Colloidal Alumina—the Chemistry and Morphology of Colloidal Boehmite

Tepper

International Journal of Smart and Nano Materials

2016

The pristine point of zero charge (p.p.z.c) and zeta potential as a function of pH of boehmite oxide/hydroxide (α-Al 2 O 3 ·H 2 O) have been determined for three filter media. The active component in the first two filter media is boehmite nanofibers, only 2 nm in diameter and about 300 nm long. Boehmite nanofibers create high zeta potential (ζ true ≥46 mV) in aqueous solutions in the pH range of 3-8. The p.p.z.c. values were determined to be 11.60 ± 0.15 for nanofibers grafted onto microglass fibers and 11.40 ± 0.15 for agglomerated nanofibers. In the third filter media, a boehmite nanolayer in the form of monocrystalline oxide/hydroxide with a thickness of approximately 1.2 nm is electroadhesively deposited onto siliceous support material with large surface area of about 50 m 2 /g, therefore forming a highly electropositive composite of boehmite nanolayer on the second highly electronegative solid. Boehmite's oxide-hydroxide nanolayer surface creates high zeta potential (ζ true ≥50 mV) in aqueous solutions in the pH range of 3-8. The p.p.z.c. value was determined to be 11.38 ± 0.15. The reported values are within accuracy, but they are much higher than the values reported in the literature. X-ray powder diffraction data were supplemented by microscopy, infrared spectroscopy in order to characterize fully synthetic boehmite surfaces.

“…void fraction (8) where k = 150 is an empirical constant established via experimentation. This pressure drop value should not be exceeded during streaming potential measurements.…”

Section: Streaming and Zeta Potential Measurement On Granular Filter mentioning

confidence: 99%

“…[7] and ref. [8]) with an average value of 8.7 ± 0.9 based on 37 out of total 40 reported values [7] where the error bound is an estimated value of 1 standard deviation (1σ).…”

Section: Introductionmentioning

confidence: 99%

Pristine point of zero charge (p.p.z.c.) and zeta potentials of boehmite’s nanolayer and nanofiber surfaces

Tepper

International Journal of Smart and Nano Materials

2016

Phil. Trans. R. Soc. A.

“…Mineral colloidal liquid crystals: the fallow years In the decades after the publication of Onsager's theory, the activity on viruses continued, for example, with the subsequent discovery of smectic phases in suspensions of TMV by Oster in 1950 [20], later supplemented by LCs found in other rod-like (although semiflexible) viruses such as fd virus [21]. However, there was little activity to prepare new rod-or plate-like mineral colloids with the exception of continued efforts on Zocher's part leading to his discovery of a nematic phase in colourless suspensions of fibrous rod-like γ-AlO(OH) particles [22], independently found by Bugosh [23].…”

Section: Introductionmentioning

confidence: 99%

Liquid crystal phase transitions in suspensions of mineral colloids: new life from old roots

Lekkerkerker

Vroege

2013

122

103

A review is given of the field of mineral colloidal liquid crystals: liquid crystal phases formed by individual mineral particles within colloidal suspensions. Starting from their discovery in the 1920s, we discuss developments on the levels of both fundamentals and applications. We conclude by highlighting some promising results from recent years, which may point the way towards future developments.

Proc. Natl. Acad. Sci. U.S.A.

“…Fibrous PB has a particularly poor crystalline structure (14,15), and its crystal structure and morphology have never been clarified even by using the modern crystallography methods such as radial distribution function analyses with synchrotron X-ray diffraction (16,17) and NMR (18). To solve such a long-standing problem with fibrous PB, we made full use of conventional transmission electron microscopy (TEM) methods, high-resolution TEM (HRTEM) imaging, and electron diffraction (ED), and successfully revealed the detailed morphologies and crystal structures, including determination of the fiber axis, of fibrous PB.…”

mentioning

confidence: 99%

One-dimensional nanowires of pseudoboehmite (aluminum oxyhydroxide γ-AlOOH)

Iijima

Yumura

Liu

2016

We report the discovery of a 1D crystalline structure of aluminum oxyhydroxide. It was found in a commercial product of fibrous pseudoboehmite (PB), γ-AlOOH, synthesized easily with low cost. The thinnest fiber found was a ribbon-like structure of only two layers of an Al-O octahedral double sheet having a submicrometer length along its c axis and 0.68-nm thickness along its b axis. This thickness is only slightly larger than half of the lattice parameter of the b-axis unit cell of the boehmite crystal (b/2 = 0.61 nm). Moreover, interlayer splittings having an average width of 1 nm inside the fibrous PB are found. These wider interlayer spaces may have intercalation of water, which is suggested by density functional theory (DFT) calculation. The fibers appear to grow as almost isolated individual filaments in aqueous Al-hydroxide sols and the growth direction of fibrous PB is always along its c axis.ow-dimensional materials such as quantum dots (1), nanowires (2, 3), and nanosheets (4) have attracted interest in academia and industry. Carbon nanotubes (5), a typical 1D inorganic material, have been investigated widely, but new 1D inorganic materials prepared by a simple and reliable method have rarely been reported.The aluminum ore bauxite primarily comprises aluminum hydroxide possessing different crystalline forms. The thermal dehydration of aluminum hydroxide produces alumina Al 2 O 3, one of the most important materials in modern industries. γ-Boehmite (γ-AlOOH) (6) is a typical aluminum oxyhydroxide with a crystal structure similar to that of lepidocrocite (γ-FeOOH) (7). These metal oxyhydroxides, represented by γ-MO(OH), where M = Fe, Ni, Mn, Sc, Ti, etc., have attracted interest in fields from energy to medicine. In a nickel-hydrogen battery, the formation of poorly crystalline γ-NiOOH on the cathode has been shown to cause the memory effect of the battery (8). Titanate nanosheets have recently attracted attention in the electronics community because of their semiconducting properties (9). Hydrogen generation by aluminum-water reactions for onboard vehicular hydrogen storage (10) and the radiolytic generation of hydrogen in conjunction with metal corrosion in water in nuclear energy and waste systems (11) both involve aluminum hydroxides as reaction products. Aluminum hydroxide has also been used as a vaccine adjuvant (12) and its biochemical mode of action in a recent medical technology is being investigated (13).Boehmite is synthesized by aging noncrystalline aluminum hydroxide sol in an aqueous solution at a specific pH, and it has the basic crystal structure of double sheet of a metal-oxygen octahedron layer piled up through hydrogen bonding, as illustrated in Fig. S1. Poorly crystallized boehmite, often called pseudoboehmite (PB), forms in various crystal morphologies, such as thin films, thin platelets, and nanometer-sized rods or fibers. Importantly, the characteristics of alumina Al 2 O 3 for industrial use prepared by thermal dehydration are influenced by the morphology of the starting boehmite c...