Foamed Body Research Articles

Preparation of cellular SiBOC foams by thermo‐foaming of polymethylvinylborosiloxane–wheat flour dough

AbstractA novel method for the preparation of SiBOC foams from a polymethylvinylborosiloxane (MVBS) solution in ethanol using wheat flour as a foam stabilizer and pore template has been reported. A dough prepared by mixing the MVBS solution and wheat flour undergoes foaming at 180°C due to the stabilization of bubbles created by ethanol vapor by the adsorption of wheat flour particles on their surface. The ceramization of the foamed body at 1500°C followed by burnout of carbon produced from the wheat flour results in SiBOC foams of hierarchical pore structure. The foam density (.68–.44 g cm−3), average cell size (1.81–.58 mm), compressive strength (3.9–1.7 MPa), and thermal conductivity (.33–.21 W m−1 K−1) decrease with an increase in wheat flour to MVBS weight ratio from .25 to 1. The population of smaller pores (∼5–50 μm) created by wheat flour particles on cell walls and struts increases with an increase in wheat flour to MVBS weight ratio. The presence of β‐SiC and turbostratic graphite nanodomains in amorphous SiBOC is evidenced by X‐ray diffraction and transmission electron microscopy analysis.

Morphology and Thermoelectric Properties of Mg<sub>3+δ</sub>Sb<sub>2</sub> Foams Manufactured Using Combustion Synthesis

Magnesium antimonide (Mg3Sb2) is a promising thermoelectric compound utilized for thermoelectric power generation. We have found out that the Mg3Sb2 compound can be made from Mg and Sb powder mixture via the combustion synthesizing reaction. In this study, we manufactured the compounds from the compacted bodies with different Mg fractions between 60.0 and 75.0 at% in an argon gas flow at 650°C for 1 hour via the combustion synthesis process. Morphology, porosity, phases and thermoelectric properties (electrical resistivity and Seebeck coefficient at room temperature to 500°C) were investigated for the manufactured samples. All samples manufactured with different Mg fractions mainly consisted of Mg3Sb2 and became foamed bodies with a porosity between 50 and 70%. The thermoelectric properties changed with the Mg fraction. The maximum power factor of 42.1 µW/mK2 at 488°C was obtained in the foamed body with the Mg fraction of 64 at%. The dimensionless figure of merit (ZT) of the sample was also estimated using the thermal conductivity, which was calculated considering its large porosity. The maximum dimensionless figure of merit (ZTmax) would be 0.13 at 488°C.

Effect of thermal conductivity of ceramic compact on the porous structures of foamed bodies via direct-foaming method

ABSTRACTThe effect of the thermal conductivity of ceramic compact on the porous structure of a foamed body formed by the direct foaming process was investigated. In order to change the thermal conductivity of the ceramic compact, three types of ceramic powder (alumina, mullite, and cordierite) with different particle sizes were used. These ceramic powders were mixed with powdered resol resin, which is a foamable thermoset resin used as both a foaming agent and binder for the ceramic powders. Ceramic compacts were prepared from the mixed starting ceramic and resol powders by press molding, and then characterized by thermal conductivity. The foamed bodies were produced from the ceramic compacts by heating to the resol foaming temperature to produce porous structures. The pore structures of the foamed bodies were strongly affected by differences in thermal conductivity in the ceramic compacts.

폐 LCD판넬로부터 붕규산유리 발포체 제조를 위한 원료 유리 제조

사용 후 발생되는 폐 LCD판넬용 유리의 재활용 방안을 마련하고자 별도의 전처리 없이 폐 LCD판넬을 습식분쇄함으로서 발포체 제조용 원료유리로 사용가능한 폐 붕규산유리의 회수 방법을 조사하였으며, 이렇게 회수된 폐 붕규산유리를 사용하여 발포체의 제조를 시도하였다. 입도 270 mesh 이하의 크기로 분쇄 조절된 폐 붕규산유리를 대상으로 폐 붕규산분말 100 g에 대해 발포제로서 탄소분을 0.3 중량 분율, 추가 발포조제로서 <TEX>$Na_2CO_3$</TEX>, <TEX>$Na_2SO_4$</TEX>, <TEX>$CaCO_3$</TEX>를 각각 1.5 중량 분율이 되도록 첨가한 원료 유리분말을 발포소성온도 <TEX>$950^{\circ}C$</TEX>에서 20 min간 발포를 진행함으로서 밀도가 <TEX>$0.3g/cm^3$</TEX> 이하되는 발포체를 제조할 수 있었다. 또한 원료 유리에 추가적으로 <TEX>$SiO_2$</TEX> 또는 <TEX>$H_3BO_3$</TEX>를 첨가함으로서 얻어지는 발포체에 효과적으로 개기공을 형성할 수 있었으며, 개기공의 형성은 흡음 등 새로운 기능을 가진 발포체의 제조 가능성을 보여주었다. In this article, the foamed body of glass was manufactured from the waste borosilicate glass produced by wet pulverization process without additional pretreatment which can be used as a recycling method for waste LCD panel glass. Each 100 g of pulverized waste borosilicate glass with the size of less than 270 mesh were mixed with 0.3 weight fraction of carbon and 1.5 weight fraction of <TEX>$Na_2CO_3$</TEX>, <TEX>$Na_2SO_4$</TEX> and <TEX>$CaCO_3$</TEX> and let them foamed for 20 minutes at <TEX>$950^{\circ}C$</TEX> to manufacture the foamed body having the density of less than <TEX>$0.3g/cm^3$</TEX>. Additionally, adding <TEX>$SiO_2$</TEX> or <TEX>$H_3BO_3$</TEX> to the mixture enabled the foamed body to have efficient formation of open pores which showed the possibility for producing the foamed body with new functionalities such as sound absorption.

Macroscopic fracture behavior of nickel foam under tension

Purpose – The samples of nickel foam with porosity of about 88 percent were uniaxially tensioned at room temperature, and the phenomena of tensile fracture were compared with that from the fully dense plate of metal nickel. The purpose of this paper is to investigate the differences between their behaviors of tensile fracture. Design/methodology/approach – The tensile test was carried out by using the tester of CMT-series microcomputer-controlled electronic universal testing machine. The difference of tensile fracture behavior between the nickel foam and the dense metal nickel was discussed by analyzing the load-displacement curve and the microscopical fracture. Findings – The results indicated that, nickel foam also displayed the feature of macroscopic plastic-deformation during tension, but it showed a macroscopic brittleness much more than that of the fully dense body. The axial apparent strain at the maximum load for the foamed sample was markedly less than that for the dense one. In addition, an obviously gradual course exhibited for the foamed body during tensile failure and a rapidly instant course for the dense body correspondingly. Originality/value – There have been some studies on the tensile behavior for metal foams, but much less than on the compression, and the relevant works are mostly for aluminum foam. The present work provides the investigations on the difference of tensile fracture behavior between the nickel foam and the dense metal nickel, as well as that of the corresponding samples in various cases with different tensile velocities. It is found that the porosity can make a remarkable decrease of the apparent strain at the maximum load and a significant increase of the macroscopical brittleness for the metallic nickel under tension.

발포공정을 이용한 경량의 연질 세라믹 보온단열재의 제조

본 연구는 유기계 보온단열재의 장점인 경량성과 연질특성을 갖는 무기계 보온단열재의 제조를 위한 새로운 개념의 무기질 저온 발포 공정에 관한 것이다. 새로운 무기질 발포 공정은 섬유상인 해포석 및 규산알루미늄으로 하여금 발포체의 골격을 형성토록 하고, 저온에서 기체 발생이 가능한 발포제를 사용하여 무기질 섬유상 골격체가 팽창되어 공동을 형성하게 하며, 이 형성된 공동 속에 낮은 열전도도를 갖는 무기질 다포체인 팽창진주암을 채우는 것이다. 총괄적으로 무기질 재료를 고온 용융함이 없이 저온에서 무기질 발포체의 제조가 가능하게 된다. 이를 위해서 섬유상인 해포석의 해섬처리과정, 발포를 위한 섬유상 슬러리의 열처리공정 등 다양한 준비공정이 필요하며, 열처리 전 슬러리의 최적 조성물 조건이 요구된다. 제조된 발포체는 경량, 연질의 보온단열재로서의 겉보기 밀도, 내력 강도, 굽힘강도, 고내열성 등의 물성을 보여주었다. A new concept of an inorganic foaming process at low temperature was demonstrated for the production of inorganic thermal insulating materials with the properties of flexible light-weight, the advantages of organic-based thermal insulation material. The foaming process was proceeded by establishing a skeleton of the foam body by using inorganic fibrous sepiolite and aluminum silicate. A cavity was formed by the expansion of fibrous skeleton body, by the gas which was generated from foaming agent at low temperature. Then the multi-vesicular expanded perlite with low thermal conductivity was filled into the cavity in a skeleton of the foam body. Finally through these overall process, a new inorganic foamed body could be obtained at low temperature without the hot melting of inorganic materials. In order to achieve this object, various preparations such as fibrous sepiolite fibrillation process, heat treatment process of the fibrous slurry were needed, and the optimal compositional condition of slurry was required. The foam body produced showed the properties of flexible light-weight thermal insulation materials such as bulk density, yield strength, flexural strength, and high heat resistance.

Fumed Silica/Ceramic Wool 무기복합재의 제조 및 열적 성질

This study examined the fabrication and thermal properties of fumed silica/ceramic wool inorganic composites. A predetermined quantity of fumed silica and ceramic wool was mixed uniformly into a slurry state and stabilized in the mold at room temperature, and converted to a massive foamed body through a complete drying process at 150 °C. Although the samples without polyvinyl alcohol (PVA) as an interfacial adhesive showed a bulk

Preparation of spherical foamed body with function of media for waste water treatment by using waste LCD glass

Using waste LCD glass as a base material helped developed the manufacturing process of the spherical foamed body and its varied functionality. Also, the manufactured spherical foamed body showed great performance as a water treatment media. By mixing 90wt% of waste LCD glass, 100 parts by weight of glass mixture that has 10wt% kaolinite as a shaping agent, 1.0 part by weight of carbon foaming agent, and mixture of each 1.5 parts by weight of Na2CO3, CaCO3 and Na2SO4 as foaming agents and the MgO as a parting agent for 10min of foaming calcination in the rotary kiln at 970–1000°C, the spherical foamed body can be manufactured effectively. The manufactured spherical foamed body performed as a great water treatment media by showing 70.5% of SS removal efficiency, 56.1% of BOD removal efficiency, 57.5% of COD removal efficiency, 28.6% of denitrification and 49.8% of phosphorous removal.

Heat insulating acoustical structure and carbody shell structure using the same

To obtain a wide passenger compartment space, the thickness of a heat insulating acoustical layer is reduced, and for this purpose, a comfortable in-car environment is obtained by using a vacuum insulating panel which combines high heat insulating performance and sound insulating performance. A heat insulating acoustical layer 20 is formed on one surface of a lightweight alloy structure 10 of double skin construction by using a vacuum insulating panel 21 as a middle member and sandwiching two surfaces of the panel with elastic sound absorbing materials 22, 23 made of a nonwoven fabric or a foamed body, and the heat insulating acoustical layer is covered with an interior material 24. Owing to this construction, the transmission loss of a noise which transmits from the double skin structure side is improved by the mutual actions of the elasticity of the sound absorbing material and the rigidity of the vacuum heat insulating panel.

Preceramic Polymer를 이용한 마이크로셀룰라 코디어라이트 세라믹스의 합성

In this study, a novel-processing route for producing microcellular cordierite ceramics has been developed. The proposed strategy for making the microcellular cordierite ceramics involves three steps: (ⅰ) fabricating ceramic-filled preceramic foams by heating a mixture of polysiloxane, expandable microspheres, talc, and alumina in a mold, (ⅱ) cross-linking the foamed body, and (ⅲ) transforming the body into microcellular cordierite ceramics by sintering. Cu jig was used for near net shaping in the foaming step. The experimental variables such as the shape of foaming jig and the content of expendable microsphere were investigated. By controlling the content of expendable microsphere, it was possible to make the porous cordierite ceramics with cell density of ~1.0×10? cells/㎤.

Processing and Mechanical Properties of Microcellular Ceramics

Recently, a novel processing route for fabricating microcellular ceramics has been developed. The strategy for making the microcellular ceramics involves: (i) forming some shapes containing a mixture of preceramic polymer, expandable microspheres and optional fillers by a conventional ceramic forming method, (ii) foaming the compact by heating, (iii) cross-linking the foamed body, and (iv) transforming the foamed body into microcellular ceramics by pyrolysis. The flexural strength and compressive strengths of the microcellular ceramics were investigated; values up to 30 MPa and 100 MPa, respectively, were obtained at room temperature. The superior mechanical properties were attributed to homogeneous distribution of cells in microcellular ceramics.

Processing of microcellular cordierite ceramics from a preceramic polymer

A novel processing route for producing microcellular cordierite ceramics has been developed. The proposed strategy for making the microcellular cordierite ceramics involves three steps: (i) fabricating ceramic-filled preceramic foams by heating a mixture of polysiloxane , expandable microspheres , talc, and alumina in a mold, (ii) cross-linking the foamed body, and (iii) transforming the body into microcellular cordierite ceramics by sintering.

Processing of Highly Porous, Open-Cell, Microcellular Silicon Carbide Ceramics by Expansion Method Using Expandable Microspheres

A refined processing route for producing highly porous, open-cell, microcellular SiC ceramics by the expansion method using expandable microspheres has been demonstrated. The strategy adopted for making microcellular SiC ceramics involved the following steps: (i) fabricating preceramic foams by heating a mixture of polysiloxane, carbon black or phenol resin (used as a carbon source), Al 2 O 3 -Y 2 O 3 (used as a sintering additive), expandable microspheres (used as sacrificial templates), and SiC (an optional inert filler); (ii) cross-linking the polysiloxane in the foamed body; (iii) transforming the polysiloxane and phenol resin by pyrolysis into silicon oxycarbide and carbon, respectively; and (iv) synthesizing SiC by carbothermal reduction. Effects of the carbon source, expandable microsphere content, and inert filler content on microstructure, porosity, and cell density were investigated in this study. By controlling the expandable microsphere and inert filler contents, it was possible to adjust the porosity within a range of 77% to 94%.

Processing of closed-cell silicon oxycarbide foams from a preceramic polymer

A novel processing route for fabricating closed-cell ceramic foams has been developed. The strategy for making the ceramic foams involves: (i) forming some shapes using a mixture of preceramic polymer and expandable microspheres by a conventional ceramic forming method, (ii) foaming the compact by heating, (iii) cross-linking the foamed body, and (iv) transforming the foamed body into ceramic foams by pyrolysis. By controlling the microsphere content and the pyrolysis temperature, it was possible to adjust the porosity ranging from 56 to 85%.

Effect of inert filler addition on pore size and porosity of closed-cell silicon oxycarbide foams

Ceramic foams are a specific class of porous materials composed of pores (usually referred to as cells), with a size ranging from a few micrometers to a few millimeters, and ceramic walls (closed-cell foams) or struts (open-cell foams). Fabrication of ceramic foams from preceramic polymers has recently attained increasing interest because of low fabrication temperatures and the unique properties of the foams, such as low density, low thermal conductivity, high permeability, high surface area, high thermal shock resistance, and high specific strength [1–4]. These characteristics make them good candidates for both structural and functional applications, such as filters, insulators, absorbents, catalyst supports, and biomedical devices [2–8]. Various processing routes have been proposed for the production of porous ceramics, including replication methods [6, 9], space holder methods [10, 11], direct foaming methods [1, 8, 12, 13], and microcellular foaming with CO2 by implementing the thermodynamic instability principle [14–16]. More recently, the generation of closed-cell ceramic foams based on the following strategy has been developed: (i) forming a compact using a mixture of preceramic polymer and expandable microspheres, (ii) forming the compact by heating, (iii) cross-linking the foamed body, and (iv) transforming the foamed body into a ceramic foam by pyrolysis [17]. In the present letter, the effect of inert filler addition on the pore (cell) size and porosity of closed-cell silicon oxycarbide foams was investigated using expandable microspheres as a blowing agent and SiO2 powder as an inert filler. A commercially available polysiloxane (YR3370, GE Toshiba Silicones Co., Ltd., Tokyo, Japan), an expandable microsphere (461DU40, Expancel, Sundsvall, Sweden), and SiO2 (0.8 μm, High Purity Chemicals, Saitama, Japan) were used as raw materials. Two batches of powder were mixed, each containing polysiloxane:microsphere in a weight ratio of 6:4, with one containing no silica and the other containing 10 wt% SiO2. The batch compositions are

Speaker equipped with diaphragm filled with foamed resin

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Improvement in the technology of manufacturing lightweight products BL-0.4

An increase in water content from 58 to 60% with a simultaneous increase in the apparent density of the foamed body up to 0.55–0.57 g/cm3 achieves a fluidity which ensures easy and perfect filling of the molds. This can substantially simplify the construction of a casting machine.

Methods of preparing foamed body for ultralightweight refractories

A technology was developed for manufacturing foam bodies with premineralization of a foam-forming agent which yielded a more stable foam and reduced the consumption of foam-forming agent by 25%.