Pure Phase Composition Research Articles

Non-invasive thermal sensing and improved recoverable energy storage density of Bi0.5Na0.5TiO3: Er3+ doped multifunctional ferroelectric ceramic

In this work, Er3+ substituted bismuth sodium titanate ceramics with the chemical composition Bi0.5-xErxNa0.5TiO3 (x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) were synthesized using conventional solid state technique. The influence of Er3+ ions on structural, optical, ferroelectric, and temperature sensing properties have been investigated. The prepared ceramic powders were initially heated at a calcination temperature 850 °C to form single phase Bi0.5-xErxNa0.5TiO3 and finally sintered at temperature 1050 °C. Formation of pure phase compositions with rhombohedral crystal structure is confirmed through X-ray diffraction studies. The typical FTIR bands near 540, 860, 910 cm−1 confirmed the presence of Ti–O stretching of octahedral groups in the perovskite structure. The decent squared shaped saturated P-E hysteresis are obtained under an electric field of 60 ≤ E ≤ 70 kV/cm, and the loops become slimmer at higher Er3+ concentrations (x = 0.04). The efficiency of energy storage density increases with Er3+ doping and an improved recoverable energy storage (Wr = 2.73 J/cm3) and a higher efficiency (η = 70.77%) are obtained for Er content, x = 0.04. The photoluminescence spectra were recorded at two excitation wavelengths (488 nm and 980 nm). Two distinct green emission bands (529 nm and 550 nm) and one weak red emission band (670 nm) were observed at both excitation wavelengths. Increasing Er3+ content beyond (x > 0.03) leads to significant quenching of light emission due to cross relaxation process and non-radiative relaxations. The pump power dependency revealed that two photons were involved in the light upconversion process. The time-resolved fluorescence spectroscopy confirmed the decrease in lifetime with increasing Er3+ concentration. The absolute and relative sensitivity of the prepared ceramic at Er3+ concentration (x = 0.03) were found to be 0.47% K−1 at 523 K and 1.1% K−1 at 303 K, respectively. These optical and electrical properties open the possibility of realizing multifunctionality in the field of energy storage and opto-electronic applications.

An enrichment-colorimetry integration strategy for nM-level Hg2+ detection in environmental waters based on an efficient Fe7S8-100 nanozyme and smartphone-based visual assay

A portable and highly sensitive Hg2+ colorimetric sensor was pioneered, in which Fe7S8-100 functioned as an efficient enrichment carrier and colorimetric catalyzer. Four types of Fe7S8-X (X = 0, 25, 50, 100) with varying pure phase compositions were fabricated by adjusting the ratios of ethylene glycol (EG) to water (H2O). The ultrapure Fe7S8-100 phase possessed superior catalytic activity and good enrichment ability. A Hg2+ detection sensor was constructed based on the pairing of Hg2+ with -SH in glutathione (GSH) using 3,3′,5,5′-tetramethylbenzidine (TMB) as the chromogenic substrate. The as-constructed platform provided a linear range (LR) of 0.01–300 μM with a detection limit of 3 nM. In addition, we developed a smartphone application (APP) for Hg2+ colorimetric assay with a detection limit of 30 nM and recovery of 86–115%. To maximize colorimetric sensitivity, an enhanced photography platform was fabricated to eliminate natural light interference and enhance photographic color intensity. Overall, the desorption-free, enrichment-colorimetry integration strategy, combined with smartphone visual detection, provides a practical solution for rapid, field monitoring of Hg2+ in environmental waters.

Optimized phase compositions and microwave dielectric properties of low loss Ca2Sn2Al2O9‐based ceramics by M4+ substitution

AbstractThe traditional solid‐state reaction method was used to prepare Ca2Sn2−xMxAl2O9 (M = Ti, Zr, and Hf) ceramics. Then, the impact of an M4+ substitution of Sn4+ on the phase transition, crystal structural parameter, and microwave dielectric properties of Ca2Sn2−xMxAl2O9 (0 ≤ x ≤ 0.4) ceramics were investigated. Ti4+ could not replace the Sn4+ of Ca2Sn2Al2O9 due to its small ionic radius, and the Al‐based second phases of Ca2Sn2−xTixAl2O9 ceramics were confirmed by the X‐ray diffractometer and EDS map scanning results. With the Zr4+ and Hf4+ substitutions of Sn4+, the SnO2 and CaSnO3 second phases of Ca2Sn2Al2O9 ceramic were inhibited, and the Ca2Sn2−xMxAl2O9 (M = Zr and Hf) (0.05 ≤ x ≤ 0.2) single‐phase ceramics with orthorhombic structure (Pbcn space group) were obtained. New MO2 (M = Zr and Hf) and CaAl2O4 second phases appeared in the Ca2Sn2−xMxAl2O9 (M = Zr and Hf) (0.3 ≤ x ≤ 0.4) ceramics, and their contents increased gradually with the increase in x. The Ca2Sn2−xMxAl2O9 (M = Zr and Hf) (0.05 ≤ x ≤ 0.2) ceramics exhibited high Q × f because of their pure phase compositions, and the Q × f of Ca2Sn2Al2O9 ceramic was improved to 77 800 GHz (12.6 GHz) in the Ca2Sn1.9Zr0.1Al2O9 ceramic. The Q × f values of Ca2Sn2−xMxAl2O9 single‐phase ceramics were mainly controlled by rc (Sn/M–O) and rc (Al–O). The τf values of single‐phase Ca2Sn2−xMxAl2O9 ceramics were related to octahedral distortions. The Zr4+ and Hf4+ substitution of Sn4+ optimized the phase compositions and microwave dielectric properties of the Ca2Sn2−xMxAl2O9 ceramics, and the Ca2Sn1.9Zr0.1Al2O9 ceramic sintered at optimal temperature exhibited excellent microwave dielectric properties (εr = 8.67, Q × f = 77 800 GHz at 12.6 GHz and τf = −69.8 ppm/°C).

Formation of Stable Lithium-Containing Ceramics Using Solid-Phase Synthesis Method

Today, one of the most promising materials for a wide range of practical applications is lithium-containing ceramics based on Li2TiO3. At the same time, despite the high potential of their practical application, a number of questions remains related to the methods of their preparation, as well as the formation of a stable crystal structure and a pure-phase composition. To solve these issues, this paper proposes a method for obtaining stable Li2TiO3 ceramics, which is based on solid-phase synthesis combined with the high-temperature sintering of ceramics. During the studies carried out using X-ray diffraction methods, temperature dependences of phase transformations of the TiO2/Li2Ti6O13 → Li2TiO3 type were determined, according to which, at temperatures above 800 °C, the formation of a stable Li2TiO3 phase characterized by a high structural ordering degree of 89–91% is observed. The dependence of changes in structural, optical and ferroelectric characteristics on the conditions of synthesis and phase composition of ceramics was also determined.

In-situ synthesis of core-shell structure W(WC) composite grains in W-Cu composites fabricated by infiltration

WC strengthened W-Cu composites have attracted much attention due to their high hardness, excellent wear resistance and well high-temperature mechanical properties. In this study, a convenient method was proposed to prepare WC strengthened W-Cu composites by in-situ solid-state reaction with binder as carbon source. The stable carbonization process was determined by thermodynamic calculation and experiments. By infiltrating copper into carbonized W skeleton, the W-Cu composite strengthened by core-shell structure W(WC) composite grain showed pure phase composition and uniform microstructure. The carbonized W-Cu composite with 1 wt% PF exhibited higher relative density of 99.4%, higher hardness of 259.7 HV, higher conductivity of 46.9%IACS compared with traditional W-Cu composite. The average friction coefficient (0.58) and mass loss (0.31 g) of carbonized WC-Cu composites 1 wt% PF were lower than those of conventional WC-Cu composites (0.76, 1.56 g). Meanwhile, the high-temperature compressive strength of carbonized W-Cu composite was higher than traditional W-Cu composite. The new method had high feasibility in the aspects of process stability and cost control advantage.

Fixation of borate-anions in lamellar AFm-phases in the system CaO–Al2O3–B2O3–H2O at 20 ​°C, 40 ​°C and 50 ​°C

Synthesis of boron containing lamellar calcium aluminum hydroxy salts were performed at different relative humidities and the behaviour and properties of the lamellar phases were investigated. The following AFm compound could be synthesized in pure form and their properties were determined:AFm-phase: 3CaOAl2O3CaHBO3.nH2O.With excess boron an Ettringite-compound AFt with the following composition is coexisting in the investigated system:Ettringite-phase: 3CaOAl2O32Ca[B(OH)4]2Ca(OH)2·30H2O.The incorporation of boron in the interlayer of LDH-phases under the influence of OH-ions at different temperatures were investigated. Carbonate was excluded by using a glove box to get definite lattice parameters. Different boron containing AFm-phases, using pure phase compositions in the system OH-lamellar AFm phase and the boron containing AFm phase, were synthesized. The solid solution between the so called compounds Monoborate and Monohydroxide at different temperatures and different relative humidities, with careful control of the different water contents of the lamellar phases, was investigated. Boron contents in solution and the uptake in the interlayer of the AFm-phases was studied [13]. The uptake of boron from pure solutions and the newly formed relevant phases with AFm structure and at higher boron contents of the ettringite structure were determined.

Interference effects on microwave absorbing properties of W-type BaZn2Fe16O27 prepared by solid method

The W-type BaZn2Fe16O27 was prepared by solid method, using zinc oxide, iron oxide and barium carbonate as raw materials. The phase composition and elemental composition were characterized using X-ray diffraction, electronic differential system. The morphology and microscopic structure were characterized using scanning electron microscopy, transmission electron microscope. The electromagnetic properties were analyzed by a vector network analyzer. The hexagonal ferrite with pure phase composition and uniform size distribution of 5–10 µm was prepared by the solid method for the best preparation condition of calcination temperature of 1300 °C, holding time of 3 h. The absorbing of microwave for as-prepared W-type ferrite is consisted of magnetic loss and dielectric loss, thus the magnetic loss is the main, and they reached the maximum 0.17 and 0.51 at 16.90 GHz and 8.14 GHz respectively. The reflection loss (RL) of W-type BaZn2Fe16O27 coating with 3.5 mm thicknesses reaches the minimum value of − 17.02 dB at 9.04 GHz, and the bandwidth of RL values exceeding − 10 dB ranges from 7.28 GHz to 11.44 GHz. The frequency position of the RL peak depends on the λ/4 (quarter wavelength) interference models.

Dark brown Cr doped CaTiO3 pigments with high NIR reflectance

Some brown CaTiO3 pigments have been synthesized by calcining the depositions of CaCO3 and Cr dopant on the surface of TiO2 particles. The pigments have a pure phase composition of perovskite and a narrow size distribution ranging from 0.5 to 1.5 μm. These pigments have a low lightness and exhibit dark brown color due to the presence of Cr6+.The doped CaTiO3 pigment with 1% Cr has high NIR reflectance of 79.7% and high solar reflectance of 58%, and the doped pigment coating can lower 8.9 °C for the inner surface of ceramic tiles.

Controlled synthesis of Na0.44MnO2 cathode material for sodium ion batteries with superior performance through urea-based solution combustion synthesis

As a promising cathode material in sodium-ion batteries (SIBs) for large-scale energy storage applications, tunnel-structured Na0.44MnO2 is prepared by a facile and controllable urea-based solution combustion synthesis (SCS) method with subsequent calcination. The phase purity, morphology, homogeneity and particle size of the samples are quite dependent on the SCS fuel condition. The optimal sample f0.75 displays pure phase composition, high crystallinity and hierarchical-structured particles with uniform size of several microns, which are the agglomerates of well-calcined nano-rods and nano-slabs. The sample exhibits the highest reversible capacity of around 117 mAh/g at 0.1 C, good rate capability and excellent cycling stability, which even presents a high capacity of 100 mAh/g at 4 C after 300 cycles. The facile and controllable production and the superior electrochemical performance of the Na0.44MnO2 makes it a promising cathode material for the development of practical SIBs.

Microwave dielectric properties of Nd:YAG transparent ceramics

In order to investigate the microwave dielectric properties of Nd:YAG transparent ceramics, the high pure raw materials were used for the preparation of samples by the conventional solid-state reaction technique. The samples were sintered at 1660–1840 °C for 8 h in the vacuum atmosphere ≤1 × 10−3 Pa. Nd:YAG ceramics sintered at 1780 °C had the pure cubic YAG phase composition and very dense microstructure with the relative density 99.85 %, so they had the pore-free microstructure and were highly transparent. Because of the pure phase composition and dense microstructure, Nd:YAG transparent ceramics had the outstanding microwave dielectric properties: ɛr = 10.66, Q × f = 2,30,400 GHz and τf = −27 ppm/°C. The high Q × f value and low dielectric constant ɛr suggested that Nd:YAG transparent ceramics were kind of promising dielectric substrate materials in microwave and millimeter wave electronic devices.

Superelastic behaviors of biomedical porous NiTi alloy with high porosity and large pore size prepared by spark plasma sintering

A process of combing use of one-step spark plasma sintering (SPS) method and space holder technique was developed to have successfully fabricated the porous NiTi alloy. To optimize porous NiTi for bone implant applications, the effects of pore characteristics and microstructures on mechanical properties and superelastic behaviors of the porous NiTi alloys were investigated by varying sintering temperatures (800–1050°C) and ammonium hydrogen carbonate (NH4HCO3) contents (0–20wt.%). The results showed that porous NiTi alloys with 18–61% porosity and 21–415μm average pore size all consisted of nearly single NiTi phase with few undesired phases Ti2Ni and Ni3Ti. The superelastic recovery strain ratio of the porous NiTi alloy could be improved up to 90% through training, but with further increasing of training cycles, the curves showed an obvious ladder shaped stress plateau, which indicated the collapse of the pores. This enhanced superelasticity will greatly degrade the mechanical mismatch between bones and porous NiTi. Furthermore, with increasing the porosity and pore size, elastic modulus and compressive strength of the porous NiTi alloys decreased. However, the compressive strength was higher or close to those of human bone and the elastic modulus was close to those of human bone. The unique combination of inter-connected pore characteristics, pure phase composition, low elastic modulus, high strength and large superelastic recovery strain made this material a good candidate for ideal long-term load-bearing hard tissue implants.

Microsecond-Resolution Recording of T4 Lysozyme Observes a Brownian Ratchet

Microsecond-Resolution Recording of T4 Lysozyme Observes a Brownian Ratchet

Experiment and Simulation Reveal the Bending Properties of Nanoscopic Lipid Domains

There has great interest in studying the mechanisms that support nanoscopic lipid domain size using model mixtures. To date, experimental studies have focused in large part on structural parameters such as thickness mismatch between phases, lacking access to mechanical properties in direct, experimental ways. The Neutron Spin Echo technique can directly measure the bending modulus of such bilayers systems by observing shape fluctuations. Furthermore, this method permits us to utilize hydrogen-deuterium contrast matching to make direct observations of the mechanical properties of nanoscopic domains themselves.I will present results detailing for the first time the bending modulus of an individual lipid domain. We have also measured both the structural and mechanical properties of each pure phase compositions of the three component lipid mixture which spontaneously forms these domains. Our results demonstrate that the liquid-ordered phase is more rigid than the liquid disordered phase. Interestingly, the value of the bending modulus in vesicles where these phases coexist as nanoscopic domains approaches that of the liquid ordered-phase, whereas our sample contrast matched so that we only probe the disordered phase in the coexisting system have a bending modulus similar to what is seen in the liquid-disordered only system. We analyze our results with the help of all atom MD simulations which accurately reproduce the structural properties of our system and agree with the trend in mechanical properties that we observe experimentally. These results have implications in determination of important properties such as the line tension which may drive domain size.

RETRACTED: A novel technique to synthesize hydroxyapatite whiskers

HA whiskers with high crystalline, uniform morphology and high aspect ratio have been successfully synthesized by the reflux-hydrothermal combined method with the aid of urea, citric acid and Na 2 EDTA additives. The effects of additives on the whiskers have been investigated in detail. The shape and composition of obtained products were characterized by XRD, FTIR, SEM, TEM and ICP-AES. It is revealed that larger aspect ratios, more uniform morphology, more pure phase composition (Ca/P), shorter reaction time and more mild reaction conditions were reached in contrast to sole reflux or hydrothermal treatment. Urea has the most remarkable effect on the aspect ratio and phase purity of HA whiskers.

Thermodynamic instability of the YBa2Cu3O7−x phase at the 1:2:3 composition

We have measured enthalpies of formation of YBa2Cu3O7−x, Y2BaCuO5, YBa2Cu4O8, and BaCuO2 using high precision isothermal solution calorimetry. Thermodynamic analysis of the calorimetric data indicates that YBa2Cu3O7−x at the pure-phase composition (1:2:3 cation ratio) is metastable at ≍873 K and 1 atm Po2.

A correction procedure for the effects of inclusions on electron probe microanalyses of fine-grained materials

Spatial resolution limits frequently do not permit the complete separation of fine-grained phases in the analysis by electron probe techniques. A general correction procedure based on iterative regression is presented, which removes the effects of such contamination and results in good approximations of the pure phase compositions. An interactive FORTRAN code (PURGIT) implementing the described method is listed in the appendix. Applications of that procedure and its limits are discussed using: (1) specially designed numerical test-problems, and (2) some actual examples from experimental petrology.