Materials Science Forum Vol. 848

Abstract: The ternary compound DyCo_0.67Ga_1.33 was synthesized and the thermal expansion of DyCo_0.67Ga_1.33 was studied in the temperature range of 309–608 K by high temperature powder X-ray diffraction technique. The volumetric coefficient of thermal expansion, , can be represented by . Its magnetic properties were measured between 30 and 300 K, and the magnetic susceptibility of DyCo_0.67Ga_1.33 was found to follow the Curie–Weiss law in the temperature range of 40–300 K. The effective magnetic moment and paramagnetic Curie temperature were estimated to be 9.86 μ_B and 40.4 K, respectively. Electrical resistivity of the compound DyCo_0.67Ga_1.33 was also measured between 5 and 300 K. Temperature variation of the electrical resistivity suggests the metallic character of the compound DyCo_0.67Ga_1.33 with an anomaly detected at 45 K. The residual resistivity ratio RRR of the compound is about 1.2.

Abstract: The rare-earth (RE) permanent magnets based on Nd₂Fe₁₄B with excellent magnetic properties have been widely used in industrial applications. In this work, the crystal structure, microstructure and magnetic properties of Nd_2.28Fe_13.58B_1.14, Ce_2.28Fe_13.58B_1.14 and Pr_2.28Fe_13.58B_1.14 alloys prepared by arc-melting were investigated. The results show that all alloys are single phase with tetragonal Nd₂Fe₁₄B-type (space group P42/mnm). The Curie temperatures (T_c) of RE_2.28Fe_13.58B_1.14 (RE=Nd, Ce, Pr) alloys are 583 K, 423 K and 557 K, respectively. On the other hand, the coercivities of Nd_2.28Fe_13.58B_1.14 and Pr_2.28Fe_13.58B_1.14 alloys are about 1.05 T and 1.23 T, respectively, while that of Ce_2.28Fe_13.58B_1.14 alloy is only about 0.25 T due to the poor squareness of hysteresis loop. Meanwhile, the saturation magnetizations of Nd_2.28Fe_13.58B_1.14 and Pr_2.28Fe_13.58B_1.14 alloys are about 135 emu/g and 113 emu/g, respectively, while that of Ce_2.28Fe_13.58B_1.14 alloy is about 97 emu/g. It was indicated that the Curie temperatures and magnetic properties of RE_2.28Fe_13.58B_1.14 alloys with the same crystal structure are dependent on light rare earth elements.

Abstract: nanosize TiO₂/SiO₂ thin films were deposited by sol-gel dip-coating method on enamel substrates. Crystal structure, micro-structure, hydrophilic property, gloss property was investigated by X-ray diffract meter, scanning electron microscope, CCD camera, enamel gloss meter. The results show that the hydrophilic property of the enamel was greatly increased by heating the enamel with coating TiO₂/SiO₂ film; the gloss property of the enamel surface greatly increased after the enamel coated with TiO₂/SiO₂ film. The main crystals in TiO₂/SiO₂ film on the enamel were anatase when the baking temperature was below the 700°C.

Abstract: Anti-fogging functional coatings have a broad application prospective in the fields of construction and transportation vehicles. In this study, superior water absorbing and anti-fogging coatings were prepared by a cure reaction using epoxy resins as water absorbent resins, hydroxyethyl ethylenediamine as a curing agent, γ-ammonia propyl triethoxy silane as a coupling agent, organic silicon sol as filler. The impact of additional polyethylene glycol (PEG) on the properties of water absorbing and antifogging coating has also been studied. The anti-fogging experiments were conducted in a 40 °C water steam bath, and the result shows that the sample with additional 4.0 % PEG has an anti-fogging time of 315 seconds (s), which is better than that without PEG (the anti-fogging time being 240s). Infrared spectroscopy and scanning electron microscope structure characterization indicate that the sample with additional PEG has an obvious three-dimensional network structure with hydroxyl groups, which leads to a great saturated water quantity and a superior anti-fogging performance.

Abstract: The effects of Modified NanoSiO₂ Agents on the morphology and performance of ultra-high-molecular weight polyethylene (UHMWPE) microporous membranes via thermally induced phase separation were investigated in this work. The NanoSiO₂ was surface modified by silane coupling agent KH570 (KH570-NanoSiO₂). Differential scanning calorimetry (DSC) and X-Ray Diffraction (XRD) were performed to obtain crystallization of UHMWPE/white oil/ KH570-NanoSiO₂ doped system. The morphology and performance of the prepared UHMWPE microporous membranes were characterized with scanning electron microscopy (SEM) and microfiltration experiments. The results showed that the morphology of UHMWPE membrane could be disturbed by KH570-NanoSiO₂. Porosity and the rejection of Bovine serum albumin (BSA) of the blend membrane increased with increasing concentration of Modified NanoSiO₂, while the water flux slightly decreased.

Abstract: Polypropylene (PP) membranes were respectively prepared using adipic acid (APA) and Sorbitol (NA-40) as nucleating agent via thermally induced phase separation (TIPS) method. The effects of nucleating agent content and cooling temperature on the structure and performance of membrane were investigated using scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). WAXD spectrogram indicates that three kinds of α, β and γ-form crystal were formed in this preparation process and the relative content of β-form crystal in membrane prepared by NA-40 system is higher than that of membrane formed by adipic acid. SEM images show that porous structure and cellular structure were observed on the surface and cross-section of membrane. The water flux, tensile strength and elongation increase with the addition of nucleating agent content and decrease with cooling temperature rising. This paper aims to choose proper nucleating agent NA-40 and coagulation temperature to improve the properties of PP membranes.

Abstract: Carbon molecular sieve membranes were prepared by pyrolysis of novolac type phenol-formaldehyde resin. The influences of pyrolysis temperature on membrane properties were investigated. By raising the pyrolysis temperature from 600 oC to 700 oC, the number of pores and effective pore size increased, thereby making the carbon membrane more productive but less selective. When the pyrolysis temperature from 700 oC to 900 oC, the effective pore size was reduced by sinter effect, thereby the gas permeation rate decreased and selectivity increased. The carbon membranes were characterized by elemental analysis, X-ray diffraction (XRD), and CO₂ adsorption. H₂, N₂, CH₄, and O₂ were used for pure gas tests to evaluate membrane performance.

Abstract: The observation of random laser (RL) with coherent feedback in transparent polymer films based on Rh6G-PVP by spin-coating was carried out in the present investigation. Some sharp peaks with FWHM identified to be 2 nm appeared on the fluorescent spectra of polymer films which pumped by Nd:YLF pulse laser (wavelength: 526nm, frequence: 1Hz, pulse duration: 1ns, energy power: 1.2mJ/pulse). The threshold of emission spectra is ~35 and the spectra range from 570 ~ 610 nm. Streak camera was used to record the temporal process of RLs and the pulse duration time was measured to ~400ps. Rh6G-PVP transparent films were a kind of polymer films with numerous nanogaps distributed randomly on the surface of the film. The photons will be multiple scatterred and amplified during the spreading in the polymer film owing to the refractive index difference between nanogaps and polymer films. As the Rh6G-PVP polymer films have characters of convenient fabrication processes, low threshold and low cost, it shows great potential application in photoelectron and laser imaging.

Abstract: Piezoelectric materials, which can couple electrical and mechanical displacements, are one of the most important functional materials nowadays. They comprises piezoelectric monocrystals, piezoelectric polycrystals (piezoelectric ceramics), piezoelectric polymers, and piezoelectric composites. Sensors made of these materials can convert pressure, acceleration, flow rate, etc. to surface charge (voltage) that can be easily processed, and at the same time generate their own energy instead of consuming it. Compared to other electromechanical transduction technologies, piezoelectric sensors have the advantages of high environmental and chemical stability, broad temperature and frequency band, as well as self-sufficiency. Piezoelectric materials can also be used in various applications such as energy harvesters, actuators, transducers, and capacitors. This paper reviews the piezoelectric materials and their recent application progress on sensors and others. These published results show the developing trend of piezoelectric sensors to become lead-free, flexible, and with high performance.

Abstract: The effect of different solvents on the acoustic property and morphology of polystyrene (PS) and the stearic acid (SA) layer was investigated in this study. The acoustic property was analyzed by using impedance analyzer and morphology of SA layer in a quartz microbalance (QCM) sensor have been studied to quantify their effects on viscoelasticity within the sensor. The polystyrene coating on a QCM sensor was created by spin-coating with various solvents, such as chloroform and toluene, which contains a 3% polystyrene solution by mass. Then, the SA coating was deposited onto the polystyrene layer using a low-vacuum evaporation method. The viscoelasticity was measured by an impedance analyzer coated with the SA layer to determine whether the material used as a coating will effectively immobilize a biomolecule and whether the material produces an acoustic load. The experimental results showed that the impedance value in the series resonant frequency was small (i.e., near 10 Ω), indicating that the deposited SA coating is rigid and that the SA coating does not produce a loading effect on the QCM sensor. Therefore, the coating technique used on the QCM sensor surface to produce the SA coating is likely to be an effective biosensor material for QCM immunosensor. Additionally, the study shows that the frequency change (Δf) of the SA layer deposited onto the polystyrene coating created with chloroform is larger than that of the coating created with toluene. This also shows that the SA layer deposited onto the polystyrene coating created with chloroform is thicker than the coating created with toluene. The Δf correlates with the mass change (Δm), according to the Sauerbrey equation, which requires that the material be rigid. The Δf value also correlates with the deposited SA mass change. From the calculation of Δf, the SA coating created with the chloroform solvent was shown to be thicker than that created with the toluene solvent. In addition, the roughness of the SA surface using a test of non-contact topography measurement system TMS TopMap-1200 showed that the SA surface roughness with the chloroform solution was 763 nm compared to that with the toluene solution, which was 424 nm.