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Iskalni niz: "ključne besede" (mehanska po��kodba) .

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1.
Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAM
Katja Traven, Mark Češnovar, Vilma Ducman, 2019, izvirni znanstveni članek

Povzetek: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Ključne besede: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Objavljeno v DiRROS: 22.11.2023; Ogledov: 203; Prenosov: 112
.pdf Celotno besedilo (2,26 MB)
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2.
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: 330; Prenosov: 245
.pdf Celotno besedilo (8,99 MB)
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3.
The preparation and characterization of low-temperature foams based on the alkali activation of waste stone wool
Majda Pavlin, Barbara Horvat, Mark Češnovar, Vilma Ducman, 2022, izvirni znanstveni članek

Povzetek: Waste mineral wool represents a huge amount of construction and demolition waste that is still not adequately returned into the value chain but needs to be landfilled. In the present study, waste stone wool (SW) was evaluated for the preparation of alkali-activated foams. For this purpose SW was milled and sieved below 63 μm, then the activator (sodium silicate) and different amounts of foaming agent (hydrogen peroxide, H2O2), varying between 1 wt% and 3 wt%, were added to the slurry and cured in moulds at an elevated temperature (70 ◦ C) for three days. In this way, foamed, highly porous materials were obtained whose density and mechanical properties were influenced by the amount of foaming agent used. The densities obtained ranged between 1.4 and 0.5 g/cm3, with corresponding mechanical properties of between 12.6 and 1.5 MPa and total porosities in the range 37.8–78.6%, respectively. In the most porous samples with the total porosity of 78.6%, a thermal conductivity of 0.092 W/(m∙K) was confirmed. The study confirmed the suitability of waste mineral wool (in our case SW) as a precursor for alkali-activated foams with potential use in the construction sector or other industrial applications.
Ključne besede: alkali activation, waste mineral wool, mechanical strength, open access, alkalijska aktivacija, odpadna volna, SEM, XRF, XRD, mehanska trdnost, odprti dostop
Objavljeno v DiRROS: 19.06.2023; Ogledov: 237; Prenosov: 181
.pdf Celotno besedilo (9,47 MB)
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Uporaba magnetno resonančnega slikanja za raziskave anatomije in vlažnosti lesa
Maks Merela, Igor Serša, Urška Mikac, Primož Oven, 2006, izvirni znanstveni članek

Povzetek: Preverjena je bila uporaba jedrske magnetne resonance (Nmr) za raziskave anatomije in vlažnosti lesa. Na tri metre visoki živi bukvi (Fagus sylvatica L.) smo uporabili 3d spin-echo mr-mikroskopsko tehniko slikanja s prostorsko resolucijo 100 mm in opazovali strukturo odrezane vejice ter spremljali dinamični odziv drevesa na mehansko poškodbo. Za potrditev struktur, vidnih na slikah, smo uporabili svetlobno mikroskopijo. Svetlobna mikroskopija je razkrila anatomsko zgradbo in triletno starost vejice bukve. Slike so jasno razkrile stržen, radialno orientirane večredne ksilemske trakove, traheje ranega lesa, vključno z mejo med ranim in kasnim lesom, kot tudi kambijevo cono s tekočim ksilemskim in floemskim prirastkom. Preučevali smo koncentracijo vode v vejici in globino dehidracije, ki je nastala v 22-tih urah po poškodbi in je segala v globino približno 5 mm od poškodbe. Hitra izguba vlažnosti odseva začetni pasivni odziv prizadetega tkiva. S pomočjo 3d mikroskopije in računalniškega programa Imagej nam je uspelo izdelati prostorski model vode v lesu, ki prikazuje tkiva v vejici z značilno višjo vlažnostjo.
Ključne besede: MR-mikroskopija, bukev, Fagus sylvatica, živi les, anatomija lesa, vlažnost, porazdelitev vode, mehanska poškodba
Objavljeno v DiRROS: 17.11.2020; Ogledov: 1307; Prenosov: 374
.pdf Celotno besedilo (1,77 MB)

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Kakovost pelet na slovenskem trgu 2015
Peter Prislan, Nike Krajnc, Mitja Piškur, 2015, elaborat, predštudija, študija

Ključne besede: kakovost pelet, mehanska obstojnost, vsebnost vode, delež pepela, lastnosti pelet
Objavljeno v DiRROS: 12.07.2017; Ogledov: 2530; Prenosov: 719
.pdf Celotno besedilo (10,55 MB)
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10.
Odziv drevesnih tkiv na poškodbe in infekcijo 2. kambijeva cona
Primož Oven, 1999, pregledni znanstveni članek

Povzetek: Odziv kambijeve cone na poškodovanja in infekcijo je kompleksen prostorski in časovni proces nastajanja zaščitnih tkiv in regeneracije sistema sekundarnih vaskularnih tkiv. Odziv na robu rane vključuje razvoj kalusa, nastanek primarne zaščitne ligno-suberinske plasti in novega periderma na površini kalusa ter novega vaskularnega kambija v osrednjem delu kalusa. Z aktivnostjo novega vaskularnega kambija se prične proces preraščanja rane. Barierna cona (CODIT) je specializirano zaščitno tkivo, ki nastaja distalno od roba rane kot odziv kambijeve cone, ki je `e obstajala v trenutku poškodovanja. Obravnavamo dejavnike, ki vplivajo na variabilnost odziva.
Ključne besede: les, mehanska poškodba, kambijeva cona, ranitev, odziv, kalus, ligno-suberinska plast, nekrofilaktični periderm, barierna cona, poranitveni les, preraščanje rane
Objavljeno v DiRROS: 12.07.2017; Ogledov: 4487; Prenosov: 1863
.pdf Celotno besedilo (1,31 MB)

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