• Macromolecular Research
• /
• v.13 no.2
• /
• pp.96-101
• /
• 2005

Thin-film humidity sensors were prepared using inorganic/organic hybrid polyelectrolytes, which were prepared from the sol-gel reaction of copolymers of [2-(methacryloyloxy)ethyl]dimethylpropylammonium bromide (MEPAB), n-butyl methacrylate (BMA), and 3-(trimethoxysilyl)propyl methacrylate (TSPM) with tetraethyl ortho-silicate (TEOS). The humidity-sensitive polyelectrolytes were composed of the copolymers having the following mole ratios of MEPAB, BMA, and TSPM: 60/30/10, 55/30/15, and 50/30/20. We found that the impedance varied with the content of MEPAB or TEOS; it ranged from $10^{7} to 10^{3}\Omega$ between 20 and $95\%$ relative humidity, which is the range required for a humidity sensor operating at ambient humidity. In addition we investigated a number of characteristics of these humidity sensors, such as their hysteresis, response time, temperature dependence, frequency dependence, water durability, and long-term stability.

• Macromolecular Research
• /
• v.12 no.3
• /
• pp.311-315
• /
• 2004

We have prepared new polyelectrolytes containing trialkoxysilyl groups by copolymerizing 3-(trimethoxysilyl)propyl methacrylate (TSPM) with either [2-(methacryloyloxy)ethyl]trimethyl ammonium chloride (METAC), [2-(methacryloyloxy)ethyl]dimethyl propyl ammonium bromide (MEDPAB), or [2-(acryloyloxy)ethyl]trimethyl ammonium chloride (AETAC). The copolymers TSPM/METAC, TSPM/MEDPAB, and TSPM/METAC having compositions of 15/85, 10/90, and 5/95, respectively, were self-crosslinkable polyelectrolytes that possess humidity-sensitive properties. We measured the impedances of the copolymers at various relative humidities (RHs) and found that the resistance was dependent on the content of METAC, MEDPAB, or AETAC. The impedance changed from 10$\^$7/ $\Omega$ at 20% RH to 10$^3$ $\Omega$ at 95% RH, which is quite a suitable range for a humidity sensor that is to be utilized at ambient humidity. We also performed tests of the materials temperature dependence, hysteresis, response time, and water durability.

• Macromolecular Research
• /
• v.16 no.2
• /
• pp.149-154
• /
• 2008

UV-curable electrolytes inks were prepared by dissolving [2-[(methacryloyloxy)ethyl]dimethyl]propylaminium bromide (MEPAB), 1,5-[bis(2-methacryloxyethyl)dimethyl ammono]penthane dibromide (MDAPD), hexafunctional reactive oligomer (SP1013), trimethylolpropane triacrylate (TMPTA) and a photoinitiator in methanol/2-methoxyethanol. The compositions of the electrolyte inks were MEPAB/MDAPD/SP1013/TMPTA=6/24/17.2/12.8, 15/15/17.2/12.8 and 24/6/17.2/12.8. Humid-membranes were deposited on a gold electrode/alumina electrode using an ink-jet printer equipped with a UV lamp followed by immediate UV curing. The humidity-sensing characteristics including hysteresis, frequency and temperature dependence, response time and water durability were estimated.

• Journal of the Korean Physical Society
• /
• v.73 no.9
• /
• pp.1334-1339
• /
• 2018

Spherical nickel ferrite nanoparticles were synthesized using the thermal decomposition method and coated with cetyl trimethyl ammonium bromide (CTAB) after the synthesis. Transmission electron microscopy images showed that the average diameter of the particles was 9.40 nm. The status of the CTAB-coating on the surface of the particles was checked using Fourier-transform infrared spectroscopy. Their hysteresis curve showed that the particles exhibited a superparamagnetic behavior. The $T_1$ and the $T_2$ relaxations of the nuclear spins were observed in aqueous solutions of the particles with different particles concentrations by using a magnetic resonance imaging (MRI) scanner, which showed that the $T_1$ and the $T_2$ relaxivities of the particles in water were $0.57mM^{-1}{\cdot}s^{-1}$ and $10.42mM^{-1}{\cdot}s^{-1}$, respectively. In addition, using an induction heating system, we evaluated their potentials for magnetic hyperthermia applications. The aqueous solution of the particles with a moderate concentration (smaller than 6.5 mg/mL) showed a saturation temperature larger than the hyperthermia target temperature of $42^{\circ}C$. These findings show that the CTAB-coated nickel ferrite particles are suitable for applications as $T_2$ contrast agents in MRI and heat generators in magnetic hyperthermia.

• Polymer(Korea)
• /
• v.31 no.4
• /
• pp.302-307
• /
• 2007

The resistive-type humidity sensors were prepared from the copolymers of [2-[(methacryloyloxy)ethyl]dimethyl]propylamonium bromide (MEPAB), [2-[(methacryloyloxy)ethyl]-2-hydroxyethyl]dimethylammonium bromide (MEHDAB), 2- [(methacryloyloxy)ethyl]trimethylammonium chloride (METAC), and n-butyl methylacrylate (MBA). Four component copolymers MEPAB/BMA/MEHDAB/METAC=4/4/1/1, 3/5/1/1, 2/6/1/1, 1/7/1/1 crosslinked with blocked-isocyanate on Ag/Pd electrode/alumina substrate showed a good durability at high humidities. The various electrical properties such as frequency dependency, temperature dependency, hysteresis, response time and water durability were examined. In the case of copolymer composed of MEPAB/BMA/MEHDAB/METAC=2/6/1/1, the resistance varied from $1.4\;M{\Omega}$ to $2.9\;k{\Omega}$ at $25^{\circ}C$ in the range of $30{\sim}90\;%RH$ and this copolymers showed a good linearity and low hysteresis.

• Polymer(Korea)
• /
• v.31 no.3
• /
• pp.194-200
• /
• 2007

The resistive-type polymeric humidity sensors were prepared from the copolymers of [2- [(methacryloyloxy)ethyl] dimethyl] propylammonium bromide(MEPAB), [2- [(methacryloyloxy)ethyl]-2-hydroxyethyl]dimethylmonium bromide (MEHDAB), n-butyl methylacrylate(MBA), 2-hydroxyethyl methylacrylate(HEMA) and styrene. Four kinds of copolymers, ie, MEPAB/styrene/MEHDAB MEHDAB/BMA/HEMA, MEPAB/BMA/MEHDAB, and MEPAB/styrene/HEMA crosslinked with blocked-isocyanate on the Ag/Pd electrode/alumina substrate showed good durability at high humidities. The various electrical properties such as frequency dependency, temperature dependency, hysteresis, response time and water durability were examined. In the case of copolymer MEPAB/BMA/MEHDAB= 3/6/1, the resistance was varied from $2.9 M{\Omega}$ to $1.84k{\Omega}$ at $25^{\circ}C$ in the range of $30{\sim}90%RH$ and this copolymers showed a good linearity and low hysteresis.

• YAKHAK HOEJI
• /
• v.40 no.1
• /
• pp.25-35
• /
• 1996

Magaldrate. an antiacid was synthesized by reacting magnesium oxide, aluminum sulfate, and dried aluminum hydroxide gel. The optimum synthesis conditions based on the yield of t he product were established by applying Box-Wilson experimental design. It was found that the optimum synthesis conditions of Magaldrate were as follows: Reaction temperature; 61~$85{\circ}C$, concentration of two reactants. Mgo and $Al(OH)_3$: 16~19.8%, molar concentration ratio of two reactants, [MgO]/[$Al(OH)_3$]; 4.2~5.0, temperature of washing water; 36~$41^{\circ}C$ and drying temperature of the product: 76~$80^{\circ}C$. Magaldrate was synthesized under the optimum synthesis conditions and identified by analyzing the chemical composition, and by differential scanning calorimetry and X-ray diffraction method. The Magaldrate sample synthesis under these conditions was used to prepare 15.6% Magaldrate original suspension which was utilized to make 13% Magaldrate suspension dispered in various concentrations of eight types of suspending agents. The acid-neutralizing capacity of 13% Magaldrate suspension dispersed in 0.25% suspending agents was examined by Rosset-Rice method. The maximum pH was reached within 1 minute in all suspension tested, and duration maintained between pH 3~5 was decreased in the order of Na alginate Na silicate(meta) Veegum HV pectin agar>Na>CMC>xanthan gum>bentonite. It was found that the hysteresis loop area was increased with temperature in the case of Riopan Plus and the addition of agar, whereas the area was decreased with temperature in the case of the addition of Na alginate and xanthan gum. 13% Magaldrate suspension tends to sediment by the addition of bentonite.

• Applied Chemistry for Engineering
• /
• v.10 no.3
• /
• pp.461-466
• /
• 1999

The humidity sensor containing ammonium salt was prepared from the copolymer of 2-methacryloxyethyl dimethyl 2-hydroxyethyl ammonium bromide (MDHAB)/MMA/DAEMA = 6/3/1. The humid membrane was fabricated on the gold/alumina electrode by dipping. The impedances were $298k{\Omega},\;11k{\Omega}$, and $2.3k{\Omega}$ at 40%RH, 70%RH and 90%RH, respectively, at $5^{\circ}C$ and the humidity-sensitive characteristics were suitable for low temperature humidity sensor. The temperature-dependent coefficient between $5^{\circ}C$ and $20^{\circ}C$ was found to be $-0.80%RH/^{\circ}C$ and the hysteresis falled in the ${\pm}2%RH$ range. The response time was found to be 38 sec for the relative humidity ranging from 34%RH to 88%RH at $20^{\circ}C$. The reliabilities such as temperature cycle, humidity cycle, high temperature and humidity resistance, electrical load stability, stability of long-term storage and water durability were measured and evaluated for the application as a humidity sensor.

• Applied Chemistry for Engineering
• /
• v.9 no.4
• /
• pp.554-560
• /
• 1998

Vinylbenzyl triphenyl phosphonium chloride(VTPC)/styrenes=3.7 copolymer was prepared for the moisture-absorptive polyelectrolyte dew sensor containing phosphonium salts. The humid membrane was fabricated on the gold/alumina electrode by dipping. The impedances were $11M{\Omega}$, $980k{\Omega}$, $50k{\Omega}$, and $11k{\Omega}$ at 70%RH, 80%RH, 90%RH and 95%RH, respectively, at $25^{\circ}C$ and the humidity-sensitive charactristic was suitable for the dew sensor. The temperature-dependent coefficient between $15^{\circ}C$ and $35^{\circ}C$ was found to be $-0.25%RH/^{\circ}C$ and the hysteresis falled in the ${\pm}2%RH$ range. The response time was found to be 45 sec for the relative humidity ranging from 70%RH to 98%RH at $25^{\circ}C$. The reliabilities such as temperature cycle, humidity cycle, high temperature and humidity resistance, electrical load stability, stability of long-term storage and water durability were measured and evaluated for the application as a dew sensor.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.17 no.3
• /
• pp.329-338
• /
• 2019

Suction of unsaturated bentonite buffers is a very important input parameter for hydro-mechanical performance assessment and design of an engineered barrier system. This study analyzed suction measurement techniques and constitutive models of unsaturated porous media reported in the literature, and suggested suction measurement techniques and constitutive models suitable for bentonite buffer in an HLW repository. The literature review showed the suction of bentonite buffer to be much higher than that of soil, as measured by total suction including matric suction and osmotic suction. The measurement methods (RH-Cell, RH-Cell/Sensor) using a relative humidity sensor were suitable for suction measurement of the bentonite buffer; the RH-Cell /Sensor method was more preferred in consideration of the temperature change due to radioactive decay heat and measurement time. Various water retention models of bentonite buffers have been proposed through experiments, but the van Genuchten model is mainly used as a constitutive model of hydro-mechanical performance assessment of unsaturated buffers. The water characteristic curve of bentonite buffers showed different tendencies according to bentonite type, dry density, temperature, salinity, sample state and hysteresis. Selection of water retention models and determination of model input parameters should consider the effects of these controlling factors so as to improve overall reliability.