Non-crystalline Inorganic Constituents of Soil

Abstract

Non-crystalline inorganic constituents of soil, such as volcanic glasses, phytoliths, laminar opaline silica, allophane, and imogolite are introduced using optical and electron microscope images and energy dispersive X-ray (EDX) analysis. The Al-humus complex and Al-rich Sclerotia grains are also introduced. The volcanic glasses are formed from magma and can be categorized as primary. All of these non-crystalline inorganic constituents are found in volcanic ash soils. Among these, phytoliths can be found under vegetation in many other soils than volcanic ash soils. Formation of allophanic materials from fresh pumice is shown stepwise using polished sections to demonstrate microscopic distribution of elements and inorganic constituents. Allophane and imogolite are rich in Al whereas their parent material, volcanic ash, is silica-rich. Changes in morphological property and element concentration of volcanic ash or volcanic glass during the formation of these secondary non-crystalline constituents are discussed.

Colloidal Stability of Imogolite Nanotube Dispersions: A Phase Diagram Study

“…Naturally occurring worldwide either in weathered volcanic soils or in Spodosols, INTs can also be synthesized easily by using low-temperature sol–gel methods, while controlling their inner diameter (1.5–3 nm), shape (single-walled: SW; or double-walled: DW structures, Figure b), or surface properties. ,, Thanks to these unique behaviors, INTs are becoming appealing for a wide range of potential applications, , ranging from nanocomposites to molecular filtration or for energy production to cite a few. Currently, it remains a very challenging task to control the packing of nanotubes before or during the processing into films, membranes, or complex hierarchical structures .…”

“…A nanotube wall is constructed from (OH) 3 Al 2 O 3 (Si,Ge)(OH) elementary units, where hydroxyl groups and atoms are labeled here from outside to inside the wall. 26,27 Naturally occurring worldwide either in weathered volcanic soils or in Spodosols, 28 INTs can also be synthesized easily by using low-temperature sol−gel methods, 29 while controlling their inner diameter (1.5−3 nm), shape (single-walled: SW; or double-walled: DW structures, Figure 1b), or surface properties. 27,30,31 Thanks to these unique behaviors, INTs are becoming appealing for a wide range of potential applications, 32,33 ranging from nanocomposites 34 to molecular filtration 35 or for energy production 36 to cite a few.…”

Influence of the Al/Ge Ratio on the Structure and Self-Organization of Anisometric Imogolite Nanotubes

“…Imogolite is a naturally occurring clay mineral which is commonly found in soils as a weathering product of volcanic glass or pyroclastic materials [1][2][3]. Therefore, this makes it a good marker of the paleoclimate transition from warm/wet to cold/dry conditions [4,5].…”

Nanomaterials From Imogolite: Structure, Properties, and Functional Materials

“…(a) Soil profile from Kiwadashima, Tochigi, Japan, (b-c) Optical observations of gel films (white arrows) found in the 2Bw1 and 3Bw5 horizons, respectively, (d) Typical transmission electron microscopy (TEM) micrograph of imogolite extracted from the gel-like film, in association with allophane (spherical particles). Adapted with permission from [3].…”

“…Its nominal composition is (OH) 3 Al 2 O 3 Si(OH), where hydroxyls groups and atoms are labelled here from outside to inside the nanotube. Imogolite nanotube consists of a curved di-octahedral gibbsite-like layer (Al(OH) 3 ) with isolated (SiO 3 )OH tetrahedron units connected via covalent bonding between three mutual oxygen atoms, as it is shown in Figure 5.3a. The curvature effect can be understood in a ultra simplified way by noting that the distance between adjacent oxygen atoms on the tetrahedron is shorter than that on the planar gibbsite-like sheet.…”