Evaluation of jet performance in drop-on-demand (DOD) inkjet printing

Inkjet printing has been widely used in many applications and has been studied for many years. However, there are not many systematic researches on the mechanism of jet formation, nor is there any reliable platform that enables us to evaluate jet performance. In this study, an approach to practically evaluate the jet stability of the dropon-demand (DOD) inkjet printing has been proposed, based on which the transient behavior of the DOD drop formation has been studied experimentally for Newtonian liquids with a range of different viscosities (1.0–11 cp) but of a comparable surface tension. For more viscous liquids, the rate of the jet retraction after a pinch-off from the nozzle was found to increase as the thread motion became more sharp and conical as a result of the shape effect. The break-up time of the jet also increased because the rate of capillary wave propagation was lower for more viscous liquids. The jet stability graph, which can be drawn in terms of jet retraction and break-up time, was employed to characterize the jetting stability, and the degree of satellite drop generation was quantitatively evaluated by two critical jet speeds. The effect of an electric pulse imposed on a piezoelectric plate inside the printhead was also studied. The single-peak electric pulse was used in this experiment for simple analysis, and the jet speed variation was measured under different operating conditions. Both the optimal dwell time and the maximum stable jetting frequency were affected by viscosity and they were explained in terms of the propagation theory.     

Development of high solid content aqueous 3Y-TZP suspensions for direct inkjet printing using a thermal inkjet printer

An aqueous 3Y-TZP suspension with 24.2 vol.% solid content was developed for “Direct Inkjet Printing” (DIP). The printing unit was a common HP-DeskJet printer. The suspension was adjusted in terms of particle size, viscosity, and pH-value, so that it became compatible with the printing system. Therefore, suspensions of various compositions were prepared and printed two-dimensionally to analyze the influence of several organic additives on printability. The printouts were evaluated and typical printing errors were classified. The composition of the suspension was optimized and successive and error free single layers of 3Y-TZP were printed. The suspension was examined and characterized in terms of particle size and distribution, composition, viscosity, surface tension, pH-value, vapour pressure, and the Ohnesorge number. A printed 3Y-TZP layer of 12 μm thickness was sintered to full density.     

Nanostructured engineering of nickel cermet anode for solid oxide fuel cell using inkjet printing

A single-step wet-chemical synthesis of NiO-SDC (Sm³⁺ doped ceria) colloidal ink for the inkjet printing (IJP) of nanostructured anodic layers with enhanced catalytic activity for solid oxide fuel cells (SOFCs) is developed and characterized. Dynamic light scattering, scanning electron microscope, and Raman spectroscopy revealed stable nanoparticles with the main size of 11.85 nm within the ink solution. Rheology parameters were analyzed, and the anode was printed. Porous post-sintered Ni-cermet layer, with a thickness of 15?25 μm contained near-spherical nanoparticles of 40?80 nm, was obtained. X-ray diffraction confirmed the phase composition of the cermet layer. Electrical impedance spectroscopy demonstrated a significant reduction, by more than 80 %, in the area-specific resistance of the IJP half-cell in comparison with the Screen-printed half-cell. The microstructure engineering using IJP provides fabrication of the cermet NiO-SDC layer with a conjugated structure, which ultimately enhances the catalytic activity of the SOFC.     

Drying stability enhancement of red-perovskite colloidal ink via ligand-derived coating for inkjet printing

Today, inkjet printing techniques has many merits such as high printing yield and mask-free process for the various field. As one of the candidate ink materials, the perovskite is appropriate for inkjet printing due to the colloidal state and excellent optoelectronic properties such as high photoluminescence quantum yield (PLQY) and narrow full width at half maximum (FWHM). Those characteristics are an advantage to fabricating ink and realize wide color-gamut in the small area with micro-patterning. However, perovskite application in inkjet printing with various color has limitations due to the low drying stability of mixed halide perovskite.Herein, we report on improving the drying stability of red perovskite by inducing aggregation during the drying process. Silane ligand has applied to induce the aggregation, and we confirmed that the thin coating layer has formed on the perovskite surface. The synthesized red-perovskite using silane ligands is well dispersed in the solvent as a colloidal state. And it maintained the emission intensity over 50% after drying. As-prepared perovskite ink has successfully printed on the ethyl cellulose film with 338 dpi with maintaining transparency of the film. These results are beneficial not only display applications but also security applications such as double anti-counterfeiting.     

Numerical simulation of gas bubbles behaviour using a three-dimensional volume of fluid method

In this paper a three-dimensional (3D) volume of fluid (VOF) method is presented featuring (i) an interface reconstruction technique based on piecewise linear interface representation, (ii) a 3D version of the CSF model of Brackbill et al. [1992, Journal of Computational Physics 100, 335]. Our model can handle a large density and viscosity ratio and a large value of the surface tension coefficient.First the results of a number of test cases are presented to assess the correctness of the advection and interface reconstruction algorithms and the implementation of the 3D version of the CSF model. Subsequently the computed terminal Reynolds numbers and shapes of isolated gas bubbles rising in quiescent liquids are compared with data taken from the bubble diagram of Grace (1973). Finally results of two calculations are reported involving the co-axial and oblique coalescence of two gas bubbles. The computed bubble shapes compared very well with the experimentally observed bubble shapes of Brereton and Korotney [1991, In: Dynamics of Bubbles and Vortices Near a Free Surface, AMD-vol. 119. ASME, New York].     

A model for turbulent binary breakup of dispersed fluid particles

Accurate predictions of particle size distributions, and therefore of the underlying processes of fluid particle breakup and coalescence are of vital importance in process design, but reliable procedures are still lacking. The present paper aims at developing a modular formulation for the turbulent particle breakup process. The model is to be included in a population balance model which is formulated such as to facilitate the direct future implementation into a full multifluid CFD model.The breakup process is described without introducing adjustable parameters. The current model is a further development of an existing model by Luo and Svendsen (AIChE J. 42 (5) (1996) 1225), which has been expanded and refined, and where an inherent weakness regarding the breakup rate for small particles and small daughter particle fragments are removed. A new criterion regarding the kinetic energy density of the colliding turbulent eddy causing breakup has been introduced. This new criterion is a novel concept describing the breakup process. The details are thoroughly discussed together with possible further modifications. The results from the new model are encouraging because the breakup rate is greatly reduced when the dispersed fluid particles are reduced in size. Further, the response to changes in system variables is reasonable and the distribution of daughter sizes vary in a reasonable way for the different collision possibilities.     

Theoretical model for multiple breakup of fluid particles in turbulent flow field

Generalized phenomenological model, based on the theories of probability and isotropic turbulence, is developed for multiple breakup of fluid particles in turbulent flow field. The approach uses a series of successive binary breakup events occur at a time scale comparable to the colliding eddy turnover time. It was found that the use of energy density, instead of energy, will increase the predicted binary breakup rate which is usually underestimated by the existing models in the literature. Generalization of the binary breakup model for multiple fragmentations is performed by defining a “remaining energy function” for the colliding eddy which means the contribution of original eddy to the later breakup events. For ternary breakage, the model shows a reasonably good agreement with the experimental data. The quaternary fragmentation frequency, however, is of negligible importance at lower energy dissipation rates but its contribution to breakage fraction at higher energy dissipation rates becomes considerable. The results also show that ternary and quaternary breakups have a considerable 90% contribution to the overall fragmentation, while pentenary and further fragmentations are of lower importance at low energy dissipation rates. At higher levels of energy dissipation rate, fragmentations up to six daughter particles contribute to more than 95% of the overall fragmentations. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4508–4525, 2016     

Influence of fluid properties on bubble formation,detachment, rising and collapse; Investigation using volume of fluid method

Numerical simulations have been carried out to investigate the formation and motion of single bubble in liquids using volume-of-fluid (VOF) method using the software platform of FLUENT 6.3. Transient conservation mass and momentum equations with considering the effects of surface tension and gravitational force were solved by the pressure implicit splitting operator (PISO) algorithm to simulate the behavior of gas-liquid interface movements in the VOF method. The simulation results of bubble formation and characteristics were in reasonable agreement with experimental observations and available literature results. Effects of fluid physical properties, operation conditions such as orifice diameter on bubble behavior, detachment time, bubble formation frequency and bubble diameter were numerically studied. The simulations showed that bubble size and bubble detachment times are linear functions of surface tension and decrease exponentially with the increase in liquid density. In contrast, only a small influence of the fluid viscosity on bubble size and detachment time was observed. Bubble collapse at a free surface simulation with VOF method was also investigated.     

Effect of milling time and pH on the dispersibility of lead zirconate titanate in aqueous media for inkjet printing

Micrometre-sized Pb(Zr_0.53Ti_0.47)O₃ (PZT) powder was dispersed in water, stabilized with the ammonium polyacrylate (PAANH₄) and milled to reduce the particle size. The influence of the pH, the amount of PAANH₄, and the milling time on the zeta potential, the PZT particle size and the particle size distribution was studied. The agglomeration took place regardless the milling time at pH 3. The suspension, containing 5 vol.% of PZT and 5 wt.% of PAANH₄, milled at pH 10 for 240 min, was stable and contained particles with a narrow, log-normal particle size distribution with the median size of 160 nm. The dissociated carboxyl groups from the PAANH₄ interacted with the PZT particles as evidenced by Fourier transform infrared spectroscopy and electrosterically stabilized the particles in water at pH 10. The PZT particle size and the stability of the suspension fitted the requirements for the ink, suitable for ink-jet printing.     

偶氮二异丁脒盐酸盐的合成新方法

以偶氮二异丁腈为原料,通过碱催化法合成了一种水溶性偶氮引发剂——偶氮二异丁脒盐酸盐,讨论了偶氮二异丁腈甲醇溶液的浓度、甲醇钠用量、氯化铵用量、第一和第二反应时间对终产物产率的影响。研究了其热分解反应动力学,并通过红外光谱法和核磁共振法对其结构进行了表征,最后将此引发剂用于乙酸乙烯酯乳液聚合制得了聚乙酸乙烯酯,并用凝胶渗透色谱仪对聚乙酸乙烯酯的相对分子质量进行了表征。结果表明:偶氮二异丁脒盐酸盐分解反应级数符合一级反应动力学规律,测定其热分解反应活化能Ea为67.39kJ/mol,制得的聚乙酸乙烯酯聚合度为4949。     

用VOF法模拟导向立体传质塔板罩内两相流

利用计算流体力学中的VOF方法对导向立体传质塔板（CTST-8）罩内气液两相流场进行了数值模拟,用Fluent的前处理软件gambit建立物理模型,在速度梯度大的地方采用局部加密网格,根据计算结果进行网格的自适应。用Fluent 6.1 对CTST-8在板孔气速为8.4 m/s,清液层高度为25 mm的工况下进行数值模拟。模拟结果显示了罩内流场的三维特性,并反映出罩内流场的相含率分布,速度分布以及压强分布等。将罩内压强的测量结果与模拟结果进行对比,两者吻合较好。说明本文数值模型具有较好的精度,可以用于CTST-8罩内两相流场的预测。     

Digital textile printing (DTP) wastewater treatment using ozone and membrane filtration

Digital textile printing (DTP) is considered as an environmentally benign process because its wastewater production is relatively small compared with the conventional textile printing system. DTP is usually practiced at building office in an urban area rather than in a textile industrial complex, so that process development for on-site treatment of the DTP wastewater is currently needed. The aim of this study was to propose a DTP wastewater treatment system suitable for operation in building and to verify if the proposed system has a rationale treatment system should be compact and reliable because it should be installed near the DTP system. Thus, a hybrid system consisting of ozone, ultrafiltration (UF) and reverse osmosis (RO) was proposed for treatment of DTP wastewater. Prior to UF and RO, ozone was introduced to the DTP wastewater to reduce organic loadings to membrane filtration as well as to treat the concentrates recycled from UF and RO. When ozone was injected with C-T value of 255 g·s/L, the removal efficiency of COD and color was 63 and 81%, respectively. Ozonation of the DTP wastewater led to aggregation of colloidal particles, so that the cake resistance (R_c) calculated after ozone and UF was lower than that of the control (= without ozonation), suggesting that pre-ozonation is beneficial to not only flux enhancement but also to good permeate water quality. Further treatment of UF permeates using RO was carried out since the UF permeates was not enough for direct discharge or reuse. Final effluents through the whole process of ozonation, UF and RO met the criteria of direct discharge and reuse, suggesting that the proposed hybrid system could be used for DTP wastewater treatment satisfactorily.     

Recycling of steelmaking electric arc furnace dust into aqueous cyan ceramic ink for inkjet printing process and its printability

Recycling of electric arc furnace dust (EAFD) has great potential for industrial applications, due to its useful metal contents, including zinc. In this study, aqueous cyan ceramic ink for ink-jet printing applications was synthesized using EAFD. More specifically, cyan ceramic pigments were synthesized using an empirical composition of Zn(EAFD)_XCo_1-XAl₂O₄, in which expensive cobalt oxide is replaced by Zn-enriched EAFD. Zn(EAFD)_0.25Co_0.75Al₂O₄, which has a vivid cyan color, was selected as the optimum composition of cyan ceramic pigments for synthesizing aqueous cyan ceramic ink for ink-jet printing applications. To prevent nozzle clogging during ink-jet printing, the cyan ceramic pigments were micronized. The micronized pigments were mixed with distilled water and dispersant to fabricate aqueous cyan ceramic ink. To determine the optimized jettability and printability of this ink, its rheological properties, including viscosity and surface tension, were adjusted and analyzed. It was concluded that the jettability and printability of aqueous cyan ceramic ink produced via ink-jet printing could be enhanced by appropriately adjusting its viscosity.     

双(2-氯乙基)醚的合成新方法

作为冠醚合成的基本原料多甘醇二卤化物,在合成上,均是依照Pedersen C J在1967年及1972年时所提出的方法[1～3],该方法是将相应的多甘醇与氯化亚硫酰在苯中吡啶存在下反应.这个方法适用于二甘醇二氯化物(即双(2-氯乙基)醚,简称二氯乙醚)合成,产率一般较高,但反应进行得很缓慢,操作环境毒性很大,目标产品的分离提纯程序较多.本文提出一种新的合成双(2-氯乙基)醚的方法,使反应时间大大缩短;避免了在毒性很大的环境下操作;反应完全以后的分离提纯简单,目标产品可以直接从反应混合物中减压蒸馏得到;降低了产品的生产成本.     

用USTER TESTER3仪器检测涤纶长丝条干不匀率的方法

介绍了USTER TESTER 3仪器的工作原理、实验条件、实验仪器组成,及用该仪器检测涤纶长丝条干不匀率的实验程序,检测过程。     

二(2-氨基乙基)-(3-氨基丙基)胺的合成新方法

以二(氰基甲基)胺及丙烯腈为原料，通过亲核加成、氢化反应合成了不等臂有机多胺化合物二(2-氨基乙基)-(3-氨基丙基)胺，标题化合物及其中间产物经多种谱学手段表征确证。在优化条件下，产物的总收率为67％，含量99.5％(HPLC)。     

Fe-Cu法预处理印染废水技术研究

为研究Fe-Cu法预处理印染废水的实际效果,并深入探讨Fe-Cu双金属法的反应机理,以印染厂调节池废水为研究对象进行了试验研究.试验结果表明,当印染废水为碱性时,铜片的加入能明显提高反应的速率,厌氧运行方式对色度去除率和可生化性提高更具优势;Fe-Cu法预处理再经后继生化处理后,出水COD和色度分别为296 mg/L、150倍,出水pH呈中性.     

Numerical study of condensing bubble in subcooled boiling flow using volume of fluid model

In this numerical study, the behavior of condensing bubble was investigated using the volume of fluid (VOF) model in the FLUENT code. In order to simulate the condensing bubble with the FLUENT code, the bubble condensation was modeled using the user-defined function (UDF). For the validation of the UDF of bubble condensation, the results of CFD simulation were compared with the results of a bubble condensation experiment performed in Seoul National University (SNU). Simulation results showed good agreements with the experimental data. Moreover, the fundamental behavior of the condensing bubble was investigated in various conditions. The effects of condensation on bubble behavior were analyzed by comparing the behavior of condensing bubbles with that of adiabatic bubbles. It was found that the behavior of the condensing bubble was different from that of the adiabatic bubble in many respects including the bubble shape, velocity, rise distance and moving trajectory.     

New method of dyeing keratin fibers using poly(ethylene imine) and its coloring mechanism

To improve the colorability of keratin fibers at lower temperatures, we developed a novel coloring method using poly(ethylene imine) (PEI) as a counterion reagent (human hair was treated beforehand with a PEI solution and then was colored with an acid dye). As a result of this new method, the coloring and color fastness to shampooing clearly improved with respect to the usual method. Next, to study the coloring mechanism with PEI, we investigated the penetration of PEI and Orange II into bleached human hair by optical microscopy. The results showed that the penetration of PEI and Orange II into bleached human hair increased with an increasing PEI treatment time and with a decreasing PEI molecular weight. With these experiments, we demonstrated that PEI, which penetrated the cortex region, exerted counterionization on Orange II, thereby increasing the penetration of Orange II into bleached human hair. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3806–3810, 2003