Dipping Time Research Articles

High Molecular Weight Conjugated Polymer Thin Films with Enhanced Molecular Ordering, Obtained via a Dipping Method

The fabrication of polymer field-effect transistors with good electrical properties requires the minimization of molecular defects caused by low molecular weight (MW) fractions of a conjugated polymer. Here we report that the electrical properties of a narrow bandgap conjugated polymer could be dramatically improved as a result of dipping a thin film into a poor solvent. The dipping time in hexanes was controlled to efficiently eliminate the low molecular weight fractions and concomitantly improve the molecular ordering of the conjugated polymer. The correlation between the structural order and the electrical properties was used to optimize the dipping time and investigate the effects of the low MW fraction on the electrical properties of the resulting thin film.

Hot-Dip Aluminizing with Silicon and Magnesium Addition II. Effect on Corrosion Resistance

The effect of silicon and magnesium addition in a molten Al bath on the morphology and corrosion resistance of the Al coating layer of steel formed during hot-dip aluminizing was investigated at the temperatures of 700, 800, and 900 ℃ for the dipping time of 1-15 minutes. The thickness of the intermetallic layer decreased with an increasing Mg or Si content within a range of 0-1 at%. Addition of Si made the intermetallic layer thin whereas addition of Mg compensated for the decrease of the thickness significantly. The shape of the intermetallic layers became less irregular than that of the hot-dip aluminizing in pure aluminum. The results of immersion corrosion tests and electrochemical corrosion tests in a solution of 3 wt% NaCl showed that the corrosion resistance of the Al-1% Si-1% Mg coated steel had increased significantly over the Al coated steel. The open circuit potential changed from .0.56324 V (vs. SCE) to .0.48872 V (vs. SCE) and the corrosion current density decreased from 9.9991 μA/cm2 to 2.1160 μA/cm2. A salt fog spray test on these specimens also showed hot-dip aluminizing with Si and Mg addition increased the corrosion resistance significantly.

In situ cross‐linked‐PDMS/BPPO membrane for the recovery of butanol by pervaporation

ABSTRACTIn this study, an in situ crosslinked polydimethylsiloxane/brominated polyphenylene oxide (c‐PDMS/BPPO) membrane on ceramic tube has been prepared for the recovery of butanol by pervaporation. A series of BPPO with different bromide‐substituted ratio were firstly synthesized through Wohl–Ziegler reaction. BPPO and PDMS were sequentially assembled and in situ crosslinked to form the final c‐PDMS/BPPO membrane. The results of solid‐state NMR and Differential Scanning Calorimeter demonstrated that the c‐PDMS/BPPO copolymer has a crosslinking structure and the SEM result proved the coverage of ceramic tube by copolymer layer. The effects of preparation conditions including dipping time and bromide‐substituted ratio of BPPO on the membrane performance were studied. The pervaporation experiments of butanol–water mixture indicated that the c‐PDMS/BPPO membrane exhibited an acceptable flux of 220 g·m−2·h−1 and high separation factor of 35 towards butanol, when the bromide‐substituted ratio was 34 wt % and the dipping time was 1.33 h. Moreover, the c‐PDMS/BPPO membrane performed excellent stability in an about 200 h continuous butanol recovery, as compared to the PDMS membrane. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40004.

Hot-Dip Aluminizing of Low Carbon Steel Using Al-7Si-2Cu Alloy Baths

Hot-dip aluminizing of low carbon steel was done in molten Al-7Si-2Cu bath at 690°C for dipping time ranging from 300 to 2400 seconds. Characterization of the intermetallics layer was done by using scanning electron microscope with energy dispersive spectroscopy. Four intermetallic phases, τ5-Al7Fe2Si, θ-FeAl3, η-Fe2Al5, and τ1-Al2Fe3Si3, were identified in the reaction layer. τ5- Al7Fe2Si phase was observed adjacent to aluminum-silicon topcoat, θ-FeAl3 between τ5 and η-Fe2Al5, η-Fe2Al5 adjacent to base material, and τ1-Al2Fe3Si3 precipitates within Fe2Al5 layer. The average thickness of Fe2Al5 layer increased linearly with square root of dipping time, while for the rest of the layers such relationship was not observed. The tongue-like morphology of Fe2Al5 layer was more pronounced at higher dipping time. Overall intermetallic layer thickness was following parabolic relationship with dipping time.

Ambulatory arterial stiffness index in children after kidney transplantation

Given the increase in CV morbidity after RTx and the scarcity of CV events in pediatrics, surrogate markers should be assessed to characterize CV damage in this population. AASI is a marker of arterial stiffness in adults, predicting cardio- and cerebrovascular morbidity. Our aim was to assess the determinants of AASI in RTx children (n=54, 15.5±3.5yr) and to examine its relationship to central PWV. AASI was calculated from 24 h ABPM. PWV was determined by applanation tonometry, body composition by multifrequency bioimpedance measurement. The dipping state, volume overload, and time on dialysis were the main predictors of AASI (p<0.05). Children with established HT (n=34) had increased AASI, extracellular body water, and BNP (p<0.05). In contrast to AASI, PWV did not differ between HT and normotensive RTx patient groups. There was no correlation between AASI and PWV. PWV was increased in children who spent more than oneyr on dialysis prior to RTx. In conclusion, increased AASI in HT RTx children better characterizes the actual volume- and pressure-dependent arterial rigidity rather than long-term morphological changes in large arteries as reflected by PWV.

Effect of molecular structure and packing density of an azo self-assembled monolayer on liquid crystal alignment

We studied the alignment of liquid crystals (LCs) on a photo-switchable azo-containing self-assembled monolayer (azo-SAM) with different packing densities and molecular structures. The packing density of the azo-SAM substrates was varied by changing the dipping time of the substrate in azosilane monomers solution (2mM in toluene). The thickness of the monolayer on the silicon substrate increased as the dipping time was increased. The relative surface packing density on the glass substrates was estimated from the surface energies of the azo-SAM. The photo-induced dynamics of liquid crystal alignment on the azo-SAM significantly varied according to the packing density of the azo-SAM and the structure of the azo-SAM molecules. The azo-SAM from long octyloxy chain-terminated azosilane (azo-S1) possessed stable homeotropic alignment even after photobuffing, while the azo-SAM from short methyl group-terminated azosilane monomer (azo-S2) showed photo-switchable homeotropic and planar alignments. However, when the packing density was increased to an excessive degree, even the azo-SAM from azo-S2 exhibited stable homeotropic alignment regardless of photobuffing.

Optimization studies on TFC membrane for Membrane Gas Absorption (MGA) application

A thin film composite (TFC) membrane has been developed by coating polydimethylsiloxane (PDMS) and glutaraldehyde (GH) on a surface porous polyvinylideneflouride (PVDF) membrane for membrane gas absorption (MGA) application. The optimum conditions for dip coating method were determined using response surface methodology (RSM). A central composite design (CCD) was used to investigate the effects of two independent factors, which PDMS concentrations (wt%) and dipping time (s) of GH on the four specific responses which are CO2 and N2 permeances, selectivity and contact angle (CA) value. The optimum conditions for PDMS concentration and GH dipping time are 10 wt% and 19 s, respectively where 354 GPU for CO2 permeance, 66 GPU for N2 permeance, 5.4 of selectivity and 132° of CA value were obtained. Through atomic force microscopy (AFM) analysis, the result shown the root mean square roughness (Rms) of the TFC membrane was 381 nm and it was double from untreated membrane Rms value. Therefore, the roughness of the surface membrane contributed to the performance of the separation in the process flow such as in MGA application. By coating PDMS, hydrophobicity of the surface membrane was improved as well

Great improvement of photoelectric property from co-sensitization of TiO2 electrodes with CdS quantum dots and dye N719 in dye-sensitized solar cells

The TiO2 film electrodes sensitized with CdS quantum dots (QDs) via chemical bath deposition method were successfully prepared as the photoanode of dye-sensitized solar cells (DSSCs). Microstructural characterizations by XRD, SEM, TEM and EDX show that the CdS nanocrystals with the cubic structure have intimate contact to the TiO2 films. The amount of CdS QDs can be controlled by varying the dipping time. The experiment results demonstrate that the CdS QDs-sensitized solar cells show a wider absorption in the solar spectrum and an enhanced surface photovoltage response. The maximal photoelectric conversion efficiency of 5.57% was achieved by the DSSC based on CdS QDs-sensitized TiO2 film with 4min. The performance improvement is ascribed to the enhancement of electron transport, the reduction of electron recombination and the long electron lifetime.

Facilitated kinetic transport of Cu(II) through a supported liquid membrane with calix[4]arene as a carrrier

Abstract In the present investigation, p-morpholinomethylcalix[4]arene (1) has been examined as a carrier in supported liquid membrane (SLM) for Cu(II) transport. The influence of different parameters, such as solvent, membrane dipping time, support membrane, co-anions, donor and acceptor pH, and carrier concentration on Cu(II) transport, was checked. The permeability values were calculated by using Danesi mass transfer model. Higher Cu(II) permeability was observed in diphenyl ether, with 1 h dipping time, Celgard 2500 and Cl− as co-anion. The optimum pH for donor phase was 2 and that for acceptor phase was neutral at 10−3 M carrier concentration. Diffusion coefficients were calculated using Reinhoudt's model, lag time measurements as well as by Wilke–Chang relation and compared. The transport was found to be diffusion-controlled in the membrane phase and the diffusion coefficient was calculated to be 1.54 × 10−10 m/s whereas the extraction constant was calculated to be 1.19 × 10−5 m/s.

Aluminising of Mild Steel Plates

Hot dip aluminising of low carbon steel was done at temperatures 690°C and 750°C for dipping time ranging from 300 to 2400 seconds. During aluminising a mixture of ZnCl2 and NH4Cl was used as flux. During aluminising components of the flux decomposed and zinc formed interacted with the Fe and Al. The aluminised samples were characterised for iron-aluminium intermetallic layer formation, morphology, and local composition. It was observed that intermetallic layer was predominantly Fe2Al5 and FeAl3 at 690°C and at 750°C coating consisted of FeAl3 layer and a layer with Al/Fe ratio greater than 3.26. For both temperatures, coating thickness increased with increase in time. For a given dipping time, deposition was less at higher temperature and this is attributed to changes in the kinetics of growth of individual layers due to dissolved zinc in the aluminium, at 750°C. Also, spalling of intermetallic layers was observed at elevated temperatures and longer dipping times.

ESTABLISHMENT OF A REGENERATION SYSTEM FOR THE GENETIC TRANSFORMATION OF GROUND-COVER CHRYSANTHEMUM 'JINDINGHONGXIN'

Ground-cover Chrysanthemum has been used in gardens due to its rich colors, excellent ornamental value. Too much precipitation in summer of north China limits its further use. In order to create chrysanthemum with high resistance to waterlogging, the Vgb (Vitreoscilla hemoglobin) and pmi (phosphomannose isomerase) genes are transferred into the genome of ground-cover chrysanthemum ‘Jindinghongxin’ by Agrobacterium tumefaciens mediated transformation in our research. This research is of profound importance to broaden the usage of ground-cover chrysanthemum in gardens. This research optimized the regeneration system of ‘Jindinghongxin’ including choosing young leaves as explants and the best regeneration culture medium (MS+2.0 mg/L 6-BA+0.5 mg/L NAA), Transformation system for ‘Jindinghongxin’ was established by pre-culturing leaf explants for 2 days. The suitable concentration of Agrobacterium tumefaciens and the suitable dipping time for transformation was OD600=0.4 for 5 minutes. Co-cultivation was done for 2 days at 28°C in the dark after infection and the explants were then put in delayed culture for 4 days. Then the explants were cultured in first selection medium with 6 g/L mannose for 15 days, and then cultured in second selection medium with 7 g/L mannose. Once the regeneration shoot was 1 cm long it was transformed into MS with 350 mg/L carbenicillin for root induction.

Antimicrobial Activities of Acetic Acid, Citric Acid and Lactic Acid against Shigella Species

AbstractThis study determined the antimicrobial activities of acetic acid, citric acid and lactic acid against four Shigella species: S. sonnei, S. flexneri, S. boydii and S. dysenteriae. Minimal inhibitory concentrations of acetic acid and citric acid against Shigella were 200 and 300 ppm, respectively. But S. sonnei was 400 ppm. Lactic acid (0.5%) in tryptic soya broth inhibited the growth of all Shigella species. Citric acid weakly inhibited the growth of S. flexneri, but it strongly inhibited the growth of S. dysenteriae, resulting in a 5‐log reduction. Acetic acid exhibited the weakest antimicrobial activity among the tested organic acids but produced the highest ratios of injured cells. When artificially inoculated lettuce was dipped in 1% organic acid solutions, the growth of S. flexneri, S. dysenteriae and S. boydii were reduced by 2 logs. And the growth was further reduced by lactic acid as the dipping time increased. The antimicrobial activities of organic acids against Shigella species differed. Acetic acid exhibited the greatest antimicrobial activity in the paper disk diffusion experiment, but lactic acid was the most effective antimicrobial agent against Shigella species artificially inoculated on lettuce.Practical ApplicationsShigellosis induced by Shigella species results in at least 600,000 deaths worldwide each year. And in the U.S.A., it is a major bacteria involved in food poisoning, reported in 10,000–20,000 patients. In the present study, organic acids were used as basic materials for controlling Shigella species, and there are potential for organic acids, which are natural antimicrobials, to be used in the development of eco‐friendly reduction technology on Shigella species.

Tuning photocurrent response through size control of CdSe quantum dots sensitized solar cells

The photovoltaic characterization of CdSe quantum dots sensitized solar cells (QDSSCs) by tuning band gap of CdSe quantum dots (QDs) through size control has been investigated. Fluorine doped tin oxide (FTO) substrates were coated with 20 nm in diameter TiO2 nanoparticles (NPs). Pre-synthesized colloidal CdSe quantum dots of different sizes (from 4.0 to 5.4 nm) were deposited on the TiO2-coated substrates using direct adsorption (DA) method. The FTO counter electrodes were coated with platinum, while the electrolyte containing I−/I3− redox species was sandwiched between the two electrodes. The current density-voltage (J-V) characteristic curves of the assembled QDSSCs were measured for different dipping times, and AM 1.5 simulated sunlight. The maximum values of short circuit current density (Jsc) and conversion efficiency (η) are 1.62 mA/cm2 and 0.29 % respectively, corresponding to CdSe QDs of size 4.52 nm (542 nm absorption edge) and of 6 h dipping time. The variation of the CdSe QDs size mainly tunes the alignment of the conduction band minimum of CdSe with respect to that of TiO2 surface. Furthermore, the Jsc increases linearly with increasing intensity of the sun light, which indicates the sensitivity of the assembled cells.

Effect of organic dye, the concentration and dipping time of the organic dye N719 on the photovoltaic performance of dye-sensitized ZnO solar cell prepared by ammonia-assisted hydrolysis technique

This work investigated the influence of the organic dyes N719, N3 and Z907 as photosensitizers on the photovoltaic parameters of ZnO nanorod dye-sensitized solar cells (DSSCs). It also evaluated the effect of the concentration and dipping time of the best dye, N719, on the performance of the cell. TiO2 nanorods, used as the photovoltaic material of the cell, were prepared via an ammonia-assisted hydrolysis technique. The platinum film as the counterelectrode of the DSSC was prepared using a platinum pellet on an ITO substrate. The redox couple of the electrolyte utilized in the DSSC was iodide/triiodide. The cells sensitized with the N719 and Z907 dyes demonstrated the best performance compared with the cell sensitized with the N3 dye. This occurred as N719 and Z907 demonstrated the highest optical absorption in the visible region. The cell sensitized with a dipping time of 6h in 0.3mM N719 performed with the highest short-circuit density, Jsc, of 1.07mAcm−2 and conversion efficiency, η, of 0.135% since it possessed the highest optical absorption in the visible region. The corresponding incident photon-to-current conversion efficiency (IPCE) of the cell was 41.0%.

Influence of Cutting Force on Bimetallic Piston Machining by a Cubic Boron Nitride (CBN) Tool

Bimetallic pistons are most widely used in diesel engine vehicles for weight reduction and enhanced performance with long life. Aluminum alloy is reinforced with cast iron insert to realize the bimetallic pistons. The bonding between aluminum and cast iron is achieved through a patented process named the Al-Fin process. To ensure better bonding, the insert is dipped in the molten aluminum bath, this dipping time playing a vital role. The present study focuses on varying the dipping time from 90 s to 5 min to find the optimum dipping time. Achieving the near net shape of the bimetallic pistons without damaging the bonding between the aluminum and cast iron is the major challenge. This investigation also obtains optimal cutting parameters in turning off such pistons with cubic boron nitride as a single tool to machine the metal. The bond integrity after machining is primarily related to the magnitude of the cutting forces. Taguchi design of experiment analysis was conducted on the inserts which are subjected to various dipping time. The optimal cutting parameters for minimized cutting forces were identified. The extent of deboning and the surface finish were measured after machining to ensure the minimum cutting force condition to satisfy the requirements.

Improving Corrosion Resistance of the Hot-Dip Aluminum Coating on 22MnB5 Steel Surface

Keywords: Hot-Dip Aluminum; Corrosion resistance; Fe-Al Intermetallic alloys Abstract. The hot-dipping Al coating was developed on 22MnB5 steel surface. Effects of corrosion resistance with different dipping time coatings were investigated in this paper. It is describes an approach to improve the corrosion resistance of 22MnB5 steel. The results of the polarization curves show that the dipping 2min coatings have the highest corrosion potential (Ecorr) and the lowest corrosion current (icorr), indicating that this coating is a best corrosion inhibitor. It is similar results with EIS for corrosion resistance, respectively. The proper thickness (~20µm) of Fe-Al compounds between Fe substrate and Al coatings must be selected (750°C, hot-dipping 2min) in order to improve corrosion resistance for 22MnB5 steel.

Effect of pattern coating thickness on characteristics of lost foam Al–Si–Cu alloy casting

An experimental study on lost foam casting of an Al–Si–Cu alloy was conducted. The main objective was to study the effect of pattern coating thickness on casting imperfection and porosity percentage as well as eutectic silicon spacing of the alloy. The results showed that increasing slurry viscosity and flask dipping time influenced the casting integrity and microstructural characteristics. It was found that thinner pattern coating produced improved mould filling, refined microstructure and higher quality castings containing less porosity.

Salt Sensitivity and Nondippers in Chronic Kidney Disease

High salt-sensitivity and nondipper blood pressure (BP) rhythm are highly associated with each other, because both are caused by impaired renal sodium excretion capability. We proposed that nocturnal hypertension and resultant pressure natriuresis could compensate for daytime sodium retention. If so, high BP may continue until sodium is sufficiently excreted at night. In fact, it takes longer for the night-time BP to fall in patients with more severe renal dysfunction. The time appears to be an essential component of the nondipper BP rhythm and, therefore, we defined the duration as the dipping time. Also, renal function was the sole determinant of a nocturnal BP dip other than age, sex, or BMI. Furthermore, we reported that diuretic therapy or dietary salt restriction, which can prevent sodium retention, restored the circadian BP rhythm into a dipper pattern. Large-scale studies are needed to explore whether these interventions can decrease the risks.

Film formation from PS/AL2 O3 nanocomposites prepared by dip-drawing method

In this study, steady state fluorescence (SSF) and UV–vis (UVV) techniques were used to examine film formation from pyrene (P) labeled polystyrene (PS) latex/Al2O3 (PS/Al2O3) composites prepared by the dip-drawing method. The effects of dip-drawing rates and dipping time in Al2O3 sol on film formation behavior and the morphology of PS/Al2O3 films were investigated. Films were prepared first by casting PS dispersion on clean glass substrates which creates a close-packed array of PS sphere (203 nm) templates. These templates were then covered with Al2O3 utilizing the dip-drawing method for various dip-drawing rates and dipping times in Al2O3 sol. The film formation of these composites was studied by annealing them at a temperature range of 100°C to 270°C and monitoring the scattered light (Isc), fluorescence (IP), and transmitted light (Itr) intensities after each annealing step. The structural properties of the composite films were analyzed with a scanning electron microscope (SEM). The results demonstrated that the film formation behavior and morphology of composites depended mainly on dipping time, and no dependence on the dip-drawing rate was observed. The optical results indicated that PS/Al2O3 films undergo complete film formation independent of the dip-drawing rate and dipping time. Additionally, the film formation stages were modeled and the corresponding activation energies were determined. After completion of film formation, PS polymers were extracted to obtain porous Al2O3 thin films. Highly ordered porous structures were observed for long dipping time in Al2O3 sol but no change was observed for different dip-drawing rates, confirming the optical data. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Tuning the Architecture of Cellulose Nanocrystal–Poly(allylamine hydrochloride) Multilayered Thin Films: Influence of Dipping Parameters

Multilayered thin films consisting of alternating cationic polyelectrolyte, poly(allylamine hydrochloride) (PAH), and anionic cellulose nanocrystals (CNs) were constructed using the dipping procedure by screening different experimental parameters: the drying step between each layer adsorption, the dipping time, the ionic strength of the PAH solution, and the concentration of CNs dispersion. We showed that the drying process and the ionic strength of PAH solution were crucial parameters for the successful construction of 8-bilayer films. Film thickness is mainly influenced by dipping time and CN concentration when using the dipping procedure without drying. Two architectures of adsorbed CN layers-a single or a double layer of CNs-were revealed on the basis of the thickness increment per bilayer, depending on experimental conditions. The layer adsorption process was investigated in real-time using quartz crystal microbalance with dissipation (QCM-D) experiments in an aqueous environment or by incorporating a drying step. On the basis of in situ construction of PAH-CN films in wet media, QCM-D data were indicative of highly hydrated films for which the progressive layer stacking is disturbed or prevented. QCM-D monitoring of CNs and PAH layer adsorption was monitored by incorporating a drying process. The impact of experimental parameters on PAH-CN multilayered construction and on CN layer configuration is discussed. This study offers new opportunities for tailoring the architecture of CN-based multilayer films.