scholarly journals Pore Architectures and Mechanical Properties of Porous α-SiAlON Ceramics Fabricated via Unidirectional Freeze Casting Based on Camphene-Templating

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 687 ◽  
Author(s):  
Zhaoping Hou ◽  
Feng Ye ◽  
Qiang Liu ◽  
Limeng Liu ◽  
Haiwei Jiang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Pore Size ◽  
Solid Loading ◽  
Solidification Velocity ◽  
Pore Morphology ◽  
Freeze Casting ◽  
Casting Method ◽  
Bottom Part ◽  
Different Parts ◽  
Freezing Direction

Porous α-SiAlON ceramics were fabricated using the camphene-based unidirectional freeze casting method, in which a gradient porous structure was formed as a result of the decreased solidification velocity in the freezing direction. Microstructure, porosity and pore size distribution of different parts of as-prepared samples were examined and compared, and correlated with their mechanical properties. For a given solid loading, the overall pore size and porosity of the top part were greater than those of the bottom part. Interestingly, despite its higher porosity, the flexural strength and fracture toughness of the top part were both higher than those of the bottom part, suggesting that apart from porosity, pore morphology and size affected mechanical properties of as-prepared porous α-SiAlON ceramics.

scholarly journals Radial-Concentric Freeze Casting Inspired by Porcupine Fish Spines

Ceramics ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 161-179 ◽  
Author(s):  
Frances Su ◽  
Joyce Mok ◽  
Joanna McKittrick
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Axial Compression ◽  
Porous Ceramics ◽  
Compressive Modulus ◽  
Splitting Tensile Strength ◽  
High Porosity ◽  
Freeze Casting ◽  
Casting Method ◽  
Multiphase Materials

Freeze casting is a technique used to manufacture porous ceramics with aligned microstructures. In conventional freeze casting, these microstructures are aligned along a single direction of freezing. However, a caveat to these ceramics has been their ensuing lack of strength and toughness due to their high porosity, especially in the direction orthogonal to the direction of alignment. In this work, a novel freezing casting method referred to as “radial-concentric freeze casting” is presented, which takes its inspiration from the radially and concentrically aligned structure of the defensive spines of the porcupine fish. The method builds off the radial freeze casting method, in which the microstructure is aligned radially, and imposes a concentric alignment. Axial compression and Brazilian tests were performed to obtain axial compressive strengths, axial compressive moduli, and splitting tensile strengths of freeze cast samples with and without epoxy infiltration. Notably, radial-concentric freeze cast samples had the greatest improvements in axial compressive modulus and splitting tensile strength with infiltration, when compared against the changes in mechanical properties of conventional and radial freeze cast ceramics with infiltration. These results provide further evidence for the importance of structure in multiphase materials and the possibility of enhancing mechanical properties through the controlled alignment of microstructures.

Microstructural and Mechanical Properties of Polymer-Based Scaffolds Reinforced by Hydroxyapatite

2007 ◽  
Vol 544-545 ◽  
pp. 765-768 ◽  
Author(s):  
Hyeong Ho Jin ◽  
Won Ki Lee ◽  
Hong Chae Park ◽  
Seog Young Yoon
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Yield Strength ◽  
Pore Size ◽  
Compressive Modulus ◽  
Precipitation Method ◽  
Pore Morphology ◽  
Composite Scaffolds ◽  
Co Precipitation

Various polymer-based scaffolds reinforced by the hydroxyapatite (HAp) for bone tissue engineering were successfully synthesized by in-situ co-precipitation method. The influence of HAp in composite scaffolds on the pore morphology, microstructure, and mechanical properties was investigated. The polymer-based scaffolds appeared to be macroporous and an interconnected open pore microstructure with pore size around 200 μm. The pore structure of the composite scaffolds was not much changed by the presence of HAp but the pore size of the composite scaffolds decreased with adding the HAp. The compressive modulus and yield strength of the polymer-based scaffolds improved by the presence of HAp.

Preparation of Oriented Porous Silicon Carbide Bodies by Freeze-Casting Process

2007 ◽  
Vol 280-283 ◽  
pp. 1287-1290 ◽  
Author(s):  
Jie Tang ◽  
Yu Feng Chen ◽  
Hua Wang ◽  
Hai Lin Liu ◽  
Qi Sheng Fan
Keyword(s):  
Silicon Carbide ◽  
Carbon Black ◽  
Pore Structure ◽  
Pore Size ◽  
Casting Process ◽  
Porous Ceramics ◽  
Solid Loading ◽  
Gradual Change ◽  
Freeze Casting ◽  
Freezing Condition

Porous ceramics green bodies of silicon carbide were formed by freeze-casting of silicon carbide/carbon black aqueous slurries in a mold where temperature distribution was controlled. The influence of solid loading on the pore structure of green bodies was investigated. Pore morphology of green bodies formed from slurries with various solid loading ranging from 25 to 50vol% experienced a gradual change. Appropriate solid loading of silicon carbide/carbon black slurry was concluded for fabrication of SiC ceramics with oriented pore structure. Two means were employed for changing ice crystallizing velocity, so that the influence of ice crystallizing velocity on pore size of green bodies was explored. It was concluded that pore size became larger under slow freezing condition, whereas smaller with the pre-cooling of silicon carbide/carbon black slurry.

scholarly journals Yttrium Oxide Freeze-Casts: Target Materials for Radioactive Ion Beams

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2864
Author(s):  
Eva Kröll ◽  
Miriana Vadalà ◽  
Juliana Schell ◽  
Simon Stegemann ◽  
Jochen Ballof ◽  
...  
Keyword(s):  
Pore Structure ◽  
Yttrium Oxide ◽  
Ion Beam ◽  
Isotope Separation ◽  
Target Material ◽  
Ion Beams ◽  
Radioactive Isotopes ◽  
Solid Loading ◽  
Radioactive Ion Beams ◽  
Freeze Casting

Highly porous yttrium oxide is fabricated as ion beam target material in order to produce radioactive ion beams via the Isotope Separation On Line (ISOL) method. Freeze casting allows the formation of an aligned pore structure in these target materials to improve the isotope release. Aqueous suspensions containing a solid loading of 10, 15, and 20 vol% were solidified with a unidirectional freeze-casting setup. The pore size and pore structure of the yttrium oxide freeze-casts are highly affected by the amount of solid loading. The porosity ranges from 72 to 84% and the crosslinking between the aligned channels increases with increasing solid loading. Thermal aging of the final target materials shows that an operation temperature of 1400 °C for 96 h has no significant effect on the microstructure. Thermo-mechanical calculation results, based on a FLUKA simulation, are compared to measured compressive strength and forecast the mechanical integrity of the target materials during operation. Even though they were developed for the particular purpose of the production of short-lived radioactive isotopes, the yttria freeze-cast scaffolds can serve multiple other purposes, such as catalyst support frameworks or high-temperature fume filters.

scholarly journals Enhancing Density-Based Mining Waste Alkali-Activated Foamed Materials Incorporating Expanded Cork

CivilEng ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 523-540
Author(s):  
Imed Beghoura ◽  
Joao Castro-Gomes
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Size ◽  
Physical And Mechanical Properties ◽  
Critical Parameters ◽  
Porous Structures ◽  
Foaming Agent ◽  
Al Powder ◽  
Highly Porous ◽  
Alkali Activated

This study focuses on the development of an alkali-activated lightweight foamed material (AA-LFM) with enhanced density. Several mixes of tungsten waste mud (TWM), grounded waste glass (WG), and metakaolin (MK) were produced. Al powder as a foaming agent was added, varying from 0.009 w.% to 0.05 w.% of precursor weight. Expanded granulated cork (EGC) particles were incorporated (10% to 40% of the total volume of precursors). The physical and mechanical properties of the foamed materials obtained, the effects of the amount of the foaming agent and the percentage of cork particles added varying from 10 vol.% to 40% are presented and discussed. Highly porous structures were obtained, Pore size and cork particles distribution are critical parameters in determining the density and strength of the foams. The compressive strength results with different densities of AA-LFM obtained by modifying the foaming agent and cork particles are also presented and discussed. Mechanical properties of the cured structure are adequate for lightweight prefabricated building elements and components.

scholarly journals The Effect of Stereocomplex Polylactide Particles on the Stereocomplexation of High Molecular Weight Polylactide Blends

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2018
Author(s):  
Muhammad Samsuri ◽  
Ihsan Iswaldi ◽  
Purba Purnama
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Nucleating Agent ◽  
Solution Casting ◽  
Casting Method ◽  
Crystalline Fraction ◽  
Crystalline Structures ◽  
Solution Casting Method

Stereocomplexation is one of several approaches for improving polylactide (PLA) properties. The high molecular weight of poly L-lactide (PLLA) and poly D-lactide (PDLA) homopolymers are a constraint during the formation of stereocomplex PLAs (s-PLAs). The presence of s-PLA particles in PLA PLLA/PDLA blends can initiate the formation of s-PLA crystalline structures. We used the solution casting method to study the utilization of s-PLA materials from high molecular weight PLLA/PDLA blends for increasing s-PLA formation. The s-PLA particles initiated the formation of high molecular weight PLLA/PDLA blends, obtaining 49.13% s-PLA and 44.34% of the total crystalline fraction. In addition, the mechanical properties were enhanced through s-PLA crystalline formation and the increasing of total crystallinity of the PLLA/PDLA blends. The s-PLA particles supported initiation for s-PLA formation and acted as a nucleating agent for PLA homopolymers. These unique characteristics of s-PLA particles show potential to overcome the molecular weight limitation for stereocomplexation of PLLA/PDLA blends.

scholarly journals Strength and Microscopic Damage Mechanism of Yellow Sandstone with Holes under Freezing and Thawing

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Huren Rong ◽  
Jingyu Gu ◽  
Miren Rong ◽  
Hong Liu ◽  
Jiayao Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Pore Size ◽  
Power Function ◽  
Damage Mechanism ◽  
Uniaxial Compression Test ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Microscopic Damage

In order to study the damage characteristics of the yellow sandstone containing pores under the freeze-thaw cycle, the uniaxial compression test of saturated water-stained yellow sandstones with different freeze-thaw cycles was carried out by rock servo press, the microstructure was qualitatively analyzed by Zeiss 508 stereo microscope, and the microdamage mechanism was quantitatively studied by using specific surface area and pore size analyzer. The mechanism of weakening mechanical properties of single-hole yellow sandstone was expounded from the perspective of microstructure. The results show the following. (1) The number of freeze-thaw cycles and single-pore diameter have significant effects on the strength and elastic modulus of the yellow sandstone; the more the freeze-thaw cycles and the larger the pore size, the lower the strength of the yellow sandstone. (2) The damage modes of the yellow sandstone containing pores under the freeze-thaw cycle are divided into five types, and the yellow sandstone with pores is divided into two areas: the periphery of the hole and the distance from the hole; as the number of freeze-thaw cycles increases, different regions show different microscopic damage patterns. (3) The damage degree of yellow sandstone is different with freeze-thaw cycle and pore size. Freeze-thaw not only affects the mechanical properties of yellow sandstone but also accelerates the damage process of pores. (4) The damage of the yellow sandstone by freeze-thaw is logarithmic function, and the damage of the yellow sandstone is a power function. The damage equation of the yellow sandstone with pores under the freezing and thawing is a log-power function nonlinear change law and presents a good correlation.

Preparation of Porous HA Bioceramics by Gelcasting and Pressureless Sintering

2011 ◽  
Vol 335-336 ◽  
pp. 1454-1458
Author(s):  
Jing Xian Zhang ◽  
Bi Qin Chen ◽  
Dong Liang Jiang ◽  
Qing Ling Lin ◽  
Zhong Ming Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Size ◽  
Pressureless Sintering ◽  
High Compressive Strength ◽  
Microstructure And Properties ◽  
Pmma Beads ◽  
Average Compressive Strength

In the present work, porous HA scaffolds with well controlled pore size, porosity and high compressive strength were prepared by aqueous gelcasting. PMMA beads with different size were used as the pore forming agent. The compositions, microstructure and properties of porous HA bioceramics were analyzed by XRD, SEM, Hg porosimetry etc. The mechanical properties were also tested. For scaffolds with the porosity as 70%, the average compressive strength was 11.9±1.7 MPa. Results showed that glecasting process can be used for the preparation of porous HA biomaterials with well controlled pore size and improved mechanical properties.

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