Search results for "hemiselluloosa"
showing 8 items of 8 documents
Säteilyn aiheuttamat värinmuutokset korkeasaantoisessa massassa
2017
Korkeasaantoisen havusulfaattimassan sähkömagneettisen säteilyn aiheuttama kellastuminen aiheutuu puun natiiveista sekä sulfaattikeiton aikana syntyvistä kromoforeista. Kromoforit ovat kemiallisia rakenteita, jotka absorboivat säteilyä näkyvän valon alueelta, minkä seurauksena syntyy värejä. Kellastumisen aiheutumiseksi kemialliseen rakenteeseen on synnyttävä kromoforisia rakenteita, jotka absorboivat näkyvää valoa sini-viher-alueella. Havupuiden osalta kromoforisia rakenteita esiintyy ligniinissä, uuteaineissa sekä hiilihydraattien johdannaisissa. Lopputyöni kirjallisessa osassa perehdytään havupuiden natiivien sekä sulfaattikeiton aikana syntyvien kromoforien ominaisuuksiin sekä muodostum…
Conduction properties of thin films from a water soluble carbon nanotube/hemicellulose complex.
2018
We have examined the conductive properties of carbon nanotube based thin films, which were prepared via dispersion in water by non-covalent functionalization of the nanotubes with xylan, a type of hemicellulose. Measurements of low temperature conductivity, Kelvin probe force microscopy, and high frequency (THz) conductivity elucidated the intra-tube and inter-tube charge transport processes in this material. The measurements show excellent conductive properties of the as prepared thin films, with bulk conductivity up to 2000 S cm−1. The transport results demonstrate that the hemicellulose does not seriously interfere with the inter-tube conductance. peerReviewed
Hiilinanoputkihemiselluloosan virtaus mikrokanavan leveyden funktiona
2017
Mikrofluidistiikka ja mikroelektroniset systeemit löytävät tiensä entistä useammin arkipäiväiseen elämään ja tutkimukseen. Vaikkakin hiilinanoputket ovat yksi tutkituimmista materiaaleista, niin lähestyimme asiaa käyttämällä hemiselluloosalla vesiliukoistettuja hiilinanoputkia. Tarkoituksena on tutkia tämän hiilinanoputki-hermiselluloosaliuoksen kuljetusta mikrofluidististen kanavien läpi. Lähestymistapamme on käyttää PDMS mikrokanavia, joita valmistimme eri halkaisijoilla. Muotit mikrokanavien valmistusta varten saimme Aalto yliopistosta. Päämäärää varten on valmistettava PDMS kanavia, suoritettava hydrofiilisyyskasittelyjä ja sonikaattorilla puhdistavia käsittelyjä. Parhaan tuloksen aikaa…
From the forest to the plate – Hemicelluloses, galactoglucomannan, glucuronoxylan, and phenolic-rich extracts from unconventional sources as function…
2021
This study aimed to characterise pressurised hot water (PHW) extracts from nonconventional sources of functional carbohydrates and phenolic compounds in terms of antioxidant capacity, antiviral activity, toxicity, and human erythrocytes’ protection antidiabetic potential. PHW extracts of Norway spruce bark (E1 + E2) and Birch sawdust (E3 + E4) contained mostly galactoglucomannan and glucuronoxylan. In contrast, samples E5 to E9 PHW extracted from Norway spruce, and Scots pine bark are rich sources of phenolic compounds. Overall, phenolic-rich extracts presented the highest inhibition of α-amylase and α-glucosidase and protection against stable non-enveloped enteroviruses. Additionally, all …
Advanced biorefinery concepts related to non-wood feedstocks
2018
Agricultural residues, such as wheat straw (Triticum aestivum), okra stalk (Abelmoschus esculentus), and giant miscanthus (Miscanthus × giganteus, a hybrid of M. sinensis and M. sacchariflorus) were investigated to assess their possible consumption for integrated lignocellulosic biorefining. The efficient fractionation and recovery of all important chemical components (cellulose, hemicelluloses, and lignin) of such feedstocks are a prerequisite for realistic biorefinery concepts. Water is one of the most eco-friendly solvents with the highest potential for industrial use, and it is also suitable for full-scale biorefinery purposes. For example, under pressure at elevated temperatures over 1…
Experimental studies on carbon nanotubes and graphene functionalized via physical adsorption with cellulose and avidin
2018
In this Thesis I have experimentally studied structural, electronic, and optical properties of hybrids of nanocarbon materials, carbon nanotubes (CNT) and graphene, and certain biomacromolecules. The latter are especially xylan, a type of hemicellulose, and avidin, an important protein. Complexes of CNT with hemicellulose are attractive because the hybrid material is soluble in water. The conductive transport properties of thin films of CNT /hemicellulose have been systematically studied with different experimental tools. These are low temperature DC conduction measurements, Kelvin probe microscopy, and optical conductivity measurements at terahertz frequencies. The results clearly indicate …
Transparent hemicellulose-DWCNT electrode
2015
Carbon nanotubes (CNTs) and graphene have shown promising potential as next-generation transparent conducting materials due to their high electrical and thermal conductance, flexibility and transparency in both visible and infrared spectral regions. In this study transparent and conductive thin films with a novel hemicellulose and double-walled carbon nanotube (HC-DWCNT) hybrid material were produced with spray-coating, droplet casting and vacuum filtration deposition methods. HC-DWCNT material is easily dispersed in water and usable for mass-production. These films showed good conductivity, stability at ambient air, very good transparency in the visible and excellent transparency in the in…
Selective hemicellulose hydrolysis of Scots pine sawdust
2019
The depletion of fossil resources is driving forward the search for new and alternative renewable feedstocks in the production of renewable chemicals, which could replace the petroleum-based ones. One such feedstock is pine (Pinus sylvestris) sawdust, which is generated enormous amounts in Finnish sawmills yearly. However, prior to the utilization in high-value applications, it needs to be fractionated into its constituents. In this work, the objective was to produce monomeric hemicellulose sugars from pine sawdust without degrading cellulose or lignin simultaneously. The influence of the reaction temperature and time, as well as acid type and concentration, was studied. Based on the result…