Person:
Astilleros García-Monge, José Manuel

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First Name
José Manuel
Last Name
Astilleros García-Monge
URI
https://hdl.handle.net/20.500.14352/75202
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Cristalografía y Mineralogía
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1998 - 199912000 - 20095
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Author: Pina Martínez, Carlos Manuel × Subject: 548 ×

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Now showing 1 - 6 of 6
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    Estudio de la influencia del carbonato en el crecimiento de la barita a nanoescala.
    (Macla, 2004) Sánchez Pastor, Nuria; Pina Martínez, Carlos Manuel; Astilleros García-Monge, José Manuel; Fernández Díaz, María Lourdes
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    Malachite Crystallisation in a Diffusing-Reacting System
    (Crystal Research and Technology, 1998) Astilleros García-Monge, José Manuel; Pina Martínez, Carlos Manuel; Fernández Díaz, María Lourdes; López De Andrés, María Sol
    The crystallisation of malachite has been studied in a system involving the counter diffusion of Cu2+ and CO3 through a silica gel column at 25 ºC. In such a system supersaturation is a function of time and position along gel column. Under these conditions kinetic variables are required in order to justify nucleation behaviour. Supersaturation rate has revealed as the most important parameter controlling nucleation features (waiting time, position of the precipitate, and metastability levels). The results presented here confirm the general nucleation behaviour reported by Prieto et al., (1989, 1991, 1994) for other carbonates. On the other hand, supersaturation changes during crystallisation process control the morphological evolution of malachite crystals.
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    Supersaturation functions in binary solid solution–aqueous solution systems
    (Geochimica et cosmochimica acta, 2003) Astilleros García-Monge, José Manuel; Pina Martínez, Carlos Manuel; Fernández Díaz, María Lourdes; Putnis, Andrew
    In this paper, we present a brief review of the thermodynamic equilibrium of binary solid solution–aqueous solution (SS-AS) systems and derive an expression hat allows us to evaluate the supersaturation or undersaturation of a given aqueous solution with respect to the whole range of solid compositions: the δ(x) function. Such an expression is based on the two conditions that define the SS-AS thermodynamic equilibrium. The derivation of the new supersaturation function, δ(x), was made by considering in detail the compositional relationships between solid and aqueous phases. To represent the new formulation on Lippmann diagrams, we have defined a new thermodynamic concept: the “actual activity.” In addition, we show how our supersaturation function behaves for both ideal and subregular solid solutions. The behaviour and applicability of both the δ(x) function and a previous supersaturation function, β(x), defined by Prieto et al. (1993), is discussed.
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    Crecimiento epitaxial de celestina sobre la superficie (001) de la barita
    (Macla, 2004) Sánchez Pastor, Nuria; Pina Martínez, Carlos Manuel; Astilleros García-Monge, José Manuel; Fernández Díaz, María Lourdes
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    The carbonatation of gypsum: Pathways and pseudomorph formation
    (The American mineralogist, 2009) Fernández Díaz, María Lourdes; Pina Martínez, Carlos Manuel; Astilleros García-Monge, José Manuel; Sánchez Pastor, Nuria
    In this paper, we present an experimental study of the interaction between gypsum (010) surfaces and aqueous solutions of Na2CO3 with different concentrations. This interaction leads to the carbonatation (i.e., the transformation into carbonate minerals) of gypsum crystals, which under ambient conditions shows the characteristics of a mineral replacement and leads to the formation of pseudomorphs consisting of an aggregate of calcite crystals. Carbonatation progress was monitored by scanning electron microscopy (SEM) and glancing incidence X-ray diffraction (GIXRD). The carbonatation advances from outside to inside the gypsum crystal and occurs through a sequence of reactions, which involves the dissolution of gypsum and the simultaneous crystallization of different polymorphs of CaCO3 [amorphous calcium carbonate (ACC), vaterite, aragonite, and calcite], as well as several solvent-mediated transformations between these polymorphs. The sequence in which CaCO3 phases form is interpreted taking into consideration nucleation kinetics and the qualitative evolution of several chemical parameters in the aqueous solution. The textural characteristics of the transformed regions are described. The degree of faithfulness of the pseudomorphs obtained is related to the kinetics of the carbonatation process, which in turn depends on the initial concentration of carbonate in the aqueous solutions. Finally, changes in the rate at which the transformation front advances are discussed on the basis of both textural and physicochemical considerations.