Materials Literature
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Oxygen adsorption on the Pd(111) surface has been studied at 100 and 300 K by temperature programmed desorption (TPD) and isotopic mixing experiments. At 100 K, the sticking coefficient is determined to be 1 up to the coverage of 0.3 O/Pd. The saturation coverage is 0.62 O/Pd, 27% of which dissociates during thermal d…
Carbon films have been deposited by rf plasma decomposition of methane at 50–1400 V negative bias and 1.3×10−3–1.3×10−1 mbar pressure. Hardness, internal stress, density, hydrogen content, and infrared absorption depending on the preparation parameters have been measured. From the IR measurements the ratio of sp3 to s…
Penrose tilings have become the canonical model for quasicrystal structure, primarily because of their simplicity in comparison with other decagonally symmetric quasiperiodic tilings of the plane. Four remarkable properties of the Penrose tilings have been exploited in the analysis of the physical issues: (1) the clas…
Time-resolved spectra of luminescence from F and ${F}^{+}$ centers in MgO excited at 248 nm are reported over 8 decades of time and intensity, from 20 ns to 2 s. The decay time of F and ${F}^{+}$ luminescence has been measured at temperatures ranging from 90 to 573 K. The luminescence yield and spectra were studied as…
Biexciton states in semiconductor quantum dots (spherical microcrystallites) are investigated variationally, and the biexciton binding energy and the oscillator strength are calculated as a function of the quantum-dot radius, the electron-to-hole mass ratio, and the dielectric constant ratio of the semiconductor to th…
The Mie theory is used to find the in situ electric dipole polarizability of a sphere of arbitrary size and material. This size-dependent polarizability, together with the Clausius-Mossotti equation, yields an effective dipole generalization of the Maxwell Garnett equation for spheres of nonzero size. Calculated effec…
The dependence of the title is shown to originate in a singular angle dependence of the distribution width of the area of the semiclassical closed orbits under the magnetic field in the reciprocal space. In quasi-two-dimensional metals with a cylindrical Fermi surface, the distribution width of the area of the orbits…
We observe several weak features between 420 and 470 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in addition to the normally observed Si-Si (\ensuremath{\sim}500 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$), Si-Ge (\ensuremath{\sim}400 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$), and Ge-Ge (\ensuremath{\sim}300 ${\mathr…
The tight-binding approximation and the recursion method are used to study the size dependence of the band gap for small CdS and ZnS crystallites (20--2500 atoms). Because of the lack of accurate experimental data, a simple model of the crystal is considered; one which has no dangling bonds and a symmetrical shape. It…
Measurements of TSD together with surface potential were used to study negative corona discharge effects on the charge stability of Teflon FEP electrets. During charging, liquid formation over the sample surface (clearly visible for long-time corona irradiation) was concluded to be responsible for a decreasing in the…
The linear electro-optic effect in GaP has been investigated in the wavelength range 0.552-1.2 mu m at applied electric field frequencies of 200 Hz and 9.45 GHz. The dispersion of the clamped and unclamped electro-optic coefficients is measured and the fitted constants in the formula describing the clamped electro-opt…
The hydrostatic pressure and temperature dependence of velocities of ultrasonic modes propagated in natural crystals of iron pyrites FeS 2 have been measured. It is confirmed that C 12 is positive; the Poisson ratio shows the usual positive sign; it becomes more positive under pressure and remains positive down to low…
An investigation of several alternative representations of modified effective-range theory (MERT) has been carried out for low-energy electron scattering from the rare gases argon, neon and krypton in an effort to determine the energy range over which they can be applied to the analysis of scattering cross sections. O…
The failure statistics of polyethylene plaques loaded with a know volume fraction of metallic particles of fixed size distribution have been determined. The results are compared with the predictions of the percolation breakdown model. It is shown that the large decrease observed in characteristic strengths at low defe…
The magnetic and structural properties of melt-spun Sm(FeT)12 alloys where T=Ti,V,Al,Cu,Ga,Si and with some containing small amounts of B and C have been studied. The samples are magnetically soft in the as-quenched state. High coercive fields are developed upon heating the samples at temperatures ranging from 750 to…
Polycarbosilane (PCS) is an organic polymer with a skeleton of Si-C bonds. SiC fiber (Nicalon) is produced from PCS in three steps: spinning, curing (rendering the material infusible), and heating. SiC fiber has high tensile strength, high elastic modulus, and excellent thermostability in high-temperature oxidizing at…
Abstract Dynamic mechanical techniques can be used for a rapid estimation of polymer crystallinity with an accuracy of better than ±20%. The advantage of our proposed procedure is that it is absolute and the crystallinity can be instantaneously estimated when the dynamic mechanical analysis (DMA) data is available. A…
Abstract An experimental procedure has been designed for the preparation of aqueous mesophases of (hydroxypropyl)cellulose (HPC) exhibiting a stable low turbidity Sandwich chiroptical filters have been made from these right‐handed cholesteric liquid crystals confined between two parallel glass plates. Their optical pr…
The major categories of homopolymers and copolymers are discussed. These include (1) linear siloxane polymers, [—SiRR'O—] n (with various alkyl and aryl R and R' side groups); (2) sesquisiloxane polymers possibly having a ladder structure; (3) siloxane—silarylene polymers, [—Si(CH 3 ) 2 OSi(CH 3 ) 2 (C 6 H 4 ) m —] n…
Abstract In an attempt to provide information for improving silk fiber and fabric properties including crease recovery and yellowing, silk modification has been studied by using succinic and glutaric anhydrides. Glutarylation has been found to protect silk fibers from yellowing caused by the high energy radiation and…