Peak decomposition

Las but not least, sample preparation is also an important issue. If we want to examine nanocrystalline powder samples. The grain size must be just a few nanometers, the layer, formed by these nanocrystals must be as thin as possible (to minimize dynamic difiraction), continuous and self-supporting. In many cases not all these requirements are fulfilled simultaneously. The nanocrystalline material to be studied is frequently present on a thin supporting carbon layer. In such cases peak decomposition can not yield an acceptable fit unless the presence of the amorphous material (in the form of a few diffuse rings) is taken explicitly into account in the model to be fitted. The size of the background is also affected by scattering in such a carbon support. 

No peaks Decomposition of TMS ether derivative due to moisture Prepare derivative again under dry conditions... 

The thermal stability of poly(vinyl chloride) is improved greatly by the in situ polymerization of butadiene or by reaction with preformed cis-1,4-polybutadiene using a diethyl-aluminum chloride-cobalt compound catalyst system. The improved thermal stability at 3-10% add-on is manifested by greatly reduced discoloration when the modified poly-(vinyl chloride) is compression molded at 200°C in air in the absence of a stabilizer, hydrogen chloride evolution at 180°C is retarded, and the temperature for the onset of HCl evolution and the peak decomposition temperature (DTA) increase, i.e. 260°-280°C and 290°-325° C, respectively, compared with 240°-260°C and 260°-280°C for the unmodified homopolymer, in the absence of stabilizer. The grafting reaction may be carried out on suspension, emulsion, or bulk polymerized poly(vinyl chloride) with little or no change in the glass transition temperature. 

Whereas the onset of decomposition, under the conditions described above, for untreated PVC was observed at approximately 240°-260°C and the peak decomposition temperature was approximately 260°-280°C, the grafted PVC prepared from the same untreated base polymer showed the onset of decomposition at approximately 260°-280°C and a peak decomposition temperature of 290°-325°C. 

The degradation and combustion behavior of polycarbonate/POSS hybrid system has been reported recently.48 Different loading contents of trisilanolphenyl-POSS (TPOSS) were melt blended with polycarbonate matrix (PC). The data shown in Table 8.4 indicate that no improvement in thermal stability parameters (i.e., onset decomposition temperature and peak decomposition temperature) was observed compared to the neat polycarbonate. The thermo-oxidative degradation process of the hybrid system proved to be a complicated process, which includes hydrolysis/alcoholysis of the carbonate linkage, free radical oxidative chain degradation, reformation, and branching and cross-linking reactions. 

Fichtner et al studied the kinetic effects of Mg(AlH4)2 doped with 2 mol% TiCl3 and mechanically milled for up to 100 minutes. The studies showed that the peak decomposition temperature was reduced in the presence of the titanium dopant. The starting point of the first decomposition step shifted to lower temperatures however, complete dehydrogenation to MgH2 still requires heating to -200 °C. 

For instance, the three carbons of the y-APS backbone are not resolved in the Cls region of the XPS spectrum of a 300 nm thick film of y-APS deposited on a silicon wafer (Fig. 4). However, the observed broad peak obviously stems from several contributions, as suggested by the Full Width at Half Maximum (FWHM) of 2.5 eV. An objective two-peaks decomposition (resulting FWHM s = 1.5 eV) fits the experimental curve correctly, but cannot be easily related to the structure of the molecule (H2N-CH2-CH2-CH2-Si(OH)3), which would suggest three peaks (one for each carbon. 

Table 1 Core-Electron Binding Energies (CEBEs, in eV) for the trihydroxy-form of y-APS, y-APS(OH)s, compared with a tentative three-peak decomposition of the Cls region of spin-coated y-APS. All values are referenced to the Fermi level of the spectrometer [22]...

Extra Peaks Extra peaks are very rarely due to a colunm problem. It is actually fairly difficult to envision a mechanism, by which tbe chromatographic column proper generates distinct peaks. Decomposition of tbe stationary phase can cause a drifting baseline, but a distinct peak can be obtained only if the injection of the sample is causing the decomposition. 

The 0.3 wt% 1,3-2,4-di(p-hydroxyl) benzylidene sorbitol improves eiystallinity and crys-talhzation degree of compression molded iPP. Increased melting peak, decomposition temperature, and improved thermal stability of iPP was also observed. The notched Izod impact strength, elongation at break, tensile strength, and flexural strength of iPP were increased by 19.37%, 44.94%, 69.59%, 47.87% and 85.34%, respectively. ... 

Fig. 14.22 Emission spectra of Luo.98V04 2.0%Bi excited at 265 nm at 10 to 300 K. Inset a Dependence of the reiative emission intensity of Luo.98VO4 2.0%Bi on temperanire on excitation of 380 nm Inset (b). Gaussian-peak decomposition of the emission spectmm at 100 K. Reproduced from Ref. [36] by permission of John Wiley Sons Ltd.

Maximum damping peak (glass transition of nitrocellulose) 446-451 K (173-178 °C), relative modulus decreases by 2-3 orders of magnitude sub-damping peak (decomposition and cross-linking of nitrocellulose) ca 456-483 K (ca 183-210 °C), relative modulus increases. 

It was also reported that the thermal stability of the aliphatic polyesters, i.e. poly (e-caprolactone) (PCL), poly(gfycolide) (PGA), and poly(D,L-lactide) (PLA) investigated under dynamic heating in an inert atmopshere, based on the peak decomposition temperature, was in the order of PCL > PGA > PLA [44],... 

These surfactants also possess sufficiently high thermal stability to survive the meltprocessing conditions of any PET grade. As shown in Figure 4.2, the decomposition temperatures of nanoclays organically modified with alkylimidazolium are above 3(X)-320 °C, with a peak decomposition temperature around 400 °C, whereas the typical... 

Smoothing reduces the noise and clarifies the information provided by the recorded spectrum. However any smoothing procedure may introduce distortion in the spectrum and should be used with caution. It is prohibited when peak decomposition is performed. The least-squares central point smoothing technique proposed by Savitsky and Golay is found on most recent data treatment systems. 

The chemical information generated by decomposition of a given peak is free from uncertainties concerning the sensitivity factors. In absence of any reason to proceed otherwise, the following two-step procedure may be recommended for peak decomposition, once the shape of the components (combinaison of Gauss and... 

Lorentz functions depending on the experimental conditions cf. the section on Peak Decomposition) and the number of components have been tentatively selected. 

This two-step decomposition procedure offers areasonable balance between avoiding bias in curve fitting, insuring the reproducibility required for a comparison of samples and providing a consistent basis for quantification. Whatever the procedure, it should be clearly stated when quantitative data are extracted from peak decomposition. 

The following examples illustrate the need to be critical in performing peak decomposition, even regarding the number of components per peak. The C Is peak of maltodextrin and poly(L-serine) in Fig. 20 shows clearly a component, which is due to C—(C, H) of surface contaminants and has been set at 284.8 eV. If the structural... 

The problem of accuracy is further illustrated by Fig. 34 for a series of strains of B. subtilis. This presents a plot of the (0+A )/C concentration ratios as a function of the proportion of carbon bound to oxygen or nitrogen (cf. the sections on Semi-Quantitative Use of Angle Resolved Analysis and Peak Decomposition and Assignment) i.e. C total-[C—(C,H)] /C total, abbreviated by Cox/C. The results obtained with two spectrometers are presented. The differences between the two spectrometers are more important along the ordinate scale than along the abscissa... 

Figure 35 presents the O Is, N Is, and C Is peaks of three different strains of Bacillus subtilis. The peak decomposition is also shown. For the C Is and O Is peak of microorganisms, it is recommended to perform the second step (cf. the section on Peak Components of Biochemical Compounds), imposing the same FWHM for all components of a given peak this value may be let to be adjusted during the iterative process or may be the average of the values obtained in the first step. 

XPS is often used to detect the changes of surface composition brought by the treatment. In many cases, each step of the modification procedure is monitored by XPS. The useful information may be limited to the appearance or the disappearance of given elements from the survey spectra. More often, careful peak decomposition allows the quantification of new chemical functions brought at the surface. In some cases, the molecules used for the surface treatment bear a tag (e.g. fluorine atoms), which facilitates their detection. In some advanced studies, the results are modeled, taking into account the formation of successive layers with different properties. The two following examples illustrate the typical approach that is used when analyzing surface-modified materials by XPS. 

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