Decagonal Quasicrystalline Phase Research Articles

Al-Ni-Co decagonal quasicrystal application as an energy-effective catalyst for phenylacetylene hydrogenation

Intermetallic catalysts, including quasicrystals, are considered a sustainable alternative to noble metal-based catalysts in hydrogenation reactions. This study discusses the manufacturing and catalytic potential of an Al-Ni-Co quasicrystalline alloy. Energy-effective and simple catalyst production was provided by a melt-spinning process. The obtained ribbons, characterized in terms of microstructure, phase and chemical composition using X-ray diffraction, scanning and transmission microscopy methods, were composed of a decagonal quasicrystalline phase with traces of crystalline phases. The form of the melt-spun ribbons ensured easy application in the phenylacetylene hydrogenation reaction. The catalyst provided a substrate conversion of approximately 80% and a styrene selectivity of 54% after 1 h of reaction carried out under mild conditions. The repeatability of the reaction course was verified, with a maximum deviation of 10%. Moreover, the catalyst recovered after the reaction was evaluated in terms of its phase composition and surface changes. X-ray diffractograms confirmed the phase stability, however, the surface degradation and oxidation occurred. The catalytic activity after three months of catalyst storage is also discussed.

Effect of Cu and Cr addition on the structure, anticorrosion and nanomechanical properties of new Al-Ni-Fe-(Cr,Cu) alloys

This work used a thermodynamic approach to design and investigate new complex compositional Al-Ni-Fe-(Cr,Cu) alloys based on aluminum. This work tends to understand the change in microstructure during the rapid solidification process and to evaluate the anticorrosion and nanomechanical properties of the developed alloys. Optimizing thermodynamic parameters such as configurational entropy and Gibbs free energy was used to predict the chemical composition of the studied alloys. The samples were cooled in two ways. The ingots were slowly cooled, while the plates were cast using fast cooling by the high-pressure die-casting method. The presence of a quasicrystalline decagonal phase D-Al71Ni24Fe5 was identified together with crystalline Al3Ni, Al3Ni2, and Al9Ni1.3Fe0.7 phases for the rapidly solidified Al72Ni24Fe4 alloy. The best electrochemical parameters were observed for the Al72Ni24Fe2.5Cr1.5 alloy. The local galvanic microcells were formed in the studied alloys due to large potential differences (>50 mV) between the Al-Ni and Al-Ni-Fe phases. The highest average indentation hardness values were observed for Al72Ni24Fe4 (9.98 ± 1.75 GPa) after normal and rapid solidification. The higher ductility of the Al72Ni24Cr1.5Fe2.5 alloy compared to Al72Ni24Fe4 and Al72Ni24Cu1.5Fe2.5 could be confirmed by the lowest average hardness and Young's modulus values.

Utilization of two-dimensional multicomponent Quasicrystal for NO2 gas detection

The two-dimensional (2D) materials provide an effective ultra-sensitive response for sensing due to the large surface area available for the analyte. Al70Co10Fe5Ni10Cu5 (Quasicrystal-QC) alloy can be effectively exfoliated into a 2D form consisting of the decagonal quasicrystalline phase. The ultrathin thickness of a few nm (∼6 nm) was achieved, exhibiting anisotropic electron-transport properties. The 2D-QC shows pseudo-conducting behavior in the planar region, which endowed the material in nanosheets to work as ultrasensitive NO2 gas sensors (1–100 ppm) at 100 °C. The fabricated device exhibits a NO2 gas response (ΔR/Ra %) of 46% compared to its bulk counterpart. In addition, the mechanism of gas sensing was further corroborated using density functional theory (DFT) simulations and strongly support the interpretation of the experimental data.

A wear-resistant Al85Cu6Fe3Cr6 spray-formed quasicrystalline composite

An Al-based quasicrystalline composite has been processed by spray-forming resulting in a microstructure containing α-Al and a decagonal quasicrystalline phases as the major constituents. Microstructural characterization was performed by scanning and transmission electron microscopy, including detailed analyses of single quasicrystalline particles. In addition, the unlubricated sliding wear behavior of the composite was studied by pin-on-disk tests using several testing parameters, with normal loads ranging from 5 to 20 N and sliding wear velocities ranging from 0.05 to 0.2 m/s. For comparison basis, an Al-Si A380 commercial alloy was tested under the same wear parameters. The quasicrystalline composite showed a significantly higher wear resistance when tested with normal loads in the range of 5 to 10 N, with wear rates ranging from 4 to 6 × 10−4 mm3/N.m against 1 to 2 × 10−3 mm3/N.m for the Al-Si alloy. When tested under higher normal loads, 20 N, both materials presented similar values of wear rates. For lower normal loads, the worn surfaces of the composite and the Al-Si alloy showed that delamination wear was the main mechanism of material removal. However, with load increase, a higher fraction of hard intermetallic particles, previously removed by delamination, introduced a strong abrasive component into the wear track, which led to higher wear rates.

COMPARISON OF CORROSION OF ALUMINUM-BASED ALLOYS FORMING DECAGONAL QUASICRYSTALS IN NaCl SOLUTION

In this work corrosion behavior of the Al72Co18Ni10, Al65Co20Cu15, and Al72Fe15Ni13 alloys forming decagonal quasicrystalline phases was tested in the neutral NaCl solution (pH = 7) which allows a comparison of their corrosion resistance under conditions comparable to application in marine climate. The microstructure of the alloys was studied by quantitative metallographic, X-ray, scanning electron microscopic, and energy dispersive analyses. The corrosion properties were determined by gravimetric and potentiodynamic methods. The Al65Co20Cu15 and Al72Fe15Ni13 alloys have been established to corrode in the sodium chloride solution more strongly than the Al72Co18Ni10 alloy. The corrosion that proceeds under electrochemical mechanism is accompanied by the formation of passive layer on the surface that retards further dissolution in the saline solution after 3–4 days of testing. Scanning electron microscopy shows the marks of pitting corrosion. The pits appear mostly where flaws and boundaries of iron- or aluminum-rich crystalline phases are located. Their quantity and size are lesser on the surface of the Al72Co18Ni10 alloy since Co and Ni in its composition are rate determining for the corrosion processes. This alloy may be recommended as starting material for plasma-spayed coatings working in marine climate.

Phase stability and phase transformations in Al-Pd-Mn quasicrystalline alloys with low-Ga content

Gallium having low surface energy (∼ 600 mJ/m2) and low melting temperature (29.76 °C), was utilized to substitute Al in Al-Pd-Mn quasicrystalline alloys, which may be considered for future development of a quaternary QC alloy with low surface energy. The influence of Ga up to 5 at% in decagonal Al70-XGaXPd10Mn20 (x = 0, 2.5, 5.0) alloys on the stability of decagonal phase was investigated systematically. The surface morphology and phase stability were studied in as-cast (slow cooling from liquid) and also in annealed condition (i.e., annealing at temperature 800 °C for 24 h). It is observed that Ga influences the stability of decagonal phase and the evolution of microstructure. The phase transformation from the mixed icosahedral and decagonal quasicrystal phases coexisting in as-cast Al70-XGaXPd10Mn20 (x = 0, 2.5, 5.0) alloys to a single decagonal quasicrystalline phase was observed on annealing, implying relative phase stability of quaternary decagonal phase around these compositions.

First-time synthesis of an unparalleled Al72Cr15Ni13 decagonal quasicrystalline phase with the help of mechanical alloying and annealing procedures: A comparative study

An X-ray diffractometer, a field-emission scanning electron microscope, and a high-resolution transmission electron microscope were utilized to characterize the structural and microstructural evolutions of the AlCrNi alloy powders. The single-phase Cr (Al, Ni) nanostructured solid-solution was synthesized through the high-energy planetary ball milling in 96 h. It was turned out that the decagonal quasicrystal obtains after the annealing treatment at 1035 °C. The formation of the decagonal quasicrystalline phase in the AlCrNi alloy system was first investigated in the present article. A differential thermal analyzer was employed for the examination of the thermal performance of the AlCrNi alloy powders. The specific surface area of the mechanically alloyed and heat-treated AlCrNi alloy powders was determined through the BET analysis without any further alkali leaching. The specific surface area of the AlCrNi alloy powders containing the decagonal quasicrystalline phase possesses a high value of 1.75 m2g−1.

Analysis of thermodynamic parameters for designing quasicrystalline Al-Ni-Fe alloys with enhanced corrosion resistance

In this work, the compositions of Al-Ni-Fe alloys were determined based on thermodynamic parameters optimization. Decagonal quasicrystalline phase D-Al70.83Fe9.83Ni19.34 was identified in the alloy with the highest Gibbs free energy of solid solution formation, i.e., Al71Ni24Fe5. According to this, the configurational entropy and enthalpy of solid solution formation must reach equilibrium to form quasicrystals in Al-Ni-Fe alloys. Differential thermal analysis and X-ray diffraction were used to describe the crystallization mechanism as a function of Fe concentration. 57Fe Mössbauer spectroscopy was used to describe the Fe local environment in crystalline alloys and quasicrystals. Moreover, the influence of quasicrystalline phases on improving the corrosion resistance was investigated. Quasicrystalline Al71Ni24Fe5 alloy had a six-times lower corrosion rate than its crystalline counterparts. Although this alloy showed the best corrosion resistance, all high-pressure cast Al-Fe-Ni alloys displayed improved corrosion resistance.

Heat Capacity of Decagonal and Icosahedral Quasicrystalline Phases at High Temperatures

The paper deals with the calculations of heat capacity of quasicrystalline decagonal Al69Co21Ni10 and icosahedral Al63Cu25Fe12 quasicrystalline phases of Al–Co–Ni and Al–Cu–Fe alloys, respectively. According to the Gruneisen law, heat capacity is an energy characteristic, which reflects the phases’ resistance to failure. For calculations of the heat capacity, structure of quasicrystalline phases is considered in the model representation of anisotropic crystals. As a result, it is found that the heat capacity of quasicrystalline phases at high temperatures is the excessive one, i.e. it exceeds the Dulong-Petit value. Therefore, quasicrystalline phases at high temperatures are more stable, than the crystalline phase. For the decagonal quasicrystalline phase, heat capacity is more than 3R in the temperature range of ~480–1500 К, and for the icosahedral quasicrystalline phase – in the temperature range of ~380–1120 К. It follows that decagonal phases remain stable at high temperatures at which the icosahedral phases are destroyed.

Quasicrystalline phase and crystalline approximant in Ni–Mn–In Heusler alloy system

Intermetallic compounds and micro-structures in Ni–Mn–In alloy system were investigated with transmission electron microscopy, selected-area and nano-beam electron diffraction, and energy-dispersive x-ray spectroscopy. Together with two types of Heusler phases, a decagonal quasicrystalline phase and a structurally related crystallite were found in the Ni–Mn–In system. As is well-known, most of the decagonal quasicrystals are aluminum-based intermetallic phases. It is interesting to investigate the aluminum-free decagonal quasicrystalline phase as a new member of the quasicrystal family. Structural characterization was carried out on the decagonal quasicrystalline phase and the crystalline approximant in the Ni–Mn–In alloy system.

Structure Formation and Corrosion Behaviour of Quasicrystalline Al–Ni–Fe Alloys

The formation of quasicrystalline decagonal phase and related crystalline phases was investigated by a combination of optical metallography, powder X-ray diffraction, atomic absorption spectroscopy and differential thermal analysis. Corrosion behaviour of quasicrystal Al–Ni–Fe alloys was studied by gravimetric and potentiodynamic polarization experiments in saline and acidic solutions at room temperature. The decagonal phase exhibits two modifications (AlFe- and AlNi-based) depending on the composition. In Al72Ni13Fe15 alloy it coexists with monoclinic Al5FeNi phase. In Al71.6Ni23Fe5.4 alloy crystalline Al13(Ni,Fe)4, Al3(Ni,Fe)2, and Al3(Ni,Fe) phases are seen adjacent to the quasicrystalline decagonal phase. Stability of quasicrystal phase up to room temperature was shown to be connected with its incomplete decomposition during cooling at a rate of 50 K/min. Al72Ni13Fe15 alloy has more than twice larger volume fraction of this phase compared to that of Al71.6Ni23Fe5.4 alloy. A dependence of microhardness on composition was observed as well, with Al72Ni13Fe15 alloy having substantially higher values. In acidic solutions, Al71.6Ni23Fe5.4 alloy showed the best corrosion performance. In saline solutions, the investigated alloys remained mainly untouched by corrosion. Mass-change kinetics exhibited parabolic growth rate.

Effect of Cr addition on the formation of the decagonal quasicrystalline phase of a rapidly solidified Al-Ni-Co alloy

Abstract The influence of Cr addition in a rapidly solidified Al-Ni-Co alloy was investigated. Melt spun samples of atomic composition Al71Ni20Co9, Al72Ni19Co7Cr2 and Al72Ni20Co5Cr3 were studied by X-ray diffraction and transmission electron microscopy. Aiming to develop quasicrystalline compositions enriched in corrosion resistant elements such as Cr and Ni this work presents, for the first time, the effect of Cr addition on the quasicrystalline phase formation of a high-Ni Al-Ni-Co rapidly solidified alloy chosen to be within the range of formation of the decagonal quasicrystalline phase observed in this ternary system. The composition of the quaternary alloys was chosen by reducing the Co content in favor of Cr on the ternary alloy and keeping the average valence electron per atom (e/a) around 1.86. The phase constitution of the ternary alloy consisted of the decagonal phase along with two intermetallic phases, Al3Ni and Al3Ni2. The addition of Cr resulted in the formation of a second quasicrystalline decagonal phase, rich in Cr. This was due to the low Cr solubility on the ternary Al-Ni-Co decagonal and intermetallic phases, which rejected Cr and resulted on the formation of the Cr-rich quasicrystal.

Формирование декагональной квазикристаллической фазы при лазерном легировании алюминия кобальтом и никелем

Формирование декагональной квазикристаллической фазы при лазерном легировании алюминия кобальтом и никелем

Phase Formation in the Rapidly Solidified Al70−xGaxPd13Mn17 Alloys

In the present investigation, the effect of Ga substitution at Al site on the phase formation and stabilization of decagonal quasicrystalline phase in the rapidly solidified Al70−xGaxPd13Mn17 alloys have been studied by employing X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray analysis. The as-cast and rapidly solidified alloys with x = 0, 2.5 and 5 have been investigated. The melt-spinning technique has been used for rapid solidification of the as-cast alloys. The alloys up to 5 at.% Ga exhibit the formation of small amount of icosahedral quasicrystalline phases along with major amount of decagonal phase in the rapidly solidied ribbons. The energy dispersive X-ray analysis investigations suggest the homogeneous presence of Ga in the quasicrystalline alloys.

Mechanical Alloying of Al73Cu11Cr16Alloy from Ion Irradiated Powders

Al73Cu11Cr16 alloys were prepared by mechanical alloying of the irradiated by Ar + ions elemental powders. Evolution of alloy structure at ball milling, as well as during the further annealing, was investigated using X-ray di raction and di erential scanning calorimetry. It was shown that ball milling leads to the Cu dissolution in Al and Cr and to the formation of Al2Cu intermetallic phase. An increase of the milling duration leads to an increase of the Al2Cu phase content in the samples. Ion irradiation of initial elemental powders results in an increase of their interaction rate at milling. In the case of irradiated powders using as initial materials, a content of Al2Cu phase after milling is higher than in the case of using non-irradiated elemental powders. No e ect of irradiation of initial elemental powders on the phase transformation at heating was observed. The annealing results in the decomposition of Aland Cr-based supersaturated solid solutions. An increase in the Al2Cu phase content at heating was observed only in the samples, which were milled for 4 h. In the samples milled for 14 h, nearly no increase in Al2Cu phase content at heating was observed. Heating up to 500 600 ◦C results in the single-phase decagonal quasicrystalline phase formation for all of the studied samples.

Phase Evolution of Al/Cu/Co Thin Films into Decagonal Quasicrystalline Phases

Quasicrystals have drawn increased scientific attention during the past decade not only for the purpose of fundamental research, but also due to their possible applications as bulk materials or thin films [1]. In particular, decagonal (d) quasicrystals could be very attractive because of their anisotropic structure being quasiperiodic in two dimensions and periodic in the third. Recently it has been shown that icosahedral quasicrystalline Al-Cu-Fe and approximant Al-Si-Cu-Fe thin films can be prepared by annealing a multilayer thin film on a sapphire or Si substrate, respectively [2]. In this work, multilayered Al/Cu/Co thin films have been deposited by magnetron sputtering onto Al2O3 (0001) and Si (001) substrates. The multilayers were produced with a multilayer period of 100 nm, repeated 3 times to a total thickness of 300 nm. The Al:Cu:Co layer thickness ratios were adjusted to obtain films with global compositions around the ideal decagonal quasicrystalline phase d-Al65Cu17.5Co17.5. The phase evolution during annealing, and the concurrent changes in film microstructure and crystal quality was investigated. The decagonal d-Al-Cu-Co and d-Al-Cu-Co-Si phases were both found by X-ray diffraction, electron diffraction, and high-resolution (scanning) electron microscopy to form at 5000C on Al2O3 and Si, respectively, and at 6000C these were the only phases present. Figure 1 shows the HRTEM micrograph of the Al-Cu-Co-Si phase after annealing to 7000C. At increasing temperatures, the quasicrystal grains grew larger in size, up to 500 nm, and the Al-Cu-Co obtained a preferred orientation with the 10-fold periodic axis aligned with the Al2O3 substrate normal. The d-Al-Cu-Co phase persisted to more than 8500C, with a complete 00001-texturing, while the d-Al-Cu-Co-Si phase was replaced by other crystalline phases at 8000C. The d-Al-Cu-Co-Si phase was also observed to grow into the Si substrate by a solid-state diffusion reaction.

Experimental Study of Al-Co-Cu Phase Diagram in Temperature Range of 800-1050 °C

Partial isothermal sections of the Al-Co-Cu phase diagram at 800, 1020, and 1050 � C were proposed based on both literature data and own experimental results. By means of x-ray diffraction, electron backscattered diffraction, electron diffraction, high-resolution scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy altogether five phases (Al5Co2, m-Al13Co4, D, B2, and rapidly solidified liquid) were identified in a number of investigated alloys falling within compositional ranges Al58-67Co18-34Cu7-20. The single-phase area corresponding in the isothermal sections to the decagonal quasicrystalline phase (D) was found to reduce in size, and to shift to lower Cu and higher Al bulk contents, both with increasing temperature. The single-phase m and Al5Co2 areas showed only small temperature-dependent changes in size and location. Moreover, an increase in temperature caused both a slow decrease of the copper solubility in B2 and an increase of the liquid stability.

Microstructure transformations in the heat-treated Mg–Zn–Y alloy

Mg–Zn–Y icosahedral quasicrystals have been prepared from the Mg63.5Zn34Y2.5 (at.%) alloy by copper and steel molds casting respectively. The phase transformations under different heat treatments have been investigated successively. Although the cooling rates of the two samples are quite different, the icosahedral quasicrystalline (I-phase) can precipitate from liquid directly almost at the same temperature. The eutectic structure (α-Mg + I-phase) forms at the later stage, while the Mg7Zn3 phase forms under a larger cooling rate (copper mold). Moreover, with a lower cooling speed, micro shrinkage cavities and cracks are easily caused by solute partitioning at the edge of petals-like I-phase. The volume fraction of I-phase is effectively increased after heat treatment at 350 °C for 50 h because I-phase can grow further in a facet manner during the heat treatment process. The I-phase in the Mg63.5Zn34Y2.5 alloy is thermodynamically unstable at 420 °C, and therefore transformations of the I-phase to the W or H-phase occur due to slow transformation kinetics and low thermodynamics driving force. In addition, few decagonal quasicrystalline phases (D-phases) can form on the I-phase/Mg7Zn3 interface. Atomic diffusion and concentration also play a crucial role in these transformations.

Solidification and microstructure of as-cast Mg65Zn32Y3 quasicrystal alloy

Stable icosahedral quasicrystal with a nominal composition of Mg30Zn60Y10 (at%) was prepared by an as-cast method. Applying X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, the equilibrium solidification microstructures of Mg65Zn32Y3 (at%) quasicrystal alloy in Mg-rich corner of the Mg–Zn–Y system was investigated. Since resistivity is one of the physical properties sensitive to structures, it is suggested that there is a reversible temperature-induced solid–liquid structural transition. Quasicrystal possesses quasi-periodic lattice structure and especial electronic structure, which indicates the resistivity of Mg65Zn32Y3 quasicrystal alloy will change greatly during the melting or solidification processes. The temperature dependence on resistivity exhibits a clear turning point. Measuring resistivity-temperature curve (ρ–T curve) and comparing with differential scanning calorimetry (DSC) first time, a study on the solidification process of quasicrystal was carried out. The icosahedral quasicrystalline phase (I-phase) surrounded by eutectic microstructure (α-Mg+decagonal quasicrystalline phase (D-phase)) is reported first time. During the solidification process, the I-phase is formed at about 423°C undergoing a peritectic reaction, and decagonal quasicrystal eutectic microstructure is formed at the later stage. The phase involved in this peritectic reaction has a composition of Mg28.93Zn46.62Y24.35 (W-phase). Furthermore, the quasicrystals with various characteristics morphologies exist some degree micro-segregation. And the microsegregation phenomenon in rod-like quasicrystalline phase is more serious than that in petals-like quasicrystalline phase.

Decagonal quasicrystalline phase in as-cast and mechanically alloyed Al–Cu–Cr alloys

Abstract Microstructure and phase composition of three Al-rich as-cast alloys of Al–Cu–Cr system were investigated by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The decagonal quasicrystalline phase is contained in all alloys under study and has grains with faceted shape, its composition lies in the range of 71–73 at.% Al, 11–12 at.% Cu and 15–18 at.% Cr. The heating in calorimeter of the mechanically alloyed Al 73 Cu 11 Cr 16 powder up to 600 °C leads to the formation of the pure decagonal phase. Total thermal effect in the temperature range 250–600 °C corresponding to the quasicrystalline phase formation is about 15 kJ/mol.