direct foaming method
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Author(s):  
Nourhan Mortada ◽  
Annabelle Phelipot-Mardele ◽  
Christophe Lanos

Reduce the impact of the building sector has become a key point of sustainable development. The production of lightweight materials for the building industry is therefore a must. To produce such materials, foaming is a process commonly used to trap air bubbles and achieve a range of low densities. A sufficient low thermal conductivity and an acceptable ability to regulate humidity variations in order to limit overall energy consumption are the sought properties. In this study, a direct foaming method is applied to formulate gypsum foams using a commercial Plaster and two biobased foaming agents based on proteins. An anionic surfactant (α-olefin sulphonate sodium salt) is used as a reference surfactant. Varying the mixing time, protein content and water content, gypsum foams were produced. The foam volume is measured continuously during the mixing step and the foam homogeneity is controlled. The densities of fresh foams and of the hardened foams are used to identify the links between formulation and foams properties. Gypsum foam specimens with different densities ranging from 300 to 750 kg/m3 are produced. The thermal conductivity and the Moisture Buffer Value measurements are performed. Such properties appear directly linked to the porosity and pore connection of the foams. The obtained results highlight the contribution of biobased surfactant to the performance of gypsum foams.


Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 4029
Author(s):  
Kang-Wei Lo ◽  
Ya-Wen Lin ◽  
Ta-Wui Cheng ◽  
Kae-Long Lin ◽  
Wei-Ting Lin

This study used silicon carbide sludge (SCS) to prepare lightweight foaming geopolymer materials (FGPs) by the direct foaming method. Results showed that when the SCS replacement level was 10%, the bulk density of the lightweight FGPs with added foaming agent amounts of 0.5% and 2.0% was 0.59 and 0.49 g/cm3, respectively; at a curing time of 28 days, the lightweight FGPs with amounts of added foaming agent of 0.5% and 2.0% had bulk densities that were 0.65 and 0.58 g/cm3, respectively. When the SCS replacement level was 10%, and the amount of added foaming agent was 2.0%, the porosity ratio of the lightweight FGP increased from 31.88% to 40.03%. The mechanical strength of the lightweight FGPs with SCS replacement levels of 10% and 20% was 0.88 and 0.31 MPa, respectively. Additionally, when the amount of foaming agent increased to 2.0%, the thermal conductivity of the lightweight FGPs with SCS replacement levels of 10% and 20% were 0.370 and 0.456 W/m×K, respectively. When the curing time was 1 day, and the amount of added foaming agent was 0.5%, the reverse-side temperature of the lightweight FGPs with SCS replacement levels of 10% and 20% were 286 and 311 °C, respectively. The k value of the O2 reaction decreased from 2.94 × 10−4 to 1.76 × 10−4 because the reaction system was affected by the presence of SiC sludge, which was caused the reaction to consume O2 to form CO2. The results have been proposed to explain that the manufactured lightweight FGPs had a low thermal conductivity (0.370−0.456 W/m×K). Therefore, recycling of silicon carbide sludge in lightweight foaming geopolymer materials has potential as fire resistance material for the construction industry.


Author(s):  
Linying Wang ◽  
Liqiong An ◽  
Jin Zhao ◽  
Shunzo Shimai ◽  
Xiaojian Mao ◽  
...  

AbstractPorous ceramics have been widely used in heat insulation, filtration, and as a catalyst carrier. Ceramics with high porosity and high strength are desired; however, this high porosity commonly results in low strength materials. In this study, porous alumina with high porosity and high strength was prepared by a popular direct foaming method based on particle-stabilized wet foam that used ammonium polyacrylate (PAA) and dodecyl trimethyl ammonium chloride (DTAC) as the dispersant and hydrophobic modifier, respectively. The effects of the dispersant and surfactant contents on the rheological properties of alumina slurries, stability of wet foams, and microstructure and mechanical properties of sintered ceramics were investigated. The microstructure of porous ceramics was regulated using wet foams to achieve high strength. For a given PAA content, the wet foams exhibited increasing stability with increasing DTAC content. The most stable wet foam was successfully obtained with 0.40 wt% PAA and 0.02 wt% DTAC. The corresponding porous alumina ceramics had a porosity of 82%, an average grain size of 0.7 µm, and a compressive strength of 39 MPa. However, for a given DTAC content, the wet foams had decreasing stability with increasing PAA content. A possible mechanism to explain these results is analyzed.


2020 ◽  
Author(s):  
Yu Zheng ◽  
Xudong Luo ◽  
Jiegang You ◽  
Zijun Peng ◽  
Shuhao Zhang

Abstract To satisfy the ever-increasing demands for high-performance ceramic foams that could be applied in catalysts loader, filtrations and adsorptions, it is critical to develop technologies for ceramic foams with open channel structure. In this work, we fabricated ceramic foams with three-dimensional porous structure specially with open channels by combining direct foaming method with adding pore-forming agent method. There are two levels of length scale present in this hierarchically porous structure, that is, foam structure with spherical pores evolved from bubbles, and open pores on the cell wall derived from silica hollow spheres with thin shell as the pore-former. Hierarchical ZrO 2 based foams with porosity of 86.5%-95.1% and compressive strength of 2.05-5.67 MPa, and Al 2 O 3 based foams with porosity of 86.2%-91.0% and compressive strength of 6.8-13.2 MPa were fabricated. The prepared ceramic foams characterized by this open channel structure are promising to perform outstandingly in the abovementioned fields due to their uniform pore size, low density as well as high mechanical strength.


2019 ◽  
Vol 45 (2) ◽  
pp. 2124-2130 ◽  
Author(s):  
Zhongpei Du ◽  
Dongxu Yao ◽  
Yongfeng Xia ◽  
Kaihui Zuo ◽  
Jinwei Yin ◽  
...  

2019 ◽  
Vol 13 (2) ◽  
pp. 202-209 ◽  
Author(s):  
Wenying Zhou ◽  
Wen Yan ◽  
Nan Li ◽  
Yuanbing Li ◽  
Yajie Dai ◽  
...  

In this study, five foamed ceramics with struts containing needle-like mullite were prepared by direct-foaming method using white clay, industrial alumina and microsilica powder as raw materials. The effects of microsilica content on the phase compositions, microstructures and properties of foamed ceramics were investigated. The results showed that the adding of microsilica decreased the average pore size and apparent porosity and increased the compressive strength and thermal conductivity of the foamed ceramics by affecting the properties of foamed slurry and reaction sintering process. The foamed ceramics with 10 wt.% microsilica content showed the best properties with high porosity of 75.8%, positive reheating linear change, compressive strength of 1.44MPa and low thermal conductivity of 0.219W/(m?K) (at 350?C).


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