Chemical binding

About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.

Artificial aggregates for self-healing of cement paste and chemical binding of aggressive ions from sea water

Abstract: In marine environments, once concrete cracks aggressive ions immediately migrate into the cracks together with sea water and can cause durability problems. In this study, an innovative self-healing agent that can bind the aggressive ions from marine environments and simultaneously promote the self-healing efficiency was designed and encapsulated as artificial aggregates. As the bulk matrix cracks, the artificial aggregates were intersected. The self-healing agent was exposed to the crack surfaces and reacted with synthetic sea water to heal the crack. Experimental results show that the reaction of the healing agent with synthetic sea water and consequently the formation of Friedel's salt, ettringite, and hydrotalcite in cracks leaded to an efficient chemical binding of Cl−, SO42−, and Mg2+ ions in the synthetic sea water. Meanwhile, for cracks with an initial width of 350–450 μm, the closure ratio due to self-healing by the healing agent was approximately 45% during the first 12 h, about 3 times that in the referenced specimens without the healing agent. Therefore, not only the aggressive ions entering into cracks can be chemically bound, but also the further ingress of aggressive ions from synthetic sea water can be hindered by the rapid crack closure due to self-healing.

A time resolved study of the mitigation of graphite chemical erosion in deuterium plasmas containing beryllium

Abstract: The interaction of the graphite strike plate material in ITER, with a divertor plasma containing beryllium, is simulated experimentally in PISCES-B. Graphite targets are exposed at 600 K to deuterium plasmas with fixed beryllium fractions ( ) in the range 0.0003 ≤ fBe ≤ 0.011. From the onset of beryllium injection, the intensity of plasma CD band optical emission caused by target chemical erosion, diminishes exponentially at a rate found to depend on fBe. The rate of chemical erosion decay, , is found to increase with fBe over the range of beryllium fractions explored and can be described by a simple power law expression, , where α = 785 ± 161 s−1 and β = 2.07 ± 0.10. Evidence of chemical binding between the surface carbon and beryllium is found in XPS analysis of targets following exposure. A reduction in available surface carbon bonds, due to the presence of beryllium, is believed to be responsible for the observed mitigation of chemical erosion.

Iron addition as a shallow lake restoration measure: impacts on charophyte growth

Abstract: Eutrophication has caused a decline of charophyte species in many shallow lakes in Europe. Even though external inputs of phosphorus are declining, internal loading of P from the sediment seems to delay the recovery of these systems. Iron is a useful chemical binding agent to combat internal phosphorus loading. However, the effects of iron addition on charophytes are not yet known. In this study we experimentally tested the potential toxicity of iron(III)chloride (FeCl3) on two different charophytes, Chara virgata Kutzing and Chara globularis Thuiller added at the concentration of 20 g Fe m−2 and 40 g Fe m−2 to the surface water. C. virgata growth was not significantly affected, whereas C. globularis growth significantly decreased with increasing iron concentrations. Nonetheless, biomass of both species increased in all treatments relative to starting conditions. The decrease of C. globularis biomass with high iron additions may have been caused by a drop in pH and alkalinity in combination with iron induced light limitation. Iron addition over a longer time scale, however, will not cause this rapid drop in pH. Therefore, we conclude that adding iron(III)chloride in these amounts to the surface water of a lake can potentially be a useful restoration method.