Reliability Potential Of Epoxy Based Encapsulants For Automotive Applications

Automotive under-the-hood electronics often have to withstand temperatures up to 175 °C in combination with harsh environment conditions. This paper gives an overview about the reliability potential of epoxy based encapsulants for automotive applications. Therefore the resistance of epoxy molding compound against typical automotive fluids at temperature of use is analyzed. Six epoxy molding compounds available on the market, showing high temperature automotive potential have been carefully selected to undergo a media resistance testing. For this purpose a dedicated mold tool has been designed and manufactured to prepare these encapsulants for material testing. Thermo-mechanical, mechanical and thermal properties had been determined in initial state directly after molding and after storage in aggressive fluids typical for automotive applications as e.g. gas oil, automatic transmission fluid (ATF), brake fluid or accumulator acid at the respective temperature of use.     

A versatile data acquisition system for time resolved X-ray scattering using gas proportional detectors with delay line readout

A data acquisition system for time resolved X-ray scattering experiments using linear, quadrant or area gas proportional detectors with delay line readout based on commercially available hardware (National Instruments) is described. The system can easily be configured for recording data from point detectors (e.g. photomultipliers and photodiodes) and/or ancillary data only. Applications involving measurements with two different types of time to digital converters illustrate the features and performances of the system.     

Fluoride catalysis at 175°C. of the reaction: Glycerol plus fatty acid

1. In uncatalyzed reactions the esterification of stearic, oleic, and linolenic acid proceeded at the same general rate though the speed was somewhat enhanced as the degree of unsaturation of the fatty acid increased. None of the reactions went to completion, after 15 hours being 72%, 83%, and 84%, respectively, completed. Only a small fraction of the distearate was converted to the triglyceride; a greater amount of the dioleate was esterified to the trioleate and about half the dilinolenate was changed to the trilinolenate.
2. Of 15 metallic fluorides studied, all afforded some catalysis, but only antimony trifluoride and zinc and cobalt fluorides were outstanding. Antimony trifluoride was the most active although in large amount it caused severe decomposition and charring of the products. Zinc fluoride had the best general properties, approaching antimony trifluoride yet causing practically no decomposition even in high concentration. Its activity was enhanced with an increase in amount, the best concentration apparently being 0.1 mole per 100 grams fatty acid. Antimony trifluoride was also better in larger amount within limits, but cobalt fluoride did not exhibit this property.
3. With zinc fluoride as catalyst the reactions of stearic, oleic and linolenic acids after 15 hours were 95%, 94%, and 92%, respectively, completed. At least three-fourths of the diglycerides were converted to triglycerides. From a study of reaction velocities, zinc fluoride caused the monoglyceride to form at a rate approximately four times that of the uncatalyzed reaction and the diglyceride at a six-fold rate. The triglyceride was formed at an almost undiminished rate whereas in the uncatalyzed reaction the formation of triglyceride was diminished rapidly.
4. Unsaturation and viscosity were not affected seriously in the presence of the fluorides except antimony trifluoride. Certain other fluorides caused severe darkening but without accompanying serious decomposition.

     

Surface segregation studied by low-energy ion scattering: experiment and numerical simulation

The changes in surface composition of metallic alloys caused by segregation can be very efficiently studied by low-energy ion scattering (LEIS) due to the specific surface sensitivity of this technique. Investigations of single-crystal surfaces of ordered alloys are of particular interest because they provide the possibility to investigate the interplay between segregation effects and the order-disorder phase transition when passing through the transition temperature. Exemplifying these effects for bimetallic alloys we consider in particular the CuAu-system.For the quantitative interpretation of energy and angle resolved LEIS intensity distributions we compare experimental results with those from numerical simulations using the MARLOWE code which we extended with a detailed trajectory analysis. This allows us to apply various discrimination criteria, such as number of collisions, distance of closest approach, identification of the scattering crystal layer, total path length, etc. On this basis structural effects, ion survival probabilities and the influence of thermal vibrations can be studied.We demonstrate this potential by using CuAu(1 0 0) as a special example. The scattering potential parameters were calibrated with elemental single crystals of known structures and the anisotropic Debye temperatures taken from the literature showed good agreement, neutralization was of minor importance in this case. Our procedure could be successfully used for the quantitative analysis of the composition of the first and second layer as a function of temperature. These results are in good agreement with theoretical predictions.     

Terahertz characterisation of building materials

To obtain realistic models for propagation channels in future pico-cellular indoor terahertz communication systems it is necessary to know the reflective properties of building materials found in a typical office environment. The angular dependent reflection coefficients of different building materials were determined using terahertz time-domain spectroscopy in transmission geometry and Fresnel's equations. This approach is more efficient than a set of measurements in reflection geometry for different angles. Verification of the method with a set of such reflection measurements shows an excellent agreement.     

Alcohol consumption as a self-handicapping strategy in women.

Assessed whether women self-handicap with alcohol consumption prior to engaging in a social evaluation task, which may be more relevant to their self-esteem than the intellectual tasks used in past self-handicapping studies on substance use. 113 women (aged 19–32 yrs), who were evaluated as normal drinkers, performed either a solvable or an insolvable social judgment task and then received either success feedback or no feedback. Ss received access to alcoholic and nonalcoholic beverages while awaiting a retest. The study terminated before the retest. The self-handicapping hypothesis that noncontingent success would produce relatively greater alcohol consumption was not supported. Regardless of feedback, insolvable test Ss consumed more alcohol than did solvable test Ss. Findings suggest that the hypothesis may be limited as a general model of alcohol consumption in both sexes. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Apolipoprotein A, fibrinogen, age, and history of stroke are predictors of death in dialysed diabetic patients: a prospective study in 412 subjects

BACKGROUND: Diabetic patients with end-stage renal failure (ESRD) have a high cardiovascular morbidity and mortality. The underlying mechanisms are not completely elucidated. The aim of our study was to define predictors of death in diabetic patients with end-stage renal disease. PATIENTS AND METHODS: We performed a prospective study in 35 dialysis centres in Germany between 1985 and 1994. To evaluate predictors and risk factors in this population we examined 412 diabetic patients at the time of admission to dialysis treatment (peritoneal dialysis (PD) or haemodialysis (HD)). Classification of the type of diabetes was done according the criteria of the National Diabetes Data Group [1,2]. Items assessed at the time of admission were coronary artery disease (CAD), peripheral occlusive disease (POD), and stroke. CAD was defined as a history of myocardial infarction with the corresponding changes in the ECG or luminal narrowing by more than 50% in at least one coronary artery upon coronarangiography; POD was defined as claudication and/or brachial-tibial ratio (BTR) less than 0.9 or a history of amputation. Assessment of the nutritional state comprised body mass index, skinfold thickness of the upper arm and lateral thorax area, and urea concentration. Cholesterol, HDL, LDL, apolipoprotein A (ApoA-I) and B (ApoB), triglycerides, lipoprotein(a) (Lp(a)), and fibrinogen were measured. As an index of disturbed cardiac innervation beat-to-beat variation was measured. Outcome measurements were causes of death (i.e. cardiac and non-cardiac) and time of survival. RESULTS: One hundred and eighty of 412 (44%) patients died during the observation period. Patients who died were older (61 +/- 12 versus 53 +/- 15 years P < 0.0001), had lower skin fold thickness (13.1 +/- 6.0 versus 15.1 +/- 7.3 mm P < 0.04), lower ApoA-I (100 +/- 35 versus 111 +/- 32 mg/dl P < 0.005) and higher fibrinogen (515 +/- 146 versus 451 +/- 155 mg/dl P < 0.02). Type II diabetic patients had a lower mean survival time than type I (34 versus 66 months P < 0.0006). The mode of renal replacement therapy (PD or HD) had no adverse effect on survival time. Survivors less frequently had a history of CAD, POD and stroke than non-survivors. In multivariate analysis ApoA-I, fibrinogen, age and stroke were independent predictors of cardiac and non-cardiac death in diabetic patients with end-stage renal failure. Lipid values and nutritional state did not independently predict the overall and cardiovascular mortality. CONCLUSION: This study in dialysed diabetic patients identifies several predictors of death, some of which are susceptible to intervention.