The intergranular interface modification of organic–inorganic hybrid perovskites (OHP) is an important issue to regulate the flexibility, stability, and resistive switching (RS) performance of resistive random-access memories (RRAMs). A novel strategy of polymer additives for OHP intergranular interface modification is explored in this work with the polyanionic backbone to improve the distribution of cage-shaped cavity molecules at the perovskite grain boundaries. Specifically speaking, poly(1-adamantylammonium acrylate) (PADAm) is first synthesized through the acid–base reaction of polyacrylic acid with 1-adamantylamine to simultaneously realize the introduction of a cage-shaped cavity molecule and the polyanionic backbone. Herein, organic ammonium cations 1-adamantylammonium (ADNH3 +) in PADAm are applied as the cage-shaped cavity molecules to tune the dielectric property by being anchored at the perovskite grain boundaries. Meanwhile, polyacrylic anions in PADAm play the role of the polyanionic backbone to produce the more uniform distribution of ADNH3 +. Simultaneously, the flexibility and stability of OHP RRAM devices are also improved due to the introduction of the polyanionic backbone. Consequently, the 4% ADNH3I-modified planar device exhibits the stable nonvolatile RS behavior with an on/off ratio of ∼104, even with one-month exposure under an ambient environment. Importantly, the introduction of PADAm in the flexible fibrous crosspoint of functional fiber Al@MAPbI3:PADAm and bare Al fiber further increases the on/off ratio to 108 due to the effectively improved distribution of hollow cage-shaped ADNH3 + at the perovskite intergranular interfaces together with the application of the fibrous crosspoint device configuration. Especially, these excellent crosspoint RRAM devices can be integrated into the woven fibrous RRAM array in the thermal plastic packaging configuration. In addition, the excellent multilevel RS behavior can also be realized in the woven fibrous RRAM array, indicating potential high-density data storage. This work provides a novel strategy of polymer additives bearing the polyanionic backbone to improve the flexibility, stability, and RS performance of perovskite RRAM devices.
To improve the application of carbon black (CB)-filled polymer composites, we investigated the relationship between the processing parameters, microstructure and electrical properties of injection moldings made from the material. Standard tensile specimens were fabricated under different injection pressures and packing pressures. Up to five layers were removed from the surfaces of the molded specimens to observe the microstructure at different positions within the moldings. Microstructures were observed with a scanning electron microscope, and electrical properties were measured at room temperature with a standard two-terminal direct current (DC) resistor. The results showed that CB particles form the best conductive path at high packing pressures combined with high injection pressures. If the packing pressure is low, the resistivity in the skin zone when loaded by high injection pressures is less than when loaded by low injection pressures, but resistivity increases in the sub-skin zone. We found that the sub-skin zone is a high-resistivity area that can be expanded under the action of higher injection pressures along with lower packing pressures. In contrast to an injection-molded single polymer, an injection-molded, CB-filled polymer composite develops a highly oriented microstructure in the core zone rather than in the skin or sub-skin zones because of the migration of CB particles. Polymer Journal (2011) 43, 930-936; doi:10.1038/pj.2011.95; published online 21 September 2011Keywords: CB particle/polymer composite; injection; resistivity INTRODUCTIONPolymers are often endowed with some outstanding properties when mixed with different fillers. Nanotechnology-stimulated research attempts to create multifunctional composites by integrating nanoparticles into polymer matrices. Nanoscale carbon black (CB) particles, a type of filler, have practical applications in manufacturing nanoparticle reinforced polymer composites because of their low cost and good moldability. In past decades, many researchers have focused on the electrical properties of CB-filled polymer composites. 1-3 For a given composite, its electrical conductivity is determined not only by the CB structure and concentration but also by the specific polymer matrix used and the morphology generated during processing. [4][5][6][7] There is extensive research on the conductive characteristics of polymer-containing CB particles with different morphologies [8][9][10] and the effect of the dispersion state of CB particles in the matrices on the electrical conductivity. 11,12 When CB particles fill a polymer matrix, it is beneficial to conductivity when the CB particles are located in the amorphous phase or in the interface between two phases. Both the conductive pathway of CB particles in the phase and the continuity of the phase in the composites are basic requirements for maintaining a conductive network through the composite. [13][14][15] When a given CB-filled polymer composite is injected into a molding chamber, the difference in conductivity levels m...
CoCrCuFeMnNix (x = 0, 0.5, 1.0, 1.5, 2.0 mol, named as Ni0, Ni0.5, Ni1.0, Ni1.5, and Ni2.0, respectively) high-entropy alloy powders (HEAPs) were prepared via mechanical alloying (MA), and XRD, SEM, EDS, and vacuum annealing were used to study the alloying behavior, phase transition, and thermal stability. The results indicated that the Ni0, Ni0.5, and Ni1.0 HEAPs were alloyed at the initial stage (5–15 h), the metastable BCC + FCC two-phase solid solution structure was formed, and the BCC phase disappeared gradually with the prolonging of ball milling time. Finally, a single FCC structure was formed. Both Ni1.5 and Ni2.0 alloys with high nickel content formed a single FCC structure during the whole mechanical alloying process. The five kinds of HEAPs showed equiaxed particles in dry milling, and the particle size increased with an increase in milling time. After wet milling, they changed into lamellar morphology with thickness less than 1 μm and maximum size less than 20 μm. The composition of each component was close to its nominal composition, and the alloying sequence during ball milling was Cu→Mn→Co→Ni→Fe→Cr. After vacuum annealing at 700~900 °C, the FCC phase in the HEAPs with low Ni content transformed into FCC2 secondary phase, FCC1 primary phase, and a minor σ phase. The thermal stability of HEAPs can be improved by increasing Ni content.
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