The formation and properties of Al/Mg scales on Al heat- exchange surfaces in desalination plant

Three types of scales containing Al and Mg have been shown to form during the corrosion of Al in seawater in the pH range 6.3–8.5. The type most frequently occurring has a structure similar to that of the natural mineral hydrotalcite. It can be formed from the Al(OH)₃ produced by the corrosion of Al and Mg²⁺ ions present above pH 6.3. The Al:Mg ratio in this compound increases with pH, resulting in a form of buffering action. In the presence of these scales anodic breakdown of the corrosion film takes place at a potential 100–200 mV more anodic than in their absence. The structures, mechanisms of formation, and effects of these scales in the operation of distillation plants with Al surfaces are discussed, as well as their effects on the operation and interpretation of laboratory corrosion tests.     

Industrial wastewater desalination using electrodialysis: evaluation and plant design

Industrial processes usually generate streams enriched with high organic and inorganic components. Due to the complexity of these streams sometimes it is not quite straightforward to predict the performance of desalination technologies. Some technologies are available for the selective removal of salts from aqueous stream, but in general these technologies are applied in high value applications where salts are either the product or limit further purification of the final product is required. These technologies are, however, not widely used in low value applications like wastewater treatment. The aim of this article is to review, improve and perform the design of electrodialysis processes for relevant industrial wastewater applications. It is focused on the determination of the critical design parameters like membrane resistance, current efficiency and limiting current density through lab scale experiments and its further use for industrial scale first approximation design. In this article, the basic equations for design are reviewed and a practical approach to obtain the number of stacks required for a certain separation is introduced. An industrial wastewater stream has been used for lab batch experiment and its following continuous plant design. The results show that it is possible to separate monovalent ions in a high rate (more than 70 %) and divalent ions were less separated (less than 50 %). The energy required for the particular case was evaluated in a range from 6 to 11 kWh/m³ of feed stream depending on the water reclamation rate.     

Objective evaluation of color design

For the evaluation of color design, a multiple linear system analogous to the human visual perceptual system was proposed. Using computer-generated random color patterns, a psychological test was performed and its results were analyzed in terms of the Fourier transform of the color patterns. It was clearly concluded that the power spectrum obtained by the Fourier transform of the patterns had characteristic meanings at regions of very-low, low, medium, and high spatial frequencies.     

Preparation and evaluation of hydrophobic surfaces of polyacrylate-polydimethylsiloxane copolymers for anti-icing

Two series of polyacrylate-polydimethylsiloxane (PDMS) copolymers, namely, polyacrylate-b-PDMS and polyacrylate-g-PDMS with three different molecular weights of PDMS blocks or side chains, were synthesized for formation of hydrophobic surfaces for anti-icing. The main purpose of this paper was to investigate the relationship between ice adhesion strength and the surface structure of the copolymers, and to find out how the prepared PDMS-containing polyacrylate copolymers are potentially used for anti-icing. The microphase-separated structure and the surface chemical composition were analyzed by transmission electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy, and ice adhesion strength was measured using a universal testing machine in a pull off mode. Results suggested that microphase separation appeared clearly in all the copolymers, especially for the block ones. The PDMS chains aggregated on the top of the polymer surfaces caused by microphase separation could weaken the interaction between the polymer surface and water, mainly hydrogen bond, which was demonstrated because of decrease of water contact angle hysteresis. Then, ice adhesion strength was decreased by the contribution of PDMS in the block copolymers or the graft copolymer with longer PDMS side chains. It is suggested that the polyacrylate-b-PDMS or polyacrylate-g-PDMS copolymers would have practical applications in preparation of anti-icing coatings.     

Co2 conversion and oxalate stability on alkali promoted metal surfaces: Sodium modified Al(100)

CO₂ conversion on alkali promoted metals in aprotic systems has been followed with surface sensitive spectroscopies. New results on sodium modified aluminum(100) are presented and compared with previous studies on magnesium [1], aluminum [2], and bulk alkali metals [3]. Electron energy loss spectra reveal two different states of CO₂ adsorption at 100 K and monolayer sodium coverage. Vibrational bands at 650 cm^–1 and 2325 cm^–1 correspond to weakly bound molecular CO₂ and a multitude of bands between 2300 cm^–1 and 460 cm^–1 to oxalate ions with low, possibly unidentate, coordination. Gentle annealing increases the coordination as apparent by vibrational shifts. This corresponds to oxalate to carbonate conversion, a process which is completed around room temperature. CO desorption was detected at 285 K and Auger measurements reveal a 13 C/O stoichiometry after high temperature annealing. We observe no release of CO₂ above 110 K but an additional weak state of CO desorption around 470 K. High temperature annealing causes decomposition of all intermediates and leaves the aluminum surface covered with an irreducible carbide and oxide overlayer. We suggest that CO₂ reduction and dimerization to C₂O₄ ^–2 is a common path to yield carbon deposition on all alkali promoted surfaces in hydrogen deficient systems. In contrast, oxalate decomposition is related to the specific chemistry of each substrate.     

A mathematical optimization framework for the design of nanopatterned surfaces

The recent explosion of capabilities to fabricate nanostructured materials to atomic precision has opened many avenues for technological advances but has also posed unique questions regarding the identification of structures that should serve as targets for fabrication. One material class for which identifying such targets is challenging are transition‐metal crystalline surfaces, which enjoy wide application in heterogeneous catalysis. The high combinatorial complexity with which patterns can form on such surfaces calls for a rigorous design approach. In this article, we formalize the identification of the optimal periodic pattern of a metallic surface as an optimization problem, which can be addressed via established algorithms. We conduct extensive computational studies involving an array of crystallographic lattices and structure‐function relationships, validating patterns that were previously known to be promising but also revealing a number of new, nonintuitive designs. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3250–3263, 2016     

Microstructure evolution and mechanical properties of a vacuum-brazed Al2O3/Ti joint with Mo-coating on Al2O3 and Ti surfaces

Au-foil was used to braze Al₂O₃ and Ti to obtain a joint with biocompatibility. Mo-coatings of thicknesses 2 or 4?μm were deposited on the surfaces of Al2O3 and Ti by magnetron sputtering before the brazing experiments. The microstructure evolution and mechanical property of the Al₂O₃/Ti joint were systematically investigated. Due to the (i) different wettabilities of Ti and Mo and (ii) thermal expansion mismatch between dissimilar components, defects were observed in the Al₂O₃Mo/Au/Ti joint when only Al₂O₃ was metallised by a Mo-coating. However, the Al₂O₃Mo/Au/MoTi joints were nearly defect free when both Al₂O₃ and Ti were coated with Mo films. The typical microstructure of an Al₂O₃Mo/Au/MoTi joint was characterised by Al₂O₃/Mo-rich phase + Au-rich phase/TiAl intermetallic compound/Au-rich phase + TiAu₂ intermetallic compound+(Ti, Mo) solid solution/Ti. The distribution of the (Ti, Mo) solid solution, width of the reaction layer, and quantity of the TiAl intermetallic compound varied with brazing temperature and holding time. The thickness of Mo-coating only affected the width of the reaction layer. Compared to those of the holding time and Mo-coating thickness, the influence of the brazing temperature on the microstructure and shear strength of joints was the most noticeable. The mechanical properties of the Al₂O₃/braze interface and seam were key factors for determining the shear strength of the Al₂O₃Mo/Au/MoTi specimens. The maximum shear strength was 208?MPa for the Al₂O₃Mo/Au/MoTi couple obtained at 1100?°C for 5?min with a Mo-coating thickness of 2?μm.     

Statistical evaluation and design of an evaporator control system

The utility of a statistical procedure suggested by Box and Jenkins is assessed for the evaluation and modification of an industrial evaporator control system. Results, obtained from the analysis of routine unperturbed operating data, indicate that this approach is (i) readily adaptable to the analysis of the dynamic behaviour of a full scale chemical unit process, (ii) characterized by effective model form identification, and (iii) extremely useful in deriving conventional and more novel control functions to supplement existing control schemes.     

Preparation and evaluation of a nanocomposite of polythiophene with Al2O3

The polymerization of thiophene (TP), in bulk and in solution in CHCl₃ by FeCl₃ resulted in the formation of a polymer which was characterized by FTIR as polythiophene (PTP). High yield was realized in the latter case. The polymerization of TP with FeCl₃ and nanodimensional Al₂O₃ resulted in the formation of a nanocomposite which was partly dispersible in aqueous and non‐aqueous media. The dispersibility appeared to be higher when the polymerization was conducted in a suspension containing a higher amount of Al₂O₃. Scanning electron micrographs showed globular particles and the presence of clusters of composite particles. Transmission electron micrographic (TEM) analyses revealed the particle size of the composite to be in the range 22–74 nm. Thermal analyses (TG/DTA) revealed the outstanding stability of PTP–Al₂O₃ composites compared to that of PTP. The conductivity of PTP and of PTP–Al₂O₃ composite was of the order of 10^?3 S cm^?1 for samples doped with I₂. © 2003 Society of Chemical Industry     

Objective evaluation of color design. II

A method to predict psychological values of color design was derived from our experimental data on 30 random color patterns previously published. This method, based on the two-dimensional Fourier transform of color patterns, was designed to evaluate psychological values of the pattern in terms of 13 rating scales such as “beautiful-ugly,” “warm-cold,” “hard-soft,” and so on. It was found that the psychological values of random color patterns could be evaluated in terms of zero-frequency (average color) and low-, medium-, and high-frequency components of the Fourier transform of the patterns. Applicability of the evaluation method to predict psychological impressions of real color design was tested with results from a new experiment on some fabric design that is described in this article.     

3D, chemical and electrochemical characterization of blasted TI6Al4V surfaces: Its influence on the corrosion behaviour

The blasting process to increase the roughness of the surface of metallic biomaterials is widely used. As a consequence, one can produce a renewed surface with different topography and chemical composition compared to the original one, which can alter the general corrosion behaviour of the samples. With this idea, the aim of this work is not only the topographical and compositional characterization of blasted surfaces of Ti6Al4V alloy but mainly its influence on the corrosion behaviour of these modified surfaces. The surfaces of Ti6Al4V alloys were blasted with SiO₂/ZrO₂ and Al₂O₃ particles of different size in order to obtain different roughnesses. To carry out the microstructural and topographical characterization of the blasted surfaces, the scanning electron microscopy (SEM) coupled with an energy dispersive X-ray (EDX), the contact profilometry method and the 3D characterization by means of stereo-Fe-SEM have been used. By means of stereo-Fe-SEM, the roughness and the real surface area of the rough surfaces have been calculated. The microstructural, topographical and compositional results have been correlated with the corrosion behaviour of the samples immersed in Hank's solution and studied by means of electrochemical impedance spectroscopy (EIS). The blasting process alters topographical and chemically the surface of the samples. These modifications induce to an increase in the capacitance values of the roughened samples due to the prevalence of the effect of electrochemically active areas of Ti6Al4V surface over the effect of the presence of Al₂O₃ and ZrO₂ particles on the blasted surfaces. However, the general corrosion behaviour of the samples is not drastically changed.     

Objective evaluation of color design. III

A psychological test was performed by using computergenerated color patterns, which were composed of ordered repeats of random color arrangements, and the effects of the repeat number were investigated. the results were analyzed in terms of power spectra of the Fourier transform of the color patterns, and it was clearly found that the psychological evaluation depended strongly not only on the amount but also on the degree of concentration (or scatter) of the power spectrum. Furthermore, in order to predict the psychological values of the color patterns, multiple regression analyses were done by using three models with 13, 14, and 15 specified variables that were obtained from the Fourier transform. It was found that the multiple correlation coefficient increased considerably by introducing the second-order term of a variable that indicates the degree of concentration of the dynamic components, especially for the evaluation of beautifulugly or interesting-boring. © 1995 John Wiley & Sons, Inc.     

Influence of surface pretreatment and electrocoating parameters on the adhesion of cathodic electrocoat to the Al alloy surfaces

Adhesion of cathodic electrocoat films to the aluminum alloys 2024-T3 bare and Alclad 2024-T3 with different pretreatments and with different cathodic electrocoat process parameters was investigated. The pretreatments studied were acetone wipe and alkaline cleaning. The cathodic electrocoat process parameters studied include variation of cathodic electrocoating voltage and time. Adhesion performance was evaluated by measuring the delamination time and percent delamination of the electrocoat from the alloy surface by placing the small specimen of the sample in the N-methyl pyrrolidinone (NMP) solution at 60°C until the film lifts off or for 2 h whichever comes first. NMP times for electrodeposited film delamination from alkaline cleaned surfaces were found to be higher than the acetone wiped and or those of as-supplied metal surfaces. There was not much effect of acetone cleaning of these alloy surfaces on the adhesion performance of the cathodic electrocoat. The voltage–current (of cathodic electrocoating process) relationships for alkaline cleaned surfaces were also found to be significantly different from the other two types of surfaces. The NMP times of cathodic electrocoat delamination at lower cathodic electrocoating voltage and lower electrocoating times were higher than those at higher cathodic electrocoating voltage and electrocoating times for alkaline cleaned 2024 bare surfaces. Electrocoat thickness developed on the surfaces during the electrodeposition process increased with increasing electrodeposition voltage and time as anticipated.     

Investigation of design parameters in generating antifouling and lubricating surfaces using hydrophilic polymer brushes

Long-term stability of hydrophilic surface coatings that prevent fouling, cell adhesion and present a lubricious interface for biomaterials has been widely investigated in recent years. As an alternative to the gold standard poly(ethylene glycol) (PEG), poly(2-oxazoline)-based coatings are promising due to their higher stability against oxidative degradation in comparison to PEG. In this study, we compare the antifouling and tribological properties of PEG and poly(2-methyl-2-oxazoline) (PMOXA) brush structures as a function of structural design parameters such as grafting density, chain length, and the monomer solubility. Brush properties such as hydration (number of H₂O molecules per monomer), shear modulus, and serum adsorption as a function of design parameters were estimated using optical waveguide lightmode spectroscopy and quartz crystal microbalance/dissipation techniques. At high monomer surface densities, PMOXA showed approximately three times higher structurally associated H₂O molecules per monomer in comparison to PEG brushes, leading to stiffer PMOXA brushes. We found that the chain stiffening of PMOXA brushes lead to higher macroscopic coefficients of friction; however presented similar adsorbed serum mass (high antifouling properties) when compared to PEG brushes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47659.     

用RFC法评价碳纤维的表面处理（第一报）

碳纤维的表现处理方法很多,评价表面处理效果的方法及手段也很多。在众多的评价方法中,大多数为取样测试及剖析,测试数据再反馈给碳纤维生产线。本文介绍相对纤维电容（RFC）法。它既可取样测试,也可在线配套监测。     

Uniform and pitting corrosion events induced by SCN anions on Al alloys surfaces and the effect of UV light

The influence of the alloying elements on the uniform and pitting corrosion processes of Al-6061, Al–4.5%Cu, Al–7.5%Cu, Al–6%Si and Al–12%Si alloys was studied in 0.50 M KSCN solution at 25 °C. Open-circuit potential, Tafel polarization, linear polarization resistance (LPR) and ICP-AES measurements were used to study the uniform corrosion process on the surfaces of the tested alloys. Cyclic polarization, potentiostatic current-time transients and impedance techniques were employed for pitting corrosion studies. Obtained results were compared with pure Al. Passivation kinetics of the tested Al samples were also studied as a function of applied potential, [SCN⁻] and sample composition by means of potentiostatic current transients. The induction time, after which the growth of stable pits occurs, decreased with increasing applied potential and [SCN⁻]. Regarding to uniform corrosion, alloyed Cu was found to enhance the corrosion rate, while alloyed Si suppressed it. Alloying elements of the tested samples diminished pitting attack to an extent depending on the percentage of the alloying element in the sample. Among the investigated materials, Al–Si alloys exhibited the highest corrosion resistance towards uniform and pitting corrosion processes in KSCN solutions. The passive and dissolution behaviour of Al was also studied under the conditions of continuous illumination (300–450 nm) based on cyclic polarization and potentiostatic techniques. The incident photons had a little influence on pit initiation and a marked effect on pit growth. These explained in terms of a photo-induced modification of the passive film formed on the anode surface, which render it more resistant to pitting. The effects of UV photons energy and period of illumination on the morphology of the pitted surfaces were also studied.     

Experimental design and statistical evaluation of a full-scale gasification project

Sasol in South Africa gasifies approximately 30 million tons of bituminous coal per year to synthesis gas, which is converted to fuels and chemicals via the Fischer–Tropsch process. Three years ago, Sasol embarked upon a unique project to optimise the gas production of the Sasol–Lurgi fixed bed dry bottom coal gasification process. Optimisation of the gasification process was carried out by utilising the method of factorial experimental design on the process variables of interest obtained from a specifically equipped full-scale test gasifier. A response surface model in the process variables was fitted for each of the performance variables. The models developed were validated and proved to be valid when considering different data sets. This paper discusses the application of factorial experimental design and the combination of process variables and mixture components in optimising a production process.     

Preparation and evaluation of nanocomposites of polyfuran with Al2O3 and montmorillonite clay

High yield oxidative polymerization of furan was accomplished in CHCl₃ solvent at 0 °C. A nanocomposite of polyfuran (PF)–Al₂O₃ was prepared through polymerization of furan in a suspension of nanodimensional Al₂O₃ in CHCl₃ at 0 °C. High yield polymerization of furan was also achieved in montmorillonite clay (MMT) without any extraneous oxidant. The formation of PF was confirmed by FTIR and elemental analysis. Thermogravimetric analyses revealed the following trends in thermal stability: PF < PF–Al₂O₃ < Al₂O₃ and PF < PF–MMT < MMT. Scanning electron microscopy showed the average particles sizes to be ca 51 nm and ca 40 nm for PF–Al₂O₃ and PF–MMT composites, respectively. The occurrence of a peak at 19.84 Å in the X‐ray diffraction pattern of the PF–MMT composite was indicative of the intercalation of PF in MMT lamellae. Transmission electron microscopic analyses for the PF–MMT composite also showed incorporation of PF moieties in‐between the MMT layers. The dc conductivity values (S cm^?1) of PF–FeCl₃, PF–Al₂O₃–FeCl₃, PF–MMT and PF–MMT–FeCl₃ systems were in the order of 10^?6, 10^?7, 10^?8 and 10^?7, respectively, and the values were significantly enhanced compared to the dc conductivity value of PF homopolymers (10^?11). Copyright © 2004 Society of Chemical Industry     

Computerized design and evaluation of improved electrodes for lead-acid batteries

A mathematical model of a positive-negative electrode pair in a lead-acid battery has been developed, and can be solved to determine the potential and current density distribution over the electrode surfaces. With the aid of a computer the model was used to improve the grid design of the positive electrode. The results were compared with those obtained by discharging full-size electrode pairs in a laboratory cell. Agreement between projections and experimental data was about 70% with the assumptions made for certain input parameters. Further development is needed before the model can be applied to the design of radial grids with curvilinear grid members.