Band 24, Heft 6

This paper used an equal volume impregnation method to produce egg yolk-egg white bimetallic-supported catalyst. Phase structure and crystal morphologies were characterized by X-ray diffraction, scanning electron microscopy, temperature programmed reduction (TPR), and inductive coupling plasma methods, and the paper discussed the effect of different metal loading, calcination temperature, and calcination time on the desulfurization activity. The experimental results showed that desulfurization performance increased first and then gradually decreased as metal loading, calcination temperature, and calcination time increased. The optimum preparation conditions of bimetallic catalyst were 8% NiO and 5% MnO 2 , the most suitable calcination temperature was 400°C, and the most suitable calcination time was 4 h. Finally, the eggshell, the egg white, and the egg yolk catalysts had its own different characteristics in the desulfurization processing: the eggshell catalyst showed a rapid reaction rate but lasted for a short time, the egg yolk catalyst showed a slow reaction rate but lasted for a long time, and the reaction rate and lasting time of the egg white were between the eggshell and the egg yolk.

As an important part of the pantograph and catenary system, the pantograph slide receives increasing attention from investigators, mainly focused on the interfacial bonding and characteristics, electrical conductivity, and friction and wear characteristics under current-carrying circumstances. In the article, hybrid reinforcements of titanium silicon carbide (Ti 3 SiC 2 ) and nano-alumina (nano-Al 2 O 3 ) particles pretreated by electroless plating process were firstly blended with copper powders and then prepressed and vacuum hot pressed to fabricate the hybrid reinforced copper-matrix pantographs (HRCPs). The relative density, mechanical and electrical properties of Ti 3 SiC 2 /Al 2 O 3 HRCPs were calculated and measured. The tribological performance of the HRCPs reinforced with 1 wt%~5 wt% of alumina particles and 20 wt%~40 wt% of Ti 3 SiC 2 reinforcements was also analyzed.

A three-dimensional micromechanical finite element model is developed to study the effects of a manufacturing environment on thermal residual stresses in a SiC/Ti-6Al-4V metal-matrix composite. The model includes a representative volume element consisting of a quarter of SiC fiber covered by relatively thick coating and an interaction layer all of which are surrounded by the Ti-6Al-4V matrix. Stress relaxation due to the viscoplastic behavior of the matrix is accounted for different manufacturing environments, that is, air and nitrogen. The results show that the presented model provides accurate predictions when compared with experimental data. It is possible to use the presented results for appropriate selection of manufacturing parameters. The results suggest that to delay the onset of interface debonding, the best choice is to use cooling rates higher than 0.64 and 0.1°C/s, respectively, for air and nitrogen environments. In order to use simple elastic-plastic models to predict residual stresses within the composite, detailed equivalent stress-free temperatures for various environments, cooling rates, and fiber volume fractions are presented.

Methylcarbazole (MCz) and its nanocomposites with Montmorillonite nanoclay and Zn nanoparticles were chemically synthesized on a stainless steel (SS304) electrode. The modified electrode was characterized by optical microscope, scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), Fourier-transform infrared spectroscopy-attenuated transmission reflectance (FTIR-ATR), four-point probe, and electrochemical impedance spectroscopy (EIS) analysis. The synthesized stainless steel/poly(methylcarbazole) (SS/P(MCz)), stainless steel/poly(methylcarbazole)/nanoclay (SS/P(MCz)/nanoclay), and stainless steel/poly(methylcarbazole)/nanoZn (SS/P(MCz)/nanoZn) were studied by potentiodynamic polarization curves. The protective behavior of these coatings in 3.5% NaCl as the corrosion medium was investigated using Tafel polarization curves, as well as electrochemical impedance spectroscopy. The corrosion protection parameters were also supported by EIS and an equivalent circuit model of R s ( Q c ( R c ( Q p R ct ))). The corrosion current of the SS/P(MCz)/nanoclay samples was found to be much lower ( i corr =0.010 μA×cm -2 ) than that of SS/P(MCz)/nanoZn ( i corr =0.031 μA×cm -2 ) and pure SS/P(MCz) samples. These results reveal that chemically synthesized SS/P(MCz), SS/P(MCz)/nanoclay, and SS/P(MCz)/nanoZn nanocomposite film coating have high corrosion protection efficiency (PE=99.56%, 99.89%, and 99.67%, respectively). Thus, based on the study findings, we posit that nanoclay and Zn nanoparticles possess favorable barrier properties, which can be employed in order to achieve improvements in chemical corrosion protection through P(MCz) coating.

In this study, a finite element model of the explosive welding process of three-layer plates composed of Ti/Al/Mg was established, and the interfacial behaviors of three-layer plates were researched. We investigated the influences that affect the quality of explosive bonding and explored the influence factors of variable physical parameters in the simulation. The finite difference engineering package AUTODYN with the smoothed particle hydrodynamics method has been used to model the collision in this work. The von Mises strength model was used to describe the behavior of Ti/Al/Mg composite plates. Wave morphology on the Al/Mg interface and straight morphology on the Ti/Al interface were produced in this study; meanwhile, jet phenomenon occurred obviously in the simulation process. The contours of velocity, pressure, shear stress, and effective plastic strain of Ti/Al/Mg were also discussed. The result of X -direction velocity showed a delay in time and location of collision point between the Ti/Al and the Al/Mg interface. The detonation point was the minimum pressure, and the collision point was the maximum pressure compared with other sections. The value of effective plastic strain must exceed a threshold to obtain a good bonding, and the shear stress was of opposite sign in the simulation.

This research investigated the structural growth of multiwalled carbon nanotubes (MWCNTs) in a double stage horizontal chemical vapor deposition (CVD) reactor. Ethylene was used as a carbon source for nucleation of nanotubes. Ferrocene catalyst weight was varied from 0.1 to 0.2 g to demonstrate the growth of MWCNTs on Si/SiO 2 /Al 2 O 3 substrate. The obtained data revealed that the weight of the catalyst significantly affects the diameter, crystallinity, alignment and yield of the nanotubes. Lower inner-shell spacing and the ratio of D-Raman peak intensity and G-Raman peak intensity (I D /I G ratio) were obtained with 0.15 g of ferrocene, which was an indication of relatively pure carbon nanotubes (CNTs) growth. Raman spectra also confirmed the highly crystalline and relatively pure CNTs structures with I D /I G ratio of 0.700. TGA data revealed the formation of 97% pure nanotubes with oxidation temperature of 620°C. However, above and below the optimum (0.15 g of ferrocene), some of the grown CNTs were found defective and few black spots were also seen in TEM micrographs.

A wear test of Ti 2 Ni/TiNi-based coating reinforced by TiC/TiB against a YG6X [94 wt.% tungsten carbide (WC) and 6 wt.% cobalt (Co)] ball in a sliding time of 712 h was carried out using a ball-on-disc reciprocating motion mode. The relationship between accumulated dissipated energy (∑ E ) and accumulated wear volume (∑ V ) was accurately established via the dissipated energy approach. Three wear stages were found: initial wear stage (0–200 min), breaking-in wear stage (200–14,520 min), and steady wear stage (14,520–42,720 min). At the initial wear stage, the relationship between ∑ E and ∑ V satisfied the equation ∑ V =42.5288∑ E +0.019. The curvilinear relationship in the other two stages was fitted into the equation ∑ V =-0.0029∑ E 4 +0.064∑ E 3-0.5353∑ E 2 +2.0653∑ E +0.9938. The wear mechanism in the entire wear process was revealed. ∑ E at the initial wear stage was mainly used for debris formation. At the breaking-in wear stage, ∑ E was dissipated by generating the friction heat, which led to the formation of a protective layer. At the steady wear stage, ∑ E was used to generate friction heat as well as to damage and restore the protective layer. The detection results of the protective layer via energy dispersive spectroscopy showed that this layer was composed of oxides and WC debris.

In this study, the failure strength of single-lap adhesively bonded joints was investigated. The glass fibre epoxy composites used as adherends were manufactured by using a vacuum-assisted resin infusion method. These composites were bonded with a commercial material of epoxy-adhesive DP-460, which can be cured easily at room temperature. The specimens were built by bonding, and then repeated axial impact loads having various energy levels (0, 5, 10, 15, and 20 J) were implemented to the single-lap adhesively bonded composite joints at different temperatures (-20°C, 0°C, 20°C, 40°C, and 60°C). Subsequently, the specimens were exposed to static tensile loading at the same temperatures as those applied during the primary impacts. The variation in failure loads due to the effects of repeated axial impact loadings at different temperatures were investigated. Generally, the increase of impact energy level from 0 to 20 J leads to a gradual decrease in failure loads at all temperature levels except for the specific value of 40°C.

The acrylate-based photopolymer consists of tetra-functional polyester acrylate (TPA), and hexanediol diacrylate (HDDA) has been successfully composited with nano barium titanate (BaTiO 3 ) and completely cured via a digital light processor RP machine. The degradation temperature, tensile strength, hardness, resistivity, and dielectric constant of samples were characterized by Thermo Gravimetric Analyzer Hi-Res TGA2950, Universal Tensile Machine JIA701, Hardness Shore D tester, Fluke 117 multimeter, and Agilent B1500A Semiconductor Device Analyzer, respectively. The morphology changes of the samples were also investigated using the JEOL JSM-6390LV scanning electron microscopy (SEM). The results show that the improvement of degradation temperature is not obvious. Furthermore, the modulus elasticity, hardness, and dielectric constant increase as the filler loading increases up to 2 phr, but the resistivity is vice versa. Interestingly, there is an inverse correlation between dielectric constant and resistivity of photopolymer/BaTiO 3 nanocomposite.

The paper focuses on the effects of the cell wall material strain hardening on the mechanical behavior of closed-cell foams subjected to the constant velocity loading. Three-dimensional Voronoi models were established to present the closed-cell foams, and the simulations were performed by employing Ls-dyna 971. The investigation found that the cell wall strain hardening could postpone the onset of the localized collapse bands and retard deformation mode transformation. Strain hardening convergence phenomenon was observed in the closed-cell foams; increasing the impact velocity could weaken the effect of the material strain hardening. The crushing stress at both impact and stationary sides were analyzed in detail. The material strain hardening could always enhance the plastic energy dissipation. Furthermore, the strain hardening convergence was also observed in the plateau stress at the impact side and plastic energy dissipation but not in the densification strain and the plateau at the stationary side.

Glass-reinforced epoxy (GRE) pipes are used as an alternative to carbon steel pipes in desert oil field applications owing to their good properties such as chemical resistance, thermal resistance and mechanical properties. In the desert oil field service, the pipes are exposed to different harsh environmental conditions such as high temperature, humidity and ultraviolet radiation. The harsh environmental conditions can affect the properties of GRE pipes, which, in turn, can impact their performance. The present study covers the effects of environment factors such as crude oil and well stream chemicals on the properties of GRE pipes. The pipe samples were aged in wet crude, effluent water and scale inhibitor to simulate the exposure to desert oil field service. The aged samples were evaluated for their mechanical properties, thermal stability and chemical resistance. The compositional change in the composite structures was characterized using Fourier transform infrared spectroscopy and matrix deterioration by scanning electron microscopy. Swelling studies revealed no significant diffusion by the chemical media. Tensile testing showed a slight change in tensile strength with aging in crude oil. In addition, all the pipe samples showed adequate thermal stability to withstand harsh environmental conditions.

In this paper, non-ionic polyoxyethylene ether was used to modify the surface of poly(vinyl alcohol) (PVA) fibers and to improve their dispersion in cement mortar. The results showed that surface modification could apparently improve the dispersion of PVA fibers in cement mortar by weakening the original intermolecular hydrogen bonds between the adjacent hydroxyl groups on the surface of PVA fibers and increasing the formation of hydrogen bonds between PVA fibers and cement mortar. After modification, the advancing contact angle and the receding contact angle of the fibers were respectively reduced from 44.2° to 34.7° and from 38.8° to 33.1°, and the dispersion coefficient of the fibers was increased from 0.85 to 0.95. Owing to the improved interactions between modified PVA fibers and cement mortar and to the good dispersion of the fibers in the matrix, the fibers had a superior energy absorption capacity and showed a ductile fracture, leading to higher flexural strength, bending modulus and toughness of fiber-reinforced cementitious composites.

This paper reports the results of an experimental investigation carried out to evaluate the bond stress behavior of basalt fiber-reinforced polymer (BFRP) bar and steel rebar (SR) in conventional C30-type concrete. The experimental program was conducted on testing 16 hinged beam specimens that were prepared according to BS 4449:2005+A2:2009 standard. Conventional C30-type concrete was used to produce hinged beams. In beam tests, bar diameter and embedment length were used as experimental variables. The bond performances of BFRP bar and SR were compared with the help of the load-slip results of hinged beam bending tests conducted on produced beam samples after 28 days of curing. Results showed that much higher bond stress values were obtained from BFRP bars compared to SR for both 12 and 8 mm bar diameters. Besides, the maximum bond stress values decreased with increasing bar diameter and embedment length for both BFRP bar and SR.

Composite lattice structures are of considerable mechanical property and multifunctional design flexibility. However, the relatively low operating temperature of polymer composite prevents its application in high temperature or fire-proofing structures. Here, we propose a type of lightweight composite lattice sandwich structure that is capable of fire proofing as well as load bearing. In our design, the composite lattice sandwich structure is filled with heat insulation materials to interdict the thermal radiation and convection between its two facesheets. The top facesheet of the structure is covered with intumescent coating to isolate fire. Moreover, thermoresistant resin or flame retardant is adopted in manufacturing the top facesheet to improve its thermoresistance. A design procedure has been developed for such kind of fire-proofing structure, by which the material and geometry of the structure can be determined according to the fire-proofing effect. It was demonstrated by experiment that a 30-mm-thick structure, designed by the present procedure, was able to isolate 945°C fire load on the exposed surface for 3600 s, keeping the unexposed surface temperature rise below 139°C.

Tape placement manufacturing process, as one of the automated forming technologies for composite material, not only substantially improves the productivity of composite component and reduces the cost of production significantly but also raises the reliability and stability of composite structure. Automated tape placement technology is mainly applied for manufacturing the fuselage and wing panel of airplane characterized by small curvature and large size. For these kinds of structural components with a non-developable surface, trajectory planning by “natural path” method could reduce the internal stress and improve the quality of composite products to a certain extent but not be optimized by quantitative characterization. On the basis of preliminary work, the theoretical model of “unnatural degree” (UD) is introduced in the first step, which could characterize the tensile and shear strain of the laying tape quantitatively. Secondly, by adjusting the iterative step and laying direction to diminish the UD, local stress could be softened in order to optimize the laying track. Ultimately, the simulation model of the non-developable surface is established under the Matlab software environment, and the “variable step-angle” algorithm is adopted to verify the adjustment effect of the tape-laying track.

A three-dimensional (3D) semi-analytical model is developed by introducing meshfree local radial point interpolation method into a Hamilton system to analyze the mechanical and thermal buckling behavior of rectangular laminated plates with embedded delaminations. A modified Hamiltonian function for mechanical and thermal buckling analysis of rectangular laminated composite plates subjected to in-plane axial compressive or thermal loads is proposed. The final governing equation is deduced with the transfer matrix technique and a spring layer model based on the modified Hellinger-Reissner variational principle. One of the main superiorities of the present model is that the scale of final governing equation, which involves only the so-called state variables at the top and bottom surfaces, is insensitive to the thickness and the number of layers of composite laminates. Several relevant numerical examples are carried out to validate the present model, and the present results are in good agreement with pre-existing results.

This paper presents an analytical approach to investigate the non-linear dynamic response and vibration of an imperfect three-phase laminated nanocomposite cylindrical panel resting on elastic foundations in thermal environments. Based on the classical laminated shell theory and stress function, taking into account geometrical non-linearity, initial geometrical imperfection, Pasternak-type elastic foundation, and temperature, the governing equations of the three-phase laminated nanocomposite cylindrical panel are derived. The numerical results for the dynamic response and vibration of the polymer nanocomposite cylindrical panel are obtained by using the Runge-Kutta method. The influences of fibres and nanoparticles, different fibre angles, material and geometrical properties, imperfection, elastic foundations, and temperature on the non-linear dynamic response of the polymer nanocomposite cylindrical panel are discussed in detail.