Chemical-Garden Formation, Morphology, and Composition. I. Effect of the Nature of the Cations (original) (raw)
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Phys. Chem. Chem. …, 2010
We have compared the behaviour of the chloride salts of the cations Ca 2+ , Sr 2+ and Ba 2+ of Group 2 of the Periodic Table in the formation of chemical gardens in silicate solutions. We performed analyses of morphology, composition and microstructure using environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). We have identified different growth regimes in these salts (jetting and budding), which are dependent on the concentration of the silicate solution. The behaviour is similar for all the cations but reactivity decreases down the group and is directly proportional to the solubility of the salts: Ca 2+ > Sr 2+ > Ba 2+ .
Journal of colloid and …, 2002
Chemical gardens are the plant-like structures formed upon placing together a soluble metal salt, often in the form of a seed crystal, and an aqueous solution of one of many anions, often sodium silicate. We have observed the development of chemical gardens with Mach-Zehnder interferometry. We show that a combination of forced convection from osmosis and free convection from buoyancy, together with chemical reaction, is responsible for their morphogenesis. C 2002 Elsevier Science (USA)
Spatially resolved analysis of calcium–silica tubes in reverse chemical gardens
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011
Reverse chemical gardens consist of hollow tubular structures that form in a downward direction from a mechanically held silicate crystal immersed in a metal salt solution. As a model case for this reaction-precipitation system, we investigate the composition, morphology, and microstructure of these tubes in the framework of an experimental model based on preselected reactant concentrations and flow rates. In these experiments, the heavier waterglass solution is being injected downward into large volumes of lighter calcium chloride solution. The resulting hollow precipitation tubes have diameters that range from 0.5 to 3.0 mm. The tube walls have a typical width measurement of 40 m and are gradient materials. Scanning electron microscopy along with energy-dispersive X-ray spectral data identify calcium and silicon as the major components within the exterior and interior surfaces, respectively. Finally, we compare the behavior, chemical composition, and morphology of tubular precipitation structures created upon the hydrodynamic injection of calcium chloride into a large volume of sodium silicate solution carried out in the upward direction.
Chemical-Garden Formation, Morphology, and Composition. II. Chemical Gardens in Microgravity
Langmuir, 2011
We studied the growth of metal-ion silicate chemical gardens under Earth gravity (1 g) and microgravity (μg) conditions. Identical sets of reaction chambers from an automated system (the Silicate Garden Habitat or SGHab) were used in both cases. The μg experiment was performed on board the International Space Station (ISS) within a temperature-controlled setup that provided still and video images of the experiment downlinked to the ground. Calcium chloride, manganese chloride, cobalt chloride, and nickel sulfate were used as seed salts in sodium silicate solutions of several concentrations. The formation and growth of osmotic envelopes and microtubes was much slower under μg conditions. In 1 g, buoyancy forces caused tubes to grow upward, whereas a random orientation for tube growth was found under μg conditions.
Reverse chemical garden reaction of cementitious materials
Japan Geoscience Union, 2014
Recent advances in the nano-scale mineralogy extend from the extraterrestrial materials known as in cosmic dusts and asteroids to ordinary industrial materials like the cementitious materials. The distinct property of nano materials can be characterized from the points of view of (1) nucleation, (2) self-assembly behavior and (3) flexibility in the form. A very common industrial material, cement is a typical one consisted of nano particles of calcium silicate hydrartes (C-S-H). Crystal growth experiment of cementitous materials can be recently performed using interferometric and nanoscopic techniques. Although the cement reaction producing C-S-H from silicates with Ca(OH) 2 (portlandite: CH) or more alkaline solution is extensively occurring at buildings under and after construction, similar reaction is expected at the interface of natural rock and concrete-building such like tunnel, dam and underground repository for radioactive wastes. Hyper alkaline alteration experiment using ve...
Microporous and Mesoporous Materials, 1998
Cu and Co ions in Na-and H-forms of ZSM-5 and ferrierite were used to elucidate siting-coordinationbondiq of bare divalent cations and cation-extra-framework ligand complexes (with NO, CO, NO,, H,O and NH,) in high silica zeolite matrices. By using a multi-spectroscopic approach involving VIS-NIR diffuse reflectance spectra of the Cu"+ and Co'+ ions, Cu + luminescence, FTIR spectra of skeletal T-O-T vibrations and vibrations of adsorbed molecules (ligands), information on the bonding of the bare cations and cation-guest-ligand complexes to the framework oxygen ligands was obtained. Based on our previous results on characteristic spectral features of the c'u siting in dehydrated ZSM-5, a correlation between coordination of the Cu ions in hydrated and dehydrated ZSM-5 zeolites at various Cu:'AI/Si ratios was established. and the importance of Al distribution in the framework (so called 'Al pairs' and single Al atoms) for the Cu ion exchange and siting in zeolites was evidenced. Owing to the stable divalency of Co-. '+ in zeolites. this cation was used to monitor coordination-bonding of bare divalent cations and cationligand complexes in ferrierite. It has been found that the Co 2 ' ions induce local perturbations of the T--O T bonds adjacent to the cation reflected in three characteristic ('deformation') shifts of the T--O--T framework vibrations. Simultaneously measured d-d transition spectra of the Co 2t ions, providing information on the symmetry of the framework oxygen atoms bonding a bare cation, indicated that the changes in T--O-T vibrations are accompanied h;y changes of VIS spectra. Depending on the strength and number of the extra-framework ligands. this local framework deformation induced by the Co 2+ ion is partly. or eventually completely, removed (T -O--T vibration 'relaxation' shift) upon adsorption of molecules with formation of cation-guest-ligand complexes (also detected via ligand vibration itself ). G
Effects of Amino Acids on Iron-Silicate Chemical Garden Precipitation
Langmuir
Understanding the structure and behavior of chemical gardens is of interest for materials science, for understanding organic−mineral interactions, and for simulating geological mineral structures in hydrothermal systems on Earth and other worlds. Herein, we explored the effects of amino acids on inorganic chemical garden precipitate systems of iron chloride and sodium silicate to determine if/how the addition of organics can affect self-assembling morphologies or crystal growth. Amino acids affect chemical garden growth and morphology at the macro-scale and at the nanoscale. In this reaction system, the concentration of amino acid had a greater impact than the amino acid side chain, and increasing concentrations of organics caused structures to have smoother exteriors as amino acids accumulated on the outside surface. These results provide an example of how organic compounds can become incorporated into and influence the growth of inorganic self-organizing precipitates in far-from-equilibrium systems. Additionally, sample handing methods were developed to successfully image these delicate structures.