L’électronisation de l’industrie a mené à l’augmentation de la pollution électromagnétique pouvant être néfaste pour les systèmes électroniques sensibles et les êtres vivants. L’un des moyens pour limiter la propagation des champs électromagnétiques est l’utilisation d’un blindage. L’étude s’est ainsi focalisée sur l’élaboration à froid d’un composite bimétallique pour le blindage magnétique. Le composite étudié allie les propriétés physiques de l’aluminium et de l’acier via le trilame Al8011/AcierDC01/Al8011. Le trilame est élaboré par colaminage à température ambiante. Il s’est avéré que la qualité de l’adhérence des interfaces Al/Acier et l’architecture du trilame dépendent fortement des paramètres du colaminage. Une préparation minutieuse des tôles et de leurs surfaces concomitantes se révèle être tout aussi importante que le colaminage en lui-même. De plus, au cours du colaminage, la tôle d’acier s’est montrée sensible à des instabilités plastiques qui amènent par la suite à sa striction et à sa fragmentation. Ces instabilités plastiques favorisent l’adhérence grâce à des soudages Al/Al mais n’en sont pas un prérequis. Au niveau de l’efficacité de blindage, le trilame s’est révélé être particulièrement intéressant puisque, grâce à sa composition et à sa structuration, il est capable d’atténuer aussi bien les champs magnétiques basses fréquences (< 1 kHz) que les champs magnétiques de plus hautes fréquences (> 1 kHz). Dans une étude à iso-masse, le trilame a présenté une meilleure efficacité de blindage que les tôles d’Al, de Cu et d’acier. Cependant, la fragmentation de l’acier dans le trilame s’est révélée être néfaste pour le blindage magnétique, nécessitant de faire alors un compromis entre tenue mécanique et efficacité de blindage. / The growth of electronic devices has led to an increase in electromagnetic pollution that can be harmful to sensitive electronic systems and living beings. One of the means of limiting the propagation of electromagnetic fields is the use of shielding. Then, the study focused on the elaboration of a bimetallic composite for magnetic shielding. The studied composite combines the physical properties of aluminum and steel via the Al8011/SteelDC01/Al8011 trilayer. The trilayer is produced by cold roll bonding (CRB). It has been found that the adherence quality of the Al/Steel interfaces and the architecture of the composite heavily depend on the CRB parameters. Careful preparation of the sheet and their concomitant surfaces is just as important as CRB itself. Furthermore, during CRB, the steel sheet was sensitive to plastic instabilities which subsequently led to its necking and fragmentation. These plastic instabilities promote adherence through Al/Al welds but are not a prerequisite. In terms of shielding effectiveness, the bimetallic composite has proved to be particularly interesting. Thanks to its composition and its structuring, it can attenuate both low (< 1 kHz) and high frequency (> 1 kHz) magnetic fields. In an iso-mass study, the composite showed a higher shielding effectiveness than Al, Cu and steel sheets. However, the steel fragmentation in the composite proved to be detrimental to magnetic shielding, then requiring a compromise between mechanical strength and shielding effectiveness.

Indiana University-Purdue University Indianapolis (IUPUI) / In adhesive dentistry, obtaining a good bond is a fundamental goal. It has been suggested that filler addition to the adhesives would increase the bonding strength of the adhesive layer. Halloysite aluminosilicate nanotubes (HNTs) are biocompatible, hydrophilic, durable, and have high mechanical strength. These advantages make them good candidates to be used as reinforcing agents for improving the properties of dental adhesives. The objective of this study was to evaluate the effect of incorporating HNTs into a commercial two-step etch-and-rinse adhesive system or one-step self-etch adhesive system on dentin shear bond strength. HNTs were incorporated into the two commercial adhesive systems in 0 wt%, 5 wt%, 10 wt%, and 20 wt%. The commercial control adhesives and the experimental adhesives were used to bond occlusal dentin of 120 extracted human molar teeth and then tested for shear bond strength by a universal testing machine with a semi-circular edge at a crosshead speed of 1.0 mm/min. Debonded specimens were examined under light microscopy to evaluate the fracture pattern. Resin-dentin interface were evaluated under scanning electron microscopy (SEM) after bonding dentin slabs using commercial control adhesives and experimental adhesive that showed numerically highest shear bond strength from each adhesive system. Two-way ANOVA was used to evaluate the effects of adhesive system and nanofiller content on shear bond strength. Pair-wise comparisons between groups were made using Fisher's (LSD) (p < 0.05). For the self-etch adhesive system, only incorporation of 5 wt% showed a significant increase in shear bond strength to dentin compared with the commercial control group. For the etch-and-rinse adhesive system, there was no significant difference in shear bond strength between HNTs filled adhesives groups and the commercial control group. Resin-dentin interface SEM evaluation showed nanotubes infiltrated into dentinal tubules. In conclusion, incorporating the self-etch adhesive system with 5 wt% HNTs increased the bond strength to dentin. Incorporation of up to 10 wt% filler concentration into both the self-etch and the etch-and-rinse adhesive systems did not adversely affect the bond strength to dentin or the handling properties. HNTs can penetrate along with resin tags into dentinal tubules, which could expand the use of their unique properties.

Indiana University-Purdue University Indianapolis (IUPUI) / Traditional resin luting agents generally have mechanical properties that are superior to the newer so-called “universal” self-etching/self-adhesive resin luting agents. However, recent reports indicate that some properties of these new luting agents have been improved, approaching those of the traditional etch and rinse resin luting agents. The objective of this study was to test some mechanical properties of four of these self-etching/self-adhesive resin luting agents [Maxcem Elite (ME), Multilink Automix (MA), RelyX Unicem (RU), SmartCem 2 (SC)] and compare them to a traditional etch and rinse resin luting agent [RelyX ARC (RA)] and a resin-modified glass ionomer luting cement [Fuji Plus (FP)], both of which have much longer histories of clinical success. By comparing the properties of the newer cements to the standards, it may be possible to determine how clinically successful the newer cements may be. The mechanical properties tested were flexural strength (FS) and shear bond strength (SBS). The FS test included making beams of each material, storing them in water for periods of time (24 hours and 90 days) and then performing a three-point bending test on a universal testing machine. The 90 day groups were thermocycled. The SBS test involved preparing human molar specimens, making flat dentin surfaces. Composite cylinders were fabricated, luted to the dentin surfaces with each of the materials tested, stored in water for periods of time (24 hours or 90 days), and then a knife edge shear test was performed on a universal testing machine. The 90 day groups were thermocycled. A Weibull-distribution survival analysis was performed. The results revealed significant differences in the FS of all materials tested at 24 hours. After 90 days and thermocycling, only SC and RA were not significantly different. At both time periods, FP had the lowest and MA the highest FS. The SBS results showed MA, RA, and RU to have the highest bond strengths; SC and ME the lowest at 24 hours. After 90 days and thermocycling, RA had significantly higher bond strength than all other groups; ME, FP and SC had the lowest. The self-etching/self-adhesive resin luting agents all performed at least as well as FP, with the exception of SC (SBS 24 hour). They did not all perform as well as RA, with the exception of SC (FS 90 day), MA (SBS 24 hour, FS 24 hour and 90 day), and RU (SBS 24 hour). The newer luting agents should expect to have clinical success, regarding flexural strength and shear bond strength, at least as good as resin-modified glass ionomer luting cements and approach the level of traditional etch and rinse resin luting agents.

Indiana University-Purdue University Indianapolis (IUPUI) / Potential problems of one-step adhesives have been identified, including water uptake and subsequent plasticization, water-and enzyme-induced nanoleakage, and the presence of voids due to phase-separation or osmosis. Clinically, adhesive failures due to marginal degradation present as retention loss, marginal discoloration, and secondary caries. However, the mechanisms of adhesive interface degradation of self-etching and self-bonding resin luting agents are not fully understood. The objective of the study was to investigate adhesive layer degradation by using a nanoleakage technique with five different resin luting agents. Materials and Methods: Five different resin luting systems, Variolink II, Panavia F2.0, RelyX Unicem, RelyX Unicem2, and Maxcem Elite were evaluated in this study. The 25 dentin specimens were randomly divided into five resin luting agent groups. Flat dentin surfaces were created mid-coronally and were luted with luting agents. Then, each tooth was sectioned occluso-gingivally. The first half of each tooth was used as a control group and the other half was used as the experimental group. The control group was immersed in artificial saliva at 37°C and SEM examination with chemical analysis was performed within 48 hours. In the tested group, all specimens were immersed in artificial saliva at 37°C for 10 days and thermocycled. For the SEM examination, the specimens were immersed in a 50-percent ammoniacal silver nitrate solution for 24 hours.22 SEM was used for observation of silver penetration of the specimens. Three scan lines were selected. For elemental analysis, natural apatite, olivine minerals, and pure silver metal were chosen as standards for Ca, Si and Ag. Data were analyzed using ANOVA with a 5-percent significance level. Results: At the bottom of the hybrid layer, there was no significant difference in silver uptake within the adhesive interface between luting agents (p > 0.05) and there was no significant change in silver uptake within the adhesive interface after thermocycling (aging) (p > 0.05). Conclusion: All resin luting agents exhibited nanoleakage after both 24-hour storage and 10-day storage with thermocycling.

No description available.

Safe, effective hydrogen fuel cells are one of the contenders for the next shift in mobile power technology. One of the solutions to the inherent risks of high pressure hydrogen fuel cells is an outer low pressure container with an inner high pressure containers containing a micro-electromechanical systems (MEMS) valve which regulating the pressure. These MEMS valves consist of several etched Si-chips stacked and bonded, which shall withstand the pressure and temperature range in the high pressure fuel cell as well as the embrittlement caused by the hydrogen gas. Hydrogen embrittlement is a phenomena where materials, mostly metals, lose their ductility due to diffusion of hydrogen atoms into their grain boundaries. A suitable method for stacking the chips is needed and thus a literature study was conducted. Several chip-to-chip bonding methods were investigated in the purpose of finding the most suitable methods tolerating temperatures between -40 to 85°C, pressure up to 1000 bar, hermetically sealing, withstanding hydrogen embrittlement and still bond with particulate contaminations caused by testing each chip. The method found to be best fitting for the purpose was anodic bonding with an alkali glass. Alternatively anodic bonding with a ceramic glass system could be considered if technique from alkali glass is adaptable.

Master of Science / Department of Civil Engineering / Kyle Riding / The durability of partial depth concrete repair is directly related to the bond strength between the repair material and existing concrete. The wait time effects of cementitous grouts, epoxy, acrylic latex, and polyvinyl acetate bonding agents were observed on bond strength. Three rapid repair materials were as a comparison to bond strength, as well as concrete samples with no bonding agents having dry conditions and saturated surface dry moisture condition. The bonding agents and rapid repair materials were tested in a controlled laboratory environment. Bond strength loss with wait times of 0, 2, 5, 10, and 30 minutes were observed when bonding agents were applied. The laboratory samples were loaded using a direct shear test. Field tests were performed using the same repair materials and bonding agents. When the agents were applied in the field the wait times used were 0, 15, 30, and 45 minutes. 7 day and 5 month pull off tensile tests were performed during the field experiment. The data from both experiments show that when using cement grout bonding agents the high bond strength can be obtained when the repair material is applied within 15 minutes of application of the cement grout, and after 15 minutes bond loss can be expected. Wait time didn't have a significant effect on epoxy and acrylic latex bonding agents as long as they were placed before setting. The polyvinyl acetate agent and repair materials can develop high bond strength in laboratory settings, but when used in the field the bond strengths experience loss. When not using bonding agents in a repair, adequate bond strength can be obtained when using saturated surface dry condition.

Doctor of Philosophy / Department of Civil Engineering / Mustaque A. Hossain / Tack coat is a thin layer of asphaltic material used to bind a newly-placed lift of hot-mix asphalt (HMA) pavement to a previously-placed lift or a new HMA overlay/inlay and existing pavement. The purpose of a tack coat is to ensure that a proper bond occurs so that traffic loads are carried by the entire HMA structure. Proper bonding exists when HMA layers act as a monolithic structure, transferring loads from one layer to the next. This depends on appropriate selection of tack coat material type and application rate, and is essential to prevent slippage failure and premature cracking in the wearing surface. This study focuses on development of a three-dimensional finite element (FE) model of HMA pavement structure in order to assess HMA interface bonding. The FE model was constructed using commercially available ABAQUS software to simulate an Accelerated Pavement Testing (APT) experiment conducted at the Civil Infrastructure Systems Laboratory (CISL) at Kansas State University. Mechanistic responses measured in the CISL experiment, such as localized longitudinal strain at the interface, were used to calibrate the FE model. Once calibrated, the model was used to predict mechanistic responses of the pavement structure by varying the tack coat property to reflect material characteristics of each application. The FE models successfully predicted longitudinal strains that corresponded to APT results.

Background: The bonding process can start to develop as early as the planning of a pregnancy and can affect the relationship between mother and child through childhood. If proper bonding is not established, the child can present symptoms of depression, failure to thrive or delays in social and emotional, language or motor development. Stimulation programs implemented during pregnancy may positively affect the bonding process that act as a protective factor against negative outcomes in childhood, adolescence and adult life, for instance substance abuse, poor social coping skills and academic failure. Objectives: To determine and describe the effectiveness of The Baby Bond comprehensive stimulation program on bonding six weeks post intervention. Method: The researcher employed an experimental, pre-test-post-test randomised control group design in this study. Experimental and control groups randomly received the same pre- and post-test: the Prenatal Attachment Inventory within the third trimester of pregnancy and the Maternal Attachment Inventory six weeks post birth. The Baby Bond sensory stimulation program was added to standard antenatal care for the experimental group and the control group received a general stimulation program and standard antenatal care. The data was analysed with the SPSS program version 22.0 by the Statistical Consultation Services at the North-West University, Potchefstroom campus. SPSS was used to compile descriptive statistics from the experimental and control groups, Mann Whitney test and the effect size. Results: The twelve participants that were included in this study were from a variety of ethnic origins, in stable relationships and their ages ranged from 20-34 years. In the results, no statistical significant changes were found between the two groups with the Mann Whitney test. The pre-intervention variables (mean = 66.45) were not significantly different from the post-intervention measurements (mean = 101.03). A medium practical significant difference was identified between the groups (d=0.52) which can indicate that some changes in bonding did take place when implementing the comprehensive sensory stimulation program: The Baby Bond. Conclusion: The Baby Bond sensory stimulation program did not indicate a significant improved bonding as compared to general antenatal care between the mother and baby at six weeks after birth. However, future research in the optimal time for bonding interventions in larger sample sizes is needed, for more conclusive findings. / MCur, North-West University, Potchefstroom Campus, 2015

Background: The bonding process can start to develop as early as the planning of a pregnancy and can affect the relationship between mother and child through childhood. If proper bonding is not established, the child can present symptoms of depression, failure to thrive or delays in social and emotional, language or motor development. Stimulation programs implemented during pregnancy may positively affect the bonding process that act as a protective factor against negative outcomes in childhood, adolescence and adult life, for instance substance abuse, poor social coping skills and academic failure. Objectives: To determine and describe the effectiveness of The Baby Bond comprehensive stimulation program on bonding six weeks post intervention. Method: The researcher employed an experimental, pre-test-post-test randomised control group design in this study. Experimental and control groups randomly received the same pre- and post-test: the Prenatal Attachment Inventory within the third trimester of pregnancy and the Maternal Attachment Inventory six weeks post birth. The Baby Bond sensory stimulation program was added to standard antenatal care for the experimental group and the control group received a general stimulation program and standard antenatal care. The data was analysed with the SPSS program version 22.0 by the Statistical Consultation Services at the North-West University, Potchefstroom campus. SPSS was used to compile descriptive statistics from the experimental and control groups, Mann Whitney test and the effect size. Results: The twelve participants that were included in this study were from a variety of ethnic origins, in stable relationships and their ages ranged from 20-34 years. In the results, no statistical significant changes were found between the two groups with the Mann Whitney test. The pre-intervention variables (mean = 66.45) were not significantly different from the post-intervention measurements (mean = 101.03). A medium practical significant difference was identified between the groups (d=0.52) which can indicate that some changes in bonding did take place when implementing the comprehensive sensory stimulation program: The Baby Bond. Conclusion: The Baby Bond sensory stimulation program did not indicate a significant improved bonding as compared to general antenatal care between the mother and baby at six weeks after birth. However, future research in the optimal time for bonding interventions in larger sample sizes is needed, for more conclusive findings. / MCur, North-West University, Potchefstroom Campus, 2015