Key Engineering Materials Vol. 845

Abstract: Nb-doped TiO₂ (TNO) thin films were prepared by a sol-gel spin coating method with Nb content of 5 at.%, and then annealed in the temperature range of 500-900 °C. The surface morphologies and the crystalline phases of the TNO thin films were investigated by using SEM and XRD patterns. The grain sizes increased with rising annealing temperature, and the crystalline phases were completely transformed from anatase into rutile when the annealing temperature was above 900 °C in air atmosphere. In addition, the optical band gap decreased and the average optical transmittance was between 75 and 70 % in the range of visible light. Furthermore, the better electrical properties were obtained at the annealing temperature of 600 °C.

Abstract: In this study, a new type of surfactant, N, N-dialkyl-3, 6-O-sulfopropyl chitosan (SPDACS) was prepared with two kinds of chitosan (Mw 10 and 50 kDa) and three kinds of alkyl groups (octyl, decyl and lauryl) respectively. The substitution degree of alkyl chain was around 1.50, and the substitution degree of sulfopropyl was around 1.70. The relationship of structure and surfactivity of chitosan-based surfactants were studied with six different structures of SPDACS.The results showed that the length of alkyl side chain and the molecular weight of chitosan main chain of SPDACS had distinct effect on the surface tension (γ) and the critical micelle concentration (CMC). CMC and γ could be reduced as the length of alkyl and the molecular weight of chitosan increased. For the products with 50 kDa of chitosan, the CMC decreased from 0.014 to 0.006 mg/mL, and γ down to 23.59 from 28.76 mN/m as the length of alkyl increased from 8C to 12C. The similar patterns happened for the products with 10 kDa of chitosan. The mean size of the blank micelles decreased with the growth of the length of alkyl, and the molecular weight of chitosan had little effect on the particle size. The zeta potential of all micelles were above -35mV which meant the micelles had good stability in the solution.The product of 5-SPDLCS (50 kDa, lauryl) with the best surfactivity were selected for the study of PTX solubilization. The optimal ratio of 5-SPDLCS/PTX was determined to be 1/1.1. The results showed the encapsulation effificiency (EE) and loading effificiency (LE) were 92.2 % and 50.36 % respectively. The solubility of PTX in water reached to 6.08 mg/mL. The solubility of PTX was 60,000 times higher than that of PTX (< 0.0001mg/mL) in pure water.

Abstract: In order to solve environmental problems and reduce the cost of building materials, this study used waste diatomite from brewing industry to develop novel cement mortar and compared it with pristine one. After pretreatment with water, soaking, drying, it is shown in the microscope that the treated diatomite has recovered its porosity. The thermogravimetric analysis also showed that the purity of treated diatomite was greater than 93%, confirming that most of the originally adsorbed organic matter was removed. Further, the diatomite after the treatment was used to prepare a novel cement mortar, and it was found that the optimum compressive strength was obtained when the water-cement ratio was 0.65 and the amount of diatomite added was 20%. It was found that the average compressive strength after 28 days was 284.03 kg/cm², which was 81.22 kg/cm² higher than that of the pristine cement mortar. It is proved that the addition of diatomite can increase the strength of the cement mortar and effectively reuse the waste diatomite.

Abstract: This paper proposed a recycling process for neodymium-iron-boron (NdFeB) magnet scrap from the end-of-life (EOL) of hard disk drives by using hydrometallurgical process. Initial chemical composition of NdFeB magnet scrap was consisted of 25.37%Nd, 6.53%Pr, 0.90%Co, 3.63%B and 63.57%Fe. After de-magnetization and crushing into proper size, magnet scraps were directly leached by H₂SO₄ solution. More than 90% dissolved into acid solution with remaining small amount of residuals and Ni-coated metal. Neodymium precipitated from leached solution by pH-control to the optimum condition at pH 0.6 using NaOH solution. Solid Nd-precipitates XRD pattern was observed in form of NaNd (SO₄)₂.(H₂O) and FeSO₄.(H₂O). Elemental analysis of Nd-precipitates by WD-XRF. The precipitates contained 26.50%Nd, 8.46%Pr and 1.19%Fe. In order to elimination of Fe, Nd-precipitates was leached by using H₂SO₄ solution to dissolve FeSO₄.(H₂O) into acid solution to obtain high concentration of Nd and rare-earth metals (REMs) compound. As a result, XRD pattern of Nd-compound after Fe-removal confirmed that the high purity NaNd (SO₄)₂.(H₂O) compound was obtained. The final composition of precipitates analyzed by WD-XRF was 26.36%Nd, 8.13%Pr with Fe as low as 0.14%Fe.

Abstract: In this study, a thermal analysis (TA) system was modified to have dual sampling cups which allowed the simultaneous pouring and data collecting. The two types of cups used were i) tellurium-containing cup and ii) non-tellurium cup. The tellurium addition ensured the iron carbide formation which gave the metastable eutectic temperature of the melts. The data were analyzed simultaneously for differences between the cooling curves. It was found that silicon increased the differences between the cooling curves (e.g. increased the ΔT_EU, ΔT_ER and ΔT_S). Both clear chill depth and total chill depth decreased with increasing silicon. Inequalities for the prediction of chill formation was proposed.

Abstract: This work investigated the influence of oxidation durations on the formation of oxide on the surface of wrought Co-28Cr-6Mo-1Si alloy. The iso-thermal oxidation was individually performed in air at 550°C for 4, 12 and 24 h. For comparison, the surface of the non-oxidized Co-28Cr-6Mo-1Si alloy was concurrently examined. The chemical compositions of the non-oxidized and oxidized alloys were principally analyzed via X-ray photoelectron spectroscopy (XPS). The XPS results revealed that the surface of the non-oxidized alloy enriched in Cr-oxide. After oxidation treatment, the Co-oxide, existing as Co²⁺ state was observed coexisting with two Cr-oxide states, Cr³⁺ and Cr⁴⁺. The low concentrations of Mo⁶⁺ were also observed on the oxidized alloy surface. With the increase in oxidation durations, the Co-oxide was suppressed by Cr-oxide. The XPS depth profile analysis indicated that the thickness of the oxide film increased with increasing the oxidation duration.

Abstract: The development of highly selective and sensitive surface plasmon resonance (SPR) immunoassay for the rapid detection of illegal compound using secondary antibody interaction labelled nanoparticle was conducted. For the construction of SPR sensor surface, the illegal compound (clenbuterol) was immobilized as antigen onto gold succinimide-terminated monolayer to perform amide-coupling reaction. In order to avoid non-specific reaction, the blocking agent (ethanol amine) was injected to the SPR system. Furthermore, indirect competitive inhibition method was employed in the detection of clenbuterol. In this work, the antibody solution (PBS solution containing clenbuterol antibody) premixed with a sample solution (PBS solution containing antigen) before the injection into the sensing system. As the premixed solution flowed over the sensor surface, the SPR senses the dielectric constant change at the interface due to the binding of the unreacted primary antibody to antigen-immobilized on the sensor surface. After this primary antibody detection, secondary antibody was injected to the SPR sensor surface. Here, we compared the signal difference of secondary antibody injection labelled Au nanoparticles (d = 40 nm). For the regeneration of the sensor surface, 0.1 M NaOH was used, so primary and secondary antibodies could be detached from the sensor surface. According to the indirect competitive inhibition method, it was found that the sensitivity for clenbuterol detection was enhanced from 2.5 ppt to 0.07 ppt.

Abstract: In the present study, an application of Ag nanoparticles (AgNPs) in order to obtain Surface-enhanced Raman spectroscopy (SERS) of disperse dyes on single cotton fiber is presented. In detail, we prepared colloid Ag by use of citrate reduction method. Add one drop of the colloid on single colored fiber and then Raman spectra recorded with excitation wavelength at 785 nm were carried out on a Renishaw Raman spectrometer coupled to a 20x object lens. Cotton fibers dyed by disperse red 17 (DR17) and disperse blue 35 (DB35) are characterized and analyzed. This method was found out to be an effectively way to identify both DR17 and DB35 on single cotton fibers. Furthermore, SERS expands methods for identification disperse dyes on fibers, and provide a good method for verify colored cotton fibers.