Rechargeable lithium ion and lithium (Li) metal batteries with high energy density and stability are in high demand for the development of electric vehicles and smart grids. Intensive efforts have been devoted to developing high capacity battery electrodes. However, the known high capacity electrode materials experience fast capacity fading and have limited cycle life due to electromechanical degradations, such as fracture of Si-based electrodes and dendrite growth in Li metal electrodes. A fundamental understanding of electromechanical degradation mechanisms of high capacity electrodes will provide insights into strategies for improving their electrochemical performance. Thus, this dissertation focuses on mechanical properties, microstructure changes, and degradation mechanisms of Si composite electrodes and Li metal electrodes. Based on these findings, possible coping strategies are proposed to improve the cycling stability of both electrodes. The poor cycling life of Si-based electrodes is caused by the repeated lithiation/delithiation-induced huge volumetric change in Si particles, which leads to the fracture of particles, excessive formation of solid electrolyte interphase on the newly exposed surface, as well as the loss of electronic conductivity between Si particles and the conductive matrix. The expansion/contraction of Si particles during cycling also causes the changes in the mechanical properties, microstructure, and porosity of Si composite electrodes. Understanding the relationship between mechanical property evolution, microstructure degradation, and capacity fading is essential for the design of Si composite electrodes. Using an environmental nanoindentation system, in situ microscope cell, and electrochemical impedance spectroscopy, I investigated the mechanical properties, cracking behavior, and lithiation/delithiation kinetics of Si composite electrodes made with different polymeric binders, including polyvinylidene fluoride, Nafion, sodium-carboxymethyl cellulose, and sodium-alginate, in their realistic working environment. The mechanical property evolution is determined by the state-of-charge, porosity, irreversible volume change, and mechanical behavior of binders. Periodical crack opening and closing happens in Si composite electrodes prepared with binders that have strong adhesion with Si. Mechanical degradations, e.g., irreversible volume change, cracking, and debonding between binders and Si particles, are correlated with the evolution of lithiation/delithiation kinetics and the capacity fading of Si composite electrodes. Based on these findings, a partial charging approach is proposed and confirmed experimentally to improve the cycling stability of Si composite electrodes. Li metal electrodes suffer from the low Coulombic efficiency, high electrochemical reactivity with the electrolytes, and the safety hazards caused by the uncontrollable dendrite growth during cycling. Mechanical suppression by using solid electrolytes and artificial SEI is a promising strategy to inhibit the formation of Li dendrites. Mechanical properties of bulk and mossy Li are required for designing mechanical inhibitors and improving the stability of the Li | inhibitor interface. Using an environmental nanoindentation system, I studied the mechanical behavior, especially the time-dependent behavior, of bulk Li and porous mossy Li at ambient temperature. By combining finite element (FE) modeling with experiments, a constitutive law was determined for the viscoplastic deformation of Li metal. FE modeling also demonstrates that the elasticity has a negligible influence on the indentation deformation of bulk Li. Flat punch indentation measurements showed that mossy Li has significantly higher deformation and creep resistance than bulk Li despite of its porous microstructure. The mechanical parameters of bulk and mossy Li may be helpful to develop of dendrite-free Li metal electrodes.

Nanoindentation is a method of contacting a material whose mechanical properties are unknown with another material whose properties are known. Nanoindentation has the advantage of being able to probe a material’s microstructure while being sensitive enough to detect variations in mechanical properties. However, nanoindentation has some limitations as a testing technique due to the specific formation and structure of some biomaterials. The main objective of this research is to identify any factors that influence the nanoindentation measurement of wood cell walls (a typical biomaterial). The function of the embedding media in describing the properties of wood cells is poorly understood. This research demonstrated that Spurr’s resin, when diffused into wood cell wall during the embedding process, enhanced both the Young’s modulus and hardness of the cell walls. A substitute sample preparation method was developed to avoid this resin penetration into cell wall and was determined to be both effective and easy to perform. The nanoindentation procedure involves the application of a monitor and an analysis of the load-displacement behavior and the response in the material. It can be anticipated that various ways of loading, including the maximum force, the loading time, and others, will cause a variety of mechanical properties. Thus, our second aim was to study the effect of load function on nanoindentation measurement in wood. It was discovered that a fast loading rate contributed to greater contact depth and lower hardness. Increasing the holding time decreased measured values for both Young’s modulus and hardness. However, no significant difference of Young’s modulus and hardness among three loading functions with different unloading rates. The final part of the research was to study the effect of moisture content on the micromechanical properties of wood material. Several nanoindentations were performed on the wood cell wall while varying the moisture content of wood. Results indicated that both the Young’s modulus and hardness decreased significantly with an increase of moisture content. A rheology model was developed to describe the nanoindentation behaviors of wood cell walls at different moisture contents. Five parameters were extracted from Burger’s model, and the relationships among those five parameters were quantified.

A considerable amount of waste is obtained as a result of edge-cutting operations during cement-bonded wood particle board (CBWPB) manufacturing. This waste material which basically contains wood chips and hydrated cement has to be disposed of and does not have any economical value. However, it can be burned in cement rotary kilns and may result in energy savings to a certain extent due to the presence of wood particles as a secondary fuel and since the hydrated cement may be decomposed and then reform clinker compounds during the calcination process. In this experimental study, the possibility of using waste CBWPB in cement manufacturing and its effects on energy consumption and cement characteristics will be investigated. The reference mix, corrective limestone, CBWPB waste and coal, were used as raw materials to prepare six different raw meals whose chemical compositions was similar to reference mix. All six raw mixes (including the reference) were calcined under the same conditions to produce clinkers. The compositions and micro structure of the clinkers obtained were comparatively analyzed by wet analysis, XRF and XRD techniques. Cements were obtained by intergrinding the clinkers with 5% (by mass) gypsum rock and standard tests were carried out on each of the cements. In addition to these, since CBWPB waste contains wood about 30% by weight, its contribution to fuel consumption during clinker production was also analyzed. The test results revealed that CBWPB waste can be used as a cement raw material since CBWPB waste has the similar chemical composition with the reference raw mix. CBWPB, which contains about 30% (by mass) wood, contributes to the heating process during calcination and results in lower amount of primary fuel requirement.

Cementitious materials with strain-hardening property and high tensile ductility are promising materials on account of their mechanical and durability performances. These materials require special ingredients which make it costly to be used in conventional constructions. Hence, potential applications of Engineered Cementitious Composites (ECC) generally focus on layered systems or repairs which require the use of ECC together with another material. For it to be used especially as a repair material, it should have sufficient dimensional compatibility for preventing restrained shrinkage cracking. In this thesis, a strain-hardening fiberreinforced cementitious composite, named Engineered Cementitious Composites, was produced with local ingredients and their mechanical performance, dimensional stability properties were investigated. For investigating the effect of materials and mix proportions on mechanical properties, compressive strength, flexural strength with mid-span beam deflections and matrix fracture toughness tests were conducted. For determining the dimensional compatibility properties, autogenous, drying and restrained shrinkage tests were conducted along with tensile creep tests. As a result it was shown that, mechanical and dimensional stability properties are affected by the ingredients and mix proportions. It was shown that especially autogenous shrinkage of mixtures was relatively high which can cause early age cracking. In order to mitigate the adverse effect of autogenous shrinkage, the effect of pre-soaked expanded perlite aggregate replacement on mechanical, shrinkage and dimensional compatibility properties was investigated. As a result it was found out that autogenous shrinkage can be mitigated by the use of pre-soaked expanded perlite aggregate replacement.

Poles are used as an important constituent of transmission, distribution and communication structures / highway and street lighting systems and other various structural applications. Concrete is the main production material of the pole industry. Concrete is preferred to steel and wood due not only to environmental and economic reasons but also because of its high durability to environmental effects and relatively less frequent maintenance requirements. Centrifugal casting is the most preferred way of manufacturing concrete poles. However, misapplication of the method may lead to a significant reduction in strength and durability of the poles. Segregation of concrete mixture is a frequent problem of centrifugal casting. The segregated concrete within the pole cross-section possesses different physical properties. In particular, the shrinkage tendency of the inner concrete, where the cement paste is accumulated, becomes significantly larger. Differential shrinkage of hardened concrete across the pole section gives rise to the development of internal tensile stresses, which, in turn, results in longitudinal cracking along the poles. There is a vast literature on experimental studies of parameters affecting differential shrinkage of centrifugally cast poles. This research aims to computationally investigate the differential shrinkage-induced internal stress development and cracking of concrete poles. To this end, two and three-dimensional mathematical models of the poles are constructed and finite element analyses of these models are carried out for different scenarios. The computationally obtained results that favorably agree with the existing experimental data open the possibility to improve the centrifugal manufacturing technique by using computational tools.

Roller Compacted Concrete (RCC) is new technology gaining popularity in the recent years due to its low cost, rapid construction, and using opportunity of by-products. RCC is widely used in the world. However, the use of RCC has been restricted to construction of few cofferdams, and limited to local use in dam construction up to date. In this thesis, two types of cement, two types of natural pozzolan, aggregates with varying gradations, and a type of water reducing chemical admixture were used. Prior to carrying out the tests, the chemical and physical properties of materials were determined. Additionally, steam curing was applied to the test specimens in order to get long term compressive strength at early ages. Differences between steam cured specimens and normal cured specimens have been discussed in the discussion part. In the study, the results indicate that usage of water reducing chemical admixture improves compressive strength of RCC. Moreover, it is revealed that usage of fine material is essential to obtain desired results since the amount of cementitious materials is considerably low in RCC. Steam curing is known as its property of providing long term compressive strength at early ages. It was observed that application of steam curing in CEM I type cement used RCC mixtures generated expected results. However, in CEM IV type cement used RCC mixtures compressive strength results did not behave in the same manner.

Microstructural and mechanical characterizations of heat treatable Al-Mg-Si-Cu based wrought aluminum alloys have been studied. The aim of this work was to produce fine grained, high strength alloy by adjusting processing conditions: deformation, solutionizing and aging. First, primary characterization was carried out via SEM-EDS analyses and tensile tests. Then an extensive experimental study has been carried out on two sets of samples. The first set has been studied to determine the ideal conditions for solutionizing and aging processes by analyzing the variation of hardness with different solutionizing and aging time and temperature. The second set, have first been mechanically deformed by swaging at four different deformations and four different temperatures, then heat treated. The hardness measurements have been carried out before and after solutionizing and also after aging. Finally, recrystallization behavior has been investigated by measuring grain size before and after solutionizing treatment using image analyzer software. The initial characterizations showed that Mg2Si and complex iron, manganese bearing intermetallics were the primary particles observed in the &amp / #945 / -Al matrix. Nearly 140HB hardness could be obtained with solutionizing at 530&deg / C and aging at 175&deg / C for 8 hours which was determined as the optimum treatment for obtaining peak hardness. When shaping (deformation) was concerned / strength loss was the overall outcome of any hot or cold deformation before solutionizing / which was most probably due to the destruction of the initial microstructure. Improvement in the percent elongation was the promising aspect of this application. Strength loss was increased for samples deformed at higher temperatures and higher reductions.

The glass-ceramics containing apatite [Ca10(PO4)6(O,F2)] and wollastonite [CaO&amp / #8226 / SiO2] crystals as the predominant crystalline phases, (A-W glass-ceramics) were produced through controlled crystallization of the glasses in the MgO-CaO-SiO2-P2O5-F system. Phases formed in the crystallized counterpart of the glasses were identified by powder X-ray diffraction (XRD) analysis. The crystal morphology of the resultant glass-ceramics was examined using a scanning electron microscope (SEM). The crystallization kinetic parameters consisting of the activation energy for crystallization, (E), the Avrami parameter, (n), and frequency factor of the glass were determined with regard to small amount of TiO2 additions using non-isothermal differential thermal analysis (DTA). The values for E and n for apatite and wollastonite were 460 kJ/mol and 433 kJ/mol, and 3.1&plusmn / 0.1 and 1.5&plusmn / 0.1, respectively. When 4 wt% TiO2 was incorporated into the base glass, the values for E decreased to 408 and 320 kJ/mol for apatite and wollastonite, respectively / but the values for n increased from 3.1&plusmn / 0.1 to 3.3&plusmn / 0.1, and from 1.5&plusmn / 0.1 to 1.9&plusmn / 0.1 for apatite and wollastonite, respectively. TiO2 is an effective nucleating agent in this glass system for promoting the precipitation of both apatite and wollastonite crystals. Structure oriented changes in the indentation microhardness and tribological properties of the A-W glass-ceramics were evidenced. The microhardness at the free surface was 650&plusmn / 12 HV, but decreased with increasing depth distance from the free surface and attained 520&plusmn / 8 HV at a distance 0.5 mm below the free surface. The wear rate at the free surface was 0.7&plusmn / 0.05 &times / 10-4 mm3/Nm, but increased as the distance from the free surface increased and became 2.9&plusmn / 0.15 &times / 10-4 mm3/Nm at a distance 0.5 mm below the free surface. Tribological properties of the A-W glass-ceramics were compared with those of commercially available dental ceramics including IPS Empress 2&reg / , Cergo Pressable Ceramic&reg / , Cerco Ceram&reg / , Super porcelain EX-3&reg / , and bovine enamel. The wear rate, friction coefficient, and wear mechanisms of the A-W glass-ceramics were similar to currently used artificial dental materials.

The aim of the present study was to investigate the effects of different levels of Saffil alumina fiber addition, magnesium content in aluminum alloy matrix and casting temperature on the mechanical behavior, microstructure and physical properties of short fiber reinforced aluminum matrix composites. The main alloying element silicon was kept constant at 10 wt%. Magnesium contents were selected as 0.3 wt% and 1 wt%. Saffil alumina fiber preforms varied from 10 to 30 vol%. The casting temperatures were fixed at 750 &deg / C and 800 &deg / C. Micro porosity was present at the fiber-fiber interactions. Closed porosity of the composites increased when fiber vol% increased, however, variation in casting temperature and magnesium content in matrix did not have influence on porosity. Hardness of the composites was enhanced with increasing fiber vol%, magnesium content in matrix and decreasing casting temperature. Alignment of fibers within the composite had an influence on hardness / when fibers were aligned perpendicular to the surface, composites exhibited higher hardness. The highest hardness values obtained from surfaces parallel and vertical to fiber orientation were 155.6 Brinell hardness and 180.2 Brinell hardness for AlSi10Mg1 matrix 30 vol% alumina fiber reinforced composite cast at 800 &deg / C and at 750 &deg / C, respectively. 30 vol% Saffil alumina fiber reinforced AlSi10Mg0.3 matrix composite cast at 750 &deg / C showed the highest flexural strength which is 548 MPa. Critical fiber content was found as 20 vol% for all composites.

The determination and following up the development of properties during the fresh state and early ages of concrete are important in order to schedule the work and to obtain the desired properties in the hardened concrete. As the traditional methods such as Vicat and Penetrometer mostly depend on the experience of the operator and do not provide a continuous picture of the development of properties, reliable and objective non-destructive test methods are needed for the quality control of fresh concrete. The purpose of this thesis is to observe the development of properties of fresh pastes and mortars continuously by longitudinal ultrasonic waves. For this purpose, cement pastes and mortars with three different w/c ratios were prepared with ordinary portland cement. The ultrasonic pulse velocities were determined continuously during hydration. The setting times were also determined by standard test methods. The flexural and compressive strength were determined at 1, 2, 3, 7 and 28 days by standard test method and the volume of permeable pores were also obtained at the same ages. Lastly, the heat of hydration of cement pastes of similar w/c ratios were determined by isothermal calorimetry. UPV (Ultrasonic Pulse Velocity) development was compared with the results of standard tests applied on the samples. The results revealed that the UPV is a useful method in monitoring the hydration process of cementitious materials.