Poly crystalline-amorphous

H. P. Klug, L. E. Alexander, X-Ray Diffraction Procedures for Poly crystalline and Amorphous Materials, Wiley, New York, NY, 1974. 

Figure 8.2. WAXS curves from semicrystalline and amorphous poly(ethylene terephthalate) (PET). Separation of the observed intensity into crystalline, amorphous, and machine background (laboratory goniometer Philips PW 1078, symmetrical-reflection geometry)... 

The melting of a crystalline-amorphous block copolymer of poly(tetrahydro-furan)-poly(isoprene) (PTHF-PI) was investigated using DSC by Ishikawa et al. (1991). They found a double melting peak, which was proposed to result from the semicrystalline structure of the crystalline PTHF layer, with less-ordered crystallites melting before those with well-ordered domains of chain-folded PTHF. Alternative explanations include fractionation of the polydisperse block copolymer or melting of crystals with different fold lengths. 

Rather recently, we have studied the solid-state structure of various polymers, such as polyethylene crystallized under different conditions [17-21], poly (tetramethylene oxide) [22], polyvinyl alcohol [23], isotactic and syndiotactic polypropylene [24,25],cellulose [26-30],and amylose [31] with solid-state high-resolution X3C NMR with supplementary use of other methods, such as X-ray diffraction and IR spectroscopy. Through these studies, the high resolution solid-state X3C NMR has proved very powerful for elucidating the solid-state structure of polymers in order of molecules, that is, in terms of molecular chain conformation and dynamics, not only on the crystalline component but also on the noncrystalline components via the chemical shift and magnetic relaxation. In this chapter we will review briefly these studies, focusing particular attention on the molecular chain conformation and dynamics in the crystalline-amorphous interfacial region. 

As pointed out above with relation to the data at 87 °C, the Tic of the crystalline-amorphous interphase is appreciably longer than that of the amorphous phase, suggesting the retention of the helical molecular chain conformation in the interphase. We also note that a Tic of 65-70 s for the crystalline phase is significantly shorter than that for other crystalline polymers such as polyethylene and poly-(tetramethylene oxide), whose crystalline structure is comprised of planar zig-zag molecular-chain sequences. In the crystalline region composed of helical molecular chains, there may be a minor molecular motion in the TiC frame, with no influence on the crystalline molecular alignment that is detected by X-ray diffraction analyses. Such a relatively short TiC of the crystalline phase may be a character of the crystalline structure that is formed by helical molecular chain sequences. 

Chris G. Van de Walle, Hydrogen Interactions with Poly crystalline and Amorphous Silicon-Theory... 

Figure 20 The spectral dependencies of the photogeneration efficiencies of vapor-deposited amorphous (lower curve) and poly crystalline (upper curve) layers of PECI. The efficiencies were computed on an incident photon basis.

Olivine occurs mainly as inclusions in enstatite and is also found in albite, spinel, and troihte (Brearley, 1989). At least three kinds of poly-crystalline clusters appear to have formed separately (i) enstatite-rich units with forsterite inclusions, (ii) coarser versions with albite and olivine inclusions, and (iii) forsterite-anorthite units with no enstatite. Enstatite crystals are intergrowths of ortho- and clinopyroxene and their microstructures indicate cooling from >1,000 °C at -1,000 °Ch Brearley (1989) suggests that the Kakangari matrix formed from amorphous or partly crystalline particles <10 p,m in size that were annealed at 1,100-1,200 °C or possibly higher, and then rapidly cooled in an hour. The chondrules in Kakangari could have formed from similar material that was heated to higher temperatures, partly melted, and quenched at comparable rates, provided that the chondrules acquired lower concentrations when molten. 

The cell efficiency of a single crystalline Si solar cell reaches 18- 0 % in the mass production line. The poly crystalline and cast Si solar cell shows 15-18% on average. The cell efficiency of amorphous Si solar cells (a-Si) is 8-9 %. Silicon solar cell generates electric power of direct current with about 1 V, a few combinations of which are suitable to apply to water-electrolysis. Therefore, if Si solar cell is combined with SPE, the system efficiency will be 10 % in practical use. This value is the highest among the systems which produce hydrogen with use of renewable energies as will be described here in-below. 

A single triplet has three resonant fields, two due to Ah7s = 1 transitions and one due to Am.s= 2 transitions. For amorphous or poly crystalline samples, two triplet powder patterns are formed due to contributions from all possible orientations of triplets with respect to the applied field. The full-field triplet powder pattern due to Ams= l transitions is centered about Hq and has the following critical points ... 

This method requires the film to be produced on a single crystal substrate. This is the best situation, since the X-ray diffraction selectivity on the single crystal makes it possible to orient the sample with an accinacy in the range of a thousandth of a degree [BOU Ola]. When the film is deposited on a poly crystalline or amorphous substrate, others methods exist, derived from the one we have just described. 

In the form of amorphous silieon, thin flexible silieon films can be fabricated as well. Because of the absence of a erystal lattiee, eleetronic performance of amorphous silicon is multiple orders of magnitude worse than the performance of (poly)crystalline silicon, but still high enough for applications like TFT backplanes. However, processing temperatures required to obtain a-Si films of this high performance are not compatible with flexible substrates either. 

Reactive Evaporation 10 4(e.g.OJ) SiO, , A1 Si02, Ti02, A1203 <0,5pm min 1 25°-400°C Amorphous Poly- crystalline + low high Filament Crucible Walls... 

Reactive Sputtering 102-1 o3 (e.g. 02/Ar) Al, Zr A1203 Zr02 <0.01pm min 1 25°-300°C Amorphous Poly- crystalline + -H- high high Walls Gases used Sources... 

Reactive Ion-Plating I O 2-10° (e.g. 02/Ar) ZnS SiO, TiO ZnS Si02, Ti02 <0,5pm min 1 25°-250°C Amorphous Poly- crystalline ++ ++ high high Filament Crucible Gases used Walls... 

Transformation of the Amorphous Si-C Network into Poly-Crystalline SIC... 

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