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1.
Molecules ; 26(4)2021 Feb 04.
Article in English | MEDLINE | ID: mdl-33557189

ABSTRACT

The physical and mechanical properties of nitrile-butadiene rubber (NBR) composites with N-cetylpyridinium bromide-carbon black (CPB-CB) were investigated. Addition of 5 parts per hundred rubber (phr) of CPB-CB into NBR improved the tensile strength by 124%, vulcanization rate by 41%, shore hardness by 15%, and decreased the volumetric wear by 7% compared to those of the base rubber-CB composite.


Subject(s)
Butadienes/chemistry , Cetylpyridinium/chemistry , Mechanical Phenomena , Nitriles/chemistry , Physical Phenomena , Rubber/chemistry , Soot/chemistry
2.
Nanotechnology ; 30(43): 435203, 2019 Oct 25.
Article in English | MEDLINE | ID: mdl-31349232

ABSTRACT

This study describes the design of a flexible narrowband organic photodiode (OPDs) with a novel structure. A bulk heterojunction of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) is introduced as a photoactive layer, with an optimized thickness of 160 nm, and a MoO3/Ag/MoO3 (MAM) multilayer electrode and polyimide (PI) film substrate were used. The OPD with the device architecture of PI/MAM/P3HT:PC70BM/Al showed narrowband photodiode performance in the 500-650 nm wavelength range. The maximum external quantum efficiency (EQE) of the OPD was 15.41% at 570 nm, which dropped to ∼0% outside the operation wavelength range. This narrowband detectivity originated from the cutoff of light at wavelengths below 500 nm by the PI substrate and photoreactivity of P3HT:PC70BM at wavelengths between 300 and 650 nm. Outer bending tests performed over 1000 cycles revealed that the average maximum EQE remained at ∼15%. The maximum responsivity of the OPD was calculated to be 0.07 A W-1 at 570 nm. The OPD device showed a narrow response spectrum with a full width at half maximum of 100 nm. This research suggests a new approach for the fabrication of flexible OPDs with high selectivity in color detection.

3.
Molecules ; 24(2)2019 Jan 09.
Article in English | MEDLINE | ID: mdl-30634465

ABSTRACT

Mixtures of layered silicates (vermiculite and kaolinite) and carbon fibers were investigated as filler materials for polytetrafluoroethylene. The supramolecular structure and the tribological and mechanical properties of the resulting polymer composite materials were evaluated. The yield strength and compressive strength of the polymer increased by 55% and 60%, respectively, when a mixed filler was used, which was attributed to supramolecular reinforcement of the composites. In addition, the wear resistance increased by 850 times when using vermiculite/kaolinite fillers, which was due to protection of the surface by the formation of hard tribofilms.


Subject(s)
Carbon Fiber/chemistry , Polytetrafluoroethylene/chemistry , Silicates/chemistry , Aluminum Silicates/chemistry , Compressive Strength , Hardness , Kaolin/chemistry , Materials Testing
4.
Molecules ; 23(9)2018 Aug 27.
Article in English | MEDLINE | ID: mdl-30150557

ABSTRACT

Sealing rubbers employed in cold climates such as the Siberian Arctic must be able to withstand temperatures as low as -50 °C while still exhibiting specific relaxation, strength, tribological characteristics, and a resistance to aggressive media. Previous investigations of propylene oxide rubber (SKPO, Tg = -73 °C) modified with polytetrafluoroethylene (PTFE) have revealed that, while the rubber composite materials exhibit double the wear resistance compared to unmodified polypropylene oxide rubber, they have poor frost resistance. In the present study, we developed materials based on SKPO and ultrafine PTFE (UPTFE), which can be characterized by its smaller particle size, low molecular weight, high tribo-technical characteristics, and resistance to aggressive media. The properties of the rubber composites were evaluated using the standard methods. The structures of the materials were investigated by electron microscopy and XRD analysis. It was shown that the materials have excellent wear resistance, resistance to aggressive media, compression set, and low-temperature resistance. The addition of UPTFE is preferable to the addition of PTFE because the desired positive effects can be attained with only 0.5⁻1 parts per hundred parts of rubber (phr) UPTFE while 20 phr PTFE would be necessary.


Subject(s)
Epoxy Compounds/chemistry , Epoxy Compounds/isolation & purification , Rubber/chemistry , Materials Testing , Mechanical Phenomena , X-Ray Diffraction
5.
Molecules ; 22(12)2017 Dec 05.
Article in English | MEDLINE | ID: mdl-29206140

ABSTRACT

In this study, the reinforcement of ultrahigh-molecular-weight polyethylene (UHMWPE) with biotite was investigated. The biotite filler was mechanically activated with different dry surfactants to improve its compatibility with UHMWPE and decrease agglomeration among biotite particles. Alkyldimethylbenzylammonium chloride (ADBAC) and cetyltrimethylammonium bromide (CTAB) were selected as cationic surfactants. The tensile strength of composites containing 1 wt % of CTAB-treated biotite was increased by 30% relative to those with untreated biotite, but was unchanged with ADBAC treatment of the same biotite content. The stereochemistry of the surfactant may be critical to the composite structure and mechanical properties of the material. The stereochemistry of CTAB was preferable to that of ADBAC in enhancing mechanical properties because the stereochemistry of ADBAC impedes favorable interactions with the biotite surface during mechanical activation.


Subject(s)
Aluminum Silicates/chemistry , Benzalkonium Compounds/chemistry , Cetrimonium Compounds/chemistry , Ferrous Compounds/chemistry , Polyethylenes/chemistry , Surface-Active Agents/chemistry , Cetrimonium , Cold Temperature , Construction Materials , Humans , Materials Testing , Tensile Strength
6.
J Nanosci Nanotechnol ; 15(11): 9030-3, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26726637

ABSTRACT

Carbon nanotubes (CNTs) have been investigated as field-emission sources owing to their high electrical conductivity and high aspect ratio. However, practical applications demand that the emission lifetime of CNTs be further improved. Since ZnO demonstrates impressive electrical and thermal conductivity, when coated on the surface of CNTs, it can allow the CNT field emitters to endure high electrical stress and high temperature. Moreover, ZnO nanostructures protect the CNT emitters from being bombarded by high-energy ions, which are accelerated by the high electric field. From the result of emission lifetime measurements at the emission current density of 100 mA/cm2, we found that the emission lifetime was increased by more than a factor of 2 when ZnO had been coated onto the CNT emitters. The observation registers as an important contribution to the practical application of CNT emitters with long-term emission stability, as well as with high emission currents. In this work, we elucidate the detailed mechanism of long-term stability that can be achieved by coating ZnO nanostructures on the surface of CNTs.

7.
Nanoscale ; 6(24): 14622-6, 2014 Dec 21.
Article in English | MEDLINE | ID: mdl-25355156

ABSTRACT

We observed giant enhancement of the Raman intensity from 4-Mpy molecules adsorbed on semiconducting one-dimensional ZnO nanostructures, nanowires and nanocones, without involving any noble metals. Interestingly, the enhancement is strongly dependent on the geometry of ZnO nanostructures and can mainly be explained by the cavity-like structural resonance of the electric field. Our results can be applied to systematically create hot spots for Raman signal enhancement using one-dimensional semiconducting nanomaterials.

8.
J Nanosci Nanotechnol ; 12(12): 8904-7, 2012 Dec.
Article in English | MEDLINE | ID: mdl-23447936

ABSTRACT

Boron-doped microcrystalline diamond (BMD) and nanocrystalline diamond (BND) thin films were grown on Si substrates by microwave-assisted chemical vapor deposition, and their field emission properties were evaluated. BND exhibited a lower turn-on field and higher field enhancement factor than BMD. Furthermore, in a long-term emission stability test, BND showed only a 4% increase in the current density after 12 h of emission, whereas the current density of BMD decreased by - 59%. These results indicate that BND is a more stable and viable current emitter than BMD.

9.
Nanotechnology ; 22(28): 285711, 2011 Jul 15.
Article in English | MEDLINE | ID: mdl-21659688

ABSTRACT

We report, for the first time, direct observation of enhanced cathodoluminescence (CL) emissions from ZnO nanocones (NCs) compared with ZnO nanowires (NWs). For direct and unambiguous comparison of CL emissions from NWs and nanocones, periodic arrays of ZnO NW were converted to nanocone arrays by our unique HCl [aq] etching technique, enabling us to compare the CL emissions from original NWs and final nanocones at the same location. CL measurements on NW and nanocone arrays reveal that emission intensity of the nanocone at ∼ 387 nm is over two times larger than that of NW arrays. The enhancement of CL emission from nanocones has been confirmed by finite-difference time-domain simulation of enhanced light extraction from ZnO nanocones compared to ZnO NWs. The enhanced CL from nanocones is attributed to its sharp morphology, resulting in more chances of photons to be extracted at the interface between ZnO and air.

10.
J Nanosci Nanotechnol ; 9(12): 7398-401, 2009 Dec.
Article in English | MEDLINE | ID: mdl-19908796

ABSTRACT

In this report, a simple wet chemical etching of ZnO nanorods to fabricate large area ZnO nanocones is demonstrated. The cone-like morphology formation utilizes anisotropic etching rate on the different crystal planes of ZnO nanorods in an aqueous solution of HCl (HCl [aq]). To form ZnO nanocones, single crystalline ZnO nanorods with a flat hexagonal shape are synthesized on p-Si(100) using hydrothermal method at 90 degrees C and then, are immersed in HCl [aq]. Electron microscopy reveals that the HCl [aq] treatment of ZnO nanorods significantly etched sidewalls of nanorods, resulting in the cone-like morphology formation. The nanocone formation is the most noticeable when the etching occurred in HCl [aq] with a pH of 2.5-3.0 for 5 min etching time. Geometrical analysis using the electron microscopy reveals that the sidewall of a ZnO nanocone have formed a plane indexed as (0-111) after the etching process.

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