scholarly journals Novel humidity sensors based on nanomodified Portland cement

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Thanyarat Buasiri ◽  
Karin Habermehl-Cwirzen ◽  
Lukasz Krzeminski ◽  
Andrzej Cwirzen
Keyword(s):  
Electrical Resistivity ◽  
Relative Humidity ◽  
Portland Cement ◽  
Threshold Value ◽  
High Humidity ◽  
Humidity Sensors ◽  
The Relationship ◽  
Humidity Range ◽  
Very High

AbstractCommonly used humidity sensors are based on metal oxides, polymers or carbon. Their sensing accuracy often deteriorates with time, especially when exposed to higher temperatures or very high humidity. An alternative solution based on the utilization of Portland cement-based mortars containing in-situ grown carbon nanofibers (CNFs) was evaluated in this study. The relationship between the electrical resistivity, CNF content and humidity were determined. The highest sensitivity was observed for samples containing 10 wt.% of the nanomodified cement which corresponded to 0.27 wt.% of CNFs. The highest calculated sensitivity was approximately 0.01024 per 1% change in relative humidity (RH). The measured electrical resistivity is a linear function of the RH in the humidity range between 11 and 97%. The percolation threshold value was estimated to be at around 7 wt.% of the nanomodified cement, corresponding to ~ 0.19 wt.% of CNFs.

scholarly journals Development of La3+Doped CeO2Thick Film Humidity Sensors

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Chunjie Wang ◽  
Aihua Zhang ◽  
Hamid Reza Karimi
Keyword(s):  
Relative Humidity ◽  
High Performance ◽  
Humidity Sensor ◽  
Humidity Sensors ◽  
Response Recovery ◽  
Relative Humidity Range ◽  
Response And Recovery ◽  
Sensitive Characteristics ◽  
Humidity Range ◽  
Maximum Humidity

The humidity sensitive characteristics of the sensor fabricated from 10 mol% La2O3doped CeO2nanopowders with particle size 17.26 nm synthesized via hydrothermal method were investigated at different frequencies. It was found that the sensor shows high humidity sensitivity, rapid response-recovery characteristics, and narrow hysteresis loop at 100 Hz in the relative humidity range from 11% to 95%. The impedance of the sensor decreases by about five orders of magnitude as relative humidity increases. The maximum humidity hysteresis is about 6% RH, and the response and recovery time is 12 and 13 s, respectively. These results indicate that the nanosized La2O3doped CeO2powder has potential application as high-performance humidity sensor.

scholarly journals Effect of Cement Types and Superabsorbent Polymers on the Properties of Sustainable Ultra-High-Performance Paste

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1497
Author(s):  
Mei-Yu Xuan ◽  
Yi-Sheng Wang ◽  
Xiao-Yong Wang ◽  
Han-Seung Lee ◽  
Seung-Jun Kwon
Keyword(s):  
Compressive Strength ◽  
Electrical Resistivity ◽  
Relative Humidity ◽  
Portland Cement ◽  
High Performance ◽  
Isothermal Calorimetry ◽  
Experimental Studies ◽  
High Rate ◽  
Superabsorbent Polymers ◽  
Internal Relative Humidity

This study focuses on the effects of superabsorbent polymers (SAP) and belite-rich Portland cement (BPC) on the compressive strength, autogenous shrinkage (AS), and micro- and macroscopic performance of sustainable, ultra-high-performance paste (SUHPP). Several experimental studies were conducted, including compressive strength, AS, isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TGA), attenuated total reflectance (ATR)–Fourier-transform infrared spectroscopy (FTIR), ultra-sonic pulse velocity (UPV), and electrical resistivity. The following conclusions can be made based on the experimental results: (1) a small amount of SAP has a strength promotion effect during the first 3 days, while BPC can significantly improve the strength over the following 28 days. (2) SAP slows down the internal relative humidity reduction and effectively reduces the development of AS. BPC specimens show a lower AS than other specimens. The AS shows a linear relationship with the internal relative humidity. (3) Specimens with SAP possess higher cumulative hydration heat than control specimens. The slow hydration rate in the BPC effectively reduces the exothermic heat. (4) With the increase in SAP, the calcium hydroxide (CH) and combined water content increases, and SAP thus improves the effect on cement hydration. The contents of CH and combined water in BPC specimens are lower than those in the ordinary Portland cement (OPC) specimen. (5) All samples display rapid hydration of the cement in the first 3 days, with a high rate of UPV development. Strength is an exponential function of UPVs. (6) The electrical resistivity is reduced due to the increase in porosity caused by the release of water from SAP. From 3 to 28 days, BPC specimens show a greater increment in electrical resistivity than other specimens.

scholarly journals Role of Carbon Nanofiber on the Electrical Resistivity of Mortar under Compressive Load

2020 ◽  
pp. 036119812094741
Author(s):  
Thanyarat Buasiri ◽  
Karin Habermehl-Cwirzen ◽  
Lukasz Krzeminski ◽  
Andrzej Cwirzen
Keyword(s):  
Electrical Resistivity ◽  
Portland Cement ◽  
Carbon Nanofibers ◽  
Ordinary Portland Cement ◽  
Carbon Nanofiber ◽  
Compressive Load ◽  
Chemical Vapor ◽  
Load Sensing

A nanomodified cement consisting of particles with in situ synthesized carbon nanofibers was developed to introduce a strong load-sensing capability of the hydrated binder matrix. The material was produced using chemical vapor deposition. The nanomodified cement contained 2.71 wt% of carbon nanofibers (CNFs). The electrical properties of the composite were determined. Several mortar samples were prepared by partially substituting ordinary Portland cement with 2, 4, 6, 8, and 10 wt% of the nanomodified cement. Additionally an ordinary Portland cement mortar was used as reference. The results show that the strongest piezoresistive response and therefore the best load-sensing was obtained for the mortar containing the highest amount of CNFs. This mortar contained 10 wt% of nanomodified cement. The fractional change in electrical resistivity of this mortar was 82% and this mortar had a compressive strength of 28 MPa.

scholarly journals Quantitative Use of Fluorescent In Situ Hybridization To Examine Relationships between Mycolic Acid-Containing Actinomycetes and Foaming in Activated Sludge Plants

2000 ◽  
Vol 66 (3) ◽  
pp. 1158-1166 ◽  
Author(s):  
Russell J. Davenport ◽  
Thomas P. Curtis ◽  
Michael Goodfellow ◽  
Fiona M. Stainsby ◽  
Marc Bingley
Keyword(s):  
In Situ Hybridization ◽  
Activated Sludge ◽  
Fluorescent In Situ Hybridization ◽  
Threshold Value ◽  
Mycolic Acid ◽  
Foam Formation ◽  
Quantification Method ◽  
Nested Analysis ◽  
The Relationship

ABSTRACT The formation of viscous foams on aeration basins and secondary clarifiers of activated sludge plants is a common and widespread problem. Foam formation is often attributed to the presence of mycolic acid-containing actinomycetes (mycolata). In order to examine the relationship between the number of mycolata and foam, we developed a group-specific probe targeting the 16S rRNA of the mycolata, a protocol to permeabilize mycolata, and a statistically robust quantification method. Statistical analyses showed that a lipase-based permeabilization method was quantitatively superior to previously described methods (P << 0.05). When mixed liquor and foam samples were examined, most of the mycolata present were rods or cocci, although filamentous mycolata were also observed. A nested analysis of variance showed that virtually all of the measured variance occurred between fields of view and not between samples. On this basis we determined that as few as five fields of view could be used to give a statistically meaningful sample. Quantitative fluorescent in situ hybridization (FISH) was used to examine the relationship between foaming and the concentration of mycolata in a 20-m3completely mixed activated sludge plant. Foaming occurred when the number of mycolata exceeded a certain threshold value. Baffling of the plant affected foaming without affecting the number of mycolata. We tentatively estimated that the threshold foaming concentration of mycolata was about 2 × 106 cells ml−1 or 4 × 1012 cells m−2. We concluded that quantitative use of FISH is feasible and that quantification is a prerequisite for rational investigation of foaming in activated sludge.

Compliant and Low-Cost Humidity Sensors Using Nano-Porous Polymer Membranes

2004 ◽  
Author(s):  
Bozhi Yang ◽  
Burak Aksak ◽  
Shan Liu ◽  
Qiao Lin ◽  
Metin Sitti
Keyword(s):  
Relative Humidity ◽  
Room Temperature ◽  
Capillary Condensation ◽  
Low Cost ◽  
Polymer Membranes ◽  
High Sensitivity ◽  
Porous Polymer ◽  
Humidity Sensors ◽  
Water Leakage Detection

This paper proposes non-fragile compliant humidity sensors that can be fabricated inexpensively on various types of nano-porous polymer membranes such as polycarbonate, cellulose acetate, and nylon membranes. The sensor contains a pair of interdigitated electrodes deposited on the nano-porous polymer membranes. The resistance and/or capacitance between these electrodes vary at different humidity levels with a very high sensitivity due to the water adsorption (capillary condensation) inside the nano-pores. The proposed sensors are low-cost in both material and fabrication. Due to its compliance, the sensors can be suitable for certain applications such as in-situ water leakage detection on roofs, where people can walk on top of them. Testing results demonstrated that the sensor changes resistance within large range of humidity values. For most sensors, the resistance changes from 0.1 GΩ to 2000 GΩ when the relative humidity changes from 39% to 100% at room temperature. It takes about 4–8 minutes for the resistance to reach steady state when the sensor was taken from 100% to 39% relative humidity at the room temperature.

Humidity Sensors Based on Nanostructured Materials

2006 ◽  
Vol 51 ◽  
pp. 197-200
Author(s):  
S. Krutovertsev ◽  
A. Tarasova ◽  
L. Krutovertseva ◽  
A. Zorin ◽  
O. Ivanova
Keyword(s):  
Relative Humidity ◽  
Nanostructured Materials ◽  
Humidity Sensor ◽  
Dew Point ◽  
Humidity Sensors ◽  
Humidity Range

Constraction and characteristics of sorption polymeric relative humidity sensors, sorption SiOx microhumidity sensors, and condensation type (dew point) sensors are compared. The characteristics of the sensors are examined in dew point range from -80 to +20oC. An integrated multifunctional humidity sensor, for measurements in wide humidity range at different conditions is developed. The sensors are intended for use in various branches of industry, and in scientific researches.

scholarly journals Climatic controls on water vapor deuterium excess in the marine boundary layer of the North Atlantic based on 500 days of in situ, continuous measurements

2014 ◽  
Vol 14 (2) ◽  
pp. 2363-2401 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
A. E. Sveinbjörnsdottir ◽  
A. J. Peters ◽  
V. Masson-Delmotte ◽  
M. P. Guishard ◽  
...  
Keyword(s):  
Water Vapor ◽  
Wind Speed ◽  
Relative Humidity ◽  
North Atlantic ◽  
Deuterium Excess ◽  
The North ◽  
Hourly Data ◽  
The North Atlantic ◽  
The Relationship

Abstract. Continuous, in situ measurements of water vapor isotopic composition have been conducted in the North Atlantic, Bermuda Islands (32.26° N, 64.88° W) between November 2011 and June~2013, using a~cavity-ring-down-spectrometer water vapor isotope analyzer and an autonomous self-designed calibration system. Meticulous calibration allows us to reach an accuracy and precision on 10 min average of δ18O, δD, and d-excess of respectively 0.14 ‰, 0.85 ‰, and 1.1 ‰, verified using two parallel instruments with independent calibration. As a result of more than 500 days with 6 hourly data the relationships between deuterium excess, relative humidity (rh), sea surface temperature (SST), wind speed and direction are assessed. From the whole dataset, 84% of d-excess variance is explained by a strong linear relationship with relative humidity. The slope of this relationship (−42.6 ± 0.4 ‰ % (rh)) is similar to the theoretical prediction of Merlivat and Jouzel (1979) for SST between 20 °C and 30 °C. However, in contrast with theory, no effect of wind speed could be detected on the relationship between d-excess and relative humidity. Separating the dataset into winter, spring, summer, and autumn seasons reveals different linear relationships between d-excess and humidity. Changes in wind directions are observed to affect the relationships between d-excess and humidity. The observed seasonal variability in the relationship between d-excess and relative humidity underlines the importance of long-term monitoring to make accurate conclusions.

scholarly journals Climatic controls on water vapor deuterium excess in the marine boundary layer of the North Atlantic based on 500 days of in situ, continuous measurements

2014 ◽  
Vol 14 (15) ◽  
pp. 7741-7756 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
A. E. Sveinbjörnsdottir ◽  
A. J. Peters ◽  
V. Masson-Delmotte ◽  
M. P. Guishard ◽  
...  
Keyword(s):  
Water Vapor ◽  
Wind Speed ◽  
Relative Humidity ◽  
North Atlantic ◽  
Deuterium Excess ◽  
Data Set ◽  
The North ◽  
The North Atlantic ◽  
The Relationship

Abstract. Continuous, in situ measurements of water vapor isotopic composition have been conducted in the North Atlantic, at the Bermuda Islands (32.26° N, 64.88° W), between November 2011 and June 2013, using a cavity ring-down spectrometer water vapor isotope analyzer and an autonomous self-designed calibration system. Meticulous calibration allows us to reach an accuracy and precision on 10 min average of δ18O, δ D, and d-excess of, 0.14, 0.85, and 1.1‰, verified using two parallel instruments with independent calibration. As a result of more than 500 days with 6-hourly data the relationships between deuterium excess, relative humidity (RH), sea surface temperature (SST), wind speed, and wind direction are assessed. From the whole data set, 84 % of d-excess variance is explained by a strong linear relationship with relative humidity. The slope of this relationship (−42.6 ± 0.4‰ % (RH)) is similar to the theoretical prediction of Merlivat and Jouzel (1979) for SST between 20 and 30 °C. However, in contrast with theory, no effect of wind speed could be detected on the relationship between d-excess and relative humidity. Separating the data set into winter, spring, summer, and autumn seasons reveals different linear relationships between d-excess and humidity. Changes in wind directions are observed to affect the relationships between d-excess and humidity. The observed seasonal variability in the relationship between d-excess and relative humidity underlines the importance of long-term monitoring to make accurate conclusions.

Chlorides In Concrete

1988 ◽  
Vol 137 ◽  
Author(s):  
Carolyn M. Hansson ◽  
Neal S. Berke
Keyword(s):  
Electrical Resistivity ◽  
Threshold Value ◽  
Cement Type ◽  
Cement Pastes ◽  
Curing Conditions ◽  
Cement Ratio ◽  
State Diffusion ◽  
Main Culprit ◽  
The Relationship ◽  
Steady State Diffusion

AbstractChlorides are currently the main culprit in the deterioration of concrete structures in most parts of North America and Europe. During the last few years the authors have investigated the following properties: (i) the steady state diffusion of chlorides through cement pastes; (ii) penetration of chlorides into mortar and concrete; (iii) the binding of chlorides in the paste phase; (iv) the threshold value of chlorides below which corrosion of reinforcement is unlikely to occur; and (v)the relationship between the electrical resistivity and diffusivity of paste, mortar, and concrete. The variables investigated include water/cement ratio, cement type, curing conditions, effects of admixtures, and pozzolanic additions and the cover depth.

Effects of graphene layer and gold nanoparticles on sensitivity of humidity sensors

2020 ◽  
Vol 3 (1) ◽  
pp. 20-27
Author(s):  
Jiawei Bao ◽  
Niloofar Hashemi ◽  
Jingshuai Guo ◽  
Nicole N. Hashemi
Keyword(s):  
Gold Nanoparticles ◽  
Relative Humidity ◽  
Graphene Layer ◽  
Humidity Sensor ◽  
Response Times ◽  
Humidity Sensors ◽  
Micro Electro Mechanical Systems ◽  
Layer Graphene ◽  
Different Response ◽  
The Relationship

Humidity sensors can be used to monitor body sweat. Here, we studied a humidity sensor that comprised of a graphene layer between two electrodes. The operating principle is that the humidity sensor will respond when vapor reaches the graphene layer from the top. Based on the humidity diffusion, the sensor measures the relative humidity (RH) with different response times. Graphene is a material with high diffusivity and small thickness that can increase the sensitivity of a sensor. Based on the micro electro mechanical systems (MEMS) method, we modeled the humidity sensor using COMSOL Multiphysics® transport of diluted species software. Additionally, we used the concentration values from the simulations to determine the relationship between capacitance and relative humidity. The sensitivity was found to be 3.379 × 10−11 pF/%RH for the 4-layer graphene, 1.210 × 10−14 pF/%RH for the 8-layer graphene, and 3.597 × 10−11 pF/%RH for the 16-layer graphene sensor. The sensitivity of 4-layer graphene with gold sensor is 3.872 × 10−13 pF/%RH which is smaller than 4-layer graphene sensor, and graphene with gold nanoparticles shows better response time than 4-layer graphene sensor.

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