THE MECHANISM OF SURFACE METALLIZATION OF POLYVINYL ALCOHOL COMPLEX METAL CHELATE FILMS

A novel method for preparing metalllzed film has been studied.The reduction process and properties of the poly(vinyl alcohol)(PVA)were probed by several analytic means.According to the etudies,a mechanism for the polymer surface reduction metallization was proposed and proved.

INTERACTION MECHANISM OF AMPHOTERIC COLLECTOR-I WITH METALLIC IONS AND MINERALS

The electronic structure and bonding nature of adsorbing bonding complexes which consist of Amphoteric Collector-I and Mg^(2+), Ca^(2+), MgPO_4^-, CaPO_^-4, CaCO_3, as well aa MgCO_3, are studied using quantum chemistry CNDO/2, It is predicted that magnesium salts are more liable to form adsorbing chelates with Amphoteric Collector-I than calcium salts, and all results coincide with that obtained in flotation.

THE STUDY ON TRE KINETICS AND MECHANISM OF THE REACTIONS OF METAL IONS WITH PnAO

The kinetics and the mechanism of the formation reactions of M(PnAO)^(2+)(M=Ni,Co,Cu)were studied with UV Spectrophotometer and Stopped Flow Spectrophotometer and a three steps mechanism was suggested.

The Dynamic Mechanisms for the Formation of Primary Metal Zoning of Cassiterite-Sulfide Deposits in the Gejiu Metallogenic Province, Yunnan

Copper and tin in cassiterite-sulfide deposits of the Gejiu metallogenic province are intimately associatedand show peculiar primary metal zoning. The authors made use of computer techniques to simulatenumerically the zoning of these ore deposits. The study shows that the regular spatial zoning probably resultedfrom the succession of multiple, intermittent and pulsatory mineralizations, The successive transports with di-verse velocities along channelways of the ore-forming solutions, taking place under conditions of definite dif-ference between metal concentrations, in solutions and wallrocks, followed by differential deposition, consti-tute possible dynamic mechanisms for the primary metal zoning.

Mathematical modeling for dynamic stability of sandwich beam with variable mechanical properties of core

The paper is devoted to mathematical modelling of static and dynamic stability of a simply supported three-layered beam with a metal foam core. Mechanical properties of the core vary along the vertical direction. The field of displacements is for- mulated using the classical broken line hypothesis and the proposed nonlinear hypothesis that generalizes the classical one. Using both hypotheses, the strains are determined as well as the stresses of each layer. The kinetic energy, the elastic strain energy, and the work of load are also determined. The system of equations of motion is derived using Hamilton＇s principle. Finally, the system of three equations is reduced to one equation of motion, in particular, the Mathieu equation. The Bubnov-Galerkin method is used to solve the system of equations of motion, and the Runge-Kutta method is used to solve the second-order differential equation. Numerical calculations are done for the chosen family of beams. The critical loads, unstable regions, angular frequencies of the beam, and the static and dynamic equilibrium paths are calculated analytically and verified numerically. The results of this study are presented in the forms of figures and tables.

Graphene-reinforced aluminum matrix composites prepared by spark plasma sintering

Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering（SPS）. The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide（Al_4C_3） is not formed during SPS processing. Further addition of graphene（above 1wt%） results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.

Interfacial Microstructure and Mechanical Properties of Al/Mg Butt Joints Made by MIG Welding Process with Zn-Cd Alloy as Interlayer

Butt joints between Mg alloy AZ31 B and pure Al 1 060 sheets were produced via metal inert gas welding process with Zn-Cd alloy foil. Crack-free Al/Mg butt joints between AZ31 B Mg alloy and pure Al 1060 sheets were obtained. Intermetallic compound layer 1 and layer 2 had formed in fusion zone/Mg alloy and the average thickness of the layer 1 was about 50 μm. The intermetallic compound layer 1 consisted of Al12Mg17 and Mg2Si phases while layer 2 consisted of Al12Mg17, Mg2Si and Mg Zn2 phases. The crack started from the IMC layer at the bottom of the joint and propagated along the brittle IMC layer, then expanded into weld metal during the SEM in situ tensile test. The highest tensile strength of the dissimilar metal butt joints could reach 46.8 MPa and the effect ofinterfacial IMC layer on mechanical property of the joint was discussed in detail in the present study.

Mechanical, electrical, and thermal expansion properties of carbon nanotube-based silver and silver–palladium alloy composites

The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver–palladium nanocomposite with CNT resulted in increases in the hardness and Young＇s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion（CTE）. The hardness and Young＇s modulus of the nanocomposites were increased by 30%？40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver–palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.

Effects of metal binder on the microstructure and mechanical properties of Al2O3-based micro-nanocomposite ceramic tool material

The Al_2O_3-（W,Ti）C composites with Ni and Mo additions varying from 0vol% to 12vol% were prepared via hot pressing sintering under 30 MPa. The microstructure was investigated via X-ray diffraction（XRD） and scanning electron microscopy（SEM） equipped with energy dispersive spectrometry（EDS）. Mechanical properties such as flexural strength, fracture toughness, and Vickers hardness were also measured. Results show that the main phases A12O3 and（W,Ti）C were detected by XRD. Compound Mo Ni also existed in sintered nanocomposites. The fracture modes of the nanocomposites were both intergranular and transgranular fractures. The plastic deformation of metal particles and crack bridging were the main toughening mechanisms. The maximum flexural strength and fracture toughness were obtained for 9vol% and 12vol% additions of Ni and Mo, respectively. The hardness of the composites reduced gradually with increasing content of metals Ni and Mo.

High plastic Zr–Cu–Fe–Al–Nb bulk metallic glasses for biomedical applications

Four Zr–Cu–Fe–Al-based bulk metallic glasses（BMGs） with Zr contents greater than 65at% and minor additions of Nb were designed and prepared. The glass forming abilities, thermal stabilities, mechanical properties, and corrosion resistance properties of the prepared BMGs were investigated. These BMGs exhibit moderate glass forming abilities along with superior fracture and yield strengths compared to previously reported Zr–Cu–Fe–Al BMGs. Specifically, the addition of Nb into this quaternary system remarkably increases the plastic strain to 27.5%, which is related to the high Poisson＇s ratio and low Young＇s and shear moduli. The Nb-bearing BMGs also exhibit a lower corrosion current density by about one order of magnitude and a wider passive region than 316 L steel in phosphate buffer solution（PBS, pH 7.4）. The combination of the optimized composition with high deformation ability, low Young＇s modulus, and excellent corrosion resistance properties indicates that this kind of BMG is promising for biomedical applications.

Mechanical Properties of Simple s-p Metals, and Defect Energies from Electron Theory and from Interatomic Force Laws

The cleavage force F(z) needed to separate parallel atomic planes by a distance z is first discussed for simple s-p metals using density functional theory.For the s-p nearly free-electron metals the linearized Thomas-Fermi equation is solved self-consistently in the cases of (a) semi-infinite planes of jellium (i.e. smeared uniform positive ions) and (b) a semi-infinite cylinder of finite radius, cleaved by a plane perpendicular to its axis. In (a), the elastic region has the form F(z)=Az ∝ Zrs-11/2, where rs is the mean interelectronic distance in the jellium model. Size effects are then considered, with possible relevance to atomic force microscopy.Defect energies are treated, using both electron theory and pair force laws.

Formation and Mechanical Properties of Zr-Nb-Cu-Ni-Al-Lu Bulk Glassy Alloys with Superior Glass-Forming Ability

Glass-forming ability（GFA） and mechanical properties of（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（100-x）Lu_x（x= 0-3 at%） alloys have been investigated.The GFA of Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy is dramatically enhanced by adding Lu.The（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（98）Lu_2 alloy possesses the highest GFA in the studied Zr-Nb-Cu-Ni-Al-Lu alloys,with its critical diameter for glass formation reaching 20 mm by copper-mould casting method,while that of the Lu-free Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy is 7 mm.The critical diameters of（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（100-x）Lu_x（x =1 at%and 3 at%） alloys are 15 mm and 12 mm,respectively.The Lu addition to Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy induces the change of initial crystallization phases from face-centred-cubic Zr_2Ni and tetragonal Zr_2Ni phases for the Lu-free Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy to an icosahedral quasi-crystalline phase for the Lu-doped alloys,which may be the origin for the enhanced GFA of the Lu-doped alloys.The compressive fracture strength and plastic strain of the bulk glassy（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（98）Lu_2 alloy are1 610 MPa and 1.5%,respectively.

Chemical, mechanical, and thermal expansion properties of a carbon nanotube-reinforced aluminum nanocomposite

In the present study,the chemical and mechanical properties and the thermal expansion of a carbon nanotube（CNT）-based crystalline nano-aluminum（nano Al） composite were reported.The properties of nanocomposites were tailored by incorporating CNTs into the nano Al matrix using a physical mixing method.The elastic moduli and the coefficient of thermal expansion（CTE） of the nanocomposites were also estimated to understand the effects of CNT reinforcement in the Al matrix.Microstructural characterization of the nanocomposite reveals that the CNTs are dispersed and embedded in the Al matrix.The experimental results indicate that the incorporation of CNTs into the nano Al matrix results in the increase in hardness and elastic modulus along with a concomitant decrease in the coefficient of thermal expansion The hardness and elastic modulus of the nanocomposite increase by 21%and 20%,respectively,upon CNT addition.The CTE of CNT/A1 nanocomposite decreases to 70%compared with that of nano Al.

Mechanical Properties of Si and Some d-electron Metals:Force Laws, Electron Correlation and Bond-breaking

The coordination-dependent force fleld of TersofF for covalently bonded Si has been used tocalculate the cleavage force as a function of interplanar separation and hence to estimate surfaceenergies. This force field is already fitted to density functional results. The relation to bond-breaking and electron correlation will be emphasized. Finnis-Sinclair-type many-body potentialshave then been used to treat some d-electron metals. In particular, results for cleavage forcein bcc Fe will be presented, and also some calculations as two perfectly planar Fe surfaces arerubbed together' at different interplanar separations. Finally, lattice dynamical models for thesteady-state propagation of a screw dislocation, and then of a crack, will be used, again within abond-breaking type of force field. For the screw dislocation propagation. a solitary wave equationis shown to follow in the 'almost continuum' limit. Energy radiated by phonons as the dislocationmoves can thereby be calculated.

Experimental determination of Cd^2＋ adsorption mechanism on low-cost biological waste

Carbonate shells have an astonishing ability in the removal of Cd^2＋ in a short time period with emphasis on being a low cost adsorbent. In the present study, the sorption capacity of carbonate shells was studied for Cd^2＋ in batch experiments. The influence of different carbonate shell sizes and physico-chemical factors were evaluated and the results were analyzed for its correlation matrices by using Predictive Analytics Software （PASW）. The miner- alogy state of aqueous solution regarding the saturation index was simulated using PHREEQC to identify the Cd^2＋ uptake mechanism. The Cd uptake rates were calculated as well as Ca^2＋, HCO3- concentration, pH, ambient humidity and temperature were measured. Cd2＋ removal of 91.52% was achieved after 5 h adsorption. The adsorption efficiencies were significantly influenced by pH as they increased with the increase of pH from acidic solution （5.50±0.02） to slightly alkaline （7.60±0.05）. In addition, the mineralogy state of aqueous solution calculated from PHREEQC confirmed that the increment of Ca^2＋ and HCO3- concentrations in solution was attributed to the dissolution of carbonate shells. Moreover, the ion exchange adsorption mechanism of Cd^2＋ toward Ca^2＋ was identified as the process involved in Cd^2＋ uptake.

Advances in photocatalytic disinfection of bacteria:Development of photocatalysts and mechanisms

Photocatalysis has attracted worldwide attention due to its potential in solar energy conversion.As a ＂green＂ advanced oxidation technology, it has been extensively used for water disinfection and wastewater treatment. This article provides a review of the recent progress in solar energy-induced photocatalytic disinfection of bacteria, focusing on the development of highly efficient photocatalysts and their underlying mechanisms in bacterial inactivation. The photocatalysts are classified into Ti O2-based and non-Ti O2-based systems, as Ti O2 is the most investigated photocatalyst. The synthesis methods, modification strategies, bacterial disinfection activities and mechanisms of different types of photocatalysts are reviewed in detail.Emphasis is given to the modified Ti O2, including noble metal deposition, non-metal doping,dye sensitization and composite Ti O2, along with typical non-Ti O2-based photocatalysts for bacterial disinfection, including metal oxides, sulfides, bismuth metallates, graphene-based photocatalysts, carbon nitride-based photocatalysts and natural photocatalysts. A simple and versatile methodology by using a partition system combined with scavenging study is introduced to study the photocatalytic disinfection mechanisms in different photocatalytic systems. This review summarizes the current state of the work on photocatalytic disinfection of bacteria, and is expected to offer useful insights for the future development in the field.

Removal of Pb(Ⅱ) from aqueous solution by hydrous manganese dioxide:Adsorption behavior and mechanism

Hydrous manganese dioxide （HMO） synthesized by redox of potassium permanganate and hydrogen peroxide was used as an adsorbent for Pb（Ⅱ） removal.The specific surface area,pore volume and BJH pore diameter of the HMO were 79.31m2/g,0.07cm3/g and 3.38 nm,respectively.The adsorption equilibrium at 298K could be well described by the Langmuir isotherm equation with q max value of 352.55mg/g.The negative values of G and the positive values of H and S indicated the adsorption process was spontaneous and endothermic.The pseudo second-order equation could best fit the adsorption data.The value of the calculated activation energy for Pb（Ⅱ） adsorption onto the HMO was 38.23 kJ/mol.The uptake of Pb（Ⅱ） by HMO was correlated with increasing surface hydroxyl group content and the main adsorbed speciation was PbOH＋.The final chemical state of Pb（Ⅱ） on the surface of HMO was similar to PbO.HMO was a promising candidate for Pb（Ⅱ） removal from aqueous solution.

The effect of metal ions with different valences on the retardation of soil–bentonite barrier materials and its mechanism

In this paper, with K＋, Ca2＋ and Fe3＋ as the objects of study, retardation of soil-bentonite （SB） barrier materials for metal ions with different valences is investigated, and the adsorption mechanism, migration patterns and permeation behavior are explored so as to provide a theoretical basis for their application. The results show that the adsorption process for metal ions with different valences by SB barrier materials is fast, and the higher the valence, the greater the adsorption capacity. The fitting of the adsorption process conforms to pseudo-second-order adsorption kinetics and Langmuir-Freundlich adsorption equation, which explains that chemical adsorption is the dominating state and that the SB surface has certain heterogeneity. The permeability coefficient of K＋, Ca2＋ and Fe3＋ in SB each has a maximum and the higher the valence, the sooner the maximum appears. Also the higher the valence, the more obvious the effect on SB retardation performance; and the sooner the ion breaks through the barrier wall completely, that is, the wall＇s retardation performance for higher valent ions may decline.

Manufacturing size effect on the structural and mechanical properties of additively manufactured Ti-6Al-4V microbeams

The size effect of Ti-6Al-4V submillimeter structures manufactured by selective laser melting,which is critical for metallic mechanical metamaterials of unique mechanical properties,for example,nega-tive Poisson’s ratio and ultrahigh modulus,which show promise in biomedical,environmental,energy-related applications,has not been systematically investigated.Presented here are the quantification of the porosities by X-ray microtomography scans,texture analysis,and mechanical characterization of the addi-tively manufactured Ti-6Al-4V microbeams.We found linearly decreasing porosities,increasing mechan-ical properties,and increasing texture in the microbeam with increasing diameter from 250 to 500μm.The variation of microstructure in microbeams of different diameters and along the sample height,result-ing from the printing parameters and the thermal conditions,leads to the discrepancy between the be-havior observed in experiments and finite element simulation.Our results provide the structure-property-processing correlation to improve the manufacturing and prediction of the mechanical behavior of metal-lic mechanical metamaterials.