Showing papers by "Ray L. Frost published in 2007"
01 Jan 2007
TL;DR: A range of surfactant molecular environments within the surface-modified montmorillonite are proposed based upon their thermal decomposition.
Abstract: Surfaces of a Wyoming SWy-2 sodium montmorillonite were modified using microwave radiation through intercalation with the cationic surfactants octadecyltrimethylammonium bromide, dimethyldioctadecylammonium bromide, and methyltrioctadecylammonium bromide by an ion exchange mechanism. Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG) and infrared (IR) spectroscopy. Different configurations of surfactants within montmorillonite interlayer are proposed based on d(001) basal spacings. A range of surfactant molecular environments within the surface-modified montmorillonite are proposed based upon their thermal decomposition. IR spectroscopy using a smart endurance single bounce diamond attenuated total reflection (ATR) cell has been used to study the changes in the spectra of CH asymmetric and symmetric stretching modes of the surfactants to provide more information of the surfactant molecular configurations.
267 citations
TL;DR: The use of organo-clays for cleaning up oil spills is feasible due to its many desirable properties such as high hydrocarbon sorption and retention capacities, hydrophobicity, and recyclability.
216 citations
TL;DR: In this paper, it was shown that the symmetry of the carbonate anion in hydrozincite is reduced and in all probability the carbonates anions are not equivalent in the hydrated carbonate structure.
119 citations
TL;DR: The main adsorption mechanism for these sorbents occurred on the external surface of the material in the pores or capillaries as mentioned in this paper, where hydrophobic and oleophilic properties are essential.
115 citations
TL;DR: Raman spectroscopy has been used to characterise synthetic mixed carbonate and molybdate hydrotalcites of formula Mg6Al2(OH)16((CO3)2-,(MoO4)2-).4H2O.
Abstract: Raman spectroscopy has been used to characterise synthetic mixed carbonate and molybdate hydrotalcites of formula Mg6Al2(OH)16((CO3)2-,(MoO4)2-).4H2O. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based upon the carbonate anion, the molybdate anion, the hydroxyl units and water units. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of carbonate anions are identified: (a) carbonate hydrogen-bonded to water in the interlayer, (b) carbonate hydrogen-bonded to the hydrotalcite hydroxyl surface, (c) free carbonate anions. It is proposed that the water is highly structured in the hydrotalcite as it is hydrogen bonded to both the carbonate and the hydroxyl surface. The spectra have been used to assess the contamination of carbonate in an open reaction vessel in the synthesis of a molybdate hydrotalcite of formula Mg6Al2(OH)16((CO3)2-,(MoO4)2-).4H2O. Bands are assigned to carbonate and molybdate anions in the Raman spectra. Importantly the synthesis of hydrotalcites from solutions containing molybdate provides a mechanism for the removal of this oxy-anion.
113 citations
TL;DR: Infrared emission spectroscopy proved to be a useful tool for the study of the thermal stability of the organoclays and provided additional evidence for the dehydration which is difficult to obtain by normal thermoanalytical techniques.
111 citations
TL;DR: In this article, Ramaman et al. reported the infrared spectra of five uranyl oxyhydroxide hydrates, becquerelite, billietite, curite, schoepite and vandendriesscheite.
Abstract: Raman and infrared spectra of five uranyl oxyhydroxide hydrates, becquerelite, billietite, curite, schoepite and vandendriesscheite are reported. Observed bands are attributed to the (UO2)2+ stretching and bending vibrations, U-OH bending vibrations, H2O and (OH)- stretching, bending and libration modes. U-O bond lengths in uranyls and O-H…O bond lengths are calculated from the wavenumbers assigned to the stretching vibrations. They are close to the values inferred and/or predicted from the X-ray single crystal structure. The complex hydrogen-bonding network arrangement was proved in the structures of all minerals studied. This hydrogen bonding contributes to the stability of these uranyl minerals.
105 citations
TL;DR: XRD patterns demonstrate that silane was intercalated into the montmorillonite gallery, as indicated by the increase of the basal spacing, and TGA curves indicate that the methyl groups penetrate into the siloxane clay are the primary reason for the decrease of the dehydroxylation temperature of the grafted products.
100 citations
TL;DR: In this paper, Ramaman spectroscopy has been used to study the structure of the humite mineral group ((A2SiO4)n−A(OH, F)2 where n represents the number of olivine and brucite layers in the structure and is 1, 2, 3 or 4 and A2+ is Mg, Mn, Fe or some mix of these cations).
Abstract: Raman spectroscopy has been used to study the structure of the humite mineral group ((A2SiO4)n–A(OH, F)2 where n represents the number of olivine and brucite layers in the structure and is 1, 2, 3 or 4 and A2+ is Mg, Mn, Fe or some mix of these cations). The humite group of minerals forms a morphotropic series with the minerals olivine and brucite. The members of the humite group contain layers of the olivine structure that alternate with layers of the brucite-like sheets. The minerals are characterized by a complex set of bands in the 800–1000 cm−1 region attributed to the stretching vibrations of the olivine (SiO4)4− units. The number of bands in this region is influenced by the number of olivine layers. Characteristic bending modes of the (SiO4)4− units are observed in the 500–650 cm−1 region. The brucite sheets are characterized by the OH stretching vibrations in the 3475–3625 cm−1 wavenumber region. The position of the OH stretching vibrations is determined by the strength of the hydrogen bond formed between the brucite-like OH units and the olivine silica layer. The number of olivine sheets and not the chemical composition determines the strength of the hydrogen bonds. Copyright © 2006 John Wiley & Sons, Ltd.
99 citations
TL;DR: Surfactant modified montmorillonitic clays synthesized by ion exchange using the hydrothermal reaction method have been compared using XRD and thermal analysis and different arrangements of the surfactant molecules in the organoclays are inferred from the changes in basal spacings.
91 citations
TL;DR: A comprehensive spectroscopic analysis consisting of Raman, infrared (IR) and near-infrared (NIR) spectroscopy was undertaken on two forms of calcium acetate with differing degrees of hydration, resulting in assignments of vibrational bands due to the acetate anion.
TL;DR: Raman spectra of carbonates from different origins including bastnasite, parisite and northupite have been used to study a series of selected natural halogenated carbonates as discussed by the authors.
Abstract: Raman spectroscopy complimented with infrared spectroscopy has been used to study a series of selected natural halogenated carbonates from different origins including bastnasite, parisite and northupite. The position of CO32- symmetric stretching vibration varies with mineral composition. An additional band for northupite at 1107 cm-1 is observed. Raman spectra of bastnasite, parisite and northupite show a single band at 1433, 1420 and 1554 cm-1 respectively, assigned to the ν3 (CO3)2- asymmetric stretching mode. The observation of additional Raman bands for the ν3 modes for some halogentaed carbonates is significant in that it shows distortion of the CaO6 octahedron No ν2 Raman bending modes are observed for these minerals. The band is observed in the infrared spectra and multiple ν2 modes at 844 and 867 cm-1 are observed for parisite. A single intense infrared band is found at 879 cm-1 for northupite. Raman bands are observed for the carbonate ν4 in phase bending modes at 722 cm-1 for bastnasite, 736 and 684 cm-1 for parisite, 714 cm-1 for northupite. Multiple bands are observed in the OH stretching region for selected bastansites and parisites indicating the presence of water and OH units in the mineral structure. The presence of such bands brings into question the actual formula of these halogenated carbonate minerals.
TL;DR: In this paper, the authors applied conventional and high resolution thermogravimetry to quantify different fractions of carbonaceous and metallic materials in raw and moderately purified single walled and multiwalled carbon nanotubes.
Abstract: Raw and purified samples of carbon nanotubes are considered as multicomponent systems with a distribution of carbonaceous, amorphous, multishell graphitic particles and nanotubes, together with the particles of metal compounds from the catalyst. With respect to the carbon nanotube fractions, a distribution of size, defect concentrations and functionalities needs to be taken into account. In order to address the problem of quantitative evaluation of purity it is necessary to measure the quality and distribution of the carbon nanotubes. In this research conventional and high resolution thermogravimetry are applied to quantify different fractions of carbonaceous and metallic materials in raw and moderately purified single walled and multiwalled carbon nanotubes. For each oxidized fraction, defined by careful line shape analysis of the derivative thermogravimetric curves (DTG), the temperature of maximum rate of oxidation, the temperature range for this oxidation, related to the degree of homogeneity, and the amount of associated material was specified The assignments of a type of carbonaceous material to each fraction in the distribution were based on several works from the literature and SEM and TEM measurements. The MWNT purified sample (1.6 wt% metal oxide) was investigated by high resolution thermogravimetry and the quantitative assessment for the carbonaceous fractions in this sample was as follow: 25 wt% of amorphous and other very defective carbonaceous including nanotubes, 54 wt% MWNT and 20 wt% multishell graphitic particles. A qualitative evaluation of these fractions was obtained from the SEM and TEM images and corroborates these results. The accuracy of the values, take into account other measurements performed for the same batch of material, should be better than ±4wt%.
TL;DR: Raman and infrared spectroscopy has enabled insights into the molecular structure of the sampleite group of minerals as mentioned in this paper, which are based upon the incorporation of either phosphate or arsenate with chloride anion into the structure and as a consequence the spectra refect the bands attributable to these anions.
Abstract: Raman and infrared spectroscopy has enabled insights into the molecular structure of the sampleite group of minerals. These minerals are based upon the incorporation of either phosphate or arsenate with chloride anion into the structure and as a consequence the spectra refect the bands attributable to these anions, namely phosphate or arsenate with chloride. The sampleite vibrational spectrum reflects the spectrum of the phosphate anion and consists of ν1 at 964, ν2 at 451 cm-1, ν3 at 1016 and 1088 and ν4 at 643, 604, 591 and 557 cm-1. The lavendulan spectrum consists of ν1 at 854, ν2 at 345 cm-1, ν3 at 878 cm-1 and ν4 at 545 cm-1. The Raman spectrum of lemanskiite is different from that of lavendulan consistent with a different structure. Low wavenumber bands at 227 and 210 cm-1 may be assigned to CuCl TO/LO optic vibrations. Raman spectroscopy identified the substitution of arsenate by phosphate in zdenekite and lavendulan.
TL;DR: In this paper, the authors used Raman and infrared spectroscopy to study the structure of dawsonite and showed that the symmetry of the carbonate anion is reduced.
Abstract: Raman spectroscopy both at 298 and 77 K complemented with infrared spectroscopy was used to study the structure of dawsonite. Previous crystallographic studies concluded that the structure of dawsonite was a simple one; however, both Raman and infrared spectroscopy show that this conclusion is incorrect. Multiple bands are observed in both the Raman and infrared spectra in the antisymmetric stretching and bending regions, showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the dawsonite structure. Multiple OH deformation vibrations centred around 950 cm−1 in both Raman and infrared spectra show that the OH units in the dawsonite structure are non-equivalent. Calculations using the position of the Raman and infrared OH stretching vibrations enabled estimates of the hydrogen-bond distances of 0.2735 and 0.27219 pm at 298 K, and 0.27315 and 0.2713 pm at 77 K to be made. This indicates strong hydrogen bonding of the OH units in the dawsonite structure. Copyright © 2007 John Wiley & Sons, Ltd.
15 Mar 2007
TL;DR: This study demonstrates that para-nitrophenol will penetrate into the untreated clay interlayer and replace the intercalated surfactant in surfactants modified clay, resulting in the change of the arrangement of the inter Caledonia bromide modified clay.
Abstract: para-Nitrophenol adsorbed on hexadecyltrimethylammonium bromide modified montmorillonite has been studied using a combination of X-ray diffraction TEM and infrared spectroscopy. Upon formation of the organoclay, the properties change from hydrophilic to hydrophobic. It is proposed that para-nitrophenol is adsorbed onto the water in the cation hydration sphere of the organoclay. As the cation is replaced by the surfactant molecules the para-nitrophenol replaces the surfactant molecules in the clay interlayer. Significant changes in the water vibrations occur in this process. Bands attributed to CH stretching and bending vibrations in general decrease as the concentration of the surfactant (CEC) increases up to 1.0CEC. After this concentration the bands increase approaching a value the same as that of the surfactant. Strong changes occur in the HCH deformation modes of the methyl groups of the surfactant. These changes are attributed to the methyl groups locking into the siloxane surface of the montmorillonite. Such a concept is supported by changes in the SiO stretching bands of the montmorillonite siloxane surface. This study demonstrates that para-nitrophenol will penetrate into the untreated clay interlayer and replace the intercalated surfactant in surfactant modified clay, resulting in the change of the arrangement of the intercalated surfactant.
TL;DR: In this article, the Raman spectra are interpreted in terms of the addition of borate and silicate spectra and three characteristic bands of ferroaxinite are observed at 1082, 1056 and 1025 cm-1 and are attributed to BO4 stretching vibrations.
Abstract: Raman spectroscopy, complemented by infrared spectroscopy has been used to characterise the ferroaxinite minerals of theoretical formula Ca2Fe2+Al2BSi4O15(OH), a ferrous aluminium borosilicate. The Raman spectra are complex but are subdivided into sections based upon the vibrating units. The Raman spectra are interpreted in terms of the addition of borate and silicate spectra. Three characteristic bands of ferroaxinite are observed at 1082, 1056 and 1025 cm-1 and are attributed to BO4 stretching vibrations. Bands at 1003, 991, 980 and 963 cm-1 are assigned to SiO4 stretching vibrations. Bands are found in these positions for each of the ferroaxinites studied. No Raman bands were found above 1100 cm-1 showing that ferroaxinites contain only tetrahedral boron. The hydroxyl stretching region of ferroaxinites is characterised by a single Raman band between 3368 and 3376 cm-1, the position of which is sample dependent. Bands for ferroaxinite at 678, 643, 618, 609, 588, 572, 546 cm-1 may be attributed to the ν4 bending modes and the three bands at 484, 444 and 428 cm-1 may be attributed to the ν2 bending modes of the (SiO4)2-.
TL;DR: The molecular structure of the uranyl mineral rutherfordine has been investigated by the measurement of the Raman spectra at 298 and 77 K and complemented with infrared spectra as mentioned in this paper.
Abstract: The molecular structure of the uranyl mineral rutherfordine has been investigated by the measurement of the Raman spectra at 298 and 77 K and complemented with infrared spectra. The infrared spectra of the (CO3)2- units in the antisymmetric stretching region show complexity with three sets of carbonate bands observed. This combined with the observation of multiple bands in the (CO3)2- bending region in both the Raman and IR spectra suggests that both monodentate and bidentate (CO3)2- units are present in the structure in accordance with the X-ray crystallographic studies. Complexity is also observed in the IR spectra of (UO2)2+ antisymmetric stretching region and is attributed to non-identical UO bonds. Both Raman and infrared spectra of the rutherfordine show the presence of both water and hydroxyl units in the structure as evidenced by IR bands at 3562 and 3465 cm-1 (OH) and 3343, 3185 and 2980 cm-1 (H2O). Raman spectra show the presence of four sharp bands at 3511, 3460, 3329 and 3151 cm-1.
TL;DR: High-resolution XPS spectra show that the modification of clay with surfactants has prominent influences on the binding energies of the atoms in both clays and Surfactants, and nitrogen is the most sensitive to the surfactant distribution within the organoclays.
TL;DR: In this article, the electronic and vibrational spectra of green and pink tourmalines have been investigated by UV-visible, NIR, IR and Raman spectroscopy.
TL;DR: In this article, the structure of uranopilite of different localities has been studied by Raman spectroscopy at 298 and 77 K. The structure of URANOPILITES has been analyzed using X-ray single crystal structure analysis.
Abstract: Uranopilite, \[(UO2)6(SO4)O2(OH)6(H2O)6](H2O)8, the composition of which may vary, can be understood as a complex hydrated uranyl oxy hydroxy sulfate. The structure of uranopilite of different localities has been studied by Raman spectroscopy at 298 and 77 K. A single intense band at 1009 cm-1 assigned to the ￮1 (SO4)2- symmetric stretching mode shifts to higher wavenumbers at 77 K. Three low intensity bands are observed at 1143, 1117 and 1097 cm-1. These bands are attributed to the (SO4)2- ν3 antisymmetric stretching modes. Multiple bands provide evidence that the symmetry of the sulphate anion in the uranopilite structure is lowered. Three bands are observed at 843 to 816 cm-1 in both 298 and 77 K spectra and are attributed to the ν1 symmetric stretching modes of the (UO2)2+ units. Multiple bands prove the symmetry reduction of the UO2 ion. Multiple OH stretching modes prove a complex arrangement of OH groupings and hydrogen bonding in the crystal structure. A series of infrared bands not observed in the Raman spectra are found at 1559, 1540, 1526 and 1511 cm-1 attributed to ￤ UOH bending modes. U-O bond lengths in uranyl and O-H…O bond lengths are calculated and compared with X-ray single crystal structure analysis. Raman spectra of uranopilites of different origin show subtle differences in spectra proving the spectra are origin and sample dependent. Hydrogen-bonding network and its arrangement in the crystal structure play an important role in the origin and stability of uranopilite.
TL;DR: In this paper, Raman at 298 and 77 K and infrared spectra of two samples of sodium-zippeite were studied and interpreted, and U-O bond lengths in uranyl were calculated and compared with those inferred from the X-ray single crystal structure data of a synthetic sodium zippite analog.
Abstract: Raman at 298 and 77 K and infrared spectra of two samples of sodium-zippeite were studied and interpreted. U-O bond lengths in uranyl were calculated and compared with those inferred from the X-ray single crystal structure data of a synthetic sodium-zippeite analog. Hydrogen-bonding network in the studied samples is discussed. O-H…O bond lengths were calculated and compared with those predicted from the X-ray single crystal structure analysis.
TL;DR: In this paper, a combination of X-ray diffraction, transmission electron microscopy (TEM), N2 adsorption, small area electron diffraction (SAED), and energy dispersive Xray analysis (EDX) was employed to characterize the resulting nano-to micro-sized structures.
Abstract: Nano- to microsized gallium oxide was prepared with and without surfactant via a hydrothermal route at low temperature through different synthesis procedures. Rodlike GaOOH crystals with average length of ∼2.5 μm and width of 1.5 μm were prepared when the initial molar ratio of Ga to OH was 1:3. β-Ga2O3 materials were derived from GaOOH by calcination at 900 °C, and the initial morphology was retained. γ-Ga2O3 nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3 nm, were achieved directly in solution with and without surfactant under hydrothermal treatment condition at 100 °C when the initial molar ratio of Ga to OH was 1:5. The combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, small area electron diffraction (SAED), and energy dispersive X-ray analysis (EDX) were employed to characterize the resulting nano- to microsized structures. Cationic and nonionic surfactants were used in this study. Detailed results are presented.
TL;DR: The surfactant molecule DDOAB combusts at 166, 244, and 304 degrees C and upon intercalation into Na-montmorillonite is retained up to 389 degrees C thus showing the organoclay is stable to significantly high temperatures well above the combustion/decomposition temperature of the organOClay.
TL;DR: In this article, the thermogravimetric analysis of single-walled carbon nanotubes (SWCN) was performed by using thermodynamic properties and electron microscopic methods.
Abstract: Thermoanalytical and electron microscopic methods were used as characterisation tools for the determination of the composition of single walled carbon nanotube samples. Acid purification method of single-walled carbon nanotubes (SWCN) proved to be effective, resulting in a three fold increase in the percentage of SWNTs present in the purified product as determined by thermogravimetric analysis. In this work we report the thermogravimetric analysis by conventional and high resolution methods of the raw SWNTs and purified SWNTs.
TL;DR: This study examines the use of laponite, a synthetic smectite, which forms exfoliated silicate layers when dispersed in water, as an inorganic support for titania nanocrystals.
TL;DR: The final nanotubes for nanomaterials without a regular interval supply of freshuminum hydroxide precipitate were longer than those with a regular aluminum hydroxides precipitate supply, which is in contrast to previously published results.
Abstract: The growth of boehmite nanostructures at low temperature using a soft chemistry route with and without (PEO) surfactant is presented. Remarkably long boehmite 1D nanotubes/nanofibers were formed within a significantly short time by changing the reaction mechanism of aluminum hydroxide. By using the PEO surfactant as a templating agent, boehmite nanotubes up to 170 nm in length with internal and external diameters of 2-5 and 3-7 nm, respectively, were formed at 100 degrees C. A slightly higher temperature (120 degrees C) resulted in the formation of lath-like nanofibers with an average length of 250 nm. Using the cationic surfactant CTAB, nanotubes rather than nanofibers were formed at 120 degrees C. Without surfactant, nanotubes counted for around 20% of the entire sample. A regular interval supply of fresh boehmite precipitate resulted in a larger crystallite size distribution of nanotubes. The morphology of nanotubes was more uniform in samples without the regular addition of aluminum hydroxide. Moreover, for the same hydrothermal time, the final nanotubes for nanomaterials without a regular interval supply of fresh aluminum hydroxide precipitate were longer than those with a regular aluminum hydroxide precipitate supply, which is in contrast to previously published results. Higher Al/PEO concentrations resulted in the formation of shorter nanotubes. A detailed characterization and mechanism are presented.
TL;DR: Raman spectroscopy has been used to characterise halotrichite FeSO4.Al2(SO4)3.22H2O and wupatkiite CoSO4 as mentioned in this paper.
Abstract: Raman spectroscopy has been used to characterise four natural halotrichites: halotrichite FeSO4.Al2(SO4)3. 22H2O, apjohnite MnSO4.Al2(SO4)3.22H2O, pickingerite MgSO4.Al2(SO4)3.22H2O and wupatkiite CoSO4.Al2(SO4)3.22H2O. A comparison of the Raman spectra is made with the spectra of the equivalent synthetic pseudo-alums. Energy dispersive X-ray analysis (EDX) was used to determine the exact composition of the minerals. The Raman spectrum of apjohnite and halotrichite display intense symmetric bands at 985 cm-1 assigned to the v1(SO4)2- symmetric stretching mode. For pickingerite and wupatkiite, an intense band at 995 cm-1 is observed. A second band is observed for these minerals at 976 cm-1 attributed to a water librational mode
The series of bands for apjohnite at 1104, 1078 and 1054 cm-1, for halotrichite at 1106, 1072 and 1049 cm-1, for pickingerite at 1106, 1070 and 1049 cm-1 and for wupatkiite at 1106, 1075 and 1049 cm-1 are attributed to the v3(SO4)2- antisymmetric stretching modes of v3(Bg) SO4. Raman bands at around 474, 460 and 423 cm-1 are attributed to the v2(Ag) SO4 mode. The band at 618 cm-1 is assigned to the 4(Bg) SO4 mode. The splitting of the v2, v3 and v4 modes is attributed to the reduction of symmetry of the SO4 and it is proposed that the sulphate coordinates to water in the hydrated aluminium in bidentate chelation.
Abstract: Selected joaquinite minerals have been studied by Raman spectroscopy. The minerals are categorised into two groups depending upon whether bands occur in the 3250 to 3450 cm−1 region and in the 3450 to 3600 cm−1 region, or in the latter region only. The first set of bands is attributed to water stretching vibrations and the second set to OH stretching bands. In the literature, X-ray diffraction could not identify the presence of OH units in the structure of joaquinite. Raman spectroscopy proves that the joaquinite mineral group contains OH units in their structure, and in some cases both water and OH units. A series of bands at 1123, 1062, 1031, 971, 912 and 892 cm−1 are assigned to SiO stretching vibrations. Bands above 1000 cm−1 are attributable to the νas modes of the (SiO4)4− and (Si2O7)6− units. Bands that are observed at 738, around 700, 682 and around 668, 621 and 602 cm−1 are attributed to OSiO bending modes. The patterns do not appear to match the published infrared spectral patterns of either (SiO4)4− or (Si2O7)6− units. The reason is attributed to the actual formulation of the joaquinite mineral, in which significant amounts of Ti or Nb and Fe are found. Copyright © 2007 John Wiley & Sons, Ltd.
TL;DR: The spectral patterns for the minerals rosasite, glaucosphaerite, kolwezite and mcguinnessite are similar to that of malachite implying the molecular structure is similar to malACHite.