Abstract: LiF is a low-firing fluoride with excellent microwave dielectric properties, however densification of LiF ceramics is challenging owing to their low surface free energy. In this study, a cold sintering process (150 °C, 250 MPa, 60 min) was employed to pre-densify LiF ceramics to 78 % relative density. Post-annealing treatments between 650 °C and 800 °C led to significant grain growth which was accompanied by an increase in relative density to 92 %. The microwave quality factor (Qf) increased with increasing annealing temperature to a maximum of 110,800 GHz at 800 °C, 1.5 times higher than the value obtained via conventional sintering (78,800 GHz), with relative permittivity er = 8.2 and temperature coefficient of resonant frequency, τf =–135 ppm/°C. Such high values of Qf and its compatibility with Ag electrode suggest that cold sintered LiF has great potential as a component or additive in low temperature co-fired ceramic formulations.
TL;DR: In this article, a brief review of powder bed fusion (PBF) processes is presented, which includes Direct Metal Laser Deposition (DMLS), Selective Laser Sintering (SLS), Selectively Laser Melting (SLM), Electron Beam Meltering (EBM), and SHS.
TL;DR: In this paper, the authors reviewed the granulation process and suitable raw materials for each hardening method, including sintering, cold-bonding, accelerated carbonation and alkaline activation.
TL;DR: It is deduced that controlling crystal growth with high-precision photonic sintering simplifies the experimental framework required to understand perovskite crystallization and opens a new empirical parameter space for these types of synthesis methods.
Abstract: The use of a solution process to grow perovskite thin films allows to extend the material processability. It is known that the physicochemical properties of the perovskite material can be tuned by altering the solution precursors as well as by controlling the crystal growth of the film. This advancement necessarily implies the need for an understanding of the kinetic phenomena for the thin-film formation. Therefore, in this work we review the state of the art of perovskite hybrid crystal growth, starting from a comprehensive theoretical description towards broad experimental investigations. One part of the study focuses on rapid thermal annealing as a tool to control nucleation and crystal growth. We deduce that controlling crystal growth with high-precision photonic sintering simplifies the experimental framework required to understand perovskite crystallization. These types of synthesis methods open a new empirical parameter space. All this knowledge serves to improve the perovskite synthesis and the thin films' quality, which will result in higher device performances.
TL;DR: In this article, the authors used a one-step sintering at 1600°C from high-purity magnesite added with silicon kerf waste in different ratios, with the emphasis on the evolution of their phase compositions, micromorphologies, and various properties.
TL;DR: In this article, a completely dry co-sintering of LLZ and cathode active material (CAM) is presented, which is fast, free of any sintering additives and coatings and suitable to fabricate dense mixed cathodes, pure LLZ separators and multilayers of the two.
TL;DR: In this article, the Ni-Zr-Al catalysts derived from Ni-Al binary hydrotalcite were used for low-temperature CO2 methanation.
Abstract: Developing Ni-based catalysts with high activity and stability in low-temperature methanation is necessary due to their sintering and coking at high temperatures. Here, we report our developed novel Ni-Zr-Al catalysts derived from Ni-Zr-Al ternary hydrotalcites synthesized by a hydrothermal process, followed by a reduction in hydrogen. Comparing with the Ni-Al catalyst derived from Ni-Al hydrotalcite and the commercial Ni-based catalyst, the Ni-Zr-Al catalysts show a remarkably higher low-temperature activity (210−270 °C) in CO2 methanation. Both the experimental and theoretical calculations confirmed the introduction of Zr into the Ni-Al binary hydrotalcite could generate synergetic effects between Ni and ZrO2, resulting in more surface oxygen vacancies, basic sites, and abundant mesopores. In-situ DRIFTS analysis showed the CO2 methanation to CH4 follows the intermediate formate route. This work provides a new theoretical understanding of CO2 activation and methanation, and a practical way to address the existing problem for Ni-based catalysts.
TL;DR: In this paper, transparent alumina ceramics were fabricated using an extrusion-based 3D printer and post-processing steps including debinding, vacuum sintering, and polishing.
Abstract: Transparent alumina ceramics were fabricated using an extrusion-based 3D printer and post-processing steps including debinding, vacuum sintering, and polishing. Printable slurry recipes and 3D printing parameters were optimized to fabricate quality green bodies of varying shapes and sizes. Two-step vacuum sintering profiles were found to increase density while reducing grain size and thus improving the transparency of the sintered alumina ceramics over single-step sintering profiles. The 3D printed and two-step vacuum sintered alumina ceramics achieved greater than 99 % relative density and total transmittance values of about 70 % at 800 nm and above, which was comparable to that of conventional CIP processed alumina ceramics. This demonstrates the capability of 3D printing to compete with conventional transparent ceramic forming methods along with the additional benefit of freedom of design and production of complex shapes.
TL;DR: In this article, the authors quantify a critical particle distance of platinum nanoparticles on carbon supports, over which the sintering can be mitigated greatly up to 900°C.
Abstract: Supported metal nanoparticles are of universal importance in many industrial catalytic processes. Unfortunately, deactivation of supported metal catalysts via thermally induced sintering is a major concern especially for high-temperature reactions. Here, we demonstrate that the particle distance as an inherent parameter plays a pivotal role in catalyst sintering. We employ carbon black supported platinum for the model study, in which the particle distance is well controlled by changing platinum loading and carbon black supports with varied surface areas. Accordingly, we quantify a critical particle distance of platinum nanoparticles on carbon supports, over which the sintering can be mitigated greatly up to 900 °C. Based on in-situ aberration-corrected high-angle annular dark-field scanning transmission electron and theoretical studies, we find that enlarging particle distance to over the critical distance suppress the particle coalescence, and the critical particle distance itself depends sensitively on the strength of metal-support interactions. Deactivation of supported metal catalysts via thermally induced sintering is a major concern in the catalysis community. Here, the authors demonstrate that enlarging particle distance to over the critical distance could suppress the particle coalescence greatly up to 900 °C.
TL;DR: In this paper, the CaAl12O19 reinforced Al 2O3-Cr2O3 composites were prepared by pressureless sintering process, and the influences of CaO content on the sinterings properties, mechanical properties, and microstructure evolution of the composites are studied.
Abstract: Al2O3-Cr2O3 refractories have excellent slag corrosion resistance and can adapt to the oxidation/reduction atmosphere in the smelting reduction ironmaking furnace. However, Al2O3-Cr2O3 refractories have poor mechanical properties and sintering properties. In order to improve the mechanical properties of Al2O3-Cr2O3 materials, the CaAl12O19 reinforced Al2O3-Cr2O3 composites were prepared by pressureless sintering process, and the influences of CaO content on the sintering properties, mechanical properties, and microstructure evolution of the composites were studied. The results show that a small amount of CaO can significantly improve the compactness of the composites, which is mainly due to the formed sheet-like CA6 fill the gap between the solid solutions, and reduces the porosity of the composites. In addition, the sheet-like CA6 makes the connection between solid solutions closer, and the intergranular fracture gradually transforms into a mixed mode of intergranular and transgranular fracture. The best mechanical propertie is observed at S4 with the CaO content of 2 wt.%. Compared with sample S0 without CaO, the hardness, compressive strength and flexural strength of the S4 were increased by 35.19 %, 49.69 %, and 68.34 %, respectively. The addition of excessive CaO will deteriorate the mechanical properties of the composites, because the formation of a large number of layered CA6 increases the porosity of the composites. Furthermore, a small amount of CaO addition can significantly improve the thermal shock resistance of the composites. After 10 and 20 thermal shock cycles, the strength loss rates of S4 are only 5.83 % and 8.74 %, respectively.
TL;DR: In this paper, the dispersion of metallic Ni particles into under-coordinated two-dimensional Ni clusters over γ-Mo2N is a thermodynamically favorable process based on the AIMD simulation.
Abstract: Reversing the thermal induced sintering phenomenon and forming high temperature stable fine dispersed metallic centers with unique structural and electronic properties is one of the ever-lasting targets of heterogeneous catalysis. Here we report that the dispersion of metallic Ni particles into under-coordinated two-dimensional Ni clusters over γ-Mo2N is a thermodynamically favorable process based on the AIMD simulation. A Ni-4nm/γ-Mo2N model catalyst is synthesized and used to further study the reverse sintering effect by the combination of multiple in-situ characterization methods, including in-situ quick XANES and EXAFS, ambient pressure XPS and environmental SE/STEM etc. The under-coordinated two-dimensional layered Ni clusters on molybdenum nitride support generated from the Ni-4nm/γ-Mo2N has been demonstrated to be a thermally stable catalyst in 50 h stability test in CO2 hydrogenation, and exhibits a remarkable catalytic selectivity reverse compared with traditional Ni particles-based catalyst, leading to a chemo-specific CO2 hydrogenation to CO. Reversing the thermal induced sintering phenomenon and forming high temperature stable fine dispersed metallic centers is one of the ever-lasting targets in heterogeneous catalysis. Here the authors report the dispersion of metallic Ni particles into under-coordinated two-dimensional Ni clusters over γ-Mo2N.
TL;DR: In this paper, a synergistic multifunctional (Ni/CeO2)@SiO2 catalyst by confining Ni nanoparticles and CeO2 nanocrystals in SiO 2 nanospheres is synthesized.
TL;DR: In this paper, the state-of-the-art additive manufacturing technologies for the fabrication of relatively pure SiC, which show great potential to retain its strength under neutron irradiation, are discussed.
02 Nov 2021-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effects of different process and thermal parameters on the porosity and mechanical properties of binder jetted 316L samples were investigated at the green and sintered stages via microstructural and compositional analysis and mechanical characterization.
Abstract: Binder Jetting is becoming increasingly important in the scenario of metal Additive Manufacturing processes due to the absence of rapid melting and solidification steps that can induce defects in most sensitive alloys and lead to unwanted reactions. However, this technology requires to consider the effects of different factors such as powder packing, wettability with the binder and sinterability to define suitable process parameters and to achieve desirable material properties. Although several research works focus on individual aspects of Binder Jetting and sintering of parts, a comprehensive understanding of material evolution under different processing conditions has not been achieved yet. The present research explores the effects of different process and thermal parameters on the porosity and mechanical properties of binder jetted 316L samples. The effect of layer thickness and binder saturation, considering the powder bed features, and debinding and sintering atmospheres, referring to the post-processing stages, were investigated at the green and sintered stages via microstructural and compositional analysis and mechanical characterization. Thermal treatments simulations were employed to determine the microstructural evolution during sintering. The 316L steel produced in this work by Binder Jetting exhibited a fine equiaxed microstructure, tensile strength values comparable to those of cast products and superior ductility compared to other additive techniques.
TL;DR: In this paper, the authors obtained a high recoverable energy storage density and a low sintering temperature simultaneously in 0.5(Bi0.5Na0,5)TiO3-0.1-1.5 mol% CuO capacitors with a large Wrec of 2.20 J/cm3 and η of 72.39% under 230 kV/cm.
Abstract: The miniaturization and integration trend of electronic applications requires high energy storage performance, and the development of multilayer ceramic capacitors (MLCC) demands the compatibility between ceramic sintering temperature and co-firing temperature of metal electrodes. Herein, we obtained a high recoverable energy storage density and a low sintering temperature simultaneously in 0.5(Bi0.5Na0.5)TiO3-0.5SrTiO3-x mol% CuO (0.5BNT-0.5ST-x mol% CuO) via the combination of adding CuO sintering aid and citrate sol-gel synthesis method. The optimum sintering temperature decreases significantly from 1130 °C for x = 0 to 820 °C for x = 2.0. The ceramic of 0.5BNT-0.5ST-1.5 mol% CuO exhibits a large Wrec of 2.20 J/cm3 and η of 72.39% under 230 kV/cm. Furthermore, the same sample also possesses a large CD of 1740.97 A/cm2, an extremely high PD of 139.28 MW/cm3 and an ultrafast discharge speed of 82 ns. These merits reveal that the ceramic of 0.5BNT-0.5ST-1.5 mol% CuO has great potential in practical MLCC production.
TL;DR: In this paper, a normal pressure sintering process was used to study the properties of chromium corundum refractory for smelting reduction iron making kiln lining, and the results of densification behavior showed that the introduction of Cr2O3 deteriorates the compactness, relative density and volume shrinkage rate of the composite material decrease with the increase of the Cr 2O3 content.
Abstract: Al2O3-Cr2O3 refractories are completely substitution solid solutions and can effectively resist slag erosion when used as an industrial furnace lining. In order to provide suitable chromium corundum refractory with excellent slag resistance and mechanical properties for smelting reduction ironmaking, Al2O3-Cr2O3 samples with different mass percentages (0, 10, 20, 30, 40 wt.%) of Cr2O3 were prepared by a normal pressure sintering process to study its sintering properties, mechanical properties, thermal shock resistance, and microstructure. The results of densification behavior showed that the introduction of Cr2O3 deteriorates the compactness, the relative density and volume shrinkage rate of the composite material decrease with the increase of the Cr2O3 content, and the apparent porosity increases accordingly. In terms of mechanical properties, the hardness, compressive strength, and flexural strength of Al2O3-Cr2O3 material decrease gradually with the increase of Cr2O3. After 10 and 20 thermal shock cycles, the flexural strengths of the samples all decreased. With the increase of Cr2O3 in these samples, the loss rate of flexural strength gradually increased. Considering the slag resistance and mechanical properties of the composite material, the Al2O3-Cr2O3 composite refractory with Cr2O3 content of 20–30% can meet the requirements of smelting reduction iron making kiln lining.
TL;DR: In this article, the authors used cuttlefish bones, mussel shells, chicken eggshells and bio-inspired amorphous calcium carbonate to synthesize hydroxyapatite nano-powders which were consolidated into cylindrical pellets by uniaxial pressing and sintering 800-1100 °C.
Abstract: Biogenic calcium carbonates naturally contain ions that can be beneficial for bone regeneration and therefore are attractive resources for the production of bioactive calcium phosphates. In the present work, cuttlefish bones, mussel shells, chicken eggshells and bioinspired amorphous calcium carbonate were used to synthesize hydroxyapatite nano-powders which were consolidated into cylindrical pellets by uniaxial pressing and sintering 800-1100 °C. Mineralogical, structural and chemical composition were studied by SEM, XRD, inductively coupled plasma/optical emission spectroscopy (ICP/OES). The results show that the phase composition of the sintered materials depends on the Ca/P molar ratio and on the specific CaCO3 source, very likely associated with the presence of some doping elements like Mg2+ in eggshell and Sr2+ in cuttlebone. Different CaCO3 sources also resulted in variable densification and sintering temperature. Preliminary in vitro tests were carried out (by the LDH assay) and they did not reveal any cytotoxic effects, while good cell adhesion and proliferation was observed at day 1, 3 and 5 after seeding through confocal microscopy. Among the different tested materials, those derived from eggshells and sintered at 900 °C promoted the best cell adhesion pattern, while those from cuttlebone and amorphous calcium carbonate showed round-shaped cells and poorer cell-to-cell interconnection.
TL;DR: In this paper, Spark Plasma Sintering (SPS) was employed to consolidate powder specimens consisting of B4C and various B4c-TiB2 compositions, achieving high theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth.
Abstract: Spark plasma sintering (SPS) was employed to consolidate powder specimens consisting of B4C and various B4C-TiB2 compositions. SPS allowed for consolidation of pure B4C, B4C-13 vol.%TiB2, and B4C-23 vol.%TiB2 composites achieving ≥99 % theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth due to long sintering times. Electron and x-ray microscopies determined homogeneous microstructures along with excellent distribution of TiB2 phase in both small and larger-scaled composites. An optimized B4C-23 vol.%TiB2 composite with a targeted low density of ∼3.0 g/cm3 exhibited 30–35 % increased hardness, fracture toughness, and flexural bend strength compared to several commercial armor-grade ceramics, with the flexural strength being strain rate insensitive under quasistatic and dynamic loading. Mechanistic studies determined that the improvements are a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B4C matrix in compression and TiB2 phase in tension, and c) TiB2 phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB2 serves as a toughening and strengthening phase, and scaling of SPS samples show promise for the manufacture of ceramic composites for body armor.
TL;DR: In this paper, a comparison of the spark plasma sintering (SPS) with other fabrication methods of MAX-phase materials is presented. But the authors focus on the comparison of SPS and other methods.
Abstract: This review focuses on the comparison of the spark plasma sintering (SPS) with other fabrication methods of MAX-phase materials. In the view of optimizing properties for prospective applications, we summarized different routes to synthesize and sinter bulk/powder MAX-phases with various microstructures, discussed the phase composition of MAX-phases obtained by SPS and other methods. In the article, we introduced the experimental features of various sintering methods and carried out the comparative analysis of “competition phenomenon” between the SPSed MAX-phases and MAX-phases prepared by other technologies. We referred to relevant reports and reviews in which one can acquire a comprehensive understanding of sintering kinetics, sintering thermodynamics, grain growth kinetics, and densification mechanisms. Furthermore, the influence of the sintering routes on the properties of the MAX-phases was discussed paying emphasis on the mechanical properties.