Nanocrystalline LaFeO3 preparation and thermal process of precursor

Nanocrystalline LaFeO₃ was synthesized by calcining precursor La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O in air. XRD analysis showed that precursor dried at 80 °C was a mixture containing orthorhombic La₂(CO₃)₂(OH)₂ and amorphous Fe₂O₃?1.5H₂O. Orthorhombic LaFeO₃ with highly crystallization was obtained when La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O was calcined at 900 °C in air for 2 h. Magnetic characterization indicated that the calcined product at 900 °C behaved weak magnetic behavior at room temperature. The thermal process of La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O experienced five steps, which involves, at first, dehydration of 0.8 absorption water, then dehydration of 0.7 crystal water, decomposition of orthorhombic La₂(CO₃)₂(OH)₂ into orthorhombic LaCO₃OH, reaction of two LaCO₃OH into hexagonal La₂O₂CO₃ and crystallization of tetragonal Fe₂O₃, at last, reaction of hexagonal La₂O₂CO₃ with tetragonal Fe₂O₃ into orthorhombic LaFeO₃. In the DTG curve, four DTG peaks indicated the precursor experienced mass loss of four steps.     

Cobalt‐Doped Nickel Phosphite for High Performance of Electrochemical Energy Storage

Compared to single metallic Ni or Co phosphides, bimetallic Ni–Co phosphides own ameliorative properties, such as high electrical conductivity, remarkable rate capability, upper specific capacity, and excellent cycle performance. Here, a simple one‐step solvothermal process is proposed for the synthesis of bouquet‐like cobalt‐doped nickel phosphite (Ni₁₁(HPO₃)₈(OH)₆), and the effect of the structure on the pseudocapacitive performance is investigated via a series of electrochemical measurements. It is found that when the cobalt content is low, the glycol/deionized water ratio is 1, and the reaction is under 200 °C for 20 h, the morphology of the sample is uniform and has the highest specific surface area. The cobalt‐doped Ni₁₁(HPO₃)₈(OH)₆ electrode presents a maximum specific capacitance of 714.8 F g^?1. More significantly, aqueous and solid‐state flexible electrochemical energy storage devices are successfully assembled. The aqueous device shows a high energy density of 15.48 mWh cm^?2 at the power density of 0.6 KW cm^?2. The solid‐state device shows a high energy density of 14.72 mWh cm^?2 at the power density of 0.6 KW cm^?2. These excellent performances confirm that the cobalt‐doped Ni₁₁(HPO₃)₈(OH)₆ are promising materials for applications in electrochemical energy storage devices.     

A Unique Double‐Layered Carbon Nanobowl‐Confined Lithium Borohydride for Highly Reversible Hydrogen Storage

Poor reversibility and high desorption temperature restricts the practical use of lithium borohydride (LiBH₄) as an advanced hydrogen store. Herein, a LiBH₄ composite confined in unique double‐layered carbon nanobowls prepared by a facile melt infiltration process is demonstrated, thanks to powerful capillary effect under 100 bar of H₂ pressure. The gradual formation of double‐layered carbon nanobowls is witnessed by transmission electron microscopy (TEM) observation. Benefiting from the nanoconfinement effect and catalytic function of carbon, this composite releases hydrogen from 225 °C and peaks at 353 °C, with a hydrogen release amount up to 10.9 wt%. The peak temperature of dehydriding is lowered by 112 °C compared with bulk LiBH₄. More importantly, the composite readily desorbs and absorbs ≈8.5 wt% of H₂ at 300 °C and 100 bar H₂, showing a significant reversibility of hydrogen storage. Such a high reversible capacity has not ever been observed under the identical conditions. The usable volumetric energy density reaches as high as 82.4 g L^?1 with considerable dehydriding kinetics. The findings provide insights in the design and development of nanosized complex hydrides for on‐board applications.     

Graphene‐Encapsulated FeS2 in Carbon Fibers as High Reversible Anodes for Na+/K+ Batteries in a Wide Temperature Range

Developing low cost, long life, and high capacity rechargeable batteries is a critical factor towards developing next‐generation energy storage devices for practical applications. Therefore, a simple method to prepare graphene‐coated FeS₂ embedded in carbon nanofibers is employed; the double protection from graphene coating and carbon fibers ensures high reversibility of FeS₂ during sodiation/desodiation and improved conductivity, resulting in high rate capacity and long‐term life for Na⁺ (305.5 mAh g^?1 at 3 A g^?1 after 2450 cycles) and K⁺ (120 mAh g^?1 at 1 A g^?1 after 680 cycles) storage at room temperature. Benefitting from the enhanced conductivity and protection on graphene‐encapsulated FeS₂ nanoparticles, the composites exhibit excellent electrochemical performance under low temperature (0 and ?20 °C), and temperature tolerance with stable capacity as sodium‐ion half‐cells. The Na‐ion full‐cells based on the above composites and Na₃V₂(PO₄)₃ can afford reversible capacity of 95 mAh g^?1 at room temperature. Furthermore, the full‐cells deliver promising discharge capacity (50 mAh g^?1 at 0 °C, 43 mAh g^?1 at ?20 °C) and high energy density at low temperatures. Density functional theory calculations imply that graphene coating can effectively decrease the Na⁺ diffusion barrier between FeS₂ and graphene heterointerface and promote the reversibility of Na⁺ storage in FeS₂, resulting in advanced Na⁺ storage properties.     

Hydronium beta″ alumina: A fast proton conductor

Single crystals of sodium beta″ alumina (0.84Na₂O·0.84MgO·5 Al₂O₃) undergo rapid ion exchange in concentrated sulfuric acid to produce “hydronium” beta alumina (0.84) H₂O·0.84MgO·5Al₂O₃·2.8H₂O). Hydronium beta″ alumina undergoes a partial, reversible dehydration between 250–300°C and irreversibly decomposes into alpha alumina and water above 700°C. The conductivity of hydronium beta″ alumina has been measured with blocking and non-blocking electrodes and is 5 × 10^?3 (ohm cm)^?1 at 25°C. The high conductivity is interpreted on the basis of a two dimensional liquid model.     

Multilayer Lead‐Free Ceramic Capacitors with Ultrahigh Energy Density and Efficiency

The utilization of antiferroelectric (AFE) materials is thought to be an effective approach to enhance the energy density of dielectric capacitors. However, the high energy dissipation and inferior reliability that are associated with the antiferroelectric–ferroelectric phase transition are the main issues that restrict the applications of antiferroelectric ceramics. Here, simultaneously achieving high energy density and efficiency in a dielectric ceramic is proposed by combining antiferroelectric and relaxor features. Based on this concept, a lead‐free dielectric (Na_0.5Bi_0.5)TiO₃‐x(Sr_0.7Bi_0.2)TiO₃ (NBT‐xSBT) system is investigated and the corresponding multilayer ceramic capacitors (MLCCs) are fabricated. A record‐high energy density of 9.5 J cm^?3, together with a high energy efficiency of 92%, is achieved in NBT‐0.45SBT multilayer ceramic capacitors, which consist of ten dielectric layers with the single‐layer thickness of 20 µm and the internal electrode area of 6.25 mm². Furthermore, the newly developed capacitor exhibits a wide temperature usage range of ‐60 to 120 °C, with an energy‐density variation of less than 10%, and satisfactory cycling reliability, with degradation of less than 8% over 10⁶ cycles. These characteristics demonstrate that the NBT‐0.45SBT multilayer ceramic is a promising candidate for high‐power energy storage applications.     

A High‐Temperature Na‐Ion Battery: Boosting the Rate Capability and Cycle Life by Structure Engineering

High‐temperature sodium ion batteries (SIBs) have drawn significant heed recently for large‐scale energy storage. Yet, conventional SIBs are in the depths of inferior charge/discharge efficiency and cyclability at elevated temperatures. Rational structure design is highly desirable. Hence, a 3D hierarchical flower architecture self‐assembled by carbon‐coated Na₃V₂(PO₄)₃ (NVP) nanosheets (NVP@C‐NS‐FL) is fabricated via a microwave‐assisted glycerol‐mediated hydrothermal reaction combined with a post heat‐treatment. The growth mechanism of NVP@C‐NS‐FL is systematically investigated, by forming a microspherical glycerol/polyglycerol‐NVP complex initially and then converting into flower‐like architecture during the subsequent annealing at a low temperature ramping rate. Benefiting from the integrated structure, fast Na⁺ transportation, and highly effective heat transfer, the as‐obtained NVP@C‐NS‐FL exhibits an excellent high‐temperature SIB performance, e.g., 65 mAh g^?1 (100 C) after 1000 cycles under 60 °C. When coupled with NaTi₂(PO₄)₃ anode, the full cell can still display superior power capability of 1.4 kW kg^?1 and long‐term cyclability (2000 cycles) under 60 °C.     

Construction of Bimetallic Selenides Encapsulated in Nitrogen/Sulfur Co‐Doped Hollow Carbon Nanospheres for High‐Performance Sodium/Potassium‐Ion Half/Full Batteries

Metallic selenides have been widely investigated as promising electrode materials for metal‐ion batteries based on their relatively high theoretical capacity. However, rapid capacity decay and structural collapse resulting from the larger‐sized Na⁺/K⁺ greatly hamper their application. Herein, a bimetallic selenide (MoSe₂/CoSe₂) encapsulated in nitrogen, sulfur‐codoped hollow carbon nanospheres interconnected reduced graphene oxide nanosheets (rGO@MCSe) are successfully designed as advanced anode materials for Na/K‐ion batteries. As expected, the significant pseudocapacitive charge storage behavior substantially contributes to superior rate capability. Specifically, it achieves a high reversible specific capacity of 311 mAh g^?1 at 10 A g^?1 in NIBs and 310 mAh g^?1 at 5 A g^?1 in KIBs. A combination of ex situ X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy tests reveals the phase transition of rGO@MCSe in NIBs/KIBs. Unexpectedly, they show quite different Na⁺/K⁺ insertion/extraction reaction mechanisms for both cells, maybe due to more sluggish K⁺ diffusion kinetics than that of Na⁺. More significantly, it shows excellent energy storage properties in Na/K‐ion full cells when coupled with Na₃V₂(PO₄)₂O₂F and PTCDA@450 °C cathodes. This work offers an advanced electrode construction guidance for the development of high‐performance energy storage devices.     

Proton conducting membranes composed of hydronium alunite

High proton conductivity, of 3 × 10^?4 ohm^?1 cm^?1 at 20°C, has been found in hydrated pressed discs of hydronium alunite, of formula (H₃O)Al₃(SO₄)₂(OH)₆. The conduction occurs within the hydrated interparticle regions into which protons have been donated, probably from the H₃O⁺ groups exposed on the crystal surfaces. The general utility of the membranes is discussed.     

A four-way catalytic system for control of emissions from diesel engine

The pollution caused by diesel-fuelled vehicles has become a subject of global concern. Presently, various separate technologies such as diesel oxidation catalyst, diesel particulate filter, selective catalytic reduction and ammonia selective catalytic reduction are used to control these pollutants. The four-way catalytic (FWC) system integrates all the separate control systems into a single compact unit. FWC technique using a combination of oxidation–reduction catalysts under various strategies has been investigated to simultaneously remove CO, HC, PM and NOx emitted from diesel engines. An oxidation catalyst (La_0.6K_0.4CoO₃) was prepared by two different methods (sol–gel and co-precipitation). The reduction catalysts: Ag/Al₂O₃ and Cu-ZSM5 were synthesized by impregnation and ion-exchange method, respectively. The FWC was characterized by N₂-sorption, X-ray diffraction, Fourier transform spectroscopy and scanning electron microscopy. The catalytic activities of FWC containing double-layer of catalysts were evaluated in a fixed-bed-tubular-reactor. The highest catalytic activity resulted by the two-layered system of La_0.6K_0.4CoO₃ (sol–gel)?+?Cu-ZSM5 showing 100% NO conversion to N₂ at 415°C, maximum-temperature of soot-combustion at 410°C, complete C₃H₈ conversion at 450°C and 100% CO conversion at 388°C. Maximum NO conversion was maintained up to 427°C; conversion started decreasing with further increase in temperature and 75.4% conversion remained up to 450°C. The performance of double-layered-catalytic-system was as follows: La_0.6K_0.4CoO₃(sol–gel)?+?Cu-ZSM5?>?La_0.6K_0.4CoO₃(sol–gel)?+?Ag/Al₂O₃?>?La_0.6K_0.4CoO₃(co-ppt)?+?Ag/Al₂O₃?>?La_0.6K_0.4CoO₃(co-ppt)?+?Cu-ZSM5.     

Lead‐Free Antiferroelectric Silver Niobate Tantalate with High Energy Storage Performance

Antiferroelectric materials that display double ferroelectric hysteresis loops are receiving increasing attention for their superior energy storage density compared to their ferroelectric counterparts. Despite the good properties obtained in antiferroelectric La‐doped Pb(Zr,Ti)O₃‐based ceramics, lead‐free alternatives are highly desired due to the environmental concerns, and AgNbO₃ has been highlighted as a ferrielectric/antiferroelectric perovskite for energy storage applications. Enhanced energy storage performance, with recoverable energy density of 4.2 J cm^?3 and high thermal stability of the energy storage density (with minimal variation of ≤±5%) over 20–120 °C, can be achieved in Ta‐modified AgNbO₃ ceramics. It is revealed that the incorporation of Ta to the Nb site can enhance the antiferroelectricity because of the reduced polarizability of B‐site cations, which is confirmed by the polarization hysteresis, dielectric tunability, and selected‐area electron diffraction measurements. Additionally, Ta addition in AgNbO₃ leads to decreased grain size and increased bulk density, increasing the dielectric breakdown strength, up to 240 kV cm^?1 versus 175 kV cm^?1 for the pure counterpart, together with the enhanced antiferroelectricity, accounting for the high energy storage density.     

High Performance Lithium‐Ion Batteries Using Layered 2H‐MoTe2 as Anode

The major challenges faced by candidate electrode materials in lithium‐ion batteries (LIBs) include their low electronic and ionic conductivities. 2D van der Waals materials with good electronic conductivity and weak interlayer interaction have been intensively studied in the electrochemical processes involving ion migrations. In particular, molybdenum ditelluride (MoTe₂) has emerged as a new material for energy storage applications. Though 2H‐MoTe₂ with hexagonal semiconducting phase is expected to facilitate more efficient ion insertion/deinsertion than the monoclinic semi‐metallic phase, its application as an anode in LIB has been elusive. Here, 2H‐MoTe₂, prepared by a solid‐state synthesis route, has been employed as an efficient anode with remarkable Li⁺ storage capacity. The as‐prepared 2H‐MoTe₂ electrodes exhibit an initial specific capacity of 432 mAh g^?1 and retain a high reversible specific capacity of 291 mAh g^?1 after 260 cycles at 1.0 A g^?1. Further, a full‐cell prototype is demonstrated by using 2H‐MoTe₂ anode with lithium cobalt oxide cathode, showing a high energy density of 454 Wh kg^?1 (based on the MoTe₂ mass) and capacity retention of 80% over 100 cycles. Synchrotron‐based in situ X‐ray absorption near‐edge structures have revealed the unique lithium reaction pathway and storage mechanism, which is supported by density functional theory based calculations.     

Compositional Control as the Key for Achieving Highly Efficient OER Electrocatalysis with Cobalt Phosphates Decorated Nanocarbon Florets

Compositional interplay of two different cobalt phosphates (Co(H₂PO₄)₂; Co‐DP and Co(PO₃)₂; Co‐MP) loaded on morphologically engineered high surface area nanocarbon leads to an increased electrocatalytic efficiency for oxygen evolution reaction (OER) in near neutral conditions. This is reflected as significant reduction in the onset overpotential (301 mV) and enhanced current density (30 mA cm^?2 @ 577 mV). In order to achieve uniform surface loading, organic‐soluble thermolabile cobalt‐bis(di‐tert‐butylphosphate) is synthesized in situ inside the nanocarbon matrix and subsequently pyrolyzed at 150 °C to produce Co(H₂PO₄)₂/Co(PO₃)₂ (80:20 wt%). Annealing this sample at 200 or 250 °C results in the redistribution of the two phosphate systems to 55:45 or 20:80 (wt%), respectively. Detailed electrochemical measurements clearly establish that the 55:45 (wt%) sample prepared at 200 °C performs the best as a catalyst, owing to a relay mechanism that enhances the kinetics of the 4e^? transfer OER process, which is substantiated by micro‐Raman spectroscopic studies. It is also unraveled that the engineered nanocarbon support simultaneously enhances the interfacial charge‐transfer pathway, resulting in the reduction of onset overpotential, compared to earlier investigated cobalt phosphate systems.     

Thermisches verhalten und phasenänderungen von ferrocinium-intercalaten des typs Fe(C5H5)+2(6FeOCl)e−

The formation and stability of the intercalation compound Fe(C₅H₅)⁺₂(6FeOCl)e^? have been studied by thermogravimetry, X-ray diffraction measurements and Mössbauer spectro-scopy. After reaction times of one week above 80°C side reactions are observed such as chlorination of the guest species and formation of α-Fe₂O₃ phases. A high-temperature intermediate phase with almost unchanged stoichiometry but with magnetically partly ordered Fe³⁺ host lattice is observed when the intercalation compound is produced by vapour transport of Fe(C₅H₅)₂ at 100 – 110°C. The ferricinium intercalate Fe(C₅H₅)⁺₂(6FeOCl)e^? is stable only up to temperatures of about 60°C.     

Joint Charge Storage for High‐Rate Aqueous Zinc–Manganese Dioxide Batteries

Aqueous rechargeable zinc–manganese dioxide batteries show great promise for large‐scale energy storage due to their use of environmentally friendly, abundant, and rechargeable Zn metal anodes and MnO₂ cathodes. In the literature various intercalation and conversion reaction mechanisms in MnO₂ have been reported, but it is not clear how these mechanisms can be simultaneously manipulated to improve the charge storage and transport properties. A systematical study to understand the charge storage mechanisms in a layered δ‐MnO₂ cathode is reported. An electrolyte‐dependent reaction mechanism in δ‐MnO₂ is identified. Nondiffusion controlled Zn²⁺ intercalation in bulky δ‐MnO₂ and control of H⁺ conversion reaction pathways over a wide C‐rate charge–discharge range facilitate high rate performance of the δ‐MnO₂ cathode without sacrificing the energy density in optimal electrolytes. The Zn‐δ‐MnO₂ system delivers a discharge capacity of 136.9 mAh g^?1 at 20 C and capacity retention of 93% over 4000 cycles with this joint charge storage mechanism. This study opens a new gateway for the design of high‐rate electrode materials by manipulating the effective redox reactions in electrode materials for rechargeable batteries.     

Nanocrystalline LaMnO3 preparation and kinetics of crystallization process

Precursor of nanocrystalline LaMnO₃ was synthesized by solid-state reaction at low heat using La(NO₃)₃·6H₂O, MnSO₄·H₂O, and Na₂CO₃·10H₂O as raw materials. XRD analysis showed that precursor was a mixture containing orthorhombic La₂(CO₃)₃·8H₂O and rhombohedral MnCO₃. When the precursor was calcined at 800 ^°C for 2 h, pure phase LaMnO₃ with rhombohedral structure was obtained. Magnetic characterization indicated that rhombohedral LaMnO₃ behaved weak magnetic properties. The thermal process of the precursor experienced four steps, which involved the dehydration of crystallization water at first, and then decomposition of manganese carbonate into MnO₂, and decomposition of La₂(CO₃)₃ and MnO₂ together into La₂O₂CO₃ and Mn₂O₃, and lastly reaction of monoclinic La₂O₂CO₃ with Mn₂O₃ and formation of rhombohedral LaMnO₃. Based on the Kissinger equation, the value of the activation energy associated with the formation of rhombohedral LaMnO₃ was determined to be 260 kJ mol^?1. The value of the Avrami exponent, n, was equal to 1.68, which suggested that crystallization process of LaMnO₃ was the random nucleation and growth of nuclei reaction.     

Rapid and Low‐Temperature Salt‐Templated Production of 2D Metal Oxide/Oxychloride/Hydroxide

2D materials have played an important role in electronics, sensors, optics, electrocatalysis, and energy storage. Many methods for the preparation of 2D materials have been explored. It is crucial to develop a high‐yield, rapid, and low‐temperature method to synthesize 2D materials. A general, fast (5 min), and low‐temperature (≈100 °C) salt (CoCl₂·6H₂O)‐templated method is proposed to prepare series of 2D metal oxides/oxychlorides/hydroxides in large scale, such as MoO₃, SnO₂, SiO₂, BiOCl, Sb₄O₅Cl₂, Zn₂Co₃(OH)₁₀ 2H₂O, and ZnCo₂O₄. The as‐synthesized 2D materials possess an ultrathin feature (2–7 nm) and large aspect ratios. Additionally, these 2D metal oxides/oxychlorides/hydroxides exhibit good electrochemical properties in energy storage (lithium/sodium‐ion batteries) and electrocatalysis (hydrogen/oxygen evolution reaction).     

Layered Ca0.28MnO2·0.5H2O as a High Performance Cathode for Aqueous Zinc‐Ion Battery

Aqueous zinc‐ion batteries are promising candidates for grid‐scale energy storage because of their intrinsic safety, low cost, and high energy intensity. However, lack of suitable cathode materials with both excellent rate performance and cycling stability hinders further practical application of aqueous zinc‐ion batteries. Here, a nanoflake‐self‐assembled nanorod structure of Ca_0.28MnO₂·0.5H₂O as Zn‐insertion cathode material is designed. The Ca_0.28MnO₂·0.5H₂O exhibits a reversible capacity of 298 mAh g^?1 at 175 mA g^?1 and long‐term cycling stability over 5000 cycles with no obvious capacity fading, which indicates that the per‐insertion of Ca ions and water can significantly improve reversible insertion/extraction stability of Zn²⁺ in Mn‐based layered type material. Further, its charge storage mechanism, especially hydrogen ions, is elucidated. A comprehensive study suggests that the intercalation of hydrogen ions in the first discharge plat is controled by both pH value and type of anion of electrolyte. Further, it can stabilize the Ca_0.28MnO₂·0.5H₂O cathode and facilitate the following insertion of Zn²⁺ in 1 m ZnSO₄/0.1 m MnSO₄ electrolyte. This work can enlighten and promote the development of high‐performance rechargeable aqueous zinc‐ion batteries.     

Dielectric properties of K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3

Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static dielectric constant at room temperature are 7.67 and 4.80 for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively.     

Conversion Synthesis of Self‐Standing Potassium Zinc Hexacyanoferrate Arrays as Cathodes for High‐Voltage Flexible Aqueous Rechargeable Sodium‐Ion Batteries

Prussian blue analogs exhibit great promise for applications in aqueous rechargeable sodium‐ion batteries (ARSIBs) due to their unique open framework and well‐defined discharge voltage plateau. However, traditional coprecipitation methods cannot prepare self‐standing electrodes to meet the needs of wearable energy storage devices. In this work, a water bath method is reported to grow microcube‐like K₂Zn₃(Fe(CN)₆)₂·9H₂O on carbon cloth (CC) using Zn nanosheet arrays as the zinc source and reducing agent, directly serving as a self‐standing cathode. Benefiting from fast ion diffusion and high conductivity, the cathode delivers a high areal capacity of 0.76 mAh cm^?2 at 0.5 mA cm^?2 and excellent capacity retention of 57.9% as the current density increases to 20 mA cm^?2. By coupling with NaTi₂(PO₄)₃ grown on CC as an anode, a quasi‐solid‐state flexible ARSIB with a high output voltage plateau of 1.6 V is successfully assembled, exhibiting a superior areal capacity of 0.56 mAh cm^?2 and energy density of 0.92 mWh cm^?2. In particular, the device shows admirable mechanical flexibility, maintaining 90.3% of initial capacity after 3000 bending cycles. This work is anticipated to open a new avenue for the rational design of self‐standing electrodes used in high‐voltage flexible ARSIBs.