Formation Of New Phase Research Articles

Salinity-Induced Reduction of Interfacial Energies and Kinetic Factors during Calcium Carbonate Nucleation on Quartz

Nucleation is a crucial nanoscale process during the formation of new phases. This study employs CaCO3 nucleation on quartz as an example system and investigates the effects of salinity on thermody...

Perda de Pb por Difusão Contínua em Zircão Ígneo: Estudo da Espectroscopia BSE, ID-TIMS e Raman em Granito Mesoproterozoico do SW do Cráton Amazônico

This work presents a detailed investigation on zircon crystals of a Mesoproterozoic granite from the SW Amazonian Craton using a combination of back scattered electron (BSE) imaging, thermal ionisation mass spectrometry (TIMS) and Raman scattering spectroscopy. Six zircon grains were analysed. The results plotted in the Concordia diagram yielded an upper intercept age of 1423.0 ± 3.8 Ma, which is interpreted as the crystallization age of the rock. The scattering of the analyses in such diagram indicates that U-Pb isotopes are volume-dependent in the studied zircon grains. BSE reveals zonation in the zircon crystals, and Hf is the main element causing the variability in the BSE intensity and U has a secondary effect. Both elements have much higher atomic number than the principal constituents of zircon (Zr, Si and O), so the substitution of Zr by U and Hf results in increasing image brightness. BSE images from the zircon grains exhibit a euhedral external shape and fine-scale euhedral oscillatory zoning. The predominance of magmatic zoned crystals points out that the granite has not suffered metamorphic heating or any other processes that induce the formation of new phases. The results of the Raman scattering technique indicate that a SiO 4 tetrahedral internal vibrational structure is sufficiently sensitive to determine the increasing degree of metamictization. Furthermore, evidence for metamictization is given by the heterogeneity of the half-width values of the Raman scattering peaks, which exhibit a decreasing trend from the core to the rims of the analysed grains. We concluded that the combination of the three techniques provides information on the Pb loss and that the degree of U-Pb isotopic discordance correlates closely with the volume of the zircon grain. The data, in addition to the lateral degree of metamictization detected by the Raman scattering technique, indicate that the loss of radiogenic Pb may be linked to the continuous diffusion of this element. The correlation of the U-Pb discordance and metamictization emphasizes the importance of the Raman scattering spectroscopy analysis to performing zircon dating. Indeed, it is a helpful tool for geochronologists.

Reaction of $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-x}$$ (YBCO) and fused silica in YBCO glass fibres

This work introduces the first reported experiments on drawing \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-x}\) (YBCO) into fibres with a fused silica cladding using a fibre draw tower to manufacture YBCO glass fibres. These fibre draw experiments allowed manufacturing fibre sections with core diameters between 50 and 200 \(\upmu \)m and a length of around 1.2 m. However, reactions between the fused silica cladding and the YBCO core were revealed by the fibre drawing process. Therefore, this study focusses on investigating these reactions (in as-drawn fibres as well as after additional heat-treatments) using energy dispersive spectroscopy analyses on an environmental scanning electron microscope as well as using X-ray photoelectron spectroscopy analyses and a cross-polarized light study. The results showed the formation of silica precipitations inside the as-drawn YBCO core, forming an interface layer between the core and the cladding regions, as well as the presence of a high silicon content inside the core with a possible silicate formation. Additional heat-treatments have shown the formation of silica and copper oxide co-precipitations at \(900{^{\circ }}\hbox {C}\). In addition, heat-treatments at higher temperatures have shown the occurrence of further reactions, which led to a degradation of the core and the formation of new phases.

Matrix morphology and the particle dispersion in HDPE nanocomposites with enhanced wear resistance

Abstract High density polyethylene nanocomposites were prepared by melt mixing of varying type of nanopowders in the presence of vinyltrimethoxysilane (VTMS) coupling agent. Three spherical/irregular-shaped nanopowders, fumed Al2O3, γ-Al2O3, cubic titanium nitride (TiN) (1.5 vol-%), and high aspect ratio graphene oxide platelets (GO) (0.5 vol-%) were investigated in a high molecular weight HDPE matrix. Significant differences in the dispersion quality between the nanopowders were found by TEM and AFM. Degree of crystallinity of the nanocomposites (DSC/XRD) was consistently lower than in the neat HDPE polymer. The particularly well dispersed fumed Al2O3, γ-Al2O3 and GO nanopowders induced significant modification on the micromechanical properties of the HDPE. For the first time, great enhancement in the sliding wear performance, and an improvement in the abrasive wear performance was found in the high molecular weight HDPE nanocomposites. DSC analyses showed elevations in the glass transition temperatures and the peak melting temperatures of the nanocomposites. XRD peak splitting in the HDPE + GO and the HDPE + γ-Al2O3 nanocomposites suggest the emergence of a concurrent orthorhombic HDPE phase. Formation of new phases was also supported by DSC analyses showing broad and multimodal melting peaks. Scherrer analyses of XRD data showed slightly increased HDPE crystalline thicknesses in the range of 15–20 nm in the nanocomposites, which was in line with the TEM and AFM observations. The great elevation in the melting temperatures of the HDPE nanocomposites with fumed Al2O3 and γ-Al2O3 could not be attributed to the polymer lamellar thickness, but rather to the altered properties of the solid amorphous phase stemming for the nanopowder additives.

Laser heat treatment of titanium GRADE 1 with iron‐nickel powder

AbstractTitanium alloys thanks to their low density and high mechanical properties are a group of materials that are being used willingly nowadays. A promising method of titanium heat treatment is laser alloying. Process parameters like laser beam power, its traverse speed, amount of alloying elements and shield gas, have influence on the resulting material. Different chemical composition and morphology can be achieved resulting in a change of properties on the surface of the material. The paper presents the investigation of titanium GRADE 1 processed with iron‐nickel powder using laser alloying. The treatment was performed using a high power diode laser. Different laser beam power values were used. Treatment resulted in obtaining good‐adhere, porous‐free, uniform composite material with no cracks. Formation of new phases and solid solution was the reason why it was possible to achieve an increase in microhardness on the surface. Light microscopy, scanning electron microscopy with energy dispersive X‐ray spectroscopy examination, microhardness results and X‐ray diffraction are presented within the paper.

The study of the degradation of refractories under the action of cyclic thermal loads

The results of thermocyclic tests of a number of products of higher refractoriness are given. It is shown that the most resistant to cyclic variable thermal loads are periclase products from fused powders coated with ZrO2. The structure of corundum products in the process of thermocyclic testing significantly degrades due to recrystallization and the formation of new phases. Products made of fused periclase powders modified with ZrO2 are recommended for the organization of the lining and heat exchange tips of test benches that are operated under conditions of variable thermal loads in pulsed piston systems. Ill. 5. Tab. 4.

Phase Formation during Heat Treatment of Zn‐ and ZnAlMg‐Coated Steels at 400 and 750 °C

In contrast to a cold‐forming process, a tempered forming process is able to deform high‐strength steel used for manufacturing automotive bodyworks in a more economic manner. Cold‐formed steel sheets are commonly coated with a Zn or ZnAlMg layer for cathodic corrosion protection. The tempering process would lead to diffusion processes at the steel/coating interface, which is accompanied by the formation of new phases in the coatings. This publication focuses on phase formation in Zn and ZnAlMg coatings on steel sheets, which are heat‐treated at 400 and 750 °C. the authors find that the pure Zn coating remains in the solid state and transforms into the intermetallic δ phase (FeZn10) during heat treatment at 400 °C. The coating melts during heating to 750 °C, but remains in the solid state after transformation into the Γ phase (Fe4Zn9) and α‐Fe. In the ZnAlMg coating, minor iron diffusion occurs at a temperature of 400 °C. Within a dwell time of 600 s, intermetallic Fe–Zn phases are not formed. During heat treatment at 750 °C, phase formation in the ZnAlMg coating is very similar to that in the pure Zn coating, during which Γ (Fe4Zn9) and α‐Fe are formed.

Interaction of ceria and ytterbia in air within temperature range 1500 – 600 °C

Phase equilibria and structure transformations in the CeO2–Yb2O3 system have been studied in air within the temperature range 1500 - 600 °C in the full concentration range using X-ray diffraction analysis (XRD) and petrography methods. It was established that the system is characterized by the formation of solid solutions on the basis of cubic modification of Yb2O3 (C- type) and fluorite CeO2 (F- type) separated by two-phase (F + C) region. The systematic study that covered whole composition range excluded formation of new phases. Solubility limits and concentration dependences of lattice parameters were determined for the phases forming in the system.

Underlying Role of Brushite in Pathological Mineralization of Hydroxyapatite.

The majority of human kidney stones are composed of multiple calcium oxalate crystals with variable amounts of brushite [dicalcium phosphate dihydrate (DCPD)] and hydroxyapatite (HAP) as a nucleus, in which fluid-mediated dissolution and reprecipitation may result in the phase transformation of DCPD to HAP. However, the underlying mechanisms of the phase transition and its modulation by natural inhibitors, such as osteopontin (OPN) proteins, remain poorly understood. Here, the in vitro formation of new phases on the DCPD (010) surface is observed in situ using atomic force microscopy in a simulated hypercalciuria milieu. We demonstrate the presence of an acidic amorphous calcium phosphate (ACP) phase with a characteristic Raman band of ν1HPO42- and the octacalcium phosphate (OCP)-like phase during the transformation process. High-resolution transmission electron microscopy analyses also confirm the existence of OCP and HAP within an amorphous matrix phase. In support of clinical observations, we further demonstrate the inhibitory effect of OPN peptide segments on the dissolution of DCPD and reprecipitation of acidic ACP. The definition of respective roles of DCPD and OPN thereby provides insights into the control of nucleus formation and subsequent inhibition of pathological mineralization.

Effect of crystallographic texture and microstructure on pitting corrosion behavior of low carbon steels: A Monte Carlo model

This work presents a model capable of describing the influence of the crystallographic texture and microstructure produced by Voronoi tessellation on the initial stage of pitting corrosion in API 5L steels. The proposed model takes into account several physical parameters of the material such as crystallographic orientation, gran size, grain boundary, number of inclusions, surface energy, and the Gibbs free energy change. The number of corrosion pits and their distribution associated with the initiation of pitting corrosion were determined using both Monte Carlo simulation and corrosion test. The good agreement between simulation results and the experimental observations verified the validity of the proposed model. The results showed that the pits initiation depends strongly on the change of surface energy due to the formation of new phases and the character of grain boundary and its distribution. The behaviour of nucleated pits is completely random, while their subsequent growth from a nucleation site has a strong influence from the crystallographic grains orientation.

A Study on the Wettability of Ion-Implanted Stainless and Bearing Steels

To satisfy the harsh service demand of stainless steel and aviation bearing steel, the anticorrosion and wettability behaviors of 9Cr18 stainless steel and M50 bearing steel tailored by ion beam surface modification technology were experimentally investigated. By controlling the ion implantation (F+, N+, N+ + Ti+) or deposition processes, different surface-modified layers and ceramic layers or composite layers with both effects (ion implantation and deposition processes) were obtained on metal surfaces. The wettability was characterized by a contact angle instrument, and the thermodynamics stabilization of ion implantation-treated metals in corrosive solution was evaluated through an electrochemical technique. X-ray photoelectron spectroscopy (XPS) was employed for detecting the chemical bonding states of the implanted elements. The results indicated that ion implantation or deposition-induced surface-modified layers or coating layers could increase water contact angles, namely improving hydrophobicity as well as thermodynamic stabilization in corrosive medium. Meanwhile, wettability with lubricant oil was almost not changed. The implanted elements could induce the formation of new phases in the near-surface region of metals, and the wettability behaviors were closely related to the as-formed ceramic components and amorphous sublayer.

Quantum efficient fast UV photodetectors based on nanocrystalline Zn1-xPxO (x = 0.00, 0.03, 0.07) thin films deposited by pulsed laser deposition technique

Here, we demonstrate the effect of phosphorous doping concentration on the structural, electrical and optical properties of ZnO thin films deposited by pulse laser deposition technique. X-ray diffraction studies performed on the deposited films reveal the polycrystalline nature of films and confirm the deposition of ZnO films in wurtzite phase. However, the incorporation of phosphorous does not lead to originate new peak in XRD patterns of the doped films, negating the formation of new phase or the formation of P2O5 phase of phosphorous. But this doping influences the peak positions of pure ZnO film which suggests that phosphorous taking the interstitially positions of Zn and compensates the incomplete bonds. The electrical conductivity of the deposited films is found to significantly increases with phosphorous doping. The prepared photo-devices have shown exceptional UV-photodetection ability under UVA light for fixed illumination intensity of 3.3 mW/cm2 and varying intensities of ~ 0.367 to 3.3 mW/cm2. All the prepared devices have fast response and high sensitivity towards UV light. The response and recovery times for the deposited films are less than 200 ms, with sensitivity as high as ~ 85% at 3.3 mW/cm2 illumination intensity for the device with 7 wt% doping of phosphorous. The high responsivity and detectivity as compared to reported literature, confirms the superior device performance and photo-characteristic of the prepared devices.

Fundamentals of the refractory wear in an industrial anode furnace used in the copper-making process

This paper presents a combination of different useful techniques to identify the fundamentals of the infiltration and chemical degradation of the refractory used in the lining of an anode furnace for fire refining of blister copper. In practice, this work was carried out at the Atlantic Copper Smelter (Huelva; Spain) by a post-mortem study of the refractory used in a one-year campaign, and thermochemical calculations using the FactSage® database. The combination of both techniques created enhanced value thanks to their synergy.The infiltrations and the formation of new phases in the reaction layer were identified using microstructural analyses. The nature of these infiltrations were identified; all the refractory brick samples had been substantially infiltrated by copper and slag elements (mainly copper and iron oxides). The new phases formed were the result of the complex chemical interaction between the slag and the constituent of the refractory. Additionally, copper was incorporated to the spinel.In order to propose a model to represent this complex process, thermochemical calculations were carried out to define a baseline to explain the microstructures obtained as a consequence of the interactions between the bath and the refractory.

Arc Thermal Spray NiCr20 Alloy Coating: Fabrication, Sealant, Heat Treatment, Wear, and Corrosion Resistances

This study presents the effect of heat treatment on porosity, phase composition, microhardness, and wear and corrosion resistances of the thermal sprayed NiCr20 coating after sealing with aluminum phosphate. The annealing temperatures were varied in a range of 400 to 1000°C. The obtained results indicated the porosity of coating decreased with increasing the annealing temperature. After treatment at temperatures in range of 800-1000°C, more than 90% of initial pores in the coating were successfully filled with the sealants. The XRD data revealed not only the formation of new phases of other compounds, but also the interaction between coating and sealant. After heat treatment, wear resistance of coating was 12 times higher than that without heat treatment. The corrosion test in H2SO4 solution indicated that the presence of sealant in coatings increased their corrosion resistance. From these findings, application of these NiCr20 coatings to protect steel against wear and corrosion appears very promising.

Электронмен сәулелендірудің және күміспен қаптау процестерінің полиимидті үлдірлердің деформациялануына әсері

The effect of silver metallization and electron irradiation on the physical and mechanical properties of polyimide films is studied. The metal layer of the polyimide base impregnated into the structure was from 1 to 5 µm thick. The coatings on the surface contained 80÷97 % of the relative silver mirror in the visible and infrared regions. The irradiation was carried out on a linear accelerator ELU-6 with an average electron beam energy of 2 MeV, an integral current of up to 1000 µa with a pulse frequency of 200 Hz and a pulse duration of 5 µs. The absorbed dose by the samples was: 10, 20, 30 and 40 MGy. Deformation of the samples was performed at room temperature in the uniaxial tension mode on the universal testing machine Instron 5982. Study of Structural changes in composite materials in the result of the impact of these physical factors was studied in the x-ray diffractometer type DRON–2M in air at 293 K, CuKa radiation (laCu=1.5418 A). A significant increase in the mechanical characteristics as a result of metallization of films compared to the pure film, so the increase in the tensile strength by ∆σ=105 MPa and plasticity by ∆e=75%, which is associated with the peculiarities of changes in the structure of metallized films and the conditions of their chemical etching. Electronic irradiation of the metallized polyimide film worsens its elastic and strength parameters, which is caused by the formation of new phases in the coating in the form of silver oxide, the concentration of which increases with increasing dose, and is also caused by a violation of the ordered structure of the material in the form of a rupture of the macromolecules of polyimide and the formation of new phases of silver in the coating. The mathematical model, which is in good agreement with the experimental data and allows to predict the elastic properties of silver metallized polyimide films, is obtained.

The stainless steel structure after pulsed plasma flow interaction

The paper presents the results of studies of modification of the surface structure of structural steels AISI 321 (12Х18Н10Т) and AISI 201 (12Х15Г9НД) after plasma treatment with several pulses. The topology of the surface and the evolution of the relief are studied depending on the main processing parameters. In particular, the sequence of phase transitions in modified layers depending on the processing multiplicity was studied. It is shown that under a small number of treatments (n = 2) in investigated stainless steel samples may occur plasma etching and redistribution of crystallites. In addition, in samples detected traces of blister formation and the presence of a layered structure, which can be due to planar and linear defects. When increasing the multiplicity of treatments to 10, the structure becomes more ordered, the columnar blocks are located relatively evenly over the surface and their tracks are located mainly along the grain boundaries. The changes in the structure of the studied structural steels are associated with the formation of new phases (iron nitride) and microarrays in the crystal lattice. A decrease in crystallites size to 16 nm was detected. It is shown that the multiple pulse plasma processing is most effective for grinding austenite crystallites, especially the iron nitride in stainless steel.

Elaboration of Inorganic Polymer for Removal of Organic Compound by Dynamic Column Test

The present research aims to synthesize inorganic polymer by geopolymerization reaction and to evaluate its ability to removal organic matter from water. The inorganic polymer was prepared by activation of metakaolin by a mixture of sodium hydroxide and sodium silicate. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to characterize the geo-adsorbent. The XRD and SEM analysis indicates that formation of new phase and aluminosilicate gel after the geopolymerization process. The adsorption of cationic dye into elaborated inorganic polymer matrix was investigated by a dynamic column test. To predict the breakthrough curves and determine the main fixed bed column parameters, three kinetic models; Tomas, Bohart-Adams and Yoon-Nelson models are applied to fit the experimental data. The kinetic models of the adsorption in dynamic column confirmed that the prepared adsorbent can be used repeatedly for decolouration of water contaminated by textile dye.

Pvc and polietilentereftalat in the processes of combustion with substandard coal

For particles of binders – gas chlorvinyl is characterized by the consolidation of particles into a solid polymer phase with a slight increase in temperature due to adhesion and the formation of larger aggregates – polymer coagulants, which is accompanied by physicochemical and thermal processes such as adsorption, adhesion, coagulation and the formation of new phases. Thus, the interfacial interaction between the surface of the coal and gaseous vinyl chloride results in the contact of condensed matter of different nature, and the adhesion of PVC in the presence of coal particles provides between the particles of the briquettes the connection of a certain strength through physical or chemical molecular forces. To produce durable briquettes were also used supplements polyethylene terephthalate improves the calorific value and energetic properties of the resulting briquettes. Experiments with different concentrations of polyethylene terephthalate showed that with increasing concentration of this binder, the calorific value of briquettes is increased linearly.

The Influence of Activation Preprocessing of the B4C and SiC Powder Mixture with Al on the Phase Composition, Structure, and Properties of Hot-Pressed Composites

The paper examines how the conditions of activation preprocessing (dry and wet grinding) of B4C–Al and SiC–Al powder mixtures in a planetary-ball mill influence the formation of phases in the mixtures and the phase composition, structure, and mechanical properties of the associated hot-pressed materials. It is shown that dry grinding, unlike the conventional powder charge preparation method, induces the mechanochemical synthesis of new phases in the B4C–Al powder mixture along with its mechanical activation. The formation of new phases in the SiC–Al powder mixture does not depend on the conditions of activation preprocessing. Secondary phases form in the hot pressing of the B4C–Al and SiC–Al powder mixtures. The structure and micromechanical characteristics of the materials indicate that dry grinding of the B4C–Al and SiC–Al powder mixtures has a greater activation effect on the hot pressing process, structural uniformity, phase composition, and mechanical properties compared to the conventional powder charge preparation method.

Metakaolin-based geopolymer: Formation of new phases influencing the setting time with the use of additives

The aim of this investigation was the development of a geopolymer grout. To achieve this goal, it is necessary to control the characteristics of the reactive mixture (i.e., between the dissolution of the mineral source and the consolidation of the binder) and its setting time. The targeted application (geological radioactive waste disposal) requires a grout with a setting time greater than 24 h, a viscosity in the range from 1 to 5 Pa·s and a moderate pH value between 10 and 11. To reach these values, a metakaolin-based geopolymer was used with the addition of mineral additives. The viscosity measurements reveal that a focused viscosity is reached and that the setting time can be easily controlled and extended above 24 h with the addition of 2.8%weight of acids (boric and phosphoric) or 10%weight of borax. The acids reduce the reactivity of the mixtures by decreasing the alkalinity and inducing slow silica/alumina dissolution. The borax extends the setting time by increasing the water content and by modifying the polycondensation reactions to form huge structural entities. The decrease in the pH value to the target (10–11) can only be reached using 10%weight of borax or 7.5%weight of lithium tetraborate due to the insertion of B[IV] in the geopolymer network.