Presence Of B2O3 Research Articles

The effect of boron oxide on the microstructure and hydration of calcium sulfoaluminate phase

Boron-rich waste causes numerous environmental problems when discharged directly into the environment. Here, various quantities of boron oxide (B2O3) were added to calcium sulfoaluminate (C4A3$) during the sintering process to demonstrate a potential use of boron-rich waste. The microstructure and hydration performance of C4A3$ with various B2O3 contents were investigated with scanning electron microscopy, x-ray diffraction, isothermal conduction calorimetry, thermogravimetric studies and compressive strength tests. B2O3-doped C4A3$ had a larger grain size than the pure phase; and were surrounded by amorphous phases. The presence of B2O3 was shown to promote the phase transition process through which C4A3$ changes from the orthorhombic to the cubic structure; and the substitution of Al3+ for B3+ in AlO4 tetrahedra was surveyed by structural refinements. As the B2O3 content increased, the induction period of C4A3$ increased while the hydration rate decreased because of the amorphous phases around the C4A3$. However, the hydration degree of doped C4A3$ increased due to the slower reaction rate. Thus, when an appropriate amount of B2O3 was added to the C4A3$ during sintering, a significant improvement in the compressive strength of pastes was observed.

Crystallization behavior and structural evaluation of cordierite base glass-ceramic in the presence of CaO and B2O3 additives

The purpose of the present work is to highlight the role of CaO and B2O3 additives on the crystallization behavior and microstructural properties of stoichiometric cordierite glass-ceramics using differential thermal analysis (DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Vickers micro-hardness and scanning electron microscopy (SEM). The results show that the presence of B2O3 and CaO in the initial glass led to the precipitation of only one exothermic peak (α-cordierite: Mg2Al4Si5O18). During the heat treatment process, the presence of calcium oxide favors crystallization of anorthite (CaAl2Si2O8) besides α-cordierite phase. It is worth mentioning that, CaO and B2O3 additives strongly encourage the formation of α-cordierite and have the opposite effect on the crystallization of μ-cordierite. In order to determine the effect of crystallization and B2O3 and CaO additives on the hardness of specimens, the micro-hardness measurement of glasses and glass-ceramics shows that the glass-ceramic containing CaO (MAS5C) exhibits the highest micro-hardness value, which depends on the high crystallinity value in this specimen.

Valorization of chitin biomass into N-containing chemical 3-acetamido-5-acetylfuran catalyzed by simple Lewis acid

3-Acetamido-5-acetylfuran(3A5AF) is a nitrogen-containing fine chemical and has broad application prospects and high research value. Herein, we report a mild and efficient method for the synthesis of 3A5AF from N-acetyl-d-glucosamine (NAG). The influence of solvent, temperature and additive on the catalytic performance was also studied. The Lewis acids with high catalytic efficiency have been smoothly screened. The highest yield (41.57%) of 3A5AF was obtained in the presence of B2O3 and MgCl2·6H2O at 180 °C for 60 min under normal atmospheric conditions. The reaction pathway was explored by LC-MS, 1H NMR, 13C NMR and FT-IR spectra. Compared with the microwave method and hydrothermal method, the optimized reaction condition was relatively mild. Moreover, the catalyst MgCl2·6H2O is low-cost and environmentally friendly.

Integrated high strength and high toughness induced by elongated TiB2 grains in reactive sintered TiB2–TiC–SiC ceramics

AbstractAlthough the addition of other phases into TiB2 matrix to form ceramic composites has been widely used to improve the mechanical properties of monolithic TiB2 ceramics, it is still difficult to greatly enhance the flexural strength and fracture toughness simultaneously. In this work, TiB2–TiC–SiC composites were successfully prepared by reactive spark plasma sintering of Ti3SiC2–B4C–Ti powder mixtures. During the sintering process, TiB2 grains grew into an elongated morphology, endowing the composites with integrated high strength and high toughness. The growth mechanism of TiB2 grains was attributed to the evaporation–condensation kinetics induced by the presence of B2O3. These findings can accelerate the exploration of ceramic composites with excellent comprehensive properties.

Optical Analysis of Metal Oxide Borosilicate (xCaO(1-x-z) SiO2 zB2O3) glasses with varying concentrations of boric oxide (B2O3)

Glass sample compositions of xCaO(1-x-z)-SiO2 zB2O3 with constant nominal CaO of x=33.33 mol% and varying concentrations of B2O3 as z=50,60 and 66.67 mol% are prepared by conventional melt quench technique. Fourier transform infrared (FTIR) spectra of xCaO(1-x-z)-SiO2 zB2O3 glass system has been measured in the spectral range 400–4000 cm−1 low-frequency region 1700cm-1 to 400cm-1 and high-frequency region 4000cm-1 to 1700cm-1) at room temperature to understand the characteristic frequencies of the chemical bonds, bonding mechanisms and structure of electron shell of atoms, for the purpose to determine the molecular structure of the composition. It is found that the melting temperature of the glasses decreases with the increase of B2O3 concentration and the melting temperature in the range of 950oC-1100oC for the samples which consist of 50, 60, and 66.67 mol% of B2O3. In the low-frequency region (1700cm-1 to 400cm-1) the spectra of high B2O3 containing glass showed an increased number of distinct peaks and several broad Gaussian in the thigh-frequency region (1700cm-1 to 400cm-1). All the spectra are based on line corrected and deconvoluted to the appropriate number of Gaussians. Fourier transform infrared (FTIR) deconvoluted spectra were analyzed to determine the exact position and relative amounts of the IR bands responsible for the different silicate borates units. The distinct peaks and peak position of the deconvoluted Gaussians are assigned to Si-O-Si, B-O-B, Si-O-Ca, Si-O etc. bonds based on the previous scientific investigations. The presence of B2O3 in the materials suggests that B3+ occupies the network position and for the linkage Si-O-B in the glasses. The amorphous nature, the surface topography and composition of the prepared glasses was checked by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques respectively on optical inspection, did not show any evidence of phase separation, and all glasses are homogeneous.

Salt-melt synthesis of B2O3, P2O5 and V2O5 modified high-alumina mullite nanocomposites with promising photoluminescence properties

High-alumina mullite (Al4.8Si1.2O9.6) nanowhiskers have been prepared by mechano-chemical activation of Al2(SO4)3–Na2SO4 molten salt mixture in the presence of B2O3, P2O5 and V2O5 as additives. Thermal evolution of the precursors has been studied by differential thermal analyzer and thermogravimetric analyzer (DTA-TG). The effect of additives on the phase formation and morphology of mullite is investigated using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscope (FESEM). Mullite whiskers with submicron sized length and diameter in the nanoscale range were obtained after calcining at 1000 °C. These nanowhiskers decomposed when sintered at 1400 °C with consequent formation of dense alumina platelets. Owing to formation of defect related structures of mullite, UV photoluminescence peaks for mullite reflected at 285, 298, 310, 325, 347, 362 and 379 nm while visible photoluminescence peaks appeared at 407, 424, 436 and 460 nm.

Near white light emission of Ce3+‐, Ho3+‐, and Sm3+‐doped oxyfluoride silicate glasses

AbstractThe Ce3+‐, Ho3+‐, and Sm3+‐ single and co‐doped oxyfluoride silicate glasses for light emitting diodes are studied. These glasses were prepared by melt quenching method and their optical and structural properties were investigated by absorption spectra, photoluminescence spectra, Commission International de I'Eclairage chromaticity coordinates, X‐ray diffraction, and Fourier transform infrared spectra. It is found that the introduction of Al2O3 in glass composition can improve the emissions of Ho3+ and Sm3+. While the presence of B2O3 has the adverse effect and can suppress the emissions of Ho3+ and Sm3+. With substituting Na2O for CaO in the glass compositions, CaF2 crystals can be formed during the melt quenching process. We find the formation of CaF2 crystals can change the emission behavior of Ho3+ and Sm3+ ions. White light emissions can be achieved in the glasses and the luminescence colors can be tuned by varying the concentrations of the doped rare‐earth ions and the composition of glass matrix. The Ce3+‐, Ho3+‐, and Sm3+‐doped oxyfluoride silicate glasses presented here demonstrate promising applications in the fields of light emitting diodes.

Stability of Fluorine-Free CaO-SiO2-Al2O3-B2O3-Na2O Mold Fluxes

B2O3 and Na2O are key components of fluorine-free mold fluxes for continuous casting, but both are highly volatile, which affects the flux stability. This paper investigated the evaporation of the SiO2-CaO-Al2O3-B2O3-Na2O fluxes (Na2O: 6 to 10 wt pct, CaO/SiO2 ratio: 0.8 to 1.3) in the temperatures ranging from 1573 K to 1673 K (1300 °C to 1400 °C) using thermogravimetric analysis. The weight loss as a result of the flux evaporation increased with the increasing temperature for all fluxes. The rate of evaporation was found to be very small for the Na2O-free flux but significantly increased with the addition of Na2O. The high evaporation rate of fluxes in the presence of B2O3 and Na2O was attributed to the formation of highly volatile NaBO2. Changing the ratio of CaO/SiO2, however, did not affect the rate of evaporation. Kinetic analysis of the evaporation processes demonstrated that external mass transfer contributed to the rate of evaporation.

Effect of B2O3 on Volume Stability and Strength of Corundum-based Castables

AbstractCalcium aluminate cements (CAC) with 0.21 wt% B2O3 and without B2O3 were used as binders of corundum-based castables. The properties of the castables with and without B2O3 after heat treatment at 110 °C, 1,100 °C and 1,450 °C were investigated, with emphasis on studying the effect of B2O3 in CAC on the volume stability and high temperature strength of the castables. It is found that a very small amount (about 0.01 wt%) of B2O3 introduced by the cement alleviates the expansion of the castables after firing at 1,450 °C and decreases the high-temperature strength of castables as the presence of B2O3 should generate liquid phase.

Lead-GlazedRustiques Figulines(Rustic Ceramics) of Bernard Palissy (1510-90) and his Followers

The glaze chemistry of a group of rustiques figulines attributed to the renowned French potter Bernard Palissy (1510–90), or to his followers and imitators, has been determined non-destructively using PIXE and PIGE analyses. The glazes are all lead silicates, the colourants being transition metal oxides—CuO, CoO, MnO and Fe2O3—with a small addition of SnO2 to some of the glazes being common. Some distinction can be made between the various fabricated objects based on details of the overall composition and on the concentrations of the various colourants. The presence of B2O3 in any glaze, even in quantities as small as 0.1–0.3%, indicates a post-16th century production. Additionally, B2O3 in larger quantities, a few per cent or greater, very probably indicates an 18th–19th century production. However, at least one object known to be of 19th century production contains no B2O3.

Effects of the calcination temperature on the photoactivity of B- and F-doped or codoped TiO2 in formic acid degradation

In the framework of a large systematic investigation on the effects of doping TiO2 with first raw p-block elements of the Period Table, we discuss here the results obtained with a series of TiO2 photocatalysts doped or co-doped with boron and fluorine, prepared by sol–gel synthesis and calcined at 500°C or at 700°C. The photocatalytic activity of such materials in the oxidative decomposition of formic acid is related to their surface and structural properties, determined by BET, XRPD and Uv–vis absorption analyses. The photoactivity of singly doped or codoped TiO2 full anatase materials calcined at 500°C appears to increase with their specific surface area and to be not related to electronic structure modifications due to the presence of the dopants. The photoactivity increase observed upon B-doping TiO2, which leads to B2O3 surface segregation, may thus simply result from their increased surface area, the presence of B2O3 having negligible effects on photoactivity. Highly crystalline F-doped or BF-codoped TiO2 materials calcined at 700°C exhibit the highest photoactivity, essentially due to the retarded anatase into rutile transformation intrinsic of fluorine-doped materials.

TiB2 Powders Synthesis by Borothermal Reduction in TiO2 Under Vacuum

TiB2 powders were synthesized by borothermal reduction in nanoscale TiO2 with boron under vacuum. Reaction processes were investigated, and the effect of by‐product B2O3 was evaluated. Results showed that TiO2 was firstly reduced by boron to form TiBO3 and Ti2O3, and then to produce TiB2 and B2O3 with increasing temperature. The reaction processes of TiB2 powders synthesis included two‐step reduction in TiO2 by boron and the removal of B2O3. The presence of B2O3, which was previously reported as the most important factor in promoting the coarsening of ZrB2 and HfB2 powders by borothermal reduction, did not lead to significant coarsening of TiB2 powders. Due to the minor effect of B2O3, TiB2 powders with small particle size and low oxygen content could be prepared by direct heat treatment of TiO2 and boron at 1550°C under vacuum for 1 h. The particle size and oxygen content of synthesized TiB2 powders were ~0.9 μm and ~1.7 wt%, respectively.

The Production of NaBH4 from Its Elements by Mechano-chemical Reaction and Usage in Hydrogen Recycle

In this study, sodium borohydride (NaBH4) is synthesized from Na and MgH2 in the presence of B2O3 that behaves as a stickiness inhibitor and boron source. All experiments are performed under argon atmosphere via ball milling, without applying high temperature or pressure. An optimum synthesized parameter is searched with reaction time and stochiometric ratio. Mechano-chemical reactor working time is varied from 100 to 1,100 min, while stoichiometry of B2O3/Na ranges over 0.6–1.4, and MgH2 is used 30% in excess. FT-IR and XRD instruments are utilized to analyze the products. Additionally, hydrogen contents of the untreated products are measured with the inverse burette technique. Consequently, results show that long reaction times favor the yield. Moreover, equalizing the amounts of B2O3 and MgH2 can raise NaBH4 yield to 25% or more.

Photovoltaic devices based on high density boron-doped single-walled carbon nanotube/n-Si heterojunctions

A simple and easily processible photovoltaic device has been developed based on boron-doped single-walled carbon nanotubes (B-SWNTs) and n-type silicon (n-Si) heterojunctions. The SWNTs were substitutionally doped with boron atoms by thermal annealing, in the presence of B2O3. The samples used for these studies were characterized by Raman spectroscopy, thermal gravimetric analysis, transmission electron microscopy, and x-ray photoelectron spectroscopy. The fully functional solar cell devices were fabricated by airbrush deposition that generated uniform B-SWNT films on top of the n-Si substrates. The carbon nanotube films acted as exciton-generation sites, charge collection, and transportation while the heterojunctions formed between B-SWNTs and n-Si acted as charge dissociation centers. The current-voltage characteristics in the absence of light and under illumination, as well as optical transmittance spectrum are reported here. It should be noted that the device fabrication process can be made amenable to scalability by depositing direct and uniform films using airbrushing, inkjet printing, or spin-coating techniques.

ChemInform Abstract: Effect of B2O3 and hBN Crystallinity on cBN Synthesis.

Four kinds of BN powders—amorphous BN with B2O3, partially crystallized BN without B2O3, well-crystallized hBN with B2O3, and well-crystallized hBN without B2O3—were prepared to determine the effect of B2O3 on the crystallization of amorphous BN and the effect of BN crystallinity on the formation of cBN under high pressure (4–5 GPa) and at high temperature (1350–1450°C). The amorphous BN with B2O3 easily crystallized and transformed to cBN in the presence of A1N catalyst, while the partially crystallized BN without B2O3 did not. The well-crystallized hBN transformed very slowly to cBN without B2O3, in contrast to fast transformation with B2O3. It is thus found that the transformation from hBN to cBN in the presence of AIN catalyst is determined by the degree of BN crystallinity as well as the presence of B2O3. Cubic BN can be synthesized only from crystallized hBN under the experimental conditions used. The formation of cBN from amorphous BN is possible through its prior crystallization, which can occur in the presence of B2O3.

Microstructural evolution and magnetic properties of size-controlled nanocrystalline Ni in Ni(OH)2–ZrO2 composite

Size-controlled nanocrystallites of Ni varying in size from 2 to 26 nm distributed in a nonmagnetic matrix of Ni(OH)2–ZrO2have been prepared by changing the reduction reaction time and by adding different concentrations of ZrOCl2solution to the initial reaction mixture. X-ray photoelectron spectroscopy indicates the presence of B2O3, Ni(OH)2, and ZrO2with Ni nanocrystals in the as-prepared composites. The room-temperature saturation magnetization and coercivity of the composites increases from ∼1.5 to 10 emu g−1and 100 to 200 Oe, respectively, when the ZrOCl2concentration in the reaction mixture increases to 0.10 M. The nanocrystals prepared without the addition of ZrOCl2exhibit a typical ferromagnetic response at 300 K, while that prepared with the addition of 0.10 M ZrOCl2shows a ferromagnetic response up to 400 K with higher saturation magnetization and coercivity.

Synthesis and Characterization of B2O3-Doped Zinc Oxide Thin Films Prepared via RF-Magnetron Sputtering

The effects of B2O3 addition on the crystal structure and morphological features of ZnO thin films prepared via RF-magnetron sputtering have been studied. Doping B2O3 into ZnO films resulted in a c-axis preferred orientation and facilitated the deposition process. The microstructures of the prepared films markedly varied with the amount of B2O3 doping and oxygen content during sputtering. The presence of B2O3 in the ZnO films played an important role in the transmission of light and resulted in enhanced transmission in the visible range. The band-gap energies of the B2O3-doped ZnO films significantly decreased as the B2O3 amount increased and the oxygen content decreased during sputtering.

The effect of B2O3 on the crystallization of zirconium titanate

Crystallization of coprecipitated zirconium-titanium hydroxide in the presence of the B2O3 melt as far as its action on ZrTiO4 powder and ceramics was studied by XRD and SEM investigations. It was found that ZrTiO4 formation from the X-ray amorphous ZT precursor is inhibited by the presence of liquid B2O3 leading to ZT decomposition, yielding Zr(Ti)O2 and Ti(Zr)O2 substitutional solid solutions. The concentration of substituents continuously decreased up to 4 mol% with increasing temperature. The decomposition process was followed by the change of oxide particle morphology due to recrystallization via incongruent dissolution of oxide phases in the B2O3 melt. Crystalline ZrTiO4 (powders and ceramics) were also found to be decomposed by the B2O3 melt treatment.

Effect of B2O3 and hBN Crystallinity on cBN Synthesis

Four kinds of BN powders—amorphous BN with B2O3, partially crystallized BN without B2O3, well‐crystallized hBN with B2O3, and well‐crystallized hBN without B2O3—were prepared to determine the effect of B2O3 on the crystallization of amorphous BN and the effect of BN crystallinity on the formation of cBN under high pressure (4–5 GPa) and at high temperature (1350–1450°C). The amorphous BN with B2O3 easily crystallized and transformed to cBN in the presence of A1N catalyst, while the partially crystallized BN without B2O3 did not. The well‐crystallized hBN transformed very slowly to cBN without B2O3, in contrast to fast transformation with B2O3. It is thus found that the transformation from hBN to cBN in the presence of AIN catalyst is determined by the degree of BN crystallinity as well as the presence of B2O3. Cubic BN can be synthesized only from crystallized hBN under the experimental conditions used. The formation of cBN from amorphous BN is possible through its prior crystallization, which can occur in the presence of B2O3.

ChemInform Abstract: Oxometalates Containing Boron Islands, Ni5MB2O10.

AbstractSingle crystals of the hitherto unknown title compounds with M: Ge or Zr are obtained from melts of the components NiO:MO2 = 5:1 in the presence of B2O3 as a flux at 1300‐1400 °C. The isotypic compounds crystallize in the space group Pbam with Z=2.