AFM Investigations Research Articles

A sulfobetaine containing-polymethylmethacrylate surface coating as an excellent antifouling agent against Chlorella sp

Biofouling represents one of the major issues in Photobioreactors (PBRs) for microalgae cultivation. At this aim, a series of zwitterionic-containing polymethylmethacrylate (PMMA) co-ter-polymers, differing in the molar percentage of sulfobetaine (SBMA)- and 2-hydroxyethylmethacrylate (HEMA) components were designed as antifouling (AF) potential coatings for inner PMMA surface of photobioreactors (PBRs). Among these, the sample named PSBM, P(HEMA-co-MMA-co-SBMA), showing the best film capabilities on PMMA slides, was selected, characterized and its AF activity investigated. High transparent and thin PSBM films, as confirmed by AFM and optical transparency investigations, were obtained by a simple drop-casting procedure using a basic isopropylalcohol/water mixture. AFM images of raw PSBM and PSBM films clearly indicate that a conformational change occurred upon treatment with electrolytes. PSBM was further characterized by ATR-FTIR Spectroscopy, Dynamic Light Scattering, X-Ray Photoelectron Spectroscopy, Thermogravimetric analysis, Differential Scanning Calorimetry and Static Water Contact Angle (WCA) investigations. Consistent with hydrophilic behavior, the PSBM surface provided a WCA of 60.9 ± 0.8° which, interestingly, decreased to 27.7 ± 1.2° after immersion in electrolyte culture media. PSBM films displayed a high satisfactory AF behavior in that a rare or no cell adhesion was observed when placed for 7 days in a suspension of the green microalga Chlorella sp. For comparison, the experiments were carried out with untreated and rough PMMA surfaces.

Repurposing trityl-substituted triphenylamine-based polyimides for gas separation membranes by blending with a fluorinated polyimide

In the attempt to develop gas separation membranes by reusing polymers with no film-forming ability but with great potential for this purpose, blending has been approached as a simple, time- and cost-effective strategy. Herein, blends of trityl-substituted triphenylamine (TTA)-based polyimides and a fluorinated polyimide (6F-PI) were involved to prepare dense membranes by drop-casting technique. The two blend components involved in variable amounts led to different film morphologies with a strong impact on most blends' properties and gas separation performance. According to optical microscopy, SEM, AFM, and FTIR investigations, the blend series containing hexafluoroisopropylidene (6F) groups in both polyimide components proved to be fully miscible at the molecular levels. When a single 6F-based component was integrated into the blend, the polymers proved to be compatible, but only partially miscible, with a two-phase structure, in which 6F-PI wrapped around the TTA-PI growth fibrillar domains. However, all blends displayed a single glass transition and FTIR bands which do not sum the ones of the polymer components, as well as a high thermal stability, close to that of 6F-PI. Regardless of their miscibility level, all blends behaved as classical polyimide films, with good mechanical properties and chemical resistance to corrosive media like acid vapors or basic solutions. The blend composition and diimide structure of TTA-PI little affected the dielectric behavior, unlike the gas separation performance that strongly depended on these characteristics. The higher amount of 6F groups in the miscible blends endowed the membranes with superior permeability and selectivity, allowing in some cases to surpass the trade-off rule. Generally, the gas permeability decreased with the increase of TTA-PI content, with some exceptions. The low intermolecular interfacial interactions promoted by TTA-PI were found to be beneficial in preserving a good selectivity of gas molecules with a small kinetic diameter (He, CO2) though their permeability is lost. The gas permeability changes as a function of the blend composition and structure were mostly due to changes in the solubility coefficient and less from gas diffusion capability, at least for CO2 and N2.

AFM Investigation as a Key Analysis to Determine the Drug Location in Electrospun Drug Delivery Systems

AbstractThe current study analyzes the possibility of determining the drug location in electrospun polymeric matrices and forecasting the release kinetics of drug delivery systems. Electrospun membranes made of polycaprolactone (PCL) loaded with dacarbazine (the drug of choice for the treatment of melanoma) and with AuM1 (a promising synthetic Au‐based complex recently proposed for antitumoral treatments) are successfully prepared. Atomic force microscopy (AFM) analysis is performed on various membranes, highlighting the relevance of investigating the three‐dimensional topology of the membranes for understanding the release kinetic. The produced mats are similar for all membranes, but significant differences in the microscopic roughness wall between the systems loaded with AuM1 and dacarbazine are observed.For AuM1, which has a low affinity with the PCL matrix, the complex aggregates on the nanofibers’ external walls, consequently increasing the roughness and causing a high burst in the first hours of release. On the other hand, dacarbazine is successfully included in the bulk core of the PCL nanofibers. Thus, the release kinetics is diffusive and well described by the Fick model.

Benzodipyrrolidone-based donor-acceptor semiconducting polymers with high hole mobility and noncovalent conformational locks

Constructing highly coplanar polymer backbone plays an important role in boosting the carrier mobility of organic field effect transistors (OFETs) devices. In this study, based on noncovalent conformational locks strategy, we synthesized the electron-acceptor (A) monomer via introducing 3-dodecylthiophene on strong electron-deficient planar benzodipyrrolidone and the electron-donor (D) monomers containing different numbers (0–2) of fluorine atoms at different positon. A series of novel D-A copolymers, namely PBDP-F0, PBDP-F1 and PBDP-F2 with different backbone conformational locks through F⋯S and F⋯H–C noncovalent interactions, were obtained via Stille polycondensation. For the application in an organic field-effect transistor, all the polymers exhibited p-type charge transport characteristics and good performance with the highest hole mobilities as 0.24 cm2 V−1 s−1 for PBDP-F0, 0.87 cm2 V−1 s−1 for PBDP-F1 and 1.93 cm2 V−1 s−1 for PBDP-F2, respectively. AFM and GIXRD investigations indicated that all polymers take predominantly edge-on orientation packing mode because of the rigid and coplanar backbone conformation and the annealing films exhibited small π-π stacking distances of 3.73, 3.71 and 3.69 Å for PBDP-F0, PBDP-F1 and PBDP-F2 respectively. This work demonstrates that modified BDP-based D-A copolymers with conformational locks has a potential application in the high-performance semiconductor materials.

Synthesis and evaluation of a novel pyridinyl thiazolidine derivative as an antioxidant and corrosion inhibitor for mild steel in acidic environments

A new synthesized (Z)-2-((3,5-dichloropyridin-2-yl)imino)thiazolidin-4-one (DICPT) was evaluated as an antioxidant and a corrosion inhibitor for mild steel (M.STL) in a 0.5 M HCl solution. The antioxidant activity of newly synthesized DICPT was screened using a DPPH assay, and the results showed that DICPT has good antioxidant activity. Electrochemical assessments were conducted utilizing potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). A new compound, DICPT, was synthesized, and its chemical structure was established and validated through various spectroscopic techniques, including including infrared (FTIR), nuclear magnetic resonance (NMR), and mass spectroscopy. PDP measurements revealed DICPT to be a mixed-type inhibitor. Charge transfer resistance (Rct) increased when inhibitor concentrations increased, according to EIS tests. The inhibition efficiency (%I) showed a corresponding rise with increasing inhibitor concentration, peaking at approximately 94.2 % at 3 × 10−5 M. Langmuir’s adsorption isotherm was found to govern the preferred adsorption mode of DICPT molecules onto the metal surface. UV–visible spectra confirmed the chemical interaction between DICPT molecules and the M.STL surface. AFM investigation indicated the formation of a protective layer on the metal surface, shielding it from corrosive environmental factors. Quantum chemical calculations were compared to experimental results to learn more about how corrosion is stopped and how well it works. Our study demonstrates the innovation of DICPT as a dual-function compound, offering both antioxidant and corrosion protection properties. This research contributes to the development of effective corrosion inhibitors for industrial applications.

The pivotal role of the polyethylene glycol amount as compatibilizing on the morphological features of silica-based blends

Silica-based hybrid blends at different molecular or nanometer scale have gained a lot of interests from the technological point of view. In particular, several inorganic-organic hybrids find application in the biomedical field. In this context, inorganic SiO2 and hybrids made up of SiO2 and polyethylene glycol (PEG) have been synthesised via the sol-gel route and characterised from the morphological (throught the Atomic Force Microscopy - AFM) and spectroscopic point of view to shed light on their features as possible hybrid biomaterials. AFM investigation allowed for an effective quantitative evaluation of surface roughness of bioactive sol-gel-based materials. The results revealed an increase in material porosity as a function of the PEG amount in the systems, thus highlighting the pivotal role of the PEG amount as compatibilizing on the morphological features of silica-based blends. The co-presence of both the inorganic and organic phases was confirmed by the Fourier-transform infrared spectroscopy (FT-IR). Moreover, the influence of PEG was also investigated by analysing the deconvoluted FT-IR spectra in the range of 1600-750 cm−1.

Melamine‐imprinted quartz crystal microbalance sensor for its detection in milk

AbstractA unique and selective molecularly imprinted polymer (MIP) was fabricated to detect melamine using a quartz crystal microbalance (QCM) surface. The MIP was synthesized by sol–gel technique utilizing 3‐(trimethoxysilyl) propyl methacrylate (TMSPMA) as the functional monomer bearing the methacrylate head group. To identify the melamine, we applied a coating of the as‐synthesized MIP over the silicon crystal of the quartz crystal microbalance (QCM) detector. High‐affinity adsorption of template molecules from the aqueous solution is the basis of the detection. Adsorption experiments performed in real‐time on MIP surfaces indicate that melamine forms strong bonds with its template molecule. We have evaluated the MIP surface using contact angle, BET, RAMAN and AFM investigations regarding wettability, reactivity, surface area, and smoothness. The real‐time adsorption experiments of template molecules on the MIP substrate reveal enhanced attachments with MIP, whereas the NIP demonstrates no interactions with the template molecules. Melamine detection in tainted milk samples further validated the MIP QCM sensor effectiveness. Melamine at a concentration ranging from 1–20 mg/L is tested. Findings conclude that the polymerization method and the QCM nanosensor for selective melamine detection were adequate substitutes for the technologies currently used for detecting melamine.

New insights into the mechanism of pyrite oxidation in copper(II)–ammonia–thiosulfate gold leaching system: An Electrochemical, AFM, Raman spectroscopy and XPS investigation

The nontoxicity, low cost, and environmental friendliness of the Cu2+–NH3–S2O32− gold leaching system make it a viable alternative to cyanide-based systems. However, the strong influence of certain sulphide minerals (e.g., pyrite) on the performance of the former system complicates its compositional regulation. Herein, the mechanism of electrochemical pyrite oxidation in the Cu2+–NH3–S2O32− system is probed by electrochemical techniques combined with surface analysis techniques. The results indicate that the anodic oxidation of pyrite can be assigned to active, passive, or transpassive regions, depending on the applied potential, with high potentials accelerating the reactions on the pyrite surface. Thiosulphate concentration is shown to influence the surface properties and the rate of surface reactions of pyrite. AFM images indicated that the morphological changes on the pyrite electrode surface became much rougher with increasing potential. Moreover, Raman spectroscopy and XPS provided strong evidence for the analysis of the surface species of pyrite surface oxidation. Our work will further explain and provide a mechanism for the oxidation of pyrite in the Cu2+–NH3–S2O32− system. More importantly, this study is expected to be able to provide a theoretical basis for guiding the regulation and control of gold leaching reagent in the Cu2+–NH3–S2O32− system.

The Application of Dextran Sodium Sulfate to the Efficient Separation of Ilmenite and Forsterite, as a Flotation Depressant

A depressant is essential to the effective flotation-based separation of ilmenite and forsterite, based on their comparable physicochemical characteristics. In this work, dextran sodium sulfate (DSS) was initially introduced as a depressant, to aid in the separation of ilmenite and forsterite. Comparing the DSS to conventional natural starch, the results indicate that the forsterite exerts a greater depression over the ilmenite. The difference in recovery of ilmenite and forsterite was 75.44% at 10 mg/L of DSS dosage. The DSS was chemisorbed strongly onto the forsterite surface via Mg active sites, whereas its interaction with the ilmenite surface via physisorption was weak, based on the XPS and molecular-dynamics-simulation analyses. The results of the AFM and QCM-D investigations showed that the DSS adsorption layer on the forsterite surface was larger than those on the ilmenite surface. Consequently, DSS may function as a depressant, to effectively separate forsterite from ilmenite ore.

Temperature-dependent photoluminescence down to 77 K of organotin molecular rotors: eco-friendly synthesis, photophysical characterization, X-ray structures, and DFT studies.

Fluorescent organotin compounds are useful in sensing, optoelectronic devices, and in vitro bioimaging. Although in vitro fluorescence bioimaging shows low resolution at room temperature, a better resolution is possible at cryotemperatures. Therefore, the search for new cryoluminescent materials with potential application in high-resolution fluorescence bioimaging remains a great challenge. Herein, we report the cryoluminescence properties of two fluorescent bis-organotin compounds, namely, BisNTHySnBu2 (5) and BisNTHySnPh2 (6), synthesized via microwave irradiation. All compounds were fully characterized using 1H, 13C, and 119Sn NMR spectroscopy, Raman spectroscopy, IR spectroscopy, and HR-MS. The 119Sn δ and 3J(1H,119Sn) of 5 and 6 indicate that two Sn-ligands are chemically and electronically equivalent, as confirmed by cyclic voltammetry. The crystal structure of 6 showed pentacoordinate tin atoms with skeleton ligands. The study of self-assembled monolayers of both Sn-complexes via STM microscopy revealed a similar supramolecular packing in lamella-like patterns, adopting a face-on arrangement, where molecules stay flat lying on HOPG in accordance with the height profile of closely packed monolayers on graphite of about 0.33 nm thickness. However, only the Sn complex 6, which bears phenyls, covers large surface areas. The photophysical properties of bis-organotin compounds were also investigated in solution (room and low temperatures) and in the solid state. Good luminescence properties in solutions with fluorescence quantum yields (Φ) of approximately 35% and 50% were found. Despite this, Φ is quenched in the solid state because of aggregation, as supported by solvent/non solvent fluorescence studies, which is in agreement with STM and AFM investigation.

Optimization of the corrosion inhibition performance of novel oxadiazole thione-based Schiff base for mild steel in HCl media using Doehlert experimental design

This study aimed to evaluate the effectiveness of 3-((dicyclohexylamino) methyl)-5-(4-((3, 4-dimethoxybenzylidene) amino) phenyl)-1, 3, 4-oxadiazole-2(3H)-thione (DMOT) in inhibiting the deterioration of mild steel in a 1 M HCl solution. Weight loss and electrochemical measurements were used to assess the inhibition performance and synthesis of DMOT. The characterization of DMOT was conducted through NMR and FTIR measurements, while SEM and AFM were used in the surface analysis. DFT calculations were used to investigate the chemical and theoretical properties of DMOT. The results of electrochemical measurements showed that the inhibition efficiency increased as the concentration of the inhibitor increased, with an optimal concentration reaching an inhibition efficiency of 99.17%. Polarization curves revealed that DMOT molecules behaved as a mixed-type inhibitor, with adsorption following the isotherm of Langmuir. The adsorption of DMOT on the corroded metal's surface was verified by SEM and AFM investigations. Using quantum chemical calculations, the quantum chemical properties of the DMOT were evaluated.

Effect of CsBr on the optical properties and electrical conductivity of PVP/PVA composite for flexible optoelectronic devices

This research contributes to the field by investigating the novel combination of PVP/PVA with CsBr NPs and elucidating the structural, optical, and electrical modifications that result from this combination, particularly focusing on the potential for energy storage and semiconductor characteristics of CsBr NPs. The insertion of CsBr NPs as a nanofiller has increased the degree of amorphousness in the PVP/PVA mixture, according to the XRD of the samples under investigation. The degree of crystallinity reduced from 32.15 to 18.56. FT-IR confirms the interaction or complexation of CsBr NPs with polymer blend. AFM investigations have revealed modifications in the surface morphology of the prepared films from smooth to rough as a result of the CsBr nanofiller. Utilizing UV/vis absorption spectra, the values of direct and indirect band gaps were determined. The optical band gaps decreased as CsBr NPs concentration increased, reaching a maximum of 3.65 eV for permitted indirect transition. By Jonscher's universal power equation, composites have a higher AC conductivity at high frequencies. It is also found to rise with increasing nanoparticle concentration. The film containing 15 wt% CsBr NP exhibits good optical properties, good conductivity, and a high dielectric constant. Dielectric constants (ε′ and ε′′) improved with increasing CsBr NPs concentration and decreased with rising frequency. The polymer nanocomposite acquired met the essential optical and electrical criteria, indicating its suitability for various electronic applications. These applications encompass functions such as energy storage devices, gas sensors, and optoelectronic devices.

NiSe integrated with polymerized reduced carbon sheet: As an effective electrocatalyst for methanol oxidation reaction

A low-energy approach was used to create ternary composites of hollow tubular Poly-N-methyl pyrrole (P-NMPy) and NiSe nanoparticles decorated onreduced graphene oxide (RGO). On the surface of RGO, P-NMPy, and NiSe nanoparticles were uniformly disseminated. The RGO/NiSe@P-NMPy (RNP) polymer nanocomposite was made utilizing a straightforward chemical oxidative process. The RGO/NiSe@P-NMPy nanocomposite was studied using FTIR spectroscopy, UV–visible, XRD, FE-SEM with EDAX, AFM, TEM and electrochemical investigations. The electrocatalytic activity of this polymer nanocomposite for the methanol oxidation reaction in alkaline environments was validated using cyclic voltammetry. The RGO/NiSe@P-NMPy electrocatalyst shows excellent electrocatalytic activity, lower oxidation potential (0.1 V), improved current density (127 mA/cm2), excellent stability and longevity (900 s) towards methanol oxidation reaction (MOR) in alkaline medium. It was observed RGO/NiSe@P-NMPy electrocatalyst, the ECSA value is 70.83 m2/g. This result clearly depicts that RGO/NiSe@P-NMPy electrocatalyst has more active sites for MOR reaction. According to the results, the P-NMPy introduction in RGO/Nickel Selenide structure can enhance the performance of methanol oxidation and increase the resistance to CO in comparison with monometallic catalysts.

The effect of periodate oxidation of basil seed gum and its addition on protein binding

This study attempted to determine the best point of basil seed oxidation by applying response surface methodology (RSM) with 3 factors of temperature (35–45 °C), pH (3–7) as well as time (3–7 h), at 3 levels. The produced dialdehyde basil seed gum (DBSG) was collected and its physicochemical properties were determined. Fitting of quadratic, linear polynomial equations was subsequently done by considering the insignificant lack of fit, as well as highly considerable R2, in order to probe the probable relationship existing between these considered variables as well as the obtained responses. So the considered optimal related test conditions, which included pH = 3, T = 45 °C as well as Time = 3 h, were specified to produce the highest percentage of aldehyde (DBSG32), optimal (DBSG34) and the (DBSG74) samples with the highest viscosity. The results obtained by FTIR and aldehyde content determination provided the indication that dialdehyde groups were formed in a way that was in equilibrium with the considered the hemiacetal form which was dominant. Furthermore, AFM investigation related to the considered DBSG34 sample displayed over-oxidation as well as depolymerization; this might be due to the enhanced hydrophobic qualities, as well as the decreased viscosity. While the DBSG34 sample had the most dialdehyde factor group with a particular tendency for the combination having the proteins' amino group, DBSG32 and DBSG74 samples could be desirable for industrial uses owing to no overoxidation.

Characterization and Assessment of PEEK/Silicon Dioxide Composite.

In the domain of dentistry, PEEK materials have been utilised as removable partial denture frameworks, implant substances, and fixed dental prostheses. Even though PEEK polymer has a low modulus of elasticity, its mechanical attributes could be fine-tuned by integrating various inorganic filler materials. The study intends to characterise and assess Nano SiO2/PEEK composite prepared by using the melt blend approach. The design of this study uses 3% SiO2 and PEEK composite made using the melt blend technique and studies their characteristics with reference to pure PEEK. The following assessments are conducted: SEM and EDX assessment with AFM investigation in addition to tensile strength test, transverse strength test, and wettability test. All data were scrutinised by SPSS software version 24 and the statistical analyses included the mean, standard deviation, and the independent sample t-test. The outcomes of this investigation pertain to the differences in characteristics of a composite of SiO2/PEEK compared with pure PEEK. The outcomes indicate that there is a statistically highly significant increase in the mean value of transverse strength was seen with the PEEK/SiO2 composite (3503.02 MPa) versus PEEK (2694.61 MPa), while there is a statistically significant decrease in the mean value of the tensile strength for PEEK/SiO2 (63.69 MPa) versus PEEK (97.62 MPa). Moreover, improvement in hydrophobic characteristics and surface roughness of PEEK/SiO2 (81.78°), (0.66 nm) versus PEEK (71.01°), (1.23 nm), respectively, thus giving more chance to composite to be investigated in human bone/implant substitution. Furthermore, the results of EDX and SEM images exhibited adequate distribution of Nano SiO2 within the PEEK matrix. There was also a statistically substantial decrease in the surface roughness and tensile strength obtained from the AFM investigation. As far as this study is concerned, a conclusion can be made that we can use 3% Nano SiO2 to prepare a composite of SiO2/PEEK by using the melt blend approach. Nano SiO2 can alter the SiO2/PEEK composite's transverse strength and reduce the hydrophobic characteristics of the surfaces with proper distribution of nanoparticles within the matrix of PEEK with less surface roughness.

Synthesis and characterization of manganese-doped FeS2 thin films via chemical spray pyrolysis

A thin film of iron disulfide (FeS2) and Mn-doped was prepared using the chemical spray pyrolysis (CSP) method at a constant temperature of the glass substrate at around 400 °C. According to XRD examination, films were structurally cubic oriented with a predominant planar orientation (201). The doping of Mn ions in the FeS2 host matrix was confirmed by a minor shift of the diffraction peak towards the lower 2θ values. The surface of the produced film for pyrite was homogeneous, according to the AFM investigations. According to the XRD data, the predicted grain size altered as the consistent manganese increased. When compared to undoped FeS2 thin films, the Mn2+- doped FeS2 thin films' desired bandgap energy showed a red shift.

Thermal and mechanical characterization of polypropylene composite membrane doped with TiO2 nanoparticles

The HVAC (Heating, Ventilating, and Air Conditioning) industry offers many opportunities for membrane-based gas separation technologies. In this study, a hollow polypropylene (poly-P) fibre membrane loaded with nanoparticles was created to dry out the indoor air. The mechanical and thermal stability of polypropylene loaded nanoparticles (TiO2/poly-P) usually improve with increasing titanium concentration. The example of poly-P with a 4% volume concentration of TiO2 nanoparticles in a polypropylene matrix shows the highest improvement in thermal stability. Atomic force and scanning electron microscopy were used to examine the nanocomposites' structure, and the results showed a correlation between the change in the thermal and mechanical characteristics and the change in TiO2/poly-P content. According to AFM investigations, when titanium nanoparticles are added to poly-P, the supramolecular structure is altered and an ordered structure is created. In comparison to 2% TiO2 doped poly-P nanocomposites, films containing 4% TiO2 demonstrated a more effective immediate moisture retention capacity, according to moisture absorption analyses. This study offers a fresh viewpoint for enhancing the poly-P composite membrane's ability to dehumidify the air.

Structural and mechanical behavior of Zr-W-Ti thin film metallic glasses prepared by multitarget co-magnetron sputtering

Zr-W-Ti thin films were deposited by magnetron co-sputtering technique with varied Ti-sputtering power between 25 and 150 W. The effect of Ti-sputtering power on their physical and mechanical properties was investigated. As a results of FE-SEM, XPS, AFM, XRD, and HR-TEM investigations, the Ti-sputtering power affected the Ti-containing structure of ZrW-based films, which exhibited an amorphous phase with a very low surface roughness layer. The mechanical properties, tested by nano-indentation, revealed the films strongest hardness and elastic modulus of 8.6 GPa and 121.3 GPa, respectively. In addition, the plastic responded, especially the serrated flow and shear banding showed that the prepared Zr-W-Ti thin films were excellent candidates for surface coating as the thin film metallic glasses (TFMGs).

Influence of Post-Deposition Thermal Treatments on the Morpho-Structural, and Bonding Strength Characteristics of Lithium-Doped Biological-Derived Hydroxyapatite Coatings

We report on hydroxyapatite (HA) of biological-origin doped with lithium carbonate (LiC) and lithium phosphate (LiP) coatings synthesized by Pulsed laser deposition onto Ti6Al4V substrates fabricated by the Additive manufacturing technique. A detailed comparison from the structural, morphological, chemical composition, wetting behavior and bonding strength standpoints of as-deposited (NTT) and post-deposition thermal-treated (TT) coatings at temperatures ranging from 400 to 700 °C (i.e., TT400–TT700), was performed. Structural investigations indicated a complete crystallization of the initially amorphous HA-based layers at temperatures in excess of 500 °C. The morphological analyses emphasized the rough appearance of the film surfaces, consisting of particulates whose dimensions increased at higher temperatures, with an emphasis on LiC coatings. AFM investigations evidenced rough surfaces, with a clear tendency to increase in corrugation with the applied temperature, in the case of LiC coatings. A hydrophobic behavior was observed for control, NTT and TT400 samples, whilst a radical shift towards hydrophilicity was demonstrated for both types of structures at higher temperatures. In the case of TT500–TT700 coatings, the pull-out adherence values increased considerably compared to control ones. Taking into consideration the obtained results, the positive influence of post-deposition thermal treatments (performed at higher temperatures) on the physical–chemical and mechanical properties of LiC and LiP coatings was indicated. Alongside these improved characteristics observed at elevated temperatures, the sustainable nature of the used BioHA materials should recommend them as viable alternatives to synthetic HA ones for bone implant applications.

Development of polymethylmethacrylate/reduced graphene oxide composite films as thermal interface materials

AbstractWith the miniaturization and integration of electronics into more powerful but smaller functional devices, major challenges arise. One of them is to efficiently dissipate the significant amount of thermal energy produced by these electronic devices. This requires interface materials with good thermal management properties. Reduced graphene oxide has attracted a lot of interest in this area due to its good thermal conductivity, similar with those of pristine graphene. In this work, polymethylmethacrylate/reduced graphene oxide (PMMA/RGO) composite thin films have been generated by drop casting mixtures of PMMA solutions and RGO suspensions, all prepared in N,N‐dimethylformamide (DMF) solvent. Raman, SEM and AFM investigations confirmed that homogenous PMMA/RGO composite thin films have been obtained, with RGO being uniformly distributed in the blending. Further measurements demonstrated that the thermal conductivity of RGO/PMMA composites increased with the concentration of RGO in the polymeric mixture: for the highest RGO content, the thermal conductivity increased by 210%, with no important modifications of electrical resistivity. These results are very promising for the development of new thermal interface materials based on PMMA/RGO composites to be used, for instance, in automotive industry.