Theory of Nucleation on Dislocations

Cahn's theory of nucleation on dislocationshas been analyzed thoroughly and the imperfectionof the theory in some cases has been discussed.Arevised theory has been proposed with applicationto the problem of precipitation of M(CN)phase inaustenite.     

Influence of Rare-Earth Elements on ElectricalProperties of Pd

The influence of RE (RE = La, Ce. Pr. Nd, Sm, Eu, Gd. Tb. Dy, Er, Yb) additives with dilute concentrations on the electrical properties of Pd has been studied. All RE elements increase the specific resistivity (ρ) and decrease the resistance temperature coefficient (α) of Pd. and (ρ.α) Pd-RE ls equal to (ρ· α)Pd.The RE elements before Gd reduce the thermo-emf of Pd on Cu. other heavy RE enhance the thermo-emf.The experimental data of normalized Pd-0.1 at.-%RE alloys indicate that the effect of light RE additives on the specific resistivity of Pd is larger than that of heavy RE and Ce. Eu and Yb show anomalous strong effect. The valence and atomic size are main factors influencing the electrical properties.     

Effect of additives on sintering of α-cristobalite

Sintering is performed for the pure α-cristobalite, with TiO₂ additive, and with CaO additive powder compacts. The sintering temperatures were 1500, 1515, and 1525 °C for different dwell times. The master sintering curve theory is applied to the densification data and the activation energies are obtained. The splitting strength is measured for the sintered specimens. It is found that CaO decreases the activation energy due to the formation of liquid phase at the used sintering temperatures. The TiO₂ increases the activation energy because it exists as solid particles at the used sintering temperatures. The measured splitting strengths of the sintered specimens are shown to be best expressed by a sigmoid function of the work of sintering.     

Research on Fault Evaluation of Armament Equipment Based on ADAMS

1 IntroductionNowadays the local wars suggest that the key of succedng is the comParison of intmptive force,though advanccd Weaponry is becOndng moe and moe impotant. As the convelltional opPrssiveweaPO, artillery still plays a necessary Psit in m(for war Howevec arhllery Inay encounter allkln(l8 of faultS in the course of maintenance alld suPpot of armament equipment fOr incorreetiyOperahng and other natural reasons, and the faults win direetly affect the wobong performace ofarhllery Rec…     

Effect of additives on microstructure of Ca α-sialon

Three kinds of additives were added into Ca α-sialon, (Ca_0.6Si_10.2Al_1.8O_0.6N_15.4). It was found that the additives resulted in more of the liquid phase during sintering, which promoted the completion of the α→α′ transformation and the development of the elongated morphology characteristic of α-sialon grains. Comparison was made concerning the effect of the amount and type of additives on the microstructural development of Ca α-sialon. Phase and property analysis was also carried out on the hot-pressed samples.     

Effects of Mg Doping on Photoconductivity of GaN Films

This paper presents the UV photoconductivity properties of GaN films doped with different Mg concentrations deposited by MOCVD. It was observed that for the undoped and weakly doped GaN films the UV photocurrent response was relatively large and the relax time was relatively short. With an increase in doped Mg content, the samples became p-type, the photocurrent response became weak and the relax time became longer.     

Catalytic Functions of Metal Nanoparticles on Polymerization of Acetylene

New spiral nano-fibers were synthesized by a polymerization process of acetylene with metal nanoparticles as catalysts which were prepared by a hydrogen arc plasma method. The microstructures, conductive property of the nano-fibers and the effects of different nanoparticles(catalysts) on the microstructures of the fibers were studied.     

Alatiacts of Selected Artleles on Metals

92A0001 Effect of Hydrogen on Debye Tempera-ture and Lattice Parameter of Ti-30MoAlloy The variations of Debye temperature andlattice parameter of Ti-30Mo alloy with differenthydrogen contents were measured by X-raydiffraction.It was found that as the hydrogen con-tent increased,the Debye temperature decreased,but the lattice parameter of the alloy increased.Theabove results experimentally support thedecohesion theory that the increase of hydrogen in     

Influence of Rare-earth Elements on Mechanical Properties of Palladium

The influence of 0.1-0.6 at.-%RE additions (RE= La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb) on themechanical properties of Pd was studied. All above RE additions increased not only the strengthproperties at ambient temperature but also the tensile strength, creep rupture time and activation en-ergy at high temperatures, simultaneously increased the elongation of Pd. In the range of dilute con-centration, the strength properties of Pd-RE alloy enhanced linearly with RE concentration. Whenthe strength properties of Pd-RE alloys were normalized at 0.1 at.-%RE, it was found that light REelements had stronger effect on the properties of Pd than heavy RE, whereas Eu, Yb, Ce had anoma-lous effect. In all Pd-RF alloys, Pd-Eu alloy had the highest strength properties, successively Pd-Yband Pd-Ce alloy. The effect mechanisms of RE in alloy, such as purifying impurities, increasingrecrystallization temperature, refining grain size. expanding crystal lattice, increasing dislocation den-sity and decreasing stacking fault energy, forming stable RE oxidation by internal oxidation, and soon, were observed. They were strengthening sensitive factors. The influence of the factors onstrength properties and elongation of Pd was discussed.     

Wetting characteristics of sodium on β″-alumina and on nasicon

The sessile drop technique was used to determine the wetting characteristics of liquid sodium on -alumina and nasicon (Na₃Zr₂Si₂PO₁₂). The effects of moisture and temperature were studied using the wetting experiments. A range of contact angles (from 0 to 160°) were observed. The samples exposed to moisture exhibited poor wetting. The fact that good wetting is a prerequisite for improved cell performance was demonstrated via Na ¦-alumina¦ Na cell tests. Cells baked out in a vacuum passed in excess of 1100 Ah cm^–2 at 4 A cm^–2 current density without any degradation. Unbaked cells under similar conditions failed under 200 Ah cm^–2.     

Effect of crystal and domain orientation on the visible-light photochemical reduction of Ag on BiFeO₃

The reduction of silver from an aqueous solution on BiFeO? surfaces, activated by visible light, was investigated as a function of crystal and ferroelectric domain orientation. When excited by light with energy between 2.53 and 2.70 eV, BiFeO? photochemically reduces silver cations from solution in patterns corresponding to the underlying ferroelectric domain structure. Silver is preferentially reduced on domains with a positive polarization directed toward the surface. The amount of reduced silver depends on whether the component of the domain polarization normal to the surface is positive or negative, but is relatively insensitive to the crystal orientation. It is concluded that the ferroelectric polarization decreases electron drift to the surface in domains with a negative polarization, causing spatially selective photochemical behavior, and that the direction of the polarization is more important than the amplitude.     

The effect of processing parameters on the properties of γ-alumina washcoats deposited on ceramic honeycombs

The coating of cordierite honeycomb specimens with -alumina slurries for the preparation of washcoats for automotive applications was investigated. The dependence of slurry viscosity on factors such as the solids content, the pH and the particle size distribution of the powder used, was determined. Slurry viscosity was correlated to the loading percentage achieved, as well as to the quality of the washcoat in terms of homogeneity and reproducibility. It was found than an adequate solids content in the slurry is necessary for the achievement of satisfactory loading per impregnation. When, though, the particle size of the powder employed is of colloidal dimensions, high solids content leads to extremely high viscosity values. Adjustment of the slurry viscosity is therefore necessary and this was achieved with the use of either HCl or ammonium poly-methacrylate, an organic polyelectrolyte. Optimum loading conditions were achieved when the slurry viscosity lied between 50–150 mPa·s. For a specific solids content, the organic polyelectrolyte led to lower viscosity slurries and resulted in better reproducibility of the loading percentage. With the use of ammonium poly-methacrylate, slurries of fine particles, up to 40 wt% solids content could be handled, resulting in reproducible loading percentages of the order of 15 wt%     

An investigation on effects of heat treatment on corrosion properties of Ni–P electroless nano-coatings

Electroless Ni–P coatings are recognized for their excellent properties. In the present investigation electroless Ni–P nano-crystalline coatings were prepared. X-ray diffraction technique (XRD), scanning electron microscopy (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were utilized to study prior and post-deposition vacuum heat treatment effects on corrosion resistance together with the physical properties of the applied coatings.     

Numerical Analysis of the Influence of Natural Convection on the Process of Condensation of Atmospheric Pollutant Compounds on the Surface of Near‐Ground Plants

Numerical investigations of the process of condensation of deleterious atmospheric impurities on the surface of nearground plants under the conditions of natural convective flows have been carried out. The influence of the latter near the surface of phytocenosis elements on the intensity of the process of condensation has been evaluated.     

Influence of Grain Bounary on Fatigue Behavior of Ni-base Bicrystals

The influence of the grain boundary on the fatigue behavior was stuied by two three-point-bending (TPB) specimens.One TPB specimen was named Bicrystal 1,whose pre-crack was along the grain boundary and the applied load paralleled to pre-crack direction,while the other TPB specimen was named Bicrystal 2,whose the pre-crack was perpendicular to the grain boundary and the applied load paralleled also to the pre-crack.It was found that the rate of the fatigue crack growth of Bicrystal 1 was about a tenfold higher than that of Bicrystal 2.The fatigue behavior of Bicrystal 2 specimens was dependent on the distance between the crack tip and grain boundary.The crack growth rate was highest when the crack tip was at a critical distance to the grain boundary,while the rate was the lowest when the crack tip reached grain boundary.After the crack was over the grain boundary,the crack growth rate increased.The crystallographic finite element method was applied to analyze the stress and strain structure ahead of the crack,in order to reveal the above characteristics of the fatigue behavior.It is the grain boundary-induced redistribution of stresses near the crack tip that induces the difference of fatigue behavior.     

Influence of Grain Boundary on Fatigue Behavior of Ni-base Bicrystals

The influence of the grain boundary on the fatigue behavior was studied by two three-point-bending (TPB) specimens. One TPB specimen was named Bicrystal 1, whose pre-crack was along the grain boundary and the applied load paralleled to pre-crack direction, while the other TPB specimen was named Bicrystal 2, whose the pre-crack was perpendicular to the grain boundary and the applied load paralleled also to the pre-crack. It was found that the rate of the fatigue crack growth of Bicrystal 1 was about a tenfold higher than that of Bicrystal 2. The fatigue behavior of Bicrystal 2 specimens was dependent on the distance between the crack tip and grain boundary. The crack growth rate was highest when the crack tip was at a critical distance to the grain boundary, while the rate was the lowest when the crack tip reached grain boundary. After the crack was over the grain boundary, the crack growth rate increased. The crystallographic finite element method was applied to analyze the stress and strain structure ahead     

Effect of processing on toughness of Ca α-sialon ceramics

The influence of processing on microstructural development of Ca -sialon composition (Ca _x Si_12–3x Al_3x O _x N_16–x ) with x = 1.8 was studied by dwelling at different intermediate temperatures before reaching the final sintering temperature. The microstructural observation results have showed the different aspect ratios of elongated grains obtained by the various processing conditions, reflecting the effect of the number of nuclei of -sialon on morphology of grains during sintering. Improved toughness was achieved by applying low temperature dwelling for Ca -sialon compositions with low x values. The toughness showed an increase of 33% and 16% for x = 0.6 and 1.0 compositions respectively with middle dwelling processing at 1350°C for 3 h before reaching 1750°C for 1 h by hot-pressing.     

Comments on ‘Effect of obstacle strength and spacing on the slope of Haasen plot’

In a recent paper, Mishra et al. [Effect of obstacle strength and spacing on the slope of Haasen plot. Mater Sci Technol. 2019;1–6. doi:10.1080/02670836.2019.1567043], discrepancy between theoretical and experimental results in the slope of the Haasen plot between pure metals and alloys were reported. The discrepancy arises from a common belief that when Haasen plot for pure metals is extended to metals with multiple strengthening mechanisms, the inverse of activation volume components can be linearly superposed. It is conjectured that the slope of the Haasen plot should remain the same for both the pure metals and alloys, as it is governed only by dislocation–dislocation interaction. The purpose of this note is to clarify that the conjecture of invariant Haasen slope is only a special case.     

Effect of Relative Reduction on Property of Steel-Mushy Cu-Graphite Composite

The rolling treatment of steel-mushy QTi3.5-3.5 graphite composite was conducted under different relative reduction at room temperature. The effect of room-temperature rolling on interfacial mechanical property of steel-mushy QTi3.5-3.5 graphite composite was studied and the relationship between interfacial shear strength and relative reduction was established. The results show that, for steel-mushy QTi3.5-3.5 graphite composite, which consists of 1.2 mm-thick 08AI steel plate and 2.8 mm-thick QTi3.5-3.5 graphite layer, there is a nonlinear relationship between interfacial shear strength and relative reduction in graphite layer. When relative reduction is smaller than 1.1%, interfacial shear strength increases with increasing the relative reduction. When relative reduction is larger than 1.1%, interfacial shear strength decreases with increasing the relative reduction. When relative reduction is 1.1%, the largest interfacial shear strength of 145.2 MPa can be obtained.