Initial Electrical Resistance Research Articles

A practical analysis to predict sample overheating in flash experiments using the current ramp methodology

AbstractThis work presents a straightforward strategy for achieving specific overheating during flash experiments by adjusting the initial electrical parameters. To do that, an extensive experimental analysis was performed to evaluate the temperature evolution of dense ZnO specimens during controlled‐current ramping at different furnace temperatures, which in turn modified the initial electrical resistance of the sample. A detailed electrical explanation of controlled‐current ramp flash processes is provided and, for the first time, a practical equivalence between current‐ramp and temperature‐ramp flash methodologies is established. By parameterizing the experiments in terms of an effective power density, a consistent heating pattern following the blackbody radiation trend was identified, despite the different electrical characteristics of each experiment. Finally, a “flash heating map” is introduced, which can be used to determine the starting electrical parameters necessary to achieve a specific temperature increase, whether employing current or temperature ramps.

The Development of a Flexible Humidity Sensor Using MWCNT/PVA Thin Films.

The exponential demand for real-time monitoring applications has altered the course of sensor development, from sensor electronics miniaturization, e.g., resorting to printing techniques, to low-cost, flexible and functional wearable materials. Humidity sensing has been used in the prevention and diagnosis of medical conditions, as well as in the assessment of physical comfort. This paper presents a resistive flexible humidity sensor composed of silver interdigitated electrodes (IDTs) screen printed onto polyimide film and an active layer of multiwall carbon nanotubes (MWCNT) dispersed in a water-soluble polymer, polyvinyl alcohol (PVA). Different MWCNT/PVA sensor sizes and MWCNT percentages are tested to study their effect on the initial electrical resistance (Ri) values and sensor response at different humidity percentages. The results show that the Ri values decrease with the increase in % MWCNT. The sensor size did not influence the sensor response, while the % MWCNT affected the sensor behavior upon relative humidity (RH) increments. The 1% MWCNT/PVA sensor showed the best response, reaching a relative electrical resistance, ΔR/R0, of 509% at 99% RH. Comparable with other reported sensors, the produced MWCNT/PVA flexible sensor is simpler, greener and shows a good sensitivity to humidity, being easily incorporated in wearable monitoring applications, from sports to medical fields.

Understanding the sensing performance alteration mechanism of a Yarn-based strain sensor after encapsulation and an effective encapsulation structural designs

Microcrack-based yarn strain sensors with non-uniform and rough structures offer high sensitivity and flexibility, making them promising for wearable electronics. However, their low mechanical endurance limits their usability. Encapsulating is a common method used to protect the conductive network and enhance environmental stability, but its impact on sensing performance is poorly understood. This work investigates the effects of thickness and tensile modulus of conformal encapsulation layer on the performance of double-threaded conductive yarns (CNT/DTY), especially focusing on the thickness variation coefficient of the conformal encapsulation layer. The results showed that the encapsulation layer affects the mechanical and electrical properties of yarn sensors. The permeation of Ecoflex transforms the conductive layer into Ecoflex/CNT composites, increasing the sensor’s initial electrical resistance. The encapsulation layer changes the rate of strain transfer from the substrate to the conductive layer, slowing strain localization. Increasing the thickness variation coefficient of the encapsulation layer improves the maximum strain range, linearity and repeatability, while decreasing the sensitivity and electromechanical hysteresis. An encapsulation layer with higher tensile modulus significantly reduces sensitivity, linearity and increases electromechanical hysteresis. Optimizing the encapsulation layer not only provides the sensors with robust mechanical support and protection but also enhance its sensing properties, including excellent water resistance. Moreover, encapsulated yarn sensors showed good potential in joint motion monitoring in water, gait analysis, and gesture recognition for wearable applications.

Additive fabrication of pressure sensitive material for flexible pressure sensor and its characteristics

The increasing interest in wearable devices and healthcare has sparked significant advancements in the development of flexible sensors for various applications. In this study, we present the fabrication and characterization of a flexible pressure sensor utilizing a three-dimensional structure of pressure sensitive material, fabricated through a layer-by-layer process. The aim of this research is to investigate the electrical response characteristics of the sensor based on the number of layers in the pressure sensitive material, both under static and dynamic pressure conditions. The pressure sensitive material, consisting of multi-walled carbon nanotubes (MWCNTs) dispersed in polydimethylsiloxane (PDMS), exhibits positive piezo-resistive properties. The flexible pressure sensor was fabricated using direct ink writing (DIW) technology, which enables precise control over the arrangement of the material. We explored the influence of layer configurations on the sensor's initial resistance and electrical resistance changes by varying the number of layers. Our experiments demonstrated a clear trend, indicating that as the number of layers increased, both the initial resistance and electrical resistance change decreased. This behavior can be attributed to the enhanced connectivity among carbon nanotubes within the material, resulting in reduced overall resistance. In addition to static pressure testing, we conducted dynamic pressure experiments to assess the sensor's response under rapidly changing pressure conditions. Our findings suggest that by manipulating the number of layers in the pressure-sensitive material, the sensor's sensitivity and detection range can be tailored to suit specific applications. This approach offers a flexible and unified method for fabricating sensors with diverse response behaviors within a single manufacturing process.

Analysis of the electromagnetic properties of 2000NN/2000NM composites with ferroelectric and polymer matrices

The results of studying the electrical properties of ferrite-dielectric composites containing inclusions of Mn-Zn and Ni-Zn spinel ferrites with the same initial magnetic permeability (grades 2000NM and 2000NN, respectively) and different electrical resistance are presented. Four matrix materials, polymer and ceramic dielectrics with a different dielectric permittivity were used in the experiments: polystyrene (PS525), polyvinylidene fluoride (grade F2MB), lead zirconate titanate (ZTS-21), and barium titanate (TBK-3). Experimental samples of composites were obtained by hot (for a polymer matrix) or cold pressing with a binder (in case of ferroelectric ceramic matrix). It has been shown that the microwave-absorbing properties of the resulting composites significantly depend on the electrical properties of the dielectric matrix and the electrical resistivity of the filler. The highest attenuation of electromagnetic waves of 25 – 27 dB in the frequency range 4 – 5 GHz is observed for ferrite-polymer composites with a semiconductor filler of 2000NM with a thickness of microwave-absorbing material of 6 mm. For composites with Mn-Zn ferrite filler, a pronounced shift in the dispersion region of magnetic permeability is also observed, which in turn changes the frequency position of peak radio absorption. For the composites with a ferroelectric matrix, the operating frequency range for both fillers shifted to the low-frequency region 1 – 4 GHz with a maximum attenuation of up to 22 dB at the same thickness. It was experimentally confirmed that at a concentration of ferrite Cm = 40 % wt., the value of the frequency of absorption peal center fc and the minimum value of the reflection loss Kref for a filler with high electrical resistance of 2000NN decrease with an increase in the dielectric constant of the matrix. As for the composites with a 2000NM filler, the (ε’ of the matrix) dependence passes through a minimum. The obtained composites can be considered as effective microwave-absorbing materials for the frequency range 1 – 6 GHz with peak attenuation of the electromagnetic wave in the range 14 – 27 dB and frequency band (less than 10 dB) in the range 1.1 – 2.5 GHz.

Laser-Formed Sensors with Electrically Conductive MWCNT Networks for Gesture Recognition Applications.

Currently, an urgent need in the field of wearable electronics is the development of flexible sensors that can be attached to the human body to monitor various physiological indicators and movements. In this work, we propose a method for forming an electrically conductive network of multi-walled carbon nanotubes (MWCNT) in a matrix of silicone elastomer to make stretchable sensors sensitive to mechanical strain. The electrical conductivity and sensitivity characteristics of the sensor were improved by using laser exposure, through the effect of forming strong carbon nanotube (CNT) networks. The initial electrical resistance of the sensors obtained using laser technology was ~3 kOhm (in the absence of deformation) at a low concentration of nanotubes of 3 wt% in composition. For comparison, in a similar manufacturing process, but without laser exposure, the active material had significantly higher values of electrical resistance, which was ~19 kOhm in this case. The laser-fabricated sensors have a high tensile sensitivity (gauge factor ~10), linearity of >0.97, a low hysteresis of 2.4%, tensile strength of 963 kPa, and a fast strain response of 1 ms. The low Young's modulus values of ~47 kPa and the high electrical and sensitivity characteristics of the sensors made it possible to fabricate a smart gesture recognition sensor system based on them, with a recognition accuracy of ~94%. Data reading and visualization were performed using the developed electronic unit based on the ATXMEGA8E5-AU microcontroller and software. The obtained results open great prospects for the application of flexible CNT sensors in intelligent wearable devices (IWDs) for medical and industrial applications.

Microwave Soldering of Low-Resistance Conductive Joints-Technical and Economic Aspects.

Soldering processes are applied in the fabrication of electronic circuits used in most modern domestic and industrial technologies. This article aims to introduce a new soldering technology based on the microwave joining of copper materials used in electronic applications. The study was focused on microwave technology used as the thermal source for soldering. A simulation model of temperature distributions in copper plates with overall dimensions of 50 × 10 × 0.8 mm was developed in order to determine the necessary microwave power for soldering. For 270 °C simulated on the surface of copper plates, the microwave-injected power was determined to be 598.89 W. An experimental program for 600, 650, 700, and 750 W was set in order to achieve soldering of copper plates in less than 1 min. Soldered copper plates were subject to electrical resistance measurements being obtained with variations up to ±1.5% of the initial electrical resistance of the base materials. The quality of joints has also been analyzed through microscopy after the soldering process. In addition, mechanical properties were determined using a universal testing machine. The results have shown similar behavior of the samples layered with SAC on the one-side and double-side but also a significantly lower force before breaking for one-side-layered samples. An economic analysis was performed and the results obtained have shown that in terms of energy efficiency and total costs for microwave soldering compared with manual soldering, microwave soldering is cost-effective for industrial processing.

Self-sensing concrete with recycled coarse aggregates and multi-walled carbon nanotubes: A sustainable and effective method

This study explores the production of self-sensing concrete using recycled coarse aggregates and Multi-walled Carbon Nanotubes (MWCNTs) in varying dosages. The objective is to reduce the usage of natural coarse aggregates and to develop an environmentally friendly and sustainable material for the future generation. The self-sensing concrete was also self-compacting (SCC), which enhances its ability to fill complicated molds without the need for external vibration. The fresh properties of the self-sensing concrete were tested, and the mix proportions with varying dosages of MWCNTs were within the prescribed limit as per European Federation of National Associations Representing for Concrete (EFNARC) code. The mechanical properties of the self-sensing concrete were also evaluated, and it was observed that incorporating MWCNTs into the concrete enhanced its strength. Incorporating MWCNT into concrete increased its strength, seen in higher compressive and split tensile strengths. Adding 0.05%, 0.1%, and 0.15% of MWCNT resulted in compressive strength increases of 1.51%, 3.21%, and 4.72%, respectively. Likewise, the inclusion of 0.05%, 0.1%, and 0.15% of MWCNT led to split tensile strength increases of 1.54%, 3.31%, and 4.82%, respectively. The SEM images of specimens with different MWCNT dosages show a random yet uniform dispersion within the concrete matrix. The initial electrical resistance plot demonstrates the transformation from conventional to self-sensing concrete, with the resistance dropping significantly from 400k-ohms to 37k-ohms. This plot establishes the critical threshold level for self-sensing at 0.10% MWCNTs. Furthermore, the study examined the stress sensing ability and crack detection properties of the self-sensing concrete, and it was found that during cyclic loading, the concrete's stress sensing ability improves with increasing MWCNT dosage. The most favorable similarity plot between stress and FCR is seen at 0.15% MWCNT. However, considering economic reasons, a dosage of 0.1% MWCNT can be considered the best option since it doesn't show a significant difference for both stress and crack detection property.

RESEARCH OF THE PROCESS OF HIGH VOLTAGE ELECTRIC DISCHARGE SINTERING OF P6M5 RAPID STEEL POWDER

Studies have been carried out to study the process of high-voltage electric-discharge sintering of powder of high-speed steel R6M5. The process of high-voltage electric-discharge sintering of powders is accompanied by a complex of electrophysical, thermodynamic and mechanical phenomena that affect the sintering processes of samples and their properties.  It was found that the process of high-voltage electric-discharge sintering of powders of P6M5 steel is accompanied by compaction of the powder as a result of sintering of particles, as well as by the action of compressive stresses on the sample from the powder. The shape and size of particles, the nature of surface films, the size and shape of the matrix have a great influence on the process of high-voltage electric-discharge sintering. Factors affecting the strength properties of samples include the particle size distribution of the powder, its initial electrical resistance, and technological processing parameters, such as discharge energy and discharge current density.

Machine learning aided design of smart, self-sensing fiber-reinforced plastics

Numerous techniques have been developed for the non-destructive evaluation (NDE) of impact damage in fiber reinforced plastics (FRPs), following the increasing demands for their safety and maintenance. Considering the large-scale detection and the vast amount of data involved, machine learning (ML) can be utilized in NDE for damage type analysis and impact damage localization. Furthermore, self-sensing using carbon fiber in FRPs is an emerging technique for NDE that can be combined with ML. In this study, ML was used to design smart FRPs by selecting the fiber type and electrode distance considering the cost and electromechanical sensitivity. Furthermore, a novel algorithm for structural health self-sensing was suggested using an artificial neural network. The developed ML algorithms are advantageous since they do not require a theoretical model when all the factors and the variables of FRPs, such as the maximum absorbed impact energy, maximum impact force, initial electrical resistance, number of electrodes, fiber types, and electrode distance, are to be considered. The algorithm was trained using given input data and the target, and the output could be successfully obtained when new input data were provided. Therefore, the proposed ML algorithms hold great potential and applicability to FRP design and for NDE methods.

Improvement of the Uniformity and Electrical Properties of Polyaniline Nanocomposite Film by Addition of Auxiliary Gases during Atmospheric Pressure Plasma Polymerization.

The morphological and chemical properties of polyaniline (PANI) nanocomposite films after adding small amounts of auxiliary gases such as argon, nitrogen, and oxygen during atmospheric pressure (AP) plasma polymerization are investigated in detail. A separate gas-supply line for applying an auxiliary gas is added to the AP plasma polymerization system to avoid plasma instability due to the addition of auxiliary gas during polymerization. A small amount of neutral gas species in the plasma medium can reduce the reactivity of monomers hyperactivated by high plasma energy and prevent excessive crosslinking, thereby obtaining a uniform and regular PANI nanocomposite film. The addition of small amounts of argon or nitrogen during polymerization significantly improves the uniformity and regularity of PANI nanocomposite films, whereas the addition of oxygen weakens them. In particular, the PANI film synthesized by adding a small amount of nitrogen has the best initial electrical resistance and resistance changing behavior with time after the ex situ iodine (I2)-doping process compared with other auxiliary gases. In addition, it is experimentally demonstrated that the electrical conductivity of the ex situ I2-doped PANI film can be preserved for a long time by isolating it from the atmosphere.

In Situ Formation of Ag Nanoparticles for Fiber Strain Sensors: Toward Textile-Based Wearable Applications

Wearable electronic devices have attracted significant attention as important components in several applications. Among various wearable electronic devices, interest in textile electronic devices is increasing because of their high deformability and portability in daily life. To develop textile electronic devices, fiber-based electronic devices should be fundamentally studied. Here, we report a stretchable and sensitive fiber strain sensor fabricated using only harmless materials during an in situ formation process. Despite using a mild and harmless reducing agent instead of typical strong and hazardous reducing agents, the developed fiber strain sensors feature a low initial electrical resistance of 0.9 Ω/cm, a wide strain sensing range (220%), high sensitivity (∼5.8 × 104), negligible hysteresis, and high stability against repeated stretching-releasing deformation (5000 cycles). By applying the fiber sensors to various textiles, we demonstrate that the smart textile system can monitor various gestures in real-time and help users maintain accurate posture during exercise. These results will provide meaningful insights into the development of next-generation wearable applications.

Model of the object of temperature control by electrostimulating action parameters

Technologies for pressure treatment of metal workpieces using powerful current pulses are becoming increasingly widespread both in Russia and abroad. Unique electromechanical processes are studied and improved in laboratory and production conditions. The process of applying an electric current to the workpiece is accompanied by a change in its physical properties as a result of the so-called electroplastic effect (EPE). At the same time, the temperature of the workpiece in the deformation zone increases. For high-quality and reliable operation of the drawing mill with electrostimulated drawing (ESW), it is necessary to use an automatic system for regulating the force and temperature. In order to implement the temperature control circuit, it is necessary to synthesize the transfer function of the control object – steel wire processed by pressure (rolling or drawing). Synthesis and analysis of parameters of the model of temperature control object are considered. The known relations are used: dependence of the pulse generator power on the calculated parameters (initial temperature, diameter, specific weight and electrical resistance of the workpiece, pulse duration); dependence of the RMS current of the generator on the amplitude and frequency of pulse reproduction; dependence of the magnetic permeability of the workpiece on its temperature; and dependence of the specific electrical resistance of the conductor material on temperature. In MATLAB – Simulink medium, a model of the temperature control object is synthesized as a function of the parameters of generator of high-power current pulses (amplitude and frequency), as well as the parameters of the workpiece to be processed (diameter, sample length, linear velocity, initial temperature, and resistivity at the initial temperature). The model is analyzed, and transients under different operating modes are presented. Using the developed model, the dependences of the temperature, power, and equivalent resistance on parameters of the generator and the workpiece are obtained for different generator pulse frequencies and workpiece diameters. The developed model can be used for laboratory studies of the electroplastic effect, as well as in production in auto-control systems with electrostimulated drawing in order to implement the object of regulation in the form of a model.

Preparation of conductive cellulose fabrics with durable antibacterial properties and their application in wearable electrodes

Electroless silver plating on fabrics can obtain conductive and antibacterial bifunctional materials which can be used as electrodes in wearable electronic products. However, these activities are deteriorated easily after washing because of the falling off of silver coating resulted from the weak adhesion. In order to improve the binding force between silver and cellulose fabrics, 3-mercaptopropytrimethoxysilane (MPTS) was applied to modify cellulose fabrics before silver electroless plating to develop the durable conductive fabrics with excellent antibacterial. The silver nanoparticles (Ag NPs) deposition process was observed via field emission scanning electron microscopy (FESEM), thermal properties were evaluated by thermogravimetric analysis (TGA). A dense and uniform silver layer was formed on the fabric. The initial electrical resistance of the conductive fabric was 0.04 Ω/sq and lowered than 2 Ω/sq after 200 washing cycles. The antibacterial efficiency of the fabric after 200 washing cycles remained 92.82%, compared to 100% with the fabric before washing. Moreover, the inhibition rate was determined by optical density of bacteria suspension at 260 nm and further substantiated by releasing of Ag+ from the fabric. The conductive fabrics were applied as wearable electrodes to capture electrocardiogram (ECG) signals of human in static states and running states.

Room-Temperature Welding of Silver Telluride Nanowires for High-Performance Thermoelectric Film.

Flexible thermoelectric materials that can harvest waste heat energy have attracted great attention because of the rapid progress of flexible electronics. Ag2Te nanowires (Ag2Te NWs) are considered as promising thermoelectric materials to fabricate flexible thermoelectric film and device because of their high Seebeck coefficient, but poor contact between the Ag2Te NWs results in low electrical conductivity. Generally, hot or cold pressing can increase the electrical conductivity between the Ag2Te NWs. However, these process tend to destroy the initial morphology of the Ag2Te NWs and/or cause only physical contact between the Ag2Te NWs. Herein, we report an approach to the room-temperature welding of Ag2Te NWs to enhance their contacts by facile combination of vacuum filtration and drop-coating methods. The obtained Ag2Te NWs film exhibits excellent Seebeck coefficient of -99.48 μV/K and high electrical conductivity of 15 335.05 S/m at room temperature, which gives the power factor of 151.76 μW m-1 K-2. Surprisingly, an optimal Seebeck coefficient of -154.96 μV/K and electrical conductivity of 14 982.42 S/m can be obtained at 420 K, giving a power factor of 359.76 μW m-1 K-2. Moreover, the electrical resistance of the Ag2Te NWs film was only 1.3 times of the initial electrical resistance after 1000 bending cycles, indicating good flexibility of the film. A finger-touch test is conducted by using the Ag2Te NWs film as thermoelectric power generator, which achieves a stable output voltage of about 0.52 mV, suggesting its great potential applications in self-powered flexible electronic devices.

Electrical properties of stretchable and skin–mountable PDMS/MWCNT hybrid composite films for flexible strain sensors

Flexible strain sensors based on carbon nanofillers have great potential in the application of skin-adhesive sensors, wearable sensors, and tactile sensors, due to their superior electrical properties. Herein, the electrical properties of highly sensitive PDMS/MWCNT strain sensors made by vacuum filtration method were investigated. In order to obtain the electrical percolation curve of the flexible conductive films, first different samples were made with the same surface area but with different wt. % of CNTs. Then, depending on CNT content, the obtained conductive films exhibited initial electrical resistance in the range of 12.5 KΩ to 22.8 MΩ. The piezoresistive films with the CNT concentration of 1.4 to 2.9 [Formula: see text] had shown superior resistance drop, so this interval was determined as the percolation threshold region. According to the SEM images, the nanocomposite layer thickness of the flexible strain sensors in this region was 790 nm to 1210 nm. Afterward, the percolation curve was obtained using curve fitting to the experimental data and the exact value of the percolation threshold was defined as [Formula: see text]. Finally, in order to determine the minimum gauge factor ([Formula: see text]) of the sensors in percolation region, a flexible strain sensor in the upper limit of this region was selected and the piezoresistive properties of the selected sample were investigated.

Silver Nanowire-Based Stretchable Transparent Electrode for Flexible Organic Light-Emitting Diode.

The new stretchable transparent electrode was proposed and fabricated based on a process which utilizes silver nanowires (AgNWs) on a Polyurethane (PU) substrate. In order to overcome the rough surface nature of the silver nanowire electrode, a titanium oxide (TiO₂) buffer layer was over-coated and then followed by a heat treatment of organo-metalic sol-gel solution. The fabricated stretchable electrodes exhibit electrical sheet resistance of 24 Ω/□, transmittance of 78% at 550 nm wavelength and average surface roughness of less than 5 nm. In addition, without adding additional conductive polymer layers, the fabricated AgNW-based electrode can maintain its initial electrical resistance even if nearly 130% strain is applied. In this letter, the critical role of a TiO₂ buffer layer in achieving the high performance of the AgNW stretchable electrode is discussed.

Knitted piezoresistive strain sensor performance, impact of conductive area and profile design

While many of the factors influencing strain sensor properties have been explained in literature, other very important parameters that influence actual design performance of sensors remain obscure. This paper investigates the impact of conductive profile and area design including post fabric treatments such as dyeing and washing on sensor performance. 1 × 1 mock rib was the fabric structure of choice, and silver-plaited nylon was the conductive yarn used in knitting all the samples. Six main polygonal shapes including ellipse, diamond shape, corrugated rectangular shape, rectangular horse shoe, rectangular dough roller shape, and plain rectangular shape were designed and knitted. Plain rectangular profile has been found to deliver the best results characterized by noiseless signals, highest gauge factor, and good result repeatability. The analysis of results also reveals a positive linear correlation between conductive path and initial electrical resistance of a sensor. The inverse is true for the relation between the conductive width values and their corresponding initial resistances. Higher conductive widths led to low initial resistance, and values less than 20 Ω for a sensor could lead to inferior sensor sensitivity. High conductive paths produced high initial resistances, and values within the range of 40–120 Ω could deliver higher sensitivity. This study thus concludes that the optimum aspect ratio range for conductive area to deliver satisfactory sensitivity results is approximately between 24:1 and 77:1 cm. Laundry and dyeing have also been found to result in reduced sensor dimensions, resistance, and sensitivity levels.

Sensing parameters as a function of the chemical structure and thickness of two poly(styrene)-type based composites with carbon black

Sensing parameters of polymer composite layers were studied as a function of the polymer matrix structure and the initial resistance of the composite layers. Composites of Poly(styrene) and 4-Chloro-poly(styrene) at the same volume fraction of carbon black (8.7% V/V) were prepared by ultrasonic dispersion. Composite layers with different thicknesses and resistances were deposited by spin coating technique on flexible substrates from commercial cellulose acetate foils. Both kind of composite layers with initial resistances of 10, 50 and 100 k? were exposed to Acetone, Tetrahydrofuran, Chloroform and Toluene. Results evidenced that selectivity is very dependent on the chemical structure of the polymer matrix and sensitivity to the initial film electrical resistance. PS-based composite series were selective to Tetrahydrofuran whereas that 4ClPS-based composite series were selective to Acetone as expected due to their solubility parameters. For both composite series sensitivity increased for layers with less than 100 k? resistances. For all tested solvents 4ClPS-based composites showed higher sensitivities than PS-based composites. The response times for both series were into the range of 2 to 150 s and recovery times were in the range of 30 to 2000 s.

Application of electro-membrane separation for recovery of acetic acid in lignocellulosic bioethanol production

Acetic acid (HAc), one of the major inhibitory compounds present in all lignocellulosic biomass hydrolysate, can reduce the rate and yield of bioethanol production. Electrodialysis (ED) is an electrochemical non-solvent based separation process that can selectively separate ionic species from aqueous solutions through the use of ion selective membranes and electric field potential. Two ED cell configurations at three constant applied potentials (5, 10, and 15V) were tested for removal and recovery of HAc from a model solution of corn stover hydrolysate. The uses of bipolar membrane (configuration 1) and cation-exchange membrane (configuration 2) in an ED stack demonstrated significantly different effects on system performance in terms of: demineralization rate, acetic acid removal rate, current efficiency, and energy consumption. The demineralization and mineralization of feed and recovery solutions, respectively, increased with increasing applied voltage for both configurations. Configuration 1 showed 1.5–2 times higher initial electrical resistance at lower applied voltages compared to configuration 2. The HAc flux and removal rate increased with increasing electric potential, and were significantly higher in configurations 2 than 1. The present work indicates that a cation exchange membrane operating at 10V is optimal for recovering HAc from a model corn stover hydrolysate solution.