Glass-forming Properties Research Articles

Glass-Forming Ability, Mechanical Properties, and Energetic Characteristics of ZrCuNiAlNbHfY Bulk Metallic Glasses.

The effects of partially substituting Al for Cu in Zr59.62Cu18.4-xNi12Al6+xNb3Hf0.78Y0.2 (x = 0, 2, 4, 6, 8 at.%) bulk metallic glasses (BMGs) on their glass-forming ability (GFA), quasi-static and dynamic mechanical properties, and energy characteristics were investigated. The results showed that an appropriate substitution of Al for Cu can improve GFA and reach a critical casting size up to 10 mm. Additionally, with Al replacement of Cu, the change in the distribution and content of free volume inside the BMGs was the main reason for the quasi-static compression plasticity. In contrast, the BMGs exhibited no plasticity during dynamic compression and high-speed impact, owing to the short loading time and thermal softening effect. In terms of energy characteristics, all alloys have a high combustion enthalpy. And on the surface of the fragments collected from impact, the active elements Zr, Al, and Nb reacted because of the adiabatic temperature rise. Further, x = 4 at.% Zr-based BMG with its superior overall performance could penetrate a 6 mm Q235 plate at a speed of 1038 m/s, combining excellent mechanical properties and energy characteristics. This study contributes to the development of Zr-based BMGs as novel energetic structural materials.

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents.

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.

Inverse design machine learning model for metallic glasses with good glass-forming ability and properties

The design of metallic glasses (MGs) with good properties is one of the long-standing bottlenecks in materials science and engineering, which has been relying mostly on far less efficient traditional trial-and-error methods. Even the currently popular machine learning-based forward designs, which use manual input to navigate high dimensional compositional space, often become inefficient with the increasing compositional complexity in MGs. Here, we developed an inverse design machine learning model, leveraging the variational autoencoder (VAE), to directly generate the MGs with good glass-forming ability (GFA). We demonstrate that our VAE with the property prediction model is not only an expressive generative model but also able to do accurate property prediction. Our model allows us to automatically generate novel MG compositions by performing simple operations in the latent space. After randomly generating 3000MG compositions using the model, a detailed analysis of four typical metallic alloys shows that unreported MG compositions with better glass-forming ability can be predicted. Moreover, our model facilitates the use of powerful optimization algorithms to efficiently guide the search for MGs with good GFA in the latent space. We believe that this is an efficient way to discover MGs with excellent properties.

Diffusion Coefficients of Variable-Size Amphiphilic Additives in a Glass-Forming Polyethylene Matrix.

Diffusion of additives in polymers is an important issue in the plastics industry since migratory-type molecules are widely used to tune the properties of polymeric composites. Predicting the diffusional behavior of new additives can minimize the need for repetitive experiments. This work presents molecular dynamics simulations at the microsecond time scale and uses the MARTINI force field to estimate self-diffusion coefficients, D, of six monounsaturated amides and their analogs carboxylic acids in polyethylene matrices (PE, MW = 5600 Da). The results are strongly influenced by the glass-forming properties of the PE matrix, which we characterize by three distinct temperatures. The metastability region (T < 325 K), the glass transition temperature (Tg = 256-260 K), and the end of the transition (T ≅ 200 K). Self-diffusion mechanisms are inferred from the results of the dependence of D on the molecular mass of the additive, observing a Rouse-like behavior at high temperatures and deviations from it within the metastability region of the matrix. Interestingly, D values are nonsensitive to the nature of the considered polar head for additives of similar size. The temperature-dependent behavior of D follows, at fixed additive size, a linear Arrhenius pattern at high temperatures and a super Arrhenius trend at lower temperatures, which is well represented with a power law equation as predicted by the Mode Coupling Theory (MCT). We offer a conceptual explanation for the observed super-Arrhenius behavior. This explanation draws on Truhlar and Kohen's interpretation of the available energies at both the initial and the transition states along the diffusion pathway. The matrix's mobility significantly affects solute self-diffusion, yielding equal activation enthalpies for the Arrhenius region or the same power law parameters for the super-Arrhenius regime. Finally, we establish a one-to-one time-equivalence of the self-diffusion processes between CG and all-atom systems for the largest additives and the PE matrix in the high-temperature regime.

Glass-forming ability and properties of Hf-Cu-Ni-Al-Ag bulk metallic glasses

A new Hf-based Hf-Cu-Ni-Al-Ag glassy alloy was synthesized to be formed by copper mold casting. The influence of Ag addition on the properties of Hf48Cu29.25Ni9.75Al13-xAgx (x=0-5at%) glassy alloys was studied by differential scanning calorimeter, X-ray diffractometer, quasi-static compression, and electrochemical corrosion test. The experimental results show that adding Ag can improve the thermal stability and glass-forming ability of glassy alloys. The Hf48Cu29.25Ni9.75Al12Ag1 exhibits the best glass-forming ability with a critical diameter of 12 mm and the highest compressive strength (2363 MPa) among glassy Hf48Cu29.25Ni9.75Al13-xAgx (x=0-5at%). The total plastic deformation of Hf48Cu29.25Ni9.75Al12Ag1 before fracture approaches 4%. In addition, there is a passivation interval of about 3 V for Hf48Cu29.25Ni9.75Al12Ag1 glassy alloy in 1 mol/L H2SO4 solution, which makes the passivation film more stable and increases the corrosion resistance. In 1 mol/L KOH solution, the corrosion tendency and rate decreased with the addition of Ag content, leading to increased corrosion resistance.

An ab initio simulation and experimental studies of the glass-forming ability and properties of Al86Ni(14-x)Zrx (x = 1∼7) alloys

In this paper, glass-forming ability (GFA) and thermal stability of melt-spun Al-Ni-Zr amorphous ribbons with different Zr content were investigated via X-ray diffraction, transmission electron microscope and differential scanning calorimetry. The electrochemical performance and hardness performance of the ribbons with different amorphous content were analyzed. It is shown that with the addition of Zr, the amorphous content and corrosion resistance first increases and then decreases. However, the hardness of the ribbons with a minor fraction of the amorphous content is the highest. To further study the influence of the Zr element on the GFA of Al-Ni-Zr alloys, ab initio molecular dynamics simulation was used to calculate the atomic structure, coordination number, and Voronoi polyhedron. The calculation results show that adding an appropriate amount of Zr affects the interaction between atoms, causing significant changes in the local structure and increasing the content of the icosahedron to improve the GFA.

Thermo-crosslinkable molecular glasses towards the low k materials at high frequency

Two molecular glasses having allyl side chains and thermo-crosslinkable benzocyclobutene (BCB) groups have been successfully synthesized. These molecules display good solubility in common organic solvents and show a typical glass-forming behavior of having no melting point and keeping a complete amorphous state. The thermally cured molecular glasses exhibit low dielectric constant (Dk) and dielectric loss (Df) at 10 GHz, as well as low water uptake (Wa) even when they are immersed in boiling water for 72 h. Among them, a fluoro-containing molecule exhibits the best properties, showing Dk of 2.53, Df of 1.93 × 10−3 and Wa of 0.19%, respectively, indicating that fluoro groups can efficiently improve the dielectric properties of the molecules. A controlling test indicates that the allyl side chains make the molecules possessing glass-forming properties.

Glass formation and properties of glasses in the system SrO–B2O3–SiO2–xAl2O3 (x=0; 10 mol.%)

The paper shows the prospects of the system SrO–Al2O3–B2O3–SiO2 as a basis for the synthesis of new vitreous and glass-ceramic materials, which are widely used as electrical insulated and high-temperature coatings, for sealing of solid oxide fuel cells, and in the production of heat resistant materials. We experimentally established the conditions of glass formation, regions of glass-forming melts and properties of glasses, the chemical composition of which is limited by the following content of components (mol.%): SrO 30–80, B2O3 10–60, SiO2 10–60, and Al2O3 0–10. It is shown that during the synthesis of glasses in the corundum crucible at the temperature of 13500С the region of glass formation in the system SrO–B2O3–SiO2 is limited by the following content of components (mol.%): SrO 30–60, B2O3 10–60, and SiO2 10–50. It is found that the introduction of Al2O3 to the composition of these glasses expands the region of glass formation towards increase of the SiO2 content in the glass up to 60 mol.%. Experimentally determined values of glass properties are within the following limits: coefficient of linear thermal expansion (67–118)10–7 К–1; glass transition temperature 570–6600С; dilatometric softening point 580–7000С; and density 2.62–3.71 g cm–3. The established patterns of influence of the components and conditions of glass formation on the physical and chemical characteristics of glasses may serve as an experimental basis for designing of new materials with a complex of specified properties, which allows solving the problems of their practical use.

Lithium-salt-based deep eutectic solvents: Importance of glass formation and rotation-translation coupling for the ionic charge transport.

Lithium-salt-based deep eutectic solvents, where the only cation is Li+, are promising candidates as electrolytes in electrochemical energy-storage devices, such as batteries. We have performed broadband dielectric spectroscopy on three such systems, covering a broad temperature and dynamic range that extends from the low-viscosity liquid around room temperature down to the glassy state approaching the glass-transition temperature. We detect a relaxational process that can be ascribed to dipolar reorientational dynamics and exhibits the clear signatures of glassy freezing. We find that the temperature dependence of the ionic dc conductivity and its room-temperature value also are governed by the glassy dynamics of these systems, depending, e.g., on the glass-transition temperature and fragility. Compared to the previously investigated corresponding systems, containing choline chloride instead of a lithium salt, both the reorientational and ionic dynamics are significantly reduced due to variations in the glass-transition temperature and the higher ionic potential of the lithium ions. These lithium-based deep eutectic solvents partly exhibit significant decoupling of the dipolar reorientational and the ionic translational dynamics and approximately follow a fractional Debye-Stokes-Einstein relation, leading to an enhancement of the dc conductivity, especially at low temperatures. The presented results clearly reveal the importance of decoupling effects and of the typical glass-forming properties of these systems for the technically relevant room-temperature conductivity.

Effects of Al replacement on glass forming ability and mechanical properties of Zr-based bulk metallic glasses

In this present study, the effects of Al substitution for Zr in Zr73-xCu12Ni12AlxNb3 (x=7.5, 10, 12.5, 15, 17.5 at.%) metallic glasses on the glass-forming ability, thermal stability, quasi-static and dynamic mechanical properties were investigated. Proper Al replacement improved the glass-forming ability, crystallization activation energy and mechanical properties of the amorphous alloys. Compared with quasi-static compression, due to the shorter loading time and more significant adiabatic temperature rise, the fracture strength decreased and no dynamic compression plasticity was observed for all alloys subjected to dynamic loading. From the aspect of atomic structure, the substitution of appropriate amount of Al not only promoted the formation of the stable short-range ordering (SRO) structure, but also changed the content and distribution of the free volume, which resulted in the improvement of GFA, strength and plasticity of the amorphous alloy.

Glass-Forming Ability and Thermal Properties of Al70Fe12.5V12.5X5(X = Zr, Nb, Ni) Amorphous Alloys via Minor Alloying Additions.

The Al70Fe12.5V12.5Ni5, Al70Fe12.5V12.5Zr5 and Al70Fe12.5V12.5Nb5 alloys were prepared via mechanical alloying. The influence of Zr, Nb or Ni addition on the glass-forming ability of Al-Fe-V amorphous alloys have been investigated. The structure of Al70Fe12.5V12.5Ni5 was amorphous and Al70Fe12.5V12.5Zr5 was not completely amorphous by transmission electron microscopy, selected area electron diffraction and differential scanning calorimetry. Different criteria were used to evaluate the influence of the addition of alloy elements on the Glass-forming ability. The Al70Fe12.5V12.5Ni5 amorphous alloys exhibits higher glass-forming ability and activation energies of crystallization. Comparison of the effective atomic size ratio and mixture enthalpy on the glass-forming ability of these amorphous alloys demonstrates that the effective atomic size ratio value becomes more significant than the values of mixture enthalpy.

Multifunctional derivatives of pyrimidine-5-carbonitrile and differently substituted carbazoles for doping-free sky-blue OLEDs and luminescent sensors of oxygen

IntroductionEvolution of organic light-emitting diodes (OLEDs) reached the point, which allows to obtain maximum internal quantum efficiency of 100% partly using heavy-metal-free emitters exhibiting thermally activated delayed fluorescence (TADF). Such emitters are also predictively perfect candidates for new generation of optical sensors since triplet harvesting can be sensitive to different analytes (at least to oxygen). Although many organic TADF emitters have been reported so far as OLED emitters, the investigation of materials suitable for both OLEDs and optical sensors remains extremely rare. ObjectivesAiming to achieve high photoluminescence quantum yields in solid-state and triplet harvesting abilities of organic semiconductors with efficient bipolar charge transport required for application in both blue OLEDs and optical sensors, symmetrical donor–acceptor-donor organic emitters containing pyrimidine-5-carbonitrile electron-withdrawing scaffold and carbazole, tert-butylcarbazole and methoxy carbazole donor moieties were designed, synthesized and investigated as the main objectives of this study. MethodsNew compounds were tested by many experimental methods including optical and photoelectron spectroscopy, time of flight technique, electrochemistry and thermal analyses. ResultsDemonstrating advantages of the molecular design, the synthesized emitters exhibited sky-blue efficient TADF with reverse intersystem crossing rates exceeding 106 s−1, aggregation-induced emission enhancement with photoluminescence quantum yields in solid state exceeding 50%, hole and electron transporting properties with charge mobilities exceeding 10-4 cm2/V·s, glass-forming properties with glass transition temperatures reaching 177 °C. Sky-blue OLEDs with non-doped light-emitting layers of the synthesized emitter showed maximum external efficiency of 12.8% while the doped device with the same emitter exhibited maximum external efficiency of 14%. The synthesized emitters were also used as oxygen probes for optical sensors with oxygen sensitivity estimated by the Stern-Volmer constant of 3.24·10-5 ppm−1. ConclusionThe developed bipolar TADF emitters with pyrimidine-5-carbonitrile and carbazole moieties showed effective applicability in both blue OLEDs and optical sensors.

B2O3-Doped LATP Glass-Ceramics Studied by X-ray Diffractometry and MAS NMR Spectroscopy Methods.

Two families of glasses in the Li2O-Al2O3-B2O3-TiO2-P2O5 system were prepared via two different synthesis routes: melt-quenching and ball-milling. Subsequently, they were submitted to crystallization and yielded the Li1.3Al0.3Ti1.7(PO4)3 (LATP)-based glass-ceramics. Glasses and corresponding glass-ceramics were studied by complementary X-ray diffraction (XRD) and 27Al, 31P, 7Li, 11B magic-angle spinning nuclear magnetic resonance (MAS NMR) methods in order to compare their structure and phase composition and elucidate the impact of boron additive on their glass-forming properties and crystallization process. XRD studies show that the addition of B2O3 improves the glass-forming properties of glasses prepared by either method and inhibits the precipitation of unwanted phases during heat treatment. MAS NMR studies allowed us to distinguish two LATP phases of slightly different chemical composition suggesting that LATP grains might not be homogeneous. In conclusion, the crystallization of boron-incorporated LATP glasses can is an effective way of obtaining LATP-based solid state electrolytes for the next generation of lithium-ion batteries provided the proper heat-treatment conditions are chosen.

Triphenylethylene-based emitters exhibiting aggregation induced emission enhancement and balanced bipolar charge transport for blue non-doped organic light-emitting diodes

New triphenylethylene-based derivatives, containing 2,6-di-tert-butylcarbazole or 9,9-dimethyl-9,10-dihydroacridine as donor moieties and phenylene or tetrafluorophenylene linking bridges were synthesised by Heck coupling and characterized. The synthesized compounds emitted blue light in the solid state with emission maxima in the range of 478–487 nm and photoluminescence quantum yields of 16–29%. In thermogravimetric analysis they demonstrated sublimation with 5% weight loss temperatures in the range of 307–355 °C. They exhibited glass-forming properties with glass-transition temperatures of 89–123 °C. The solid-state ionization potentials and electrochemical band gaps ranged from 5.88 to 6.37 eV and from 3.30 to 3.57 eV, respectively. Three compounds demonstrated bipolar semiconducting properties. Derivative of triphenylethylene and 2,6-di-tert-butylcarbazole with phenylene bridge showed highest hole and electron drift mobilities reaching 3.07 × 10−3 cm2/Vs and 4.2 × 10−3 cm2/Vs respectively at high electric field. Utilizing compounds in organic light‐emitting diodes as emitters external quantum efficiency of 2% was observed.

Preparation of CoMoPC bulk metallic glasses using fluxing treatment and J-quenching technique

ABSTRACT A new series of Co80-x Mo x P14C6 (x = 8, 9 and 10 at.%) bulky glassy rods have been prepared by combining fluxing treatment and J-quenching technique. The glass-forming ability, thermal stability, magnetic and mechanical properties of the present CoMoPC bulk metallic glasses (BMGs) have been investigated. For the present Co80-x Mo x P14C6 (x = 8, 9 and 10 at.%) BMGs, the critical diameter for glass formation reaches the maximum value of 1.5 mm when x = 9, and the saturation magnetisation gradually decreases from 0.35 T (39 emu/g) to 0.17 T (19 emu/g) as increasing Mo content from x = 8 to x = 10. The present CoMoPC BMGs exhibit a fracture strength of 2.13–2.32 GPa and nearly zero plasticity.

Designing electrolytes with polymerlike glass-forming properties and fast ion transport at low temperatures

In the presence of Lewis acid salts, the cyclic ether, dioxolane (DOL), is known to undergo ring-opening polymerization inside electrochemical cells to form solid-state polymer batteries with good interfacial charge-transport properties. Here we report that LiNO3, which is unable to ring-open DOL, possesses a previously unknown ability to coordinate with and strain DOL molecules in bulk liquids, completely arresting their crystallization. The strained DOL electrolytes exhibit physical properties analogous to amorphous polymers, including a prominent glass transition, elevated moduli, and low activation entropy for ion transport, but manifest unusually high, liquidlike ionic conductivities (e.g., 1 mS/cm) at temperatures as low as -50 °C. Systematic electrochemical studies reveal that the electrolytes also promote reversible cycling of Li metal anodes with high Coulombic efficiency (CE) on both conventional planar substrates (1 mAh/cm2 over 1,000 cycles with 99.1% CE; 3 mAh/cm2 over 300 cycles with 99.2% CE) and unconventional, nonplanar/three-dimensional (3D) substrates (10 mAh/cm2 over 100 cycles with 99.3% CE). Our finding that LiNO3 promotes reversibility of Li metal electrodes in liquid DOL electrolytes by a physical mechanism provides a possible solution to a long-standing puzzle in the field about the versatility of LiNO3 salt additives for enhancing reversibility of Li metal electrodes in essentially any aprotic liquid electrolyte solvent. As a first step toward understanding practical benefits of these findings, we create functional Li||lithium iron phosphate (LFP) batteries in which LFP cathodes with high capacity (5 to 10 mAh/cm2) are paired with thin (50 μm) lithium metal anodes, and investigate their galvanostatic electrochemical cycling behaviors.

Glass formation, nanocrystallisation and magnetic properties of the (Fe1–xCox)79Nb3B18 (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75) metallic glasses

Abstract The glass-forming ability (GFA), nanocrystallisation, electrical resistivity and soft magnetic properties of (Fe1-xCox)79Nb3B18 (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75) glassy alloys were investigated. We found that the substitution of Fe by Co is beneficial for improving the GFA. As-spun (Fe0.55Co0.45)79Nb3B18 glassy alloys show the best GFA, along with excellent soft magnetic properties in the supercooled liquid region, with a saturation magnetisation and coercivity of 140 A · m2 · kg-1 and 19.9 A · m-1, respectively, at 60 K. With increasing Co content, the electrical resistivity initially decreases rapidly, and then fluctuates around approximately 70 ± 4 μΩ cm. With increasing the annealing temperature, the saturation magnetisation improves initially, but then decreases for the (Fe0.4Co0.6)79Nb3B18 alloy, and the coercivity does not significantly improve. These newly developed FeCoNbB multicomponent alloys exhibit appreciable GFA, good magnetic properties and low material cost, and they can serve as a promising soft magnetic material for use in industrial applications.

Glass formation, nanocrystallisation and magnetic properties of the (Fe1–xCox)79Nb3B18 (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75) metallic glasses

Abstract The glass-forming ability (GFA), nanocrystallisation, electrical resistivity and soft magnetic properties of (Fe1-xCox)79Nb3B18 (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75) glassy alloys were investigated. We found that the substitution of Fe by Co is beneficial for improving the GFA. As-spun (Fe0.55Co0.45)79Nb3B18 glassy alloys show the best GFA, along with excellent soft magnetic properties in the supercooled liquid region, with a saturation magnetisation and coercivity of 140 A · m2 · kg-1 and 19.9 A · m-1, respectively, at 60 K. With increasing Co content, the electrical resistivity initially decreases rapidly, and then fluctuates around approximately 70 ± 4 μΩ cm. With increasing the annealing temperature, the saturation magnetisation improves initially, but then decreases for the (Fe0.4Co0.6)79Nb3B18 alloy, and the coercivity does not significantly improve. These newly developed FeCoNbB multicomponent alloys exhibit appreciable GFA, good magnetic properties and low material cost, and they can serve as a promising soft magnetic material for use in industrial applications.

Composition dependence of the glass-forming ability and soft magnetic properties of Fe-rich Fe–Nb–B ternary alloys

AbstractThe glass formation, crystallization behavior, and soft magnetic properties of Fe80−xNbxB20 (x = 3, 6, and 9) and Fe82.5−yNbyB17.5 (y = 3.5, 5, 6, and 7) metallic glasses prepared by melt spinning were investigated. Differential scanning calorimetry analysis indicated that an increased Nb content results in increased thermal stability and glass-forming ability for both Fe80−xNbxB20 and Fe82.5−yNbyB17.5 glassy alloys. The supercooled liquid region increases from 26 to 50 K for Fe80−xNbxB20 alloys and from 32 to 48 K for Fe82.5−yNbyB17.5 alloys. Magnetic measurements reveal that saturation magnetization ranges from 65 to 137 emu g−1 for Fe80−xNbxB20 glassy alloys and varies from 91 to 121 emu g−1 for Fe82.5−yNbyB17.5 glassy alloys. The superior magnetic properties, high glass-forming ability, and low cost of raw materials make the current Fe–Nb–B ternary alloys promising for potential applications in the electronics industry.

Diphenylsulfone-based hosts for electroluminescent devices: Effect of donor substituents

In this work, we report on a series of diphenylsulfone derivatives substituted by 2-(trifluoromethyl)-phenothiazinyl, 10,11-dihydro-5H-dibenz[b,f]azepinyl, 5H-dibenz[b,f]azepinyl, 4-methoxy-carbazolyl and 1,2,3,4-tetrahydrocarbazolyl moieties. Utilization of such donating units provided high triplet levels (2.99–3.12 eV) of the designed compounds. The compounds were characterized by glass-forming properties (with glass transition temperatures of 68–162 °C) and ionization potentials of 5.61–5.99 eV. Depending on the donor substitution pattern, either hole or electron transport was observed for the studied compounds with charge mobilities in the range from 5.3 × 10−6 to 2.8 × 10−4 cm2/V at electric fields higher than 3.1·105 V/cm. Hosting properties of the compounds were studied using widely known emitter exhibiting thermally activated delayed fluorescence. Among the studied compounds, bis(4-(4-methoxy-9H-carbazole-9-yl)phenyl)sulfone showed the best performances in both guest:host solid films (photoluminescence quantum yield of 87%) and electroluminescent devices (maximum external quantum efficiency over 20%).