Study of an alkaline bath for tin deposition in the presence of sorbitol and physical and morphological characterization of tin film

Effects of sorbitol concentration on the deposition of tin on to platinum were studied by cyclic voltammetry. It was observed that sorbitol affected the tin-plating rate and also the thermodynamics of the deposition process. Rotating disk electrode studies showed that the deposition rate is controlled by mass transport and that the diffusion coefficient of the Sn(II) complex decreases with increasing sorbitol concentration. The presence of sorbitol in the plating bath was beneficial since a plating current efficiency of ∼70% was obtained, while in its absence it was ∼19%. Scanning electron microscopy showed that sorbitol works as a brightener since tin crystallites were much smaller than those obtained from alkaline solution in the absence of sorbitol. Also, at 1.0 M, sorbitol produced a very smooth film. X-ray spectra showed that β-Sn was deposited.     

Effects of some additives on the corrosion behaviour and preferred orientations of zinc obtained by continuous current deposition

The effect of thiourea, urea and guanidin on zinc deposits obtained from chloride baths under continuous current conditions are described and discussed. The corrosion behaviour of the deposits was investigated in an aerated 3.5% NaCl solution; anodic polarization curves, polarization resistance (R _p) measurements and weight-loss studies were performed. The corrosion resistance of zinc deposits improved in the presence of urea. The deposit morphology was analyzed using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) was used to determine the preferred crystallographic orientations of the deposits. The preferred crystallographic orientations of zinc deposits (112) do not change in the presence of urea and guanidin except for an increase in the peak intensity of the (112) plane. In the presence of thiourea, zinc deposits crystallise in two textures; (100) and (110). The influence of each additive and the difference between additives on the zinc deposits are also discussed.     

典型碱金属、碱土金属对不同变质程度煤焦溶损反应的催化作用

试验研究发现,添加碱金属、碱土金属对低变质程度煤焦反应性的催化作用小于焦煤等中等变质程度煤焦反应性。它们对焦炭溶损反应的催化作用顺序为：K〉Na〉Ca〉Mg,且随着添加量的增加,催化作用越强。随反应时间和典型金属添加量的增加,以及温度的升高,焦炭转化率越大。     

碱性锌-钴合金镀液中锌、钴含量的测定

为获得耐蚀性良好的锌 钴合金镀层 ,必须维持镀液中的锌 钴含量在工艺范围内。采用EDTA滴定和分光光度相结合的方法测定碱性锌 钴合金镀液中的锌、钴含量。介绍了该方法的分析步骤 ,探讨了测量波长的确定 ,亚硝酸钠、镀液共存组分、酸度以及铜离子和铁离子等杂质对测量结果的影响。结果表明 ,在 530nm波长下 ,钴浓度在 0 - 3μg/mL范围内所测吸光度与钴浓度间的关系遵守比耳定律 ,该方法准确度高 ,回收率达 97% - 1 0 3 5%。     

The anodic dissolution of zinc and zinc alloys in alkaline solution. I. Oxide formation on electrogalvanized steel

The polarization behaviour of zinc in alkaline solution has been investigated using atomic emission spectroelectrochemistry. By independently measuring the oxidation rate of zinc (electrical current) and the rate of Zn²⁺ dissolution (partial elemental current) it is possible to calculate the amount of insoluble zinc cations produced at any instant. Assuming the insoluble cations are present as a zinc oxide film, the growth of this film as a function of potential and time was determined. On the basis of kinetic evidence, it was found that at least three forms of zinc based oxide/hydroxide films form during polarization experiments. Type I oxide formation occurs when the metal/electrolyte interface becomes locally saturated with Zn²⁺ ions. Type II oxide forms on the metal surface underneath the film of Type I oxide but has little inhibiting effect on zinc dissolution. Type III oxide is produced in much smaller quantity and results in a transition to the passive state. This may be due to a potential induced transition of Type II → Type III oxide.     

低碳环保型碱性镀锌自动生产线工艺设计

阐述了某军工企业无氰镀锌工艺设计秉持的原则和依据.介绍了2699型碱性镀锌智能化生产线的工艺流程,其主要包括:化学除油,除锈,阳极电解除油,浸碱液,镀锌,硝酸出光,彩色钝化或三价铬厚膜钝化,热水洗,烘干,检验,装箱.给出了各工序的溶液组成及工艺条件.从槽液带出损失及废水处理方面,比较了该工艺与高氰镀锌工艺的运行成本.实...     

A close correlation between nucleation sites,growth and final properties of ZnO nanorod arrays: Sol-gel assisted chemical bath deposition process

Different ZnO seed layers are synthesized by changing sol-gel parameters, including precursor concentration, type of solvent, and type of additive in order to systematically investigate the importance of seed layer properties on the nucleation, growth, and final properties of zinc oxide (ZnO) nanorod (NR) arrays. The X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) show the importance of the seed layer on ZnO NRs properties. Results verify that the relative intensity (RI factor) of (002) polar planes in the XRD patterns of ZnO nanoparticles (NPs) together with the aspect ratio, density, and alignment of ZnO NRs control the structural characteristics of those arrays. For instance, the RI factor of ZnO NPs and NRs follow the same trend when changing precursor concentration in sol preparation step. However, the importance of other parameters, including aspect ratio, density, and alignment of NRs is confirmed by changing solvent and additive. In addition, FESEM images show that the density of ZnO NRs is proportional to NPs density and inversely proportional to the size of ZnO NPs in the seed layers. Besides, the significant role of wrinkled inter-layer on NRs properties, together with the formation mechanism of that inter-layer are profoundly investigated.     

Electrochemical deposition of zinc oxide on a thin nickel buffer layer on silicon substrates

Electrochemical deposition of ZnO from aqueous nitrate solutions on nickel and platinum electrodes was investigated using the voltammetry technique to determine the optimal regimes in both potentiostatic and galvanostatic modes for acquiring polycrystalline ZnO films. Scanning electron microscopy, X-ray diffractometry, and X-ray microanalysis of the formed ZnO films are presented, showing a polycrystalline structure of the ZnO films with a preferable orientation in the (0 0 0 2) direction and an exact stoichiometric composition. The deposited ZnO films demonstrate a strong visible yellow-greenish photoluminescence at room temperature with a maximum at 600 nm that can be referred to crystal lattice oxygen defects. The maximum of the photoluminescence excitation spectrum at 370 nm corresponds to the band gap of ZnO (3.3–3.35 eV) confirming that band-to-band excitation mechanism takes place.     

The effect of feedstock and process conditions on the synthesis of high purity CNTs from aromatic hydrocarbons

High purity multi-walled carbon nanotubes were synthesized from aromatic hydrocarbons (benzene, toluene, xylene and trimethyl benzene) using ferrocene as the source of Fe catalyst. Screening studies of aromatic feeds at 675 °C, residence time of 14 s and Fe/C atom ratio of 1.07%, resulted in feedstock carbon conversion of 20-31%, CNT yield of 19.8-30.5%, and catalyst yield of 5.3-8.3 (g CNT/g catalyst). While the quality of the CNTs as determined by TGA, SEM, TEM and Raman spectroscopy, were high and comparable for different feedstocks; their carbon conversion, CNT yield and catalyst yield differed noticeably. A process optimization study for toluene feed showed that carbon conversion of more than 39%, CNT yield of 38.7% and catalyst yield of 18.3 can be achieved at temperature of 800 °C, Fe/C atom ratio of 0.47%, and residence time of 10-20 s.     

The influence of hydrogen- and cation-underpotential deposition on oxide-mediated Pt dissolution in proton-exchange membrane fuel cells

In order to fully understand the influence of a lower potential limit on platinum dissolution and the likely mechanism for mass and surface-area loss under potential cycling conditions, the dissolution of a Pt catalyst in a N₂-saturated 0.5 M H₂SO₄ solution was examined using an electrochemical quartz nanobalance (EQCN) flow cell, a rotating ring-disk electrode (RRDE) and inductively coupled plasma mass spectroscopy (ICP-MS). Due to the observation that cycling to a lower potential limit, which coincides with the hydrogen under-potential (H_UPD) region, results in a decrease in the dissolution rate, cations capable of interfering with the hydrogen UPD process (Zn²⁺, Li⁺, Na⁺, K⁺, and Cd²⁺) were introduced to the solution. Larger rates of mass loss were observed in the presence of these cations during the cycling process in the UPD region, despite apparently negligible effects on the behavior with more positive lower potential limits or on oxide formation and stripping. It was found that the quantity of soluble Pt species produced during the electrochemical reduction of PtO₂ was proportional to the charge associated with oxide stripping at the disk electrode during the RRDE experiment.     

Transformation of alkali and alkaline earth metals in low rank coal during gasification

Transformation of alkali and alkaline earth metals (AAEM) in low rank coals during gasification was examined by combining computer-controlled scanning electron microscopy (CCSEM) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Two sub-bituminous coals were pyrolyzed at 1500 °C using a drop tube furnace, and the resultant chars were then gasified in CO₂ atmosphere at the same temperature. Total amounts of AAEM species in the raw coals and the chars were determined by ICP-AES. Minerals in the raw coals and ash particles in the chars were analyzed by CCSEM.AAEM species were mainly present in the raw coals as dispersed species, organically associated cations or fine mineral particles (<1 μm), which cannot be quantified by CCSEM. It was found that the dispersed Ca species were first converted into fine ash particles upon the devolatilization and then most of the particles interacted with inherent clay minerals to form complex aluminosilicates. In the case of Na and K, the dispersed species mostly vaporized and the interaction with inherent minerals was not observed.     

The effects of arsenic and lead impurities on the current efficiency and deposit composition in alkaline zinc electrowinning

The influence of lead and arsenic impurities on zinc deposition, current efficiency and deposit composition was examined in the alkaline zinc electrowinning system. It was observed that lead slightly decreases the current efficiency of zinc deposition, and that the detrimental effect on zinc current efficiency which was observed with arsenic was largely suppressed in the presence of lead. This beneficial effect is related to the fact that the arsenic content of the deposit decreased when lead was present in the electrolyte. It was also found that arsenic promotes the deposition of lead. Tin has no effect on the current efficiency of zinc deposition in alkaline solutions, with or without arsenic. The addition of salicylaldehyde to the solution alleviates the deleterious influence of arsenic on zinc current efficiency, but it somewhat increases the cell voltage.     

Effect of processing parameters on flexural properties of 3D-printed polyetherketoneketone using fused deposition modeling

Polyetherketoneketone (PEKK) is an engineering plastic with ultrahigh mechanical performance and has attracted considerable attention in the medical and technical fields. Printing parameters during fused deposition modeling (FDM) for PEKK have a significant impact on final part quality. In this study, a relationship between the process parameters and flexural properties of PEKK was investigated by conducting three-point bending tests, and scanning electron microscopy was employed to analyze the microstructure of fracture surfaces. Nozzle temperature, layer thickness, and infill density affected flexural properties by changing the porosity and interlayer bonding strength. Interlayer separation is the main failure mode of the upright orientation samples, while intralayer failure is likely to occur in the on-edge orientation samples. The flexural properties of FDM-printed PEKK under optimum parameters are comparable to those of mandibular bones, indicating that PEKK is a potential candidate for repairing mandibular defects. The results highlighted in this study are fundamental to the optimal design of complex ultralight, highly efficient structures.     

镀锌钢板墨绿色钝化膜分析研究

对镀锌层上墨绿色钝化膜进行了扫描电子显微镜(SEM)和x射线光电子能谱(XPS)分析.SEM观察表明,钝化膜表面较为均匀平整,钝化膜层与镀锌层之间以及镀锌层与钢铁基体之间均结合紧密,没有裂纹等组织缺陷出现,镀锌层及钝化膜层较厚,共12.423μm,其中墨绿色钝化膜层厚度为1.734 μm.XPS分析结果表明,钝化膜由Cr、O、P、N、Zn等元素组成,并可能以CrOOH、Cr(OH)3、Cr2O3、ZnO、Zn3(PO4)2·4H2O、FeOOH、Fe(OH)3、Cr2(SO4)3等化合物的形式存在于钝化膜中.经墨绿色钝化工艺处理的环保锌覆层钢板,外观呈墨绿色,色泽均匀,光度柔和,满足了客户要求.     

镀锌彩色钝化膜脱落褪色的原因探讨及解决

分析了镀锌彩色钝化膜脱落褪色的原因并提出了解决方法     

Removal of zinc from dilute aqueous solutions by galvanochemical treatment

The possibility of zinc removal, a common toxic metal, from simulated liquid effluents by the application of a novel treatment method, termed galvanochemical, was investigated. The galvanochemical process is considered as a simple, economic, friendly to the environment, method, which does not create harmful end‐products. Synthetic wastewaters were examined, these contained concentrations of zinc commonly found in real wastewaters from small‐to‐medium size industrial units, such as metal‐plating or metal‐treatment plants. These liquid wastes pose an important environmental problem, due to the content of heavy metals. The optimization of the main operating parameters was the objective of the study. The galvanic pair scrap ratio iron:coke was used for these investigations. It was found that the use of the galvanic pair mixture of 80 g dm^?3 (weight per solution volume ratio), agitated at 160 rpm for 5 h, removed more than 90% of zinc from the initial solution, containing initially 50 mg dm^?3 of zinc. The scanning electron microscopy/energy disperse spectrometry (SEM/EDS) analysis performed on the products showed that zinc was adsorbed onto the coke to a small extent and that the zinc removal was mainly based on the adsorption of zinc onto the surface of active iron oxides formed as a result of galvanochemical reactions. Copyright © 2005 Society of Chemical Industry     

Effect of tantalum nitride supporting layer on growth and morphology of carbon nanotubes by thermal chemical vapor deposition

The role of tantalum nitride (TaNx) thin films as buffer layers on the control of nucleation and growth of aligned carpet-like carbon nanotubes (CNTs) has been proved. TaNx thin films have been deposited on Si by controlled magnetron sputtering process. Multiwall CNTs have been synthesized at 850 °C using an aerosol of ferrocene diluted in toluene. Electron microscopy images show a strong correlation between the growth rate and morphology of the CNTs and the initial composition of the TaNx thin films. Multi-scale investigations reveal that both morphology and structure of the CNTs are determined by the properties of the TaNx films. Raman and X-ray photoelectron spectroscopy, high resolution TEM imaging at the submicrometric and atomic scales have been used to confirm these hypotheses.     

在以EDTA和柠檬酸为配位剂的酸性硫代硫酸盐-亚硫酸盐镀液中电沉积金

以乙二胺四乙酸或柠檬酸作配位剂,在无氰的硫代硫酸盐–亚硫酸盐体系中研究了金在镀镍铜基底上的电沉积。在温度为60°C,pH为6和电流密度为2A/dm2的条件下,研究了不同配位剂对电流效率、镀速、镀层硬度及镀液分散能力的影响。最佳的镀液组成为0.5mol/L硫代硫酸钠–亚硫酸钠 0.2mol/L乙二胺四乙酸(或0.3mol/L柠檬酸)。该镀液具有良好的分散能力及高达98%的电流效率。采用扫描电镜、原子力显微镜及X射线衍射分析了镀态金镀层的表面形貌和晶体结构。所得的金镀层几乎无孔(孔隙率<2~4个/cm2),结合力良好,硬度适中(80~130HV)。     

Influences of zinc oxide and an organic additive on the electrochemical behavior of pure aluminum in an alkaline solution

The corrosion behavior of pure aluminum in inhibited and uninhibited 4 MKOH was investigated by means of hydrogen collection, polarization curve measurement and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion of pure aluminum was greatly inhibited by the addition of ZnO and dimethyl amine epoxy propane (designated as DE). EIS and EDAX analyses revealed that ZnO produces its effect by depositing on the aluminum surface, which increases the overpotential of hydrogen evolution. It was also found that the addition of DE could greatly improve the deposition of zinc layers.     

Chemical vapor deposition of pyrolytic carbon on carbon nanotubes: Part 1. Synthesis and morphology

The chemical vapor deposition of the pyrocarbon from a CH₄+H₂ mixture is investigated using nanofilamentous substrates. The process consists of growing carbon nanotubes via a catalytic process, which then are thickened by pyrolytic carbon deposition to reach diameters in the nanometer to micrometer range. A key characteristic of the experimental reactor used was the long length of its isothermal zone, preceded (and followed) by a low thermal gradient zone. This allowed us to investigate the role of the variation of the local gas phase composition, which depends on the post-cracking secondary reactions, and on the quantity and quality of the deposited carbon. The ‘time of flight’ of the reactive species was found to be a leading parameter in the pyrolytic carbon deposition process. Various nanometric and micrometric morphologies, several of which are new, were synthesised and found constituted with an association of different sub-morphologies. The various morphologies, that can be sorted following a factor of morphological complexity, were investigated by scanning electron microscopy.