Functionally Gradient Materials

Rabin, B. H.; Shiota, Ichiro

doi:10.1557/s0883769400048855

Cited by 150 publications

(54 citation statements)

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“…A functionally graded material differs from a uniform composite in that it has varying composition and property from one side of the material to the other side, either continuously, or stepwise as in a layered structure [43,44]. Our simple bi-layer structure consisted of a first layer serving the function of macropores for cell infiltration and for rapid integration of the implant with the surrounding bone.…”

Section: Functionally Gradedmentioning

confidence: 99%

Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures

Burguera

Carey

2007

Biomaterials

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Calcium phosphate cement (CPC) is highly promising for clinical uses due to its in situ-setting ability, excellent osteoconductivity and bone-replacement capability. However, the low strength limits its use to non-load-bearing applications. The objectives of this study were to develop a layered CPC structure by combining a macroporous CPC layer with a strong CPC layer, and to investigate the effects of porosity and layer thickness ratios. The rationale was for the macroporous layer to accept tissue ingrowth, while the fiber-reinforced strong layer would provide the needed early-strength. A biopolymer chitosan was incorporated to strengthen both layers. Flexural strength, S (mean±sd; n = 6) of CPC-scaffold decreased from (9.7±1.2) to (1.8±0.3) MPa (p<0.05), when the porosity increased from 44.6% to 66.2%. However, with a strong-layer reinforcement, S increased to (25.2±6.7) and (10.0±1.4) MPa, respectively, at these two porosities. These strengths matched/exceeded the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. Relationships were established between S and the ratio of strong layer thickness/specimen thickness, a/h:S = (17.6 a/h +3.2) MPa. The scaffold contained macropores with a macropore length (mean±sd; n = 147) of (183 ±73) μm, suitable for cell infiltration and tissue ingrowth. Nano-sized hydroxyapatite crystals were observed to form the scaffold matrix of CPC with chitosan. In summary, a layered CPC implant, combining a macroporous CPC with a strong CPC, was developed. Mechanical strength and macroporosity are conflicting requirements. However, the novel functionally graded CPC enabled a relatively high strength and macroporosity to be simultaneously achieved. Such an in situ-hardening nano-apatite may be useful in moderate stress-bearing applications, with macroporosity to enhance tissue ingrowth and implant resorption.

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Section: Functionally Gradedmentioning

confidence: 99%

Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures

Burguera

Carey

2007

Biomaterials

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“…Th us, composites can be constituted in some cases of carbide ceramics, oxide ceramics and metals, and they can be used, for example in application at high temperatures such as in the construction of gas turbine engines in order to increase their thermal cycle effi ciency [4][5]. Th erein, the mechanical and physical properties of such type of composites have been studied, as well as their production processes [6][7][8]. In spite of this, the high temperature cementation of metal-dispersed carbide composites has not been investigated in detail and there are not suffi cient reports on the high temperature cementation of thermal barrier composite-coatings [9].…”

Section: Introductionmentioning

confidence: 99%

Alumina-based composites strengthened with titanium and titanium carbide dispersions

Rocha–Rangel¹,

Hernández-Silva²,

Térres‐Rojas³

et al. 2010

Epitoanyag-JSBCM

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The synthesis of Al 2 O 3 -based composites having different amount of fine titanium and titaniumdispersed carbide reinforcement-particles has been explored. Two experimental steps have been set for the synthesis; namely, solid sintering of Al 2 O 3 -titanium powders which were thoroughly mixed under high energy ball-milling, pressureless-sintered and then for the second step it was induced formation of titanium carbide at 500 °C by the cementation packing process. SEM analyses of the microstructures obtained in cemented bodies were performed in order to know the effect of the activated carbon used as cementant on the microstructure of titanium for each studied composite. It was observed that a titanium carbide layer growth from the surface into the bulk and reaches different depth as the titanium content in the composites was increased. The use of reinforcing titanium significantly enhanced density level and fracture toughness of the composites.

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“…3 Indeed such materials were mainly designed for increased resistance to thermal stresses. The different methods known to produce gradient materials can be classified in two categories: constructive processes and transport based processes.…”

Section: Introductionmentioning

confidence: 99%

Gradient porosity poly(dicyclopentadiene)

Martina

Hilborn

2001

J. Mater. Res.

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This article describes the preparation of gradient porosity thermoset polymers. The technique used is based on polymerizing a solution of cross-linkable dicyclopentadiene and 2-propanol. The forming polymer being insoluble in 2-propanol, phase separation occurs. Subsequent drying of the 2-propanol gives porosities up to 80%. An apparatus was built to produce a gradient in 2-propanol concentration in a flask, resulting in polymerized gradient porosity rods. The resulting materials have been characterized by scanning electron microscopy (SEM) and density measurements. A mathematical model which allows prediction of the gradient produced is also presented.

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Functionally Gradient Materials

Cited by 150 publications

References 0 publications

Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures

Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures

Alumina-based composites strengthened with titanium and titanium carbide dispersions

Gradient porosity poly(dicyclopentadiene)

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