Study of Phase Formation Processes in Li2ZrO3 Ceramics Obtained by Mechanochemical Synthesis

The article is dedicated to the study of the phase formation processes in Li2ZrO3 ceramics obtained by the method of solid phase synthesis. Interest in these types of ceramics is due to their great potential for use as blanket materials in thermonuclear reactors, as well as being one of the candidates for tritium breeder materials. Analysis of the morphological features of the synthesized ceramics depending on the annealing temperature showed that the average grain size is 90–110 nm; meanwhile the degree of homogeneity is more than 90% according to electronic image data processing results. The temperature dependences of changes in the structural and conducting characteristics, as well as the phase transformation dynamics, have been established. It has been determined that a change in the phase composition by displacing the impurity LiO and ZrO2 phases results in the compaction of ceramics, as well as a decrease in their porosity. These structural changes are due to the displacement of LiO and ZrO2 impurity phases from the ceramic structure and their transformation into the Li2ZrO3 phase. During research, the following phase transformations that directly depend on the annealing temperature were established: LiO/ZrO2/Li2ZrO3 → LiO/Li2ZrO3 → Li2ZrO3. During analysis of the obtained current-voltage characteristics, depending on the annealing temperature, it was discovered that the formation of the Li2ZrO3 ordered phase in the structure results in a rise in resistance by three orders of magnitude, which indicates the dielectric nature of the ceramics.

A 3D LTCC-Based Ceramic Microfluidic System with RF Dielectric Heating of Liquids

The design, fabrication and functional evaluation of the radio-frequency dielectric heating of liquids in an LTCC-based ceramic microfluidic system are described and discussed. The device, which relies on the dielectric heating of liquids, was fabricated using a low temperature co-fired ceramic (LTCC) technology. A multilayered ceramic structure with integrated electrodes, buried channels and cavities in micro and millimetre scales was fabricated. The structure with the dimensions of 35 mm × 22 mm × 2.4 mm includes a buried cavity with a diameter of 17.3 mm and a volume of 0.3 mL. The top and bottom faces of the cavity consist of silver/palladium electrodes protected with 100 μm thick layers of LTCC. The power, used to heat a polar liquid (water) in the cavity with the volume of 0.3 mL, ranges from 5 to 40 W. This novel application of RF dielectric heating could enable the miniaturization of microfluidic systems in many applications. The working principle of such a device and its efficiency are demonstrated using water as the heated medium.

Investigation of the structure glass-ceramic materials according to data of IR spectroscopy

The efficiency of the use of IR spectroscopy in studying the structure of magnesium-aluminosilicate glass-ceramic materials was analyzed. It was established that the formation of the structure of these glass-ceramic materials during the heat treatment is associated with a distortion of the cordierite structure. The presence of solid solutions, high and low cordierite in the structure of the materials under study was detected according to the systems of bands F2, E2, C2 and D2, depending on the temperature of their heat treatment. The mechanism of phase formation in magnesium-aluminosilicate glass-ceramic materials has been determined, which consists in the formation of future crystals of -cordierite and spinel at the initial stages of nucleation, and crystals of -cordierite and mullite at the stage of crystallization. Formation of a finely dispersed glass-ceramic structure with a predominant content of -cordierite or mullite under conditions of low-temperature heat treatment is a decisive factor in ensuring high thermal and mechanical properties of glass-ceramic materials. This allows them to be used as structural elements of devices and equipment under thermal and mechanical loads.

Toughening of Ceramic Shell Mould with Rice Husk Fiber (CSm-RH) to Improve Strength Property and Mould Performance

For ages, ceramic shell mould (CSm) have been extensively applied in investment casting industry. The formation of CSm requires multiple steps of dipping, layering drying and firing stages. The later steps are very crucial as the solidification thin layer CSm that consist of loose ceramic particles easily cracks when exposed to the higher thermal effect. The inclusion of fiber or any reinforces phases is able to enhance fired ceramic body and also strengthen the green ceramic structure. Thus, the feasibility of rougher NaOH treated rice husk fiber (RHT) prior embedded into composited structure has shown a significant CSm improvement by induced a better adhesion properties and larger bonding area with brittle ceramic matrix, resulted in increased green strength (1.34 MPa) and fired body strength (4.32 MPa). Owing to the decomposed of lignin layer in CSm with untreated rice husk fiber (CSm-RHU) exhibited a higher porosity that provide a better permeation paths of air flow during molten metal pouring as increased 30 % from the standard CSm permeability, giving an enormous benefit for investment casting cooling process. Overall, the incorporation of RHT fiber in a CSm matrix of both green and fired body governed in toughening of brittle ceramic body, hence avoid failure to the casting mould.

How much calcium to shell out? Eggshell calcium carbonate content is greater in birds with thinner shells, larger clutches and longer lifespans

The avian eggshell is a bio-ceramic structure that protects the embryo. It is composed almost entirely of calcium carbonate and a small amount of organic material. An optimal amount of calcium carbonate in the eggshell is essential for the embryo's development, yet how the ratio of calcium carbonate to organic matter varies between species has not been investigated. Calcium is a limiting resource for most birds, so its investment in their eggs should be optimized for a bird's life history. We measured the relative calcium carbonate content of eggshells in 222 bird species and tested hypotheses for how this trait has evolved with the life-history strategies of these species and other traits of their respective egg physiologies. We found that (i) eggshell calcium carbonate content was positively correlated with species having thinner eggshells and smaller than expected eggs relative to incubating parental mass, (ii) species with small mean clutch sizes had lower calcium carbonate content in their eggshells, and (iii) for species with larger clutch sizes, eggshell calcium carbonate content was negatively correlated with their mean lifespan. The pattern of lower eggshell calcium carbonate in longer lived, larger clutched birds suggests that calcium provision to the eggshell has long-term costs for the individual.

Fano-Resonant Hybrid Metamaterial for Enhanced Nonlinear Tunability and Hysteresis Behavior

Artificial resonant metamaterial with subwavelength localized filed is promising for advanced nonlinear photonic applications. In this article, we demonstrate enhanced nonlinear frequency-agile response and hysteresis tunability in a Fano-resonant hybrid metamaterial. A ceramic cuboid is electromagnetically coupled with metal cut-wire structure to excite the high-Q Fano-resonant mode in the dielectric/metal hybrid metamaterial. It is found that the significant nonlinear response of the ceramic cuboid can be employed for realization of tunable metamaterials by exciting its magnetic mode, and the trapped mode with an asymmetric Fano-like resonance is beneficial to achieve notable nonlinear modulation on the scattering spectrum. The nonlinear tunability of both the ceramic structure and the ceramic/metal hybrid metamaterial is promising to extend the operation band of metamaterials, providing possibility in practical applications with enhanced light-matter interactions.

Mechanical Properties and Tribological Characteristics of B4C-SiC Ceramic Composite in Artificial Seawater

To improve the mechanical properties and tribological characteristics of boron carbide (SiC) ceramic, silicon carbide as incorporation phase was added into boron carbide (B4C) matrix. The results showed that the incorporation of SiC phase led to denser microstructure and lower porosity. When the content of SiC was 20 wt.%, the composite presented higher bending strength of 447.6MPa and fracture toughness of 7.21 MPa·m1/2. Meanwhile, when the composite slid against PEEK in seawater, lower friction coefficient of 0.052 and wear rate were obtained. The excellent tribological performance would be attributed to the denser ceramic structure, weakened abrasive wear and tribo-chemical removal.

The (1-x)BiFeO3-xBaTiO3-Bi(Zn0.5Ti0.5)O3 high temperature lead-free piezoelectric ceramics with strong piezoelectric properties

The structure, microstructure, piezoelectric properties, ferroelectric properties and Curie temperature of (1- x )BiFeO 3 - x BaTiO 3 -Bi(Zn 0.5 Ti 0.5 )O 3 +MnO 2 +Li 2 CO 3 ceramics were investigated experimentally by improved solid-state reaction approach. The crystalline structures were examined by X-ray diffractometry. When x = 0.3, the rhombohedral and pseudocubic phases coexist in the ceramic structure. It is considered that the morphotropic phase boundary was formed here. At the same time, the piezoelectric performance d 33 , Curie temperature T C , and depolarization temperature are as high as 184 pC/N, 550°C, 530°C at x = 0.3, respectively. It is worth noting that when x = 0.24, the ceramics have a high T C = 580°C and low dielectric loss tan δ = 1.9%. These results show that the BFBT-BZT system ceramics are applicable ceramics with high piezoelectric properties in high temperature fields.

Characterization of (Mg1.0Zn0.0)TiO3+4 wt%Bi2O3 Ceramics for Application as Resonator in Dielectric Resonator Oscillator Circuit

MgTiO3-based ceramics have potential applications in telecommunications systems at microwave frequencies, such as resonators in dielectric resonator oscillator (DRO) circuits. This paper reports the results of (Mg1.0Zn0.0)TiO3+4wt% Bi2O3 (abbreviated MZT0+4wt%Bi2O3) ceramic fabrication to assess its potential to be used as a resonator in the DRO circuit. We characterized its structure, microstructure, and bulk density. The addition of 4wt%Bi2O3 to MZT0 crystalline powder was carried out via ball-mill. The milled powder was compacted using a die press to obtain pellets. All pellets were sintered at 1100ºC for 4, 6, and 8 h. Ceramic structures of the 4 and 6 h holding time consists of MgTiO3 phase (94.33±2.68) and (95.34±1.95)% molar respectively, while the rest phase was TiO2. The 8-h ceramic structure comprises (96.11±2.94) % molar MgTiO3 accompanied by Mg2TiO5 and TiO2. The ceramics' microstructure consists of a cluster of grains with an average diameter of 1.32-2.24 μm and pores. Bulk density decreases with the increase of sintering holding time. The DRO characterization records a resonance signal each at 5.207, 5.005, and 5.121GHz with power approaching 0 dBm, suggesting that the MZT0+4wt%Bi2O3 ceramics can be used as a resonator in the DRO circuit working in microwave frequencies, especially at 5.0-5.2GHz.