Amorphous state processing methods

Aluminum nitride UFPs have been synthesized by thermal decomposition from many kinds of precursor such as polyminoalanef l/ ) AIH(NR)] (50), aluminum polynuclear complexes of basic aluminum chloride (BAC) or basic aluminum lactate (BAL) (51), and (hydroxo)(succinato) aluminum(lll) complex, A1(0H)(C4H404) jfLO (52). These precursors were calcined under N2 or NH, gas flow. The calcination temperatures, which depend on the individual precursor, can be lower by 600-200°C than the 1700°C in ihe conventional carbothermal reduction method. The XRD measurements at intermediate stages of the calcination process showed the phase change from an amorphous state to a trace of y-alumina with very fine grains and finally to wurtzite-type AIN (51,52). Lowering the calcination... 

Solid-state nuclear magnetic resonance (NMR) has been extensively used to assess structural properties, electronic parameters and diffusion behavior of the hydride phases of numerous metals and alloys using mostly transient NMR techniques or low-resolution spectroscopy [3]. The NMR relaxation times are extremely useful to assess various diffusion processes over very wide ranges of hydrogen mobility in crystalline and amorphous phases [3]. In addition, several borohydrides [4-6] and alanates [7-11] have also been characterized by these conventional solid-state NMR methods over the years where most attention was on rotation dynamics of the BHT, A1H4, and AlHe anions detection of order-disorder phase transitions or thermal decomposition. There has been little indication of fast long-range diffusion behavior in any complex hydride studied by NMR to date [4-11]. 

The amorphous state, therefore, can be arrived at by methods other than melting and quenching and all such methods result in the loss of crystalline order. All these processes introduce additional enthalpy into the disordered material. Therefore amorphous materials crystallize irreversibly when heated to a temperature, below T of the parent crystalline material and the process is exothermic. The free energy of the amorphous state of a material is higher than that of its crystalline state. Thus the enthalpy addition (A//) during amorphization has to be generally... 

To control the properties of the fabricated thin films, it is necessary to operate under vacnnm to minimize the interaction between residnal gases and the surface of growing films. The thin films can be obtained in the crystalline or amorphous state by controlling the concentration of the vapor. The process of the film formation by this method involves the following three stages (1) evaporation or sublimation of the charge to form vapor, (2) transfer of atoms or molecnles from evaporation source to the substrate, and (3) condensation of vapor on the snbstrate. 

The higher-order structures (morphologies) of processed PP which should be considered are crystalline form, lamellar thickness, spherulite size, crystallinity, molecular orientation, crystal orientation, amorphous orientation, dispersion state of blended polymer, length and orientation of filled fibers, crystalline texture (skin-core structure), etc. In this chapter, morphological changes induced by various processing methods are described. 

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