The effect of monoaluminum phosphate (Al(H
2
PO
4
)
3
) addition in the thermochemical process of a kaolinitic clay was studied and compared with the pure clay. Monoaluminum phosphate incorporation ...is of technological interest for the widely use of this material as an effective binder. From this point of view is important to clarify the processing strategy of kaolinitic clay-MAP based ceramics. This work comprised the characteristics of the obtained ceramics using differential thermal analysis, thermogravimetric analysis (TG), dilatometric analysis, X-ray powder diffraction with Rietveld refinement, mechanical resistance and textural properties. The addition of MAP did not affect the temperature of the kaolinite dehydroxilation (600–500 °C) but reduced this transformation as it was observed in TG curve. The amount of mullite decreased and cristobalite formation was stimulated with MAP presence in the samples fired at 1400 °C. Mullite cell parameters were not modified. The present study gives information for further clay-based materials designed with MAP. It can be concluded that the incorporation of low percentages of MAP in the potential formulation of technological ceramics would not imply important changes in the macroscopic properties of these type of ceramic materials.
Porous ceramic materials exhibit high permeability, specific surface, and thermal shock resistance, and therefore they may be used successfully in the production of filters, membranes, and as a ...substrate for catalytic reactions, etc. One method for preparing high material porosity is addition of a pore-forming substance. Porosity (open and closed), pore size distribution, their size and shape, depend on the nature, amount, and morphology of pore-forming substance. In this article the effect is elucidated of three different types of carbon additives on porosity of ceramic prepared from clay and chemical binder precursor. Carbon materials are studied in an x-ray diffractometer. Ceramic material properties are studied using a mercury porosimeter, the Archimedes method, scanning electron and optical microscopes, and microcomputer tomography.
The incorporation of high thermal neutron capture elements in ceramic materials is relevant for the design of traceable proppants for obtaining information in petrology, such as the location and ...height of fractures in unconventional gas and oil wells. Among these, GdAlO3 has attracted interest because of its good thermo-mechanical properties. In this work, four Al2O3/GdAlO3 reaction sintered composites were prepared using Gd2O3 and Al2O3 powders as raw materials and high-energy ball milling followed by sintering at 1600 °C. This combination of ball milling and reaction sintering is considered as a mechanism to produce large bulk ceramics with different Al2O3/GdAlO3 compositions. The composite formulations range from pure alumina to eutectic ceramic. The obtained materials were characterized using X-ray diffraction for identifying the crystalline phases, Archimedes method for the textural properties, scanning electron microscopy for the microstructure, and Vickers indenter and three-point bending tests for the mechanical properties. In addition, the macroscopic capture cross-section Σ for thermal neutrons was estimated considering each composite formulation. It was found that the processing route is very suitable for producing low-porosity Al2O3/GdAlO3 composites, which present similar mechanical properties to those of alumina. Both the material density and Σ increase with increasing the starting amount of Gd2O3, in a way that for the eutectic composite the density is 50% higher than that of pure alumina, and Σ is about 550000 c.u. The effect of the material porosity on Σ was also considered. The obtained results indicate that the proposed processing route is very attractive for producing these ceramic composites for technological applications.
The effect of monoaluminum phosphate (Al(H.sub.2PO.sub.4).sub.3) addition in the thermochemical process of a kaolinitic clay was studied and compared with the pure clay. Monoaluminum phosphate ...incorporation is of technological interest for the widely use of this material as an effective binder. From this point of view is important to clarify the processing strategy of kaolinitic clay-MAP based ceramics. This work comprised the characteristics of the obtained ceramics using differential thermal analysis, thermogravimetric analysis (TG), dilatometric analysis, X-ray powder diffraction with Rietveld refinement, mechanical resistance and textural properties. The addition of MAP did not affect the temperature of the kaolinite dehydroxilation (600-500 °C) but reduced this transformation as it was observed in TG curve. The amount of mullite decreased and cristobalite formation was stimulated with MAP presence in the samples fired at 1400 °C. Mullite cell parameters were not modified. The present study gives information for further clay-based materials designed with MAP. It can be concluded that the incorporation of low percentages of MAP in the potential formulation of technological ceramics would not imply important changes in the macroscopic properties of these type of ceramic materials.
This article aims to shed light on the drivers underlying the role and scope of intentional governance of the structural dynamics of whole interorganizational networks. Prior research has ...distinguished networks that are emergent from networks that are orchestrated. While empirical studies have shown situations in which the role and scope of intentional governance of whole interorganizational networks has changed in time, and there is a growing interest regarding the endogenous drivers of network dynamics, the dimensions that influence intentional governance of network structure dynamics and the way this is carried out remain still to be elucidated. In order to pinpoint these drivers, we leverage the models of network structure dynamics elaborated within studies conducted at the intersection between network research and complexity science to propose a multilevel interpretive framework that clarifies the role and scope of intentional agency at different structural levels of interorganizational networks. Our framework advances a twofold conceptual contribution: on one hand, we tackle the change in the role and scope of intentional governance of network structures in both the early stages and the later stages of network evolution. On the other, we interpret the network of formal ties as resembling the accelerating network model, with the network of informal ties being akin to the scale-free (or truncated scale-free) network model of complex networks theory.
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