Study of the relationship between thermal insulation behavior and microstructure of a fire‐resistant gel containing silica during heating

Adding a transparent gel containing silica between 2 sheets of glass could improve the fire resistance of laminated glazing by its thermal intumescent behavior at high temperature. In this study, a custom fire test shows that the glazing reaches the highest thermal insulation rating of 40 minutes when the molar ratio of SiO₂ and Na₂O in the gel is 4.0, but above this ratio, the thermal insulation rating of the glazing decreases with the increasing silica content. Thermal and scanning electron microscopic analyses have been used to investigate the thermal behavior and microstructure of the residual layer, respectively. The results indicate that, although the high silica content is responsible for the high amount of residue that is essential in the formation of a protection barrier between fire‐exposed and unexposed sides of the glass, it is not the only factor that resulted in the improved thermal insulation of the glazing.     

Enhancing Concrete Strength and Thermal Insulation Using Thermoset Plastic Waste

Structural concrete is the most frequently used construction material in the world because of its known advantageous characteristics. However, concrete has some limitations, such as its low tensile strength, low strength-to-weight ratio and moderate thermal insulation. Improving these characteristics was the aim of a laboratory-based investigation into the behavior of concrete made in the presence of ground melamine-formaldehyde (MF) thermosetting plastic waste as a sand replacement. The MF is a cross-linked thermoset polymer that cannot be recycled or reprocessed, presenting a serious solid waste disposal problem. The laboratory-based program included tests of tensile and compressive strengths, unit weight and thermal insulation characteristics. The tests were carried out on concrete and mortar with various water-to-cement (w/c) ratios, and sand was replaced by MF at different percentages that ranged from 0% to 60%. The results indicated that replacing sand with MF resulted in a lighter-weight concrete with improved characteristics. In general the strengths were increased as the percentage of MF was increased to reach maximum values at approximately 30% MF. In comparison with control specimens without MF, the strength/weight ratio of concrete was increased by up to 47% and the tensile strength of mortar was increased up to 16%. With regards to thermal insulation, a drop in temperature up to 30% was recorded in specimens with 60% MF. In conclusion, this investigation showed that the addition and reuse of MF in concrete mixes significantly improved the mechanical and thermal characteristics of concrete. This would be an effective approach when added to other protection methods of solid waste, as it addresses the specific waste of MF.     

Performance of glass-ceramic-based lightweight aggregates manufactured from waste glass and muck

Lightweight aggregates (LWAs) with microcrystalline diopside as the main constituent were prepared in this study. Waste glass and waste muck were used as the main raw materials, and the formula was designed according to the chemical composition of diopside, rather than using the Riley scheme. The effects of the glass content and nucleating agent on the mechanical properties, mineral composition, and microstructure of LWAs were studied. The results indicated that the presence of diopside crystallites can significantly improve the mechanical properties of LWAs. With an increase in the glass content from 0 wt % to 70 wt %, the strength of the LWAs increased from 12.21 MPa to 19.31 MPa with similar densities in the range of 1.667–1.687 g/cm³. The addition of a nucleating agent has a fluxing effect and promotes the formation and growth of diopside, which provides aggregates with high strength and low density. For example, the addition of CaF₂ decreased the density of the LWAs from 1.687 g/cm³ to 1.461 g/cm³ and increased the strength from 17.59 MPa to 20.81 MPa under the same calcination regime. The effect of the pore structure on the mechanical properties of the LWA in this experiment was far less than that of the crystal phase composition. With the addition of a nucleating agent, the diopside was co-precipitated from both the muck and glass. If no nucleating agent is added, diopside mainly precipitates from glass, and muck mainly forms a glass phase.     

Usage of marble wastes in traditional artistic stoneware clay body

Recycling of industrial wastes aids environmentally friendly production and has the advantage of lowering costs. Marble production generates large amounts of waste. Recycling of such wastes by incorporating them into ceramic industry is a practical solution for pollution problem. The aim of this work is to assess the possibility of the recycling of marble wastes in the production of stoneware clay bodies as a raw material for ceramic artwork production. Five different clay body mixes containing marble waste up to 27% were prepared and evaluated for firing color, water emission, morphology, microstructure, thermal expansion coefficient and thermal behavior. The results of the tests show that the utilization of marble waste in stoneware body is feasible for ceramic artwork production.     

Facile preparation for gelatin/hydroxyethyl cellulose-SiO2 composite aerogel with good mechanical strength,heat insulation,and water resistance

The advanced thermal insulation materials with low cost and high mechanical properties play an important role in transport packaging and thermal protection fields. An inorganic/organic composite aerogel was prepared through hydrogen bonds and chemical crosslinking among silica aerogel particles, gelatin (GA), and hydroxyethyl cellulose (HEC). The as-prepared GA/HEC-SiO₂ composite aerogels were characterized by compression tests, scanning electron microscopy, Fourier transform infrared, thermogravimetric analyzer, and contact angle tests to investigate the chemical composition and physical structure. The GA/HEC-SiO₂ composite aerogels exhibited a strong mechanical strength (0.53–4.01 MPa), a high compression modulus (1.33–11.52 MPa), a lower volume density (0.035–0.081 g/cm³), thermal conductivity as low as 0.035 W/[m K]), a porosity of more than 93%, and hydrophobic angle as high as 150.01° after hydrophobic modification. These results indicate that biopolymer composite aerogels embedded with SiO₂ aerogel particles display a bright future in thermal insulation.     

Refractory aspects of some dolomitic magnesite rocks

The samples studied were two types of magnesite containing calcium oxide (dolomite) as the principal impurity. Mixes were made with appropriate addition of serpentine and/or chromite rocks and an attempt was made to assess their suitability as magnesite refractories. The phase reactions that occurred during the firing at 1600° of refractory body mixes containing the five-component system CaO-MgO-Fe₂O₃-Al₂O₃-SiO₂ and the six-component system CaO-MgO-Fe₂O₃-Al₂O₃-Cr₂O₃-SiO₂ were investigated The free lime content and the phase constituents of the fired mixes, determined experimentally and calculated from the available thermal equilibrium data, were in close agreement, which indicated that the chemical reactions had attained equilibrium in the fired mixes. The physical and refractory properties of the selected mixes were found to comply with the standard international specifications.     

Extruded polystyrene foams with bimodal cell morphology

Extrusion foaming using supercritical carbon dioxide (CO₂) as the blowing agent is an economically and environmentally benign process. However, it is difficult to control the foam morphology and maintain its high thermal insulation comparing to the conventional foams based on fluorocarbon blowing agents. In this study, we demonstrated that polystyrene (PS) foams with the bimodal cell morphology can be produced in the extrusion foaming process using CO₂ and water as co-blowing agents and two particulate additives as nucleation agents. One particulate is able to decrease the water foaming time so both CO₂ and water can induce foaming simultaneously, while the other increases the CO₂ nucleation rate with little effect on the CO₂ foaming time. Our experimental results showed that a dual particulate combination of nanoclay and activated carbon provided the best bimodal structure. The bimodal foams exhibited much better compressive properties and slightly better thermal insulation for PS foams.     

Improving the transient thermal response and ablation properties of epoxy-modified silicone rubber composites by adding fluxing agent

In this work, transient thermal response and ablation behavior of liquid silicone rubber composites containing fluxing/ceramic forming fillers were investigated under different heat flows using an oxyacetylene flame. The results indicated that the introduction of zinc borate (ZB) and aluminum oxide (Al₂O₃) effectively reduced the temperature at various depths of the samples, and they improved the thermal insulation properties and lowered pyrolysis rates. The above finding was attributed to the heat absorption arising from water release and melt filling as well as the vitrified reaction of solid melt due to the decomposition of ZB. Besides, the melting and exfoliation of Al₂O₃ and the formation of aluminum silicate (Al₂SiO₅) caused heat absorption effect. Additionally, the mass ablation rates and line ablation rates increased with rising heat flows coupling with a decrease of compressive strength of the char layers. In a nutshell, the effect of adding ZB/Al₂O₃ on the thermal insulation behavior of epoxy-modified vinyl silicone rubber (EMVSR) composites under different heat flows was elucidtaed. This work served as a reference for the design and preparation of flexible ablative materials for thermal protection applications.     

Flame temperature analysis of biodiesel blends and components

Meeting sustainable energy demand with minimum environmental impact is a major area of concern in the energy sector. Alternative fuels such as biodiesel, ethanol etc. have been quite promising for fulfilling both these aspects. While biodiesel reduces emissions of CO, life cycle CO₂, SO_x, volatile organic compounds (VOC) and particulate matter (PM) significantly, the propensity for the production of NO_x is an important problem that requires extensive research. NO_x emission from a direct-injection diesel engine is mainly due to formation of thermal NO that is described by Zeldovich mechanism. Thus, studying temperature profile during biodiesel combustion can provide useful insights to the formation and destruction of NO_x. The main objective of this work is to investigate the effect of component methyl esters of biodiesel on open air flame temperature distribution and the effect of blending biodiesel with diesel and oxygenates (ethanol and methyl acetate) on open air flames. This objective was achieved by obtaining thermocouple measurements and thermal infrared imaging of local flame temperatures of wick-generated open air flames. A relationship between blend proportions and relative flame temperatures were obtained. In general, it was found that blending oxygenates such as ethanol and methyl acetate into petroleum diesel tended to increase the flame temperature in comparison with straight diesel fuel. The analyses of relative flame temperatures of different components of biodiesel were performed to evaluate the effect of unsaturation level and the hydrocarbon chain length on the flame temperature. It was found that the saturated methyl esters resulted in greater flame temperatures in comparison to unsaturated methyl esters. It was also revealed that shorter chained fatty acid methyl esters lead to higher flame temperatures as compared to its longer chained counterparts.     

Preparation and characterization of transparent fluorocarbon emulsion doped with antimony tin oxide and TiO2 as thermal-insulating and self-cleaning coating

A transparent thermal insulation and self-cleaning coating was prepared from a fluorocarbon emulsion doped with antimony tin oxide (ATO) and anatase TiO₂ nanoparticles. The thermal insulation and self-cleaning properties of the coating film were optimized by adjusting the amount of ATO and anatase TiO₂ nanoparticles in the fluorocarbon emulsion. The fluorocarbon coating containing 2.0 wt% ATO and 0.1 wt% TiO₂ possessed good comprehensive properties of thermal resistance, self-cleaning, weathering resistance, etc. Compared with the blank glass substrate, the mean light transmittance of the coating film only decreased by about 12% in the visible range. The temperature in the chamber covered with the coated glasses decreased 7°C lower than the common glass chamber without coating. The methyl red painted on the coating was completely faded after three days of ultraviolet irradiation, so the coating film exhibited an excellent self-cleaning property. The transparent coating with excellent thermal insulation and good self-cleaning will be developed for a potential building glass paint used for energy saving and environmental protection.     

Effect of Evening Primrose (Oenothera biennis) Oil Cake on the Properties of Polyurethane/Polyisocyanurate Bio-Composites

Rigid polyurethane/polyisocyanurate (RPU/PIR) foam formulations were modified by evening primrose (Oenothera biennis) oil cake as a bio-filler in the amount of 5 to 50 wt.%. The obtained foams were tested in terms of processing parameters, cellular structure (SEM analysis), physico-mechanical properties (apparent density, compressive strength, brittleness, accelerated aging tests), thermal insulation properties (thermal conductivity coefficient, closed cells content, absorbability and water absorption), flammability, smoke emission, and thermal properties. The obtained results showed that the amount of bio-filler had a significant influence on the morphology of the modified foams. Thorough mixing of the polyurethane premix allowed better homogenization of the bio-filler in the polyurethane matrix, resulting in a regular cellular structure. This resulted in an improvement in the physico-mechanical and thermal insulation properties as well as a reduction in the flammability of the obtained materials. This research provided important information on the management of the waste product from the edible oil industry and the production process of fire-safe RPU/PIR foams with improved performance properties. Due to these beneficial effects, it was found that the use of evening primrose oil cake as a bio-filler for RPU/PIR foams opens a new way of waste management to obtain new “green” materials.     

EPS颗粒对超轻水泥基复合保温材料性能的影响

聚苯乙烯泡沫塑料颗粒(EPS颗粒)作为水泥基复合保温材料的超轻骨料,对水泥基复合保温材料力学性能、热工性能影响显著。以水泥为胶凝材料,EPS颗粒、混合材、泡沫剂和改性剂、水等为主要原料,采用物理发泡工艺制备干表观密度不大于120 kg/m³的超轻水泥基复合保温材料(UCIM)。通过设计不同体积掺量的EPS颗粒,分析EPS颗粒掺量对泡沫混凝土基体孔结构、超轻水泥基复合保温材料强度和热工性能的影响规律。结果表明,适宜掺量EPS颗粒可显著提高超轻水泥基复合保温材料抗压强度和抗拉强度,并确保超轻水泥基复合保温材料具有良好的热工性能,即通过EPS颗粒与泡沫混凝土基体的协同作用,协调力学性能和热工性能,制备出高性能超轻水泥基复合保温材料。     

Investigation of factors impacting the in-service degradation of aerospace coatings

The impact of in-service environmental stressors on the durability of exterior decorative aerospace coating systems was investigated using accelerated weathering for a high-gloss polyurethane-based monocoat with and without clearcoat. Color, gloss, surface roughness, hardness, and chemical composition changes were studied by varying UV irradiance, temperature, thermal extremes, particulate matter, and acid environment while using constant moisture condensation conditions. The use of a clearcoat was found to enhance the resistance to gloss loss regardless of the stressors applied; however, the clearcoat system also produced a larger increase in hardness under all experimental conditions and a larger color shift for all stressors except for the particulate matter and particulate matter combined with acid. A correlation between color shift and chemical degradation was established by monitoring changes in amide and carbonyl functional groups as a function of UV irradiance, temperature, and thermal extremes. The particulate matter, with or without acid was found not to affect chemical degradation, but produced large color shifts for both coating systems and some loss of gloss at high radiant exposures for the clearcoat system. For the accelerated tests studied here, only the highest UV irradiance and temperature level, with or without additional stressors, produced changes in the clearcoat relative to the monocoat system without clearcoat that correlate with in-service performance observations.     

Biodiesel combustion,emissions and emission control

The use of biodiesel is rapidly expanding around the world, making it imperative to fully understand the impacts of biodiesel on the diesel combustion process, pollutant formation and exhaust aftertreatment. Because its physical properties and chemical composition are distinctly different from conventional diesel fuel, biodiesel can alter the fuel injection and ignition processes whether neat or in blends. As a consequence, the emissions of NO_x and the amount, character and composition of particulate emissions are significantly affected. In this paper, we survey observations from a spectrum of our earlier studies on the impact of biodiesel on diesel combustion, emissions and emission control to provide a summary of the challenges and opportunities that biodiesel can provide.     

Improving Thermal Stability and Electrical Insulation of Gamma‐Irradiated Silicone Rubber Nanocomposites

Room temperature vulcanized silicone rubber (RTVSR) nanocomposites were prepared by mixing of surface‐modified montmorillonite nanoclay or nano fumed silica, or both of them with RTVSR to improve thermal stability, electrical insulation, and flame retardant. Their tensile strength, elongation, swelling, and solubility properties at different doses of gamma radiation were investigated to study the effect of gamma radiation on the properties of the nanocomposites. The thermal stability, flammability properties, and volume resistivity of the nanocomposites were also investigated. The nanocomposite which containing fumed silica has the best thermal, mechanical properties, electrical insulation and fire retardancy. The thermal characteristics, namely, T_onset, T_10%, T_comp, and T_max, of the nanocomposite sample containing fumed silica were 22, 23, 13, and 11 °C higher than those of the blank, respectively. The tensile strength (TS) increased when the radiation dose was increased up to 100 kGy, but elongation, swelling, and solubility decreased when the radiation dose was increased up to 150 kGy. It can be generally concluded that the nanocomposites containing fumed silica and irradiated to 100 kGy are characterized by having outstanding mechanical, thermal, fire retardant, and electrical insulation properties and hence, they may have wide industrial applications as good thermal and electrical insulating materials. J. VINYL ADDIT. TECHNOL., 26:354–361, 2020. © 2019 Society of Plastics Engineers     

Prolong the durability of La2Zr2O7/YSZ TBCs by decreasing the cracking driving force in ceramic coatings

Service lifetime and thermal insulation performance are both crucial for the application of thermal barrier coatings (TBCs). In this study, layered structure design under equivalent thermal insulation conception is introduced to lower the cracking driving force in TBCs, and with the goal of prolonging TBCs lifetime. Three groups of layered LZO/YSZ TBCs were designed with same thermal insulation of 500?μm YSZ, the LZO layers were deliberately designed with different initial elastic modulus. Virtual crack closure technique (VCCT) calculation result showed that the energy release rates at the crack tips are 28.2, 22, and 18.8?N/m corresponding to the initial elastic modulus of 70, 60, and 50?GPa. After gradient thermal cyclic tests with surface temperature of 1300?°C, TBCs with lowest initial elastic modulus showed the longest lifetime, and more than double of pure YSZ TBCs. This study provides a new option for the improvement of TBCs lifetime.     

Thermal and mechanical properties of diglycidylether of bisphenol A/ trimethylolpropane triglycidylether epoxy blends cured with benzylpyrazinium salts

The effect of blend composition on thermal stability and mechanical properties of diglycidylether of bisphenol A (DGEBA)/trimethylolpropane triglycidylether (TMP) epoxy blends cured with benzylpyrazinium salts (N‐benzylpyrazinium hexafluoroantimonate, BPH) as a thermal latent catalyst was investigated. The thermal stability, characterized by the initial decomposition temperature, temperature of maximum rate of weight loss, integral procedural decomposition temperature, and activation energy for decomposition, increase in DGEBA‐rich compositions. This could be due to the long repeat unit and stable aromatic ring in the DGEBA. The mechanical properties are also discussed in terms of the fracture toughness (K_IC), flexural and impact tests for the blend composition studied. The addition of TMP into DGEBA gives systematic improvements in fracture toughness, which results from the increase in aliphatic and flexible chain segments of TMP. © 2002 Society of Chemical Industry     

Operation characteristics of 1 ton/day-scale coal gasifier with additional stage

A one-stage coal gasifier was modified to accommodate the two stages of coal feeding. Operating characteristics were compared between the one-stage and two-stage gasification in terms of syngas composition, carbon conversion, shape and inner structure of produced slags, characteristics of particle size distribution in entrained fines, and effects on particulate removal facilities. Temperature at the second stage of the gasifier resulted in lower values, which confirms the performance of the second stage as a reduction area by endothermic reactions. The results suggest that the 10–20% increase in coal feeding to the second stage might not cause much loss in carbon conversion. Produced slag and the performance of metal filters and water scrubber were similar with the earlier results from one-stage gasification tests. The two-stage gasification appears to help in increasing the cold gas efficiency for the certain operating range. Two-stage gasification had an impact on the 0.1–1 μm size of entrained fines, which appear to be cenospheres that occur during the rapid quenching in temperature.     

Sensitivity of Diesel Particulate Material Emissions and Composition to Blends of Petroleum Diesel and Biodiesel Fuel

A number of investigations have examined the impact of the use of biodiesel on the emissions of carbon dioxide and regulated emissions, but limited information exists on the chemical composition of particulate matter from diesel engines burning biodiesel blends. This study examines the composition of diesel particulate matter (DPM) emissions from a commercial agriculture tractor burning a range of biodiesel blends operating under a load that is controlled by a power take off (PTO) dynamometer. Ultra-low sulfur diesel (ULSD) fuel was blended with soybean and beef tallow based biodiesel to examine fuels containing 0% (B0), 25% (B25), 50% (B50), 75% (B75), and 100% (B100) biodiesel. Samples were then collected using a dilution source sampler to simulate atmospheric dilution. Diluted and aged exhaust was analyzed for particle mass and size distribution, PM_2.5 particle mass, PM_2.5 organic and elemental carbon, and speciated organic compounds. PM_2.5 mass emissions rates for the B25, B50, and B75 soybean oil biodiesel mixtures had 20%–30% lower emissions than the petroleum diesel, but B100 emissions were about 40% higher than the petroleum diesel. The trends in mass emission rates with the increasing biodiesel content can be explained by a significant decrease in elemental carbon (EC) emissions across all blending ranges and increasing organic carbon (OC) emissions with pure biodiesel. Beef tallow biodiesel blends showed similar trends. Nevertheless, it is important to note that the study measurements are based on low dilution rates and the OC emissions changes may be affected by ambient temperature and different dilution conditions spanning micro-environments and atmospheric conditions. The results show that the use of biodiesel fuel for economic or climate change mitigation purposes can lead to reductions in PM emissions and a co-benefit of EC emission reductions. Detailed speciation of the OC emissions were also examined and are presented to understand the sensitivity of OC emissions with respect to biodiesel fuel blends.

Copyright 2012 American Association for Aerosol Research     

Sintering behavior of a nanostructured thermal barrier coating deposited using electro-sprayed particles

During high temperature service, a series of microstructure and phase evolutions occur in thermal barrier coatings (TBCs), which result in degradation of thermal insulation and durability. In this study, the sintering behavior of an air plasma sprayed 8 wt% YSZ coating deposited using electro-sprayed nanostructured particles (ESP) as feedstock powder was investigated and compared with conventional YSZ coating deposited using hollow spherical powders (HOSP). Due to the distinct asymmetric porous structure formed by nanosized YSZ particles, the ESP powder was partially melted in the plasma jet during the deposition, which resulted in the formation of a nanostructured coating that consisted of porous nanozones and dense zones. The ESP coating not only shows a significantly lower initial thermal conductivity of 0.70 W/mK, but also exhibits a stronger sintering resistance in terms of phase stability and thermal insulation compared to the conventional coating. When subjected to prolonged sintering at 1400°C for 128 hours, the thermal conductivity of the ESP coating would gradually increase to about half that of the HOSP coating at 1.29 W/mK. These differences are ascribed to the interaction among different sintering behavior between nanozones and dense zones.