Nucleation Model Research Articles

Effects of the burner on SiO2 formation and deposition in the OVD process

The burner of outside vapor deposition (OVD) is of great significance for enhancing the yields and quality of the optical fiber preform. This study aims to numerically investigate the effects of the burner on silica particles formation and its corresponding deposition performance in the OVD process. This work is based on our recently developed integrated Eulerian-Eulerian multiphase OVD process model combined with a particle nucleation model. The effects of the distance between the burner and target, the horizontal offset of the target to the burner, the shape of burners, swirl burners as well as double burners are investigated. The results demonstrate that there exists an optimal value for the distance between the burner and target to yield the largest deposition efficiency. However, the deposition efficiency monotonically declines as the horizontal offset of the target to the burner increases. The elliptic burner potentially provides a better match with the target surface for particle deposition. An optimal number of helical vanes installed inside the O2–1 inlet is observed in the counter-swirling burner of O2–1 and H2 inlets, which yields the largest deposition efficiency of 33.4%. Double burners could promote the deposition rate, but could not enhance the particle deposition efficiency. The results provide a deeper understanding of the burner design and OVD process optimization.

In situ observation of the phase transformation kinetics of bismuth during shock release

A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth. Results reveal a retarded transformation from the shock-induced Bi-V phase to a metastable Bi-IV phase during the shock release, instead of the thermodynamically stable Bi-III phase. The emergence of the metastable Bi-IV phase is understood by the competitive interplay between two transformation pathways towards the Bi-IV and Bi-III, respectively. The former is more rapid than the latter because the Bi-V to B-IV transformation is driven by interaction between the closest atoms while the Bi-V to B-III transformation requires interaction between the second-closest atoms. The nucleation time for the Bi-V to Bi-IV transformation is determined to be 5.1±0.9 ns according to a classical nucleation model. This observation demonstrates the importance of the formation of the transient metastable phases, which can change the phase transformation pathway in a dynamic process.

Condensation characteristics of ammonia vapor during supersonic separation: A novel approach to ammonia-hydrogen separation

Ammonia has gained significant attention as a prospective hydrogen energy carrier. However, the effective separation of ammonia and hydrogen becomes a crucial aspect after the decomposition of ammonia into hydrogen. In this study, a novel method for ammonia separation is introduced, which leverages the phase transition behavior in supersonic flow. Consequently, this study presents the development of a mathematical model to elucidate the non-equilibrium condensation phenomenon of ammonia, and the accuracy of this model is validated. The simulation results reveal that, in comparison to classical nucleation theory (CNT) and internally consistent classical theory (ICCT), the Lothe-Pound (L-P) nucleation model more accurately characterizes the nucleation process of ammonia at low temperatures. Furthermore, numerical simulations demonstrated that increasing the inlet pressure from 1.2 bar to 1.8 bar led to a 2.66% enhancement in ammonia condensation efficiency. In contrast, raising the inlet temperature from 271 K to 283 K resulted in a decrease in condensation efficiency and a reduction in the radius of the exit droplets, potentially affecting subsequent separation efficiency. When the inlet ammonia molar fraction was elevated from 11% to 14%, the ammonia condensation efficiency increased from 13.7% to 14.5%, with only a minor decrease in outlet droplet radius (from 3.42 × 10−7 m to 3.39 × 10−7 m). These findings indicate that increasing pressure, decreasing temperature, and raising ammonia concentration can all stimulate ammonia condensation. These results have potential implications for the design and optimization of separators.

Welding of P355NH steel for the construction of a medium-pressure gas pipeline

AbstractThere is an increasing demand for welding of steel pipes meant for pressure purposes. P355NH (1.0473) steel became an important construction material used for structuring and restructuring of a medium-pressure gas pipeline due to its properties, such as significant tensile strength at the level of 600 MPa and increased yield point. These properties ensure appropriate service life of the principal pipeline structures. When welding P355NH steel, processes that enable high-quality welds without significant changes in the chemical composition of the base material, are applied. It is recommended to use the TIG welding process to produce joints, although P355NH steel joints are considered as difficult to weld. During welding, various welding defects might appear, which mainly include sticking and lack of fusion. Creation of joints with the desired properties, including those used in the construction of medium pressure gas pipelines, with the required class B quality, requires selection of appropriate parameters and compliance with the welding process practice. This is very important for the service life of the structure. Therefore, the article aims to select the most appropriate parameters and thermodynamic conditions for welding P355NH steel in order to obtain the best mechanical properties. The most important of the tested welding parameters of P355NH steel is welding speed, welding current, preheating temperature, interpass temperature and, above all, the role of various shielding gases. (Three different shielding gases containing argon and helium additives were tested.) The obtained joints were tested by: non-destructive tests, such as VT—visual examination; MT—magnetic particle testing, PT—penetration tests, UT—ultrasonic testing and by the destructive methods, such as tensile strength, impact toughness, bending test, light microscopy and scanning electron microscopy. The cause-and-effect relationships between the obtained joint structure and its mechanical properties were determined. The considerations were supported by the nucleation model and the mechanisms of formation of the acicular ferrite phase in the joint material. The chosen parameters of TIG process allow to obtain joint with adequate strength for the production of the gases pipeline, without welding defects. The results have a practical implication, the developed production technology for the obtaining the joints. The presented solution gives the possibility of producing correct welded joints, which can be used in the responsible steel construction. The originality of manuscript is the presentation the newly, uncomplicated solution of obtaining joint with good mechanical properties included the thin-walled tubular structure with a thickness of 3.6 mm. A novelty in the article is a clear indication of the importance of detailed thermodynamic welding conditions and obtained weld structure on the mechanical properties of the P355NH steel joint, which lead to the formation of various non-metallic titanium inclusions, which have a decisive impact on the mechanical properties of the joint, especially its strength and impact strength.

Synergetic effect of microfluidic flow and ultrasonication on chains pre-ordering in conjugated polymer solution

Multi-physical fields solution processing strategy provides a universal and facile way to prepare various conjugated polymer (CP) films and high-performance devices, whereas the hierarchical structures evolution and crystallization of the polymer chains are elusive particularly under the far-from-equilibrium state in solution. In this work, we employed a combined microfluidic flow and ultrasonication strategy (FU) for CP solution processing and found a pronounced synergetic effect of these fields in promoting the pre-ordering of chains in solution. This conformation order and anisotropy of the solution were revealed by using UV–Vis absorption, polarized optical microscopy (POM) and cryogenic transmission electron microscopy (Cryo-TEM) characterizations. A non-classical nucleation model for the conjugated polymer crystallization in the procedure of non-equilibrium solution processing was confirmed. The roles of microfluidic flow and ultrasonication on the chain aggregation and crystallization were addressed with the aim of a multi-physical simulation based on pressure acoustics streaming, fluid heat transfer and thermoviscous boundary layer impedance. Compared to pristine solutions, the FU strategy showed improved solution anisotropy and crystallization kinetics, substantially giving rise to a larger crystallinity in films and much increased mobilities for the organic field-effect transistor (OFET) devices by more than an order of magnitude. With an appropriate balance between the solvation and interchain interactions, the FU processing strategy is universal for regulation of chains conformation and aggregation in conjugated polymer solution.

First principle-based rate equation theory for the carbonation kinetics of CaO with CO2 in calcium looping

Calcium oxide (CaO), a CO2 sorbent and key ingredient in the process of making cement, exhibits excellent potential for carbon capture, utilization, and storage (CCUS) applications through calcium looping and integrated carbon capture and utilization, owing to its outstanding kinetic properties and high recyclability. From a fundamental standpoint, it is important to establish a comprehensive and precise carbonation kinetic model for CaO. In the present study, a density functional theory (DFT)-based rate equation was developed to predict the gas–solid reaction kinetics of CaO carbonation with CO2 in calcium looping. The reaction pathway of CaO carbonation, including surface reactions and structural transformations, was obtained by a transition state search of DFT calculations, and the transition state theory was used to calculate the reaction rate constants. The nucleation model was implemented in the mean-field surface reaction model to describe the nucleation of the CaCO3 product at the gas–solid interface. A grain model was developed to couple the surface reaction and CO2 diffusion through the product layer. The developed theory was validated using a wide range of experimental data, and the negative activation energy of CaO carbonation close to equilibrium was accurately predicted. The developed first principle-based rate equation provides a detailed theoretical framework for predicting CaO performance and optimizing the microstructure of Ca-based sorbents.

Insights Into Curie‐Temperature and Phase Formation of Ferroelectric Hf1−xZrxO2 with Oxygen Defects from a Leveled Energy Landscape

AbstractThe phase composition of HZO thin films is critical for the ferroelectric and electrical properties of the films and the devices they are integrated into. Optimization is a major challenge since the phase formation depends significantly on many influencing variables that are only partially understood so far. The Curie temperature is identified as an important parameter for understanding the behavior, since it depends sensitively on Zr content, the density of oxygen‐related defects, layer thickness, and external stress. A two‐step process, phase formation by pure kinetic transformation followed by nucleation, is proposed for phase formation. This is necessary because nucleation theory alone cannot explain the experimentally observed dependence on oxygen content. The classical nucleation model is modified at two crucial points. First, the polycrystalline structure is incorporated which allows the size effect to be implemented. Furthermore, the interface energies between the child and parent phase, which result from static ab initio calculations, are rescaled from dynamical effects. The resulting model is used to calculate the phase fractions during thermal processing. The results for the most important influencing variables are discussed and compared with experimental results. The causes of the undesired monoclinic phase are further analyzed.

Modeling the Precipitation of Aluminum Nitride Inclusions during Solidification of High‐Aluminum Steels

High‐aluminum advanced high‐strength steels have received increasing interest due to their excellent combination of strength and ductility. The control of nonmetallic inclusions in steel is among the most important issue for the production of high‐aluminum steel. This study proposes a model for the evolution of size distributions of AlN inclusions during solidification of steel based on the Kampmann–Wagner numerical model and microsegregation calculation. Both homogeneous (pure AlN) and heterogeneous precipitations (AlN+oxide or MnS) are described using homogeneous nucleation and free growth models of Greer et al. respectively. The model is applied to calculate the size distributions of AlN in high‐Al (up to 5%) Fe–Cr–Al steels and high‐ and medium‐manganese steels and validated by the experimental data in the literature. The model correctly describes the influence of cooling rates on the precipitation of AlN in Fe–Cr–Al steels and high‐manganese steels, and the sizes of AlN are reduced and the number densities of AlN inclusions are increased by increasing the cooling rate. The effects of nitrogen and aluminum concentration in medium‐manganese steel on inclusion precipitation are investigated by the model calculation. The increases in nitrogen and aluminum concentration facilitate the homogeneous precipitation of AlN inclusions.

Electrocrystallization and Morphology of Copper Coatings in the Presence of Organic Additives

Copper coatings with refined grains and smooth surface morphology were electrodeposited from electrolytes comprising a novel accelerator, the disodium salt of 4,4-dithiobenzene disulfonic acid (DBDA), with sodium chloride and polyethylene glycol (PEG) as inhibitors and 2-aminobenzothiazole (ABT) as a leveler. It was found that the morphology of the coatings strongly depends on the presence and type of additives. In the presence of only DBDA and NaCl, large crystallites are formed, whereas the addition of PEG and ABT significantly decreases their size, and the most fine-grained, smooth, and defect-free copper coating is formed with the combined use of all additives. To establish the correlation between the observed morphology and the kinetics of the additive-assisted copper electrocrystallization in the proposed electrolytes, the nucleation mechanism and its parameters were determined by transient electrochemical characterization. The extended nucleation model, which takes into account not only the copper deposition but also the electric double-layer charging and hydrogen reduction process, was used to establish the electrocrystallization kinetics in the presence of the additives. The results of such kinetic analyses can help to explain the morphological effect. By using the chronopotentiometry method, it was found that the addition of the disodium salt of 4,4-dithiobenzene disulfonic acid with chloride ions gives a catalytic effect, while the sequential introduction of polyethylene glycol and 2-aminobenzothiazole provides an increasing inhibitory effect. Voltamperometry and chronoamperometry tests showed that the process is controlled by the diffusion of ions to the growing three-dimensional cluster of a new phase. The introduction of additives into the electrolyte slows down the copper electroplating process at comparatively negative potentials and increases the probability of transition from instantaneous to progressive nucleation. Moreover, the rate of the process and the density of nucleation active sites increase (up to 2–3 times) with the addition of DBDA but decrease significantly (up to 5–8 times) in the presence of PEG and ABT, which additionally confirms their catalytic and inhibitory effects, respectively, and explains the significant smoothing effect on the morphology of the Cu-coatings.

Mesoscale dislocation dynamics modeling of incipient plasticity under nanoindentation

A mesoscale dislocation dynamics model which couples three-dimensional dislocation dynamics (DD), and finite element method (FEM) was used to investigate the mechanical response of Aluminum (Al) single crystal under spherical nanoindentation. Together with an atomistically informed nucleation model, the dislocation dynamics model can capture both the dynamic evolution of dislocations under the complex stress state of indentation and the corresponding constitutive response of material. The resulting load-displacement curves and the evolution of dislocation microstructures were analyzed to provide insights into the underlying deformation mechanism for incipient plasticity under nanoindentation. Our model could show the transition of the governing mechanism for plasticity from nucleation-controlled plasticity to pre-existing source-driven plasticity with increasing indenter size, as shown in recent experiments. In addition, it could capture a clear picture on incipient plasticity including the formation of prismatic loops through successive cross-slips of nucleated dislocations, such as rhombus loop and prismatic helical structures, which agrees well with atomistic modeling results.

Super-flat and uni-oriented cobalt film electrodeposited by modulating the crystal nucleation and growth behavior

A precise control of the microstructure of electrodeposited cobalt film is crucial for attaining the desired and reproducible electrical performance in edge nanoelectronic devices. Here we realize the super-flat and uni-oriented cobalt film through a one-step electrodeposition process using benzenesulfinic acid (BNS) as additive. We find that the unsaturated sulfite group in BNS plays a key role in the super-flat cobalt electroplating. Molecular activity analysis and electrochemical test results suggested that the electron donating ability of the sulfite group was higher than that of the sulfonate group, resulting in stronger adsorption of BNS on the cobalt surface and enhanced cathodic polarization. Nucleation model fitting and surface morphology evolution studies revealed that the cobalt nucleation with BNS shifted to progressive nucleation from instantaneous nucleation in the additive-free electrolyte, leading to a more uniform and compact film morphology. Furthermore, equilibrium adsorption calculations indicated that the selective and strong adsorption of BNS on cobalt planes was responsible for the preferential orientation of the (002) crystal plane growth. After annealing, cobalt films prepared with BNS exhibited substantial grain growth and impurity diffusion, which further improved the electrical performance.

Effects of In addition on microstructure and properties of SAC305 solder

In powderswith different contents (0.5−10 wt.%)were melted into the Sn−3.0Ag−0.5Cu (SAC305) solder to change the microstructure and thus improve the properties of the solder. The results showed that β-Sn(In), Ag3(Sn,In) and Cu6(Sn,In)5 phases existed in all the In-added solders, and an additional phase of InSn4 was found in the SAC305−10In solder. With increasing In addition amount, the β-Sn nucleation sites were increased and the nucleation model was changed from {101} to {301}, which refined the β-Sn grains and transformed the β-Sn morphology from large grains to interlaced grains and finally to multiple grains. As a result, a combined effect of fine grain strengthening and solid solution strengthening was achieved to increase the microhardness of the SAC305−xIn solders with increasing In addition amount.

Refining mechanism for TiN and solidification structure through a nucleating chain in magnesium-yttrium-treated ultrapure ferritic stainless steel

To investigate the refining phenomena of TiN inclusion and macro-/microstructure through heterogeneous nucleation of δ-Fe at TiN encapsulating oxide during solidification in ultrapure ferritic stainless steel, five samples were prepared, denoted as the initial, low-yttrium-treated, moderate-yttrium-treated, high-yttrium-treated, and magnesium-yttrium-treated samples. Based on the results of TiN inclusions, the minimum value of the average size (2.61 μm) and the maximum value of the number density (346.70 mm−2) were observed after magnesium-yttrium (Mg–Y) treatment. Combined with the mechanism analysis, these results reveal that the TiN can be refined because of the following three reasons: (ⅰ) the pure oxides, possessing low planar and/or linear disregistry with TiN; (ⅱ) the complex oxides, including the phase, which possesses extremely low disregistry with TiN; and/or (ⅲ) the increasing number of the oxides. By comparison, finer macrostructures were yielded with the addition of Y-/Mg–Y-based modifiers because of the decreasing nucleation barrier, and the finest macrostructure with equiaxed grain ratio of 100% and average grain size of 1.099 mm was observed in the Mg–Y-treated sample. Coupled with the results of TiN inclusions, therefore, the refining efficiency of macrostructure increases with the number of TiN. Referring to the results of differential scanning colorimetry, a general rule of solidification for metallic materials has been revealed. In addition, the in-situ nucleation-growth of δ-Fe was observed using high temperature laser confocal microscopy, and the microstructures were refined after Y/Mg–Y treatment. Eventually, the interfacial wetting-lattice mismatch heterogeneous nucleation model is successfully applied to evaluate the refining phenomenon of macro-/microstructures.

Improving biomass fuel obtained from Brazil nut residues via torrefaction: A case of kinetic and thermodynamic study

The residues of Brazil nuts (Bertholletia excelsa) were evaluated, in their natural state and in torrefied form, for their energy potential after pyrolysis. Samples of shells (BNS) and husks (BNH) were torrefied at 220, 260 and 300 ºC for 30 and 60 min, and were characterized for their chemical and energetic composition. It was also determined which samples showed, simultaneously, the lowest hemicellulose content and the highest cellulose content after torrefaction via analysis of the decomposition profile at 10 ºC/min under pyrolysis. The evolution of gases such as H2O, CO2 and/or C3H8, and CH4 was observed by simulated pyrolysis on a microscale in a thermogravimetric analyzer coupled to a mass spectrometer (TGA-MS). In addition, the kinetics of the pyrolysis of untorrefied and torrefied samples were evaluated using the Flynn-Wall-Ozawa (FWO) and Vyazovkin (VYZ) models in order to obtain the activation energy, pre-exponential factor and thermodynamic parameters. The predominant reaction mechanism was determined by Criado Master-plot method. The mean value of the activation energies ranged from 132.24 to 134.95 kJ/mol for BNS, from 135.53 to 138.47 kJ/mol for ST263, from 149.10 to 150.96 kJ/mol for BNH and from 145.83 to 148.14 kJ/mol for HT263. It was found that D2 and D4 diffusion mechanisms are prevalent in the decomposition of untorrefied samples, while torrefied samples were better adjusted to the F1/A2/A3/A4 overlapping nucleation models. High pre-exponential factor values indicated the presence of multiple intermolecular collisional reactions. The thermodynamic parameters evaluated, as well as the variations in enthalpy, Gibbs free energy and entropy, indicated that the evaluated process is endothermic, though requires little energy. As a whole, in view of the optimized parameters and elevation of the thermal stability of the material, the results demonstrate good potential for the use of Brazil nut shells and husks torrefied at 260 ºC for 30 min as biochar. In addition, pyrolyzed Brazil nut residues also have great potential in the production of bio-oil and biogas, in view of the high content of volatile matter released during the decomposition of the hemicellulose and lignin.

Surface atom migration-involved two-dimensional nucleation and growth of nanotwinned copper in DC electrodeposition

Direct-current (DC) Electrodeposited nanotwinned copper (nt-Cu) is a promising candidate for interconnection materials in integrated circuit for its excellent mechanical, electrical and thermal properties. However, the formation mechanism of nanotwins during DC electrodeposition of nt-Cu remains unclear. In this study, a two-dimensional nucleation and growth model of nt-Cu is established. The critical nucleation size and average twin spacing were evaluated theoretically. The results demonstrate a relatively high probability of twin nucleation through random stacking with the average twin spacing derived to be only ∼1 nm. The gap between theoretical and observed twinning probability can be ascribed to the surface migration-induced dissipation of nuclei. Molecular dynamics simulation further confirms the formation and subsequent dissipation of nuclei during deposition of Cu. By providing a clear illustration of nanotwin formation process, this study contributes to the understanding of nt-Cu electrodeposition.

Facet-engineered growth of non-layered 2D manganese chalcogenides

Non-layered two-dimensional (2D) materials have sparked much interest recently due to their atomic thickness, large surface area, thickness- and facet-dependent properties. Currently, these materials are mainly grown from wet-chemistry methods but suffer from small size, low quality, and multi-facets, which is a major challenge hindering their facet-dependent property studies and applications. Here, we report the facet-engineered growth (FEG) of non-layered 2D manganese chalcogenides (MnX, X ​= ​S, Se, Te) based on the chemical vapor deposition method. The as-grown samples exhibit large-area surfaces of single facet, high-crystallinity, and ordered domain orientation. As a proof-of-concept, we show the facet-dependent electrocatalytic property of non-layered 2D MnSe, proving they are ideal candidates for fundamental research. Furthermore, we elucidate the underlying mechanism of FEG during the vapor growth process by the interfacial energy derived nucleation models. The method developed in this work provides new opportunities for regulating and designing the structure of 2D materials.

Pyrolysis behavior of bastnaesite in an air environment: Thermodynamics, phase transition and kinetics

BackgroundOxidation roasting is an eco-friendly pre-treatment process that is utilized before leaching bastnaesite concentrate, and it is currently the main process for pretreating bastnaesite concentrate in China. Despite this, there is still a lack of systematic and detailed studies on the pyrolysis behavior of bastnaesite concentrate in an air environment. MethodsThe reaction thermodynamics, pyrolysis characteristics, phase transition and kinetics of bastnaesite pyrolysis in air were studied in detail by thermogravimetric and mass spectrometric, in-situ X-ray diffraction, and advanced kinetic parameter analysis method recommended by ICTAC. Significant findingsCe7O12, CeF3, and CO2 were the primary pyrolysis products of bastnaesite in the air. Spontaneous reactions dominated during the process, and the oxidation of pyrolysis products released heat. Bastnaesite pyrolysis initially occurred within the temperature range of 400°C to 500°C, with higher temperatures facilitating easier pyrolysis. The non-isothermal pyrolysis kinetic triplets for bastnaesite concentrate in the air were determined, which included activation energy (Eα) of 161.52 kJ/mol, pre-exponential factor (lnA) of 26.70 s−1, and appropriate kinetic mechanism of random nucleation and growth model (n=3/2–2).

Nucleation and crystallization of deeply supercooled benzocaine, a rapidly crystallizing organic compound: A Fast scanning calorimetry investigation

Investigation of nucleation and crystal growth in rapidly crystallizing systems represents a serious experimental challenge. Fast Scanning Calorimetry (FSC) was successfully used to study isothermal nucleation and crystallization in deeply supercooled melts of polymers and metallic glasses, but only limited attention was devoted to small organic molecules. In the present work, we present data on the nucleation and crystallization of the rapidly crystallizing organic compound benzocaine. We demonstrate that benzocaine can nucleate and crystallize far below the glass transition temperature. In deeply supercooled conditions, the nucleation and crystallization of benzocaine can be described using the equations derived from the Classic Nucleation Theory (CNT). However, at moderate supercooling, nucleation is not observed. Since the crystal growth rate is high at such temperatures, crystallization occurs only in prenucleated samples. The transition between the different behaviors is sharp, and the temperature of the transition is sample dependent. The presented results show a venue for the development of theories and models of nucleation, and demonstrate an important precedent of nuclei development far in the glassy state that must be considered for the application of amorphous drugs.

Sulfuric Acid Nucleation Potential Model Applied to Complex Reacting Systems in the Atmosphere

AbstractAtmospheric aerosol particles impact Earth's radiation balance by acting as seeds for cloud droplet formation. Over half of global cloud seed particles are formed by nucleation, a process where gas‐phase compounds react to form stable particles. Reactions of sulfuric acid (SA) with a wide variety of atmospheric compounds have been previously shown to drive nucleation in the lower troposphere. However, global climate models poorly predict particle nucleation rates since current nucleation models do not describe nucleation for systems containing tens to hundreds of precursor compounds. The nucleation potential model (NPM) was recently developed to model SA nucleation of complex mixtures by measuring an effective base concentration using a 1‐nm condensation particle counter. This technique for estimating particle nucleation rates can be deployed at a much higher spatial and temporal resolution than current methods which require detailed knowledge of all nucleation reactions and measurements, typically using a mass spectrometer, of all nucleation precursor gases. This work expands NPM by showing that this model can capture enhancement and suppression of SA nucleation rates within a complex mixture of organic and inorganic acids, ambient air, and across a range of atmospherically relevant relative humidities. In addition, an expression for calculating atmospheric nucleation rates was also derived from the NPM. Ultimately, NPM provides a simple way to measure and model the extent compounds in a complex mixture enhance SA nucleation rates using a condensation particle counter.

Unveiling the potential and mechanisms of 3,3′-bicarbazole-based quaternary ammonium salts as levelers

It is important to introduce an effective leveler into electroplating bath to meet the desired requirement in the electronic industry. This work explored the impact of larger backbone structures of four 3,3′-bicarbazole quaternary ammonium salts on the performance of promising levelers in light of the ambiguous mechanism of action. For the first time, these four compounds have been functionalized and identified as promising levelers for copper electrodeposition in through holes. Electrochemical measurements, theoretical calculations, and dynamics simulations collectively revealed that among these levelers, BCz-BPD exhibits the tendency of optimal adsorption on the cathode with the strongest inhibition of copper deposition. Chronoamperometry tests were carried out to analyze the copper nucleation model during electroplating. By measuring the electrostatic potential, average local ionization energy, and planarity, the leveling mechanism of BCz-BPD leveler was analyzed. In order to confirm the high through-hole filling and excellent leveling performance of BCz-BPD in actual PCB plating, TP value measurement, SEM, and XRD tests were carried out sequentially. In addition, galvanostatic measurements were performed to study the interaction of BCz-BPD leveler with other kinds of additives.