Amorphous exothermic reaction

The results of the thermal analytical studies of Pd-montmorillonite produced from [Pd(NH3)2]2+ and [Pd(en)2]2+ further demonstrate that palladium ions are sorbed on the edge sites. Pd-montmorillonite shows the usual thermal processes of montmorillonites, with two new exothermic reactions at 338°C and 548°C. At around 338°C (maximum) exothermic reaction, a slight weight loss of the sample is also observed in a wide temperature range. It may indicate the partial amorphization of bentonite. At 548°C, the reduction of Pd(II) to Pd(0) may happen. 

When a wet chip (typically 0.5% moisture) falls into the fluid bed, the surface moisture is rapidly evaporated. As the chip is then further heated, crystallization occurs. This amorphous-to-crystalline transformation of PET is an exothermic reaction and the heat given off is quite sufficient to raise the surface temperature of PET to above the softening point. If the chips are not moving as they do in the fully developed fluidized state, this will produce large solid lumps of agglomerated chips. 

This is largely amorphous and is made by heating white in closed vessels at about 280-350°C for 48 h. The product of the exothermic reaction is wet milled, boiled with alkali to remove traces of... 

Baird JA, Taylor LS (2012) Evaluation of amorphous solid dispersion properties using thermal analysis techniques. Adv Dmg Deliv Rev 64(5) 396 21. doi 10.1016/j.addr.2011.07.009 Becker CR, Currano LJ, Churaman WA, Stoldt CR (2010) Thermal analysis of the exothermic reaction between galvanic porous silicon and sodium perchlorate. ACS Appl Mater Interfaces 2( 11 ) 2998-3003. doi 10.1021 /am100975u... 

It is shown in fig. 129 that b,f of the amorphous Laj5Al25Ni2o ribbon remains unchanged in the T, range below 406 K, decreases from 1.0 to 0.04 in the narrow Tg range between 406 and 434 K and shows a nearly constant value of about 0.03 in the Tg range above 434 K. The change in b,f with 7), indicates that the amorphous ribbon becomes brittle at 416 K in the case of an annealing time of 1.8 ks. The exothermic reaction for the as-quenched sample as well as the endothermic reaction for the annealed sample is a reversible process for the La-Al-Ni amorphous alloy with a wide supercooled liquid... 

The reactivity of crystalline silicon with tetrafluoromethane, CF4, has been investigated by Holcombe et al. [36]. They found a mild exothermic reaction with onset at about 500 °C (peak at 530 °C) with no significant mass change and the onset of a strongly exothermic reaction at 990 °C (peak at 1020°C) with a significant mass loss indicative of volatile SiFx formation. Samples held under CF4 atmosphere for 75 min at 1030 °C exhibited both S-SiC and metastable carbon formation on the sttrface of Si. The exotherm at 500°C is believed to occur from highly reactive amorphous silicon present on the surface of crystalline Si. The formation of metastable carbon, particularly diamond phase on both Si and SiC substrates by thermal treatment in fluorocarbon atmosphere has been the subject of a disclosure by Holcombe et al. [37]. 

Binary amorphous silicon/PTFE pyrolants have been investigated by Cudzilo eta . [25, 39]. A combined TG/DTA trace for (Si/PTFE) (50/50) is displayed in Figure 5.31. Following the PTFE melting endotherm at 330°C, the exothermic reaction commencing at 500°C is due to formation of volatile Sip4 causing the observed mass loss of 50%. 

Boric oxide, B2O3, the simplest and only commercially important oxide of boron, exists primarily as an amorphous glass that has a 3-D arrangement of three-coordinate boron centers (BO3) that share oxygen atoms [9]. It finds application mainly in glass and ceramics. It is water soluble, although it dissolves relatively slowly in an exothermic reaction with water. It is often referred to as anhydrous boric acid, as it converts to and behaves like boric acid on contact with water. 

There exists, however, an upper limit to the dealumination temperature (ref.27). Beyer et a1. reported that the contact of dehydrated NaY with SiCl4 at temperatures over 750 K produces a violent exothermic reaction resulting in the formation of an amorphous product (ref.27). On the contrary, Klinowski et al. seemed to succeed in the preparation of an essentially aluminium-free faujasite structure from zeolite Y by reaction with SiCl4 vapor at 833 K (ref.44). However, it is not clear whether temperature programming or not was used in the latter case. 

In most cases, CVD reactions are activated thermally, but in some cases, notably in exothermic chemical transport reactions, the substrate temperature is held below that of the feed material to obtain deposition. Other means of activation are available (7), eg, deposition at lower substrate temperatures is obtained by electric-discharge plasma activation. In some cases, unique materials are produced by plasma-assisted CVD (PACVD), such as amorphous siHcon from silane where 10—35 mol % hydrogen remains bonded in the soHd deposit. Except for the problem of large amounts of energy consumption in its formation, this material is of interest for thin-film solar cells. Passivating films of Si02 or Si02 Si N deposited by PACVD are of interest in the semiconductor industry (see Semiconductors). 

The reaction is exothermic and may form polymer from a molecular weight of 1000 to well over 1 million. The high-pressure process, which normally produces types I and II, uses oxygen, peroxide, or other strong oxidizers as catalyst. Pressure of reaction ranges from 15.000 to 50.000 psi ( 1,020-3,400 atmospheres). The polymer formed in this process is highly branched, with side branches occurring every 15-40 carbon atoms on the. chain backbone. Ciystallinity of this polyethylene is approximately 40-60%, Amorphous content of the polymer increases as the density rs reduced,... 

An example of a reaction that can be induced by the presence of water vapor is the crystallization of amorphous lactose, a subject that has been reviewed by Buckton and Darcy (34). After a period of exposure to any particular RH amorphous lactose exhibits a crystallization exotherm (Fig. 8) (35). It can be shown that the rate of onset of crystallization varies with... 

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