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1.
Cold sintering process for ZrO2‐based ceramics: significantly enhanced densification evolution in yttria‐doped ZrO2
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Hanzheng Guo Jing Guo Amanda Baker Clive A. Randall 《Journal of the American Ceramic Society》2017,100(2):491-495
We recently developed a novel technique of cold sintering process (CSP) to obtain dense ceramics at extraordinarily low temperatures. In this communication, we demonstrate the feasibility of applying CSP to zirconia‐based ceramics. As exemplified by 3Y‐TZP ceramics, a significantly enhanced densification evolution is observed. Water is simply utilized as a sintering aid to assist the ceramic densification under an applied external pressure. The low‐temperature advantage of CSP outstands in contrast to the densification curves compiled from other sintering techniques. A gradual monoclinic‐to‐tetragonal phase transformation is revealed in correspondence to the densification development, as well as contributes to the mechanical hardness evolution. A Vickers Hardness reaches ~10.5 GPa after annealing the cold‐sintered ceramics at 1100°C, which is comparable to those values reported in the previous studies at higher sintering temperatures. Such a sintering methodology is of significant importance as it provides a roadmap for cost‐effective processing of zirconia‐based ceramics and composites that enable broad practical applications. 相似文献
2.
Single CaO accelerated densification and microstructure control of highly transparent YAG ceramic
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Le Zhang Tianyuan Zhou Farida A Selim Hao Chen 《Journal of the American Ceramic Society》2018,101(2):703-712
In this work, a small amount of CaO single dopant was adopted to realize the densification and microstructure control of fine grained YAG ceramic with excellent optical quality, by a simple solid‐state reaction and one‐step vacuum sintering method. Then, highly transparent YAG ceramics (T = 84.4% at 1064 nm) were obtained just after vacuum sintering at 1820°C for 8 hours. The average grain size was only 2.7 μm, when the total amount of CaO was as low as 0.045 wt%. The effect of CaO on the microstructural evolution and optical property of the as‐fabricated YAG ceramics was systematically investigated in detail. It was found that CaO dopant promoted both densification and grain growth of YAG ceramics when the sintering temperature was lower than 1660°C, however, it dramatically inhibited grain growth when the sintering temperature was further increased. 相似文献
3.
Mattia Biesuz Woinshet D. Abate Vincenzo M. Sglavo 《Journal of the American Ceramic Society》2018,101(1):71-81
Porcelain stoneware was consolidated by flash sintering under DC polarization using current densities in the range 4‐20 mA/mm2. The results show the applicability of this innovative sintering technology to a material whose densification occurs by vitrification, thus allowing to extend the possible application field of flash sintering to traditional ceramics. Using appropriate current density, the flash‐ sintered samples are dense, homogeneous, and well‐vitrified. XRD and microstructural analysis points out the formation of primary mullite while secondary mullite is only sporadically observed. In addition, comparison between flash sintering and fast firing shows that the densification obtained in the selected ceramic system via the former route cannot be reproduced just by a rapid heating process. 相似文献
4.
Ke Wang Fang‐Yuan Zhu Li‐Qian Cheng Fang‐Zhou Yao 《Journal of the American Ceramic Society》2013,96(12):3677-3696
Environment‐friendly lead‐free piezoelectric ceramics have been studied extensively in the past decade with great progress particularly in systems based on a niobate perovskite compound formulated as (K, Na)NbO3 (abbreviated as KNN). A comprehensive review on the latest development of KNN‐based piezoelectric ceramics is presented in this article, including the phase structure, property enhancement approaches, and sintering processes as well as the status of some promising applications. The phase structure of KNN was reexamined and associated with the effect of chemical modification on its tetragonal‐to‐orthorhombic transition. Then, a special focus is placed on the temperature dependence of piezoelectric properties of KNN‐based ceramics, followed by reviewing the recent approaches devoted to the temperature‐stability enhancement. The processing fundamentals related to the sintering of KNN‐based ceramics are also presented with an emphasis on compositional and microstructural control. Finally, this review introduces several industrial attempts of traditional piezoceramic products using KNN‐based ceramics and the studies on some promising application in authors' laboratory. 相似文献
5.
Rémy Boulesteix Alexandre Maître Lucie Chrétien Yoël Rabinovitch Christian Sallé 《Journal of the American Ceramic Society》2013,96(6):1724-1731
Controlling residual amount of defects in transparent ceramics is a major challenge for laser applications. This study was focused on microstructural evolution of Nd:YAG ceramics during their reactive solid‐state sintering which was correlated to their optical transmittance. From microstructural observations, the microstructural maps and grain size‐density and grain size‐pore size sintering trajectories of Nd:YAG ceramics were established as a function of silica content. For densities higher than 99.7%, the occurrence of intragranular porosity was correlated to a critical pore radius of 0.16 μm. Silica appears to favor the formation of intragranular porosity which was attributed to the increasing of the grain growth rate compared with the densification one. An analytical model was established by coupling the analytical laws derived from sintering trajectories and the classical theory of light diffusion, allowing to correlate the microstructural features of transparent Nd:YAG ceramics to their optical properties. 相似文献
6.
Competition between densification and microstructure development during spark plasma sintering of B4C–Eu2O3
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Kannan Sairam Bathula Vishwanadh Jitendra K. Sonber Tammana S. R. Ch. Murthy Sanjib Majumdar Tarasankar Mahata Bikramjit Basu 《Journal of the American Ceramic Society》2018,101(6):2516-2526
The densification of nonoxide ceramics has been a known challenge in the field of engineering ceramics. The amount and type of sinter‐aid together with sintering conditions significantly influence the densification behavior and microstructure in nonoxide ceramics. In this perspective, the present work reports the use of Eu2O3 sinter‐aid and spark plasma sintering towards the densification of B4C. The densification is largely influenced by the solid‐state sintering reactions during heating to 1900°C. Based on the careful analysis of the heat‐treated powder mixture (B4C–Eu2O3) and sintered compacts, the competitive reaction pathways are proposed to rationalize the formation of EuB6 as dominant microstructural phase. An array of distinctive morphological features, including intragranular and intergranular EuB6 phase as well as characteristic defect structures (asymmetric twins, stacking faults and threaded dislocations) are observed within dense B4C matrix. An attempt has been made to explain the competition between microstructure development and densification. 相似文献
7.
Rémy Boulesteix Loïck Bonnet Alexandre Maître Lucie Chrétien Christian Sallé 《Journal of the American Ceramic Society》2017,100(3):945-953
Silica (SiO2) is widely used as sintering aid during vacuum sintering of YAG (Y3Al5O12)‐based transparent ceramics. These ceramics are mainly used for laser applications when they are doped with rare‐earth luminescent elements such as Yb3+ or Nd3+. By means of microstructural, chemical, dilatometry, and thermogravimetry analyses, this study has evidenced that sufficiently high amount of silica (ie above the solubility limit in YAG) forms intergranular transient liquid phase of mixed composition Y‐Al‐Si‐O that vaporizes rapidly for temperatures higher than 1350°C. As a result, silica content after sintering remains always lower than the solubility limit in YAG ceramics (ie lower than 900 ppm). Finally, vacuum sintering with an external source of gaseous Si was proven to be suitable to manufacture highly transparent Nd:YAG ceramics. 相似文献
8.
《Ceramics International》2022,48(3):2988-2998
Spark plasma sintering (SPS) is an efficient method for fabricating various bulk dense materials, including ceramics. Reactive spark plasma sintering (RSPS) of the exothermic reaction systems involves an initial powder mixture that allows chemical transformation with release of an additional energy during the SPS process. Thus, a deep understanding of the chemistry is critical for controlling the microstructure and thus the properties of the obtained materials. Recent publications have revealed that the RSPS is widely used for manufacturing of variety of materials including ultrahigh-temperature ceramics, high-entropy ceramics, and thermoelectrics. However, the thermodynamics and kinetics of the chemical reactions occurring during RSPS are not well understood. The goals of the present critical review are as follows: (i) to provide the fundamental definitions of chemistry related parameters of RSPS; (ii) to analyze the thermodynamics and kinetics of the RSPS processes; (iii) to emphases the influence of the microstructure of the consolidated media on the chemistry of RSPS; (iv) briefly overview recent publications on RSPS of ceramics. We also provide some recommendations for future work in the field of RSPS. 相似文献
9.
《Journal of the European Ceramic Society》2022,42(14):6599-6607
Cerium dioxide (CeO2) was densified by conventional and field assisted sintering techniques in order to examine the effect of a range of sintering parameters on the resultant pellet microstructure, namely: temperature, hold time, atmosphere, electric field strength and polarity. CS at 1400 °C for 2 h in static air atmospheres provided the highest densities and grain sizes compared with an argon atmosphere, due to the retention of near stoichiometry maintaining sintering kinetics. SPS produced dense ceramics at similar sintering temperatures (1300 °C), but with greatly reduced sintering hold (5 min) and cycle times. However, microstructural inhomogeneity arose from the direct current polarity which led to oxygen ion diffusion toward the positive electrode. FS was performed with an alternating current electric field and produces samples of comparable density at sintering temperatures of ~1100 °C for a hold time of around 1 h with no inhomogeneity due to the alternating current employed. 相似文献
10.
《Ceramics International》2021,47(21):29815-29823
The use of additives as a sintering aid for promoting densification is well-known in processing structural ceramics. In leaky ferroelectric ceramics (e.g., BiFeO3-based systems), additives are also used to reduce the leakage current, improve the poling efficiency and the piezoelectric response of a material. A less investigated aspect is how additives affect the multiferroic (ferroelectric and magnetic) features of BiFeO3-based ceramics. In this work, we report a systematic study of the effect of different additives viz, MnO2, CuO, K2CO3 and KMnO4 on the microstructural, electromechanical, and magnetic properties of Dy-modified BiFeO3–PbTiO3. We found that all the additives help in the precipitation of the ferrimagnetic dysprosium iron garnet phase. The additives containing potassium (K) tend to suppress the grain size. We found that the best combination of ferroelectric and ferromagnetic behaviour was found in a mixture of additives. 相似文献
11.
An oscillatory pressure sintering of zirconia powder: Rapid densification with limited grain growth
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Yao Han Shuang Li Tianbin Zhu Zhipeng Xie 《Journal of the American Ceramic Society》2017,100(7):2774-2780
A novel oscillatory pressure sintering (OPS) process is reported to prepare high‐quality ceramics. The oscillatory pressure was applied at three stages (initial, intermediate, and final) during sintering process of zirconia ceramics for the first time. The microstructure of the samples prepared by OPS develops in a more homogeneous manner, leading to a higher final density, a smaller average grain size, and a narrower distribution of grain sizes compared with the samples prepared by conventional pressureless sintering (PS) and hot‐pressing (HP) processes. Remarkably, the OPS samples was obtained at relatively lower heating temperature and less soaking time for 1300°C and 0.5 hours than the samples prepared by other two techniques at 1450°C and 1 hour. The current results suggest that OPS is an effective technique for preparing high‐quality zirconia ceramics with low heating temperature and short sintering time, thus, it obviously reduces cost. 相似文献
12.
Combined-Stage Sintering Model 总被引:8,自引:0,他引:8
James D. Hansen Richard P. Rusin Mao-Hua Teng D. Lynn Johnson 《Journal of the American Ceramic Society》1992,75(5):1129-1135
By focusing on the similarities between the three stages of sintering, a single equation is derived that quantifies sintering as a continuous process from beginning to end. The microstructure is characterized by two separate parameters representing geometry and scale. The dimensionless geometry parameter, denoted T, comprises five scaling factors that relate specific microstructural featuers (e.g., surface curvature) to the scale (grain diameter). Calculations of T from experimental data show (a) agreement with computer simulations of initial-stage sintering, (b) the effect of surface diffusion on T, and (c) changes in T with microstructural evolution during sintering. Application of the model to the design of firing schedules and the study of microstructural geometry effects on sintering is discussed. 相似文献
13.
《Journal of the European Ceramic Society》2022,42(13):5669-5674
Flash sintering is arousing growing interest because high-density ceramics can be obtained at lower temperatures and shorter dwell times than conventional sintering. However, not only temperature and dwell times should be controlled during flash sintering but also parameters such as the electric field and electric current should be considered. Controlling all the parameters during the processing allows comprehensive control of the microstructure and, consequently, functional properties can be improved. In this work, it is evidenced that an exhaustive control of the flash electric current is a crucial factor for tailoring the microstructure of BaTiO3 ceramics. The results reveal that the most suitable way to control the sintering process is by using non-linear current profiles because better densification and improved grain growth is achieved. Although the results focus on BaTiO3, this work offers a new pathway to tailor the microstructure of flash sintered ceramics, which may be extended to other materials. 相似文献
14.
Most technical ceramics require processing up to and including final-stage sintering to obtain a high-density bulk while inhibiting grain growth as dominant sintering process as far as possible. The literature typically highlights the qualitative interdependence of the sintering variables and microstructural parameters, focusing on very simple particulate systems. However, a quantitative method to achieve optimum sintering of actual polycrystalline solids is still lacking.This paper puts forward such a method, which has been satisfactorily tested by the authors. The method consists of a mathematical model, based on the physical phenomena that take place during solid-state sintering. The method leads to two differential equations: a densification rate and a pore-dragged normal grain growth rate equation during final-stage sintering, which mainly depend on sintering temperature and shaping conditions. Simultaneous numerical integration of these two rate equations allows design of an optimal thermal cycle (enhancing densification and controlling grain growth) to obtain the targeted sintered polycrystalline microstructure. Application of this method yields staggered thermal cycles, in addition to the number of steps, as well as the sintering temperature and dwell time in each step. 相似文献
15.
Utilizing the Cold Sintering Process for Flexible–Printable Electroceramic Device Fabrication
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Amanda Baker Hanzheng Guo Jing Guo Clive Randall 《Journal of the American Ceramic Society》2016,99(10):3202-3204
Conventional thermal sintering of ceramics is generally accomplished at high temperatures in kilns or furnaces. We have recently developed a procedure where the sintering of a ceramic can take place at temperatures below 200°C, using aqueous solutions as transient solvents to control dissolution and precipitation and enable densification (i.e., sintering). We have named this approach as the “Cold Sintering Process” because of the drastic reduction in sintering temperature and time relative to the conventional thermal process. In this study, we fabricate basic monolithic capacitor array structures using a ceramic paste that is printed on nickel foils and polymer sheets, with silver electrodes. The sintered capacitors, using a dielectric Lithium Molybdenum Oxide ceramic, were then cold sintered and tested for capacitance, loss, and microstructural development. Simple structures demonstrate that this approach could provide a cost‐effective strategy to print and densify different materials such as ceramics, polymers, and metals on the same substrate to obtain functional circuitry. 相似文献
16.
Meng Cao Wen Bin Hong Xiao Dong Yang Ying Qiang Jia Lei Li Shu Ya Wu Hang Sheng Yang Xiang Ming Chen 《Journal of the American Ceramic Society》2023,106(3):1668-1680
Dense and strong calcite (CaCO3) ceramics were prepared by room-temperature cold sintering with the aid of water and high pressure of up to 900 MPa. Under atmospheric pressure, calcite is barely soluble in water. However, the microstructure evolution and stress-strain analysis during cold sintering revealed that the dissolution-precipitation, plastic deformation, and pressure-solution-creep mechanisms played a crucial role in the densification and mechanical robustness of calcite ceramics, which was attributed to the significantly enhanced solubility of calcite in water under high pressure. The calcite ceramic cold sintered under 900 MPa from micron powder exhibited the highest relative density of 92.1% and best mechanical properties with compressive strength, flexural strength, hardness, and Young's modulus of 276.5 MPa, 52.5 MPa, 1.64 GPa, and 53.7 GPa, respectively. The as-prepared calcite ceramic was stronger and harder than most stones and cement, indicating its promising application as novel building and biomimetic materials. The present study also provides a new strategy for densifying ceramics with low solubility by cold sintering. 相似文献
17.
快速烧结技术在节省时间和能源方面的巨大优势使其成为一直以来的研究热点。近几十年来,快速烧结技术(如火花等离子烧结、闪电烧结、选区激光烧结、感应烧结、微波烧结和传统烧结装置中的快速烧结等)的发展,使陶瓷材料的快速烧结成为可能。本文综述了近20年来先进陶瓷领域中的快速烧结技术和烧结机理,并对火花等离子烧结中直流脉冲电流和机械压力对微观结构、材料性能和烧结机理的影响进行了深入分析和总结。同时指出,快速烧结技术今后的发展一方面是对烧结机理的进一步研究并应用到先进陶瓷材料的制备中,另一方面是解决快速烧结技术工业化生产中大尺寸、大批量生产的难题。 相似文献
18.
19.
Gregory N. Hassold I-Wei Chen David J. Srolovitz 《Journal of the American Ceramic Society》1990,73(10):2857-2864
A Monte Carlo model for simulating final-stage sintering has been developed. This model incorporates realistic microstructural features (grains and pores), variable surface difusivity, grain-boundary diffusivity, and grain-boundary mobility. A preliminary study of a periodic array of pores has shown that the simulation procedure accurately reproduces theoretically predicted sintering kinetics under the restricted set of assumptions. Studies on more realistic final-stage sintering microstructure show that the evolution observed in the simulation closely resembles microstructures of real sintered materials over a wide range of diffusivity, initial porosity, and initial pore sizes. Pore shrinkage, grain growth, pore breakaway, and reattachment have all been observed. The porosity decreases monotonically with sintering time and scales with the initial porosity and diffusivity along the grain boundary. Deviations from equilibrium pore shapes under slow surface diffusion or fast grain-boundary diffusion conditions yield slower than expected sintering rates. 相似文献
20.
S. Ramesh N. Zulkifli C.Y. Tan Y.H. Wong F. Tarlochan S. Ramesh W.D. Teng I. Sopyan L.T. Bang Ahmed A.D. Sarhan 《Ceramics International》2018,44(8):8922-8927
In this research, the comparison between microwave sintering and conventional sintering on the mechanical properties and microstructural evolution of 3?mol% yttria-stabilised zirconia were studied. Green bodies were compacted and sintered at various temperatures ranging from 1200?°C to 1500?°C. The results showed that microwave assisted sintering was beneficial in enhancing the densification and mechanical properties of zirconia, particularly when sintered at 1200?°C. It was revealed that as the sintering temperature was increased to 1400?°C and beyond, the grain size and mechanical properties for both microwave- and conventional-sintered ceramics were comparable thus suggesting that the sintering temperature where densification mechanism was activated, grain size was strongly influenced by the sintering temperature and not the sintering mode. 相似文献