Development Of Crystalline Phases Research Articles

Obtaining and Characterizing the Dielectric and Ferroelectric Properties of the PZT-Pms Complex System Through Solid State Reactions and Spark Plasma Sintering

Abstract In this paper B-oxide sintering process and Spark plasma Sintering (SPS) method is used to synthesize 0.88Pb(Zr0.52Ti0.48)O3 – 0.12Pb(Mn1/3Sb2/3)O3 – x at%Pr complex system where x = 0 and 0.02. The sintering temperature used in the SPS technique is considerably lower than that used in the B-oxide method (200 to 400oC) with significant decrease of the duration of the sintering route, arriving to some minutes instead of some hours. The aim of the study is the investigation of the effect of sintering technique on the dielectric and ferroelectric properties of such piezoelectric materials. The properties of the developed ceramic materials were determined: the development of crystalline phases was investigated by X-ray diffraction technique and the microstructural behavior by scanning electron microscopy was observed. The composition obtained by the SPS technique shows a lower remnant polarization and maximum strain, as well as a higher coercive field, compared to the those obtained using the same composition produced by B-oxide method.

Bioactive antibacterial borate glass and glass-ceramics

This work aimed to study bioactive glass-ceramics obtained by controlled crystallization, as a function of the heat treatment time, in system 59.5B2O3-2P2O5-9.5CaO-19.5Na2O-9CaF2-0.5Ag2O (mol %). The samples were prepared by the melt-quench method, and thermally treated at 530 °C, with different times: 0, 4, 8, 12, 24 and 36 h. Results of DTA, XRD, FTIR, density and molar volume are shown. The results of XRD revealed the development of crystalline phases during the heat treatment (CaNaB5O9, Ca3(PO4)2, Na2B6O10 and Ag°). The percentage of crystallization and in the size of the crystallite show increases with the time of the heat treatment, as expected. In vitro bioactivity of the samples was analyzed by immersion in SBF for 7, 14, 21 and 28 days. XRD patterns and FTIR spectra after immersion proved HA precipitation. The pH results reveal a higher ion exchange rate for the crystallized samples. This can be associated with the microstructure changes that occur on the surface of the samples during the heat treatment and the solubility of the crystalline phases. In addition, glass and crystallized samples showed antibacterial action against E. coli, independently of the crystallization time. It is possible to conclude that glass-ceramics can potentially be used as biomaterials in the treatment of bone fractures.

Application of varieties of technogenic raw materials in cement technology

The possibility of manufacturing a mineral binder using large-tonnage waste from other industries has been studied. The object of the research are mixtures for the manufacture of cement clinker based on systems of chalk – clay – scope of paper production and chalk – clay – husks of rice processing. At the same time, urgent tasks of developing the raw material base for cement production and resource conservation were solved. The development of new initial mixtures was carried out taking into account the peculiarities of the chemical and mineralogical composition of varieties of technogenic raw materials. According to the chemical composition, rice alkali is characterized by a content of 15.6 wt. % SiO2 with a large quantitative ratio of SiO2:Al2O3=65.2 and a small amount of alkaline earth and alkaline oxides. Scop differs from alkali in a large amount of CaO (25.8 wt. %), a lower content of SiO2 at a quantitative ratio of SiO2:Al2O3=1.3. In this case, there are quantitative ratios of oxides CaO:SiO2=2.5, CaO:Al2O3=3.3, CaO:SiO2:Al2O3=3.3:1.4:1, which determine the probable phase transformations during firing. The main rock-forming mineral in rice husks is amorphous silica; Scope is marked by the presence of crystalline phases of calcite, quartz, and kaolinite. The analysis of the possible content of the studied wastes and the determination of the compositions of the raw mixtures were carried out using the computer program «Clinker». Analysis of computer calculations and experiments indicates the possibility of reducing by 11–16 wt. % consumption of natural raw materials in the composition of mixtures for the manufacture of clinker in comparison with the known production composition. According to X-ray phase analysis, the features of the development of crystalline phases during the firing of mixtures using varieties of technogenic raw materials at a maximum temperature of 1400 ºС were established. Based on the data of technological testing, the differences in indicators of binding properties were determined - the setting time of cement when used in the composition of raw mixtures of rice husk and paper scope.

Evolution of C–S–H in lime mortars with nanoparticles: Nanostructural analysis of afwillite growth mechanisms by HRTEM

AbstractThis work studies the formation of calcium–silicate–hydrates (C–S–H) in lime mortars prepared with additions of nano‐Ca(OH)2 and nano‐SiO2 at 23.3°C. Mineral identification was carried out by X‐ray diffraction after 10, 30, 90, and 120 days of curing. The nanoscale study starts from the generation of amorphous phases until the development of crystalline phases. Observations of binder mortar made by transmission electron microscopy (low magnification and high resolution TEM) after 30 and 110 days of curing showed the formation of two types of C–S–H with different degrees of crystallinity depending on the curing time. The development of short‐range order C–S–H globular phases was visible after 30 days. C–S–H evolved into lamellar crystalline phases visible after 110 days of curing. The crystalline phase corresponds to the C–S–H known as afwillite (Ca3(SiO3OH)2·2H2O), first reported to affect cement and concrete's mechanical and hydration properties. It appears as isolated fibers, growing epitaxially along the edges of the calcite (product of the carbonation of Ca(OH)2), and advancing inward aided by atomic defects (grain boundaries, stacking faults). In addition, high‐resolution transmission electron microscopy tools and electron diffraction simulation confirmed a monoclinic symmetry for afwillite crystals. These results contribute to analyzing the presence of crystalline/amorphous C–S–H in lime mortars, providing information on the structure of afwillite and its possible effects on the binder materials.

Study on Temperature-Dependent Properties and Fire Resistance of Metakaolin-Based Geopolymer Foams.

This paper presents temperature-dependent properties and fire resistance of geopolymer foams made of ground basalt fibers, aluminum foaming agents, and potassium-activated metakaolin-based geopolymers. Temperature-dependent properties of basalt-reinforced geopolymer foams (BGFs) were investigated by a series of measurements, including apparent density, water absorption, mass loss, drying shrinkage, compressive and flexural strengths, XRD, and SEM. Results showed that the apparent density and drying shrinkage of the BGFs increase with increasing the treated temperature from 400 to 1200 °C. Below 600 °C the mass loss is enhanced while the water absorption is reduced and they both vary slightly between 600 and 1000 °C. Above 1000 °C the mass loss is decreased rapidly, whereas the water absorption is increased. The compressive and flexural strengths of the BGFs with high fiber content are improved significantly at temperatures over 600 °C and achieved the maximum at 1200 °C. The BGF with high fiber loading at 1200 °C exhibited a substantial increase in compressive strength by 108% and flexural strength by 116% compared to that at room temperature. The enhancement in the BGF strengths at high temperatures is attributed to the development of crystalline phases and structural densification. Therefore, the BGFs with high fiber loading have extraordinary mechanical stability at high temperatures. The fire resistance of wood and steel plates has been considerably improved after coating a BGF layer on their surface. The coated BGF remained its structural integrity without any considerable macroscopic damage after fire resistance test. The longest fire-resistant times for the wood and steel plates were 99 and 134 min, respectively. In general, the BGFs with excellent fire resistance have great potential for fire protection applications.

Ways of Formation and Features of Development of the Crystal Phase in Amorphous Material (A Review)

An analytical review of the publications in the field of research of factors that have a significant impact on the process of controlled crystallization in various glass systems is carried out. An integrated approach to the given problem is proposed, which includes the use of a number of theoretical calculation methods and effective practical research methods, which are most informative in the field of studying the formation and development of crystalline phases in amorphous material.

Structure and morphology of new PbBr2-B2O3 glasses analyzed by spectroscopic techniques

Different glasses were prepared using the normal slowly cooled melting technique in the binary xPbBr2(100 − x)B2O3 (10 ≤ x ≤40 mol%) system. The methods used to analyze the microstructure of the binary PbBr2-B2O3 glasses are Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). The structural units of the borate matrix are established from spectroscopy of 11B NMR. The main structural species which build up the borate network are the triangle BO3, boroxol-like rings and tetrahedral BBr4 groups. FTIR spectroscopic technique also supported the existence of these borate units. The PbBr2 cannot be used as an additive modifier but it produces a crystalline Pb2B5O9Br mixture that is impeded in the glass matrix. The species BO3 is the primary complement of the species Pb2B5O9Br. NMR and FTIR spectroscopy confirmed the nature of BO3 components. On the other hand, there is no evidence of BO4 species in the material being studied. NMR spectroscopy reveals a very low concentration of (BBr4) tetrahedral (boron combined with Br). In these materials, the TEM and SEM micrographs as well as EDP (electron diffraction patterns) and x-ray diffraction analyses reported the development of crystalline Pb2B5O9Br phases. The electrical resistivity is extremely high in the investigated samples, their value close to the fused B2O3 limit.

Electrical and magnetic response of a phosphate glass - NiFe2O4 composite. A novel magnetic sensor design

NiFe O spinel ndash phosphate Bi Ba Li glass composite was synthesized by solid state reaction New crystalline magnetic phases was developed inside the glassy matrix through a controlled heat treatment New NF LBPB magnetic nanocomposite material was study Complex impedance analysis has shown that mobile ions inside the matrix induce the development of complementary crystalline phases resulting in a composite material with excellent magnetic response An innovative homemade device was designed to test the nanocomposite magnetic response nbsp

Crystallization kinetics of basalt-based glass-ceramics for solid oxide fuel cell application

Solid oxide fuel cell (SOFC) is a very efficient and clean source of energy. The glass and glass-ceramics are the most suitable and compatible sealing materials for SOFC. The crystallization kinetics of glass sealants is an essential parameter to check the suitability of glass as a sealant. In this study, the crystallization behavior of a novel sealing glass developed from the volcanic rock basalt suitable as an SOFC sealant is investigated via differential thermal analysis using the Kissinger kinetic model with several different heating rates. Development of crystalline phases on thermal treatments of the glass at various temperatures has been followed by X-ray diffraction. Augite and diopside are the primary crystalline phases in crystallized glass-ceramic seals. The results show that the basalt base glass-ceramic sealant material exhibited promising properties to use for SOFC.

Fe-Doped Sol-Gel Glasses and Glass-Ceramics for Magnetic Hyperthermia.

This work deals with the synthesis and characterization of novel Fe-containing sol-gel materials obtained by modifying the composition of a binary SiO2-CaO parent glass with the addition of Fe2O3. The effect of different processing conditions (calcination in air vs. argon flowing) on the formation of magnetic crystalline phases was investigated. The produced materials were analyzed from thermal (hot-stage microscopy, differential thermal analysis, and differential thermal calorimetry) and microstructural (X-ray diffraction) viewpoints to assess both the behavior upon heating and the development of crystalline phases. N2 adsorption–desorption measurements allowed determining that these materials have high surface area (40–120 m2/g) and mesoporous texture with mesopore size in the range of 18 to 30 nm. It was assessed that the magnetic properties can actually be tailored by controlling the Fe content and the environmental conditions (oxidant vs. inert atmosphere) during calcination. The glasses and glass-ceramics developed in this work show promise for applications in bone tissue healing which require the use of biocompatible magnetic implants able to elicit therapeutic actions, such as hyperthermia for bone cancer treatment.

Effect of quenching on the structural and dynamic properties of non-aqueous lyotropic mesophases

ABSTRACTWe focused to highlight the effect of quenching on the development and ordering of non-aqueous lyotropic liquid crystalline phases. Lyotropic mesophases are prepared from binary mixtures of sodium dodecyl sulphate and ethylene glycol at varying concentrations 30:70 and 50:50 wt%. The obtained self-assembled phases are characterised by X-ray diffraction, polarisation optical microscopy, differential scanning calorimetry and dielectric spectroscopy to evaluate the structural, optical, thermal and dielectric behaviours. Structural and textural measurements confirmed mesomorphic and crystalline phases for both mixtures. Calorimetric study gives insight about the growth of new phases at ≈335 K and isotropic temperatures of these mixtures. Both the mixtures are quenched from 335 K to the 303 K to analyse the effect of quenching on the structure and ordering of mesophases. We noticed well-defined hexagonal liquid crystalline mesophases for both concentrations after quenching at 303 K. Dielectric and relaxation behaviours of quenched mesophases were also examined. Higher capacitance and dielectric strength are noticed for quenched mixtures. The application prospective of such phases is also discussed.

Selective Magnetic Evolution of MnxFe1–xO Nanoplates

Iron–manganese oxide (MnxFe1–xO) nanoplates were prepared by the thermal decomposition method. Irregular development of crystalline phases was observed with the increase of annealing temperature. Magnetic properties are in accordance with their respective crystalline phases, and the selective magnetic evolution from their rich magnetism of MnxFe1–xO and MnFe2O4 is achieved by controlling the annealing conditions. Rock-salt structure of MnxFe1–xO (space group Fm3m) is observed in as-synthesized nanoplates, while MnFe2O4 and MnxFe1–xO with significant magnetic interactions between them are observed at 380 °C. In nanoplates annealed at 450 °C, soft ferrites of Mn0.48Fe2.52O4 with MnxFe1–xO are observed. It is assumed that the differential and early development of crystalline phase of MnxFe1–xO and the inhomogeneous cation mixing between Mn and Fe cause this rather extraordinary magnetic development. In particular, the prone nature of divalent metal oxides to cation vacancy and the prolonged annealing time o...

Development of crystalline phases in sintered glass-ceramics from residual E-glass fibres

The crystalline phase evolution during firing of glass-ceramic materials from residual E-glass fibres was investigated as a function of temperature and time. The thermal stability and the mechanism of crystallisation were studied by differential scanning calorimetry (DSC). The mineralogical and microstructural characterisation of the sintered glass-ceramics was carried out by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The crystallisation behaviour was depicted by the TTT (Time–Temperature–Transformation) curve. The activation energies for crystallisation were calculated by the Friedman differential isoconversional, ASTM and Kissinger methods. The results show that devitrification of the glass leads to a series of glass-ceramic materials composed of wollastonite and plagioclase s.s. Their microstructure is composed of a dense network of crystals, which is responsible for the high mechanical properties exhibited by these materials.

Sintering, crystallization, and properties of a low-viscosity SnO–MgO–P2O5 glass

A lead-free, low-viscosity SnO–MgO–P2O5 glass powder was fabricated. Sinterability, wetting, flowability, crystallization, and the resulting properties of the glass powder were investigated. It is shown that the powder compact can be fully densified above 362 °C and show good wet to the substrate above 417 °C. The properties (coefficient of thermal expansion and chemical durability) of the sintered glass depend on the sintering temperature and are discussed in terms of the development of crystalline phases during sintering.

Development and stabilization of liquid crystalline phases in hydrogen-bonded systems

This review addresses the description of fundamental principles underlying the development of liquid crystalline phases in hydrogen-bonded complexes. Low-molecular-mass models and polymers systems are considered, where hydrogen bonding is used as an efficient means for modifying polymer structure and designing new materials.

Surface characteristics and protein adsorption on combinatorial binary Ti‐M (Cr, Al, Ni) and Al‐M (Ta, Zr) library films

Systematic studies of protein adsorption onto metallic biomaterial surfaces are generally lacking. Here, combinatorial binary library films with compositional gradients of Ti(1-x)Cr(x), Ti(1-x)Al(x), Ti(1-x)Ni(x) and Al(1-x)Ta(x), (0 <x < 1) and Al(1-y)Zr(y) (0 < y <0.5) as well as corresponding pure metal films were sputtered onto clean Si surfaces. Bulk and surface chemistry, film microstructure, and surface roughness were subsequently correlated to fibrinogen or albumin adsorption measured using a high throughput wavelength dispersive spectroscopy technique. X-ray diffraction revealed these binary films to have crystalline phases present primarily at either extreme of the compositional library and an amorphous zone dominating along the gradient. These mirror-like films were generally found by atomic force microscopy to have a roughness of less than 8 nm, with any relative increases in roughness consistent with the development of crystalline phases. Surface chemistry by quantitative high-resolution X-ray photoelectron spectroscopy differed significantly from bulk film composition as measured by electron microprobe, with TiO(2) and Al(2)O(3) preferentially forming on the binary film surfaces. Correspondingly, protein adsorption onto these films closely correlated with their surface oxide fractions. Aluminum deposited as either a constant-composition film or as part of a binary library consistently adsorbed the least amount of albumin and fibrinogen, with alumina-enrichment of the surface oxide correlating with this adsorption. Overall, this combinatorial materials approach coupled with high-throughput surface analytical methods provides an efficient method of screening potential metallic biomaterials that may enable as well systematic studies of surface properties driving protein adsorption on these metal / metal oxide systems.

Vitrification of low silica fly ash: suitability of resulting glass ceramics for architectural or electrical insulator applications

The study concerns the recycling of the fly ash (FA) derived from the thermal power stations of Ptolemaida (Greece) and its potential use of this FA as precursor in production of bulk nucleated GCs. The first attempt was addressed to produce a glass from the fine powder of as received FA without any additives. To overcome some drawbacks such as spontaneous crystallisation upon cooling of FA based glass and to improve its working properties, production of pyroxene based glasses from FA was undertaken. The parent glass approached the composition of CaMg0⋅75Al0⋅4Fe0⋅1Si1⋅75O6, derived from CaMg0⋅75Al0⋅5Si1⋅75O6, which belongs to diopside–Ca-Tschermak solid solutions. Cr2O3 nucleated fine grained mono mineral glass ceramics of augite were produced from the glasses comprising FA and additives of SiO2, Al2O3 and MgCO3. The influence of Cr2O3 content on the development of crystalline phases, the properties and the microstructure of the resultant glass ceramics crystallised at different temperatures was investigated.

Iron environment in calcium-soda-phosphate glasses and vitroceramics

The structure of calcium-soda-phosphate glasses and vitroceramics with relatively high iron content was investigated by X-ray diffraction, electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. The X-ray diffraction analysis proves the vitreous state of the as prepared samples and the development of crystalline phases in the annealed samples. The ferric ions disposed in sites that give rise to the absorption line with g ef ≈ 4.3 in the EPR spectra of vitreous samples are not more evidenced in the spectra of the annealed samples, from which only of a symmetric and narrowed line with g ef ≈ 2 is recorded. The room temperature 57Fe Mössbauer spectra both of glass and vitroceramic samples consist of two quadrupole doublets characteristic for octahedral sites of Fe 2+ and Fe 3+ ions. The isomer shift for glass samples decreases and for vitroceramic samples increases with the iron oxide content.

Non-isothermal crystallization kinetics of ZnO–BaO–B 2O 3–SiO 2 glass

Glass of composition 40SiO 2–30BaO–20ZnO–10B 2O 3 (mol%) was made by conventional melting and casting process. Crystallization kinetics of above glass has been investigated under non-isothermal conditions, using the formal theory of transformations for heterogeneous nucleation. The procedure is applied to the experimental data obtained by differential thermal analysis (DTA), using continuous-heating techniques. The crystallization results are analyzed, and both the activation energy of crystallization process as well as the crystallization mechanism is characterized. Dilatometric measurement of this glass was also done and data obtained was used to calculate the viscosity of the formed glass. Development of crystalline phases on thermal treatments of the glass at various temperatures has been analyzed by X-ray diffraction. Microstructure of the crystalline phases was investigated by scanning electron microscopy (SEM) and the development of various structural features with variation in heat treatment cycle was observed. The nucleation and growth of these phases in the matrix of glass has been described and discussed.

Recycle of Waste Glass into “Glass–Ceramic Stoneware”

The reuse of soda–lime–silica scrap or waste glasses as additives for traditional ceramics has been investigated extensively in the literature. Although interesting, this solution does not generally allow large quantities of glass to be recycled. This study reports a novel high glass recycle approach that replaces, in the formulation of porcelain stoneware, the feldspar flux with finely powdered glass derived from the melting of different waste products, e.g. lime from fume abatement systems, feldspar mining residues, and scrap soda–lime glass. At an optimized glass/clay ratio, the “glass–ceramic stoneware” samples sinter at 1000°C. The “glass–ceramic stoneware” has a bending strength approaching 90 MPa and a fracture toughness exceeding 2.0 MPa·m0.5, similar to those of conventional porcelain stoneware, which requires sintering at higher temperatures. The high strength and fracture toughness are attributed to the interaction between the glass and clay residues upon sintering, which allows the development of several different crystalline phases.