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Crystallinity, analysis

To determine the crystallinity of a sample, many structure-insensitive properties can be used, since they can be separated into contributions from the amorphous and the crystalline phase. Three examples are given in this section X-ray, infrared, and [Pg.512]

Difiradion pattern of drawn polyethylene, showing oriented crystals (110 and 200 refledions) and the unoriented amorphous halo. [Pg.513]

A technique that leads to quantitative data for the determination of the volume-fraction crystallinity is the infrared analysis. As an example, in Fig. 5.84 one can see the two areas in the IR spectrum of polyethylene where amorphous and crystalline samples are largely different (frequencies A and C). The equation in the upper right-hand comer permits now a quantitative evaluation, as is documented in Fig. 5.85 for [Pg.514]

For bulk materials, all techniques based on structure-insensitive properties, as described in this section and elsewhere, yield closely similar data. The crystallinity model is thus a valid defect concept to describe structure-insensitive properties of semicrystalline polymers. It breaks down for three-phase systems, consisting, for example, of a crystalline phase, a mobile amorphous phase, and a rigid-amorphous fraction (see Chap. 6). In addition, one does not expect valid answers for structure-sensitive properties. [Pg.516]


Miller, A. G., Burnell, J. M. The Effect of Crystal Size Distributions on the Crystallinity Analysis of Bone Mineral. Calc. Tiss. Res. 24, 105 (1977)... [Pg.123]

Preparation of Platinum Tetrafluoride.—The platinum tetrafluoride-bromine trifluoride adduct was prepared by Sharpe s method and heated to 180° under vacuum for 12 hr., which removed most of the bromine trifluoride. The remainder was displaced as bromine penta-fluoride by fluorinating with diluted fluorine at 250°. Platinum tetrafluoride prepared in this way was yellow-brown and crystalline. Analysis wa.s by pyrohydrolysis to 300 (Found F, 27-8 Pt, 71-7 Br, absent. Calc, for Ptp4 F, 28-0 Pt, 72-0%). [Pg.267]

Crushed, ground, deslimed in tap water, run through magnetic separator, washed in 0.5 M HCI, and in cold and hot water, crystalline, analysis (15 elements) available. [Pg.730]

The X-ray diffraction (XRD) measurements were performed on a Bmker AXS-D8 Advance model system. The diffracted intensity of Cn Ka radiation (0.154 nm, 40 kV and 40 mA) was measured in a 20 range between 10° and 70°. Ground kenaf fibers and hydrolyzed cellulose sample were subjected to crystallinity analysis. [Pg.199]

Another technique for crystallinity analysis is the measurement of pole figures. It is widely applied for thin films, LPE films, melt-processed polycrystalline samples with a noticeable texture (Goyal et al. 1993). In fig. 33, a good crystallinity of the Y123 LPE film is evidently obtained due to a specific growth mechanism, mentioned above (sect. 5.4), despite the large misfit between the film and the MgO substrate. Differential interference contrast (DIM or Nomarski) microscopy can be successfully applied to observe misorientation on flat ( mirror-like ) surfaces (Klemenz and Scheel 1993). [Pg.180]

The pillar[5]arene moiety in H5.23 formed a stable host-guest complex with 1,4-dicyanobutane (G5.29) [kT=(6.1 0.2)xl0 (run 118)]. In contrast, the crown ether moiety in H5.23 captured paraquat (G5.49) stably [iir=(2.6 0.6)xl0 (run 119)]. When the two guest molecules were added to H5.23 at the same time, the selective inclusion of two guest molecules by pillar[5]arene and crown ether rings took place, which was confirmed by single X-ray crystalline analysis of the complex. [Pg.114]

The powder dried/annealed at 500°C for 5 h is used as the 100% crystalline reference for the crystallinity analysis. The crystallite sizes were calculated using Scherrer s equation ... [Pg.67]

Crystallization fraaionation (CRYSTAF) " and temperature-rising elution fractionation (TREF) are used for chemical composition or crystallinity analysis. For copolymers, CRYSTAF and TREF provide information about the CCD. The drawbacks of these methods are that (1) they are very time consuming and (2) they work only for crystal-lizable polyolefins. [Pg.57]

Toby B FI and Egami T 1992 Accuracy of pair distribution function analysis applied to crystalline and noncrystalline materials Aota Crystaiiogr.k 48 336-46... [Pg.1383]

Because x-rays are particularly penetrating, they are very usefiil in probing solids, but are not as well suited for the analysis of surfaces. X-ray diffraction (XRD) methods are nevertheless used routinely in the characterization of powders and of supported catalysts to extract infomration about the degree of crystallinity and the nature and crystallographic phases of oxides, nitrides and carbides [, ]. Particle size and dispersion data are often acquired with XRD as well. [Pg.1791]

Boron trioxide is not particularly soluble in water but it slowly dissolves to form both dioxo(HB02)(meta) and trioxo(H3B03) (ortho) boric acids. It is a dimorphous oxide and exists as either a glassy or a crystalline solid. Boron trioxide is an acidic oxide and combines with metal oxides and hydroxides to form borates, some of which have characteristic colours—a fact utilised in analysis as the "borax bead test , cf alumina p. 150. Boric acid. H3BO3. properly called trioxoboric acid, may be prepared by adding excess hydrochloric or sulphuric acid to a hot saturated solution of borax, sodium heptaoxotetraborate, Na2B407, when the only moderately soluble boric acid separates as white flaky crystals on cooling. Boric acid is a very weak monobasic acid it is, in fact, a Lewis acid since its acidity is due to an initial acceptance of a lone pair of electrons from water rather than direct proton donation as in the case of Lowry-Bronsted acids, i.e. [Pg.148]

First, considerably greater emphasis has been placed on semimicro techniques and their application to preparations, separations, analysis and physical determinations such as those of molecular weight. We have therefore greatly expanded the section on Manipulation on a semi-micro scale which was in the Third Edition, and we have described many more preparations on this scale, some independent and others as alternatives to the larger-scale preparations which immediately precede them. Some 40 separate preparations on the semi-micro scale are described in detail, in addition to specific directions for the preparation of many classes of crystalline derivatives required for identification purposes. The equipment required for these small-scale reactions has been selected on a realistic basis, and care has been taken not to include the very curious pieces of apparatus sometimes suggested as necessary for working on the semi-micro scale. [Pg.585]

Using density as the property measured to determine crystallinity, evaluate 0 as a function of time for these data. By an appropriate graphical analysis, determine the Avrami exponent (in doing this, ignore values of 6 < 0.15, since errors get out of hand in this region). Calculate (rather than graphically evaluate) the value of K consistent with your analysis. [Pg.267]

In milk fat, cholesterol is associated with Hpoproteins in the milk fat globule. It is also a component of animal membranes and controls rigidity and permeabihty of the membranes. Cholesterol has interesting surface properties and can occur in Hquid crystalline forms. Plants contain sterols such as P-sitosterol [83-46-5] (4b) or stigmasterol [83-48-7] (4c). Their functions in plant metaboHsm are not yet well understood. Analysis of sterols has proven useful for detection of adulteration of edible fats (9). [Pg.124]

Microscopy (qv) plays a key role in examining trace evidence owing to the small size of the evidence and a desire to use nondestmctive testing (qv) techniques whenever possible. Polarizing light microscopy (43,44) is a method of choice for crystalline materials. Microscopy and microchemical analysis techniques (45,46) work well on small samples, are relatively nondestmctive, and are fast. Evidence such as sod, minerals, synthetic fibers, explosive debris, foodstuff, cosmetics (qv), and the like, lend themselves to this technique as do comparison microscopy, refractive index, and density comparisons with known specimens. Other microscopic procedures involving infrared, visible, and ultraviolet spectroscopy (qv) also are used to examine many types of trace evidence. [Pg.487]

Oxidation of a glycol can lead to a variety of products. Periodic acid quantitatively cleaves 1,2-glycols to aldehydes and is used as an analysis method for glycols (12,13). The oxidation of propylene glycol over Pd/C modified with Pb, Bi, or Te forms a mixture of lactic acid, hydroxyacetone, and pymvic acid (14). Air oxidation of propylene glycol using an electrolytic crystalline silver catalyst yields pymvic aldehyde. [Pg.366]


See other pages where Crystallinity, analysis is mentioned: [Pg.58]    [Pg.77]    [Pg.329]    [Pg.108]    [Pg.512]    [Pg.333]    [Pg.29]    [Pg.126]    [Pg.291]    [Pg.58]    [Pg.77]    [Pg.329]    [Pg.108]    [Pg.512]    [Pg.333]    [Pg.29]    [Pg.126]    [Pg.291]    [Pg.299]    [Pg.368]    [Pg.133]    [Pg.341]    [Pg.307]    [Pg.1264]    [Pg.1381]    [Pg.1384]    [Pg.2598]    [Pg.2860]    [Pg.2907]    [Pg.2935]    [Pg.272]    [Pg.332]    [Pg.166]    [Pg.167]    [Pg.350]    [Pg.458]    [Pg.285]    [Pg.333]   
See also in sourсe #XX -- [ Pg.560 ]




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