The Er3+, Yb3+ co-doped cerium(IV) oxide powders were synthesized by inverted co-precipitation method and calcined at 1000 °C and 1500 °C, respectively. The influence of dopant concentration and ...calcination temperatures on the luminescence efficiency under excitation with 980 nm laser light was systematically investigated. The maximum intensity of upconversion luminescence (UCL) was observed for CeO2:Yb5Er2 calcined at 1000 °C and CeO2:Yb2Er0.5 calcined at 1500 °C, respectively. Luminescence intensity ratios (LIR) in two Stark sub-levels in green and red regions were used for the determination of temperature sensitivity of CeO2:Yb2Er0.5 sintered at 1500 °C for 1 h. The sensitivity increased for the investigated coupled sub-levels from 0.001 K-1 to 0.003 K-1 (green region) and from 0.0011 K-1 to 0.0025 K-1 (red region). Thus Er3+/Yb3+ doped CeO2 phosphors with high temperature stability seem to be promising materials for low temperature optical measurement under vacuum.
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•100 times enhancement of CeO2:Yb2Er0.5 luminescence with annealing temperature.•Best composition at 1000 °C: CeO2:Yb5Er2 - > dominant red colour.•Best composition at 1500 °C: CeO2:Yb2Er0.5 - > dominant green colour.•Ultra low temperature sensing based on luminescence intensity ratio (LIR).•CeO2:Yb2Er0.5 promising candidate as remote sensor for cryogenic temperatures.
Selected layered clay minerals of smectite group with different chemical composition (e.g. synthetic hectorite, synthetic smectite and natural smectite) were modified by rare earth cations such as ...Er3+ and a stochiometric mixture of Er3+/Yb3+. Raw and modified smectites were systematically heated up to temperatures ensuring their dehydration (400 °C), dehydroxylation (800 °C) and formation of new high temperature phases (1200 °C). The products of heating were investigated by terahertz-time domain spectroscopy to follow changes of their dielectric properties in the far-infrared region. The frequency-dependent refractive index of raw and modified clays was determined in the range of 0.2–3.8 THz (6.6–126.5 cm−1). The heating at 800 °C and above resulted in increase frequency dependent index of refraction and decrease absorption coefficient in comparison to the raw clays. The ion-exchanged smectites by rare earth cations further decreased the absorption coefficient of the samples heated at 1200 °C. Raw natural smectite sample revealed a low frequency band at 0.86 THz, already reported in the literature, which shifted to 0.67 THz after sample modification by rare earth cations. Heating of modified JP to 1200 °C resolved a new absorption band at ∼3.40 THz in the ceramic phase produced from raw natural smectite.
•Cation exchange reaction was used for modification of clays by selected rare earth elements.•Effect of sample heating up to 400, 800 and 1200 °C was studied.•Terahertz time domain spectroscopy was used to study the refractive index dispersion.•The frequency dependence of absorption in THz region resolved new typical absorption bands.•The high temperature treatment can be used for synthesis of new ceramic phosphor materials.
Boron carbide is the third hardest material known, with a high melting point (2450 °C) and poor sintering ability. Therefore, boron carbide is a challenging material for shaping by conventional ...processing routes and can still be considered as unsuitable for commercial production of ceramics parts by additive manufacturing technologies. This work reports the first successful preparation of boron carbide ceramics fabricated by fused filament fabrication from a newly developed composite filament containing 65 wt% of micron-sized boron carbide powder dispersed in a thermoplastic binder. A commercial FFF desktop printer with a 0.40 mm nozzle was used for manufacturing of complex-shaped green bodies. Almost fully dense boron carbide ceramics with printed parts sized up to 4 centimeters and relative density higher than 96% after sintering were prepared. The DTA/TG analysis of composite filament and heat microscopy technique were used to set the debinding temperature program with critical temperature at 140 °C, due to the thermal decomposition of the binder. Microstructure SEM images after sintering showed excellent material homogeneity, while micro-CT images showed very well retained experimental shapes of collimator-like printed grids. The x-ray diffraction proved the presence of boron carbide phase with the free carbon phase at the level of about 1 wt% without significant influence on the measured hardness value of 29.88 ± 1.27 GPa.
•A novel highly filled filament containing the thermoplastic binder and 65 wt% boron carbide powder was successfully developed.•B4C filament was successfully tested on the low-cost desk top 3D-printer.•Complex-shaped boron carbide parts were debinded and sintered without shape collapsing and deformation.•Samples after sintering exhibited excellent relative densities on the level of 96% and very fine microstructure.
This study investigates the parametric quality and reliability of 3D-printed scaffolds using a composite filament comprising a thermoplastic polymer and hydroxyapatite in 1:1 wt ratio. Employing a ...fused filament fabrication printer, we verified the 3D printing strategy, sintering temperature range, and preparation of hydroxyapatite scaffolds. To complete the study, in vitro cytotoxicity tests using animal and human cell models were conducted. The calcium-deficient hydroxyapatite (Ca/P ∼ 1.54) used in preparation of filament exhibited after sintering differences in crystalochemical phases in different rations, comparing to stoichiometric hydroxyapatite (Ca/P ≅ 1.67). The FFF process successfully produced scaffold macropores suitable for tissue vascularization (∼380 µm or smaller). Optimal sintering temperature for cell proliferation was identified at 1300 °C, especially effective for used investigated calcium-deficient hydroxyapatite. Cytotoxicity assessment with murine and human fibroblastic cells demonstrated differing behaviour, emphasizing the need for careful material property modifications for practical scaffold utilization.
Additive manufacturing.Sintered hydroxyapatite.Personalized scaffolds.Biocompatibility.Cytotoxicity.
Regenerative dentistry has experienced remarkable advancement in recent years. The interdisciplinary discoveries in stem cell applications and scaffold design and fabrication, including novel ...techniques and biomaterials, have demonstrated immense potential in the field of tissue engineering and regenerative therapy. Scaffolds play a pivotal role in regenerative dentistry by facilitating tissue regeneration and restoring damaged or missing dental structures. These biocompatible and biomimetic structures serve as a temporary framework for cells to adhere, proliferate, and differentiate into functional tissues. This review provides a concise overview of the evolution of scaffold strategies in regenerative dentistry, along with a novel analysis (Bard v2.0 based on the Gemini neural network architecture) of the most commonly employed materials used for scaffold fabrication during the last 10 years. Additionally, it delves into bioprinting, stem cell colonization techniques and procedures, and outlines the prospects of regenerating a whole tooth in the future. Moreover, it discusses the optimal conditions for maximizing mesenchymal stem cell utilization and optimizing scaffold design and personalization through precise 3D bioprinting. This review highlights the recent advancements in scaffold development, particularly with the advent of 3D bioprinting technologies, and is based on a comprehensive literature search of the most influential recent publications in this field.
Composite filaments with diameter ∼1.75 mm suitable for fused deposition of ceramics were prepared from commercial hydroxyapatite powders (HAp-0, d50 ≤ 35 μm and HAp-1, d50 ≤ 16 μm) and thermoplastic ...polymer - polyvinyl alcohol. The filament printability in FDC applicable as specific bone-part replacements, is connected to its mechanical strength and slenderness ratio affecting the resistance to buckling. The HAp content in prepared composite filaments was at the level of ∼ 50 % and their mechanical properties were compared to commercial filament based on polylactic acid and ∼ 27 % of gypsite used as inorganic filler. The tensile strength of laboratory prepared filaments was about 3 times lower than strength found for commercial filament. The critical buckling pressure calculated from Euler buckling analysis using measured intrinsic Young´s modulus revealed underestimated critical pressure values ∼ 2.5–5.0 times if compared to values of maximal filament compressive pressure loads simulating buckling.
Within this work, the preparation of yttrium tetraboride (YB4) in the form of powder as well as bulk material was investigated.
Powders were synthesized via four different reaction methods, including ...direct synthesis from elemental powders, reduction of yttrium oxide with boron, boron carbide reduction, and combined boron carbide/carbothermal reduction at 1500 °C, 1700 °C and 1900 °C. Pure YB4 powder was successfully synthesized using the combined boron carbide/carbothermal reduction method. Secondary phases, especially Y2O3, YB2 or YBO3, were found in powders prepared using the other three methods.
Bulk material was prepared using direct synthesis from elements by reactive hot-pressing. Influence of temperature and boron content on densification and phase evolution of samples was studied. In situ reaction sintering was performed using conventional hot-pressing at temperatures from 1100 °C to 1800 °C in vacuum. The amount of boron varied from the stoichiometric content to 5 and 10 wt% excess (with respect to the reaction from elemental powders). Stoichiometric reactions led primarily to the formation of YB2 and YB4 and several secondary phases such as Y2O3, YBO3 and Y16.86B8O38. YB4 as a main phase was formed only at elevated temperatures (1700 °C and 1800 °C) but certain content of impurities was still present. Excess of B resulted in the formation of YB4 as a primary phase in all prepared samples with a small content of YBO3 and/or Y16.86B8O38. Moreover, SEM analysis revealed the presence of unreacted boron.
Titanium diboride (TiB
2
) represents a perspective material for innovations in aluminium technology. This refractory ceramic material has superior thermal and electrical conductivity and ...considerable chemical stability at high temperatures (>1000°C). Furthermore, excellent wettability by molten aluminium at operating temperatures is required for the application of TiB
2
as an inert cathode in aluminium electrolysis process. The wettability of various TiB
2
-based materials has been studied in literature at different conditions in temperature ranges above to 1000°C. The present paper surveys the current state of knowledge on aluminium wettability of TiB
2
at high temperatures and examines the wettability of pure hot-press sintered TiB
2
material with different values of surface roughness at low temperatures, i.e. below 900°C.
Cermets containing TiB2 and single or mixed metals were produced by conventional hot-pressing technique at 2100°C for 1h. Nickel, tantalum and their mixtures were used as alloying substances to ...enhance the density of TiB2 composites. The influence of metal addition on the microstructure and tribological properties were investigated. The addition of Ta powder greatly refined the microstructure of sintered samples. Similarly, the mixture of Ni and Ta metals hindered the grain growth of TiB2 particles during the hot-pressing while the samples were sintered up to 98% of theoretical density. The wear behaviour of the composites was assessed by ball on disk tests. The wear rate against alumina counterbody varied in the range of (5.9–21.2)×10−6mm3/Nm. The friction coefficient was not affected significantly by the alloying substances and only slightly increased from 0.58 for pure TiB2 to 0.67 for samples with Ta addition.
Authors present a pilot study of the development of innovative flow cytometry-based assay with a potential for use in tuberculosis diagnostics. Currently available tests do not provide robust ...discrimination between latent tuberculosis infection (TBI) and tuberculosis disease (TB). The desired application is to distinguish between the two conditions by evaluating the production of a combination of three cytokines: IL-2 (interleukin-2), IFNɣ (interferon gamma) and TNFɑ (tumor necrosis factor alpha) in CD4+ and CD8+ T cells.
The study was conducted on 68 participants, divided into two arms according to age (paediatric and adults). Each arm was further split into three categories (non-infection (NI), TBI, TB) based on the immune reaction to Mycobacterium tuberculosis (M.tb) after a close contact with pulmonary TB. Each blood sample was stimulated with specific M.tb antigens present in QuantiFERON tubes (TB1 and TB2). We inferred TBI or TB based on the predominant cytokine response of the CD4+ and/or CD8+ T cells.
Significant differences were detected between the NI, TBI and the TB groups in TB1 in the CD4+TNFɑ+parameter in children. Along with IL-2, TNFɑ seems to be the most promising diagnostic marker in both CD4+and CD8+ T cells. However, more detailed analyses on larger cohorts are needed to confirm the observed tendencies.
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•Innovative flow cytometry assay with potential for diagnosing tuberculosis in the clinics.•Differentiation between TB infection and TB disease.•Evaluation of IL-2, IFNɣ and TNFɑ production by CD4+ and CD8+ T cells.
