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The energy efficiency of buildings can be greatly improved by decreasing the energy embodied in installed materials. In this contribution, we investigated the possibility of foaming waste bottle glass in the air atmosphere with the addition of water glass, which would reduce the energy used in the production of foamed glass boards. The results show that with the increased addition of water glass, the crystallinity and the thermal conductivity decrease, however, the remaining crystal content prevents the formation of closed-porous foams. The added water glass only partly protects the carbon from premature oxidation, and the foaming mechanism in the air is different than in the argon atmosphere. The lowest obtained foam density in the air atmosphere is 123 kg m−3, while the lowest thermal conductivity is 53 mW m−1 K−1, with an open porosity of 50% for the sample obtained in the air, containing 12 wt% of water glass, 2 wt% of B2O3, 2 wt% AlPO4 and 2 wt% K3PO4. [ABSTRACT FROM AUTHOR]

The built environment is the largest single emitter of CO2 and an important consumer of energy. Much research has gone into the improved efficiency of building operation and construction products. Life Cycle Assessment (LCA) is commonly used to assess existing buildings or building products. Classic LCA, however, is not suited for evaluating the environmental performance of developing technologies. A new approach, anticipatory LCA (a‐LCA), promises various advantages and can be used as a design constraint during the product development stage. It helps overcome four challenges: (i) data availability, (ii) stakeholder inclusion, (iii) risk assessment, and (iv) multi‐criteria problems. This article's contribution to the line of research is twofold: first, it adapts the a‐LCA approach for construction‐specific purposes in theoretical terms for the four challenges. Second, it applies the method to an innovative prefabricated modular envelope system, the CleanTechBlock (CTB), focusing on challenge (i). Thirty‐six CTB designs are tested and compared to conventional walls. Inclusion of technology foresight is achieved through structured scenario analysis. Moreover, challenge (iv) is tackled through the analysis of different environmental impact categories, transport‐related impacts, and thickness of the wall assemblies of the CTB. The case study results show that optimized material choice and product design is needed to reach the lowest environmental impact. Methodological findings highlight the importance of context‐specific solutions and the need for benchmarking new products. [ABSTRACT FROM AUTHOR]

Abstract: Foam glasses are usually prepared through a chemical approach, that is, by mixing glass powder with foaming agents, and heating the mixture to a temperature above the softening point (106.6 Pa s) of the glass. The foaming agents release gas, enabling expansion of the sintered glass. Here, we use a physical foaming approach to prepare foam glass. First, closed pores filled with inert gases (He, Ar, or N2) are physically introduced into a glass body by sintering cathode ray tube (CRT) panel glass powder at high gas pressure (5‐25 MPa) at 640°C and, then cooled to room temperature. The sintered bodies are subjected to a second heat treatment above the glass transition temperature at atmospheric pressure. This heat treatment causes expansion of the pores due to high internal gas pressure. We found that the foaming ability strongly depends on the gas pressure applied during sintering, and on the kinetic diameters of the gases. The pressure for attaining maximum expansion, that is, lowest density and highest porosity, is found to be around 20 MPa. [ABSTRACT FROM AUTHOR]

The process of foaming glass is very dependent on the chemical composition of the glass. In this study we used a foaming-agent/oxidizing-agent couple and a crystallization inhibitor to foam cullets of flat, container and CRT-panel glass. Foamed glass with a density of 110–120 kg m –3 , a thermal conductivity of 50–52 mW m –1 K –1 and a homogeneous pore structure was obtained from a mixture of panel glass, 0.33 wt% carbon and 4.45 wt% Fe 2 O 3 . We also showed that it is possible to fabricate foamed glass with the same density or pore structure as mentioned above by adding up to 50 wt% container cullet or 70 wt% flat glass to the mixture. In the foamed samples with a low content of panel glass, crystals form, resulting in an increased open porosity, density and inhomogeneous pore structure. The crystallization can, however, be inhibited by adding calcium phosphate, so enabling the preparation of high-quality foamed glass from flat glass or flat/container-glass mixture. The pore gas is predominantly CO 2 and the pressure inside the pores is 0.36–0.47 bar. The reduced effect of the composition on the foaming process suggests that there is a great potential for stabilizing the production of foamed glass and ensuring the product's quality. [ABSTRACT FROM AUTHOR]

The gas-releasing reaction is the most important process in the preparation of foam glass. In this paper we investigated the gas-releasing reactions by means of thermogravimetry coupled with mass spectrometry. We used carbon (activated charcoal and carbon black) and/or manganese oxides (MnO 2 , Mn 2 O 3 , and Mn 3 O 4 ) as the foaming additives. We show that manganese oxides have different functions in the foaming process. The thermal decomposition of MnO 2 below the sintering temperature has a negative impact on the foaming process as it shifts the foaming to higher temperatures, increases the mass-loss rate, leading to open pores, and burns out the carbon. When foaming in an oxidizing atmosphere, the carbon is burnt out by the oxygen from the atmosphere. Instead, Mn 2 O 3 can be used as the foaming agent in an oxidizing atmosphere. In the oxygen-free atmosphere, Mn 3 O 4 can be used as the oxidizing agent , supporting the oxidation of carbon and the foaming process. The redox equilibrium of manganese (Mn 2+ /Mn 3+ ), influenced by the oxygen partial pressure in the pores and physically dissolved oxygen in the glass, shows the strongest influence on the foaming process. The CO/CO 2 ratio in the evolved gases depends on the carbon source and the temperature. [ABSTRACT FROM AUTHOR]

Optical monitoring techniques can record in situ the size of glass samples during a dynamic heating process. This allowed us to study the sintering and expansion rate of panel glass from cathode ray tube using MnO2 as foaming agent. We show the maximum expansion rate of glass melt foaming ( in situ value) correlates to 50% closed porosity, and we define a universal temperature window for foaming glass melts based on the sintering-expansion curves obtained with a heating microscope. The sample size obtained at the maximum expansion rate can be used to quickly evaluate various foaming parameters such as type and concentration of foaming agent, glass composition, and particle size to obtain foam glass with high porosity and closed pores. Using this approach, we show that the foaming of bottle glass is preferentially conducted at a SiC concentration of 1-4 wt%. [ABSTRACT FROM AUTHOR]

Cellulose II gels from a product line of the Lyocell fiber process were transformed into spherical nanoparticles by carboxymethylation and subsequent homogenization. Three populations of nanoparticles were synthesized and their particle size analysis by TEM and DLS revealed a dependence of the size on the amount of introduced carboxylate groups. The higher the amount of functionalization, the smaller the particle sizes. The three synthesized nanocolloidal populations feature a mean size of 73 nm, 107 nm and 129 nm and degree of substitution of 0.15, 0.09 and 0.04, respectively. After drying, the particles can easily be redispersed in water which distinguishes them from most alternative cellulosic nanomaterials. [ABSTRACT FROM AUTHOR]

The dependence of the permittivity on the uniaxial compressive stress was investigated for the case of Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3ceramics. For the morphotropic sample the results showed a strong increase in the stress dependence compared to pure Na0.5Bi0.5TiO3. Nevertheless, a threshold stress was observed, below which the domain switching was hindered. The threshold stress value and, thus, the “hardness” of the materials increased with increasing K0.5Bi0.5TiO3content. In the “hard” tetragonal samples the permittivity increased with the stress loading; however, if the mechanical load exceeded a threshold level, the “hardening” effect vanished. The results are discussed in terms of the defect dipole model for the stabilization of the domain configuration. The stabilization was the highest in pure K0.5Bi0.5TiO3, for which a poled remanent state was preserved at stresses higher than 200 MPa. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the kinetics and dynamics of the reaction between Na2CO3 and the cathode ray tube panel glass powder at 923–1173K. The reaction causes foaming of the glass melt. After the reaction, the T g decreases with increasing Na2CO3 content and reaches a minimum value of T g. However, this T g value is even lower than that of the homogeneous bulk glass with the same chemical composition. The lower T g of the foam glass could be attributed to inhomogeneous incorporation of Na in the glass, leading to Na-rich domains that cause an overall decrease of T g. Remarkably, after 5min treatment at 1073K, the T g drops by 120K, indicating that the reaction between Na2CO3 and glass is very fast. Increasing treatment duration causes a slight increase of T g likely due to both a more homogeneous Na distribution and the compositional change of the glass as a result of Na2SrSi2O6 crystal formation. [Copyright &y& Elsevier]

The recycling of glass from obsolete cathode ray tubes (CRT) has hitherto only occurred to a very limited extent, but the production of foam glass used as an insulation material component has recently been proposed as a promising recycling method. CRT panel glass has high recycling potential due to its non-hazardous composition. Here we report on the foaming of CRT panel glass using Na2CO3 as the foaming agent. We explore how heat treatment temperature and concentration of Na2CO3 affect the density and porosity of the foam glasses, and whether Na2O is incorporated in the glass network. The optimum foaming temperature for minimising density and maximising closed porosity is found to be between 1023 and 1123 K. The pore structure depends on the amount of added Na2CO3, viz, the pores generally become more open with increasing Na2CO3 content. A minimum density of 0 ⋅ 28 g/cm³ is found when 14 wt% Na2CO3 is added and the heat treatment temperature is 1023 K. Interestingly, the glass transition temperature (Tg) of the final foam glass decreases linearly with increasing [Na2CO3], indicating that the Na2O is incorporated into the glass network. [ABSTRACT FROM AUTHOR]

Abstract: The dependence of the dielectric permittivity on the uniaxial compressive stress was investigated for the case of Na0.5Bi0.5TiO3–KTaO3 ceramics. Special attention was focused on the reversibility of the permittivity–stress dependence. The results were connected with the transition from the ferroelectric to the relaxor state in the concentration region between 5 and 10mol% of KTaO3. With this transition, the permittivity–stress dependence changes from non-linear, irreversible and time dependent to linear, instantaneous and reversible. In samples with 10–30mol% of KTaO3 some minor relaxations were observed, which were suppressed under a small pre-stress. The stress sensitivity was higher at a lower measuring frequency and the reversible change of the permittivity was the highest in the sample with 20mol% of KTaO3 (the absolute and relative changes of permittivity were 196.5 and 10.3%, respectively, at a pressure change between 8 and 219MPa). The obtained results are discussed in terms of the macrodomains/microdomains’ reorientation under applied pressure and the transition from one to another with a change of the KTaO3 concentration. The use of Na0.5Bi0.5TiO3–KTaO3 ceramics for device applications is described. [Copyright &y& Elsevier]

Abstract: A novel (1− x)Bi0.5Na0.5TiO3–xKTaO3 system was characterized using X-ray powder diffraction, scanning electron microscopy, as well as dielectric and ferroelectric measurements. The results showed the formation of solid solutions across the whole concentration range; however, using a solid-state reaction method it was not possible to obtain single-phase ceramics. The secondary phases formed in the system were alkali-hexatitanate and -tetratantalate. The formation of the solid solutions initially starts with the formation of the Bi0.5Na0.5TiO3- and KTaO3-rich phases, which then react towards the nominal composition at higher temperatures. We observed that the structural and dielectric properties are strongly influenced by the heat-treatment conditions. Typical relaxor properties with a frequency dispersion of the dielectric maximum were obtained only after annealing at a higher temperature, which considerably improved the homogeneity of the perovskite phase. In accordance with the decreasing temperature of the permittivity maximum, ferroelectric measurements showed a changing of the properties from ferroelectric through relaxor to paraelectric with an increasing content of KTaO3. [Copyright &y& Elsevier]

We have investigated the voltage-tunable characteristics of the Na0.5Bi0.5TiO3-NaTaO3 homogeneity region, for which samples were prepared using a conventional solid-state reaction. The highest value of the relative tunability (nr) was obtained for the sample with 5 mol% of NaTaO3, i.e., 47% at 1 MHz and a 70 kV/cm dc bias field. This sample also showed the highest value of the dielectric losses (tan ö) and temperature coefficient of the dielectric constant (Tε), i.e., 0.05 and 4478 ppm/K, respectively. As the concentration of NaTaO3 increased up to 90 mol% nr, tanδ, and Tε gradually decreased toward 22%, 0.0002 and -899 ppm/K, respectively. The dielectric constant of the samples varied in a similar manner between 662 and 130. At microwave frequencies, the dielectric losses of the samples substantially increased due to their relaxor-type nature. The lowest value was obtained for the samples with 90 mol% of NaTaO3, i.e., 0.002. The tunable characteristics of the samples are related to the ferroelectric and dielectric properties, and it appears that the dielectric tunability of the Na0.5Bi0.5TiO3-NaTaO3 system originates from its relaxor-type behavior. [ABSTRACT FROM AUTHOR]

X-ray diffraction analyses and scanning electron microscopy revealed that Na0.5Bi0.5TiO3 (NBT) and NaTaO3 (NTa) form solid solutions across the whole concentration range. With increasing NTa content the symmetry of the solid solutions gradually changed from rhombohedral, on the NBT-rich side, to orthorhombic, on the NTa-rich side. No morphotropic phase boundary was found between these phases. With increasing NTa content, the perovskite lattice parameter ( ap) and the sintering temperature increase, whereas the grain size decreases. In the case of pure NTa, ceramics with a secondary phase were obtained, identified as Na2Ta8O21, which was formed during the sintering process. A study of the dielectric properties showed that with an increasing concentration of NTa, there was a reduction and broadening of the permittivity maximum, a reduction of the temperatures of the dielectric anomalies, and a reduction of the dielectric losses. [ABSTRACT FROM AUTHOR]

The dependence of the dielectric properties on the uniaxial compressive stress and the stress-strain properties was investigated for the case of (1-x)Na0.5Bi0.5TiO3-xNaTaO3 ceramics. Special attention was focused on the time component and the reversibility of the permittivity-stress dependence. The results were interpreted according to the samples' polar and symmetry states and the ferroelasticity. The time dependence and irreversible changes of the dielectric properties were connected with the domain structure of the materials, which is modified under the applied stress. The irreversible changes observed in the macroscopically nonferroelectric compositions were related to the ferroelastic properties. The stress sensitivity increased with the addition of NaTaO3 from 3% in pure Na0.5Bi0.5TiO3 to 14% in the sample with 15 mol% of NaTaO3 (at 200 MPa and 1 MHz). The reversibility was improved by mechanical modification of the samples' domain state, while the dielectric response remained time dependent. [ABSTRACT FROM AUTHOR]

For thermal insulation to be sustainable, its performance and production efficiency must be considered. Foamed glass prepared from the mixture of waste cathode ray tube panel glass (CRT), Mn 3 O 4 and carbon could become such a material assuming that its production efficiency could be improved. In light of this, the aim of the study was to engineer the transfer of the foaming process from inert to air atmosphere without drastically disturbing the primary mechanism of expansion. Foaming of carbon-containing mixtures in air atmosphere is normally a challenge due to premature oxidation of carbon by the oxygen from the air. Here, we systematically investigate how the addition of water glass (WG) affects the process by thermogravimetry coupled with mass spectrometry (TG/MS) and heating-stage microscopy analysis. Further, we propose an explanation about how WG protects the carbon and show that the addition of WG allows for the process to be successfully performed in air atmosphere. Two direct sources of expansion were identified (carbon-Mn 3 O 4 reaction and WG) and quantitatively evaluated, allowing determination of an optimal addition of WG, 12 wt %, for the foaming temperature of 800 °C. The obtained foamed glass samples have a relatively low density and degree of open porosity, which reflects in their low thermal conductivity (λ). The lowest λ obtained was 39 mW m−1 K−1 at a density of 145 kg m−3, which is comparable to the samples prepared in inert atmosphere and best commercial products. Image 1 • Water vapours displace the air and form less oxidative atmosphere within the sample. • Main expansion source identified from different combinations of additives. • Water glass content with minimum effect on primary foaming mechanism determined. • Obtained product with similar properties as in a controlled atmosphere. • Effective use of the process in the air atmosphere provides environmental benefits. [ABSTRACT FROM AUTHOR]

• Glass foams are made from CRT panel cullet, Mn 3 O 4 , carbon and alkali phosphates. • Pore structures are analyzed by X-ray tomography. • High porosity glass foams are obtained with varying average pore size. • The impact of pore size on the thermal conductivity is discovered. The thermal conductivity (λ) of glass foams is thought to depend on pore size. We report on the impact of pore size, determined using X-ray microtomography, and percentage porosity on the λ of glass foams. Glass foams were prepared by heating powder mixtures of obsolete cathode ray tube (CRT) panel glass, Mn 3 O 4 and carbon as foaming agents, and K 3 PO 4 as additive, to a suitable temperature above T g , and subsequent cooling. Here, we report for the first time a correlation between λ and pore size in the range 0.10–0.16 mm showing a decrease from 57 to 49 mW m−1 K−1 with increasing the pore size for glass foams with porosities of 87–90%. This indicates that the pore structure should be optimized in order to improve the insulating performance of glass foams. [ABSTRACT FROM AUTHOR]

• Low thermal conductivity foams prepared from recycled panel glass have been produced. • The mechanisms of heat transfer through glass foams of varying density and microstructure are evaluated. • A new model accounting for the scattering of radiation in foams with bimodal cellular structures is proposed. • The contribution of each heat transfer mechanism and the thermal conductivity of glass foams at different temperatures are predicted by the model. • The model is validated using experimental measurements and the deviation is below 2%. Glass foams are highly sustainable materials with enormous potential to replace traditional thermal insulators. Current research on glass foams is focused on improving thermal insulation by reducing density, but this is somehow a limited approach. Selecting the best approach to reduce thermal conductivity relies on establishing a detailed knowledge on the heat transfer mechanisms playing the most significant role. We have studied the mechanisms of heat transfer in a set of cathode-ray-tube (CRT) panel glass foams. The influence of relative density, cellular structure, gas composition, glass distribution between cell walls and struts, and radiation on heat transfer is addressed. From a detailed characterisation and state-of-the-art models, we have created a new analytical model adapted to the peculiarities of the foams under analysis. Additionally, the thermal conductivity for varying temperature conditions has been predicted. The obtained results point out to a significant contribution of the heat transfer by radiation for foams with porosities higher than 0.96. The predicted values of thermal conductivity indicate the existence of a plateau region at high porosities. Temperature is proven to shift the contributions of heat transfer, increasing the weight of radiation and gas conduction. The predictions of the new analytical model have been contrasted with experimental measurements of the thermal conductivity at different densities and temperatures obtaining differences below 2%. [ABSTRACT FROM AUTHOR]