Structural characterization and colour of MgxCu3-xV2O8 (0<=x<=3) and MgyCu2-yV2O7 (0<=y<=2) compositions

In this study, MgxCu3-xV2O8 (0 ≤ x ≤ 3) and MgyCu2-yV2O7 (0 ≤ y ≤ 2) compositions were synthesized by the chemical coprecipitation method and characterized by X-ray diffraction, UV–vis-NIR spectroscopy and CIE L* a* b* parameters measurements. Melting points of compounds Cu3V2O8 and Cu2V2O7 are 780°C and 790°C, respectively. The addition of small amounts of Mg (II), MgxCu3-xV2O8 (x < 1.0) and MgyCu2-yV2O7 (y < 0.5) fused compositions, was not sufficient to stabilize structures at 800°C. For the Mg2CuV2O8 (x = 2.0) composition fired at 800°C, Mg (II) incorporated into the monoclinic Cu3V2O8 structure stabilizes this crystalline phase. At 1000°C, orthorhombic Mg3V2O8 structure from this composition was obtained. Solid solutions with orthorhombic symmetry were detected from the prepared compositions fired at 1000°C when 1.0 ≤ x ≤ 3.0. The difference of coloration of Cu, Mg vanadates might be explained by the presence of a strong charge transfer band in visible spectra

Cobalt Minimisation in Violet Co3P2O8 Pigment

This study considers the limitations of cobalt violet orthophosphate, Co3P2O8, in the ceramic industry due to its large amount of cobalt. MgxCo3−xP2O8 (0 ≤ x ≤ 3) solid solutions with the stable Co3P2O8 structure were synthesised via the chemical coprecipitation method. The formation of solid solutions between the isostructural Co3P2O8 and Mg3P2O8 compounds decreased the toxically large amount of cobalt in this inorganic pigment and increased the melting point to a temperature higher than 1200 °C when x ≥ 1.5. Co3P2O8 melted at 1160 °C, and compositions with x ≥ 1.5 were stable between 800 and 1200 °C. The substitution of Co(II) with Mg(II) decreased the toxicity of these materials and decreased their price; hence, the interest of these materials for the ceramic industry is greater. An interesting purple colour with a* = 31.6 and b* = −24.2 was obtained from a powdered Mg2.5Co0.5P2O8 composition fired at 1200 °C. It considerably reduced the amount of cobalt, thus improving the colour of the Co3P2O8 pigment (a* = 16.2 and b* = −20.1 at 1000 °C). Co3P2O8 is classified as an inorganic pigment (DCMA-8-11-1), and the solid solutions prepared were also inorganic pigments when unglazed. When introducing 3% of the sample (pigment) together with enamel, spreading the mixture on a ceramic support and calcining the whole in an electric oven, a colour change from violet to blue was observed due to the change in the local environment of Co(II), which could be seen in the UVV spectra of the glazed samples with the displacement of the bands towards higher wavelengths and with the appearance of a new band assigned to tetrahedral Co(II). This blue colour was also obtained with Co2SiO4, MgCoSiO4 or Co3P2O8 pigments containing a greater amount of cobalt

Usos del e-learning en las Universidades Andaluzas: Estado de la situación y análisis de buenas prácticas. (Versión completa)

Secretaría General de Universidades, Investigación y Tecnología P07-SE-J.0267

Beige materials for the ceramic industry: AlxVyFe1-xP1-yO4 (0.0 ≤ x ≤ 0.3, 0.0 ≤ y ≤ 0.1) solid solutions

AlxVyFe1-xP1-yO4 (0.0 ≤ x ≤ 0.3, 0.0 ≤ y ≤ 0.1) compositions were synthesized via the chemical co-precipitation method. At 500 °C, α-FePO4 berlinite crystallizes together with FePO4 tridymite, Fe(III) occupying tetrahedral sites in both structures. The variation in the unit cell confirms the formation of solid solutions with α-FePO4 berlinite structure. These AlxVyFe1-xP1-yO4 (0.0 ≤ x ≤ 0.3, 0.0 ≤ y ≤ 0.1) solid solutions are stable between 800 and 1000 °C and when x > 0.2 at 1200 °C. Fe7P6O24 with Fe(II) and Fe(III) is detected in the compositions with the highest amount of Fe(III) at 1200 °C. The materials are paramagnetic between 100 and 300 K and the variation in their magnetic susceptibilities fits the Curie-Weiss law with negative Weiss constants (antiferromagnetism). At 1200 °C, the presence of small amounts of Fe(II) is associated with a slight decrease in μeff. The presence of vanadium in samples (y > 0) decreases their μeff. Optimal beige materials to work without sample fusion at 1200 °C are reported

Characterization of MgxM2 − xP2O7 (M = Cu and Ni) solid solutions

In this study, MgxM2 − xP2O7 (M = Cu, Ni; 0 ≤ x ≤ 2) and Mg3 − yNiy(PO4)2 (0 ≤ y ≤ 3) compositions were synthesized by the chemical coprecipitation method and characterized by X-ray diffraction, UV–vis–NIR spectroscopy and CIE L* a* b* (Commission Internationale de l’Eclairage L* a* b*) parameters measurements. Solid solutions with α-Cu2P2O7 and α-Ni2P2O7 structures and solid solutions with Ni3(PO4)2 structure were obtained from diphosphate and orthophosphate compositions respectively. Isostructurality of α-Ni2P2O7 and α-Mg2P2O7 structures enlarges the compositional range of solid solution formation respect to the MgxCu2 − xP2O7 solid solutions one. The CIE L* a* b* parameters in MgxNi2 − xP2O7 samples were obtained comparable with these parameters in others yellow materials suitable for ceramic pigments. Mg0.5Ni1.5P2O7 composition fired at 800 °C or 1000 °C is the optimal composition to obtain yellow materials with α-diphosphate structure in conditions of this study

Influence of the structure of CrPO4 on the formation of CrVxP1−xO4 solid solutions and their colour

CrVxP1-xO4 (0 = 0.7. At 800 degrees C, two isostructural phases with orthorhombic symmetry are detected. At this temperature, beta-CrPO4 is present when x = 0.7

Influence of the structure of CrPO4 on the formation of CrVxP1−xO4 solid solutions and their colour

CrVxP1-xO4 (0 = 0.7. At 800 degrees C, two isostructural phases with orthorhombic symmetry are detected. At this temperature, beta-CrPO4 is present when x = 0.7

Estudi químic de la dinàmica de les aigües litorals del delta del Millars a l'estiu del 1989

The results obtained by analyzing different chemical parameters in samples of litoral waters picked up in a systematic way along the summer of 1989, at the north of river Millars delta («Pinar» beach in Castelló de la Plana) and at the south(«Grau» of Borriana), are presented in this work. As a result of a didactid experiment in environmental education in the field of chemistry, the contents in total solids, chlorides, pH, conductivity, hardness, nitrates and other factors in the waters are determined here, which alows us to give data about the evolution of the quantity of the waters all along the summer, and its climatic and litoral ocurrences in the studied time

Ceramic pigments from CoxNi3-xP2O8 (0 ≤ x ≤ 3) solid solutions

CoxNi3-xP2O8 (0 ≤ x ≤ 3) solid solutions were synthesized via the chemical co-precipitation method. Variation of unit cell parameters and interatomic distances indicated that these solid solutions with the Ni3P2O8 structure are stable between 800 and 1200 °C in compositions with 0 ≤ x ≤ 1.5 and between 800 and 1000 °C when (0 ≤ x ≤ 3). When (2.5 ≤ x ≤ 3.0), the solid solutions lead to the Co3P2O8 structure, being stable between 800 and 1000 °C. The yellow colour of the Ni3P2O8 compound changes to pink or red when Co(II) ions are incorporated in the structure as Ni3P2O8 solid solutions are formed. Bands corresponding to second and third electronic transitions of the Co(II) ions in octahedral coordination appear in the 450–600 nm in the UV-V spectra, and they are responsible of the observed changes in the colour. Absorbance in the visible spectra was also obtained from enamelled samples but a new band at 650 nm with considerable absorbance when x > 1.0 increased the blue amount, and colour of the enamelled samples was yellowish brown, brown, green and blue.Funding for open access charge: CRUE-Universitat Jaume

Nanocomposite Fe2O3–SiO2 inclusion pigments from post-functionalized mesoporous silicas

High-surface mesoporous silicas with different pore sizes were employed for the first time as silicon precursors in the synthesis of reddish Fe2O3–SiO2 inclusion pigments. Interestingly, the size of included Fe2O3 nanoparticles was partially controlled through confinement effects into silica mesopores. Notably, impregnated samples showed a more homogeneous and efficient encapsulation of smaller and monodisperse hematite nanoparticles (sizes around 10–35 nm). Moreover, they resulted in an improved reddish color at 1000 °C within a ceramic glaze. The best red shade (a* ≈ 18) was associated to nanocomposite with smaller hematite nanoparticles (around 5 nm). These promising results suggest the possibility to improve the reddish coloration and thermostability of Fe2O3–SiO2 ceramic pigments through and adequate control of confinement effects into sintered mesoporous silicas