Subject thermal treatment

The combined effects of a divalent Ca counterion and thermal treatment can be seen from studies of PMMA-based ionomers [16]. In thin films of Ca-salts of this ionomer cast from methylene chloride, and having an ion content of only 0.8 mol%, the only observed deformation was a series of long, localized crazes, similar to those seen in the PMMA homopolymer. When the ionomer samples were subject to an additional heat treatment (8 h at 100°C), the induced crazes were shorter in length and shear deformation zones were present. This behavior implies that the heat treatment enhanced the formation of ionic aggregates and increased the entanglement strand density. The deformation pattern attained is rather similar to that of Na salts having an ion content of about 6 mol% hence, substitution of divalent Ca for monovalent Na permits comparable deformation modes, including some shear, to be obtained at much lower ion contents. 

Moreover, free radical block copolymerization has been performed by means of low-molecular initiators containing two azo groups of different thermal reactivity. The first thermal treatment at a relatively low temperature in the presence of a monomer A results in a polymeric azo initiator. The more stable azo functions being situated at the end of A blocks can be subjected to a second thermal treatment at a higher temperature in the presence of monomer B. 

As with most other metal and alloys systems, nickel and certain of its alloys may suffer intergranular corrosion in some circumstances. In practice, intergranular corrosion of nickel alloys is usually confined to the vicinity of welds as a result of the effects produced by the welding operation on the structure of the material in those regions. Alloys that are subjected to other similarly unfavourable thermal treatments may also become susceptible. The compositions of most commercial nickel alloys that are marketed today are. 

When the reaction is performed at relatively low temperatures that prevent strong thermal decomposition of the alkali metal carbonate, the formation of C02 will be related only to the reaction and will indicate the stoichiometry of the process. Fig 8 presents mass loss isotherms of Nb02F - M2CO3 mixtures (in which M - Li, Na, K, Rb, Cs) that were subjected to thermal treatment in air at 850°C [84, 85]. It is important to mention that parallel experiments performed without the addition of Nb02F, resulted in alkali metal carbonate mass losses that were in the same order of magnitude as the measurement errors at temperatures below 850°C. 

We heated the substrate of zinc oxide containing 10 cm 2 of silver atoms (in this case there was already no emission after completion of deposition) at 300 C. Such thermal treatment results in formation of microcrystals, rather than evaporation adatoms on the surface of the substrate made of zinc oxide. In paper [34] it was shown that microcrystals with diameter 100 A deposited on the zinc oxide surface are acceptors of electrons, therefore the formation of microcrystals results in increase of resistivity of a sensor substrate above the initial value (prior to silver deposition). In this case the initial value of the resistance of sensor-substrate was 2.1 MOhm, after adsorption of silver atoms it became 700 kOhm, and as a result of heating at 300°C and formation of microcrystals - acceptors of electrons it in increased up to 12 MOhm. If such a substrate is subject to deposition of 3-10 5 cjjj-2 silver again, then emission of silver atoms gets detected. From the change of resistivity of sensor-detector due to deposition of silver atoms one can conclude that in this case the emission of atoms is 4 times as low than in experiment with pure substrate made of zinc oxide, which confirms the supposition made on the mechanism of emission of adatoms. 

It is useful to treat the raffinate to recover the two acids it contains. The raffinate can first be subjected to a thermal treatment which decomposes it into insoluble metallic oxides, hydrofluoric acid and sulfuric acid. In a first scrubbing, sulfuric acid is recovered, whilst in a second stage, hydrofluoric acid is absorbed. When put into operation, this process not only causes a reduction in the amount of sludges but also leads to acid production for return to the process. 

In conclusion, the lesson learned from the research carried out to date on the subject of polycarbosilanes is that the general rule that linear, noncrosslinked polymers are not suitable preceramic polymers applies here as well. Crosslinked network-type polymers are needed. Such structures can be generated in more than one way, but in the case of the polycarbosilanes they have, to date, been obtained mainly by thermolytic routes thermal treatment (with or without other chemical additives) in the case of the Yajima polycarbosilanes and the thermolysis of tetramethylsilane in the case of the Bayer process-derived polycarbosilane. 

William Randall Seeker received his Ph.D. in engineering (nuclear and chemical) from Kansas State University. He is the senior vice president and a member of the board of directors of Energy and Environmental Research Corporation. Dr. Seeker has extensive experience in the use of thermal treatment technologies and environmental control systems for managing hazardous waste. He is a member of the Executive Committee of the Environmental Protection Agency s Science Advisory Board. Dr. Seeker has authored over 100 technical papers on various aspects of technology and environment subjects. 

A physical approach was also applied to reduce the allergenicity of psyllium and psyllium-containing food products (Wullschleger, 1993). Psyllium was subjected to a thermal treatment imder certain pressure and moisture content for a predetermined time period to destroy the allergenic proteins. The preferred treatment conditions included a temperature of 245-265 °F, pressure range of 14—20 psi, and a time period between 55 and 75 min. This procedure may eliminate up to 100% of the allergenicity of psyllium. 

Unlike MOE, there does not appear to be any increase in MOR when wood is subjected to thermal treatment, even for short time periods (Figure 5.7). This is because MOR is actually the equivalent stress in fibres at the point of failure and, as such, is related to the ultimate bending strength of the wood (Dinwoodie, 2000). 

Tjeerdsma etal. (1998a) subjected thermally modified wood to soft rot decay in unsterile soil tests. Although decay resistance was enhanced by thermal treatment, it was not possible to prevent attack entirely. Treatments giving the best performance in terms of decay resistance also exhibited the highest strength losses. Viitanen etal. (1994) have also reported on some preliminary experiments on heat-treated wood in unsterile soil. 

B40 panels were also subjected to heat treatment. As shown in Figure 2, no dependence of the open circuit potential on post-thermal treatment temperature is observed. This suggested that the open circuit potential measurements reflected changes at the coating/B40 panel interface and not in the B40 panel alone. 

A second set of solutions were prepared from aliquots of the first solutions by subjecting them to a further thermal treatment of 160°C for 1 hour in an oven. 

For this reason, the dissolution of hydrous oxides does not require a high energy of activation. If hydrous oxides are dehydrated, they become dry oxides, which therefore acquire higher resistance to anodic dissolution. The most straightforward way to obtain dry oxides is to subject hydrous oxides to thermal treatments or better to prepare them as thin surface films by a non-electrochemical technique (thermal decomposition, chemical vapor deposition, reactive sputtering, etc.). 

Cyclization is a key reaction in the production of carbon fibers from polyacrylonitrile (PAN) (acrylic fiber see Sec. 3-14d-2). The acrylic fiber used for this purpose usually contains no more than 0.5-5% comonomer (usually methyl acrylate or methacrylate or methacrylic acid). Highly drawn (oriented) fibers are subjected to successive thermal treatments—initially 200-300°C in air followed by 1200-2000°C in nitrogen [Riggs, 1985]. PAN undergoes cyclization via polymerization through the nitrile groups to form a ladder structure (XXVII). Further reaction results in aromatization to the polyquinizarine structure (XXVIII)... 

Precursor Techniques A homogeneous sample containing all of the non-volatile constituents is prepared first. Stoichiometry is easily maintained in the precursor and reasonable reaction times and temperatures can be employed. Generally, the precursor will be a mixture of phases, however. Then, the precursor and volatile constituents are formed into an intimate mixture and are subjected to a brief thermal treatment to form the desired phase. 

Taking this data into account, we subjected the chemically dehydrochlorinated polymer to thermal treatment firstly at 200°C for 2 h to enrich the product with carbon via thermal dehydrochlorination and then at 350°C for 30 min to allow the formation of carbon-like structures. 

Fig. 4.2 Thermogravimetric analysis of the chemically dehydrochlorinated olyvinyUdene chloride 1 - not subjected to thermal treatment 2 - heated at 200°C (for 2 h) 3 - heated at 200°C (2 h) and then at 350°C (0.5 h)...

The results obtained are consistent with the existing views on the tendency of polyconjugated systems towards spontaneous stabilization upon thermal treatment heating makes the system more resistant to thermal degradation. TGA curves (Fig. 4.2) of the samples subjected to thermal treatment at 200 and 350°C are shifted to higher temperatures, with retention of the general pattern of weight loss. Thus, the carbon-rich structures were formed at relatively low temperatures. 

Currently, a wide range of technological applications is based on the sorptive and catalytic properties of sepiolite [2], Sepiolite is increasingly being used as a decolorizing agent [3], as a catalyst or catalyst carrier [4-6], and as odorant adsorbents in environmental applications [7-9], Several papers have appeared recently that examine the structural, textural and sorptive properties of untreated sepiolite [10-12] and of sepiolite subjected previously to acid and/or thermal treatment [13-16], Sepiolite has also been used recently as... 

Finally, the smallest crystallite size sample was subjected to severe thermal treatment. After calcining to 450, 500, 600, 780, and 920°C, the catalyst was... 

Depending on the choice of processing conditions PPT fibres can be produced with significantly different mechanical performance. Perhaps the best known commercially available variants are Kevlar 29 and Kevlar 49 80). Although production details are confidential, it is probable that the latter has been subjected to a thermal treatment. 

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