热镀锌层上硅酸盐膜的耐蚀性和自愈性

热镀锌(HDG)钢片经SiO2∶Na2O摩尔比为1.00和3.50的硅酸钠溶液中处理后,在其表面获得硅酸盐转化膜。用中性盐雾(NSS)试验、塔菲尔极化和电化学阻抗谱(EIS)研究了硅酸盐膜试样的耐蚀性,将被刀片划伤的硅酸盐膜试样进行NSS腐蚀后,用扫描电镜(SEM)和能谱仪(EDS)观察和分析了划痕处的腐蚀,以探讨硅酸盐膜的自愈性。结果表明:在较高SiO2∶Na2O摩尔比溶液中获得的硅酸盐转化膜具有较好的耐蚀性和自愈性,腐蚀过程中硅酸负离子从膜层中迁移划痕处形成新的保护膜(由Zn,O和Si组成)抑制了划痕处锌的腐蚀。AFM观察发现,在摩尔比为3.50中获得的试样的膜层表面更加致密,这有利于阻止腐蚀介质的侵入和提供充裕的硅酸负离子迁移。并对硅酸盐转化膜试样的划痕的腐蚀过程的细节进行了分析和讨论。     

Mechanism of dehydration and intumescence of soluble silicates

The properties and structure of films prepared from solutions of potassium silicate were studied by thermal analysis, IR spectroscopy, and X-ray diffraction. Various SiO₂:K₂O molar ratios from 2.55 to 4.72 were prepared and studied to determine the effect of molar ratio on the hygroscopic nature, solubility, and intumescence. The results provided insight into the physical structure, and mechanism of water absorption of the potassium silicate films. The molar ratio has a profound effect on the solubility, water absorption, and intumescence of the potassium silicate film. The primary mechanism of water absorption and retention is by ionic hydration. Decrease in the ionic hydration driving force as the molar ratio is increased results in decreasing solubility. Since intumescence results from the release of water vapour, the degree of intumescence decreases as the amount of ionically bonded water decreases with increase in molar ratio.     

Alkali silicate binders: effect of SiO2/Na2O ratio and alkali metal ion type on the structure and mechanical properties

The influence of SiO₂:Na₂O molar ratio and the nature of an alkali metal (Na vs. K) in commercial aqueous alkali silicate on the microstructure, textural properties, phase composition, and hydrolytic stability of an alkali silicate binder have been investigated using scanning electron microscopy, nitrogen adsorption/desorption technique, X-ray diffractometry, thermal analysis, and dissolution tests. It has been found that microstructure and textural properties of the alkali silicate binder depend both on silica to alkali molar ratio and type of alkali metal (Na vs. K). Sodium silicate binder obtained from commercial silicate solution with lower SiO₂:Na₂O molar ratio (2.2) exhibits a globular microstructure of silica xerogel with high content of micropores, whereas the binder formulated with SiO₂:Na₂O molar ratio 3.2 is characterized by more open cluster structure with lower content of micropores. It is observed that surface specific area estimated by Brunauer, Emmett, and Teller method and mesopore volume obtained by the Barrett–Joyner–Halenda method for sodium silicate binder are substantially higher than those for potassium silicate binder. The ultimate hydrolytic stability of the sodium silicate binder increases slightly with increase in the silica to alkali molar ratio within the studied range. Decreasing in SiO₂:Na₂O molar ratio and replacement of sodium silicate solution by potassium silicate solution in the corresponding filled composition lead to the improvement of mechanical properties and decrease in open porosity.     

电解液对微弧氧化陶瓷膜结构与耐蚀性的影响

在3种不同的电解液体系中,利用微弧氧化技术在AZ91D镁合金表面原位生长了陶瓷膜．通过扫描电镜、X射线衍射、电化学分析等方法研究了陶瓷膜的形貌特征、相结构及耐府蚀性能．研究表明,在相同反应条件下,不同电解液体系中生成的陶瓷膜结构和性能不同,硅酸钠体系中生成的陶瓷膜厚度大、偏铝酸钠体系中生成的陶瓷膜较薄,偏铝酸钠与硅酸钠的混合体系中生成的陶瓷膜致密、耐腐蚀性能较好．三体系中生成的陶瓷膜中都含有MgO,偏铝酸钠体系陶瓷膜中含有MgAl2O4、硅酸钠体系中含有Mg2SiO4,混合体系中则这两种物质都存在．     

TC4钛合金微弧氧化因素对生物陶瓷膜中Ca,P相对含量的影响

为了提高钛合金陶瓷膜的生物相容性,采用微弧氧化技术在TC4钛合金表面制备了一层富含Ca,P的生物活性陶瓷膜。采用SEM,EDS,XRD研究了电流密度、溶液中Ca,P摩尔比、添加剂EDTA.2Na浓度对膜层中Ca,P相对含量(原子分数)及Ca,P摩尔比的影响及微弧氧化生物陶瓷膜层的形貌及组成。结果表明:随着电流密度的增大,膜层中的Ca,P相对含量增加,Ca,P摩尔比也逐渐增加;增大溶液中Ca,P摩尔比,膜层中Ca相对含量有所增加,Ca,P摩尔比也逐渐增加;当加入添加剂EDTA.2Na时,膜层中的Ca相对含量显著增加,从而使膜层中Ca,P摩尔比显著增加;氧化膜由致密的内膜层和多孔的外膜层构成,主要由Ca,P,O,Ti,V元素组成,其相成分主要为金红石和板钛矿型TiO2,并含有一定量的非晶相Ca,P化合物。     

水性环氧聚氨酯富锌涂料的防腐蚀性能研究

为制得环保且防腐蚀性能优异的富锌涂料,引入环氧树脂来改性水性聚氨酯,以水性环氧聚氨酯为基料制备富锌涂料,通过对其腐蚀电位和电化学阻抗谱(EIS)的测试分析,研究了添加不同含量锌粉的富锌涂层在3%NaCl溶液中的腐蚀电化学行为,并与添加少量铝粉的富锌涂料及传统富锌涂料进行了对比.结果表明,水性环氧聚氨酯富锌涂料的防腐蚀能力比传统环氧富锌底漆强;锌粉的添加量对涂层的防腐蚀效果有一定的影响,添加少量铝粉能提高涂层的防腐蚀性能.     

Deposition and corrosion behavior of silicate conversion coatings on aluminum alloy 2024

Potassium silicate was deposited on AA2024 aluminum alloy as environmentally friendly conversion coatings and its corrosion behavior were examined by means of electrochemical impedance spectroscopy, potentiodynamic polarization and surfaces techniques. Potentiodynamic polarization curves show significant decrease in corrosion current density of silicate coated aluminum in NaCl solution. The corrosion resistance was increased with increasing silicate concentration of coating baths. The results indicated that the coating applied from 3 molar silicate baths is more uniform and continuous. The X‐ray diffraction (XRD) and energy discharge spectroscopy (EDS) spectra confirm the existence of silicate film on the AA2024 surface. The coating performance was evaluated in acidic and basic NaCl solution and the results show the stability of silicate conversion coating in these solutions.     

镁合金微弧氧化着色膜研究

镁合金在电子工业中的快速发展对装饰性能提出了更高的要求.主要研究了如何在微弧氧化的同时进行氧化着色.膜层制备选取的基材为AZ91,电解溶液由硅酸盐为主的碱性溶液组成,配方为:Na2SiO3 5～30g/L,KMnO4 1～20g/L,NaOH 1～5g/L,KF 5～8g/L,Na3 C6H5O70.5～2g/L,EDTA 0.5～2g/L.在电解液中添加着色盐KMnO4,形成了颜色各异的黄色陶瓷膜层.研究发现,膜层呈现出黄色主要是由于在膜层中生成了Mg6MnO8相,该物相在氧化膜中含量不同和分布差异将导致样品颜色深浅不同.     

A SEM study on the galvanic protection of zinc-rich paints

The research is focused directly to the cahodic protection mechanism of zinc-rich paints (ZRP). It is based on a systematic scanning electron microscope (SEM) observation of cross-sections of several ZRP coatings exposed for different time intervals to a 3% (by weight) sodium chloride solution. The effect of vehicle (binder) used in the paint formula and the effect of zinc particle content are considered.As the anodic behaviour of zinc particles depends very closely on coating microstructure, SEM observation of the latter is very useful to investigate the galvanic performance of ZRP. This study confirms that high zinc particle contents and the use of ethyl silicate as a vehicle favour the degree and duration of the cathodic protection.Depending upon whether the zinc particles act anodically or not their attack mechanism is radically different. Accordingly, two attack mechanisms of the zinc particles are proposed.     

Single-layered porous silica films on polyethylene terephthalate substrates for antireflection coatings

Single-layered porous silica films were prepared on polyethylene terephthalate (PET) substrates as antireflection coatings for efficient, large-scale flexible optoelectronic devices. Cetyltrimethylammonium bromide (CTAB)-templated synthesis was employed to form porous silica films. Without using high temperature treatment, CTAB was removed by washing in water to create a porous structure in the films. To spin-coat on PET substrates, contact angle between silica sol and PET surface was measured to optimize the molar ratio of the solution. Pore size and surface sharpness were estimated using atomic force microscope data. The average reflectance of as-prepared AR coatings on PET substrates was ≤ 2%.     

铝合金表面等离子体电解氧化陶瓷涂层在NaCl溶液中的电化学阻抗谱研究

通过调整电解液中硅酸钠的浓度, 利用等离子体电解氧化(PEO)技术在铝合金LY12表面制备了各种陶瓷涂层, 利用光学显微镜、XRD、电化学阻抗谱(EIS)对涂层的形貌、成分和涂层在NaCl溶液中耐腐蚀性能进行了研究. 结果表明: 提高电解液中硅酸钠的浓度可以使得涂层的总厚度增加, 但过高或过低的浓度都会导致致密层厚度的减薄. 当浓度为20g/L时, 所制备的涂层的成分以氧化铝为主; 当浓度为40g/L时, 涂层的成分主要是莫来石和氧化铝; 当浓度超过60g/L 时, 涂层的成分主要为非晶相. EIS的研究表明, 涂层耐腐蚀性取决于涂层中的致密层, 增加致密层的厚度可以提高PEO涂层的耐腐蚀性, 在中性、酸性、碱性腐蚀介质中, PEO涂层都显示出对基体良好的保护作用.     

Influence of Electrolytes on the Microstructure of Microarc Oxidation Coatings on Ti—6Al—4V Alloy

Dense ceramic oxide coatings of about 50μm may be prepared on Ti-6Al-4V alloy surface by alternating-current microarc oxidation in aluminate and silicate solutions, respectively.Their phase constituent and microstructure sere characterized using X-ray diffraction (XRD) and scanning electron microscopy(SEM). The results show that the electrolytic ions have incorporated into the interior of the coatings.The coating formed in aluminate solution is composed of the rutile TiO2 and TiAl2O5 phases rather than the rutile, anatase and amorphous SiO2 phases for the coating formed in silicate solution.However,TiAl2O5 content in the outer layer of the two coatings is much higher than in the inner layer.It is suggested that all these oxides may result from a rapid solidification of the molten coating in the microarc discharge zone.     

磷酸酯改性环氧粉末涂料

在环氧粉末涂料中,添加6%的十二烷基磷酸酯与固化剂双氰胺所成的盐(对于钢铁类底材,还应加1/2磷酸酯摩尔数的黄血盐),金属材料可以不经预处理而直接涂膜.所得涂膜具有良好的附着力,高的耐冲击强度和耐老化性能.此类涂料可节省约40%的涂装费.     

金属锆微弧氧化电解液体系和氧化时问对陶瓷膜层的影响

分别用钨酸钠、偏铝酸钠、硅酸钠电解液体系在金属锆表面上制备了氧化锆陶瓷膜。探讨了电解液种类、氧化时间对膜层相结构、微观形貌和耐蚀性的影响。结果表明：氧化膜成分、组织结构、形貌和耐蚀性受电解液种类影响较大;钨酸钠、偏铝酸钠体系陶瓷膜由单斜相组成,而硅酸钠体系则形成了异常的正交相及单斜相,其膜层的耐蚀性不同程度地优于钨酸钠...     

偏态酸为原料制备六钛酸钾晶须机理研究

采用以偏钛酸与碳酸钾按原料摩尔比为1∶3.5混合均匀,通过一步烧结法合成六钛酸钾晶须。采用改变不同焙烧温度和焙烧时间为条件,研究了六钛酸钾的生长机理,同时还研究了水浸处理对产物的影响,并利用XRD和SEM对样品的物相及形貌进行了分析。结果表明,反应温度达到600℃时生成K2Ti8O17中间体,随着温度升高八钛酸钾向六钛酸钾及四钛酸钾转化,当温度继续升高四钛酸钾向六钛酸钾发生了转化。     

Hydrolytic stability of sodium silicate gels in the presence of aluminum

Polycondensation in alkali silicate solutions comprises a fundamental process of the geopolymerization technology. Previous works had shown that the hydrolytic stability of sodium silicate gels depends on the SiO₂/Na₂O ratio. Sodium silicate gels totally insoluble in water can be produced at SiO₂/Na₂O molar ratios higher than 4.4. This article aims at elucidating the effect of tetra-coordinated aluminum addition on the hydrolytic stability of sodium silicate gels. According to the results, the aluminum addition stabilizes the sodium silicate gels in an aqueous environment. A sodium silicate gel with SiO₂/Na₂O molar ratio 3.48, which is totally soluble in deionized water at ambient temperature, can be transformed to insoluble sodium hydroaluminosilicates with the addition of tetrahedral aluminum at Al/Si molar ratios higher than 0.08. In addition, this article studies the structure of prepared sodium hydroaluminosilicates and draws very useful conclusions for the geopolymerization technology.     

硫酸铜浓度对镁合金微弧氧化膜层热控性能的影响

为了提高镁合金的热防护性能,在硅酸盐、磷酸盐、铝酸盐等电解液体系中引入硫酸铜,采用微弧氧化技术在MB15镁合金表面制备微弧氧化膜层。通过扫描电镜(SEM)、X射线衍射仪(XRD)、能谱仪(EDS)和CIE颜色系统研究了电解液中硫酸铜浓度对涂层的色度、厚度、粗糙度和热控性能的影响。结果表明:微弧氧化膜层微观上具备典型的多孔结构,铝酸盐涂层主要由MgAl_2O_4晶相组成,硅酸盐涂层主要由MgO晶相和Mg_2SiO_4晶相组成,磷酸盐涂层主要由MgO晶相组成,而各膜层中的Cu元素均以非晶相形式存在;随着硫酸铜浓度增加,3种体系制备的膜层表面颜色均向黑色过渡,微孔数量增多;硅酸盐体系和磷酸盐体系中制备的微弧氧化膜层具有高吸收率和高发射率等特点,而铝酸盐体系中制备的微弧氧化膜层具有高吸收率和低发射率的特点。     

Effect of ferrous/ferric ions molar ratio on reaction mechanism for hydrothermal synthesis of magnetite nanoparticles

Magnetite nanoparticles were prepared by hydrothermal synthesis under various initial ferrous/ferric molar ratios without adding any oxidizing and reducing agents in order to clarify effects of the molar ratio on the reaction mechanism for the formation of magnetite nanoparticles. The magnetite nanoparticles prepared were characterized by a scanning electron microscope, powder X-ray diffractometer, and superconducting quantum interference device (SQUID). At the molar ratio corresponding to the stoichiometric ratio in the synthesis reaction of magnetite from ferrous hydroxide and goethite, the nucleation of magnetite crystals progressed rapidly in an initial stage of the hydrothermal synthesis, resulting in formation of the magnetite nanoparticles having a smaller size and a lower crystallinity. On the other hand, at higher molar ratios, the particle size and crystallinity increased with increasing molar ratio because using surplus ferrous hydroxide the crystallites of magnetite nanoparticles grew up slowly under hydrothermal conditions according to the Schikorr reaction. The magnetite nanoparticles prepared under various molar ratios had good magnetic properties regardless of the molar ratio.     

化学氧化合成N-乙基苯胺与苯胺共聚物的防腐性能

通过开路电位法详细研究了掺杂酸种类、掺杂状态和共聚单体摩尔比等对化学氧化合成的N-乙基苯胺与苯胺(EA/AN)共聚物的防腐性能的影响。结果表明,所有EA/AN共聚物的防腐性能均优于两种单体的均聚物,单体喂入摩尔比EA/AN为20/80的去掺杂态共聚物表现出最优防腐效果。盐酸掺杂共聚物的防腐性能优于其它酸掺杂共聚物的,去掺杂态共聚物又优于掺杂态共聚物。尤其是在强酸性腐蚀介质中,以该共聚物为底漆,环氧树脂为面漆的复合涂层钢板的开路电位在浸泡过程中出现了不降反升现象,涨幅达110 mV左右,较裸露钢板相应正移了约545 mV,较聚苯胺复合涂层涂覆的钢板相应正移了约90 mV,在长达半年的浸泡后,涂层不脱落、不起泡,也无锈点出现。     

固化温度对硅酸钠防锈膜性能的影响及其成膜机理

将钢板浸入到硅酸钠溶液中,取出后在不同温度下固化,形成连续透明的保护膜。通过露天耐候试验、塔菲尔极化、中性盐雾试验(NSS)研究了不同温度固化后硅酸钠膜的耐蚀性及耐溶性能,采用扫描电子显微镜(SEM)、傅里叶红外仪、热重(TG-DSC)等对硅酸钠防锈膜的表面形貌及微观结构进行了分析,并对防锈膜的成膜机理进行了探讨。结果表明:高温固化的硅酸钠防锈膜的耐腐蚀性能优于低温固化的硅酸钠膜,200℃固化的硅酸钠膜耐常温水溶解效果最好;随固化温度的升高,膜体系主要发生了2Q3→Q4+H2O,2Q2→Q3+H2O,Q2+Q3→Q3+Q4+H2O等反应,导致膜层中含4个桥氧原子的硅氧四面体(Q4)不断增多,从而形成了致密、均一的三维网状结构硅酸钠膜,膜层耐蚀性更好。