Analysis of Bonding Properties of Corroded Reinforcement Concrete

In order to investigate the degradation of bonding properties between corroded steel bars and concrete,this study employs the half-beam method to conduct bond-slip tests between corroded steel bars and concrete after impressed-current accelerated corrosion of the steel bars in concrete.The effects of steel corrosion rate,steel bar diameter,steel bar strength grade,and concrete strength grade on the bonding properties between concrete and corroded steel bars were analyzed.The influence of different corrosion rates on specimens’bonding strength and bond-slip curves was determined,and a constitutive relationship for bond-slip between corroded steel bars and concrete was proposed.The results indicate that the ultimate bonding strength of corroded reinforced concrete specimens decreases with increasing corrosion rate.Additionally,an increase in corrosive crack width leads to a linear decrease in bonding strength.Evaluating the decline in adhesive properties through rust expansion crack width in engineering applications is feasible.Furthermore,a bond-slip constitutive relationship between corroded steel bars and concrete was established using relative bond stress and relative slip values,which aligned well with the experimental findings.

Bond of Seawater Scoria Aggregate Concrete to Stainless Reinforcement

This study investigates the bond between seawater scoria aggregate concrete(SSAC)and stainless reinforcement(SR)through a series of pull-out tests.A total of 39 specimens,considering five experimental parameters—con-crete type(SSAC,ordinary concrete(OC)and seawater coral aggregate concrete(SCAC)),reinforcement type(SR,ordinary reinforcement(OR)),bond length(3,5 and 8 times bar diameter),concrete strength(C25 and C30)and concrete cover thickness(42 and 67 mm)—were prepared.The typical bond properties(failure pattern,bond strength,bond-slip curves and bond stress distribution,etc.)of seawater scoria aggregate concrete-stainless rein-forcement(SSAC-SR)specimen were systematically studied.Generally,the failure pattern changed with the con-crete type used,and the failure surface of SSAC specimen was different from that of OC specimen.SSAC enhanced the bond strength of specimen,while its effect on the deformation of SSAC-SR was negative.On aver-age,the peak slip of SSAC specimens was 20%lower while the bond strength was 6.7%higher compared to OC specimens under the similar conditions.The effects of variables on the bond strength of SSAC–SR in increasing order are concrete type,bond length,concrete strength and cover thickness.The bond-slip curve of SSAC-SR specimen consisted of micro-slipping,slipping and declining stages.It can be obtained that SSAC reduced the curve curvature of bond-slip,and the decline of curve became steep after adopting SR.The typical distribution of bond stress along bond length changed with the types of concrete and reinforcement used.Finally,a specific expression of the bond stress-slip curve considering the effects of various variables was established,which could provide a basis for the practical application of reinforced SSAC.

Synthesis,Structure,Fluorescent Property and Natural Bond Orbital(NBO) Analysis of a One-dimensional Cobalt(III) Complex Containing 1,3-Benzenedicarboxylate and 2-Methyldipyrido[3,2-f:2',3'-h]quinoxaline Ligand

A novel metal-organic coordination polymer [Co（m-BDC）（Medpq）·2H2O]n（m-H2BDC = benzene-1,3-dicarboxyalic acid,Medpq = 2-methyldipyrido[3,2-f：2＇,3＇-h]quinoxaline） has been hydrothermally synthesized and structurally characterized by elemental analysis,IR spectrum and single-crystal X-ray diffraction.The title compound crystallizes in monoclinic,space group C2/c with a = 19.986（4）,b = 15.789（3）,c = 16.292（3）（A°）,β = 126.54（3）°,V = 4130.3（14）（A°）^3,C23H18N4O6Co,Mr = 505.34,Dc = 1.625 g·cm^-3,Z = 8,μ = 0.883 mm^-1,F（000） = 2072,the final R = 0.0772 and wR = 0.1428.The crystal structure of complex 1 is an infinite zigzag-like chain of hexacoordinate Co^3＋ ions,in which the Co^3＋ ions are bridged in two coordination modes by m-BDC^2＋ ligands and decorated by Medpq ligands,showing a slightly distorted octahedral geometry.Additionally,the compound shows strong fluorescence in the solid state at room temperature.Natural bond orbital（NBO） analysis is performed by using the NBO method built in Gaussian 03 Program.The calculation results show a covalent interaction between the coordinated atoms and Co^3＋ ions.

Effect of Ultraviolet Aging on the Bonding and Tensile Properties of Polymer-Cement Composite

In this paper,the specimens of polymer-cement composites after 1 d,7 d,15 d,and 30 d aging without aging and UV aging are subjected to fixed extension test and tensile test.By observing the mode of the composite in the fixed-elongation test,and measuring the elastic recovery rate,tensile strength,elongation at break,peak tensile strain,tensile toughness and pre-peak tensile toughness of the composite,the effects of UV aging on the bonding and the tensile properties of the composite were studied.And combining with scanning electron microscopy experiments,the micro-mechanism of the effect of ultraviolet aging on the properties of composite was analyzed.The results showed that the composite had a good bonding property,and no damage was observed after UV aging for 30 days.The UV aging increased the elastic recovery rate and peak tensile within a certain range.The elastic recovery rate and peak tensile strain of the composite increased by 6.60%and 23.55%respectively after UV aging for 15 days.Therefore,the UV aging could enhance the tensile property and the tensile energy consumption performance of the composite.The tensile strength of the composite increased by 65.36%after UV aging for 30 days.The tensile toughness and pre-peak tensile toughness of the composite were increased by 43.29%and 101.83%respectively after UV aging for 15 days.The elongation at break of composite decreased continuously after UV aging due to the photo-oxygen reaction,as well as secondary hydration reaction and cross-linking curing reaction of cement.

Experimental Study on Bonding Properties Between Steel Strand and Concrete at Cryogenic Temperatures

To study the bonding properties between steel strand and concrete at room and cryogenic temperatures, a series of center pullout experiments were conducted on 96 bonding anchorage specimens at the lowest temperature of-165 ℃. The impacts on the bonding property of such parameters as the temperature, concrete strength, the relative concrete cover thickness, and the relative anchorage length were analyzed. The test results indicate that the changes in temperature have a clear effect on the bonding property between steel strand and concrete. As the temperature decreases, the bond stress, which corresponds to a 1 mm slip of steel strand in relation to concrete, and the ultimate bond strength initially increase and subsequently decrease at the inflection point of-80 ℃. The impact of the concrete strength on the bonding property, as shown by the tensile strength and the moisture content interaction, indicates that the bond stress vs concrete strength curve initially increases and later decreases with a decrease in temperature; the bond stress vs concrete cover thickness curve linearly increases, but the bond stress vs anchorage length curve linearly decreases at first and finally levels off.

Effect of Mechanical Surface Treatment on the Bonding Mechanism and Properties of Cold‑Rolled Cu/Al Clad Plate

In the case of valuable cold-rolled Cu/Al clad plates,billet surface treatment before rolling is a significant process that can affect the bonding efficiency and quality.While the current studies primarily focus on the influence of rolling parameters,insufficient attention has been paid to surface treatment.In this study,the effects of mechanical surface treatment on the bonding mechanism and bonding properties of cold-rolled Cu/Al clad plates were investigated.The results showed that different mechanical surface treatments have significant effects on the surface morphology,roughness,and residual stress.In addition,the effect of surface mechanical treatment on bonding quality was also observed to be critical.When the grinding direction was consistent with the rolling direction(RD),the bonding quality of the Cu/Al clad plates was significantly improved.After surface treatment along the RD for 20 s,the Cu/Al clad plates showed the highest shear strength(78 MPa),approximately four times as high as that of the unpolished samples.Simultaneously,the peel strength of this process was also significantly higher than that achieved via the other processes.Finally,on the basis of the surface morphology,roughness,and residual stress,the effect of surface treatment on the bonding mechanism and bonding properties of Cu/Al clad plates was analyzed.This study proposes a deeper understanding of the bonding behavior and bonding mechanism for cold rolled clad plates processed via mechanical surface treatment.

Experimental and Theoretical Study on Bonding Properties between Steel Bar and Bamboo Scrimber

To further verify the feasibility of newly designed reinforced bamboo scrimber composite(RBSC)beams used in building construction,the bonding properties between steel bar and bamboo scrimber were investigated by anti-pulling tests.Results indicated that the anti-pulling mechanical properties were significantly correlated to the diameter,thread form and buried depth of steel bar,forming density of bamboo scrimber as well as the heat treatment of bamboo bundle.There were two failure modes for anti-pulling tests:the tensile fracture and pulling out of steel bar.Both the ultimate load and average shear strength of anti-pulling specimen could be increased greatly with the ribbed bar,high forming density of bamboo scrimber and un-heated bamboo bundle.Furthermore,a theoretical calculation model of the bonding interface between steel bar and bamboo scrimber was developed.Based on the theoretical calculation model,the change laws of normal stress of bamboo scrimber,and shear stress of glue layer along the buried depth of steel bar were revealed.This study is beneficial for the safety application of RBSC beams in building construction.

Effect of Aluminum Addition on Microstructure and Properties of SiO_2-B_2O_3-Al_2O_3-CaO Vitrified Bond

Influence of aluminum addition on the structures and properties of SiO_2-B_2O_3-Al_2O_3-CaO vitrified bond at low sintering temperature and high strength was discussed. FTIR and XRD analyses were used to characterize the structures of the basic vitrified bond with different contents of aluminum. The bending strength and the thermal expansion coefficients were also tested. Meanwhile, the microstructures of composite specimens at sintering temperature of 660 ℃ were observed by scanning electron microscope（SEM）. The experimental results showed that the properties of vitrified bond with 1wt% aluminum were improved significantly, where the bending strength, Rockwell hardness, and thermal expansion coefficient of the vitrified bond reached 132 MPa, 63 HRB, and 6.73×10^（-6） ℃^（-1）, respectively.

Synthesis,Structure and Electrochemical Property of a Supramolecular Compound(H_2en)_2[Cu(en)_2(H_3O)_2][Mo_8O_(28)]

A supramolecular compound（H2en）2[Cu（en）2（H3O）2][Mo8O28]（en=ethylenediamine） was hydrothermally prepared and confirmed by elemental analysis and TG analysis.Single-crystal X-ray analysis reveals that the crystal crystallizes in the triclinic system,space group P1 with a=9.4635（4）,b=9.8645（5）,c=10.9794（5）A,α=69.2050（10）,β=72.3730（10）,γ=78.4510（10）o,Mr=1559.55,V=908.24（7）A^3,Z=1,Dc=2.851 g/m^3,F（000）=749,μ=3.350 mm^-1,S=1.000,the final R=0.0217 and wR=0.0567.The compound consists of（H2en）^2＋,[Mo8O28]^8-anion and [Cu（en）2（H3O）2]^2＋ cations and constructs a 3D supramolecular structure through hydrogen bonds between the nitrogen atoms from en of [Cu（en）2（H3O）2]^4＋ fragments and the terminal oxygen atoms from the [Mo8O28]^8-polyoxoanions.The electrochemical behavior of this compound has been studied in detail based on a solid bulk modified carbon paste electrode of compound（CPE）.

Theoretical Investigation of Structures,Bonding and Electronic Properties for the Complexes of 6-Mercaptopurine and Ag8 Clusters

The Ag clusters have been investigated widely theoretically and experimentally. In particular, it has recently shown that the neutral Ag8 clusters embedded in an argon matrix have a strong fluorescence signal. As we can know, the metal clusters may have important effects on the structures and properties of biomolecules. More and more attention is paid to the interaction between nanomaterials and biomolecules. In this work, the B3LYP method in density functional theory was used on the complexes between the 6-mercaptopurine（6MP） and Ag8 clusters combined with 6-311＋＋G＊＊ as well as LANL2DZ base sets. The geometries of all the complexes were optimized with full degree of freedom and the structures, chemical bonds, orbital properties as well as Mulliken charges for ten possible complexes were analyzed based on the same theory level. In addition, the influence of temperature and pressure on the stabilities of the four complexes was further explored using standard statistical thermodynamic methods ranging from 50 to 500 K and at 100 kPa or 100 bar. The results show that the complex Ag8-6 MP-7-5 can be the most stable one among the investigated complexes, in which the Ag（11） atom interacts with the S（10） atom forming the strong chemical bond. The Mulliken charges also show that the Ag–S chemical bond is formed and the related charge has transferred. Additionally, the temperature and pressure can significantly influence the stability of the four stable complexes.

Ideal Strengths and Bonding Properties of UO2 under Tension

By performing density functional theory plus U calculations, we systematically study the structural, electronic, and magnetic properties of U02 under uniaxial tensile strain. The results show that the ideal tensile strengths along the [100], [110], and [111] directions are 93.6, 2Z7, and 16.4 GPa at strains of 0.44, 0.24, and 0.16, respectively. After electronic-structure investigation for tensile stain along the [001] direction, we find that the strong mixed ionic/covalent character of U-O bond is weakened by the tensile strain and there will occur an insulator to metal transition at strain over 0.30.

First-principles calculation of the electronic structure, chemical bonding, and thermodynamic properties of β-US_2

The electronic structure, magnetic states, chemical bonding, and thermodynamic properties of β-US2 are investigated by using first-principles calculation through the density functional theory（DFT） ＋U approach. The obtained band structure exhibits a direct band gap semiconductor at Γ point with a band gap of 0.9 e V for β-US2, which is in good agreement with the recent experimental data. The charge-density differences, the Bader charge analysis, and the Born effective charges suggest that the U–S bonds of the β-US2 have a mixture of covalent and ionic characters, but the ionic character is stronger than covalent character. The Raman-active, infrared-active, and silent modes at the Γ point are further assigned and discussed. The obtained optical-mode frequencies indicate that the three apparent LO–TO（longitudinal optical–transverse optical） splittings occur in B1 u, B2 u, and B3 umodes, respectively. Furthermore, the Helmholtz free energy ？F, the specific heat ？E, vibrational entropy S, and constant volume CVare studied over a range from 0 K-100 K. We expect that our work can provide some valuable information for further experimental investigation of the dielectric properties and the infrared reflectivity spectrum of uranium chalcogenide.

AROMATIC BOND INCLUDING METALLIC ATOM IN COORDINATE COMPOUNDS AND SOME OF ITS PROPERTIES

Aromatic bond including metallic atom (Ni) is investigated by EHMO calculation.The NMR spectra and the mechanism for hydrolysis are discussed on the ground of results of computation.

Experimental and numerical studies of titanium foil/steel explosively welded clad plate

Ti/Fe clad plate had attracted extensive attention because of its important application. In order to reduce the titanium layer thickness, the explosive welding of TA1 titanium foil to Q235 steel plate was carried out. The interfacial bonding performance was analyzed by micromorphology analysis and mechanical property test, and the formation process of interfacial wave and molten block in the vortex was simulated by smoothed particle hydrodynamics(SPH) method. The results showed that salt as pressure transfer layer used in explosive welding could play a good buffer effect on the collision between flyer and base layers. Regular waveforms were formed on the bonding interface, and the titanium foil/steel clad plate exhibited good welding quality and bonding property. The crest of the observed interfacial wave moved 200 μm from the beginning to the final formation, and it was important of jet on the formation of interfacial waveform. The interface was mainly bonded in the form of molten layer, and the grains near the interface were streamlined. Molten block containing intermetallic compounds and metal oxides appeared in the vortex of wave crest.

Effect of vibration on interfacial microstructure and mechanical properties of Mg/Al bimetal prepared by a novel compound casting

In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated.The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal,but it did not change the phase compositions of the interface,which was composed of layerⅠ(Al3Mg2+Mg2Si),layerⅡ(Al_(12)Mg_(17)+Mg_(2)Si)and layerⅢ(Al_(12)Mg_(17)/δ-Mg).Without vibration,the Mg_(2)Si phase with a needle-like morphology mainly aggregated in the layerⅡof the interface.After the application of the vibration,the SEM and EBSD analysis results showed that the Mg_(2)Si and Al3Mg2phases in the interface were obviously refined,and the distribution of the Mg_(2)Si became more uniform,due to the strong forced convection of the molten metal resulting from the vibration.The TEM analysis indicated that the interface between the A_(l3)Mg_(2) and Mg_(2)Si phases was non-coherent,suggesting the Mg_(2)Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface.Compared to the Mg/Al bimetal without vibration,the shear strength of the Mg/Al bimetal with vibration increased by about 50%from 31.7 MPa on average to 47.5 MPa,and the hardness of the layer I of the interface increased,and the hardness of the layerⅢdecreased.The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.

Theoretical Study on the Intermolecular Interactions of Tetrazole Dimers

Tetrazole monomers （Ⅰ, Ⅱ） and all of their possible stable dimers （1, 2, 3, 4, 5, 6, 7 and 8） were fully optimized by DFT method at the B3LYP/6-311＋＋G^＊＊ level. Among the eight dimers, there were two 1H-tetrazole dimers, three 2H-tetrazole dimers and three hetero dimers of 1H-tetrazole and 2H-tetrazole. Vibrational frequencies were calculated to ascertain that each structure was stable （no imaginary frequencies）. The basis set superposition errors （BSSE） are 2.78, 2.28, 2.97, 2.75, 2.74, 2.18, 1.23 and 3.10 kJ/mol, and the zero point energy （ZPE） corrections for the interaction energies are 4.88, 4.18, 3.87, 3.65, 3.54, 3.22, 2.87 and 4.34 kJ/mol for 1, 2, 3, 4, 5, 6, 7 and 8, respectively. After BSSE and ZPE corrections, the greatest corrected intermolecular interaction energy of the dimers is -43.71 kJ/mol. The charge redistribution mainly occurs on the adjacent N-H…N atoms between submolecules. The charge transfer between two subsystems is very small. Natural bond orbital （NBO） analysis was performed to reveal the origin of the interaction. Based on the statistical thermodynamic method, the standard thermodynamic functions, heat capacities （C^0P）, entropies （S^0T） and thermal corrections to enthalpy （H^0T）, and the changes of thermodynamic properties from monomer to dimer in the temperature range of 200.00 K to 700 K have been obtained. 1H-tetrazole monomer can spontaneously turn into two stable dimers at 298.15 K.

Theoretical Investigations on the Structure,Density,Thermodynamic and Performance Properties of Bis(2,2-dinitropropyl) formal

Density functional method was used to investigate the IR spectrum, heat of forma- tion and thermal stability of a new energetic material bis（2,2-dinitropropyl） formal （BDNPF）. The detonation velocity and pressure were evaluated by using the Kamlet-Jacobs equations based on the theoretical density and heat of formation. The bond dissociation energies for the weakest bonds were analyzed to investigate the thermal stability of the title compound. The results show that the C（I ）-N（I ） bond is predicted to be the trigger bond during pyrolysis. The crystal structure obtained by molecular mechanics belongs to the P21 space group, with the lattice parameters to be Z = 2, a = 11.5254, b = 6.2168, c = 9.5000 A andp= 1.66 g/cm3.

Microstructure and mechanical properties of Mg-5Li-1Al sheets prepared by accumulative roll bonding

Ultrafine-grain and high-strength Mg-SLi-1Al sheets were prepared by accumulative roll bonding （ARB） process. Evolution of microstructure and mechanical properties of ARB-processed Mg-5Li-1Al sheets was investigated. Results show that, during ARB process, the evolution of deformation mechanism oft Mg-5Li-1Al alloy is as follows： twinning deformation, shear deformation, forming macro shear zone, and finally dynamic recrystallization （DRX）. The grain refining mechanism changes from twin DRX to rotation DRX. With the increase in ARB cycles, strength of the Mg-5Li-1Al sheets is enhanced, whilst elongation varies slightly. With the increase in rolling cycles, anisotropy of mechanical properties decreases. It is conclusive that strain hardening and grain refinement dominate the strengthening mechanism of Mg-5Li-1Al alloy.

Detailed Evolution Mechanism of Interfacial Void Morphology in Diffusion Bonding

Similar diffusion bonding of 1Cr11Ni2W2MoV stainless steel was conducted at different bonding tem- peratures. The interface characteristics and mechanical properties of joints were examined, and the evolution of interracial void morphology was analyzed in detail The results showed that there were four typical interfacial void shapes generating sequentially： the large scraggly voids, penny-shaped voids, ellipse voids and rounded voids. The variation of interracial void shape was dominated by surface diffusion, while the reduction of void volume was ascribed to the combined effects of plastic flow of materials around voids, interface diffusion and volume diffusion. Owing to the elimination of void from the bonding interface, the sound joint obtained could exhibit nearly full interracial contact, and present excellent mechanical properties, in which the microhardness and shear strength of joint matched those of base material.

Effect of laser-discrete-quenching on bonding properties of electroplated grinding wheel with AISI 1045 steel substrate and nickel bond

To improve the bonding strength between the nickel bond and the hub of the electroplated diamond grinding wheel,a hybrid technique was proposed to combine laser prequenching steel substrate and post-electroplating nickel.To validate the effectiveness of the proposed technique,AISI 1045 substrate was nickel-coated.The bonding properties between the electroplated nickel coating and substrate with or without laser-discrete-quenching were discussed comparatively by scratch,indentation,and thermal shock tests.The results show that the prequenching treatment leads to phase transformation of AISI 1045 microstructure from the mixed pearlite and ferrite phases into the martensitic phase.Since the martensitic phase is characterized as a high corrosion resistance,the interface of substrate/coating is smooth and flat in the prequenched zone,and the coating is bonded well with the steel substrate.In contrast to the steel substrate without pre-quenching treatment,the proposed technique significantly enhanced the bonding strengths of the electroplated nickel-coating.On one hand,the average hardness of electroplated nickel-coating on the laser pre-quenched zone is increased by 18.7%,and the scratch depth with the same load become narrower and shallower.On the other hand,the coefficient of friction(CoF)and the vibration amplitude are reduced,and the coating is bonded effectively with the substrate to inhibit the crack initialization at the interface.This prevents effectively the coating from peeling off and improves significantly the thermal shock resistance property.