Interatomic Spacing Research Articles

Systematic study of Mn atoms, artificial dimers, and chains on superconducting Ta(110)

Magnetic adatoms coupled to an $s$-wave superconductor give rise to local bound states, so-called Yu-Shiba-Rusinov states. Focusing on the ultimate goal of tailoring chains of such adatoms into a topologically superconducting phase, we investigate basic building blocks - single Fe and Mn adatoms and Mn dimers on clean superconducting Ta(110) - using scanning tunneling microscopy and spectroscopy. We perform a systematic study of the hybridizations and splittings in dimers, and their dependence on the crystallographic directions and interatomic spacings, in order to identify potentially interesting chain geometries for this novel sample type. Subsequently, we study the spin structure as well as the length dependent Shiba band structure in Mn chains of those geometries using spin-resolved scanning tunneling spectroscopy. All results are compared to the according properties of structurally identical dimers and chains on the previously studied Nb(110), which has almost identical surface structure and electronic properties, but an about three times smaller spin-orbit interaction.

Microscopic dynamics and Bose–Einstein condensation in liquid helium

We review fundamental problems involved in liquid theory including both classical and quantum liquids. Understanding classical liquids involves exploring details of their microscopic dynamics and its consequences. Here, we apply the same general idea to quantum liquids. We discuss momentum condensation in liquid helium which is consistent with microscopic dynamics in liquids and high mobility of liquid atoms. We propose that mobile transit atoms accumulate in the finite-energy state where the transit speed is close to the speed of sound. In this state, the transit energy is close to the oscillatory zero-point energy. In momentum space, the accumulation operates on a sphere with the radius set by interatomic spacing and corresponds to zero net momentum. We show that this picture is supported by experiments, including the measured kinetic energy of helium atoms below the superfluid transition and sharp peaks of scattered intensity at predicted energy. We discuss the implications of this picture including the macroscopic wave function and superfluidity.

Mechanism of grain refinement in Al-Cu alloy by adding trace La and Al-5Ti-1B

<sec>Grain refinement of aluminium alloys can not only reduce the defects (such as segregation and hot tearing) but also improve the mechanical properties. Adding Al-5Ti-1B master alloy to the melt has become a common method to refine the solidification microstructure of aluminium alloys. A lot of researches have been carried out to uncover the grain refining mechanisms as well as to show the microstructure formation under the effect of grain refiner. These researches demonstrated that the grain refining efficiency is closely related to the number density of TiB<sub>2</sub> particles as well as the solute Ti concentration in the melt. However, there exist still problems to be resolved, such as the limited grain refinement potency of Al-5Ti-1B master alloy. Recently, the addition of trace La to the melt has attracted much attention to control the microstructure of aluminium alloys. The Al-Cu alloys are widely applied to the automobile and aerospace fields due to their high strength, good ductility and high temperature properties. It has been reported that Cu can segregate to Al/TiB<sub>2</sub> interface in the Al-Cu melt inoculated with Al-5Ti-1B master alloy. But the effect of Cu segregation on the grain refinement result is not clear yet. Meanwhile, whether the grain refinement effect of Al-5Ti-1B master alloy on Al-Cu alloy can be improved by the addition of trace La has not been reported.</sec><sec>Solidification experiments are carried out for Al-2Cu alloy with the addition of Al-5Ti-1B master alloy+ trace La. The synergistic effect of trace La and Al-5Ti-1B on the solidification microstructure of Al-2Cu alloy is investigated. It is found that trace La can effectively enhance the refinement result of Al-2Cu alloy and further diminish the nucleation undercooling. Experimental and calculated results demonstrate that solute Cu segregates to the Al/TiB<sub>2</sub> interface and thus increases the interatomic spacing mismatch between Ti (0001) plane of the TiB<sub>2</sub> particles and the interfacial monolayer, while La segregation reduces the interatomic spacing mismatch. The trace La addition reduces the interfacial energy between <i>α</i>-Al and TiB<sub>2</sub> particles, improves the potency of TiB<sub>2</sub> particles to nucleate <i>α</i>-Al, and thus enhances the grain refinement result of Al-5Ti-1B master alloy.</sec>

Ultrahigh resistance of hexagonal boron nitride to mineral scale formation

Formation of mineral scale on a material surface has profound impact on a wide range of natural processes as well as industrial applications. However, how specific material surface characteristics affect the mineral-surface interactions and subsequent mineral scale formation is not well understood. Here we report the superior resistance of hexagonal boron nitride (hBN) to mineral scale formation compared to not only common metal and polymer surfaces but also the highly scaling-resistant graphene, making hBN possibly the most scaling resistant material reported to date. Experimental and simulation results reveal that this ultrahigh scaling-resistance is attributed to the combination of hBN’s atomically-smooth surface, in-plane atomic energy corrugation due to the polar boron-nitrogen bond, and the close match between its interatomic spacing and the size of water molecules. The latter two properties lead to strong polar interactions with water and hence the formation of a dense hydration layer, which strongly hinders the approach of mineral ions and crystals, decreasing both surface heterogeneous nucleation and crystal attachment.

Peritectic-eutectic transformation of intermetallic in Zn alloy: Effects of Mn on the microstructure, strength and ductility

Zn alloy containing peritectic intermetallic compound usually has fine grains, so they show relatively high strength. But the intermetallic compound is coarse, which is blamed for the brittleness. In this work, a strategy to transform the peritectic intermetallic phase of Zn-Fe alloy into eutectic intermetallic phase is proposed by adding Mn. In detail, Mn co-precipitates with Fe and Zn to form a (Fe, Mn)Zn13 phase, which provides nucleation substrate and increase the nucleation rate of the MnZn13 eutectic phase because of their low interatomic and interplanar spacing misfit according to the edge-to-edge matching model. The intermetallic compound formed via eutectic reaction is finer than that formed by peritectic reaction. Results show that the intermetallic in Zn-Fe-Mn is refined by 79% compared with that of Zn-Fe. Moreover, the MnZn13 phase forms a semi-coherent interface with negligible lattice misfit (0.09%) in (01¯11¯) orientation with Zn matrix, which is believed to decrease the intergranular fracture ratio. Consequently, Zn-Fe-Mn alloy has a compression yield strength, ultimate tensile strength and elongation of 135.98 MPa, 226.8 MPa, and 15.9%, respectively, which are 28%, 25% and 87% higher than those of Zn-Fe alloy. The strength is improved by dislocation shearing: lattice dislocations cut precipitates to advance through the alloy. The ductility is improved by significantly refined Zn grains, smaller second phase particles and their semi-coherent interfaces with the matrix.

Crystal Prediction and Design of Tunable Light Emission in BTB‐Based Metal‐Organic Frameworks

AbstractMetal‐organic frameworks (MOFs) have recently been shown to exhibit unique mechanisms of luminescence based on charge transfer between structural units in the framework. These MOFs have the potential to be structural tuned for targeted emission with little or no metal participation. A computationally led, material design and synthesis methodology is presented here that elucidates the mechanisms of light emission in interpenetrated structures comprised of metal centers (M = In, Ga, InGa, InEu) and BTB (1,3,5‐Tris(4‐carboxyphenyl)benzene) linkers, forming unique luminescent M‐BTB MOF frameworks. Gas phase and periodic electronic structure calculations indicate that the intensity of the emission and the wavelength are overwhelmingly controlled by a combination of the number of interacting stacked linkers and their interatomic spacings, respectively. In the MOF, the ionic radii of the metal centers primarily control the expansion or shrinkage of the linker stacking distances. Experimentally, multiple M‐BTB‐based MOFs are synthesized and their photoluminescence was tested. Experiments validated the modeling by confirming that shifts in the crystal structure result in variations in light emission. Through this material design method, the mechanisms of tuning luminescence properties in interpenetrated M‐BTB MOFs have been identified and applied to the design of MOFs with specific wavelength emission based on their structure.

Langmuir-Blodgett monolayer of electrochemically synthesized PANI-TiO2 nanocomposites for MSG biosensor

Nanocomposites of polyaniline titanium oxide (PANI-TiO2) have been synthesized by employing the electrochemical technique and their monolayers were prepared on a pre-chemical treated indium tin oxide (ITO) surface through Langmuir-Blodgett (LB) process. The TEM images show the well dispersion of an average ∼ 5 nm diameter TiO2 particles in the film of PANI-TiO2 with ∼ 0.35 nm interatomic spacing of titanium atoms in the anatase crystalline plane (101). X-ray photoelectron (XPS) spectra of LB film of PANI-TiO2 also confirmed the presence of Ti atoms as a similar observation was also confirmed in energy dispersive X-ray analysis (EDX) analysis of the film surface. Electrochemical conductivity of the PANI-TiO2 LB films showed enhancement in peak current, and subsequent immobilization of monoclonal antibodies specific to l-glutamic acid was achieved. Differential pulse voltammetry (DPV) measurements showed a linear response in the peak current with MSG concentration varying from 1 nM to 500 µM and 1 µM to 250 µM in the electrolyte and tomato sauce, respectively. The detection sensitivity of the immunosensor was ∼ 37 mA/nM.

Nanocomposite (S3Sb2) x (S2Ge)100−x chalcogenide glasses: structural and physical properties

The current paper shows the different effects of the incorporation of sulfur (S)–antimony (Sb) on both the structural and physical properties of nanocomposite (S3Sb2) x (S2Ge)100−x chalcogenide glass for x = 15, 30, 45 and 60. Different physical parameters such as lone-pair electrons, average coordination number, interatomic spacing and field of strength increase with the addition of antimony–sulfur, while other parameters such as heat of atomization and polaron radius show the reverse behavior. The stoichiometry (R > 1) shows that the studied compounds are rich in chalcogen atoms, and an increase in lone-pair electrons indicates the good glass-forming ability of the studied compound.

An Al-12Si/ZnS powder inoculant for eutectic silicon in Al-12Si alloy

To obtain high-performance Al-Si-based cast alloys, refinement and modification of Si phases are required. An Al-12Si/ZnS powder inoculant was designed and fabricated using a chemical bath deposition method. The efficiency of the inoculant for modifying the eutectic Si phase in as-cast Al-12Si alloy was studied. Results show that Al-12Si/ZnS powder can significantly refine the eutectic Si in Al-Si cast alloys. The best refinement effect for eutectic Si is achieved with 17.5wt.% Al-12Si/ZnS powder. Coarse long needle-shaped eutectic Si with a length of 18 µm was modified into approximately spherical shape with a diameter of 6.53 µm, which is evenly distributed throughout the alloy. The E2EM model calculation indicates that the inter-plane misfit (Fp) and inter-atomic spacing misfit (Fr) between ZnS and Si are all less than 0.5%, which confirms that ZnS is a potential nucleation site for Si phase. The hardness, tensile strength, and elongation of Al-12Si alloys modified with 17.5% Al-12Si/ZnS powder increase 6.30%, 16.18% and 55.45%, respectively, compared to the unmodified Al-12Si alloy. The fracture behavior of the alloy with 17.5wt.% Al-12Si/ZnS powder is dominated by transgranular fracture supplemented by intergranular fracture.

Structural, optical, electric and dielectric characterization of a NaCu0.2Fe0.3Mn0.5O2 compound.

The compound NaCu0.2Fe0.3Mn0.5O2 was synthesized using a solid-state method and it crystallized in a hexagonal system with a R3̄m space group in an O3-type phase. The optical properties were measured using UV-Vis absorption spectrometry to determine the absorption coefficient α and the optical band gap Eg. The optical band gap energy of this sample is 2.45 eV, which indicates that it has semiconductor characteristics. Furthermore, the electrical and dielectric properties of the material were investigated using complex impedance spectroscopy between 10−1 Hz and 106 Hz at various temperatures (333–453 K). The permittivity results prove that there are two types of polarization, dipolar polarization and space charge polarization. The Nyquist diagrams show the contribution of the effects of the grain, grain boundary, and electrode properties. The frequency dependence of the conductivity was interpreted in terms of Jonscher's law. The DC conductivity follows both the Mott and Arrhenius laws at low and high temperature, respectively. The temperature dependence of the power law exponent(s) suggests that the overlapping large polaron tunneling (OLPT) model is the dominant transport process in this material. The optimum hopping length of the polaron (4 Å) is large compared with the interatomic spacing (2.384 Å for Na–O and 2.011 Å for Cu, Fe, Mn–O).

Physicochemical Properties of Zinc and Lactose in Solid Mixtures: Influence of Trituration Process.

Recent experimental results supporting the dynamization process show modification in the characteristics of solid mixtures. The present work aims to evaluate the physicochemical properties of metallic zinc and lactose, evidencing the interactions between all chemical components presented in dynamized solid mixtures by analytical techniques. Mixtures of zinc and lactose (1:9 w/w) were successively triturated at the same proportion according to the Brazilian Homeopathic Pharmacopoeia, receiving the designation of 10-1 - 10-6 (1dH - 6dH). All samples were submitted to the following characterization techniques: Atomic Absorption Spectrometry (AAS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), and Raman Spectroscopy (RS). AAS results detected 97.0% of zinc in the raw material, and the triturated zinc lactose system (ZnMet) presented mean values similar to those expected for the physical mixtures: i.e., 9.94%, 1.23%, and 0.11% in the three first proportions (10-1, 10-2, 10-3), respectively. SEM images showed particle size reduction due to the trituration process. The XRD assays of ZnMet 10-3 and 10-6 indicated peak changes at 12.3° and 43.26°, probably associated with modifications of inter-atomic crystalline spacing. The thermal analysis results of dynamized samples suggest modifications in the chemical interaction between zinc and lactose induced by the physical forces applied. RS experiments showed variation in vibration frequencies due to the dynamization procedure, in which marked ZnMet 10-6 spectral modifications were detected at 357, 477, 1086 and 1142 cm-1, and in the wavelength range 860-920 cm-1. These results highlight the importance of applying suitable characterization methods to improve our understanding of the properties of homeopathic solid mixtures, whereas the uses of sensitive tools evidence the influence of trituration on the crystalline properties and in the enthalpy variation of dynamized samples.

Remarkable ductility in metastable refractory high entropy alloys via BCC-FCC/α″ martensitic transformations

Designing metastable refractory high entropy alloys (RHEAs) with transformation induced plasticity (TRIP) effects is an effective approach for solving the low ductility of RHEAs. However, the traditional martensitic transformations (MTs) in RHEAs generally result in limited ductility improvement. In the present work, we designed a metastable RHEA Zr2Hf4Nb0.5Ta (Nb7Ta13) with severe lattice distortion, and two MTs, BCC-to-FCC/α″, were found in Nb7Ta13. During tension deformation, BCC-to-FCC/α″ MTs appeared after yielding, causing the TRIP effect; after the MTs are completed, the FCC martensite showed excellent deformability and effectively promoted the following deformation of Nb7Ta13. Finally, Nb7Ta13 RHEAs show a remarkable ductility (∼60%). By analyzing the variation of interplanar spacing and interatomic spacing during DIMTs, we believed that the FCC martensite is generated by relaxing the lattice distortion.

Calculation of energy and magnetic susceptibility of Fe atomic system during dislocation motion in magnetic field

PurposeThe purpose is to calculate the change in the total energy of a small fragment of an idealized lattice of iron (in its pure form and with impurity atoms) containing an edge dislocation during its elementary motion at one interatomic spacing, both under the influence of a constant magnetic field and without it. The introduction of a magnetic field into the system is aimed at checking the adequacy of the description of the phenomenon of magnetoplasticity by changing the total energy of the atomic system.Design/methodology/approachThe design procedure is based on a quantum-mechanical description of the switching process of the covalent bond of atoms in the dislocation core. The authors used the method of density functional theory in the Kohn-Shem version, implemented in the GAUSSIAN 09 software package. Using the perturbation theory, the authors modeled the impact of an external constant magnetic field on the energy of a system of lattice atoms.FindingsThe simulation results confirmed the effect of an external constant magnetic field on the switching energy of the covalent bond of atoms in the dislocation core, and also a change in the magnetic susceptibility of a system of atoms with a dislocation. This complements the description of the magnetoplastic effect during the deformation of metals.Originality/valueThe authors created quantum-mechanical models of the dislocation motion in the Fe crystal lattice: without impurities, with a substitutional atom Cr and with an interstitial atom C. The models take into account the influence of an external constant magnetic field.

Mean Free Path of Photoelectronic Excitations in Hydrogenated Amorphous Silicon and Silicon Germanium Alloy Semiconductors

Hydrogenated amorphous silicon germanium alloy (a‐Si1−x Ge x :H) films are prepared by plasma enhanced chemical vapor deposition (PECVD) and characterized by in situ real time spectroscopic ellipsometry (RTSE). From complex dielectric function spectra extracted, the broadening width energy (Γ) of the primary absorption feature centered near 3.7 eV is quantified using the Cody–Lorentz oscillator model. Mean free path length of photoelectronic excitations is calculated from Γ based on reasonable estimates for speed of electron–hole photoexcitations. A model is applied with excited state lifetime assumed to be limited by scattering from network disorder and provides a relative measure of short‐range order. The simple model applied is an extension of that widely used to characterize broadening of optical transitions in polycrystalline semiconductors. Decreases in mean free path of up to ∼30% occur with germanium. Relative increases in mean free path with increased hydrogen during PECVD a‐Si:H, a‐Si0.73Ge0.27:H, and a‐Si0.60Ge0.40:H occur from ∼5% to ∼8% and with hydrogen plasma treatment of a‐Si:H by ∼6%. Mean free path changes are tracked with thickness to provide short range order evolution and the effect of the underlying material. Mean free path of photoexcitations in electronic quality a‐Si1−x Ge x :H is estimated at ∼3.5 Å, on the same order as interatomic spacing.

Elastic Behavior of Nb2O5/Al2O3 Core-Shell Nanowires in Terms of Short-Range-Order Structures.

Single-crystalline niobium pentoxide nanowires (NWs) of length 10-15 μm and diameter 100-200 nm are synthesized by thermal oxidation of niobium substrates in a mild vacuum (3-10 mbar). Amorphous Al2O3 shells of varying thicknesses (10, 30, 40, and 50 nm) are deposited on top of the wires using atomic layer deposition. Bending tests of the uncoated Nb2O5 NWs and the Nb2O5/Al2O3 core-shell NWs are carried out inside a scanning electron microscope using a micromanipulator with a force measurement tip. The experimental deflection curves are modeled with Euler-Bernoulli (E-B) beam theory, and the Young's modulus is manipulated to determine the best fit. The Nb2O5 NWs with no shell are determined to have a Young's modulus of 67 ± 10 GPa, which agrees with the published data on Nb2O5 thin films. For core-shell NWs, only small deflections of the wires with 10 and 30 nm thick shells can be fitted with the E-B model when utilizing constant Young's modulus values of 67 GPa for the Nb2O5 core and about 160 GPa for the Al2O3 shell. When allowing for a change in the Young's modulus of the Al2O3 shell, the Young's modulus is determined to be at 120 ± 10 GPa for 10 nm and 145 ± 12 GPa for 30 nm at the highest applied load. For thicknesses of 40 nm and 50 nm, we observed a reduced but constant 120 ± 11 and 111 ± 10 GPa, respectively. Such behavior may result from structural disordering of the amorphous Al2O3 through reducing fractions of the densely packed polyhedra, while the fractions of the loosely packed polyhedra increase as a result of the increasing strain or the fabrication process. The increased disorder is associated with increased average interatomic spacing. Thus, the atomic bonding force and also the Young's modulus decrease.

Photon-induced atom recoil in collectively interacting planar arrays

The recoil of atoms in arrays due to the emission or absorption of photons is studied for sub-wavelength interatomic spacing. The atoms in the array interact with each other through collective dipole-dipole interactions and with the incident laser field in the low intensity limit. Shining uniform light on the array gives rise to patterns of excitation and recoil in the array. These arise due to the interference of different eigenmodes of excitation. The relation between the recoil and the decay dynamics is studied when the array is in its excitation eigenstates. The recoil experienced by a subradiant collective decay is substantially larger than from independent atom decay. A method to calculate the rate of recoil when steady state has been achieved with a constant influx of photons is also described.

Structure-Dependent Doppler Broadening Using a Generalized Thermal Scattering Law

The thermal scattering law (TSL), i.e., S(α,β), represents the momentum and energy exchange phase space for a material. The incoherent and coherent components of the TSL correlate an atom’s trajectory with itself and/or with other atoms in the lattice structure. This structural information is especially important for low energies where the wavelength of neutrons is on the order of the lattice interatomic spacing. Both thermal neutron scattering as well as low energy resonance broadening involve processes where incoming neutron responses are lattice dependent. Traditionally, Doppler broadening for absorption resonances approximates these interactions by assuming a Maxwell–Boltzmann distribution for the neutron velocity. For high energies and high temperatures, this approximation is reasonable. However, for low temperatures or low energies, the lattice structure binding effects will influence the velocity distribution. Using the TSL to determine the Doppler broadening directly introduces the material structure into the calculation to most accurately capture the momentum and energy space. Typically, the TSL is derived assuming cubic lattice symmetry. This approximation collapses the directional lattice information, including the polarization vectors and associated energies, into an energy-dependent function called the density of states. The cubic approximation, while valid for highly symmetric and uniformly bonded materials, is insufficient to capture the true structure. In this work, generalized formulation for the exact, lattice-dependent TSL is implemented within the Full Law Analysis Scattering System Hub (FLASSH) using polarization vectors and associated energies as fundamental input. These capabilities are utilized to perform the generalized structure Doppler broadening analysis for UO2.

Spectroscopic tools to probe multiple dopant induced elastic strain effect in doped ceria matrix: As electrolyte for ITSOFCs

Ionic conductivity of electrolyte is vital to decide efficiency and operating conditions of electrochemical energy conversion devices. Engineering electrolyte structure by strategically introducing elastic strain is rationalized approach to improve its ionic conductivity. In general, elastic strain in bulk material is introduced by doping effect; size-valence mismatch of dopant especially multiple valence dopant incorporate the local elastic strain. Dopant induced strain alter energy landscape near the local strained region and create un-equilibrium site; which provoke low potential ion diffusion path by modifying charge transfer barrier and thus ion conductivity. The accompanied changes in migration energy barrier, adsorption energy, dissociation barrier etc. reduced diffusion kinetics. In the present attempt, we consider multiple-dopant effect in ceria systems to incorporate strain. The local straining effect is monitored by various spectroscopic probe like Extended X-ray Absorption fine Edge spectroscopy (EXAFS), Raman spectroscopy and X-ray absorption near edge spectroscopy (XANES). Dopant induced variation in local surrounding in terms of coordination number (CN) and interatomic spacing (IS) at nearest neighbor (NN) and next nearest neighbor (NNN)-site are revealed by EXAFS. The study exhibits detectable changes in CNs and IS at NN and NNN site. Raman spectra also depict dopant induced straining in ceria. High temperature Raman spectra reveal systematic disappearance of Raman modes associated with oxygen vacancies ordering. The XANES study exhibits existence of Ce in both oxidation state (Ce3+ & Ce4+); which is manipulated by dopant effect. The dopant modulated elastic straining effect enhanced conductivity of multiple doped ceria systems by one order as compared to singly doped ceria system at intermediate to low temperature range.

Quasilocalized Vibrations in Vitreous Silica

The properties of quasilocalized atomic vibrations in numerical models of vitreous silica are studied by means of a demixing technique. The low‐frequency vibrational modes are decomposed into bare non‐localized (plane‐wave‐like) modes and bare localized modes (BLMs). The BLMs are shown to exhibit three distinct spatial regions, characterized by different decay behaviors of the displacement field amplitude: the core, tail, and crossover regions. In the core region near the center of localization, the displacement amplitude decays exponentially with a typical localization length being on the order of the interatomic spacing. In the tail region, the decay of the displacement amplitude follows approximately a power law characterized by a decay exponent α, found to be in the range . The crossover between the core and tail regions takes place at about 10 Å. By means of a local symmetry‐mode comparative projection technique, a distinct similarity in the local vibrational motion for quasilocalized modes in vitreous silica and optic phonons in α‐cristobalite is demonstrated.

Grain refinement of commercially pure aluminum with addition of Ti and Zr elements based on crystallography orientation

The edge-to-edge matching (E2EM) model and electron back-scatter diffraction (EBSD) technique are used to explore the grain refinement mechanism of commercially pure Al through the addition of Ti and Zr elements. EBSD results show that there are favorable crystallography orientation relationships (ORs) between both Al3Ti and Al3Zr particles with α-Al matrix. Due to these ORs Al3Ti and Al3Zr particles act as the heterogeneous nucleation site during solidification nucleation of Al–Ti and Al–Zr alloys, respectively. Furthermore, both Al3Ti and Al3Zr particles have small values of interplanar spacing mismatch and interatomic spacing misfit with respect to α-Al matrix by using E2EM. It shows that micro-addition of Ti and Zr element is efficient heterogeneous nucleation refiner in commercial purity Al or Al alloys. Besides, there may be some other mechanisms in grain refinement of Al alloys with addition of Ti grain refiner.