Thermal Storage Time Research Articles

Thermal history effects on the ionic conductivity of PEO-salt electrolytes

The ionic conductivity of polyethylene oxide (PEO)-based electrolytes has been known to be greatly enhanced by filling with nano ceramic particles, though it is strongly dependent on thermal treatment schedule and decreases slowly for long aging. The unstableness of the conductivity was attributed to the change of crystallization kinetics caused by some kind of interactions among polymer chains and incorporated ceramic particles. In this paper, ceramic-free PEO n LiClO 4 polymer electrolytes were studied by measuring ionic conductivity and optical micrographs. We show that the unstableness of the ionic conductivity is inherent in the semicrystalline state of ceramic-free PEO-salt electrolytes and the conductivity below melting temperature can be variant by almost two orders of magnitude according to thermal treatment and storage time, although it may be changed by introducing ceramic particles. The melting temperature T m increases with storage time due to the stiffening of spherulites, and the increment of T m is more pronounced for higher salt ratio. All these are primarily concerned with the two-phase nature and the slow re-crystallization kinetics of PEO.

Changes in Mushroom Texture and Cell Wall Composition Affected by Thermal Processing

ABSTRACT: The effects of thermal processing, calcium, and storage time on texture and cell wall composition of mushrooms were investigated. Whole fruit‐bodies were blanched and retorted with addition of 0, 5, or 25 mMCaCl2. Firmness was determined as force for puncturing and toughness as shear force. Alcohol‐insoluble fractions were extracted from fresh, blanched, and processed mushrooms. Proteins, carbohydrates, and chitin were analyzed in sequential extracts of alcohol‐insoluble solids. Blanching caused an increase in force for puncturing but reduced force for shear. Further retorting did not affect texture, but toughness increased during storage. Calcium increased values for both textural characteristics possibly due to formation of cross‐links between proteins and polysaccha‐rides.

Molecular Orientation of Polymer Lubricant Films: Its Tribological Consequence

The objective of this paper is to demonstrate, from experiments and modeling, how and why molecular orientation of functional end groups of perfluoro-polyether (PFPE) lubricants play an important role in the tribological performance of thin film magnetic disks. These disks typically have an amorphous carbon overcoat upon which a thin lubricant layer is deposited using dip-coating technique. Glancing-angle FTIR (Fourier Transform Infra-Red Spectrometry) is used for measuring molecular orientation of planer functional end groups. A molecular orientation index (MOI) was defined as 1 for randomly oriented functional end groups. The MOI is mathematically derived as 3 (maximum) for lubricant molecules oriented with their functional end groups perpendicular to the surface, and as 0 (minimum) if lubricant molecules oriented with their functional end groups parallel to the surface. The MOI is shown to depend on processing conditions and lubricant film thickness. The tribological performance of the lubricant films was evaluated using drag-mode contact start-stop testing. It was found that wear durability of the lubricant films (~2 nm) with MOI ~ 1.5 is a few times better than those with MOI ~ 0.5 to 1.0. No significant difference in the amount of bonded lubricant film was detected over the range of MOI studied. Nor was there a detectable relationship with hydrophobicity. It was inferred from decreased MOI values due to thermal effects and storage time that a smaller MOI value corresponds to a lower free energy state of the lubricant film. Interestingly, MOI values for bonded lubricant films for Process A are found to be close to 3.0, suggesting that almost all functional end groups in the bonded films are oriented perpendicular to the carbon surface, close to 2.0 for process B, and close to 0 for process C, meaning that almost all functional end groups in the bonded films from process C are oriented parallel to the carbon surface. Relationship between physical/chemical bonding configurations and MOI values are graphically presented in detail. Based on this relation, a simple model on lubricant film structures for the three processes studied is presented. The model MOI values agree very well with measured MOI values as a function of lubricant thickness for all three processes, and the model also appears to account for the observed tribology performance for the MOI values studied (0.5 ~ 1.5).

Effects of thermal history on lithium salt-poly(ethylene oxide) complex polymer electrolytes

Abstract Effects of thermal history and storage time on electrochemical properties, morphology and stability of the polymer composite electrolytes of poly(ethylene oxide) with LiClO 4 and LiCF 3 SO 3 have been studied. Complex ac impedance, dc polarization, thermogravimetric analysis, and differential scanning calorimetry have been used. These electrolytes were prepared as thin films by solution casting and had various thermal histories. It is considered that the different effects of thermal history result from different recrystallization kinetics of composite electrolytes.

A Summary of the Joint Discussion at Patras on Solar Luminosity Variations

The most interesting result in solar luminosity studies in the past decade has been the detection of significant variations in the total irradiance by precision radiometers on the NIMBUS-7 and SMM spacecraft. A substantial fraction of the observed variation can be attributed to sunspot blocking. Thermal storage models indicate that the blocked flux can be stored in a slight increase of the thermal and potential energy of the convective zone. The thermal storage time is likely to far exceed one solar activity cycle, implying an 11-year modulation of the solar constant at a level of about 0.1%. Direct observations of the 11-year or longer variations are more difficult but there is some evidence for secular trends below about 0.4% amplitude over the 14-year period of modern sampling. Ongoing stellar photometric programs suggest that luminosity changes exceeding 1% may have been detected in young, chromospherically active stars.H. S. Hudson (University of California, San Diego) reviewed observations of short-term solar irradiance variations from spacecraft, commenting principally on the precision measurements of the solar constant (S) made by the Active Cavity Radiometer (ACRIM) on the Solar Maximum Mission (SMM) spacecraft (Willson et al., 1981).

The power rating of semiconductor rectifiers

The widespread use of semiconductor rectifiers, with their extremely high conversion efficiency, ability to operate at high reverse voltages and consequent small size, has brought in its train problems peculiar to these devices. It is most important, therefore, that the electrical ratings should be established on both a systematic and rigorous basis with the specific problems in mind. Certain electrical parameters such as forward and reverse voltage and current, thermal resistance and junction temperature, have obvious effects on the electrical rating of the rectifier. Others, such as thermal capacitance and carrier storage time, affect the rating indirectly, but are no less important. In the paper, some of the factors which influence the rating of germanium and silicon junction rectifiers are considered, and the procedure for obtaining the curves of rectified current rating as function of ambient temperature is given. Determination of overload characteristics and the associated use of thermal-electrical analogue techniques are described. Methods for deriving the derating factor for parallel operation, operation at higher mains frequency and at high altitude are also given.