Introduction of nanocarbons, such as graphene and carbon nanotubes, to metal matrices, may enhance the electrical and thermal transport, mechanical properties and some other properties of the composite materials. However, uniform distribution of the nanocarbon phase in the matrix material and manufacturing the composites in large scale can be challenging using traditional mixing methods. In this study, a facile method to fabricate metal-nanocarbon composites was developed. Firstly, copper (Cu)-polydopamine (PDA) composite was fabricated by coating Cu powders with the bioinspired PDA polymer, which was then converted to a graphite-like structure during the subsequent sintering. In terms of the properties, compared to the pure Cu sample, the Cu-PDA composite showed increased electrical and thermal conductivity, higher microindentation hardness, and enhanced wear resistance. These findings suggest the inclusion of nanocarbon phase converted from PDA can simultaneously improve the electrical, thermal, and mechanical properties of sintered Cu materials. Effect of sintering temperature and coating time (carbon content) on the microstructure and properties of the composites were discussed. Secondly, aluminum (Al)-copper nanoparticles (CuNP)-PDA composite was fabricated with a new method, to improve the sintering behavior of Al for serving as feedstock materials of additive manufacturing (AM). CuNPs were synthesized by directly reducing Cu ions in the aqueous solution. With the assistance of the PDA coating, the CuNPs can be better attached to the Al powder surfaces. The composite samples showed better sintering behavior by exhibiting higher electrical conductivities and mechanical properties, which may be due to local nanosized alloying phases generation after sintering. These findings illustrated that the composite powders could be a good candidate feedstock material for AM. The structural characterizations of the metal nanocarbon powders and the composites were performed with SEM, TEM, XRD and Raman spectroscopy. With the help of these techniques, the formation of the targeted structures in the composite was studied, including graphite-like structures of cPDA and nano alloying phases in Al-CuNP-PDA composites. Apart from the composite materials fabrication, a novel and facile manufacturing method based on metal powders was also developed. In this study, a new type of Cu- binder paste was formed, which not only can be utilized with direct ink/paste printing but also can be casted into a soft silicone rubber mold. Three-dimensional (3D) metal parts can then be subsequently obtained after sintering. Comparing to other additive manufacturing methods that involve high energy laser or electron beams, this new approach does not require expensive facilities, and it is less time-consuming. Moreover, the silicone rubber molds can be easily removed and reused. In summary, the composite powders fabricated in this study can be utilized as feedstock materials for additive manufacturing of metals and alloys. The new soft-mold casting could be used as an alternative method to manufacture 3D metal components. Therefore, the materials and the processing methods developed in the current study could have broad applications in various metal industries. / Mechanical Engineering

Studies were conducted to determine the role of bioflocculation in the activated sludge unit processes. Laboratory and full-scale studies revealed that bioflocculation is important in determining settling, dewatering, effluent and digested sludge properties (activated sludge properties) and may be vital to the function of all processes related to the above properties. In these studies, it was shown that divalent cations such as calcium and magnesium improved activated sludge properties, whereas monovalent cations such as sodium, potassium and ammonium ions were detrimental to these properties. The divalent cations promoted bioflocculation through charge bridging mechanisms with negatively charged biopolymers (mainly protein and polysaccharide). It was found that oxidized iron plays a major role in bioflocculation and determination of activated sludge properties through surface interactions between iron and biopolymers. Oxidized iron was effective in removing colloidal biopolymers from solution in coagulation and conditioning studies. The research included experiments evaluating effects of potassium and ammonium ions on settling and dewatering properties; effects of magnesium on settling properties; effects of sodium, potassium, calcium and magnesium on effluent quality; effect of solids retention time on effluent quality; and evaluation of floc properties during aerobic and thermophilic digestion. A floc model is proposed in which calcium, magnesium and iron are important to bioflocculation and the functionality of aeration tanks, settling tanks, dewatering equipment and aerobic or anaerobic digesters. It is shown that activated sludge floc properties affect wastewater treatment efficiency. / Ph. D.

For the first time, a novel processing method of co-refining wood and polyolefin (PO) by steam-explosion was scientifically explored for wood-thermoplastic composites without a coupling agent. Traditional studies have addressed the improvement of adhesion between components of wood thermoplastic composites through the use of coupling agents such as maleated PO. The objective of this study was to increase adhesion between wood and PO through reactive processing conditions of steam-explosion. PO characteristics, such as type (polyethylene or polypropylene), form (pellet, fiber, or powder) and melt viscosity were studied along with oxygen gas content of the steam-explosion reactor vessel. Modification of co-processed wood fiber was characterized in four studies: microscopy analysis of dispersion of PO with wood fiber, sorption properties of co-processed material, chemical analysis of fractionated components, and morphological investigation of co-processed material. Two additional studies are listed in the appendices that relate to adsorption of amphiphilic polymers to the cellulose fiber surface, which is one hypothesis of fiber surface modification by co-steam-explosion. Microscopy studies revealed that PO melt viscosity was found to influence the degree of dispersion and uniformity of the steam-exploded material. The hygroscopic nature of the co-processed fiber declined as shown by sorption isotherm data. Furthermore, a water vapor kinetics study found that all co-refined material had increased initial diffusion coefficients compared to the control fiber. Chemical changes in fractionated components were PO-type dependent. Lignin extracted from co-processed wood and polyethylene showed PO enrichment determined from an increase of methylene stretching in the Fourier Transform infrared subtraction spectra, while lignin from co-processed wood and polypropylene did not. Additionally, extracted PO showed indirect signs of oxidation as reflected by fluorescence studies. Solid state nuclear magnetic resonance spectroscopy revealed a number of differences in the co-processed materials such as increased cellulose crystallinity, new covalent linkages and an alternative distribution of components on the nanoscale reflected in the T1Ï relaxation parameter. Steam-explosion was shown to modify wood fiber through the addition of "non-reactive" polyolefins without the need for coupling agents. In light of these findings, co-refining by steam-explosion should be viewed as a new reactive processing method for wood thermoplastic composites. / Ph. D.

Various combinations of multi-stage thermophilic and/or mesophilic anaerobic sludge digestion systems were studied to evaluate their solids reduction, odor generation after centrifugal dewatering and indicator organism reduction in comparison to single-stage thermophilic and/or mesophilic anaerobic digestion systems. Pre-aeration of sludge in a thermophilic temperature was also tested followed by single or multi-stage anaerobic digestion systems. It was found that multi stage systems were capable of greater solids removal and placing thermophilic system in multi stage system enhanced indicator organism destruction below EPA Class A biosolids requirement. However, all the digestion systems in the study showed less than 3 log reduction of indicator organism DNA/g solids, which was much smaller than indicator organism reduction measured by standard culturing method. It was also found that the thermophilic anaerobic digestion system could increase organic sulfur-based odors from dewatered biosolids while placing a mesophilic digester reduced odors. It was exclusively observed from sludges containing high sulfate such as ones in this study. A combined anaerobic and aerobic sludge digestion system was also studied to evaluate their solids and nitrogen reduction efficiencies. The aerobic digester was continuously aerated to maintain dissolved oxygen level below 1 ppm and intermittently aerated. It was found that 90 % or more nitrogen removal was possible at the aerobic SRT greater than 3 days and the optimum aeration ratio could be determined. / Ph. D.

<p dir="ltr">A new class of bioplastics polymer materials synthesized from hemp-derived cannabinoids are demonstrated through a lifecycle approach. The poly(cannabinoid) material platform is utilized to develop application-specific polymers for the fabrication of electrocardiogram electrodes and on-skin heaters. A rigid homopolymer pCBD-adipate is synthesized to formulate conductive composite inks and a CBD/CBG block copolymer is developed as an adhesive. Inks are printed using the DIW process allowing for versatile and rapid prototyping of devices. ECG performance assessments yield comparable performance to conventional wet gel electrodes in ambient conditions, and improved performance in submerged testing. Heating devices are demonstrated for conformality by application to a joint, as well as self-regulating capabilities by controller-free joule heating. Following device applications, pCBD-adipate homopolymer conductive composite is used to demonstrate disposal routes of poly(cannabinoid)s through mechanical and chemical recycling. Mechanical recycling exhibits high conductivity over multiple cycles but notably diminishes. Chemical recycling achieved through base-catalyzed hydrolysis of the ester bonds is successfully shown to yield cannabidiol monomer after filtration, thereby paving the path towards full circularity of poly(cannabinoid)s.</p>

The effect of solids retention time (SRT) or sludge age on activated sludge properties and effluent quality was investigated using laboratory scale reactors. It was found that an increase in SRT resulted in an increase in effluent solution polysaccharide, with the < 3,000 daltons (3K) size fraction contributing up to 68 percent of solution polysaccharides. The feed consisted of low molecular weight, readily degradable protein, suggesting that the observed increases in protein and polysaccharide were due to increased release of exocellular microbial product (EMP). The increase in solution protein and polysaccharide resulted in an increase in effluent chemical oxygen demand (COD). The increase in effluent COD was not accompanied by a similar increase in effluent biological oxygen demand (BOD), indicating that the EMPs released were resistant to biodegradation. At the highest SRT, the resistance to shear decreased and the capillary suction time (CST) increased. Following an initial increase, the sludge volume index (SVI) decreased at higher SRT. / Master of Science

Autothermal thermophilic aerobic digestion (ATAD) of sludge has been used to produce class A biosolids. With stringent EPA guidelines, more and more municipalities are looking to use this process for digestion of sludge. However the large polymer costs associated with dewatering these sludges has made the use of this technology unfavorable. Several studies have been conducted in the past which have looked into the mechanism leading to such a poor dewatering of sludge. Some of these studies have attributed the release of protein and polysaccharide during the high temperature digestion to be responsible for the poor dewatering. However the exact mechanism leading to the poor dewatering is still not totally clear. Laboratory scale studies were conducted to evaluate the mechanism leading to the poor dewatering of these sludges and also to be able to economically condition these sludges. ATAD sludge samples were collected from ATAD processing facilities in Ephrata, PA, Cranberry, PA, Titusville, FL and College Station, TX. The research included experiments evaluating the protein and polysaccharide concentrations in solution, cations and anions, iron and aluminum, zeta potential and capillary suction time. It was found that during digestion large amounts of protein and polysaccharide were released which were in the colloidal range, and the dewatering of each of these sludges became poorer as the amount of protein and polysaccharide in the solution increased. The release of protein and polysaccharide was related to the monovalent to divalent cation ratio and the iron and aluminum concentration in the sludge. Also during the digestion process, the pH of the sludge increased appreciably and the divalent cations precipitated out. The zeta potential of the ATAD digested sludge was also found to be positive. Different chemical coagulants were used to condition the sludge, but even with high polymer doses the dewatering of the sludge was not satisfactory. A combination of iron (or cationic polymer) followed by anionic polymer was found to improve the dewatering to a desired level. The use of this combination of sludge conditioning also provides an economical solution to the problem of dewatering. The role of iron in improving the dewatering of the sludges was found to be important, with the sludge dewatering being better for sludges with a high iron content. The combination of high pH, divalent cation precipitation, iron deficiency and biopolymer release all contribute to the poor dewatering of ATAD sludge. / Master of Science

For more than a century, plastics have become an increasingly important part of the human society. Thanks to the durability and the many varieties of plastic it has a wide range of applications, but unfortunately the traditional plastic made from fossil oil has its drawbacks. Neither the fact that fossil oil is used, nor that these plastics won’t degrade in nature, are in any way sustainable for the environment in the long run. But out of the shadow of these problems, new technologies for the manufacturing of bioplastics are born. This thesis aims towards mapping out properties of different plastics, fossil based as well as bio-based, and investigating the possibilities to manufacture plastic material from algae, so called blue plastics. Additionally, the thesis shed light on terms related to plastic production and bioplastics.  The result shows that there are multiple approaches to the manufacturing of blue plastics; several divergent polymers (e.g. starch, protein and alginate) can be extracted from algae for the production of plastic material, and there is a large number of algae strains and methods to use. Blue plastics are still not produced in large scale, and therefore suffer from high production costs, which makes it challenging to replace traditional plastics. Another obstacle is bad durability and mechanical properties of some algae-based materials. But the blue side of the spectrum of plastics is still a young field of study and new innovations are yet to be discovered. / I över ett sekel har plast blivit en allt viktigare del i det mänskliga samhället. Tack vare sin tålighet och mångsidighet har plast en mängd olika användningsområden, men tyvärr har den traditionella plasten även sina nackdelar. Varken det faktum att fossil olja används, eller det faktum att dessa plaster inte bryts ned i naturen, kan anses hållbart i längden. Men ur skuggan av dessa problem träder nya tekniker fram, som möjliggör tillverkning av bioplaster. Detta projekt syftar till att kartlägga egenskaperna hos olika plaster, fossilbaserade såväl som biobaserade, samt möjligheterna att tillverka plast med alger som råvara. Dessutom läggs fokus på att förklara vissa termer relaterade till plaster, bioplaster och dess livscykel.  Resultatet visar att det finns ett flertal tillvägagångssätt för tillverkningen av algbaserade plaster. Flera olika polymerer (t.ex. stärkelse, protein och alginat) kan extraheras från alger för vidare produktion av plastmaterial, och dessutom finns ett stort antal olika algarter och tillverkningsmetoder som kan användas. Idag produceras algplaster ännu inte i stor skala, något som innebär att produktionskostnaderna fortfarande är höga och att det således är svårt att konkurrera ekonomiskt med traditionella plaster. Ett annat hinder för algbaserade plaster är i vissa fall låg resistans och sämre mekaniska egenskaper jämfört med traditionella plaster. Men den algbaserade delen av plastspektrumet är fortfarande ung och outforskad, fortfarande finns nya upptäckter och möjligheter som väntar på att bli funna.

Biopolymers are becoming more attractive as advanced wound dressings because of their naturally derived origin, abundance, low cost and high compatibility with the wound environment. Arabinoxylan (AX) is a class of polysaccharide polymers derived from cereal grains that are primarily used in food products and cosmetic additives. Its application as a wound dressing material has yet to be realized. In this two-pronged project, arabinoxylan ferulate (AXF) was fabricated into electrospun fibers and gel foams to be evaluated as platforms for wound dressing materials. In the first study, AXF was electrospun with varying amounts of gelatin. In the second study, AXF was dissolved in water, enzymatically crosslinked and lyophilized to form gel foams. The morphology, mechanical properties, porosity, drug release kinetics, fibroblast cell response and anti-microbial properties were examined for both platforms. Carbohydrate assay was conducted to validate the presence of arabinoxylan ferulate in the electrospun GEL-AXF fibers. Swelling and endotoxin quantification studies were done to evaluate the absorptive capacity and sterilization agent efficacy respectively in AXF foams. The results indicated successful fabrication of both platforms which validated the porous, absorptive, biocompatibility and drug release properties. The results also exhibited that silver impregnated AXF scaffolds inhibited growth of Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecalis bacteria species, anti-microbial properties necessary to function as advanced wound dressing materials. Future work will be done to improve the stability of both platforms as well as evaluate its applications in vivo.

Orientador: Rui Seabra Ferreira Júnior / Resumo: Terapias efetivas de lesões na dura-máter representam um enorme desafio à medicina, devido à dificuldade de suturas com êxito e de vedação das meninges, aumentando os índices de mortalidade e morbidade destes pacientes. Biomateriais que possam favorecer a regeneração e impedir o extravasamento de líquido cefalorraquidiano sem produzir efeitos adversos são alvos da indústria farmacêutica. Este estudo avaliou a biocompatibilidade do Biopolimero de Fibrina (BPF) derivado de peçonha de serpente como arcabouço tridimensional para células-tronco mesenquimais (CTMs) em lesões na dura-máter de ratos wistar (Rattus norvegicus). As CTMs foram caracterizadas na quinta passagem por citometria de fluxo (ICAM, CD90, CD34, CD45, CD11b) e diferenciadas em linhagens osteogênica e adipogênica. Foram utilizados 4 grupos (n=20) de ratos Wistar machos adultos. O grupo C (controle) foi submetido à durotomia. Os grupos tratados foram submetidos à durotomia seguido de: Tratamento com Biopolimero de fibrina (BPF); células-tronco mesenquimais (CTMs); e BPF+CTMs, formado pela associação do Biopolimero de fibrina e células-tronco mesenquimais. As CTMs marcadas e associadas ao BPF foram avaliadas por imageamento da fluorescência in vivo. Os animais foram avaliados neurológica e clinicamente quanto à sensibilidade dolorosa, deiscência de pontos, infecção da ferida, consumo de alimento e água e habilidades motoras. Foram realizadas eutanásias dos animais aos 7 e 28 dias após cirurgia e coletado material pa... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Effective therapies to treat dura mater injuries represents a major challenge to medicine due to its lack of sutures with high seal properties upon meninges, increasing the rate of mortality and morbidity among these patients. Biomaterials that promotes regeneration and prevent extravasation of cerebrospinal fluid, without producing adverse effects, are targets of the pharmaceutical industry. The present study aimed to evaluate the biocompatibility of the use on Fibrin Biopolymer (FBP) derived from snake venom as tridimensional scaffold to mesenchymal stem cells (MSC) on rat’s dura mater injury. Mesenchymal stem cells characterization was performed at fifth passage by flow cytometry (ICAM, CD90, CD34, CD45, CD11b) and differentiated into osteogenic and adipogenic lineages. Four groups (n=20) os male Wistar rats were used. Group C (control) animals were submitted to durotomy only. Treatment groups were submitted to durotomy followed by: Fibrin Biopolymer (FBP); mesenchymal stem cells (MSC); and FBP+MSCs, consisting on the association between fibrin biopolymer and mesenchymal stem cells. Marked MSCs associated to FBP were evaluated through in vivo fluorescence imaging. Animals were evaluated neurologically and clinically regarding pain sensitivity, dehiscence of suture, wound infection, feeding e motor capacity parameters. Animals were euthanized at seven and 28 days after surgical procedure, and biological material was collected to histological and proteomic analysis. Protein ... (Complete abstract click electronic access below) / Doutor