40 research outputs found
Mechanical reinforcement of electrospun poly(vinyl alcohol) by Ī±āFeOOH nanowires
Get PDFThe authors kindly acknowledge the financial support of the Estonian Research Council for the post-doctoral research grants of personal research funding in projects PUT1096 and PUTJD578 as well as Institutional Research Funding Projects, IUT20-17, and IUT23-7.We report the mechanical performance of Ī±āFeOOH nanowire reinforced poly(vinyl alcohol) (PVA) composite nanofiber mat, fabricated using straightforward aqueous processing methods. Goethite (Ī±āFeOOH) nanocrystals have a high elastic modulus and āOH rich surface, ensuring strong interactions with hydrophilic polymers and effective reinforcement. Needleāless electrospinning resulted in alignment of the nanowires along fibre axis, as confirmed by transmittance electron microscopy studies. Produced composite PVA nanofibers containing 10 wt% goethite nanoparticles exhibited an outstanding fivefold increase in Young's modulus and 2.5āfold improvement of tensile strength compared to mats of neat PVA. The addition of Ī±āFeOOH had a significant influence on glass transition temperature indicating formation of interphase regions around nanowire inclusions. Observed properties are explained by nanowire grafting in the precursor solution, extensive interactions between the adsorbed PVA chains and the matrix and percolation of interphase regions at 10 wt% Ī±āFeOOH.Estonian Research Council PUT1096 and PUTJD578; Institutional Research Funding Projects, IUT20-17, and IUT23-7; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Unionās Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART
Identifying iron-bearing nanoparticle precursor for thermal transformation into the highly active hematite photo-fenton catalyst
Get PDFFunding: This reseach was funded by the European Regional Development Fund within the Activity 1.1.1.2 āPost-doctoral Research Aidā of the Specific Aid Objective 1.1.1 āTo increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructureā of the Operational Programme āGrowth and Employmentā (No. 1.1.1.2/VIAA/1/16/157).The hematite photo-Fenton catalysis has attracted increasing attention because it offers strong oxidation of organic pollutants under visible light at neutral pH. In the present work, aqueous synthesis of hematite photo-Fenton catalysts with high activity is demonstrated. We compare photo-Fenton activity for hematite obtained by hydrolyzation at 60ā¦C or by a thermally induced transformation from iron-bearing nanoparticles, such as amorphous iron oxyhydroxide or goethite. A link between their structure and visible light photo-Fenton reactivity is established. The highest activity was observed for hematite obtained from goethite nanowires due to oblong platelet-like structure, high surface area and the presence of nanopores.European Regional Development Fund 1.1.1.2/VIAA/1/16/157; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Unionās Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART
Lignocelulozes nanoŔķiedru divkomponenŔu pavedienu struktūra, tehnoloģijas un īpaŔības
No full textDarba literatÅ«ras apskatÄ apkopota informÄcija par bezatkritumu integrÄtajÄm tehnoloÄ£ijÄm, polimÄru nanokompozÄ«tiem un to pildvielu ietekmei uz materiÄla Ä«paŔībÄm, nanocelulozes iegÅ«Å”anas metodÄm un tÄs integrÄÅ”anu polimÄru nanokompozÄ«tos. PastiprinÄta uzmanÄ«ba pievÄrsta elektrovÄrpÅ”anas procesam, tÄ ietekmÄjoÅ”ajiem faktoriem un ietekmei uz nanoŔķiedru morfoloÄ£iju un Ä«paŔībÄm, kÄ arÄ« apzinÄtas nanoŔķiedru lietojuma jomas.
Darba metodiskajÄ daÄ¼Ä aprakstÄ«ts pÄtÄ«jumu procesÄ lietoto metožu, tehnoloÄ£iju un testÄÅ”anas metožu spektrs: nanocelulozes un polimÄra nanoŔķiedru iegÅ«Å”anas tehnoloÄ£ijas, aprÄ«kojums, tehnoloÄ£isko procesu norise un režīmi, kÄ arÄ« lietotÄs pÄtÄ«Å”anas metodes un nosakÄmie parametri.
Darba eksperimentÄlajÄ daÄ¼Ä aprakstÄ«ta tvaika sprÄdziena auto-hidrolÄ«zes procesa parametru ietekme uz biomasu, celulozes nanopildvielas ietekme uz vÄrpÅ”anas Ŕķīdumu Ä«paŔībÄm, nanoŔķiedru tÄ«mekļa morfoloÄ£iju, fizikÄlajÄm un mehÄniskajÄm. Pamatoti izvÄlÄtie laika režīmi, temperatÅ«ras, Ŕķīdumu koncentrÄcijas diapazons, noteikti optimÄlie darba parametri. PÄtÄ«jumu rezultÄtÄ izveidotajÄ tehnoloÄ£iju kopumÄ iegÅ«ts jauns ar celulozes nanopildvielu pastiprinÄts polimÄra nanoŔķiedru neaustais materiÄls ar vairÄkkÄrtÄ«gi paaugstinÄtu mehÄnisko stiprÄ«bu un noturÄ«bu Å«dens vidÄ.
Promocijas darbs uzrakstÄ«ts latvieÅ”u valodÄ, satur ievadu un 3 galvenÄs nodaļas: literatÅ«ras apskatu, metodisko daļu, eksperimentu rezultÄtu apkopojumus un to izvÄrtÄjumu, kÄ arÄ« secinÄjumus. Darba apjoms satur 85 attÄlus un ilustrÄcijas, 17 tabulas, 26 formulas, kopÄ 144 lappuses. LiteratÅ«ras sarakstÄ izmantots 351 informÄcijas avots
Tekstiliju virsmas modifikÄcija ar materiÄlu izputinÄÅ”anas tehnoloÄ£iju
No full textPÄtÄ«jumÄ apskatÄ«ta informÄcija par tekstiliju virsmas modifikÄciju ar materiÄliem plÄno kÄrtiÅu veidÄ. TÄ ir daudzsoloÅ”a tehnoloÄ£ija tekstiliju funkcionalizÄcijai, kas ļauj izveidot metÄlu, oksÄ«du, polimÄra un kompozÄ«tu pÄrklÄjumus uz tekstila materiÄla virsmas. Procesa rezultÄtÄ tekstilmateriÄlam lÄ«dztekus esoÅ”ajÄm unikÄlajÄm Ä«paŔībÄm tiek pieŔķirtas paredzamajam lietojumam nepiecieÅ”amÄs papildÄ«paŔības. ProduktÄ«vÄkÄ no plÄno kÄrtiÅu iegÅ«Å”anas tehnoloÄ£ijÄm ir materiÄlu izputinÄÅ”ana ar plazmas joniem. TÄs svarÄ«gÄkÄs priekÅ”rocÄ«bas salÄ«dzinÄjumÄ citÄm tekstilmateriÄlu virsmu pÄrklÄjumu iegÅ«Å”anas metodÄm: 1) ir viegli izputinÄmi pat visgrÅ«tÄk kÅ«stoÅ”ie materiÄli; 2) iegÅ«tajÄm pÄrklÄjumu kÄrtiÅÄm ir labÄka adhÄzija ar materiÄlu; 3) kÄrtiÅas biezumu, sastÄvu, struktÅ«ru un vienmÄrÄ«gumu ir viegli kontrolÄt pielÄgojot parametrus uzputinÄÅ”anas procesa laikÄ atbilstoÅ”i materiÄla Ä«paŔībai
Electrospinning of Poly(Vinyl Alcohol) Nanofiber Mats Reinforced by Lignocellulose Nanowhiskers
No full textThis article reports on electrospun poly(vinyl alcohol) (PVA) modification with lignocellulose nanowhiskers (LCNWs) produced from hemp shives without using harsh preparation steps. LCNWs were obtained by using steam explosion (SE) pretreatment, ball milling, and ultrasonication. Formation of LCNWs was confirmed by atomic force microscopy. Obtained LCNWs were used to modify the mechanical properties of electrospun PVA nanofibers. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analyses provided clear evidence of the presence of cellulose nanowhiskers in the PVA/LCNW electrospun mats. It was found that tensile stress at break increases more than fivefold for PVA nanofiber mats reinforced with LCNWs
Multifunctional Materials from Hemp Fibres Treated with Steam Explosion Technology
No full textMultifunctional materials include properties of smart material systems (e.g. smart textiles) as well as biologically synthesized materials (case of biomimetic). Natural wood, flax and hemp fibres are examples of such multifunctional materials ā polymer composite systems. In current research attempt has been made to analyse hemp fibres treated with steam explosion (SE) technology. Disintegration of hemp fibres separated from non-retted, dew-retted and dried stems of hemp (āPuriniā) by alkali treatment and steam explosion (SE) were investigated. An average intensive SE in combination with the hydro-thermal and alkali after-treatment allows decreasing the diameter of hemp fibres and reduce the concentration of non-celluloses components, among them hemicelluloses, lignin, pectin, waxes and water
UV radiÄcijas absorbÄtÄju ietekme uz UV aizsardzÄ«bas efektivitÄti
No full textPÄtÄ«jumÄ apkopota sistematizÄta informÄcija par ultraviaoleto (UV) starojumu un siltumstarojuma iedarbÄ«bu un progresÄ«vÄm metodÄm aizsardzÄ«bas nodroÅ”inÄÅ”anai pret UV un siltumstarojumu gan uzturoties ÄrvidÄ, gan regulÄjot mikroklimatu telpÄs, kÄ arÄ« apzinÄtas iespÄjas izmantot metÄlus un to oksÄ«dus aizsargpÄrklÄjumu veidoÅ”anai, sniegti to raksturojumi, kÄ arÄ« metodikas ZnO iegÅ«Å”anai un auduma apstrÄdei. Eksperimenti veikti uznesot vakuumÄ termoiztvaicÄÅ”anas procesÄ dažÄda biezuma Zn pÄrklÄjumus uz kokvilnas un kokvilnas Ä·emdzijas auduma, kÄ arÄ« linu auduma, kas ir biežÄk lietotie tekstilmateriÄli ekovides veidoÅ”anai. Eksperimenta gaitÄ salÄ«dzinÄtas dažÄdu materiÄlu paraugu ar atŔķirÄ«gu pÄrklÄjuma biezumu starojuma caurlaidÄ«bas, kÄ arÄ« virsmu mikrogrÄfijas, kas ļauj secinÄt, ka vakuuma termoiztvaicÄÅ”anas procesÄ iespÄjams iegÅ«t pat 0,12 Ī¼m vienmÄrÄ«gu gludu Zn pÄrklÄjumu uz kokvilnas auduma, palielinot pÄrklÄjuma biezumu lÄ«dz 0,21 Ī¼m caurejoÅ”Äs starojuma plÅ«sma samazinÄs par 35 %. Uz linu auduma pavedieniem uznestÄ Zn kÄrtiÅas struktÅ«ra ir graudaina, jo lielÄks ir kÄrtiÅas biezums, jo Zn klasteri kļūst rupjÄki, lÄ«dz ar to pÄrklÄjums ekspluatÄcijÄ mazÄk noturÄ«gs. TÄ kÄ aplÅ«kotÄ fizikÄlÄ metode ultraplÄnu metÄlpÄrklÄjumu uzneÅ”anai uz tekstilmateriÄliem atŔķirÄ«bÄ no Ä·Ä«miskajÄm apstrÄdÄm nerada vides piesÄrÅojumus, ir mÄrÄ·tiecÄ«gi turpinÄt pÄtÄ«jumus adhÄzijas uzlaboÅ”anai, kÄ arÄ« meklÄt veidus, kÄ pieŔķirt metÄlpÄrklÄtajai virsmai papildnetÄ«rumus nepiesaistoÅ”as Ä«paŔība
Electrospun Herbal Extract Derived Polymer Nanocomposites for Medical Applications
No full textHerbal plants have been used in medicine since
ancient times due to their health benefits. The research in this
field continues to reveal advantages of these plants such as
antibacterial activity against multidrug-resistant bacteria and
possibility to integrate extracts in fibers by electrospinning.
Electrospinning is a simple, yet versatile method of creating
polymer-based nanofiber web, which can be used for wound
dressings, tissue engineering and drug delivery systems. In
production of electrospun nanofibers a solution of biocompatible
polymer and a plant extract is needed. Therefore exploration of
such composition ingredients is importan
Fabrication of Lead Titanate PbTiO3 Nanofiber Mats Via Electrospinning
No full textWe report an electrospinning approach to producing PbTiO3 polycrystalline nanofibers. The influence of the polymer concentration
in the solution on the obtainable PbTiO3 nanofiber morphology was investigated. Nanofibers were characterized by
high-resolution scanning electron microscopy (HR-SEM) and Raman spectroscopy. After annealing at 500Ā°C for 3 h, the continuous
structure of nanofibers remained intact. Only tetragonal PbTiO3 was identified by Raman spectroscopy. Piezoelectric behavior
of PbTiO3 nanofiber mats was demonstrated by making a nanomat-based voltage generator with peak output voltage >1 V
Processing Parameters Influence on Disintegration Intensity of Technical Hemp Fibres
No full textIn recent years, an increasing number of researches are dedicated to the identification of local
cellulose sources to understand their specifics and develop environmentally friendly technologies
according to the field of usage. Since the cellulose mass in hemp cells varies from 45% to 70%,
hemp stems and their processing products can be considered as the raw material for various products,
including cellulose. The article analyses the phloem fiber variety of a hemp sort grown in
Latvia named Bialobrzeskie. Treatment in sodium alkali solution and steam explosion technology
have been applied to split technical fibers into elementary fibers. This has the aim to find the best
way to produce fiber without using environmentally harmful chemical treatments and to solve problems
for further environmentally friendly nano-level disintegration of cellulose with further integration
into the structure of composite materials. The influence of the treatment intensity on the residue
carried out in the first stage of research is reflected and an analysis of the steam explosion process
temperature and pressure influence on the fiber chemical component proportion changes during
different treatments are carried out
