Crystalline Microstructure Research Articles

Designing transition metal-based porous architectures for supercapacitor electrodes: a review.

Over the past decade, transition metal (TM)-based electrodes have shown intriguing physicochemical properties and widespread applications, especially in the field of supercapacitor energy storage owing to their diverse configurations, composition, porosity, and redox reactions. As one of the most intriguing research interests, the design of porous architectures in TM-based electrode materials has been demonstrated to facilitate ion/electron transport, modulate their electronic structure, diminish strain relaxation, and realize synergistic effects of multi-metals. Herein, the recent advances in porous TM-based electrodes are summarized, focusing on their typical synthesis strategies, including template-mediated assembly, thermal decomposition strategy, chemical deposition strategy, and host-guest hybridization strategy. Simultaneously, the corresponding conversion mechanism of each synthesis strategy are reviewed, and the merits and demerits of each strategy in building porous architectures are also discussed. Subsequently, TM-based electrode materials are categorized into TM oxides, TM hydroxides, TM sulfides, TM phosphides, TM carbides, and other TM species with a detailed review of their crystalline phase, electronic structure, and microstructure evolution to tune their electrochemical energy storage capacity. Finally, the challenges and prospects of porous TM-based electrode materials are presented to guide the future development in this field.

Enhanced supercapacitor performance of porous carbon through tuning maceral composition proportion of coal.

Porous carbons (PCs) have been widely investigated as electrode materials for supercapacitors. However, during the preparation process, intense pore formation reactions result in an amorphous carbon structure, which limits the rate performance of the electrode material. Herein, coal is chosen as a carbon source and making use of different reaction characteristics of vitrinite and inertinite with a KOH activator, an interconnected porous structure carbon material with an abundant graphite microcrystalline structure is obtained; the organic relationships between the ratio of vitrinite and inertinite, carbonization conditions, material structure and capacity performance were researched. At the ratio of vitrinite to inertinite of 1 : 2, the sample shows a specific surface area of 2507 m2 g-1 and its ID1/IG is 1.31, which is lower than that of raw coal (1.36). Due to the synergistic effect of the pore structure and graphite microcrystals, PC-900-40 exhibits an improved specific capacitance of 229.40 F g-1 at a current density of 1.0 A g-1, and even at a high current density of 10.0 A g-1 it delivers a specific capacitance of 170.04 F g-1. The PC-900-40//PC-900-40 symmetrical capacitor retains 96% of its initial capacitance after 20 000 cycles.

Experimental study on municipal sludge/coal co-combustion preheated by self-preheating burner: Self-preheating two-stage combustion and NOx emission characteristics

To achieve efficient and low-pollution sludge treatment, this study explored the first-time application of self-preheating combustion technology in sludge/coal co-combustion, and subsequently investigated the influences of sludge blending ratio (BR) and tertiary air types on self-preheating two-stage combustion and NOx emission characteristics in a 30 kW self-preheating combustion system with a novel two-stage down-fired combustor (DFC). This system was well adaptable for fuels, and still ran steadily even if BR was as high as 50 %. During preheating, properly increasing BR improved carbon microcrystalline structure of preheated carbon-based fuel and increased its specific surface area, but its carbon microcrystalline structure was gradually deteriorated at BR>20 %. Fuel properties of preheated coal gas were deteriorated with increasing BR. During combustion, combustion efficiency (η) increased first and then decreased with increasing BR, while NOx emission increased. For tertiary air nozzle located at top of burnout region, the structures of center symmetry and ring hedge had less effect on η and NOx emission, both of which remained at high levels, exceeding 98.5 % and 160 mg/m3. Notably, properly shifting injection position down reduced NOx emission significantly, albeit at the expense of reduction in η. Excessively low injection position had less effect on further NOx emissdddction.

Preparation of Nearly Stoichiometric SiC(Ti) Fibers with Highly Crystalline Microstructure from Polytitanocarbosilane

Preparation of Nearly Stoichiometric SiC(Ti) Fibers with Highly Crystalline Microstructure from Polytitanocarbosilane

Insights into orientation-dependent plasticity deformation of HfNbTaTiZr refractory high entropy alloy: An atomistic investigation

HfNbTaTiZr refractory high entropy alloy has emerged as a prospective structural material suitable for high-temperature applications owing to its remarkable combination of high strength, good tensile ductility and excellent high-temperature properties. However, the insufficient understanding of the mechanical responses of this refractory high entropy alloy has hindered the improvement of performance in alloy design and potential for engineering applications. Therefore, the orientation-dependent tensile behaviors of HfNbTaTiZr refractory high entropy alloy are investigated from nanoscale using molecular dynamics simulations. The simulation results show that the mechanical responses under uniaxial tension are strongly correlated to the crystallographic orientation with respect to the loading direction, and the highest Young's modulus and yield strength are achieved along [111] direction. In addition, the deformation twinning and phase transformations are charactered. The tensile behavior oriented along [001] direction is dominated by the BCC-FCC phase transformation, while that oriented along [110] or [111] direction by the BCC-HCP phase transformation. The results reveal the critical role of tensile direction in generating specific crystalline microstructures under high-strain-rate loading conditions, which can enlighten new design strategy in engineering refractory high entropy alloys with specific orientations for extreme environments.

Halloysite nanotubes decorated with Co(OH)F nanorods as a novel binary composite for the enhanced electrocatalytic water oxidation

Oxygen evolution reaction is central to several emerging electrochemical energy conversion and storage technologies. This study reports the synthesis, characterization, and OER electrocatalytic performance of binary nanocomposites composed of halloysite nanotubes (HNTs) and Co(OH)F. Five Co(OH)F/HNT with different compositions were fabricated by a facile hydrothermal synthesis. The crystalline phase and microstructure of the as-prepared materials were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized Co(OH)F (pristine or mixed with HNTs in the nanocomposites) revealed an orthorhombic crystal system with a nanorod morphology. The nanocomposite with ∼19 wt% of Co (designated as Co(OH)F/HNT_3) was found to possess an appreciably improved activity in OER compared to the pristine HNTs, Co(OH)F, and other Co(OH)F/HNT nanocomposites. Co(OH)F/HNT_3 displayed an overpotential of 252 mV (at the current density of 10 mA cm−2), a Tafel slope of 51.1 mV dec−1, and a robust operational performance under harsh alkaline conditions. Furthermore, nitrogen adsorption–desorption isotherms indicated a much higher specific surface area for this nanocomposite than its components. Overall, the versatile synthesis and outstanding catalytic performance of Co(OH)F/HNT_3 make it an auspicious earth-abundant transition metal-based electrocatalyst for OER in an alkaline medium.

Accelerated aging resistance, abrasion resistance and other properties of alkali-activated slag mortars containing limestone powder

The Earth's crust is widely recognized for its abundance of limestone (LS). Limestone powder (LSP) has a wide range of potential properties that make it suitable for various applications and fields. It has found extensive usage in Portland cement-based materials. Recently, the incorporation of LSP into geopolymers is becoming more of a concern than before and has become a hot topic. In this article, high range of LSP (2.5–50 wt%) was introduced into alkali-activated slag (AAS) mortars activated with NaOH and sodium silicate solution as a substitution of slag. For the first time, the effect of LSP on the accelerated aging resistance and abrasion resistance of AAS mortars was examined. In addition, the typical traditional routine properties such as flowability, setting time, mechanical strength, water absorption, and total porosity were studied. Sophisticated equipment was utilized to observe the changes in crystalline phases, hydration products, and microstructures of selected samples. The results showed higher flowability and longer setting time with including LSP. As the amount of LSP increased as the flowability and setting time increased. The introduction of 2.5–25% LSP positively affected the mechanical strength, aging resistance, abrasion resistance and transport properties. In contrast, the introduction of 35% did not show an essential change, whilst the introduction of 50% LSP negatively affected the mentioned properties.

High strength Y2O3-stabilized zirconia continuous fibers up to 1500°C: Crystalline phase and microstructure evolution as well as grain growth kinetics

For zirconia continuous fibers, tensile strength is a very important performance parameter, which is affected by the crystal phase, its stability, grain size, processing temperatures, and so on. In this paper, the crystalline phases were adjusted through the Y2O3 contents and heat treatment temperatures in the range of 1000–1500°C. We found that interfacial segregation of Y3+ at high temperatures led to crystal phase instability, which was observed near the grain boundaries of the 13.8YSZ fibers. At high temperatures, the grain growth of different fibers occurred to different degrees. The regularities between the tensile strength, the strength retention and temperature, Y2O3 contents were discussed in detail. According to the highest tensile strength of a single fiber and Weibull modulus m, we found that the 5.4YSZ fibers were the most stable with the highest tensile strength and slow grain growth rate. The average strength was 1.6 GPa after heat-treating at 1500°C and the strength retention rate was about 54% under 1500°C for 60 min. Finally, the twistable 5.4YSZ continuous fibers with high strength were obtained by dry spinning technology. These results can provide reliable theoretical support and data sources for its high-temperature applications.

Promotion effect of Ga3+ in ZnAlGa-x mixed oxides obtained from their layered double hydroxides on the enhancement in the transient photocurrent response, the inhibition in the recombination rate of photogenerated (e−, h+) charges and the photocatalytic activity in the photodegradation of 4-chlorophenol

ZnAlGa-x (x = 0, 0.5, 0.8, 1.0, 2.0 and 3.0 mol % of Ga3+) mixed oxides (MOs) obtained by calcination of their corresponding layered double hydroxides (LDHs) were characterized and evaluated in the photodegradation of 4-chlorophenol in aqueous media (4-CP) using UV light irradiation. Structural studies by X-ray diffraction (XRD) of ZnAlGa-x MOs indicated that the incorporation of a small molar concentration of Ga3+ (0.5–0.8 mol %) within the ZnAl LDH structure changed the micro-crystalline structure to an amorphous structure. A small molar content of Ga3+ in the ZnAlGa3+ MOx promotes the formation of a high amount of structural oxygen vacancies as evidenced by Raman and EPR spectroscopy studies. Transient photocurrent response (TPC) and fluorescence spectroscopy experiments reveal that the incorporation of a small molar concentration of Ga3+ in the structure of ZnAl MO promotes the enhancement in the transient photocurrent response, the separation of photogenerated charges and the inhibition of the recombination rate of (e−, h+) pairs. Furthermore, ZnAlGa-x MOs with a small molar concentration of Ga3+ reduced their band gap energies below of 3.0 eV. ZnAl MO photodegradated 69.0 % of 4-CP after 4 h of reaction. However, the photoconversion % of 4-CP increased to 80–90 % at 3 h of reaction using ZnAlGa-x MOs with a small molar concentration of Ga3+. ZnAlGa-x with small Ga3+ concentration mineralized approximately 70–75 % of total disolved organic carbon at 3 h of reaction. The photocatalytic degradation reaction of 4-CP fitted well to a pseudo-first order kinetics of Langmuir-Hinshelwood-type. The kinetic parameters of ZnAlGa-x MOs confirmed that ZnAlGa-0.8 MO was the best photocatalyst to photodegradate 4-CP in aqueous media. The highest photocatalytic activity and efficacy of ZnAlGa-0.8 MO to mineralize 4-CP in aqueous medium may be due to its higher amount of oxygen vacancies contained in its structure promoting a better separation of charges and the inhibition of the recombination rate of photogenerated (e−, h+) charges.

Effect on the oxidation characteristic at lignite of two types of endogenous microorganisms from coal

In recent years, coal biotechnology has gained considerable popularity due to its economic, eco-friendly, and sustainable advantages, which offer a novel perspective and pathway for the development of green technologies aimed at preventing and controlling coal spontaneous combustion (CSC). Two endogenous microorganisms from lignite were succeeded in extracting in this work, namely Aspergillus and Bacillus velezensis. Subsequently, the effect of these microorganisms on the microscopic structure and macroscopic oxidation characteristics of coal was investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The results revealed that both Aspergillus and Bacillus velezensis treatments altered the microcrystalline structure of the coal, disrupting the aliphatic hydrocarbon structure and oxygen-containing functional groups of the coal molecules. Particularly, the OH − O hydrogen bond of two kinds of microbial treatment coal samples content respectively decreased significantly by 17.29 % and 11.06 % compared to the raw coal sample. However, the effects of different microorganisms on coal varied. Thermodynamic behavior demonstrated that the critical temperature of the two treated coal samples was delayed by 29.44 °C and 26.62 °C, and the ignition temperature was delayed by 11.31 °C and 5.18 °C. Overall, all characteristic temperature points of the Aspergillus group were delayed, but the maximum weight loss rate temperature and the burn-out temperature of the Bacillus velezensis group exhibited slight advancement. The thermal mass loss characteristics also changed during the oxidation combustion stage. In addition, the average activation energies of oxidized combustion stage calculated by the Kissinger-Akahira-Sunose method were 74.26 kJ/mol and 78.61 kJ/mol, respectively, and 82.41 kJ/mol and 86.15 kJ/mol for the Friedman method, which were both increased compared to the raw coal. The results indicate that both Aspergillus and Bacillus velezensis have effects with varying degrees on the coal oxidation characteristics. It can be observed that the effect of treatment with Aspergillus is better than Bacillus velezensis from the overall changes in characteristic temperature points. This work lays the foundation for investigating the effect of microbial action on the oxidative properties of CSC.

Regulating Graphitic Microcrystalline and Single‐Atom Chemistry in Hard Carbon Enables High‐Performance Potassium Storage

AbstractHard carbon (HC) has attracted considerable research interest as the most promising anode for potassium‐ion batteries (PIBs) due to its tunable interlayer spacing and abundant voids to accommodate K+. However, the practical application of hard carbon is severely hampered by low initial Coulombic efficiency (ICE) and high plateau potential. Herein, a manganese ion‐catalyzed pyrolysis strategy is explored to regulate the graphitic microcrystalline structure and localized electron distribution in hard carbon that greatly improve K+ plateau storage and ICE. Systematic experimental measurements, in situ/ex situ observations, dynamic analysis, and density functional theory calculations elucidate that the introduction of Mn2+ ions could catalyze the formation of short‐ordered graphitic nanodomains in hard carbon to provide abundant insertions of K+, and meanwhile induce localized electron distribution through the Mn─N3─C coordination structure to enable dynamic K+ diffusion and electron transfer kinetics. Consequently, the modulated hard carbon exhibits a high low‐potential–plateau capacity, excellent rate capability, and high initial Coulombic efficiency in potassium half‐cell configurations. More importantly, the charge storage mechanism of “adsorption–intercalation” is proposed based on the correlation between carbon structures and discharge/charge plateau. This work provides an in‐depth insight into the fundamentals of microstructure regulation of hard carbon anode for high‐performance PIBs.

Owens-Wendt Method for Comparing the UV Stability of Spontaneous Liquid-Repellency with Wet Chemical Treatment of Laser-Textured Stainless Steel.

The liquid-repellent properties of AISI 304 stainless steel surfaces textured with a femtosecond laser were studied, both after spontaneous hydrophobization and when treated with stearic acid and octyltrimethoxysilane. Surface topography has been shown to play a critical role in determining these properties. Although textures containing only LIPSS exhibited poor liquid-repellency, the performance was significantly improved after engraving the microtexture. The most effective topography consisted of 45 µm-wide grooves with a pitch of 60 µm and protrusions covered with a rough microcrystalline structure. Liquid-repellency, chemical treatment efficiency, and UV resistance were compared using derived Owens-Wendt parameters. The surface of femtosecond-laser-textured steel after spontaneous hydrophobization was found to be significantly less stable under UV irradiation than surfaces treated with stearic acid or octyltrimethoxysilane modifiers.

Effect of Reaction Temperature on the Degradation and Oxidation Behavior of Particulate Matter by Nonthermal Plasma

Diesel particulate matter (PM), especially small particle size PM, has been highlighted as a hazard to the environment and people. Nonthermal plasma (NTP) has shown significant low temperature (<200°C) advantage for PM degradation. In this paper, we conducted online PM degradation experiments at different reaction temperatures with a self-built NTP injection system to investigate the changes of PM particle size distribution, micro-nano structure, graphitization degree and oxidation characteristics of elemental carbon (EC) before and after NTP action. The maximum removal rate increased from 90 ℃ (25% load) to 130 ℃ (100% load) with the increase of the load, and there was a “trade-off” effect between PM decomposition and NTP pyrolysis. The average microcrystalline length, microcrystalline spacing and microcrystalline curvature of PM particles showed an overall trend of decreasing and then increasing with the increase of temperature. When the reaction temperature was 130 ℃ (75% load), the microcrystalline structure parameters of the carbon particles showed extreme values, and the newly exposed “shells” were rearranged under the action of van der Waals force, and the graphitization of PM increased and the overall oxidation activity was weakened. The reaction between NTP and carbon particles goes through the process of surface oxidation, simultaneous oxidation of surface and interior, and the fragmentation of carbon particles to complete disappearance.

The influence of microcrystalline structure and crystalline size on visible light transmission of polyvinyl alcohol optical films

The crosslinking degrees and microcrystalline structure determine the light transmission of polyvinyl alcohol (PVA) optical films and mechanical properties. Preparing a PVA optical film satisfying these two aspects with a low swelling propensity is still challenging. Herein, PVA optical films were prepared by solution casting with environment-friendly water as a solvent. Based on PVA's unique monoclinic lamellar crystal structure, the optical properties, such as light transmission and haze, were revealed by changing the original molecular weight, polymer concentration, and heat treatment conditions. We systematically investigated the effect of the original molecular weight and polymer concentration on the PVA crosslinking degrees. The crystal size effect on the optical properties was investigated through a heat treatment for the crosslinked PVA films. The rotational rheometer and swelling tests revealed the PVA crossling degrees. DSC and XRD are utilized to systematically investigate the relationship between the crystalline structure of PVA and its optical transparency and mechanical properties. The PVA optical films (F2099-8%) derived from 8 wt% PVA2099/water solution exhibit excellent light transmission with transparency of 90.2 % and haze of 0.4 % due to the smallest crystal size of 3.29 nm. An appropriate heat treatment process could further improve the mechanical and swelling-resistant properties. The F2099-8% sample after heat treatment (<200 °C, 30 min) had a significant enhancement of mechanical strength (200 % increase) and swelling resistance (300 % decrease), but only 6 % transmittance decreased, and 2 % haze increased because of crystal size increasing. The PVA optical films prepared in this work showed relatively high light transmission and high mechanical and swelling-resistant properties, which have a good potential application in display panels and camera lenses.

A Universal Method for Regulating Carbon Microcrystalline Structure for High-Capacity Sodium Storage: Binding Energy As Descriptor.

Sodium-ion batteries (SIBs) are attracting worldwide attention due to their multiple merits including abundant reserve and safety. However, industrialization is challenged by the scarcity of high-performance carbon anodes with high specific capacities. Here, we report the metal-assisted microcrystalline structure regulation of carbon materials to achieve high-capacity sodium storage. Systematic investigations of in situ thermal-treatment X-ray diffraction and multiple spectroscopies uncover the regulation mechanism of constructing steric hindrance (C-O-C bonds) to restrain the aromatic polycondensation reaction. The carbon precursor of polycyclic aromatic hydrocarbon-type pitch contributes to a high carbon yield rate (40%) compared with those of resin and biomass precursors. The as-synthesized carbon materials deliver high capacities of up to 390 mAh g-1, surpassing many reported carbon anodes for SIBs. Through correlating specific capacity with ID/IG values in Raman spectra and theoretical calculation of carbon materials regulated by different metal elements (Mn, Nb, Ce, Cr, and V), we identify and propose the binding energy as the descriptor for characterizing the capability of regulating the carbon microcrystalline structure to promote sodium storage. This work provides a universal method for regulating the carbon structure, which may lead to the controlled design and fabrication of carbon materials for energy storage and conversion and beyond.

Molecular aggregation state and electrochemical performance of mesophase pitch fluoride

Lithium/carbon fluoride batteries utilizing carbon fluoride as the cathode material have the highest energy density among primary batteries. However, the demanding synthesis conditions for carbon fluoride result in high-production costs, which hinders the widespread adoption of lithium/carbon fluoride batteries. Mesophase pitch fluoride, which exhibits microstructures similar to those of carbon fluoride, has the potential to be used as a low-cost cathode material. In this study, a facile low-temperature fluorination method was employed to synthesize a mesophase pitch fluoride with a high F/C ratio. Solvent-induced dipolar coupling was employed to segregate the mesophase pitch fluoride selectively into two distinct aggregated states with varying structures. When employed as a cathode material for lithium primary batteries, the ordered microcrystalline structure of the mesophase pitch fluoride exhibited a discharge capacity of 743 mA h g−1. Furthermore, it exhibited electrochemical behaviors that were distinguishable from those of conventional carbon fluoride materials. This study introduces a novel research perspective for exploring the viability of low-cost fluorinated pitches in the energy storage domain.

Utilization of investment casting shell waste in the production of cordierite-mullite-zircon composites for radiation shielding: The influence of La2O3 additive

Cordierite-mullite-zircon ceramic composites were produced via reaction sintering of investment casting shell waste, Al2O3, and MgO at 1350 °C. The influence of La2O3 addition on the crystalline phase composition, microstructure, densification behavior, mechanical strength, and radiation shielding capabilities of the cordierite-mullite-zircon composites has been investigated. The X-ray diffraction (XRD) analysis confirmed the successful synthesis of cordierite-mullite-zircon composites with up to 5 wt% La2O3 additive content. However, a higher La2O3 content, exceeding 7 wt% resulted in cordierite decomposition. Furthermore, the addition of La2O3 significantly enhanced the densification behavior and microstructural development, leading to improved flexural strength and enhanced shielding against fast neutron and gamma radiation. This research suggests the potential of the fabricated ceramic composites derived from investment casting shell waste for applications in radiation shielding.

Accelerated removal of sulfadiazine by heterogeneous electro-Fenton system with Pt-FeOX/graphene single-atom alloy cathodes

Heterogeneous electro-Fenton (EF) process is emerging as an attractive treatment technology for removal of sulfadiazine (SDZ), in which in situ generation of H2O2 and Fe(II) are crucial steps. In this study, Pt-FeOX/G was synthesized as a heterogeneous EF catalyst by incorporating Pt single atoms into a FeOX nanocrystal. The optimized Pt1-FeOX/G cathode exhibited an SDZ conversion of >90% within 30 min over a broad pH range (3–11). The Pt1-FeOX/G cathode under a strong alkaline medium exhibited very prominent selectivity to H2O2 via 2e− oxygen reduction reaction with a maximum H2O2 concentration of 211.93 mg L−1. The hydroxyl radicals in the cathodic chamber were mainly derived from the in situ conversion of generated H2O2 in the heterogeneous EF system. The structure-activity results of Pt-FeOX/G suggested that the SDZ removal efficiency was closely related to the decentralized morphology and electronic configuration of the Pt-FeOX microcrystalline structure. Three possible SDZ degradation pathways, dominated by S–N bond cleavage, were proposed based on the stage products. The toxicity of the major products was determined using the ecological structure-activity relationship model in conjunction with trophic aquatic organisms. This study demonstrated the feasibility of enhancing heterogeneous EF catalysis for antibiotic-polluted water using multifunctional single-atom alloy cathodes.

Petal-like Patterning of Polylactide/Poly (Butylene Succinate) Thin Films Induced by Phase Separation.

Biodegradable plastics are attracting attention as a solution to the problems caused by plastic waste. Among biodegradable plastics, polylactide (PLA) and poly (butylene succinate) (PBS) are particularly noteworthy because of their excellent biodegradability. However, the drawbacks of their mechanical properties prompts the need to compound them to achieve the desired strength. The characteristics of the interface of the composite material determine the realization of its final performance. The study of the interface and microstructure of composites is essential for the development of products from degradable polymers. The morphology evolution and microcrystal structure of spin-casted fully biodegradable (PLA/PBS) blend films were investigated using atomic force microscopy (AFM)-based nanomechanical mapping. Results show that intact blend films present an obvious phase separation, where the PBS phase is uniformly dispersed in the PLA phase in the form of pores. Furthermore, the size and number of the PBS phase have a power exponential relationship and linear relationship with PBS loading, respectively. Intriguingly, after annealing at 80 °C for 30 min, the PLA phase formed an orderly petal-like microcrystalline structure centered on the PBS phase. Moreover, the microcrystalline morphology changed from a "daisy type" to a "sunflower type" with the increased size of the PBS phase. Since the size of the PBS phase is controllable, a new method for preparing microscopic patterns using fully biodegradable polymers is proposed.

Investigation of the hydrophilic nature and surface energy changes of HfO2 thin films prepared by atomic layer deposition

The wettability of metal oxides, which is directly related to the surface free energy (SFE), is used in a wide range of robust functional coatings, from hydrophilic to hydrophobic. Because wettability is significantly affected by solid surface properties, several studies on the determinant factors and their correlations have been conducted through the thin-film coating of metal oxides. Herein, we found that HfO2 thin films deposited via atomic layer deposition (ALD) are intrinsically hydrophilic. Simultaneously, a thickness-dependent wettability change is observed. These observations were investigated by measuring water contact angles (WCAs), film surface compositions, roughness, morphologies, and microcrystalline structures of the ALD-grown HfO2 thin films. It was deduced that the surface oxygen species significantly affected the intrinsic hydrophilicity of HfO2 thin films. In addition, the crystalline orientations evolved with film thickness, and thermal annealing was used to determine the thickness-dependent WCA trend. In particular, the transformation of the preferred m(-111) crystal orientation with a low SFE had a dominant impact on the SFE change in the HfO2 thin films. Considering the lack of fundamental studies on the SFE of ALD-grown HfO2 thin films, we believe that this study will help understand the wettability of HfO2 and its overall surface science.