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Surface imperfections are detrimental roots to various defect sites in halide perovskites (HPs) films affecting device performance and stability. To mitigate such fabrication defects, we introduced a new class of all-organic surface modifiers consisting of alkylammonium and alkanoate ions on the surface of HP layer passivating interfacial defects and improve moisture tolerance. Compared to iodidebased salts, these robust carboxylate anions display higher resistant towards oxidation and superior stability across different organic solvents. Resultant perovskites with traceless low dimensional structure demonstrate remarkable device performance with power conversion efficiency (PCE) more than 18.5% and enhanced operational stability retaining 85% initial PCE in ambient over 1500 hours.

MATERIALS FOR HUMANITY (MH 21)

Effects of All‐Organic Interlayer Surface Modifiers on the Efficiency and Stability of Perovskite Solar Cells

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poster

Introduction - Phase Change Materials (PCMs) 1) Promising thermal energy storage (TES) materials. - High heat capacity. - Narrow operating temperature range. 2) Wide range of applications - Eg: energy efficient buildings, food packaging, and solar panels. 3) Organic PCMs (oPCMs) are most commonly used.2 - Eg: paraffins, fatty acids, alcohols, or esters. - Stable, no phase separation, little super-cooling. 4) Key problem: High Flammability of oPCMs.

Phase Change Materials with lowered flammability

ABSTRACT Since 2003 the European Union has accelerated the immediate replacement of hazardous materials from consumer products, especially lead and lead-based systems from electrical and electronic equipment, by lead-free systems. However, inspite of significant research across the globe a suitable alternative to potential lead based system PZT has not been identified. Barium Calcium Zirconium Titanate (Ba0.89 Ca0.11 Zr0.10 Ti0.90) O3,is a promising lead free system which exhibit functional response at par or better than the prominent lead based systems like PZT or PMN-PT. In this report we will present our study primarily focussed on realization of BCZT ceramic by using sintering aid, which could bring down sintering temperature below 1400 oC, so that firing of the ceramic could be carried out at ordinary lab furnace. Structural and microstructural features of the synthesized ceramic BCZT – xPr (x = 0.00, 0.02,0.04, and 0.06) along with functional attributes will be analyzed in the presentation. Various steps taken to realize quality ceramic will be illustrated. The average piezoelectric constant d33 was obtained in the range of 144 – 150 pC/N and was lower than expected value. The dielectric maxima were observed near the Curie point as expected. Well defined slim ferroelectric hysteresis loop of BCZT – (x)Pr prepared with varying Pr6O11concentration indicates, the capability and stability of the ceramics at high voltage (3900 V) and frequency (50 Hz).The doped ceramic were found to be stable even at high voltage and high frequency and hence will be useful for diverse applications.

REALIZATION OF LOW TEMPERATURE SINTERED BCZT CERAMIC, THROUGH Pr DOPING AND RUDIMENTARY ANALYSIS

Continuous fiber reinforced thermoplastic polymer composites (CFRTP) are becoming more significant in industrial applications because of their unique advantages such as excellent mechanical and chemical performance, light weight, short molding cycle, secondary molding and waste recycling. However, the difficulty in developing CFRTP is how to combine fiber with thermoplastics due to the significant difference in surface property between fiber and thermoplastic matrix. In this work, we presented the method to create the strong interaction between polymer matrix and fiber to improve the interface adhesion. The result from this study indicates that the strength of the CFRTP increase both along and cross fiber direction by introducing the interface interaction. The breaking behavior of the CFRTP suggests the different breaking mechanism of the CFRTP. This method is also applicable for production scale as the interaction was created within second time scale.

Composite resin to enhance interface between matrix and fiber in continuous fiber reinforced thermoplastic composites

Absorbing the moisture from sweat evaporation would prevent the accumulation of sweat, and thus inhibit the growth of bacteria or fungi, providing a healthy and comfortable microclimate for people. However, there have been almost no such attempts. On the other hand, sweat has always been considered a waste resource and attempts to tap this free resource in the form of energy are relatively sparse. To realize these ideas, here we developed a cobalt-complex based super-hygroscopic material (Co-SHM). Integrating the Co-SHM into breathable and waterproof PTFE membranes, we designed new kinds of armpit pad, shoe lining, and insole, which can rapidly absorb the moisture from sweat evaporation to prevent sweat accumulation. The absorbed sweat can be transduced to energy through a Co-SHM based wearable energy harvesting device that consists of an eight-series-connection of electrochemical cells.

Super-Hygroscopic Film Based Wearables for Expediting Sweat Evaporation and Energy Harvesting

Polylactic acid (PLA) mixed with long-persistent phosphor (Ca2BO3Cl: Eu2+, Dy3+) was prepared in this study. The sustainable yellow luminescence of the composites could be clearly observed. The mechanical properties of the composite filaments were tested, including maximal force and elasticity modulus. In particular, the influence of humidity on mechanical properties was studied and optimal mixing conditions were found. Finally, the prepared composite filaments were printed into a hollow dodecahedron and presented in this study.

PLA/Ca2BO3Cl: Eu2+, Dy3+, A Novel Sustainable Luminescence Composite Material for 3D Printing

Microporous structure plays a significant role in bone tissue engineering, to influence inductive bone formation and elevate bone ingrowth inside microporous scaffolds. We hereby fabricated microporous scaffolds by 3D printing with mixture of porogens and photopolymerizing resin. We tuned the microporosity of scaffolds from 0% to 36% by varying the porogen concentration in the inks from zero to 60 vol%. The microporosity and microspore size of scaffolds can affect in vitro expansion of preosteoblast cells. Our studies revealed that preosteoblast cells’ in vitro adhesion and proliferation were significantly mediated by the printed scaffolds. Cells proliferation on scaffolds with 20-30% microporosity showed much higher rate than on other scaffolds. In this microporosity range, scaffolds also showed much better cell spreading and morphologies. At a low level of microporosity (<7%), the cell proliferation rate was even lower than the solid scaffolds, which indicates that the microporous structure is “toxic” for cells at low microporosity range. A higher microporosity (> 35%) led to very poor cell attachment and is unfavorable for the proliferation of MC3T3-E1 cells. Furthermore, the printed dual macro-/micro-porous scaffolds showed higher proliferation rate of MC3T3-E1 cells as compared to mono-pore sized scaffolds, either the macro-porous or microporous structure.

3D printing fabricated bone scaffolds with macro and micro porous structures

Stabilizing Effect of the Polymer Matrix on Sputter-Anneal Fabricated Nanocomposite Thin Films

The flame retardancy for polymers is very demanding as a lot of polymers are flammable and decompose into small and volatile hydrocarbons upon pyrolysis. In the past, most effective flame retardants for polymers are halogen-based. With the increasing regulatory requirements on safety and environments, halogen-based flame retardants are gradually being replaced with non-halogenated flame retardants. Inorganic metal hydroxides, mainly aluminum hydroxide (ATH) and magnesium hydroxide (MDH), are the largest class of flame retardants by volume. Other non-halogenated flame retardants, such as phosphorus-, nitrogen- and silicon-based, show promises for this property. The up-to-date technique gaps are: (1) for inorganic flame retardants, high loading of 40 - 60 wt% is required, leading to worse mechanical properties and heavy weight, (2) for current non-halogenated ones, most of them are small molecules. Such small flame retardant molecules have relatively poor thermal stability and mechanical strength, and will slowly leach out from the composites surface, leading to performance deterioration and possible environmental pollution. The development of new flame retardants with higher efficacy, lower loading, higher strength and high stability are therefore in need. Targeting this, we have developed new flame retardants with polymeric nature, which theoretically possess the above advantages over the current ones, and demonstrated their effectiveness in various polymers like polypropylene, polyamide. The flame retardant long chains will entangle with polymer matrix chains, stabilizing the whole composites without leaching issues.

Polymeric Flame Retardants: a Promising Category for Enhanced Performance

Compatible polymer blends with synergetic performance play an integral part in modern society from household, automobiles to aerospace. Conventional miscible polymer systems often relies on strong chemical interactions, while the inherent entropy effects are often neglected. Using a combination of experiments and simulation, we show that entropy driving forces could control the phase structure and mechanical properties of polymer blends from commercial plastics, creating ultrahigh extensibility (~146%), while maintaining its transparency and high strength (~70MPa).

Entropy-driven Ultratough Biodegradable Polymer Blends

With the increasing demand for the high strength and high fracture toughness composites in aerospace, automobile and other structural applications, great efforts have been devoted to the development of carbon fiber reinforced thermoplastic composites. However, the majority of commercial carbon fibers are sized for reactive thermosetting epoxy matrix, and therefore cannot be used directly for thermoplastic resin impregnation due to the high processing temperatures and poor interfacial interactions with polymer matrix. In this work, novel surfactant-free aqueous dispersions were derived from commercial polyimide resins through emulsion/solvent evaporation technique. The obtained nano-dispersions with uniform particle size around 100 nm and a high Zeta potential of -48.1 mV were deposited on carbon fibers via electrochemical deposition and dip coating method, respectively. The sized carbon fibers were characterized by scanning electron microscopy (SEM) and thermogravimetric (TGA) analysis, and the sizing performance was assessed by single fiber pull-out testing using polyetherimide (PEI) as the polymer matrix. The results show that the prepared polyimide sizing presents a positive effect on the interfacial adhesion of carbon fiber/PEI composites. Moreover, the carbon fibers sized by electrochemical deposition method exhibit higher interfacial shear strength (IFSS) compared to the dip-coated ones due to the increased van der Waals forces between the PEI matrix and sizing layer as well as the chemical bonding between the sizing layer and carbon fiber surface. The developed aqueous polyimide nano-dispersions exhibit great potential for application in the manufacturing of continuous carbon fiber reinforced thermoplastic prepregs.



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Phase Change Materials with lowered flammability

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