Changes In Surface Topography Research Articles

Analysis of Surface Topography Changes during Friction Testing in Cold Metal Forming of DC03 Steel Samples

Predicting changes in the surface roughness caused by friction allows the quality of the product and the suitability of the surface for final treatments of varnishing or painting to be assessed. The results of changes in the surface roughness of DC03 steel sheets after friction testing are presented in this paper. Strip drawing tests with a flat die and forced oil pressure lubrication were carried out. The experiments were conducted under various contact pressures and lubricant pressures, and lubrication was carried out using various oils intended for deep-drawing operations. Multilayer perceptrons (MLPs) were used to find relationships between friction process parameters and other parameters (Sa, Ssk and Sku). The following statistical measures of contact force were used as inputs in MLPs: the average value of contact force, standard deviation, kurtosis and skewness. Many analyses were carried out in order to find the best network. It was found that the lubricant pressure and lubricant viscosity most significantly affected the value of the roughness parameter, Sa, of the sheet metal after the friction process. Increasing the lubricant pressure reduced the average roughness parameter (Sa). In contrast, skewness (Ssk) increased with increasing lubrication pressure. The kurtosis (Sku) of the sheet surface after the friction process was the most affected by the value of contact force and lubricant pressure.

Process and Design Challenges for Hybrid Bonding

Achieving high-quality interconnect interfaces for fine pitch integration is crucial in today's advanced electronic systems. Among various interconnect options, hybrid bonding stands out as a superior choice due to its ability to accommodate a high input/output (I/O) count, enabling high-density memory integration, increased power delivery, and improved signal speed. To ensure the utmost quality in hybrid bonding, embedding Cu interconnects within the dielectric layer has proven effective. Furthermore, the surface planarization process, accomplished through chemical mechanical polishing (CMP), plays a pivotal role. In this regard, the final CMP process typically involves a meticulous two-step procedure involving copper bulk CMP followed by barrier CMP. The latter yields the desired surface finish crucial for successful hybrid bonding. Several key surface properties, including copper recess (referred to as dishing) in the vias, erosion and roughness of the dielectric layer, and surface topography changes from high-density to low-density copper vias, significantly impact the overall bond yield. To optimize these parameters, a comprehensive understanding of the design of the interconnect layer for the CMP process is essential. In this study, we explore the impact of via scaling and via density for interconnect pitches from 5 μm to 1 μm and the surface topography due to dummy vias of the final bonding surface.

Shape-Morphing Photoresponsive Hydrogels Reveal Dynamic Topographical Conditioning of Fibroblasts.

The extracellular environment defines a physical boundary condition with which cells interact. However, to date, cell response to geometrical environmental cues is largely studied in static settings, which fails to capture the spatiotemporally varying cues cells receive in native tissues. Here, a photoresponsive spiropyran-based hydrogel is presented as a dynamic, cell-compatible, and reconfigurable substrate. Local stimulation with blue light (455nm) alters hydrogel swelling, resulting in on-demand reversible micrometer-scale changes in surface topography within 15min, allowing investigation into cell response to controlled geometry actuations. At short term (1h after actuation), fibroblasts respond to multiple rounds of recurring topographical changes by reorganizing their nucleus and focal adhesions (FA). FAs form primarily at the dynamic regions of the hydrogel; however, this propensity is abolished when the topography is reconfigured from grooves to pits, demonstrating that topographical changes dynamically condition fibroblasts. Further, this dynamic conditioning is found to be associated with long-term (72h) maintenance of focal adhesions and epigenetic modifications. Overall, this study offers a new approach to dissect the dynamic interplay between cells and their microenvironment and shines a new light on the cell's ability to adapt to topographical changes through FA-based mechanotransduction.

Soft matter with magnetically oriented macro - micro structure for improving microwave absorption efficiency

The key challenge for the most widely used magnetic absorbers is how to simultaneously combine low filling with efficient electromagnetic absorption performance. This paper exploited carbonyl iron particles (CIPs) to develop some soft material that possessed orderly orientated structure via applying an external excitation signal, so as to reduce hyperosmotic threshold of conductive loss network, improve impedance matching pattern and thus modulate absorption efficiency. The arch test results showed that effective absorption band (EAB, RL<−10 dB) and reflection loss (RL) efficiency of oriented structure (40 wt%−300mT sample) was much higher than that of unoriented structure (60 wt%−0mT sample), and the reflection loss intensity was reduced to − 15.2 dB, especially EAB was expanded by 8.1 GHz, which significantly alleviated the critical conflict between low filling and electromagnetic loss performance. Also, it was attempted to reveal surface topography changes caused by multiple magnetized particles interaction, and how excitation signal intensity, magnetic particles filling concentration and structural parameters affect microwave absorption efficiency and bi-directional frequency conversion. Thus, a magnetic-manipulated absorbing material proposed laid a theoretical foundation for improving loss efficiency of magnetic materials at low filling concentration.

Fabrication of superhydrophobic surface by a dimensional change in surface topography of microchannel on polymer substrate through induction-aided hot embossing: parametric investigation and optimization

Hot embossing (HE) is a micro-fabrication technique employed to create micron-scale patterns on the polymer substrate. An in-house induction-assisted hot embossing (IHE) setup was fabricated to complete the embossing in a short duration as compared to traditional hot embossing process. This work alters the polymer surface topography to make it superhydrophobic for self-cleaning. Fiber laser machining was used to produce four-microchannel designs on an Aluminum-6061 plate in which the microchannel width was varied from 600 μm to 150 μm while maintaining a constant adjacent distance of 300 μm. This textured plate is employed as a mold in the IHE setup. IHE process parameters, embossing temperature, pressure, time, and deembossing temperature were varied to emboss the mold designs on a polyethylene terephthalate substrate. Thereafter, the embossed microchannel height, surface roughness, and water contact angle perpendicular to the embossed microchannels (WCA⟂) were calculated. The parametric analysis examined how operational factors affected the output. The experiment was done as per the central composite design (experimental design) part of the design-of-experiments useful in the response surface model. Parametric research demonstrates that embossed microchannel height and width had a maximum effect on WCA⟂. Type-IV microchannels with 150 μm width demonstrated the highest WCA⟂. The WCA⟂ was mostly impacted by embossed microchannel height; hence a regression model was created using type-IV channel height data. Analysis of variance showed that embossing temperature mainly impacts microchannel height. The recently invented Jaya-algorithm optimized this model to increase embossed microchannel height and WCA⟂. Setting the parameters at the best level predicted by Jaya-algorithm yielded an embossed microchannel height inaccuracy of 2.18%. The WCA⟂ measured on the surface of a sample prepared at the best parameters was found to be 154.71° 2°. Lastly, FTIR (Fourier-transform-infrared-spectroscopy) test showed no chemical composition change between the embossed and bare samples.

Multiprotein Adsorption from Human Serum at Gold and Oxidized Iron Surfaces Studied by Atomic Force Microscopy and Polarization-Modulation Infrared Reflection Absorption Spectroscopy.

Multiprotein adsorption from complex body fluids represents a highly important and complicated phenomenon in medicine. In this work, multiprotein adsorption from diluted human serum at gold and oxidized iron surfaces is investigated at different serum concentrations and pH values. Adsorption-induced changes in surface topography and the total amount of adsorbed proteins are quantified by atomic force microscopy (AFM) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS), respectively. For both surfaces, stronger protein adsorption is observed at pH 6 compared to pH 7 and pH 8. PM-IRRAS furthermore provides some qualitative insights into the pH-dependent alterations in the composition of the adsorbed multiprotein films. Changes in the amide II/amide I band area ratio and in particular side-chain IR absorption suggest that the increased adsorption at pH 6 is accompanied by a change in protein film composition. Presumably, this is mostly driven by the adsorption of human serum albumin, which at pH 6 adsorbs more readily and thereby replaces other proteins with lower surface affinities in the resulting multiprotein film.

Ultrasonic-aided extraction and degossypolization of cottonseed meal protein: Optimization and characterization of functional traits and molecular structure

Cottonseed meal (CM) is a useful protein resource, but the presence of gossypol (a toxic compound) limits it utilization in industry. To reduce the gossypol content, the use of ultrasonication in extracting protein from CM was explored. Following single-factor experiments, operative limits of independent variables affecting removal ratio of total-gossypol (RRTG) and extractability of CM protein (CMP) were achieved as temperature (35–55 °C), sonication power (250–350 W), time (12–24 min), and NaOH concentration (2–6 g/L). Box-Behnken’s Design centered on a 3–level-4–factor was employed to optimize ultrasonication conditions on the yield and RRTG of CMP. The predictive models were statistically adequate (p < 0.0001) to reflect the experimental results of the responses as verified by insignificant lack-of-fit (p ≥ 0.1333) and high coefficient of determination (R2 ≥ 0.976) values. The optimized sonication conditions for two responses were 53 °C, 320 W, 21 min, and 4.6 g-NaOH/L. Under optimized conditions, the observed removal ratio of free- and total-gossypol and yield values were 93.21 %, 87.56 %, and 58.23 %, which substantially increased by 15.64 %, 12.88 %, and 29.56 %, respectively over control (alkaline extraction). Furthermore, sonicated isolate showed an increase in solubility and emulsion property relative to control, buttressed by particle sizing and zeta potential outcomes. Sodium dodecyl sulfide polyacrylamide gel electrophoresis (SDS-PAGE), Fourier Transform Infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and amino acid data showed notable changes in molecular weight, functional groups, surface topography, and hydrophobic amino acid content of CMP, respectively (i.e., after sonication), suggesting partial unfolding in CMP conformation. Accordingly, CMP isolates (especially the sonicated protein) could be considered edible because of the observed low gossypol content (< 0.045 %) and thus can be utilized as natural additives in food formulations.

2-DG Regulates Immune Imbalance on the Titanium Surface after Debridement.

Peri-implantitis requires clinical treatments comprised of mechanical and chemical debridement to remove bacterial biofilms. Bone regeneration on the titanium surface after debridement has been a topical issue of peri-implantitis treatments. Increasing evidence has revealed that the immune microenvironment plays a key role in regulating the bone regeneration process. However, it remains unclear what kind of immune microenvironment the titanium surface induces after debridement. In the study, model titanium surface after debridement was prepared via biofilm induction and mechanical and chemical debridement in vitro. Then, the macrophages and naïve CD4+ T lymphocytes were cultured on the titanium surface after debridement for immune microenvironment evaluation, with the original titanium surface as the control. Next, to regulate the immune microenvironment, 2-DG, a glycolysis inhibitor, was further incorporated to regulate macrophages and CD4+ T lymphocytes at the same time. Surface characterization results showed that the bacterial biofilms were completely removed, while the micro-morphology of titanium surface altered after debridement, and the element composition did not change. Compared with the original titanium disc, titanium surface after debridement can lead to the inflammatory differentiation of macrophages and CD4+ T lymphocytes. The percentage of M1 and Th17 inflammatory cells and the expression of their inflammatory factor genes are upregulated. However, 0.3 mmol of 2-DG can significantly reduce the inflammatory differentiation of both macrophages and CD4+ T lymphocytes and inhibit their expression of inflammatory genes. In conclusion, although bacterial biofilms were removed from titanium surface after debridement, the surface topography changes could still induce immune imbalance and form an inflammatory immune microenvironment. However, this inflammatory immune microenvironment can be effectively reversed by 2-DG in vitro, thus creating an immune microenvironment conducive to osteogenesis, which might provide a new perspective for future therapy of peri-implantitis.

Comparison of Surface Topography Changes from Conventional Metal Brackets and Self-Ligating Metal Brackets after Immersion in Three Different Mouthwashes using Atomic Force Microscopy: An in vitro Study.

The main aim of this study is to compare and evaluate the surface changes from conventional metal brackets and self-ligating metal brackets after immersion in three different mouthwashes. Sixteen conventional metal brackets and sixteen metal self-ligating brackets were evenly grouped and immersed in deionized water, chlorhexidine mouthwash, herbal mouthwash, and betadine mouthwash for seven days and the surface changes were evaluated using nondestructive AFM. The surface roughness was evaluated at 30 μm and the results showed that more surface roughness was observed P < 0.05 in betadine mouthwash groups and followed by herbal mouthwash and least in chlorhexidine mouthwash. Based on the AFM results, the surface changes were more pronounced in both groups which were immersed in betadine and herbal mouthwash than others and the choice of mouthwash should be considered before prescribing to the patients.

Evaluation of remineralizing efficiency of two calcium-based non-fluoridated remineralizing agents for the prevention of white spot lesions (WSL): A comparative FESEM &amp; EDS in-vitro study

This research work was designed to appraise and equate the remineralizing efficiency of two calcium-based phosphate delivery agents, Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) and Calcium Sucrose Phosphate (CaSP) for preventing the development of White Spot Lesions (WSL) around the orthodontic brackets. Forty orthodontically removed premolar teeth were randomly allocated to Group 1(n=20) - (CPP-ACP) and Group 2(n=20) - (CaSP). All the specimens were subjected to FESEM and EDS analysis before the initial demineralization phase and after 14 days of the pH cycling phase, to observe and record changes in surface topography and mineral content (Ca/P ratio % wt.). Statistical data for the Intragroup comparison were analyzed by using Paired sample t-test, whereas for the Intergroup comparison, an Unpaired t-test was performed. Furthermore, the One-way ANOVA test was applied for comparing Intragroup data and the Post-hoc Tukey test was applied to compare Intergroup data. Group 1 samples showed an 11.3%increase in remineralization and Group 2 samples showed a 21.3%increase in remineralization, indicating a statistically significant (p &amp;#60; 0.05) 11% of greater remineralizing efficiency of CaSP. The use of Calcium Sucrose Phosphate (CaSP) tooth cream around the orthodontic brackets seems to produce significantly better remineralization effects.

Wind redistribution of snow impacts the Ka- and Ku-band radar signatures of Arctic sea ice

Abstract. Wind-driven redistribution of snow on sea ice alters its topography and microstructure, yet the impact of these processes on radar signatures is poorly understood. Here, we examine the effects of snow redistribution over Arctic sea ice on radar waveforms and backscatter signatures obtained from a surface-based, fully polarimetric Ka- and Ku-band radar at incidence angles between 0∘ (nadir) and 50∘. Two wind events in November 2019 during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition are evaluated. During both events, changes in Ka- and Ku-band radar waveforms and backscatter coefficients at nadir are observed, coincident with surface topography changes measured by a terrestrial laser scanner. At both frequencies, redistribution caused snow densification at the surface and the uppermost layers, increasing the scattering at the air–snow interface at nadir and its prevalence as the dominant radar scattering surface. The waveform data also detected the presence of previous air–snow interfaces, buried beneath newly deposited snow. The additional scattering from previous air–snow interfaces could therefore affect the range retrieved from Ka- and Ku-band satellite altimeters. With increasing incidence angles, the relative scattering contribution of the air–snow interface decreases, and the snow–sea ice interface scattering increases. Relative to pre-wind event conditions, azimuthally averaged backscatter at nadir during the wind events increases by up to 8 dB (Ka-band) and 5 dB (Ku-band). Results show substantial backscatter variability within the scan area at all incidence angles and polarizations, in response to increasing wind speed and changes in wind direction. Our results show that snow redistribution and wind compaction need to be accounted for to interpret airborne and satellite radar measurements of snow-covered sea ice.

Thermal transformation of bamboo sawdust for its advanced cementitious composites

This paper investigates a vacuum heat treatment (VHT) technology at 160℃, 200℃ and 240℃ for 6–14 h to modify bamboo sawdust (BS) and then BS/cement composites for the development of low carbon construction materials. The hydration process, thermal stability, micro-morphology and crystallinity, and chemical and mechanical changes for both VHT BS and composites are examined by FTIR, TG-DTG, XRD and SEM analyses. The mechanism of improving the mechanical properties of modified BS on composite materials is further elaborated together with the physical and mechanical properties and durability. The results show that the flexural strength and compressive strength of the modified BS/cement composites after VHT at 200℃ for 10 h are increased by 61.2% and 13.8%, respectively, compared with those in the untreated group, and the composites have better durability in the modified group. VHT resulted in cellulose and hemicellulose degradation to certain degrees, lignin undergoes cross-linked condensation reaction and cellulose crystallinity increases. These changes reduce the number of BS hydrophilic groups and result in changes in BS microstructure and surface topography, providing favorable conditions for the bonding and interface development of BS/cement composites. The impact of BS/cement composites on the carbon footprint in the production stage was analyzed, showing that the carbon emissions of BS/cement composites after VHT were reduced by 5.7% compared with that of the corresponding OPC composites.

Electrically Controlled Liquid Crystal Elastomer Surfaces for Dynamic Wrinkling

Liquid crystal elastomers (LCEs) are becoming increasingly popular as a shape memory material for soft robot actuators that operate in a contractile or flexural mode. There have been previously studies on the use of LCEs for reversible changes in surface topography. However, surface protrusions have typically been limited to the order of 1 μm or depend on light, heat, or electrical stimulation that are difficult to locally control or require relatively high voltage. This article presents a novel operation mode of LCE actuators based on the wrinkling behavior of an LCE‐elastomer bilayer architecture. Embedding a liquid‐metal‐based conductive ink within the LCE enables electrical control of surface wrinkling through Joule heating. The actuator cells can generate wrinkles with amplitudes ranging from 17 to 45 μm within 30 s under an input power of 2 W and a voltage on the order of 1 V. As the bilayer is composed entirely of soft materials, it is highly deformable, flexible, and can be integrated into a multi‐cell array capable of bending on curved surfaces.

Corrosion of copper nickel titanium archwire in chlorhexidine, sodium fluoride, and chitosan mouthwashes.

Copper (Cu), nickel (Ni), chromium (Cr) ion release, and surface topography change from the orthodontic wire are the initial processes of corrosion that may affect the mechanical properties of the archwire. In this study, we aim to evaluate the effect of CHX, NaF, and chitosan on the corrosion of CuNiTi wire nickel and copper ions released, surface roughness change, and archwire deflection. Ninety samples of CuNiTi Tanzo™ archwires were divided into five groups according to their immersion solution: Artificial Saliva, CHX, NaF, CHX-NaF, and chitosan group. Each group was further divided into three subgroups (n=6) corresponding immersion time, i.e., two, four, and six weeks. The corrosion of the samples was analyzed with an atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM), and universal testing machine (UTM). The amount of nickel ion releases was increasing, but the copper ion releases were reduced by the time of observations. The highest nickel ion was released in the CHX-NaF group and the lowest in the chitosan group for six-week immersion. It also corresponded to the surface topography by SEM analysis which showed the most extended cracks and deep pits in the CHX-NaF group and a smoother surface in the chitosan group. Copper ion release showed the highest ion release in the NaF group and the lowest release in the chitosan group. The unloading force of CuNiTi archwire deflection remains the same at week two and week four for all mouthwashes. The use of mouthwashes that contained CHX, NaF, and chitosan could further alter the passive layer and cause higher nickel and copper ion release and increased CuNiTi archwire surface structure porosity. But there is no distinction between mouthwashes to release the unloading force within two until four weeks.

Operando Scanning Electrochemical Probe Microscopy during Electrocatalysis.

Scanning electrochemical probe microscopy (SEPM) techniques can disclose the local electrochemical reactivity of interfaces in single-entity and sub-entity studies. Operando SEPM measurements consist of using a SEPM tip to investigate the performance of electrocatalysts, while the reactivity of the interface is simultaneously modulated. This powerful combination can correlate electrochemical activity with changes in surface properties, e.g., topography and structure, as well as provide insight into reaction mechanisms. The focus of this review is to reveal the recent progress in local SEPM measurements of the catalytic activity of a surface toward the reduction and evolution of O2 and H2 and electrochemical conversion of CO2. The capabilities of SEPMs are showcased, and the possibility of coupling other techniques to SEPMs is presented. Emphasis is given to scanning electrochemical microscopy (SECM), scanning ion conductance microscopy (SICM), electrochemical scanning tunneling microscopy (EC-STM), and scanning electrochemical cell microscopy (SECCM).

Wear induced changes in surface topography during running-in of rolling-sliding contacts

Running-in occurs in rolling-sliding contacts under mixed-friction conditions and typically involves asperity smoothing through mild wear and plastic deformation. To improve the prediction of service life or friction of rolling-element bearings under mixed-friction conditions, knowledge of surface topography changes during running-in and their dependence on the operating condition is an important prerequisite. Therefore, this study aims to describe the surface mechanisms due to wear, during running-in and their dependence on one of the variables, slip.AISI 52100 steel specimens were tested in a mini traction machine (MTM) instrumented with friction and contact potential measurement in the presence of a PAO base oil, operating in the mixed lubrication regime. A novel method of pre and post-test surface relocation with 3-D optical profilometry and scanning electron microscopy (SEM) was implemented. Rolling-sliding tests were performed to study the effect of slide-roll ratio on the surface topography changes during running-in. Additional tests were conducted to track the changes to surface topography during this period.The results exhibit the rapid nature of running-in and how most of the surface topography changes occur in the first few load cycles. Surface topography transitions such as asperity removal due to wear, increase in the load-bearing area of the asperities and in tests with slip, plastic flow of material from peaks into adjacent valleys are shown at high magnification. Surface profilometry measurements show that the reduction in depth of the valleys due to plastic flow adds to the reduction in roughness, thus accurately identifying the surface mechanism, and redressing the consensus that the reduction in roughness during running-in is mainly due to wear and plastic deformation diminishing the height of the peaks, which is true for ideal running-in alone.

Exploring the Lunar Regolith's Thickness and Dielectric Properties Using Band‐Limited Impedance at Chang’E‐4 Landing Site

AbstractThe Yutu‐2 rover onboard China's Chang’E‐4 was the first to land in the Von Kármán crater on the lunar farside, where structural and dielectric properties may provide previously unknown clues to lunar formation and evolution. Based on the Lunar Penetrating Radar (LPR) with 500 MHz onboard the Yutu‐2 rover, we proposed a band‐limited impedance (BLIMP) inversion method to generate continuous dielectric 2‐D profiles with the help of dielectric constants retrieved from point reflectors (e.g., buried rocks), which provide low‐frequency information that may be lost or distorted in the LPR data pre‐processing. The dielectric constants retrieved from point reflectors were transformed from dielectric constant fitting curves, where these discrete dielectric constants were calculated using the hyperbolic fitting method. We estimated that the top fine‐grained regolith thickness along the rover path varies from ∼5.3 to ∼15.0 m in the first 27 lunar days of operation. The thickness variation could most likely be attributed to changes in ancient surface topography buried underground and ejecta from nearby craters. Compared to methods based on a singular dielectric constant, the estimated 2‐D dielectric profile in this study can reduce the uncertainties in lunar regolith thickness estimation, especially in the shallow layers. The BLIMP method and the estimated regolith thickness can improve our understanding of lunar subsurface structure and formation.

Correlative Analysis of Ion-Concentration Profile and Surface Nanoscale Topography Changes Using Operando Scanning Ion Conductance Microscopy.

Although various spectroscopic methods have been developed to capture ion-concentration profile changes, it is still difficult to visualize the ion-concentration profile and surface topographical changes simultaneously during the charging/discharging of lithium-ion batteries (LIBs). To tackle this issue, we have developed an operando scanning ion conductance microscopy (SICM) method that can directly visualize an ion-concentration profile and surface topography using a SICM nanopipette while controlling the sample potential or current with a potentiostat for characterizing the polarization state during charging/discharging. Using operando SICM on the negative electrode (anode) of LIBs, we have characterized ion-concentration profile changes and the reversible volume changes related to the phase transition during cyclic voltammetry (CV) and charge/discharge of the graphite anode. Operando SICM is a versatile technique that is likely to be of major value for evaluating the correlation between the electrolyte concentration profile and nanoscale surface topography changes.

Topography of high-speed steel substrates sputter cleaned by an Ar/Ti cathodic arc plasma

Hard coated high-speed steels are often used for tooling applications and consist of three different microstructural constituents: a martensitic matrix, M6C and MC carbides. The behavior of these three during the various tool manufacturing steps has a detrimental effect on the final tool performance. The focus of the current work is the surface topography change due to variation of the substrate bias voltage applied during the Ar/Ti arc plasma sputter cleaning process which changed the sputtering behavior of the high-speed steel's microstructural constituents and the appearance of droplets on the sputtered surface. The surface topography was characterized by laser confocal and scanning electron microscopy. Furthermore, microstructural analysis was carried out on cross-section lamellae prepared by a focus ion beam technique and analyzed by transmission electron microscopy. At each of the three investigated substrate bias voltages (Ub) of −600, −800 and −1000 V during the Ar/Ti arc plasma sputter cleaning process, the mentioned microstructural constituents behaved differently. At an Ub threshold of −600 V, sputter erosion starts at M6C carbides in an inhomogeneous material erosion pattern. At −800 V, a homogeneous sputter behavior was established for the entire sample. M6C carbides showed the highest sputter erosion rate, on MC carbides Ti deposition occurred instead of sputter erosion, and the martensitic matrix was smoothened, as peaks and exposed features were sputtered preferentially. As of Ub = −1000 V, the sputter erosion behavior of the martensitic matrix changed and exposed features were preserved. The reason for this change was identified to be Ti+ ion implantation indicated by Monte Carlo simulations and the associated increase of the matrix' cohesive strength, calculated using Density Functional Theory. The published results in this study will help to further utilize Ar/Ti arc plasma sputter cleaning processes for intentional surface topography design.

Corrosion of copper nickel titanium archwire in chlorhexidine, sodium fluoride, and chitosan mouthwashes

Background: Copper (Cu), nickel (Ni), chromium (Cr) ion release, and surface topography change from the orthodontic wire are the initial processes of corrosion that may affect the mechanical properties of the archwire. In this study, we aim to evaluate the effect of CHX, NaF, and chitosan on the corrosion of CuNiTi wire nickel and copper ions released, surface roughness change, and archwire deflection. Methods: Ninety samples of CuNiTi Tanzo™ archwires were divided into five groups according to their immersion solution: Artificial Saliva, CHX, NaF, CHX-NaF, and chitosan group. Each group was further divided into three subgroups (n=6) corresponding immersion time, i.e., two, four, and six weeks. The corrosion of the samples was analyzed with an atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM), and universal testing machine (UTM). Results: The amount of nickel ion releases was increasing, but the copper ion releases were reduced by the time of observations. The highest nickel ion was released in the CHX-NaF group and the lowest in the chitosan group for six-week immersion. It also corresponded to the surface topography by SEM analysis which showed the most extended cracks and deep pits in the CHX-NaF group and a smoother surface in the chitosan group. Copper ion release showed the highest ion release in the NaF group and the lowest release in the chitosan group. The unloading force of CuNiTi archwire deflection remains the same at week two and week four for all mouthwashes. Conclusion: The use of mouthwashes that contained CHX, NaF, and chitosan could further alter the passive layer and cause higher nickel and copper ion release and increased CuNiTi archwire surface structure porosity. But there is no distinction between mouthwashes to release the unloading force within two until four weeks.