Evaluation of the subtle trade-off between physical stability and thermo-responsiveness in crosslinked methylcellulose hydrogels

Soft Matter ◽  
2020 ◽  
Vol 16 (24) ◽  
pp. 5577-5587 ◽  
Author(s):  
Lorenzo Bonetti ◽  
Luigi De Nardo ◽  
Fabio Variola ◽  
Silvia Fare'
Keyword(s):  
Mechanical Properties ◽  
Physical Stability ◽  
Fine Tuning ◽  
Chemical Crosslinking ◽  
Trade Off ◽  
Responsive Behavior

Fine-tuning of the chemical crosslinking in MC-based hydrogels increases their physical stability and mechanical properties while preserving their thermo-responsive behavior.

scholarly journals Development of Novel Lightweight Al-Rich Quinary Medium-Entropy Alloys with High Strength and Ductility

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4223
Author(s):  
Po-Sung Chen ◽  
Yu-Chin Liao ◽  
Yen-Ting Lin ◽  
Pei-Hua Tsai ◽  
Jason S. C. Jang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Compressive Strain ◽  
High Strength ◽  
Fine Tuning ◽  
Face Centered Cubic ◽  
Transportation Industry ◽  
High Entropy ◽  
Good Potential ◽  
Face Centered

Most high-entropy alloys and medium-entropy alloys (MEAs) possess outstanding mechanical properties. In this study, a series of lightweight nonequiatomic Al50–Ti–Cr–Mn–V MEAs with a dual phase were produced through arc melting and drop casting. These cast alloys were composed of body-centered cubic and face-centered cubic phases. The density of all investigated MEAs was less than 5 g/cm3 in order to meet energy and transportation industry requirements. The effect of each element on the microstructure evolution and mechanical properties of these MEAs was investigated. All the MEAs demonstrated outstanding compressive strength, with no fractures observed after a compressive strain of 20%. Following the fine-tuning of the alloy composition, the Al50Ti20Cr10Mn15V5 MEA exhibited the most compressive strength (~1800 MPa) and ductility (~34%). A significant improvement in the mechanical compressive properties was achieved (strength of ~2000 MPa, strain of ~40%) after annealing (at 1000 °C for 0.5 h) and oil-quenching. With its extremely high specific compressive strength (452 MPa·g/cm3) and ductility, the lightweight Al50Ti20Cr10Mn15V5 MEA demonstrates good potential for energy or transportation applications in the future.

scholarly journals Dynamic Mussel-Inspired Chitin Nanocomposite Hydrogels for Wearable Strain Sensors

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1416 ◽  
Author(s):  
Pejman Heidarian ◽  
Abbas Z. Kouzani ◽  
Akif Kaynak ◽  
Ali Zolfagharian ◽  
Hossein Yousefi
Keyword(s):  
Mechanical Properties ◽  
Polyacrylic Acid ◽  
Strain Sensors ◽  
Self Healing ◽  
Network Stability ◽  
Ferric Ions ◽  
Trade Off ◽  
Nanocomposite Hydrogels ◽  
Healing Efficiency ◽  
Hydrogel Network

It is an ongoing challenge to fabricate an electroconductive and tough hydrogel with autonomous self-healing and self-recovery (SELF) for wearable strain sensors. Current electroconductive hydrogels often show a trade-off between static crosslinks for mechanical strength and dynamic crosslinks for SELF properties. In this work, a facile procedure was developed to synthesize a dynamic electroconductive hydrogel with excellent SELF and mechanical properties from starch/polyacrylic acid (St/PAA) by simply loading ferric ions (Fe3+) and tannic acid-coated chitin nanofibers (TA-ChNFs) into the hydrogel network. Based on our findings, the highest toughness was observed for the 1 wt.% TA-ChNF-reinforced hydrogel (1.43 MJ/m3), which is 10.5-fold higher than the unreinforced counterpart. Moreover, the 1 wt.% TA-ChNF-reinforced hydrogel showed the highest resistance against crack propagation and a 96.5% healing efficiency after 40 min. Therefore, it was chosen as the optimized hydrogel to pursue the remaining experiments. Due to its unique SELF performance, network stability, superior mechanical, and self-adhesiveness properties, this hydrogel demonstrates potential for applications in self-wearable strain sensors.

scholarly journals Sintering of Ti-based biomedical alloys with increased oxygen content from elemental powders

2020 ◽  
Vol 321 ◽  
pp. 05010
Author(s):  
J. Stráský ◽  
J. Kozlík ◽  
K. Bartha ◽  
D. Preisler ◽  
T. Chráska
Keyword(s):  
Mechanical Properties ◽  
Oxygen Content ◽  
High Strength ◽  
Simple Approach ◽  
Fine Tuning ◽  
Powder Metallurgy Method ◽  
Ti Alloys ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Low Modulus

Revived interest for beta Ti alloys with increased oxygen content is motivated by the prospect of achieving material with low modulus and high strength simultaneously. Fine tuning of amount of oxygen and beta stabilizing elements is critical for achieving good mechanical properties. This study shows that powder metallurgy method of spark plasma sintering is capable of producing Ti-Nb-Zr-O alloys from elemental powders. This simple approach allows for quick sampling and production of several alloys with various chemical composition. Elemental powders were mixed with appropriate amount of titanium dioxide to achieve Ti-29Nb-7Zr-0.7O alloy. Sintering was performed at 1400 - 1500 °C for 15 – 30 minutes.

scholarly journals Mechanical properties of metal–organic frameworks

2019 ◽  
Vol 10 (46) ◽  
pp. 10666-10679 ◽  
Author(s):  
Louis R. Redfern ◽  
Omar K. Farha
Keyword(s):  
Mechanical Properties ◽  
Porous Materials ◽  
Metal Organic Frameworks ◽  
Physical Stability ◽  
Metal Organic

As the field of metal–organic frameworks (MOFs) continues to grow, the physical stability and mechanical properties of these porous materials has become a topic of great interest.

scholarly journals Stereocomplexation of Poly(lactic acid) and Chemical Crosslinking of Ethylene Glycol Dimethacrylate (EGDMA) Double-Crosslinked Temperature/pH Dual Responsive Hydrogels

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2204
Author(s):  
Zhidan Wang ◽  
Jie Wu ◽  
Xiaoyu Shi ◽  
Fei Song ◽  
Wenli Gao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Ethylene Glycol ◽  
Crosslinking Agent ◽  
Ethylene Glycol Dimethacrylate ◽  
Poly Lactic Acid ◽  
Chemical Crosslinking ◽  
Glycol Dimethacrylate ◽  
Dual Responsive ◽  
Responsive Hydrogels ◽  
Physical Crosslinking

Physical crosslinking and chemical crosslinking were used to further improve the mechanical properties and stability of the gel. A temperature/pH dual sensitive and double-crosslinked gel was prepared by the stereo-complex of HEMA-PLLA20 and HEMA-PDLA20 as a physical crosslinking agent, ethylene glycol dimethacrylate (EGDMA) as a chemical crosslinking agent, and azodiisobutyronitrile (AIBN) as an initiator for free radical polymerization. This paper focused on the performance comparison of chemical crosslinked gel, a physical crosslinked gel, and a dual crosslinked gel. The water absorption, temperature, and pH sensitivity of the three hydrogels were studied by a scanning electron microscope (SEM) and swelling performance research. We used a thermal analysis system (TGA) and dynamic viscoelastic spectrometer to study thermal properties and mechanical properties of these gels. Lastly, the in vitro drug release behavior of double-crosslinked hydrogel loaded with doxorubicin under different conditions was studied. The results show that the double-crosslinked and temperature/pH dual responsive hydrogels has great mechanical properties and good stability.

scholarly journals A trade-off between Energy Efficiency and Spectral Efficiency in macro-femtocell networks

2021 ◽  
Author(s):  
Joydev Ghosh
Keyword(s):  
Energy Efficiency ◽  
Spectral Efficiency ◽  
Analytical Framework ◽  
Weighting Factor ◽  
Base Station ◽  
Fine Tuning ◽  
Pareto Optimal ◽  
Femtocell Networks ◽  
Transmit Power ◽  
Trade Off

<div>Obtaining large spectral efficiency (SE) and energy efficiency (EE) subject to quality of experience (QoE) is one of the prime concerns for the wireless next generation networks, however a major confrontation with its trade-off which is becoming apparent while optimizing both SE and EE parameters concurrently. In this work, an analytical framework for a cognitive-femtocell network is proposed to be dealt with and overcome the situations regarded as unwelcome. Here, the conflict of SE-EE trade-off in downlink (DL) transmission is expressed methodically by Pareto Optimal Set (POS) based on a multi-empirical most effective use of a resource scheme as a function of femto base station (FBS) and macro base station (MBS) transmit power and base station (BS) density, respectively. Then, SE and EE are formulated in a utility function by applying Cobb-Douglas production function to transform the multi- mpirical difficulty into the single-empirical optimization case. Besides, it is analytically shown that the SE-EE trade-off can be optimize through a distinctive universal optimum among the Pareto optimal by fine tuning the weighting metric other than BS transmit power and density, respectively. Simulation results validate that it is possible to obtain the EE-SE trade-off with SINR threshold at different weighting factor.</div>

scholarly journals Active Transiency: A Novel Approach to Expedite Degradation in Transient Electronics

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1514
Author(s):  
Reihaneh Jamshidi ◽  
Yuanfen Chen ◽  
Reza Montazami
Keyword(s):  
Mechanical Properties ◽  
Citric Acid ◽  
Electronic Device ◽  
Physical Stability ◽  
Dissolution Mechanism ◽  
Proof Of Concept ◽  
Complex Chemical ◽  
Novel Approach ◽  
Control Devices ◽  
And Diffusion

Transient materials/electronics is an emerging class of technology concerned with materials and devices that are designed to operate over a pre-defined period of time, then undergo controlled degradation when exposed to stimuli. Degradation/transiency rate in solvent-triggered devices is strongly dependent on the chemical composition of the constituents, as well as their interactions with the solvent upon exposure. Such interactions are typically slow, passive, and diffusion-driven. In this study, we are introducing and exploring the integration of gas-forming reactions into transient materials/electronics to achieve expedited and active transiency. The integration of more complex chemical reaction paths to transiency not only expedites the dissolution mechanism but also maintains the pre-transiency stability of the system while under operation. A proof-of-concept transient electronic device, utilizing sodium-bicarbonate/citric-acid pair as gas-forming agents, is demonstrated and studied vs. control devices in the absence of gas-forming agents. While exhibiting enhanced transiency behavior, substrates with gas-forming agents also demonstrated sufficient mechanical properties and physical stability to be used as platforms for electronics.

scholarly journals Controllable thermal and pH responsive behavior of PEG based hydrogels and applications for dye adsorption and release

RSC Advances ◽  
2018 ◽  
Vol 8 (17) ◽  
pp. 9334-9343 ◽  
Author(s):  
Hailong Huang ◽  
Lifeng Hou ◽  
Feng Zhu ◽  
Juan Li ◽  
Min Xu
Keyword(s):  
Mechanical Properties ◽  
Dye Adsorption ◽  
Adsorption Properties ◽  
Ph Responsive ◽  
Responsive Behavior ◽  
Stimuli Response ◽  
Adsorption And Release ◽  
Responsive Hydrogels

Controllable thermal and pH responsive hydrogels not only showed good stimuli-response and mechanical properties, but also have excellent adsorption properties.

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