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Frank W. Zok - One of the best experts on this subject based on the ideXlab platform.

  • strength and notch sensitivity of Porous Matrix oxide composites
    Journal of the American Ceramic Society, 2005
    Co-Authors: Michael A. Mattoni, Frank W. Zok
    Abstract:

    The effects of Matrix strength on the notched and unnotched tensile properties of a family of Porous-Matrix oxide composites are examined both experimentally and theoretically. Experiments are performed on three composites, distinguished from one another by the amount of binding alumina within the Matrix. Increases in alumina concentration produce elevations in unnotched tensile and shear strengths, but the benefits are offset by an increase in notch sensitivity. The degree of notch sensitivity is rationalized on the basis of a model that accounts for interactions between notch tip tensile and shear bands. The model predictions are cast in terms of the ratio of the notch length to a characteristic bridging length scale. These results, in turn, form the basis for a simple analytical formula for notched strength, accounting for effects of elastic anisotropy and finite sample size. The utility of this formula in predicting notched strength is assessed. Issues associated with bridging law shapes and bridging length scales are addressed. The effect of alumina concentration on notch sensitivity is discussed in terms of its influence on the bridging length scale, dictated by the interplay between the unnotched tensile strength, the longitudinal Young's modulus, the degree of in-plane elastic anisotropy, and the fracture energy. The net result is a decreasing bridging length scale and hence increasing notch sensitivity as the Matrix is strengthened with alumina.

  • effects of Matrix porosity on the mechanical properties of a Porous Matrix all oxide ceramic composite
    Journal of the American Ceramic Society, 2001
    Co-Authors: Michael A. Mattoni, James Y. Yang, Carlos G Levi, J. Yang, Frank W. Zok
    Abstract:

    The effects of Matrix porosity on the mechanical properties of an all-oxide ceramic composite are investigated. The porosity is varied through impregnation and pyrolysis of a ceramic precursor solution. Mechanical tests are performed to assess the role of the Matrix in both Matrix-dominated and fiber-dominated loading configurations. The results demonstrate a loss in damage tolerance and tensile strength along the fiber direction as the porosity is reduced. Concomitantly, some improvements in interlaminar strength are obtained. The latter improvements are found to be difficult to quantify over the entire porosity range using the standard short beam shear method, a consequence of the increased propensity for tensile fracture as the porosity is reduced. Measurements of interlaminar shear strength based on the double-notched shear specimen are broadly consistent with the limited values obtained by the short beam shear method, although the former exhibit large variability. In addition, effects of precursor segregation during drying on through-thickness gradients in Matrix properties and their role in composite performance are identified and discussed. An analysis based on the mechanics of crack deflection and penetration at an interphase boundary is presented and used to draw insights regarding the role of Matrix properties in enabling damage tolerance in Porous-Matrix composites. Deficiencies in the understanding of the mechanisms that enable damage tolerance in this class of composites are discussed.

  • microstructural design of stable Porous matrices for all oxide ceramic composites
    Zeitschrift Fur Metallkunde, 1999
    Co-Authors: Carlos G Levi, Frank W. Zok, Michael A. Mattoni, J. Yang, J P A Lofvander
    Abstract:

    A nonconventional paradigm for enabling damage tolerance in all-oxide ceramic composites is examined. The strategy is based on the use of a Porous Matrix for crack deflection and frictional dissipation, obviating the need for the debonding interphases used in the more conventional materials. The principles guiding the microstructural design are reviewed, and the different design concepts are compared and contrasted. The discussion focuses on a microstructural design concept that affords stability of the Porous structure, and hence preserves the damage tolerance properties, upon prolonged exposure to high temperature. The key feature of the design is the use of two particulate oxide constituents, in different size scales and with distinctly different sintering kinetics, to form the Porous Matrix. The implementation of the concept is described, with emphasis on the factors that influence the scale and uniformity of distribution of the porosity and their relationship with the process. The resulting material is shown to achieve the design goals in terms of its damage tolerance characteristics, as well as its long-term stability at temperatures up to 1200°C. It is anticipated that the concept can be extended to higher temperatures once fibers with improved capabilities become available.

A K Bajpai - One of the best experts on this subject based on the ideXlab platform.

  • designing of hydroxyapatite gelatin based Porous Matrix as bone substitute correlation with biocompatibility aspects
    Express Polymer Letters, 2008
    Co-Authors: H Bundela, A K Bajpai
    Abstract:

    In the present study polyacrylamide (PAm)-gelatin-hydroxyapatite (HA) composites have been synthesized by suspension polymerization method. The prepared composites were characterized by Fourier transform spectroscopy (FTIR) which revealed the presence of functional groups in the composite. The X-ray diffraction (XRD) studies indicated that HA powder was present in nano size. Thermogravimetric analysis (TGA) revealed that composite is more thermally stable than the polymer Matrix alone. The morphology of composite studied by optical microscopy (OPM) and scanning electron microscopy (SEM) suggested that pore size was between 3-20 μm. The composites showed adequately good mechanical properties as evident from the varying compressive strength and modulus in the range 31.57±8.16 MPa and 745±388 MPa, respectively. The water sorption behavior was found to be dependent on the chemical composition of the Matrix and the sorption data were used to calculate network parameters. The porosity of composite varied between 4 to 30.66%.The in vitro blood compatibility indicated that the adsorption of bovine serum albumin (BSA) varied from 0.11 to 0.24 mg·g -1 , the percentage haemolysis was between 2.4 to 6.9% and the weight of blood clot formed on the composite surfaces were found in the range 11 to 52 mg.

  • designing of hydroxyapatite gelatin based Porous Matrix as bone substitute correlation with biocompatibility aspects
    Express Polymer Letters, 2008
    Co-Authors: H Bundela, A K Bajpai
    Abstract:

    In the present study polyacrylamide (PAm)-gelatin-hydroxyapatite (HA) composites have been synthesized by suspension polymerization method. The prepared composites were characterized by Fourier transform spectroscopy (FTIR) which revealed the presence of functional groups in the composite. The X-ray diffraction (XRD) studies indicated that HA powder was present in nano size. Thermogravimetric analysis (TGA) revealed that composite is more thermally stable than the polymer Matrix alone. The morphology of composite studied by optical microscopy (OPM) and scanning electron microscopy (SEM) suggested that pore size was between 3-20 μm. The composites showed adequately good mechanical properties as evident from the varying compressive strength and modulus in the range 31.57±8.16 MPa and 745±388 MPa, respectively. The water sorption behavior was found to be dependent on the chemical composition of the Matrix and the sorption data were used to calculate network parameters. The porosity of composite varied between 4 to 30.66%.The in vitro blood compatibility indicated that the adsorption of bovine serum albumin (BSA) varied from 0.11 to 0.24 mg·g -1 , the percentage haemolysis was between 2.4 to 6.9% and the weight of blood clot formed on the composite surfaces were found in the range 11 to 52 mg.

Yuri I. Aristov - One of the best experts on this subject based on the ideXlab platform.

  • thermal conductivity of composite sorbents salt in Porous Matrix for heat storage and transformation
    Applied Thermal Engineering, 2013
    Co-Authors: Yuri Yu Tanashev, Alexandr V Krainov, Yuri I. Aristov
    Abstract:

    Abstract The thermal conductivity of composites “inorganic salt in Porous Matrix” was measured as function of the water uptake w by a “hot wire” method. Three hygroscopic salts (CaCl2, MgCl2, LiBr) were confined to the pores of a commercial KSK silica gel. For CaCl2, an alumina was used as host Matrix, too. Similar dependencies λ(w) were found for the three silica based sorbents: a smooth rise at w   ν* the solution starts to leak out of the pores to form a liquid film on the external surface of silica particles that strongly facilitates the heat transfer between adjacent particles and enhances the heat conductivity of the whole bed. No such threshold behaviour was found for CaCl2/alumina composites. The data obtained can be used for analysing open and closed adsorptive units for heat transformation, gas drying, extraction of potable water from the atmosphere, etc. For user friendliness, the experimental λ(w)-dependences were approximated by polynomial equations.

  • Composites "binary salts in Porous Matrix" for adsorption heat transformation
    Applied Thermal Engineering, 2013
    Co-Authors: Larisa G. Gordeeva, Alexandra D. Grekova, Tamara Krieger, Yuri I. Aristov
    Abstract:

    A family of Composites “Salt inside Porous Matrix” (CSPM) has been considered as promising for adsorption heat transformation (AHT) due to their high sorption capacity, steep sorption isobars and opportunity to harmonize CSPM properties with boundary conditions of the AHT cycle. In this communication, we extend the harmonizing tools by confinement of one more salt to the Matrix pores. Novel CSPMs based on a binary mixture of lithium, calcium, and barium halides inside various mesoPorous matrices were synthesized with wide variation of the relative salts content. Their phase composition and sorption equilibrium with water, methanol and ammonia vapour were studied by XRD and TG techniques. It was shown that the formation of a homogeneous solid solution of the salts led to changing the equilibrium temperature (pressure) of the solvation. Thus, the confinement of binary salt systems to the Matrix pores can be an effective tool for designing innovative materials with predetermined sorption properties adapted to particular AHT cycles.

Michael A. Mattoni - One of the best experts on this subject based on the ideXlab platform.

  • strength and notch sensitivity of Porous Matrix oxide composites
    Journal of the American Ceramic Society, 2005
    Co-Authors: Michael A. Mattoni, Frank W. Zok
    Abstract:

    The effects of Matrix strength on the notched and unnotched tensile properties of a family of Porous-Matrix oxide composites are examined both experimentally and theoretically. Experiments are performed on three composites, distinguished from one another by the amount of binding alumina within the Matrix. Increases in alumina concentration produce elevations in unnotched tensile and shear strengths, but the benefits are offset by an increase in notch sensitivity. The degree of notch sensitivity is rationalized on the basis of a model that accounts for interactions between notch tip tensile and shear bands. The model predictions are cast in terms of the ratio of the notch length to a characteristic bridging length scale. These results, in turn, form the basis for a simple analytical formula for notched strength, accounting for effects of elastic anisotropy and finite sample size. The utility of this formula in predicting notched strength is assessed. Issues associated with bridging law shapes and bridging length scales are addressed. The effect of alumina concentration on notch sensitivity is discussed in terms of its influence on the bridging length scale, dictated by the interplay between the unnotched tensile strength, the longitudinal Young's modulus, the degree of in-plane elastic anisotropy, and the fracture energy. The net result is a decreasing bridging length scale and hence increasing notch sensitivity as the Matrix is strengthened with alumina.

  • effects of Matrix porosity on the mechanical properties of a Porous Matrix all oxide ceramic composite
    Journal of the American Ceramic Society, 2001
    Co-Authors: Michael A. Mattoni, James Y. Yang, Carlos G Levi, J. Yang, Frank W. Zok
    Abstract:

    The effects of Matrix porosity on the mechanical properties of an all-oxide ceramic composite are investigated. The porosity is varied through impregnation and pyrolysis of a ceramic precursor solution. Mechanical tests are performed to assess the role of the Matrix in both Matrix-dominated and fiber-dominated loading configurations. The results demonstrate a loss in damage tolerance and tensile strength along the fiber direction as the porosity is reduced. Concomitantly, some improvements in interlaminar strength are obtained. The latter improvements are found to be difficult to quantify over the entire porosity range using the standard short beam shear method, a consequence of the increased propensity for tensile fracture as the porosity is reduced. Measurements of interlaminar shear strength based on the double-notched shear specimen are broadly consistent with the limited values obtained by the short beam shear method, although the former exhibit large variability. In addition, effects of precursor segregation during drying on through-thickness gradients in Matrix properties and their role in composite performance are identified and discussed. An analysis based on the mechanics of crack deflection and penetration at an interphase boundary is presented and used to draw insights regarding the role of Matrix properties in enabling damage tolerance in Porous-Matrix composites. Deficiencies in the understanding of the mechanisms that enable damage tolerance in this class of composites are discussed.

  • microstructural design of stable Porous matrices for all oxide ceramic composites
    Zeitschrift Fur Metallkunde, 1999
    Co-Authors: Carlos G Levi, Frank W. Zok, Michael A. Mattoni, J. Yang, J P A Lofvander
    Abstract:

    A nonconventional paradigm for enabling damage tolerance in all-oxide ceramic composites is examined. The strategy is based on the use of a Porous Matrix for crack deflection and frictional dissipation, obviating the need for the debonding interphases used in the more conventional materials. The principles guiding the microstructural design are reviewed, and the different design concepts are compared and contrasted. The discussion focuses on a microstructural design concept that affords stability of the Porous structure, and hence preserves the damage tolerance properties, upon prolonged exposure to high temperature. The key feature of the design is the use of two particulate oxide constituents, in different size scales and with distinctly different sintering kinetics, to form the Porous Matrix. The implementation of the concept is described, with emphasis on the factors that influence the scale and uniformity of distribution of the porosity and their relationship with the process. The resulting material is shown to achieve the design goals in terms of its damage tolerance characteristics, as well as its long-term stability at temperatures up to 1200°C. It is anticipated that the concept can be extended to higher temperatures once fibers with improved capabilities become available.

H Bundela - One of the best experts on this subject based on the ideXlab platform.

  • designing of hydroxyapatite gelatin based Porous Matrix as bone substitute correlation with biocompatibility aspects
    Express Polymer Letters, 2008
    Co-Authors: H Bundela, A K Bajpai
    Abstract:

    In the present study polyacrylamide (PAm)-gelatin-hydroxyapatite (HA) composites have been synthesized by suspension polymerization method. The prepared composites were characterized by Fourier transform spectroscopy (FTIR) which revealed the presence of functional groups in the composite. The X-ray diffraction (XRD) studies indicated that HA powder was present in nano size. Thermogravimetric analysis (TGA) revealed that composite is more thermally stable than the polymer Matrix alone. The morphology of composite studied by optical microscopy (OPM) and scanning electron microscopy (SEM) suggested that pore size was between 3-20 μm. The composites showed adequately good mechanical properties as evident from the varying compressive strength and modulus in the range 31.57±8.16 MPa and 745±388 MPa, respectively. The water sorption behavior was found to be dependent on the chemical composition of the Matrix and the sorption data were used to calculate network parameters. The porosity of composite varied between 4 to 30.66%.The in vitro blood compatibility indicated that the adsorption of bovine serum albumin (BSA) varied from 0.11 to 0.24 mg·g -1 , the percentage haemolysis was between 2.4 to 6.9% and the weight of blood clot formed on the composite surfaces were found in the range 11 to 52 mg.

  • designing of hydroxyapatite gelatin based Porous Matrix as bone substitute correlation with biocompatibility aspects
    Express Polymer Letters, 2008
    Co-Authors: H Bundela, A K Bajpai
    Abstract:

    In the present study polyacrylamide (PAm)-gelatin-hydroxyapatite (HA) composites have been synthesized by suspension polymerization method. The prepared composites were characterized by Fourier transform spectroscopy (FTIR) which revealed the presence of functional groups in the composite. The X-ray diffraction (XRD) studies indicated that HA powder was present in nano size. Thermogravimetric analysis (TGA) revealed that composite is more thermally stable than the polymer Matrix alone. The morphology of composite studied by optical microscopy (OPM) and scanning electron microscopy (SEM) suggested that pore size was between 3-20 μm. The composites showed adequately good mechanical properties as evident from the varying compressive strength and modulus in the range 31.57±8.16 MPa and 745±388 MPa, respectively. The water sorption behavior was found to be dependent on the chemical composition of the Matrix and the sorption data were used to calculate network parameters. The porosity of composite varied between 4 to 30.66%.The in vitro blood compatibility indicated that the adsorption of bovine serum albumin (BSA) varied from 0.11 to 0.24 mg·g -1 , the percentage haemolysis was between 2.4 to 6.9% and the weight of blood clot formed on the composite surfaces were found in the range 11 to 52 mg.