Poly Methyl Methacrylate Solutions Research Articles

Wettability of a Polymethylmethacrylate Surface by Fluorocarbon Surfactant Solutions

To clarify the adsorption behavior of fluorocarbon surfactants on PMMA surfaces, the contact angles of two nonionic fluorocarbon surfactants (FNS-1 and FNS-2) and an anionic fluorocarbon surfactant (FAS) on polymethylmethacrylate (PMMA) surface were determined using the sessile drop method. Moreover, the effects of molecular structures on the surface tension, adhesion tension, solid–liquid interfacial tension, and adhesion work of the three fluorocarbon surfactants were investigated. The results demonstrate that the adsorption amounts for three fluorocarbon surfactants at the air–water interface are 4~5 times higher than those at the PMMA–solution interface. The three fluorocarbon surfactants adsorb on the PMMA surface by polar groups before CMC and by hydrophobic chains after CMC. Before CMC, FNS-2 with the smallest molecular size owns the highest adsorption amount, while FAS with large-branched chains and electrostatic repulsion has the smallest adsorption amount. After CMC, the three fluorocarbon surfactants form aggregates at the PMMA-liquid interface. FAS possesses the smallest adsorption amount after CMC. Besides, FNS-1 possesses a higher adsorption amount than FNS-2 due to the longer fluorocarbon chain and the lower CMC value of FNS-1. The adsorption behaviors of nonionic and anionic fluorocarbon surfactants on the PMMA surface are different. FAS forms interfacial aggregates before CMC, which may be attributed to the electrostatic interaction between the anionic head of FAS and the PMMA surface.

Doping a highly charged, water-soluble lanthanide complex into a hydrophobic polymer for the preparation of luminescent films

Doping a highly charged water-soluble complex in a hydrophobic polymethyl methacrylate (PMMA) to form transparent film is demonstrated with using a heptaanionic tri-TbIII complex of thiacalix[4]arene-p-tetrasulfonate (TCAS), formulated as Tb3TCAS2. A bulky hydrophobic countercation, trihexyl(tetradecyl)phosphonium (THTDP+), enabled the isolation of the Tb3TCAS2 salt, which was soluble in a PMMA solution in chloroform. The drop casting of a polymer solution containing 10 wt% THTDP–Tb3TCAS2 salt yielded a transparent film with energy-transfer luminescence. Near-infrared emitting films with Yb3TCAS2 and Nd3TCAS2 were also prepared. The luminescence lifetime (τ) (1.15 ms) of 1.0 wt% Tb3TCAS2-doped PMMA films surpassed that of the salt (0.924 ms), while the luminescence quantum yield (Φ) of the film (0.17) was smaller than that of the salt (0.33). DMSO was the suitable solvent for the salt, providing longer τ (1.40 ms) and larger Φ (0.44) at 0.50 wt%. A low salt concentration in PMMA resulted in a long lifetime. Spin-coated films had longer lifetimes (1.47 ms) at 1.0 wt% owing to a solution-like PMMA environment preventing Tb3TCAS2 aggregation. Drop-casted films had larger Φ values than spin-coated films, as the former might contain salt-like Tb3TCAS2 aggregates.

Surface feature of PMMA films on NiTi alloy substrate by the spin coating method

Polymethylmethacrylate (PMMA) films are deposited on NiTi shape memory alloy by using the spin coating method. Different ratios of PMMA powder to Toluene were mixed with magnetic stirrer for a duration of 12 h. The various concentrations of solution (mol. %) were used for the spin coating method on the substrate NiTi to produce thin films. The samples were cured in various environment from room to furnace temperature. The surface features of PMMA films were investigated by using an optical microscope. Thermal and mechanical behavior of the NiTi substrate and composites was and studied in the paper. The spin coating and post-processing conditions determined the surface morphology that is featureless or dominate by pinholes and other surface defects. The spin-coated coating at 200 rpm improved film surfaces with 4 mol % PMMA solution. Surface defects in the form of pinholes appear on the surface of the film obtained by spin-coating at 3200 rpm from 8 mol % solution and post-baked at 80 °C for 60 min on a hot plate in an oven inside a vacuum chamber. Different coating properties depends on the preparation parameters by spin coating and thermal and microstructural, mechanical properties are explained and discussed in the paper.

Fabrication of Porous Carbon-Composite Nanofibers Via Electrospinning and Their Application in Ion Storage System

Nanoporous materials have attracted considerable attention for various potential applications in sensors, optical, magnetic and electronic devices due to their high specific surface area and distinctive physicochemical properties. Particularly, porous carbon-composite materials can be used in the field of catalysis, separation, purification, capture and energy storage/conversion systems. In this work, we prepared highly porous carbon-composite nanofibers with hollow-structures by electrospinning combined with hundreds of nanometers sized silica nanoparticles and 2D MXene flakes and demonstrated the applications in ion storage systems. Firstly, nanoparticles and MXene flakes embedded-polyacrylonitrile(PAN) was electrospun with single and dual nozzles, respectively. In the case of electrospinning via dual nozzle , PAN/Mxene solution and polymethyl methacrylate (PMMA) solution were used as shell and core materials, respectively. After the electrospinning process, the nanofibers were stabilized at 280oC, followed by a carbonization at 800oC for 1h. Selective removal of silica nanoparticles by HF solution after the carbonization and the decomposition of PMMA at 400oC resulted in the well defined hollow-structured carbon-composite nanofibers. The morphologies of the nanofibers depends on the concentration and size of silica nanoparticles and Mxene flakes and the each specific surface area was higher about 6 and 7 times than those of normal carbon nanofibers. Particularly, the carbonization of MXene-embedded nanofibers successfully removed the functional groups on the MXene such as –F and –OH which are known to hinder Li-ion transport. The hollow structured carbon composite nanofibers with tailored surface terminations and the increased specific surface area were utilized as a electrode materials of ion storage systems and showed improved electrochemical performance compared to normal carbon nanofibers or carbon-MXene composite paste. Figure 1

Electrospun PMMA fibers blended with core‐shell PCM/PS microspheres for thermal regulating applications

AbstractPhase changing materials (PCMs) have been widely investigated because of their unique properties and applications. In recent years, PCMs have been embedded into polymer fibers for thermal regulating purposes. The PCM‐containing polymer fibers, however, usually suffer the leakage problem because PCMs are not covered well by polymers in fibers. To solve this problem, in this study, we develop a facile strategy to fabricate PCM‐containing polymer fibers without the leakage problem. The PCM/polystyrene (PS) core‐shell microspheres are first prepared by suspension polymerization, in which n‐hexadecane is used as the PCM. By blending the PCM/PS microspheres into polymethyl methacrylate (PMMA) solutions, The PMMA fibers blended with core‐shell PCM/PS microspheres can be prepared via electrospinning. Acetic acid is chosen as the solvent, which can selectively dissolve PMMA and cannot dissolve PS. Therefore, the morphologies of the core‐shell PCM/PS microspheres can be maintained during the electrospinning processes. The microspheres and fibers are characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Thermal imaging results demonstrate that the PCM‐containing fibers can effectively regulate temperatures and fibers with higher contents of PCM exhibit better thermal regulating behaviors. Repeated thermal regulating experiments are also conducted for up to 4 cycles.

Spin-casting of Micron-Scale Thick PMMA Films with Embedded Au Nanoparticles Formed by Laser Ablation in Liquid

Background: A Facile, scalable approach to fabrication of organic thin films with an embedded layer of nanoparticles in the ambient environment. The approach is based on step-bystep spin-coating of polymethylmethacrylate (PMMA) films and a nanoparticle layer. Objective: The goal of the present work is to fabricate a sandwich structure of the PMMA films for the top and bottom layers of a sandwich structure as well as a middle layer of nanoparticles formed in solution by the Laser Ablation in Liquid (LAL) method. Methods: First, a PMMA thin film was fabricated by spin-casting of PMMA solution in ethylacetate. Secondly, a solution of Au nanoparticles synthesized by laser ablation in ethanol was spin-cast on a prefabricated PMMA film. The distribution of Au nanoparticles and the morphology of the resulting film were analyzed using scanning electron microscopy (SEM), optical microscopy, and atomic microscopy (AFM). Finally, another PMMA layer was spin-cast on the nanoparticle-decorated film. Results: A hybrid organic film with the embedded layer of nanoparticles was fabricated using the spin-casting method for top and bottom layers as well as for the middle layer of Au nanoparticles fabricated by laser ablation in ethanol by a pulsed UV laser. Statistical and fractal analysis shows uniform distribution of nanoparticles on length scale above ten microns. Conclusion: Spin-cast-based layer-by-layer approach to fabrication of sandwich structures of organic films with embedded nanoparticlesis a facile and scalable method for hybrid organic - nanoparticle films. This approach can be extended for the fabrication of multi-layered hybrid structures.

Deposition of Organic-Inorganic Nanocomposite Coatings for Biomedical Applications

Polymethylmethacrylate (PMMA) is a material of choice for many biomedical coating applications. However, such applications are limited due to the toxicity of the traditional solvents used for the solution processing of PMMA coatings and composites. This problem is addressed using an isopropanol-water co-solvent, which allows for the dissolution of high molecular mass PMMA and the fabrication of coatings by a dip-coating method from concentrated PMMA solutions. The use of the co-solvent offers a versatile strategy for PMMA solubilization and coating deposition, despite the insolubility of PMMA in water and isopropanol. Composite coatings are obtained, containing hydroxyapatite, silver oxide, zinc oxide, micron size silica and nanosilica. Such coatings are promising for the manufacturing of implants with enhanced biocompatibility, bioactivity and antimicrobial properties and the fabrication of biosensors. Ibuprofen, tetracycline and amoxicillin are used as model drugs for the fabrication of PMMA-drug composite coatings for drug delivery. The microstructure and composition of the coatings are analyzed. The versatile dip-coating method of this investigation provides a platform for various biomedical applications.

The High Flux of Superhydrophilic-Superhydrophobic Janus Membrane of cPVA-PVDF/PMMA/GO by Layer-by-Layer Electrospinning for High Efficiency Oil-Water Separation.

A simple and novel strategy of superhydrophilic-superhydrophobic Janus membrane was provided here to deal with the increasingly serious oil-water separation problem, which has a very bad impact on environmental pollution and resource recycling. The Janus membrane of cPVA-PVDF/PMMA/GO with opposite hydrophilic and hydrophobic properties was prepared by layer-by-layer electrospinning. The structure of the Janus membrane is as follows: firstly, the mixed solution of polyvinylidene fluoride (PVDF), polymethylmethacrylate (PMMA) and graphene oxide (GO) was electrospun to form a hydrophobic layer, then polyvinyl alcohol (PVA) nanofiber was coated onto the hydrophobic membrane by layer-by-layer electrospinning to form a composite membrane, and finally, the composite membrane was crosslinked to obtain a Janus membrane. The addition of GO can significantly improve the hydrophobicity, mechanical strength and stability of the Janus membrane. In addition, the prepared Janus membrane still maintained good oil-water separation performance and its separation efficiency almost did not decrease after many oil-water separation experiments. The flux in the process of oil-water separation can reach 1909.9 L m−2 h−1, and the separation efficiency can reach 99.9%. This not only proves the separation effect of the nanocomposite membrane, but also shows its high stability and recyclability. The asymmetric Janus membrane shows good oil-water selectivity, which gives Janus membrane broad application prospects in many fields.

High‐Efficiency Vivid Color CIGS Solar Cell Employing Nondestructive Structural Coloration

Structural coloration is an effective method for coloring a solar cell with minimum optical loss. For the application of building integrated photovoltaics, it is desirable to integrate structural colors directly onto the solar cell without damaging it with an economical process. Herein, a solution‐processed distributed Bragg reflector (sDBR) is introduced to realize efficient and vividly colored CuInxGa(1−x)Se2 (CIGS) solar cells. The sDBR is directly combined with the CIGS solar cell at room temperature without damaging the photoactive layer. The sDBR is fabricated on CIGS solar cells by spin coating alternate layers of solution‐processable TiO2 nanoparticles bound with acetylacetone and a polymethyl methacrylate solution. The vividly colored CIGS solar cells exhibit high reflectivity and narrow bandwidth at the designated wavelength, resulting in pure red, green, and blue. The reduction in the photocurrent by the coloring is minimized due to the narrow bandwidth characteristics of the sDBR, while a gain in the photocurrent is obtained at wavelengths outside of the range used for coloring due to the antireflection effect of the sDBR. As a result, the power conversion efficiency of R, G, and B sDBR/CIGS solar cells is 97.2%, 99.4% and 102%, respectively, compared to a conventional CIGS solar cell.

Cytocompatibility of Polymethyl Methacrylate Honeycomb-like Pattern on Perfluorinated Polymer.

In this study, we present a simple approach for developing a biocompatible polymer scaffold with a honeycomb-like micropattern. We aimed to combine a plasma treatment of fluorinated ethylene propylene (FEP) substrate with an improved phase separation technique. The plasma exposure served for modification of the polymer surface properties, such as roughness, surface chemistry, and wettability. The treated FEP substrate was applied for the growth of a honeycomb-like pattern from a solution of polymethyl methacrylate (PMMA). The properties of the pattern were strongly dependent on the conditions of plasma exposure of the FEP substrate. The physico-chemical properties of the prepared pattern, such as changes in wettability, aging, morphology, and surface chemistry, were determined. Further, we have examined the cellular response of human osteoblasts (U-2 OS) on the modified substrates. The micropattern prepared with a selected combination of surface activation and amount of PMMA for honeycomb construction showed a positive effect on U-2 OS cell adhesion and proliferation. Samples with higher PMMA content (3 and 4 g) formed more periodic hexagonal structures on the surface compared to its lower amount (1 and 2 g), which led to a significant increase in the pattern cytocompatibility compared to pristine or plasma-treated FEP.

OBTAINING COMPOSITE FIBROUS MATERIALS BY ELECTROSPINNING FROM SOLUTIONS OF POLYMETHYL METHACRYLATE WITH THE ADDITION OF CARBON NANOTUBES

The article is devoted to the research and testing of a method for producing nonwoven material from nano- and microfibres saturated with carbon nanotubes by the method of electrospinning, the study of the effect of ultrasonic treatment of a polymer solution and the addition of carbon nanotubes on the properties of the solution and the morphology of the resulting material. As a result of the study, samples of materials were obtained from solutions of polymethylmethacrylate, treated and not treated with ultrasound, organoleptic and microscopic studies of the obtained samples were carried out. A decrease in the viscosity of a polymer solution treated with ultrasound and a significant decrease in the diameter of fibres obtained from such solutions were found.

MXene (Ti3C2Tx) anodes for asymmetric supercapacitors with high active mass loading

MXene (Ti3C2Tx) is an emerging material choice for advanced energy storage. However, the relatively low areal capacitance is a bottleneck in developing asymmetric supercapacitors with enhanced energy-power characteristics in large voltage windows. A simple and straightforward approach is proposed to design and fabricate Ti3C2Tx-multiwalled carbon nanotube (Ti3C2Tx-CNT) composite electrodes. Polymethylmethacrylate (PMMA) is used as a binder for electrodes with 40 mg cm−2 high active mass loadings (AML); meanwhile, both multilayered Ti3C2Tx and CNT are efficiently dispersed in PMMA solution. The fabricated Ti3C2Tx-CNT electrodes with different CNT contents are tested in a −1.1~-0.3 V negative potential window and analyzed by different electrochemical techniques. The optimization of Ti3C2Tx-CNT-PMMA composition facilitates the design of anodes with capacitance of 2.26 F cm−2 in Na2SO4 electrolyte, which is essentially higher than literature results for Ti3C2Tx. The ability to obtain high capacitance in the Na2SO4 electrolyte is a crucial result, which facilitates the fabrication of asymmetric aqueous devices operating at 1.6 V. The Ti3C2Tx-CNT anode is combined with a MnO2-CNT cathode in an asymmetric cell, which shows a 1.24 F cm−2 capacitance at 3 mA cm−2.

Pickering emulsion strategy for high compressive carbon aerogel as lightweight electromagnetic interference shielding material and flexible pressure sensor

Lightweight and elastic carbon aerogels (CAs) are promising candidates for use in the development of pressure sensors and electromagnetic interference (EMI) shielding materials. However, the development of a simple strategy for the fabrication of CAs with the properties of high compression and excellent fatigue resistance is still significantly challenging. In this study, Pickering emulsion gel technology, which depends on the aqueous dispersion of cellulose nanofibrils (CNF), graphene oxide (GO), and 1, 2-dichloroethane solution of polymethyl methacrylate (PMMA) that occurs in mixture, emulsification, gelation, and freeze-drying process, was used to form a CNF-GO/PMMA composite aerogel. Subsequently, the final carbon aerogel (C-RGO/P) was obtained through annealing treatment. The resultant C-RGO/P exhibits super compressibility and excellent elasticity, and can resist an extreme compressive strain of 99.3% while maintaining 92.6% of the height retention after 5000 cycles at the strain of 80%. Additionally, it exhibits high sensitivity at the working pressure range of 0–1000 Pa, and can thus act as a wearable pressure sensor for the accurate monitoring of human physiological signals. Moreover, it can be used as an EMI shielding material with satisfactory EMI shielding effectiveness (SE) of 36.75 dB and specific shielding effectiveness (SSE) of 29400 dB cm3 g−1.

Development of a special cell for optical and electrochemical measurements using 3D printing and modern electronic base

A special design of the measuring cell was proposed, which makes it possible to determine the optical and electrochemical characteristics of thin-film electrochromic electrodes simultaneously. Also, the proposed cell provides constant temperature control using a small-sized thermostating unit built on Peltier elements and digital boards of W1209 thermostats. The cell was made using 3D printing with ABS plastic by the fused deposition method (FDM), followed by a sealing stage using a solution of polymethyl methacrylate dissolved in dichloroethane. In the course of the research, the use of a green laser with a wavelength of 520 nm was substantiated. Separately, the linearity of optical readings, the dependence of the indicators of the optical characteristics measurement system on temperature, as well as the uniformity of electrolyte heating in the cell, were studied. In addition, the pattern of the electric field was determined, which was an indicator of the uniformity of the current density distribution on the measured electrode. The obtained dependences made it possible to assert that the characteristics of the cell and the measuring system as a whole are suitable for the stated research purposes. It was also shown that the cost of the cell, together with the optical measuring system and the constant temperature control system, is more than two times cheaper than simple electrochemical cells offered by manufacturers. The proposed algorithm for the development of the cell design, the approach to the selection of components, as well as the given technical details, allow us to manufacture measuring equipment for the specific goals of the researcher. In this case, the given schematic, structural, and hardware solutions can be used separately from each other

Copper (II) Phthalocyanine (CuPc) Based Optoelectronic Memory Device with Multilevel Resistive Switching for Neuromorphic Application

AbstractThe 1D nanotubular organic semiconductor, copper (II) phthalocyanine (CuPc), embedded in poly‐methyl methacrylate (PMMA) is employed for the first time for multilevel resistive switching (RS) and neuromorphic applications. Single–double bonded planar CuPc tubes are synthesized via simple solvothermal methods and dispersed in the PMMA solution with different weight concentrations. The composite sample is deposited on an ITO coated transparent, flexible and conducting PET substrate to form Ag/CuPc@PMMA/ ITO device. I–V characterizations of the cell reveal a formation free, bipolar, non‐volatile, multilevel RS effect. The device shows a significantly large resistance ON/OFF ratio of 104, low threshold operating voltage (<2 V), large endurance (>104 cycles) and long retention time (>104 s) at room temperature. The multilevel resistive states are induced by visible light illumination. Based on the experimental data, the conduction mechanism of this type of RS memory device under the optical and the electrical impulse is attributed by the charge trapping and detrapping methods. The synaptic short‐term and long‐term potentiation are also studied on the device during the identical pulse training process. The proposed RS active material is a potential candidate for future artificial neural systems that simulate characteristics of human memory.

PMMA passivated CsPbI2Br perovskite film for highly efficient and stable solar cells

Cesium-based inorganic perovskite solar cells (PSCs), especially for the CsPbI2Br-based solar cells, have attained extensive attention due to its excellent thermal and phase stability. Solution-prepared CsPbI2Br films usually have some defects which demand to be passivated for PSCs and also their degradations often happen at the grain boundaries (GBs). Herein, by using polymethylmethacrylate (PMMA) solution, we optimize the perovskite film growth and further investigate the effect of PMMA treatment on the properties of the CsPbI2Br films. Time-resolved photoluminescence (TRPL) displays that the PMMA coating can improve the photoluminescence lifetime of CsPbI2Br perovskite films. Therefore, it is proved that PMMA coating film can effectively passivate the defects of the pure CsPbI2Br films, suppress the charge recombination with increased electron extraction efficiency, which improves the performance of solar cells. Consequently, the devices based on CsPbI2Br films with PMMA solution treatment exhibit average power conversion efficiency (PCE) over 11.18%, which is much higher than the efficiency of 9.69% for pure CsPbI2Br-based solar cells.

Light angle dependence of photothermal properties in oxide and porphyrin thin films for energy-efficient window applications

The photothermal experiments on the incident light angle dependence are carried out using simulated solar light on thin films of both iron oxides (Fe3O4 and Fe3O4@Cu2-xS) and porphyrin compounds (chlorophyll and chlorophyllin). Fe3O4 and Fe3O4@Cu2-xS are synthesized using various solution methods that produce mono-dispersed nanoparticles on the order of 10 nm. Chlorophyll is extracted from fresh spinach and chlorophyllin sodium copper is a commercial product. These photothermal (PT) materials are dispersed in polymethyl methacrylate (PMMA) solutions and deposited on glass substrates via spin coating that result in clear and transparent thin films. The iron-oxide based thin films show distinctive absorption spectra; Fe3O4 exhibits a strong peak near UV and gradually decreases into the visible and NIR regions; the absorption of Fe3O4@Cu2-xS is similar in the UV region but shows a broad absorption in the NIR region. Both chlorophyll and chlorophyllin are characterized with absorption peaks near UV and NIR showing a “U”-shaped spectrum, ideally required for efficient solar harvest and high transparency in energy-efficient single-pane window applications. Upon coating of the transparent PT films on the window inner surfaces, solar irradiation induces the photothermal effect, consequently raising the film temperature. In this fashion, the thermal loss through the window can be significantly lowered by reducing the temperature difference between the window inner surface and the room interior, based on a new concept of so-called optical thermal insulation (OTI) without any intervention medium, such as air/argon, as required in the glazing technologies. Single-panes are therefore possible to replace double- or triple panes. As OTI is inevitably affected by seasonal and daily sunlight changes, an incident light angle dependence of the photothermal effect is crucial in both thin film and window designs. It is found that the heating curves reach their maxima at small angles of incidence while the photothermal effect is considerably reduced at large angles. This angle dependence is well explained by light reflection by the thin film surface, however, deviated from what is predicted by the Fresnel's law, attributable to non-ideal surfaces of the substrates. The angle dependence data provide an important reference for OTI that window exposure to the sun is greater at winter solstice while that is considerably reduced in the summer. This conclusion indicates much enhanced solar harvesting and heat conversion via optically insulated windows in the winter season, resulting in much lower U-factors.

The Effect of Carbon Coatings on the Electrochemical Performance of Composite Electrodes

This work focuses on the effects of sample preparation and particle size on the dielectric properties of polymer nanocomposites. A comparison between the dielectric permittivity and dielectric loss of Polymethyl methacrylate (PMMA) samples, prepared by solution casting and compression molding, has been achieved. A Time Domain Spectrometer and an Agilant (HP) 4284A LCR precision meter, were furbished and used to measure the dielectric properties of insulating nanocomposite materials. The cast samples have shown different dielectric responses from the melt-pressed samples. These differences diminish with lengthening the dry time of the cast samples under vacuum. In addition, nanocomposite and microcomposite samples were prepared by solution casting of PMMA solution and Titanium dioxide (TiO2) particles. The dielectric properties of the nanocomposites were different from the polymer samples where a decrease in the dielectric permittivity of the nanocomposite has been observed. These differences in the dielectric response of the PMMA sample and the nano/micro composite samples might be due to many issues such as, sample preparation or the aggregation of the TiO2 nanoparticles in the polymer matrix. Furthermore, polymer-blends samples of PEO and PMMA have been prepared by solution casting method. The results reported in this work show similar trend compared to those reported in the literature.

Multicolor carbon dots with concentration-tunable fluorescence and solvent-affected aggregation states for white light-emitting diodes

Multicolor emissive carbon dots (M-CDs) have tremendous potential applications in manifold fields of bioimaging, biomedicine and light-emitting devices. Until now, it is still difficult to produce fluorescence tunable CDs with high quantum yield across the entire visible spectra. In this work, a type of M-CDs with concentration-tunable fluorescence and solvent-affected aggregation states was synthesized by solvothermal treatment of citric acid (CA) and 1-(2-pyridylazo)-2-naphthol (PAN) and the formation mechanism was monitored by different reaction time and raw material ratio. The fluorescence spectra of M-CDs in organic solvents can range from 350 to 750 nm by adjusting the concentration. M-CDs possess different aggregation states in water and organic solvents, accompanied by different fluorescence emission, which is attributed to the different surface states of various component CDs in M-CDs. Moreover, the obtained products can be uniformly dispersed into polymethylmethacrylate (PMMA) solutions as well as epoxy resins to fabricate transparent CDs/PMMA films and CDs/epoxy composites, which can effectively prevent the aggregation and produce multicolor and white light-emitting diodes (WLED). In addition, the prepared WLED with Commission Internationale de L’Eclairage (CIE) of (0.29, 0.31) by using M-CDs/epoxy resin as packages, demonstrating the M-CDs exhibit potential applications for light-emitting devices.

Effect of Slide Burnishing on the Surface Layer and Fatigue Life of Titanium Alloy Parts

Abstract The paper presents the results of a study investigating the effect of slide burnishing on the surface roughness, surface layer microhardness and fatigue life of Ti6Al2Mo2Cr titanium alloy parts. The burnishing process was performed with the use of a diamond tip tool. Different machining fluids were used as machining media. Prior to burnishing, the samples were subjected to turning. The burnishing process led to reduced surface roughness (average roughness Ra decreased by 3.5 times and roughness Rz decreased by 2.5 times) as well as increased surface layer microhardness (microhardness maximum increase by 12%) and fatigue life of the tested parts. A relationship between the machining medium and the burnishing effects was also observed. The addition of a surface-active polymethyl methacrylate solution to the machining medium led to an increase in the surface layer microhardness and fatigue life of the workpiece.