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1. Cold sintering-enabled interface engineering of composites for solid-state batteries

   https://doi.org/10.3389/fenrg.2023.1149103  

   Nie, Bo; Liu, Tengxiao; Alcoutlabi, Mataz; Basu, Saurabh; Kumara, Soundar; Li, Mingxin; Lian, Jie; Sun, Hongtao (February 2023, Frontiers in Energy Research)

   The cold sintering process (CSP) is a low-temperature consolidation method used to fabricate materials and their composites by applying transient solvents and external pressure. In this mechano-chemical process, the local dissolution, solvent evaporation, and supersaturation of the solute lead to “solution-precipitation” for consolidating various materials to nearly full densification, mimicking the natural pressure solution creep. Because of the low processing temperature (<300°C), it can bridge the temperature gap between ceramics, metals, and polymers for co-sintering composites. Therefore, CSP provides a promising strategy of interface engineering to readily integrate high-processing temperature ceramic materials (e.g., active electrode materials, ceramic solid-state electrolytes) as “grains” and low-melting-point additives (e.g., polymer binders, lithium salts, or solid-state polymer electrolytes) as “grain boundaries.” In this minireview, the mechanisms of geomimetics CSP and energy dissipations are discussed and compared to other sintering technologies. Specifically, the sintering dynamics and various sintering aids/conditions methods are reviewed to assist the low energy consumption processes. We also discuss the CSP-enabled consolidation and interface engineering for composite electrodes, composite solid-state electrolytes, and multi-component laminated structure battery devices for high-performance solid-state batteries. We then conclude the present review with a perspective on future opportunities and challenges. 

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2. A new neural network approach to density calculation on ceramic materials

   https://doi.org/10.1142/S0217984921505497  

   Mitic, Vojislav V.; Ribar, Srdjan; Randjelovic, Branislav M.; Aleksic, Dejan; Fecht, Hans; Vlahovic, Branislav (January 2022, Modern Physics Letters B)

   The materials’ consolidation, especially ceramics, is very important in advanced research development and industrial technologies. Science of sintering with all incoming novelties is the base of all these processes. A very important question in all of this is how to get the more precise structure parameters within the morphology of different ceramic materials. In that sense, the advanced procedure in collecting precise data in submicro-processes is also in direction of advanced miniaturization. Our research, based on different electrophysical parameters, like relative capacitance, breakdown voltage, and [Formula: see text], has been used in neural networks and graph theory successful applications. We extended furthermore our neural network back propagation (BP) on sintering parameters’ data. Prognosed mapping we can succeed if we use the coefficients, implemented by the training procedure. In this paper, we continue to apply the novelty from the previous research, where the error is calculated as a difference between the designed and actual network output. So, the weight coefficients contribute in error generation. We used the experimental data of sintered materials’ density, measured and calculated in the bulk, and developed possibility to calculate the materials’ density inside of consolidated structures. The BP procedure here is like a tool to come down between the layers, with much more precise materials’ density, in the points on morphology, which are interesting for different microstructure developments and applications. We practically replaced the errors’ network by density values, from ceramic consolidation. Our neural networks’ application novelty is successfully applied within the experimental ceramic material density [Formula: see text] [kg/m 3 ], confirming the direction way to implement this procedure in other density cases. There are many different mathematical tools or tools from the field of artificial intelligence that can be used in such or similar applications. We choose to use artificial neural networks because of their simplicity and their self-improvement process, through BP error control. All of this contributes to the great improvement in the whole research and science of sintering technology, which is important for collecting more efficient and faster results. 

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3. Cold Sintering: Progress, Challenges, and Future Opportunities

   https://doi.org/10.1146/annurev-matsci-070218-010041  

   Guo, Jing; Floyd, Richard; Lowum, Sarah; Maria, Jon-Paul; Herisson de Beauvoir, Thomas; Seo, Joo-Hwan; Randall, Clive A. (July 2019, Annual Review of Materials Research)

   Cold sintering is an unusually low-temperature process that uses a transient transport phase, which is most often liquid, and an applied uniaxial force to assist in densification of a powder compact. By using this approach, many ceramic powders can be transformed to high-density monoliths at temperatures far below the melting point. In this article, we present a summary of cold sintering accomplishments and the current working models that describe the operative mechanisms in the context of other strategies for low-temperature ceramic densification. Current observations in several systems suggest a multiple-stage densification process that bears similarity to models that describe liquid phase sintering. We find that grain growth trends are consistent with classical behavior, but with activation energy values that are lower than observed for thermally driven processes. Densification behavior in these low-temperature systems is rich, and there is much to be investigated regarding mass transport within and across the liquid-solid interfaces that populate these ceramics during densification. Irrespective of mechanisms, these low temperatures create a new opportunity spectrum to design grain boundaries and create new types of nanocomposites among material combinations that previously had incompatible processing windows. Future directions are discussed in terms of both the fundamental science and engineering of cold sintering. 

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4. Cold Sintering of PZT 2-2 Composites for High Frequency Ultrasound Transducer Arrays

   https://doi.org/10.3390/act10090235  

   Gupta, Shruti; Wang, Dixiong; Shetty, Smitha; Meddeb, Amira; Dursun, Sinan; Randall, Clive A.; Trolier-McKinstry, Susan (September 2021, Actuators)

   Medical ultrasound and other devices that require transducer arrays are difficult to manufacture, particularly for high frequency devices (>30 MHz). To enable focusing and beam steering, it is necessary to reduce the center-to-center element spacing to half of the acoustic wavelength. Conventional methodologies prevent co-sintering ceramic–polymer composites due to the low decomposition temperatures of the polymer. Moreover, for ultrasound transducer arrays exceeding 30 MHz, methods such as dice-and-fill cannot provide the dimensional tolerances required. Other techniques in which the ceramic is formed in the green state often fail to retain the required dimensions without distortion on firing the ceramic. This paper explores the use of the cold sintering process to produce dense lead zirconate titanate (PZT) ceramics for application in high frequency transducer arrays. PZT–polymer 2-2 composites were fabricated by cold sintering tape cast PZT with Pb nitrate as a sintering aid and ZnO as the sacrificial layer. PZT beams of 35 μm width with ~5.4 μm kerfs were produced by this technique. The ZnO sacrificial layer was also found to serve as a liquid phase sintering aid that led to grain growth in adjacent PZT. This composite produced resonance frequencies of >17 MHz. 

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5. Additive Manufacturing and size-dependent mechanical properties of three-dimensional microarchitected, high-temperature ceramic metamaterials

   https://doi.org/https://doi.org/10.1557/jmr.2018.11  

   Cui, Huachen; Hensleigh, Ryan; Chen, Hongshun; and Zheng, Xiaoyu (February 2018, Journal of materials research)

   3D microarchitected metamaterials exhibit unique, desirable properties influenced by their small length scales and architected layout, unachievable by their solid counterparts and random cellular configurations. However, few of them can be used in high-temperature applications, which could benefit significantly from their ultra-lightweight, ultrastiff properties. Existing high-temperature ceramic materials are often heavy and difficult to process into complex, microscale features. Inspired by this limitation, we fabricated polymer-derived ceramic metamaterials with controlled solid strut size varying from 10-µm scale to a few millimeters with relative densities ranging from as low as 1 to 22%. We found that these high-temperature architected ceramics of identical 3D topologies exhibit size-dependent strength influenced by both strut diameter and strut length. Weibull theory is utilized to map this dependency with varying single strut volumes. These observations demonstrate the structural benefits of increasing feature resolution in additive manufacturing of ceramic materials. Through capitalizing upon the reduction of unit strut volumes within the architecture, high-temperature ceramics could achieve high specific strength with only fraction of the weight of their solid counterparts. 

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