Matt Hales - Academia.edu (original) (raw)

Papers by Matt Hales

Controlled rate thermal analysis (CRTA) of a series of synthetic aurichalcite (Zn,Cu2+)5(CO3)2(OH... more Controlled rate thermal analysis (CRTA) of a series of synthetic aurichalcite (Zn,Cu2+)5(CO3)2(OH)6 with the ratio of Cu/Zn varying from 0.1 to 0.5 proves that the dehydroxylation and carbonate loss occur as non-isothermal and isothermal decompositions. The temperature of the thermal decomposition increases as the Cu/Zn ratio increases. Thermal decomposition of aurichalcite provides a method for preparing mixed oxide catalysts at

Thermochimica Acta, 2008

1. Mechanism for decomposition of aurichalcite-A controlled rate thermal analysis study. Therm... more 2008) Mechanism for decomposition of aurichalcite-A controlled rate thermal analysis study. Thermochimica Acta 468(1-2):pp. 81-86.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011

The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR... more The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450 • C. The strong IR band at 934 cm −1 is evidence for MgOH deformation modes supporting the concept of HCO 3 − units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm −1 are attributed to the symmetric stretching modes of HCO 3 − and CO 3 2− units. Infrared bands at 1419, 1439, 1511, and 1528 cm −1 are assigned to the antisymmetric stretching modes of CO 3 2− and HCO 3 − units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO 3 )·2H 2 O.

Journal of Thermal Analysis and Calorimetry, 2008

The reaction of magnesium minerals such as brucite with CO 2 is important in the sequestration of... more The reaction of magnesium minerals such as brucite with CO 2 is important in the sequestration of CO 2 . The study of the thermal stability of hydromagnesite and diagenetically related compounds is of fundamental importance to this sequestration. The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process for the removal of atmospheric CO 2 . This work makes a comparison of the dynamic and controlled rate thermal analysis of hydromagnesite and nesquehonite. The dynamic thermal analysis of synthetic hydromagnesite proves that dehydration and dehydroxylation take place in two steps at 135 and 184°C, and decarbonation at 412°C and 474°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the second quasi-isothermal at 108 and 145°C, respectively. The carbon dioxide is evolved in an isothermal decomposition at 370°C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition.

Journal of Thermal Analysis and Calorimetry, 2008

Thermogravimetric analysis of synthetic smithsonite and hydrozincite, two secondary minerals of z... more Thermogravimetric analysis of synthetic smithsonite and hydrozincite, two secondary minerals of zinc, was used to determine their relative thermal stability. Thermal decomposition of smithsonite occurs at 293 °C and hydrozincite at 220 °C showing that the carbonate mineral is more stable than the hydroxy-carbonate mineral hydrozincite. Hot stage Raman spectroscopy confirms the decomposition of smithsonite and hydrozincite by 300 and 250 °C respectively. Thermogravimetry shows that a small amount of hydrozincite is formed during the synthesis of smithsonite. No evidence is found for the separate loss of the carbonate and hydroxyl units from hydrozincite.

Journal of Thermal Analysis and Calorimetry, 2008

The thermal decomposition of the clay mineral attapulgite has been studied using a combination of... more The thermal decomposition of the clay mineral attapulgite has been studied using a combination of dynamic and controlled rate thermal analysis. In the dynamic experiment two dehydration steps are observed over the 20-114 and 114-201°C temperature range. In the dynamic experiment three dehydroxylation steps are observed over the temperature ranges 201-337, 337-638 and 638-982°C. The CRTA technology enables the separation of the thermal decomposition steps. Calculations show the amount of water in the attapulgite mineral is variable. Dehydration in the CRTA experiment occurs as quasi-isothermal equilibria. Dehydroxylation occurs as a series of non-isothermal decomposition steps. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of a clay mineral such as attapulgite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial collapse of the layers of attapulgite as the attapulgite is converted to an anhydride.

Journal of Thermal Analysis and Calorimetry, 2009

The precursors of carbonate minerals have the potential to react with 12 greenhouse gases to form... more The precursors of carbonate minerals have the potential to react with 12 greenhouse gases to form many common carbonate minerals. The carbonate bearing 13 minerals, magnesite, calcite, strontianite and witherite, were synthesised and analysed 14 using a combination of thermogravimetry and evolved gas mass spectrometry. The 15 DTG curves show that as both the mass and the size of the metal cationic radii 16 increase, the inherent thermal stability of the carbonate also increases dramatically. It 17 is proposed that this inherent effect is a size stabilisation relationship between that of 18 the carbonate and the metal cation. As the cationic radius increases in size, the radius 19 approaches and in the case of Sr 2+ and Ba 2+ exceeds that of the overall size of the 20 carbonate anion. The thermal stability of these minerals has implications for the 21 geosequestration of greenhouse gases. The carbonates with the larger cations show 22 significantly greater stability. 23 24

Journal of Thermal Analysis and Calorimetry, 2008

Thermal stability of synthetic aurichalcite -implications for making mixed metal oxides for use a... more Thermal stability of synthetic aurichalcite -implications for making mixed metal oxides for use as catalysts.

Journal of Raman Spectroscopy, 2008

Pure nesquehonite (MgCO 3 ·3H 2 O)/Mg(HCO 3 )(OH)·2H 2 O was synthesised and characterised by a c... more Pure nesquehonite (MgCO 3 ·3H 2 O)/Mg(HCO 3 )(OH)·2H 2 O was synthesised and characterised by a combination of thermo-Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo-Raman spectroscopy shows an intense band at 1098 cm −1 , which shifts to 1105 cm −1 at 450°C, assigned to the n 1 CO 3 2− symmetric stretching mode. Two bands at 1419 and 1509 cm −1 assigned to the n 3 antisymmetric stretching mode shift to 1434 and 1504 cm −1 at 175°C. Two new peaks at 1385 and 1405 cm −1 observed at temperatures higher than 175°C are assigned to the antisymmetric stretching modes of the (HCO 3 ) − units. Throughout all the thermo-Raman spectra, a band at 3550 cm −1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm −1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175°C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo-Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO 3 )·2H 2 O.

Journal of Near Infrared Spectroscopy, 2008

The importance of NIR spectroscopy has been successfully demonstrated in the present study of smi... more The importance of NIR spectroscopy has been successfully demonstrated in the present study of smithsonite minerals. The fundamental observations in the NIR spectra, in addition to the anions of OH-and CO32-are Fe and Cu in terms of cation content. These ions ...

Polyhedron, 2008

Frost, Ray and Hales, Matthew (2007) Synthesis and vibrational spectroscopic characterisation of ... more Frost, Ray and Hales, Matthew (2007) Synthesis and vibrational spectroscopic characterisation of synthetic hydrozincite and smithsonite. Polyhedron 26(17):pp. 4955-4962.

Matt C. (2008) Synthesis and vibrational spectroscopic characterisation of nickel containing auri... more Matt C. (2008) Synthesis and vibrational spectroscopic characterisation of nickel containing aurichalcite. Polyhedron 27(3):pp. 1033-1040. Synthesis and vibrational spectroscopic characterisation of nickel containing aurichalcite Abstract:

Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2008

The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR... more The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450 • C. The strong IR band at 934 cm −1 is evidence for MgOH deformation modes supporting the concept of HCO 3 − units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm −1 are attributed to the symmetric stretching modes of HCO 3 − and CO 3 2− units. Infrared bands at 1419, 1439, 1511, and 1528 cm −1 are assigned to the antisymmetric stretching modes of CO 3 2− and HCO 3 − units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO 3 )·2H 2 O.

Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2008

The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR... more The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450 • C. The strong IR band at 934 cm −1 is evidence for MgOH deformation modes supporting the concept of HCO 3 − units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm −1 are attributed to the symmetric stretching modes of HCO 3 − and CO 3 2− units. Infrared bands at 1419, 1439, 1511, and 1528 cm −1 are assigned to the antisymmetric stretching modes of CO 3 2− and HCO 3 − units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO 3 )·2H 2 O.

Polyhedron, 2007

ABSTRACT Raman spectroscopy complimented with supplementary infrared spectroscopy has been used t... more ABSTRACT Raman spectroscopy complimented with supplementary infrared spectroscopy has been used to characterise the vibrational spectrum of aurichalcite a zinc/copper hydroxy carbonate, (Zn,Cu2+)5(CO3)2(OH)6. XRD patterns of all specimans show high orientation and indicate the presence of some impurities such as rosasite and hydrozincite. However, the diffraction patterns for all samples are well correlated to the standard reference patterns. SEM images show highly crystalline and ordered structures in the form of micron long fibres and plates. EDAX analyses indicate variations in chemical composition of Cu/Zn ratios ranging from 1/1.06 to 1/2.87. The symmetry of the carbonate anion in aurichalcite is Cs and is composition dependent. This symmetry reduction results in multiple bands in both the symmetric stretching and bending regions. The intense band at 1072 cm-1 is assigned to the ν1 (CO3)2- symmetric stretching mode. Three Raman bands assigned to the ν3 (CO3)2- antisymmetric stretching modes are observed for aurichalcite at 1506, 1485 and 1337 cm-1. Multiple Raman bands are observed in 800 to 850 cm-1 and 720 to 750 cm-1 regions and are attributed to ν2 and ν4 bending modes confirming the reduction of the carboante anion symmetry in the aurichalcite structure. An intense Raman band at 1060 cm-1 is attributed to the δ OH deformation mode.

Journal of Raman Spectroscopy, 2008

Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smith... more Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smithsonites from different origins. An intense sharp band at 1092 cm−1 is assigned to the CO32− symmetric stretching vibration. Impurities of hydrozincite are identified by a band around 1060 cm−1. An additional band at 1088 cm−1 which is observed in the 298 K spectra but not in the 77 K spectra is attributed to a CO32− hot band. Raman spectra of smithsonite show a single band in the 1405–1409 cm−1 range assigned to the ν3 (CO3)2− antisymmetric stretching mode. The observation of additional bands for the ν3g modes for some smithsonites is significant in that it shows distortion of the ZnO6 octahedron. No ν2 bending modes are observed for smithsonite. A single band at 730 cm−1 is assigned to the ν4 in phase bending mode. Multiple bands be attributed to the structural distortion are observed for the carbonate ν4 in phase bending modes in the Raman spectrum of hydrozincite with bands at 733, 707 and 636 cm−1. An intense band at 304 cm−1 is attributed to the ZnO symmetric stretching vibration. Copyright © 2007 John Wiley & Sons, Ltd.

Journal of Raman Spectroscopy, 2008

Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smith... more Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smithsonites from different origins. An intense sharp band at 1092 cm −1 is assigned to the CO 3 2− symmetric stretching vibration. Impurities of hydrozincite are identified by a band around 1060 cm −1 . An additional band at 1088 cm −1 which is observed in the 298 K spectra but not in the 77 K spectra is attributed to a CO 3 2− hot band. Raman spectra of smithsonite show a single band in the 1405-1409 cm −1 range assigned to the n 3 (CO 3 ) 2− antisymmetric stretching mode. The observation of additional bands for the n 3 g modes for some smithsonites is significant in that it shows distortion of the ZnO 6 octahedron. No n 2 bending modes are observed for smithsonite. A single band at 730 cm −1 is assigned to the n 4 in phase bending mode. Multiple bands be attributed to the structural distortion are observed for the carbonate n 4 in phase bending modes in the Raman spectrum of hydrozincite with bands at 733, 707 and 636 cm −1 . An intense band at 304 cm −1 is attributed to the ZnO symmetric stretching vibration.

Controlled rate thermal analysis (CRTA) of a series of synthetic aurichalcite (Zn,Cu2+)5(CO3)2(OH... more Controlled rate thermal analysis (CRTA) of a series of synthetic aurichalcite (Zn,Cu2+)5(CO3)2(OH)6 with the ratio of Cu/Zn varying from 0.1 to 0.5 proves that the dehydroxylation and carbonate loss occur as non-isothermal and isothermal decompositions. The temperature of the thermal decomposition increases as the Cu/Zn ratio increases. Thermal decomposition of aurichalcite provides a method for preparing mixed oxide catalysts at

Thermochimica Acta, 2008

1. Mechanism for decomposition of aurichalcite-A controlled rate thermal analysis study. Therm... more 2008) Mechanism for decomposition of aurichalcite-A controlled rate thermal analysis study. Thermochimica Acta 468(1-2):pp. 81-86.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011

The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR... more The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450 • C. The strong IR band at 934 cm −1 is evidence for MgOH deformation modes supporting the concept of HCO 3 − units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm −1 are attributed to the symmetric stretching modes of HCO 3 − and CO 3 2− units. Infrared bands at 1419, 1439, 1511, and 1528 cm −1 are assigned to the antisymmetric stretching modes of CO 3 2− and HCO 3 − units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO 3 )·2H 2 O.

Journal of Thermal Analysis and Calorimetry, 2008

The reaction of magnesium minerals such as brucite with CO 2 is important in the sequestration of... more The reaction of magnesium minerals such as brucite with CO 2 is important in the sequestration of CO 2 . The study of the thermal stability of hydromagnesite and diagenetically related compounds is of fundamental importance to this sequestration. The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process for the removal of atmospheric CO 2 . This work makes a comparison of the dynamic and controlled rate thermal analysis of hydromagnesite and nesquehonite. The dynamic thermal analysis of synthetic hydromagnesite proves that dehydration and dehydroxylation take place in two steps at 135 and 184°C, and decarbonation at 412°C and 474°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the second quasi-isothermal at 108 and 145°C, respectively. The carbon dioxide is evolved in an isothermal decomposition at 370°C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition.

Journal of Thermal Analysis and Calorimetry, 2008

Thermogravimetric analysis of synthetic smithsonite and hydrozincite, two secondary minerals of z... more Thermogravimetric analysis of synthetic smithsonite and hydrozincite, two secondary minerals of zinc, was used to determine their relative thermal stability. Thermal decomposition of smithsonite occurs at 293 °C and hydrozincite at 220 °C showing that the carbonate mineral is more stable than the hydroxy-carbonate mineral hydrozincite. Hot stage Raman spectroscopy confirms the decomposition of smithsonite and hydrozincite by 300 and 250 °C respectively. Thermogravimetry shows that a small amount of hydrozincite is formed during the synthesis of smithsonite. No evidence is found for the separate loss of the carbonate and hydroxyl units from hydrozincite.

Journal of Thermal Analysis and Calorimetry, 2008

The thermal decomposition of the clay mineral attapulgite has been studied using a combination of... more The thermal decomposition of the clay mineral attapulgite has been studied using a combination of dynamic and controlled rate thermal analysis. In the dynamic experiment two dehydration steps are observed over the 20-114 and 114-201°C temperature range. In the dynamic experiment three dehydroxylation steps are observed over the temperature ranges 201-337, 337-638 and 638-982°C. The CRTA technology enables the separation of the thermal decomposition steps. Calculations show the amount of water in the attapulgite mineral is variable. Dehydration in the CRTA experiment occurs as quasi-isothermal equilibria. Dehydroxylation occurs as a series of non-isothermal decomposition steps. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of a clay mineral such as attapulgite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial collapse of the layers of attapulgite as the attapulgite is converted to an anhydride.

Journal of Thermal Analysis and Calorimetry, 2009

The precursors of carbonate minerals have the potential to react with 12 greenhouse gases to form... more The precursors of carbonate minerals have the potential to react with 12 greenhouse gases to form many common carbonate minerals. The carbonate bearing 13 minerals, magnesite, calcite, strontianite and witherite, were synthesised and analysed 14 using a combination of thermogravimetry and evolved gas mass spectrometry. The 15 DTG curves show that as both the mass and the size of the metal cationic radii 16 increase, the inherent thermal stability of the carbonate also increases dramatically. It 17 is proposed that this inherent effect is a size stabilisation relationship between that of 18 the carbonate and the metal cation. As the cationic radius increases in size, the radius 19 approaches and in the case of Sr 2+ and Ba 2+ exceeds that of the overall size of the 20 carbonate anion. The thermal stability of these minerals has implications for the 21 geosequestration of greenhouse gases. The carbonates with the larger cations show 22 significantly greater stability. 23 24

Journal of Thermal Analysis and Calorimetry, 2008

Thermal stability of synthetic aurichalcite -implications for making mixed metal oxides for use a... more Thermal stability of synthetic aurichalcite -implications for making mixed metal oxides for use as catalysts.

Journal of Raman Spectroscopy, 2008

Pure nesquehonite (MgCO 3 ·3H 2 O)/Mg(HCO 3 )(OH)·2H 2 O was synthesised and characterised by a c... more Pure nesquehonite (MgCO 3 ·3H 2 O)/Mg(HCO 3 )(OH)·2H 2 O was synthesised and characterised by a combination of thermo-Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo-Raman spectroscopy shows an intense band at 1098 cm −1 , which shifts to 1105 cm −1 at 450°C, assigned to the n 1 CO 3 2− symmetric stretching mode. Two bands at 1419 and 1509 cm −1 assigned to the n 3 antisymmetric stretching mode shift to 1434 and 1504 cm −1 at 175°C. Two new peaks at 1385 and 1405 cm −1 observed at temperatures higher than 175°C are assigned to the antisymmetric stretching modes of the (HCO 3 ) − units. Throughout all the thermo-Raman spectra, a band at 3550 cm −1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm −1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175°C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo-Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO 3 )·2H 2 O.

Journal of Near Infrared Spectroscopy, 2008

The importance of NIR spectroscopy has been successfully demonstrated in the present study of smi... more The importance of NIR spectroscopy has been successfully demonstrated in the present study of smithsonite minerals. The fundamental observations in the NIR spectra, in addition to the anions of OH-and CO32-are Fe and Cu in terms of cation content. These ions ...

Polyhedron, 2008

Frost, Ray and Hales, Matthew (2007) Synthesis and vibrational spectroscopic characterisation of ... more Frost, Ray and Hales, Matthew (2007) Synthesis and vibrational spectroscopic characterisation of synthetic hydrozincite and smithsonite. Polyhedron 26(17):pp. 4955-4962.

Matt C. (2008) Synthesis and vibrational spectroscopic characterisation of nickel containing auri... more Matt C. (2008) Synthesis and vibrational spectroscopic characterisation of nickel containing aurichalcite. Polyhedron 27(3):pp. 1033-1040. Synthesis and vibrational spectroscopic characterisation of nickel containing aurichalcite Abstract:

Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2008

The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR... more The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450 • C. The strong IR band at 934 cm −1 is evidence for MgOH deformation modes supporting the concept of HCO 3 − units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm −1 are attributed to the symmetric stretching modes of HCO 3 − and CO 3 2− units. Infrared bands at 1419, 1439, 1511, and 1528 cm −1 are assigned to the antisymmetric stretching modes of CO 3 2− and HCO 3 − units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO 3 )·2H 2 O.

Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2008

The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR... more The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450 • C. The strong IR band at 934 cm −1 is evidence for MgOH deformation modes supporting the concept of HCO 3 − units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm −1 are attributed to the symmetric stretching modes of HCO 3 − and CO 3 2− units. Infrared bands at 1419, 1439, 1511, and 1528 cm −1 are assigned to the antisymmetric stretching modes of CO 3 2− and HCO 3 − units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO 3 )·2H 2 O.

Polyhedron, 2007

ABSTRACT Raman spectroscopy complimented with supplementary infrared spectroscopy has been used t... more ABSTRACT Raman spectroscopy complimented with supplementary infrared spectroscopy has been used to characterise the vibrational spectrum of aurichalcite a zinc/copper hydroxy carbonate, (Zn,Cu2+)5(CO3)2(OH)6. XRD patterns of all specimans show high orientation and indicate the presence of some impurities such as rosasite and hydrozincite. However, the diffraction patterns for all samples are well correlated to the standard reference patterns. SEM images show highly crystalline and ordered structures in the form of micron long fibres and plates. EDAX analyses indicate variations in chemical composition of Cu/Zn ratios ranging from 1/1.06 to 1/2.87. The symmetry of the carbonate anion in aurichalcite is Cs and is composition dependent. This symmetry reduction results in multiple bands in both the symmetric stretching and bending regions. The intense band at 1072 cm-1 is assigned to the ν1 (CO3)2- symmetric stretching mode. Three Raman bands assigned to the ν3 (CO3)2- antisymmetric stretching modes are observed for aurichalcite at 1506, 1485 and 1337 cm-1. Multiple Raman bands are observed in 800 to 850 cm-1 and 720 to 750 cm-1 regions and are attributed to ν2 and ν4 bending modes confirming the reduction of the carboante anion symmetry in the aurichalcite structure. An intense Raman band at 1060 cm-1 is attributed to the δ OH deformation mode.

Journal of Raman Spectroscopy, 2008

Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smith... more Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smithsonites from different origins. An intense sharp band at 1092 cm−1 is assigned to the CO32− symmetric stretching vibration. Impurities of hydrozincite are identified by a band around 1060 cm−1. An additional band at 1088 cm−1 which is observed in the 298 K spectra but not in the 77 K spectra is attributed to a CO32− hot band. Raman spectra of smithsonite show a single band in the 1405–1409 cm−1 range assigned to the ν3 (CO3)2− antisymmetric stretching mode. The observation of additional bands for the ν3g modes for some smithsonites is significant in that it shows distortion of the ZnO6 octahedron. No ν2 bending modes are observed for smithsonite. A single band at 730 cm−1 is assigned to the ν4 in phase bending mode. Multiple bands be attributed to the structural distortion are observed for the carbonate ν4 in phase bending modes in the Raman spectrum of hydrozincite with bands at 733, 707 and 636 cm−1. An intense band at 304 cm−1 is attributed to the ZnO symmetric stretching vibration. Copyright © 2007 John Wiley & Sons, Ltd.

Journal of Raman Spectroscopy, 2008

Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smith... more Raman spectroscopy at both 298 and 77 K has been used to study a series of selected natural smithsonites from different origins. An intense sharp band at 1092 cm −1 is assigned to the CO 3 2− symmetric stretching vibration. Impurities of hydrozincite are identified by a band around 1060 cm −1 . An additional band at 1088 cm −1 which is observed in the 298 K spectra but not in the 77 K spectra is attributed to a CO 3 2− hot band. Raman spectra of smithsonite show a single band in the 1405-1409 cm −1 range assigned to the n 3 (CO 3 ) 2− antisymmetric stretching mode. The observation of additional bands for the n 3 g modes for some smithsonites is significant in that it shows distortion of the ZnO 6 octahedron. No n 2 bending modes are observed for smithsonite. A single band at 730 cm −1 is assigned to the n 4 in phase bending mode. Multiple bands be attributed to the structural distortion are observed for the carbonate n 4 in phase bending modes in the Raman spectrum of hydrozincite with bands at 733, 707 and 636 cm −1 . An intense band at 304 cm −1 is attributed to the ZnO symmetric stretching vibration.