Sharif Digital Repository

In the present study, thermally oxidized nanodiamond (OND) was first modified non-covalently with dodecylamine (DDA) as corrosion inhibitor. In this respect, reactive primary amine of DDA molecule with high isoelectric point (IEP) could interact easily with negative charge carboxylic acid groups of OND. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) proved that OND nanoparticle was successfully functionalized by DDA up to approximately 5 wt% grafting contnet. Both OND and dodecylamine modified OND (DND) were loaded in epoxy (EP)/polyamine hardener matrix at the same concentration of 1 wt% and applied on mild steel substrate. Morphology of EP-DND and... 

In this work, the effects of the surface-modified nanodiamond particles (NDs) on the barrier, rheological, mechanical and thermal properties of ethylene vinyl acetate (EVA) composites for the packaging applications were investigated. Fourier transform infrared spectroscopy, as well as thermal gravimetric analysis were employed to study the grafting of vinyltriethoxy silane (VTS) on the surface of NDs. Afterwards, EVA samples containing 0, 0.1, 0.5, 1, 1.5 and 2 wt% of surface-modified NDs were prepared by a two-stage process including the solution and injection processes. In order to evaluate the physicochemical, rheological, mechanical and thermal properties of the EVA/NDs samples, field... 

There are numerous functions for laser in modern implant dentistry including surface treatment, surface coating, and implant manufacturing. As laser application may potentially improve osseointegration of dental implants, we systematically reviewed the literature for in vitro biological responses to laser-modified or processed titanium dental implants. The literature was searched in PubMed, ISI Web, and Scopus, using keywords “titanium dental implants,” “laser,” “biocompatibility,” and their synonyms. After screening the 136 references obtained, 28 articles met the inclusion criteria. We found that Nd:YAG laser was the most commonly used lasers in the treatment or processing of titanium... 

The alkaline treatment condition plays a crucial role in governing the ultimate properties of flax fibers. In this study, flax fibers were modified with mild alkalization and severe mercerization conditions to give fundamental insight into how the molecular-scale changes in cell wall fine structure and cellulose supramolecular structure can affect the macroscopic properties of fibers. SEM, FTIR, XRD, TGA, and DSC techniques were employed to characterize the variations in morphology, composition, crystalline structure, and thermal properties of fibers. Also, tensile tests evaluated their reinforcing performance in polypropylene-based composites. The results indicated that alkalization in 5%... 

The purpose of this research is to explain the surface modification of fabricated polyamide reverse osmosis (RO) membranes using UV-initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g L−1). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm) followed by the same UV irradiation times was investigated. After that, the membranes modification was done by grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. The characterization of membranes surface properties and their performance were systematically carried out. The results... 

Heavy metal removal from water and wastewater was investigated by using raw and modified diatomite from Iranian mines. Modification of diatomite was done by impregnating the diatomite surface with 0.35 g of manganese oxide in one gram of diatomite. This modified diatomite was named Mn-Diatomite. The surface area measurements for Mn-diatomite showed a 2.2 fold increase, hence higher removal capacity for the heavy metals. The results of the removal showed an increase in adsorption capacity which was for Pb2+ about 40 mg/g, for Ni 2+ about 34mg/g and for Cu2+ about 33mg/g. The filtration quality of diatomite was significantly enhanced with surface modification by manganese oxide  

In this study, a new facile and cost effective method is used to modify polysulfone membrane surface in order to improve the hydrophilicity, antifouling, and blood compatibility. This modification was performed by adding two functional monomers on the dialysis membrane. Polysulfone (PSF) membranes containing polyvinylpyrrolidone were prepared via phase inversion technique. In the next step, free radical polymerization combined with surface polymerization was used to introduce acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) onto the polysulfone membrane surface via circulation of initiator and monomer solutions across the membrane surface, respectively. Various monomer concentrations... 

Herein, the facile and tunable technique for the preparation of novel multi-stimuli-responsive nanocomposites via RAFT polymerization for DOX delivery is reported. The influence of the molecular weight of pH- and thermo-sensitive poly (acrylic acid-co-NIPAM) (PNAx), as a macro-RAFT agent, on the nanocomposites size and drug release rate was investigated. The outcome of this study reveals that macro-RAFT agent with lower molecular weight can be attached to the surface of magnetic nanoparticles with higher content of polymeric layer than can macro-RAFT agent with higher molecular weight. Also, it was observed that the particle size, polymer grafting density, DOX loading capacity, and DOX... 

Environmentally responsive surface-modified nanoparticles are colloidal nanoparticles coated with, at least, two physicochemically distinct surface groups. Recent advances in the synthesis and production of nanoparticles have enabled the production of environmentally responsive surface-modified nanoparticles with both hydrophilic and hydrophobic surface groups. These nanoparticles act like colloidal surfactants. In this paper, environmentally responsive surface-modified silica nanoparticles are synthesized and used for enhancement of oil recovery. For this purpose, silica nanoparticles are coated with polyethylene glycol chains as hydrophilic agent and propyl chains as hydrophobic agent at... 

Reverse osmosis (RO) membrane process has become the most promising technology for desalination to produce purified water. Among numerous polymeric materials used to fabricate RO membranes, aromatic polyamide thin film composite (TFC) membranes are dominant in commercial RO membrane processes because of their high salt rejection and water permeability as well as their excellent chemical, thermal, and mechanical stability. However, the major hindrance to the effective application of polyamide TFC RO membranes is membrane fouling. Furthermore, polyamide TFC RO membranes have limited stability to chlorine, which is commonly used as disinfect to control membrane biofouling. These two factors... 

In this experimental study, AA7075 aluminum alloy was subjected to pure severe shot peening (SSP), pure ultrasonic nanocrystalline surface modification (UNSM) and the combination of these two treatments. The treated specimens were analyzed with detailed microstructure analysis, micro-hardness, surface roughness, XRD investigations and wear-friction tests. The results demonstrated that UNSM exhibited fine surface finish and provided minimum surface roughness with the Ra value of 0.8 µm. Moreover, UNSM played an important role in the reduction of Ra as a secondary treatment. Electron back scatter diffraction (EBSD) analysis, full width at half maximum (FWHM) evaluations and compressive... 

The electrophoretic deposition (EPD) of chitosan on metallic substrates was investigated. The electrophoretic mobility of the natural biopolymer in aqueous solution as a function of pH was studied. Because the protonation/deporotonation of chitosan is pH-dependent, the electrophoretic mobility and deposition rate is shown to increase with increasing pH from 2.9 to 4.1. The film growth rate is estimated to vary in the range 0.02-0.08 μm/s depending on the pH value. At high growth rates (> 0.05 μm/s), a porous film is obtained due to hydrogen entrapment. The EPD method developed here is applicable for the surface modification of metal implants by chitosan to develop novel bioactive coatings. ©... 

In this study, titanium alloy (Ti-6Al-4V) and austenitic stainless steel (AISI 304) biomedical alloys were subjected to surface severe plastic deformation (SSPD) via severe shot peening (SSP) with the conditions of A28-30 Almen intensity. SSP is widely accepted as much more effective than the conventional surface modification techniques since it forms a nano-grain layer with large number of dislocations and grain boundaries. The SSP treatment in this study was led to a very thin rough layer in Ti-6Al-4V titanium alloy compared to that of AISI 304. The thicker layer of AISI 304 was created by twin-twin intersections and a martensite structure transformations. SSP treatment was resulted in a... 

S500MC high strength low alloy automotive steel is exposed to bulk severe plastic deformation (SPD) via constrained groove pressing (CGP) and surface severe plastic deformation (S2PD) via severe shot peening (SSP) and ultrasonic nanocrystal surface modification (UNSM). SSP and UNSM could create a nanocrystallization layer till 50–100 µm away from outmost surface. EBSD investigations showed average nano-grain size obtained via SSP and UNSM was found to be below 100 nm regime. The strength was improved via 1st to 4th pass of CGP, but elongation percentage decreased abruptly. UNSM achieves both strength-ductility improvement with gradient structure. SSP improves the total elongation however a... 

In this study, the fatigue performance of AISI 304 subjected to shot peening (SP), ultrasonic nanocrystal surface modification (UNSM) and the combination of SP + UNSM processes was systematically assessed by rotary bending fatigue (RBF) tester at different stress levels. The purpose of combining SP and UNSM processes is to find out whether SP following UNSM process can further improve the fatigue life of AISI 304 in comparison with the SP and UNSM processes alone. Interestingly, the fatigue strength of AISI 304 was deteriorated by the combination of SP + UNSM processes in comparison with the UNSM process alone, but the combination of SP + UNSM processes demonstrated a higher fatigue strength... 

Functionally graded cemented carbonitrides (FGCCs) are applied in cutting tools industry. Indexable inserts made from mentioned alloys have superior cutting performance and tool life thanks the formation of a surface modified layer with enhanced properties as well as crater wear resistance. Cemented carbonitrides are made of hard carbide/nitride/carbonitride particles that have been embedded in a metallic binder. Excellent wetting ability of tungsten carbide with cobalt has made this metal the first choice as binder. However, cobalt has high cost and environmental pollution impacts. Substitution of cobalt with other metals has always been figured out. Some other metals that have been used as... 

CO2-laser irradiation was used to modify the surface properties of thin-film composite (TFC) polyamide reverse osmosis (RO) membranes. These membranes were first synthesized via interfacial polymerization of m-phenylenediamine (MPD) monomers and trimesoyl chloride (TMC) over porous polysulfone ultrafiltration support, followed by a CO2-irradiation. AFM, ATR-FTIR, SEM and contact angle measurements were used to characterize the surface properties of these membranes. The ATR-FTIR results indicated that CO2-laser irradiation did not induce any functional groups on the membrane surface. However, it was found that the laser irradiation enhanced the NaCl salt rejection and slightly reduced the... 

Nature-inspired coating with polydopamine (PDA) is a promising way to improve the performance of graphene oxide (GO) based nanocomposites due to its high ability to enhance interactions in matrix-disperse systems. Here, we examined the capability of two types of PDA to develop the reinforced polyvinyl alcohol (PVA)/GO hydrogels. In the first mode, dopamine hydrochloride was polymerized as nanoparticles and then incorporated into PVA solution with GO nanoplatelets (P-NG hydrogel). In the second mode, polydopamine was polymerized in the presence of GO nanoparticles to obtain PDA surface-modified GO and then PVA nanocomposite hydrogel (P-CG sample). Rheological and tensile findings revealed... 

The direct growth of self-supported metal-organic frameworks (MOFs) thin film can be considered as an effective strategy for fabrication of the advanced modified electrodes in sensors and biosensor applications. However, most of the fabricated MOFs-based sensors suffer from some drawbacks such as time consuming for synthesis of MOF and electrode making, need of a binder or an additive layer, need of expensive equipment and use of hazardous solvents. Here, a novel free-standing MOFs-based modified electrode was fabricated by the rapid direct growth of MOFs on the surface of the glassy carbon electrode (GCE). In this method, direct growth of MOFs was occurred by the formation of vertically... 

In this study, the in-vitro bone regeneration ability of commercial pure titanium (CP-Ti) surface modified via electrospun polyvinylidene/hydroxyapatite (PVP/HA) masking and subsequent Nd-YAG pulsed laser treatment was investigated. The ratio of HA to PVP played a significant role in achieving a perfect homogenous mask on the CP-Ti. In the laser treatment process, the parameter of area scanning speed (ASS) had an important influence on the final surface morphology. A favorable range was defined for this parameter where these two conditions were satisfied: no PVP remaining and no severe substrate melting. Within a favorable range of ASS, as decreasing ASS exchanged the surface structure from...