Functionally graded porous ceramics with dense surface layer produced by freeze-casting

2011 ◽  
Vol 37 (8) ◽  
pp. 3717-3722 ◽  
Author(s):  
Changqing Hong ◽  
Jiancong Du ◽  
Jun Liang ◽  
Xinghong Zhang ◽  
Jiecai Han
Keyword(s):  
Surface Layer ◽  
Porous Ceramics ◽  
Functionally Graded ◽  
Freeze Casting

Fabrication of α-TCP, HAp Functionally Graded Porous Beads

2008 ◽  
Vol 57 ◽  
pp. 135-138
Author(s):  
Yuji Kajihata ◽  
Teruo Asaoka ◽  
Katsuko S. Furukawa ◽  
Takashi Ushida ◽  
T. Tateishi
Keyword(s):  
Surface Layer ◽  
High Strength ◽  
Functionally Graded ◽  
The Body ◽  
Acid Solutions ◽  
Bioactive Material ◽  
Hydrolytic Reaction ◽  
Rate Of Absorption ◽  
Porous Beads ◽  
Good Cell

HAp (Hydroxyapatite) and α-TCP (alpha tribasic calcium phosphate) are non-toxic to human cells and, thus, have been studied for applications as biomaterials. HAp is a bioactive material that is not readily absorbed by the body; it offers both high strength and better tissueadhesive properties than α-TCP. In contrast, α-TCP is highly bioabsorbable; it is quickly absorbed by the body, and, therefore, for example, disappears before bone is completely replaced. If porous beads could be fabricated that would take advantage of the useful properties of α-TCP and HAp, they could be used as excellent scaffolds for cultivating cells. In the present study, ceramic beads with α-TCP at the center were fabricated and coated with a functionally graded film of HAp. A scaffold based on this configuration would be expected to have the following characteristics: good cell adhesion; strong beads; and a rate of absorption into the body that would be easy to control. In addition, to accelerate the formation of porous structure, some acid solutions were used to dissolve the beads surface layer and to penetrate pores toward inside of the bead. HAp formation through hydrolytic reaction seemed to be promoted by these acid solutions.

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.

Freeze casting of aqueous coal fly ash/alumina slurries for preparation of porous ceramics

2010 ◽  
Vol 71 (4) ◽  
pp. 503-506 ◽  
Author(s):  
Hyung Bin Ji ◽  
Won Young Kim ◽  
Tae Young Yang ◽  
Seog Young Yoon ◽  
Byung Kyu Kim ◽  
...  
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Porous Ceramics ◽  
Freeze Casting

Preparation, Microstructure and Properties of ZrO2 Gradient Porous Ceramics by Freeze-Casting Process

2015 ◽  
Vol 816 ◽  
pp. 226-230 ◽  
Author(s):  
Tao Tao Ai
Keyword(s):  
Electron Microscopy ◽  
Compressive Strength ◽  
Porous Structure ◽  
Cross Section ◽  
Lamellar Structure ◽  
Sintering Temperature ◽  
Casting Process ◽  
Porous Ceramics ◽  
Freeze Casting ◽  
Scanning Electron

The ZrO2gradient porous ceramics were prepared by a novel freeze-casting process. The porous structure of the ZrO2ceramics was investigated by scanning electron microscopy (SEM). And the porosity and compressive strength were also measured. Experimental results indicated that the porous structure of the specimens was remarkably affected by the sintering temperature. The dendritic pores were obtained after sintered at 1300 °C. The porosity and compressive strength of the specimen were 56.79% and 4.37 MPa, respectively. As the sintering temperature reached to 1500 °C, a lamellar structure was obtained on the cross-section of the specimen. Meanwhile, the porosity decreased to 26.77% and the compressive strength increased to 8.26 MPa. The ceramics can be divided subsequently into three distinctive zones along the solidification direction, i.e. lamellar zone, transition zone and cellular zone.

scholarly journals Potential of electrospun chitosan fibers as a surface layer in functionally graded GTR membrane for periodontal regeneration

2017 ◽  
Vol 33 (1) ◽  
pp. 71-83 ◽  
Author(s):  
Saad B. Qasim ◽  
Shariq Najeeb ◽  
Robin M. Delaine-Smith ◽  
Andrew Rawlinson ◽  
Ihtesham Ur Rehman
Keyword(s):  
Surface Layer ◽  
Periodontal Regeneration ◽  
Functionally Graded

Toughness Enhancement of Al2O3/Ce-TZP Functionally Graded Materials by Annealing in Inert Atmosphere

2005 ◽  
Vol 492-493 ◽  
pp. 699-704 ◽  
Author(s):  
Jef Vleugels ◽  
Chao Zhao ◽  
Omer Van der Biest
Keyword(s):  
Surface Layer ◽  
Functionally Graded Materials ◽  
Inert Atmosphere ◽  
Functionally Graded ◽  
Pressureless Sintering ◽  
Graded Materials ◽  
Gradient Layer ◽  
Annealing Cycle ◽  
Toughness Enhancement ◽  
Annealing Experiments

CeO2-stabilised ZrO2-based functionally graded materials (FGMs) can be successfully produced using electrophoretic deposition and pressureless sintering in air. A cylindrical Al2O3/ZrO2 FGM, for instance, shows an ideal structure for applications such as drill blanks. It has a central hole with a diameter less than 0.5 mm, a tough Ce-ZrO2 core with a diameter of about 3 mm, a gradient layer of about 1 mm, and a hard Al2O3-rich surface layer. The Ce-ZrO2 core shows a Vickers hardness between 10 and 11 GPa and an excellent toughness (>10 MPa m1/2). In the gradient layer, hardness and toughness vary continuously along the radius. The Al2O3-rich surface layer has a hardness of 15.2 GPa but a modest toughness of 2 MPa m1/2. Annealing experiments of the air-sintered FGM in inert atmosphere (Ar + 5 vol % N2) allows a significant toughness enhancement, especially in the surface layer (up to 8 MPa m1/2). The experimental results indicate that a proper controlled reduction of the Ce-TZP phase allows a modification of the toughness of the Ce-TZP phase. The influence of the annealing cycle on the properties of the FGM are reported and elucidated.

Suspension- and solution-based freeze casting for porous ceramics

2017 ◽  
Vol 32 (17) ◽  
pp. 3372-3382 ◽  
Author(s):  
Maninpat Naviroj ◽  
Peter W. Voorhees ◽  
Katherine T. Faber
Keyword(s):  
Porous Ceramics ◽  
Freeze Casting ◽  
Image Position

Abstract

scholarly journals Alumina Porous Ceramics Obtained by Freeze Casting: Structure and Mechanical Behaviour under Compression

Ceramics ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 83-97 ◽  
Author(s):  
Dominique Hautcoeur ◽  
Maurice Gonon ◽  
Carmen Baudin ◽  
Véronique Lardot ◽  
Anne Leriche ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Mechanical Behaviour ◽  
Volume Fraction ◽  
Mechanical Test ◽  
Porous Alumina ◽  
Microstructural Analysis ◽  
Porous Ceramics ◽  
Sem Analysis ◽  
Deformation Pattern ◽  
Freeze Casting

The aim of the work is to analyse the mechanical behaviour of anisotropic porous alumina ceramics processed by freeze casting (ice templating). The freeze cast specimens were characterised by a lamellar structure with ellipsoidal pore shape, with a size ranging from 6 to 42 µm and 13 to 300 µm for the minor and major axes, respectively, as a function of the freezing rate and the powder and binder contents. The pore volume fraction ranged from 40 to 57%. SEM analysis of the porous structures after the compression test showed a typical deformation pattern caused by the porosity gradient through the specimen, as determined by X-ray radiography. The apparent elastic modulus of the anisotropic porous alumina ranged from 0.2 to 14 GPa and the compressive strength from 6 to 111 MPa, varying as a function of the process parameters which determine the pore network characteristics. The relationships between stress-strain behaviour in compression and the microstructure and texture were established. An analytical model based on a Gibson and Ashby relationship was used and adapted from SEM microstructural analysis after a mechanical test in order to predict the compressive strength of processed anisotropic alumina.

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