Surface Morphology Research Articles

Cobalt ferrite (CoFe2O4)–activated carbon fabric (ACF) based composite electrode material for supercapacitor application

In the present article, rayon based activated carbon fiber/fabric (ACF) has been developed and explored as an active electrode material in combination with metal oxide for ultracapacitor application. Herein, the ACF is derived from rayon-based carbon fabric through activation and carbonization processes in a tubular furnace and prepared composite material of cobalt ferrite (CoFe2O4, Cof) and activated carbon fabric/fiber. The ACF, cobalt ferrite, and electrode material derived thereof are analyzed by FTIR, XPS, BET surface area analyzer, and XRD methods. The surface morphology and composition of prepared composite is examined by FESEM and EDX. The electrochemical properties of Cof-ACF composite are scrutinized by cyclic voltammetry. The composite material produces considerably high electrochemical supercapacitances in the order of 1287 F/g and 788 F/g at a potential sweep rate of 2 mV/s in 0.5 M phosphoric acid and 0.5 M sulphuric acid electrolytes, respectively. The electrochemical behavior of the cobalt ferrite decorated ACF electrode material exhibits a slightly higher energy density (176.98 Wh/kg) in H3PO4 than in H2SO4 (150.79 Wh/kg) electrolyte. The stability (~74 %) of electrode materials is retained even after 3500 cycles of charge/discharge in acid electrolytes. Thus, Cof-ACF composite material could be used as a cost-effective, compact, and light-weight electrode material with enhanced stability and improved performance for ultracapacitor and energy storage device applications in acid electrolytes.

Experimental study of picosecond laser-assisted grinding of GH4169 nickel-based superalloy

The nickel-based superalloy GH4169 exhibits excellent thermal stability and fatigue resistance, making it widely utilized in the aerospace and marine manufacturing industries. However, the high mechanical strength of the nickel-based superalloy GH4169 leads to issues such as high grinding forces during grinding and poor surface morphology of the material after grinding. To improve the processing quality of GH4169, this study employs ultrafast pulse laser texturing to create two distinct biomimetic structures on its surface. The study explores the impact of laser parameters on both the recast layer and surface hardness. Subsequently, grinding experiments are conducted on both structured and non-structured workpieces. The grinding forces and surface roughness during grinding are analyzed, and the surface morphology of the workpiece after grinding and the corrosion resistance of the material are also tested. According to the test results, the grinding forces of the fishbone-like and nacre-like structure workpieces are reduced compared with those of the non-structured workpieces, and the maximum tangential grinding forces are reduced by 38.54 % and 35.98 %, and the maximum normal grinding forces are reduced by 30.24 % and 29.6 %, respectively. In addition, the corrosion resistance of the surface of the structured workpieces after grinding is better compared to the non-structured workpieces, and the best corrosion resistance is obtained for the fishbone-like structure.

Does the internal surface treatment technique for enhanced bonding affect the color, transparency, and surface roughness of ultra-transparent zirconia?

To investigate the effects of different surface treatments and thicknesses on the color, transparency, and surface roughness of ultra-transparent zirconia. A total of 120 Katana ultra-translucent multi-layered zirconia specimens were divided into 12 groups according to the thickness (0.3, 0.5, and 0.7mm) and surface treatment (control, airborne particle abrasion [APA], lithium disilicate coating, and glaze on). Color difference (ΔE00) and relative translucency parameter (RTP00) were calculated using a digital spectrophotometer. The surface roughness (Ra, Rq, Sa, and Sq) was measured using a non-contact profile scanner. The surface morphologies and microstructures of the samples were observed using a tungsten filament scanning electron microscope. Statistical analyses were performed by one-way and two-way analysis of variance (ANOVA) followed by post hoc multiple comparisons and Pearson's correlation (α = 0.05). The results showed that the surface treatment, ceramic thickness, and their interactions had significant effects on ΔE00 and RTP00 (p < 0.001). The surface treatment significantly altered the micromorphology and increased the surface roughness of the ceramic samples. APA exhibited the lowest transparency, largest color difference, and highest surface roughness. Zirconia with 0.3mm and 0.7mm thicknesses showed strong negative correlations between Sa and RTP00. The three internal surface treatments significantly altered the surface roughness, color difference, and transparency of ultra-transparent zirconia. As the thickness increased, the influence of the inner surface treatment on the color difference and transparency of zirconia decreased. For new zirconia internal surface treatment technologies, in addition to considering the enhancement effect on the bonding properties, the potential effects on the color and translucency of high-transparency zirconia should also be considered. Appropriately increasing the thickness of zirconia restorations helps minimize the effect of surface treatment on the optical properties.

A Scalable and Surfactant-Free Emulsion Method for Producing Microbeads from Varied Biomass Feedstocks.

Despite national and international regulations, plastic microbeads are still widely used in personal care and consumer products (PCCPs). These exfoliants and rheological modifiers cause significant microplastic pollution in natural aquatic environments. Microbeads from nonderivatized biomass like cellulose and lignin can offer a sustainable alternative to these nondegradable microplastics, but processing this biomass into microbeads is challenging due to limited viable solvents and high biomass solution viscosities. To produce biomass microbeads of the appropriate size range for PCCPs (ca. 200-800 μm diameter) with shapes and mechanical properties comparable to those of commercial plastic microbeads, we used a surfactant-free emulsion/precipitation method, mixing biomass solutions in 1-ethyl-3-methylimidazolium acetate (EMImAc) with various oils and precipitating with ethanol. While yield of microbeads within the target size range highly depends on purification conditions, optimized protocols led to >90% yield of cellulose microbeads. Kraft lignin was then successfully incorporated into beads at up to 20 wt %; however, higher lignin contents result in emulsion destabilization unless surfactant is added. Finally, the microbead shape and surface morphology can be tuned using oils of varying viscosities and interfacial tensions. Dripping measurements and pendant drop tensiometry confirmed that the higher affinity of cellulose for certain oil/IL interfaces largely controlled the observed surface morphology. This work thus outlines how biomass composition, oil viscosity, and interfacial properties can be altered to produce more sustainable microbeads for use in PCCPs, which have desirable mechanical properties and can be produced over a wide range of shapes and surface morphologies.

Investigation of open air and under water laser surface texturing on surface roughness and wettability of Al-Mg alloy

Aluminum-Magnesium (Al-Mg) alloy is widely used in aerospace and marine related applications due to its high corrosion resistance, tensile strength and ductility properties. However, due to hydrophilic nature, its applications are restricted in areas where water absorption may cause problems like corrosion. In this research work, high speed laser texturing was carried out on Al-Mg alloy (AA5754) to improve hydrophobic properties of the material surface. Four different types of pattern, namely lines, grids, concentric circles and concentric rectangles were created on the material surface using a nanosecond fiber laser. Scanning speed was varied at two levels i.e., 500 mm/s and 1000 mm/s. Line density of texture designs was also varied at two levels of 10 lines per mm and 15 lines per mm. The texturing process was carried out in two different processing environment namely open air and in underwater condition. Distilled water with 1 mm thickness above the surface was used during underwater texturing condition. Surface morphology, surface roughness and wettability of all the surfaces were studied for all the experimental conditions. It was observed that lower scanning speed of 500 mm/s resulted in higher values of surface roughness and contact angles. Also, larger texture density leads to lower surface roughness and contact angles for all the pattern designs. Among all the studied texture patterns, grid structures, textured at 500 mm/s of scanning speed resulted in largest surface roughness and surface hydrophobicity.

Anisotropy of surface morphology of carbonate rocks after reaction with acid

AbstractIn acid fracturing, acid is injected into artificial fracture to dissolve the rock, and the rock surface is shaped into the non-uniform morphology. This non-uniform morphology is the main cause of fracture conductivity after acid etching. The effects of acid type, flow rate, contact time and rock type on the non-uniform morphology of acid-etched rock surface have been studied. However, when the direction of acid flow is determined, the difference of dissolution characteristics in different directions of rock surface is not investigated. In this paper, acid rock reaction experiment and analysis of rock surface morphology after acid etching are carried out by using rock samples with flat surface. The difference of morphological characteristic parameters of rock surface in different directions under the condition of acid flow is discussed. It was found that the mean drop height, drop height range and roughness coefficient increase with the increase of acid rock reaction rate on flat rock surface. The morphological characteristic parameters of acid-etched rock face of limestone are greater than those of dolomite, which is conducive to forming acid-etched channels. According to the statistics of all experimental data, the larger average drop height of rock surface is distributed in the direction of parallel acid flow, the larger drop height range is distributed in the direction of vertical acid flow and other directions, and the larger roughness coefficient is distributed in other directions.

Dope dyeing of tannic acid modified ultra‐high molecular weight polyethylene fabric

AbstractIn this study, we examined dyeing behavior of tannic acid modified ultra high molecular weight polyethylene fabric. Whole study was conducted to see the effect of tannic acid on dope dyeing performance of the fabric. Tannic acid and its complex with sodium salt TA‐Na+ complex were used for pretreatment. After dope dyeing, the color strength of fabrics, color fastness, surface morphology, and fiber structure were characterized by k/s value, color difference, scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR), respectively. The effect of treatment conditions was also discussed. The results had shown better color strength and washing fastness were obtained after tannic acid treatment, especially after TA‐Na+ complex treatment. SEM observation indicated the tannic acid adhesion on fabric surface. Both EDS and FTIR results showed the enhancement of surface polarity. And the UHMWPE fabric treated with 1% (w/v) TA‐Na+ with pH ranging 4–5 for 6 h showed better color durability over time. Approach was suitable because of sustainable, green behavior of tannic acid and entire process had a low cost.

Investigation on the Mechanical Properties of Wood-Plastic Composites for theApplication of Ceiling Panels

Abstract Wood-plastic composites are relatively novel composite materials that consist of a blend of wood flour waste with high-density polyethylene and polypropylene plastic waste, designed for use in ceiling applications. Various samples were produced using different ratios from the total weight, including 20:80, 30:70, and 40:60, with sieve sizes of 0.425mm, 1.18 mm, and 2mm. The composites were created by melting plastics and sawdust at a temperature of1800c utilizing the hot-press moldings technique employing diverse formulations. The properties of sample composites were analyzed experimentally based on ASTM standards to investigate water absorption levels as well as flexural strength, impact resistance hardness along with surface morphology via the design of experiments. This research study indicates that nine composite formulations consisting of HDPE and PP plastics combined with wood flour can produce favorable physio-mechanical properties. Among these various combination specimens tested in this study FS3/FC30N exhibited excellent physio-mechanical properties; including desirable values such as water absorption level at 5.5103%, flexural strength at 61.12 Mpa, impact resistance measuring 33.45J/cm2, and hardness rating up to 80 RHB. Thus it is highly recommended for use in chipboard ceiling panel applications due to its potential benefits.

Integrated choline chloride/citric acid-microwave pretreatment for efficient nanolignin extraction and bioethanol production from cocoa pod husk waste

The necessity to address environmental issues has driven efforts toward exploring sustainable bio-based materials as a viable alternative to conventional energy sources. The current study explores the utilization of cocoa pod husk (CPH) biomass for lignin extraction and cellulose production, aiming to contribute to the eco-friendly production of lignin nanoparticles and bioethanol. A synergistic green deep eutectic solvent (DES) (choline chloride/citric acid)-microwave method was employed to effectively fractionate CPH biomass, resulting in an impressive 77.58% lignin removal at 600 W microwave power. The extracted lignin (211.56 mg/g biomass) was utilized to synthesize lignin nanoparticles that were subsequently characterized. Enzyme-driven hydrolysis of the residual cellulose yielded a reducing sugar content of 198.34 mg/g biomass, demonstrating a saccharification efficiency of 70.78%. Fermentation of monomeric sugars by Saccharomyces cerevisiae and Scheffersomyces stipitis, respectively, gave a maximum ethanol yield of 130 mg/g biomass with a high fermentation efficiency (67.17%). The alterations in the CPH's surface structure and morphology following sequential pretreatment were assessed through FT-IR, BET, and SEM analyses, facilitating effective enzymatic hydrolysis. The current investigation adds to the increasing recognition of sustainable approaches in leveraging waste biomass resources toward a more environmentally conscious future.

Scaffold microstructure evolution via freeze‐casting and hydrothermal phase transformation of calcium phosphate

AbstractExtensive research efforts have been focused on customizing the microstructure, macrostructure, and phase composition of calcium phosphate for enhanced biocompatibility and bioactivity in scaffolds for bone substitutes. Despite significant progress, achieving precise phase composition and microstructure remains a challenge, primarily due to the necessity of scaffold sintering. This study addresses the challenges in developing customized patient‐specific bone substitutes by proposing a sequential approach that reduces processing steps while providing control over the phase and morphology of the scaffolds’ structure. The methodology utilizes freeze‐casting and sintering for highly porous the scaffolds’ preparation, followed by hydrothermal treatment to modify the microstructure. The introduction of CaCO3 induces a phase transformation of tricalcium phosphate, increasing the hydroxyapatite content, while the overall macrostructure retains the characteristics of freeze‐casting. The surface morphology undergoes a transition from equiaxial grains to whiskers‐like structures and hexagonal rods, impacting compressive strength. Following hydrothermal treatment, the formation of whiskers‐like hydroxyapatite grains leads to a notable strength increase from 2.8 to 5.7 MPa. Remarkably, the scaffolds undergo nearly complete phase transformation, shifting from 100% tricalcium phosphate to 99% hydroxyapatite, all while conserving the macrostructure.

Phase Preparation of Xiao-chai-hu Decoction and its Pharmacodynamics of Acute Liver Injury.

Self-emulsifying nano-phase of traditional Chinese medicine are a research hotspot. Xiao-Chai-Hu decoction is a commonly used compound decoction in clinical practice, which is of great research significance. The aim of this study was to isolate and characterize the self-emulsifying nano-phase and other phases of Xiao-Chai-Hu decoction, and to study the effects of each phase on acute liver injury. The liquid medicine was prepared employing centrifugation followed by dialysis. Single- factor investigation methodology was utilized to optimize the preparation parameters for both phases. Characterization of the formulated phase involved analyses such as surface morphology assessment, measurement of nanoparticle size and Zeta potential using an analyzer, observation of the Tyndall effect, conducting diffusion and dilution tests, examination under a microscope, and structural visualization via transmission electron microscopy (TEM). Furthermore, an acute liver injury model was established in rats through intraperitoneal injection of D-Galactosamine (D-Gal- N). To assess hepatic function and oxidative stress status, serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content in liver tissue were quantified. The liver coefficients for each group were calculated as an additional parameter. For histopathological evaluation, liver tissue sections from the experimental group were stained with Hematoxylin and Eosin (H&E) and examined microscopically under light conditions. These revisions aim to enhance clarity, correct minor grammatical errors (such as capitalization of "HE" to "H&E"), and ensure a smoother flow of information without altering the scientific content of your original text. Successful establishment and separation of four distinct phases were achieved, including the self-emulsifying nano-phase, precipitation phase, suspension phase, and true solution phase. The self-emulsifying nano-phase was characterized as spherical particles with an average diameter of approximately 100 nm. Pharmacodynamic assessments revealed that both Xiao-Chai-Hu decoction and its self-emulsifying nano-phase significantly reduced liver coefficients and alanine aminotransferase (ALT) levels compared to controls (P<0.05). However, no statistically significant differences were observed in regards to aspartate aminotransferase (AST) concentrations, malondialdehyde (MDA) content, or superoxide dismutase (SOD) activity between the treatment groups and control (P>0.05). These findings indicate that both Xiao-Chai-Hu decoction and its self-emulsifying nano-formulation ameliorated D-GalN-induced acute liver injury, albeit without statistically distinguishable efficacy between them (P>0.05). The presence of a self-emulsifying nano-phase within Xiao-Chai-Hu decoction is confirmed, and this nano-phase emerges as a therapeutically efficacious component in mitigating acute liver injury.

Mechanical and Structural Characterization of Resole Resin Composites Reinforced with Sabai Grass-Derived Cellulose Fibers

Cellulose fibers were extracted from Sabai grass (Eulaliopsis binata) using mechanical and chemical treatments. The grass was ground to ~250 µm powder and bleached with hydrogen peroxide and acetic acid. The bleached fibers were treated with 6% sodium hydroxide solution and incorporated into resole resin at various weight percentages to prepare the composites. The prepared samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and compressive strength tests. The XRD and FTIR showed a nanometric crystallite size of 3.84 nm and effective removal of non-cellulosic compounds, respectively, leading to a compressive strength increase from 15.60 MPa to 25.26 MPa at 3 wt.-% cellulose fiber. The compressive strength improved up to 3 wt.-% cellulose fiber, which however declined upon adding more filler. SEM revealed modified surface morphology in the composites with cellulose fibers.

Human surface morphology representation and shape subdivision driven by space vector on female “waist-to-thigh” zone

Human surface morphology representation and shape subdivision driven by space vector on female “waist-to-thigh” zone

Enhanced Corrosion Resistance of Mild Steel in Acidic Media Using PVA‐Chitosan‐Dopamine Composite Coatings

AbstractIn this study, corrosion control of mild steel in acidic media was conducted in the presence of polyvinyl alcohol (PVA)‐chitosan and PVA‐chitosan‐dopamine composite coatings. Weight loss, polarization, and electrochemical impedance spectroscopy (EIS) studies were conducted to study the protective mechanisms and performance of PVA‐chitosan coatings. The results showed a substantial reduction in weight loss, corrosion rates, and corrosion current densities for coated specimens indicating the effectiveness of the composite coatings. PVA‐chitosan and PVA‐chitosan‐dopamine coatings showed high inhibition efficiencies (IE) up to 90.65 % and 96.01 % respectively. The electrochemical findings were supported using surface characterization techniques such as SEM to obtain a complete understanding of the coatings’ morphology and composition. The topographical analysis confirmed that dopamine significantly influenced the surface morphology and behavior of the nanocomposite. The FTIR spectrum of composite B, which combined PVA and chitosan, exhibited notable changes, including a decrease in both the intensity and frequency of the OH band. The potential of PVA‐chitosan‐dopamine coatings as effective corrosion inhibitors for mild steel in acidic environments offered practical solutions for diverse industrial applications.

Fabrication, structural, morphological, and mechanical behaviour of fly ash doped clay ceramics based CO2 gas sensor

Various attempts have been made to fabricate fly ash-doped clay composites via solid state reaction method. Additionally, to investigate the structural, mechanical, surface morphology, and CO2 gas sensing behavior, the fabricated clay composites were sintered at three different temperatures 1000, 1100, and 1200 °C (COF1, COF2, COF3) for 4 h. The green and sintered densities of the fabricated composites were found to be in the range of 2.17–2.13 g cm−3 and 1.38 to 1.30 g cm−3. Further, various characterization techniques such as x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, universal testing machine (UTM) and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDAX) were carried out. Moreover, to determine the compressive strength and Young’s modulus values, a universal testing machine (UTM) was used. The fracture toughness of the fabricated composites, COF2 and COF3 were found to be 7.84 MPa-m1/2 and 2.22 MPa-m1/2. The COF3 composite exhibited a sensing response, response time, recovery time of 3.39 at 1200 ppm CO2, 16.95 s and 18.05 s respectively. Consequently, this porous clay composite can be fabricated in a cost-effective and eco-friendly manner, hence beneficial for CO2 gas sensing applications.

Assessment of biodegradability and biocompatibility: An experimental and comparative analysis of magnesium and magnesium-(zinc-tin)/hydroxyapatite composites

This study presents the fabrication and comparative assessment of biodegradation and biocompatibility behaviors of pure Mg, Mg/HA (Hydroxyapatite), Mg-Zn/HA, and Mg-Sn/HA composites with fixed 5 wt% HA and 1 wt% each of Zn and Sn, using novel ultrasonic-assisted rheo casting technology. Characterization techniques, including X-ray diffractometry and scanning electron microscopy integrated with energy dispersive spectroscopy, were employed to analyze phase formation, surface morphology, and elemental composition. Microhardness tests were conducted to assess indentation resistance, while in vitro corrosion performance was evaluated in simulated bodily fluid to compare degradation behavior. Results indicate a uniform distribution of reinforced particles within the matrix with minimal casting defects. Intermetallic phases MgZn and Mg2Sn precipitated along grain boundaries in Mg-Zn/HA and Mg-Sn/HA composites. The Mg-Sn/HA composite exhibited peak microhardness (94.8 HV) due to precipitation strengthening. In contrast, Mg-Zn/HA samples showed a low degradation rate (0.19 mm/yr) and H2 gas evolution rate (0.035 ml/mm2), attributed to uniform distribution of secondary phases and fine grains that mitigate galvanic cell formation and control degradation. Cell viability assay results demonstrated that Mg-Zn/HA composite outperformed all other samples, showing a 94% relative cell growth rate of osteosarcoma MG-63 cells after 2 h of incubation, attributed to strong apatite formation (rich in Ca and P) on the surface post-immersion, promoting cell proliferation.

Development of Novel Peptide Inhibitors Adapted to the Surface Property and Morphology of S Protein RBD

Development of Novel Peptide Inhibitors Adapted to the Surface Property and Morphology of S Protein RBD

Synthesis and characterization of additively manufactured microcapsule‐reinforced polylactic acid composites for autonomous self‐healing

AbstractMaterial extrusion‐based additive manufacturing (AM) process builds the objects/structures through a precise feedstock deposition in a layer‐by‐layer manner. Polylactic acid (PLA) is a popular biodegradable feedstock in AM, while octyl methoxycinnamate (OMC) is known for its eco‐friendliness and ultraviolet (UV) protection properties. The present study focuses on the novel infusion methodology of OMC‐based microcapsules into PLA to develop self‐healing composite filaments. Post‐composition iterations, the optimum compositions for the filler and plasticizer were determined, and the filaments were extruded. Microcapsule‐infused PLA and the neat PLA samples were printed as per the American Society for Testing and Materials (ASTM) standard. The uniaxial tensile test results showed that the failure strain endured by the microcapsule‐infused samples was about 10 times more than the neat PLA counterparts. It is attributed to the effective load distribution and the complex polymerization reaction (due to the interaction of OMC with the matrix). Fracture surface morphology of the samples via optical microscopy (OM) and field emission scanning electron microscope (FESEM) affirmed the strong PLA‐OMC interface. A depreciation in the Brinell Hardness for the microcapsule‐based samples was due to the localized indenter force, causing greater damage in a narrow area than microcapsule ruptures' healing ability.Highlights The optimized composition of PLA: plasticizer:microcapsule is 1:0.04:0.05. Microcapsule‐infused PLA has improved Young's modulus and failure strain. Interaction with microcapsules improves elastic behavior and self‐healing. FESEM reveals close bonding of microcapsule with the PLA matrix.

Structural, optical and magnetic properties of chemically grown copper oxide nanoparticles: An insight into anticancer activities

Self-assembling nanorods like copper oxide (CuO) nanoparticles (NPs) have been successfully synthesized using two different copper cationic precursors to investigate their structural, optical, and magnetic properties. These NPs are employed in anticancer applications. Both the CuO-NPs have been tested for their toxicity on human cells. The XRD patterns confirm the formation of monoclinic crystal structures for both the systems. The FESEM microstructural surface morphology shows high agglomeration and a typical elemental composition is evaluated from EDAX analysis. The HRTEM analysis reveals high crystalline CuO nanorods with diameters in the range of 60 ∼ 94 nm and 09∼ 22 nm for two different nanoparticles named CuO-NPs1 and CuO-NPs2, respectively. The optical band gap of CuO-NPs has been calculated from UV–visible absorption spectra and is found to be 2.18 eV and 2.55 eV for CuO-NPs1 and CuO-NPs2, respectively. FTIR analysis provides insights into the chemical compositions of both the CuO-NPs. Magnetization study using vibrating sample magnetometer (VSM) indicates antiferromagnetic-like properties associated with weak ferromagnetic behaviour. Cytotoxicity tests on MCF-7 cell lines show that CuO-NPs2 exhibit more pronounced effect with IC50 of 22.95 μg/mL. The toxicity of both the CuO-NPs are also assessed using human lymphocytes, suggesting that CuO-NPs could be promoted as anticancer agents while remaining non-toxic to biological systems.

Research on the surface morphology of titanium alloy ultrasonic elliptical vibration cutting considering flank extrusion and material rebound

Research on the surface morphology of titanium alloy ultrasonic elliptical vibration cutting considering flank extrusion and material rebound