Materials Literature
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Thermal conductivity data of polycrystalline chemical vapor deposited cubic silicon carbide are calculated from thermal diffusivity and heat capacity data in the temperature region of 80–300 K. Below 200 K, a linear dependence of the thermal conductivity with the product of grain size of the silicon carbide and cubic…
A method is described that enables the simultaneous or consecutive determination of the specific heat, the thermal diffusivity, the dielectric constant, and the pyroelectric coefficient of thin pyroelectric films. The sample is heated by the absorption of intensity modulated light at one surface. The pyroelectric curr…
Methods for the determination of the frequency dependent hyperpolarizabilities, β(−2ω;ω,ω), β(−ω;ω,0), and β(0;ω,−ω) at the self-consistent field (SCF) level of theory are discussed and compared. Two efficient alternatives are proposed; one involves determination of appropriate response vectors which arise in first-or…
The objective of this research is to establish a shape-memory effect in sputter-deposited films of nickel titanium. The alloy, generically called nitinol, was prepared from sputtering targets in two different compositions. Films were deposited up to 10 μm in thickness on glass substrates using a dc magnetron sputterin…
The electronic properties of tin dioxide single-crystalline (110) surfaces have been studied in correlation with their structure by low-energy electron diffraction, angle-integrated and resonant photoemission using synchrotron radiation [ultraviolet photoemission spectroscopy (UPS)]. Energy distribution curves were me…
Full phonon-dispersion curves of the graphitic layer on some transition-metal carbides were measured by using high-resolution electron-energy-loss spectroscopy. The graphitic layer on (111) surfaces of TaC, HfC, and TiC showed anomalous softening within the layer, whereas the graphite layer on TaC(001) is similar to b…
A physically based methodology is developed for modeling the behavior of electrical circuits containing nonideal ferroelectric capacitors. The methodology is illustrated by modeling the discrete ferroelectric capacitor as a stacked dielectric structure, with switching ferroelectric and nonswitching dielectric layers.…
We study electron-phonon coupling in the case of Fr\"ohlich or polar interaction, with special emphasis on the size dependence of the coupling strength for semiconductor nanospheres exhibiting quantum confinement of the carriers. We first derive the expression of the vibrational LO (longitudinal optic) and SO (surface…
The paper presents results of experiments undertaken to elucidate the behaviour of polyethylene under the influence of high electric fields. Especially when using virgin samples, some 'anomalies' occur that are a result of a slow transition of the polymer to a preloaded state. It is shown that if two sets of traps are…
In recent years investigations of the use of digital evaluation of partial discharges have become increasingly important. Such methods of evaluation greatly improve the recognition of discharge patterns and the correlation of these patterns with various types of defects. Conventional methods of oscillographic observat…
Measurements of electrical breakdown, high-field conduction current and pre-breakdown current are made on various kinds of polymeric insulating films. The experimental results on electrical breakdown and conduction indicate that the electrical breakdown current starts to increase rapidly at about 1 ms before breakdown…
The time dependence of the discharge processes in dielectric bounded voids of 40 mm have been studied under power frequency voltage. Fast oscilloscopic techniques were used to observe the pulse shape of single discharges or clusters of discharges. Synchronous optical registration of discharge images was performed usin…
A narrow size distribution of irregular aluminium particles was blended into power cable insulation grade polyethylene. Some batches of the resulting material were then melt-filtered to reduce the size of particles present and narrow the distributions further. The failure statistics of the loaded polymers were then de…
The photoluminescence of Ti-doped sapphire (Ti:Al 2 O 3 ) crystals excited using the second (532 nm) and fourth (266 nm) harmonics of a high power pulsed Nd:YAG laser has been investigated. Excitation at 532 nm into the crystal field band of Ti 3+ produces the well known broad infrared emission band corresponding to t…
Energy gap and hydrogen concentration have been measured in hydrogenated amorphous carbon (a-C:H) after bombardment with 100 keV He+ and 300 keV Ar+ ion beams, up to ion fluences 3×1016 ions/cm2. a-C:H films have been obtained by ion irradiation at low ion fluences of polystyrene layers and with a subsequent low-tempe…
Direct measurements of the surface recombination velocity (SRV) on etched InP(110) and at its interfaces with various metals deposited by thermal evaporation have been performed using ultrafast time-resolved photoluminescence. The results show that the original InP low SRV is retained when these surfaces are coverd wi…
We report the growth of epitaxial τ-MnAl ferromagnetic films on GaAs substrates by molecular beam epitaxy (MBE). Reflection high-energy electron diffraction and x-ray diffraction show that the τ-phase films grow with the c axis of the tetragonal unit cell normal to the {100}GaAs substrate surface. In the bulk, τ-MnAl…
We describe a new type of color display consisting of polymer-dispersed droplets of chiral liquid crystal having negative dielectric anisotropy. In the field-off state, the droplets scatter light randomly. In the field-on state the droplets selectively reflect a bright color. Measurements of reflectivities and switchi…
The temperature dependence of the room pressure Raman spectra of the GeO 2 (hexagonal and tetragonal) and SiO 2 (quartz, coesite, and stishovite) polymorphs is presented. Several transformations upon heating are reported: α‐β quartz, coesite‐cristobalite, stishovite‐silica glass (with Si in four‐fold coordination). Fo…
Abstract Surface properties of fluoroalkylsilicone—poly(methyl methacrylate) block copolymers and their poly(methyl methacrylate) (PMMA) blends have been intensively studied to draw a relationship between surface segregation behavior and adhesion performance. The fluoroalkylsilicone—PMMA block copolymers containing th…