The Experts below are selected from a list of 31236 Experts worldwide ranked by ideXlab platform

Graham Hungerford - One of the best experts on this subject based on the ideXlab platform.

  • photophysics of mesoporphyrin ix in solution and confined in sol gel derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M. Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control Chemical Additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrix pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrix environment, although differences were encountered between the various matrix forms.

  • Photophysics of mesoporphyrin IX in solution and confined in sol–gel-derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M. Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control Chemical Additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrix pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrix environment, although differences were encountered between the various matrix forms.

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

  • photophysics of mesoporphyrin ix in solution and confined in sol gel derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M. Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control Chemical Additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrix pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrix environment, although differences were encountered between the various matrix forms.

  • Photophysics of mesoporphyrin IX in solution and confined in sol–gel-derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M. Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control Chemical Additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrix pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrix environment, although differences were encountered between the various matrix forms.

Gerhard Emig - One of the best experts on this subject based on the ideXlab platform.

  • sol gel based precursors for manufacturing refractory oxide fibres
    Journal of Materials Science, 1994
    Co-Authors: Gerhard Emig, R Wirth, R Zimmermannchopin
    Abstract:

    Several kinds of mixed refractory oxide fibres containing the oxides of Zr, Ti, Al, Cr and Ce were produced from sol/gel precursors via a melt spinning process from 50 to 110°C. For the synthesis of precursor sols the n-propoxides of Zr and Ti were reacted with chelating agents acetylacetone, ethyleneglycole, acetic acid and hydrolysis water. The surplus of solvents was distilled off, to adjust the viscosity. The viscosity and spinnability were improved by the use of N,N-dimethylformamide (DMF) as drying control Chemical Additive (DCCA) and different organic polymers as plastifiers. The elements Al, Cr and Ce were added to the precursor sols as chlorides, basic chlorides or basic acetates. The precursors were spun into bundles of thin gel-fibres with minimum diameters of ca. 45 μm by extrusion though multifilament spinnerets. The gel fibres were cured in air at 105°C and converted into fine grained ceramic fibres by pyrolysis at 1450°C. The decomposition process was investigated by thermogravimetric measurements (TG/DTA) and thermomechanical analysis (TMA).

  • Sol/gel-based precursors for manufacturing refractory oxide fibres
    Journal of Materials Science, 1994
    Co-Authors: Gerhard Emig, R Wirth, R. Zimmermann-chopin
    Abstract:

    Several kinds of mixed refractory oxide fibres containing the oxides of Zr, Ti, Al, Cr and Ce were produced from sol/gel precursors via a melt spinning process from 50 to 110°C. For the synthesis of precursor sols the n-propoxides of Zr and Ti were reacted with chelating agents acetylacetone, ethyleneglycole, acetic acid and hydrolysis water. The surplus of solvents was distilled off, to adjust the viscosity. The viscosity and spinnability were improved by the use of N,N-dimethylformamide (DMF) as drying control Chemical Additive (DCCA) and different organic polymers as plastifiers. The elements Al, Cr and Ce were added to the precursor sols as chlorides, basic chlorides or basic acetates. The precursors were spun into bundles of thin gel-fibres with minimum diameters of ca. 45 μm by extrusion though multifilament spinnerets. The gel fibres were cured in air at 105°C and converted into fine grained ceramic fibres by pyrolysis at 1450°C. The decomposition process was investigated by thermogravimetric measurements (TG/DTA) and thermomechanical analysis (TMA).

Banjo Ayobami Akinyemi - One of the best experts on this subject based on the ideXlab platform.

  • Response of coir fibre reinforced cement composites to water repellent Chemical Additive and microwave accelerated curing
    Cellulose, 2019
    Co-Authors: Banjo Ayobami Akinyemi, Adeola Bamidele, Enoch Joel
    Abstract:

    The present investigation deals with performance of coir fibre reinforced cement boards subjected to matrix modification by silane-based water repellent Chemical Additive and microwave accelerated curing (MC). The fibre-cement boards were tested for water absorption, modulus of rupture (MOR) and modulus of elasticity (MOE). Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the composite samples. 84% reduction in water penetration was achieved through the use of the water repellent Additive while MC samples had higher MOR and MOE values than the water cured samples. SEM characterization showed that MC provided good interfacial adhesion between the matrix and the reinforcement while the Chemical Additive reduced the occurrence of voids and pores on the surface. FTIR indicated prominent bands at 3423, 1425.44 and 875.41 cm^−1 which are indicative of O–H stretching of the portlandite, C-H denoting the lignin deformation with aromatic ring stretching and C-O representing bend of carbonates. Therefore, MC and use of water repellent Additive are recommended to improve the performance of cellulose fibre cement based applications.Graphical abstract

  • Influence of water repellent Chemical Additive and different curing regimes on dimensional stability and strength of earth bricks from termite mound-clay
    Elsevier, 2019
    Co-Authors: Banjo Ayobami Akinyemi, Adeola Bamidele, Adeoye Oluwanifemi
    Abstract:

    This article is focussed on evaluating the effects of water repellent admixture and different curing regimes on characteristics of clay from termite hills used for production of earth bricks. Water absorption, thickness swelling and compressive strength characteristics of the specimens with different compositions of cement, hydrated lime and water repellent Additive subjected to different curing regimes were measured. The samples were characterised by SEM and FTIR. The least water absorption was at 3.3% while thickness swelling ranged from 0.78 to 3.21 % for the samples. Saturated curing condition resulted in an average compressive strength of 35.5 N/mm2, cured curing recorded an average value of 32.9 N/mm2 while dry curing condition produced an average compressive strength of 26.9 N/mm2 and the wet curing condition resulted in 25 N/mm2. SEM characterisation of sample containing 70% termite soil, 30% cement and 0.05 Hydropruf indicated fewer voids, regular and smooth appearance in comparison with others. FTIR analysis showed distinctive broad bands at wave numbers of 3439 cm−1 for O-H stretching, and 1033.83–1008.80 cm−1 for O–H bending for all samples tested. The best performing composition in terms of the dimensional stability test was 70% termite mound clay, 10% cement, 20% hydrated lime and 0.05 Hydropruf Additive. The highest mechanical strength was from composition of 70% termite mound clay, 30% cement, no hydrated lime and 0.05 Hydropruf Additive. It is concluded that saturated and cured method showed better performance than the wet and dry curing regimes. The termite secretions similarly improved the clay composition in conjunction with cement, lime and Chemical admixture in the internal structure of the bricks. Keywords: Materials science, Civil engineerin

Joao A Ferreira - One of the best experts on this subject based on the ideXlab platform.

  • photophysics of mesoporphyrin ix in solution and confined in sol gel derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M. Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control Chemical Additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrix pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrix environment, although differences were encountered between the various matrix forms.

  • Photophysics of mesoporphyrin IX in solution and confined in sol–gel-derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M. Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control Chemical Additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrix pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrix environment, although differences were encountered between the various matrix forms.