Specific Low Density Research Articles

Hierarchical CoP@Ni(OH)2·0.75H2O core-shell nanosheet arrays on carbon cloth for high-performance supercapacitors

The research on the structure tuning of CoP in supercapacitors has received extensive attention. However, low specific capacitance and energy density limit its further development. Here, we successfully synthesize the CoP@Ni(OH)2·0.75H2O core-shell nanosheets structure on carbon cloth. CoP nanowires, as the core, can provide efficient charge transportation path for electron transfer, while the thin Ni(OH)2·0.75H2O nanosheets shell can increase the specific surface area and curtail the transport distance. As a result, the as-prepared CoP@Ni(OH)2·0.75H2O nanosheet arrays electrode presents an outstanding specific capacity of 168.61 mAh g−1 at 1 A g−1. The assembled asymmetric supercapacitor (ASC) of CoP@Ni(OH)2·0.75H2O//activated carbon displays the highest energy density of 33.78 W h kg−1 at 800 W kg−1, as well as the remarkable cycling stability (capacitance retention of 98.5% after 10,000 cycles). Furthermore, ten parallel LEDs can be powered up by two ASCs connected in series. Thus, this article provides a new idea for the core-shell structure prepared by using CoP as the skeleton.

An activated carbon cloth anode obtained with a fast molten salt method for high-performance supercapacitors

Abstract Carbon materials are the most important anode materials used in supercapacitors. However, there are still great challenges in improving their low specific capacitance and energy density. In this study, a fast molten salt method was developed for the preparation of a super-high capacity activated carbon cloth anode. The nitrogen-activated carbon cloth electrode (NCC) showed better electrochemical performance than most of the carbon-based materials reported on previously. The maximum areal capacitance of the nitrogen-activated carbon cloth electrode was 6.72 F cm−2 at the current density of 2 mA cm−2. By employing the first-principle calculations method, it was derived that the adsorption energy of the K atoms on the graphite increased with the increase in nitrogen doping, especially on the pyridinic nitrogen (N-6). In addition, when the NCC and Ni-Co-S@CC electrodes were assembled into an asymmetric supercapacitor (ASC), the ASC demonstrated an operation in a large potential window of 1.8 V, and it achieved a high volumetric energy density of 23.51 mWh cm−3 at a power density of 1808 mW cm−3. This work showed the super high capacity of activated carbon cloth as a new anode material for high-performance supercapacitors prepared using a simple molten salt method.

Development of a High Energy Density, Long Cycle Life and Safety Enhanced Li-S Battery

Rechargeable lithium-sulfur (Li-S) batteries are widely considered the most promising “Beyond Li-ion” candidates, notably for their high theoretical energy density. The low and moderate atomic weight of Li and S, respectively, translates to a battery chemistry pairing that is lightweight. Since each S atom can ultimately host two lithium ions (Li+), compared with 0.5–0.7 Li+ per host atom in Li-ion batteries [1], the Li-S battery chemistry offers a much higher Li storage capacity potential. Assuming a complete redox couple reaction, S8 + 16Li+ + 16e- ↔ 8Li2S, the S cathode can have a high theoretical specific capacity of 1672 mAh/g with an average discharge voltage of ~2.1V (vs. Li/Li+), which leads to a theoretical specific energy of ~2500 Wh/kg based on the active material weight of a Li-S cell [2]. Other compelling attributes of Li-S batteries include high S natural abundance, low cost of S materials and safety characteristics owing to an intrinsic tolerance to overcharge [3]. In addition, the primary constituents of Li-S batteries are non-toxic and environmentally friendly [4].However, currently no commercial Li-S battery exists due to some significant technical challenges that have thus far prevented the realization of the tremendous energy density and performance potentials of Li-S batteries. These technical challenges include: low practical specific energy or energy density yield, significant capacity loss with cycling, high self-discharge rates, low Coulombic efficiency and safety concerns due to the use of Li metal anode [5].We will present our efforts in the development of a high energy density, long cycle life, safe and economically scalable Li-S battery technology via a holistic approach to nanoengineer/functionalize cell components including active components (i.e., S cathode, Li metal anode) and inactive components (e.g., separator, electrolyte), to address the Li-S battery cycle life degradation challenges and safety concerns. We will show that our comprehensive approaches afforded high discharge specific capacity, Coulombic efficiency (CE) and stable cycle life of the resultant Li-S cells (Figure 1).Our study demonstrates that the holistic approach of nanoengineering/functionalizing the active and inactive cell components represent a very promising strategy to develop a high energy density, long cycle life and safety enhanced Li-S battery technology.

Defect-Rich, Graphenelike Carbon Sheets Derived from Biomass as Efficient Electrocatalysts for Rechargeable Zinc–Air Batteries

Rechargeable Zinc–air batteries (RZABs) have attracted much attention due to their low cost, environmental benignity, high safety, and specific energy density. The bottleneck blocking the large-sca...

Fishnet-Like, Nitrogen-Doped Carbon Films Directly Anchored on Carbon Cloths as Binder-Free Electrodes for High-Performance Supercapacitor.

The low specific capacitance and energy density of carbon electrode has extremely limited the wide application of supercapacitors. For developing a high‐performance carbon electrode using a simple and effective method, a fishnet‐like, N‐doped porous carbon (FNPC) film is prepared by calcining the KOH‐activated polyindole precoated on carbon cloths. The FNPC film is tightly anchored on carbon cloths without any binder. The FNPC film with 3.8 at% N content exhibits a fairly high specific capacitance of 416 F g−1 at 1.0 A g−1. Moreover, the assembled button‐type cell with two FNPC film electrodes shows a high energy density of 16.4 Wh kg−1, a high power density of 67.4 kW kg−1, and long‐term cyclic stability of 92% of the initial capacitance after 10 000 cycles at 10 A g−1. The high performances mainly came from the integration of pseudocapacitance and electrical double‐layer capacitance behavior, wettability, fishnet‐like nanostructure, as well as the low interfacial resistivity. This strategy provides a practical, uncomplicated, and low‐cost design of binder‐free flexible carbon materials electrode for high‐performance supercapacitors.

Optimizing the micropore-to-mesopore ratio of carbon-fiber-cloth creates record-high specific capacitance

Abstract The application of commercial carbon fiber cloth (CFC) in energy storage equipment is limited by its low specific capacitance and energy density. By a simple one-step activation treatment, the specific surface area of CFCs with porous structure can be increased considerably from 3.9 up to 875 m2/g and the electrochemical properties of CFCs can be improved by three orders of magnitude (1324 mF/cm2). Moreover, the hydrophobicity of CFCs can be transformed into superhydrophilicity. However, the electrochemical performance of CFCs does not show a positive correlation with specific surface area but have a strong relationship with the hierarchical pore distribution forged by the annealing treatment. Only moderate micropore and mesoporous ratio enables optimizing the electrochemical performance of CFCs.

Review on Recent Progress in the Development of Tungsten Oxide Based Electrodes for Electrochemical Energy Storage.

Current progress in the advancement of energy-storage devices is the most important factor that will allow the scientific community to develop resources to meet the global energy demands of the 21st century. Nanostructured materials can be used as effective electrodes for energy-storage devices because they offer various promising features, including high surface-to-volume ratios, exceptional charge-transport features, and good physicochemical properties. Until now, the successful research frontrunners have focused on the preparation of positive electrode materials for energy-storage applications; nevertheless, the electrochemical performance of negative electrodes is less frequently reported. This review mainly focuses on the current progress in the development of tungsten oxide-based electrodes for energy-storage applications, primarily supercapacitors (SCs) and batteries. Tungsten is found in various stoichiometric and nonstoichiometric oxides. Among the different tungsten oxide materials, tungsten trioxide (WO3 ) has been intensively investigated as an electrode material for different applications because of its excellent charge-transport features, unique physicochemical properties, and good resistance to corrosion. Various WO3 composites, such as WO3 /carbon, WO3 /polymers, WO3 /metal oxides, and tungsten-based binary metal oxides, have been used for application in SCs and batteries. However, pristine WO3 suffers from a relatively low specific surface area and low energy density. Therefore, it is crucial to thoroughly summarize recent progress in utilizing WO3 -based materials from various perspectives to enhance their performance. Herein, the potential- and pH-dependent behavior of tungsten in aqueous media is discussed. Recent progress in the advancement of nanostructured WO3 and tungsten oxide-based composites, along with related charge-storage mechanisms and their electrochemical performances in SCs and batteries, is systematically summarized. Finally, remarks are made on future research challenges and the prospect of using tungsten oxide-based materials to further upgrade energy-storage devices.

Surface-functionalized Fe2O3 nanowire arrays with enhanced pseudocapacitive performance as novel anode materials for high-energy-density fiber-shaped asymmetric supercapacitors

Fiber-shaped asymmetric supercapacitors (FASCs) have potential applications in next-generation wearable and portable electronics due to their high power density, remarkable flexibility, fast charge-discharge capability, long cycle life and light weight. However, low specific capacitance and energy density hinder their practical applications. To obtain anode materials with high conductivity and high specific capacity, we first synthesize Fe2O3 nanowire arrays (NWAs) on carbon nanotube fibers as negative electrodes and then obtain FeS2 and FeP NWAs negative electrodes by sulfuration and phosphorization, respectively. The transformation processes effectively enhance the desirable properties of the electrode materials, improving the areal capacitance from 292 mF cm−2 to 833 mF cm−2 (sulfuration) and 1135 mF cm−2 (phosphorization) at a current density of 1 mA cm−2, demonstrating a significant improvement compared to Fe2O3 NWAs and, importantly, that phosphorization produces better results than sulfuration. Furthermore, the fabricated FASC exhibits outstanding mechanical flexibility and weavability and thus has great potential in for practical application in novel wearable and portable supercapacitors, which are expected to be the next generation of flexible energy-storage devices.

Study of mechanical and morphological properties of jute-tea leaf fiber reinforced hybrid composites: Effect of glass fiber hybridization

Fiber reinforced plastic composites replace wood and metals due to their light weight, high strength to weight ratio, noncorrosive nature and stiffness. Bio based fibers are used in place of petroleum based fibers because of environmental concerns. Natural fibers exhibit low specific strength and light density, processing and recycling are simple. New materials are being developed and grow every day. The high strength, light weight and biodegradability of natural fiber composites such as sisal, jute, kenaf, snake grass and banana fiber has made polymer composites were more attractive. The fiber is subjected to chemical pretreatments using alkali treatment (mercerization). This research has created composites of glass-jute-tea leaf fiber-reinforced polymers and assessed their mechanical characteristics such as tensile, flexural and impact test. Scanning Electron Microscopy (SEM) is being used to evaluate the interfacial characteristics, inner cracks and inner structures of broken surfaces. The experimental results showed 10% glass fiber, 20% jute fiber and 10% tea leaf fiber produced the optimum mechanical properties and it can be alternative material for pure glass fiber reinforced polymer composite.

Clarifying the decisive factors for utilization efficiency of Mg anodes for primary aqueous batteries

Low anodic efficiency of metallic Mg, which results in low discharge capacity and specific energy density, hinders the wider application of aqueous primary Mg batteries. In this work, we clarify the decisive factors effecting the utilization efficiency of Mg anodes. Anodic efficiency of several Mg anodes at different current densities is measured in 3.5 wt% NaCl electrolyte. The contribution of self-corrosion at open circuit potential and at constant applied current to efficiency of Mg anodes is compared. Additionally, efficiency loss caused by detachment of undissolved metallic portions, namely “chunk effect”, is determined with a proposed new approach. The effect of self-corrosion and “chunk effect” on anodic efficiency is assessed accordingly. The results indicate that “chunk effect” can also result in large efficiency loss of Mg anodes, especially at low current densities, which, in some cases, could exceed the loss caused by other mechanisms of self-corrosion of anode substrate. Hence, attention should be paid to both aspects when developing novel Mg anodes with high anodic efficiency, particularly for application in long-term low-power battery system.

Substantiation of the Results of Morphological Examination of the Urinary Bladder Wall in Experimental Diabetic Cystopathy

Measurement of consumed water and daily diuresis proved the pathomorphological manifestations of streptozotocin-induced cystopathy in the experiment on rats according to the results of biochemical studies of blood and urine.
 It is argued that the desquamation of cells in the transitional epithelium, its atrophy, stratification violation, and baring of the basal membrane are caused by a large volume of urine, which excessively stretches the urinary bladder, destroying the intercellular contacts of the urothelial layer. It is proved that primary hyperglycemia leads to widening of the lumen of the arterioles and moderate thickening of the basal membrane of the micro-hemovessels, and high chronic hyperglycemia – directly triggers the whole cascade of pathomorphological changes: on the 42nd day of the experiment it causes vasoconstriction of the arterioles, and at the later terms – the secondary expansion of the arterioles and venules of the microcirculatory bed of UB (urinary bladder); is the cause of dystrophic changes of endothelial cells, further thickening and lamellar transformation of the basal membrane and plasma permeation of the perivascular connective tissue; causes the appearance of dark involutional myocytes with few organelles and sarcoplasm sequestration.
 Hydropic dystrophy of smooth myocytes has been found to be associated with the hydration of blood plasma as a result of excessive polydipsia in diabetic animals, and vacuole dystrophy of urothelial cells, enlargement of their size and interstitial edema – with low specific urinary density due to the multiple fast increase of diuresis. It has been established that prolonged high glucosuria and decreased diuresis lead to a decrease in urothelial cell size, compaction of their cytoplasm and ultrastructural readjustment. The increase of the content of glycosylated hemoglobin during the experiment justified the appearance and increase of the sludge-syndrome.

Microstructure and mechanical properties of friction stir welded dissimilar 5754-H111-6013-T6 aluminum alloy joints

Abstract Aluminum alloys exhibit good strength, excellent corrosion resistance and good forming properties along with low specific density. Due to these superior properties, they are widely used in the automotive, chemical, and food industries, especially in shipbuilding and the yacht industry. It is important to join these alloys used in the mentioned industrial areas. However, it is very difficult to join Al and its alloys via traditional welding methods despite its widespread use. In this study, 5754-H111 and 6013-T6 aluminum alloys were joined by friction stir welding. Welding operations were carried out at 1250 rpm using welding feed rates of 12.5, 25, and 32 mm × min−1. Metallographic investigations were carried out to determine the microstructural and macrostructural properties of the weld zones. Tensile, bending, and hardness tests were also performed to determine the mechanical properties of the welded samples. The results obtained as a result of the tests were evaluated and interpreted. Micro-void defects were found to occur in the weld metal–HAZ transition zones. It was established that the welding speed affected the tensile strength. The highest tensile strength was obtained at a feed rate of 25 mm × min−1. It was determined that no cracking or fraction occurred in the welded samples as a result of the bending test.

Exploring the Effect of Strong Complexing Agents As Electrolyte Additives on Anode Performance in Mg-Air Primary Batteries

Mg-air primary batteries have drawn increasing attention recently due to their low cost, safety, and high theoretical specific power density. However, high self-corrosion rate and anode fouling during discharge (mainly due to the formation of Mg(OH)2/MgO) lead to particularly lower delivered voltage and utilization efficiency. Modification of the battery electrolyte chemistry plays a crucial role in tackling these shortcomings and improving battery performance. Remarkable enhancements to the Mg anode’s performance by addition of group of organic complexing agents in the Mg-air battery electrolyte has recently been reported [1]. In this study, the effect of two strong organic complexing agents (i.e. disodium 4,5-dihydroxy-1,3-benzenedisulfonate(Tiron) and Nitrilotriacetic acid(NTA)) as additives to the Mg-air battery electrolyte was investigated. Commercially pure magnesium with relatively high Fe impurity level (i.e. 220ppm) has been chosen as the anode material in order to have a better understanding of the interaction of the complexing agents with pure Mg and the common Fe impurity. Half-cell measurements were conducted to evaluate the discharge performance of the anode in the presence of the complexing agents. The electrochemical and corrosion behavior were studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve. The morphology of the anode surface after discharge was investigated by scanning electron microscope (SEM). The results indicate that strong complexing agents can remarkably improve the discharge potential by activating the Mg anode surface and mitigating the high cathodic activity stemmed from Fe impurities. A possible downside of adding strong complexing agents is the tendency to accelerate the corrosion rate of the Mg anode. However, tuning the complexing agent concentration in the electrolyte can significantly improve the utilization efficiency at the expense of a slight decrease in the battery delivered voltage. [1] D. Höche, S.V. Lamaka, B. Vaghefinazari, T. Braun, R.P. Petrauskas, M. Fichtner, M.L. Zheludkevich, Performance boost for primary magnesium cells using iron complexing agents as electrolyte additives, Scientific Reports, 8 (2018).

Positive, zero and negative Poisson’s ratio non-stochastic metallic cellular solids: Dependence between static and dynamic mechanical properties

Cellular solids are attractive materials due to their high specific static and dynamic mechanical properties. Even though these mechanical domains are interdependent, they are generally studied separately. This study uses a combination of additive manufacturing and vacuum assisted investment casting to manufacture low specific density (0.042–0.098) non-stochastic metallic cellular solids. An in-situ unitary cell geometric control is used to produce samples with positive, zero and negative Poisson’s ratios. The different values of this elastic constant allow the analysis of the distinct deformation in auxetic and non-auxetic behaviors. Deformation models are used to describe the static and dynamic behavior of the referred samples. It is shown that auxetic samples display higher values of apparent modulus and plastic collapse stress due to their densification effect. In terms of dynamic properties, samples with slightly negative and zero rib angles show higher values of damping. This is attributed to the more favorable flexure component of deformation and variations in material volume that influence the hysteretic damping. Overall, it is suggested that the most beneficial combination of specific density, static and dynamic mechanical properties is observed in samples with a rib angle of −10° and a Poisson’s ratio of −0.34.

Nanoengineered Separators for a High Energy Density, Long Cycle Life Li-S Battery

Rechargeable lithium-sulfur (Li-S) batteries are widely considered the most promising “Beyond Li-ion” candidates, notably for their high theoretical energy density. The low and moderate atomic weight of Li and S, respectively, translates to a battery chemistry pairing that is lightweight. Since each S atom can ultimately host two lithium ions (Li+), compared with 0.5–0.7 Li+ per host atom in Li-ion batteries [1], the Li-S battery chemistry offers a much higher Li storage capacity potential. Assuming a complete redox couple reaction, S8 + 16Li+ + 16e- ↔ 8Li2S, the S cathode can have a high theoretical specific capacity of 1672 mAh/g with an average discharge voltage of ~2.1V (vs. Li/Li+), which leads to a theoretical specific energy of ~2500 Wh/kg based on the active material weight of a Li-S cell [2]. Other compelling attributes of Li-S batteries include high S natural abundance, low cost of S materials and safety characteristics owing to an intrinsic tolerance to overcharge [3]. In addition, the primary constituents of Li-S batteries are non-toxic and environmentally friendly [4]. However, currently no commercial Li-S battery exists due to some significant technical challenges that have thus far prevented the realization of the tremendous energy density and performance potentials of Li-S batteries. These technical challenges include: low practical specific energy or energy density yield, significant capacity loss with cycling, high self-discharge rates, low Coulombic efficiency and safety concerns due to the use of Li metal anode [5]. We will present our efforts in the development of a high energy density and long cycle life Li-S battery technology via nanoengineered battery separators. We will show that our atomic and/or molecular level, functional material coated separators exhibit much improved physical properties including tensile strength, thermal shrinkage, and electrolyte wettability (Figure 1). When used in Li-S cells, the nanoengineered separators (coated) afforded a significant increase in specific capacity compared with the control (uncoated) separator, as illustrated in Figure 2. The enhanced Li-S cell performance suggests polysulfide blockage from the nanoscale functional material coated separators used in the resultant Li-S cells. Our study demonstrates that the nanoengineered separator approach represents a very promising strategy to develop a high energy density, long cycle life, safe and economically scalable Li-S battery technology. References Bullis, “Revisiting Lithium-Sulfur Batteries” MIT Review, May 22, 2009.Arumugam Manthiram, Yongzhu Fu, and Yu-Sheng Su, Acc. Chem. Res., 46 (5), pp 1125–1134 (2013)James R. Akridge, “Lithium Sulfur Rechargeable Battery Safety”, Battery Power Products & Technology, October 2001.Yongguang Zhang, Yan Zhao, Kyung Eun Sun and P. Chen, The Open Materials Science Journal, 5, 215-221 (2011).Monica Marinescu, Laura O’Neill, Teng Zhang, Sylwia Walus, Timothy E. Wilson, and Gregory J. Offer, J. Electrochem. Soc, 165 (1) A6107-A6118 (2018). Figure 1

Porous Carbon Materials with Ultrahigh Surface Area for High Energy Density Supercapacitors and High Power Density Electrochemical Thermocell.

Low energy density of energy storage devices such as supercapacitors1-5 and thermocells6 has always been a problem to be solved urgently, which is due to the low specific surface area and low density of the electrode materials. The graphene based materials with high surface area have successfully increased the energy density of energy storage devices, but the density of graphene materials is still low, which leads to low energy density based on the weight of the whole devices. Currently most efforts have been focused on increasing the specific surface area of graphene materials, instead of increasing the density of graphene. Herein, we have successfully synthesized graphene based materials with both high specific surface area and density. Phenolic precursors were in-situ polymerized on the surface of graphene 3D network through the hydrothermal reaction. The mass ratio between the phenolic precursors and graphene oxide was varied from 1:4 to 1:100. The results indicated that when the mass ratio between the phenolic resin precursor and graphene oxide is 1:16, graphene based 3D cross-linked nano-composites with high density can be realized. The corresponding specific surface area is 700 m2/g and the density is 0.55 g/cm3; Chemical activation by using activation agents to the as-prepared products was performed for the further increasing of the surface area. Different activation agents such as potassium hydroxide, sodium hydroxide and potassium carbonate were used, in which the chemical activation effect is the best for potassium hydroxide is the best. The optimal mass ratio between potassium hydroxide and Intermediate products ratio is 4:1, while the optimized activation temperature is 900 oC. The optimized graphene based materials have the specific surface area up to 3000 m2/g and the density about 0.5 g/cm3, which was used as the electrode materials for supercapacitors and thermocells3,6. Supercapacitors based on our materials exhibited a high energy density of 90 wh/kg in organic electrolyte, which is much higher than 54 wh/kg for supercapacitors based on the commercial activated carbon. Thermocells based on our materials achieved a output power of 12 W/m2, which is also much higher than 2 W/m2 for thermocells based on the traditional carbon materials. This project provides a key material for energy storage devices to achieve high energy density and output power. Furthermore, it will strongly promote the research and development of supercapacitors and thermocells for their application in the area of small ignition device and harvesting the low-grade and wasted thermal energy. Reference: (1) Long Zhang; Xi Yang; Fan Zhang; Guankui Long; Tengfei Zhang; Kai Leng; Yawei Zhang; Yi Huang; Yanfeng Ma; Mingtao Zhang; Yongsheng Chen*. Controlling the effective surface area and pore size distribution of sp(2) carbon materials and their impact on the capacitance performance of these materials. J Am Chem Soc 2013, 135, 5921-5929. (2) Fang Yang; Duo Tang; Tengfei Zhang; Wenzhi Qin; Yongsheng Chen; Liang Wang; Jun Wang; Haibin Zhang; Yi Li; Long Zhang*. A free-standing laser energy converter based on energetic graphene oxide for enhanced photothermic ignition. J Mater Chem A 2018, 6, 13761-13768. (3) Long Zhang; Fan Zhang; Xi Yang; Guankui Long; Yingpeng Wu; Tengfei Zhang; Kai Leng; Yi Huang; Yanfeng Ma; Ao Yu; Yongsheng Chen*. Porous 3D graphene based bulk materials with exceptional high surface area and excellent conductivity for supercapacitors. Sci Rep 2013, 3, 1408. (4) Long Zhang; Fan Zhang; Xi Yang; Kai Leng; Yi Huang; Yongsheng Chen*. High-performance supercapacitor electrode materials prepared from various pollens. Small 2013, 9, 1342-1347. (5) Long Zhang; Jiajie Liang; Yi Huang; Yanfeng Ma; Yan Wang; Yongsheng Chen*. Size-controlled synthesis of graphene oxide sheets on a large scale using chemical exfoliation. Carbon 2009, 47, 3365-3368. (6) Long Zhang; Taewoo Kim; Na Li; Tae June Kang; Jun Chen; Jennifer M. Pringle; Mei Zhang; Ali H. Kazim; Shaoli Fang; Carter Haines; Danah Al-Masri; Baratunde A. Cola; Joselito M. Razal; Jiangtao Di; Stephen Beirne; Douglas R. MacFarlane; Anuncia Gonzalez-Martin; Sibi Mathew; Yong Hyup Kim; Gordon Wallace; Ray H. Baughman*. High Power Density Electrochemical Thermocells for Inexpensively Harvesting Low-Grade Thermal Energy. Adv Mater 2017, 1605652-n/a. Figure 1

The hydraulic efficiency-safety trade-off differs between lianas and trees.

Hydraulic traits are important for woody plant functioning and distribution. Associations among hydraulic traits, other leaf and stem traits, and species’ performance are relatively well understood for trees, but remain poorly studied for lianas. We evaluated the coordination among hydraulic efficiency (i.e., maximum hydraulic conductivity), hydraulic safety (i.e., cavitation resistance), a suite of eight morphological and physiological traits, and species’ abundances for saplings of 24 liana species and 27 tree species in wet tropical forests in Panama. Trees showed a strong trade‐off between hydraulic efficiency and hydraulic safety, whereas efficiency and safety were decoupled in lianas. Hydraulic efficiency was strongly and similarly correlated with acquisitive traits for lianas and trees (e.g., positively with gas exchange rates and negatively with wood density). Hydraulic safety, however, showed no correlations with other traits in lianas, but with several in trees (e.g., positively with leaf dry matter content and wood density and negatively with gas exchange rates), indicating that in lianas hydraulic efficiency is an anchor trait because it is correlated with many other traits, while in trees both efficiency and safety are anchor traits. Traits related to shade tolerance (e.g., low specific leaf area and high wood density) were associated with high local tree sapling abundance, but not with liana abundance. Our results suggest that different, yet unknown mechanisms determine hydraulic safety and local‐scale abundance for lianas compared to trees. For trees, the trade‐off between efficiency and safety will provide less possibilities for ecological strategies. For lianas, however, the uncoupling of efficiency and safety could allow them to have high hydraulic efficiency, and hence high growth rates, without compromising resistance to cavitation under drought, thus allowing them to thrive and outperform trees under drier conditions.

Application of Low-Temperature Postradiation Polymerization of Polytetrafluoroethylene for Hydrophobization of Porous Ceramic Materials Based on Oxide Fibers

Porous ceramic materials based on oxide fibers, which have lower specific density and thermal conductivity, are able to function at temperatures exceeding 1000°C, including in an oxidizing atmosphere, which allows this class of materials to have a wide range of applications in various industries. The disadvantage of such materials is the hydrophilicity caused by the chemical composition of the fibers and the highly developed porous structure, which severely limits their use, particularly in arctic and subarctic climates characterized by high humidity. The authors have investigated and proposed a method of hydrophobization using the technology of low-temperature postradiation graft polymerization of tetrafluoroethylene molecules. The technology makes it possible to apply polymer coatings to oxide fibers, providing high hydrophobic properties, which is manifested in the increased value of the contact angle of wetting the surface of the material, which in turn substantially improves their operational characteristics and expands the possibilities of practical application as heat-shielding and heat-insulating materials.

Plant Functional Traits Are the Mediators in Regulating Effects of Abiotic Site Conditions on Aboveground Carbon Stock-Evidence From a 30 ha Tropical Forest Plot.

Understanding the relative contribution of abiotic and biotic factors to the formation of ecosystem functioning across scales is vital to evaluate ecosystem services. Here, we elucidate the effects of abiotic site conditions (i.e., soil and topographic properties) and plant functional traits on variations of stand aboveground carbon (AGC) stock in an old-growth tropical montane rain forest. The response-effect framework in functional ecology is adopted in examining how plant functional traits respond to environmental changes and affect ecosystem functioning. We measured specific leaf area and wood density of 270 woody plant species and estimated stand AGC stocks in a 30-ha forest plot. The relationships among environmental factors (ENVIRONMENT), community-weighted means of functional traits (TRAITS) and stand AGC stocks across nested spatial scales were disentangled by structural equation modeling. The results showed that the stands composed of ‘acquisitive’ species (high specific leaf area and low wood density) had low AGC, whereas stands composed of ‘conservative’ species (low specific leaf area and high wood density) had high AGC. TRAITS responded to ENVIRONMENT and affected AGC directly. ENVIRONMENT had an indirect effect on AGC through its direct effect on TRAITS. TRAITS were more important than ENVIRONMENT in driving variations of AGC. The effects of TRAITS on AGC increased, while the effects of ENVIRONMENT on AGC decreased with the increase of spatial scales in the tropical montane rain forest. Our study suggests that plant functional traits are the mediators in regulating effects of abiotic site conditions on ecosystem functions.

Evaluation of productivity at the leaf level of juvenile poplars

The purpose of this research was the comparative study of the morphological traits of the poplars assimilation apparatus and their possible use in the selection process. Leaf area, not leaf length, was taken as a unit of the plastochronic index for the first time in this work. Analysis of the sigmoidal curve of the growth of the fifth leaf of the apical shoot of poplar showed that 80% of the maximum leaf surface is reached through an interval of 2.2 plastochrons and corresponds to the 20-day calendar age of the leaf. It is noted that the raw biomass of the cross-section poplar ‘Hybrid e.s.-38’ was significantly higher than in other compared varieties. Two groups of genotypes with a high and a low specific surface leaf density were identified. Average size of the leaf area, as well as the total amount of the assimilating surface of the apical shoot of the poplar ‘Hybrid e.s.-38’, 2 and more times exceeded the similar parameters of the poplars studied. Such changes in the current increment and age dynamics of the photosynthetic apparatus of the cross-section ‘Hybrid e.s.-38’ allow to recommend it in breeding as a parent material for creating promising varieties of poplars.