Papers by Keyword: Boron Oxide

Abstract: Boron Oxide (B₂O₃) was doped in fused silica using slip casting technique. Effects of addition of B₂O₃ on mechanical as well as dielectric properties along with microstructure were studied. It was observed that B₂O₃ acts as devitrification inhibitor by reducing the formation of cristobalite content during sintering of fused silica. Mechanical properties were improved by addition of B₂O₃. Density and flexural strength with (3% by weight) addition of B₂O₃ was 1.89 g/cc and 52MPa respectively.

Abstract: The use of fluorspar in modern metallurgical slags, incl. slags of the argon-oxygen decarburization (AOD) process, as a fluxing agent, is associated with many disadvantages. Those disadvantages can be solved by using boron oxide as an alternative, which also provides conditions for direct microalloying of steel with boron. The paper presents the results of thermodynamic modeling of the effect of basicity and boron oxide content in slags of the CaO–SiO₂–B₂O₃–Cr₂O₃–Al₂O₃–MgO system on the equilibrium interphase distribution of sulfur and boron, and their equilibrium content in the metal. Modeling was carried out using the HSC 8.03 Chemistry software package (Outokumpu). Slag from the desulfurization period of the AOD-process was used as the oxide phase. As a result, it was shown that, in the range of basicities 2.0-2.5 and a content of 2-4% B₂O₃, it is possible to carry out desulfurization of the metal, providing a sulfur content of 0.001-0.007%, and simultaneous microalloying of steel with boron in an amount of up to 0.0103%.

Abstract: The results of the development of the flux CaO-Li₂CO₃-B₂O₃, operating in the oxidizing environment of the furnace, are shown. Flux is used to protect the melt from oxidation and removal of oxides from the coated sample surface. The use of this flux in open furnaces made it possible to apply high-quality nickel coatings with a thickness of 18 μm, which is comparable to the thickness of coatings obtained in vacuum furnaces in argon atmosphere. The negative effect of flux components on the sample surface was noted during prolonged contact under the conditions of the oxidizing environment of the furnace. Practical application of the research results will provide high-quality diffusion coatings on metal products. In addition, economic efficiency is maintained through accessibility of the equipment and flux components.

Abstract: Magnesium diboride obtained from magnesium and boron oxide by magnesium-thermal reduction in SHS mode under the high-pressure inert gas (argon) was investigated. The effect of pressure of inert gas on the temperature of synthesis and the yield of final product (magnesium diboride) was determined. As energy additives were used powerful oxidizers - potassium chlorate salt (KClO₃) and ammonium nitrate (KNO₃) to increase the reactivity of the system Mg - B₂O₃. The composite material containing up to 20% of magnesium diboride phase was obtained. The acidic separation of final product from impurities was suggested. The microstructure and characteristic of particle size was defined. The products had a dense grain structure with a particle size 200-500 nm.

Abstract: The ZrB₂ powders with different morphology were prepared by pressureless reactions, using ZrO₂, B₂O₃, B₄C, and graphite as raw materials. Three kinds of chemical reaction system were employed. The ratio of raw materials and reaction temperature were adjusted to prepare ZrB₂ powders of different morphology and particle size. The phase composition and purity of the as-prepared powders were analyzed by XRD, while the morphology and particle size were analyzed by SEM. The ZrB₂ powders were purified by removing impurities at 600 °C in a muffle furnace in air atmosphere. The results showed that in the reaction systems of ZrO₂-B₂O₃-C and ZrO₂-B₄C-C, the ZrB₂ could be generated at 1500 °C. The morphology of the as-prepared ZrB₂ powders were particles, rod-like or near spherical for ZrO₂-B₂O₃-C system and particles for ZrO₂-B₄C-C system. In the reaction system of ZrO₂, B₂O₃, B₄C, and C with a mole ratio of 3:2:1:8, the ZrB₂ powders with high purity could be produced at 1700 °C. The ZrB₂ powder was near spherical. After heat treatment, the particle size and morphology changed to some extent.

Abstract: Glasses in the system [wt%: (55-x)% SiO₂-(15+x)% B₂O₃-15% P₂O₅-10% Na₂CO₃-5% Fe₂O₃] where 15 ≤ x ≤ 40 % have been prepared with the different amount (35-55 wt%) of boron oxide. The compositions were limited by fixing the P₂O₅ at 15 wt%, Na₂CO₃ at 10 wt% and fixing the Fe₂O₃ at 5 wt%. The objective of this study is to determine the effect of boron oxide on phosphate ion released from borosilicate glass in seawater. The glass has been prepared by melting in the alumina crucible within 2 hours of soaking time at 1300 °C in the furnace and cooled to room temperature. The obtained glass was crashed and sieved with yielding a mean size of 710 μm. The samples were immersed in seawater under dynamic condition by stirring at 310 rpm. The water sample was taken 6 times at every 15 minutes until 75 minutes and analyzed using Discrete Auto Analyzer. The functional group and morphological characterization on the glass surface have been investigated using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). Analysis of the data indicates that the amount of 50 wt% boron was the best and optimum for the phosphate ion release which is 126.53 ppm.

Abstract: A B₂O₃-modified ZrSiO₄ outer coating was prepared by Pulsed arc Discharge Deposition on the surface of SiC bonding layer coated carbon fiber reinforced carbon (C/C) composites. The phase compositions of the prepared coatings were analyzed by X-ray diffraction (XRD), the morphologies of the multi-layer coatings were observed by scanning electron microscopy (SEM). The influence of pulsed arc discharge deposition electric voltage and time on the phase composition, microstructure of the mixed coatings was particularly investigated. And the invalidation behavior of the as-prepared coating coated samples at 1273K was analyzed. XRD results show that the outer layer of the coating was mainly composed of B₂O₃ and ZrSiO₄ phase. When the deposition electric voltage was 400V, single deposition time was 8 min, total time was 32min, the structure and thickness of the outer layer was compact and uniform. The coating prepared at optimal technological conditions could effectively protect C/C composites from oxidation at 1273K in air for 600min with a weight loss of 4.063%. The failure of the coating at intermediate temperature is due to the generation of some cross-cracks in the coating and sectional volatilization of B₂O₃.

Abstract: In this study, pure boron-containing phenol-formaldehyde resin (BPFR) and boron oxide (B₂O₃) modified BPFR have been pyrolyzed at elevated temperatures in air and their thermal decomposition behavior is mainly explored. The structural evolution and chemical composition change during pyrolysis are characterized by thermal gravity (TG), Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). It is shown that the mass residues of pure BPFR are 27.1 and 8.7 wt.% after being pyrolyzed at 600 and 1000 °C for 2 h, respectively. In comparison with the pure BPFR, the mass residue of B₂O₃ modified BPFR is obviously higher, with the values of 72.9 and 39.7 wt.% at 600 °C and 1000 °C, respectively. The results of FT-IR prove the degradation and failure of the resin matrix are mainly resulted from the fracture of methylene and the release of small molecules. The XRD characterization shows the residues are amorphous carbon and B₂O₃. FE-SEM exhibits the melting B₂O₃ layer formed on the surface of the samples which could prevent oxygen from diffusing into composites during oxidation to some extent.

Abstract: The melting temperature of CaO-SiO₂-B₂O₃-(boron mud, CaF₂) slag system was investigated. The slag melting temperature was measured by using the hemisphere method. The results indicate that B₂O₃ has a significant fluxing effect on the slag system. When 1%-11% B₂O₃ was employed as fluxing agent, the melting temperature of the slag changed from 1525°C to 1200°C. When the content of B₂O₃ is 5% and the range of basicity is 1.5~3.5, the melting temperature of the slag increases with the increase of the basicity. However, when boron mud or CaF₂ was added to the slag, the melting temperature of the slags decreased with the increase of addition at a fixed B₂O₃ content (5%) and a fixed basicity (R=2.5). Furthermore, the melting temperature of the slag system which contains CaF₂ is lower than the slag system which contains boron mud.

Abstract: This paper presents a laboratory study on active belite cement clinker using boron oxide as dopant to stabilize high temperature phases of Dicalcium silicate (C₂S), and mineral waste as siliceous materials in complete replacement of clay. The clinker samples were soaked in Muffle Furnace at different burning temperatures and for various time durations, and then, cooled down to room temperature using air blower. Quantitative X-ray Diffraction analysis (QXRD) by Rietveld method indicates that major mineral components are Dicalcium Silicate (C₂S), Ferrite (C₂ (A_0.48F_1.52) O₅) and trace amount of Tricalcium Silicate (C₃S) in the cement clinkers. Among them, Dicalcium silicate is over 85 percent, Ferrite around 10 percent and Tricalcium silicate less than 10 percent. Thermogravimetric and Differential Scanning Calorimetric (TGA-DSC) spectrum shows that there is no significant phase change while cement clinker was cooling down, which means significant amount of high temperature polymorphic C₂S was stabilized during cooling process. It is agreeable with the results from QXRD analysis. Specifically, among polymorphic belite phases, α_H-C₂S accounts for around 66% of cement clinker, and α_L-C₂S for about 22% of cement clinker. In addition, massive belite phase was identified by Scanning Electronic Microscope (SEM) analysis and Light Microscopy analysis. At last, the mechanical tests on active belite cement show that active belite cement clinker has a slow strength development at early ages, but rapid strength gain at 28 days in comparison with belite clinker without adding boron oxide. Thus, this active belite cement clinker demonstrates very promising prospect in sustainable cement industry development. Keywords: Active Belite Cement Clinker; Doped; Boron Oxide; α_H-C₂S; α_L-C₂S; Strength Development