Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 6 uppsatser.

Diss. (sammanfattning) Linköping : Univ., 2005.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2007. / Härtill 4 uppsatser.

Diss. Linköping : Univ., 2002.

Vatten- och energiförbrukning är ett av mänsklighetens största nuvarande och framtida problem då världens vattenkonsumtion ständigt ökar på grund av bättre levnadsstandard samt ständigt ökande population och industrialisering. Förorenat vatten orsakar sjukdomar, sänkt livstid, reducerad sanitet och försämrad hälsa. Att rena vatten på ett energi- och miljöeffektivt sätt så att det kan återanvändas är därför ett måste för en hållbar framtid. En undersökning av koaguleringsförmågan för ett antal utvalda organiska föreningar via elektrokoagulation har utförts hos företaget Axolot Solutions AB. Axolot Solutions AB är ett företag som arbetar med rening av industriella vatten med elektrokemiska metoder, framförallt elektrokoagulation. De organiska föreningar som undersökts har delats in i grupperna sockerarter (maltos, raffinos, glukos samt laktos), organiska syror (myrsyra, citronsyra, hexansyra, smörsyra, oktansyra), alkoholer (1-propanol, 2-propanol), fettsyror (lecitin) och övriga (formaldehyd, vanillin, nonylfenol, α-pinen). Även ett industriellt vatten från en barkavvattningsprocess har undersökts samt modellvatten av ämnena xylan och lignin som kan hittas i barkvatten. Reningsförmågan av processen har undersökts genom att mäta COD halter före och efter behandling med ett kontinuerligt elektrokoagulationssystem. Varje förening har undersökts vid fyra olika initial pH: 4, 6, 7,5 och 9 och dessutom såväl järnanod och aluminiumanod testats. Även olika strömstyrkor har undersökts för ett par av de organiska föreningarna. Resultaten visar ingen COD reduktion för vatten innehållande xylan, sockerarter, organiska syror och alkoholer. Tekniken visade mycket god reduktion av ämnena: lecitin (85,5%) och lignin (98,1%). En mindre reduktion skedde även för vatten innehållande nonylfenol (33,6%), α-pinen (42,1%), och barkvatten (21,5%). En reduktion av COD skedde även för vanillinvatten med initial pH 4 vid användandet av aluminiumanod, detta var dock det enda vattnet innehållande vanillin som påverkades. Det går inte att dra någon generell slutsats kring vilket initial pH och vilken anod som bör användas vid elektrokoagulation då den mest effektiva anordningen inte är densamma för de olika undersökta föreningarna. / Water- and energy consumption is one of humanities biggest current and future problems because of ever increasing global water consumption and because of better living conditions, increasing population and industrialization. Polluted water results in diseases, reduced life expectancy, sanitation and reduced overall health of those affected. Purifying water in an energy and environmentally effective way is therefore a must for a sustainable future. A study of the coagulation capabilities for a select number of organic compounds by electrocoagulation has been performed at Axolot Solutions AB. Axolot Solutions AB is a company developing electrochemical water treatment solutions, with a focus on the electrocoagulation process. The compounds that have been studied are sugars (raffinose, maltose, glucose, lactose), organic acids (formic acid, citric acid, hexanoic acid, butyric acid, octanoic acid), alcohols (1-propanol, 2-propanol), fatty acids (lecithin), others (formaldehyde, vanillin, nonylphenol, α-pinene). Industrial water coming from a debarking process was also investigated as well as two compounds that are often present in this type of water, xylan and lignin. The treatment efficiency was determined by measuring the COD values of the investigated water before and after the electrocoagulationprocess. Each compound was studied by using an iron anode and an aluminum anode at four different initial pH values: 4, 6, 7.5, 9. Different current densities were also studied for some of the investigated compounds. The results show no COD reduction for sugars, alcohols, organic acids and xylan. The process resulted in large reductions of the compounds lecithin (85.5%) and lignin (98.1%). A lesser reduction was found for the waters containing: nonylphenol (33.6%), α-pinene (42.1%) and barkwater (21.5%). A reduction of COD was also found in the water containing vanillin with an initial pH of 4 that was treated with an aluminum anode was affected. The most efficient setup for the investigated compounds varies. For that reason, no conclusion as to which initial pH and anode that should be for electrocoagulation processes in general can be drawn.

<p>Since the discovery in 1977 that conjugated polymers can be doped to achieve almost metallic electronic conduction, the research field of conducting polymers has escalated, with applications such as light emitting diodes, solar cells, thin film transistors, electrochemical transistors, logic circuits and sensors. The materials can be chemically modified during their synthesis in order to tailor the desired mechanical, electronic and optical properties of the final product. Polymers are also generally possible to process from solution, and regular roll-to-roll printing techniques can therefore be used for manufacturing of electronic components on flexible substrates like plastic or paper. On top of that, the nature of conjugated polymers enables the creation of devices with novel properties, which are not possible to achieve by using inorganic materials such as silicon.</p><p>The work presented in this thesis mainly focuses on devices that utilize two rather unique properties of conducting polymers. Conducting polymers are generally electrochromic, i.e. they change color upon electrochemical oxidation or reduction, and can therefore be used as both conductor and pixel element in simple organic displays. As a result of the electrochemical reaction, some polymers also alter their surface properties and have proven to be suitable materials for organic electronic wettability switches. Control of surface wettability has applications in such diverse areas as printing techniques, micro-fluidics and biomaterials.</p><p>The aim of the thesis is to briefly describe the physical and chemical background of the materials used in organic electronic devices. Topics include molecular properties and doping of conjugated polymers, electrochromism, surface tension etc. This slightly theoretical part is followed by a more detailed explanation of device design, functionality and characterization. Finally, a glance into future projects will also be presented.</p> / ISRN/Report code: LiU-TEK-LIC-2005:50

<p>In polymer electrolyte fuel cells (PEFC) chemical energy, in for example hydrogen, is converted by an electrochemical process into electrical energy. The PEFC has a working temperature generally below 100 °C. Under these conditions water management and transport of oxygen to the cathode are the parameters limiting the performance of the PEFC.</p><p>The purpose of this thesis was to better understand the complex processes in different parts of the PEFC. The rate-limiting processes in the cathode were studied using pure oxygen while varying oxygen pressure and humidity. Mass-transport limitations in the gas diffusion layer using oxygen diluted in nitrogen or helium was also studied. A large capacitive loop was seen at 1-10 Hz with 5-20 % oxygen. When nitrogen was changed to helium, which has a higher binary diffusion coefficient, the loop decreased and shifted to a higher frequency.</p><p>Steady-state and electrochemical impedance spectroscopy (EIS) models have been developed that accounts for water transport in the membrane and the influence of water on the anode. Due to water drag, the membrane resistance changes with current density. This gives rise to a low frequency loop in the complex plane plot. The loop appeared at a frequency of around 0.1 Hz and varied with <em>D</em>/<em>L_m</em>², where <em>D</em> is the water diffusion coefficient and <em>L_m</em> is the membrane thickness. The EIS model for the hydrogen electrode gave three to four semicircles in the complex plane plot when taking the influence of water concentration on the anode conductivity and kinetics into account. The high-frequency semicircle is attributed to the Volmer reaction, the medium-frequency semicircle to the pseudocapacitance resulting from the adsorbed hydrogen, and the low-frequency semicircles to variations in electrode performance with water concentration. These low-frequency semicircles appear in a frequency range overlapping with the low-frequency semicircles from the water transport in the membrane. The effects of current density and membrane thickness were studied experimentally. An expected shift in frequency, when varying the membrane thickness was seen. This shift confirms the theory that the low-frequency loop is connected to the water transport in the membrane.</p>

Avzinkningshärdiga och blyfria mässingslegeringar används i stor utsträckning för att ersätta blyinnehållande mässingslegeringar som används för dricksvattensapplikationer. På grund av det begränsade antalet korrosionsstudier av dessa legeringar är syftet med denna studie att belysa hur vattensammansättning, temperatur och exponeringstid kan påverka legeringarnas korrosionsegenskaper. Tre avzinkningshärdiga mässingslegeringar studerades i kranvatten; två blyfria mässingslegeringar (CW511L och CW724R) och en blyinnehållande mässingslegering (CW602N) som betraktades som ett referensmaterial. En kombination av elektrokemiska, mikroskopiska och ytanalystekniker användes för att utforska korrosionstyp, mekanismer samt korrosionshastighet. Även om samtliga legeringar visade godkända egenskaper i avzinkningstestet enligt ISO 6509-1:2014 var målet att bedöma deras korrosionsbeteende i kranvatten. Vattenkemin justerades för att undersöka effekten av pH, kloridkoncentration och alkalinitet hos de tre mässingslegeringarna under kortvarig exponeringstid (24 timmar). Vattnets korrosivitet varierade beroende på mässingslegeringens sammansättning. Det visade sig att CW511L var känsligare för höga kloridkoncentrationer (44.7 mg/L) och hög alkalinitet (310 mg/L) än för lågt pH (6.9). Det motsatta observerades dock för både CW724R och CW602N. Testvattnets aggressivitet påverkades också av temperaturen när den ökades från 22 °C till 50 °C under exponering i 24 timmar. Medan ingen tydlig avzinkning upptäcktes observerades en kombination av både allmän och lokal korrosion i varierande utsträckning mellan de olika legeringarna. Initieringen av det lokala korrosionsangreppet varierade både med testvattnets kemi och med legeringssammansättningen. Medan CW724R och CW602N bägge uppvisade hög känslighet för lokal korrosion i vattnet med högst pH (8.2), var CW511L mer känslig i det vatten med lågt pH (6.9) vid 50 °C. Effekten av exponeringstid undersöktes i vattnet med högst pH (8.2) för de tre mässingslegeringarna upp till 72 dagar. Korrosionshastigheten baserad på viktminskning visade en förväntad hög korrosionshastighet som minskade med kontinuerlig exponeringstid, vilket ledde till en låg korrosionshastighet för alla tre mässingslegeringarna efter 72 dagar. De blyfria mässingslegeringar uppvisade ur detta perspektiv goda korrosionsegenskaper som är konkurrenskraftiga med mässing som innehåller bly. / Dezincification resistant (DZR) and lead-free brass alloys continue to be widely applied replacing lead containing brasses in the drinking water sector. Due to the limited number of corrosion studies of these alloys in tap water, the present thesis was initiated with the aim to understand how the water type, its temperature and exposure duration can affect the corrosion behavior. Three DZR brass alloys were studied in order to evaluate their corrosion behavior in tap water of varying characteristics. The alloys included were two lead-free brasses (CW511L and CW724R) and a leaded brass alloy (CW602N) considered as a reference material. A combination of electrochemical, microscopic and surface analytical techniques were adopted to explore the corrosion form, mechanisms and corrosion rate. While these alloys passed the dezincification test as per ISO 6509-1:2014, the aim was to assess their corrosion performance in tap water. The influence of water chemistry parameters including pH, chloride concentration and alkalinity on the corrosion resistance of the three DZR alloys was investigated in short-term exposures (24 h). Depending on the brass alloy, the corrosivity of the test waters varied. The results show grade CW511L to be more sensitive in tap water of higher chloride concentration (44.7 mg/L) and alkalinity (310 mg/L) compared with low pH (6.9). However, opposite results were obtained for both CW724R and CW602N. The corrosivity of the test water was also affected by the temperature when increased from 22°C to 50°C during 24 h of immersion. While no dezincification features were observed on the surfaces, a combination of general and localized corrosion was observed to a largely variable extent between the alloys. The extent of initiation of localized corrosion varied with test water and alloy composition. While CW724R and CW602N showed similar high susceptibility to localized corrosion in the alkaline (pH 8.2) tap water, CW511L was more prone to pitting corrosion in tap water of low pH (6.9). The effect of exposure duration was explored in the alkaline test water for the three brasses up to 72 days. Corrosion rates based on weight loss showed an expected initial high corrosion rate which declined with continuous immersion, leading to low and similar corrosion rates for all three brass alloys after 72 days. Thus, at given test conditions, the lead-free brasses showed good corrosion behavior being competitive to the performance of lead containing brass. Therefore, lead-free brass alloys are good candidates to substitute lead-containing brasses in tap water applications.