This study focuses on implementation of a data-based leak detection method in a heat exchanger in a petroleum refinery. We have studied on the two real leakage cases in a heat exchanger in Izmit TUPRAS Refinery. Leaks are one of the major problems that occur in operations. The autoencoder (AE) method is implemented for leak detection. Reconstruction error is used as the leak indicator. In case of leakage, the reconstruction value is expected to increase. For both cases examined, the reconstruction error is found to be around 1-5 under normal operating conditions. On the other hand, reconstruction error is observed to change between 10 and 60 under the conditions with leakage. Besides, the AE is able to indicate the start of one leakage case before the process engineers noticed it.

Pt/Al2O3 catalysts prepared via supercritical deposition (SCD), with supercritical CO2, wet impregnation (WI) methods and a selected benchmark catalyst, were evaluated for the dehydrogenation of perhydro-dibenzyltoluene (H18-DBT) at 300 °C in a batch reactor. After ten dehydrogenation runs, the average performance of the catalyst prepared using SCD was the highest compared to the benchmark and WI-prepared catalysts. The pre-treatment of the catalysts with the product (dibenzyltoluene) indicated that the deactivation observed is mainly due to the adsorbed H0-DBT blocking the active sites for the reactant (H18-DBT). Furthermore, the SCD method afforded a catalyst with a higher dispersion of smaller sized Pt particles, thus improving catalytic performance towards the dehydrogenation of H18-DBT. The particle diameters of the SCD- and WI-prepared catalysts varied in the ranges of 0.6–2.2 nm and 0.8–3.4 nm and had average particle sizes of 1.1 nm and 1.7 nm, respectively. Energy dispersive X-ray spectroscopy analysis of the catalysts after ten dehydrogenation runs revealed the presence of carbon. In this study, improved catalyst performance led to the production of more liquid-based by-products and carbon material compared to catalysts with low catalytic performance.

Chemical absorption of CO2 into aqueous amine solutions using a nonstirred bubble column was experimentally investigated. The performance of CO2 absorption of four different primary and secondary amines including monoethanolamine (MEA), piperazine (PZ), 2-piperidineethanol (2PE), and homopiperazine (HPZ) were compared. The effects of initial concentration of amine, the inlet mole fraction of CO2, and solution temperature on the rate of CO2 absorption and CO2 loading (mol CO2/mol amine) were studied in the range of 0.02-1 M, 0.10-0.15, and 25-40 °C, respectively. The effect of the presence of copper ions in the amine solution on CO2 loading was also studied. By comparison of the breakthrough curves of the amines at different operational conditions, it was revealed that the shortest and longest time for the appearance of the breakthrough point was observed for MEA and HPZ solutions, respectively. CO2 loading of MEA, 2PE, PZ, and HPZ aqueous solutions at 25 °C, 0.2 M of initial concentration of amine, and 0.15 of inlet mole fraction of CO2 were 1.06, 1.14, 1.13, and 1.18 mol CO2/mol amine, respectively. By decreasing the inlet mole fraction of CO2 from 0.15 to 0.10, CO2 loading slightly decreased. As the initial concentration of amine and temperature decreased, CO2 loading increased. Also, the presence of copper ions in the absorbent solution resulted in a decrease in the CO2 loading of MEA and HPZ aqueous solutions. In case of PZ and 2PE amines, adding copper ions led to precipitation even at low copper ion concentrations.

Supercritical fluid reactive deposition (SFRD) is a promising process intensification technique for synthesis of a wide variety of nanostructured materials. The enhanced mass transfer characteristics of supercritical fluids (SCFs) coupled with high solubilities of reducing gases in SCFs provide many advantages related to equipment size and time minimization over conventional techniques. Among SCFs, the emphasis has been placed on supercritical CO2 (scCO2) which is non-toxic, cheap and leaves no residue on the treated medium. Moreover, in SFRD, multiple processes such as dissolution, adsorption, reaction, and purification are combined in a single piece of equipment which is an excellent example of process integration for process intensification. In this review, the fundamental thermodynamic and kinetic aspects of the technology are described in detail. The studies in the literature on synthesis of a wide variety of nanostructured materials including supported nanoparticles, films, and ion-exchanged zeolites by SFRD are reviewed and summarized. The applications of these materials as catalysts and sensors are described. The review hopes to lead to further studies on further development of this technology for a wide variety of applications.

Supercritical fluid-based technologies are increasingly being used to develop novel functional nanostructured materials or improve the properties of existing ones. Among these, supercritical deposition (SCD) is an emerging technique to incorporate metals on supports. It has been used to deposit a wide variety of single or multi-metallic morphologies such as highly dispersed species, nanoparticles, nanorods and conformal films on high surface area supports, polymers and crystalline substrates. SCD is also attracting increasing attention for preparation of micro or nano-architectured functional materials in a highly controllable manner for electrochemical energy conversion and storage systems. Increasing number of studies in the literature demonstrates that materials synthesized using SCD are comparable or superior in performance as compared to their conventional counterparts. In this review, an overview of the fundamentals of the SCD technique is presented. Properties of a wide variety of nanostructured functional materials such as supported nanoparticles and films prepared using SCD for electrochemical applications are summarized. The electrochemical performance of these materials in electrochemical tests and also in fuel cells, electrolyzers and Li-ion batteries are also presented.

Spherical calcium alginate gel particles were synthesized by dripping method. The effects of temperature, pressure, particle size and CO2 flow rate on kinetics of supercritical drying of alginate gel particles in a packed bed were investigated. Increase in CO2 flow rate, increase in temperature and decrease in particle size increased the drying rate and decreased the drying time. A mathematical model based on (i) the diffusion of the solvent inside the pores of gel particles, (ii) external mass transfer of the solvent from the surface of the gel particles into the flowing fluid stream, and (iii) convection and axial dispersion of the solvent in the flowing fluid stream was developed. A correlation for predicting external mass transfer coefficients for supercritical drying of alcogel particles was developed by fitting the model to experimental data. A good agreement between the experimental data and model results was achieved using the developed correlation.

A series of spherical ionotropic alginate gel particles with different diameters ranging from 2.8mm to 5.0mm and porosities ranging from 0.899 to 0.976 were prepared by dripping a Na-alginate solution into a solution of salts of divalent cations (Ca2+, Mn2+, Ni2+, Co2+, Cu2+ and Zn2+). After solvent exchange with ethanol, kinetics of supercritical drying of these ionotropic alginate gel particles in a packed bed was investigated at 308-338 K and 100-120 bar. Experimental data were compared with predictions of a model which considers diffusive transport inside the pores and convection in the flowing fluid stream. The model predicted drying profiles by taking into account only the changes in porosity and diameter of the gel particles. A convective mass transfer coefficient correlation that was originally developed for supercritical drying of Ca-alginate gel particles was found to be suitable for M-alginate gel particles. (C) 2019 Elsevier B.V. All rights reserved.

Aerogels are nanoporous materials with unique properties such as high porosities, high surface areas and high pore volumes that are tunable by manipulation of synthesis conditions. Recently, aerogels in the form of particles are attracting increased attention for development of a wide variety of products for drug delivery, sensing, adsorption and catalysis. Supercritical drying is the most important step in production of aerogel particles. Therefore, kinetics of supercritical drying of gel particles is important for design, scale-up and optimization of industrial scale aerogel production facilities. In this study, we investigated supercritical drying of alginate gel particles in a packed bed. Spherical calcium alginate hydrogel particles with an average diameter of 0.4 cm were prepared by dripping a 1.5 wt% aqueous alginate solution into a 0.2 M aqueous CaCl2 solution. The hydrogel particles were subjected to a stepwise solvent exchange procedure with ethanol before supercritical drying. The effects of temperature, pressure and CO2 flow rate on the drying kinetics were investigated. A large fraction of the ethanol inside the pores was extracted in a very short time. Results indicate that although temperature affected the exit ethanol concentration profiles, drying time was not affected considerably. The CO2 flow rate had a significant effect on drying times. A drying model which takes into account diffusion inside the pores, external mass transfer from the surface of the gel particles into the flowing CO2 stream and convection and axial dispersion in the fluid phase was developed.

ABSTRACT Metallo‐organic complexes with nickel as the metal center have been shown to exhibit high electrical conductivities warranting investigation of their thermoelectric potential. A review of metallo‐organic n‐type thermoelectrics is presented with a focus on nickel‐sulfur coordination compounds. Herein, we also investigate the extent of oxidation on thermoelectric properties of poly(Ni‐1,1,2,2‐ethenetetrathiolate) (Ni‐ETT) based materials. Elemental analysis and X‐ray photoelectron spectroscopy are used to characterize samples with different air exposure times, leading to differing levels of oxidation. When blended with an inert polymer matrix, the sample exposed to air for 30 min resulted in an eight times enhancement in electrical conductivity compared to the sample exposed to air for 24 h. Furthermore, the elemental composition of the 30 min sample fit the empirical formula A x (MC 2 S 4 ) postulated in literature, while the 24 h sample does not, which we attribute to decomposition during the oxidation process and presence of disulfides. The Seebeck coefficient remains largely unchanged as a function of oxidation time, indicating that this may be a viable technique to decouple Seebeck and electrical conductivity for high‐performance organic thermoelectric materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44402.

Polymers can be used as temporary place holders in the fabrication of embedded air gaps in a variety of electronic devices. Embedded air cavities can provide the lowest dielectric constant and loss for electrical insulation, mechanical compliance in devices where low-force deformations are desirable, and can temporarily protect movable parts during processing. Several families of polymers have been used as sacrificial, templating polymers including polycarbonates, polynorbornenes (PNBs), and polyaldehydes. The families can be distinguished by chemical structure and decomposition temperature. The decomposition temperature ranges from over 400 °C to below room temperature in the case of low ceiling temperature polymers. Overcoat materials include silicon dioxide, polyimides, epoxy, and bis-benzocyclobutene (BCB). The methods of air-gap fabrication are discussed. Finally, the use of photoactive compounds in the patterning of the sacrificial polymers is reviewed.

This study aims at investigating a polymer-based air-gap creation method for the packaging of microelectromechanical systems (MEMS), and exploring the chemical composition of the polymer residue on the final package. Polymer-based air-gap formation utilizes thermal decomposition of a sacrificial polymer, poly(propylene carbonate) (PPC), encapsulated within an overcoat polymer. BCB (Cyclotene 4026-46) was used as the overcoat material because decomposition products of sacrificial polymer are able to permeate through it, leaving an embedded air-gap structure around the MEMS device. Size-compatibility and cleanliness of MEMS devices are important attributes of the polymer-based air-gap MEMS packaging approach. This study provides a framework for size-compatible and clean air-gap formation by selecting the type of PPC, optimizing thermal treatment steps, identifying air-gap formation options, assessing air-gap formation performance, and analyzing the chemical composition of the residue. The air-gap formation processes using photosensitive PPC films had at least twice the residue compared to processes using nonphotosensitive PPC films. The major contribution to the residue in photosensitive PPC films was from the photoacid generator (PAG), which was used to catalyze the thermal decomposition of the PPC. BCB is compatible with PPC, and provides mechanical stability during creation of the air-gaps. The polymer-based air-gaps provide a monolithic, low-cost, integrated circuit compatible MEMS packaging option.

Frequency and time domain models are developed for backplane (BP), printed circuit board (PCB), and silicon interposer (SI) links using six-port transfer matrices (ABCD matrices) for bumps, vias and connectors, and coupled multiconductor transmission lines for traces. The six-port transfer matrix approach enables easy computation of the transfer function, as well as near-end and far-end crosstalk. The intersymbol interference is accounted for by computing the pulse response for the worst case bit pattern. Furthermore, the models developed here are used to optimize the data-rate and trace width for each of the links, so that the aggregate bandwidth obtained per joule of energy supplied to the link is maximized. The modeling and optimization approach developed here serves as a good platform to compare the air-gap interconnects against BP, PCB, and SI interconnects on lossy dielectrics. It is shown that air-gap interconnects can provide an aggregate bandwidth improvement of 3x-4x for BP links at a comparable energy per bit, and a 5x-9x improvement in aggregate bandwidth of PCB links at the expense of 20% higher energy per bit. For SI links, airgap interconnects are shown to provide a 2x-3x improvement in aggregate bandwidth and a 1x-1.5x improvement in energy per bit.

The improvements in microelectromechanical systems (MEMS) have been traditionally focused more on the functionality and sensitivity of devices. However, packaging of MEMS devices has become a bottleneck mainly due to a wide range of device dimensions and packages being device-specific. Even though MEMS packaging sector is estimated to grow 2x faster than integrated circuit (IC) packaging sector, MEMS packaging is still one of the least explored components of MEMS technology compromising up to 20-40% of the total material and assembly cost [1, 2, 3]. One essential concern is the cleanliness of surface of MEMS devices after packaging, since the contaminants might interfere with the device performance and reliability. In order to address these issues, we pursue sacrificial polymer-based airgap MEMS packaging as a low-cost, clean, IC-compatible, high volume, semi-hermetic, wafer-level packaging solution. The intention is to stabilize and secure the movable MEMS components inside a protective envelope so that the MEMS chip can then be treated like an integrated circuit (IC) and enjoy the benefits of low-cost, high-volume IC packaging, such as lead-frame, or plastic overmolding packaging. The airgap creation process uses complete thermal decomposition of a sacrificial polymer, poly(propylene carbonate) (PPC), encapsulated with overcoat materials, such as BCB (Cyclotene) and/or epoxy-molding compound (EMC), and permeation out of PPC decomposition products through the overcoat materials. To this end, we have previously demonstrated a minimal decrease in resonant frequency (<0.1%) and a small change in the quality factor (<5.2%) in airgap packaged MEMS resonators using PPC with BCB overcoat (i.e. no EMC overmolding) [4]. In this study, in order to minimize the material and processing cost and to simplify the previously developed packaging process, we will use a thin layer of patterned BCB only for patterning non-photosensitive PPC with O 2 plasma, not for the overcoat. MEMS resonators with patterned PPC (and BCB) will be wire-bonded on a lead-frame package, and finally EMC overmolding will be done during which the decomposition of PPC and the curing of EMC and BCB will be achieved simultaneously, i.e. “in-situ airgap creation”. Apart from that, PPC will be subjected to a purification procedure by which lower decomposition temperatures (T d ) were recently obtained in our group compared to unpurified PPC (T d difference about 20°C). After obtaining the complete airgap packaged MEMS resonators, an aging study will be performed in order to determine the change in resonant spectra over time. References 1. MEMS Packaging Market and Technology Trends Report, Yole Développement, 2012. 2. M. Gaitan, MEMS Technology Roadmapping, Nano-Tec Workshop 3, 31 May 2012. 3. R.H. Grace, M. A. Maher, “MEMS: Think outside the chip... at the package level”, Hearst Electronic Products 2010, http://www.electronicproducts.com/Packaging_and_Hardware/Prototyping_Tools_Equipment_Services/MEMS_Think_outside_the_chip_at_the_package_level.aspx 4. E. Uzunlar, Paul A. Kohl, “Low-cost MEMS Packaging using Polymer-based Air-gaps”, 225 th Electrochemical Society (ECS) Meeting, Orlando, FL, May 11 th – May 15 th 2014.

In this study, we are pursuing an ultra low-loss interconnect pathway for 3D chip-chip connectivity, incorporating air-clad planar interconnects, air-clad TSVs, and gradual vertical-horizontal transitions. The motivation is to create an air-gap technology that offers the lowest possible effective k-value and near zero loss tangent minimizing the dielectric loss. The design and modeling of air-gap interconnection is presented. The fabrication challenges in air-clad interconnect lines are discussed. A monolithic inverted air-gap horizontal transmission line structure is proposed as a means for further decreasing the dielectric loss. Extension of air-clad TSV technology for optical transmission is briefly discussed.

Electroless copper deposition was investigated on epoxy laminate substrates (Isola 185HR) using a silver-based catalyst, and a non-roughening surface treatment method based on sulfuric acid. The current challenges in electroless copper deposition include (i) high cost of Pd-based catalysts, (ii) deterioration of electrical performance of deposited metal at high frequency due to electron scattering at the roughened surface, and (iii) limited adhesion strength of electroless layers to substrates. We investigated an electroless copper deposition procedure composed of a H2SO4 surface pretreatment, two-step Sn/Ag nano-colloidal catalyst seeding, and immersion in a traditional formaldehyde-containing electroless copper bath. The H2SO4 pretreatment activated the epoxy surface for electroless deposition. Other strong acids did not lead to deposition. The H2SO4 treatment cleaned the substrate and provided the adhesion of the catalyst and electroless copper without increasing the surface roughness. XPS results showed a decrease in the carbonyl groups (C=O), and acid/ester functionalities (O-C=O) at the surface. Adsorbed sulfate on the substrate from the H2SO4 treatment led to Sn(II) sensitization. The tin-silver activation step resulted in Sn(IV) and Ag(0) products in the form of a Sn/Ag nano-colloidal catalyst. The Sn/Ag colloid acted as a catalyst for electroless copper deposition on the epoxy laminate substrates. (C) 2013 The Electrochemical Society. All rights reserved.

The frequency response of ferromagnetic nickel microcantilevers with lengths ranging between 200 mu m and 400 mu m immersed in gaseous, liquid and supercritical carbon dioxide (CO2) was investigated. The resonant frequency and the quality factor of the cantilever oscillations in CO2 were measured for each cantilever length in the temperature range between 298 K and 323 K and the pressure range between 0.1 MPa and 20.7 MPa. At a constant temperature, both the resonant frequency and the quality factor were found to decrease with increasing pressure as a result of the increasing CO2 density and viscosity. Very good agreement was found between the measured cantilever resonant frequencies and predictions of a model based on simplified hydrodynamic function of a cantilever oscillating harmonically in a viscous fluid valid for Reynolds numbers in the range of [1;1000] (average deviation of 2.40%). At high pressures of CO2, the experimental Q-factors agreed well with the predicted ones. At low CO2 pressures, additional internal mechanisms of the cantilever oscillation damping caused lowering of the measured Q-factor with respect to the hydrodynamic model predictions. (C) 2013 Elsevier B.V. All rights reserved.

The thermal and photolytic decomposition of poly(propylene carbonate) (PPC) in the presence of a photoacid generator (PAG) was studied. The mechanism of previously observed shifts in the decomposition temperature of PPC was investigated. The decomposition temperature of PPC can be altered when PPC/PAG films contact copper metal. X-ray photoelectron spectroscopy (XPS) analysis showed that a small amount Cu(I) was incorporated into the PPC/PAG film causing the increased stability and the Cu(I) concentration was similar to that of the PAG. PPC/PAG temperature stability was studied for a number of iodonium and sulfonium-based PAGs. Every iodonium-based PAG showed a PPC decomposition temperature shift and no sulfonium-based PAG showed the thermal stability effect. It appears that Cu(I) interacts with iodonium in the cation of the PAG causing a change in the acid creation mechanism of the PAG.

In this study, the electroless deposition of copper and silver was investigated on epoxy and silicon dioxide-based substrates. A cost-efficient, Sn/Ag catalyst was investigated as a replacement for the Sn/Pd catalyst currently used in board technology. The surface of the epoxy based polyhedral oligomeric silsesquioxane (POSS) films was modified by plasma and chemical etching for electroless activation without the creation of a roughened surface. The electroless copper deposited on the modified POSS surface exhibited excellent adhesion when annealed at 180 degrees C in nitrogen for 90 min or at room temperature for 24 hr. Electroless copper deposition was also demonstrated on oxidized silicon wafers for through silicon via sidewall deposition.

In this paper we present the design and fabrication of air-clad planar transmission lines and TSVs that can be used as horizontal and vertical chip-chip interconnects. Performance improvement by using heterogeneous air-clad dielectric is presented for these two types of interconnect structures that establishes the basic motivation for fabricating these structures. The design data is verified by performing simulation using 3D full-wave solver HFSS. We outline the process flow for air-clad transmission lines and TSVs in detail. Several challenges in the fabrication of air-clad structures are also discussed.