Reactor Wall Research Articles

Utilization of Cocoa Pod Husk Waste as Fuel for Downdraft Type Gasification Reactor of 960 Liters Capacity in Berau Regency

This experiment aims to investigate the performance characteristics of a downdraft gasification reactor fueled by cocoa pod husk as a technological solution for obtaining alternative renewable energy sources to replace fossil fuels and natural gas. The research was conducted experimentally on a gasification reactor made of SS310 thermal resistant carbon steel material. The reactor has dimensions of 35 centimeter in diameter and 250 centimeter in height. Measurement of gasification zone using 7 units of K-type thermocouples that was installed along the reactor wall. Fuel was feeding continuously at a rate of 4kg/hour. The research was conducted by varying the temperature in oxidation zone, specifically at 900 ºC, 950 ºC, 1000 ºC, 1050 ºC, and 1100 ºC. Data collection was carried out in different temperature variations and processed to determine the performance parameters of the gasification reactor, including gas composition, temperature distribution on the reactor wall, and the lower heating value (LHV) of the syngas production. The results showed the highest temperature distribution of the reactor in the drying zone 205ºC, pyrolysis zone 575ºC and reduction zone 520 ºC that be obtained at the oxidation temperature of 1100 ºC . Meanwhile the optimum value of syngas quality was obtained at the oxidation temperature of 1000 ºC with the composition of flamable syngas CO, H2, and CH4 are 27.08%, 8.53% and 2.41% , with the highest LHV 5206 kJ/m3. In general the increasing of the oxidation temperature lead to a positive contribution to the performance of the gasification reactor using cocoa pod husk waste.

Visualization study of the effects of polycarboxylates on CO2 hydrate generation and interfacial property.

Marine carbon sequestration, with its high potential and low risk of leakage, is an attractive technology for effectively addressing global climate change and reducing greenhouse gas emissions. A current concern about marine sequestration lies in the potential negative effects of the carbon sequestration process on the marine environment. CO2 hydrate sequestration is considered to be one of the most stable method of sequestration, and researchers are actively searching for promoters that facilitate hydrate sequestration and are friendly to the marine environment. Therefore, the development and utilization of environment-friendly promoters are of great significance for marine carbon sequestration by the hydrate method. In this study, two novel kinetic promoters, polycarboxylates (SP-409 and SPC-100), were applied. The changes in kinetic properties of CO2 hydrate generation and gas-liquid interfacial properties were investigated under different promoter types and concentrations, temperatures, and pressures. Visual observation reveals that the formation of hydrate first occurs at the gas-liquid interface and on the reactor wall, then gradually starts to diffuse into the interior of the solution, forming a white cylindrical solid with a hollow interior. After a comprehensive comparison of temperatures, pressures, and concentrations, the SP-409 solution promoted hydrate generation better than the SPC-100 solution, and the optimal promotion concentration was 1000ppm. In addition, there is an exponential relationship between the rate of hydrate formation and interfacial tension (IFT), which means that the rate of hydrate generation can be quickly estimated from the interfacial tension data at a certain temperature and pressure.

Malachite Green Dye Removal in Water by Using Biochar Produced from Pinus patula Pellet Gasification in a Reverse Downdraft Reactor

The efficiency of the elimination of malachite green dye (MG) in water was investigated using biochar (BC) obtained from Pinus patula wood pellets (BC-WP). The biomass was gasified, reaching a temperature of 391.07 °C near the reactor wall. During the adsorption tests, three independent factors were considered: the solution pH, BC concentration, and the BC particle size, which were optimized using different study ranges (4–10, 6–12 g/L, and 150–600 μm, respectively) at 30 min of contact time. The response surface methodology was used through a face-centered central composite design for this purpose. The experimental results were analyzed to develop a quadratic regression model that fitted the experimental data achieved. The highest removal percentage of MG by BC-WP (94.25%) was attained under a solution pH of 10, a BC concentration of 12 g/L, and an average BC particle size of 225 μm. Furthermore, the validated regression model was found to explain 94.72% of the obtained results, demonstrating the ability of BC-WP to remove the target dye. Thus, a new and sustainable alternative to conventional systems for treating dye-polluted water is proposed, utilizing the solid by-product of the thermochemical process, contributing to the circular economy.

Structured catalysts for steam and steam-air conversion of ethanol into synthesis gas: I. Preparation and catalytic properties

Steam reforming and autothermal reforming of ethanol produce synthesis gas suitable for both powering solid oxide fuel cells and serving as a feedstock for chemical industry applications. For these reactions to occur effectively, heat transfer must be controlled. In the case of endothermic steam reforming of ethanol, the problem of heat transfer from the reactor walls to the catalyst bed arises. For thermoneutral autothermal reforming (steam-air conversion) of ethanol, the problem arises of redistributing the heat released in the front part of the catalyst layer as a result of the oxidation of ethanol with oxygen along the catalyst layer to compensate for the endothermic effect of steam reforming of ethanol. To solve these problems, structured catalysts based on heat-conducting substrates—metal meshes, foam metals, and other supports—are well suited. Such catalysts are a complex composite material with a multi-level structure “structured metal substrate-structural oxide component-active oxide-nanoparticles of metals or alloys”, which combines the functions of a heat exchanger, a flow distributor and the catalyst itself. This work presents the results of the preparation of Pt, Rh, Pd, Ru, Ni, and Co-containing structured catalysts supported on a FeCrAl mesh support and the study of their catalytic properties.

A versatile setup for hydrogen isotope permeation studies.

The Testbed for Analysis of Permeation of Atoms in Samples (TAPAS) is an experimental setup for ion-driven permeation studies with a focus on investigating wall materials for nuclear fusion devices. A monoenergetic, mass-filtered high-intensity keV ion beam is focused and directed onto the permeation sample by electrostatic ion optics and decelerated to the desired ion energy by a dedicated set of apertures close to the sample. We were able to obtain ion energies as low as 170 eV/D with a D3+ ion beam with an ion flux density of the order of 1020 D/m2s on a beam-wetted area of ∼33mm2. These conditions avoid sputtering of W targets by the ion beam and are representative of the particle flux and energy spectrum impinging on the first wall of a prospective nuclear fusion power reactor. Permeation samples can be heated up to 1000K in an ultra-high vacuum. The design of the deceleration system, together with a high pumping speed in the loading chamber, ensures a low pressure of recycling hydrogen isotope molecules in front of the sample. In addition to ion-driven permeation, TAPAS provides a limited capability for gas-driven permeation at low pressures up to nearly 1mbar. Permeating hydrogen isotopes are detected with a quadrupole mass spectrometer in the downstream ultra-high vacuum chamber. After a detailed description of the setup and calibration procedures for implanted particle flux, mass spectrometer, and neutral gas pressure, benchmark experiments on recrystallized, 50μm thick tungsten foils are shown, demonstrating that diffusion-limited boundary conditions for permeation were reached.

LIA-QMS method for the quantity analysis of the hydrogen isotopes retention in first-wall components of Globus-M2 tokamak

The technique based on quadrupole mass spectrometry of the material ejected by laser-induced ablation – LIA-QMS is proposed as a tool to measure H/D/T content in carbon co-deposits in the first wall and divertor regions of tokamak reactors. Tungsten tiles exposed in Globus-M2 tokamak were taken for validation experiments. Measurement accuracy was determined by comparison with the results obtained by laser-induced desorption – LID-QMS and conventional thermal desorption spectroscopy (TDS). Total amount of deuterium in hydrocarbon deposits was found to be 2.8 × 1017 D/cm2, when measured by – LIA-QMS, 3.0 × 1017 D/cm2 for LID-QMS and 2.9 × 1017 D/cm2 for TDS. The main uncertainty of D surface concentration are caused by inhomogeneity of the deposit thickness over the sample area or by presence of hydrocarbon species in the released gas.

Polycyclic aromatic hydrocarbons formed during the pyrolysis of dimethoxymethane (DMM). Comparison with other oxygenated additives

The influence of the temperature (1075 – 1475 K) and inlet concentration of fuel (33,333 and 50,000 ppmv) on the formation of the 16 EPA-priority Polycyclic Aromatic Hydrocarbons (PAH) from the pyrolysis of dimethoxymethane (DMM) was analyzed. PAH were detected in different phases (gas phase, adsorbed on soot, and stuck on the reactor walls) and quantified by gas chromatography-mass spectrometry (GC–MS). Additionally, the toxicity of the PAH samples, expressed as B[a]P-eq, was analyzed in all experiments. A comparison with the results obtained from the pyrolysis of other oxygenated compounds was also performed and similar behaviors were observed. The main results showed that, at low temperatures, the highest concentrations of PAH were found in the gas phase, while at high temperatures were found on soot. For both inlet concentrations of DMM, the light PAH, such as naphthalene and acenaphthylene, were found in major concentrations, in all phases and temperatures. The heavy PAH, such as fluoranthene and pyrene, increased its concentration on soot at highest temperatures. The highest formation of soot was obtained at 1475 K and follows the trend: 2,5DMF < tert-butanol < 2MF < 2butanol < iso-butanol < 1-butanol < ethanol < DMC < DMM. The highest formation of PAH was at 1275 K with the tendency: tert-butanol < 2-butanol < 1-butanol < 2,5DMF < 2MF < iso-butanol < ethanol < DMC < DMM. The highest B[a]P-eq value was found in the pyrolysis of 2,5DMF, and the lowest in the pyrolysis of DMM.

The Effect of Y Addition on Oxidation Resistance of Bulk W-Cr Alloys.

The self-passivating tungsten-based alloy W-11.4Cr-0.6Y (in wt.%) is a potential plasma-facing material for the first wall of future fusion reactors, which has been shown to suppress oxidation of tungsten and withstand temperatures of up to 1000 °C. In this study, the effect of Y addition on the microstructure and oxidation behavior of W-11.4Cr alloy at 1000 °C is analyzed by comparing it with W-11.4Cr-0.6Y, both prepared using identical synthesis routes. While the binary W-Cr alloy already exhibits improved oxidation resistance over pure W due to the formation of an outer Cr2WO6 layer, it still shows a tendency for spallation and, hence, is not protective. A continuous passivating chromia layer is only obtained with the addition of Y, and we demonstrate that it results in a 50-fold decrease in the oxide growth rate and eliminates the preferred growth of the oxide at edges seen in the binary alloy. Although a porous, complex oxide scale containing mixed oxide layers and WO3 is formed in both cases, the addition of Y results in lower porosity, which makes the oxide scale more adherent.

Quantitative Modelling of Residual Molecular Contamination in Low-Pressure Processing Environments

During the fabrication, micro-chips circuits are very sensitive to all kinds of contamination present in the environments fluid in contact with the wafers.A previous study [1] describes the issue of wafer molecular surface contamination as a result of exposure to clean room air. If needed clean room air can be purified to the desired level using appropriate chemical filters.A lot of state-of-the-art processing steps occur in low pressure environments, or so called vacuum cluster tools comprising a wafer handler equipped with different chambers. All of these chambers have a finite residual base pressure (typically on the order of 1 Pa).A major part of the residual gas may consist of rather harmless inert gas such as N2 or Ar. A fraction of the background ambient may consist of uncontrolled residual gas that could originate from different sources (e.g. desorption from reactor walls or wafer backside, back diffusion from vacuum pumps, )Such uncontrolled molecules could adhere to the wafer surface and leave some surface contaminants that can negatively impact the subsequent process step (e.g.).The current study quantitatively describes this issue.In a gas ambient the ideal gas law provides eq.1Where: C i is the volume concentration of impurity ih i : the fraction of the number of impurity molecules, i, over the total number of all molecules p is the total pressure of all residual gas. In the current study we assume the sticking coefficient to be 1. This is a safe worst-case scenario and also the scenario for the impurity molecules that stick the best and are thus most detrimental and of major concern.The thermal contamination build-up on the surface, si, is determined by the mean thermal velocity. The surface concentration of contaminant i building up on the surface, normalized to its volume concentration in the gas phase, is given by the average thermal bombardment velocity on the surface (= arrival velocity) multiplied with the exposure time. The thermal velocity is roughly independent of pressure and is primarily determined by the temperature and the mass of the molecules: for room temperature air it is as high as 500 m/s. this implies that molecules travel very fast. The normalized concentration is then given by eq.2This normalized concentration has the dimension of length (expressed in units of m).One can compare this length to the characteristic space available in the vacuum chamber perpendicular to the wafer surface. For most systems this is expected to be on the order of 1 to 10 cm.3 numerical examples are provided in Table I.These examples show that significant amounts of contamination (1e11 to 1e13 at/cm2) can readily build-up on the surface.As can be seen, on Figure 1 the normalized deposition reaches already 10 cm in as little 1 msec implying that all available contamination gas inside the reactor would have deposited on the wafer surface in only 1 msec.In real cases there is typically a continuous supply of impurity molecules to the gas phase (from desorption from other surfaces etc..) with the surface with the highest sticking coefficient ultimately collecting the most contaminants.Figure 1 shows the surface concentration of surface contamination normalized to the impurity volume concentration in the ambient as a function of time.References P.W. Mertens, ECSTransactions 92, p.237, (2019); Figure 1

Two-dimensional P1 approximation (P1-2D) for the Description of the Radiant Field on Cylindrical Solar Photocatalytic Reactors

The local volumetric rate of photon absorption (LVRPA) was formulated by solving the radiative transfer equation (RTE) in polar coordinates with the P1 approximation approach (P1-2D) for the description of the radiant field in cylindrical solar photocatalytic reactors. A general expression of the LVRPA was formulated that can be employed on cylindrical photocatalytic reactors with an incident radiation constant along the reactor length. CPC and tubular photocatalytic reactors were used as reactor models and Lambert's cosine law (irradiance) was considered when using the boundary conditions. Simulations were carried out using the commercial TiO2-P25, its optical properties taken from the literature. The LVRPA was found to decrease exponentially from the reactor wall to its center. literature rate of photon absorption per unit of reactor length (VRPA/H) increased exponentially with the catalyst loading until a value where no significant increase was observed and was found to increase with reactor radius, information that agrees with the literature. The optimum catalyst loading with the CPC reactor was about 0.364 g/L with a reactor radius equal to 1.65 cm similar to that found in the literature when using the six-flux model in two dimensions (SFM-2D). The apparent optical thickness τ_App1 newly formulated with the P1 approximation was introduced for optimization purposes and was found more reliable than the optical thickness τ. This parameter not only removes the dependence of the optimum catalyst loading on the reactor's radius but also its dependence on catalyst albedo. τ_App1 was found about 9.73 and 14.6 for CPC and tubular reactors respectively and provides the optimum catalyst loading and the reactor radius that optimize the radiation absorption inside both reactors.

Study of spectral features and depth distributions of boron layers on tungsten substrates by ps-LIBS in a vacuum environment

Boronization is used in present-devices as wall condition technique due to its effectiveness in reducing oxygen and other impurities in the vessel as well as improving plasma performance. The technique is also currently under consideration as wall conditioning method for the proposed full-tungsten (W) wall of the International Thermonuclear Experimental Reactor (ITER). However, the impact of the deposited Boron (B) layer thickness, and its homogeneity after the boronization process is uncertain as well as knowledge about the layer lifetime and improved conditions. In this study, an approach of the picosecond-laser-induced breakdown spectroscopy (ps-LIBS) is investigated to analyze the depth distribution of B-films on W-substrates by using three optical spectrometers in a vacuum environment. The depth distribution of two types of B-films on W-substrates with the thicknesses of 130 nm and 260 nm were sequentially measured under different laser spot sizes (varying the laser fluence). The B-films on the W-substrates were made by magnetron sputtering to simulate the thin B layers during the boronization. The measured average ablation rate of ps-LIBS shows a notable decrease with increasing laser spot size. Additionally, the spectral lines of B and W exhibit distinct intensity distributions under different spot sizes due to the different excitation thresholds of the B-films and the W-substrates. The interface between B-films and W-substrates, as well as the thickness of the B-films, were determined using the normalized intensity and intensity ratio method, respectively. The results from ps-LIBS measurements regarding the depth are in good agreement with those obtained through the Focused Ion Beam combined with Scanning Electron Microscopy (FIB-SEM) and Energy Dispersive X-ray Spectroscopy (EDS). These initial findings verify the feasibility to characterize the thickness and uniformity of thin B films in the order of 100 nm and below on W-substrates using ps-LIBS.

Enhanced Catalytic Probe Design for Mapping Radical Density in the Plasma Afterglow.

The electrification of chemical processes using plasma generates an increasing demand for sensors, monitoring concentrations of plasma-activated species such as radicals. Radical probes are a low-cost in situ method for spatially resolved quantification of the radical density in a plasma afterglow using the heat from the exothermal recombination of radicals on a catalytic surface. However, distinguishing recombination heating from other heat fluxes in the system is challenging. In this study, we present a heat flux analysis based on probe measurements inside the reactor, with simultaneous IR imaging monitoring of the temperature of the reactor wall. The impact of radiation heat on a single thermocouple as well as the advantage of a dual thermocouple setup (using a catalytic unit together with a reference thermocouple) is shown. We add a heat sink with a monitored temperature to the dual thermocouple setup, allowing the determination of conductive and radiative heat fluxes. The heat sink gives more information on the measurement and reduces ambiguities in the evaluation used by others. The probe was tested by mapping N atom densities throughout the plasma afterglow of our reactor, enabling evaluation of the recombination kinetics of the radicals in the gas phase. Three-body recombination was shown to be the main pathway of recombination, with a recombination rate of krec = (2.0 ± 0.9)·10-44 m6/s, which is in line with the known literature findings, demonstrating that the measured species are N radicals and the probe did not influence the plasma or recombination reactions in the afterglow.

Heat transport regimes in structured reactors: CFD analysis and influence of reactor diameter and length

Temperature control in catalytic reactors is critical to ensure high yields and a stable process for highly exothermic reactions. To better understand the processes within structured reactors, it has already been shown that heat source based Computational Fluid Dynamics (CFD) is a simple and valid way to mimic the heat intake of catalytic surface reactions and to capture general heat transport properties. In case of structured reactors, the heat transport is highly dominated by thermal conduction. Building on these achievements, this work systematically investigates the influence of the reactor diameter and length on heat transfer and temperature distribution in a Periodic Open Cell Structure (POCS) reactor. It is found that the typically high percentage of thermal conductivity is reduced by up to 50 % if the reactor diameter changes from 20 mm to 50 mm. Furthermore, heat transport regimes are introduced along the reactor axis separating reactor parts with different predominant heat transfer mechanisms. This provides a fundamental comprehension of heat transfer in structured reactors and highlights the necessity to consider a sufficient reactor length. Lastly, the influence of thermal radiation is isolated. In addition to lowering the temperature increase significantly (from 1,300 K to 500 K in a specific case), it can also change the share of heat conduction through the solid by modifying the temperature distribution in the reactor. Although the heat source simulations are a simplification, they are ideal to understand the reactor systems from a heat transport perspective.

Theoretical study of particle and energy balance equations in locally bounded plasmas

In this study, new particle and energy balance equations have been developed to predict the electron temperature and density in locally bounded plasmas. Classical particle and energy balance equations assume that all plasma within a reactor is completely confined only by the reactor walls. However, in industrial plasma reactors for semiconductor manufacturing, the plasma is partially confined by internal reactor structures. We predict the effect of the open boundary area ( ) and ion escape velocity ( ) on electron temperature and density by developing new particle and energy balance equations. Theoretically, we found a low ion escape velocity ( / ) and high open boundary area ( ) to result in an approximately 38% increase in electron density and an 8% decrease in electron temperature compared to values in a fully bounded reactor. Additionally, we suggest that the velocity of ions passing through the open boundary should exceed under the condition .

Modeling Freeze‐Lining Formation: A Case Study in the Slag Fuming Process

Slag fuming (SF) is a metallurgical process designed to recycle Zn‐containing slags derived from various industrial residues. To protect the reactor from corrosive molten slag, a deliberate as‐solidified slag layer, known as a freeze lining (FL), is formed on the reactor walls using intense water‐cooled jackets. In this article, a computational‐fluid‐dynamics‐based model capable of simulating FL formation in a SF furnace is presented. To capture the complex multiphase flow dynamics, heat transfer, and FL formation during SF, a volume‐of‐fluid model is coupled with a mixture continuum solidification model. Three phases are considered: gas, liquid bulk slag, and solid slag (FL). Moreover, two types of FL are distinguished: one that solidifies on the reactor wall in the bulk slag region and another that solidifies on the reactor wall in the freeboard region owing to slag splashing. Comparisons between calculated FL thickness and heat fluxes and corresponding industrial data demonstrate satisfactory agreement. In this outcome, the robustness of the model is underscored and confidence in its accuracy is instilled. In the simulation results, valuable insights are provided into the evolution of the fuming process, particularly regarding the slag bath temperature, slag splashing dynamics, FL formation, local heat fluxes through the reactor wall, and global net energy balance.

Experimental investigation on product and temperature distribution in a continuous flow packed-bed reactor for dodecahydro-N-ethylcarbazole dehydrogenation

The dehydrogenation of dodecahydro-N-ethylcarbazole (H12-NEC) generates enormous gas accompanied by intense heat absorption, affecting heat and mass transfer in porous catalysts. A packed-bed reactor equipped with a temperature measurement device was designed to investigate the continuous flow dehydrogenation of H12-NEC. The effects of weight hourly space velocity (WHSV), reaction temperature, catalyst particle size, and pressure were evaluated. The results reveal that the volume flow rate of hydrogen will increase with the increase of WHSV. And the reduction of gas–liquid ratio and catalyst particle size facilitates heat transfer causing a more uniform axial temperature distribution within the reactor. As the temperature rises, the hydrogen yield increases along with more by-products. 456 K and 2 mm of catalyst particle size are determined to be the optimal reaction conditions in the study, achieving the hydrogen production rate of 9.61 molH2·gPd-1·h-1. With pressure increasing, the hydrogen yield gradually decreases, but the decreased evaporation of H12-NEC results in a smaller temperature difference between the reactor and heating wall. A comparison with the thermodynamic equilibrium model reveals that the effect of pressure on chemical equilibrium may be more significant than the temperature.

Seeded-growth synthesis of 20–60 nm monodisperse citrate-capped gold nanoparticles in a millifluidic reactor

Gold nanoparticles have diverse applications, requiring advancements in their synthesis that facilitate scale up, size control and reproducibility. Using a seeded-growth method in a 20 mL two-phase flow reactor (ID 2.4 mm) at 35 °C, highly monodisperse gold nanoparticles of any chosen size from 20 to 60 nm were produced. Heptane was utilised as the segmenting fluid to transport the aqueous reagent-containing droplets through a coiled PTFE reactor preventing their interaction with the reactor walls and thus reactor fouling. Gold seeds ~ 12 nm were produced via a passivated Turkevich synthesis by reduction of high pH Au(III) solution using citric acid as reducing agent. For the seeded-growth in flow, the reagents utilised were the seed solution (diluted accordingly), a stabilising Tris base solution, tetrachloroauric(III) acid trihydrate and hydrogen peroxide as reducing agent. Seeded-growth synthesis was also performed using as seeds commercial 10 nm gold nanoparticles, with excellent Coefficient of Variation (CoV) and Optical Density (OD) of the grown particles (CoV < 8% and OD ≥ 1) demonstrating that they are monodisperse and have high concentration. The synthesis was able to produce 18 mL/h of grown nanoparticles solution at 2.2–2.8 mg Au/h without any divergence in the quality of the produced particles for over eight hours.

Dependence of Heat Removal Rate of Pebble-Based Rods on Inter-Pebble Matrix Fill Fraction

Carbon pebble rods are a promising candidate for use in high heat flux regions of magnetic fusion energy reactor walls. Under high (10 to 50 MW/m2) heat loads, carbon pebble rods release hot pebbles from the exposed surface, carrying away heat as the pebble rod surface recedes. In this work, we show that the surface recession rate during heating can be adjusted by changing the mechanical strength of the extruded rods, modifying the heat removal rate; this is accomplished here by varying the fill fraction of the inter-pebble matrix. A three-dimensional finite element model is presented that captures many experimental observations, including the sphere temperature and the surface recession rate. The model predicts that pebble release is caused by thermally driven crack propagation through the matrix and that the matrix strength against breaking is the single most important material parameter setting the pebble release rate; this prediction is supported by experimental results.

The interplay of shape and catalyst distribution in the yield of compressible flow microreactors.

We develop a semi-analytical model for transport in structured catalytic microreactors, where both reactant and product are compressible fluids. Using lubrication and Fick-Jacobs approximations, we reduce the three-dimensional governing equations to an effective one-dimensional set of equations. Our model captures the effect of compressibility, corrugations in the shape of the reactor, and an inhomogeneous catalytic coating of the reactor walls. We show that in the weakly compressible limit (e.g., liquid-phase reactors), the distribution of catalyst does not influence the reactor yield, which we verify experimentally. Beyond this limit, we show that introducing inhomogeneities in the catalytic coating and corrugations to the reactor walls can improve the yield.

Influence of Cobalt and Cobalt–Manganese Oxide Coating Thickness Deposited by DLI-MOCVD as a Barrier Against Cr Diffusion for SOC Interconnect

The influence of cobalt and cobalt–manganese oxide coating thickness on its ability to be a good diffusion barrier against Cr outward diffusion was investigated for stainless steel interconnects (AISI 441) of a solid oxide cell (SOC). The coatings were all synthesized using a DLI-MOCVD (Direct Liquid Injection-Metal Oxide Chemical Vapor Deposition) hot wall reactor. The study shows that a minimum cobalt oxide thickness of 300 nm was needed to be a good diffusion barrier against Cr for the 500-h exposure test. This observation was linked to the Mn concentration reached in the cobalt spinel during exposure. Indeed, during exposure at high temperature, Mn diffused from the substrate into the cobalt coating and transformed cobalt spinel into Co-Mn spinel. Whereas pure cobalt spinel was a good Cr diffusion barrier, cobalt-manganese spinel, Co3-xMnxO4, was not when x > 2. The thickness of the cobalt coatings must be chosen so that the Mn quantity coming into it from diffusion from the substrate does not degrade the protectiveness of the coating.