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1.
Nanomaterials (Basel) ; 9(11)2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31671586

RESUMO

It is essential to develop a novel and versatile strategy for constructing electrically conductive adhesives (ECAs) that have superior conductivity and high mechanical properties. In this work, easily synthesized polyaniline@cellulose (PANI@CNs) nanowhiskers with a high aspect ratio and excellent solubility in 1,4-dioxane were prepared and added to conventional Ag-containing adhesives. A small amount of PANI@CNs can dramatically tune the structure of the ECAs' conductive network and significantly improve the conductivity of the ECAs. Good solubility of PANI@CNs in solvents brings excellent dispersion in the polymer matrix. Thus, a three-dimensional (3D) conducting network formed with dispersed PANI@CNs and Ag flakes can enhance the conductivity of ECAs. The conductivity of the ECAs (with 1.5 wt% PANI@CNs and 55 wt% Ag flakes) showed three orders of magnitude higher than that of the ECAs filled with 55 wt% Ag flakes and 65 wt% Ag flakes. Meanwhile, the integration of PANI@CNs with Ag flakes in polymer matrices also significantly enhanced the mechanical compliance of the resulted ECAs. The resistivity remained unchanged after rolling the PANI@CNs-containing ECAs' film into a 4 mm bending radius for over 1500 cycles. A bendable printed circuit was fabricated using the above PANI@CNs-containing ECAs, which demonstrated their future potential in the field of flexible electronics.

2.
ACS Omega ; 4(4): 6092-6096, 2019 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-31459756

RESUMO

By using pulse electrodeposition, a copper nanopillar array (CuNPA) was filled into porous anodized aluminum oxide (AAO) films to achieve a highly thermal conductive interconnector with anisotropic property. After 120 min pulse deposition, CuNPA uniformly filled the pores of AAO with a pore-filling percentage of 99.4%, as the ion concentration in AAO pores can re-equilibrate to electrolyte concentration during the current-off period. The CuNPA-filled AAO film showed a high thermal conductivity of 153.12 W/(m·K) in the vertical direction and a low thermal conductivity of 3.43 W/(m·K) in the horizontal direction. Hence, the anisotropic ratio of the thermal conductivity reached 44.64. Moreover, the fabrication process was facile and cost-effective, showing a potential application prospect in the field of high-density packages and power electronic devices.

3.
Nanomaterials (Basel) ; 9(7)2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31266135

RESUMO

Electrically conductive adhesives (ECAs) are one of the low temperature bonding materials. It can be used to replace toxic Sn-Pb solder. The key issue for the application of ECAs is how to improve their electrical properties. In the present study, we develop an effective method to promote the electrical properties of ECAs by addition of polyaniline (PANI) nanoparticles. PANIs were synthesized via a facile one-step chemical oxidative polymerization method. After adding 0.5 wt% PANI nanoparticles, the conductivity of ECAs increased dramatically by an order of magnitude. The bulk resistivity of 8.8 × 10-5 Ω·cm is achieved for 65 wt% silver fillers with 0.5 wt% PANIs loaded ECAs. Besides, this improvement has no negative effect on the shear strength and the aging life of ECAs. Moreover, the use of PANIs not only lowers the percolation threshold of ECAs, but also reduces the cost and improves the bonding reliability. Finally, PANIs enhanced ECAs patterns were successfully printed by a stencil printing method, which proved their potential applications in replacing conventional solder pastes and printing functional circuits.

4.
Artigo em Inglês | MEDLINE | ID: mdl-31299362

RESUMO

We developed an online solid phase extraction procedure using a hydrophilic-lipophilic balance sorbent, with reversed-phase liquid chromatography-high-resolution mass spectroscopy for the determination of oxcarbazepine and its active metabolite licarbazepine in plasma samples. The analytes were detected using a high-resolution Q Orbitrap mass spectrometer with targeted-selected ion monitoring (t-SIM) in positive scan mode. Under the optimized conditions, the method was linear with R2 values >0.99. The method was linear from 0.008 to 2.000 µg mL-1 and the lower limit of quantification was 0.008 µg mL-1 for both oxcarbazepine and licarbazepine. Recoveries ranged from 92.34 to 104.27% and from matrix-matched samples from 94.26 to 104.19%. The intraday and interday precision RSD values were <9.13% with an associated accuracy of 92.71 to 104.06%. The total time for the one step online procedure was only 8 min. This method provides a direct and accurate measurement for therapeutic drug monitoring of oxcarbazepine and its active metabolite licarbazepine.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Dibenzazepinas/isolamento & purificação , Oxcarbazepina/isolamento & purificação , Extração em Fase Sólida/métodos , Espectrometria de Massas em Tandem/métodos , Dibenzazepinas/sangue , Humanos , Oxcarbazepina/sangue
5.
ACS Appl Mater Interfaces ; 11(24): 21850-21858, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31132241

RESUMO

Silver nanowires (Ag NWs) are key materials to fabricate next-generation flexible transparent electrodes (FTEs). Currently, the applications of Ag NWs are impeded by the large wire-wire contact resistance. Herein, a self-limited nanosoldering method is proposed to reduce the contact resistance by epitaxially depositing silver nanosolders at the Ag NW junctions, which have a negligible effect on the optical transparency, while decreasing the sheet resistance of the Ag NW film from 18.6 to 7.7 Ω/sq at a transmittance of 90%. In addition, the deposited nanosolders at the junctions remarkably improve the electrical and mechanical stabilities of the Ag NW electrodes. Notably, this simple nanosoldering process can be rapidly conducted under room temperature and ambient conditions and is free of any technical support or specific equipment. This technique is easily applied to the nanosoldering of 210 × 297 mm FTEs. Based on these FTEs, a high-performance flexible transparent heater with a sheet resistance 3.7 Ω/sq at a transmittance of 82.5% is constructed. Because of the high heating rate (4.8 °C/s), the heater can produce uniform heating (145 °C) at a short response time (30 s) and low input voltage (6 V).

6.
Materials (Basel) ; 12(4)2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30781620

RESUMO

Poly(p-phenylene benzobisoxazole) (PBO) fiber shows fascinating properties including excellent mechanical performance, high crystallinity, and fairly good heat resistance as a kind of polymer fiber. Its properties make it a possible candidate as a precursor of carbon fiber. This paper mainly investigates the possibility of yielding carbon fiber from PBO by direct carbonization using a continuous process and multiple properties of yielded fiber treated under different heat treatment temperature (HTT). The results show that PBO fiber was able to sustain an HTT as high as 1400 °C under the inert atmosphere and that the shape of fiber was still preserved without failure. Using thermal gravimetric analysis (TGA) and TGA coupled with mass spectroscopy (TGA-MS), it was found that a significant mass loss procedure happened around 723.3 °C, along with the emission of various small molecules. The mechanical performance first suffered a decrease due to the rupture of the PBO structure and then slightly increased because of the generating of graphite crystallite based on the broken structure of PBO. It was observed that PBO's microstructure transformed gradually to that of carbonaceous material, which could be the reason why the change of mechanical performance happened.

7.
Micromachines (Basel) ; 9(7)2018 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-30424279

RESUMO

Recently, nanosilver pastes have emerged as one of the most promising high temperature bonding materials for high frequency and high power applications, which provide an effective lead-free electronic packaging solution instead of high-lead and gold-based solders. Although nanosilver pastes can be sintered at lower temperature compared to bulk silver, applications of nanosilver pastes are limited by long-term sintering time (20⁻30 min), relative high sintering temperature (>250 °C), and applied external pressure, which may damage chips and electronic components. Therefore, low temperature rapid sintering processes that can obtain excellent nanosilver joints are anticipated. In this regard, we present a review of recent progress in the rapid sintering of nanosilver pastes. Preparation of nanosilver particles and pastes, mechanisms of nanopastes sintering, and different rapid sintering processes are discussed. Emphasis is placed on the properties of sintered joints obtained by different sintering processes such as electric current assisted sintering, spark plasma sintering, and laser sintering, etc. Although the research on rapid sintering processes for nanosilver pastes has made a great breakthrough over the past few decades, investigations on mechanisms of rapid sintering, and the performance of joints fabricated by pastes with different compositions and morphologies are still far from enough.

8.
Talanta ; 188: 124-134, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30029354

RESUMO

Pressure sensitive paints (PSP) containing oxygen probes were primarily used to measure air pressure. In this perspective, a polymerizable methacrylate-derived tetraphenylporphinato platinum(II) (PtTPP-MA) monomer was copolymerized with acrylic/vinyl monomers to produce four different copolymers. Octafluoropentyl methacrylate (OCFPM) and pentafluorophenyl acrylate (PFPA) were used as fluorinated monomers. Methyl methacrylate (MMA) and styrene (S) were used as non-fluorinated monomers. The structures and physical properties of the polymers were confirmed by 1H NMR, 19F NMR, GPC, and DSC. Experimental conditions were optimized to get fine nanofibers. Pressure sensing electrospun membranes and spin coated films were fabricated. Nanofibers showed fast response and good sensitivity towards gaseous oxygen. The influence of types of substrate and polymer natures on response time, oxygen sensitivity, and pressure responses were deliberated. Among our synthesized copolymers, poly(PS-co-PFPA-co-OCFPM-co-PtTPPMA) (Polymer P3) showed fast response time and good pressure sensitivity both as spin coated films and nanofibers.

9.
Sci Rep ; 8(1): 5260, 2018 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-29588503

RESUMO

A facile method for producing high-performance nickel enhanced silver nanowire (Ag NW) transparent electrodes on a flexible substrate is reported. The modified electroplating method called enhanced nickel ion bridge joining of Ag NWs, which provides a new route for improving the loose junctions in bare Ag NW networks. The sheet resistance of Ag NW electrode drops from over 2000 Ω sq-1 to 9.4 Ω sq-1 with excellent thermal uniformity after the electroplating process within 10 s. Nickel enhanced Ag NW transparent films are applied on flexible heaters with good thermal stability (165 °C for 2 h) and mechanical flexibility (3500 cycles under 2.5 mm bending radius) after mechanical bending process. Moreover, the mechanism of nickel growth is also confirmed that the nickel electroplating of the Ag NWs obeyed Faraday's Laws.

10.
Sci Rep ; 8(1): 1775, 2018 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-29379073

RESUMO

In this paper, electric currents with the densities of 1.0 × 102 A/cm2 and 2.0 × 102 A/cm2 were imposed to the Cu-liquid Sn interfacial reaction at 260 °C and 300 °C with the bonding times from 15 min to 960 min. Unlike the symmetrical growth following a cubic root dependence on time during reflowing, the Cu6Sn5 growth enhanced by solid-liquid electromigration followed a linear relationship with time. The elevated electric current density and reaction temperature could greatly accelerate the growth of Cu6Sn5, and could induce the formation of cellular structures on the surfaces because of the constitutional supercooling effect. A growth kinetics model of Cu6Sn5 based on Cu concentration gradient was presented, in which the dissolution of cathode was proved to be the controlling step. This model indicates that higher current density, higher temperature and larger joint width were in favor of the dissolution of Cu. Finally, the shear strengths of joints consisted of different intermetallic compound microstructures were evaluated. The results showed that the Cu6Sn5-based joint could achieve comparable shear strength with Sn-based joint.

11.
ACS Appl Mater Interfaces ; 8(9): 6190-9, 2016 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-26830466

RESUMO

Copper nanowire (CuNW) conductors have been considered to have a promising perspective in the area of stretchable electronics due to the low price and high conductivity. However, the fabrication of CuNW conductors suffers from harsh conditions, such as high temperature, reducing atmosphere, and time-consuming transfer step. Here, a simple and rapid one-step photonic sintering technique was developed to fabricate stretchable CuNW conductors on polyurethane (PU) at room temperature in air environment. It was observed that CuNWs were instantaneously deoxidized, welded and simultaneously embedded into the soft surface of PU through the one-step photonic sintering technique, after which highly conductive network and strong adhesion between CuNWs and PU substrates were achieved. The CuNW/PU conductor with sheet resistance of 22.1 Ohm/sq and transmittance of 78% was achieved by the one-step photonic sintering technique within only 20 µs in air. Besides, the CuNW/PU conductor could remain a low sheet resistance even after 1000 cycles of stretching/releasing under 10% strain. Two flexible electronic devices, wearable sensor and glove-shaped heater, were fabricated using the stretchable CuNW/PU conductor, demonstrating that our CuNW/PU conductor could be integrated into various wearable electronic devices for applications in food, clothes, and medical supplies fields.


Assuntos
Cobre/química , Eletrônica , Nanofios/química , Dimetilpolisiloxanos/química , Eletrodos , Desenho de Equipamento , Microscopia Eletrônica de Varredura , Nanofios/ultraestrutura , Fótons , Poliuretanos/química , Temperatura Ambiente
12.
Phys Chem Chem Phys ; 17(46): 31110-6, 2015 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-26536570

RESUMO

Copper nanowire transparent electrodes have received increasing interest due to the low price and nearly equal electrical conductivity compared with other TEs based on silver nanowires and indium tin oxide (ITO). However, a post-treatment at high temperature in an inert atmosphere or a vacuum environment was necessary to improve the conductivity of Cu NW TEs due to the easy oxidation of copper in air atmosphere, which greatly cancelled out the low price advantage of Cu NWs. Here, a high intensity pulsed light technique was introduced to sinter and simultaneously deoxygenate these Cu NWs into a highly conductive network at room temperature in air. The strong light absorption capacity of Cu NWs enabled the welding of the nanowires at contact spots, as well as the removal of the thin layer of residual organic compounds, oxides and hydroxide of copper even in air. The Cu NW TE with a sheet resistance of 22.9 Ohm sq(-1) and a transparency of 81.8% at 550 nm has been successfully fabricated within only 6 milliseconds exposure treatment, which is superior to other films treated at high temperature in a hydrogen atmosphere. The HIPL process was simple, convenient and fast to fabricate easily oxidized Cu NW TEs in large scale in an air atmosphere, which will largely extend the application of cheap Cu NW TEs.

13.
Am J Primatol ; 77(2): 135-51, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25224271

RESUMO

Understanding the effects of climate change on primate ranging patterns is crucial for conservation planning. Rhinopithecus roxellana is an endangered primate species distributed in mountainous forests at the elevation of 1500-3500 m a.s.l. in China. Our study site, the Shennongjia National Nature Reserve, represents the eastern-most distribution of this species. This area has experienced significant habitat loss and fragmentation because of human population growth, increased farming and logging, and climate change. To estimate how changes in temperature and rainfall will affect the presumed future distribution of this species, we examined eco-geographic factors including bioclimate, habitat (vegetation type, landcover, etc.), topography, and human impact (human population, gross domestic product, etc.), and provide suggestions for management and conservation. We used a maximum entropy approach to predict the location and distribution of habitats suitable for R. roxellana in the present, 2020, 2050, and 2080 based on 33 environmental parameters, three general circulation models, three emissions scenarios, and two dispersal hypotheses. According to the ensemble modeling, we found range reductions of almost 30% by 2020, 70% by 2050, and over 80% by 2080. Although no obvious differences were found in distribution change based on full and zero dispersal assumptions, our results revealed range reductions in response to elevational, latitudinal, and longitudinal gradients, with the monkeys forced to migrate to higher elevations over time. Bioclimte factors, such as temperature, precipitation, evapo-transpiration, and aridity condition, were dominant contributors to range shifting. As habitat loss due to human influence and climate change is likely to be even more severe in the future, we considered three conservation hot-spots in the Shennongjia area and recommended: (i) securing existing reserves and establishing new reserves, (ii) re-designing management systems to include the Shenongjia reserve and the surrounding reserves and highlighting ecosystem protection at higher elevations, and (iii) using finer-scale research to guide the conservation planning and education in order to enhance protection and awareness in the local community. National and provincial conservation policies should integrate projections of climate change in making effective conservation strategies.


Assuntos
Distribuição Animal , Mudança Climática , Colobinae/fisiologia , Conservação dos Recursos Naturais , Altitude , Animais , China , Ecossistema , Espécies em Perigo de Extinção , Geografia , Atividades Humanas
14.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 1): o62, 2007 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-21200939

RESUMO

In the title compound, C(14)H(15)N(3)O(2), the C=C(H)-C=O grouping and the imidazolidine ring are coplanar as a result of an intra-molecular N-H⋯O hydrogen bond and extended electronic conjugation. Inter-molecular N-H⋯O and O-H⋯N hydrogen bonds help to establish the packing.

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