Metallic porous materials have many interesting combinations of physical and geometrical properties with very low specific weight or high gas permeability. In this study, highly porous Cu foam is successfully fabricated by a slurry coating process. The Cu foam is fabricated specifically by changing the coating amount and the type of polyurethane foam used as a template. The processing parameters and pore characteristics are observed to identify the key parameters of the slurry coating process and the optimized morphological properties of the Cu foam. The pore characteristics of Cu foam are investigated by scanning electron micrographs and micro-CT analyzer, and air permeability of the Cu foam is measured by capillary flow porometer. We confirmed that the characteristics of Cu foam can be easily controlled in the slurry coating process by changing the microstructure, porosity, pore size, strut thickness, and the cell size. It can be considered that the fabricated Cu foams show tremendous promise for industrial application.

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• Preparation and comparative evolution of mechanical behavior of Fe and Fe2O3 foams and their polymer composites
  Vemoori Raju, Roy Johnson, Asit Kumar Khanra
  Journal of Alloys and Compounds.2018; 750: 71.     CrossRef

This study investigated the microstructure and tensile properties of a recently made block-type Ni-Cr-Al powder porous material. The block-type powder porous material was made by stacking multiple layers of powder porous thin plates with post-processing such as additional compression and sintering. This study used block-type powder porous materials with two different cell sizes: one with an average cell size of 1,200 μm (1200 foam) and the other with an average cell size of 3,000 μm (3000 foam). The γ-Ni and γ’-Ni₃Al were identified as the main phases of both materials. However, in the case of the 1,200 foam, a β-NiAl phase was additionally observed. The relative density of each block-type powder porous material, with 1200 foam and 3000 foam, was measured to be 5.78% and 2.93%, respectively. Tensile tests were conducted with strain rates of 10⁻²~10⁻⁴ sec⁻¹. The test result showed that the tensile strength of the 1,200 foam was 6.0~7.1 MPa, and that of 3,000 foam was 3.0~3.3 MPa. The elongation of the 3,000 foam was higher (~9%) than that (~2%) of the 1,200 foam. This study also discussed the deformation behavior of block-type powder porous material through observations of the fracture surface, with the results above.

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• Effect of Strut Thickness on Room and High Temperature Compressive Properties of Block-Type Ni-Cr-Al Powder Porous Metals
  B.-H. Kang, M.-H. Park, K.-A. Lee
  Archives of Metallurgy and Materials.2017; 62(2): 1329.     CrossRef
• Fabrication and Shape Memory Characteristics of Highly Porous Ti-Nb-Mo Biomaterials
  Y.-W. Kim, T.W. Mukarati
  Archives of Metallurgy and Materials.2017; 62(2): 1367.     CrossRef

The porous metals are known as relatively excellent characteristic such as large surface area, light, lower heat capacity, high toughness and permeability. The Fe-Cr-Al alloys have high corrosion resistance, heat resistance and chemical stability for high temperature applications. And then many researches are developed the Fe-Cr-Al porous metals for exhaust gas filter, hydrogen reformer catalyst support and chemical filter. In this study, the Fe-Cr-Al porous metals are developed with Fe-22Cr-6Al(wt) powder using powder compaction method. The mean size of Fe-22Cr-6Al(wt) powders is about 42.69 μm. In order to control pore size and porosity, Fe-Cr-Al powders are sintered at 1200~1450°C and different sintering maintenance as 1~4 hours. The powders are pressed on disk shapes of 3 mm thickness using uniaxial press machine and sintered in high vacuum condition. The pore properties are evaluated using capillary flow porometer. As sintering temperature increased, relative density is increased from 73% to 96% and porosity, pore size are decreased from 27 to 3.3%, from 3.1 to 1.8 μm respectively. When the sintering time is increased, the relative density is also increased from 76.5% to 84.7% and porosity, pore size are decreased from 23.5% to 15.3%, from 2.7 to 2.08 μm respectively.

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• Fabrication of a Porous Ni-Based Metal with a Multi-pore Structure by a Screen Printing Process
  Yu-Jeong Yi, Min-Jeong Lee, Jung-Yeul Yun, Byoung-Kee Kim
  Metals and Materials International.2019; 25(5): 1272.     CrossRef

In this study, effect of core-shell structure on compaction behavior of harmonic powder is investigated. Harmonic powders are made by electroless plating method on Fe powders. Softer Cu shell encloses harder Fe core, and the average size of Fe core and thickness of Cu shell are 34.3 μm and 3.2 μm, respectively. The powder compaction procedure is processed with pressure of 600 MPa in a cylindrical die. Due to the low strength of Cu shell regions, the harmonic powders show better densification behavior compared with pure Fe powders. Finite element method (FEM) is performed to understand the roll of core-shell structure. Based on stress and strain distributions of FEM results, it is concluded that the early stage of powder compaction of harmonic powders mainly occurs at the shell region. FEM results also well predict porosity of compacted materials.

This study investigates the microstructure and thermal shock properties of polycrystalline diamond compact (PDC) produced by the high-temperature, high-pressure (HPHT) process. The diamond used for the investigation features a 12~22 μm- and 8~16 μm-sized main particles, and 1~2 μm-sized filler particles. The filler particle ratio is adjusted up to 5~31% to produce a mixed particle, and then the tap density is measured. The measurement finds that as the filler particle ratio increases, the tap density value continuously increases, but at 23% or greater, it reduces by a small margin. The mixed particle described above undergoes an HPHT sintering process. Observation of PDC microstructures reveals that the filler particle ratio with high tap density value increases direct bonding among diamond particles, Co distribution becomes even, and the Co and W fraction also decreases. The produced PDC undergoes thermal shock tests with two temperature conditions of 820 and 830, and the results reveals that PDC with smaller filler particle ratio and low tap density value easily produces cracks, while PDC with high tap density value that contributes in increased direct bonding along with the higher diamond content results in improved thermal shock properties.

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• HPHT sintering and performance investigation of PDC with different interfacial geometry substrates for trimodal diamond particle size
  Jianbo Tu, Xueqi Wang, Haibo Zhang, Baochang Liu
  Ceramics International.2024;[Epub]     CrossRef

WS₂-W-WC embedded carbon nanofiber composites were fabricated by using electrospinning method for use in high-performance supercapacitors. In order to obtain optimum electrochemical properties for supercapacitors, WS₂ nanoparticles were used as precursors and the amounts of WS₂ precursors were controlled to 4 wt% (sample A) and 8 wt% (sample B). The morphological, structural, and chemical properties of all samples were investigated by means of field emission photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. These results demonstrated that the embedded phases of samples A and B were changed from WS₂ to WS₂-W-WC through carbothermal reaction during carbonization process. In particular, sample B presented high specific capacitance (~119.7 F/g at 5 mV/s), good high-rate capacitance (~60.5%), and superb cycleability. The enhanced electrochemical properties of sample B were explained by the synergistic effect of the using 1-D structure supports, increase of specific surface area, and improved conductivity from formation of W and WC phases.

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• WS2 Nanoparticles Embedded in Carbon Nanofibers for a Pseudocapacitor
  Ki-Wook Sung, Jung Soo Lee, Tae-Kum Lee, Hyo-Jin Ahn
  Korean Journal of Materials Research.2021; 31(8): 458.     CrossRef

In this study, titanium(Ti) meshes and porous bodies are employed to synthesize carbon nanotubes(CNTs) using methane(CH₄) gas and camphene solution, respectively, by chemical vapor deposition. Camphene is impregnated into Ti porous bodies prior to heating in a furnace. Various microscopic and spectroscopic techniques are utilized to analyze CNTs. It is found that CNTs are more densely and homogeneously populated on the camphene impregnated Ti-porous bodies as compared to CNTs synthesized with methane on Ti-porous bodies. It is elucidated that, when synthesized with methane, few CNTs are formed inside of Ti porous bodies due to methane supply limited by internal structures of Ti porous bodies. Ti-meshes and porous bodies are found to be multi-walled with high degree of structural disorders. These CNTs are expected to be utilized as catalyst supports in catalytic filters and purification systems.

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• Solvent induced surface modifications on hydrogen storage performance of ZnO nanoparticle decorated MWCNTs
  Madhavi Konni, Anima S. Dadhich, Saratchandra Babu Mukkamala
  Sustainable Energy & Fuels.2018; 2(2): 466.     CrossRef
• Influence of nickel nanoparticles on hydrogen storage behaviors of MWCNTs
  Ye-Ji Han, Soo-Jin Park
  Applied Surface Science.2017; 415: 85.     CrossRef

Porous W with controlled pore structure was fabricated by thermal decomposition and hydrogen reduction process of PMMA beads and WO₃ powder compacts. The PMMA sizes of 8 and 50 μm were used as pore forming agent for fabricating the porous W. The WO₃ powder compacts with 20 and 70 vol% PMMA were prepared by uniaxial pressing and sintered for 2 h at 1200°C in hydrogen atmosphere. TGA analysis revealed that the PMMA was decomposed at about 400°C and WO₃ was reduced to metallic W at 800°C. Large pores in the sintered specimens were formed by thermal decomposition of spherical PMMA, and their size was increased with increase in PMMA size and the amount of PMMA addition. Also the pore shape was changed from spherical to irregular form with increasing PMMA contents due to the agglomeration of PMMA in the powder mixing process.

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• Synthesis of Porous Silica Particles Using Sodium Silicate Precursor for Water-Repellent Surfaces
  Young-Sang Cho, Nahee Ku, Young-Seok Kim
  JOURNAL OF CHEMICAL ENGINEERING OF JAPAN.2019; 52(2): 194.     CrossRef

The monolayer engineering diamond particles are aligned on the oxygen free Cu plates with electroless Ni plating layer. The mean diamond particle sizes of 15, 23 and 50 μm are used as thermal conductivity pathway for fabricating metal/carbon multi-layer composite material systems. Interconnected void structure of irregular shaped diamond particles allow dense electroless Ni plating layer on Cu plate and fixing them with 37-43% Ni thickness of their mean diameter. The thermal conductivity decrease with increasing measurement temperature up to 150°C in all diamond size conditions. When the diamond particle size is increased from 15 μm to 50 μm (Max. 304 W/mK at room temperature) tended to increase thermal conductivity, because the volume fraction of diamond is increased inside plating layer.

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• Effect of heat treatment on corrosion resistance and adhesion property in Zn-Mg-Zn multi-layer coated steel prepared by PVD process
  Jong Min Byun, Su-Ryong Bang, Hyun Woo Kim, Tae-Yeob Kim, Suk-Jun Hong, Young Do Kim
  Surface and Coatings Technology.2017; 309: 1010.     CrossRef
• High-temperature thermo-mechanical behavior of functionally graded materials produced by plasma sprayed coating: Experimental and modeling results
  Kang Hyun Choi, Hyun-Su Kim, Chang Hyun Park, Gon-Ho Kim, Kyoung Ho Baik, Sung Ho Lee, Taehyung Kim, Hyoung Seop Kim
  Metals and Materials International.2016; 22(5): 817.     CrossRef