Ballistic behavior of Heracron®-based composites: effect of fiber density and fabrication method

In this study, a Heracron^® aramid fiber-based helmet was made, and its ballistic properties were investigated. The effect of fiber density was studied in depth. For the same weight and number of plies, a helmet manufactured from the HT-2820-based composite showed improved ballistic properties compared with one made from the HT-15000-based composite. This result suggested that fiber density may strongly affect the ballistic properties of armor. HT-2820, containing more multifilament fibers, provides more efficient energy absorption and dissipation. The influence of fabrication method on the ballistic behavior of a helmet was studied. The V₅₀ of a helmet made by the film laminating method was 10% better than that for a helmet made by the resin dipping approach. Based on these findings, the film laminating method, which forms the composite by directly attaching aramid fabric to the matrix film, may be a good candidate for improving the ballistic behavior. The required composite interfacial strength will be application-dependent. Greater fiber-matrix adhesion may be advantageous in certain cases.     

Influence of the light-curing unit, storage time and shade of a dental composite resin on the fluorescence

The aim of this study was to determine the influence of three light-curing units, storage times and colors of the dental composite resin on the fluorescence. The specimens (diameter 10.0 ± 0.1 mm, thickness 1.0 ± 0.1 mm) were made using a stainless steel mold. The mold was filled with the microhybrid composite resin and a polyethylene film covered each side of the mold. After this, a glass slide was placed on the top of the mold. To standardize the top surface of the specimens a circular weight (1 kg) with an orifice to pass the light tip of the LCU was placed on the top surface and photo-activated during 40 s. Five specimens were made for each group. The groups were divided into 9 groups following the LCUs (one QTH and two LEDs), storage times (immediately after curing, 24 hours, 7 and 30 days) and colors (shades: A₂E, A₂D, and TC) of the composite resin. After photo-activation, the specimens were storage in artificial saliva during the storage times proposed to each group at 37°C and 100% humidity. The analysis of variance (ANOVA) and Tukey’s posthoc tests showed no significant difference between storage times (immediately, 24 hours and 30 days) (P > 0.05). The means of fluorescence had difference significant to color and light-curing unit used to all period of storage (P < 0.05). The colors had difference significant between them (shades: A₂D < A₂E < TC) (P < 0.05). The Ultraled (LED) and Ultralux (QTH) when used the TC shade showed higher than Radii (LED), however to A₂E shade and A₂D shade any difference were found (P > 0.05).     

Synthesis of photosensitive poly(methyl methacrylate-co-glycidyl methacrylate) for optical waveguide devices

Photosensitive poly(MMA-co-GMA) for optical waveguide was synthesized, and the refractive index of the polymer film was tuned in the range of 1.481–1.588 at 1550 nm by mixing with bis-phenol-A epoxy resin. The film, which was made by spinning coated the poly(MMA-co-GMA) with photo initiator, had good UV light lithograph sensitivity, high glass transition temperature (T _g : 153°C, after crosslinking) and good thermal stabilities (T _d : up to 324°C, after crosslinking). The optical waveguides with very smooth top surface were fabricated from the resulting polymer by direct UV exposure and chemical development. For waveguides with cladding, the propagation losses of the channel waveguides were measured to be below 3 dB/cm at 1550 nm.     

Photocatalytic hydroxyapatite/titanium dioxide multilayer thin film deposited onto glass using an rf magnetron sputtering technique

Hydroxyapatite (HA)/titanium dioxide (TiO₂) thin film was deposited on glass using a radio frequency magnetron sputtering. X-ray diffraction (XRD), Fourier-transform infrared spectrometry, ultraviolet-visible spectroscopy and measurement of its photocatalytic activity by the decomposition of formaldehyde gas and the bacterial survival test of Escherichia coli (E. coli) cells were applied to characterize the film. After heat treatment (at 500 °C), XRD analysis of the HA/TiO₂ film showed a crystalline TiO₂ crystal structure with anatase phase. The transmittance of the HA/TiO₂ film decreased after the heat treatment, however, the average transmittance remained at 87% in the visible light range.In the decomposition of formaldehyde gas, the HA/TiO₂ film showed a higher decomposition rate than either the TiO₂ or the HA film alone. However, in the bacterial survival test, survival of cells on the HA/TiO₂ film was higher than that on the TiO₂ film, which indicates the HA/TiO₂ film has a lower bactericidal effect than the TiO₂ film alone.     

Inkjet-printed gold nanoparticulate patterns for surface finish in electronic package

Gold (Au) pads for surface finish in electronic package were developed by the inkjet printing method. The Au ink for printing was prepared by Au nanoparticles (NPs) coated with capping molecules of dodecylamine (C₁₂H₂₅NH₂). The microstructures of the inkjet-printed Au films were characterized after sintering in various gas flows. The film sintered in air showed that bonding between NPs was not enough for further grain growth due to the incomplete decomposition of the capping layer. The film sintered under nitrogen (N₂) had NPs existing on the surface and the bottom which did not participate in sintering. When the film was sintered under N₂-bubbled through formic acid (FA/N₂), a large portion of the pores were observed to make a holey pancake-like structure of the film. The microstructures of the inkjet-printed Au film became denser with grain growth when Au NPs were sintered under mixed gas flows of FA/N₂ and N₂. The resistivity of film was 4.79 μΩ cm, about twice the bulk value. Organic analysis showed that about 0.43% of residual organics was left in the film. Therefore, this Au film was chosen for solder ball shear test because the microstructure was denser compared to the films sintered under other gasses such as N₂ or FA/N₂ and less organic residue was found from organic analyses. Even though the film sintered under N₂ showed the best electrical property (4.35 μΩ cm), it was not adopted in the shear test because NPs remaining on the bottom of the film could lead to the poor adhesion between the film and substrate and show low shear strength. The shear force was 8.04 newton (N) on average and the strength was 64 MPa. This shear strength is good enough to substitute the inkjet-printed Au nanoparticulate film for electroplating in electronic package.     

Evolution from vanadium pentoxide xerogel to sodium-containing vanadates in thin films on ITO-coated glasses

In this work, the mechanism of the “gelation” process and the thermal-induced structural modifications of thin film of vanadium pentoxide xerogels deposited on indium tin oxide (ITO)-coated glasses have been studied. Vanadium pentoxide xerogel has been prepared by using the sol–gel proton exchange resin route without any resin pretreatment. To monitor the effect of the “resin efficiency” on the gelation process, the solution coming out from the resin has been collected in a sequence of different containers (vials), separately investigated by Raman spectroscopy. After the spin coating deposition, the thin films of vanadium pentoxide gel have been subjected to different annealing treatments. The highest thermal treatment (600 °C) induces a complete transformation of the gel phase into an anhydrous polycrystalline phase of a sodium-containing vanadate, different from the usual V₂O₅ crystal. It is due to the diffusion of foreign ions (mainly sodium) coming from the substrate into the vanadium oxide layer.     

Low temperature deposition and characterization of TiO2 photocatalytic film through cold spray

Cold spray was employed as a novel low temperature approach to deposit titanium dioxide (TiO₂) photocatalytic film. The film microstructure was characterized using X-ray diffraction and scanning electron microscopy. The photocatalytic performance was examined through acetaldehyde degradation under ultraviolet illumination. Results showed that TiO₂ film was successfully deposited on substrate surface through cold spray. The film thickness reached up to 15 μm. The film presented a rough surface and porous structure. Owing to the low temperature of spray powder, no phase and particle size changes occurred to TiO₂ during deposition. It was found that the cold-sprayed TiO₂ film was active for photodegradation of acetaldehyde.     

Al2O3绝缘层的AlGaN/GaN MOSHEMT器件研究

在研制AlGaN/GaN HEMT器件的基础上,采用ALD法制备了Al₂O₃ AlGaN/GaN MOSHEMT器件.通过X射线光电子能谱测试表明在AlGaN/GaN异质结材料上成功淀积了Al₂O₃薄膜.根据对HEMT和MOSHEMT器件肖特基电容、器件输出以及转移特性的测试进行分析发现：所制备的Al₂O₃薄膜与AlGaN外延层间界面态密度较小,因而MOSHEMT器件呈现出较 关键词： 2O₃')" href="#">Al₂O₃ ALD GaN MOSHEMT     

Microstructure of thermoelectric (Bi0.15Sb0.85)2Te3 film

The film of thermoelectric ternary p-type (Bi_0.15Sb_0.85)₂Te₃ was deposited on polyimide foil substrate at 168 °C using direct-current magnetron sputtering. Microstructural investigations of the film were performed by electron microscopy techniques. SEM observations showed that the film surface consisted of large-sized particulates with small-sized particles and also mound-like crystal agglomerates in some areas. Chemical composition of the film was analyzed using energy-dispersive X-ray spectrometer (EDS). It has been observed that the EDS results were in an agreement with nominal composition for the film. Detailed microstructural investigations were carried out using transmission electron microscopy (TEM). TEM images and selected area electron diffraction patterns showed that the film has randomly oriented polycrystalline grain structure. High-resolution TEM images indicated that the microstructure of film also contained nano-crystal structure, smaller than 10 nm.     

Crystallization of amorphous Co2MnSi thin film

Amorphous Co₂MnSi thin film was deposited using radio-frequency sputtering. The amorphous film crystallized into a single-phased L2₁ structure at 500 °C, which was highly disordered. The structure was meta-stable as the crystallized film decomposed upon further heating. Increasing the annealing temperature to 600 °C precipitated fcc Co together with Co₂MnSi. Magnetic measurements showed that the as-deposited amorphous film was paramagnetic, exhibiting a spin glass state below 44 K. The phase transition at 500 °C produced a ferromagnetic Co₂MnSi thin film whose saturation magnetic moment was considerably lower than reported values due to the disordered structure of the crystallized film.     

Preparation and conducting performance of LaNiO3/Ag film and its interface reaction

LaNiO₃ thin film with perovskite structure was successfully prepared on Ag substrate via an amorphous heteronuclear complex LaNi(DTPA)·6H₂O as a precursor. The influences of precursor concentration and PEG additive with different molecular weight on the texture of the film were carefully studied. The interface states of LaNiO₃/Ag film were revealed by using AES analysis. The effect of annealing time on the interface diffusion of the LaNiO₃/Ag film was shown by using AES depth profile spectrum. The relationship between the electric resistivity of the film and the environmental temperature was measured by using four-probe method. The results showed the film had good metallic conductivity from 300 down to 77 K.     

有序结构氟聚合物压电驻极体的制备和压电性研究

描述了一种有序微孔结构压电聚合物功能膜的制备方法,利用模板的高度有序实现薄膜微孔结构的精确控制.将此制备方法用于氟聚合物压电驻极体薄膜的制备,通过扫描电子显微镜(SEM)对其微观结构的观察表明薄膜具有理想的有序结构.对氟聚合物压电驻极体压电性的研究则是利用正压电效应测量准静态压电系数d₃₃,通过等温衰减和压强依赖性的测量考察其压电性能.结果表明:有序结构氟聚合物压电驻极体的准静态压电系数d₃₃可高达300 pC/N;与无序结构氟聚合物     

Photocatalytic reduction of potassium chromate by Zn-doped TiO2/Ti film catalyst

The aim of this work was to investigate the photocatalytic (PC) reduction of potassium chromate by Zn-doped TiO₂/Ti film catalysts. The film catalyst was prepared by plasma electrolytic oxidation method in H₂SO₄ solution with different dosages of ZnSO₄. The composition and structure of the film catalysts was studied by XRD, SEM and EPMA. The removal rate of potassium chromate was investigated under the conditions of the different dosages of ZnSO₄ and the initial concentration of chromate potassium, and the reductive product during the PC reduction process was analyzed. The results showed that the film catalyst was composed of anatase TiO₂ and rutile TiO₂ with the porous structure. When the dosage of ZnSO₄ was 0.2 g/L, the film catalyst presented the highest catalytic activity, which related to the amount and the crystal grain size of anatase TiO₂ in the film. The PC reduction of potassium chromate by the film catalyst obeyed the pseudo-first-order kinetic equation. The UV-vis spectrum and XPS analyses proved that chromate Cr(VI) was reduced to Cr(III), which existed in the form of insoluble Cr(OH)₃.     

退火气压对Bi3.25La0.75Ti3O12铁电薄膜的微观结构和铁电性能的影响

采用sol-gel法在Pt/TiO₂/SiO₂/p-Si(100)衬底上制备了Bi_3.25La_0.75Ti₃O₁₂(BLT)铁电薄膜,研究了在750 ℃时不同退火气压(p_{O2:10^-4—3 atm)对薄膜微观结构和电学性能的影响.XRD和拉曼光谱结果表明在10^-4和3 atm氧气压下退火 关键词： 3.25}La_0.75Ti₃O₁₂')" href="#">Bi_3.25La_0.75Ti₃O₁₂ 铁电性能 sol-gel法 正交化度     

Parallel upper critical field of niobium/graphite bilayers

The influence of the superconducting proximity effect to the upper critical field (H_C) in niobium/graphite bilayers was studied and related to the ratio : and are the transition temperature of Nb/KG film and that of Nb film respectively. The thickness of niobium (Nb) film was controlled about 40 nm, and that of graphite (kish graphite: KG) film ranged from 120 nm to 140 nm. For making a specimen, Nb was deposited on a KG film and a quartz glass substrate simultaneously, and magnetic field was applied parallel to the Nb/KG interface. H_C of Nb/KG film () lowered from that of Nb film () at all temperatures within this work, and the value of ΔH_C defined as showed different temperature dependence among samples, depending on whether < or 1.00. This behavior of H_C suggests the additional existence of the interference of electrons in the clean KG film.     

Synthesis and characterization of brookite/anatase complex thin film

TiO₂ films were prepared on a silicon or soda-glass substrate using a sol suspension. The TiO₂ film on the silicon substrate was composed of pure anatase phase and showed almost no contaminations. In contrast, the TiO₂ film on the soda-glass substrate was composed of anatase and brookite phases. The diffusion of Na into the TiO₂ film on the soda-glass substrate was observed by XPS, and Na was concentrated on the surface of the film. The yield of the brookite phase increased with decreasing distance from the surface of the film on the soda-glass substrate. Na promoted the formation of the brookite phase, although the preparative procedure was used for anatase synthesis.     

Dip coated TiO2 nanostructured thin film: synthesis and application

TiO₂ thin film was fabricated by dip coating method using titanium IV chloride as precursor and sodium carboxymethyl cellulose as thickening as well as capping agent. Structural and morphological features of TiO₂ thin film were characterized by X-ray diffractometer and field emission scanning electron microscope, respectively. Crystallinity of the film was confirmed with high-intensity peak at (101) plane, and its average crystallite size was found to be 28 nm. The ethanol-sensing properties of TiO₂ thin film was studied by the chemiresistive method. Furthermore, various gases were tested in order to verify the selectivity of the sensor. Among the several gases, the fabricated TiO₂ sensor showed very high selectivity towards ethanol at room temperature.     

Investigation of the chemical state of ultrathin Hf-Al-O films during high temperature annealing

Al₂O₃ incorporated HfO₂ films grown by atomic layer deposition (ALD) were investigated by high-resolution X-ray photoelectron spectroscopy (HRXPS). The core level energy state of a 15 Å thick film showed a shift to higher binding energy, as the result of a silicate formation and Al₂O₃ incorporation. The incorporation of Al₂O₃ into the HfO₂ film had no effect on silicate formation at the interface between the film and Si, while the ionic bonding characteristics and hybridization effects were enhanced compared to a pure HfO₂ film. The dissociation of the film in an ultrahigh vacuum (UHV) is effectively suppressed compared to a pure HfO₂ film, indicating an enhanced thermal stability of Hf-Al-O. Any dissociated Al₂O₃ on the film surface was completely removed into the vacuum by vacuum annealing treatment over 850 °C, while HfO₂ contributed to Hf silicide formation on the film surface.     

Effect of nickel on the initial growth behavior of electroless Ni-Co-P alloy on silicon substrate

In this work the small amounts of NiSO₄ was added to a basic electroless plating bath of CoSO₄ with Na₂H₂PO₂ as reducing agent for the deposition of Co-Ni-P film on a silicon substrate. The initial growth behavior, containing plating rate, chemical composition, crystal structure, surface morphology and micro-structure, of the electroless plating film was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the growth morphology variation of the Co-Ni-P films deposited in the basic CoSO₄ + small amounts of NiSO₄ bath is the same as that of Co-P film deposited in the basic CoSO₄ bath, the plating rate of the Co-Ni-P film is much more rapid than that of the Co-P film, the Ni/Co wt.% in the Co-Ni-P film is greatly larger than that in the plating bath, and the structure of as-deposited film is crystalline at first stage and later stage.     

Silane effects on the surface morphology and abrasion resistance of transparent SiO2/UV-curable resin nano-composites

Transparent ultraviolet curable nano-composite coatings consisting of nano-sized SiO₂ and acrylate resin have been developed to improve the abrasion resistance of organic polymers. The nano-sized SiO₂ particles were surface-modified using various amounts of 3-methacryloxypropyltrimethoxysilane. The 3-methacryloxypropyltrimethoxysilane concentration effects on the surface morphology and abrasion resistance of the transparent SiO₂/ultraviolet-curable resin nano-composites were investigated using scanning electron microscopy, atomic force microscopy, and ultraviolet-visible spectrophotometer. The results showed that as the 3-methacryloxypropyltrimethoxysilane/SiO₂ weight ratio increased from 0.2 to 0.6, the dispersion, compatibility and cross-linking density between the 3-methacryloxypropyltrimethoxysilane-modified SiO₂ particles and acrylate resin were improved, leading to an increase in abrasion resistance. However, as the 3-methacryloxypropyltrimethoxysilane/SiO₂ weight ratio was increased to 1.5, the additional 3-methacryloxypropyltrimethoxysilane may exceed that needed to fill the pores with the probability of SiO₂ nano-particles existing on the coating surface was lower than that for samples with a 3-methacryloxypropyltrimethoxysilane/SiO₂ weight ratio of 0.6. This produced a decrease in abrasion resistance.