Search Results (26)

Modification of the composition by doping is an effective way to develop new substrate materials for 5G/6G communication systems. This paper aims to study the impact of AlF₃-CaB₄O₇ doping on dielectric properties at very high frequencies, sintering temperature, microstructure, and feasibility in LTCC/ULTCC (low/ultra-low temperature cofired ceramics) technology of four low dielectric permittivity materials based on CuB₂O₄, Zn₂SiO₄, LiBO₂, and Li₂WO₄. Sintering behavior, microstructure, elemental and phase composition, and dielectric properties in the terahertz range were characterized using a heating microscope, SEM, EDS, XRD methods, and time domain spectroscopy. The developed ceramics exhibit excellent dielectric behavior at terahertz frequencies and are feasible in ULTCC or LTCC technology. These properties make them good candidates for substrates in 5G/6G communication systems. Full article

The aim of this study was to investigate the possibility of Ag nanoparticle crystallization in B₂O₃–Bi₂O₃ glass using a heat treatment method and to investigate the possible influence of the obtained nanoparticles on the emission intensity of Eu³⁺ ions. Borate–bismuth glasses with different B₂O₃:Bi₂O₃ molar ratios of 50:50, 60:40 and 70:50 with Ag and Eu³⁺ ions were successfully synthesized. The structure of the glasses was studied using XRD and FTIR methods. The XRD results exhibited a characteristic amorphous halo, confirming the absence of long-range order in the samples. The glass transition temperatures of various compositions, required to select the annealing temperature, were measured using DTA analysis. The strong maximum in the UV–Vis spectrum of the sample with the highest Bi₂O₃ content clearly indicated the presence of Ag nanoparticles in the glass. Moreover, a color change was observed for this sample, from slightly yellow to red. The presence of Ag nanoparticles was further confirmed via TEM and XPS studies. However, with a high content of Ag nanoparticles in the matrix, their positive effect on luminescence intensity was not observed. The obtained results show that B₂O₃–Bi₂O₃ glass and glass ceramics, with Ag nanoparticles and rare-earth (Re) ions, could be considered as a new phosphor for light-emitting diodes (LEDs). Full article

Current research in bone tissue engineering is focused not only on basic parameters of the materials, such as biocompatibility and degradation rate but also on intrinsic osteogenic and antimicrobial properties, essential to provide a rapid tissue regeneration without negative effects due to periprosthetic infections, that may result in revision surgeries. One of the major strategies to enhance the osteogenic and antimicrobial performance of calcium phosphates is the ionic substitution, in particular, with magnesium and borates. In this study, we focused on the synthesis of boron-substituted tricalcium phosphate (B-TCP) with a target of 5 mol.% substitution via the solid-state synthesis with mechano-activation. Synthesis from raw precursors, without the preliminary brushite wet precipitation, led to the primary phase of β-TCP, which was proved by the XRD analysis. According to the IR-spectroscopy and ³¹P NMR analysis, boron substitution occurred in the synthesized sample. The developed material showed a modest antibacterial performance against E. coli, with 13.5 ± 5.0% growth inhibition, and E. faecalis, with 16.7 ± 5.5% inhibition. The biocompatibility of β-TCP and B-TCP was tested through the MTT assay and osteogenic differentiation of the mesenchymal stromal cells. The proposed synthesis approach can be useful for the fabrication of B-TCP ceramics for bone tissue engineering. Full article

The glass-ceramic materials studied in this work are designed using combinations of lithium vanadate borate glass matrices and lanthanum/rare earth (RE) vanadate nanoparticles. Three different techniques of sintering of the glass matrix and vanadate nanoparticles are investigated. The morphological characteristics and spectral properties of the glass-ceramic samples obtained by different techniques are investigated and analyzed in comparison with the properties of the original glass matrices and nanoparticles. The luminescence spectra of all glass-ceramic samples consist of a wideband glass matrix emission and the characteristic line emission of the RE ions that are incorporated into the glass matrices as nanoparticles. The RE luminescence of these glass-ceramics is promising for various optoelectronic applications. Full article

Addressing periprosthetic infections, which present significant healing challenges that often require revision surgeries, necessitates the development of novel antibacterial materials and implants. Current research focuses on creating materials that hinder bacterial adhesion, colonization, and proliferation in surrounding tissues. Boron (B)-containing compounds are known for their antibacterial properties and potential in bone metabolism for regenerative medicine. In this study, we synthesized B-containing tricalcium phosphate (0.3B-TCP) with 1.1 wt.% B content via precipitation from aqueous solutions and sintering at 1100 °C. X-ray diffraction confirmed the ceramic’s primary crystalline phase as β-TCP, with B evenly distributed according to energy-dispersive spectroscopy data. Electron paramagnetic resonance (EPR) data verified stable paramagnetic borate anions, indicating successful BO₃³⁻ substitution for phosphate groups. The microstructural properties of 0.3B-TCP ceramic were assessed before and after soaking in a saline solution. Its bending strength was approximately 30 MPa, and its porosity was about 33%. 0.3B-TCP ceramic demonstrated significant antimicrobial efficacy against various bacterial strains and a fungus. Cytotoxicity evaluation using equine adipose tissue-derived mesenchymal stem cells and osteogenic differentiation assessment were conducted. The combination of antibacterial efficacy and good cytocompatibility suggests 0.3B-TCP ceramic as a promising bone substitute material. Full article

Microwave dielectric ceramics composed of Na_1+xSrB₅O_9+0.5x (0 ≤ x ≤ 0.125) were synthesized via a traditional solid-state reaction approach. The effects of non-stoichiometric Na on the crystal structures, phase compositions, chemical bond characteristics, and microwave dielectric properties of the Na_1+xSrB₅O_9+0.5x ceramics were systematically studied. All Na_1+xSrB₅O_9+0.5x ceramics sintered at optimum temperatures consisted of a NaSrB₅O₉ solid-solution phase and a SrB₂O₄ phase. Appropriate excess Na could suppress the generation of the SrB₂O₄ phase, and the lowest content of the SrB₂O₄ phase was achieved at x = 0.075. The ε_r values of the Na_1+xSrB₅O_9+0.5x ceramics were primarily affected by the relative density and molecular polarization. The Q × f values showed a positive correlation with the lattice energy. The τ_f value was correlated to the SrB₂O₄ phase content, bond valence, and bond energy. Typically, the Na_1.075SrB₅O_9.0375 ceramic sintered at 825 °C possessed good microwave dielectric properties of ε_r = 5.61, Q × f = 31, 937 GHz, and τ_f = −3.09 ppm/°C, which are suitable for high-frequency, low-temperature co-fired ceramics (LTCCs) substrate applications. Full article

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. Full article

Fibers represent a type of structure of great interest in catalysis since they combine high area to volume ratio and can be fabricated from many types of materials, such as ceramic oxides, polymers, and alloys. They can be used in isolated form or structured, as in the case of the ceramic papers synthesized in this work, following a modified papermaking technique. The addition of cationic and anionic polyelectrolytes improved the retention of ceramic fibers during the ceramic paper formation stage by adsorption processes, through the formation of floccules. In the complex aqueous system containing charged macromolecules, the amounts of polyelectrolytes to be added were determined by titrations. To enhance mechanical properties of ceramic papers, different classes of nanoparticle suspensions can be used as binders. As a novel alternative, we have used different borate-type compounds. Among them, we selected natural ulexite, which was purified and used as a binder of ceramic fibers. In order to improve mechanical resistance and flexibility, measured from tensile indexes and elastic module, the amounts of NaCaB₅O₆(OH)₆.5H₂O and the calcination temperature were varied. In this contribution, to take advantage of the unique characteristics of the ulexite-containing ceramic papers, they were impregnated with Co,Ce and Co,Ba,K and tested for diesel soot combustion. Full article

Different types of ceramics and glass have been extensively investigated due to their application in brachytherapy, radiotherapy, nuclear medicine diagnosis, radioisotope power systems, radiation processing of food, geological and archaeological dating methods. This review collects the newest experimental results on the thermoluminescent (TL) properties of crystalline and glassy materials. The comparison of the physico-chemical properties shows that glassy materials could be a promising alternative for dosimetry purposes. Furthermore, the controlled process of crystallization can enhance the thermoluminescent properties of glasses. On the other hand, the article presents information on the ranges of the linear response to the dose of ionizing radiation and on the temperature positions of the thermoluminescent peaks depending on the doping concentration with rare-earth elements for crystalline and glassy materials. Additionally, the stability of dosimetric information storage (fading) and the optimal concentration of admixtures that cause the highest thermoluminescent response for a given type of the material are characterized. The influence of modifiers addition, i.e., rare-earth elements on the spectral properties of borate and phosphate glasses is described. Full article

Glass-ceramics with the composition B₂O₃-Bi₂O₃-SrF₂ were synthesized by the conventional melt-quenching technique and subsequent crystallization of the parental glasses. The temperature at which the ceramization was carried out was selected based on differential scanning calorimetry (DSC) analysis. The structure of the studied materials and the formation of SrF₂ nanocrystals were confirmed by the Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. It was found that the amount of strontium fluoride introduced into the parental borate-bismuth glass has a significant impact on the growth of SrF₂ nanocrystals. In particular, the influence of the crystalline SrF₂ phase on luminescence intensity and kinetics was studied using Eu₂O₃-doped samples. An increase in luminescence intensity was observed in the samples in which SrF₂ nanocrystals were formed. This is most likely related to the fact that some of the Eu³⁺ ions were (after annealing of the glass) located in the crystalline structure of strontium fluoride. This was confirmed both by the luminescence lifetime obtained based on the luminescence decay curves and the calculated Judd–Ofelt parameters, Ω₂ and Ω₄. The results achieved confirm that the glasses and glass-ceramics described in this work could be considered as a new phosphor for light-emitting diodes (LEDs). Full article

New ceramic materials based on two copper borates, CuB₂O₄ and Cu₃B₂O₆, were prepared via solid state synthesis and sintering, and characterized as promising candidates for low dielectric permittivity substrates for very high frequency circuits. The sintering behavior, composition, microstructure, and dielectric properties of the ceramics were investigated using a heating microscope, X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy, and terahertz time domain spectroscopy. The studies revealed a low dielectric permittivity of 5.1–6.7 and low dielectric loss in the frequency range 0.14–0.7 THz. The copper borate-based materials, owing to a low sintering temperature of 900–960 °C, are suitable for LTCC (low temperature cofired ceramics) applications. Full article

This work presents a method for reducing acoustic resonances in ferroelectric barium strontium titanate (BST)-based bulk ceramic varactors, which are capable of operation in high-power matching circuits. Two versions of parallel-plate varactors are manufactured here: one with pure BST and one with 10 vol-% magnesium borate, Mg₃B₂O₆ (MBO). Each varactor includes a 0.85-mm-thick ferroelectric layer. Acoustic resonances that are present in the pure BST varactor are strongly suppressed in the BST-MBO varactor and, hence, the Q-factor is increased over a wide frequency range by the addition of small amounts of a low-dielectric-constant (LDK) MBO. Although the tunability is reduced due to the presence of non-tunable MBO, the increased Q-factor extends the varactor’s availability for low-loss and high-power applications. Full article

Thermal evolutions of calcium-tungstate-borate glasses were investigated for the development of luminescent glass-ceramics by using Eu³⁺ dopant in a borate glass matrix with calcium tungstate, which was expected to have a combined character of glass and ceramics. This study revealed that single-phase precipitation of CaWO₄ crystals in borate glass matrix was possible by heat-treatment at a temperature higher than glass transition temperature T_g for (100−x) (33CaO-67B₂O₃)−xCa₃WO₆ (x = 8−15 mol%). Additionally, the crystallization of CaWO₄ was found by Raman spectroscopy due to the formation of W=O double bondings of WO₄ tetrahedra in the pristine glass despite starting with the higher calcium content of Ca₃WO₆. Eu³⁺ ions were excluded from the CaWO₄ crystals and positioned in the borate glass phase as a stable site for them, which provided local environments in higher symmetry around Eu³⁺ ions. Full article

An europium doped BaO–B₂O₃–BaCl₂ chloroborate glass-ceramic containing a BaCl₂ nanocrystalline phase was produced by melt-quenching followed by glass crystallization during annealing. Structural and morphological investigations using x-ray diffraction and scanning electron microscopy have shown fvBaCl₂ nanocrystals of about tens of nm size accompanied by a smaller amount of the BaB₂O₄ crystalline phase. Photoluminescence spectra have indicated the reduction of Eu³⁺ to Eu²⁺ during processing in air or a reducing atmosphere. The spectra analysis showed the presence of Eu³⁺ ions in the borate glass matrix, while the Eu²⁺ were incorporated in both the BaCl₂ nanocrystals and glass matrix. Thermoluminescence properties were due to the recombination of F(Cl) centers and Eu²⁺ related hole centers produced by irradiation within the BaCl₂ nanocrystals. The color impression of the samples and the photoluminescence quantum efficiency were influenced by the glass processing. Full article

Fluid Catalytic Cracking (FCC) has maintained its crucial role in refining decades after its initial introduction owing to the flexibility it has as a process as well as the developments in its key enabler, the FCC catalyst. Boron-based technology (BBT) for passivation of contaminant metals in FCC catalysts represents one such development. In this contribution we describe Fourier Transform Infrared Spectroscopy (FTIR) characterization of boron-containing catalysts to identify the phase and structural information of boron. We demonstrate that FTIR can serve as a sensitive method to differentiate boron trioxide and borate structures with a detection limit at the 1000 ppm level. The FTIR analysis validates that the boron in the FCC catalysts studied are in the form of small borate units and confirms that the final FCC catalyst product contains no detectable isolated boron trioxide phase. Since boron trioxide is regulated in some parts of the world, this novel FTIR methodology can be highly beneficial for further FCC catalyst development and its industrial application at refineries around the world. This new method can also be applied on systems beyond catalysts, since the characterization of boron-containing materials is needed for a wide range of other applications in the fields of glass, ceramics, semiconductors, agriculture, and pharmaceuticals. Full article