Dong Mei Luo

Compressive Properties of Hot-Rolled Mg-Zr-Ca Alloys for Biomedical Applications

This paper investigated the microstructures and compressive properties of hot-rolled Mg-Zr-Ca alloys for biomedical applications. The microstructures of the Mg-Zr-Ca alloys were examined by X-ray diffraction analysis and optical microscopy, and the compressive properties were determined from compressive tests. The experimental results indicate that the hot-rolled Mg-Zr-Ca alloys with 1% Ca are composed of one single a phase and those alloys with 2% Ca consist of both Mg2Ca and a phase. The hot-rolled Mg-Zr-Ca alloys exhibit typical elongated microstructures with obvious fibrous stripe, and have much higher compressive strength and lower compressive modulus than pure Mg. All the studied alloys have much higher compressive yield strength than the human bone (90~140 MPa) and comparable modulus with the human bone, suggesting that they have a great potential to be good candidates for biomedical applications.

Detection of Trace Formaldehyde Gas Based on Quartz Crystal Microbalance Sensor in Living Environment

Using four types of calixarene derivatives (RCT, PCT, MRCT, TBCA) as coating materials, quartz crystal microbalance (QCM) sensors have been examined for detection of toxic formaldehyde gas indoors. The results showed that PCT was the most efficient adsorption coating material for host-guest recognition of formaldehyde molecule, when the coating mass was 43.93 μg. The PCT based QCM sensor possessed a linear response range of 109 ~ 2721 ppm formaldehyde gas. In comparison with gas chromatography method, the QCM sensor had a recovery of 97.98~104.59 % with a good reversibility, stability and reproducibility, showing that the PCT based QCM sensor can be well used for the determination of trace formaldehyde in the living environment.

Tetra-(N-Phenylpyrazole)-Porphyrin/β-Cyclodextrin Incorporated CNT Film Modified Hemoglobin Sensor

An electrochemical sensor modified with tetra-(N-phenylpyrazole)-porphyrin/b- cyclodextrin/carbon nanotube (TPPyPh/b-CD/CNT) film was fabricated for determination of hemoglobin (Hb) in this paper. The electrochemical behavior of the proposed sensor was investigated by cyclic voltammetry (CV). TPPyPh has been shown preferably for the fabrication of electrochemical sensor. The peak currents decreased significantly with the increase of the Hb concentration in solution. The response mechanism of TPPyPh/b-CD/CNT film for Hb was suggested to be based on the coordinated interaction between Hb and TPPyPh. It showed excellent selectivity for the determination of Hb in PBS.

Comparison of the Models to Predict the Effective Young's Modulus of Hybrid Composites Reinforced with Multi-Shape Inclusions

In this paper, two kinds of micro-mechanical models are utilized to predict the effective Youngs modulus for hybrid composites including fiber-like, spherical and needle inclusions in an isotropic matrix. The two models of Multi-Phase Mori-Tanaka Model (MP model) and Multi-Step Mori-Tanaka Model (MS model) are proposed by the authors in a series of interrelated research. The results show that the shape and the Young’s modulus of inclusion, aspect ratio of fiber-like inclusion are the controlling factors to influence the Youngs modulus, and MP model is more rational to predict the effective Young’s modulus of hybrid composites reinforced with multi-shape inclusions.

A Closed-Form Solution of Effective Young's Modulus for Composites Including Multi-Shape Inclusions Using Improved Mori-Tanaka Model

In this paper, an improved model is proposed by combining Mori-Tanaka method with Eshelbys equivalent inclusion concept to derive a closed-form solution of the effective Youngs modulus E11 for hybrid composites reinforced with multi-shapes inclusions. When only the fiber-like inclusions are considered in the model, the results are consistent with those from Tandons unidirectional aligned composites based on Mori-Tanaka theory. For composites reinforced with fiber-like and spherical inclusions, the homogenization theory is employed to verify the effects of the proposed model. The influence of volume fraction and Youngs modulus of each phase on effective Youngs modulus E11 is investigated, and the results show that E11 is sensitive to the inclusion shapes, and the model is practicable to predict the effective mechanical properties of composites reinforced by several inclusions with different shapes.

Microstructures and Various Properties of Hot-Extruded Mg-Zr-Ca Alloys for Biomedical Applications

The microstructures, mechanical properties, corrosion behavior, and biocompatibility of hot-extruded Mg-Zr-Ca alloys have been investigated for potential use in orthopedic applications. The microstructures of the alloys are examined by X-ray diffraction analysis and optical microscopy. The mechanical properties of Mg-Zr-Ca alloys are determined from compressive tests, the corrosion behavior is studied using immersion tests, and biocompatibility is evaluated by cell growth factor using osteoblast-like SaOS2 cell. The experimental results indicate that the hot-extruded alloys have much higher compressive strength than the as-cast alloys and the human bone, and can offer good mechanical properties for orthopedic applications. The hot-extrusion significantly enhances corrosion resistance of the alloys. Among the alloys, the hot-extruded Mg-0.5Zr-1Ca and Mg-1Zr-1Ca alloys possess good combination of mechanical properties, corrosion resistance, and biocompatibility, suggesting that they have a great potential to be good candidates for orthopedic applications.

Effective mechanical properties for composites with three-phase randomly distributed aggregates predicted by multi-step mori-tanaka method

Multi-step Mori-Tanaka method (MMT) is applied to the estimation of the effective mechanical properties for composites with three-phase randomly distributed aggregates in this paper. The Multi-phase Homogenization Theory (MHT) which is based on mathematical homogenization method and is employed to verify the results of MMT method. Results show that MMT method is reasonable and practicable to predict the effective mechanical properties of composites with several phases, and the Young’s moduli and Poisson’s ratios of each phase may have some effects on the effective mechanical properties of multi-phase composites.

Electrochemical Determination of Nitrite Based on Gd Doped Nano Titanium Dioxide-Modified Gold Electrode

A simple and reliable method for electrochemical determination of nitrite based on Gd doped nano titanium dioxide (Gd-nano-TiO2) modified gold electrode was well developed in this paper. Using cyclic voltammetry, the modified electrode shows electrocatalytic activity for oxidation of nitrite in 0.10 mol×L-1 sulfuric acid solution (pH=0.70). The catalytic peak current was found to be linear with nitrite concentration in the range of 2.0´10-6 ~ 2.0´10-4 mol×L-1, with a detection limit of 1.1´10-6 mol×L-1 (S/N=3). Compared with spectrophotometry, the Gd-nano-TiO2 modified Au electrode could be used for the determination of nitrate in the ham sausage samples with a satisfactory recovery of 95.9 ~ 103.2%, showing its promising application in safety evaluation for food.

Fabrication of Piezoelectric Thickness-Shear-Mode Acoustic Wave Sensing Device and its Application

The piezoelectric thickness-shear-mode (TSM) acoustic wave sensing device was fabricated by coating with a calixarene derivative on the surface of gold electrode of quartz crystal, then connecting with a transistor-transistor-logic (TTL) oscillator, a frequency counter and a computer. Among four coating materials, the compound of calixarene I was the most efficient active material for adsorption of carbinol molecule based on a host-guest recognition mechanism. In comparison with gas chromatography (GC) method, the calixarene based TSM device can be used for on-line determination of the poisonous carbinol vapor in the range of 0 ~ 3000 ppm around our living environment with good selectivity, reproducibility and high stability. The detection limit can be evaluated to be 1.41 ppm.

Sensing Analysis of Aluminum Alloy Materials Based on Chemical Acoustic Emission Signals

The frequency domain power spectra of acoustic emission (AE) signals from different metal-acid reaction processes such as 6111 Al-alloy-hydrochloric acid (HCl) and 7070 Al-alloy-HCl for evolving hydrogen gases were obtained by fast Fourier transform (FFT) program and used for chemical analysis of different metal materials. Averaged power spectra from these processes and their corresponding characteristics were extracted. The characteristic AE frequency signals could be used for chemical pattern recognition of different metal materials like 6111 and 7050 aluminum alloys from the metal-acid reaction processes, that the principal component analysis (PCA) with appropriate frequency selection procedure gave a satisfactory classification with a correct rate of 78.1%. The back-propagation (BP) algorithm of artificial neural network (ANN) could give better recognition of AE signals for 6111 and 7050 alloys with a correct rate of 100%. Moreover, the AE energetic parameters are linearly correlated with the pH value of the acidic buffer solution, which opens a new possibility for quantitatively analytical application of AE signals on metal materials.