Dynamics of small molecules within the F127 PEO-PPO-PEO triblock copolymer gel and sol phases studied at the molecular scale

The dynamics of naphthalene derivatives with different hydrophobicities bound to F127 polyethyleneoxide-polypropyleneoxide-polyethyleneoxide (PEO-PPO-PEO) micelles in the gel and sol phases were studied using a quenching methodology for the triplet excited states of the naphthalenes. Studies with triplet excited states probe a larger reaction volume than the volumes accessible when using fluorescent singlet excited states. The use of triplet excited states enables the determination of the dynamics between different compartments of a supramolecular system, which in the case of F127 micelles are the micellar core, the micellar corona and the aqueous phase. This report includes laser flash photolysis studies for the four naphthalene derivatives in the F127 gel and sol phases. The triplet excited states were quenched using the nitrite anion as the quenchers. The association and dissociation rate constants of the naphthalenes from the micelles and the quenching rate constants for the naphthalenes bound to the micelles were determines from the curved quenching plot (observed decay rate constant vs. nitrite concentration).

Исследование влияния технологических факторов на неопределенность результатов измерения теплопроводности методом лазерной вспышки

The estimation of the deviation in the measurements of thermal conductivity by the laser flash method for materials with different thermal conductivity coefficients, arising due to the presence of a graphite coating on the sample and the small thickness of the sample, is carried out. A computer model of the method was created in the Comsol Multiphysics software environment. For bulk samples with a graphite coating thickness of 20 μm, the deviation is 5.5 %. The thickness of bulk samples does not affect the measurement results. For materials with low thermal conductivity, a sharp increase in the deviation is observed, reaching 60%. For thermally conductive materials, the deviation is 16-18%. For thin samples less than 10 μm thick, the thickness of the graphite coating does not affect the measurement results. The decisive factor is the duration of the laser pulse.

Thermal diffusivity of corrosion-resistant coating SDP-1

In the present work, the thermal diffusivity of the SDP-1 grade nickel alloy was investigated in the wide temperature range of 300-1476 K. The SDP-1 alloy (Ni-Co-Cr-Al-Y) is the heat-resistant coating for blades of gas turbine plants, providing protection against sulfide-oxide corrosion in the temperature range of 1070-1220 K. The measurements were performed by laser flash method using LFA-427 apparatus. The estimated errors of the obtained data were 2-5% depending on temperature. The thermal diffusivity approximation equations and a table of reference values for various scientific and practical applications were obtained.

Thermophysical properties of NP2 brand nickel

The heat capacity and the thermal diffusivity of NP2 brand nickel were investigated in the temperature interval 296–1000…1375 K of the solid-state, including the region of the magnetic phase transformation. Measurements were carried out on samples from one initial ingot by laser flash technique and method of differential scanning calorimetry using LFA-427 and DSC 404 F1 setups, respectively. The thermal conductivity was calculated based on the measured thermophysical properties. The estimated errors of the obtained results were 2–4%, 3–5%, and 2–3% for thermal diffusivity, thermal conductivity, and heat capacity, respectively. For investigated thermophysical properties the fitting equations and the reference table have been received.

Thermophysikalische Charakterisierung von Wärmedämmschichten

Zusammenfassung Die Effizienzsteigerung moderner Gasturbinen erfordert die stetige Anhebung der Betriebstemperatur. Die derzeitigen Brenngastemperaturen liegen mit über 1400 °C signifikant über der kritischen Temperatur der verwendeten Turbinenstähle. Zur Gewährleistung der Betriebssicherheit werden die Turbinenschaufeln neben Aktivkühlung durch Beschichtung mit thermischen Schutzschichten, sogenannten thermal barrier coatings (TBC), geschützt. Da es sich bei den TBC um Keramikschichten handelt, ist für die Erhöhung der Haftfestigkeit das Aufbringen eines Haftvermittlers (Verbindungsschicht) notwendig. Da die Eigenschaften dünner Schichten stark von den Eigenschaften des Bulkmaterials abweichen können und zudem von der Herstellungsmethode beeinflusst werden, ist eine Untersuchung der thermischen und infrarot-optischen Eigenschaften der tatsächlichen Schichtstrukturen unumgänglich, insbesondere im Hochtemperaturbereich. Hierfür wurden Proben des reinen Trägerstahls, des Trägerstahls mit Haftvermittlerschicht und des kompletten Schichtsystems aus Trägerstahl, Haftvermittlerschicht und Wärmedämmschicht verschiedener Dicken hergestellt und mittels Laser-Flash-Methode untersucht. Die Auswertung erfolgte dabei analytisch, ausgehend von der Trägerstahl-Einschichtprobe, über die Zweischicht- und Dreischichtsysteme. Vervollständigt wurden diese Untersuchungen durch infrarot-optische Charakterisierungen, mit denen sich die Wärmeausbreitung durch die Schichtsysteme beschreiben lässt. Zusammen mit den Laser-Flash Messungen erlaubt dies eine spätere Quantifizierung der einzelnen, bei Keramiken auftretenden, Wärmetransportmechanismen.

Thermal conductivity measurement of infrared optical fibers based on silver halide solid solution crystals

The aim of the study is to measure the thermal conductivity of silver halide light guides based on crystals of the AgCl-AgBr system used in PSD production technologies. The conductivity temperature coefficient of the samples under study were determined by the laser flash method using the LFA 467 (Hyper Flash) installation. We studied mono- and polycrystalline samples of solid solutions with the composition AgCl0,25AgBr0,75 in the temperature range 298–523 K. The thermal conductivity of the investigated materials was then calculated using literature data on density and heat capacity. The thermal conductivity coefficient ranges from 0.80±0,04 to 0.53±0,03 (W/mK), depending on the microstructure of the sample.

Uncertainty Assessment for Very High Temperature Thermal Diffusivity Measurements on Molybdenum, Tungsten and Isotropic Graphite

The French National Metrology Institute LNE has improved its homemade laser flash apparatus in order to perform accurate and reliable measurements of thermal diffusivity of homogeneous solid materials at very high temperature. The inductive furnace and the associated infrared (IR) detection systems have been modified and a specific procedure for the in situ calibration of the used radiation thermometers has been developed. This new configuration of the LNE’s diffusivimeter has been then applied for measuring the thermal diffusivity of molybdenum up to 2200 °C, tungsten up to 2400 °C and isotropic graphite up to 3000 °C. Uncertainties associated with these high temperature thermal diffusivity measurements have been assessed for the first time according to the principles of the “Guide to the Expression of Uncertainty in Measurement” (GUM). Detailed uncertainty budgets are here presented in the case of the isotropic graphite for measurements performed at 1000 °C, 2000 °C and 3000 °C. The relative expanded uncertainty (coverage factor k = 2) of the thermal diffusivity measurement is estimated to be between 3 % and 5 % in the whole temperature range for the three investigated refractory materials.