Chelants to inhibit magnesia (MgO) hydration

Amaral, Luís; Oliveira, I. R.; Bonadia, P.; Salomão, R.; Pandolfelli, V. C.

doi:10.1016/j.ceramint.2011.01.030

Cited by 74 publications

(39 citation statements)

References 12 publications

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“…This [6MgOH + ·(PO3)6 6-](insoluble)layer forms a stable protective coating on MgO particles which prevents further hydrolysis of MgO [18]. The good agreement between the experimental pH and Mg concentrations and the expected pH and total dissolved Mg in a calculation without phosphates, suggests that in this case a large part of the sodium hexametaphosphate has formed the insoluble variant and adsorbed on the MgO particles.…”

Section: Mg 2+ (Aq) + 2oh -(Aq) → Mg(oh)2(s)mentioning

confidence: 56%

Role of sodium hexametaphosphate in MgO/SiO2 cement pastes

Jia

Wang

et al. 2016

Cement and Concrete Research

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The extent of reaction between magnesium oxide (MgO) and silica fume (SiO2) is normally limited and mixes require high water contents to give suitable rheology. The use of considerably lower water contents and the formation of magnesium silicate hydrate (M-S-H) gel as a binding phase is made possible by adding sodium hexametaphosphate (Na-HMP) to the mix water prior to the addition of MgO and SiO2. This results in the formation of extensive reaction products and cured samples with high compressive strength and low porosity. In this work, the effect of Na-HMP on the hydration of MgO/SiO2 mixes is investigated using high water to solids ratio samples to allow monitoring of pH and the solution chemistry during hydration. It is shown that a relatively small amount of Na-HMP inhibits the formation of Mg(OH)2 when MgO is hydrolyzed. It is proposed that this is due to adsorption of phosphate species on the MgO which inhibits the nucleation of the Mg(OH)2.. This gives rise to high Mg 2+ species in solution and elevated pH (>12) conditions relative to when Mg(OH)2 forms. In contrast, the phosphate does not suppress formation of M-S-H gel. In combination with the enhanced dissolution rate of SiO2 at high pH, M-S-H gel can form quickly without competition for Mg 2+ ions by Mg(OH)2 precipitation. Incorporating the optimum concentration of Na-HMP into the mix water therefore transforms the properties of cement paste and mortar samples formed by reacting MgO and SiO2.

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Section: Mg 2+ (Aq) + 2oh -(Aq) → Mg(oh)2(s)mentioning

confidence: 56%

Role of sodium hexametaphosphate in MgO/SiO2 cement pastes

Jia

Wang

et al. 2016

Cement and Concrete Research

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“…Por exemplo, nos processos de extração e processamento do minério, o sínter de MgO passa por tratamento térmico a elevadas temperaturas, sendo possível reconstituir as imperfeições geradas na etapa de calcinação e obter cristais maiores, com menos contornos de grão e menor área superficial. Devido a isso, esse tratamento pode afetar diretamente a reatividade do óxido resultante [3]; 2) Presença de aditivos/impurezas nas composições refratárias: especialmente em concretos, a presença de aditivos (como dispersantes) e ligantes (cimento de aluminato de cálcio, alumina hidratável ou microssílica) também podem causar mudanças significativas na evolução da hidratação [11,[13][14][15]. Estes últimos conferem resistência mecânica aos concretos refratários durante as etapas iniciais de processamento.…”

Section: Introductionunclassified

“…o ácido cítrico) reduzem consideravelmente a hidratação do MgO pela presença de moléculas que, em meio aquoso, apresentam espécies negativas que se ancoram na superfície da magnésia carregada positivamente. Com este ancoramento devese gerar uma camada protetora ou película insolúvel de citrato de magnésio na superfície da magnésia, o que pode impedir os íons de OH -de se aproximarem para formar o hidróxido [15]. Os compostos com essas características, além de apresentarem nas suas estruturas dois ou mais agrupamentos negativos, ainda têm afinidades por íons metálicos (como o Mg 2+ ).…”

Section: Introductionunclassified

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Influência dos sais MgCl 2 e CaCl 2 no comportamento de hidratação do MgO

et al. 2018

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INTRODUÇÃOO óxido de magnésio (MgO) ou magnésia é uma importante matéria-prima para a indústria de refratários e entre as diversas fontes disponíveis deste material, sínter, magnésia cáustica ou grãos eletrofundidos, isoladamente ou em combinação com alumina (Al 2 O 3 ) ou cromita (Cr 2 O 3 ), são os mais utilizados para tal finalidade. O potencial de aplicação do MgO em refratários se deve ao fato deste apresentar elevada refratariedade e contribuir para o aumento da resistência à corrosão destes produtos quando em contato com escórias alcalinas. Além disso, quando em combinação com o óxido de alumínio e exposto a temperaturas acima de 1200 °C, o MgO pode levar à formação de espinélio

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“…Sintering strengthens the ceramic scaffold and dehydrates the brucite to MgO. Many processing parameters influence the amount of brucite formation such as pH (Fruhwirth et al, 1985;Merwe et al, 2004;Phillips et al, 1977), drying time, and surface-active additives (Amaral et al, 2011), which in turn affect the porosity and ionic conductivity of the separator. The effects of some of these factors will be reviewed as well.…”

Section: Introductionmentioning

confidence: 99%

New composite separator pellet to increase power density and reduce size of thermal batteries

Mondy

Roberts

Grillet

et al. 2013

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We show that it is possible to manufacture strong macroporous ceramic films that can be backfilled with electrolyte to form rigid separator pellets suitable for use in thermal batteries. Several new ceramic manufacturing processes are developed to produce sintered magnesium oxide foams with connected porosities of over 80% by volume and with sufficient strength to withstand the battery manufacturing steps. The effects of processing parameters are quantified, and methods to imbibe electrolyte into the ceramic scaffold demonstrated. Preliminary single cell battery testing show that some of our first generation pellets exhibit longer voltage life with comparable resistance at the critical early times to that exhibited by a traditional pressed pellets. Although more development work is needed to optimize the processes to create these rigid separator pellets, the results indicate the potential of such ceramic separator pellets to be equal, if not superior to, current pressed pellets. Furthermore, they could be a replacement for critical material that is no longer available, as well as improving battery separator strength, decreasing production costs, and leading to shorter battery stacks for long-life batteries. 4

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Chelants to inhibit magnesia (MgO) hydration

Cited by 74 publications

References 12 publications

Role of sodium hexametaphosphate in MgO/SiO2 cement pastes

Role of sodium hexametaphosphate in MgO/SiO2 cement pastes

Influência dos sais MgCl 2 e CaCl 2 no comportamento de hidratação do MgO

New composite separator pellet to increase power density and reduce size of thermal batteries

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