Borate Layers Research Articles

Dendrite-free zinc metal anode for long-life zinc-ion batteries enabled by an artificial hydrophobic-zincophilic coating

Considering the desired energy density, safety and cost-effectiveness, rechargeable zinc-ion batteries (ZIBs) are regarded as one of the most promising energy storage units in next-generation energy systems. Nonetheless, the service life of the current ZIBs is significantly limited by rampant dendrite growth and severe parasitic reactions occurring on the anode side. To overcome these issues caused by poor interfacial ionic conduction and water erosion, we have developed a facile strategy to fabricate a uniform zinc borate layer at the zinc anode/electrolyte interface (ZnBO). Such protective layer integrates superhydrophobic-zincopholic properties, which can effectively eliminate the direct contact of water molecules on the anode, and homogenize the interfacial ionic transfer, thereby enhancing the cyclic stability of the zinc plating/stripping. As a result, the as-prepared ZnBO-coated anode exhibits extended lifespan of 1200 h at 1 mA cm−2 and demonstrates remarkable durability of 570 h at 20 mA cm−2 in Zn||Zn symmetric cells. Additionally, when coupled to an NH4V4O10 (NVO) cathode, it also delivers a superior cyclability (203.5 mAh/g after 2000 cycles at 5 A/g, 89.3 % capacity retention) in coin full cells and a feasible capacity of 2.5 mAh at 1 A/g after 200 cycles in pouch full cells. This work offers a unique perspective on integrating hydrophobicity and zincophilicity at the anode/electrolyte interface through an artificial layer, thereby enhancing the cycle lifespan of ZIBs.

Hydroflux Synthesis and Structural Phase Transition of Rare-Earth Borate Hydroxides Na2[RE(BO3)(OH)2] (RE = Y, Gd-Er).

Reacting RE2O3 and H3BO3 in an ultra-alkaline NaOH hydroflux at about 250 °C yielded pure, crystalline samples of Na2[RE(BO3)(OH)2] (RE = Y, Gd-Er). The compounds dehydrate to Na3RE(BO3)2 upon heating in air to about 500 °C. Na2[RE(BO3)(OH)2] (RE = Tb-Er) are photoluminescent under UV radiation. Their UV-Vis spectra show the typical absorptions associated with 4f-4f transitions and absorption edges in the UV (band gaps ≥ 5.7 eV). The RE3+ cation is coordinated by seven oxygen atoms, which define a distorted pentagonal bipyramid. The bipyramids share trans-edges of their base forming infinite chains. Triangular (BO3)3- groups connect the chains into layers. The crystal structure of Na2[Ho(BO3)(OH)2] was investigated at various temperatures in the range 100 K ≤ T ≤ 320 K. Above 310(2) K, the compound crystallizes in the orthorhombic space group Cmcm (β-phase), below, it undergoes a displacive phase transition of second order resulting in a monoclinic structure in space group C2/c (α-phase). The critical exponents derived from different structural parameters indicate a cooperative distortion of the borate layers, but a rather uncorrelated adaptation of the sodium cations to their local environment. The other compounds of the series also adopt the structure of the α-phase at 296 K.

Separation of carbohydrates using dynamically adsorbed borate stationary phase for hydrophilic interaction liquid chromatography

In this work, a chromatographic method for the separation of carbohydrates was proposed. Tris-(hydroxymethyl)-amine (TRIS) functionalized silica-based hydrophilic interaction liquid chromatography (HILIC) stationary was synthesized. The dynamically absorbed borate layer is generated by using borate buffer as a polar modifier due to the complexation of borate with TRIS ligand in the stationary phase. The chromatographic systems were analyzed by the linear solvation energy relationship model. The calculated system constants revealed the enhancement of anionic exchange by the addition of borate in the mobile phase system. In addition, ligand exchange is critical for the retention and elution order of sugars and sugar alcohols. Carbohydrates displayed prolonged retention with different selectivity profiles relating to their complexation coefficients with borate. Experiment results showed that the effect of borate in this chromatographic system was stable within the range of pH 3–7 and borate concentration of 5–15 mM. This work provides a complementary solution for the separation of carbohydrates. It can also be extended to the separation of glycosides.

Structure and properties of boride layers on low-carbon steel after plasma alloying with boron carbide

Wear is known to limit the life of tools and machines. To achieve high wear resistance, the hard phases must be individually adapted to the tribological system and especially to the interaction with abrasive objects. Comparison of the hardness of carbides, nitrides and borides of the same stoichiometry shows that borides usually have the highest hardness. Plasma doping with boron is an effective way to obtain boride layers with high wear resistance. In the work, a study of the microstructure, determination of the chemical composition in local places, measurement of microhardness and testing for adhesion to the substrate of the doped layer after processing were carried out. Based on the results of the research, it was found that the technology of plasma alloying with boron makes it possible to obtain a boride layer with high hardness and good adhesion to the substrate. According to the results of the study, the layer consists of several characteristic zones: hypereutectic, eutectic and heat-affected zones. The highest microhardness value of the alloyed layer is 1174 HV. It is noted that the hardening depth is 1.5 mm and is 5—6 times higher compared to the diffusion borated layer.

High‐pressure Synthesis, Structure, IR Spectroscopy, and Theoretical Calculations of the New Silver Tetraborate Ag2B4O7 with a Unique Crystal Structure

AbstractAg2B4O7 is synthesized at high‐pressure/high‐temperature conditions of 11 GPa and 1073 K in a multianvil device. It crystallizes in the monoclinic centrosymmetric space group P21/c (no. 14) with four formula units per unit cell (Z=4). The cell parameters are a=787.53(3), b=651.63(2), c=943.88(3) pm, β=107.911(2)°, and V=460.90(3) Å3. Ag2B4O7 crystallizes in a unique crystal structure that consists of complex anionic borate layers with Ag+ ions in between. Additionally, the silver cations show argentophilic interactions. The compound was analysed via single‐crystal and powder diffraction as well as infrared spectroscopy. Furthermore, theoretical calculations at HSEsol level were conducted.

Oxidation behavior of Al3BC3 powders at 800–1400 °C in ambient air

The non-isothermal and isothermal oxidation behavior of Al3BC3 powders at 800–1400 °C in the air was studied. The results revealed that the oxidation resistance of Al3BC3 powders was better than that of “Al8B4C7” powders. At 800–1100 °C, the sintering accelerated the adhesion between the aluminum borate layer and the Al3BC3 core. No micro-crack was observed on both surface and cross-section, thus effectively blocking the diffusion of oxygen and volatilization of reactant gases. The oxidation behavior changed due to the oxidation products growing into a rod shape higher than 1200 °C. The interlocking structure of Al18B4O33 micro-rods made the surface of oxidized powder porous. Therefore, the oxygen diffused quickly into Al3BC3 through the porous structure on its surface, leading to rapid oxidation. Jander model could deal with oxidation kinetics and be in good agreement with the experimental data. The calculated apparent activation energy of Al3BC3 powder was equal to 212.76 kJ/mol at 800–1100 °C.

DETERMINATION OF THE OPTIMAL PARAMETERS OF LASER BORIDING TO IMPROVE THE WEAR RESISTANCE OF PISTON RINGS

Purpose. The goal was to determine the effect of laser heating parameters on the structure and depth of the borated layer, since the properties of piston rings depend on the depth of the latter.
 Research methods. Microstructural and X- ray phase analyzes were used to determine the structural state of piston rings.
 Results. Application of traditional boriding methods associated with diffusion of boron into the solid phase leads to formation of the working layer having high brittleness. The conducted studies revealed that the increase in the speed of displacement of the part in the process of laser heating reduces the depth of the borated layer. Such a dependence is observed both at 0.15 mm thickness of coating and at a thickness of 0.30 mm. For all modes of workpiece displacement speed for the used boron containing envelope with the above-specified thickness a higher thickness of the borated layer and the heat affected area corresponds to a higher thickness of coating. Increase of the spot size leads to an increase in the depth of the layer. By X- ray and metallographic diffraction there were decoded the phases and structural constituents of the borated layer.
 Scientific novelty. An approach to solving the problem of increasing the wear resistance of piston rings without crumbling is shown. The use of laser heating during drilling ensures the formation of a new layer with special properties. However, optimal properties can be achieved only after establishing a relationship between the parameters of the process and the depth of the boron layer. X-ray and metallographic analysis determined the relationship between the rate of irradiation and the proportion of high-boron structures in the layer. It is shown that the borated layer in high-strength cast iron contains such phases as FeB, Fe2B, α- phase, borocementite Fe3(B,C).
 Practical value. Increased wear resistance of piston ring materials, which often limits the growth of machine productivity and their service life. Research results can be extended to other parts subject to intensive wear.

Investigation of the structure and properties of surface composite layers on multi-alloyed steels

In this work were studied the structures and properties of surface composite layers obtained by chemical-thermal treatment and combined chemical-thermal treatment, combining liquid-free electrolysis-free boriding with gas nitriding. The properties of surface composite layers on steels with different alloys are analyzed depending on various parameters of chemical-thermal treatment. The study showed that, during boriding, phases of iron borides FeB, Fe2B are formed on the surface of the samples, and their volume ratio strongly depends on the degree of steel alloying. A strong effect of carbon on the morphology of surface layers was revealed. Finely dispersed strengthening particles were found in the borated layers on the VKS-5 steel, large superhard particles on the Ch12MF steel near the borated layers. The study of the microstructure of the composite layers showed that during gas nitriding, a layer 80 μm in size is obtained, which penetrates deep into the borated layer. The study of the properties of surface layers showed that carbon has the greatest influence on the formation of borated layers. The resulting composite layers are characterized by reduced microbrittleness and increased corrosion resistance.

Effect of Thermochemical Boronizing of Alumina Surface on the Borate Crystals Growth and Interaction with Nickel and Nickel Alloy

Wettability at the metal-ceramic interface is highly important for the development of modern composite materials. Poor wettability by metal melts restricts the use of alumina in protective metal matrix composite (MMC) coatings. In the present experimental study, the possibility to modify wetting properties of alumina by thermochemical surface boronizing was investigated. The results of SEM, EDS, XRD and XPS characterisation of surfaces revealed the formation of oxygen containing Al–B compounds identified as aluminium borates (Al18B4O33/Al4B2O9); no signs of non-oxide Al–B compounds were observed. The shape of the single splats deposited on the boronized alumina surface by the thermal spray and re-melted in the furnace revealed that significant wetting improvement by self-fluxing nickel alloy did not occur. However, the improvement of adhesion between the nickel/nickel alloy and Al2O3 surface was obtained due to formation of an intermediate layer consisting of B, O, Al and Si between the metal and ceramic surfaces at the presence of some silicon at the modified surfaces. The presented study demonstrates that the thermochemical boronizing of alumina in amorphous boron medium is a simple method to obtain a thin aluminium borate layer consisting of oriented nano-rod-like crystals, whose growing direction is predetermined by the orientation of the alumina grains’ faces at surface.

Improving the technology of chemical-thermal treatment of tool steels

The paper presents data on the study of the intensification of chemical-thermal treatment processes. Diffusion saturation of the surface of steels and alloys is most often carried out under high-temperature isothermal or isothermal-step exposure with complete recrystallization of steel into an austenitic state. This leads to overheating — the structure and mechanical properties, in addition to hardness and wear resistance, deteriorate. the main regularities and mechanisms of boration of ferritoperlite steels are investigated and described. It is shown that cyclic heating and cooling significantly accelerate the kinetics of the CTO process of iron-carbon alloys. It was found that thermal cycling during boration leads to an increase in the layer thickness up to 80% on carbon steels, with an increase in the degree of alloying, the effect decreases from 70% (cast steel 5KHNM) to 20% (steel X12M). With an increase in the carbon content in steel, the depth of the borated layer decreases both after isothermal high-temperature boration and after thermocyclic boration.

Enhanced Interlayer Interaction and Second-Harmonic-Generation Response in a KBe2BO3F2-Type Inorganic-Organic Hybrid Zinc Borate.

A new inorganic-organic hybrid zinc borate was prepared under hydrothermal conditions. This compound is the first KBe2BO3F2 (KBBF) derivative with zinc borate layers linked by mononegatively charged amino acids. Notably, it exhibits a relatively large second-harmonic-generation response of about 2.0 times that of KBBF and a moderate birefringence for phase matching in the UV region. The enhanced interlayer interaction was evaluated by theoretical calculations based on density functional theory.

Magnetically Recovered Co and Co@Pt Catalysts Prepared by Galvanic Replacement on Aluminum Powder for Hydrolysis of Sodium Borohydride.

Magnetically recovered Co and Co@Pt catalysts for H2 generation during NaBH4 hydrolysis were successfully synthesized by optimizing the conditions of galvanic replacement method. Commercial aluminum particles with an average size of 80 µm were used as a template for the synthesis of hollow shells of metallic cobalt. Prepared Co0 was also subjected to galvanic replacement reaction to deposit a Pt layer. X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and elemental analysis were used to investigate catalysts at each stage of their synthesis and after catalytic tests. It was established that Co0 hollow microshells show a high hydrogen-generation rate of 1560 mL·min−1·gcat−1 at 40 °C, comparable to that of many magnetic cobalt nanocatalysts. The modification of their surface by platinum (up to 19 at% Pt) linearly increases the catalytic activity up to 5.2 times. The catalysts prepared by the galvanic replacement method are highly stable during cycling. Thus, after recycling and washing off the resulting borate layer, the Co@Pt catalyst with a minimum Pt loading (0.2 at%) exhibits an increase in activity of 34% compared to the initial value. The study shows the activation of the catalyst in the reaction medium with the formation of cobalt–boron-containing active phases.

Investigation of the structure and properties of the surface composite layer on VKS-5 steel

sIn this work, were studied the structure and properties of the surface composite layer on heat-resistant steel VKS-5, obtained by combined chemical and thermal treatment, combining liquid electrolysis-free boriding with gas and ion-plasma nitriding. The properties of the surface composite layer are analyzed depending on various parameters of chemical and thermal treatment to determine the optimal mode. The study of the microstructure and properties of borated layers has shown that the most optimal properties can be obtained in the boron mode at a temperature of 1010 °C with an exposure time of 8 hours. The study of the microstructure of composite layers has shown that gas nitriding produces a layer of 80 microns in size, which penetrates deep into the borated layer, and in ion-plasma nitriding, the layer size is so small that it is not possible to determine it using optical microscopy. A study of the properties of composite layers obtained by combined chemical-thermal treatment has shown that combined chemical-thermal treatment, combining boriding and ion-plasma nitriding, allows you to get the best combination of high hardness and reduced microfragility.

High-temperature cyclic oxidation behavior and mechanism of Mo2FeB2-based cermets with various boron contents

In this study, cyclic oxidation behavior and mechanism of Mo2FeB2-based cermets have been investigated by varying the boron content. The parabolic curves of mass gain confirmed the formation of the protective oxide layer. Mo2FeB2-based cermets with boron content of 6 wt.% had the lowest mass gain due to the denser and continuous oxide layer. A typical multi-layer structure could be observed in the cross-section, which was mainly composed of Fe oxide, borate and molybdate. The borate layer could effectively inhibit the diffusion of oxygen to protect the matrix from rapid oxidation. Furthermore, higher boron content could facilitate the oxide layer to be denser, which is beneficial to the oxidation resistance. However, the “pesting oxidation” would appear after 50 h oxidation at 800 °C, which causes the curves of mass gain to transform from parabolic to linear trend.

Lithium metal anode with lithium borate layer for enhanced cycling stability of lithium metal batteries

Lithium metal is one of the most promising next generation anode materials to make a leap of the energy density of conventional lithium-ion batteries. However, lithium metal has fatal problems to overcome in cycling stability and safety. In this study, lithium metal is pre-treated to form a lithium borate layer (LBL) on the surface to suppress dendritic growth of lithium and stabilize the interface between the carbonate-based electrolyte and anode. The pre-treated lithium metal greatly enhances the cycling stability of the cells (Li || Li symmetric and LiMn2O4 (LMO) || Li cells). Especially, cycling test with the LMO || Li cell reveals the pre-treatment with boric acid is more effective approach than addition of boric acid in the electrolyte because water is continuously generated during charge/discharge in the latter case and it causes side reactions and degrades the cycling performance. The LBL along with LiF stabilizes the solid electrolyte interface (SEI) layer and suppresses the dendritic growth of lithium. Due to the lithium-ion conducting ability of lithium borate, the pre-treated lithium anode also shows lower interfacial resistance than the pristine lithium and enhances rate capability.

Laser processing for increasing the durability of the piston rings

Abstract. Problem. In the process of operation piston rings are subject to wear. Non-sufficient wear resistance of piston ring materials often limits the growth of productivity of machines and the timing of their operation. It is not always that the desired set of properties of piston rings made of cast iron can be achieved by traditional methods of thermal or chemical-thermal treatment. Thus, application of traditional boriding methods associated with diffusion of boron into the solid phase leads to formation of the working layer having high brittleness. Therefore, the actuality of the problem is to increase the wear resistance of piston rings without embrittlement. Use of laser heating at boriding provides the formation of a new layer with special properties. However, the optimum properties can only be achieved after establishing a relationship between the parameters of running a process and the depth of the borated layer. The goal was to determine the effect of laser heating parameters on the structure and depth of the borated layer, since the properties of piston rings depend on the depth of the latter. The studies conducted revealed that the increase in the speed of displacement of the part in the process of laser heating reduces the depth of the borated layer. Such a dependence is observed both at 0.15 mm thickness of coating and at a thickness of 0.30 mm. For all modes of workpiece displacement speed for the used boron containing envelope with the above-specified thickness a higher thickness of the borated layer and the heat affected area corresponds to a higher thickness of coating. Increase of the spot size leads to an increase in the depth of the layer. By X-ray and metallographic diffraction the phases and structural constituents of the borated layer were decoded. X-ray diffraction and microstructural analysis revealed an association between the exposure speed and share of high-boron layer structures. It is shown that the borated layer in the ductile iron includes such phases as FeB, Fe2B, α-phase, and borocementite Fe3 (B, C). The research results can be extended to other parts subject to intensive wear.

La3 B6 O13 (OH): The First Acentric High-Pressure Borate Displaying Edge-Sharing BO4 Tetrahedra.

La3B6O13(OH) was obtained by a high‐pressure/high‐temperature experiment at 6 GPa and 1673 K. The compound crystallizes in the space group P21 (no. 4) with the lattice parameters a=4.785(2), b=12.880(4), c=7.433(3) Å, and β=90.36(10)°, and is built up of corner‐ as well as edge‐sharing BO4 tetrahedra. It represents the first acentric high‐pressure borate containing these B2O6 entities. The compound develops borate layers of „sechser“‐rings with the La3+ cations positioned between the layers. Single‐crystal and powder X‐ray diffraction, vibrational and MAS NMR spectroscopy, second‐harmonic generation (SHG) and thermoanalytical measurements, as well as computational methods were used to affirm the proposed structure and the B2O6 entities.

Two‐Dimensional Uranyl Borates: From Conventional to Extreme Synthetic Conditions

A systematic investigation of uranyl borates under different synthetic conditions resulted in five new 2D compounds, namely, (H3O)[(UO2)(BO3)], Li[(UO2)(BO3)]·(H2O), α‐K4[(UO2)5(BO3)2O4], β‐K4[(UO2)5(BO3)2O4] and K2.5[(UO2)5(BO3)2O2.5(OH)1.5]·(H2O)2.5. (H3O)[(UO2)(BO3)] and Li[(UO2)(BO3)]·(H2O) were obtained from hydrothermal reactions at 220 °C using the same mineralizer. Both materials possess the uranophane sheet topology with different symmetry of the unit cells. In the structure of (H3O)[(UO2)(BO3)] and Li[(UO2)(BO3)]·(H2O), UO7 pentagonal bipyramids share edges and vertexes with four BO3 planar triangles. α‐K4[(UO2)5(BO3)2O4] and β‐K4[(UO2)5(BO3)2O4] are polytypes. α‐K4[(UO2)5(BO3)2O4] was synthesized from a high‐temperature solid‐state reaction under ambient pressure; whereas β‐K4[(UO2)5(BO3)2O4] was obtained from a high‐temperature/high‐pressure (HT/HP) reaction. Both structures have an identical anion topology, but β‐K4[(UO2)5(BO3)2O4] crystallizes in space group with higher symmetry. In K2.5[(UO2)5(BO3)2O2.5(OH)1.5]·(H2O)2.5, which was obtained from a hydrothermal reaction, UO7 polyhedra share vertexes and edges with two independent BO3 triangles, forming the most complex uranyl borate layers among all five compounds. The different synthetic routes, novel topologies, thermal behavior and Raman spectra are discussed.

CHOICE OF TEMPERATURE AND TIME CONDITIONS OF HEATING FOR THE COMBINED PROCESS OF BORATING AND VOLUME TRAINING OF LARGE STAMPS OF 5KhNM STEEL

The stamps for hot deformation are widely adopted in industry. In use they are affected by high temperatures, tension (close to a fluidity limit) and variable thermal loadings. High-hardenability tool steels with high mechanical characteristics are used for stamps production. In this article, the possibility of use of 5KhNM steel for this goal is considered. One of technological operations at production of stamps is training in oil. It is rational to apply volume and superficial hardening, in particular chemical heat treatment, to improve operational characteristics of stamps, including wear resistance. The way of superficial hardening by the combined heating under chemical and thermal and heat treatment is presented. As a superficial way of hardening of largesize stamps of hot deformation, it is offered to use borating. Optimum temperature and time parameters of heating under the combined heat treatment are chosen and confirmed. The offered mode of chemical heat treatment allows receiving the necessary thickness of the borated layer providing high hardness and corrosion resistance in the working range of temperatures of a stamp. Also the influence of heat treatment on structure and grain size of the samples has been researched. It is shown that with increase in temperature and hold time, the size of grain increases. It leads to decrease in strength, fluidity, hardness and impact strength that can negatively influence operational properties of stamps. For definition of mechanical characteristics, the samples (in the studied range of temperatures and excerpts) have been tested for stretching and impact strength. All tests were carried out according to the existing state standard specifications. On the basis of these results, temperature and time of borating are chosen providing high mechanical properties and thickness of a borated layer. The offered approach has allowed reducing economic costs of stamps production from 5KhNM steel by exception from technological process of repeated heating for training with saving the required operational characteristics of largesize stamps.

Synthesis of the first nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6· (H3BO3)

Abstract The novel potassium nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) was obtained from a simple hydrothermal synthesis in a stainless-steel autoclave at T = 513 K starting with nickel dichloride hexahydrate, and boric and nitric acid with the pH adjusted to 8 by KOH. Single-crystal X-ray diffraction data provided the basis for the structure analysis and refinement. The compound crystallizes in the trigonal space group R3̅ (no. 148) with the lattice parameters a = 1222.29(8) and c = 5478.4(4) pm. Generally, K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) is comprised of nitrate layers and complex nickel borate layers surrounded by boric acid, nitrate anions, and potassium cations.