纳米结构304不锈钢在硫酸溶液中的腐蚀行为

采用高频表面机械研磨方法在304不锈钢中制备出纳米晶和纳米孪晶结构。采用腐蚀失重试验和极化曲线测试等方法测试两种纳米结构304不锈钢在室温及80℃条件下5%硫酸溶液中的耐腐蚀性能,并利用透射电镜和扫描电镜分析其腐蚀性能和微观结构的关系。失重试验结果表明在80℃条件下5%硫酸溶液中,纳米孪晶比纳米晶结构的304不锈钢耐腐蚀性能好,以均匀腐蚀为主,点蚀为辅;而纳米晶则发生严重的点蚀。电化学测试结果表明:在室温条件下,纳米孪晶结构304不锈钢呈现高的自腐蚀电位和宽的钝化区间,但在80℃条件下,纳米晶和纳米孪晶结构304不锈钢的耐腐蚀性比粗晶不锈钢差。     

压水堆条件下加锌对304NG不锈钢腐蚀的影响

在模拟压水堆一回路工况下,对304NG不锈钢在含锌0ppb和50ppb两种水化学条件下分别进行了1200h的动水腐蚀试验,用SEM、XPS及AES对腐蚀后样品表面氧化膜的微观结构及成分进行了分析,用失重法对均匀腐蚀和均匀腐蚀速率进行了定量评估。结果表明,304NG不锈钢表面均生成了外层富Fe,内层富Cr的氧化膜,其中在50ppb锌条件下氧化膜成分主要为Zn(Cr,Fe)2O4。与0ppb锌溶液中形成的氧化膜相比,50ppb锌条件下的氧化膜厚度明显减薄,结构更加致密,加锌能有效提高材料的抗腐蚀性能。     

304不锈钢表面纳米铝改性有机硅涂层的高温氧化和电化学行为

研究了纳米铝改性有机硅高温涂层的固化、抗650℃高温氧化性能和耐3.5% NaCl水溶液电化学腐蚀性能。当聚氨酯:有机硅的质量分数达到1:3或更高时,有机硅涂料可以在24 h内完成常温固化。制备出的纳米铝改性有机硅高温涂层表面致密,没有微观裂纹等缺陷。纳米铝改性的有机硅涂层显著提高了304不锈钢抗氧化性能,经1028 h氧化实验,基体几乎没有发生氧化,涂层没有出现开裂和剥落。纳米铝改性的有机硅涂层还显著提高了氧化后的304不锈钢耐氯化钠水溶液腐蚀性能,无涂层的304不锈钢氧化后形成的氧化膜低频阻抗仅3.2 Ω·cm²,而涂装涂层的不锈钢的低频阻抗约为1.1×10⁵ Ω·cm²。     

不锈钢表面阴极微弧电沉积氧化铝膜层的性能

以0.4 mol/L Al（NO₃）₃乙醇溶液为电解液,用阴极微弧电沉积方法在304不锈钢表面制备了80μm厚的氧化铝膜层。分析了膜层的形貌、成分和相组成,测试了膜层的抗高温氧化和电化学腐蚀性能。结果表明.电沉积膜层由γ-Al₂O₃和α-Al₂O₃组成。膜层中含有少量的Fe、Cr、Ni元素,表明膜/基界面附近的不锈钢基体在微弧放电作用下也参与氧化铝膜层的沉积和烧结过程。氧化铝膜层使不锈钢在800℃恒温氧化速率明显降低,表明其抗高温氧化性能得到提高。同时,其腐蚀电位正向移动,腐蚀电流密度降低1个数量级,表明其耐腐蚀性能得到提高。     

不锈钢表面防护TiC/a-C∶H纳米复合薄膜的耐腐蚀性能

采用直流反应磁控溅射技术在304不锈钢表面沉积TiC/a-C∶H纳米复合薄膜,并研究了TiC/a-C∶H纳米复合薄膜对不锈钢耐腐蚀性能的影响。通过扫描电子显微镜(SEM)和原子力显微镜(AFM)观察,结果表明薄膜表面光滑且薄膜结构均匀致密。Raman光谱和XRD测试结果表明,薄膜具有纳米晶TiC镶嵌非晶碳基质的典型纳米复合微结构。通过测量薄膜的静态接触角分析薄膜的润湿性,不锈钢表面沉积TiC/a-C∶H纳米复合薄膜后疏水性能明显提高,水接触角高达98°。电化学腐蚀测试结果表明,不锈钢表面沉积TiC/a-C∶H纳米复合薄膜体系在质量分数为3.5%的NaCl溶液中自腐蚀电位约为-0.09V,腐蚀电流密度为2.43×10-8 A·cm-2,与无薄膜防护的裸露不锈钢相比,其耐腐蚀性能得到明显改善。     

锌铝离子对304L不锈钢在高温水环境中形成的氧化膜性质的影响

为明确304L不锈钢在核电站一回路中的腐蚀机理，将304L不锈钢浸泡在290℃的含不同浓度锌铝离子的模拟核电站第一回路水环境溶液中168 h使其表面形成氧化膜，并对形成氧化膜的试样进行动电位扫描、交流阻抗谱测试、Mott-Schottky曲线测试和光电化学测试，得到氧化膜的极化曲线、电化学参数、半导体类型、平带电位、载流子浓度、禁带电位及物相组成。结果表明：锌铝离子的同时添加可明显降低304L不锈钢的腐蚀速率，模拟溶液中的锌离子浓度为40μg/L,铝离子浓度为90μg/L时，304L不锈钢表面形成的氧化膜的腐蚀电流密度最小，此时304L不锈钢表面氧化膜的耐蚀性最佳；相比于核电站一回路单独注入锌离子金属的氧化膜，该条件下304L不锈钢的氧化膜均呈现双层结构，其半导体类型为n型，平带电位负移，载流子浓度降低。与未加入锌铝离子的条件下形成的氧化膜相比，304L不锈钢在同时加入锌铝离子的条件下形成的氧化膜的物相组成中多了ZnAl₂O₄和α-FeOOH两相，因此向高温高压状态下的模拟溶液中添加锌铝离子能够有效增加304L不锈钢的耐腐蚀性。     

低温低压电弧等离子体渗氮处理316不锈钢的耐腐蚀性能

在低温下对316奥氏体不锈钢进行低压电弧等离子体渗氮处理,研究了渗氮处理对不锈钢耐腐蚀性能的影响。结果表明:渗氮层有两个子层,由纳米晶扩张奥氏体和少量的Cr N化合物组成的外表层和单一结构的扩张奥氏体内层。由于低压电弧等离子体浓度高,在400℃渗氮1 h得到的渗氮层厚度达到15μm,表现出很高的渗氮速率。纳米晶外表层是渗氮不锈钢耐腐蚀性能的关键,促进了钝化膜的生成,渗氮后试样表面形成的钝化膜厚度达到27 nm,比原始不锈钢钝化膜的2倍还多。渗氮不锈钢试样的腐蚀电流(3.55×10~(-8)A/cm~2)比基材的腐蚀电流(1.99×10~(-7)A/cm~2)降低一个数量级,表明渗氮后试样的耐腐蚀性能提高了。     

不锈钢表面纳米TiO2膜的制备及其耐蚀性能

电化学方法合成钛酸乙酯，加入乙酰丙酮改性，经溶胶-凝胶过程在不锈钢表面制备了纳米TiO2晶膜，FTIR，AFM和XRD法分别对TiO2膜进行了表征，基体表面修饰的TiO2膜具有均匀完整的纳米结构，晶粒粒径20nm，晶型结构主要为锐钛矿型，采用阳极极化曲线和浸泡实验测试了纳米TiO2晶膜在硫酸介质中的腐蚀行为，实验表明不锈钢表面覆盖纳米TiO2晶膜后耐蚀性能大幅度提高。     

不同钝化工艺对S22053不锈钢腐蚀行为的影响

针对同一种材料经不同钝化工艺处理后钝化膜的形成、耐蚀性的优劣、钝化后腐蚀行为的比较鲜有报道,为此,通过极化曲线、电化学阻抗谱、临界点蚀温度、再钝化温度测试等方法考察了自然钝化、阳极钝化和酸洗钝化3种钝化工艺对S22053不锈钢耐腐蚀性能的影响,并通过扫描电镜观察了腐蚀前后试样表面的表面形貌。结果表明:阳极钝化和酸洗钝化都可以提高S22053不锈钢的耐腐蚀性能,采用20%(质量分数)硝酸酸洗钝化后不锈钢的耐腐蚀性能最好;不同钝化工艺对S22053不锈钢的点蚀电位影响并不显著,但会显著改变不锈钢的阻抗和临界点蚀温度;点腐蚀发生后腐蚀前沿有明显的沿晶腐蚀倾向,同时伴随有奥氏体晶粒的优先溶解。     

不锈钢载波氧化膜/聚噻吩复合膜的制备及耐蚀性能研究

采用红外光谱、扫描电镜与原子力显微镜表征了304不锈钢载波氧化膜/聚噻吩复合膜,通过电化学测试技术考察了复合膜的耐蚀性能。结果表明:通过载波钝化后在304不锈钢氧化膜上电沉积聚噻吩(PTH)膜,制备了304SS/氧化膜/PTH的复合膜,膜层致密。复合膜中的PTH层的分子结构按α-α′规则连接,并具有良好的电化学氧化还原可逆性。复合膜的电导率在5～10S/cm的范围内。304SS/PTH和304SS/AV800/PTH,304SS/AV1020/PTH复合膜的界面结合强度分别为0.81,4.98MPa和5.10MPa。在1M H2SO4溶液中耐蚀性能测试结果,两种复合膜的腐蚀电位正移0.80V,使304不锈钢基体保持在钝化状态,抑制了304不锈钢基体的阳极活性溶解,提高了耐蚀性能。比较而言,由于304SS/AV1020表面多孔性与PTH膜形成多孔氧化物的嵌合层,使得304SS/AV1020/PTH复合膜的电化学、电学及界面结合强度均优于304SS/AV800/PTH复合膜。     

Microstructure and optical properties of plasmapolymer thin films with embedded silver nanoparticles

Plasmapolymer thin films with embedded silver nanoparticles were deposited by simultaneous plasma polymerization and metal evaporation. The particle size and shape were determined by transmission electron microscopy (TEM) and analysed by optical image processing. The optical properties in the UV/ VIS/NIR spectral region were determined by the plasma resonance absorption of the silver particles. Transmittance spectra were calculated with the Bergman effective medium theory and compared with experimental spectra.     

Dielectric and pyroelectric properties of Ba-modified lead lanthanum zirconate stannate titanate ceramics

(Pb_0.97−xLa_0.02Ba_x)(Zr_0.75Sn_0.12Ti_0.13)O₃ ceramics in the composition range 0.1 ≤ x ≤ 0.16 were prepared by conventional solid state reaction process. On increasing Ba content from 0.1 to 0.16 mol, the specimens underwent phase transition from the first order to the second order and the Curie temperature decreased from 85 to 35 °C. With x = 0.16, the specimen showed good pyroelectric properties for practical applications. When a 500 V/mm dc bias field was applied, the specimen showed the maximum pyroelectric coefficient of 5800 μC/m² K and figure of merit of 58 × 10⁻⁵ Pa^−0.5 at Curie temperature.     

Engineering properties of concrete containing natural zeolite as supplementary cementitious material: Strength,toughness, durability,and hygrothermal performance

A complex analysis of engineering properties of concrete containing natural zeolite as supplementary cementitious material in the blended Portland-cement based binder in an amount of up to 60% by mass is presented. The studied parameters include basic physical characteristics, mechanical and fracture–mechanics properties, durability characteristics, and hygric and thermal properties. Experimental results show that 20% zeolite content in the blended binder is the most suitable option. For this cement replacement level the compressive strength, bending strength, effective fracture toughness, effective toughness, and specific fracture energy are only slightly worse than for the reference Portland-cement concrete. The frost resistance, de-icing salt resistance, and chemical resistance to MgCl₂, NH₄Cl, Na₂SO₄, and HCl are improved. The hygrothermal performance of hardened mixes containing 20% natural zeolite, as assessed using the measured values of water absorption coefficient, water vapor diffusion coefficient, water vapor sorption isotherms, thermal conductivity, and specific heat capacity, is satisfactory.     

Facile preparation of poly(vinyl alcohol) nanocomposites with pristine layered double hydroxides

In this paper, nano-sized Mg–Al layered double hydroxide (LDH) was synthesized by a fast nucleation and slow aging method. The structures of LDH were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and photon correlation spectroscopy (PCS). Poly(vinyl alcohol) (PVA) nanocomposites with different LDH loadings were prepared by water solution casting method. TEM observations show that the LDH nanoplatelets are uniformly dispersed in the PVA matrix. Tensile tests indicate that the elastic modulus and the tensile strength of PVA are improved by about 15% and 54%, respectively, when incorporating with 2 wt% LDH. The improvement of mechanical properties of PVA can be attributed to fine dispersion of LDH, good compatibility and strong interaction between PVA and LDH. In addition, the presence of LDH decreases the decomposition rates at the second stage and improves the amount of residues of PVA. Meanwhile, the transparency of the nanocomposite films is maintained compared with neat PVA.     

Properties of high performance concrete containing fine-ground ceramics as supplementary cementitious material

This paper presents experimental work regarding the basic physical characteristics, mechanical and fracture-mechanics properties, durability characteristics, hydric and thermal properties of high performance concrete (HPC) with up to 60% of Portland cement replaced by fine-ground ceramics. Experimental results show that the amount of the ceramics in the mix is limited mainly by the resistance against de-icing salts which is found satisfactory only up to the cement replacement level of 10%. The mechanical and water transport properties are not significantly impaired by ceramic additions of up to 20%, whereas the effective fracture toughness, specific fracture energy, and chemical resistance (to MgCl₂, NH₄Cl, Na₂SO₄, HCl) are effectively maintained up to 40%. The frost resistance, water vapor transport and storage parameters and thermal properties are not significantly impaired even up to a 60% replacement level.     

Mechanochemical synthesis,structural, magnetic,optical and electrooptical properties of CuFeS2 nanoparticles

The rapid mechanochemical synthesis of nanocrystalline CuFeS₂ particles prepared by high-energy milling for 60?min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS₂ nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38?±?1?nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5–30?nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS₂ support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5?K to 300?K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS₂ nanoparticles has been detected to be 1.05?eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nano-size effect. Photoresponses of CuFeS₂ nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS₂ with good structural, magnetic, optical and electrooptical properties.     

基于第一性原理研究Heusler合金Fe2CuGa的结构和性能

采用基于密度泛函理论的第一性原理,系统研究了Heusler合金Fe2CuGa的结构、磁性、弹性性能和电子性质.计算结果表明:立方相的基态结构是铁磁态的Hg2CuTi结构.立方到四方的相变几乎是体积不变的,这是形状记忆合金的特性.奥氏体和马氏体的磁矩分别是4.48和4.56μB/f.u..另外,预测了Fe2CuGa的弹性系数.Fe2CuGa的立方结构在力学上是不稳定的而四方结构是稳定的.根据体模量和剪切模量的比值,发现Fe2CuGa在本质上是可延展的.利用态密度的方法解释了Fe2CuGa马氏体相变的来源.     

Preparation and characterization of organic pigments and their fluorescence properties depending on bulk structure

Fluorescent pigments, based on the optical or electrooptical properties of dyes, are the main component in fluorescent coatings and inks. In this study, three kinds of dyes (Rhodamine B, Light Green SF Yellowish, Coumarin) with four different ratios (2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%) were employed as luminophor, and the melamine-formaldehyde (MF) resin was used as curing resin to prepare fluorescent pigments in different color. Fourier transform infrared spectroscopy and X-ray diffractometry were carried out to analyze the structure of the fluorescent pigments. Scanning electron microscopy and particle size distribution were used to present the morphology of fluorescent pigments. UV–vis and fluorescence spectrum were used to demonstrate the optical properties. It can be concluded that, coumarin pigments possessed consecutive structure in MF resin while rhodamine B might be the best for the preparation of printing inks among the three kinds of dyes from the view of particle size. The TG results presented that all the pigments showed good thermal stability, which might possess potential application in high speed printing industry.     

X-cor夹层结构的力学性能试验研究

X-cor夹层结构比强度高,比刚度大,有望取代传统蜂窝夹层结构作为航空航天器的主承力结构材料。采用真空固化成型工艺,通过改变Z-pin的植入参数制备了X-cor夹层结构,研究了Z-pin植入角度、植入间距和直径对其平压、剪切和拉伸性能的影响。研究结果表明,Z-pin的植入参数对X-cor夹层结构的力学性能影响显著。随Z-pin植入角度的增加X-cor夹层结构的平压性能降低,剪切性能增强,拉伸模量减小,拉伸强度先增加后减小。随Z-pin植入间距和直径增加,X-cor夹层结构力学性能均增加。与泡沫夹层结构相比,X-cor夹层结构压缩、剪切和拉伸模量的测试值分别提高了1.26～5.15倍、2.50～13.56倍和1.90～2.71倍,压缩、剪切和拉伸测试值分别提高了1.63～9.20倍、1.28～2.03倍和1.01～2.30倍。