Carbon fiber (CF) 8-harness satin weave, T650/Neximid system of [(+45/-45)/(0/90)]2S and [(0/90)]4S layup was manufactured using resin transfer molding (RTM). The material was cut into 3-point bending specimens and treated for 24 hours in a burn oven at T=(320,350,375,400,450 & 500)°C. The material was tested according to ASTM E1640-13 using dynamic mechanical thermal analysis (DMTA). Un-treated material showed Tg levels of 384°C and 392°C for the respective layups. It was found that pre-Tg treatment between 320-375°C affected this material parameter up to similar levels as previous studies of post Tg exposure for 2h to ~420°C [4]. Subjecting the material for post-Tg exposure at 400°C showed a rapid change up to ~480°C for [(0/90)]4S laminate. Indications that this resin system could reach levels above 500°C was found for [(+45/-45)/(0/90)]2S layup. However, one of these specimens were unfit for testing. DMTA tested material for 400°C showed indications of degradation, found by a broadening of the tan delta peak. This can be put in relation to epoxy where a similar behavior appear after 24h exposure at 150°C. Furthermore, it was showed that poor quality laminate, elevated mass loss at this temperature. When the material was subjected to as high temperatures as 450°C only remaining fibers were found. At 500°C these were almost fully oxidized. 400°C data was predicted by the use of activation energy along with TG extrapolation. It was possible to show that ~1/8 out of this 8-layered structure, (½ of each surface layer), was degraded after 400°C exposure for 24h, resulting in diffusion limited oxidation (DLO). Last but not least, DLO assumptions was used to predict the storage modulus change for thermo-oxidative degradation of 400°C samples with Classic Laminate Theory (CLT). A ~4% stiffness decrease was predicted by this method. The drop is regarded as a loss in tensile stiffness of the outer damaged layer. This was compared by 3-point bending DMTA data showing a ~7% decrease. This model could thus be regarded as a contributing factor for the stiffness decrease of this complex degradation process. / Kolfiber, 8-harness satin väv, T650/NEXIMID system med [(+45/-45)/(0/90)]2S och [(0/90)]4S orientering, tillverkades via RTM. Från materialet tillverkades 3-punkts böjprover. Dessa behandlades i 24 timmar vid T=(320, 350, 375, 400, 450 & 500)°C, i en brännugn. Materialet testades i enighet med ASTM E1640-13 via DMTA. Obehandlat material visade Tg nivåer av 384°C och 392°C för de respektive uppläggningarna. Pre-Tg exponering, vid 320-375°C, påverkade Tg upp till liknande nivåer som tidigare studier, (post-Tg 2h), ~420°C [4]. När materialet utsätts för post Tg exponering under 24 timmar vid 400°C kunde man se en snabb förändring av Tg, upp till ~480°C för [(0/90)]4S laminatet. Från [(+45/-45)/(0/90)]2S laminatet kunde man dessutom se indikationer på att nivån kunde nå över 500°C. Däremot var en av dessa prov inte kvalificerad för test efter behandlingen. DMTA testat material för 400°C visade indikationer av nedbrytning, via en breddning av piken för tan-delta kurvan. Det var dessutom möjligt att se att laminat av sämre kvalitet påverkade viktminskningen signifikant högre vid denna exponering. När material utsattes för så höga temperaturer som 450°C var endas fiber kvar efter test, vilket vid 500°C nästan var fullt nedbrutna. 400°C data förutspåddes via extrapolering av TG och Arrhenius beräkning. Beräkningen ledde till en övre gräns för nedbrytningen. Vidare var det möjligt att visa att ~1/8 av dessa 8-lager bröts ner efter 24 timmars exponering vid 400°C. Nedbrytningen motsvarar ½ av vartdera ytlager via diffusions begränsad oxidation (DLO). Sist men inte minst, kunskapen om DLO användes för att förutspå styvhetsförändringen vid termo-oxiderande nedbrytning med hjälp av klassisk laminat teori (CLT). DLO antogs resultera i en volymfraktionsförändring i det yttersta lagret. Detta implementerades i CLT där man kunde beräkna en ~4% styvhetsminskning via denna modell där det yttre skadade lagret har en reducerad dragstyvhet. Från testade böjprover i DMTA kunde man se en verklig ~7% styvhetsminskning för samma exponeringsvillkor. Modellen kan därmed ses som en bidragande del av denna komplexa nedbrytningsprocess.

Polymeric systems near their glass transition are known to exhibit heterogeneous dynamics that evolve both over space and time, yet many of the underlying principles of these dynamics are still poorly understood. In this thesis, experimental single molecule studies aimed at uncovering the dynamics of polystyrene near its glass transition temperature are described. In a first approach, the influence of temperature on the timescales associated with dynamic heterogeneity – also referred to as exchange times – are identified by following the dynamics of a fluorescent perylene diimide probe embedded in a high-molecular weight polystyrene host. No clear influence on the lifetime of dynamics is found in the temperature regime Tg to Tg + 10 K. In a second study, heterogeneous dynamics are investigated in the context of molecular weight and fragility. In a similar experimental approach to that of the first study, two fluorescent dyes are utilized to report on the rotational dynamics of low- to high-molecular weight polystyrene hosts. In accordance with previous reports, the stretching exponent, β, is found to be correlated with the system’s molecular weight, even on a single molecule level. However, no clear correlation with the system’s exchange time was found. In a final study, several single molecule approaches aimed at uncovering the dynamics in confined polystyrene films are described. As no evidence for previously-described mobile surface molecules has been found, this final chapter is meant to provide a basis for future single molecule studies in confined systems.

The flexible substrate was fabricated by BaTi4O9 mixed with O-Cresol Novolac Epoxy, polyether imide or surface active agents. The electrical and physical characteristic measured had been finished. The dielectric property influence of substrate was changed from percentage of BaTi4O9. The dielectric constant model was used by Jayasundere and Smith equation (J. S. eq.) and Lichtenecker equation (L. eq.) The study of crystalline grain, orientation and phase transfer temperature was used by SEM, XRD, and DSC, respectively. The dielectric constant and dielectric loss tangent of the composite was measured using an HP4294A impedance analyzer. The TM mode calculated by resonate frequency of the composite was measured using an HP4156C network analyzer. The dielectric constant was obtained to TM mode at high frequency. The result was showed that dielectric constant at low frequency of BaTi4O9, OCN Epoxy and PEI are 57, 5.8 and 3.65, respectively. OCN Epoxy is better than PEI of electrical characteristic. However, OCN Epoxy is not flexible. For this reason, the PEI was focused on electrical property at high frequency. The BaTi4O9 exhibited a dielectric constant of 39 at frequency during 3~10 GHz. The dielectric constant was measured of 10 at frequency during 2~16 GHz with 70 wt% PEI composite. The dielectric constant is higher than FR-4 substrate to 6.4 of the composite. The low dielectric constant is obtaining to reduce stuffing.

Using low-temperature (650¢J) Ce3+:YAG doped glass (LTCeYDG) phosphor layer instead of conventional Ce:YAG doped silicone phosphor layer applied to high-power phosphor-converted white-light-emitting diodes (PC-WLEDs) is demonstrated.The glass transition temperature (Tg) of silicone is 150¢J but glass is 750¢J,it shows the glass were employed in high power LED than silicon. The uniformity of phosphor powder doped glass is an important item to discriminates between good and bad. Quantize the uniformity of glass phosphor by image processing software and Distribution Uniformity (Du). Calculate the uniformity of phosphor powder mix with glass powder which has different particle size and measurement optical properties of glass phosphor which has different uniformity. The Du of glass phosphor are 64.46%, 84.65%, 85.24% , 91.85% and the quantum efficiency are 18.49%, 28.31%, 29.73%, 28.56% ,respectively. By using Ceramic tube and low temperature glass powder sintering glass phosphor is a new fabrication. Compare with last fabrication, new fabrication reduce 100¢Jfabrication temperature from 750¢J to 650¢J, 70% material savings and high luminous efficiency. The quantum efficiency and lumen per watt were improved about 7 percentage point from 22.3% to 29.1% and 4.2 lm/W from 36.4 lm/W to 40.68 lm/W. We used the XRD to analyze the glass phosphor of last fabrication and new fabrication and the results show that the higher thermal stress destroys the structure of YAG, lower fabrication temperature used to get higher luminous efficiency.

Not available / text

The properties of polymers, thin films or bulk, are profoundly influenced by interactions at interfaces with dissimilar materials. Thin, supported, polymer films are subject to interfacial instabilities, due largely to competing intermolecular forces, that cause them to rupture and dewet the substrate. The addition of nanoparticles (such as clay sheets, metallic or semiconductor nanocrystals, carbon nanotubes, etc.) to polymers can substantially affect bulk properties, such as the glass transition and viscosity, and influence the processability of the material. In this dissertation, we contribute to a fundamental understanding of the role of interfacial interactions on both the instabilities exhibited by polymer thin films and the properties displayed by polymer-nanoparticle mixtures. While conditions under which the destabilization of compositionally homogeneous thin films occurs are relatively well understood, the mechanisms of film stabilization in many two-component thin film systems are still unresolved. We demonstrate that the addition of a miscible component to an unstable film can provide an effective means of stabilization. The details of the stabilization mechanism are understood in terms of the compositional dependence of both the macroscopic wetting parameters and the effective interface potential for the system. We find that the suppression of dewetting in the system is not an equilibrium stabilization process and propose a mechanism by which the increased resistance to dewetting may occur. There is also significant interest in understanding the extraordinary property enhancement of polymers that are enabled by the addition of only small concentrations of nanoparticles. If these effects could be distilled down to a few simple rules, they could be exploited in the design of materials for specific applications. In this work, the influence of C60 nanoparticles on the bulk dynamical properties of three polymers is examined. Based on the findings from a range of measurement techniques, including differential scanning calorimetry, dynamic mechanical analysis, dynamic rheology and neutron scattering, we propose that the changes in the glass transition temperature for the polymer-C₆₀ mixtures can be understood in terms of a percolation interpretation of the glass transition. The proposed mechanism is also characterized computationally. / text

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 153-161).

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 217-223). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 217-223). Also available on the Internet.