Hydrogen temperature sensitivity

Steels are normally ductile at ambient temperatures, although they are often close to brittle behaviour, as is indicated by the ductile-brittle transition temperature. If the conditions at the tip of a sharp crack are considered, it can be seen that brittle fracture will occur if it is easier to break the atomic bond at the tip of the crack than it is to emit a dislocation to blunt the crack (see Thompson and Lin ). As dislocation emission is more temperature sensitive than the bond strength it becomes more difficult at low temperatures and brittle fracture occurs. The very severe effects of hydrogen on the performance of steels can be attributed to its role in allowing brittle fracture... 

New pH/temperature-sensitive polymer systems with transitions resulting from both polymer-polymer and polymer-water interactions have been demonstrated and their pH/temperature-induced phase transition has been investigated. Intra/intermolecular interactions via hydrogen bond play an important role in determining the phase transition. By manipulating the... 

Certain correlations are possible but it must be kept in mind that comparisons of activity in heterogeneous catalysis are likely to be treacherous. Minor differences in surface pretreatment may make major differences in properties. Nevertheless, it is clear that there are recognizable patterns of extrinsic field effects. The several kinds are shown in Fig. 22 wherein AkH is plotted against H (log scale). The curves drawn are meant to be representative, but except for relatively minor details, all of the samples studied to date fall into one of the six patterns shown. This covers over 30 different catalyst preparations, a variety of temperature-sensitive magnetic phases, and various pretreatments. Figure 22 shows one example of catalysts found to have the indicated kind of field effect. Pretreatment conditions are stated in Table IV which includes all samples on which measurements have been made. Pretreatments are abbreviated as follows (H2773q298) means that the sample had been heated in hydrogen for an hour or more at 773 K and then cooled rapidly to 298 K. One or two temperatures at which each A k pattern has been observed are also shown in Table IV. 

Since the rate of hydrogenation is sensitive to operating conditions (temperature, pressure, catalyst quantity, solvent and agitation), relative rates determined in competitive hydrogenation of binary mixtures are considered to be more reliable than measuring individual rates50. Relative reactivities thus measured are determined by the ratio of rate and adsorption constants. 

In a human tumor xenograft model, Kong et al.21 compared the antitumor effect of doxorubicin encapsulated in three types of liposome formulations, a nonthermosensitive liposome (NTSL), a traditional thermosensitive liposome (TTSL), and a low-temperature-sensitive liposome (LTSL). All three liposomes are sterically stabilized with PEG grafted on their surface. All the liposomes have a long circulation time and can accumulate selectively in tumor tissue. However, the lipid compositions of the three formulations are different. The NTSL was composed of saturated long-chain lipids such as hydrogenated soybean... 

In the addition of dichlorovinylene carbonate to isobutylene at low temperature, sensitized by acetone, the two-step nature has been illustrated [105], Thus, at — 20 °C a normal rc2 + tc2 adduct is formed. At lower temperature — 70 °C, a hydrogen transfer reaction competes with the cycloaddition to give the ene adduct ... 

Adsorption isotherms of oxygen, nitrogen, carbon dioxide, and sulfur dioxide on hydrogen-mordenite were measured at several temperatures in the range of O —IOO C. The SO2 and CO2 had considerably greater affinity for the adsorbent than the O2 and Ng. Using the pure-component data, multi-component isotherms were predicted and compared with experimental results. The more strongly adsorbed species completely overwhelm the lesser adsorbed components (e.g., SO2 vs. N2). Wherever 2 species of approximately equal affinity are adsorbed (e.g., CO2 + SOg), the temperature sensitivity of the individual components influences the extent of the competition. 

Staab introduced azolides as versatile reagents in organic synthesis. The reaction of carbonyldiimid-azolide with carboxylic acids produces imidazolides under mild conditions which can be converted by the action of hydrogen halides to acid halides in high yield (equation 20). The method does not even require the isolation of the imidazolides, but can be carried out as a one-pot synthesis. The possibility of carrying out this reaction at low temperatures allows the preparation of temperature sensitive compounds. Formyl chloride, which decomposes at -40 °C, has been prepared in this way. 

Here, hydrogen and carbon dioxide react to form water vapor (and carbon monoxide via water-gas shift), which hydrolyzes the aluminum trichloride. If the deposition surface is temperature sensitive, a metal-organic precursor is preferred. Again, an alkoxide is generally used ... 

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