fi=215 Teknillinen kemia, kemian prosessitekniikka|sv=215 Teknisk kemi, kemisk processteknik|en=215 Chemical engineering|https://www.doria.fi:443/handle/10024/920802024-03-28T22:36:58Z2024-03-28T22:36:58ZAI-guided design of compatible composites of birch lignin and polylactic acid for 3D printingSalomäki, Timhttps://www.doria.fi:443/handle/10024/1884742024-01-22T13:30:22Z2024-01-22T13:23:46ZAI-guided design of compatible composites of birch lignin and polylactic acid for 3D printing
Salomäki, Tim
In this study, a novel design of composites involving polylactic acid (PLA) and alkaline-extracted birch lignin was explored to produce a sustainable replacement material for additive manufacturing or 3D printing. Due to the large difference in chemical characteristics of two composite components, the challenge focuses on finding an optimal recipe where lignin can partially replace PLA however still being able to maintain the performance as a material in different applications. The optimization of this recipe would have required a large number of experiments, thus in this study, machine learning was implemented in the design of experiments (DOE) to try to optimize data utilization, thereby attempting to reduce the required number of data points and experiment numbers. This implementation introduces a secondary focus of the study, which centers on streamlining the composite creation process and optimizing these composites to the desired characteristics.
It is known that when blending PLA with a large quantity of unmodified lignin, the material’s mechanical properties begin to degrade, making the material brittle. To counter this, two different plasticizers, polyethylene glycol (PEG2000) and triethyl citrate (TEC) were introduced in various amounts. To analyze the material characteristics of the composites, the thermal, mechanical, and morphological properties of the composites were analyzed. Results show that when increasing the amount of plasticizer, the glass transition temperature (Tg) decreases rapidly with blends showing a Tg as low as 7 °C. Materials were also observed to retain a much more elastic characteristic in the form of having a torsional strength of 3182.79 Mpa with a lignin to PLA ratio of up to 25% w/w.
2024-01-22T13:23:46ZPrototyping of lactate biosensor for non-invasive biomarker monitoringLeino, Liisahttps://www.doria.fi:443/handle/10024/1883322023-12-15T13:30:17Z2023-12-15T13:10:22ZPrototyping of lactate biosensor for non-invasive biomarker monitoring
Leino, Liisa
Biosensors are widely used in diagnostics and health monitoring in different applications. They are simple, and cost-effective tools to monitor health and diseases and, therefore, they have attracted significant interest especially during the recent years. Lactate biosensors have got into focus since lactate is an important parameter of health and fitness.
The objective of this thesis was to prepare prototypes of lactate biosensors for non-invasive biomarker monitoring. Lactate oxidase was used as a biorecognition element, which produces H2O2 during the conversion of lactate and oxygen that can be measured amperometrically. Different immobilization methods were used to investigate the possibilities of increasing the long-term stability and sensitivity of biosensors. For that, the enzyme was entrapped in a chitosan and in a Nafion matrix, it was immobilized with PEGDE and cross-linked with GA.
Three of the different methods gave promising results and with further optimizations, it is possible to increase the stability and sensitivity even further.
2023-12-15T13:10:22ZEnzyme-mediator coupling for non-invasive glucose monitoringWeckström, Ciahttps://www.doria.fi:443/handle/10024/1882692023-12-12T09:00:21Z2023-12-12T08:57:05ZEnzyme-mediator coupling for non-invasive glucose monitoring
Weckström, Cia
The aim of this work was to modify the enzymes glucose oxidase (GOx) and glucose dehydrogenase (GDH) with electron relays for wearable glucose biosensor applications. The significance of glucose biosensors lies in their great impact on the field of diabetes management. The main drawback of the glucose biosensors that are currently on the market is their reliance on invasive blood sampling that causes pain and discomfort to people living with diabetes. Therefore, there is a need for non-invasive and wearable glucose biosensors for the management of diabetes. Most of the available glucose biosensors are amperometric enzymatic biosensors. The biosensors fabricated in this work that were modified with GOx utilized Prussian blue, ferrocenecarboxylic acid, and a Ru-complex as electron relays, while the biosensors that were modified with GDH utilized phenazine methosulfate (PMS), ferrocenecarboxylic acid, and a Ru-complex as electron relays. The analytical performance of the fabricated biosensors was mainly investigated with chronoamperometry and cyclic voltammetry. All the biosensors modified with GOx responded linearly to the glucose additions and showed potential as functioning glucose biosensors. Furthermore, the modification of GDH with PMS worked well and the biosensors responded linearly to the glucose additions. The attachment of molecular relays (ferrocenecarboxylic acid and the Ru-complex) to GDH did not work.
2023-12-12T08:57:05ZKorrosion orsakad av delikvescent ZnCl2 i förbränning av sidoströmmarMannisto, Topiashttps://www.doria.fi:443/handle/10024/1882552023-12-11T09:00:22Z2023-12-11T08:37:04ZKorrosion orsakad av delikvescent ZnCl2 i förbränning av sidoströmmar
Mannisto, Topias
Utnyttjande av biomassa och sidoströmmar i energiproduktionen är ett alternativ att minska användningen av fossila bränslen och öka självförsörjningen av energi. Egenskaperna hos olika biomassor och sidoströmmar varierar mycket och beläggningar som bildas kan leda till flera utmaningar i deras användning. En av dessa utmaningar är den ökade mängden av hygroskopiska salter som kan bildas i förbränningsanläggningens kalla ända och förorsaka korrosion. I denna avhandling studerades en av dessa salters, zinkkloridens (ZnCl2), hygroskopiska egenskaper och hur saltet kan orsaka lågtemperaturkorrosion.
Zinkkloridens delikvescenstemperatur vid 25 volymprocent vattenånga (vol% H2O) bestämdes genom att mäta saltets konduktivitet med kronoamperometri. Saltets korrosivitet på rostfritt stål (AISI 347) och kolstål (P235GH) studerades vidare både under och ovanför saltets delikvescenstemperatur. För att simulera förhållanden i kalla ändan av en förbränningsanläggning- användes en rörugn och syntetisk rökgas. En ånggenerator användes för att producera en jämn ström av vattenånga. Efter varje experiment analyserades proven gravimetriskt och korrosionsprodukterna analyserades med mikroskop och SEM-EDX.
Delikvescenspunkten bestämdes vara 156 °C vid 25 vol% H2O, vilket motsvarar en relativ fuktighet på ca 5 %. Det konstaterades också att korrosionshastigheten är beroende på stålet och temperaturen vid förhållanden då delikvescens sker. Det rostfria stålet visade sig vara resistent emot korrosionen vid alla testade temperaturer, emedan kolstålet korroderade kraftigt. Korrosionshastigheten var högst vid den lägsta temperaturen (100 °C). Vid högre temperaturer var korrosionshastigheten lägre. Detta berodde på att ZnCl2 bildade ett salt med Zn/Cl molförhållandet ca 1, vilket indikerar bildning av ZnOHCl. Detta salt är inte lika hygroskopiskt som ZnCl2. På basis av resultaten kunde man dra slutsatsen att det rostfria stålet gav ett mycket bättre skydd gentemot korrosion orsakad av hygroskopiskt ZnCl2.
2023-12-11T08:37:04Z