The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform

M. Giulietti - One of the best experts on this subject based on the ideXlab platform.

  • Production of defluorinated Dicalcium Phosphate from Phosphate rock concentrate
    Nutrient Cycling in Agroecosystems, 1997
    Co-Authors: A.m.b. Freitas, M. Giulietti
    Abstract:

    A new process to produce defluorinated Dicalcium Phosphate (DCP) using Phosphate rock concentrate has been developed. This new process has as main characteristic the low concentration of P2O5 in the liquid phase. The process comprises three main steps: solubilization of the Phosphate rock concentrate with sulfuric acid, defluorination of the phosphoric acid solution with potassium sulfate and neutralization of the phosphoric acid solution with calcium hydroxide. The P2O5 precipitated in the pH range between 2.00 and 5.00 consisted basically of anhydrous Dicalcium Phosphate.

  • Clean process for the production of defluorinated Dicalcium Phosphate using Phosphate rock
    Journal of Hazardous Materials, 1994
    Co-Authors: M. Giulietti
    Abstract:

    Abstract A new process for the production of defluorinated Dicalcium Phosphate using Phosphate rock was developed. This new process has the main characteristic of being clean, without the production of any liquid waste. The process has essentially three main steps: Phosphate rock digestion, defluorination and neutralization. In the first step a Phosphate rock slurry is batch digested with concentrated sulfuric acid in the presence of some additives that retain the fluorine in the solution, as well as enable the adequate growth of the calcium sulfate crystals and maximize the Phosphate dissolution. At the end of the digestion the slurry is filtrated and the mother licquor is sent to the next step. The second step of the process is a fluorine salt precipitate sedimentation carried out by the addition of a potassium or sodium salt. The clear solution containing mainly a weak phosphoric acid is then neutralized, in the third step, in order to produce the final Dicalcium Phosphate product. After filtration the Dicalcium Phosphate is dried and the mother licquor is recycled to the first step of the process, the Phosphate rock digestion. All the liquids of the process are recycled and no wastes are produced. This new process is economically interesting because it uses a very cheap raw material, the Phosphate rock, instead of the conventional defluorinated phosphoric acid.

  • Production of Dicalcium Phosphate by treatment of Phosphate rock concentrate with nitric acid
    Fertilizer Research, 1993
    Co-Authors: R Marcato, M. Giulietti
    Abstract:

    This paper presents results laboratory experiments to test a new process for manufacture of Dicalcium Phosphate. The process is based on the nitric acidulation of Phosphate rock concentrate, followed by neutralization of the extract liquor with calcium carbonate. The precipitated Dicalcium Phosphate is then separated from calcium nitrate solution by filtration. The Dicalcium Phosphate thus obtained contains 44–47% total P2O5 and can be used as fertilizer or, with an additional low pH filtration step, as animal feed supplement.

Matthias Leitritz - One of the best experts on this subject based on the ideXlab platform.

  • Compression force/time-profiles of microcrystalline cellulose, Dicalcium Phosphate dihydrate and their binary mixtures—a critical consideration of experimental parameters
    European Journal of Pharmaceutics and Biopharmaceutics, 1997
    Co-Authors: Peter C. Schmidt, Matthias Leitritz
    Abstract:

    Abstract Compression force/time-profiles of microcrystalline cellulose and Dicalcium Phosphate dihydrate and mixtures thereof were compared on a modern rotary press by three different methods of compression: compression to a constant tablet weight, compression to a constant tablet height and compression from a constant filling depth. Compression was carried out at three different compression force levels. The differences obtained by analysing the area under the curve in the compression, dwell and decompression phase could be explained by differences of the in-die working density of the powders and their respective compression behaviour. From data of the compression phase as well as from the area-quotient-index obtained from the dwell time it was possible to estimate the percolation threshold of Dicalcium Phosphate dihydrate in a mixture with microcrystalline cellulose to ~ 50% (w/w) corresponding to 30% (v/v).

  • compression force time profiles of microcrystalline cellulose Dicalcium Phosphate dihydrate and their binary mixtures a critical consideration of experimental parameters
    European Journal of Pharmaceutics and Biopharmaceutics, 1997
    Co-Authors: Peter C. Schmidt, Matthias Leitritz
    Abstract:

    Abstract Compression force/time-profiles of microcrystalline cellulose and Dicalcium Phosphate dihydrate and mixtures thereof were compared on a modern rotary press by three different methods of compression: compression to a constant tablet weight, compression to a constant tablet height and compression from a constant filling depth. Compression was carried out at three different compression force levels. The differences obtained by analysing the area under the curve in the compression, dwell and decompression phase could be explained by differences of the in-die working density of the powders and their respective compression behaviour. From data of the compression phase as well as from the area-quotient-index obtained from the dwell time it was possible to estimate the percolation threshold of Dicalcium Phosphate dihydrate in a mixture with microcrystalline cellulose to ~ 50% (w/w) corresponding to 30% (v/v).

  • Compression force/time-profiles of microcrystalline cellulose, Dicalcium Phosphate dihydrate and their binary mixtures: a critical consideration of experimental parameters
    European Journal of Pharmaceutics and Biopharmaceutics, 1997
    Co-Authors: Peter C. Schmidt, Matthias Leitritz
    Abstract:

    Abstract Compression force/time-profiles of microcrystalline cellulose and Dicalcium Phosphate dihydrate and mixtures thereof were compared on a modern rotary press by three different methods of compression: compression to a constant tablet weight, compression to a constant tablet height and compression from a constant filling depth. Compression was carried out at three different compression force levels. The differences obtained by analysing the area under the curve in the compression, dwell and decompression phase could be explained by differences of the in-die working density of the powders and their respective compression behaviour. From data of the compression phase as well as from the area-quotient-index obtained from the dwell time it was possible to estimate the percolation threshold of Dicalcium Phosphate dihydrate in a mixture with microcrystalline cellulose to ~ 50% (w/w) corresponding to 30% (v/v).

M. Freche - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneous crystallization of Dicalcium Phosphate dihydrate on titanium surfaces.
    Journal of Materials Science: Materials in Medicine, 1999
    Co-Authors: Christèle Combes, M. Freche, Christian Rey, B Biscans
    Abstract:

    The kinetics of nucleation and crystal growth of Dicalcium Phosphate dihydrate (DCPD, CaHPO4. 2H2O) on titanium powders with different grain sizes have been investigated using the constant composition crystal growth method at 37°C and pH = 5.50. Nucleation is independent of titanium powder size while crystal growth rate is strongly size-dependent. A minimum relative supersaturation ratio, σmin, required in the system for a detectable crystal growth rate to occur, taking into account the presence of the foreign substrate in the system, was determined. Based on the kinetic data and on the various characterizations by X-ray photoelectron spectroscopy and by scanning electron microscopy, we propose a crystal growth kinetic equation as a function of two parameters: the size of the substrate and the excess of supersaturation (σ−σmin) which is squared, indicating a spiral growth mechanism. © 1999 Kluwer Academic Publishers

  • Nucleation and crystal growth of Dicalcium Phosphate dihydrate on titanium powder
    Journal of Materials Science: Materials in Medicine, 1995
    Co-Authors: Christèle Combes, M. Freche, Christian Rey
    Abstract:

    The nucleation and crystal growth of Dicalcium Phosphate dihydrate (CaHPO4 · 2H2O DCPD or brushite) on titanium powder surface has been studied in metastable supersaturated solutions at 37°C and pH=5.50. These experiments were carried out using the constant composition method. In order to determine the effect of substrate size on the kinetics of brushite formation, we used four ranges of titanium particle size (

  • Effect of humic compounds and some organic acids added during Dicalcium Phosphate dihydrate crystal growth process
    Journal of Alloys and Compounds, 1992
    Co-Authors: M. Freche, J.l. Lacout
    Abstract:

    Abstract A constant composition method was used to investigate the influence of humic compounds and phytic, mellitic and citric acids on the crystal growth of Dicalcium Phosphate dihydrate (DCPD). The additives studied strongly inhibit the crystallization of DCPD. The inhibition effect can be attributed to an interaction between functional groups and calcium ions on the crystal surface.

Peter C. Schmidt - One of the best experts on this subject based on the ideXlab platform.

  • Compression force/time-profiles of microcrystalline cellulose, Dicalcium Phosphate dihydrate and their binary mixtures—a critical consideration of experimental parameters
    European Journal of Pharmaceutics and Biopharmaceutics, 1997
    Co-Authors: Peter C. Schmidt, Matthias Leitritz
    Abstract:

    Abstract Compression force/time-profiles of microcrystalline cellulose and Dicalcium Phosphate dihydrate and mixtures thereof were compared on a modern rotary press by three different methods of compression: compression to a constant tablet weight, compression to a constant tablet height and compression from a constant filling depth. Compression was carried out at three different compression force levels. The differences obtained by analysing the area under the curve in the compression, dwell and decompression phase could be explained by differences of the in-die working density of the powders and their respective compression behaviour. From data of the compression phase as well as from the area-quotient-index obtained from the dwell time it was possible to estimate the percolation threshold of Dicalcium Phosphate dihydrate in a mixture with microcrystalline cellulose to ~ 50% (w/w) corresponding to 30% (v/v).

  • compression force time profiles of microcrystalline cellulose Dicalcium Phosphate dihydrate and their binary mixtures a critical consideration of experimental parameters
    European Journal of Pharmaceutics and Biopharmaceutics, 1997
    Co-Authors: Peter C. Schmidt, Matthias Leitritz
    Abstract:

    Abstract Compression force/time-profiles of microcrystalline cellulose and Dicalcium Phosphate dihydrate and mixtures thereof were compared on a modern rotary press by three different methods of compression: compression to a constant tablet weight, compression to a constant tablet height and compression from a constant filling depth. Compression was carried out at three different compression force levels. The differences obtained by analysing the area under the curve in the compression, dwell and decompression phase could be explained by differences of the in-die working density of the powders and their respective compression behaviour. From data of the compression phase as well as from the area-quotient-index obtained from the dwell time it was possible to estimate the percolation threshold of Dicalcium Phosphate dihydrate in a mixture with microcrystalline cellulose to ~ 50% (w/w) corresponding to 30% (v/v).

  • Compression force/time-profiles of microcrystalline cellulose, Dicalcium Phosphate dihydrate and their binary mixtures: a critical consideration of experimental parameters
    European Journal of Pharmaceutics and Biopharmaceutics, 1997
    Co-Authors: Peter C. Schmidt, Matthias Leitritz
    Abstract:

    Abstract Compression force/time-profiles of microcrystalline cellulose and Dicalcium Phosphate dihydrate and mixtures thereof were compared on a modern rotary press by three different methods of compression: compression to a constant tablet weight, compression to a constant tablet height and compression from a constant filling depth. Compression was carried out at three different compression force levels. The differences obtained by analysing the area under the curve in the compression, dwell and decompression phase could be explained by differences of the in-die working density of the powders and their respective compression behaviour. From data of the compression phase as well as from the area-quotient-index obtained from the dwell time it was possible to estimate the percolation threshold of Dicalcium Phosphate dihydrate in a mixture with microcrystalline cellulose to ~ 50% (w/w) corresponding to 30% (v/v).

Christian Rey - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneous crystallization of Dicalcium Phosphate dihydrate on titanium surfaces.
    Journal of Materials Science: Materials in Medicine, 1999
    Co-Authors: Christèle Combes, M. Freche, Christian Rey, B Biscans
    Abstract:

    The kinetics of nucleation and crystal growth of Dicalcium Phosphate dihydrate (DCPD, CaHPO4. 2H2O) on titanium powders with different grain sizes have been investigated using the constant composition crystal growth method at 37°C and pH = 5.50. Nucleation is independent of titanium powder size while crystal growth rate is strongly size-dependent. A minimum relative supersaturation ratio, σmin, required in the system for a detectable crystal growth rate to occur, taking into account the presence of the foreign substrate in the system, was determined. Based on the kinetic data and on the various characterizations by X-ray photoelectron spectroscopy and by scanning electron microscopy, we propose a crystal growth kinetic equation as a function of two parameters: the size of the substrate and the excess of supersaturation (σ−σmin) which is squared, indicating a spiral growth mechanism. © 1999 Kluwer Academic Publishers

  • Nucleation and crystal growth of Dicalcium Phosphate dihydrate on titanium powder
    Journal of Materials Science: Materials in Medicine, 1995
    Co-Authors: Christèle Combes, M. Freche, Christian Rey
    Abstract:

    The nucleation and crystal growth of Dicalcium Phosphate dihydrate (CaHPO4 · 2H2O DCPD or brushite) on titanium powder surface has been studied in metastable supersaturated solutions at 37°C and pH=5.50. These experiments were carried out using the constant composition method. In order to determine the effect of substrate size on the kinetics of brushite formation, we used four ranges of titanium particle size (