Silica cycle measurement

Degree of crystallinity, onset- and peak temperatures for melting inf and 2" heating-cooling cycle for two parallel polypropylene samples containing PIB grafted silicas were measured. The true mass fraction of polypropylene in each composite was used in the calculation of crystallinity from the heat of fusion for 100% crystalline PP (190 J/g). 

It is demonstrated that the quasi-static stress-strain cycles of carbon black as well as silica filled rubbers can be well described in the scope of the theoretic model of stress softening and filler-induced hysteresis up to large strain. The obtained microscopic material parameter appear reasonable, providing information on the mean size and distribution width of filler clusters, the tensile strength of filler-filler bonds, and the polymer network chain density. In particular it is shown that the model fulfils a plausibility criterion important for FE applications. Accordingly, any deformation mode can be predicted based solely on uniaxial stress-strain measurements, which can be carried out relatively easily. 

Thickness and, correspondingly, capacitance variation was less than 2%. The absence of impurity peaks in XPS spectra of silica-coated specimens clearly demonstrates the achieved purity. Yield, defined as the percentage of functioning vs. total measured capacitors, was 100%. Breakdown field strength was in the range 1.1-5.4 MV/cm and leakage current was about lO -lO A/cm at 0.5 MV/cm. Capacitance density was 23-350 nF/cm dependent on thin film thickness and materials. No breakdown was observed after 20 cycles between 0-40 V. Time dependent dielectric breakdown (TDDB) was 185 s at 40 V for ten of the patterned capacitors. 

Fig. 5. Receding angle on a pollution layer of fumed silica af lied to a silicone rubber sample, measuring new samples with different LMW contents (left) and repeated measuring during cycles of pollution and cleaning (right).

A controlled gas-solid phase reaction of titanium(IV) isopropoxide with silica surface pretreated at 600°C was achieved at between 110 and 180°C in an atomic layer deposition (ALD) reactor. Element determinations and DRIFTS measurements suggested the formation of two isopropoxide ligand containing complex on silica with a titanium density of -1.25 atoms/nm upport- At reaction temperatures exceeding 180°C the growth was no longer determined by the surface. The reaction at 160°C was followed by a calcination treatment at 500°C and the consecutive precursor - oxygen cycles were repeated from one to seven times. 

FIGURE 5.64 Consecutive cycles of exhaustion and reactivation of mixed oU-silica compound in 10mM solution of the anionic surfactant sodium dioctyl-sulfosuccinate (AOT). An initially active antifoam (defoaming time 5 s) gradually loses its activity with the number of foam formation/destruction cycles in a standard shake test. The introduction of silicone oil results in a perfect restoration of the antifoam activity. Five exhaustion curves (indicated by roman numbers the symbols indicate the experimentally measured defoaming time) and the corresponding four reactivation events (the vertical dashed lines) are shown. (Adapted from Denkov et ah, Langmuir, 16, 2525, 2000.)... 

There are no published studies of silica on coral reefs. Silica minerals are not abundant on coral reefs, so the biogeochemistry of silica has been ignored. It is evident, however, from the results of our uptake experiments (we measure silica in all our experiments) that silica concentrations in the water sometimes decreases and sometimes increases. This result is probably related to whether benthic diatoms are occupying the reef surfaces. At Biosphere 2 coral reef mesocosm, silica goes through a distinct seasonal cycle related to blooms of benthic diatoms (Atkinson etal., 2001). Concentrations of silica in pore-water can also change seasonally (Falter, 1998). 

Thermal cycling will be lessened if the control (but not the measuring) thermocouple is placed between the liner and the furnace wall. It is highly advisable that the fused silica jacket about the welded container be sufficiently long to extend from the end of the furnace to permit condensation of the tetrahalide, should a leak develop. Unless a thermal gradient is required, the tantalum tube itself should be centered in the furnace. Although the explosion hazard is very slight if these procedures are followed, the open ends of the furnace should still be shielded from workers. 

Redox experiments and ESR determination of Cu2+ were performed with a circulation all-glass apparatus equipped with a magnetically driven pump. The sample (0.2 to 1.0 g) was placed in a silica reactor equipped with a side ESR tube. All the samples before the redox cycles were treated in O2 at 773 K. The redox cycles consisted of (i) heating in He flow at 823 K for 2h, followed by evacuation at 773 K and heating in O2 at 773 K (ii) evacuation at RT followed by reduction with CO at 773 K (iii) evacuation at 773 K followed by a second treatment with O2 at 773 K. During the treatments (i) to (iii), the pressure of O2 or CO was monitored with a pressure transducer (MKS Baratron, sensitivity 1 Pa) until a nearly constant pressure was reached. All these measurements allowed the variation of the average oxidation number of copper to be followed. The acquisition or loss of electrons are expressed as e/Cu (number of electrons/total number of Cu atoms). At the end of treatments (i) to (iii), ESR spectra of Cu2+ species were recorded at RT. ESR measurements were carried out on a Varian E-9 spectrometer equipped with an on line computer. Absolute concentrations of... 

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