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Experimental investigation on thermal properties of carbon nanotubes/zinc silicate composites prepared by powder processing

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DIAMOND AND RELATED MATERIALS 2023年第1期134卷

作者： Chan, Kar Fei Zaid, Mohd Hafiz Mohd Mamat, Md Shuhazlly Tanemura, Masaki Liza, Shahira Miyazaki, Hidetoshi Maruyama, Takahiro Sako, Katsuya Sharma, Kamal Prasad Osman, Nurul Huda Saat, Nor Kamilah Mazlan, Hazeem Ikhwan Yaakob, Yazid Univ Putra Malaysia Fac Sci Dept Phys Serdang 43400 Selangor Malaysia Nagoya Inst Technol Grad Sch Engn Dept Phys Sci & Engn Gokiso ChoShowa Ku Nagoya 4668555 Japan Univ Teknol Malaysia Malaysia Japan Int Inst Technol TriPrem I Kohza Kuala Lumpur 54100 Malaysia Meijo Univ Nanomat Res Ctr Tempaku Ku Nagoya 4688502 Japan Meijo Univ Dept Appl Chem Tempaku Ku Nagoya 4688502 Japan

Carbon nanotubes (CNTs) as fillers in ceramic matrix composites have been widely explored to enhance the thermal properties due to its excellent thermal transport mechanism. Zinc silicate (ZS) is a crystalline ceramic with good fluorescence properties but low thermal diffusivity and effusivity. The introduction of CNTs into ZS is a good approach to improve the thermal transport parameters of the ceramic. Carbon nanotubes/zinc silicate (CNTs/ZS) composites with various CNTs mass fractions, ranging from 0 to 3.0 wt%, were fabricated using a combination of powder processing and pressureless sintering. The measured surface hardness, alternating current (AC) conductivity and thermal diffusivity of CNTs-free ZS composites are 285 HV, 2.31 x 10(-7) Sm-1, and 0.25 mm(2)s(-1), respectively. Paradoxically, the composite's surface hardness and thermal diffusivity decreased by 90.3 % and 72.1 %, respectively, when 3.0 wt% CNTs were added, while the AC conductivity increased by 10(5) times. The reduced bulk density and the high degree of phonon scattering in grain boundaries led to a reduction in surface hardness and thermal diffusivity. In addition, the micro-morphology observations revealed that the CNTs aggregation rate increased proportionally with the CNTs mass fraction. The CNTs aggregation formed a soft phase at the composite's surface and a phonon scattering site, which further degraded the material's mechanical and thermal properties. The enhanced AC conductivity of the composites was attributable to the introduction of an efficient free electron flow path formed by the CNTs network. The combination technique of powder processing and pressureless sintering provided a fabrication route to prepare the CNTs/ZS composite with minimal complexity and expense. Through this fabrication method, the results allowed the CNTs-ceramic research path to be navigated in the better direction and served the scientific community in the development of micro-optoelectronic and passive heat

关键词： Carbon nanotubes Thermal diffusivity Zinc silicate Ceramic composites powder processing

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Entering a New Dimension in powder processing for Advanced Ceramics Shaping

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ADVANCED MATERIALS 2023年第8期35卷 2208653-2208653页

作者： Saenger, Johanna Christiane Pauw, Brian Richard Riechers, Birte Zocca, Andrea Rosalie, Julian Maass, Robert Sturm, Heinz Guenster, Jens BAM Fed Inst Mat Res & Testing Eichen 87 D-12205 Berlin Germany Univ Illinois Dept Mat Sci & Engn Urbana IL 61801 USA Tech Univ Berlin IWF Pascalstr 8-9 D-10587 Berlin Germany Tech Univ Clausthal Inst Nonmetall Mat D-38678 Clausthal Zellerfeld Germany

Filigree structures can be manufactured via two-photon polymerization (2PP) operating in the regime of nonlinear light absorption. For the first time, it is possible to apply this technique to the powder processing of ceramic structures with a feature size in the range of the critical defect sizes responsible for brittle fracture and, thus, affecting fracture toughness of high-performance ceramics. In this way, tailoring of advanced properties can be achieved already in the shaping process. Traditionally, 2PP relies on transparent polymerizable resins, which are diametrically opposed to the usually completely opaque ceramic resins and slurries. Here a transparent and photocurable suspension of nanoparticles (resin) with very high mass fractions of yttria-stabilized zirconia particles (YSZ) is presented. Due to the extremely well-dispersed nanoparticles, scattering of light can be effectively suppressed at the process-relevant wavelength of 800 nm. Sintered ceramic structures with a resolution of down to 500 nm are obtained. Even at reduced densities of 1-4 g cm(-3), the resulting compressive strength with 4.5 GPa is equivalent or even exceeding bulk monolithic yttria-stabilized zirconia. A ceramic metamaterial is born, where the mechanical properties of yttria-stabilized zirconia are altered by changing geometrical parameters, and gives access to a new class of ceramic materials.

关键词： ceramics meta materials powder processing transparency two-photon polymerization yttria-stabilized zirconia

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From a laboratory curiosity to a commercial powder processing plant-A personal perspective

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powder TECHNOLOGY 2023年 418卷

作者： Weimer, Alan W. Univ Colorado Boulder Dept Chem & Biol Engn Boulder CO 80309 USA

The commercial path is described for two new powder processing technologies that resulted in two new busi-nesses. Both developments started out as laboratory curiosities and had to overcome significant skepticism and technical and financial challenges along the way. One was an industrial endeavor with a major chemical com-pany to start a new business for the synthesis of advanced non-oxide powder materials using a newly discovered processing route. The other was an academic endeavor resulting in a spinoff company from the university lab, bootstrapping, merging, and finally making technology believers out of skeptics for the novel coating of particles to functionalize surfaces. Both represented significant advances in the two respective project areas. Key to both successes was an understanding of scientific and engineering fundamentals, intellectual property to protect the risk takers, and viable market opportunities for products providing for cost/performance advantages over the competition and lower cost products for the end-user. An inside perspective is provided for these two success stories with the hope that others with similar opportunities can plod forward in the face of similar inevitable headwinds. It's easy to quit and the road from a laboratory curiosity to a commercial process/product is not an easy one.

关键词： powder processing Commercialization Non-oxide Particle ALD Carbothermal reduction

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Optimizing the Design of an HF Plasma Discharge powder processing System for Enhanced Tail Flame Stabilization: A Mathematical Modeling Approach

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LOBACHEVSKII JOURNAL OF MATHEMATICS 2023年第11期44卷 5072-5094页

作者： Tsivilskiy, I. V. Kugurakova, V. V. Kazan Fed Univ Kazan 420008 Tatarstan Russia

A novel, self-consistentmodel for analyzing the electromagnetic and heat-mass transfer phenomena within a conducting gas has been developed. This model, although based on well-established Maxwell's and Navier-Stokes equations, is tailored for technological powder processing plasma system. The gas is treated as compressible, and its electrical conductivity, as well as radiative losses of hot plasma, are dependent on local temperature. Maxwell's equations are reformulated into a frequency domain equation using complex values of the magnetic vector potential. This equation is further split into real and imaginary parts, resulting in a system of coupled equations, which are discretized and solved in the ANSYS Fluent using the finite volume method through the user-defined scalar and user-defined functions application programming interface in C. This model operates allows for the calculation of temporal-spatial distributions of electromagnetic fields, temperature and velocity of gas flow with particles within the torch and cooling chamber. Simulation results firstly have revealed unwanted gas-driven effects, particularly in the form of vortices downstream of the plasma tail flame. These vortices negatively impact the predictability of particle synthesis and may trap particles, preventing them from following the desired temperature history. Given the primary application of plasmatron systems in the production and processing of metal powder materials for additive manufacturing, the goal is to optimize the cooling chamber's design. This aims to promote laminar gas flow inside the chamber and prevent particle deposition on its walls, thereby minimizing material losses. The calculations performed using this developed model enable the identification of adverse gas dynamic effects during particle synthesis. Based on a series of calculations, new design solutions have been proposed to mitigate these adverse effects. This work encompasses two approaches to shape optimization: auto

关键词： finite volume method Maxwell's and Navier-Stokes equations time-frequency domain inductively coupled discharge powder processing optimization

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Experimental investigation on powder processing and its flow properties of AlSi10Mg alloy with niobium carbide for additive manufacturing

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART E-JOURNAL OF PROCESS MECHANICAL ENGINEERING 2022年第4期236卷 1421-1429页

作者： Radhakrishnan, Raj Mohan Ramamoorthi, Venkatraman Srinivasan, Raghuraman Shanmugha Arts Sci Technol & Res Acad SASTRA Deem Sch Mech Engn Thanjavur 613401 Tamil Nadu India

In this study, aluminium-silicon alloy AlSi10Mg powder of spherical morphology was mixed with niobium carbide powder had irregular morphology in weight percentages of 2, 4, 6 and 8 and processed in a planetary ball mill apparatus. The optimal conditions for powder processing were a mixing time of 1.95 h and a speed of 71 RPM without milling balls. The use of milling balls was avoided to maintain the morphology of AlSi10Mg from degradation and improve the flowability of composite powder. To evaluate the flowability of processed powders, flow properties such as apparent density, tapped density, Hausner's ratio, Carr index, static angle of repose and Hall flow rate were determined. Selective laser melting was used to fabricate AlSi10Mg composite specimens with varying percentages of niobium carbide. Finally, at 6% niobium carbide, the selective laser melting cube specimen had a maximum relative density of 99.21%.

关键词： Alloy ceramic mixture morphology powder processing

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Focusing on powder processing in dry powder inhalation product development, manufacturing and performance

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INTERNATIONAL JOURNAL OF PHARMACEUTICS 2022年第0期614卷 121445-121445页

作者： Stegemann, Sven Faulhammer, Eva Pinto, Joana T. Paudel, Amrit Graz Univ Technol Inst Proc & Particle Engn Inffeldgasse 13 A-8010 Graz Austria Res Ctr Pharmaceut Engn GmbH Inffeldgasse 13 A-8010 Graz Austria

Dry powder inhalers (DPI) are well established products for the delivery of actives via the pulmonary route. Various DPI products are marketed or developed for the treatment of local lung diseases such as chronic obstructive pulmonary disease (COPD), asthma or cystic fibrosis as well as systemic diseases targeted through inhaled delivery (i.e. Diabetes Mellitus). One of the key prerequisites of DPI formulations is that the aerodynamic size of the drug particles needs to be below 5 mu m to enter deeply into the respiratory tract. These inherently cohesive inhalable size particles are either formulated as adhesive mixture with coarse carrier particles like lactose called carrier-based DPI or are formulated as free-flowing carrier-free particles (e.g. soft agglomerates, large hollow particles). In either case, it is common practice that drug and/or excipient particles of DPI for-mulations are obtained by processing API and API/excipients. The DPI manufacturing process heavily involves several particle and powder technologies such as micronization of the API, dry blending, powder filling and other particle engineering processes such as spray drying, crystallization etc. In this context, it is essential to thor-oughly understand the impact of powder/particle properties and processing on the quality and performance of the DPI formulations. This will enable prediction of the processability of the DPI formulations and controlling the manufacturing process so that meticulously designed formulations are able to be finally developed as the finished DPI dosage form. This article is intended to provide a concise account of various aspects of DPI powder pro-cessing, including the process understanding and material properties that are important to achieve the desired DPI product quality. Various endeavors of model informed formulation/process design and development for DPI powder and PAT enabled process monitoring and control are also discussed.

关键词： DPI powder processing Micronization powder filling powder-PAT Multi-scale modeling

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Ultrafine grained metals and metal matrix nanocomposites fabricated by powder processing and thermomechanical powder consolidation

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PROGRESS IN MATERIALS SCIENCE 2022年 123卷 100853-100853页

作者： Zhang, Deliang Northeastern Univ Sch Mat Sci & Engn Shenyang Peoples R China Northeastern Univ State Key Lab Rolling & Automat Shenyang Peoples R China

Ultrafine grained metals and metal matrix nanocomposites with enhanced strength and good tensile ductility for structural applications have been successfully fabricated by processing and thermomechanically consolidating powders and, in some cases, post-consolidation heat and thermomechanical treatments. This paper provides an overview of the substantial amount of research work mainly published by the author?s research groups rather than a comprehensive review of the vast amount of very active research work published in this area. The microstructures and tensile properties of the samples fabricated and the correlations between them strongly suggest that the synergistic effects of grain boundary strengthening and intragranular ceramic (and other hard) nanoparticles are highly desirable for significantly enhancing the tensile yield strength and maintaining generally good tensile ductility. The extra boundaries between hard regions and soft regions introduced by heterogeneous microstructure can further enhance the strength of the material without sacrificing tensile ductility by inducing back stress in the soft regions. However, these boundaries also induce forward stress in the hard regions which has a weakening effect on them and needs to be managed by dispersing nanoparticles in the hard regions or other means.

关键词： Ultrafine grained structure Metals and alloys Metal matrix nanocomposites powder processing powder consolidation Mechanical properties

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Unmasking hidden ignition sources: A new approach to finding extreme charge peaks in powder processing

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JOURNAL OF LOSS PREVENTION IN THE PROCESS INDUSTRIES 2024年 92卷

作者： Grosshans, Holger Xu, Wenchao Jantac, Simon Ozler, Gizem Wilms, Christoph Phys Tech Bundesanstalt PTB Braunschweig Germany Otto von Guericke Univ Inst Apparat & Environm Technol Magdeburg Germany

powders acquire a high electrostatic charge during transport and processing. Consequently, in the aftermath of dust explosions, electrostatic discharge is often suspected to be the ignition source. However, definite proof is usually lacking since the rise of electrostatic charge cannot be seen or smelled, and the explosion destroys valuable evidence. Moreover, conventional methods to measure the bulk charge of powder flows, such as the Faraday pail, provide only the aggregate charge for the entire particle ensemble. Our simulations show that, depending on the flow conditions, contacts between particles lead to bipolar charging. Bipolar charged powder remains overall neutral;thus, a Faraday pail detects no danger, even though individual particles are highly charged. To address this gap, we have developed a machine learning-enhanced measurement technology to resolve the powder charge spatially. The first measurements have revealed a critical discovery: a localized charge peak near the inner wall of the conveying duct that is 85 times higher than the average charge that would be measured by the Faraday pail. This finding underscores the possibility of extremely high local charges that can serve as ignition sources, even though they remain undetected by conventional measurement systems. Our new technology offers a solution by spatially resolving the charge distribution within powder flows, unmasking hidden ignition sources, and preventing catastrophic incidents in the industry.

关键词： Industrial explosions powder processing Electrostatics Measurement Simulation

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Strengthening bioceramic through an approach of powder processing

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ADVANCED powder TECHNOLOGY 2020年第10期31卷 4180-4186页

作者： Chang, Hao-Yu Chen, Ying-Cen Hsu, Pei-Yi Tuan, Wei-Hsing Kondo, Akira Kozawa, Takahiro Naito, Makio Natl Taiwan Univ Dept Mat Sci & Engn Taipei 106 Taiwan Natl Taiwan Univ Sci & Engn Dept Mat Sci & Engn Taipei 106 Taiwan Osaka Univ Joining & Welding Res Inst Osaka Japan

Bioactive ceramics, such as calcium phosphate and calcium sulfate, have gained attention with the increase of aged population. Contrast to bio-inert ceramics, such as alumina and zirconia, the strength of bioactive ceramics is much lower. The strength of calcium sulfate (CaSO4) is the lowest among all. In the present study, two approaches, involving the refinement of microstructure and the addition of nano-particles, are combined to enhance the strength. Various powder-processing treatments are adopted to facilitate these approaches. A pre-grinding treatment is applied first to reduce the matrix CaSO4 grain size. The nano-silica (SiO2) particles are then fixed onto the CaSO4 particles through an attrition milling process. The strength of CaSO4 is enhanced by 60% by adding only 1 mass% nano-SiO2 particles. The strength of the SiO2-CaSO4 composites follows the Orowan-Petch relationship, indicating that their strength is dominated by the flaws. The addition of nano-particles refines the matrix grain size, consequently, the flaw size. (C) 2020 The Society of powder Technology Japan. Published by Elsevier B.V. and The Society of powder Technology Japan. All rights reserved.

关键词： Bioceramic Strength powder processing Microstructure engineering Nano-particles

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Ultrafine grained metals and metal matrix nanocomposites fabricated by powder processing and thermomechanical powder consolidation

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PROGRESS IN MATERIALS SCIENCE 2021年 119卷 100796-100796页

作者： Zhang, Deliang Northeastern Univ Sch Mat Sci & Engn Shenyang Peoples R China Northeastern Univ State Key Lab Rolling & Automat Shenyang Peoples R China

关键词： Ultrafine grained structure Metals and alloys Metal matrix nanocomposites powder processing powder consolidation Mechanical properties

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