Abstract: Improved fabrication processes of a micro electroosmotic flow pump using hot embossing are described. The microchannels in the micropump were fabricated by hot embossing on a polymethylmethacrylate (PMMA) substrate. A silicon micromachined mold was pressed into the PMMA substrate at a temperature of 145 °C to form microchannel patterns on the substrate. The depth and width of the microchannels were 50 μm and 100 μm, respectively. Aluminum electrodes were deposited using thermal vacuum deposition. A UV ozone treatment was performed to improve adhesion between the PMMA substrate and a PMMA capping layer. This UV ozone treatment enhanced adhesion and resulted in the reduction of the adhesion temperature as low as 70 °C, and nearly no deformation of the microchannels was observed. As a result, the electroosmotic flow pump exhibited the flow rate of 0.5 μl/min when a voltage of 50 V was given between the electrodes separated 8 mm each other.
Abstract: A series of waterborne cationic polyurethanes dispersions (CWPU) was prepared through prepolymerization method by reacting polyethylene glycol (PEG1000) and isophorone diisocyanate (IPDI) with N-methyl diethanol amine (MDEA) as chain extender. Then FeCl3 was employed as oxidant, therefore CWPU/polypyrrole (CWPU/PPy) conductive composite was prepared by in situ chemical oxidative polymerization of pyrrole (Py) in CWPU dispersions. Effects of molar ratio of FeCl3 to Py, Py concentration on the resistivity of the CWPU/PPy composite films were investigated. The structure, morphology and thermal stability were also characterized by Fourier infrared spectra (FT-IR), light scattering, TEM, and TGA. FT-IR demonstrated the presence of hydrogen-bonding interactions between CWPU and PPy. The average particle size of CWPU/PPy increased from 10.61nm to 30.29nm compared with pure PU, and corresponding size distribution decreased from 0.850 to 0.346. It was also found that CWPU/PPy displayed as spherical morphology, and no aggregation among particles was detected among particles. TGA certified CWPU/PPy was endowed with better thermal stability. In addition, conductivity stability of composites films was also studied. It was found that composite films not only displayed low resistivity but also improved conductivity stability.
Abstract: The temperature measure principle of unbalanced electric bridge is expounded by means of temperature characteristics of thermistor. A method to deal with nonlinear function is proposed. The experiment indicts that the thermistor digital thermometer based on unbalanced electric bridge is in accordance with the design request. Its circuit is simple and it has certain practical value.
Abstract: The influence of hydrogen dilution (D) on glass/stainless steel-based intrinsic amorphous/microcrystalline silicon thin film prepared was investigated by PECVD technology. The crystallization ratio and grain size of the silicon thin film at different hydrogen dilution is studied. The results reveal that the crystallization ratio and grain size of silicon thin film changed along with D. The crystallization ratio and grain size of the silicon thin film become larger when D is higher. However, the deposition rate is slow when the D value is too high. On this work, optimal μc-Si:H can be obtained at D of about 98% in the suitable experimental conditions.
Abstract: The forsterite-structure Mg2SiO4 was successfully synthesized by the aqueous sol-gel method using Si sols dioxide and magnesium nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscope (SEM), respectively. The results showed that the calcination process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized Mg2SiO4 powders were successfully obtained at 850 °C with particle size of 60~80 nm.
Abstract: Polyethylene (PE) has found widespread use as a packaging material. Plastics waste disposal, as one of the serious environmental issues, has caused much criticism. The environmental oxidative- and bio- dual degradable linear low-density polyethylene (LLDPE) samples containing Eco-Benign Plastics (EBP) pro-oxidant additives were submitted to an investigation aimed at evaluating their preliminary oxidative degradation in natural environment or accelerated oven aging and their ultimate biodegradation in solid incubation substrate or soil composting conditions. Original and test samples submitted to abiotic oxidation including photo degradation and thermal degradation were characterized by means of FT-IR and GPC. Biodegradation test simulating soil burial and composting conditions reveals that the biodegradation degree exceeded 30%. The degradation process is accompanied by a dramatic change in the structural characteristics of the test samples. It is clear that LLDPE-EBP formulations are effective in promoting the oxidation and subsequent biodegradation of polyethylene in natural and soil environment.
Abstract: An in situ thermal oxidation strategy was proposed for synthesizing different SnO2 nanostructures, using our homemade SnS2 nanoplates as a precursor. The characterization results from X-ray diffraction, energy dispersive X-ray spectroscopy, and field emission scanning electron microscope revealed that the heating temperature played an important role in the microstructure and composition of the resultant products. By heating the SnS2 nanoplates in air at 400, 600 and 800 °C for 5 h, nanoplates, a mixture of nanoplates and nanoparticles, and nanoparticles of SnO2 were synthesized, respectively. The residual S was about 2.2 mol % in the product synthesized at 400 °C, while no residual S was detected in the products synthesized at 600 and 800 °C.
Abstract: In alkaline earth aluminoborosilicate glasses CaO-B2O3-Al2O3-SiO2, the changes of structure and properties caused by variations in the ratio Al2O3/B2O3 were investigated. The structure was investigated by Fourier transform infrared spectroscopy. The dielectric constant and tangent loss were measured at 1 MHz. Chemical durability was evaluated by weight losses of glass samples after immersion in HCl and NaOH solutions. The results indicated that the fraction of four-coordinated boron atoms (N4), chemical durability and dielectric properties increased with increasing Al2O3/B2O3 replacements.
Abstract: High yield ZnO nanorods are synthesized by a simple wet chemical method. The crystal morphology and structure of the ZnO nanorods are examined by transmission electron microscopy (TEM) and X-Ray Diffraction (XRD), respectively. The properties of the excitonic luminescence are investigated by temperature dependent photoluminescence (PL) spectra. Barely observed visible emission band indicates the good optical quality of the ZnO nanorods and the abnormal position and intensity changes of the emission peaks indicates the localization property of exciton.
Abstract: A novel electrochemical method was proposed for detection of hydrogen peroxide (H2O2) based on electrochemical reduction of graphene oxide (GO) modified glassy carbon electrode (GCE). The electrochemically reduced graphene oxide (RGO) was characterized using cyclic voltammetry (CV). Under the optimized conditions, the RGO modified GCE showed much wide linear range for H2O2 from 2.0 to 600 M with the detection limit of 0.67 M (S/N = 3). The proposed method is simple, low-cost and convenient and will be a promising alternative for H2O2 sensing.