Comparative Study of the Thermal and Mechanical Properties of Foamed Concrete with Local Materials

Living in a habitat with comfort is requested by all. Cinder block bricks have poor thermal properties, leading people to use fan heaters and air conditioners to regain comfort. To overcome this problem of thermal discomfort in buildings, we used lightweight concrete such as foamed concrete which is a material that has improved thermal properties for thermal comfort. In addition, this material was compared with local materials used for the construction of buildings such as BTC, adobe and BLT mixed with binders. The results showed that foamed concrete is a material that has good thermal and mechanical properties compared to local materials mixed with binders. The foamed concrete having acceptable thermo-mechanical properties was that having a density of 930 kg/m3. It has a thermal resistance of 0.4 m2·K/W for a thickness of 20 cm. The foamed concrete having acceptable thermo-mechanical properties was that having a density of 930 kg/m3. It has a thermal resistance of 0.4 m2·K/W for a thickness of 20 cm. For sunshine on a daily cycle equal to 12 hours, the characteristic thickness achieved by this material is 7.29 cm. It also has a shallow depth of heat diffusion having a lower thickness than other materials. This shows that foamed concrete is a promising material for the construction of buildings.

Effect of Cellular Structure on Mechanical Properties of Polyurethane Foam Curing Materials

Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m^3.

Effect of Post-Added Water Amount on Pre-Concentrated Bark Foaming Materials by Mechanical Stirring

In this study,pre-concentrated bark,furfuryl alcohol and other biomass raw materials were used to prepare foaming materials by high-speed mechanical stirring without using a foaming agent.We investigated the effect of the postadded water amount on the properties of foaming materials.In particular,we determined basic physical properties of these materials,including the limiting oxygen index(LOI),porosity,thermal conductivity,thermogravimetric analysis,pore size distribution,and microstructure.The results of scanning electron microscopy(SEM)indicated that the pore size distribution was uniform and the pore size increased with increasing water volume.Thermogravimetric analysis(TG/DTG)showed that when the temperature reached 410°C,the foam was easily decomposed,the final residual mass was only 2.8%,and water addition had little effect on it.Moreover,the amount of post-added water is 5–30 g,the density and compression strength of the foamed materials gradually decreased,while the degree of pulverization increased.LOI ranged from 26.1%to 30.79%,and porosity ranged from 81%to 83%.The change in water volume greatly affected the foam’s performance,the performance of foamed material deteriorated as the amount of added water increased,but the effect on thermal conductivity was not very obvious.The highest thermal conductivity was only 0.0179 W/(m·K),still providing excellent thermal insulation.

Molten Salts/Ceramic-Foam Matrix Composites by Melt Infiltration Method as Energy Storage Material

A new type of high temperature energy storage material was obtained through the melt infiltration method, using compounding SiC ceramic foam as matrix and Na2SO4 as phase change material. The resulting composite material was measured by XRD, SEM, TG-DSC methods. The experimental results indicate that the composite is composed of silicon carbide, sodium sulfate and square quartz, and no chemical reactions occurs between Na2SO4 and SiC matrix. Na2SO4 has a good bonding with the SiC ceramic foam matrix. As the composite material is characterized by high thermal energy storage density and high thermal conductivity, it is suit for energy storage under high temperature.

Carbon foams prepared from coal tar pitch for building thermal insulation material with low cost

A new approach is provided to resolve the large-scale applications of coal tar pitch. Carbon foams with uniform pore size are prepared at the foaming pressure of normal pressure using coal tar pitch as raw materials. The physical and chemical performance of high softening point pitch(HSPP) can be regulated by vacuumizing owing to the cooperation of vacuumizing and polycondensation. Results indicate that the optimum softening point and weight ratio of quinoline insoluble are about 292℃ and 65.7%, respectively. And the optimum viscosity of HSPP during the foaming process is distributed in the range of 1000-10000 Pa·s. The resultant carbon foam exhibits excellent performance, such as uniform pore structure, high compressive strength(4.7 MPa), low thermal conductivity(0.07 W·m^(-1) ·K^(-1)), specially, it cannot be fired under the high temperature of 1200 ℃.Thus, this kind of carbon foam is a potential candidate for thermal insulation material applied in energy saving building.

Fatigue analysis of closed-cell aluminium foam using different material models

The fatigue analyses of AlSi7 closed-cell aluminium foam were performed using a real porous model and three different homogenised material models:crushable foam model,isotropic hardening model and kinematic hardening model.The numerical analysis using all three homogenised material models is based on the available experimental results previously determined from fatigue tests under oscillating tensile loading with the stress ratio R=0.1.The obtained computational results have shown that both isotropic and kinematic hardening models are suitable to analyse the fatigue behaviour of closed-cell aluminium foam.Besides,the kinematic hardening material model has demonstrated significantly shorter simulation time if compared to the isotropic hardening material model.On the other hand,the crushable foam model is recognized as an inappropriate approach for the fatigue analyses under tension loading conditions.

Compression properties of cost-efficient porous expanded clay reinforced AA7075 syntactic foams fabricated by industrial-oriented die casting technology

In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution.At this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a problem-solver.Owing to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors nowadays.In this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF studies.Additionally,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses.Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works.Besides,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.

Stabilized multifunctional phase change materials based on carbonized Cu-coated melamine foam/reduced graphene oxide framework for multiple energy conversion and storage

The leakage of organic phase change materials(OPCMs)at temperatures above their melting point severely limits their large-scale application.The introduction of porous supports has been identified as an efficient leakageproofing method.In this study,a novel carbonized Cu-coated melamine foam(MF)/reduced graphene oxide(rGO)framework(MF/rGO/Cu-C)is constructed as a support for fabricating stabilized multifunctional OPCMs.MF serves as the supporting material,while rGO and Cu act as functional reinforcements.As a thermal energy storage material,polyethylene glycol(PEG)is encapsulated into MF/rGO/Cu-C through a vacuum-assisted impregnation method to obtain PEG@MF/rGO/Cu-C composite with excellent comprehensive performance.PEG@MF/rGO/Cu-C exhibits high phase change enthalpies of 148.3 J g^(-1)(melting)and 143.9 J g^(-1)(crystallization),corresponding to a high energy storage capability of 92.7%.Simultaneously,MF/rGO/Cu-C endues the composite with an enhanced thermal conductivity of 0.4621Wm^(-1) K^(-1),which increases by 463%compared to that of PEG@MF.Furthermore,PEG@MF/rGO/Cu-C displays great light-to-thermal and electric-to-thermal conversion capabilities,thermal cycle stability,light-tothermal cycle stability,and shape stability,showing promising application prospects in different aspects.

Experiment on Mode Ⅰ/Ⅱ Mixed Interfacial Fracture Characterization of Foam Core Sandwich Materials at Elevated Temperatures

Foam-cored sandwich materials have been widely used in the civil engineering due to their advantages such as lightweight,high strength,and excellent anti-corrosion ability. However,the interfacial bonding strength of foamcored sandwich materials is weakened at elevated temperatures. In practice,the effect of high temperature cannot be ignored,because the composites and foams are sensitive to the change of temperature in the environment. In this study,a series of single-leg bending beams were tested at different temperatures to evaluate the influences of high temperatures on Mode Ⅰ/Ⅱ mixed interfacial fracture of foam core sandwich materials. The temperature was from29 ℃ to 90 ℃,covered the glass transition temperature of composites and foam core,respectively. The Mode Ⅰ/Ⅱ mixed interfacial crack prorogation and its corresponding interfacial strain energy release rate were summarized.

Seamless Bra Cup Moulding of Fabric-Foam Laminated Materials

Seamless bra cup moulding is an important manufacturing technique for the apparel industry,and in particular,for bra production.Polyurethane(PU)foams and/or fabric-foam laminated sheets are moulded into a desirable cup shape in order to fit the three-dimensional(3D)breast contour.Such foam cups not only provide a wide range of designs combined with different levels of softness and support,but also reduce production costs with minimum cutting and sewing of seams.In this study,two selected PU foam and fabric materials typically used for bra cup moulding were examined.Their respective performance behaviour in relation to different moulding temperatures and time changes were recorded and analyzed.The results reveal that cup heights are greatly affected by the use of foam and/or fabric-foam laminated materials.High moulding temperatures and/or prolonged dwell time could be required when deforming laminated materials and setting large cup sizes.Nevertheless,cup height cannot be taken as the only criteria to determine the optimal moulding conditions,and this is especially the case for large cup sizes.The design of mould heads is a major factor that affects the dimension changes of foam cups.In this respect,to control the foam moulding process,it is suggested that bra manufacturers examine the fabric/foam material properties to determine the optimal moulding condition,and quantify the shape of foam cups to enhance the design and development process of aluminum mould heads.

Construction utilization of foamed waste glass

Foamed waste glass(FWG) material is newly developed for the purpose to utilize the waste glassware and other waste glass. FWG has a multi-porous structure that consists of continuous or discontinuous voids. Hence lightweight but considerable stiffness can be achieved. In the present study, the manufacture and engineering properties of FWG are introduced first. Then, the utilizations of FWG are investigated in laboratory tests and field tests. Some case studies on design and construction work are also reported here. Through these studies we know that the discontinuous void material can be utilized as a lightweight fill material, ground improvement material and lightweight aggregate for concrete. On the other hand, the continuous void material can be used as water holding material for the greening of ground slope and rooftop, and as clarification material for water.

Mechanical Property of Foamed Metal

A comprehensive study on the mechanical behavior of foamed metals was demonstrated.The relationship among their mechanical properties,preparation method,porosity and the structure was briefly studied as well.

Enhanced CO2 decomposition via metallic foamed electrode packed in self-cooling DBD plasma device

A self-cooling dielectric barrier discharge reactor, packed with foamed Cu and Ni mesh and operated at ambient conditions, was used for the composition of CO2 into CO and O2.The influences of power, frequency, and other discharge characteristics were investigated in order to have a better understanding of the effect of the packing materials on CO2 decomposition.It is found that porous foamed Cu and Ni not only played a role as the carrier of energy transformation and electrode distributed in discharge gaps but also promoted the equilibrium shifting toward the product side to yield more CO by consuming some part of O2 and O radicals generated from the decomposition of CO2.The maximum CO2 decomposition rates of 48.6%and 49.2% and the maximum energy efficiency of 9.71% and 10.18% were obtained in the foamed Ni and Cu mesh, respectively.

Role of Composite Phase Change Material on the Thermal Performance of a Latent Heat Storage System: Experimental Investigation

Paraffin wax is a perfect phase change material(PCM)that can be used in latent heat storage units(LHSUs).The utilization of such LHSU is restricted by the poor conductivity of PCM.In the present work,a metal foam made of aluminium with PCM was used to produce a composite PCM as a thermal conductivity technique in PCM⁃LHSU and water was used as heat transfer fluid(HTF).An experimental investigation was carried out to evaluate the heat transfer characteristics of LHSU using pure PCM and composite PCM.The study included time⁃dependent visualization of the PCM during the melting and solidification processes.Besides,a thermocouple network was placed inside the heat storage to record the temperature profile during each process.Results showed that better performance could be obtained using composite PCM⁃LHSU for both melting and solidification processes.The melting time of composite PCM⁃LHSU was about 83%faster than that of a simple PCM⁃LHSU,and the percentage decreasing in the solidification time was about 85%due to the provision of metal foam.

A comparative study of combustible cartridge case materials

Foamed combustible material based on polymer bonded RDX was fabricated using CO_2 as foaming agent.The inner structures of felted and foamed combustible materials were presented by SEM. The two materials presented different formulations and inner porous structures. The combustion behaviors of felted and foamed materials were investigated by closed vessel test. Simultaneously, the co-combustion behavior of combustible cartridge case with 7-perf consolidated propellants was also investigated. The results of closed vessel test is applicable to gun system which is made of the foamed combustible material as component.

Preparation of Magnesia Insulation Materials by Walnut Shell Powder Impregnated with Silica Sol

In order to reduce the thermal energy loss of high temperature kilns and furnaces and lower the surface temperature of the kiln body,magnesia insulation materials were prepared using self-made magnesia porous aggregates(using high purity magnesia powder as starting material and potassium oleate as the foaming agent),middle grade magnesia powder,calcium aluminate cement,and SiO_(2) micropowder as starting materials,introducing walnut shell powder impregnated with silica sol(short for Sws)as a pore-forming agent.The effects of the Sws addition(0,10%,15%,and 20%,by mass)and the sintering temperature(1300,1350,1400,and 1480℃)on the properties of magnesia insulation materials were studied.The results show that(1)for the specimens fired at 1480℃,when the Sws addition is 10%,the cold compressive strength is 22 MPa;when the Sws addition is 20%,the thermal conductivity is 0.368 W·m^(-1)·K^(-1)(350℃);(2)nano-silica in the silica sol reacts with MgO in the matrix to form forsterite,which encapsulates the pores volatilized from the walnut shell powder and forms closed pores.

LDPE/MLLDPE共混改性及发泡性能

以低密度聚乙烯(LDPE)为基体树脂、4,4'-氧代双苯磺酰肼(OBSH)为发泡剂、茂金属线性低密度聚乙烯(MLLDPE)为改性剂,采用化学发泡法和辐照交联技术制备一系列LDPE/MLLDPE发泡材料。研究不同MLLDPE含量对LDPE/MLLDPE复合材料的熔体流动速率、热性能、发泡行为及力学性能的影响。结果表明,MLLDPE能提高LDPE/MLLDPE复合体系的结晶度,降低其熔体流动速率。随着MLLDPE含量的增加,LDPE/MLLDPE复合发泡材料的拉伸强度、撕裂强度和压缩永久变形呈现先上升后下降的趋势,而断裂伸长率、回弹率逐渐提高。当MLLDPE含量为15份时,LDPE/MLLDPE复合发泡材料的表观密度、拉伸强度、撕裂强度和压缩永久变形量分别提高了6.8%、24.4%、11.4%和24.2%。当辐照剂量为80 kGy、LDPE∶MLLDPE=85∶15时,LDPE/MLLDPE复合发泡材料的力学性能和泡孔结构更佳,满足胶带型片材的综合性能要求。

调控聚氨酯发泡材料中的热分布控制高温体积收缩和泡孔结构

为解决在烤漆等高温环境下,车内发泡材料因体积收缩(空隙)而导致的阻隔、缓震作用失效及行驶风噪等问题,以高导热铜粉为改性填料、软质和硬质聚氨酯发泡材料为基体,制备并研究了不同的聚氨酯/铜粉复合材料。结果发现:铜粉含量不仅能有效控制发泡材料在高温下体积收缩现象,且泡孔尺寸和发泡密度也能得到提高;当铜粉含量达到4 wt.%时,软质和硬质聚氨酯发泡材料的体积收缩率分别降低为6.56%和1.77%,发泡密度分别达到0.106 g/cm^(3)和0.171 g/cm^(3),发泡材料的吸水率降低50%左右。因此,添加铜粉后的聚氨酯发泡材料具有防潮和低体积收缩特性。

生物质基泡沫材料的研究进展

本文综述了生物质基泡沫材料的研究进展,详述了生物质基泡沫材料的主要原料及种类(纤维素、木质素、淀粉和壳聚糖)、制备方法和性能(热学、力学和环境稳定性)的改善方法,以及其在建筑绝缘材料、包装材料和其他潜在领域的应用现状,并对其未来研发方向进行了展望。

防治煤自燃的高堆积固化泡沫的制备及应用

漏风是引发矿井煤自燃的重要原因,而煤自燃火灾影响了矿井的正常生产。为解决传统无机固化泡沫(TISF)在充填堵漏过程中存在胶凝时间长、堆积能力弱的问题,提出经液态硅酸钠(LSS)改性制备的速凝无机固化泡沫(RISF)。研究了不同掺量的LSS对泡沫浆液胶凝时间、堆积能力等性能的影响规律,采用抗压强度、稳定性测试等表征手段,确定了LSS的最优添加量为5%(质量分数),RISF的28 d抗压强度达2.49 MPa,是TISF的1.7倍,最大密度比R为1.11,稳定性提升20%左右;胶凝时间和堆积能力的测试结果表明,与TISF相比,RISF的凝结时间大幅缩短(从683 s缩短到52 s),堆积能力提升(最大堆积高度提高1.9倍)。基于此,结合扫描电子显微镜(SEM)和X射线衍射(XRD)对RISF的速凝固化机理进行了探究。试验结果表明,RISF具有更多的水化产物且不同的水化产物紧密交织,颗粒水化过程中,LSS水解生成原硅酸根与溶液中的钙离子结合,加快水化反应,缩短了泡沫浆液的胶凝时间。但也发现,当LSS添加量超过5%时,RISF的抗压强度降低,稳定性下降,这主要是因为过量的LSS使溶液中的钙硅比例低于1.0,导致生成了低强度的水化产物。堵漏风试验和灭火试验结果表明,与TISF相比,RISF具有较高的堵漏效率和优良的防灭火性能,堵漏效率最高提升26.3%,并且在扑灭煤火时未出现复燃。RISF在利民煤矿矸石山的现场应用表明,其具有良好的降温灭火效果,有效解决了矸石山的高温难题,确保了矿井的正常生产。