回转体表面喷射电沉积Ni-P-ZrO2复合镀层耐腐蚀性能研究

为延长回转体零件的使用寿命,提高其耐腐蚀性能,本文利用喷射电沉积技术在45钢外圆表面制备Ni-P合金镀层和Ni-P-ZrO₂复合镀层,采用扫描电镜、腐蚀失重法和电化学测试分析等测试手段对Ni-P-ZrO₂复合镀层、Ni-P合金镀层和45钢基体在50 g/L NaCl溶液中的表面形貌和耐腐蚀性能进行研究,并探究腐蚀机理。研究表明:Ni-P-ZrO₂镀层相对Ni-P镀层表面致密度更高,缺陷较少;浸泡相同时间, Ni-P-ZrO₂镀层的失重量最小,腐蚀速率最小;电化学测试实验中,Ni-P-ZrO₂复合镀层的腐蚀电流最低(43.2×10^-5 A/cm²),共沉积ZrO₂颗粒后,Ni-P-ZrO₂复合镀层容抗弧半径更大,极化电阻值R_p增大为Ni-P合金的3倍,双层电容值C_d由4.743 8 μF/cm²降低为3.887 2 μF/cm²。在相同条件下腐蚀后,Ni-P-ZrO₂复合镀层的表面较为完好,腐蚀产物较少;Ni-P合金次之,有较多黑色腐蚀产物;45钢表面形貌最差。综上,采用喷射电沉积在回转体表面制备的Ni-P-ZrO₂复合镀层相对Ni-P合金镀层和45钢基体表现出更优良的耐腐蚀性能。     

热处理对Ni-P-A12O3化学复合镀层摩擦磨损性能的影响

热处理可显著提高镀层的硬度和耐磨性能。采用化学镀的方法在45钢表面制备了Ni-P-纳米A12O3复合镀层,并以不同温度对其热处理,研究了镀层热处理前后的物相、硬度和耐磨性能。结果表明：400℃热处理后,Ni-P-A12O3复合镀层达到稳态,稳定相是Ni＋Ni3P＋NiO＋A12O3;镀层的显微硬度随热处理温度的升高而先增加后降低;随着镀液中纳米A12O3,（n-A12O3）颗粒含量的增加,热处理前后镀层的显微硬度和耐磨性能均先增加后降低;镀液中n-A1203颗粒含量为2．0g／L,400℃热处理1h的复合镀层的显微硬度和耐磨性能最佳。     

PET接枝改性纳米ZrO2/PC复合材料的力学性能

采用接枝聚合反应在纳米ZrO₂表面接枝聚对苯二甲酸乙二醇酯 (PET) 低聚物,以提高其与聚碳酸酯(PC)的相容性;改性纳米ZrO₂与PC经过共混挤出,制备了纳米ZrO₂/PC复合材料。采用FTIR、XPS、TEM、TG、接触角等测试方法对接枝改性后的纳米ZrO₂进行了表征,结果表明,PET化学键合到了纳米ZrO₂表面,使ZrO₂疏水性显著增强,微观颗粒分散性好。对纳米ZrO₂/PC复合材料进行了力学性能测试,探讨了纳米ZrO₂的添加量与复合材料力学性能的关系。结果表明：纳米ZrO₂/PC复合材料的力学性能较纯PC有明显改善;随着改性纳米ZrO₂含量的增加,缺口冲击强度和拉伸强度都呈现出先增加后降低的趋势,分别在ZrO₂质量分数为1%和0.3%时达到最大值;弯曲强度在实验范围内一直呈上升趋势,最大弯曲强度比纯PC提高2.54 MPa。     

钨酸钠和次磷酸钠浓度对脉冲电镀CeO2-SiO2/Ni-W-P纳米复合薄膜组织及性能的影响

通过Ni、W、P与CeO₂和SiO₂纳米颗粒的脉冲共沉积,在碳钢表面制备了CeO₂-SiO₂/Ni-W-P纳米复合薄膜,主要研究了电解液中钨酸钠和次磷酸钠浓度对纳米复合薄膜组织及性能的影响,采用化学组成、沉积速率、显微硬度和表面形貌进行表征。结果表明,当钨酸钠和次磷酸钠浓度分别为100和4 g/L时,纳米复合薄膜的沉积速率和显微硬度较高,分别为25.03 μm/h和HV649。增加钨酸钠浓度,纳米复合薄膜晶粒得到细化。当钨酸钠浓度提高到160 g/L时,基质金属晶粒轮廓清晰,细小而均匀,呈规则的圆球型,CeO₂、SiO₂纳米颗粒均匀弥散分布在Ni-W-P基质金属中。次磷酸钠浓度的增加对纳米复合薄膜的表面形貌影响较小,但会明显降低显微硬度。     

超重力下燃烧合成ZrO2(4Y)/Al2O3的成分、显微组织与力学性能

采用超重力下燃烧合成技术,通过调整ZrO₂体积分数,制备出不同成分与显微组织形态的ZrO₂(4Y)/Al₂O₃复合陶瓷,研究了材料成分、显微组织与力学性能之间的关系。XRD、SEM和EDS结果表明：当ZrO₂体积分数低于37%,陶瓷熔体生成为生长取向各异且以ZrO₂四方相亚微米纤维镶嵌于α-Al₂O₃上的棒状共晶团为基体的复合陶瓷;当ZrO₂体积分数高于40%,复合陶瓷基体则生长为略呈球形的ZrO₂四方相微米晶粒。性能测试结果显示,随着ZrO₂体积分数增加 , 陶瓷相对密度逐渐降低,陶瓷硬度与断裂韧性均在ZrO₂体积分数为33%时出现最高值,而陶瓷弯曲强度则在ZrO₂体积分数为29%达到最大值。     

纳米Al_2O_3-Ni-P化学复合镀层的制备及其摩擦学性能

为了获得摩擦学性能优良的镀层,在20#钢基材上实施了纳米Al_2O_3-Ni-P化学复合镀,采用正交试验法优选了镀液配方,研究了镀液中纳米Al_2O_3含量、镀液温度对复合镀层显微硬度、摩擦和磨损性能的影响,用扫描电子显微镜对复合镀层表面形貌进行观察。结果表明,镀液中纳米Al_2O_3含量是影响复合镀层硬度和耐磨性能最主要因素。纳米Al_2O_3能有效改善Ni-P合金镀层结构,在镀层中分布较均匀,使复合镀层硬度和耐磨性能明显提高。当纳米Al_2O_3含量为6 g/L时,纳米粒子在复合镀层中分布致密、均匀,复合镀层硬度和耐磨性最佳,与基材20#钢结合性较好。镀液温度对复合镀层硬度和耐磨性能有一定影响,最佳镀液温度为85℃,此时复合镀层硬度和耐磨性较好。     

Cr3C2粒径对等离子堆焊铁基合金层组织与耐磨性能的影响

在低碳钢表面利用等离子堆焊技术分别制备Fe50堆焊层及添加40％(质量分数)微米和纳米Cr₃C₂的(Fe50+40%微米/纳米Cr₃C₂)复合堆焊层,比较研究添加不同粒径的Cr₃C₂对Fe50合金堆焊层的显微组织与磨损性能的影响。采用X射线衍射仪(XRD)分析堆焊层的相组成,利用扫描电镜(SEM)和能谱分析仪(EDS)观察堆焊层的显微组织形貌及微区成分,通过显微硬度计测试了堆焊层的硬度分布,使用滑动磨损及冲击磨损试验机分别考察了复合堆焊层的磨损性能。结果表明:Fe50等离子堆焊层组织主要由柱状晶α-Fe及其间的网状共晶α-Fe+Cr₂₃C₆组成;而Fe+40%微米/纳米Cr₃C₂堆焊层凝固方式为过共晶,由大量的先共晶碳化物及其间细密、均匀的枝晶与共晶组织组成,并增加了γ-Fe、Cr₇C₃和未熔Cr₃C₂等相;但Fe+40%纳米Cr₃C₂涂层比Fe+40%微米Cr₃C₂涂层析出更多且细小、致密的先共晶碳化物。与Fe50等离子堆焊涂层相比,Fe+40%微米Cr₃C₂涂层的显微硬度、滑动磨损性能及冲击磨损性能分别提高了21%、1.5倍和0.8倍;而Fe+40%纳米Cr₃C₂涂层的显微硬度、滑动磨损性能及冲击磨损性能则分别提高了34.1%、2.4倍和1.7倍,表面的犁沟和剥落及塑性变形明显减少,耐磨性能显著提高。因此,添加纳米Cr₃C₂颗粒可以显著细化铁基合金等离子堆焊层的显微组织并提升其耐磨性能。     

Al2O3颗粒粒径和含量对α-Al2O3/Cu复合镀层性能的影响

本文研究了复合电沉积法制备的α-Al₂O₃/Cu 复合材料的性能和磨损特征, 测定了Al₂O₃粒径在0. 5～ 5Lm, 含量在4～ 16% 时Al₂O₃/Cu 复合镀层的硬度和磨损率, 用扫描电镜对磨损形貌进行了分析, 并对其磨损机制进行了探讨。结果表明, 镀层中硬度随Al₂O₃含量增加呈线性增长, 且含大颗粒Al₂O₃镀层的硬度略高于小颗粒镀层,Al₂O₃颗粒含量和粒径大小对磨损率和磨损机制有显著影响。     

Y2O3添加量对Al2O3/ZrO2共晶陶瓷显微组织及力学性能的影响

为探索第三组元Y₂O₃添加对Al₂O₃/ZrO₂共晶陶瓷显微组织与机械性能的影响,本文利用低温度梯度的高温熔凝法制备了直径为20 mm的Al₂O₃/ZrO₂(Y₂O₃)共晶陶瓷块体,采用SEM、EDS及XRD技术对共晶陶瓷进行微结构分析,并利用维氏压痕法对其硬度和断裂韧性进行测试。SEM结果表明,凝固组织由群集的共晶团结构组成,随着Y₂O₃添加量的增加,共晶团形态由胞状转变为枝晶状,内部相间距在1~2 μm范围内变化。力学测试表明,Y₂O₃摩尔分数小于1.1%时,由于组织内部存在低硬度m-ZrO₂及微裂纹缺陷,故陶瓷硬度较低,约为(9.53±0.22 )GPa;当Y₂O₃摩尔分数为1.1%时,陶瓷硬度最大,约为(18.05±0.27)GPa;当Y₂O₃的摩尔分数大于1.1%时,由于共晶团边界区内气孔缺陷及粗大组织增多,引起陶瓷硬度值略有下降。低Y₂O₃摩尔分数添加时,陶瓷断裂韧性相对较高,约为(6.30±0.16)MPa·m^1/2,这与其内部存在大量微裂纹缺陷有关;随着Y₂O₃添加量的增加,陶瓷的微裂纹数量减少、边界区内缺陷增多,断裂韧性降低。     

纳米SiC-MoS2/Ni基复合电刷镀层组织与耐磨性能

通过对纳米SiC颗粒进行表面修饰处理,采用电刷镀技术制备纳米SiC-MoS2/Ni基复合刷镀层,分析探讨了纳米SiC和MoS2的含量对镀层形貌和耐磨性能的影响。结果表明,镀液中加入经表面修饰的纳米SiC颗粒可以提高镀层硬度,同时在干滑动磨损试验条件下,纳米SiC-MoS2复合刷镀层具有良好的耐磨减摩性能。     

恒功率工况对锂离子电池循环性能的影响

为掌握锂离子电池在恒功率充放电工况下的运行特性,并探究该充放电方式对电池循环性能的影响,对磷酸铁锂电池、钴酸锂电池和锰酸锂电池进行3 h时率恒流恒压充电/恒流放电和恒功率充放电测试,对比分析了两种工况下电池的容量、能量、效率等性能参数。结果表明在3 h充放电倍率下,恒功率充放电工况对磷酸铁锂电池和锰酸锂电池的循环性能并未产生显著的不良影响。经过100次循环后,两种工况下磷酸铁锂扣式电池均表现出超过90%的容量保持率;商品磷酸铁锂电池容量和能量保持率则均超过99%,能量效率达95%。但是,相比于恒流恒压工况,磷酸铁锂电池在恒功率工况下释放的容量、能量略低。锰酸锂电池在两种工况下的容量和能量性能高度重合,但衰减都比较快,100次循环后的容量保持率仅为81.7%。对于钴酸锂电池,恒功率工况显著加剧了其容量和能量的衰减速度,100次循环后能量保持率仅为55.5%,远低于恒流恒压工况下的75.2%。     

Influence of the demineralisation on the chemical activation of Kraft lignin with orthophosphoric acid

The preparation of activated carbons (ACs) from the thermal decomposition of mixtures of orthophosphoric acid (PA) and either as-received softwood Kraft lignin, KL, or demineralised one, KL(d), has been investigated. Activation with PA has been studied for a PA/lignin ratio of 1 (dry ash-free basis) and 1h carbonisation time at final temperatures of 400, 500 and 600 degrees C. The yield, surface area, porosity, surface chemistry and methylene blue adsorption capacity have been determined. All ACs were found to be essentially microporous, with surface areas higher than 800 m(2)/g and a maximum value of nearly 1200 m(2)/g for the carbon prepared at 600 degrees C from KL. In order to study the influence of temperature on the properties of the ACs prepared from KL and KL(d), the latter precursors were analysed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). We have concluded that the very different characteristics of the ACs obtained from KL and KL(d) are due to the presence or not of mineral matter during carbonisation, but mainly to the demineralisation process itself, which produces polymerisation of the raw lignin. Methylene blue adsorption was found to be higher for ACs prepared from KL, mainly because of their higher ash and sulphur contents.     

Real-time investigations on the formation reactions during annealing of sulfurized Cu-Sn precursors

The quaternary compound kesterite Cu₂ZnSnS₄ (CZTS) is a promising candidate for the production of low-cost thin film solar cells.Depending on the precursor composition and deposition technique several intermetallic precursor phases may appear, affecting the formation reactions during the crystallization process of the thin film absorber. A better understanding of these formation reactions in the system Cu-Zn-Sn-S is required for the optimization of CZTS absorbers and future development of solar modules.The crystallization of CZTS is completed by the reaction of Cu₂SnS₃ and ZnS. The formation of Cu₂SnS₃ itself depends on the different available precursor compounds after sulfur evaporation. Incomplete conversion of binary sulfides during annealing may lead to the formation of undesirable compounds, i.e. the transformation of Cu₂SnS₃ into Cu₄SnS₄ via reaction with Cu_2-xS, which affect or even inhibit the crystallization of CZTS.Therefore a precise knowledge about formation reactions of binary and ternary Cu-Sn sulfides during annealing at low temperatures is important to crystallize a monophase CZTS absorber. Real-time investigations on the formation reactions in the quaternary and also the ternary subsystems of Cu-Zn-Sn-S while annealing stacked elemental layers elucidate the reaction paths of binary and ternary sulfides.We report on results of time-resolved and angle-dispersive XRD experiments during annealing comparing the formation reactions in sulfurized Cu-Sn precursors prepared by different deposition techniques.     

Thickness dependence of high-k materials on the characteristics of MAHONOS structured charge trap flash memory

The electrical characteristics of tunnel barrier engineered charge trap flash (TBE-CTF) memory of MAHONOS (Metal/Al₂O₃/HfO₂/SiO₂/Si₃N₄/SiO₂/Si) structure were investigated. The stack of SiO₂/Si₃N₄/SiO₂ films were used as engineered tunnel barrier, HfO₂ and Al₂O₃ films were used as charge trap layer and blocking oxide layer, respectively. For comparison, the electrical characteristics of MONOS (Metal/SiO₂/Si₃N₄/SiO₂/Si), MONONOS (Metal/SiO₂/Si₃N₄/SiO₂/Si₃N₄/SiO₂/Si), and MAHOS (Metal/Al₂O₃/HfO₂/SiO₂/Si) were also evaluated. The energy band diagram was designed by using the quantum-mechanical tunnel model (QM) and then the CTF memory devices were fabricated. As a result, the optimized thickness combination of MAHONOS structure was confirmed. The tunnel barrier engineered MAHONOS CTF memory showed a considerable enhancement of program/erase (P/E) speeds, retention time and endurance characteristics.     

Influence of reemission of neutrals on the shape of etched grooves

The plasmochemical etching of silicon in CF₄+O₂ plasma is considered. The chemical composition of plasma and values of reaction rate constants, determined in previous works, were used to calculate the etched groove profiles at real dimensions. The profiles of etched grooves are calculated as a function of mask dimensions, fluxes of chemically active components and reemission of chemically active components from the surface of groove. The etching anisotropy is reduced when the reemission of F and O atoms from the surface takes place. The increase of etching anisotropy at high O₂ content in the feed (>60%) is explained by the complete sidewall oxidation and decreased concentration of F atoms in the plasma. The influence of reemission of F and O atoms on the shape of etched grooves becomes pronounced for mask width >1 μm.     

The effect of H2-anneal on the adhesion of Al2O3 scales on a Fe3Al-based alloy

Abstract

The cyclic (1,100°C, air) and isothermal (1,000°C, O₂) oxidation behavior of a Fe-28Al-5Cr (at%) alloy, with and without a prior H₂-anneal heat treatment at 1,200°C for 100 h, was studied. Changes in interfacial chemistry were evaluated using Scanning Auger Microscopy after removal of the oxide film in ultra high vacuum. This was achieved by making a scratch on the specimen surface, which caused spallation of the film at various locations along the scratch. The scale thickness and the temperature drop at which spallation took place during cooling were utilized to semi-quantitatively compare the adherence of the scales. Porosity at the scale–alloy interface and the scale microstructure were determined from scanning electron microscope observations. It was found that H₂-anneal greatly improved scale adhesion and resulted in a pore-free and sulfur-free interface. The effects were similar to that of a 0.1 at% Zr-containing alloy, except that the improvement in scale adhesion was not as great as that from Zr doping. This implies that oxide/alloy interfaces are not intrinsically strong and the effect of reactive elements, such as Zr, is more than preventing impurity from segregating to the interface. Results are also compared with the effect of H₂-anneal on other model alloys, such as NiCrAl, FeCrAl and NiAl, and on single crystal superalloys.     

Effect of thermal exposure on the stability of carbides in Ni-Cr-W based superalloy

The microstructure evolutions of Ni-Cr-W based superalloy during thermal exposure have been investigated systematically. M₆C carbides in the alloy decompose into M₂₃C₆ carbides at temperatures from 650 to 1000 °C due to its high content of Cr. The M₆C carbides decompose dramatically from 800 to 900 °C. At temperatures up to 1000 °C, a few M₂₃C₆ carbides form on the surface of M₆C carbides. The decomposition behavior of primary M₆C can be explained by the following reaction: M₆C → M₂₃C₆ + Me (W, Ni, Cr, Mo). At temperatures below 900 °C, coarse lamellar M₂₃C₆ carbides precipitate at the grain boundaries. The carbide lamellae line almost perpendicular to the grain boundaries. While the temperature is above 1000 °C, discrete M₂₃C₆ carbides precipitate at the grain boundaries. Moreover, there are lots of small M₂₃C₆ particles precipitated around M₆C carbides from 650 to 1000 °C.     

The New Method for the Synthesis of Fullerols Based on Radical Reaction

Abstract

The method for the synthesis of fullerols C₆₀(OH) _x was developed, allowing to obtain products with low number of hydroxy groups attached to fullerene molecule. At the first stage, product C₆₀(tert‐BuO) _x was obtained by the radical reaction of C₆₀ with tert‐butyl‐peroxide under heating or UV‐irradiation. At the second stage, fullerol C₆₀(OH) _x was synthesized after the elimination of tert‐butyl groups by acid treatment. Several samples C₆₀(OH) _x containing different numbers (x = 2–5) of hydroxy groups were obtained, the main product had x = 2. The structure of the fullerols was confirmed by UV‐ and Fourier‐transform infrared (FTIR)‐spectroscopy and MALDI‐TOF mass‐spectrometry.