注聚过程中预交联部分水解聚丙烯酰胺凝胶颗粒的防窜性能

针对地层非均质性所造成的注聚过程中聚合物的窜流,研究了东营预交联凝胶颗粒(DY)和辽河预交联凝胶颗粒(LH)的膨胀性能和封窜性能.结果表明,与LH相比,膨胀倍数合适并具有一定强度和黏弹性的DY具有更好的防窜性能,其突破压力为0.18 MPa/0.09m;二者使得高渗透层和低渗透层的采收率分别提高至20.26%和53.75%.     

低能粒子与X射线在碳纳米管(绳)内传输研究的现状

高能粒子(沟道)传输时, 粒子质量与入射能量有关。 低能粒子(沟道)传输时, 粒子(静止)质量与入射能量无关。 与其说高低能量区别, 不如说质量观念区别; 因此两者研究是不同观念的研究。 沟道连续势阱的柱状对称性与碳纳米管结构的变化无关。 X射线(沟道)传输表现为两方面: 在波动性方面, 它遵守光学散射规律; 在粒子性方面, 它被沟道连续势阱束缚。 For high energy particle transmission, its mass depends on its incident energy. For low energy particle transmission, its (static) mass is independent of its incident energy. The difference between the mass ideas is rather than that between high and low energies. Thus, these two transmission studies are very different in ideas. The column symmetry of transverse continuum potential well is independent of the nanotube structure. X ray transmission consists of two aspects: as wave, it is scattered by the laws of ray optics; as particle, it is captured in the transverse continuum potential well.     

Nuclear tracks created by 90 MeV carbon ions in ZnO crystal

The distribution of the lengths of the tracks, created by 90 Mev Carbon ions in Zno crystal consists of three groups with an average value about 52, 67 and 102 micrometers. The first group of the tracks may be treated as unchannelling particles. The second group corresponds to channeling particles and the third one represents superchannelling particles.     

Spectral method in quantum theory of channeling phenomena of fast charged particles in crystals

We show the possibility of using the spectral method to determine the quantum characteristics of interaction between fast charged particles and crystal when the channeling occurs. Basing on this method, we have developed the procedure for calculation of particles transversal motions eigenlevels for plane channeling. We considered origin of new levels with increasing of particle's energy and zone structure forming from these levels with increasing number of potential wells. We discuss also the possibility of using the spectral method in number of other problems of quantum theory of channeling.     

A study of the degree of relaxation of AlGaN epilayers on GaN template

The strain state of 570 nm Al_xGa_1−xN layers grown on 600 nm GaN template by metal organic chemical vapor deposition was studied using Rutherford backscattering (RBS)/channeling and triple-axis X-ray diffraction measurements. The results showed that the degree of relaxation (R) of Al_xGa_1−xN layers increased almost linearly when x0.42 and reached to 70% when x=0.42. Above 0.42, the value of R varied slowly and Al_xGa_1−xN layers almost full relaxed when x=1 (AlN). In this work the underlying GaN layer was in compressive strain, which resulted in the reduction of lattice misfit between GaN and Al_xGa_1−xN, and a 570 nm Al_xGa_1−xN layer with the composition of about 0.16 might be grown on GaN coherently from the extrapolation. The different shape of (0 0 0 4) diffraction peak was discussed to be related to the relaxation.     

Growth of Ni-Al alloys on Ni(1 1 1), from Al deposits of various thicknesses: (II) Formation of NiAl over a Ni3Al interfacial layer

This paper describes the second part of a study devoted to the growth of thin Ni-Al alloys after deposition of Al on Ni(1 1 1). In the previous paper [S. Le Pévédic, D. Schmaus, C. Cohen, Surf. Sci. 600 (2006) 565] we have described the results obtained for ultra-thin Al deposits, leading, after annealing at 750 K, to an epitaxial layer of Ni₃Al(1 1 1). In the present paper we show that this regime is only observed for Al deposits smaller than 8 × 10¹⁵ Al/cm² and we describe the results obtained for Al deposits exceeding this critical thickness, up to 200 × 10¹⁵ Al/cm². Al deposition was performed at low temperature (around 130 K) and the alloying process was followed in situ during subsequent annealing, by Auger electron spectroscopy, low energy electron diffraction and ion beam analysis-channeling measurements, in an ultra-high vacuum chamber connected to a Van de Graaff accelerator. We evidence the formation, after annealing at 750 K, of a crystallographically and chemically well-ordered NiAl(1 1 0) layer (whose thickness depends on the deposited Al amount), over a Ni₃Al “interfacial” layer (whose thickness—about 18 (1 1 1) planes—is independent of the deposited Al amount). The NiAl overlayer is composed of three variants, at 120° from each other in the surface plane, in relation with the respective symmetries of NiAl(1 1 0) and Ni₃Al(1 1 1). The NiAl layer is relaxed (the lattice parameters of cc-B2 NiAl and fcc-L1₂ Ni₃Al differ markedly), and we have determined its epitaxial relationship. In the case of the thickest alloyed layer formed the results concerning the structure of the NiAl layer have been confirmed and refined by ex situ X-ray diffraction and information on its grain size has been obtained by ex situ Atomic Force Microscopy. The kinetics of the alloying process is complex. It corresponds to an heterogeneous growth leading, above the thin Ni₃Al interfacial layer, to a mixture of Al and NiAl over the whole Al film, up to the surface. The atomic diffusion is very limited in the NiAl phase that forms, and thus the progressive enrichment in Ni of the Al film, i.e. of the mean Ni concentration, becomes slower and slower. As a consequence, alloying is observed to take place in a very broad temperature range between 300 K and 700 K. For annealing temperatures above 800 K, the alloyed layer is decomposed, Al atoms diffusing in the bulk of the substrate.     

Simulation of electromagnetic shower formation in a Germanium crystal

Abstract

When high-energy electrons penetrate crystalline matter, the successive processes of photon emission and pair production form an electromagnetic shower. If the incident electrons are directed along the crystal axis, the cross section for photon emission is drastically enhanced because electrons in ‘channeling’ states feel a strong electric field continuously. Experiments designed to detect this effect were performed at CERN. The results showed an anomalous peak in the energy loss spectrum of the emerging electrons. In this paper, we report results of a Monte-Carlo simulation of shower formation in a Germanium crystal. Our results agree with the experimental data more quantitatively than previous simulations. We simulated a shower formation by incident photons as well.     

Collision damage processes due to energetic heavy ions in silver chloride

The optical absorption band induced by energetic heavy ions implanted into AgCl single crystals at 77°K must be connected with the formation of silver colloids. The experimental (primitization and E.P.R. spectra) and theoretical study, makes it possible to obtain an approximate value of cluster radius. The colloid concentration is correlated with nuclear stopping power. It is shown that the collision efficiency is modified by a chemical effect. Finally the conditions of cluster formation are analysed.     

Lattice location of implanted As in ZnO

Radioactive ⁷³As ions were implanted into a ZnO single crystal at room temperature with 60 keV up to a fluence of 2×10¹³ cm⁻². Subsequently, the angular emission channeling patterns of emitted conversion electrons were recorded by means of a position-sensitive detector in the as-implanted state and following annealing up to 900 C, and were compared to simulated emission yields for a variety of different lattice sites. We find that As does not occupy substitutional O sites, but mainly occupies the substitutional Zn sites. The fraction of As on O sites was at most a few per cent. Arsenic in ZnO is thus an interesting example of an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system. Possible consequences with respect to the role of arsenic as a p-type dopant in ZnO are being discussed.     

Molecular dynamics study of ion transport in CaF2(10 mol % LaF3)

Abstract

We present the results of a molecular dynamics study of CaF₂(10 mol % LaF₃). No diffusion of fluorine ions is observed in pure CaF₂ below the transition temperature (T_C ≈ 1460K) to the fast-ion phase. However, doping with La³⁺ ions promotes fluorine ion diffusion in this temperature range, and tends to suppress it above T_C. Various ion migration mechanisms are discussed.