The hydrogen bonding of hydromagnesite

Akao, Masaru; Iwai, Shin-ichi

doi:10.1107/s0567740877005834

Cited by 73 publications

(89 citation statements)

References 3 publications

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“…Changes in the carbonate FTIR spectra showed that there was interaction between these groups and the water molecules as they realigned themselves into the crystal structure. This may well have been due to hydrogen bonding of the water molecules to the carbonate groups as discussed by Akao [45].…”

Section: Comparison Of Synthetic Hydromagnesite With Naturally Occurrmentioning

confidence: 99%

“…The strong C-O bonds of the carbonate ion reinforce the crystal by forming a triangular structure with three oxygen atoms from three different octahedra. In a subsequent publication [45] in 1977 Akao further developed understanding of the structure by determining in greater detail the positions of the remaining water molecules and the hydroxyl group. The hydroxyl group was shown to be shared between three MgO 6 octahedra and does not take part in any hydrogen bonding, while the water molecules are located at unshared corners of the MgO 6 octahedron and form a network of hydrogen bonds.…”

Section: Chemical Formula and Crystal Structure Of Hydromagnesitementioning

confidence: 99%

“…The chain consists of one hydrogen atom in each water molecule forming a hydrogen bond to its neighbouring water molecule and the other hydrogen atom forming a hydrogen bond with oxygen in the carbonate groups. The three dimensional structures has been characterised in the excellent works of Akao [45,46] where detailed tables of interatomic distances, bond angles, diagrams of the crystal structures and in depth discussion and comment is given.…”

Section: Chemical Formula and Crystal Structure Of Hydromagnesitementioning

confidence: 99%

“…Various studies [41][42][43][44][45][46] have been made on the crystalline structure of hydromagnesite. Murdoch [43] concludes that it is a monoclinic crystal with a pseudo-orthorhombic structure.…”

Section: Chemical Formula and Crystal Structure Of Hydromagnesitementioning

confidence: 99%

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The thermal decomposition of huntite and hydromagnesite—A review

2010

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Naturally occurring mixtures of hydromagnesite and huntite are important industrial minerals. Their endothermic decomposition over a specific temperature range, releasing water and carbon dioxide, has lead to such mixtures being successfully used as fire retardants, often replacing aluminium hydroxide or magnesium hydroxide. The current understanding of the structure and thermal decomposition mechanism of both minerals and their combination in natural mixtures is reviewed. The crystalline structure of both minerals has been fully characterised. The thermal decomposition of huntite has been characterised and is relatively simple. However, the thermal decomposition mechanism of hydromagnesite is sensitive to many factors including rate of heating and the composition of the atmosphere. The partial pressure of carbon dioxide significantly affects the decomposition mechanism of hydromagnesite causing magnesium carbonate to crystallise and decompose at a higher temperature instead of decomposing directly to magnesium oxide.Keywords: hydromagnesite, huntite, fire, flame, retardant, mineral This review critically examines the sometimes conflicting reports in the published literature. It draws together current knowledge of the structure and thermal decomposition of hydromagnesite and huntite, in order to provide an insight into the thermal behaviour of mixtures of these minerals and to optimise their selection and applications. Industrial use of Mineral Fillers as Fire Retardant AdditivesThe largest group of mineral fire retardants are metal hydroxides. Their endothermic decomposition and associated release of inert gasses or water vapour, above the processing temperature but below the thermal decomposition temperature of polymers suppresses the ignition, while the accumulation of a solid inert residue on the surface of the burning polymer reduces the heat release rate. Aluminium hydroxide (ATH) and magnesium hydroxide are the most widely used [1]. Globally aluminium hydroxide is the highest tonnage fire retardant [2,3]. It decomposes according to the following reaction:The endothermic loss of water resulting from the thermal decomposition of ATH has been variously reported [3][4][5] between 1170 and 1300 Jg Magnesium hydroxide is used less widely than ATH. It decomposes through a similar endothermic mechanism to ATH, giving off water. Mg(OH) 2(s) → MgO (s) + H 2 O (g)The endotherm for this reaction is quoted at values between 1244 to 1450 Jg -1 by various authors [3,[5][6][7]. It starts to decompose at about 300 -330°C giving off water [5]. L.A. Hollingbery, T.R. Hull / Thermochimica Acta 509 (2010) 1-112 Although ATH and magnesium hydroxide are the most well known mineral fire retardants, Rothon [5] has identified a number of minerals (Table 1) that could be of potential benefit in polymers. Each decomposes endothermically with the evolution of either carbon dioxide, water or both. Of these minerals, hydromagnesite is the one that has probably seen most commercial interest. Hydromagnesite is naturally occurring...

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Section: Comparison Of Synthetic Hydromagnesite With Naturally Occurrmentioning

confidence: 99%

Section: Chemical Formula and Crystal Structure Of Hydromagnesitementioning

confidence: 99%

Section: Chemical Formula and Crystal Structure Of Hydromagnesitementioning

confidence: 99%

Section: Chemical Formula and Crystal Structure Of Hydromagnesitementioning

confidence: 99%

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The thermal decomposition of huntite and hydromagnesite—A review

2010

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“…There has been much work published regarding the structure [18][19][20][21][22][23] and thermal decomposition [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] of hydromagnesite and huntite. A recent article [40], by the current authors, reviews this body of work in detail.…”

Section: Hydromagnesite and Huntite As Fire Retardant Additivesmentioning

confidence: 99%

The fire retardant behaviour of huntite and hydromagnesite – A review

Hollingbery

Hull

2010

Polymer Degradation and Stability

136

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Naturally occurring mixtures of hydromagnesite and huntite have found important industrial use. Their endothermic decomposition over a temperature range similar to that of commonly used polymers and their release of water and carbon dioxide, has led to such mixtures being successfully used as fire retardants. They have replaced aluminium hydroxide and magnesium hydroxide in many applications. The current understanding of the thermal decomposition mechanism of both minerals and their combination in natural mixtures has been reviewed and related to their fire retardant action. Both minerals contribute to the reduction in flammability of polymers although the extent of these interactions has not been fully investigated. However, the fire retardant mechanism of these minerals appears more complicated than either aluminium hydroxide or magnesium hydroxide. This paper critically examines the literature on the fire retardant behaviour of mixtures of hydromagnesite and huntite, providing information of particular use to formulators of fire retardant polymers using these minerals. It also highlights the gaps in understanding of the fire retardant mechanisms of mixtures of hydromagnesite and huntite and areas that require further research.

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