Effect of a dislocation forest on the bauschinger effect during the twinning of zinc single crystals

A study was made of the effect of a dislocation in the {{11¯22}} 11¯23 system (pyramidal slip) on the characteristics of the Bauschinger effect during the twinning of single crystals of zinc and of the alloy Zn + 0.6% Cu. The dislocation forest retards the backward motion of the twinning dislocations, leading to the effect.Translated from Izvestiya VUZ. Fizika, No. 5, pp. 101–104, May, 1971.In conclusion the authors thank candidates of physicomathematical sciences F. F. Lavrent'yev for useful discussion.     

Spinodal twinning of a deformed crystal

We propose the possibility of a spinodal mechanism for deformation twinning in addition to the nucleation and growth mechanism assumed in all existing studies of twinning, using the thermodynamic stability analysis of a homogeneously deformed crystal by examining its energy landscape as a function of strain along the twinning direction obtained from first-principles calculations. Twinning occurs continuously owing to thermodynamic instability with respect to twinning at large shear strains, whereas it can only take place through the nucleation and growth mechanism at small shear strains.     

杂质对KDP晶体光学质量的影响

 研究了几类可能出现在KDP晶体的生长溶液中的有机物杂质和无机阴离子杂质基团对KDP晶体散射、透过率、光损伤阈值等光学质量的影响，结果表明，不同种类的杂质的影响并不相同，造成这一结果的根本原因在于杂质离子的结构及其与晶体表面原子成键能力的不同。     

杂质对KDP晶体光学质量的影响

研究了几类可能出现在KDP晶体的生长溶液中的有机物杂质和无机阴离子杂质基团对KDP晶体散射、透过率、光损伤阈值等光学质量的影响,结果表明,不同种类的杂质的影响并不相同,造成这一结果的根本原因在于杂质离子的结构及其与晶体表面原子成键能力的不同。     

Effect of crystal anisotropy on superconductivity in zinc

The effect of crystal anisotropy on superconductivity in zinc has been studied making use of the recently observed highly anisotropic vibrations of a zinc atom in its crystal. The effect of crystal anisotropy on superconductivity turns out to be quite involved and significant.     

On the effect of impurities on the critical resolved shear stress of zinc single crystals

The dependence of the critical resolved shear stress of zinc single crystals on the impurity content and the dislocation density is observed. It is shown that the effect of impurities on the critical resolved shear stress is indirect.

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锌添加对大尺寸金刚石生长的影响

利用温度梯度法,在6.2—6.4 GPa,1270—1400℃条件下,通过在NiMnCo-C体系中添加不同比例的锌粉成功合成出3 mm左右的大尺寸金刚石单晶.研究了锌添加对金刚石颜色、形貌、内部氮杂质以及晶体结晶度的影响.结果表明:随着锌添加量逐渐增加,晶体的颜色逐渐变浅,晶体的透光性增强;当锌添加比例达到3 wt.%时,晶体表面出现大量不规则的凹坑;晶体内氮杂质主要以C心形式存在,随着锌添加量的增多晶体内氮含量逐渐降低,基于锌的除氮能力总结出两种可能的除氮机制;拉曼光谱测试结果表明,在锌添加量小于3.0 wt.%的研究范围内,锌的添加有利于提高晶体的结晶度.本研究不仅有助于天然金刚石形成机制的探究,而且对丰富金刚石的种类以及扩展人工合成金刚石的应用领域都有着重要意义.     

Effect of doping with nickel ions on the structural state of a zinc oxide crystal

The fine structure of a hexagonal zinc oxide crystal doped with nickel ions of the composition Zn_{1 − x} Ni _x O has been studied using neutron diffraction and magnetic measurements. It is established that even at very low doping levels (x = 0.0004), the crystal undergoes local distortions in basal planes of the initial hexagonal lattice. The local distortions are assumed to be sources of the formation of ferromagnetism in compounds of this class.     

The effect of Al and Cr additions on pack cementation zinc coatings

Zinc is widely used as a protective coating material due to its corrosion resistant properties. The structure and oxidation resistance of Al and Cr mixed zinc coatings, deposited by pack cementation process, is thoroughly examined in this work. The morphology and chemical composition of the as-deposited and oxidized samples was accomplished by electron microscopy while the phase identification was performed by XRD diffraction analysis. The experimental results showed that the addition of aluminum or chromium in the pack mixture forms only Al and Cr rich phases on the surface of the specimens without affecting significantly the phase composition of the rest zinc coatings. In the case of Zn-Al coatings, the overlying layer contains high concentrations of Al together with lower amounts of zinc and iron and in Zn-Cr coatings this layer contains Cr, Fe and Zn atoms and has much smaller thickness. The presence of these additional layers promotes significantly the oxidation resistance of the zinc pack coatings and they preserve most of their initial thickness and chemical content when exposed to an aggressive environment while their oxidation mass gain was measured at low levels during the oxidation tests.     

Effect of nonlinearity on the steady motion of a twinning dislocation

We consider the steady motion of a twinning dislocation in a Frenkel-Kontorova lattice with a double-well substrate potential that has a non-degenerate spinodal region. Semi-analytical traveling wave solutions are constructed for the piecewise quadratic potential, and their stability and further effects of nonlinearity are investigated numerically. We show that the width of the spinodal region and the nonlinearity of the potential have a significant effect on the dislocation kinetics, resulting in stable steady motion in some low-velocity intervals and lower propagation stress. We also conjecture that a stable steady propagation must correspond to an increasing portion of the kinetic relation between the applied stress and dislocation velocity.     

Effect of impurities on cadmium density during cyclic thermal treatment

A study has been made of the effects of 0.05 wt.% of Ag, Au, Bi, Cu, Hg, In, Mg, Pb, Sb, Sn, and Zn on the cadmium density during cyclic thermal treatment in the temperature range 20–300 °C. The density decreases if the impurity is relatively insoluble and forms a eutectic system with cadmium. On the other hand, the density may not change if the maximum temperature of the cycle does not exceed the melting point of this eutectic system, or if the samples are not subjected to sufficiently high thermal stresses.Translated from Izvestiya Vysshikh Uchenbykh Zavedenii, Fizika, Vol. 12, No. 7, pp. 74–80, July, 1969.     

Energy and impurity solubility in a crystal containing interstitial impurities

The energy and the impurity solubility are calculated for a crystal containing impurities in octahedral, tetrahedral, and triangular interstitial sites. The energy advantage is derived for distribution of implanted atoms in various types of interstitial sites, along with the accompanying increase in the impurity solubility that accompanies this process.State University, Dnepropetrovsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 31–38, August, 1994.     

Atomic simulations of influence of twinning on crack propagation of Al

Molecular dynamics simulation was performed to investigate the influence of twin boundary(TB) spacing on crack propagation of Al.This study reveals the orientation of initial crack may affect the mechanism of crack growth obviously.TB strengthens Al when the crack orientation is parallel with TB because of the hinderance of TB to the emission of the dislocations.The results indicate that there is an optimal TB spacing for mechanical properties of the Al,exhibiting reverse HP(Hall-Petch) and HP effect when the TB spacing is near the critical TB spacing.Furthermore,we find that there is a yield strength hardening effect in nanotwinned Al when the crack orientation is perpendicular to the TB,and the Young’s modulus is smaller in the nanotwinned Al than that of twin free Al.The studies also demonstrate that this distinctive deformation behavior is related to nucleation of dislocations and the repulsive force of TB to the dislocations and crack propagation,as well as the distance between the crack tip and the TB.     

Statics and dynamics of “soft” impurities in a crystal

We investigate the effect of an impurity on the local static and dynamic behaviour of a crystal undergoing a displacive phase transition. It is shown that in mean-field approximation there may occur a freezing-out of local order driven by a soft local mode above the phase transition of the host. For a crystal containing a dilute impurity concentration, the impurity contribution to the static structure factor is calculated. The results are discussed in detail for the specific cases of a displacive and an Ising-type impurity.Work supported by the Swiss National Science FoundationThe results of this paper were presented at the Spring Meeting of the German Physical Society, Münster 1977 (Verhandlungen DPG (VI) 12, 1977)     

Charging and interaction of individual impurities in a monolayer organic crystal

We use a scanning tunneling microscope to study the charging of Ag-doping centers in a monolayer of C(60) molecules supported on a thin Al(2)O(3) film grown on the NiAl(110) surface. Differential conductance spectroscopy shows that charging affects the conduction through C(60) molecules located around the doping centers. This effect is used to observe the electrostatic interaction of a pair of centers. Charging of one doping center affects the energy levels of the other, an analogue of the field-effect action.