Autoclave Synthesis Research Articles

High Yield Autoclave Synthesis of pure M2B12H12 (M = Na, K)

Metal dodecaborates (MxB12H12) are a versatile class of materials used in polymer chemistry and cancer treatment and are promising candidates as electrolytes for solid-state batteries. However, a general and scalable approach has not yet been developed for producing high-purity B12H122- derivatives. In this work, we report a simple, efficient, and environmentally benign solvothermal method to prepare diffraction and 11B NMR pure Na2B12H12 (85% yield) and K2B12H12 (84% yield). This new synthetic approach is based on the use of the borane dimethyl sulfide complex (DMS·BH3) and borohydrides (NaBH4, KBH4) heated at different temperatures in diglyme in an autoclave. It was found that high-purity Na2B12H12·diglyme solvate is obtained via an intermediate formation of B3H8-, B9H14-, and B11H14-, which are all soluble in diglyme. Heating under vacuum is shown to be efficient for removing the coordinated diglyme, allowing the formation of unsolvated Na2B12H12. Autoclave synthesis starting from KBH4 directly yields solvent-free K2B12H12, and ball-milling KBH4 prior to the synthesis enabling us to significantly improve the final yield. The new synthetic method paves the way for large-scale synthesis of MxB12H12 derivatives, enabling to envisage a wider scope of practical applications.

Investigation of the morphological, optical and electrochemical capabilities of V2O5/MWCNT nanoparticles synthesized using a microwave autoclave technique

Metal oxide composites containing nanostructured carbons have been extensively researched to overcome difficulties such as low intrinsic electronic conductivity, significant irreversible capacity loss, and poor coulombic efficiency in lithium-ion batteries (LIBs). A time-efficient microwave autoclave synthesis technique was approached to fuse V2O5 to MWCNT strands. V2O5/MWCNT is a hybrid nanoparticle with crucial features for the electrode needed for a supercapacitor that has been investigated and reported. Due to X-ray diffraction (XRD) peak investigation, the nanoparticles' phase structure, space group, and strain(ε) have been determined. The particle size was calculated in Debye-Scherrer, modified Scherrer, and uniform deformation modeling (UDM) modes. The interaction between light photons and electrons is thoroughly addressed using UV–Vis technology. Optical constants like refractive index (n), absorption coefficient (α), and destructive coefficient (k) is addressed as a result of this. Nanoparticles' dielectric function (εrand εi), and direct bandgap have also been reported. Along with V2O5/MWCNT's strong Photoluminescence (PL) emission, interpretation of unique optical properties and considerable potential for practical applications have been intensively studied. V2O5/MWCNT is confirmed by data acquired by Fourier Transform Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) for vanadium, oxygen, and carbon. The formation of nanoparticles with the dimensions of V2O5/MWCNT is proven by Scanning Electron Microscopic (SEM) micrographic imagery. A Cyclic Voltammetry (CV) analyzer measures the material's highest specific capacity when exposed to electrochemical action, 632 Fg-1. The median power density (E) is predicted to be 146 Whkg-1, and the power density (P) is 1.52 ​kW kg-1 in the Galvanostatic Charge/Discharging (GCD) rating. These values are beneficial for describing the capabilities of supercapacitors.

Autoclave Synthesis of Finely Divided Nickel Powders

Autoclave Synthesis of Finely Divided Nickel Powders

UHMWPE/CaSiO3 Nanocomposite: Mechanical and Tribological Properties.

This paper studied the effect of additives of 0.5–20 wt.% synthetic CaSiO3 wollastonite on the thermodynamic, mechanical, and tribological characteristics and structure of polymer composite materials (PCM) based on ultra-high-molecular weight polyethylene (UHMWPE). Using thermogravimetric analysis, X-ray fluorescence, scanning electron microscope, and laser light diffraction methods, it was shown that autoclave synthesis in the multicomponent system CaSO4·2H2O–SiO2·nH2O–KOH–H2O allows one to obtain neeindle-shaped nanosized CaSiO3 particles. It was shown that synthetic wollastonite is an effective filler of UHMWPE, which can significantly increase the deformation-strength and tribological characteristics of PCM. The active participation of wollastonite in tribochemical reactions occurring during friction of PCM by infrared spectroscopy was detected: new peaks related to oxygen-containing functional groups (hydroxyl and carbonyl) appeared. The developed UHMWPE/CaSiO3 materials have high wear resistance and can be used as triboengineering materials.

Electrochemical Growth and OER Catalytic Activityof Ultrathin Epitaxial Cobalt Oxide Films

Iron-group oxides are among the best earth abundant catalysts for the oxygen evolution reaction (OER) in alkaline and neutral electrolytes [1],[2]. Such oxides have been prepared with an amorphous or a crystalline structure, using thermal salt decomposition [3], autoclave synthesis [4], photochemical reactions [5], sol-gel synthesis [6], metal electrodeposition and subsequent oxidation, [7] and direct oxide electrodeposition [1], [8].This work focuses on well-defined epitaxial CoOx [9] electrocatalysts grown by direct electrodeposition on Au(111) according to an approach similar to that introduced by Switzer [8]. The growth modes of catalysts and the mechanisms of deposition will be discussed based on electrochemical characterizations, XRD characterizations and microscopic observations. In particular to explain that CoOOH may be obtained at a potential of +1V/RHE by oxidation of a Co(II) complex diluted in an alkaline solution while thermodynamics predicts that Co3O4 should be formed. The electrochemical properties in pre-OER and within OER will be discussed as a function of the surface structure and morphology of layers. In particular to show that the large pseudocapacitance measured at the electrode is not related to its ECSA but to electrical charging within the bulk of the electrode.[1] M. W. Kanan and D. G. Nocera, Science 321, 1072 (2008).[2] C. C. L. McCrory, S. Jung, I. M. Ferrer et al., Journal of the American Chemical Society 137, 4347 (2015).[3] C. Pirovano and S. Trasatti, Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 180, 171 (1984).[4] D. Yuming, H. Kun, Y. Lin et al., Nanotechnology 18, 435602 (2007).[5] S. R. Alvarado, Y. Guo, T. P. A. Ruberu et al., The Journal of Physical Chemistry C 116, 10382 (2012).[6] A. Bergmann, E. Martinez-Moreno, D. Teschner et al., Nature Communications 6, 8625 (2015).[7] M. W. Louie and A. T. Bell, Journal of the American Chemical Society 135, 12329 (2013).[8] J. A. Koza, Z. He, A. S. Miller et al., Chem. Mat. 24, 3567 (2012).[9] F. Reikowski, F. Maroun, I. Pacheco et al., ACS Catalysis 9, 3811 (2019).

Composite Cements with Mineral Additives of Intrusive and Metamorphic Rocks of Central Aldan (Yakutia)

The creation of new compositions with mineral additives requires fundamental research of the chemical activity of mineral additives. As an active mineral additive used waste production of chromdiopside and phlogopite –dunite and diopside Aldan region (Yakutia). The use of overburden reduces the cost of production of building materials and improves the environmental situation in the region. The obtained dependence of the strength developed in cements, their composition, preparation of the raw mix, modes of curing and keeping maturing. For the first time, using a set of technological approaches including pre-annealing, mechanical activation and autoclave synthesis, a high-strength composite cement with additives of magnesium silicates exceeding the strength of Portland cement by 56.8% was obtained. In our previous experiments, the introduction of up to 40% diopside in Portland cement did not increase the strength of the cement stone due to the chemical inertness of the additive. Magnesium chloride - MgCl2 was used for mixing in order to activate hydration. It is shown that the high rate of formation of the solid phase during the closure with magnesium chloride leads to the development of stresses and strains leading to a decrease in strength in the later stages of hardening. The optimal technological approach is water mixing and autoclave synthesis. Possible consumers can be cement plants, enterprises for the production of building materials, representatives of medium and small businesses, as well as enterprises of the mining industry interested in the disposal of waste production.

Autoclave Synthesis of Composite Cements on Magnesium Silicates

The use of various mineral additives in the production of cements and concretes is one of the urgent tasks of building materials science, as it reduces the consumption of Portland cement clinker, the production of which is accompanied by a large consumption of electricity and the release of CO2 during its production. The use of mixed cements reduces not only the cost of building materials, but also solves the environmental safety of the environment. The work is devoted to the development of composite cements using mineral additives - dunite of one of the widespread magnesia rocks in Central Aldan (Yakutia). Dunit composes inagli Massif and is located in the industrially developed area of Central Aldan. Petrographic and thermographic studies became the basis for the preliminary preparation of the charge. Pre-annealing, fine joint grinding and additional mechanical activation of the charge are applied. Selected resource-saving, optimal mode of autoclave synthesis of composite binder. It is shown that the autoclave synthesis was able to obtain a high-strength cement stone twice the strength of the cement stone from Portland cement PC 500. It is found that increasing the mechanical strength of the products curing at autoclave composite binders the synthesis achieved by the introduction of a system of micro - silicates of magnesium (serpentinization of dunite). At the same time, finely ground and pre-annealed magnesium silicates perform the role of a micro-filler in the system, contributing to an increase in the density of the formed stone, and the active component involved in the formation of a strong crystallization structure.

Green syntheses of silver nanoparticles using babassu mesocarp starch (Attalea speciosa Mart. ex Spreng.) and their antimicrobial applications

Starches have mainly been used in nanobiotechnology in the development of metallic nanoparticles, due to their reduction and stabilization capacities. Babassu (Attalea speciosa Mart. ex Spreng.) mesocarp is a source of starch (BMS) which can be used to reduce and stabilize metallic nanoparticles. The present study aims to evaluate whether BMS has the required properties for use in the preparation of silver nanoparticles, and also verify its antibacterial effect. The syntheses were performed by mixing 1·10−3 mol·L-1 AgNO3 and 0.1 g·L-1 of BMS exposed to three different catalysts. The times of exposure to microwaves, autoclaves and water baths were 180, 900 and 3600 s, respectively. The samples were characterized by optical microscopy, FT-IR, UV–vis spectroscopy, DLS, Zeta Potential, PdI and AFM. Antibacterial activity was assessed by determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Staphylococcus aureus and Escherichia coli. The autoclave synthesis route offered a more efficient conversion of silver nitrate in AgNPs, followed by the microwave route. Chemical characterization indicated the formation of spherically shaped nanoparticles, which were well dispersed and stable during storage. An antimicrobial effect against S. aureus and E.coli, especially Gram-negative bacteria, was observed, resulting in notable membrane damage. The present study paves the way for the development of a promising product for treatment against Staphylococcus aureus and Escherichia coli.

Influence of synthetic calcium silicates on the strength properties of fine-grained concrete

The effect of additives based on acicular calcium hydrosilicates (xonotlite and tobermorite) and wollastonite, obtained from boric acid production waste in autoclave synthesis at a temperature of 220 °C, on the strength of fine-grained concrete, has been studied in this paper. It was shown that when the calcium hydrosilicates and wollastonite are introduced, an increase in the strength characteristics of concrete is observed. After heat and moisture treatment, the maximum increase in strength is observed with the addition of 4% of mass content of calcium hydrosilicates and 6% of mass content of wollastonite. After 28 days of hardening under normal conditions, the maximum increase in strength of concrete is observed with the addition of 4% of mass content of both types of additives. It was shown that the water absorption of concrete decreases with a maximum when 4% of mass content is added, as in the case of the introduction of calcium hydrosilicates, and wollastonite. With a further increase in the number of additives, the amount of water absorption increases, but these values remain below the values for the control sample without additives.

REMOVAL OF DIQUATERNARY AMMONIUM CATIONS FROM AS-SYNTHESIZED SSZ-16 ZEOLITE

Zeolites are stable microporous aluminosilicates with numerous applications in chemical technology such as separation of species and catalytic transformations. Our study is focused on a weakly explored zeolite SSZ-16 with pore constrictions defined by 8-membered oxygen rings. Key results are the preparation of Et6-diquat-5 dication used as a structure directing agent (SDA) and finding the optimum synthesis conditions with respect to zeolite phase purity. Stability of SDA was examined in conditions similar to those of autoclave synthesis (concentration, pH, temperature). Moreover, the content and location of SDA species in zeolite phase and conditions of SDA decomposition were investigated.

Synthesis of bulk nanocrystalline HfB2 from HfCl4–NaBH4–Mg ternary system

This study reports on the synthesis and consolidation of pure HfB2 powders starting from HfCl4–NaBH4–Mg blends via autoclave processing, annealing and purification followed by pressureless sintering (PS, with 2 wt% Co aid) or spark plasma sintering (SPS). During autoclave reactions conducted at 500 °C for 12 h under autogenic pressure, excess amounts of NaBH4 were utilized to investigate its effects on the reaction products and mechanism. A subsequent washing (with distilled water), annealing (at 750, 1000 and 1700 °C) and acid leaching (HCl) were applied on the as-synthesized products. Pure HfB2 powders with an average particle size of 145 nm were obtained after autoclave synthesis in the presence of 200 wt% excess NaBH4, washing, annealing at 1000 °C for 3 h and 6 M HCl leaching. SPS sample has higher relative density and microhardness values (94.18% and 20.99 GPa, respectively) than those of PS sample (90.14% and 14.85 GPa). Relative wear resistance was improved considerably (8.2 times) by employing SPS technique.

Microwave vs Autoclave Synthesis of Nanodisperse ZrN Powder

The synthesis of nanodisperse powers of zirconium nitride ZrN was studied using exothermal reactions initiated by microwave radiation. The obtained ZrN powders were investigated by x-ray phase analysis and scanning electron microscopy. The results showed that nanodisperse materials can be synthesized by means of exothermal reactions upon heating by microwave radiation.

Mechanical activation-assisted autoclave processing and sintering of HfB2-HfO2 ceramic powders

This study reports on the synthesis and consolidation of HfB2-HfO2 ceramic powders via mechanical activation-assisted autoclave processing followed by pressureless sintering (PS) or spark plasma sintering (SPS). HfCl4, B2O3 and Mg starting powders were mechanically activated for 5min to obtain homogeneously blended precursors with active particle surfaces. Autoclave synthesis was carried out at a relatively low temperature at 500°C for 6 or 12h. As-synthesized powders were purified from reaction by-products such as MgO and MgCl2 by washing and acid leaching treatments. The characterization investigations of the as-synthesized and purified powders were performed by using an X-ray diffractometer (XRD), stereomicroscope (SM), scanning electron microscope (SEM) and particle size analyzer (PSA). The purified powders with an average particle size of about 190nm comprised the HfB2 phase with an amount of 79.6wt% in addition to the HfO2 phase and a very small amount of Mg2Hf5O12 phase after mechanical activation for 5min and autoclave processing for 12h. They were consolidated at 1700°C both by PS for 6h and SPS for 15min. The Mg2Hf5O12 phase decomposed during sintering and bulk samples only had the HfB2 and HfO2 phases. The bulk properties of the sintered samples were characterized in terms of microstructure, density, microhardness and wear characteristics. The HfB2-HfO2 ceramics consolidated by PS exhibited poor densification rates. A considerable improvement was obtained in the relative density (~91%), microhardness (~16GPa) and relative wear resistance (2.5) values of the HfB2-HfO2 ceramics consolidated by SPS.

Formation of tavorite-type LiFeSO4F followed by in situ X-ray diffraction

The tavorite-type polymorph of LiFeSO4F has recently attracted substantial attention as a positive electrode material for lithium ion batteries. The synthesis of this material is generally considered to rely on a topotactic exchange of water (H2O) for lithium (Li) and fluorine (F) within the structurally similar hydrated iron sulfate precursor (FeSO4·H2O) when reacted with lithium fluoride (LiF). However, there have also been discussions in the literature regarding the possibility of a non-topotactic reaction mechanism between lithium sulfate (Li2SO4) and iron fluoride (FeF2) in tetraethylene glycol (TEG) as reaction medium. In this work, we use in situ X-ray diffraction to continuously follow the formation of LiFeSO4F from the two suggested precursor mixtures in a setup aimed to mimic the conditions of a solvothermal autoclave synthesis. It is demonstrated that LiFeSO4F is formed directly from FeSO4·H2O and LiF, in agreement with the proposed topotactic mechanism. The Li2SO4 and FeF2 precursors, on the other hand, are shown to rapidly transform into FeSO4·H2O and LiF with the water originating from the highly hygroscopic TEG before a subsequent formation of LiFeSO4F is initiated. The results highlight the importance of the FeSO4·H2O precursor in obtaining the tavorite-type LiFeSO4F, as it is observed in both reaction routes.

SYNTHESIS OF ULTRA-SMALL CdSe QUANTUM DOTS

Monodisperse CdSe quantum dots (QDs) of low dimensions are of great interest due to their high performance being propel by nearly continuous electronic energy levels of highly energetic sizespecific QDs. Ultra-small synthesis of CdSe QDs reported in this paper provides a new pathway that supports their fundamental scientific interest and easier processing for a variety of technological applications. Three methods for preparing ultra-small CdSe QDs comprising organometallic injection method, low temperature method and hydrothermal autoclave synthesis produce QDs of different particle sizes. Broad optical absorption and sharp emission peaks propelled by their strong oscillating strength near the band edge and their customizable bandgaps energies indicated the optoelectrical properties of the QDs are in hold of desirable light absorber properties. Elemental analysis of XPS survey spectral quantification and XRD pattern of the crystal phases at diffraction angle 2-Theta from 10 o to 80 o depicted the absence of impurity in the s ynthesized CdSe QDs. The XRD pattern of the QDs obtained at 2θ angle showed that CdSe the Br agg’s reflection slightly broadened due to narrow particle size distribution at different lattice spacing d (A). The hkl plane of CdSe QDs were 1 1 1, 2 2 0 and 3 1 1. The synthesis methods are reproducible and represents alternative pathway to decompose pyrophoric organometallic complexes at lower temperatures for a more competitive technological innovations.

The Influence of the Solvent on the Shape of the Titanium Dioxide Crystals during the Solvothermal Autoclave Synthesis

By the solvothermal synthesis the TiO2nanocrystals with different shapes were obtained. It was found that the morphology of TiO2nanoparticles determines the type of solvent and their crystallinity, and the size depends on the temperature and time of synthesis. The conditions are defined, under which the anatase nanocrystals are formed in the form of spherical particles with a diameter of 10-15 nm, cubic particles with a size of 50-70 nm and edges of nanowires with a diameter of 50-100 nm and a length of more than 100 microns.

A Novel Method for Preparation of Zn-Doped CuInS2Solar Cells and Their Photovoltaic Performance

In this study, a novel method was proposed to synthesize high quality Zn-doped CuInS2 nanocrystals under high frequency magnetic field at ambient conditions. The magnetic Zn-doping gave superparamagnetic heating of the resulting nanocrystals via magnetic induction, causing an accelerating growth rate of the doped CuInS2 under ambient conditions faster than conventional autoclave synthesis. Shape evolution of the Zn-doped CuInS2 nanocrystals from initially spherical to pyramidal, to cubic, and finally to a bar geometry was detected as a function of time of exposure to magnetic induction. These colloidal solvents with different shaped nanocrystals were further used as “nanoink” to fabricate a simple thin film solar device; the best efficiency we obtained of these crystals was 1.01% with a 1.012 μm thickness absorber layer (bar geometry). The efficiency could be promoted to 1.44% after the absorber was thickened to 2.132 μm.

Magnetically-induced synthesis of highly-crystalline ternary chalcopyrite nanocrystals under ambient conditions

We report a novel and facile method to synthesize phase pure, chemically homogeneous, and highly crystalline CuInS2, an important element for optoelectronics, optics, and solar energy applications. This ternary semiconductor compound is grown by magnetic Zn doping under high-frequency magnetic induction at ambient conditions. The magnetic doping gives superparamagnetic heating of the resulting nanocrystals via magnetic induction, causing an accelerating growth rate of the doped CuInS2 under ambient conditions of 2–3 orders of magnitude faster than conventional autoclave synthesis. Shape evolution of the Zn doped CuInS2 nanocrystals from initially spherical, to pyramidal, cubic, and finally to a bar geometry, was detected as a function of time of exposure to magnetic induction. These newly-synthesized nanocrystals demonstrated considerably improved optical emission properties compared to those prepared via conventional autoclave methods. Nanostructural development of the nanocrystals was well characterized and a mechanism of crystal growth was proposed.

2,5,8‐Trihydrazino‐s‐heptazine: A Precursor for Heptazine‐based Iminophosphoranes

AbstractThe title compound C6N7(NHNH2)3 (1) was obtained from melem C6N7(NH2)3 or melon [C6N7(NH2)NH]n and hydrazine by an autoclave synthesis. Upon treatment with a 10 % HCl solution it is transformed into the trihydrochloride [C6N7(NHNH3)3]Cl3 (2). Compounds 1 and 2 were analysed with 13C NMR, 15N NMR, FTIR and Raman spectroscopy. Furthermore, the single‐crystal X‐ray structure of the pentahydrate of 2 is reported (P\bar{1}, a = 674.96(3), b = 1214.17(6), c = 1272.15(6) pm, α = 66.288(2)°, β = 75.153(2)°, γ = 80.420(2)°, V = 920.30(8)·106 pm3, Z = 2, T = 90(2) K). The thermal decomposition of 1 and 2 was investigated with TG/DTA. Reaction of 1 with NaNO2/HCl yields triazido‐s‐heptazine, C6N7(N3)3 (3). Tris(tri‐n‐butylphosphinimino)‐s‐heptazine (4) was synthesised from 3 and characterised by means of 13C, 31P, 1H NMR, FTIR and MALDI‐TOF spectroscopy. Similar to s‐heptazine derivative 3, compounds 1 and 4 are precursors for graphitic carbon nitrides, which have attracted considerable attention recently, and to various potential applications, such as flame retardants and (photo) catalysis.

水素貯蔵技術と高圧科学 ―水素貯蔵タンクと貯蔵材料―

First of all, hydrogen energy related government budgets in Japan, USA and EU were summarized. Among a number of required technology to introduce hydrogen society, the hydrogen storage technique was focused in this article. The technique is classified in three ways, such as pressurized hydrogen, liquid hydrogen and hydrogen storage medium tank. In each technique, the high pressure science and technology is important to materialize applications of hydrogen storage systems. In addition, the recent research of new hydrides prepared by autoclave synthesis and high-pressure work in solid-state was also mentioned.