Search

Electrical discharge machining (EDM) has demonstrated its promising potential for surface modification. The integration of materials from tool electrode or powder that is mixed into the dielectric fluid has proven to modify the workpiece surface to enhance its mechanical properties, realize antibacterial effects, or increase biocompatibility. Recent EDM studies showed that due to non-contact forces, properties of the modified surface such as roughness values and the thickness of modified layer were significantly influenced when using magnetic field assisted EDM. Consequently, in this study, an external magnetic field with a strength of 0.66 T is used to assist the material transfer from tool electrode to workpiece surfaces during the EDM process. Pure silver and copper tools with a diameter of 2 mm are used to modify surfaces of Ti6Al4V workpieces at a discharge energy of 125 µJ with different polarities. Results show that the assistance by magnetic field significantly increases the content of transferred material from tool electrode to the workpiece surface. Additionally, it increases material removal rate and reduces the modified layer thickness. Magnetic field assisted EDM is a potential technology for improving the efficacy of the EDM surface modification. [ABSTRACT FROM AUTHOR]

The paper investigates the dependence of the sputtering yields by light ions bombardment of the surface layers of titanium and tungsten, modified with carbon, on the thickness of the layer. The theoretical study was conducted on the basis of a sputtering model (previously adapted to describe the sputtering of two-component targets and layered-inhomogeneous surfaces), based on two sputtering mechanisms, which allows to analyze the obtained dependencies. Theoretical calculations of the total yields sputtering by helium ions bombardment of the surface layers of titanium and tungsten modified with carbon are given in comparison with the results of computer simulation obtained using the SRIM-2013pro program. [ABSTRACT FROM AUTHOR]

The object of this research is the integrated processing of industrial waste from various industries, which makes it possible to reduce the use of material and energy resources and improve the ecological state of the environment. Waste from the chemical, petrochemical, and machine-building industries was subject to integrated technological processing. The common link that united the investigated complex technological cycles was the use of a regenerated mixed sorbent (activated carbon+kieselguhr), on the surface of which topochemical transformations of chemicals that were part of industrial waste took place. Using a regenerated mixed sorbent, exhausted industrial oil which was the mineral basis of the developed new C, S, N-containing plastic lubricants was purified. In particular, we have established the conditions for obtaining diethyl ammonium chloride from unusable pesticides of the formula R¹R²R³R4C6HCOOH∙HN(C2H5)2, whose topochemical interaction on the surface of the mixed sorbent leads to the formation of a sorbed fragment [sorbent (activated carbon+ +kieselguhr)]∙[(C2H5)2NC(=S)SK]. Subsequent interaction of aqueous solutions containing copper(II) ions with such a fragment leads to the formation of bis–(diethyldithiocarbamate)copper(II) on the surface of mixed sorbent. The resulting substances of the general composition [sorbent (activated carbon + kieselguhr)]∙{[(С2H5)2NC(=S)S]2Cu} were studied as thickeners and active polyfunctional components of the obtained plastic lubricants. Research into the tribological properties of new C, S, N-containing plastic lubricants showed their high anti-wear and heat-resistant properties and the possibility of effective use in highly loaded friction nodes. [ABSTRACT FROM AUTHOR]

This article presents the results of a study on the effect of electrolyte-plasma cementation on the phase composition of the surface-modified layer and the mechanical properties of 20X steel using different solutions. It has been determined that electrolyte-plasma cementation followed by quenching in solutions containing (a) 10% calcined soda (Na2CO3), 10% urea (CH4N2O), 10% glycerin (C3H8O3) and 70% distilled water and (b) 10% calcined soda (Na2CO3), 20% urea (CH4N2O) and 70% distilled water, results in the formation of a modified structure on the surface of 20X steel. This structure mainly consists of the α-Fe phase, along with separate particles of reinforcing phases, Fe3C and Fe3C7 carbides and martensitic αx-Fe phase. The plasma of the electrolyte was used to heat the samples. Then these samples were partially immersed in the electrolyte and held at a temperature of 950 ℃ for 5 min, followed by quenching. As a result of this process, it was found that 20X steel exhibits higher hardness. After the electrolyte plasma cementation, it was observed that the friction coefficient of the modified surface of the steel samples significantly decreased. Additionally, the wear volume was reduced by more than 6.5 times compared to the initial state. The average microhardness after the electrolyte-plasma cementation is 660 HV, which is nearly four times higher than that of the initial material.

A unique method for synthesizing a surface modifier for metallic hydrogen permeable membranes based on non-classic bimetallic pentagonally structured Pd-Pt nanoparticles was developed. It was found that nanoparticles had unique hollow structures. This significantly reduced the cost of their production due to the economical use of metal. According to the results of electrochemical studies, a synthesized bimetallic Pd-Pt/Pd-Ag modifier showed excellent catalytic activity (up to 60.72 mA cm−2), long-term stability, and resistance to COads poisoning in the alkaline oxidation reaction of methanol. The membrane with the pentagonally structured Pd-Pt/Pd-Ag modifier showed the highest hydrogen permeation flux density, up to 27.3 mmol s−1 m−2. The obtained hydrogen flux density was two times higher than that for membranes with a classic Pdblack/Pd-Ag modifier and an order of magnitude higher than that for an unmodified membrane. Since the rate of transcrystalline hydrogen transfer through a membrane increased, while the speed of transfer through defects remained unchanged, a one and a half times rise in selectivity of the developed Pd-Pt/Pd-Ag membranes was recorded, and it amounted to 3514. The achieved results were due to both the synergistic effect of the combination of Pd and Pt metals in the modifier composition and the large number of available catalytically active centers, which were present as a result of non-classic morphology with high-index facets. The specific faceting, defect structure, and unusual properties provide great opportunities for the application of nanoparticles in the areas of membrane reactors, electrocatalysis, and the petrochemical and hydrogen industries. [ABSTRACT FROM AUTHOR]

This article presents the results of a study on the effect of electrolyte-plasma cementation on the phase composition of the surface-modified layer and the mechanical properties of 20X steel using different solutions. It has been determined that electrolyte-plasma cementation followed by quenching in solutions containing (a) 10% calcined soda (Na2CO3), 10% urea (CH4N2O), 10% glycerin (C3H8O3) and 70% distilled water and (b) 10% calcined soda (Na2CO3), 20% urea (CH4N2O) and 70% distilled water, results in the formation of a modified structure on the surface of 20X steel. This structure mainly consists of the &#945-Fe phase, along with separate particles of reinforcing phases, Fe3C and Fe3C7 carbides and martensitic α'-Fe phase. The plasma of the electrolyte was used to heat the samples. Then these samples were partially immersed in the electrolyte and held at a temperature of 950 °C for 5 min, followed by quenching. As a result of this process, it was found that 20X steel exhibits higher hardness. After the electrolyte plasma cementation, it was observed that the friction coefficient of the modified surface of the steel samples significantly decreased. Additionally, the wear volume was reduced by more than 6.5 times compared to the initial state. The average microhardness after the electrolyte-plasma cementation is 660 HV, which is nearly four times higher than that of the initial material. [ABSTRACT FROM AUTHOR]

A unique method for synthesizing a surface modifier for metallic hydrogen permeable membranes based on non-classic bimetallic pentagonally structured Pd-Pt nanoparticles was developed. It was found that nanoparticles had unique hollow structures. This significantly reduced the cost of their production due to the economical use of metal. According to the results of electrochemical studies, a synthesized bimetallic Pd-Pt/Pd-Ag modifier showed excellent catalytic activity (up to 60.72 mA cm−2), long-term stability, and resistance to COads poisoning in the alkaline oxidation reaction of methanol. The membrane with the pentagonally structured Pd-Pt/Pd-Ag modifier showed the highest hydrogen permeation flux density, up to 27.3 mmol s−1 m−2. The obtained hydrogen flux density was two times higher than that for membranes with a classic Pdblack/Pd-Ag modifier and an order of magnitude higher than that for an unmodified membrane. Since the rate of transcrystalline hydrogen transfer through a membrane increased, while the speed of transfer through defects remained unchanged, a one and a half times rise in selectivity of the developed Pd-Pt/Pd-Ag membranes was recorded, and it amounted to 3514. The achieved results were due to both the synergistic effect of the combination of Pd and Pt metals in the modifier composition and the large number of available catalytically active centers, which were present as a result of non-classic morphology with high-index facets. The specific faceting, defect structure, and unusual properties provide great opportunities for the application of nanoparticles in the areas of membrane reactors, electrocatalysis, and the petrochemical and hydrogen industries.

A brief review is presented of studies in the field of heat-transfer enhancement and for increasing the critical heat fluxes (CHFs) during boiling and evaporation in thin horizontal liquid layers. The effect of the liquid layer height on heat-transfer efficiency at various heat fluxes has been analyzed. Decreasing the film thickness enhances heat transfer at low heat fluxes, while heat-transfer augmentation occurs at high heat fluxes in films whose height is greater than the capillary constant. The heat-transfer coefficient (HTC) first rises with a layer height, and then decreases to pool boiling values. The structures formed in thin liquid layers are examined in a wide range of layer heights and pressures. The mechanisms of formation of various structures and the effect on heat-transfer enhancement depending on process conditions were also discussed. The existence of regimes with heat-transfer enhancement during evaporation of a liquid layer at reduced pressures has been demonstrated. The heat-transfer coefficient in these regimes is higher than during nucleate boiling in a layer of the same height at a higher pressure. This is caused by the effect of the structures formed in these regimes. It has been found that CHF rises with an increase in the layer thickness to pool boiling values. The heat-transfer coefficients during nucleate boiling in thin films on capillary-porous surfaces are approximately three to five times higher than on a smooth surface. It has been demonstrated that there is an optimal film surface at low pressures, which provides higher heat-transfer coefficients than those on a smooth surface. Higher heat conductivity coatings of the same shape considerably increase CHFs in the entire pressure range for liquid layer thicknesses of the order of the capillary constant. It was found that, with a characteristic spacing between the coating fins, which is equal to the capillary constant of the liquid, the highest heat-transfer coefficients are attained in the experiments. [ABSTRACT FROM AUTHOR]

The wetting dynamics of modified capillary-porous surfaces made of aluminum and titanium was experimentally studied at free-convective heat exchange with the environment. The influence of the concentration of ethyl alcohol and its initial temperature on the wetting front velocity has been established. The volume concentration of alcohol in the mixture varied from 0 to 95.5 %. The characteristic modes of changes in the height of the liquid rise over capillary-porous surfaces over time have been expressed in the form of power dependences. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Computer-Aided Design & Computer Graphics / Jisuanji Fuzhu Sheji Yu Tuxingxue Xuebao is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, an experimental study investigating the effect of the geometrical shape of the circular and rectangular pin fins on the heat transfer performance and the boiling phenomenon is presented. A pool boiling experiment in the HFE-7100 dielectric working fluid under atmospheric pressure was conducted. Boiling curves and boiling heat transfer coefficients of different test cases were plotted to evaluate the heat transfer performance as well as the captured images of the boiling phenomenon on the test samples. Two quantities, flow resistance and wetted perimeter, were calculated to understand the behaviour of the boiling physics due to variation of fin geometrical shape and, hence, their effect on the heat transfer performance. It was found that the cooling performance of the rectangular pin fins was higher than that of the circular pin fins, despite having a slightly higher flow resistance of 4% and 7%, respectively. This is believed to be the result of the longer wetted perimeter up to 27%, whereby the nucleation site has a higher probability of generating more bubbles in the same boiling surface area. For the tested modified boiling surface with 196 and 144 pin fins, the average heat transfer performances were found to have differences of up to 3.54 and 1.58 times larger, respectively.

The effect of thermohydrogen treatment and vacuum ion–plasma nitriding on the determination of the volume and surface structure of ball heads made of Ti–6Al–4V alloy was studied. It was found that the submicrocrystalline structure formed in the head during thermohydrogen treatment makes it possible to achieve hardness values of 39–41 units HRC and a surface roughness of 0.02 μm. It was shown that the creation of a modified layer consisting of ε (TiN) and δ (Ti2N) titanium nitrides on the surface of a ball head and the solid interstitial solution of nitrogen in α-titanium makes it possible to completely eliminate material wear when testing for friction on ultra-high-molecular-weight polyethylene. The equivalent analysis was also conducted with a ball head that had been implanted in a human body for 12 years. It was found that the change in the color of the head, from slightly golden after nitriding to metallic, is due to the formation of an oxynitride nanoscale layer on the surface. It was shown that in contrast with films made of titanium oxide, the film developed in this study has high wear resistance.

The anthracite granules were coated with iron oxide by a solution combustion synthesis method in a muffle furnace oven. As for iron precursor, an iron-containing precipitate of water treatment plants was used. The influence of four different reducing reagents on surface phase composition and properties of the modified materials was investigated. Obtained samples were investigated using different diffraction and spectroscopic methods. Using the solution combustion synthesis method, anthracite granules formed fine dispersed and crystalline structures of iron oxides on their surface with the iron content up to 40.7 wt%. This had a positive effect on the catalytic capacity of the material for deironing of underground water as well as for the increase in specific surface area. The catalytic properties of the obtained samples and the effectiveness of deferrization of groundwater were investigated. The use of tested materials makes it possible to reduce of catalytic layer height of the filter media from 50 to 20 cm for the filtration rate 12 m/h and enhance the treatment efficiency during the first start-up of filters after regeneration up to 3 times. [ABSTRACT FROM AUTHOR]

In most industrial processes, heat exchangers are used for preheating, condensation and evaporation. Within these apparatuses, undesirable deposits often form. These deposits are known as fouling and cause a multitude of operational problems, such as a reduction in heat transfer, an increase in the pressure drop or a contamination of the product. Likewise, more frequent cleaning cycles are necessary to comply with hygiene standards. In view of the technical and economic requirements, strategies to reduce fouling are increasingly important. The modification of the surface of a heat exchanger offers a suitable means to reduce fouling. This review presents the current state of research concerning the influence of modified surfaces on fouling and cleaning in the food processing industry, with a focus on the energetic characteristics of different surfaces and their interactions with soilants. A special emphasis is placed on mineral and organic deposition as an essential part of food fouling. The goal is to establish a strategy for assessing the surface modifications that can mitigate complex food fouling. The chemical, thermal and mechanical resistance of coatings are evaluated based on the currently available literature. Finally, practical experience and economic considerations that contribute to a holistic view of fouling and cleaning processes are appraised, and the need for further research is addressed. [ABSTRACT FROM AUTHOR]

The poor interface of carbon fiber (CF) reinforced composites has long been one that researchers want to facilitate. A hierarchical structure of nano‐SiO2 and small‐sized graphene oxide (sGO) on CF was constructed by a layer‐by‐layer method. The electrochemically treated CF was evenly coated with sGO sheets as a medium layer, which made nano‐SiO2 uniformly spread over CF by electrostatic adsorption. The hierarchical structure could provide the synergistic reinforcement on the mechanical properties of CF composite by improving interface adhesion, mechanical interlocking, and chemical bonding. The interlaminar shear strength value of SiO2‐sGO‐CF/epoxy composite reached 71.1 MPa, which was increased by 33.45% compared with the electrochemical etching CF/epoxy composite. The results show that the sizing of sGO and nano‐SiO2 plays a positive synergistic effect by hierarchical reinforcement. [ABSTRACT FROM AUTHOR]

• A magnetic field changes the ferrofluid droplet-surface interaction and cooling performance. • Ferrofluid cooling with a magnet is from 28% to 263% higher than that without it. • A silicon substrate under a magnetic field shows the best heat transfer performance. • Superhydrophobic surfaces do not foul after ferrofluid droplet impact and evaporation. [Display omitted] This paper documents the spreading characteristics and heat transfer of a single ferrofluid droplet impinging onto dry solid surfaces with and without a magnetic field. Three surfaces were investigated: a pure silicon substrate, a silicon substrate with a thin titanium film, and a superhydrophobic coating. Fluid dynamics and cooling results of a ferrofluid droplet were compared to that of pure water and water-surfactant droplets for the same Weber number (We = 61) and initial surface temperature (T 0 = 95 ∘ C). Our results show that the magnetic field (magnetic Bond number Bo m = 2186) increased the droplet spreading diameter up to 12% and suppressed droplet rebound, thus improving the cooling performance of a ferrofluid droplet. The highest heat transfer rates were measured for the pure silicon substrate under a magnetic field with an average value of 14 W. The lowest cooling performance was observed for the superhydrophobic surface without a magnetic field with a peak value of 0.82 W. However, using the magnetic field, the superhydrophobic surface achieved 263% higher heat transfer rate than the non-magnetic case because of the suppression of droplet rebound. Moreover, the surface did not foul from ferrofluid deposition, an advantage for spray cooling applications when using any nanofluid. [ABSTRACT FROM AUTHOR]

In this work, a photobioreactor with microalgae biofilm was proposed to enhance CO2 biofixation and protein production using nickel foam with the modified surface as the carrier for immobilizing microalgae cells. The results demonstrated that, compared with microalgae suspension, microalgae biofilm lowered mass transfer resistance and promoted mass transfer efficiency of CO2 from the bubbles into the immobilized microalgae cells, enhancing CO2 biofixation and protein production. Moreover, parametric studies on the performance of the photobioreactor with microalgae biofilm were also conducted. The results showed that the photobioreactor with microalgae biofilm yielded a good performance with the CO2 biofixation rate of 4465.6 µmol m−3 s−1, the protein concentration of effluent liquid of 0.892 g L−1, and the protein synthesis rate of 43.11 g m−3 h−1. This work will be conducive to the optimization design of microalgae culture system for improving the performance of the photobioreactor. [ABSTRACT FROM AUTHOR]

In this study, nitrate (NO3-) removal from aqueous solutions was investigated using granular activated carbon (GAC) modified with CaCl2. Batch sorption studies were performed as a function of sorbent dose, initial nitrate concentration and pH. Sorption was maximized between pH 3 and 9. Studies on the effect of pH showed that the ion exchange mechanism might be involved in the sorption process. The percentage of nitrate removed increased with increasing sorbent concentration, and the ideal sorbent dose was found to be 20 g•L-1. Four isotherm models-Langmuir, Freundlich, Redlich-Peterson and Sips-were used to fit the experimental data. The Redlich-Peterson isotherm model explained the sorption process well and showed the best coefficient of determination (0.9979) and Chi-square test statistic (0.0079). Using the Sips isotherm model, the sorption capacity (qe) was found to be 1.93 mg nitrate per g of sorbent. Kinetic experiments indicated that sorption was a fast process, reaching equilibrium within 120 min. The nitrate sorption kinetic data were successfully fitted to a pseudo-second-order kinetic model. The overall results demonstrated potential applications of modified GAC for nitrate removal from aqueous solutions.

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The early diagnosis of cataract formation, alcoholism, chronic renal failure, Parkinson’s disease, Alzheimer’s disease, malignant disorders, ageing, arthritis, epilepsy and diabetes plays a critical role in the clinical treatment. Therefore, there is an intensive research for the determination of reduced glutathione (GSH) in human blood serum. In order to protect human health from these pathophysiologic conditions, it is very important to design and develop simple, sensitive and rapid sensors for GSH detection and quantifying GSH concentrations in human blood serum. In this context, electrochemical GSH sensors appear promising among all GSH sensors in which electrode material and architecture play major roles in achieving stable and sensitive detection. This review is focussed on the use of various carbon electrodes like glassy carbon, carbon paste, carbon microfiber, basal plane pyrolytic graphite and screen-printed electrodes in the electrochemical detection of GSH. Finally, the analytical applications of carbon electrodes based electrochemical sensors for glutathione electroanalysis are discussed. [ABSTRACT FROM AUTHOR]

The processes of electrodeposition of Ge and Ge-In from ammonia-tartrate solutions have been studied. The nature of interactions in thin-film systems obtained by germanium and indium codeposition has been investigated by means of potentiodynamic voltammetry in the inversion mode. The role of electrodesurface modification has been emphasized for deposition of a germanium film of a preset thickness from aqueous solutions. As was shown by the atomic force microscopy study, glossy films with a nanocrystalline structure had been formed. It has been established that, to develop silicon-germanium technologies, deposition of thin films must be performed from ionic liquids. [ABSTRACT FROM AUTHOR]

Abstract: Investigation into the mechanism involved in the control of layer growth through the reduction of diazonium salts by using 2,2‐diphenylpicrylhydrazyl (DPPH). This approach, previously assumed to be based on the radical capture of highly reactive aryl intermediates via the scavenging activity of DPPH, actually rests on redox cross reactions involving its electro‐reduced form. A numerical approach was developed to model the proposed processes, involving a redox reaction between diazonium cations and the reduced species of DPPH as a central step. Extension of this approach was validated by using substituted benzoquinones instead of DPPH, leading to good control of the radical polymerization to give sub‐monolayer surface coverage. Modulation of the surface coverage can be obtained by adjusting the concentration of the redox mediator and a near‐monolayer can be prepared in this way. The difference in formal redox potential between the diazonium salt and the electro‐reducible mediator was identified as a key parameter, and could be exploited to generalize the grafting control. [ABSTRACT FROM AUTHOR]

Cocondensation and postfunctionalization methods were employed to synthesize a mesoporous silica with large surface area (795.1 ± 1.1 m2 g-1) modified with 4-amino-5-hydrazino-1,2,4-triazole-3-thiol, which was successfully applied to adsorb and preconcentrate Cu(II), Co(II), and Cd(II) from aqueous media. Infrared spectroscopy of the adsorbent material demonstrated N-H stretching bonds related to primary amines existing in the ligand molecule, elemental analysis revealed the presence of 0.132 mmol g-1 of nitrogen, scanning electron microscopy indicated globularly shaped particles with average size of 10 μm, and the point of zero charge was found to be 7.2. Kinetic data were applied to the pseudo-second-order model, indicating that a chemisorption mechanism is probably involved in the uptake of metal ions from aqueous solutions. According to the Langmuir model, the adsorption capacities for the different ions obey the following order: Cu(II) > Co(II) > Cd(II). Through a preconcentration system, a preconcentration factor of 18-, 15-, and 20-fold was attained for Cu(II), Cd(II), and Co(II), respectively. The proposed method was applied in the determination of trace metals in natural river water (Tietê River) and the results were validated through standard reference material analysis. The results also indicated that the packed column proved to be stable over 24 adsorption/desorption cycles, demonstrating that the developed material is potentially suitable for the determination of trace-level metal ions in aqueous samples. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study investigates the influence of electrolyte compositions with acetone, glycerol, sucrose, ethylene glycol and ammonium chloride on the properties and structure of commercial pure titanium (CP-Ti) in the process of anode plasma electrolytic carburizing (PEC). The wear of the samples was measured using pin-disk friction in lubricated testing conditions. The effects of electrolyte composition on corrosion resistance of the PEC samples were examined by means of potentiodynamic polarization in a solution of sodium sulfate. It is shown that anode PEC of CP-Ti samples leads to formation of solid solution of carbon in titanium and external oxide layer in all studied electrolytes. The mechanism of carbon transfer from electrolytes containing sucrose, ethylene glycol and acetone to treated CP-Ti is found. The anode PEC of CP-Ti samples at 850 °C during 5 min was established to result in decrease in their surface roughness R a from 1.13 ± 0.01 μm to 0.04 ± 0.01 μm and friction coefficient from 0.29 ± 0.01 to 0.10 ± 0.01. The treatment in the aqueous solution of ammonium chloride (10 wt.%) and sucrose (10 wt.%) resulted in the decrease in the wear rate by 3–3 orders. The base-sucrose electrolyte conditioned a decrease in the corrosion current density by a factor 18 due to passivating effect of the oxide layer. [ABSTRACT FROM AUTHOR]

In this work, we investigate the properties of the low-alloy steel (0.4% C, 1% Cr) which is obtained as a result of anode plasma electrolytic nitriding (PEN) followed by hardening in the same electrolyte. An X-ray diffractometer and a scanning electron microscopy (SEM) were used to characterize the phase composition of the modified layer and its surface morphology. Surface roughness was studied with the use of a roughness tester. The hardness of the treated and untreated samples was measured using a microhardness tester. A pin-on-disk tribometer was occupied to evaluate weight loss of the untreated and treated samples at lubricated conditions. Corrosion properties of the samples treated surfaces were evaluated using potentiodynamic polarisation tests in solution of sodium sulfate. The effect of nitriding regimes on the weight wear and corrosion resistance of treated steel is considered. It is established that competition of the anodic dissolution and iron oxidation determined the oxide layer thickness affects microhardness layer, surface roughness, and wear and corrosion resistance. The electrolyte composition (10 wt% ammonium chloride, 5 wt% ammonia) and processing mode (650 °C, 5 min) of low-alloy steels allowing one to obtain the hardened surface layer with microhardness 780 HV and with decrease in the weight loss after lubricant wear testing of 3 times or 4.6 times for dry friction are proposed. The anode PEN (800 °C, 5 min) can decrease the corrosion current density of steel in 0.05 mol/L solution of sodium sulfate by a factor of 7.7. [ABSTRACT FROM AUTHOR]

The aim of this study is to undertake a clinical and radiographic evaluation between two different patient groups: machined versus modified surface, to find out if there is statistically significant difference that support the use of implants with different surface properties. Sixty screw, external hex connection implants were examined: one group with 30 machined surface implants (SuperCAT®), and a second group with 30 implants with modified surface (RBM®), for restoring a single tooth. The surgical procedure was performed according with the manufacturer’s protocol. After six months the second phase surgery was performed and the temporary restoration was placed. At this point, the first radiographic evaluation was made. The Roos et al (1997) parameters were followed for the clinical and radiographic evaluation. A 100% of osseointegration was accomplished in both groups. The average marginal bone loss was 0.78 mm, without significant differences between the groups. All implants were reported as success grade 1, with no complications. There are not significant differences between the two groups of machined and modified implant surfaces for single tooth restoration.

The structure of the low-alloy steel after plasma electrolytic nitriding (PEN) in electrolyte containing ammonium nitrate was investigated. The cross-sectional microstructure, composition, and phase constituents of modified layer under different processing conditions were characterized. It is shown that anode PEN provides the saturation of steel with nitrogen and formation of α-FeO, FeO, and FeO oxides, FeN nitride, and martensite. The aqueous solution that contained 15 wt.% NHCl and 5 wt.% NHNO allows one to obtain the hardened layer with a thickness of 80 μm and a microhardness up to 740 HV during 5 min at 850 °C. Surface roughness decreases from 1.5 to 0.8 μm after 5-min PEN at 650 °C. The proposed electrolyte and processing mode (750 °C, 10 min) enable to obtain the decrease in the weight loss after lubricate wear testing by a factor of 2.7. The base-nitrate electrolyte conditioned a decrease in the corrosion current density by a factor of 9 due to passivating effect of the oxide and nitride of iron. [ABSTRACT FROM AUTHOR]

Deposition of bioactive coatings composed of zinc oxide, cyclodextrin and cefepime (ZnO/CD/Cfp) was performed by the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The obtained nanostructures were characterized by X-ray diffraction, IR microscopy and scanning electron microscopy. The efficient release of cefepime was correlated with an increased anti-biofilm activity of ZnO/CD/Cfp composites. In vitro and in vivo tests have revealed a good biocompatibility of ZnO/CD/Cfp coatings, which recommend them as competitive candidates for the development of antimicrobial surfaces with biomedical applications. The release of the fourth generation cephalosporin Cfp in a biologically active form from the ZnO matrix could help preventing the bacterial adhesion and the subsequent colonization and biofilm development on various surfaces, and thus decreasing the risk of biofilm-related infections. [ABSTRACT FROM AUTHOR]

Fine powders with a modified surface have been prepared via treatment of unbleached softwood cellulose with titanium tetrachloride solutions in hexane. Titanium and chlorine have been detected in the composition of the aglomerates adsorbed onto the powder particles surfaces. Physicochemical properties of the samples have been shown to be dependent on Ti(IV) content on the modified surface. [ABSTRACT FROM AUTHOR]

The superhydrophobic surface has the potential for use in functional applications. This study reports a novel method for coupling a sintering process with a traditional technique based on the solution-immersion method to prepare a stable superhydrophobic surface. The use of a sintering process aids in the enhancement of the adhesive strength and acid resistance of the surface structure. The advantage of using this method lies in its flexibility in regulating the processing parameters and functional behaviours. The influences of different processing parameters were experimentally investigated. The surface treated with a sintering process remains superhydrophobic with a contact angle of >150° after immersion in an acid solution for 120 h. The sintered surface maintains good integrity after experiencing ultrasonic vibration for 5 min. The results indicate that the sintering temperature must be optimized to increase the adhesive strength and maintain sufficient hydrophobicity. The modification time is an important factor related to the level of hydrophobicity. [ABSTRACT FROM AUTHOR]

In this study, nitrate removal from aqueous solutions was investigated using granular activated carbon (GAC) modified with CaCl2. Batch sorption studies were performed as a function of sorbent dose, initial nitrate concentration and pH. Sorption was maximized between pH 3 and 9. Studies on the effect of pH showed that the ion exchange mechanism might be involved in the sorption process. The percentage of nitrate removed increased with increasing sorbent concentration, and the ideal sorbent dose was found to be 20 g•L-1. Four isotherm models -- Langmuir, Freundlich, Redlich-Peterson and Sips -- were used to fit the experimental data. The Redlich-Peterson isotherm model explained the sorption process well and showed the best coefficient of determination (0.9979) and Chi-square test statistic (0.0079). Using the Sips isotherm model, the sorption capacity (qe) was found to be 1.93 mg nitrate per g of sorbent. Kinetic experiments indicated that sorption was a fast process, reaching equilibrium within 120 min. The nitrate sorption kinetic data were successfully fitted to a pseudo-second-order kinetic model. The overall results demonstrated potential applications of modified GAC for nitrate removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

Surface-modified silica nanoparticles have a plenty of applications, such as coatings, dyes or biomarkers, catalysts and encapsulated products. When modified with 3-(trimethoxysilyl)propyl methacrylate (SiO 2 -MPS) or covered with a polymeric shell obtained from a reaction between divinylbenzene and styrene (SiO 2 -Pol), these SiO 2 nanoparticles induced distinct arrangements in polymer nanocomposites (PNC) prepared with commercial carboxylated nitrile rubber (XNBR). The hydrophilicity character of the modified SiO 2 nanoparticles was also altered, improving their interaction with the XNBR macromolecules. Consequently, choosing the PNC properties for different conditions and applications became possible due to the adjustment of the nanoparticle surface characteristics. Although the final characteristics of the nanocomposites films varied according to the nanoparticle used, the PNC prepared with SiO 2 -Pol presented better homogeneity than those with SiO 2 -MPS. [ABSTRACT FROM AUTHOR]

• Successive droplet impingement cooling on hydrophilic (uncoated) and superhydrophobic (coated) surfaces is investigated experimentally. • A new hybrid heat transfer solution using the integral transform technique is explained and used. • Single droplet impingement onto the uncoated surface showed higher heat transfer rates than for the coated surface. • Successive droplet impingement onto the coated heated surface allows surface refreshing with potential benefits for spray cooling. New high-performance electronic components generate a massive amount of heat per unit of area, and spray cooling is a field of interest for this application. Spray cooling achieves higher heat transfer coefficients than commonly used forced air convection cooling systems. In this study, we performed multiple droplet impingement experiments over heated surfaces in the non-boiling regime, a scenario that is closer to the phenomena of spray cooling than individual droplet impact. This paper focuses on the effects of droplet interactions with surfaces exhibiting distinct wettabilities. A surface thermocouple was used concomitantly as the impact surface and the temperature sensor. The surface thermocouple was originally hydrophilic (uncoated), which later we treated with a low cost commercial superhydrophobic coating (coated). High-speed imaging showed the droplet motion during impact. We proposed a one-dimensional inverse heat conduction semi-analytical solution, adopting a time-dependent droplet heat flux as one of the boundary conditions to represent the droplet cooling effect. We compared the heat transfer performances of both uncoated and coated surfaces for different droplet velocities but same initial temperature. The results showed higher heat transfer rates on uncoated surface relative to the coated one. Also, higher droplet velocities showed higher heat transfer mainly due to the increase in the droplet spreading diameter in contact with the solid. Successive droplets showed lower heat flow for the uncoated surface because of the low thermal effusivity and thickness of the heated solid, where most of the heat is removed by the first droplet. The first droplet thermal resistance and damping effects for the subsequent droplets, reduced the overall cooling performance. On the other hand, for the coated surface we found that the consecutive droplets continued to transfer heat with a similar rate as the previous one, which is desirable for spray cooling. However, the reduced overall heat transfer performance for the coated surface can be explained by the air pockets within the coating structure. [ABSTRACT FROM AUTHOR]

Deposition of bioactive coatings composed of zinc oxide, cyclodextrin and cefepime (ZnO/CD/Cfp) was performed by the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The obtained nanostructures were characterized by X-ray diffraction, IR microscopy and scanning electron microscopy. The efficient release of cefepime was correlated with an increased anti-biofilm activity of ZnO/CD/Cfp composites. In vitro and in vivo tests have revealed a good biocompatibility of ZnO/CD/Cfp coatings, which recommend them as competitive candidates for the development of antimicrobial surfaces with biomedical applications. The release of the fourth generation cephalosporin Cfp in a biologically active form from the ZnO matrix could help preventing the bacterial adhesion and the subsequent colonization and biofilm development on various surfaces, and thus decreasing the risk of biofilm-related infections.

Abstract: The lack of pendant functional groups on the PCL backbone has been a great challenge for surface bioactivation of poly(ε-caprolactone) (PCL). In the present study, covalently galactosylated PCL (GPCL) was developed through coupling between the amino-functionalized PCL (NPCL) and the lactobionic acid (LA) and its potential application in maintenance of physiological functions of HepG2 cells was further evaluated. The structure and properties of GPCL were explored by 1H NMR, FT-IR, GPC and DSC. Moreover, the incorporation of galactose ligands onto GPCL membranes not only promoted higher wettability, but also radically changed surface morphology in comparison with PCL and NPCL according to the contact angle measurement and atomic force microscopy. When HepG2 cells were seeded onto these membranes, the cells on GPCL membranes showed more pronounced cell adhesion and tended to form aggregates during the initial adhesion stage and then progressively grew into multi-layer structures compared to those without galactose ligands by the observation with fluorescence microscope and scanning electron microscopy. Furthermore, live–dead assay and functional tests demonstrated that HepG2 cells on GPCL membranes had superior viability and maintained better liver-specific functions. Collectively, GPCL has great potential for hepatic tissue engineering scaffolds. [Copyright &y& Elsevier]

Abstract: This paper deals with the method of decreasing the size of heat exchanger surfaces by increasing the heat transfer coefficients and the importance of heat transfer enhancement for vaporization. We report an experimental study on surfaces modified by passive methods applied to heat transfer surfaces mechanically processed, covered with sleeves made by metallic tissues or covered with metallic porous layers performed using welding procedures. Experiments are made to investigate the heat transfer coefficient on copper tubes with a 22mm external diameter using heat from inner source to outer vaporizing liquid. There are developed specific heat transfer correlations for each group of enhanced surfaces. The experimental data and new proposed correlations are compared with well known correlations. The results are in best agreement with the Cornwell–Houston correlation. [Copyright &y& Elsevier]

Silica gel modified with 3-aminopropyltrimethoxysilane was anchored with nicotinaldehyde to prepare a new chelating surface (or matrix). It was synthesized and characterized by elemental analysis, cross-polarization magic-angle spinning C nuclear magnetic resonance (NMR) spectroscopy, diffuse reflectance infrared Fourier-transform spectroscopy, nitrogen adsorption-desorption isotherm, Brunauer-Emmett-Teller surface area, and Barrett-Joyner-Halenda pore sizes. The new surface exhibits good chemical and thermal stability as determined by thermogravimetry curves. This new organic-inorganic material was used for preconcentration of Hg(II), Pb(II), Zn(II), and Cd(II) from water prior to their determination by inductively coupled plasma atomic emission spectrometry. The optimum pH for quantitative sorption of these metal ions is in the range of 6-8, and the sorption capacity is in range of 486-1,449 μmol/g. By batch method, 95 % extraction takes ≤30 min. All the metals could be desorbed with a solution of hydrochloric acid (6 N) without loss of the expensive ligand. Solutions of the metal ions were prepared by dissolution of the nitrate solution. [ABSTRACT FROM AUTHOR]

In this paper, an experimental study investigating the effect of the geometrical shape of the circular and rectangular pin fins on the heat transfer performance and the boiling phenomenon is presented. A pool boiling experiment in the HFE-7100 dielectric working fluid under atmospheric pressure was conducted. Boiling curves and boiling heat transfer coefficients of different test cases were plotted to evaluate the heat transfer performance as well as the captured images of the boiling phenomenon on the test samples. Two quantities, flow resistance and wetted perimeter, were calculated to understand the behaviour of the boiling physics due to variation of fin geometrical shape and, hence, their effect on the heat transfer performance. It was found that the cooling performance of the rectangular pin fins was higher than that of the circular pin fins, despite having a slightly higher flow resistance of 4% and 7%, respectively. This is believed to be the result of the longer wetted perimeter up to 27%, whereby the nucleation site has a higher probability of generating more bubbles in the same boiling surface area. For the tested modified boiling surface with 196 and 144 pin fins, the average heat transfer performances were found to have differences of up to 3.54 and 1.58 times larger, respectively. [ABSTRACT FROM AUTHOR]

This study investigated the effect of an Argon-based nonthermal plasma (NTP) surface treatment-operated chairside at atmospheric pressure conditions applied immediately prior to dental implant placement in a canine model. Surfaces investigated comprised: Calcium-Phosphate (CaP) and CaP + NTP (CaP-Plasma). Surface energy was characterized by the Owens-Wendt-Rabel-Kaelble method and chemistry by X-ray photoelectron spectroscopy (XPS). Six adult beagles dogs received 2 plateau-root form implants ( n = 1 each surface) in each radii, providing implants that remained 1 and 3 weeks in vivo. Histometric parameters assessed were bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Statistical analysis was performed by Kruskall-Wallis (95% level of significance) and Dunn's post-hoc test. The XPS analysis showed peaks of Ca, C, O, and P for the CaP and CaP-Plasma surfaces. Both surfaces presented carbon primarily as hydrocarbon (CC, CH) with lower levels of oxidized carbon forms. The CaP surface presented atomic percent values of 38, 42, 11, and 7 for C, O, Ca, and P, respectively, and the CaP-Plasma presented increases in O, Ca, and P atomic percent levels at 53, 12, and 13, respectively, in addition to a decrease in C content at 18 atomic percent. At 1 week no difference was found in histometric parameters between groups. At 3 weeks significantly higher BIC and BAFO were observed for CaP-Plasma treated surfaces. Surface elemental chemistry was modified by the Ar-based NTP. Ar-based NTP improved bone formation around plateau-root form implants at 3 weeks compared with CaP treatment alone. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A:98-103, 2013. [ABSTRACT FROM AUTHOR]

ABSTRACT Introduction: Smoking affects the survival of turned titanium implants. Although smoking has less impact on the failure rate of rough surface implants, the effect on bone loss on rough surface implants has not been studied yet and may be an important factor in biological stability. Aim: To determine the effect of smoking on early implant failures and bone remodeling around moderately rough implants (Southern Implants®, Southern Implants, Irene, South Africa). Materials and Methods: Three hundred twenty-nine patient records, containing information on 712 installed implants, were scrutinized retrospectively and periapical radiographs were analyzed for interproximal bone level. Mann-Whitney U-test and Fisher's exact test were performed to compare bone level and implant survival in smokers and nonsmokers. Only implants with at least 6 months of function time were analyzed for bone level changes. Results: The overall survival rate was 98.3%. Implants in smokers had a threefold higher failure rate compared with nonsmokers (5/104 = 4.8% vs 7/608 = 1.2%). This was statistically significant on implant level ( p = .007) but not on patient level (1/41 vs 7/288, p = .997). Readable radiographs from 363 implants in 169 patients were available with a mean follow-up of 12 months (SD 5.11; range 6-28). The mean interproximal bone level was 1.36 mm ( n = 363; SD 0.41; range 0.48-3.70). Bone levels were independent of jaw location. Sixty implants from 21 smokers lost statistically significantly ( p = .001) more bone (mean 1.56; SD 0.53; range 0.75-3.22) than the 303 implants in 148 nonsmokers (mean 1.32 mm; SD 0.38; range 0.48-3.7). The maxilla is especially prone to bone loss compared with the mandible (1.70 mm vs 1.26 mm, p < .001). Conclusion: The Southern Implants® system demonstrated a high absolute survival rate. Although smokers are not more prone to implant loss, more pronounced peri-implant bone loss was observed, especially in the maxilla. Whether this affects future biological complications remains to be investigated in prospective long-term studies. [ABSTRACT FROM AUTHOR]