Surface Crystal Orientation Research Articles

Crystal Grain Rotation during Tensile Test of Polycrystalline Pure Titanium Thin Sheet Based on Surface Height and Crystal Orientation

Crystal Grain Rotation during Tensile Test of Polycrystalline Pure Titanium Thin Sheet Based on Surface Height and Crystal Orientation

Oxides Induced Preferential Growth of {110} Planes for Superior Performance Single-Crystal LiMn2O4 through Solid-State Process.

Polycrystalline lithium manganese oxide (LMO) is known to suffer from severe surface structure degradation and electrochemical polarization due to its mixed crystal plane orientations. A hexagonal prism single-crystal LMO (LMOS-HP), engineered through the SrO-induced preferential growth effect, features the most stable {111} top surfaces and the fastest Li+ diffusion {110} side surfaces, effectively addressing these challenges. Consequently, LMOS-HP exhibits superior electrochemical capability, with only 0.021% capacity fading per cycle after 500 cycles and achieves a discharge capacity of 81.9 mAh g-1 at 20C. This innovative design offers a promising approach for tuning surface crystal orientation to improve performance.

The Effect of the Rare Earth Element Cerium on the Electrocrystallization and Microstructure of Nickel Electrodeposits in Industrial Electrolytes

To meet the industrial production needs for high-quality and precisely controllable structured high-end nickel foils, rare Earth compounds are added as additives in complex industrial electrolytes to improve the quality of the nickel deposition layer. This study investigates the effects of adding rare Earth compounds to the existing industrial production electrolytes (which already contain various organic and inorganic additives in a mixed acid solution) on the surface microstructure, cerium content, grain size, and crystal orientation of the nickel deposition layer. Using direct current electrodeposition, different concentrations of rare Earth compounds were added to the industrial electrolyte, and the cerium content, grain size, and crystal orientation were characterized. The results show that adding 0.8 g·l−1 CeCl3 accelerates the nucleation rate and shortens the nucleation relaxation time. The addition of rare Earth elements promotes multi-directional preferential growth, resulting in uniform and fine grain size, improved grain structure of the deposition layer, and reduced surface roughness of the nickel plating layer. Therefore, rare Earth elements can be used to regulate the structure, microstructure, and grain refinement of the nickel deposition layer without affecting its composition.

Influence of electrodeposition parameters on the fabrication of Ni–Co/SiC + TiN composite films through pulse current electrodeposition

In this investigation, pulsed current electro-deposition (PCE) was used to prefabricate Ni–Co/SiC + TiN composite coatings (NCSTCCs) on mild steel surfaces. The research focused on the influence of two electrodeposition parameters, pulse frequency (PF) and duty cycle (DC), on NCSTCF features including microscopic surface morphology, crystal orientation, grain size, microhardness, SiC and TiN nanoparticles (NPs), deposition quantity, and corrosion resistance properties. The results indicated that NCSTCCs produced under a 10% DC showed minimal SiC and TiN contents with a percent volume of just 5.6 v/v% and 5.4 v/v% respectively under the fixed condition of 60 Hz PF. However, the three-dimensional surface diagram indicated that the Ni–Co/SiC + TiN composite film deposited at 50% DC and 10 Hz PF displayed the highest SiC and TiN contents (11.6 v/v% and 11.7 v/v%) among all the films. Furthermore, NCSTCCs deposited under 50% DC and 10 Hz PF had peak microhardness at 667.4 kg/mm2, while the composite film achieved a microhardness of 514.1 kg/mm2 when prepared using 10% DC and 60 Hz PF. Moreover, when the DC and PF were at 50% and 10 Hz respectively, the Ni–Co/SiC + TiN composite film presented the maximum charge transfer resistance (4915.7–4927.2 Ω·cm2), indicating an excellent corrosion resistance.

Electrochemistry of Molybdenum Single Crystals and Thin Wires in Cyanide and Gold Cyanide Electrolytes

Thin wires of molybdenum coated with gold are used for space applications and the adhesion of the gold layer is decisive for their use. The surface morphology of the wires is determined by the manufacturing process and preferential orientation of single crystal surfaces is expected. In this work three different single crystal surfaces were studied together with a 20 μm molybdenum wire to elucidate the importance of surface morphology on the electrodeposition process for gold. Electrochemical impedance spectroscopy was used to study the molybdenum samples in the absence and presence of gold cyanide complexes. The results show large pseudocapacitance prior to gold deposition, indicating the presence of a thin molybdenum oxide film on the surface. Thus, the electrodeposition takes place on the surface oxide and is afflicted with a nucleation overpotential. The overpotential is only slightly dependent on the single crystal orientation, while it is more negative for the wire. The adhesion of gold on the flat single crystal surfaces is weak but marginally better on the wire. This clearly shows that strong chemical binding to the surface is absent and that other processes, such as physical interlocking of the gold layer is necessary for good adhesion.

Crystal Facet Engineering on SrTiO3 Enhances Photocatalytic Overall Water Splitting.

Single-crystal semiconductor-based photocatalysts exposing unique crystallographic facets show promising applications in energy and environmental technologies; however, crystal facet engineering through solid-state synthesis for photocatalytic overall water splitting is still challenging. Herein, we develop a novel crystal facet engineering strategy through solid-state recrystallization to synthesize uniform SrTiO3 single crystals exposing tailored {111} facets. The presynthesized low-crystalline SrTiO3 precursors enable the formation of well-defined single crystals through kinetically improved crystal structure transformation during solid-state recrystallization process. By employing subtle Al3+ ions as surface morphology modulators, the crystal surface orientation can be precisely tuned to a controlled percentage of {111} facets. The photocatalytic overall water splitting activity increases with the exposure percentage of {111} facets. Owing to the outstanding crystallinity and favorable anisotropic surface structure, the SrTiO3 single crystals with 36.6% of {111} facets lead to a 3-fold enhancement of photocatalytic hydrogen evolution rates up to 1.55 mmol·h-1 in a stoichiometric ratio of 2:1 than thermodynamically stable SrTiO3 enclosed with isotropic {100} facets.

Dependence on the crystallographic orientation of Au single crystal surfaces modified with homocysteine toward enantioselective redox reactions

Abstract Effects of enantioselective interactions on redox reactions of chiral molecules were studied using Au single crystal electrodes modified with amino acids. The redox peak current densities of R(+)- or S(−)-N, N-dimethyl-1-ferrocenylethylamine on Au(111) modified with L- or D-homocysteine (L-/D-Hcy) depended on the combination of these chiralities. Hcy/Au(100) showed no dependence on redox peak current densities. The difference in the molecular arrangement of Hcy between Au(111) and Au(100) greatly affects enantioselective redox reactions at the electrode interface.

Investigation of edge effect on wurtzite gallium nitride in nanoindentation using molecular dynamics simulation

In practical applications, block materials frequently experience edge collapse, yet our grasp of this phenomenon at the nanoscale remains limited. Understanding this is crucial, as nanoscale material behaviors can trigger intricate microscale effects that elude easy observation or comprehension at the macroscopic level. This work researched the edge effect of the wurtzite GaN with {0001} surface crystal orientation at different nanoindentation distances by molecular dynamics simulation. The results show that the GaN indentation edge effect is anisotropic. The atomic displacement directions prolonged [2–1–10], [–12–10], and [–1–120], which is hexagonal distributing, similar to the crystal structure. The dislocations are around the indenter and close to the upper surface, similar to the negative von Mises stress distributions. The closer the indenter is to the edge of the sample, the more atoms are extruded from the specimen edge, and the more serious the damage is to the edge generally. However, analysis of the mechanical response and phase transition shows that the damage to the edge can be weakened while the crystal structure is destroyed more severely at some specific locations of the indenter. This work reveals the evolution of GaN crystal structure under different nanoindentation distances and the mechanism of squeeze-out atoms from the edge at the atomic scale.

CH3Cl Dissociation, CH3 abstraction, and Cl adsorption from the dissociative scattering of supersonic CH3Cl on Cu(111) and Cu(410)

To study the elementary steps in the Rochow-Müller process, we bombarded Cu(111) and Cu(410) with 0.7–1.9 eV supersonic molecular beams (SSMB) of CH3Cl. We then identified the corresponding adsorbed species using X-ray photoemission spectroscopy (XPS) in conjunction with synchrotron radiation (SR). We found Cl as the dominant adsorbed species (much higher than that of adsorbed carbonaceous species) coming from the dissociative scattering of CH3Cl. We also found that the threshold kinetic energy of the reaction depends on the crystal surface orientation.

Molecular dynamics simulations of ultrasonic vibration-assisted grinding of polycrystalline iron: Nanoscale plastic deformation mechanism and microstructural evolution

Ultrasonic vibration-assisted grinding (UVAG) has attracted plenty of attention to significantly improve surface integrity. However, existing research has not systematically investigated the effect of vibration directions during UVAG at atomic and nanoscales, limiting our understanding of the plastic deformation mechanisms and microstructural evolution of ultra-precision machining. To address this issue, we proposed an MD model for multi-abrasive UVAG of polycrystalline iron considering various vibration directions. We comprehensively analyzed atomic flow fields, surface atom distributions, temperature fields, grinding forces, stress distributions, crystal orientations, and dislocation distributions. The simulation results demonstrate that UVAG effectively reduces grinding force and results in instantaneous grinding forces greater than conventional grinding (CG), and the instantaneous load impact phenomenon of radial vibration is more obvious. In surface morphology, axial vibration contributes to reducing surface roughness, while radial vibration is detrimental to surface smoothness. Microstructural evolution is mainly induced by stress. The primary plastic deformation mechanisms in UVAG of polycrystalline iron involve lattice rotation and dislocation mediation. Compared to axial vibration-assisted grinding (AVAG), radial vibration-assisted grinding (RVAG) and elliptical vibration-assisted grinding (EVAG) exhibit finer grain refinement, with RVAG leading to the highest dislocation density.

Preparation of 2024-T351 aluminum alloy superhydrophobic surface by laser peening without absorption layer and without confinement layer

The purpose of this study was to investigate the preparation of superhydrophobic surfaces on 2024-T351 aluminum alloy by laser peening without absorption layer and without confinement layer (LPwAC). The wettability, residual stress and microhardness of the treated specimens were measured. The surface morphology of the specimen was characterized by scanning electron microscopy, and the surface elements and crystal orientation were analyzed. The experimental results showed that the micro-nanoporous structure appeared on specimen surface after LPwAC treatment. The superhydrophobic state was observed after chemical modification reduced the surface energy. Additionally, the crystallinity of the surface was increased, the hardness was improved, and residual compressive stress was generated inside the material. LPwAC is an effective process for the preparation of stable 2024-T351 aluminum alloy superhydrophobic surfaces.

Electrochemical polishing of chemical vapor deposited niobium thin films

Combining chemical vapor deposition (CVD) with electrochemical polish (EP) operation is a promising route to producing performance-capable superconducting films for use in the fabrication of cost-effective components for superconducting radiofrequency (SRF) particle accelerators and superconducting quantum computers. The post-deposition EP process enables a critically necessary reduction in surface roughness of niobium (Nb) thin films to promote optimal superconducting surface conditions. This work investigated surface morphology, roughness, and crystal orientation of the CVD-grown and EP-polished Nb films. The CVD films were found to comprise steps and pyramidal features, resulting in undesirable large peak-to-valley distances. EP was demonstrated to significantly diminish the height of pyramids and effectively minimize the overall surface roughness. EP results showed a probable dependence on the crystal orientation. These understandings identify the EP principles tied to CVD-grown Nb films that allow further refinement of surface profiles for film-based SRF applications.

The Modulated Magnetic Domain Structure in the La0.67Sr0.33MnO3 Ferromagnetic Films by Strain Engineering

Novel magnetic domain structures attract much attention due to their potential applications in the high performance of spintronic devices. Herein, the magnetic domains of La0.67Sr0.33MnO3 (LSMO) thin films, which epitaxially grown on (100)-, (110)-, and (111)-oriented (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) substrates, are systematically investigated. The (100)- and (110)-LSMO films show a stripe domain pattern. After in-plane magnetic field saturation, the direction of the stripe domains in (100)-LSMO no longer rotates with the change of magnetic field, while the stripe domains in (110)-LSMO rotate continuously. The (111)-LSMO films produce randomly distributed bubble-like magnetic domains, which gradually connect into strips with the increase of the external magnetic field, and the stability of the magnetic domain in (111)-LSMO is better than the ones in (100)- and (110)-LSMO under a magnetic field. In addition, it is found that with the increase of thickness, the random domains in (111)-LSMO films are gradually transformed into mazy domains. These phenomena can be understood by the regulable strain anisotropy and the magnetic anisotropy. Herein, an effective way is suggested to modify the magnetization anisotropy and magnetic domain because spin polarization depends strongly on the crystal surface orientation as well as epitaxial strain.

Effect of polyethylene glycol molecular weight on the electrodeposition of nanostructured nickel

Electrodeposition is an attractive approach to synthesize nanostructured metals and their microstructure can be effectively controlled by tuning the process parameters. Here, two molecular weight (MW) types of polyethylene glycol (PEG) were used as additives for nickel electrodeposition in Watts bath. The surface morphology, crystal orientation, microstructure and microhardness of the Ni film were investigated. Experimental results revealed that the MW of PEG played a decisive role in controlling the microstructure of the deposits. As the current density increased from 25 to 100 mA/cm2, the microstructure of the Ni film deposited from the PEG600-containing bath evolved from ultrafine grains with nanotwin lamella perpendicular to the substrate surface to randomly oriented nanotwins, where the average grain size decreased from 118 nm to 78 nm. Within the same current density range, the Ni film obtained from the PEG10000-containing bath presented fine nanograins with multifold nanotwins (e.g., fivefold nanotwins) in random orientations with the average grain sizes of around 10 nm, little influenced by the current density. Such microstructure transition could be attributed to that the addition of PEG facilitated the formation of twins, and higher MW PEG induced a greater inhibition effect, promoting significant grain refinement.

Investigation on surface generation mechanism of single-crystal silicon in grinding: Surface crystal orientation effect

Investigation on surface generation mechanism of single-crystal silicon in grinding: Surface crystal orientation effect

Mechanism of Pt3Co nanocatalysts to improve the performance for oxygen reduction reactions: DFT study on oxygen adsorption and durability of different facets

Pt3Co nanocatalyst shows better oxygen reduction reaction (ORR) activity and durability toward Pt. In this paper, the oxygen adsorption, durability and the ORR mechanism of Pt3Co are investigated based on density functional theory (DFT) calculations by CASTEP code. The adsorption energy of O atom at each site on (100), (110), and (111) surfaces indicated that the adsorption strength of O atom on Pt3Co surface follows the order (100) > (110) > (111). In addition, the ORR mechanism is explored through the electron density difference, d-band center, and the ORR elementary reactions. The results are consistent with the tendency for adsorption energy and prove that the O hydrogenation step is the rate-determining step on Pt3Co (111). Furthermore, the calculation of surface Pt vacancy formation energy reveals that the Pt3Co (111) catalyst has the best durability. The results could guide the design of surface crystal orientation of Pt3Co nanocatalyst for ORR.

Termination Control of (001) and (110) NdGaO3 Single-Crystal Substrates by Selective Chemical Etching

Controlling the surface morphology and composition of the perovskite substrates is a critical aspect in tuning the final properties of the deposited films and of their interfaces. The paper reports on a chemical etching method developed for (110) and (001) NdGaO3 single crystal substrates in order to obtain a well-defined GaO2−x-terminated surface. The etching process is based on a HF + NH4OH solution and includes an annealing step performed in air or under O2 flow at temperatures of 800–1000 °C. In order to obtain the desired composition and surface morphology, the etching procedure was optimized for the vicinal step density at the surface and substrate crystal orientation. Growth nucleation studies of one-unit-cell MeO films (Me = Ti, Sr, Ba) on chemically etched and on only annealed substrates were performed in order to determine the composition of the substrate topmost layer. The results indicate that the chemically etched NdGaO3 substrate surface has a predominantly GaO2−x termination, with a lower free surface energy compared to the NdO1+x termination.

Interfacial charge transfer and electronic structure of diamond/c-BN heterointerface

In this work, the interfacial structures and electronic properties of diamond and cubic boron nitride heterostructures are investigated using first principles calculation. It is found that the n-type (p-type) surface doping appears at the heterostructures with interface CN (C—B) bonds, which is attributed to the interface charge transfer. The doping feature of heterostructures is determined by the interface bonds, and it is not related to the surface functionalization and crystal orientation. The areal electron (hole) density values are 6.57 × 1013 — 1.57 × 1014 cm−2 (2.24 × 1014 — 3.72 × 1014 cm−2). This work is helpful for promoting diamond applied in electronic and opto-electronic devices.

Planar and dendrite-free zinc deposition enabled by exposed crystal plane optimization of zinc anode

The low Coulombic efficiency and limited cycle life of zinc (Zn) metal anode resulting from the severe side reactions and dendrite growth are the major bottlenecks restricting the commercial applications of the rechargeable aqueous Zn metal batteries (ZMBs). Considering that the crystal orientation of the electrode surface determines the growth direction of the newly deposited metal, however, limited by the crystal heterogeneity of commercial Zn foil, it can easily lead to inhomogeneous deposition morphology. Therefore, Zn electrode with more exposed (002) plane is considered as an effective strategy for planar and dendrite-free Zn deposition. In this review, we first provide the advantages of the preferred Zn (002) plane for achieving flat Zn deposition and elucidate the effect of electrode surface crystal orientation on Zn metal deposition behavior by correlating crystallography and deposition morphology. Then, we summarize the recent progress in the design and optimization strategies for directional deposition of Zn metal along the (002) orientation. Finally, the challenges, potential solutions, and perspectives for further exploration of planar and dendrite-free Zn deposition are proposed, which are expected to spur more insightful works toward advanced aqueous ZMBs.

Anomalous durability of (001) plane against oxygen vacancy injection at electrode/rutile-TiO[formula omitted] interfaces

We have investigated the electro-coloration of a rutile TiO2 single crystal by the voltage-bias annealing in dry air between a point cathode and a flat anode. The electro-coloration is due to the conductive VO filament that grows from the cathode/TiO2 interface to mm size. We proposed that the growth mechanism of this macroscopic size VO filament is the oxygen (O2−) transfer reaction at the anode interface followed by the thermally assisted-electric field-induced VO diffusion to the cathode. It was found that no electro-coloration occurs on (001), whereas it occurs on (110) and (100). This striking contrast between the surface crystal orientations was found to be due to the anisotropic VO diffusion that was found to be much faster perpendicular to [001] than parallel. Accordingly, VO is not injected into the anode/(001) interface in the oxygen transfer reaction. The proposed mechanism was examined by the surface-sensitive TOF-SIMS and the bulk-sensitive dynamic SIMS for analyzing the VO spatial distribution using the 18O isotope tracer. The anomalous durability of the (001) plane against the VO injection suggests that the atomic arrangement of TiO2 at the electrode interface is crucial for controlling the VO filament growth in resistive switching devices.