scholarly journals Electrical Monitoring as a Novel Route to Understanding the Aging Mechanisms of Carbon Nanotube-Doped Adhesive Film Joints

2020 ◽  
Vol 10 (7) ◽  
pp. 2566 ◽  
Author(s):  
Xoan F. Sánchez-Romate ◽  
Alberto Jiménez-Suárez ◽  
María Sánchez ◽  
Silvia G. Prolongo ◽  
Alfredo Güemes ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Theoretical Calculations ◽  
Electrical Response ◽  
Partial Recovery ◽  
Initial State ◽  
Scanning Calorimetry ◽  
Resistance Change ◽  
Adhesive Film ◽  
Lap Shear ◽  
Aging Conditions

Carbon fiber-reinforced plastic bonded joints with novel carbon nanotube (CNT) adhesive films were manufactured and tested under different aging conditions by varying the surfactant content added to enhance CNT dispersion. Single lap shear (SLS) tests were conducted in their initial state and after 1 and 2 months immersed in distilled water at 60 °C. In addition, their electrical response was measured in terms of the electrical resistance change through thickness. The lap shear strength showed an initial decrease due to plasticization of weak hydrogen bonds, and then a partial recovery due to secondary crosslinking. This plasticization effect was confirmed by differential scanning calorimetry analysis with a decrease in the glass transition temperature. The electrical response varied with aging conditions, showing a higher plasticity region in the 1-month SLS joints, and a sharper increase in the case of the non-aged and 2-month-aged samples; these changes were more prevalent with increasing surfactant content. By adjusting the measured electrical data to simple theoretical calculations, it was possible to establish the first estimation of damage accumulation, which was higher in the case of non-aged and 2-month-aged samples, due to the presence of more prevalent brittle mechanisms for the CNT-doped joints.

scholarly journals Mechanical and Crack-Sensing Capabilities of Mode-I Joints with Carbon-Nanotube-Reinforced Adhesive Films under Hydrothermal Aging Conditions

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2290
Author(s):  
Xoan F. Sánchez-Romate ◽  
Jesús Martin ◽  
María Sánchez ◽  
Alejandro Ureña
Keyword(s):  
Carbon Nanotube ◽  
Crack Propagation ◽  
Electrical Resistance ◽  
Crack Detection ◽  
Electrical Response ◽  
Mode I ◽  
Hydrothermal Aging ◽  
Unstable Crack ◽  
Plasticization Effect ◽  
Aging Conditions

The fracture behavior and crack sensing of mode-I joints with carbon nanotube (CNT)-reinforced adhesive films were explored in this paper under hydrothermal aging conditions. The measured fracture energy of CNT-reinforced joints in grit blasting conditions is higher for non-aged samples than for neat adhesive joints (around 20%) due to the nanofiller toughening and crack bridging effects. However, in the case of brushed surface-treated adherents, a drastic decrease is observed with the addition of CNTs (around 70%) due to the enhanced tribological properties of the nanofillers. Hydrothermal aging has a greater effect in the CNT-reinforced samples, showing a more prevalent plasticization effect, which is confirmed by the R-curves of the specimens. The effects of surface treatment on the crack propagation properties was observed by electrical resistance monitoring, where brushed samples showed a more unstable electrical response, explained by more unstable crack propagation and reflected by sharp increases of the electrical resistance. Aged specimens showed a very uniform increase of electrical resistance due to slower crack propagation, as induced by the plasticization effect of water. Therefore, the proposed adhesive shows a high applicability for crack detection and propagation without decreasing the mechanical properties.

scholarly journals Directional Response of Randomly Dispersed Carbon Nanotube Strain Sensors

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2980
Author(s):  
Alfredo Güemes ◽  
Angel Renato Pozo Morales ◽  
Antonio Fernandez-Lopez ◽  
Xoan Xose F. Sanchez-Romate ◽  
Maria Sanchez ◽  
...  
Keyword(s):  
Electrical Response ◽  
Tensile Load ◽  
Epoxy Adhesive ◽  
Resistance Change ◽  
Adhesive Film ◽  
Bonded Joint ◽  
Individual Strain ◽  
Strain Components ◽  
The Individual ◽  
Transverse Strains

Tests on a double lap bonded joint, with transverse strips of randomly oriented carbon nanotubes (CNT) sprayed onto an epoxy adhesive film, showed a positive increment in electrical resistance under tensile load, even though the transverse strains were negative. Other experiments included in this work involved placing longitudinal and transversal CNT sensors in a tensile loaded aluminum plate, and, as reported by other authors, the results confirm that the resistance change is not only dependent on the strains oriented with the electrode line, while the other strain components also influence the response. This behavior is quite different to that of conventional strain gages which have a near zero sensitivity to strains not aligned to the sensor direction. The dependence of the electrical response on all the strain components makes it quite difficult, possibly unfeasible, to experimentally determine the individual strain components with this kind of sensors; however, the manufacturing of aligned CNT sensors could deal with this issue.

scholarly journals Monitoring of Curing and Cyclic Thermoresistive Response Using Monofilament Carbon Nanotube Yarn Silicone Composites

2021 ◽  
Vol 7 (3) ◽  
pp. 60
Author(s):  
Tannaz Tayyarian ◽  
Omar Rodríguez-Uicab ◽  
Jandro L. Abot
Keyword(s):  
Carbon Nanotube ◽  
Heating Rate ◽  
Electrical Resistance ◽  
Room Temperature ◽  
Electrical Response ◽  
Negative Temperature ◽  
Curing Kinetics ◽  
Curing Process ◽  
Resistance Change ◽  
Electrical Resistance Change

The curing process and thermoresistive response of a single carbon nanotube yarn (CNTY) embedded in a room temperature vulcanizing (RTV) silicone forming a CNTY monofilament composite were investigated toward potential applications in integrated curing monitoring and temperature sensing. Two RTV silicones of different crosslinking mechanisms, SR1 and SR2 (tin- and platinum-cured, respectively), were used to investigate their curing kinetics using the electrical response of the CNTY. It is shown that the relative electrical resistance change of CNTY/SR1 and CNTY/SR2 monofilament composites increased by 3.8% and 3.3%, respectively, after completion of the curing process. The thermoresistive characterization of the CNTY monofilament composites was conducted during heating–cooling ramps ranging from room temperature (RT~25 °C) to 100 °C. The thermoresistive response was nearly linear with a negative temperature coefficient of resistance (TCR) at heating and cooling sections for both CNTY/SR1 and CNTY/SR2 monofilament composites. The average TCR value was −8.36 × 10−4 °C−1 for CNTY/SR1 and −7.26 × 10−4 °C−1 for CNTY/SR2. Both monofilament composites showed a negligible negative residual relative electrical resistance change with average values of ~−0.11% for CNTY/SR1 and ~−0.16% for CNTY/SR2 after each cycle. The hysteresis amounted to ~21.85% in CNTY/SR1 and ~29.80% in CNTY/SR2 after each cycle. In addition, the effect of heating rate on the thermoresistive sensitivity of CNTY monofilament composites was investigated and it was shown that it reduces as the heating rate increases.

Salts of purine alkaloids caffeine and theobromine with 2,6-dihydroxybenzoic acid as coformer: structural, theoretical, thermal and spectroscopic studies

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Mateusz Gołdyn ◽  
Anna Komasa ◽  
Mateusz Pawlaczyk ◽  
Aneta Lewandowska ◽  
Elżbieta Bartoszak-Adamska
Keyword(s):  
Hydrogen Bonds ◽  
Water Solubility ◽  
Theoretical Calculations ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
Dihydroxybenzoic Acid ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Purine Alkaloids ◽  
Vis Spectroscopy

The study of various forms of pharmaceutical substances with specific physicochemical properties suitable for putting them on the market is one of the elements of research in the pharmaceutical industry. A large proportion of active pharmaceutical ingredients (APIs) occur in the salt form. The use of an acidic coformer with a given structure and a suitable pK a value towards purine alkaloids containing a basic imidazole N atom can lead to salt formation. In this work, 2,6-dihydroxybenzoic acid (26DHBA) was used for cocrystallization of theobromine (TBR) and caffeine (CAF). Two novel salts, namely, theobrominium 2,6-dihydroxybenzoate, C7H9N4O2 +·C7H5O4 − (I), and caffeinium 2,6-dihydroxybenzoate, C8H11N4O2 +·C7H5O4 − (II), were synthesized. Both salts were obtained independently by slow evaporation from solution, by neat grinding and also by microwave-assisted slurry cocrystallization. Powder X-ray diffraction measurements proved the formation of the new substances. Single-crystal X-ray diffraction studies confirmed proton transfer between the given alkaloid and 26DHBA, and the formation of N—H...O hydrogen bonds in both I and II. Unlike the caffeine cations in II, the theobromine cations in I are paired by noncovalent N—H...O=C interactions and a cyclic array is observed. As expected, the two hydroxy groups in the 26DHBA anion in both salts are involved in two intramolecular O—H...O hydrogen bonds. C—H...O and π–π interactions further stabilize the crystal structures of both compounds. Steady-state UV–Vis spectroscopy showed changes in the water solubility of xanthines after ionizable complex formation. The obtained salts I and II were also characterized by theoretical calculations, Fourier-transform IR spectroscopy (FT–IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis.

Microstructure of Sn-20In-2.8Ag solder and mechanical properties of joint with Cu

2019 ◽  
Vol 31 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Fen Peng ◽  
Wensheng Liu ◽  
Yunzhu Ma ◽  
Chaoping Liang ◽  
Yufeng Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Eutectic Reaction ◽  
Scanning Calorimetry ◽  
Good Reliability ◽  
Content Type ◽  
Dsc Measurements ◽  
Lap Shear ◽  
Evolution Characteristics ◽  
Three Phase ◽  
Melting And Solidification

Purpose To explore substitutes for traditional Sn-Pb solder, Sn-20In-2.8Ag was considered because of its appropriate melting temperature, good reliability and high ductility at less than 100°C. However, the mechanical properties of Sn-20In-2.8Ag were not satisfactory. The reason for the poor mechanical properties of the Sn-20In-2.8Ag/Cu joint was revealed, and a way to solve the problem was found. Design/methodology/approach The microstructure evolution, characteristics of melting and solidification and joining performance with Cu were investigated using scanning electron microscopy (SEM), electron probe microanalysis, differential scanning calorimetry (DSC) and mechanical testing. Findings SEM results showed that the microstructure of Sn-20In-2.8Ag was composed of coarse dendritic Ag2In and γ phases, with Ag2In distributed at the grain boundaries. DSC measurements revealed that small amount of low temperature eutectic reaction, L → Ag2In + β + γ, occurred at 112.9°C. This reaction was caused by the segregation of indium, which is a process that has a strong driving force. In the lap-shear testing, a crack propagated along the grain boundary of the solder, and failure showed an intergranular fracture. This failure was connected with the three-phase eutectic and coarse Ag2In. Thus, to improve the mechanical properties, segregation of indium should be reduced and coarsening of Ag2In should be prevented. Originality/value The reason for the unsatisfactory mechanical properties of Sn-20In-2.8Ag was revealed via microstructural observations and solidification analysis, and the way to solve this problem was found.

Electro-flexure response of multi-functional natural fiber hybrid composites

2020 ◽  
pp. 073168442095739
Author(s):  
Christopher Meninno ◽  
Vijaya Chalivendra ◽  
Yong Kim
Keyword(s):  
Carbon Fiber ◽  
Carbon Fibers ◽  
Fiber Length ◽  
Natural Fiber ◽  
Hybrid Composites ◽  
Electrical Response ◽  
Linear Increase ◽  
Resistance Change ◽  
Flax Fibers ◽  
Flexural Loading

An experimental study was conducted to investigate the electro-flexure response of conductive natural fiber hybrid laminate composites. The composites were composed of laminates of jute and flax fibers, and the composites were subjected to flexural loading for the electrical and bending response. Multi-walled carbon nanotubes were shear mixed and ultrasonicated into the epoxy matrix. Short carbon fibers were reinforced in-between the laminates using “wet flocking” technique. To measure the electrical response under flexural loading, a four-point circumferential probe method was used. A parametric study was conducted to investigate flexural performance and damage sensing by varying carbon fiber lengths (150 and 350 µm) and the carbon fiber densities (500, 1000, 1500, and 2000 fibers/mm2). The addition of carbon fibers decreased the flexural strength for most of the cases, however increased the flexural strain at break for all composites of carbon fiber length of 150 µm. During the nonlinear deformation, the composites of carbon fiber length of 150 µm demonstrated a linear increase in resistance; however, that of carbon fiber length of 350 µm showed increasing slope of resistance. Overall, the composites of carbon fiber length of 350 µm showed lower resistance change at break compared to that of carbon fiber length of 150 µm.

Thermodynamics kinetics of boron carbide under gamma irradiation dose

2019 ◽  
Vol 33 (09) ◽  
pp. 1950073 ◽  
Author(s):  
Matlab Mirzayev ◽  
Ertugrul Demir ◽  
Khagani Mammadov ◽  
Ravan Mehdiyeva ◽  
Sakin Jabarov ◽  
...  
Keyword(s):  
Activation Energy ◽  
Boron Carbide ◽  
Gamma Irradiation ◽  
Irradiation Time ◽  
Energy Levels ◽  
Initial State ◽  
Scanning Calorimetry ◽  
Gas Atmosphere ◽  
Quantitative Changes ◽  
Kinetics Of

In this paper, high purity boron carbide samples were irradiated by [Formula: see text]Co gamma radioisotope source (0.27 Gy/s dose rate) with 50, 100, 150 and 200 irradiation hours at room-temperature. The unirradiated and irradiated boron carbide samples were heated from 30[Formula: see text]C to 1000[Formula: see text]C at a heating rate of 5[Formula: see text]C/min under the argon gas atmosphere of flow rate 20 ml/min. Thermogravimetric (TG) and Differential Scanning Calorimetry (DSC) were carried out in order to understand the thermodynamic kinetics of boron carbide samples. The weight kinetics, activation energy and specific heat capacity of the unirradiated and irradiated boron carbide samples were examined in two parts, T [Formula: see text] 650[Formula: see text]C and T [Formula: see text] 650[Formula: see text]C, according to the temperature. The dynamic of quantitative changes in both ranges is different depending on the irradiation time. While the phase transition of unirradiated boron carbide samples occurs at 902[Formula: see text]C, this value shifts upto 940[Formula: see text]C in irradiated samples depending on the irradiation time. The activation energy of the unirradiated boron carbide samples decreased from 214 to 46 J/mol in the result of 200[Formula: see text]h gamma irradiation. The reduction of the activation energy after the irradiation compared to the initial state shows that the dielectric properties of the irradiated boron carbide samples have been improved. After the gamma irradiation, two energy barrier states depending on the absorption dose of samples were formed in the irradiated samples. The first and second energy barriers occurred in 0.56–0.80 and 0.23–0.36 eV energy intervals, respectively. The existence of two energy levels in the irradiated boron carbide indicates that the point defects are at deep levels, close to the valence band.

scholarly journals Engineering efficient bifunctional electrocatalysts for rechargeable zinc–air batteries by confining Fe–Co–Ni nanoalloys in nitrogen-doped carbon nanotube@nanosheet frameworks

2020 ◽  
Vol 8 (48) ◽  
pp. 25919-25930
Author(s):  
Xiannong Tang ◽  
Rui Cao ◽  
Longbin Li ◽  
Bingyu Huang ◽  
Weijuan Zhai ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Theoretical Calculations ◽  
Nitrogen Doped ◽  
Bifunctional Electrocatalysts ◽  
Nitrogen Doped Carbon ◽  
Zinc Air Batteries

Fe–Co–Ni nanoalloys embedded in nitrogen-doped carbon nanotube@nanosheet frameworks (FeCoNi-NC) is prepared as excellent bifunctional ORR/OER electrocatalyst, which is confirmed by experimental observations and theoretical calculations.

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