timer Asked: Apr 17th, 2020

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My research paper talks about studying the crystal structure and morphology of halloysite clay mineral.

Step one

  • I want you to write a literature review about dehydrating the hydrated halloysite.
  1. Explains the crystal structure of both hydrated and dehydrated halloysite and the difference in the morphology of both dehydrated and hydrated halloysite (which one is prismatic and which is cylindrical).
  1. (I need you to explain the transformation throughout certain techniques which have been mentioned in literature, I will send you some papers that helps understanding this transformation. Also, it would be better if you look at specific techniques such (TGA- thermogravimetry analysis /DTA-differential thermal analysis, XRD- X-ray diffraction, Raman microscope spectroscopy, and SEM/TEM); those are the important techniques that I want you to focus on.
  • Could you please provide the diameter change that occurs to the halloysite when it transfer from the hydration to dehydration.

You can use relevant graphs and results from literature for verification and could you please provide below the figures explaining the science behind the figures and results .

Step two:

  1. What work being done for hydrating the dehydrated halloysite. To be specific, after transferring the hydrated halloysite to dehydrated halloysite; try to find what compounds or any organic compound that can restore this hydrated halloysite.
  2. Use the above techniques that helps explain the restoration of the dehydrated halloysite to hydrated halloysite.

I want you to follow the above structure while writing this literature review. Also, I will attach some helpful article papers that will save a lot of time for you, but you should also seek out references of your own. Also, I will attach powerpoint slides that could support you while writing this research paper. Please if you need any question let me know.

Please don't panic while reading the guidelines structure, I just want to explain you carefully what I want in this research paper.

Unformatted Attachment Preview

Clay Minerals, (2016) 51, 325–350 Correlations among the mineralogical and physical properties of halloysite nanotubes (HNTs) S T E P H E N H I L L I E R 1 , 2 , * , R I K B RY D S O N 3 , E V E LY N E D E L B O S 1 , TO N Y F R A S E R 1 , N I A G R AY 1 , H E L E N P E N D LO W S K I 1 , I A N P H I L L I P S 1 , J E A N RO B E RT S O N 1 A N D I A N W I L S O N 4 2 1 The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK Department of Soil and Environment, Swedish University of Agricultural Sciences (SLU), Uppsala SE-75007, Sweden 3 Institute for Materials Research, SCaPE, University of Leeds, Leeds LS2 9JT, UK 4 Withielgoose Farmhouse, Withiel, Bodmin, Cornwall PL30 5NW, UK (Received 10 January 2016; revised 11 May 2016; Guest editor: Jock Churchman) A B S T R AC T : Twenty one samples of relatively pure tubular halloysites (HNTs) from localities in Australia, China, New Zealand, Scotland, Turkey and the USA have been investigated by X-ray diffraction (XRD), infrared spectroscopy (IR) and electron microscopy. The halloysites occur in cylindrical tubular forms with circular or elliptical cross sections and curved layers and also as prismatic tubular forms with polygonal cross sections and flat faces. Measurements of particle size indicate a range from 40 to 12,700 nm for tube lengths and from 20 to 600 nm for diameters. Size distributions are positively skewed with mean lengths ranging from 170 to 950 nm and mean diameters from 50 to 160 nm. Cylindrical tubes are systematically smaller than prismatic ones. Features related to order/ disorder in XRD patterns e.g. as measured by a ‘cylindrical/prismatic’ (CP) index and IR spectra as measured by an ‘OH-stretching band ratio’ are related to the proportions of cylindrical vs. prismatic tubes and correlated with other physical measurements such as specific surface area and cation exchange capacity. The relationships of size to geometric form, along with evidence for the existence of the prismatic form in the hydrated state and the same 2M1 stacking sequence irrespective of hydration state (i.e. 10 vs. 7 Å) or form, suggests that prismatic halloysites are the result of continued growth of cylindrical forms. KEYWORDS: halloysite, nanotubes, HNTs, cylindrical, prismatic, polygonal, length, diameter, specific surface area. Although it is probably less abundant in nature than kaolinite, the mineral halloysite is of widespread occurrence in many soils (Dixon, 1989) and also forms important economic accumulations in deposits mainly of hydrothermal origin (Wilson & Keeling, 2016, this issue). Halloysite has fascinated investigators ever since it was first discovered; in obvious contrast to the other kaolin subgroup minerals, namely * E-mail: DOI: 10.1180/claymin.2016.051.3.11 kaolinite, dickite and nacrite which occur primarily in planar platy or blocky forms, many halloysites adopt an unusual tubular morphology. Spheroidal halloysite is also very well documented especially from soils, but here our focus will be entirely on the tubular form of halloysite, increasingly referred to as halloysite nanotubes or ‘HNTs’ due to a rapidly expanding range of applications in a wide variety of technologies. Aside from its unusual morphologies, halloysite is also distinct amongst the other kaolin polytypes in that it is hydrated with H2O molecules positioned in the interlayer space between the fundamental 1:1 layer © 2016 The Mineralogical Society 326 S. Hillier et al. combination of tetrahedral and octahedral sheets that form the basic kaolin structure. Indeed, according to Churchman & Carr (1975) the single most important characteristic that identifies, defines, and distinguishes halloysite as a distinct kaolin mineral is the presence, or evidence of the former presence, of molecules of H2O in the interlayer space. Interlayer H2O in halloysite is exceedingly labile and in response to changing environmental conditions, both naturally in the field or subsequently in the laboratory, it is readily and irreversibly lost. In its fully hydrated state halloysite contains two interlayer H2O molecules accounting for 12.25 wt.% of the molecular formula unit which can be written as Al2Si2O5(OH)4·2H2O. With this full complement of interlayer H2O, halloysite has a primary basal spacing, as observed in XRD patterns, of ∼10 Å. Because the loss of the interlayer H2O is generally not a reversible process, depending on the handling and storage history, halloysites are most commonly observed with smaller H2O contents by mass and smaller basal spacings. In an essentially dehydrated state the layer spacing approaches the 7 Å basal spacing characteristic of all other kaolin polytypes. Due to this variability of basal spacing as a function of the degree of hydration it has been recommended that the approximate basal spacing should be appended to the name, e.g. halloysite (10 Å) and halloysite (7 Å) would signify hydrated and dehydrated specimens, respectively (Bailey, 1980). In the older literature some workers referred to fully hydrated halloysite as “endellite” and the dehydrated form as “metahalloysite”, but both of these terms are now regarded as obsolete (see Brindley (1984), p. 153, for a brief summary of halloysite nomenclature past and present). Most investigators now accept that the primary form of halloysite, i.e. at the time of its formation, is the fully hydrated 10 Å form and that other forms with less H2O and consequent smaller basal spacings have undergone some degree of postformation dehydration. Although there are earlier reports, Bates et al. (1950) are usually attributed with discovering the tubular morphology of halloysite perhaps because they immediately offered an explanation for the cylindrical form as being the result of a mechanism to compensate for the lateral misfit between a larger tetrahedral and a smaller octahedral sheet of the basic kaolin 1:1 layer type. More recently, Singh (1996) has suggested that rolling is energetically favored in halloysite because it offers the least resistance from Si-Si Coulombic repulsion. Putting aside the various explanations for the curvature of the layers and the consequent rolled or cylindrical form of halloysite, it was nonetheless evident, even in the earliest literature on halloysite, that in addition to cylindrical tubes, polygonal tubes with a prismatic structure exhibiting flat faces present another distinctive morphology of tubular halloysite (Bates & Comer, 1957; Hoffman et al., 1962; Chukhrov & Zvyagin, 1966; Bailey, 1990; Kogure et al., 2013). In the present manuscript it is demonstrated that there are systematic relationships between the XRD patterns, IR spectra, cation exchange capacity (CEC), particle size, specific surface area and porosity of tubular halloysites all of which are fundamentally related to the proportions and structures of cylindrical tubular vs. prismatic polygonal tubular forms present in any given sample. Furthermore, it is emphasized that prismatic forms are not rare morphologies, but occur widely in many halloysite samples. The understanding presented of the interrelation of form (cylindrical vs. prismatic) and properties should be useful in the wide variety of emerging applications of HNTs and the relationships demonstrated may also help to constrain models of tubular halloysite formation and growth. M AT E R I A L S A N D M E T H O D S Twenty one different samples of tubular halloysite were studied. The samples were obtained from halloysite occurrences in Australia, China, New Zealand, Scotland, Turkey and the USA including various commercially exploited deposits, (Table 1). Sample 1Au is from the Eucla basin in S. Australia and is equivalent to sample CLA-1 described previously by Keeling et al. (2011) and Pasbakhsh et al. (2013). Six samples originate from halloysite deposits in China, including the Zunyi region (2Ch), Dafang region (3Ch, 4Ch), the Bifa deposit (5Ch), the Wan Jiar deposit (6Ch) (Wilson, 2004; Wilson & Keeling, 2016, this issue), and one sample (7Ch) is from an unknown location in China. The former were collected by one of the current authors (Ian Wilson), and the latter was supplied by IMERYS, courtesy of Mr Jeremy Hooper. Three samples are from New Zealand. The sample supplied by IMERYS (8NZ) is believed to originate from the well-known Matauri Bay deposit, North Island, as are the other two samples. That supplied by Jock Churchman (9NZ) was also described by Joussein et al. (2005) where it corresponds to the sample shown in fig. 5a (incorrectly captioned as 5c in Joussein et al., 2005; Churchman pers. comm. 2008), whilst the exact source of the third sample (10NZ) is unknown. The sample from Scotland (11Sc) is from Mineralogical and physical properties of HNTs 327 TABLE 1. Origin and provenance of halloysite samples investigated. Sample Country Location Source of samples 1Au 2Ch 3Ch 4Ch 5Ch 6Ch 7Ch 8NZ 9NZ 10NZ 11Sc 12Tu 13Tu 14US 15US 16US 17US 18US 19US 20US 21US Australia China China China China China China New Zealand New Zealand New Zealand Scotland Turkey Turkey USA USA USA USA USA USA USA USA Ecula Basin, S. Australia Zunyi region, Guizhou Province Dafang region, Guizhou Province Dafang region, Guizhou Province Bifa deposit, Yunnan Province Wan Jiar depoist, Yunnan Province Unknown location Matauri Bay, North Island Matauri Bay, North Island Matauri Bay, North Island Hospital Quarry, Elgin, Scotland Unknown location Balikesir region Dragon Mine, Utah Dragon Mine, Utah Dragon Mine, Utah Dragon Mine, Utah Dragon Mine, Utah Dragon Mine, Utah Dragon Mine, Utah Bovill deposit, Idaho John Keeling Ian Wilson Ian Wilson Ian Wilson Ian Wilson Ian Wilson IMERYS IMERYS Jock Churchman Unknown Heddle’s halloysite IMERYS Unknown Applied Minerals. Inc Applied Minerals. Inc Applied Minerals. Inc Applied Minerals. Inc Applied Minerals. Inc IMERYS Sigma Aldrich, Lot No MKBQ2512V Iminerals Inc the Macaulay Collection at the James Hutton Institute; it originates from Hospital Quarry, Elgin, as described previously by Hillier & Ryan (2002) and was collected by Heddle (1882); a counterpart ‘Spec. 493.1’ of this sample is held in the National Museum of Scotland in Edinburgh. A recent visit to the site showed that this halloysite occurs in a brecciated zone of Permian sandstone. Two samples were obtained from deposits in Turkey, one (12Tu) of unknown provenance was provided by IMERYS whilst the other (13Tu) originates from the Balikesir region, halloysite deposits of which have been described previously by Ece & Schroeder (2007). The remaining eight samples are all from the USA. Seven originate from the Dragon Mine in Utah, five of which were supplied by Applied Minerals, who now own and operate the mine. Additional samples from the Dragon mine include one (19US) supplied by IMERYS, and one which can be purchased from Sigma Aldrich (20US). The remaining sample (21US) from the USA is from the Bovill deposit, Idaho, supplied courtesy of IMinerals Inc. Chemical analyses (by X-ray Fluorescence – XRF), all using fused glass beads but made in a variety of different laboratories, were available for all samples. Due to differences in reporting, such as including or not including loss on drying or loss on ignition, for ease of comparison the analyses are compiled in Table 2 normalized to a theoretical kaolinite composition. X-ray diffraction For powder XRD analyses, 3 g samples were McCrone milled for 12 min in ethanol and the resulting slurry spray dried at 60°C directly from the mill to form random powder specimens (Hillier, 1999). Note that drying at 60°C from ethanol results in all halloysites dehydrating to the 7 Å form. Specimens were loaded into a Siemens D5000 X-ray diffractometer and scanned between 2 and 70°2θ, counting for 2 s per 0.02° step using Co-Kα radiation selected by a diffracted-beam monochromator. Diffraction patterns were also recorded from 3 to 70°2θ in 0.0167° steps on a Panalytical Xpert Pro diffractometer using Ni-filtered Cu radiation and counting for 100 s/step using an Xcelerator detector. Peak positions, intensities and peak width as Full Width at Half Maximum (FWHM) were measured using Bruker Diffrac Eva software, using data obtained from the D5000. Quantitative mineralogical analysis of all samples was made by a 45.91 47.37 46.60 45.77 45.33 45.93 46.39 47.24 48.20 50.13 45.81 44.97 46.92 46.39 46.05 45.78 46.23 45.58 46.26 45.73 48.81 46.55 1Au 2Ch 3Ch 4Ch 5Ch 6Ch 7Ch 8NZ 9NZ 10NZ 11Sc 12Tu 13Tu 14US 15US 16US 17US 18US 19US 20US 21US Kaolinite 38.91 37.97 39.37 39.63 39.87 39.89 39.15 38.20 37.43 35.52 36.16 39.25 38.32 39.43 39.75 37.55 39.08 39.93 39.07 39.60 35.46 39.50 Al2O3 0.09 0.05 0.00 0.01 0.07 0.00 0.00 0.10 0.09 0.07 0.19 0.20 0.04 0.00 0.00 0.10 0.00 0.00 0.02 0.01 0.14 0.00 TiO2 0.86 0.41 0.05 0.09 0.34 0.11 0.28 0.40 0.25 0.26 3.02 1.12 0.64 0.10 0.07 2.52 0.43 0.00 0.51 0.22 0.95 0.00 Fe2O3 0.00 0.01 0.00 0.02 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.02 0.00 Mn3O4 0.17 0.03 0.00 0.09 0.05 0.00 0.04 0.08 0.00 0.00 0.23 0.09 0.05 0.07 0.05 0.00 0.08 0.34 0.02 0.07 0.16 0.00 MgO 0.00 0.18 0.02 0.25 0.17 0.11 0.13 0.01 0.00 0.07 0.13 0.12 0.06 0.09 0.13 0.09 0.22 0.11 0.16 0.36 0.23 0.00 CaO 0.09 0.03 0.00 0.03 0.20 0.00 0.04 0.00 0.00 0.00 0.48 0.30 0.02 0.00 0.00 0.00 0.00 0.03 0.00 0.04 0.22 0.00 K2O 0.00 0.00 0.00 0.15 0.00 0.00 0.00 0.00 0.07 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.05 0.00 0.02 0.05 0.00 Na2O All data normalized to theoretical kaolinite basis (86 wt.%) which is also shown for comparison. Note that elements beyond Si and Al may occur variably as isomorphous substitutions (e.g. Fe), exchangeable cations (e.g. Mg, Ca, K, Na) or in associated impurities. SiO2 Sample TABLE 2. Chemical compositions (wt.%, XRF) of the samples. 328 S. Hillier et al. Mineralogical and physical properties of HNTs full-pattern fitting method using experimental patterns as standards for all minerals identified. The method is as described by participant 18 in the 3rd (2006) Reynolds Cup competition (quantitative clay mineralogy) (Omotoso et al., 2006), but without the addition of an internal standard. For halloysite, standard patterns were extracted from the sample set, based on the best examples and on verification of purity by multiple analytical methods. Patterns for all other minerals were obtained from examples held in the Macaulay mineral collection. In all cases extensive cross checks on purity were performed. The presence or absence of kaolinite in the samples was also verified by formamide intercalation (Churchman et al., 1984). Samples were ground gently under a small amount of water to produce a slurry that was pipetted onto a glass slide; once air dry the specimens were scanned from 5 to 15°2θ on the Panalytical Xpert Pro diffractometer detailed above with a total scan time of 9 min. The sample was then sprayed with a formamide/water (10%) solution, allowed to stand for 40 min and then rerun on the diffractometer using the same 9 min scan; as such, the total exposure time to formamide was ∼50 min. Transmission electron microscopy Samples for transmission electron microscopy (TEM) were prepared by dispersing powders in methanol and drop casting onto holey carbon supports on copper TEM grids. This preparation method was compared with a procedure involving simply dusting powders onto TEM grids; for both methods similar results were obtained. The TEM specimens were examined using bright-field, dark-field and phasecontrast imaging, selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) spectroscopy at 200 kV using an FEI CM200 field emission TEM/STEM. Electron diffraction patterns were recorded on photographic film. Scanning electron microscopy For SEM secondary electron imaging either powders or fractured surfaces of specimens were mounted onto standard aluminium stubs using double-sided carbon tabs as the adhesive, and sputter coated with a thin layer of platinum to reduce charging under the electron beam. Analysis was conducted using a Carl Zeiss Sigma VP Field Emission Scanning Electron Microscope (FEG-SEM) in variable pressure mode at an accelerating voltage of 15 kV. 329 For image analysis of particle-size distributions, specimens of a few milligrams were prepared by ultrasonic dispersion for 5 min into 100 mL of deionized water to which two drops of ‘Calgon’ (a dispersing agent) were added, resulting in dispersions with turbidity readings varying between 7 and 96 nephelometric turbidity units (ntu). A single drop of the dispersion was then placed on a nickel TEM grid (90 µm diameter square holes) supported on a silicon wafer and the drop allowed to air dry in a desiccator. The grid serves to break the drying droplet into smaller micro droplets and seems to assist in obtaining more homogenous dispersion of particles on the surface of the silicon wafer to facilitate subsequent image analysis. The wafers were coated with an Au/Pd mixture and examined by SEM. Image analysis was performed using the freely available ImageJ software (Rasband, 1997–2015). All images were converted to 8 bit binary, calibrated using the scale bars, adjusted manually for threshold, filtered manually to reduce noise, and converted to binary images. Distributions of particle length and diameter were measured on multiple images for each sample using the particleanalysis function of ImageJ by fitting ellipsoids. In addition, maximum and minimum lengths and maximum and minimum diameters of halloysite particles were measured by a manual survey of each set of images. These values were then used as limits to filter the semi-automated particle measurements obtained using ImageJ such that apparently larger or smaller particles than the manually determined limits were rejected. Particles with aspect ratios of <1.5 were also rejected to assist in the elimination of aberrant measurements, such as from particles of the wrong shape, or of groups of overlapping particles. Specific surface area and porosity Specific surface area and porosity were measured by nitrogen gas adsorption using a Coulter SA 3100 Plus instrument. The specific surface area was calculated according to the BET equation using five points in the relative pressure range 0.05–0.20, and pore-size distributions were calculated from the adsorption isotherms according to the BJH model. Prior to analysis, all samples were outgassed under vacuum at 100°C for 1 h. Infrared spectroscopy A small quantity of each sample in the as-received state was transferred, in turn, onto the sample area of a single reflection diamond attenuated total reflectance (DATR) 330 S. Hillier et al. accessory, fitted with a KRS-5 substrate. Infrared spectra were then recorded using a Bruker Vertex 70 Fourier Transform Infrared (FTIR) Spectrometer in the midinfrared region (4000 to 400 cm−1). The FTIR spectrometer is dry-air purged to prevent interference in the IR spectra caused by water vapour and CO2. An ATR correction, to allow for the variation in depth of penetration with wavelength, was applied to all IR spectra using the OPUS software (Bruker). Cation exchange capacity The CEC was measured using a cobalt hexammine trichloride method based on the ISO 23470 standard at ambient sample pH, wherein the exchangeable cations on the sample are replaced by trivalent cobalt hexammine ions and the CEC of the sample is determined by absorption colorimetry. The sample reference state is oven dried at 105°C. The method is described in more detail by Gray et al. (2016, this issue). R E S U LT S Morphology by SEM Comparison of the samples in the SEM reveals that some samples are composed of relatively fine tubular forms and are circular or oval in cross section, whilst others are very obviously prismatic in form with long flat faces giving rise to an ...
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