IMPROVEMENT ON TENSILE PROPERTIES AND CREEP RESISTANCE OF Fe 3Al BASED ALLOYS

Effects of alloying processing on tensile test properties of Fe 3Al based alloys have been studied. Results show that microalloying of cerium is very effective on increasing the room temperature ductility of Fe 3Al based alloys. Surface analysis by XPS demonstrates that cerium addition causes the change in the oxide chemistry and provides rapid passivation of the specimen surface. The high temperature strength and creep resistance of Fe 3Al based alloys can be significantly enhanced by alloying additions of tungsten, niobium or molybdenum, especially when combined additions of tungsten with niobium or molybdenum are used. The additions of tungsten, niobium or molybdenum also result in the significant microstructural refinement and the formation of fine precipitates which are identified as M 6C type carbide in the alloys containing tungsten.

浓相输灰技术在鄂州电厂灰库外送中的应用

介绍了浓相输灰技术在鄂州电厂一期、二期灰库外送至三期灰库中的应用,该灰库外送系统输送管道爬高47 m、90°弯头18个、输送距离最远950 m,单根输送管道最大出力大于70 t/h,输送的飞灰既有原灰库的原灰,又有分选后粗灰库的粗灰及细灰库的细灰,系统于2019年投运至今运行稳定、出力大、对飞灰料性变化适应性强,对有灰库外送需求的火力发电厂提供了良好的借鉴。

Plastic characterization of metals by combining nanoindentation test and finite element simulation

Materials with the same elastic modulus E and representative stress and strain （σr,εr） present similar indentation-loading curves, whatever the value of strain hardening exponent n. Based on this definition, a good approach was proposed to extract the plastic properties or constitutive equations of metals from nanoindentation test combining finite element simulation. Firstly, without consideration of strain hardening, the representative stress was determined by varying assumed representative stress over a wide range until a good agreement was reached between the computed and experimental loading curves. Similarly, the corresponding representative strain was determined with different hypothetical values of strain hardening exponent in the range of 0-0.6. Through modulating assumed strain hardening exponent values to make the computed unloading curve coincide with that of the experiment, the real strain hardening exponent was acquired. Once the strain hardening exponent was determined, the initial yield stress ay of metals could be obtained by the power law constitution. The validity of the proposed methodology was verified by three real metals： AISI 304 steel, Fe andA1 alloy.

Synthesis and properties of single-crystal Ni-rich cathode materials in Li-ion batteries

Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigated by X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical performance was characterized by long-term cycling, cyclic voltammetry, and in-situ impedance spectroscopy. The results indicated that high temperature rendered layered oxides to lose lithium/oxygen in the interior and exterior, and induced cationic disordering. Besides, the solid-phase synthesis process promoted phase transformation for electrode materials, causing the coexisting multi-phase in a single particle. High temperature can foster the growth of single particles, but it caused unstable structure of layered phase.

The Influence of Transmutation Conditions on the Adulteration Performance of Nano-scale Nickel Hydroxide

Spherical Nano-scale nickel hydroxide was prepared through precipitation transmutation method by controlling the transmutation conditions in this paper. The measurement results of XRD and TEM indicate that the crystallization of the nano-scale nickel hydroxide isβ-style and its shape is spherical with a diameter of 40～70 nanometer. The adulteration experiment shows that the adulteration ratio of nano- scale Ni(OH) 2 in common spherical micrometer-scale Ni(OH) 2 exists a optimal value (1∶9). And at this point, the utilization ratio of Ni(OH) 2 in electrodes can be raised by 10%, and the nano-scale nickel hydroxide with sphericity shape shows a better adulteration performance than that with needle shape.

Deformation behavior of high performance fiber reinforced cementitious composite prepared with asphalt emulsion

A novel engineered cementitious composite(ECC) was prepared with the complex binder of Portland cement and asphalt emulsion.By adjusting the amount of asphalt emulsion,different mixture proportions were adopted in experiments,including four-point bending test,compressive test,and scanning electric microscopy(SEM).The SEM observation was conducted to evaluate the contribution of polyvinyl alcohol(PVA) fiber and asphalt emulsion to the composite toughening mechanism.The tests results show that the most remarkable deflection-hardening behavior and saturated multiple cracking are achieved when the content of asphalt emulsion is 10%.However,excessive content of asphalt emulsion causes severe damages on the deformation behavior as well as loss in compressive strength of the mixture.SEM observation indicates that the influence of asphalt emulsion on the fiber/matrix interfacial property changes the dominant fiber failure type from rupture into pull-out mode,and thus causes beneficial effects for strain-hardening behavior.

Study on How to Adapt Raw Clay Housing to Climate Change： Locust Bean Tree （Parkia Biglobosa） Used as Protecting Material

The use of raw clay in housing construction dates back from ancient times and is still living on. Traditional habitat comprising various buildings all over different places of our planet, give evidence. Among any other pathologies affecting naked earthen walls, the rain water wash remains a major concern and deserves careful consideration. Which justifies the interest of this research focused on the protection means of such types of walls. This article relates the experiment conducted on low walls made out of raw clay mixed with composite protecting products （traditional and modern ones as well）, being tested to intensive water floods. The result of the tests assessed through efficiency of the protecting materials, shows that the locust bean tree （local tree） fruit husk extract added to raw clay mortar and carefully blended seems to provide better ability to protect walls against water assault. Moreover, consistency check and plasticity reveal better performance in clay material properties.

Effect of Ultraviolet Aging on Asphalt Rheological Properties

This paper simulated the ultraviolet aging process of asphalt and used dynamic mechanic analysis （DMA） method to evaluate the effect of ultraviolet aging on the asphalt theological properties. After having experienced ultravio- let aging, the low temperature performance of asphalt binder decreased significantly, with its complex modulus increased and phase angle decreased along with changing rheological properties as compared to the performance of original asphalt binder. The ultraviolet aging process would make asphalt binder more sensitive to brittle and fatigue failure. On the basis of the time-temperature superposition principle （TTSP）, the viscoelastic transition frequency （coT） is proposed to evaluate the effect of ultraviolet aging. It is found that with the increase in ultraviolet aging time, the cox moves to the lower frequency range gradually. Since the viscoelastic transition frequency is sensitive to the effect of aging, it can be used as an indicator of ultraviolet aging.

Examination of Archival Data for Inhomogeneities and Determination of Climate Change in North America

Numerous articles have examined archival weather observations and attributed climate changes on time scales ranging from centuries to decades and in one case even days to human activity. This article gives examples showing how climate variability and sudden changes in instruments affect trend determination. In particular, surface temperature and water vapor pressure trends in North America during 1948-2010 are discussed. Over 1/4 billion hourly observations taken at 309 stations, were first carefully examined for inhomogeneities. Positive and negative steps, for both temperature and water vapor pressure were found to not be evenly distributed in time. Inclusion of such data in a trend analysis would overstate decadal changes in temperature and water vapor. Time series free of such discontinuities show a statistically significant warming has primarily affected the western Arctic, Canadian prairies and the Midwestern U.S. during winter. Increases in water vapor pressure are most pronounced in summer in the eastern U.S. The decadal water vapor pressure trends are somewhat smaller than found in other studies that examined data for far shorter time periods. The claim of a change in the DTR （diurnal temperature range） during the 3 day flight ban following Sept. 11, 2011, is not substantiated. The observed change in the DTR was likely caused by a reduction in cloudiness during the flight ban.

Free Vibration of Geometrically Nonlinear Functionally Graded Micro-switches under Electrostatic Force and Temperature Change

The free vibration characteristics of functionally graded micro-switches under combined electrostatic, axial residual stress and temperature change is investigated, with an emphasis on the effect of geometric nonlinear deformation due to mid-plane stretching, the influence of volume fraction profile parameter and temperature change. The micro-switch considered in this study is made of either homogeneous material or non-homogeneous functionally graded material with two material phases. Taking the temperature-dependency of the effective material properties into consideration, the Voigt model is used to simulate the material properties of the FGMs （functionally graded materials）. The principle of virtual work is used to derive the nonlinear governing differential equation. The eigenvalue problem which describes free vibration of the micro-beam at its statically deflected state is then solved using DQM （differential quadrature method）. The natural frequencies of clamped-clamped micro-switches are obtained. The solutions are validated through direct comparisons with experimental results reported in previous studies. A parametric study is conducted to show the effects of geometric nonlinearity, material composition, temperature change and geometrical parameters for the natural frequencies.

Potential Effects of Global Change to Urban Vegetation： Vulnerability and Adaptations

An urban area is a space with high population density which develops new, major and complex structures in comparison to the areas surrounding it. In order to develop these structures and maintain population and its activity, the metabolism of urban areas needs a lot of external sources of energy and nutrients （water, food, materials...）, which produces heat waste, garbage, sewage and pollution which are some of the major problems for urban sites, and the related areas from it. This metabolism promotes major environmental changes in the urban areas, which promote stress on vegetation used in gardening. The main environmental factors that affect vegetation in urban areas are the same that have been defined in literature from long time ago, but now they are acting as the sum of complementary and synergic effects of these classical stresses at the same moment, in the same place, which happen due to the incredibly amount of energy that we place in the systems. This is called global change. Ecophysiological studies can provide objective information to be used as a tool to improve the vegetation management in urban areas from design to process, and consequently avoiding the potential vulnerabilities associated with global change. Present paper tries to show several examples about the plant response, measurement tools and vulnerabilities and adaptations to global change under urban conditions. It can be concluded that the large availability of vegetal material and the great technical development can be highlighted as strong points of gardening and urban landscaping while, as weak points, it could be mentioned the changing taste of consumers, which can force the introduction of new vegetal material with no time for adaptation, Urban gardening and landscaping can be considered to be exposed to global change, but in our opinion it is necessary to carry out more studies to determine the real degree of vulnerability of this activity to this complex kind of stress.

Light emission properties of sapphire under shock loading in the stress range of 40-120 GPa

The measurement of emissions from the window material of sapphire was performed through multi-wavelength pyrometer and spontaneous spectroscopic techniques in the pressure range of 40 -120 GPa. The results showed that the spectral distribution with wavelength clearly fit well with the grey-body spectrum. We have analyzed the emissions and discovered they mostly came from the shear banding, which is a typical thermal radiation. The radiance intensity changing linearly with time revealed it was a volume effect. All of the data from pyrometer can be explained by the model of Boslough＇s study, especially for pres- sures over megabar. The color temperature of shocked sapphire changing with increased stress disagrees with the computed melt curve which is likely explained by the differcnt phase structures of sapphire.

A macroscopic constitutive model of shape memory alloy considering cyclic effects

This paper presents a macroscopic constitutive model reproducing the hysteretic behaviors of the superelastic shape memory alloy (SMA) under cyclic loading. The progressive increase of residual strain with the increased cycle number in such materials is assumed to be a consequence of the progressive increase of residual stress-induced martensitic volume fraction upon the cyclic effects. The progressive decrease of phase transformation critical stresses with the increased cycle number in such materials is assumed to be a result from the progressive increase of phase transformation critical temperatures upon the cyclic effects. A cyclic evolution equation is supposed to describe the influences of cycle effects on the material properties of the SMA under cyclic loading. A phase transformation equation expressing the phase transformation behaviors of the SMA under cyclic loading is established based on the differential relationship between martensitic volume fraction and the free energy increment of phase transformation. A mechanical constitutive equation predicting the mechanical characteristics of the SMA under cyclic loading is developed on the basis of thermodynamics and continuum mechanics. The cyclic evolution equation, phase transformation equation, and mechanical constitutive equation together compose the presented macroscopic constitutive model considering cyclic effects. Results of the numerical simulations illustrate that it can well reproduce the superelastic hysteretic behaviors of the SMA under cyclic loading.

A comparative analysis of dielectric properties of oil-paper insulation and polymer materials before and after thermal aging

The shortcomings of oil-immersed transformer solid insulation like low high-temperature resistance of the insulation paper and the uneven distribution of electric field caused by the large difference of dielectric constants between insulation paper and transformer oil,restricted the development of transformer with smaller size and larger capacity.In view of this situation and the transformer’s demand for the dielectric physicochemical and mechanical property of insulation material,polycarbonate,polyester film and polyphenylene sulfide with high high-temperature resistance were chosen for the comparison analysis in this paper We did the 300-day thermal aging experiment on four samples in transformer oil under different aging temperatures of90°C,110°C and 130°C,then analyzed the changes of their dielectric properties.The experiment results are as follows;the permittivity and dielectric dissipation factor of the three polymer materials are apparently smaller than those of the paper both before and after 300-day aging;the volume resistivity and partial discharge inception voltage of the three materials are higher than those of the paper both before and after aging;and the breakdown field strength of polycarbonate is higher than that of the paper both before and after aging,while that of polyester film and polyphenylene sulfide are slightly lower than that of the paper.

Nonlinear dynamical behavior of Xenon atoms along dislocation lines in UO_(2+x) nuclear fuel

Experimental results showed that there are a few Xenon atom bubbles connected by the dislocation line in the UO2+x nuclear fuel, and the largest radius of bubbles is about 45 nm. This phenomenon is in contrast to traditional bubble formation mechanism. This phenomenon is very important in understanding the properties of nuclear fuel. In this work, we apply a time- dependent microscopic atom transport equation and take into account stress coherent potential in the boundary of the dislocation. Using the equation, we numerically solved the stress coherence effect and studied the transfer properties of Xenon atoms along the dislocation line. Our numerical results show that the transport of the Xenon atoms along the dislocation changes nonlinearly with the external driving energy, and reaches at the saturation values. It explains the growth limit of Xenon atom bubbles that is in agreement with the experiment results.