氧化铁(α-Fe2O3)在铁-石墨体系中对合成金刚石的影响

在国产六面顶压机上，研究了在高温高压条件下(5．7GPa，～1600℃)，氧化铁(α-Fe2O3)粉末对铁-石墨体系合成金刚石的影响。研究发现，在上述合成条件下，氧化铁(α-Fe2O3)同石墨发生氧化还原反应，生成Fe3O4和FeO，同时由于氧化铁(α-Fe2O3)的存在，对铁-石墨体系中金刚石成核具有明显的抑制作用。     

高温高压下Ni70Mn25Co5+Cu触媒对合成金刚石成核的影响

用六面顶金刚石压机研究了高温高压条件下，铜在Ni70Mn25Co5合金触媒中的扩散和形成含铜合金触媒的过程。同时，研究了这种不同含铜量的合金触媒在金刚石合成过程中对金刚石成核和生长的影响。研究发现在1670K、5．0GPa条件下，铜很容易进入Ni70Mn25Co5合金中形成NiMnCoCu合金触媒。这种含铜触媒对金刚石的成核有抑制作用，而且触媒随着铜含量的增加这种抑制作用越明显。在本研究的实验条件下，NiMnCo触媒中铜含量低于5％时，可以有效地使金刚石均匀成核并生长成大小均匀的金刚石。     

金刚石合成过程中的再结晶石墨与金刚石成核

本文采用通常金刚石合成用的石墨片，溶剂一触媒金属片交替叠装方式的试样，在4．5GPa、1450℃的条，牛下，分别经过90秒、150秒、240秒的预热处理，再升高压力到5．4GPa进行了金刚石合成实验。得到了随预热处理时回延长，金刚石产量降低，粒度增粗、成核数量减少的结果。通过晶体的溶解度与其粒径的关系，推出了再结晶石墨粒径与其溶解度及金刚石晶核溶解度的关系，解释了再结晶石墨对金刚石成核的影响。进一步指出在预热处理中可以通过控制再结晶石墨的生长，来达到控制金刚石核量的目的。     

片状与粉末触媒对石墨转化成金刚石的催化效率研究

为了研究片状与粉末的镍基或铁基触媒对石墨转化为金刚石的催化性能的影响,采用金刚石成核和生长动力学方法分别计算了片状与粉末触媒参与下金刚石生长的活化能与比表面能。结果表明,无沦是片状还是粉末触媒,这两种触媒对金刚石生长活化能与比表面能的影响差异很小,比表面能与金刚石的结晶形态有关,决定于合成的温度压力条件。然而,粉末触媒的催化效率比片状触媒高得多,更有利于石墨转化为金刚石。     

静压法合成金刚石的成核研究

针对静高压合成技术中片状样品的组装工艺特点,分析了在高温（约1500K)高压（约5GPa）下石墨与触媒之间的相互扩散过程和金刚石在合成腔中的成核几率。根据外界提供给石墨的能量大小,判断出纳米石墨微晶是形成金刚石晶核的基本单元。金刚石成核很可能是纳米石墨微晶转化为金刚石晶核的结构相变过程。讨论了在触媒的参与下金刚石的成核率与温度压力变化的关系,证明了压力是控制金刚石成核的有效参数,而温度不宜作为金刚石成核的控制参数。     

石墨-FeNi核-壳结构复合微球的制备

以硫酸亚铁、硫酸镍、碳酸钠和石墨微球为主要原料，利用非均相成核工艺制备出水合氧化铁和碱式碳酸镍均匀包覆石墨的前驱体微球：通过对前驱体进行热还原处理得到了晶粒约为50nm的γ-FeNi合金颗粒层包覆石墨的产物微球。利用SEM，EDS，XRD对前驱体和产物的形貌、成分、物相分别进行了表征，并利用TG／DSC对前驱体热分解过程进行了分析。通过研究，得出了制备这种核．壳结构复合微球的优化工艺参数。     

用铁基粉末触媒合成金刚石的研究

本文利用五种铁基粉末触媒 (FeNiXn,n =1,2 ,3 ,4,5Xn代表Fe在触媒中的含量 ,Xn>Xn -1)在国产六面顶压机上进行了金刚石单晶的合成实验 ,研究了高温高压条件下 (～ 5 4GPa ,～ 14 0 0℃ ) ,铁基粉末触媒随铁含量的改变 ,石墨碳-铁基触媒体系合成金刚石条件的变化规律以及金刚石单晶的生长特性 ,利用穆斯堡尔谱对金刚石中铁元素形成的包裹体进行了检测。结果表明 ,随着铁基粉末触媒中铁含量的增加 ,合成金刚石的压力和温度条件逐渐增高 ,金刚石生长的“V形区”上移 ,同时得出了铁基粉末触媒适合高温区 ( 110 )和 ( 111)面生长以及金刚石中铁元素以FeNi和Fe3 C形式存在的结论     

CN200610085563．0合成金刚石成核抑制剂

发明属于人工合成金刚石用触媒材料技术领域，其由一种含锌、铅、铋、镧、铜、钙、锡、锂、硼、磷、硫等元素中的一砷或几种元素合成。其用于金刚石合成的方法为：采用石墨原料为二砂石墨，触媒为：Ni重量比30％，Fe重量比70％的普通铁镍粉末合金，本发明所述合成金刚石成核抑制剂用量为石墨的0．1％～5％，触媒用量为石墨的25％～40％。     

化学镀NiCoB合金对人造金刚石抗氧化的影响

化学镀ＮｉＣＯＢ合金对人造金刚石抗氧化的影响关长斌，周振君，于金库（燕山大学秦皇岛０６６００４）人造金刚石由石墨十触媒合金在高温超高压下合成，因此是一种亚稳相，耐热性差。在空气中加热到７００℃以上就会明显氧化和石墨化，使强度降低，影响应用。如制作磨具...     

添加剂La2O3对FeNi粉末触媒合成金刚石的影响

本文研究了添加剂La2O3对FeNi粉末触媒合成金刚石的影响。实验结果表明，La2O3对金刚石的成核具有明显的抑制作用；借助于光学显微镜，我们发现Fe—La2PO3-C体系合成出的晶体晶形完整，但透明度变的很差，且表面变得很粗糙。     

Mechanism of cathodic delamination control of zinc-aluminum phosphate pigment in waterborne coatings

The propagation of the cathodic delamination and blistering was studied for different waterborne paint systems, with or without the zinc aluminum phosphate (ZAP) pigment. The mechanism by which ZAP reacts at the metal-coating interface to improve coating performance against cathodic delamination and blister formation was investigated by means of scanning acoustic microscopy (SAM), pull-off test and surface analysis. The presence of the pigment clearly enhanced the adhesion and delamination resistance of the coating upon immersion. It has been evidenced how the pH buffer properties of the ZAP pigment play an important role in reducing the advancement of the delamination front. A compact film constituted of zinc and sodium phosphates was found, on the substrate surface, solely within the delaminated area. The precipitation of this phosphate layer on the cathodic sites is thought to polarize the cathodic reaction, contributing to slowing down the delamination reaction.     

De-alloying of type 316 stainless steel in hot, concentrated sodium hydroxide solution

The formation of “nickel” layers on austenitic stainless steel in strong caustic solutions was reported in 1979. We now report a detailed study that clarifies the nature of this de-alloying process and establishes firm links with other metal-environment systems that show de-alloying and associated stress corrosion cracking. De-alloying of iron from 316SS in 50% NaOH at 140 °C proceeds only as far as a solid solution with a Ni/Fe atomic ratio of ca. 1.3 (56 at.% Ni if we neglect the other elements present). Chromium is mostly dissolved and/or reprecipitated during this process. X-ray diffraction shows that the residue is a solid solution of intermediate composition, not a mixture of pure Ni and stainless steel. The removal of only half the iron conveniently explains why the de-alloyed layer is a connected porous network. Electrode capacitance measurements and FEG-SEM examination show that the de-alloyed layer has extremely fine nanoporosity.     

Effects of alloy and solution chemistry on the fracture of passive films on austenitic stainless steel

The Taguchi analysis method was used to simultaneously study the effects of alloy chemistry, pH, and halide ion concentrations on the fracture of electrochemically grown passive films using a nanoindentation technique. Three austenitic stainless steels, 304L, 316L, and 904L were potentiostatically polarized in hydrochloric acid solutions. The fracture load was dominated primarily by alloy chemistry. Passive films mechanically weaken as the atomic iron concentration increases in the film. Prolonged anodic ageing time increases the fracture load of passive films.     

Corrosion resistance properties of glow-discharge nitrided AISI 316L austenitic stainless steel in NaCl solutions

Glow-discharge nitriding treatments can modify the hardness and the corrosion resistance properties of austenitic stainless steels. The modified layer characteristics mainly depend on the treatment temperature. In the present paper the results relative to glow-discharge nitriding treatments carried out on AISI 316L austenitic stainless steel samples at temperatures ranging from 673 to 773 K are reported. Treated and untreated samples were characterized by means of microstructural and morphological analysis, surface microhardness measurements and corrosion tests in NaCl solutions. The electrochemical characterization was carried out by means of linear polarizations, free corrosion potential-time curves and prolonged crevice corrosion tests. Nitriding treatments performed at higher temperatures (>723 K) can largely increase the surface hardness of AISI 316L stainless steel samples, but decrease the corrosion resistance properties due to the CrN precipitation. Nevertheless nitriding treatments performed at lower temperatures (?723 K) avoid a large CrN precipitation and allow to produce modified layers essentially composed by a nitrogen super-saturated austenitic metastable phase (S-phase) that shows high hardness and very high pitting and crevice corrosion resistance; at the same polarization potentials the anodic current density values are reduced up to three orders of magnitude in comparison with untreated samples and no crevice corrosion event can be detected after 60 days of immersion in 10% NaCl solution at 328 K.     

Characteristics and lacquer adhesion on dip and CDC chromium passivated tinplate

Chromium passivation and lacquering are typically used to improve the corrosion resistance of tinplate in packed food. In this work, the nature of the chromium passivation layer formed during dip or CDC passivation treatments, as a function of operational parameters, and its influence on lacquer adhesion, was investigated using electrochemical polarisation, XPS, Auger and lacquer peel-off tests. It was found that dip passivated tinplate provide the best lacquer adhesion, and that the adhesion on CDC treated tinplate could be improved by buffering or lowering the pH of the chromium (VI) solution.     

Determination of corrosion rate of reinforcement with a modulated guard ring electrode; analysis of errors due to lateral current distribution

The main source of errors in measuring the corrosion rate of rebars on site is a non-uniform current distribution between the small counter electrode (CE) on the concrete surface and the large rebar network. Guard ring electrodes (GEs) are used in an attempt to confine the excitation current within a defined area. In order to better understand the functioning of modulated guard ring electrode and to assess its effectiveness in eliminating errors due to lateral spread of current signal from the small CE, measurements of the polarisation resistance performed on a concrete beam have been numerically simulated. Effect of parameters such as rebar corrosion activity, concrete resistivity, concrete cover depth and size of the corroding area on errors in the estimation of polarisation resistance of a single rebar has been examined. The results indicate that modulated GE arrangement fails to confine the lateral spread of the CE current within a constant area. Using the constant diameter of confinement for the calculation of corrosion rate may lead to serious errors when test conditions change. When high corrosion activity of rebar and/or local corrosion occur, the use of the modulated GE confinement may lead to significant underestimation of the corrosion rate.     

The nature of the surface film on steel treated with cerium and lanthanum cinnamate based corrosion inhibitors

The corrosion inhibition mechanisms of new cerium and lanthanum cinnamate based compounds have been investigated through the surface characterisation of the steel exposed to NaCl solution of neutral pH. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to identify the nature of the deposits on the metal surface and demonstrated that after accelerated tests the corrosion product commonly observed on steel (i.e. lepidocrocite, γ-FeOOH) is absent. The cinnamate species were clearly present on the steel surface upon exposure to NaCl solution for short periods and appeared to coordinate through the iron. At longer times the Rare Earth Metal (REM) oxyhydroxide species are proposed to form as identified through the bands in the 1400-1500 cm⁻¹ region. These latter bands have been previously assigned to carbonate species adsorbed onto REM oxyhydroxide surfaces. The protection mechanism appears to involve the adsorption of the REM-cinnamate complex followed by the hydrolysis of the REM to form a barrier oxide on the steel surface.     

Zr57Cu15.4Ni12.6Al10Nb5块体非晶合金晶化行为研究

用示差扫描量热仪（DSC）研究了Zr57Cu15.4Ni12.6Al10Nb5块体非晶合金的匀速升温晶化与等温晶化的晶化行为。在匀速升温晶化方式下，用Kissinger法与Ozawa法获得了块体非晶合金的激活能，对第一晶化峰分别为320．5kJ／mol和316．6kJ／mol，对第二晶化峰分别为324．5kJ／mol和320．5kJ／mol。该非晶合金的晶化表现出明显的动力学效应。在等温晶化方式下，用Johnson-Mehl-Avrami方程获得了晶化的Avrami指数为1．61，表明非晶合金的晶化受原子扩散控制。     

Corrosion behavior of glassy Ni55Co5Nb20Ti10Zr10 alloy in 1 N HCl solution studied by potentiostatic polarization and XPS

Corrosion resistance of glassy Ni₅₅Co₅Nb₂₀Ti₁₀Zr₁₀ (at.%) alloy in 1 N HCl solution was investigated with respect to the electrochemical behavior and the compositions of the passive film and the underlying alloy surface just below the passive film. The potentiostatic polarization curve indicated that the alloy was spontaneously passivated with a low passive current density of the order of 10⁻³ A m⁻². The quantitative X-ray photo-electron spectroscopy (XPS) analysis revealed that the thickness of the surface film increased linearly with an anodizing ratio of 1.5 nm V⁻¹. The high corrosion resistance of the glassy alloy was due to the formation of niobium, titanium and zirconium-enriched passive film. The growth mechanism of the passive films is also discussed.     

Pit-to-crack transition in pre-corroded 7075-T6 aluminum alloy under cyclic loading

Pit-to-crack transition experiments were conducted on 1.600 mm and 4.064 mm 7075-T6 aluminum alloy. Specimens were corroded using a 15:1 ratio of 3.5% NaCl solution and H₂O₂ prior to fatigue loading. Cracks originating from corrosion pits were visually investigated in order to understand how pit-to-crack transitions occur.All prior corroded specimens in the study fractured from cracks associated with pitting. Pit-to-crack transition was successfully acquired visually. Corroded 7075-T6-4.064 mm specimens experienced more of an overall fatigue life reduction than 7075-T6-1.600 mm specimens. Results indicated that quantities such as pit surface area and surrounding pit proximity are as important as pit depth in determining when and where a crack will form.