Objective: Toothbrushing with fluoride toothpaste followed by rinsing with mouthwash is a routine procedure to maintain good oral hygiene. It is unknown to what extent these rinses can modulate the effect of fluoride in its ability to prevent erosion/abrasion.The aim of this in-vitro study was to investigate and compare the impact of chlorhexidine (CHX), essential oils (EO) and cetylpyridinium chloride (CPC) mouthrinses on erosive tooth wear protection afforded by conventional fluoride toothpastes. Materials and Methods: The following experimental factors were considered: five rinses: CHX, EO, CPC, a fluoride rinse, and deionized water, two fluoride toothpastes: stannous fluoride (SnF2) or sodium fluoride (NaF) and two models: (erosion/ erosion+abrasion). Slabs of bovine enamel and dentin were prepared and embedded in resin blocks and generated 10 enamel and dentin testing groups (n = 8). UPVC tapes were placed on the sides of each slab leaving 1mm area exposed in the center. The blocks were subjected to a five-day cycling model. Then, the blocks were placed in a brushing machine and exposed to fluoride toothpaste slurry (one side was brushed and the other wasn’t). The blocks were then exposed to rinse treatments. Artificial saliva was used to remineralize the specimens after erosions and treatment challenges, and as storage media. After the fifth day of cycling, surface loss (in micrometers) was determined by profilometer. Data were analyzed using ANOVA (α = 0.05). Results: There was no interaction among the three factors (type of toothpaste, mouthrinse and abrasion or not (dentin p = 0.0520, enamel p = 0.4720). There were no significant two-way interactions as SL was only affected by toothpaste and mouthrinse. NaF caused less SL than SnF2 (4.60 vs. 5.83 μm; p < 0.0001) in dentin, whereas the opposite was found in enamel (5.20 vs. 3.56 μm; p < 0.0001). Toothbrushing abrasion caused comparatively more SL in enamel (6.53 vs. 2.23 μm; p < 0.0001) than in dentin (6.06 vs. 4.38 μm; p < 0.0001). None of the tested mouthrinses affected SL. Conclusion: Commonly used mouthrinses containing antimicrobial agents or additional fluoride, do not impair the erosion/abrasion protection afforded by fluoride toothpastes. Tested SnF2 dentifrice offered greater protection against enamel surface loss and NaF dentifrices showed more protection for the dentin surface. Clinical relevance: The understanding of the interaction between commonly used rinses and fluoride dentifrices will help dentists provide better recommendations to patients with erosive lesions.

A flexible nanofibrous PVDF-BaTiO3 composite material is prepared for impact sensing and biomechanical energy harvesting applications. Dielectric polyvinylidene fluoride (PVDF) and barium titanate (BaTiO3)-PVDF nanofibrous composites were made using the electrospinning process based on a design of experiments approach. The ultrasonication process was optimized using a 2k factorial DoE approach to disperse BaTiO3 particles in PVDF solution in DMF. Scanning electron microscopy was used to characterize the microstructure of the fabricated mesh. The FT-IR and Raman analysis were carried out to investigate the crystal structure of the prepared mesh. Surface morphology contribution to the adhesive property of the composite was explained through contact angle measurements. The capacitance of the prepared PVDF- BaTiO3 nanofibrous mesh was a more than 40% increase over the pure PVDF nanofibers. A comparative study of dielectric relaxation, thermodynamics properties and impact analysis of electrospun polyvinylidene fluoride (PVDF) and 3% BaTiO3-PVDF nanofibrous composite are presented. The frequency dependent dielectric properties revealed micro structural features of the composite material. The dielectric relaxation behavior is further supported by complex impedance analysis and Nyquist plots. The temperature dependence of electric modulus shows Arrhenius type behavior. The observed non-Debye dielectric relaxation in electric loss modulus follows a thermally activated process which can be attributed to a small polaron hopping effect. The particle induced crystallization is supported with thermodynamic properties from differential scanning calorimetric (DSC) measurements. The observed increase in piezoelectric response by impact analysis was attributed to the interfacial interaction between PVDF and BaTiO3. The interfacial polarization between PVDF and BaTiO3 was studied using density functional theory calculations and atomic charge density analysis. The results obtained indicates that electrospinning offers a potential way to produce nanofibers with desired crystalline nature which was not observed in molded samples. In addition, BaTiO3 can be used to increase the capacitance, desired surface characteristics of the PVDF nanofibers which can find potential application as flexible piezoelectric sensor mimicking biological skin for use in impact sensing and energy harvesting applications.

Höchste Magnetfelder haben sich zu einem unverzichtbaren Werkzeug der Festkörperphysik entwickelt. Sie werden insbesondere verwendet, um die elektronischen Eigenschaften von modernen Materialien zu erforschen. Da Magnetfelder oberhalb von 45 Tesla nicht mehr mit statischen (z.B. supraleitenden) Feldern zu erreichen sind, haben sich weltweit verschiedene Labore auf die Erzeugung gepulster Magnetfelder mit angestrebten Maximalwerten von 100 Tesla spezialisiert. In der vorliegenden Arbeit werden Anwendungsmöglichkeiten der kernmagnetischen Resonanz (NMR) in gepulsten Magnetfeldern aufgezeigt. Es ist gelungen, die starke Zeitabhängigkeit der gepulsten Magnetfelder mittels NMR präzise zu vermessen. Die genaue Kenntnis des Magnetfelds nach dem Puls ermöglicht, die Zeitabhängigkeit aus den Daten zu entfernen, sodass auch eine kohärente Signal-Mittelung möglich ist. Davon ausgehend werden erstmalig Messungen der chemischen Verschiebung, der Knight Shift, der Spin-Gitter-Relaxationsrate 1/T1 und der Spin-Spin-Relaxationsrate 1/T2 diskutiert. Schließlich werden die im Zusammenhang mit gepulsten Magnetfeldern erarbeiteten Gleichungen in vereinfachter Form zur genauen Messung und Analyse des freien Induktions-Zerfalls von 19F Kernspins in Calciumfluorid verwendet. Durch Messung des Zerfalls über sechs Größenordnungen wird eine genaue Analyse bezüglich einer neuartigen Theorie ermöglicht, welche den Zerfall basierend auf der Annahme mikroskopischen Chaos\'' erklärt. Diese Theorie hat das Potenzial, zu einem tieferen Verständnis von Quantenchaos in makroskopischen Vielteilchensystemen zu führen.

Indiana University-Purdue University Indianapolis (IUPUI) / Etching of enamel caries lesions has been demonstrated to enhance remineralization. However, this effect reaches a plateau after a period of time. This study aimed at investigating the effectiveness of additional acid etching on remineralization. Forty 1 mm × 2 mm human enamel blocks with chemically induced artificial incipient lesions were used. Ten specimens were randomly selected at the end of demineralization for transverse microradiography (TMR) analysis. The remaining specimens were then divided into three groups (n = 10). Group A was remineralized by a pH cycling system with 1100 ppm sodium fluoride for 20 days. In group B, the specimens were etched with 35-percent phosphoric acid for 30 s and then remineralized. Group C was remineralized by same procedure as group B plus and given an additional acid etch after 10 days of remineralization. Mineral density was measured by x-ray microtomography (µ-CT). The volumetric mineral content [VM (µm3×105)] was determined between 91 and 0-wt%. The µ-CT % mineral recovery (%) was calculated using the formula 100×(remineralize VM - demineralization VM) / (sound VM - demineralization VM). One-hundred-μm sections of demineralized and remineralized specimens were used to assess the mineral loss (IML: vol%×µm) and lesion depth (µm) using TMR. The three groups showed no significant difference in mineral change or mineral content for µ-CT or TMR lesion depth. The TMR IML showed a significant difference between the demineralized specimens and the three remineralized groups. The correlation between TMR IML and TMR lesion depth was 0.66 (p < 0.0001). The µ-CT percent mineral recovery from demineralization was correlated with neither TMR IML nor TMR lesion depth. When evaluated with µ-CT, the twice-acid-etched group presented lower mineral gain values than the group etched only once with acid. Also, the twice-etched group presented lower mineral gain and greater TMR IML compared with the non-acid etch group. TMR images revealed reduction of surface layer in the acid-etched groups, especially in the twice-etched group, in which significant reduction or loss of surface layer occurred. Based on these results, we conclude that additional acid etching with 35-percent phosphoric acid does not enhance remineralization compared with a single application of acid etching. We believe that the viable existence of the surface layer is essential for remineralization of the lesion. Further investigations into the accuracy of µ-CT to detect minute mineral changes in incipient caries lesions are probably needed.

Indiana University-Purdue University Indianapolis (IUPUI) / Hypothesis: The interaction between the abrasive level and fluoride concentration of dentifrice slurries modulates the surface loss (SL) and remineralization of incipient enamel caries (IEC). Methods: Three types of IEC were created and six experimental slurries with different combinations of fluoride content and abrasive level were tested. In experiment 1, the three IEC were subjected to brushing (with experimental slurries) and remineralization cycles for 5 days. Fluoride concentrations (0 and 275 ppm as NaF) and abrasive levels (Low and High) were tested. SL was determined by optical profilometry at baseline and after 1, 3, and 5 days. In experiment 2, changes in IEC mineral content (Δ(ΔZ)C) and depth (ΔLC) were investigated at baseline and after the 5-day cycling with transverse microradiography. In experiments 3 and 4, SL of MeC and CMC lesions were further studied, respectively; testing not only fluoride concentration (275 and 1250 ppm as NaF) and abrasivity (low and high) of the slurry, but also the brushing frequency (1x, 2x, and 3x/day). Brushing-remineralization cycles were performed for 7 days. Statistical analyses were performed at 5% significance level. Results: Experiment 1: overall, brushing with the high-abrasive slurry caused more SL than with the low-abrasive. For CMC and MeC lesions, 0 ppm F had more SL than 275 ppm F only after day 3. Fluoride had no effect on the SL of HEC lesions. Experiment 2: fluoride and abrasives did not have a significant effect on IEC. HEC had significantly lower Δ(ΔZ)C than CMC and MeC, with CMC and MeC not differing from each other. Lesion type had no effect on ΔLC. Experiment 3: brushing CMC lesions 3x/day with 1250 ppm F increased SL compared to 1x/day, after 5 and 7 days. Study 4: brushing MeC lesions with high abrasive slurry containing 1250 ppm F increased SL after 5 and 7 days. Conclusions: The IEC tested showed different SL and remineralization behaviors. The fluoride content and abrasive level of the toothpaste showed to be relevant modulating the SL of enamel caries lesions as well as their remineralization behavior.

No description available.

Wire-grid polarizers (WGPs) offer superior extinction, durability, angle of incidence, and heat resistance when compared to traditional organic polarizers. WGPs are found in applications such as high lumen lighting, laser devices, high lumen digital cinema projectors, LED packaging, and other integrated optical applications and are driving the need for over-coatings. Over-coating a WGP has been found to increase lifetime and durability. This research provides lifetime data on coated and uncoated WGPs. WGPs over-coated with 100nm of SiO2, 300nm of MgF2, and with no over-coating were heated to temperatures of 450 ºC, 500 ºC, and 550 ºC and timed until they reached a predetermined optical failure point. The activation energies were calculated by applying the Arrhenius model to the failure data. WGPs with no over-coating were found to have an activation energy ≥ 1.5329 eV, with silicon dioxide an activation energy ≥ 1.7197 eV, and with magnesium fluoride an activation energy ≥ 2.4577 eV. It has been shown that coating a WGP with an over-coating of silicon dioxide or magnesium fluoride slows the oxidation process of the aluminum nano-wires, thus increasing the lifetime of the WGP by 208% and 27,904%, respectively. Parasitic chemical reactions were not found to exist with silicon dioxide or magnesium fluoride when used as an over-coating.

<p>    An all-additive manufacturing technique was developed to print piezoelectrically active polymeric materials, primarily poly(vinylidene fluoride) (PVdF), for use in pressure sensors in soft robotics. The research proceeded in three stages. The initial stage used Fused Deposition Modeling (FDM) and electric poling independently to create piezoelectric PVdF pressure sensors. The second stage merged FDM and electric poling processes. The third stage introduced electrospinning to create flexible, high-output piezoelectric PVdF materials, which were combined with three-dimensional (3D) printed soft structures for stretchable pressure sensors.</p> <p>    The main achievement of the research was the development of the Electric Poling-assisted Additive Manufacturing (EPAM) technique, combining electric poling and FDM 3D printing to print piezoelectric materials with custom structures at lower costs. β-phase in semicrystalline PVdF materials is mainly responsible for piezoelectricity. A higher β-phase content results in superior sensor performance. This technique was evaluated by measuring the piezoelectric output voltage of the printed PVdF films, and β-phase content was quantified using Fourier-transform Infrared spectroscopy (FTIR). The developed EPAM technique was combined with Direct Ink Writing (DIW), becoming a hybrid 3D printing technique. This is the first demonstration of applying a hybrid printing technique to print piezoelectric PVdF-based sensors directly. The sensor was constructed using FDM printed PVdF film as the dielectric sandwiched between two parallel DIW printed silver electrodes. The PVdF sensors have both piezoelectric pressure sensing and capacitive temperature sensing functionalities. The application of the capacitive temperature sensor was demonstrated by applying heating-and-cooling cycles while measuring the capacitance as a function of temperature at a constant frequency, showing improved sensitivities at higher frequencies (i.e., 105 Hz) after dielectric polarization.</p> <p>    The third stage of research was motivated by the need for soft piezoelectric pressure sensors for soft robotics. Challenges were twofold: requiring soft piezoelectric materials with high coefficients for excellent sensors and fabrication techniques to incorporate soft materials into designed structures. Inspired by the EPAM technique, a method combining electrospinning and DIW was used to create soft piezoelectric PVdF/thermal plastic polyurethane (TPU) blend microfiber-based pressure sensors. The soft sensor was integrated with an FDM printed soft structure for a stretchable pressure sensor with both piezoelectric sensing and capacitive sensing mechanisms.</p>

Übergangsmetallfluoridverbindungen sind sehr vielversprechende Kandidaten für die nächste Generation von Kathoden für Alkaliionenbatterien. Dennoch verhindern einige Nachteile dieser Materialklasse ihre Anwendung in Energiespeichermedien. Metallfluoride haben eine stark isolierende Wirkung, außerdem bewirken die Mechanismen beim Lade-/Entladevorgang, große Volumenänderungen und somit eine drastische Reorganisation des Materials, welche nur geringfügig umkehrbar ist. Um diese Nachteile zu reduzieren, werden in dieser Arbeit innovative Syntheserouten für die Umwandlung von Metallfluoridverbindungen sowie deren Anwendung in Alkaliionenbatterien vorgestellt. Im ersten Teil werden MFx Verbindungen (M = Co, Fe; x = 2 oder 3) untersucht. Diese Materialien zeigen eine hohe Ausgangskapazität aber nur bei sehr geringen C-Raten und zudem sehr geringe Zyklisierbarkeiten. Ex-situ-XRD und -TEM zeigen, dass die geringe Umkehrbarkeit der Prozesse hauptsächlich aus der Umwandlungsreaktion während des Be-/Entladens resultieren. Im zweiten Teil werden sowohl die Synthesen als auch die elektrochemischen Eigenschaften von Perowskiten aus Übergangsmetallfluoriden vorgestellt. NaFeF3 zeigt hierbei exzellente Leistungen und Reversibilitäten. Die Untersuchung der Mechansimen durch ex-situ und operando XRD während der Be- und Entladeprozesse hinsichtlich verschiedener Alkalisysteme zeigt, dass das kristalline Netzwerk über den Zyklus erhalten bleibt. Dies führt zur hohen Reversibilität und hohen Leistung selbst bei hohen C-Raten. Der Erhalt der Kristallstruktur wird durch elektrochemische Stabilisierung der kubischen Konformation von FeF3 ermöglicht, welche normalerweise erst bei hohen Temperaturen (400 °C) beobachtet wird und durch geringere Reorganisationen innerhalb des Kristallgerüsts erklärt werden kann. Ähnliche elektrochemische Eigenschaften können für KFeF3 und NH4FeF3 beobachtet werden, wobei erstmalig von Ammoniumionen als Ladungsträger in Alkaliionensystemen berichtet wird. / Metal fluoride compounds appear as very appealing candidates for the next generation of alkali-ion battery cathodes. However, many drawbacks prevent this family of compounds to be applicable to storage systems. Metal fluorides demonstrate a high insulating character, and the mechanisms involved during the discharge/charge processes atom engender large volume changes and a drastic reorganization of the material, which induces poor reversibility. In order to answer these problematics, the present thesis reports the elaboration of innovative synthesis routes for transition metal fluoride compounds and the application of these fluoride materials in alkali-ion battery systems. In a first part, MFx compounds (M = Co, Fe; x = 2 or 3) are studied. Those compounds exhibit high initial capacity but very poor cyclability and low C-rate capabilities. Ex-situ X-ray diffraction and transmission electron microscopy demonstrate that the low reversibility of the processes is mainly due to the conversion reaction occurring during their discharge/charge. In the second part, the syntheses of transition metal fluoride perovskites are reported, as well as their electrochemical properties. NaFeF3 demonstrates excellent performances and reversibility. The study of the mechanisms occurring during its charge/discharge processes towards different alkali systems by ex-situ and operando X-ray diffraction reveals that its crystalline framework is maintained along the cycles, resulting in high reversibility and excellent C-rate performance. This retention of the crystal framework is possible by an electrochemical stabilization of a cubic conformation of FeF3, which is usually only observable at high temperature (400 °C), and can be explained by lower reorganizations within the crystal framework. Similar electrochemical properties could be observed for KFeF3 and NH4FeF3, where ammonium ions are reported for the first time as a charge carrier in alkali-ion systems.

Poly(vinylidene fluoride) PVDF is a semi-crystalline fluoropolymer that attracted researchers' attention more than a decade ago due to its remarkable properties, such as mechanical strength, thermal stability, chemical resistance, good processability, and excellent aging resistance. Due to these excellent properties, PVDF is applied in many applications such as membranes and filtration, biomedical applications, drug delivery, batteries, energy generation, energy storage, sensors, actuators, and energy harvesting applications. The dissertation was inspired by PVDF’s outstanding properties and applications. First of all, the effect of chain topology of on the crystallization and polymorphism between linear and star PVDF homopolymers were studied. Well-defined linear and stars PVDF homopolymers architectures were synthesized by reversible addition−fragmentation chain transfer (RAFT) polymerization. The non-isothermal crystallization study showed an increase in the amount of ferroelectric β-phase with respect to the paraelectric α-phase as the number of arms in the PVDF stars increases. This finding is explained by the increased topological complexity in the stars of several arms, which leads to the preferential formation of the less thermodynamically stable ferroelectric β-phase. Moreover, the isothermal crystallization kinetics of the PVDF stars was faster than the linear PVDF as a result of their speedier nucleation. Secondly, we report the synthesis of poly(n-isopropylacrylamide)-b-poly(vinylidene fluoride) (PNIPAM-b-PVDF), amphiphilic block copolymers with linear and star architectures by RAFT sequential living polymerization. Due to the presence of a lower critical solution temperature (LCST) for PNIPAM (coil-globule transition around 32 °C), the synthesized PNIPAM-b-PVDF block copolymers have thermo-responsive behavior, therefore, potential application in the fabrication of thermo-responsive membranes. All fabricated membranes by nonsolvent-induced phase separation (NIPS) method exhibited thermo-responsive behavior with water permeability and PEG rejection experiments. Moreover, the several heating-cooling cycles showed that the thermal-responsive behavior of these membranes are reversible and stable. Finally, a suggested potential future work is given to synthesize other PVDF-based block copolymers via sequential living polymerizations.