Exploring the hindering mechanism of element Ti on the adherence of CoO-bearing one-coat enamel/steel

The effect of element Ti on adherence between a CoO-bearing single-layer enamel coating and steel was investigated. Falling-weights tests were carried out and cross-sections at interface of the enamel/substrate were analyzed with a scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Results show that addition of TiO₂ reduced adherence of the enamel coating by hindering the formation of anchor-like alloy precipitates. The decrease of anchor points lies in the following three reasons: I. The diffusion path of Co²⁺ ions to the interface was lengthened because of the blocking effect of rutile and the FeTiO₃ crystals; II. Formation of CoTiO₃ crystals leads to a reduction of free Co²⁺ ions; III. Co–Fe precipitates form away from the enamel/substrate interface, as FeTiO₃ crystals provide extra surface for the nucleation of Fe–Co alloy precipitates.     

Nature of Adherence of Porcelain Enamels to Metals

An investigation of the fundamentals of the adherence of porcelain enamels to metals indicated that good adherence is the result of metal-to-metal bonds between the atoms in the base metal and the proper metallic ions in the enamel. To accomplish this type of bond, the enamel must meet certain chemical and thermodynamic requirements: (1) The enamel at the interface must be saturated with an oxide of the metal and (2) this oxide must be one which, when in solution in the glass, will not be reduced by the metal. In the case of iron, the oxide is FeO. Many of the phenomena observed in commercial enameling were investigated and found to be related to adherence, but not essential for its development. An example is the precipitation of metallic particles in the enamel. Much of the complexity in commercial enameling arises from the limitations imposed by practical considerations. For example, because enamels usually are fired in air, the heavy scale developed during the early stages of firing must be removed before adherence can be developed. Likewise, as the conditions of the enamel-metal interface change rapidly during firing, "adherence-promoting oxides" are used to help maintain the necessary conditions for the time required in commercial enameling. Surface roughness, although not necessary for excellent adherence, was found to improve the apparent adherence when the bond between the enamel and the metal was relatively weak.     

IRON OXIDE IN ENAMEL GLASS AS DISSOLVED FROM THE METAL BASE*

The iron oxide content of an enamel glass was measured by the use of a predetermined curve representing iron oxide versus the index of refraction. It was found that the iron oxide content of the glass adjoining the interface between the enamel and the iron base rises sharply in the early stages of firing to a value close to the solubility limit of the glass after which it gradually falls to a constant value. The iron content at the surface remains low until that at the interface decreases, whereupon the surface concentration correspondingly increases. The cobalt additions resulted in a lower iron content in solution at the interface, but they increased the dendrite content of the glass. A decrease in the cobalt content resulted in an opposite effect. There was a direct relation between the amounts of cobalt and dendrites and the adherence. The effects of temperature and thickness of application are given, and the results are discussed.     

低温覆铝锌钢板搪瓷的密着性能研究

通过对覆铝锌钢板搪瓷样品的密着测试,研究了搪瓷的密着性能。通过金相、扫描电镜等测试,分析了铝锌钢板搪瓷断面结合的微观结构,通过能谱测试分析铝锌钢板搪瓷的元素分布,探讨铝锌搪瓷的密着机制。结果表明,铝锌钢板搪瓷的密着性能良好,铝锌镀层与搪瓷层之间有明显的过渡层和元素扩散,中间过渡层与金属铝的结合主要通过金属键来实现,中间过渡层与瓷釉层的结合主要是通过离子键和共价键来实现。     

一次搪耐酸搪瓷界面过渡层结构研究

采用合理配方设计,使用一次涂搪工艺,制备出了同时具有优良密着性能和耐酸性能的搪瓷板。采用扫描电子显微镜和能谱仪对一次搪耐酸搪瓷板界面显微结构和元素进行分析,研究结果表明,密着性能优良的一次搪耐酸搪瓷界面呈现咬合齿轮状,元素分析表明瓷层元素和金属元素相互扩散,相互渗透,在性能上表现为密着强度优良。     

Role of ethylamines on the electrochemical behaviour of Fe–Ni alloy films

Cyclic voltammetric experiments were carried out on platinum in acidic solution (pH 3) containing ferrous sulfate, nickel sulfate and ethylamines (EtNH₂, Et₂NH, Et₃N). Spectral ultraviolet absorption studies indicate the complexation of both Fe²⁺ and Ni²⁺ ions with ethylamines. The results under transient polarisation conditions indicate the reduction of Fe²⁺ ions through the intermediate species FeOH⁺, with second electron transfer as a slow step. The higher charge transfer rate of FeOH⁺ over NiOH⁺ reduction causes the anomalous codeposition of Fe–Ni alloy film. Among the ethylamines, Et₃N considerably assists the alloy deposition process. A gradual variation in free energy of alloy formation with Fe²⁺:Ni²⁺ (mol:mol) in the bath suggests the formation of an alloy intermediate phase rich in iron. Stripping voltammetric curves indicate the preferential dissolution of iron from iron rich alloy intermediate phase. X-ray diffraction studies further confirm the phase to be b.c.c. Fe–Ni alloy. The extent of corrosion of the Fe–Ni alloy film in the presence of ethylamines is in the following order: Et₃N > Et₂NH > EtNH₂.     

Fundamentals of Glass-to-Metal Bonding: VII, Wettability of Iron by Molten Sodium Silicate Containing Iron Oxide

Contact angles, and adherence of sodium disilicate glasses with varying iron oxide additions on platinum and iron were studied at 1000°C. in vacuum. In the glass-platinum systems the iron concentration in the glass did not affect either the contact angle or the adherence. No devitrification occurred in the glass-platinum systems. The glass-iron systems showed a lowering of the contact angle with increasing iron content in the glass, ranging exponentially from 55° to approximately 22°. Adherence was poor with no iron in the glass, and it increased as the iron content and reaction at the interface increased. Crystals, identified as fayalite (Fe₂SiO₄), were observed in some of the glass drops from the glass-iron systems. Polished cross sections of the glass-iron assemblies showed a greater attack of the metal surface as the iron content in the glass increased. The configuration suggests greater attack along the grain boundaries.     

Effect of coloring impurities on the absorption in neodymium phosphate laser glass at a lasing wavelength

This paper reports on the results of the investigation of KGSS 0180/35 neodymium phosphate glasses produced on an industrial scale under oxidizing conditions and glasses prepared under experimental conditions in which iron and copper in small amounts rather than neodymium are introduced into the glass composition. The experimental glasses are synthesized by varying the redox conditions of melting. The oxidation states of transition metal impurities (Cu, Fe, V, Ni, Co) and the nonactive absorption coefficients of glasses at the lasing wavelength are determined. It is revealed that the main contribution to the nonactive absorption coefficient of the KGSS 0180/35 glass produced on an industrial scale is made by Cu²⁺ ions at a concentration higher than 0.5 ppm. At a lower copper concentrations, the total contribution of Fe²⁺, V⁴⁺, Ni²⁺, and Co²⁺ impurity ions to the nonactive absorption coefficient is comparable to that of Cu²⁺ ions. It is demonstrated that a decrease in the concentration of coloring impurities in glasses and the optimization of redox conditions of melting make it possible to prepare phosphate laser glasses with a nonactive absorption coefficient of the order of 0.001 cm^?1. In terms of the nonactive absorption coefficient, these glasses are on a par with similar glasses of foreign manufacture and satisfy the requirements imposed on glasses by developers of high-power high-energy laser facilities.     

瓷釉涂层/金属基体界面分形维数的研究

研究瓷釉涂层和金属基体界面形貌的分形特征,建立了分形曲线的提取模型,用计盒维数法计算分形维数,并和落球冲击试验结果相比较,发现分形维数的变化和瓷层的密着性的好坏呈现相同的变化趋势.分形理论为研究喷瓷管道的密着性提供了一种新的方法,为深入研究瓷层的密着性奠定了基础.     

Oxide films on iron and iron-copper alloys: An imaging atom probe investigation

An imaging atom probe has been used to analyse the oxide films formed by room-temperature oxidation and atmospheric rusting on iron and on an ironcopper alloy. Both rusted and oxidised specimens field evaporated as Fe²⁺ Fe⁺, O⁺, FeO⁺ and FeO²⁺. In addition, hydroxylated iron species field evaporated from rust. Exposure of the specimen to sulphate ions during rusting led to incorporation of sulphate in the rust. Oxide films grown on the iron-copper alloy were enriched in copper. Cu⁺ and Cu²⁺ field vaporated from this oxide, but CuO species were not detected. All the oxide films examined consisted of a mixture of amorphous iron hydroxide and magnetite. It is suggested that the copper in the oxide film may have been present as a substitutent in the magnetite lattice.     

X-ray Diffraction Characterization of the Enamel–Steel Interface

In the enameling of steel, the oxide is generally regarded as being completely dissolved by the fusing enamel, with the enamel–metal bond forming directly between oxide-saturated glass and metal. According to this model, the adherence of the oxide layer present on the surface of the steel as the enamel begins to fuse is irrelevant, because none of the original oxide layer remains in the matured enamel–steel bond. This model has not been completely verified, however, and some researchers have presented evidence for the presence of a layer of wüstite (FeO) at the enamel–steel interface on the order of 1 to 4 μm in thickness. Whether such a layer exists has important implications regarding the mechanism of enamel–steel adherence. In the present study, a method was developed to concentrate whatever crystalline material might be present in the interfacial zone to make it more amenable to detection by X-ray diffraction. Through the use of wüstite standards, the present technique was shown to be capable of detecting a layer of wüstite at the enamel–steel interface as thin as 0.3 μm. However, in neither one-coat nor two-coat enameling could a layer of wüstite be demonstrated at the enamel–steel interface. Hence, there does not appear to be a 1-to-4-μm-thick wüstite layer at the enamel–steel interface. If a layer of iron oxide is present at the interface, it must be thinner than 0.3 μm.     

Functionalized graphene sheets coordinating metal cations

Interactions of metal cations such as Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ with ammonia-treated graphene sheets (G) and thermal stability of metal cations coordinated with oxygen- and nitrogen-containing functional groups on G were investigated by rinsing G coordinated with metal cations (G-Metal) in 2-propanol using sonication and by heating G-Metal at 773 K, respectively. Monovalent alkali metal cations, divalent alkaline-earth metal cations, divalent transition metal cations such as Mn²⁺, and the other metal cation such as Zn²⁺ were removed by rinsing because of either no interaction or weak interactions between metal cations and G including various thermally stable nitrogen- and oxygen-containing functional groups. Trivalent transition metal cations such as Cr³⁺ and Fe³⁺ were agglomerated by heat treatment at 773 K, whereas divalent transition metal cations such as Co²⁺, Ni²⁺, and Cu²⁺ remained without severe agglomeration. Phenanthroline-like groups on edges of graphene showed the strongest interaction with Ni²⁺ among all of investigated nitrogen- and oxygen-containing functional groups as results of density functional theory calculation. The thermal stability of NNi bonding was confirmed as above 873 K as results of heat treatment of a standard compound (Ni phthalocyanine) in a glass ampoule.     

NICKEL FLASHING AND ITS RELATION TO ENAMEL ADHERENCE*

Nickel flashing as applied to enameling stock is shown to be primarily metallic nickel. The role of nickel in developing enamel adherence is apparently bound up with the retardation of oxidation which the nickel flash imparts in the enameling cycle. The problem of adherence may be considered to be a corrosion phenomenon of the base iron developed by the action of gases and other agents which may be present at enameling temperatures. As such, the degree of adherence is a function of oxygen pressure at the interface when the glass is fused. The equilibria developed are strongly affected by the presence of nickel. Using cover coats directly on iron, the amount of nickel required will vary with each particular enamel composition. Şome evidence as to the nature of the adherence-promoting oxide is presented.     

Concentration and separation of aqueous solutions of Cu2+, Ni2+, Fe3+ by dextran

The effects of water-soluble polymers on the concentration and separation of the aqueous solutions of the metal ions have been studied. The separation of metal ions can be possible by ultrafiltration-complexation process. The effect of Dextran, which is a water-soluble polymer, on the concentration and separation of metal ions (Cu²⁺, Ni²⁺, Fe³⁺) have been investigated by using EC-PEG 4000 alloy membranes. The permeability of these membranes for metal ions has been rrecorded at constant pressure but different pH values. It has been notices that the highest water-permeable membrane is also permeable towards Cu²⁺ and Ni²⁺, but has shown a considerable retention for Fe³⁺ as a result of the hydrolysis of Fe³⁺. The retentions of metallic ions and metallic-ion-Dextran couples have been determined at constant pressure but different pH and polymer concentration values. It has been shown that Fe³⁺/Ni²⁺ and Fe³⁺/Cu²⁺ couples can be separated by using Dextran. © 1995 John Wiley & Sons, Inc.     

Synthesis,Characterization, and Analytical Applications of a New Composite Cation Exchange Material Acetonitrile Stannic(IV) Selenite: Adsorption Behavior of Toxic Metal Ions in Nonionic Surfactant Medium

A composite cation exchange material acetonitrile stannic(IV) selenite was prepared under different experimental conditions. The ion exchange capacity of the material was improved from 0.75 to 1.83 meq g^?1 in comparison to its inorganic counterpart, stannic selenite. The material was characterized on the basis of X-ray, TGA, FTIR, and SEM studies. Ion-exchange capacity, pH titration, elution behavior, and distribution studies were also carried out to determine the preliminary ion-exchange properties of the material. Furthermore, it was investigated that this ion exchange material has a good reusability after 8 times regeneration. The sorption behavior of metal ions was studied in nonionic surfactants namely triton x-100 and tween. On the basis of distribution coefficient studies, several binary separations of metal ions viz- Pb²⁺-Th⁴⁺, Ni²⁺-Th⁴⁺, Ni²⁺-Zn²⁺, Cu²⁺-Ce⁴⁺, Al³⁺-Bi³⁺, and Al³⁺Zn²⁺ was achieved on the packed column of this ion exchange material. The practical applicability of this cation-exchanger was demonstrated in the separation of Th⁴⁺ from a synthetic mixture of Th⁴⁺, Ca²⁺, Sr²⁺, Ni²⁺, and Mg²⁺ as well as Cu²⁺ and Zn²⁺ from a brass alloy sample. Thus, all the studies suggest that acetonitrile stannic(IV) selenite has excellent potential for the removal of metal ionic pollutant species from aqueous media effectively.     

Study of Some Phenomena Associated with the Adherence of Sheet Iron Ground Coats

Cobalt and nickel are deposited on the surface of the base metal during the firing of sheet iron ground coats. These deposits, which are metallic in nature, at least at higher firing temperatures, increase with increasing firing temperature. They also increase with the amount of cobalt and nickel present in any one frit and with the fluidity of the enamel. One reason why cobalt is generally considered a better adherence agent than nickel is that cobalt has a greater tendency to deposit during firing. Ground-coat adherence is generally associated with a certain amount of deposition of cobalt and nickel on the metal surface. This deposition in turn is associated with a roughening of the metal surface which is believed to be a large contributory factor in enamel adherence.     

覆铝钢板搪瓷密着机理研究

通过对覆铝钢板搪瓷界面形貌、结构、元素分布等的分析 ,从化学反应动力学、热力学以及界面能探讨了密着机理 ,本质是界面化学反应产生络合物、氧化物以及合金相 ,并溶解在界面区瓷釉中 ,在界面形成的化学键使瓷层与基体紧密结合在一起     

Wavelength Tailorability of Broadband Near‐Infrared Luminescence in Cr4+‐Activated Transparent Glass‐Ceramics

Four Cr⁴⁺‐activated transparent glass‐ceramics containing different species of silicate nano‐crystals (Zn₂SiO₄, Mg₂SiO₄, Li₂ZnSiO₄, and Li₂MgSiO₄) were successfully prepared. Absorption spectra, photoluminescence spectra, lifetime decay curves, and quantum yield of these transparent glass‐ceramics were measured. According to the crystal field strength of Cr⁴⁺‐incorporated tetrahedral sites, the broadband near‐infrared (NIR) luminescence of Cr⁴⁺ can be tailored from 1130 to 1350 nm and the lifetime of Cr⁴⁺ luminescence can be prolonged from 6 to 100 μs. Quantum yield in the transparent glass‐ceramics containing Li₂ZnSiO₄ nano‐crystals reached at 17%, which is the highest value of NIR luminescence in transition‐metal‐activated glass materials.     

Novel design of YIG/MTC heterogeneous joint bonded by glass ceramic after amorphous glass cladding

A new method of pre-cladding amorphous glass and glass-ceramic brazing was invented to obtain a high-reliability bonding of yttrium iron garnet ferrite (YIG) and magnesium titanate ceramic (MTC) at a relatively low temperature of 725^oC. The amorphous glass cladding could alleviate the stress generated by thermal expansion difference between the glass ceramic and base materials. The microstructure shows that micron-scale and nanoscale CoFe₂O₄ phases were dispersed in the glass seam. The joint shear strength reached 117 ± 6.6 MPa due to the enhancement of CoFe₂O₄ phases, which was twice as that of the joint directly brazed by amorphous bismuth glass. Correspondingly, the joint weak area was transferred from the glass matrix to the vicinity of the interface and the base material, providing a direct evidence that the glass seam was strengthened by the glass ceramic. It is significant for improving high reliability of the microwave devices for long-term service.     

Sorption Studies of Terpolymers Based on p-Nitrophenol,Triethylenetetramine, and Formaldehyde

Terpolymer resins have been synthesized by condensation of p-nitrophenol, triethylenetetramine, and formaldehyde in the presence of 2 M NaOH as a catalyst with different molar proportions of monomers. Newly synthesized terpolymers were proved to be selective chelation ion exchangers for metal ions like Fe³⁺, Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺. A batch equilibrium study was carried out over a wide pH range, shaking time, and in media of various ionic strengths of different electrolytes and shows higher selectivity for Hg²⁺, Cd²⁺, and Pb²⁺. Distribution ratios of metal ions were found to be increased by increasing pH of solutions; hence the resins can be used to recover certain metals from waste solutions and removal of iron from boiler water.