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Journal ArticleDOI

Kinetic studies of mixed powder compact system between zinc oxide and aluminium oxide

TL;DR: In this article, the addition reaction between the compacted powders of zinc oxide and aluminium oxide was studied and the reaction rate changed to a constant value after an initial phase boundary process.
About: This article is published in Materials Science and Engineering.The article was published on 1975-01-01. It has received 7 citations till now. The article focuses on the topics: Aluminium oxide & Reaction rate constant.
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Journal ArticleDOI
TL;DR: The adhesion of human bone marrow stromal cells (hBMSCs) and proliferation characteristics of various scaffolds, which consist of biodegradable materials, fabricated using a multi-head deposition system (MHDS) that was developed.
Abstract: Scaffolds composed of biodegradable polymers and biocompatible ceramics are being used as substitutes for tissue engineering. In the development of such techniques, scaffolds with a controllable pore size and porosity were manufactured using solid free-form fabrication (SFF) methods to investigate the effects of cell interactions such as cell proliferation and differentiation. In this study, we describe the adhesion of human bone marrow stromal cells (hBMSCs) and proliferation characteristics of various scaffolds, which consist of biodegradable materials, fabricated using a multi-head deposition system (MHDS) that we developed. The MHDS uses novel technology that enables the production of three-dimensional (3D) microstructures. Fabrication of 3D tissue engineering scaffolds using the MHDS requires the combination of several technologies, such as motion control, thermal control, pneumatic control and computer-aided design/computer-assisted manufacturing software. The effects of a polymer and ceramic on a tissue scaffold were evaluated through mechanical testing and cell interaction analysis of various kinds of scaffolds fabricated using polycaprolactone, poly-lactic-co-glycolic acid and tri-calcium phosphate for bone regeneration applications. Based on these results, the feasibility of application to the tissue engineering of SFF-based 3D scaffolds fabricated by the MHDS was demonstrated.

58 citations

Journal ArticleDOI
TL;DR: The effectiveness of electrospun PLGA scaffolds as a suitable candidate for regenerative medicine, capable of being manipulated and combined with other polymers to create three-dimensional microenvironments with adjustable tensile properties to mimic native tissues is demonstrated.
Abstract: Within the past two decades polylactic-co-glycolic acid (PLGA) has gained considerable attention as a biocompatible and biodegradable polymer that is suitable for tissue engineering and regenerative medicine. In this present study, we have investigated the potential of PLGA, collagen I (ColI), and polyurethane (PU) scaffolds for ligament tissue regeneration. Two different ratios of PLGA (50:50 and 85:15) were used to determine the effects on mechanical tensile properties and cell adhesion. The Young's modulus, tensile stress at yield, and ultimate tensile strain of PLGA(50:50)-ColI-PU scaffolds demonstrated similar tensile properties to that of ligaments found in the knee. Whereas, scaffolds composed of PLGA(85:15)-ColI-PU had lower tensile properties than that of ligaments. Furthermore, we investigated the effect of fiber orientation on mechanical properties and our results indicate that aligned fiber scaffolds demonstrate higher tensile properties than scaffolds with random fiber orientation. Also, human fibroblasts attached and proliferated with no need for additional surface modifications to the presented electrospun scaffolds in both categories. Collectively, our investigation demonstrates the effectiveness of electrospun PLGA scaffolds as a suitable candidate for regenerative medicine, capable of being manipulated and combined with other polymers to create three-dimensional microenvironments with adjustable tensile properties to mimic native tissues. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 39–46, 2015.

44 citations

Journal ArticleDOI
TL;DR: Through the fabrication and cell interaction analysis of two kinds of scaffolds using polycaprolactone and poly-lactic-co-glycolic acid, feasibility of application to the tissue engineering of the developed SFF-based precision deposition system is demonstrated.
Abstract: Recent developments in tissue-engineering techniques allow physicians to treat a range of previously untreatable conditions. In the development of such techniques, scaffolds with a controllable pore size and porosity have been manufactured using solid free-form fabrication methods to investigate cell interaction effects such as cell proliferation and differentiation. In this study, we describe the fabrication of scaffolds from two types of biodegradable materials using a precision deposition system that we developed. The precision deposition system uses technology that enables the manufacture of three-dimensional (3D) microstructures. The fabrication of 3D tissue-engineering scaffolds using the precision deposition system required the combination of several technologies, including motion control, thermal control, pneumatic control and CAD/CAM software. Through the fabrication and cell interaction analysis of two kinds of scaffolds using polycaprolactone and poly-lactic-co-glycolic acid, feasibility of application to the tissue engineering of the developed SFF-based precision deposition system is demonstrated.

40 citations

Journal ArticleDOI
TL;DR: DSCs, isolated from rat dura mater, were evaluated and compared to bone marrow stem cells for proliferative and differentiative properties in vitro and suggest that DSCs are promising for cell-based bone tissue engineering therapies, particularly those applications involving regeneration of cranial bones.
Abstract: The rational design of biomimetic structures for the regeneration of damaged or missing tissue is a fundamental principle of tissue engineering. Multiple variables must be optimized, ranging from the scaffold type to the selection and properties of implanted cell(s). In this study, the osteogenic potential of a novel stem cell was analyzed on biodegradable poly(lactic-co-glycolic acid) (PLGA) bio-materials as a step toward creating new cell-materials constructs for bony regeneration. Dura mater stem cells (DSCs), isolated from rat dura mater, were evaluated and compared to bone marrow stem cells (BMSCs) for proliferative and differentiative properties in vitro. Experiments were carried out on both tissue culture plastic (TCP) and 2D planar films of PLGA. Proliferation of DSCs on both TCP and PLGA films increased over 21 days. Positive fold inductions in all five bone marker genes were observed at days 7, 14, 21 in all experimental samples compared with day 0 controls. DSCs demonstrated greater cell coverage and enhanced matrix staining on 2D PLGA films when compared with BMSCs. These cells can be isolated and expanded in culture and can subsequently attach, proliferate, and differentiate on both TCP and PLGA films to a greater extent than BMSCs. This suggests that DSCs are promising for cell-based bone tissue engineering therapies, particularly those applications involving regeneration of cranial bones.

31 citations

Journal ArticleDOI
H. Okada1, H. Kawakami1, Minoru Hashiba1, Eiji Miura1, Yukio Nurishi1, Taizo Hibino1 
TL;DR: In this article, the rate of ZnA12O4 formation for binary powder mixtures of znO and α-Al2O3 (dense coarse particles and weak agglomerates of fine powder) fired in air or O2 atmospheres was measured and the microstructures of those systems were observed by scanning electron microscopy.
Abstract: The rate of ZnA12O4 formation for binary powder mixtures of ZnO and α-Al2O3 (dense coarse particles and weak agglomerates of fine powder) fired in air or O2 atmospheres was measured and the microstructures of those systems were observed by scanning electron microscopy. With dispersed dense particles of α-Al2O3, the Al2O3 surfaces were covered with ZnO and the spinel grew into the particles maintaining essentially a constant reaction interface area. Calculations based on geometric measurements and use of Jander's equation gave a similar high activation energy, 354 kJ/mol, which corresponds to the activation energy of volume diffusion of Zn2+ in ZnAl2O4. An oxygen atmosphere had no effect. With a matrix of fine α-Al2O3 powder and dispersed granules of ZnO, a higher reaction rate occurred because of an increase in reaction interface area due to penetration of the powder compact matrix by ZnO vapor, which was enhanced by an O2 atmosphere. The reaction layer grew into the alumina matrix adjoining the ZnO granules with a parabolic rate law. Apparent activation energies below ∼200 kJ/mol were calculated.

24 citations

References
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Book
01 Dec 1960
TL;DR: In this paper, the authors present a model for the development of the MICROSTRUCTURE in CERAMICS based on phase transformation, glass formation and glass-Ceramics.
Abstract: INTRODUCTION. Ceramic Processes and Products. CHARACTERISTICS OF CERAMIC SOLIDS. Structure of Crystals. Structure of Glasses. Structural Imperfections. Surfaces, Interfaces, and Grain Boundaries. Atom Mobility. DEVELOPMENT OF MICROSTRUCTURE IN CERAMICS. Ceramic Phase Equilibrium Diagrams. Phase Transformation, Glass Formation and Glass--Ceramics. Reactions with and between Solids. Grain Growth. Sintering and Vitrification. Microstructure of Ceramics. PROPERTIES OF CERAMICS. Thermal Properties. Optical Properties. Plastic Deformation, Viscous Flow and Creep. Elasticity, Anelasticity and Strength. Thermal and Compositional Stresses. Electrical Conductivity. Dielectric Properties. Magnetic Properties.

6,650 citations

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01 Jan 1963

3,257 citations

Book
01 Jan 1941

1,025 citations

Journal ArticleDOI
TL;DR: In this paper, the authors give numerical tables of F(α) in relation to α, and to (t/t0.5) where t 0.5 is the time for 50% reaction and A is a calculable constant depending on the form of F (α).
Abstract: Many solid state reactions can be represented by equations of the type F(α) =kt, where α is the fraction of material reacted in time, t. These equations can be expressed in the form F(α) =A(t/t0.5) where t0.5 is the time for 50% reaction and A is a calculable constant depending on the form of F(α). Numerical tables are given of F(α) in relation to α, and to (t/t0.5), for nine equations corresponding to reactions which are diffusion controlled, or are reaction-rate controlled, or obey first order kinetics, or follow the equations of Avrami and Erofe'ev. The application of the tables to the analysis of experimental data is described.

801 citations