Why foams containing colloidal hydrophilic particles are unstable?

Vivaldini, D. O.; Luz, A.P.; Salvini, V. R.; Pandolfelli, V. C.

doi:10.1016/j.ceramint.2013.01.007

Cited by 12 publications

(5 citation statements)

References 15 publications

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“…In the case of foam stability the adsorption and thermal energy ratio represents the main evaluation parameter. From the pre-experimental results can be derived that in the case of silica fume suspensions the stabilization effect occurs when the adsorption energy is higher of three orders of magnitude then thermal energy which is the reason why the foams created by inorganic hydrophilic fine particles are unstable where its adsorption and thermal energy are comparable [3]. In AAC technology there is necessary to work with relatively high temperatures (due to stable releasing of hydrogen) and with very fine materials (reduction of volume weight) to reach low thermal conductivity.…”

Section: Experimental Studymentioning

confidence: 99%

The Basics of Low Volume Weight Aerated Autoclaved Concrete Preparation

Koutný¹,

Opravil²

2016

MSF

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This work deals with the basics and possibilities of preparation non-bearing, heat-insulating material based on autoclaved aerated concrete. The ultra-low volume weight (under 200 kg/m3) and sufficient compressive strength is achieved using standard industrial technology. The low volume weight and therefore low heat conductivity can be reached due to highly porous structure. Such a material can be prepared by foaming very fine material powder like silica fume and very finely ground sand. Unfortunately, foams consisting of fine inorganic hydrophilic particles are highly unstable. Therefore it is necessary to use an effective stabilization mechanism. In this work the stabilization mechanism is based on addition of small amount of water-soluble organic admixtures.

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Section: Experimental Studymentioning

confidence: 99%

The Basics of Low Volume Weight Aerated Autoclaved Concrete Preparation

Koutný¹,

Opravil²

2016

MSF

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“…The energy is consumed due to the adsorption processes. The energy reduction at a flat interface can be mathematically described by Equation 1 [11]:…”

Section: Theoreticalmentioning

confidence: 99%

“…where the particle thermal energy is defined by k B T, where k B is the Boltzmann constant and T the thermodynamic temperature [11]. The value k B T can therefore be considered as a parameter affecting the stability of the gasliquid interface with adsorbed particles.…”

Section: Theoreticalmentioning

confidence: 99%

“…In the case of foam stability the adsorption and thermal energy ratio represents the main evaluation criterion. From previous experimental results it can be concluded that in the case of silica fume suspensions the stabilization effect occurs when the adsorption energy is by three orders of magnitude higher than the thermal energy [11]. Unfortunately, these foams have naturally very low stability.…”

Section: Theoreticalmentioning

confidence: 99%

“…Unfortunately, these foams have naturally very low stability. The reason why the foams created by inorganic hydrophilic fine particles are unstable can be found in the values of its adsorption and thermal energy which are in the most cases comparable [11,13].…”

Section: Theoreticalmentioning

confidence: 99%

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Preparation of Ultra-Low Volume Weight Autoclaved Aerated Concrete

Koutný¹

2016

Ceramics - Silikaty

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Autoclaved aerated concrete is a modern construction material that gains its popularity especially due to its thermal insulation performance resulting from low volume weight and porous structure with sufficient mechanical strength. Nowadays, there are attempts to use this material for thermal insulation purposes and to replace current systems, which have many disadvantages, mainly concerning durability. The key for improvement of thermal insulation properties is therefore obtaining a material based on autoclaved aerated concrete with extremely low volume weight (below 200 kg•m-3) ensuring good thermal isolation properties, but with sufficient mechanical properties to allow easy manipulation. This material can be prepared by foaming very fine powder materials such as silica fume or very finely ground sand. This paper deals with the possibilities of preparation and summarizes the basic requirements for successful preparation of such a material.

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