Synthesis and Characterization of Nanocrystalline SrAl_2O_4∶Eu, Dy Long Afterglow Phosphors by Sol-Gel Method

Eu 2+, Dy 3+ co-doped nanocrystalline strontium aluminate phosphor powders with brightness and long afterglow were synthesized by the sol-gel method at 1200 ℃ for 2 h. The samples were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results of XRD show that the single crystalline phase is α-SrAl2O4. According to the observation of SEM, the particles of the samples are needle-like. Compared with the samples synthesized by solid state reaction, the grain size of the sol-gel method is to nanometer grade. A clear blue shift occurs in the excitation and emission spectra. The blue shift in nanocrystalline SrAl2O4∶Eu, Dy phosphor can be attributed to the quantum-size-effect of the luminescent particles.

Microwave Plasma Chemical Vapor Deposition of Diamond Films on Silicon From Ethanol and Hydrogen

Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition (MPCVD) from a gas mixture of ethanol and hydrogen at a low substrate temperature of 450 ℃. The effects of the substrate temperature on the diamond nucleation and the morphology of the diamond film have been investigated and observed with scanning electron microscopy (SEM). The microstructure and the phase of the film have been characterized using Raman spectroscopy and X-ray diffraction (XRD). The diamond nucleation density significantly decreases with the increasing of the substrate temperature. There are only sparse nuclei when the substrate temperature is higher than 800 ℃ although the ethanol concentration in hydrogen is very high. That the characteristic diamond peak in the Raman spectrum of a diamond film prepared at a low substrate temperature of 450 ℃ extends into broadband indicates that the film is of nanophase. No graphite peak appeared in the XRD pattern confirms that the film is mainly composed of SP3 carbon. The diamond peak in the XRD pattern also broadens due to the nanocrystalline of the film.

Physicochemical properties and in vitro antioxidant activities of pyroligneous acid prepared from brushwood biomass waste of Mangosteen, Durian, Rambutan, and Langsat

Physicochemical characteristics and in vitro antioxidant activities of four pyroligneous acids carbonized from the wastes of wood species including Mangosteen (Garcinia mangostana Linn.), Durian (Durio zibethinus L.), Rambutan (Nephelium lappaceum L.), and Langsat (Lansium domesticum Serr.) were assessed. Appearing as transparent liquors with pH 3.9–4.2, the pyroligneous acid samples under test possessed acetic acid (23.22–25.46%) as the dominant component. The total soluble tar, total acid, and water content were 0.15 - 0.28 wt%, 99–192 mg KOH/g and 84.5–93.5 wt%, respectively. Phenolic compounds namely: 2,6-dimethoxyphenol (6.88–9.69%),phenol (2.97–5.88%), 4-methylsyringol (3.10–3.56%), guaiacol (2.36–3.55%), and 2-methoxy-4-methylphenol (1.08–1.28%) were found. All had in vitro antioxidant activities especially mangosteen pyroligneous acid, which showed activity roughly similar to BHT (P>0.05) against anti-lipid peroxidation. Nitric oxide scavenging capacities of all pyroligneous acids were significantly higher than BHT (P<0.05). Our results suggest that pyroligneous acids from the four types of branch waste could be used as sources of beneficial natural antioxidants, possibly as food or feed additives to protect against lipid peroxidation, and potentially also in veterinary medicine in anti-inflammatory products.

Isothermal and Non-Isothermal Crystallization Kinetics of Conductive Polyvinylidene Fluoride/Poly(Ethylene Terephthalate) Based Composites

This work deals with isothermal and non-isothermal crystallization kinetics of electrically conductive polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET) based composites. It completes our previous work in which we related the crystallinity of these conductive PVDF/PET based composites to their through-plane resistivity [1]. Isothermal crystallization was described using the logarithmic form of the Avrami equation and it was observed that the crystallization rate of the PVDF phase inside the composite became slower compared to that of neat PVDF. In non-isothermal crystallization, the Avrami exponent of PVDF phase did not show any noticeable variation;however, that of PET phase, which contains the major part of the conductive carbon black (CB) and graphite (GR) additives, showed an evident decrease compared with neat PET. It was also observed that, at the same cooling rate, the crystallization rate of PVDF and PET phases inside the composite was slower than that of neat PVDF and PET.

Doping organic hole-transport materials for high-performance perovskite solar cells

Single-junction and tandem perovskite solar cells(PSCs)have achieved impressive power conversion efficiencies(PCEs)of 25.7%and 31.3%,respectively,which makes it to be one of next-generation photovoltaic technologies[1−9].Inter-face engineering[3,5,10−12],composition engineering[13]and ad-ditive engineering[7,14,15]have made remarkable contribu-tions to efficiency enhancement.Compared with efficiency,the long-term operational stability of PSCs jogs along,which is far from the requirements of commercialization.Currently,almost all regular n-i-p PSCs were accomplished with classic-al organic hole-transport materials(HTMs),i.e.,PTAA[16]and spiro-OMeTAD[2,4,6].However,the highly efficient PSCs with the above organic hole-transport layers(HTL)usually suffer from instability.To facilitate hole transport and extraction,LiTF-SI and tBP are frequently employed to dope organic HTLs but this would sacrifice device stability.The use of these hygro-scopic p-dopants endows the devices with poor moisture sta-bility.

Role of CO_2 in the initial stage of atmospheric corrosion of AZ91 magne-sium alloy in the presence of NaCl

The effect of CO2 and NaCl on the initial stage of atmospheric corrosion of AZ91 magnesium alloy was studied. The observation of surface morphology by optical microscopy (OM), scanning electron microscopy (SEM) and the analysis of corrosion products by X-ray diffraction (XRD) were integrated to investigate corrosion evolution. The results showed that NaCl stimulated the corrosion by promoting the formation of thin electrolyte film, increasing the conductivity and breaking the protective film in the absence of CO2. The morphology of the corroded samples with deposited NaCl was more homogenous in the presence of CO2. It was suggested that NaCl-induced corrosion was inhibited in the presence of CO2 by the formation of slightly soluble corrosion products containing hydroxy carbonates and hydroxy chlorides that provided a partly protective layer on the surface of the magnesium alloy.

Physicochemical characterization of Baizhi particles by ultrafine pulverization

Baizhi, as a medicinal plant, has been demonstrated to be useful for the treatment of aches and pains in China. The physicochemical characterization of Baizhi particles is greatly influenced by ultrafine pulverization. To study the physicochemical characterization of Baizhi, the raw plant material of Baizhi was ground to 6 μm particles by a high speed centrifugal sheering (HSCS) pulverizer. The micron particles were characterized by optical microscopy and scanning electron microscopy (SEM). Imperatorin is one of the active ingredients of Baizhi, and its extraction yield is determined to evaluate the chemical characterization of Baizhi powder. Imperatorin was analyzed by high performance liquid chromatography (HPLC). The results show that after ultrafine pulverization, the plant cell walls are broken into pieces and the extraction yield of imperatorin is increased by 11.93% compared with the normal particles.

STUDY ON THE STABILITY OF T'PHASE IN THE Al-Zn-Cu TERNARY SYSTEM

The phase constitutes and phase compositions in the eight alloys designed with different compositions of Al-Zn-Cu system have been determined after the homogenous treatment and then equilibrium cooling to 20℃ by use of optical microscope, electron probe microanalysis and X-ray diffraction. It has been found that there existed the T phase in the seven alloys. Consequently, it was testified that the T phase was stable at room temperature. At the same time, the phase relationship was not locally right for the isothermal section of 20℃ of Al-Zn-Cu system of the ASM published in 1997.

XPS analysis of passive film formed on the G3 nickel-base alloy tubing under corrosive conditions

In the present study,the passive film formed on the G3 nickel-base alloy tubing under corrosive conditions including H_2S,CO_2,and Cl^- at 130℃and 205℃is studied with X-ray photoelectron spectroscopy(XPS).The results reveal that the passive film formed at 205℃consists of Cr,Ni,Fe,S and O elements and is over 470 nm in thickness. The passive film can be divided into three layers,the outer-layer is composed of NiS,and Cr_2S_3,the intermediate-layer of Cr(OH)_3,Ni(OH)_2,NiS_2,Cr_2S_3 and a small quantity of NiO and Cr_2O_3,and the inner-layer of NiO,Cr_2O_3,and alloy elements.Due to the invasion of S^(2-) into the passive film and the decrease of the content of chromium oxide in the film,the corrosion resistance of the G3 alloy in the sour environment at 205℃is weakened.

Corrosion behavior of LY12CZ aluminum alloy in simulated acid rain solution

The variations of corrosion potential, electrochemical impedance and surface morphology of LY12 aluminum alloy with pH of simulated acidic rain solutions were investigated with EIS and SEM. It is found that corrosion potential shifts to less noble value with increasing pH in the solutions of pH lower than 3.1 and shifts to more noble value in the solutions of pH higher than 3.1. In the solutions of pH lower than 3.1,the electrochemical impedance diagram has a capacitive loop at higher frequency and an inductive loop at lower frequency and the magnitude of high frequency loop decreases with decreasing pH and increasing period of immersion. However, in the solutions of pH higher than 3.4 two capacitive loops appear and the magnitude of high frequency loops increases with pH and period of immersion. Observation of SEM shows that the pitting intensity increases with decreasing pH in the range of pH2.0～3.4, no evident pits are observed at pH higher than 3.4. The experiment results were discussed from resistance of oxide film and adsorption processes of anions in simulated acid rain solution.

电源模式对镁合金微弧氧化生物膜层性能的影响

目前对不同电源模式下微弧氧化制备生物膜层的研究较少。为此,采用全阶段恒压、全阶段恒流、恒压-恒流、恒流-恒压4种电源模式在ZK60镁合金基体表面制备微弧氧化生物膜层,实时记录并分析了不同电源模式下反应过程中电压/电流随时间的变化情况,并采用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)及共聚焦显微镜等手段考察了不同电源模式下获得的微弧氧化生物膜层的物相、膜层微观组织结构、膜层元素分布、膜层表面粗糙度及膜层表面接触角等。结果表明:4种模式下制备的微弧氧化膜层物相为Mg、MgO及Ca_(3)(PO_(4))_(2)等钙磷产物。但电源模式不同,膜层厚度及耐蚀性能均不同。由于后期击穿力不足,恒压模式下制备的生物膜层厚度最小,远小于其他3种电源模式下制得的膜层的,该模式下制得的微弧氧化生物膜层粗糙度也最小。恒流模式由于后期能量过高导致部分膜层脱落,膜层质量较差。恒压-恒流模式则避免了单一恒压和单一恒流模式的缺陷,该复合模式下制备的膜层与其他电源模式下制备的膜层相比,具有微观形貌均匀致密的特点,厚度较大,约为55μm。电化学测试显示,该复合模式下制备的微弧氧化生物膜层具有较好的耐腐蚀性能,同时该复合模式能耗最低,符合节能降耗的要求。此外,恒压-恒流复合模式下制备的微弧氧化生物膜层还具有较好的生物相容性。

Effects of Pt diffusion barrier layer on the interface reaction and electric properties of PZT film/Si (111) sample

The effects of the Pt diffusion barrier layer on the interface diffusion and reaction, crystallization, dielectric and ferroelectric properties of the PZT/Si(111) sample have been studied using XPS, AES and XRD techniques. Hie results indicate that the Pt diffusion barrier layer between the PZT layer and the Si substrate prohibits the formation of TiCx TiSix and SiO2 species in the PZT layer. The Pt barrier layer also completely interrupts the diffusion of Si from the Si substrate into the PZT layer and impedes the diffusion of oxygen from air to the Si substrate greatly. Although the Pt layer can not prevent completely the diffusion and reaction between oxygen and silicon, it can prevent the formation of a stable SiO2 interface layer on the interface of PZT/Si. The Pt layer reacts with silicon to form PtSix species on the interface of Pt/Si, which can intensify the chemical binding strength between the Pt layer and the Si substrate. To play a good role as a diffusion barrier layer, the Pt barrier

Interface diffusion and chemical reaction of PZT layer/Si (111) sample during the annealing treatment in air

The interface diffusion and chemical reaction between a PZT (PbZrxTi1-xO3) layer and a Si(111) substrate during the annealing treatment in air have been studied by using XPS (X-Ray Photoelectron Spectroscopy) and AES (Auger Electron Spectroscopy). The results indicate that the Ti element in the PZT precursor reacted with residual carbon and silicon, diffused from the Si substrate, to form TiCx, TiSix species in the PZT layer during the thermal treatment. A great interface diffusion and chemical reaction took place on the interface of PZT Si also. The silicon atoms diffused from silicon substrate onto the surface of PZT layer. The oxygen atoms, which came from air, diffused into silicon substrate also and reacted with Si atoms to form a SiO2 interlayer between the PZT layer and the Si (111) substrate. The thickness of SiO2 interlayer was proportional to the square root of treatment time. The formation of the SiO2 interlayer was governed by the diffusion of oxygen in the PZT layer at low annealing

Recent advances in biomaterials for 3D scaffolds: A review

Considering the advantages and disadvantages of biomaterials used for the production of 3D scaffolds for tissue engineering,new strategies for designing advanced functional biomimetic structures have been reviewed.We offer a comprehensive summary of recent trends in development of single-(metal,ceramics and polymers),composite-type and cell-laden scaffolds that in addition to mechanical support,promote simultaneous tissue growth,and deliver different molecules(growth factors,cytokines,bioactive ions,genes,drugs,antibiotics,etc.)or cells with therapeutic or facilitating regeneration effect.The paper briefly focuses on divers 3D bioprinting constructs and the challenges they face.Based on their application in hard and soft tissue engineering,in vitro and in vivo effects triggered by the structural and biological functionalized biomaterials are underlined.The authors discuss the future outlook for the development of bioactive scaffolds that could pave the way for their successful imposing in clinical therapy.

PRINCIPAL SHEARING STRESS LOCUS THEORY OF AXISYMMETRICALLY PLASTIC FLOW

The slip-line method is one of the fundamental solving methods for the plastic deformation. However, the existing slip-fine theory, strictly speaking, is only confined to solving a rigid-perfectly plastic material under the plane strain conditions. Although some authors (such as Shield) have made an extension to the axisymmetdeally plastic problems with the aid of the "perfect plasticity" hypothesis, more axisymmetric problems still cannot be solved by the method. For this reason, in the present note, a new hypothesis is proposed for analysing the axisymmetric plastic problems, and then, according to this hypothesis,

Porous Co_(x)Ni_(1-x)TiO_(3) nanorods for solar photocatalytic degradation of ethyl paraben

Porous Porous Co_(x)Ni_(1-x)TiO_(3) nanorods were successfully synthesized through a solution-based method following an ethylene glycol route at room temperature.The effect of calcination temperature from 300℃to 900℃ for NiTiO_(3) and CoTiO_(3) nanorods was studied using X-ray diffractometry and scanning electron microscopy in order to investigate their structural and morphological properties.The optimum calcination temperature to prepare pure ilmenite type structure rods with high crystallinity and hexagonal shape was 600Co_(x)Ni_(1-x)TiO_(3) exhibited the highest photocatalytic activity for the degradation of ethyl paraben,an endocrine disrupting compound,under simulated solar or visible light irradiation.Nearly complete(i.e.92%)paraben degradation occurred after 5 h of solar irradiation and this decreased to 48%when only the visible part of the radiation was employed.The solar photocatalytic activity of CoTiO_(3) and NiTiO_(3) was found to be 42%and 67%,respectively.

A-site Cation Defects(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)Perovskites as Active Oxygen Evolution Reaction Catalyst in Alkaline Electrolyte

Main observation and conclusion Perovskites(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(x=0.02,0.05,0.1 denoted as BSCF-0.98,BSCF-0.95,BSCF-0.9,respectively)with A-site cation defects are synthesized by simple and efficient sol-gel method and are proved to have better OER catalytic effect than the well-known(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)oxides.BSCF-0.95 exhibits the best OER catalytic activity in the series perovskite.The current density of BSCF-0.95 is about 56%higher than that of BSCF oxide at a potential of 1.7 V.The experimental studies have shown that compared with BSCF,BSCF-0.95 oxide has a larger electrochemical surface area(ECSA),a higher content of O_(2)^(2–)species related to surface oxygen vacancies,and faster charge transfer rate,which may be the factors for the enhancement of OER activity.The theoretical calculation results prove that the center positions of the O 2p-band of perovskite with A-site cation defects are closer to the Fermi level than BSCF oxide,which agrees with the OER performance trend of the material.