Temperature scans

McIntyre B J, Salmeron M and Somorjai G A 1993 A variable pressure/temperature scanning tunnelling microscope for surface science and catalysis studies Rev. Sc/. Instrum. 64 687... 

Gdhde W, Tittel J, Basche T, Brauchle C, Fischer U C and Fuchs H 1997 A low-temperature scanning confocal and near-field optical microscope Rev. Sc/. Instrum. 68 2466-74... 

VSP experiments allow the comparison of various process versions, the direct determination of the wanted reaction adiabatic temperature rise, and the monitoring of the possible initiations of secondary reactions. If no secondary reaction is initiated at the wanted reaction adiabatic final temperature, a further temperature scan allows the... 

Fig. 9.15 HS fraction in the region of the transition temperature measured by NFS on [Fe(tpa) (NCS)2]. The values derived during a temperature scan with increasing (decreasing) temperature are marked with upward directed triangles (downward directed triangles). (Taken from [41])...

Fig. 2.4. (a) Thermal desorption blank experiment. The Pt electrode was held at 0.45 V vs. RHE in the base electrolyte (5 x 10 2 M H2S04) during 120 s and then transferred to the UHV. (b) Thermal desorption spectra of adsorbed CO on Pt after adsorption from an aqueous solution. Temperature scan 5 K/s. 

Our laboratories are currently equipped with three UHV Omicron microscopes, a variable-temperature scanning tunneling microscope (STM), a room-temperature atomic force microscope (AFM)/STM, and a low-temperature liquid helium bath cryostat STM, all of which are currently driven by Omicron Scala software and electronics. 

Isochronal temperature scans reflect or contain information about the relaxation parameters. It is apparent (Figure 1) that the relaxed and unrelaxed moduli, Ep E(j are approximated by the high and low... 

These parameters are determined by non-linear least-squares optimization of the fit of the function to both the experimental storage and loss moduli curves. As emphasized, the two determiners of temperature-scan peak width referred to above (i.e., in terms of equation (2), activation energy AH of x0 and a ) have features that allow distinguishing... 

Safety studies of the graphite anode samples were performed using a Perkin-Elmer Differential Scanning Calorimeter (DSC, model Pyris 1) instrument. The temperature scanning rate was 10 C/min over a temperature range of 50 to 375°C. 

Bellec A, Riedel D, Dujardin G (2008) Dihydride dimer structures on the Si(100) H surface studied by low-temperature scanning tunneling microscopy. Phys Rev B 78 165302... 

DSC can be used effectively in the isothermal mode as well. In this case, the container with the sample is inserted into the DSC preheated to the desired test temperature. This type of experiment should be performed to examine systems for induction periods that occur with autocatalytic reactions and with inhibitor depletion reactions. (Reactions with induction periods can give misleading results in the DSC operated with increasing temperature scans.) Autocatalytic reactions are those whose rates are proportional to the concentration of one or more of the reaction products. Some hydroperoxides and peroxy esters exhibit autocatalytic decomposition. Inhibitor depletion can be a serious problem with certain vinyl monomers, such as styrene and acrylic acid, that can initiate polymerization at ambient temperatures and then selfheat into runaways. Isothermal DSC tests can be used to determine a time to runaway that is related to the inhibitor concentration. 

Method involves placing a specimen between parallel plate capacitors and applying a sinusoidal voltage (frequencies ranging from 1 mHz to 1 MHz) to one of the plates to establish an electric field in the specimen. In response to this field, a specimen becomes electrically polarized and can conduct a small charge from one plate to the other. Through measurement of the resultant current, the dielectric constant and dielectric loss constant for a specimen can be measured. The sharp increases in both the dielectric constant and the dielectric loss constant during a temperature scan are correlated with the occurrence of Tg... 

J.S. Shah and A. Beckett, A preliminary evaluation of moist environment ambient temperature scanning electron microscopy (MEATSEM), Micron, 10 13-23, 1979. 

Glass transition temperatures of the uv-hardened films were measured with a Perkin Elmer Model DSC-4 differential scanning calorimeter (DSC) that was calibrated with an indium standard. The films were scraped from silicon substrates and placed in DSC sample pans. Temperature scans were run from -40 to 100-200 °C at a rate of 20 ° C/min and the temperature at the midpoint of the transition was assigned to Tg. 

During a temperature scan from RT to 1100°C the effusion of C02 and H20 has been observed from an anodic oxide film, as shown in Fig. 5.8. The detected amount of C02 could be explained by a monolayer of hydrocarbons adsorbed on... 

FIGURE 15.6. Cyclic voltammograms of PtSn-1 and RSn-2 in 0.5M H2SO4 at room temperature, scan rate lOOmV/s. 

FIGURE 15.7. Cyclic voltammograms of PtSn electrodes in 0.5 M CH3CH2OH/O.I M HCIO4 electrolyte at room temperature. Scan rate 50 mV/ s. 

A sample of the polymer to be studied and an inert reference material are heated and cooled in an inert environment (nitrogen) according to a defined schedule of temperatures (scanning or isothermal). The heat-flow measurements allow the determination of the temperature profile of the polymer, including melting, crystallization and glass transition temperatures, heat (enthalpy) of fusion and crystallization. DSC can also evaluate thermal stability, heat capacity, specific heat, crosslinking and reaction kinetics. 

The heat capacity is the amount of energy required to increase the temperature of a unit mass of material. It is commonly measured using a differential scanning calorimeter (DSC). The heat capacity depends on the resin type, additives such as fillers and blowing agents, degree of crystallinity, and temperature. A temperature scan for the resin will reveal the Tg for amorphous resins and the peak melting temperature and heat of fusion for semicrystalline resins. The heat capacities for LDPE and PS resins are shown in Fig. 4.15. 

Katano, S., Herceg, E., Trenary, M., Kim, Y. and Kawai, M. (2006) Single molecule observations of the adsorption sites of methyl isocyanide on Pt(lll) by low-temperature scanning tunneling microscopy. J. Phys. Chem. E, 110, 20344-9. 

Thermal analysis, moisture uptake and dynamic mechanical analysis was also accomplished on cured specimens. Thermal analysis parameters used to study cured specimens are the same as those described earlier to test resins. The moisture uptake in cured specimens was monitored by immersing dogbone shaped specimens in 71 C distilled water until no further weight gain is observed. A dynamic mechanical scan of a torsion bar of cured resin was obtained using the Rheometrics spectrometer with a temperature scan rate of 2°C/minute in nitrogen at a frequency of 1.6Hz. The following sections describe the results obtained from tests run on the two different BCB resin systems. Unless otherwise noted all tests have been run as specified above. 

Figure 4. TICA temperature scan of uncured BCB/BMI resin blend. Tan the in-phase (a) response and the out-of-phase (b) response are given as a function of temperature.

In DSC the sample is subjected to a controlled temperature program, usually a temperature scan, and the heat flow to or from the sample is monitored in comparison to an inert reference [75,76], The resulting curves — which show the phase transitions in the monitored temperature range, such as crystallization, melting, or polymorphic transitions — can be evaluated with regard to phase transition temperatures and transition enthalpy. DSC is thus a convenient method to confirm the presence of solid lipid particles via the detection of a melting transition. DSC recrystaUization studies give indications of whether the dispersed material of interest is likely to pose recrystallization problems and what kind of thermal procedure may be used to ensure solidification [62-65,68,77]. 

A typical paper on cryo-crystallographic applications is usually concluded by the author s encouragement to study more and more samples at lower and lower temperature. The message from this chapter is instead somewhat different and can be summarized as follows (1) use temperature critically and think carefully when it is necessary to measure structures or properties of crystals at lower temperature] (2) use all the additional information available when studying the sample at low temperature] (3) do not limit the temperature scans in the range below ambient conditions (even when studying organic crystals). 

Figure 3. Thermal gravimetric analysis of DuPont PI2545. Conditions temperature scan, 4°C/min precured 20 min at 70°C and 30 min at 120°C sample weight,...

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