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Iskalni niz: "ključne besede" (microwave irradiation) .

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1.
Dehydration with microwave irradiation
Anže Tesovnik, Barbara Horvat, 2024, zaključena znanstvena zbirka raziskovalnih podatkov

Povzetek: The dataset supports the results shown in the tables and figures in the article entitled “Rapid immobilisation of chemical reactions in alkali-activated materials using solely microwave irradiation” (doi: https://doi.org/10.3390/min14121219). It contains measurements of mechanical and structural evaluation, as well as chemical and mineralogical analysis.
Ključne besede: measurments, alkali-activated materials, geopolymers, slag, fly ash, rock wool, glass wool, metakaolin, microwave irradiation, dehydration, stopping of chemical reactions, efflorescence
Objavljeno v DiRROS: 12.08.2024; Ogledov: 84; Prenosov: 11395
.xlsx Raziskovalni podatki (4,87 MB)

2.
Green transition in slovenian building and civil engineering industry : 10 years of research on alkali-activated materials and alkali-activated foams
Barbara Horvat, Branka Mušič, 2024, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje)

Povzetek: The building and civil engineering industry yearly causes more than 40% of man-made CO2 and consumes raw materials for two-thirds of Mont Everest. To decrease the carbon footprint and consumption of raw materials, alkali-activated materials (AAMs) are researched as an alternative to conventional building and civil engineering products like cements, mortar, and ceramics. Ideally, locally available waste materials are used as ingredients: (i) as precursors that react with alkali and form an aluminosilicate network, and (ii) as fillers that get permanently encapsulated and safely stored in AAMs. The addition of gas bubbles and lightweight fillers transforms AAMs into alkali-activated foams and alkali-activated lightweight materials that have the potential to be used as thermal and acoustic insulation materials. Although AAMs are researched worldwide, this review focuses on the state-of-the-art localised solely to Slovenia, particularly on the materials and curing procedures used, as well as on the scientific contribution of the basic research. Besides, the year 2024 marks 10 years of research on alkali activation of raw and waste inorganic materials in Slovenia.
Ključne besede: secondary raw material, alkali-activated material, alkali-activated foams, alkali, circular economy, microwave irradiation, mechanical strength
Objavljeno v DiRROS: 12.03.2024; Ogledov: 554; Prenosov: 447
.pdf Celotno besedilo (84,58 MB)
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3.
Influence of ammonium polyphosphates and 2,4,6-triamino-1,3,5-triazine on the mechanical-physical properties of polyurethane and alkali-activated materials
Branka Mušič, Barbara Horvat, 2024, objavljeni znanstveni prispevek na konferenci

Povzetek: In building constructions, the tendency towards an ever-better material directs us to composite materials. In this work, we prepared an organic-organic and organic-inorganic composite material by incorporating fire retardants, ammonium polyphosphates, and 2,4,6-triamino-1,3,5-triazine, into a polyurethane network and an aluminosilicate network (ASN) of alkali-activated material. Polyurethane foams (PUR) are well-known materials that, due to their properties, such as low weight-to-strength ratio, low electrical and thermal conductivity, flexibility, and relatively simple preparation process, are used in various industries, also in the construction industry, e.g., for thermal insulation of windows and doors or fixing and sealing joinery. Opposite, the ASN of alkali-activated metakaolin, successfully paves the way for new applications, such as high-temperature protection. In this paper, these interactive properties of prepared composites are studied using thermal testing and mechanical analysis. It was found that inhibitors significantly increase the fire resistance of PUR systems while they slightly reduce the mechanical properties. Incorporating polymer flame retardant into ASN in building products, such as façade panels , can decrease the mechanical properties but can offer the non-flammable building envelope not get heated from burning surroundings, i.e., not becoming a convection heat source, but rather represent a fire-distinguisher for flammable materials.
Ključne besede: flame retardants, polyurethane, alkali activated material, metakaolin, microwave irradiation, mechanical strength
Objavljeno v DiRROS: 12.03.2024; Ogledov: 629; Prenosov: 466
.pdf Celotno besedilo (2,52 MB)
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4.
Waste rubber incorporated in the alkali-activated metakaolin’s aluminosilicate network enhanced by microwave irradiation
Barbara Horvat, Branka Mušič, 2024, objavljeni znanstveni prispevek na konferenci

Povzetek: Building materials represent the possibility of prolonging the life of waste materials. The key is to ensure that the products are suitable for their function. So we activated metakaolin with the alkaline Na-silicate solution in the ratio that ensures the prevention of efflorescence and high mechanical strength (Horvat and Ducman, 2019). As the waste material (to be incorporated in the aluminosilicate network (ASN) of the alkali-activated metakaolin) ground waste rubber from electric cables was used in the preselected mass ratios. Its inclusion in products, like paving stones, can reduce stiffness, improve durability, dampen vibrations, and reduce road noise. The mechanical strengths of test samples with rubber present on the active surface or slightly below were higher compared to samples where rubber was encapsulated throughout the volume. Compressive strength was higher when samples were irradiated with low powers of microwaves while irradiation with higher powers led to the foaming of alkali-activated slurry. The encapsulation quality of the ground rubber was evaluated by SEM while the chemical influence on ASN was determined by EDS, FTIR, and XRD. Slipperiness change on the active surface of pavement stones proved that the addition of the ground rubber enhanced the walking safety of the product.
Ključne besede: secondary raw material, alkali activated material, waste rubber, metakaolin, encapsulation of organic in inorganic material, microwave irradiation, mechanical strength
Objavljeno v DiRROS: 12.03.2024; Ogledov: 888; Prenosov: 550
.pdf Celotno besedilo (13,99 MB)
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5.
Thermal insulation and flammability of composite waste polyurethane foam encapsulated in geopolymer for sustainable building envelope
Barbara Horvat, Nataša Knez, Uroš Hribar, Jakob Koenig, Branka Mušič, 2024, izvirni znanstveni članek

Povzetek: Polyurethane foam (PUR) is a lightweight, thermally insulating, widely used, and highly flammable material that has after its use an adverse effect on the environment, i.e., PUR disposal is considered hazardous. Its flammability can be mitigated using various fire retardants, but they do not change the hazardous nature of waste PUR. Therefore, in the current study, waste PUR with and without flame retardants based on N and P was incorporated into a geopolymer, the alkali-activated material (AAM) based solely on metakaolin, to evaluate the potential recycling route of waste PUR while taking into account its flammability, so it can enter safely into the circular economy through the building industry. To enhance the mechanical properties of the composite, a fresh mixture was irradiated with microwaves. However, the irradiation of geopolymer containing PUR negatively influenced mechanical performance, which led to the evaluation of the behaviour of the complex dielectric constant of PUR and fire retardants. Materials and composites were evaluated regarding their chemistry, mineralogy, microstructure, and porosity to connect the structure with extrinsic properties like geometrical density, thermal conductivity, and fire properties. Nonetheless, positive influences of PUR being encapsulated in the geopolymer were lowered density (from 1.8 to 1.6 kg/l) and improved thermal insulation ability (from 940 to 860 mW/(m·K)) of the composites: with the inclusion of <5 % of PUR, thermal insulation improved by nearly 10 %. However, the contribution of PUR to the composite originated from its skeleton, which has more than 15 times bigger geometrical density (0.81 kg/l) compared to the density of the skeleton (0.047 kg/l). This offers an open field for further advancements of thermal properties, but would also lead to a decrease of the compressive strength, which was already lowered from 90 MPa for 30 % with <5 % of added grated PUR. Furthermore, the flammable nature of PUR and its other drawbacks can be controlled by permanent embedding in the noncombustible structure of geopolymer, making the envelope of sustainable buildings green and safer. Overall, including grated waste PUR in geopolymer represents a promising, easy, cost-effective recycling path with low energy consumption, where the composite cannot develop fire on a scale of pure PUR, even in the worst-case scenario, but only if the composite is designed in a way, that flammable materials cannot join flames during their combustion. This paper gives prospects to other flammable waste materials to be safely used in the circular economy, and to porous materials to shape properties of the composite by their intrinsic and/or extrinsic properties.
Ključne besede: waste polyurethane foam, polymeric flame retardants, alkali activated material, metakaolin, microwave irradiation, thermal-fire behaviour, mechanical strength
Objavljeno v DiRROS: 01.03.2024; Ogledov: 947; Prenosov: 890
.pdf Celotno besedilo (29,74 MB)
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6.
PUR in geopolymer
Barbara Horvat, Nataša Knez, Uroš Hribar, Jakob Koenig, Branka Mušič, 2024, zaključena znanstvena zbirka raziskovalnih podatkov

Povzetek: The dataset supports the results shown in the tables and figures in the article entitled “Thermal insulation and flammability of composite waste polyurethane foam encapsulated in geopolymer for sustainable building envelope” (doi: 10.1016/j.jclepro.2024.141387). It contains measurements of fire-behaviour characteristics, thermal conductivity, the behaviour of the material in the electromagnetic field in relation to the frequency, mechanical and structural evaluation, as well as chemical and mineralogical analysis.
Ključne besede: measurements, waste polyurethane foam, polymeric flame retardants, alkali activated material, metakaolin, microwave irradiation, thermal-fire behaviour, mechanical strength
Objavljeno v DiRROS: 20.02.2024; Ogledov: 806; Prenosov: 302
.xlsx Raziskovalni podatki (2,51 MB)
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7.
Microwave irradiation of alkali - activated metakaolin slurry
Barbara Horvat, Branka Mušič, Majda Pavlin, Vilma Ducman, 2023, objavljeni znanstveni prispevek na konferenci

Povzetek: The building and civil engineering industry generates more than 40% of man-caused carbon emissions, consumes a lot of energy just to produce building materials, generates a large amount of waste through construction and demolition, and consumes a large amount of natural resources. One of the possible solutions is to use alkali-activated materials, which can use waste instead of raw materials and are produced at lower temperatures, with less energy consumption and in less time than traditional building products. All of this lowers the carbon footprint, which could be further reduced by the timely-short implementation of microwave irradiation in the early stages of alkali-activation synthesis. Therefore, metakaolin activated with Na-water glass in a theoretically optimal ratio was irradiated with microwaves of 2.45 GHz at powers of 100 W and 1000 W for 1 min, and compared to non-irradiated reference cured only at room conditions. Samples prepared at higher power, i.e., 1000 W, solidified completely and foamed. TG-DTA was performed on all samples in the early stages of curing, mechanical strengths were measured on 3 and 28-day- old samples, and leaching tests on aged samples.
Ključne besede: metakaolin, alkali activated material, alkali activated foams, microwave irradiation
Objavljeno v DiRROS: 28.11.2023; Ogledov: 731; Prenosov: 307
.pdf Celotno besedilo (791,17 KB)
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8.
Influence of microwaves in the early stage of alkali activation on the mechanical strength of alkali-activated materials
Barbara Horvat, Majda Pavlin, Vilma Ducman, 2023, izvirni znanstveni članek

Povzetek: This study focuses on the influence of microwave irradiation dosimetry on alkali-activated slurry in its early stages. The impact on the chemistry and mineralogy along with the mechanical properties were evaluated by changing the power of microwaves and their duration of exposure. This influenced the dissolution of amorphous content, diffusion, and self-assembly into an aluminosilicate network. The precursors used in this study were metakaolin, a non-waste material commonly used in geopolymerisation technology, and local fly ash and ladle furnace slag as secondary materials. Furthermore, they were chemically and mineralogically analysed, and their mixtures with NaOH and Na-water glass provided the optimal ratio of the amount of elements obtained using the pre-calculation approach. However, the potential extra addition of water was experimentally determined to allow complete wetting of the material and solid workability during moulding. Using Fourier-transform infrared spectroscopy, the influence of water was further investigated in alkali-activated slag and fly ash irradiated with microwaves, which resulted in the highest values of mechanical strength in the dosimetry-mapping part of the analysis. In addition to the time dependence of the expected mechanical strength on the ageing of the alkali- activated material, the synthesised material exhibited a significant dependence on the dose of microwave irra- diation, which was different for every precursor as well as every mixture with different chemistries.
Ključne besede: odpadni material, alkalijska aktivacija, obsevanje z mikrovalovi, mehanska trdnost, waste material, alkali activation, microwave irradiation, mechanical strength
Objavljeno v DiRROS: 12.07.2023; Ogledov: 743; Prenosov: 574
.pdf Celotno besedilo (8,99 MB)
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