Microstructure and properties of ZrO2-, TiO2-doped Ca–Si–B based ceramics

The microstructure, sintering and dielectric properties of ZrO₂-, TiO₂-doped Ca–Si–B based ceramics prepared by solid-phase process were investigated, and the effects of ZrO₂, TiO₂ content on these performances were analyzed. The Ca–Si–B based ceramics without additive (ZrO₂ or TiO₂) showed a high sintering temperature (1,100?°C) and had the dielectric properties: dielectric constant (ε_r) of 8.38, dielectric loss (tanδ) of 1.51?×?10^?3 at 1?MHz, and volume density of 2.47?g/cm³. The addition of ZrO_2, TiO₂ was revealed to lower the sintering temperature of Ca–Si–B based ceramics to 1,000?°C and enhance the sintering and dielectric properties: ρ?=?2.61?g/cm³, ε_r?=?5.85, tanδ?=?1.59?×?10^?4 (1?MHz) with ZrO₂ addition, and ρ?=?2.65?g/cm³, ε_r?=?6.12, tanδ?=?6.4?×?10^?4 (1?MHz) with TiO₂ addition, which are superior to the pure Ca–Si–B. The results show that ZrO₂, TiO₂ as nucleating agents, are conducive to the precipitation of crystals, thus decrease the sintering temperature and improve the dielectric properties of Ca–Si–B based ceramics.     

Characterization of SiO2–Na2O–Fe2O 3–CaO–P2O 5–B 2O 3 glass ceramics

Bioactivity and magnetic properties were investigated in glass and glass ceramics based on the SiO₂–Na₂O–Fe₂O₃–CaO–P₂O₅–B₂O₃ system to find their suitability as thermoseed for hyperthermia treatment of cancer. The effect of change in compositions on bioactivity was examined in simulated body fluids. The glass ceramic samples exhibit Na₃CaSi₃O₈ and Na_3-XFe_XPO₄ phases. After dipping the glass ceramic samples in simulated body fluids silica hydrogel first forms, followed by an amorphous calcium phosphate layer. Magnetic and microwave resonance experiments further demonstrate the potential of these glass ceramics for possible use in hyperthermia.     

Characterisation of Ga2O3–Na2O–CaO–ZnO–SiO2 bioactive glasses

The structural role of Gallium (Ga) is investigated when substituted for Zinc (Zn) in a 0.42SiO₂–0.40–xZnO–0.10Na₂O–0.08CaO glass series, (where x = 0.08). Each starting material was amorphous, and the network connectivity (NC) was calculated assuming Ga acts as both a network modifier (1.23), and also as a network former. Assuming a network forming role for Ga the NC increased with increasing Ga concentration throughout the glass series (Control 1.23, TGa-1 2.32 and TGa-2 3.00). X-ray photoelectron spectroscopy confirmed both composition and correlated NC predictions. Raman spectroscopy was employed to investigate Q-structure and found that a shift in wavenumbers occurred as the Ga concentration increased through the glass series, from 933, 951 to 960 cm^?1. Magic angle spinning nuclear magnetic resonance determined a chemical shift from ?73, ?75 to ?77 ppm as the Ga concentration increased, supporting Raman data. These results suggest that Ga acts predominantly as a network former in this particular Zn-silicate system.     

BaWO4–BaCuO2–Y2Cu2O5–“1010” Section of the Y2O3–BaO–WO3–CuO System

The phase region of cubic perovskite-like solid solutions (a = 8.28–8.40 Å) in the Y₂O₃–BaO–WO₃–CuO system is outlined, and the phase compatibility diagram of the BaWO₄–BaCuO₂–Y₂Cu₂O₅–1010 (1010 = Y₂WO₆ + Y₂W₃O₁₂) is constructed.     

TlInSe2–TlSmSe2 System

The phase diagram of the TlInSe₂–TlSmSe₂ system was mapped out using differential thermal analysis, microstructural examination, and x-ray diffraction data. The system was found to contain a partial solid-solution series (0–9 mol % TlSmSe₂ at room temperature) and a quaternary compound of composition Tl₂InSmSe₄, which melts congruently at 1250 K. The electrical conductivity and Hall coefficient of TlInSe₂–TlSmSe₂ alloys were measured as a function of temperature. With increasing Sm content, the lattice parameters of the solid solution increase linearly, while its band gap decreases.     

ZrO2–TiO2Materials

The magnetic, electrical, catalytic, and photocatalytic properties of ZrO₂–TiO₂materials were studied. The ZrO₂–TiO₂system was shown to contain ZrO₂-, TiO₂, and ZrTiO₄-based solid solutions. Procedures for the preparation of high-activity ZrO₂–TiO₂photocatalysts and photostable pigments were developed.     

CuGaTe2–CuAlTe2 System

It was shown by x-ray diffraction and differential thermal analysis that CuGaTe₂ and CuAlTe₂ form a continuous series of solid solutions. CuGaTe₂, CuAlTe₂, and CuAl _x Ga_{1 – x} Te₂ crystals consisting of large blocks were grown by the horizontal Bridgman process, and their thermal expansion and near-edge transmission and reflection spectra were measured. The thermal expansion coefficient was shown to vary linearly across the solid-solution series, while the band gap is a nonlinear function of composition.     

Texture and microstructure characterization in laser additive manufactured Ti–6Al–2Zr–2Sn–3Mo–1.5Cr–2Nb titanium alloy

Laser additive manufacturing (LAM) is a novel manufacturing technique in which metal components can be fabricated layer by layer. In this study, a recently developed damage tolerance titanium alloy TC21 (Ti–6Al–2Zr–2Sn–3Mo–1.5Cr–2Nb) was deposited by LAM process. Texture and microstructure characterization have been investigated by XRD, SEM and EBSD. Prior β grains texture analysis indicates that the (100) poles concentrate in build direction with a texture intensity about 18.7. During cooling down from β phase field, the β to α phase transformation follows the Burger orientation relationship and a pronounced variant selection occurred. Besides, morphology and scale of α phase are quite different along the build direction due to different thermal history. Very fine rib-like α phase with the length less than 2 μm and acicular martensite α' can be obtained at the bottom and the top of the sample, respectively. In the middle position, distribution and morphology of α phase is quite uneven and the precipitation sequence of α phase is α_GB → α_WGB → α_WM → α_S. The reasons by which they formed are discussed.     

Dynamic tensile properties of Ti–47Al–2Mn–2Nbs alloy

Room temperature tensile properties of polycrystal Ti–47Al–2Mn–2Nb alloy with near lamellar (NL) microstructures were investigated at the strain rates between 10–5 and 1000 s–1 using a self-designed Split-Hopkinson tensile bar setup with a rotating disk and conventional testing machine. It was found that tensile ductility varies within a narrow range with the strain rate, while dynamic strengths (d) of the alloy are obviously higher than static strengths (s). There exists linear relationship between s and the logarithm of the strain rate (ln ), and between d and the strain rate itself (). Fractography analysis indicates that the alloy fractures in a mixed mode of predominant transgranular cleavage and minor intergranular cracking under static and dynamic strain rates. Environmental effect is excluded from the main cause for the room temperature brittleness of the investigated alloy.     

Microwave dielectric properties of CaO–La2O3–Nb2O5–TiO2 ceramics

A series of ceramics with a general formula Ca_1+xLa_4?xNb_xTi_5?xO₁₇ (0 ≤ x ≤ 4) were fabricated using the solid-state ceramic route. The phase, microstructure, and microwave dielectric properties varied distinctly with composition or the value of x. X-ray diffraction results showed that the two end member phases, CaLa₄Ti₅O₁₇ and Ca₅Nb₄TiO₁₇, crystallized into single phases with orthorhombic and monoclinic crystal structure, respectively. For intermediate compounds with x = 1, 2, and 3, mixture phases CaLa₄Ti₅O₁₇ and Ca₅Nb₄TiO₁₇ coexisted and a trace amount of second phase was detected. The ceramics showed high ε _r in the range of 45–52, relatively high quality factors with Q × f in the range of 9,870–15,680 GHz and τ _f value in the range between ?38 and ?126.4 ppm/°C. τ _f of CaLa₄Ti₅O₁₇ can be tuned to a near-zero value by addition of suitable amount of TiO₂.     

Effects of Li2O3–B2O3–SiO2 addition on dielectric properties and microstructure of MgO–TiO2–ZnO–CaO ceramics

The effect of Li₂O₃–B₂O₃–SiO₂ (LBS) liquid-phase additives on the sintering, microstructures, and dielectric properties of MgO–TiO₂–ZnO–CaO (MTZC) ceramics was investigated. It was found that the sintering temperature could be lowered easily, and the dielectric properties of MTZC ceramics could be greatly improved by adding a small amount of LBS solution additives. With the addition of 10 wt% LBS, the ceramics sintered at 900 °C showed favorable dielectric properties with ε_r = 21.7, Qf = 5.0 × 10⁴ GHz, and TCF = ?21.6 ppm/ °C. The distructive physical analysis showed an excellent co-firing interfacial behavior between the MTZC ceramic and the Ag electrode. It indicated that MTZC ceramics with LBS solution additives have a number of potential applications on passive integrated devices based on the low-temperature co-fired ceramics technology.     

TlInS2–TlCeS2Solid Solutions

TlInS₂–TlCeS₂solid solutions were characterized by x-ray diffraction and electrical measurements. The solubility limit of TlCeS₂in TlInS₂was found to be 8 mol %. The electrical conductivity and Hall coefficient of TlIn_{1 – x} Ce _x S₂(0 x 0.08) were measured from 300 to 1100 K. It was found that, as the Ce content of the solid solution increases, the band gap decreases, and the lattice parameters increase.     

Sol–gel derived ZrO2–SiO2 highly reflective coatings

In this paper, colloid-based highly reflective coatings consisting of alternating layers of quarterwave thick high- and low-refractive index components were deposited on glass substrates by a sol–gel spin-coating method. SiO₂ was used as the low-refractive index component, and ZrO₂ as the high-refractive index material. The colloidal suspension of ZrO₂, prepared by hydrothermal hydrolysis of ZrOCl₂, contained monoclinic nanocrystalline ZrO₂, with an average particle size of 15 nm. A minimum transmittance of 1% near 1064 nm was obtained from a 20-layer SiO₂–ZrO₂/PVP multilayer film. The ZrO₂ particles were deposited in an ethanolic suspension containing polyvinylpyroldione (PVP) as a binder. The maximum transmittance in the visible range was about 85%. A 1-on-1 laser-induced damage threshold of 16 J/cm² for the 20-layer SiO₂–ZrO₂/PVP film was observed using a Q-switched Nd:YAG high power laser at a wavelength of 1.06 μm and with a pulse width of 2.5 ns.     

Phase Relations in the Na2O–Al2O3–Nb2O5and CaO–Al2O3–Nb2O5Systems

Phase relations in the Na₂O–Al₂O₃–Nb₂O₅and CaO–Al₂O₃–Nb₂O₅systems were studied. The Na₂O system was found to contain neither ternary compounds nor niobate–aluminate solid solutions. In the CaO system, a ternary compound of composition 4CaO · Al₂O₃·Nb₂O₅was identified (cubic structure, a= 7.628 Å, Z= 2, _meas= _x= 4.43 g/cm³).     

Contribution to ternary system Al–Ti–B Part 2 – Study of alloys in Al–AlB2–TiB2 triangle

Abstract

In arc melted and aluminothermically prepared alloys with composition in the triangle Al–AlB₂–TiB₂ four solid phases are observed: α-Al, ρ-AlB₁₂, AlB₂, and TiB₂. The univariant reaction between L, ρ-AlB₁₂, and TiB₂ is the eutectic one L? α-AlB₁₂ + TiB₂. During the reaction TiB₂ platelets are sequentially formed on facets of α-AlB₁₂, but their formation may be completely suppressed by the presence of primary TiB₂. Decomposition of α-AlB₁₂ does not occur on cooling, but only during isothermal annealing under 900°C probably according to the transition reaction L + α-AlB₁₂ → TiB₂ + AlB₂. Dissolution of α-AlB₁₂ and growth of AlB₂ take place in afaceted manner owing to their high entropies of solution. The low temperature AlB₂ phase is not formed at all on cooling of concentrated alloys with an overall composition lying on the AlB₂-TiB₂ tieline, whereas in less concentrated alloys it is usually formed on the primary TiB₂ particles in the regions distant from α-AlB₁₂     

Properties of Phases and Alloys of the Mo–Ni–B System in the Ni–MoNi–Mo2NiB2–Ni2B Region

Materials Science - For alloys of the Mo–Ni–B system annealed at subsolidus temperatures (and some as-cast alloys) in the Ni–MoNi–Mo2NiB2–Ni2B region, we study the...     

Electrical conductivity studies of Bi2O3–Li2O–ZnO–B2O3 glasses

Ac conductivity measurements and its analysis has been performed on xBi₂O₃–(65?x)Li₂O–20ZnO–15B₂O₃ (0 ≤ x ≤ 20) glasses in the temperature range 30–300 °C and a frequency range of 100 Hz to 1 MHz. The dc conductivity increased and the activation energy decreased with lithium content. The frequency dependent conductivity has been analyzed employing conductivity and modulus formalisms. The onset of conductivity relaxation shifts towards higher frequencies with temperature. The Almond–West conductivity formalism is used to explain the scaling behavior, and the relaxation mechanism is independent of temperature.     

Liquid-phase bonding of silicon nitride ceramics using Y2O3–Al2O3–SiO2–TiO2 mixtures

Hot-pressure sintered β-Si₃N₄ ceramic was bonded to itself using Y₂O₃–Al₂O₃–SiO₂–TiO₂ mixtures. Reactive behavior at interface between Si₃N₄ and Y₂O₃–Al₂O₃–SiO₂–TiO₂ mixtures during silicon nitride ceramic joining was studied by means of scanning electron microscopy (SEM), electron probe microanalyses (EPMA), X-ray diffraction (XRD) and auger electron spectroscopy (AES). The joint strength under different bonding conditions was measured by four-point bending tests. The results of EPMA, AES and XRD analyses show that the liquid glass solder reacts with silicon nitride at interface, forming the Si₃N₄/Y–Si–Al–Ti–O–N glass/TiN/Y–Si–Al–O glass gradient interface. From the results of four-point bending tests, it is known that with increase of bonding temperature and holding time, the joint strength increased reaching a peak, and then decreased. The maximum joint strength of 200 MPa measured by the four-point bending tests is obtained for silicon nitride bonded at 1823 K for 30 min.     

Synthesis of W–Zr–Ti Alloy via Combustion in the WO3–ZrO2–TiO2–Mg System

Inorganic Materials - We have studied the self-propagating high-temperature synthesis (SHS) process due to the combustion of a WO3 + ZrO2 + TiO2 + Mg multicomponent mixture. The ratio of the oxide...