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Temperature pre-treatment of gypsum for powder based 3D printing technology
Vesna Zalar Serjun, Lidija Korat, 2021, objavljeni znanstveni prispevek na konferenci

Povzetek: In recent years many researchers have been involved in studies in the field of pre-treatment of various raw materials. Temperature treatment of materials results in several advantages, which have been already recognised and successfully applied in various fields of applications. Where at the same time, the practices has been adopted also in the field of 3D printing. Enhanced strength and stiffness, assuring desirable performance criteria of the 3D printed models, reflect the most important characteristics. 3D printing binder jetting technology is based on the application of liquid binders onto powdered material, where gypsum powders have been commercially used as a base raw material. As natural raw materials can be replaced by other materials, such as recycled industrial by products, the aim of this research work was to evaluate the potential usage of three synthetic gypsum powders from different industrial processes for 3D printing. The investigation covered (a) mineralogical and microstructural characteristics of gypsums from different origin and (b) the effect of pre-treatment of gypsum powders at different temperatures (up to 500 °C). On the basis of the results, the most promising temperature regime for each different waste gypsum powder treatment, reflecting in the most optimal setting time, was defined. Synthetic gypsums were characterized by X-ray diffraction (QXRD), scanning electron microscopy (SEM) and differential thermal analysis (TG/DTA). The results showed that all three synthetic gypsums (calcium sulfate dihydrate, CaSO 4∙2H2O) thermally degrade into calcium sulfate anhydrite (CaSO 4) via an intermediate calcium sulfate hemihydrate (CaSO 4∙ ½H2 O, bassanite) phase. Microstructural and mineralogical differences were observed when temperature treated gypsums from different origins were compared. The detailed knowledge of gypsum powder properties at different temperature regime is important parameter for the assurance of 3D printing key parameters such as flowability, roughness and wettability, especially for determination of saturation levels and setting time. After all, these parameters define final mechanical properties of 3D printed structures. By using such approach, the understanding of material compatibility for 3D printing technology can be defined and improved if necessary.
Ključne besede: 3D print, additive manufacturing, gypsum, temperature
Objavljeno v DiRROS: 25.01.2024; Ogledov: 156; Prenosov: 102
.pdf Celotno besedilo (9,29 MB)
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16.
Mud from the Sitarjevec mine as a pigment for textile printing
Darja Rant, Mateja Štefančič, Vesna Zalar Serjun, Mateja Golež, 2021, objavljeni znanstveni prispevek na konferenci

Povzetek: The Sitarjevec mine, located near the town of Litija (Central Slovenia), is recognized by the strong yellow colour of its dripstone structures and mine mud deposits. The mine mud, composed predominantly of goethite, accumulates on the ground of the mine shafts as the result of the interaction between percolating underground water, iron ore minerals and microorganisms. Since the accumulation of limonite mine mud is an ongoing process, larger quantities of mud have been deposited in the mine shafts since its closure. These deposits present a real threat of unleashing a mine mud spill on the town of Litija. Such a scenario has already previously occurred. In order to find new potential routes for recycling larger quantities of this mine mud, the present research work was performed to assess the use of mine mud as a pigment in the dye industry. In the first stage, the chemical (XRF) and microstructural (SEM) characteristics of the mine mud were defined together with the identification of its phase composition (XRD), particle size distribution and specific surface area (BET). Furthermore, the pigment was used to colour textile printing paste on a laboratory scale. To define the most appropriate quality of textile prints the rheological response of the various textile printing paste samples was investigated in terms of their plastic viscosity, indicating their suitability for use in textile printing. Test prints wereconducted, and the properties of leaching and fastness in the prints were assessed.
Ključne besede: mine mud, recycling, pigment, printing paste, textile, rheology
Objavljeno v DiRROS: 25.01.2024; Ogledov: 149; Prenosov: 94
.pdf Celotno besedilo (9,29 MB)
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17.
Hydrogeological characterization of karst springs of the white (Proteus anguinus anguinus) and black olm (Proteus anguinus parkelj) habitat in Bela krajina (SE Slovenia)
Katja Koren, Rok Brajkovič, 2023, izvirni znanstveni članek

Povzetek: The springs west of Črnomelj, in SE Slovenia, are the habitat of the black (Proteus anguinus parkelj) and the white olm (Proteus anguinus anguinus). Some of these springs are also the only known habitat in the world of endemic species of black olm. A steady decline in olm populations has been observed in this area over the past decades. Owing to the rapid runoff and groundwater flow high-resolution monitoring is essential in providing better insight into the hydrogeological characterization of the catchment area of springs. Specific factors and critical parameters of water behind said olm degradation have not yet been defined. Because the olm’s environment is largely aquatic, one potential critical parameter could be the higher water temperatures (>12 °C) or higher nitrate concentration (>9.2mg/l). The six-month observation of the springs (July – December 2021) point to water temperature as a potential critical parameter since the water temperature of the springs exceeded 12 °C in months July and August. Nitrate concentrations could also be a second critical parameter in the degradation of the olm’s habitat. Maximum nitrate concentrations above 9.2mg/l throughout much of the observation period (except for Dobličica spring). Due to less agricultural activity in December in the spring catchment area and a higher dilution rate due to reduced evapotranspiration and increased effective precipitation during this time of the year, the nitrate concentrations are decreased. The results of the measured parameters of groundwater could show the hydrogeological connection between the Otovski and Pački breg springs and between Šotor, Jamnice and Dobličica. The Obršec spring has an independent catchment area. A detailed estimation of the springs catchment area is possible due to a detailed geologic map. It is necessary to determine the origin of the nitrate (nitrate isotope analysis), to quantify the threshold values of the critical parameters, to define precisely all the causes of the olm deterioration, and to make proposals for appropriate measures to limit or even stop the decline of the olm population.
Ključne besede: hydrogeology, olm, ecology, nitrate, monitoring
Objavljeno v DiRROS: 16.01.2024; Ogledov: 143; Prenosov: 48
.pdf Celotno besedilo (13,65 MB)

18.
Povezanost med rakom in onesnaževali, ki nastanejo v procesih sežiga in sosežiga odpadkov: krovni pregled literature
Teja Oblak, Tanja Carli, Vesna Zadnik, Niko Samec, Andreja Kukec, 2023, pregledni znanstveni članek

Povzetek: Izhodišča: V procesih sežiga in sosežiga odpadkov ter proizvodnje cementa se v okolje sproščajo izpusti, ki vsebujejo različna onesnaževala. Z namenom oceniti povezanost med rakom pri poklicno izpostavljenih in okoliških prebivalcih ter izpostavljenostjo okoljskim onesnaževalom iz sežigalnic, naprav za sosežig in cementarn smo si za cilj zadali izdelavo krovnega pregleda literature. Metode: V krovni pregled literature so bile vključene metaanalize in sistematični pregledi literature v angleščini v obdobju od leta 1980 do leta 2023. Iskanje je bilo izvedeno v štirih podatkovnih zbirkah (PubMed, Scopus, Web of Science, Cochrane Reviews). Kakovost je bila ocenjena z orodjema AMSTAR-2 (metodologija) in GRADE (dokazi). Rezultati: Izmed 7.701 opredeljenih dokumentov jih je bilo v končno analizo vključenih 14 (pet metaanaliz, devet sistematičnih pregledov). Obstajajo nizki do zmerni dokazi o povezanosti med sarkomom mehkih tkiv in ne-Hodgkinovim limfomom z izpostavljenostjo dioksinom v okolici sežigalnic I. generacije, česar študije niso dokazale za sežigalnice naslednjih generacij. Zaenkrat ne razpolagamo z dokazi za sosežig. Pri delavcih v cementarnah I. do II. generacije obstaja nekaj zmernih dokazov o povezanosti med incidenco vseh rakov, pljučnega raka, raka ustne votline in žrela, prostate in želodca z izpostavljenostjo šestvalentnemu kromu. Velika večina dokazov je omejenih zaradi mešanih rezultatov, razlik v tehniki vprašanj, heterogenosti in potencialni pristranosti. Zaključek: Obstajajo omejeni dokazi o povezanosti med rakom in izpostavljenostjo onesnaževalom iz sežigalnic I. in cementarn I. do II. generacije. Za oceno morebitne povezanosti med rakom in onesnaževali iz najsodobnejših naprav za sosežig je smiselno načrtovati ciljane epidemiološke študije in študije notranje izpostavljenosti z uporabo humanega biomonitoringa.
Ključne besede: rak, odpadki, sežig, sosežig, cementarna, onesnaževala
Objavljeno v DiRROS: 08.01.2024; Ogledov: 181; Prenosov: 68
.pdf Celotno besedilo (189,92 KB)
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19.
Epidemiologija raka dojk
Vesna Zadnik, Sonja Tomšič, 2023, objavljeni strokovni prispevek na konferenci

Ključne besede: rak dojk, epidemiologija, register raka
Objavljeno v DiRROS: 05.01.2024; Ogledov: 138; Prenosov: 35
.pdf Celotno besedilo (154,94 KB)

20.
Epidemiologija malignega melanoma
Maja Primic-Žakelj, Tina Žagar, Vesna Zadnik, 2007, objavljeni znanstveni prispevek na konferenci

Objavljeno v DiRROS: 06.12.2023; Ogledov: 146; Prenosov: 43
.pdf Celotno besedilo (1,20 MB)

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