Advanced Materials Research Vols. 79-82

Abstract: The structural damage of mortar caused by simulated crack was evaluated using embedded PZT sensor combining with dynamic electromechanical impedance technique. The influence of embedded PZT sensors layout on detecting structural damage induced by the simulated cracks was also investigated. The results indicate that with increasing the simulated crack depth, the impedance real part of PZT sensors shift leftwards accompanying with the appearance of new peaks in the spectra. When more simulated cracks occur, the shift of the impedance curve becomes more obvious, and the amounts of new peaks in the impedance spectra also increase. RMSD indices of the structures with PZT sensors embedded in them with different layout can show the structural incipient damage clearly. With increasing more simulated cracks in the mortar structures, RMSD values of the structures with different PZT sensors layout become larger, under the same depth, RMSD indices of the structures with PZT sensor embedded transversely and horizontally in them show the increasing trend.

Abstract: Carbon materials have a very large surface area and various surface functional groups. They have been widely used as the adsorbent alone or the modified surface to adsorb pollutants. In the process of producing of yellow phosphorus by electric furnace, about 3000 m3 tail gas will be let out for one ton yellow phosphorus production. Tail gases consist of 90% of carbon monoxide (CO) and phosphine (PH3). The PH3 prevents the highly efficient utilization of CO and is an irritant and general systemic poison. Therefore, it is necessary to study how to effectively remove PH3 in tail gases. Due to the fact that selective adsorption of non-modified activated carbon (AC) is not enough to remove PH3 with a high efficiency, modification of AC might be an attractive route to improve the adsorption capacity. In this paper, experiments were carried out to study the factors influencing the adsorption of PH3 on the modified AC such as the concentration of impregnant, reaction temperature, oxygen content and space velocity. The results showed that the 5% HCl was the optimum concentration of impregnant. In the presence of oxygen, the adsorption capacity of modified AC was more than that in the absence of oxygen. In addition, with the improvement of the reaction temperature, the adsorption capacity of modified AC was increasing initially then decreasing, because of the transition from physical adsorption to chemical adsorption as priority. The adsorption capacity of the modified AC was enhanced initially with the increasing of oxygen content. Once the oxygen content was enhanced over 1%, there was no significant increase in the adsorption capacity of modified AC. The adsorption capacity of modified AC was decreased with the increasing of space velocity. The optimum parameters of reaction were 5% HCl of impregnant, 70°C of reaction temperature, 1% of oxygen content, and space velocity 10～20min-1.

Abstract: The graft copolymerization of mixed grafting monomers vinyl acetate and butyl acrylate onto grafting skeleton of corn starch have been investigated using ammonium persulfate as initiator. Starch based wood adhesive prepared by in emulsion synthesis have green material, superior property, low cost. The effects of various factors on the graft copolymerization were studied such as reaction time, reaction temperature, initiator concentration as well as match of mixed monomers. By single-factor tests, the optimum graft copolymerization conditions with higher grafting efficiency and grafting percent ratio correspond to the reaction time of 3h, the graft polymerization reaction temperature of about 65°C, the initiator concentration of 9.7×10-3mol/L, the mixed grafting monomers concentration of 1.0 mol/L, the volume ratio of vinyl acetate to butyl acrylate of 5:5. The starch graft copolymer after purification was characterized, and its properties were determined. IR spectra of graft copolymers indicated that the carbonyl group characteristic absorption peak existed at 1730～1740cm-1 besides that of starch. The XRD pattern showed there were several dispersion peaks, therefore the graft copolymerization was the concomitant structure of a little crystalline state and amorphous state. TG and DTA curves confirmed the occurrence of graft copolymerization, and showed that the thermal stability of starch copolymer was better than that of pure corn starch. Starch based wood adhesive is white or cream white emulsion paste, excellent emulsive properties and high temperature stability. All properties of starch based wood adhesive can meet the national standard HG/T2727 - 95 of polyvinyl acetate wood adhesive, and the compressive shear strength outdistances the national standard especially.

Abstract: A nanocomposite electrode of vertically aligned multi-walled carbon nanotubes (MWCNTs) on gold was fabricated to improve the specific capacitance and power density of the conventional supercapacitor. The novel supercapacitor built from MWCNTs and gold electrode showed a very high specific capacitance of 92.74 F/g using cyclic voltammetry (CV) at 10 mV/s, and 96.43 F/g was measured at 100 Hz. This nanocomposite electrode greatly enhanced the utilization efficiency of supercapacitor electrode material, low material cost and provided both high capacitance and power density. It was shown that the nanocomposite electrode based on vertically aligned carbon nanotube electrode had the characteristics of high specific capacitance.

Abstract: Hydroxyapatite (HAP) was synthesized in Triton X-100 microemulsion and was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS). Particle size analysis results showed that the particles has nanometer size, high surface area and loose structure. The prepared HAP had high adsorption capacity to human serum protein and the adsorption of human serum protein on the surface of HAP was confirmed by SEM. The factors which influenced the adsorption capacity such as the acidity, reaction time and the concentration of adsorbent were investigated in detail and the adsorption isothermal was also obtained. The adsorption capacity reduced while the pH value increased, and the adsorption reached equilibrium when shaking time was up to 40 min. The adsorption isotherm could be fitted by the pseudo-Langmuir type. The adsorption of human serum albumin on HAP was investigated, and the influences of adsorption on the conformation of human serum albumin were studied by infrared and ultraviolet spectroscopy. It can be seen from the FT-IR spectra that the intensity of flex vibration of C=O, N-C bonds all weakened. The calculation results of ultraviolet spectrum indicated that the quantity of α spiral structure reduced from 44% to 17.12%.

Abstract: The unique memory function of Ni-Ti alloy makes it unique durative self-press function as the orthopaedics internal fixator devices, the durative embracing force provides a good mechanical condition for the bone healing in clinical orthopaedics. Through the special embracing force testing device and using self-designed experiment device which arms at this kind of arm-embracing Internal fixator experiment to observe the effect of the extended distance of arms on the embracing force when Ni-Ti shape memory alloy arm-embracing fixes fractures. It is researched that the state affected embracing force under the resistance effect, and fully realizes the law of embracing force’s variety. The investigation has been done to the clutching internal fixator which frequently used in clinical treatment of orthopedic and find that the embracing force increases with time and stabilizes finally, when the open end of arm-embracing internal fixator is in the equal temperature and opening under the resistive effect; it observes the character of embracing force which increasing along with the opening degree of the arms when the open end is at the same temperature and different opening degree; it also researches that the embracing force has the rule of change that it will reduce in repeated experiment at the same temperature, at the same place of the memory alloy arm-embracing clip. The research provides the instructions and references based on mechanics for clinical treatment.

Abstract: Despite that piezoelectric ceramic lead zirconate titanate (PZT) has been used for structural health monitoring (SHM) in various engineering systems, limited work has been conducted on real size concrete structures. Beam-column connections are critical regions in reinforced concrete (RC) moment-resisting frame structures. The vulnerability of RC beam-column joints has been identified from structural damage investigations over the past decades, especially in the area of earthquake engineering. In the context of a terrorist bomb attack, the beam-column joints are very vulnerable, especially when the perimeter columns lose their load carrying capacity due to damage and the beam-column joints become one of the crucial load transfer mechanism of the structural frame. To avoid catastrophic failures, it is important to monitor beam-column joints under existing gravitational loads. In this paper, an experiment is carried out on four real size concrete frame structures with different detailing subjected to gradually increased loads. A number of PZT sensors are bonded to the frame structure to acquire PZT electro-mechanical (EM) admittance signature. The structural mechanical impedance (SMI) is extracted from the PZT EM admittance signature and its sensitivity is compared with that of the EM admittance. The relations between the damage index and the loading step and tip deflection of the concrete structure are obtained. Finally the sensitivity of the PZT sensors in detection of the critical loading level is discussed. The results show that the PZT sensors are capable of monitoring the integrity and behavior of the real size concrete structures.

Abstract: Piezoelectric ceramic lead zirconate titanate (PZT) based electro-mechanical impedance (EMI) technique for structural health monitoring (SHM) has been successfully applied to various engineering systems [1-5]. In the traditional EMI method, statistical analysis methods such as root mean square deviation indices of the PZT electromechanical (EM) admittance are used as damage indicator, which is difficult to specify the effect of damage on structural properties. This paper proposes to use the genetic algorithms (GAs) to identify the structural parameters according to the changes in the PZT admittance signature. The basic principle is that structural damage, especially local damage, is typically related to changes in the structural physical parameters. Therefore, to recognize the changes of structural parameters is an effective way to assess the structural damage. Towards this goal, a model of driven point PZT EM admittance is established. In this model, the dynamic behavior of the structure is represented by a multiple degree of freedom (DOF) system. The EM admittance is formulated as a function of excitation frequency and the unknown structural parameters, i.e., the mass, stiffness and the damping coefficient of many single DOF elements. Using the GAs, the optimal values of structural parameters in the model can be back-calculated such that the EM admittance matches the target value. In practice, the target admittance is measured from experiments. In this paper, we use the calculated one as the target. For damage assessment, these optimal values obtained before and after the appearance of structural damage can be compared to study the effects of damage on the structural properties, which are specified to be stiffness and damping in this study. Furthermore, the identified structural parameters could be used to predict the remaining loading capacity of the structure, which serves the purpose for damage prognosis.

Abstract: Hydrogen with ultrahigh density confined in single-walled carbon nanotubes (SWCNTs) was investigated using density functional theory (DFT) and first principles molecular dynamics simulations (MDSs). Hydrogen atoms injected in to the cages of the SWCNTs via atomic collisions gradually form solid H2 molecular lattice with a characteristic of spiral multi-strands structure. The concentration of H2 confined in the SWCNTs can be as high as ~ 1.77×1023H2 /cm3, and the pressure between the H2 lattice and the wall of the SWCNT can be as high as ~ 77 GPa. When the system was heated to temperature higher than 700K, a solid-liquid phase transition was observed. When temperature rose to 1000K, a few H2 molecules dissociated forming a mixed liquid of H atoms, H2 molecules, and hydrogen trimers. Electron states near the Fermi level were appeared, which were attributed to the H atoms and the trimers. The electronic properties of the quasi-one-dimensional hydrogen confined in the SWNTs were thus substantially changed.

Abstract: In this paper, the resistance to H2S attack of pastes made from slag-fly ash blended cement used in oil well (SFAOW) was studied, in which fly ash (FA) was used at replacement dosages of 30% to 60% by weight of slag. Samples of SCOW and SFAOW pastes were demoulded and cured by immersion in fresh water with 2 Mp H2S insulfflation under 130oC for 15 days. After this curing period, compression strength and permeability of the samples were investigated. The reaction mechanisms of H2S with the paste were carried out through a microstructure study, which included the use of x-ray diffraction (XRD) patterns and scanning electron microscope (SEM). Based on the obtained data in this study, incorporation of FA into SCOW results in the comparable effects in the resistance to H2S attack. When the replacement dosage of slag is about 40%, the paste exhibits the best performance on resistance to H2S attack with compression strength 36.58Mp.