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  • 1
    Electronic Resource
    Electronic Resource
    Bone repair of defects filled with a phosphocalcic hydraulic cement: an in vivo study (1993)
    Springer
    Journal of materials science 4 (1993), S. 337-344 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: A quickly setting calcium phosphate-based hydraulic cement mixed with particles of tricalcium phosphate (TCP) ceramic was implanted in 56 metaphysial defects made in the long bones of ten adult mongrel dogs. Microradiography, histology and scanning electron microscopy (SEM) demonstrated the slow resorption of the cement and the bony incorporation of the calcium phosphate ceramic particles which were consistently embedded in bone. The original structural pattern of the bone tended to be restored 7 months after implantation. The cement did not hinder the incorporation of the calcium phosphate ceramic particles, neither did it elicit any inflammatory or foreign-body response. The cement was easily shaped and allowed a perfect filling of any defect, resulting in close contact of the whole implant surface with the host bone at the time of surgery, associated with appreciable mechanical strength. Most of the practical problems associated with the use of calcium phosphate ceramics in the repair of bone defects could be overcome with the cement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122290
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  • 2
    Electronic Resource
    Electronic Resource
    Composition effects on the pH of a hydraulic calcium phosphate cement (1997)
    Springer
    Journal of materials science 8 (1997), S. 675-681 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The pH of a hydraulic calcium phosphate cement (HCPC) made of monocalcium phosphate monohydrate (Ca(H2PO4)2·H2O; MCPM), β-tricalcium phosphate (β-(Ca3(PO4)2; β-TCP) and water was measured as a function of reaction time and composition at room temperature. During setting, the cement pH varies from very acidic pH values, i.e., 2.5, to almost neutral pH values, i.e., 6. The cement pH profile significantly depends on the initial cement composition. However, all profiles are characterized by a sharp initial decrease of the pH due to the dissolution of MCPM crystals and the precipitation of dicalcium phosphate dihydrate (CaHPO4· 2H2O; DCPD) crystals. With an excess of MCPM, the final pH stays low, and its value can be predicted from the initial composition of the cement and solubility data. With an excess of β-TCP, the end pH is close to 5, which is much lower than 5.9, the value predicted by calculation. Results suggest that the difference may be due to the presence of impurities in the cement. Replacing MCPM by phosphoric acid renders the cement paste very acidic for the initial 30 s, but then the pH profile follows that obtained with MCPM. Adding pyrophosphate ions into the cement paste postpones the position of the pH minimum. The delay, which is proportional to the concentration of pyrophosphate ions, is thought to be due to the inhibiting action of pyrophosphate ions on the precipitation of DCPD crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018583706335
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of several additives and their admixtures on the physico-chemical properties of a calcium phosphate cement (2000)
    Springer
    Journal of materials science 11 (2000), S. 111-116 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Combinations of citrate (C6H5O 7 3-− ), pyrophosphate (P2O 7 4− ) and sulfate (SO 4 2− ) ions were used to modify the physico-chemical properties of a calcium phosphate cement (CPC) composed of β-tricalcium phosphate (β-TCP) and phosphoric acid (PA) solution. The results obtained with only one additive at a time are similar to those previously published. New facts are: the positive effect of C6H5O 7 3− ions on cement failure strain and their negative effect on cement pH. The position of the setting time maximum measured at an SO 4 2− concentration of 0.09 M was not displaced by the addition of C6H5O 7 3− and P2O 7 4− ions. However, the effect of SO 4 2− ions on the setting time was depressed by C6H5O 7 3− ions. Moreover, no increase in tensile strength was observed when increasing amounts of SO 4 2− were added into a C6H5O 7 3− -containing cement. The latter results suggest a competitive effect of C6H5O 7 3− and SO 4 2− on setting time and tensile strength. Anhydrous dicalcium phosphate (DCP; CaHPO4) appeared in cement samples dried just after setting, but not in cement samples incubated for 24 h in deionized water before the drying step. It is believed that the setting reaction is stopped by the drying step, leaving a low internal pH in the sample, hence providing favorable conditions for the transformation of dicalcium phosphate dihydrate (DCPD) into DCP. Interestingly, even though C6H5O 7 3− ions dramatically lowered the equilibrium pH of the cement with 5 ml of deionized water, they still prevented the occurrence of the transformation of DCPD into DCP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008997118576
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of β-TCP granularity on setting time and strength of calcium phosphate hydraulic cements (1996)
    Springer
    Journal of materials science 7 (1996), S. 34-39 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The effects of β-tricalcium phosphate (β-TCP) granularity on the properties of calcium phosphate hydraulic cements (CPHC) have been investigated. A model system based on mixtures of (β-TCP) and aqueous solution of orthophosphoric acid has been used. Powders with different shapes (irregular agglomerates or spheres) and sizes (d 50=7 to 130 μm) were prepared from two different calcium phosphate sources: Ca-deficient hydroxyapatite (DAP) or hydroxyapatite dicalcium phosphate mixtures (HAP-DCP). The cements exhibited setting times (ST) ranging from 65 to 510 s; they are mainly affected by the specific surface area (S BET) of the β-TCP powders, longer ST corresponding to lower S BET. In general, lower S BET and shorter ST values were obtained with HAP-DCP powders. Diametral tensile strengths (DTS) ranging from 3.5 to 10.4 MPa were obtained. The results show that DTS is affected in a complex way by the experimental variables. In general, DTS is higher with irregular agglomerates compared to spheres (+1.2 MPa), while better results are obtained with HAP-DCP powders (+0.9 MPa). The dependence of DTS on particle size is variable according to powder source and shape. The highest DTS (10.4 MPa) was obtained with irregular agglomerates prepared from HAP-DCP mixtures (d 50=16 μm), and the lowest (3.5 MPa), with irregular agglomerates prepared with DAP (d 50=123 μm). It can be concluded from this work that specific CPHC formulations can give quite different cement properties, such as setting time and ultimate mechanical strength, depending on the characteristics of the raw materials used. In the case of β-TCP based cements, the granularity of the starting cement powder, including particle size, shape and specific surface area, is of crucial importance and should be specified when the performances of different formulations are to be compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121187
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis, X-ray diffraction and solid-state 31P magic angle spinning NMR study of α-tricalcium orthophosphate (1996)
    Springer
    Journal of materials science 7 (1996), S. 457-463 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The effects of synthesis conditions on the quantitative preparation of α-tricalcium phosphate (α-TCP) have been investigated. The following parameters of the synthesis were considered: nature of the starting material-Ca-deficient hydroxyapatite, DAP, versus hydroxyapatite-anhydrous dicalcium phosphate mixtures (HAP-DCPA); Ca/P atomic ratio of the mixture, calcination temperature and time, and cooling rate. The yield and crystallinity of the final product have been estimated using X-ray diffraction (XRD) and solid state 31P magic angle spinning NMR (MAS-NMR) techniques. The results show that pure, well-crystallized α-TCP powders exhibiting nearly ideal MAS-NMR spectra, can be obtained by reactive sintering of HAP-DCPA (Ca/P=1.50...1.52) mixtures, at 1400°C for 8 h. The broadening of MAS-NMR spectra can be used as an indicator of structural order in the final product. The α-TCP yield with DAP was always less than 50%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122016
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  • 6
    Electronic Resource
    Electronic Resource
    One damage law for different mechanisms (1997)
    Springer
    Computational mechanics 20 (1997), S. 84-88 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We consider here a general three-dimensional kinetic damage law. It uses the thermodynamic of irreversible processes formalism and the phenomenological aspects of isotropic damage. It gives the damage rate as a function of its associated variable, the strain energy density release rate and the accumulated plastic strain rate. Associated with different plastic constitutive equations, this damage law takes into account brittle damage, ductile damage, low and high cycle fatigue and creep damage. In this paper we mainly focus on creep-fatigue interaction and high cycle fatigue. Associated to a viscoplastic constitutive equation having kinematic hardening, the damage law gives the non linear creep-fatigue interaction. The agreement with experiments is good. Associated to plastic constitutive equations also having kinematic hardening but introduced in a micromechanical two scale model based on the self-consistent scheme, it models the non linear accumulation of damage induced by a succession of sequences of different amplitudes as well as the effect of the mean stress and the influence of non proportional loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660050221
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  • 7
    Electronic Resource
    Electronic Resource
    Diffusive properties of motion on a bumpy plane (1998)
    Springer
    The European physical journal 3 (1998), S. 377-385 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.20.-y Statistical mechanics[:AND:] 64.60.-i General studies of phase transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report on experiments studying the statistical properties of the motion of balls on a bumpy surface. This motion is found to be diffusive. In the direction of the mean flow, the coefficient of diffusion is found to attain a constant value, independent of the size of the ball and the inclination angle. The diffusion transverse to the mean flow is characterized by a coefficient which decreases with the inclination of the plane, and scales with the size of moving ball.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050325
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  • 8
    Electronic Resource
    Electronic Resource
    Calcination and morphological evolution of cubic copper oxalate particles (2000)
    Springer
    Journal of materials science 19 (2000), S. 1073-1075 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006711724828
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  • 9
    Electronic Resource
    Electronic Resource
    New morphology of calcium oxalate trihydrate precipitated in a segmented flow tubular reactor (2000)
    Springer
    Journal of materials science 19 (2000), S. 749-750 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006771428827
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  • 10
    Electronic Resource
    Electronic Resource
    Study of the sintering mechanism of kaolinite at 900 and 1050° C; influence of mineralizers (1977)
    Springer
    Journal of materials science 12 (1977), S. 2056-2064 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a study, by means of isothermal dilatometry, of the often very important (10%) shrinkage phenomenon which occurs when heating clay ceramic materials, and especially of the influence of mineralizers on the shrinkage of kaolinite at 900 and 1050° C. We found that the isothermal shrinkage versus time curve of kaolinite at both temperatures was well described by the following equation: $$\lambda = \frac{t}{{\alpha + \beta t}}$$ where λ is the linear shrinkage (relative to the initial length of the bar),t the time, andα andβ two constants. The presence of various mineralizers at different concentrations did not affect the basic shape of this curve at either 900 or 1050° C, but affected the values of parametersα andβ. A sintering mechanism is proposed which takes into account the most recent data concerning the structural transformation of kaolinite in the 900 to 1050° C temperature range. The kaolinite sintering mechanism is of the viscous-flow type proposed by Frenkel [1] involving an amorphous phase, the viscosity of which increases with time due to its progressive recrystallization. The influence of mineralizers is then explained in terms of their action on the viscosity of the amorphous phase and their action on recrystallization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00561979
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