Surface Characterization and Tribology Behavior of PMMA Processed by Excimer Laser

Polyoxymethylene methacrylate (PMMA) is widely used in ophthalmic biomaterials. Misuse of PMMA in extreme environments is likely to damage the ocular surface and intraocular structures. The surface characterization and tribological behavior of PMMA processed using an excimer laser were investigated in this study by contrasting diferent lubrication conditions and friction cycles. The results show that the roughness of the material surface increases with laser processing, which changes its physical structure. Under lubrication, the laser-treated PMMA exhibits better hydrophilicity, especially during the use of eye drops. No obvious relationship exists between the laser-processing time and friction behavior. However, the laser treatment may contribute to the formation of friction and wear mechanisms of PMMA materials. Laser-treated PMMA in saline solution exhibits better abrasive resistance by showing a lower wear rate than that in eye drops, although it has a higher friction coefcient. In this study, the diferent friction stages in laser-treated PMMA were clarifed under two lubrication conditions. The wear rates of the laser-treated PMMA were found to decrease with the number of cycles, and the friction coefcient has a similar variation tendency. The wear behavior of the laser-treated PMMA is dominated by the main abrasive wear and secondary transferred flm formation. This study provides a theoretical basis for the development and application of ophthalmic biomaterials in complex environments by examining the material surface interface behavior and wear mechanism after laser processing using PMMA as the research matrix.

Surface Characteristics Measurement Using Computer Vision:A Review

Computer vision provides image-based solutions to inspect and investigate the quality of the surface to be measured.For any components to execute their intended functions and operations,surface quality is considered equally significant to dimensional quality.Surface Roughness(Ra)is a widely recognized measure to evaluate and investigate the surface quality of machined parts.Various conventional methods and approaches to measure the surface roughness are not feasible and appropriate in industries claiming 100%inspection and examination because of the time and efforts involved in performing the measurement.However,Machine vision has emerged as the innovative approach to executing the surface roughness measurement.It can provide economic,automated,quick,and reliable solutions.This paper discusses the characterization of the surface texture of surfaces of traditional or non-traditional manufactured parts through a computer/machine vision approach and assessment of the surface characteristics,i.e.,surface roughness,waviness,flatness,surface texture,etc.,machine vision parameters.This paper will also discuss multiple machine vision techniques for different manufacturing processes to perform the surface characterization measurement.

Surface characterization and corrosion behavior of calcium phosphate(Ca-P)base composite layer on Mg and its alloys using plasma electrolytic oxidation(PEO):A review

Magnesium has been known as an appropriate biological material on account of its good biocompatibility and biodegradability properties in addition to advantageous mechanical properties.Mg and its alloys are of poor corrosion resistance.Its high corrosion rate leads to its quick decomposition in the corrosive ambiance and as a result weakening its mechanical properties and before it is repaired,it will vanish.The corrosion and degradation rate must be controlled in the body to advance the usage of Mg and its alloys as implants.Different techniques have been utilized to boost biological properties.Plasma electrolytic oxidation(PEO)can provide porous and biocompatible coatings for implants among various techniques.Biodegradable implants are generally supposed to show enough corrosion resistance and mechanical integrity in the body environment.Much research has been carried out in order to produce PEO coatings containing calcium phosphate compounds.Calcium phosphates are really similar to bone mineral composition and present great biocompatibility.The present study deals with the usage of calcium phosphates as biocompatible coatings applied on Mg and its alloys to study the properties and control the corrosion rate.

Position-resolved Surface Characterization and Nanofabrication Using an Optical Microscope Combined with a Nanopipette/Quartz Tuning Fork Atomic Force Microscope

In this work, we introduce position-resolved surface characterization and nanofabrication using an optical microscope(OM) combined with a nanopipette-based quartz tuning fork atomic force microscope(nanopipette/QTF-AFM) system. This system is used to accurately determine substrate position and nanoscale phenomena under ambient conditions. Solutions consisting of 5 nm Au nanoparticles, nanowires, and polydimethylsiloxane(PDMS) are deposited onto the substrate through the nano/microaperture of a pulled pipette. Nano/microscale patterning is performed using a nanopipette/QTF-AFM, while position is resolved by monitoring the substrate with a custom OM. With this tool, one can perform surface characterization(force spectroscopy/microscopy) using the quartz tuning fork(QTF) sensor. Nanofabrication is achieved by accurately positioning target materials on the surface, and on-demand delivery and patterning of various solutions for molecular architecture.

Electrolyte-dependent formation of solid electrolyte interphase and ion intercalation revealed by in situ surface characterizations

The formation of solid electrolyte interphase(SEI) and ion intercalation are two key processes in rechargeable batteries, which need to be explored under dynamic operating conditions. In this work, both planar and sandwich model lithium batteries consisting of Li metal | ionic liquid electrolyte | graphite electrode have been constructed and investigated by a series of in situ surface analysis platforms including atomic force microscopy, Raman and X-ray photoelectron spectroscopy. It is found that the choice of electrolyte, including the concentration and contents, has a profound effect on the SEI formation and evolution, and the subsequent ion intercalation. A smooth and compact SEI is preferably produced in highconcentration electrolytes, with FSI^(-) salt superior to TFSI^(-) salt, facilitating the lithiation/delithiation to achieve high capacity and excellent cycle stability, while suppressing the co-intercalation of electrolyte solvent ions. The innovative research scenario of well-defined model batteries in combination with multiple genuinely in situ surface analysis methods presented herein leads to insightful results, which provide valuable strategies for the rational design and optimization of practical batteries, and energy storage devices in general.

Surface characteristics analysis of fractures induced by supercritical CO_(2)and water through three-dimensional scanning and scanning electron micrography

Morphology of hydraulic fracture surface has significant effects on oil and gas flow,proppant migration and fracture closure,which plays an important role in oil and gas fracturing stimulation.In this paper,we analyzed the fracture surface characteristics induced by supercritical carbon dioxide(SC-CO_(2))and water in open-hole and perforation completion conditions under triaxial stresses.A simple calculation method was proposed to quantitatively analyze the fracture surface area and roughness in macro-level based on three-dimensional(3D)scanning data.In micro-level,scanning electron micrograph(SEM)was used to analyze the features of fracture surface.The results showed that the surface area of the induced fracture increases with perforation angle for both SC-CO_(2)and water fracturing,and the surface area of SC-CO_(2)-induced fracture is 6.49%e58.57%larger than that of water-induced fracture.The fractal dimension and surface roughness of water-induced fractures increase with the increase in perforation angle,while those of SC-CO_(2)-induced fractures decrease with the increasing perforation angle.A considerable number of microcracks and particle peeling pits can be observed on SC-CO_(2)-induced fracture surface while there are more flat particle surfaces in water-induced fracture surface through SEM images,indicating that fractures tend to propagate along the boundary of the particle for SC-CO_(2)fracturing while water-induced fractures prefer to cut through particles.These findings are of great significance for analyzing fracture mechanism and evaluating fracturing stimulation performance.

Characterization on Surface and Interfacial Properties of Nitramine Crystal Fillers and Polymeric Bonding Agents

The surface and interfacial properties of polymeric bonding agents and nitramine crystal fillers were studied. The surface free energy and adhesion work of polymeric bonding agents and nitramine fillers were calculated by using Kaeble′s equations. It was observed that the hydroxyl values of neutral polymeric bonding agents (NPBA) correlate well with the polar components of surface free energies. On the basis of the measurements of swelling ratio and initial modulus, the interfacial bonding through highly crosslinked polymeric shell formation around the nitramine particles and generating interfacial reinforcement were rationalized. The application of Tapping Mode AFM (atomic force micro scope) to observing the surface morphology of NPBA reveals that methyl acrylate monomer appears to play a role for aiding the formation of network like structure when nanometer scale images of NPBA are created.

Surface characterization of steel/steel contact lubricated by PA06 with novel black phosphorus nanocomposites

In the present work,two types of novel nano additives,titanium sulfonate ligand/black phosphorus(TiLi/BP)and titanium dioxide/black phosphorus(TiCVBP)nanocomposites,were prepared.The tribological behavior of the steel/steel friction pairs lubricated by polyalphaolefins type 6(PA06)containing the nanocomposites under boundary lubrication was studied.The worn surfaces were analyzed using modem surface techniques.The experimental results show that the rubbed surfaces became smooth and showed little wear with the addition of the nanocomposites.TiO_(2)/BP nanocomposites can significantly improve the lubricity of BP nanosheets under high contact stress.The synergistic roles of the load-bearing abilities and rolling effect of TiO_(2) nanoparticles,the slip induced by the BP with its layered structure,and the establishment of a tribofilm on the sliding interface are the basis of the tribological mechanisms.

Surface characterization of metal oxides-supported activated carbon fiber catalysts for simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide

The sol–gel method was used to synthesize a series of metal oxides-supported activated carbon fiber (ACF) and the simultaneous catalytic hydrolysis activity of carbonyl sulfide (COS)and carbon disulfide (CS2) at relatively low temperatures of 60°C was tested.The effects of preparation conditions on the catalyst properties were investigated,including the kinds and amount of metal oxides and calcination temperatures.The activity tests indicated that catalysts with 5 wt.%Ni after calcining at 400°C (Ni(5)/ACF(400)) had the best performance for the simultaneous catalytic hydrolysis of COS and CS2.The surface and structure properties of prepared ACF were characterized by scanning electron microscope-energy disperse spectroscopy (SEM-EDS),Brunauer–Emmett–Teller (BET),X-ray diffraction (XRD),carbon dioxidetemperature programmed desorption (CO2-TPD) and diffuse reflectance Fourier transform infrared reflection (DRFTIR).And the metal cation defects were researched by electron paramagnetic resonance (EPR) method.The characterization results showed that the supporting of Ni on the ACF made the ACF catalyst show alkaline and increased the specific surface area and the number of micropores,then improved catalytic hydrolysis activity.The DRFTIR results revealed that-OH species could facilitate the hydrolysis of COS and CS2;-COO and-C–O species could facilitate the oxidation of catalytic hydrolysate H2S.And the EPR results showed that high calcination temperature conditions provide more active reaction center for the COS and CS2 adsorption.

Characterization of Read/Write Head Shield Asperities in Hard Disk Drives

A new way to characterize asperities on metallic surfaces at the nanometer scale is proposed. Asperities are often treated using conventional statistical descriptors such as average and root mean square roughness, which do not provide adequate mechanistic insight into surface defect formation and mitigation. The new rationale revolves around developing a mathematical description of the evolution of the area occupied by asperities at each height slice on a topography image, with direct implications on how asperity instances are tracked and their risk of breakage leading to potential exposure and degradation of the metal surface upon thermo-mechanical stresses during the operation of read/write heads is assessed. The technique was shown to be disruptive by surpassing all other surface quality metrics, such as conventional roughness and static area % asperity at 0.5 nm height, in its ability to statistically differentiate surfaces coming from various manufacturing process iterations tailored to produce different surface conditions in the hard disk drive industry. A theoretical formulation proposing that the static asperity technique is fundamentally insufficient, is presented and validated experimentally.

THE CHARACTERIZATION OF SILVER SUBCOLLOID USED IN SURFACE ENHANCED RAMAN SPECTROSCOPY

A clear light-yellow silver sol which has the visible spectral absorption at 390 nm, when adsorbed phenylmercaptotetrazole(PMT) or mercaptobenzothiazole(MBT), has a new absorption at 510-550 nm. It was found that the adsorption of halide ions competes with PMT and MBT. However, halide ions have a completely different influence from PMT and MBT on the spectral absorption of the silver sol. The differences may result from the change of the properties of the surface of the silver subcolloidal particles and from the bond forms combining adsorbates with the substrates.

Acetic acid additive in NaNO_(3)aqueous electrolyte for long-lifespan Mg-air batteries

Mg-air batteries have attracted tremendous attention as a potential next-generation power source for portable electronics and e-transportation due to their remarkable high theoretical volumetric energy density,environmental sustainability,and cost-effectiveness.However,the fast hydrogen evolution reaction(HER)in NaCl-based aqueous electrolytes impairs the performance of Mg-air batteries and leads to poor specific capacity,low energy density,and low utilization.Thus,the conventionally used NaCl solute was proposed to be replaced by NaNO_(3)and acetic acid additive as a corrosion inhibitor,therefore an electrolyte engineering for long-life time Mg-air batteries is reported.The resulting Mg-air batteries based on this optimized electrolyte demonstrate an improved discharge voltage reaching~1.8 V for initial 5 h at a current density of 0.5 mA/cm^(2) and significantly prolonged cells'operational lifetime to over 360 h,in contrast to only~17 h observed in NaCl electrolyte.X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were employed to analyse the composition of surface film and scanning electron microscopy combined with transmission electron microscopy to clarify the morphology changes of the surface layer as a function of acetic acid addition.The thorough studies of chemical composition and morphology of corrosion products have allowed us to elucidate the working mechanism of Mg anode in this optimized electrolyte for Mg-air batteries.

SURFACE MODIFICATION OF TITANIUM FILMS WITH SODIUM ION IMPLANTATION:SURFACE PROPERTIES AND PROTEIN ADSORPTION

Sodium implanted titanium films with different ion doses were characterized to correlate their ion implantation parameters. Native titanium films and ion implanted titanium films were characterized with combined techniques of X-ray photoelectron spectroscopy （XPS）, atomic force microscopy （AFM）, and light microscopy （LM）. The surface presented increased sodium concentration on treated titanium films with ion dose increasing, except for the group with the highest ion dose of 4×10^17ions/cm^2. XPS depth profiling displayed that sodium entered titanium film around 25-50nm depth depending on its implantation ion dose. AFM characterization showed that sodium ion implantation treatment changed the surface morphology from a relatively smooth titanium film to rough surfaces corresponding to different implantation doses. After sodium implantation, implanted titanium films presented big particles with island structure morphology. The surface morphology and particle growth displayed the corresponding trend. Fibrinogen adsorption on these titanium films was performed to correlate with the surface properties of treated titanium films. The results show that protein adsorption on ion-implanted samples with dose of 2×10^17 and 4×10^17 are statistically higher （p 〈0.01） than samples treated with dose of 5×10^16 and 1×10^17, as well as the control samples.

Monitoring of CO_2 geological storage based on the passive surface waves

Carbon dioxide （CO2） capture and geological storage （CCS） is one of promising technologies for greenhouse gas effect mitigation. Many geotechnical challenges remain during carbon dioxide storage field practices, among which effectively detecting CO2 from deep underground is one of engineering problems. This paper reviews monitoring techniques currently used during CO2 injection and storage. A method developed based on measuring seismic microtremors is of main interest. This method was first successfully used to characterize a site in this paper. To explore its feasibility in C02 storage monitoring, numerical simulations were conducted to investigate detectable changes in elastic wave signatures due to injection and geological storage of CO2. It is found that, although it is effective for shallow earth profile estimation, the surface wave velocity is not sensitive to the CO2 layer physical parameter variations,especially for a thin CO2 geological storage layer in a deep underground reservoir.

Revealing the effect of electrolyte coordination structures on the intercalation chemistry of batteries

In-depth understanding of the electrolyte-dependent intercalation chemistry in batteries through direct operando/in situ characterizations is crucial for the development of the high-performance batteries.Herein,taking the Al/graphite battery as a model system,the effect of electrolyte coordination structure on the intercalation processes has been investigated over the batteries with either 1-hexyl-3-methylimidazolium chloride(HMICl)-AlCl_(3) or 1-ethyl-3-methylimidazolium chloride(EMICl)-AlCl_(3) ionic liquid electrolyte using operando X-ray photoelectron spectroscopy(XPS)and X-ray diffraction.With a weaker anion-cation interaction in HMI-based electrolyte,the XPS-derived atomic ratio between cointercalated N and intercalated Al is 0.9,which is lower than 1.6 for EMI-based electrolyte.Attributed to the additional de-solvation process,the batteries with the HMI-based electrolyte show a lower ionic diffusion rate,capacity,and cycling performance,which agree with the operando characterization results.Our findings highlight the critical role of the electrolyte coordination structure on the(co-)intercalation chemistry.

Does acid pickling of Mg-Ca alloy enhance biomineralization?

The mechanical and physical properties of biodegradable magnesium(Mg)alloys make them suitable for temporary orthopaedic implants.The success of these alloys depends on their performance in the physiological environment.In the present work,surface modification of Mg-Ca binary alloy by acid pickling for better biomineralization and controlled biodegradation is explored.The corrosion rates of nitric and phosphoric acid treated samples were analysed by conducting electrochemical corrosion tests.In vitro degradation behaviour was studied using immersion test in simulated body fluid(SBF).The sample surfaces were characterized using scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS).It is seen that acid pickling leads to significant improvement in biomineralization and develop in situ calcium phosphate(Ca P)coating on the sample surfaces.In addition,the treated samples recorded a reduced degradation rate in the SBF compared to untreated samples.Thus,acid pickling is suggested as an effective surface treatment method to tailor the biomineralization and degradation behaviour of the Mg-Ca alloy in the physiological environment.

Formation mechanisms of sub-micron pharmaceutical composite particles derived from far-and near-field Raman microscopy

Surface enhanced Raman spectroscopy(SERS) and confocal Raman microscopy are applied to investigate the structure and the molecular arrangement of sub-micron furosemide and polyvinylpyrrolidone(furosemide/PVP) particles produced by spray flash evaporation(SFE). Morphology, size and crystallinity of furosemide/PVP particles are analyzed by scanning electron microscopy(SEM) and X-ray powder diffraction(XRPD). Far-field Raman spectra and confocal far-field Raman maps of furosemide/PVP particles are interpreted based on the far-field Raman spectra of pure furosemide and PVP precursors.Confocal far-field Raman microscopy shows that furosemide/PVP particles feature an intermixture of furosemide and PVP molecules at the sub-micron scale. SERS and surface-enhanced confocal Raman microscopy(SECo RM) are performed on furosemide, PVP and furosemide/PVP composite particles sputtered with silver(40 nm). SERS and SECo RM maps reveal that furosemide/PVP particle surfaces mainly consist of PVP molecules. The combination of surface and bulk sensitive analyses reveal that furosemide/PVP sub-micron particles are formed by the agglomeration of primary furosemide nanocrystals embedded in a thin PVP matrix. Interestingly, both far-field Raman microscopy and SECo RM provide molecular information on a statistically-relevant amount of sub-micron particles in a single microscopic map;this combination is thus an effective and time-saving tool for investigating organic sub-micron composites.

Surface morphology characterization of unidirectional carbon fibre reinforced plastic machined by peripheral milling

This paper aims to characterise surface morphology and 3D roughness parameters of unidirectional carbon fibre reinforced plastic(UD-CFRP)milled at 0°,45°,90°,and 135°fibre orientation angles(FOAs).Side milling experiments are conducted on UD-CFRP laminates.Surface damage forms and texture direction of milled surface are analysed.Spatial frequency of defects on CFRP surface is quantitatively determined using radially averaged 2D PSD.The kinematicdynamic surface topography is reconstructed considering feed,runout and vibration,then the ideal roughness parameters,S_(a),S_(q),S_(sk),and S_(ku)are calculated and compared with the measured ones,finally the material factor-induced roughness components are quantified.Results show that CFRP surface has no regular feed marks.The frequency of fibre breakage or surface defects is greater than tooth passing frequency.FOAs sorted by their average S_(a)in descending order is135°>90°>45°>0°,where surface defects contribute 93.9%,77.1%,73.2%,72.2%of the total roughness respectively,which suggests that surface defects show a more important role than tool kinematics and vibration in formation of milled surface.The negative Skewness(Ssk<0)and high Kurtosis(S_(ku)=4.0–11.5)of milled surface signify porosity and the presence of many anomalous deep valleys in milled surface,respectively.

Biomechanical Evaluation of Nano-Zirconia Coatings on Ti-6Al-7Nb Implant Screws in Rabbit Tibias

The clinical success of dental implants can be improved by achieving optimum implant properties, such as their biomechanical and surface characteristics. Nano-structured coatings can play an important role in improving the implant surface. The purpose of the present study was to determine the most appropriate conditions for electrophoretic deposition （EPD） of nano-zirconia coatings on Ti-6A1-7Nb substrates and to evaluate the structural and biomechanical characteristics of these deposited coatings on the dental implants. EPD was used with different applied voltages and time periods to obtain a uniform layer of nano-zirconia on Ti-6A1-7Nb samples. The coated samples were weighed and the thickness of the product layer was measured. Surface analysis was performed by using optical microscopical examination, scanning electron microscope and X-ray diffraction phase analysis. For in vivo examination, 48 screw-designed implants （24 uncoated and 24 nano-zirconia coated） were implanted in both tibiae of 12 white New Zealand rabbits and evaluated biomechanically after 4- and 12-week healing intervals. Results revealed that the use of different conditions for EPD affected the final coating film properties. Increasing the applied voltage and coating time period increased the deposited nano-zirconia film thickness and weight. By selecting the appropriate coating conditions, and analyzing scanning electron microscopical examination and XRD patterns, this technique could produce a thin and continuous nano-zirconia layer with a uniform thickness of the Ti-6A1-7Nb samples. Mechanically, the nano-zirconia-coated implants showed a highly statistically significant difference in removal torque values, while histologically these coated implants enhanced and promoted osseointegration after 4 and 12 weeks of healing, compared with the uncoated ones. In conclusion, EPD is an effective technique for providing a high quality nano-zirconia coating film on dental implant surfaces. Moreover, the osseointegration of these coated dental implants is improved compared with that of uncoated ones.

The removal of Cr(Ⅵ) through polymeric supported liquid membrane by using calix[4]arene as a carrier

In this work, the transport and removal of Cr(Ⅵ) were achieved through supported liquid membrane(SLM) by using a 5,17, di-tert-butyl-11,23-bis[(1,4-dioxa-8-azaspiro [4,5]decanyl)methyl]-25,26,27,28-tetrahydroxy calix[4]arene carrier, dissolved in 2-nitrophenyl octyl ether dichloromethane.The studied parameters are the solvent effect in the membrane phase, the effect of carrier concentration, and the acid type in the donor phase.The Celgard 2500 was used as a membrane support.We used the Danesi mass transfer model to calculate the permeability coefficients for each studied parameter.In addition, AFM and SEM techniques were used to characterize the surface morphology of the prepared Celgard 2500 membrane that included the calix[4]arene carrier.