Hydroxyapatite/titania nanocomposites derived by combining high-energy ball milling with spark plasma sintering processes

Hydroxyapatite-reinforced nanocomposites with titania nanocrystals addition are prepared by a homogeneous mixing of hydroxyapatite nanoparticles and titania nanocrystals based on high-energy ball milling and spark plasma sintering processes. The microstructural and mechanical properties of the HA/titania composites are studied by X-ray diffractometry analysis, Raman spectrometry, and scanning electron microscopy. The hardness and Young's modulus of the composites are characterized by a nanoindenter and they show that the incorporation of the titania nanocrystals improves the mechanical properties of the composites obviously and the improvement should be ascribed to the main solitary effect of the ceramic as additives as well as a denser composites due to combining high-energy ball milling with spark plasma sintering techniques. The bioactivity of the HA/titania composites is evaluated by immersing the spark plasma sintering (SPS) compact disk in the simulated body fluid (SBF) and the results indicate that the bioactivity of the composites is related to the addition of titania by inducing apatite nucleation on the sample's surface after being immersed in SBF.     

Thermal and mechanical properties of epoxy resin reinforced with modified iron oxide nanoparticles

Epoxy polymers, having good mechanical properties and thermal stability, are often used for engineering applications. Their properties can be further enhanced by the addition of iron oxide (Fe₃O₄) nanoparticles (NPs) as fillers to the resin. In this study, pristine Fe₃O₄ NPs were functionalized with polydopamine (PDA), (3-glycidoxypropyl)trimethoxysilane (GPTMS), and (3-aminopropyl)trimethoxysilane (APTES). X-ray diffraction and scanning electron microscopy (SEM) were used to study any changes in the crystal structure and size of the NPs while Fourier-Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were used to ensure the presence of functional groups on the surface. The mechanical properties of the Fe₃O₄-based nanocomposites generally improved except when reinforced with Fe₃O₄/PDA. The maximum improvement in tensile strength (∼34%) and fracture toughness (∼13%) were observed for pristine Fe₃O₄-based nanocomposites. Dynamic mechanical analysis (DMA) showed that the use of any of the treated NPs improved the material's initial storage modulus and had a substantial impact on its dissipation potential. Also, it was observed that the glass transition temperature measurements by DMA and differential scanning calorimetry were below that of pure epoxy. SEM of the cracked surfaces shows that the incorporation of any NPs leads to an enhancement in its thermal and mechanical properties.     

Novel nanocomposite of epoxy resin by introduced reactive and nanoporous material

A reactive and nanoporous particle (OG) was introduced to UV-cured epoxy resin to form great low D _k material for electronic industrial. We expected the porous cage of OG to decrease the dielectric constant of UV-cured epoxy resin and multiple reactive functional groups (oxirane ring) of OG reacted with photoinitiator to increase the curing density of UV-cured epoxy resin. The glass transition temperatures (T _g) of epoxy increases with the increase of the OG content up to 10 phr due to the increase of crosslinking density. Excessive aggregation at highest OG content of 15 phr results in the reduced crosslinking density and T _g. The char yield of the composite increases with increase of OG content because stable Si and SiO₂ are formed after thermal decomposition. The presence of OG results in the higher porosity and thus the lower dielectric constant.     

Fluidised-bed jet milling of pharmaceutical powders

Jet milling is often employed to produce very fine product or to tackle materials that are difficult to mill. This paper analyses particle breakage in a single jet region in a fluidised bed with a view to identify the role of jet hydrodynamics and material properties. By making a number of simplifying assumptions, the particle breakage in the jet can be estimated by coupling a hydrodynamic model of the jet with the kinetics of single-particle impact breakage. This approach works satisfactorily for a number of particulate solids, e.g., α-lactose monohydrate, but poorly for some others, e.g., paracetamol.The underlying cause of this feature is unclear, although it is likely to be due to the hydrodynamic mechanism. In this work, a sensitivity analysis has been carried out which highlights the importance of some of the hydrodynamic parameters on particle flow and breakage in the jet region. A more general model of jet hydrodynamics is needed to predict reliably the particle behaviour in this region.     

Laser-induced oxidation assisted micro milling of spark plasma sintered TiB2-SiC ceramic

In this work, a novel process of laser-induced oxidation assisted micro milling (LOMM) was proposed. TiB₂-SiC ceramic with hardness of 24.6 ± 0.8 GPa was prepared by spark plasma sintering and used as the workpiece material. The cutting force, surface quality and tool wear mechanisms were investigated. Under laser irradiation and oxygen assistance, a porous oxide layer and relatively dense sub-layer were formed. The hardness of the sub-layer was found to be 12.8 ± 0.7 GPa which was far lower than that of the substrate. Both the cutting and thrust forces increased with increasing the feed per tooth and depth of cut in micro milling of the sub-layer material. The material removal mechanism was dominated by a transition from ductile to brittle mode as the feed per tooth increased from 0.3 μm/z to 1.2 μm/z. The surface roughness Ra of 46 nm was achieved when the cutting speed, feed per tooth and depth of cut were 31.4 m/min, 0.3 μm/z and 2 μm, respectively. The tool wear mechanism was characterized by the flank wear and coating spalling. As a case study, a micro slot having width of 0.5 mm and aspect ratio of 2 was fabricated by the LOMM. For comparison, the conventional micro milling was also carried out using the same cutting parameters. The surface quality fabricated by LOMM was better than that by the conventional micro milling. The machining efficiency in LOMM was improved by 104% as compared to the conventional micro milling.     

纳米颗粒对环氧树脂胶粘剂／钢铁附着强度的影响

采用纳米Al2O3、纳米CaCO3、纳米SiO2三种纳米颗粒,机械混合对环氧树脂胶粘剂进行改性,并对纳米颗粒改性的环氧树脂胶粘试样进行了附着强度的检测。结果发现,通过改变纳米颗粒的种类和含量,环氧胶粘剂／钢铁基体之间的附着强度得到不同程度的提高,其中添加2％纳米Al2O3颗粒的环氧胶粘剂与钢铁基体的附着强度提高了4倍左右。通过断面形貌特征和不同基体粗糙度下对添加纳米颗粒环氧胶与钢铁基体之间附着强度的检测,对此现象产生的原因进行了分析和讨论。     

Role of non-functionalized oxide nanoparticles on mechanical properties and toughening mechanisms of epoxy nanocomposites

Over the past few decades, the use of epoxy resins has gained significant attention from worldwide researchers due to its advantages in structural applications in various sectors like automotive, construction, and aerospace industries. This article summarizes and reviews the research on mechanical properties and toughening mechanism of epoxy composites filled with non-functionalized oxide nanoparticles. The incorporation of nanomaterials into the polymer matrix has been considered to be the most effective route to improve the mechanical properties of polymer composites. But the inherent brittle nature and cross-linking ability of epoxy makes it vulnerable to crack initiation and crack growth and limits its use in advanced structural applications. Recently, various kinds of nanofillers such as carbon nanotubes (CNTs), organic and inorganic oxide nanoparticles have attracted industrial interest due to their excellent mechanical, thermal, and electrical properties which can provide a dramatic improvement in the properties of epoxy composites but their dispersion issue, agglomeration and bundling problems deteriorate several important mechanical parameters of the epoxy composites. To date, no review article focused on the role of non-functionalized oxide nanoparticles on the improvement in mechanical properties of the reinforced epoxy composites. This review article assesses and summarizes some most recent findings on the de-agglomeration process, mechanical properties, and toughening mechanisms of epoxy nanocomposites reinforced with four types of most preferred non-functionalized oxide nanoparticles such as Al₂O₃, TiO₂, SiO_2, and ZrO₂.     

Effect of milling type on the microstructural and mechanical properties of W-Ni-ZrC-Y2O3 composites

This study reports the effect of milling type on the microstructural, physical and mechanical properties of the W-Ni-ZrC-Y₂O₃ composites. Powder blends having the composition of W-1 wt% Ni-2 wt% ZrC-1 wt% Y₂O₃ were milled at room temperature for 12 h using a Spex™ 8000D Mixer/Mill or cryomilled in the presence of externally circulated liquid nitrogen for 10 min using a Spex™ 6870 Freezer/Mill or sequentially milled at room temperature and cryogenic condition. Then, powders were compacted in a hydraulic press under a uniaxial pressure of 400 MPa and green bodies were sintered at 1400 °C for 1 h under Ar/H₂ atmosphere. Phase and microstructural characterization of the milled powders and sintered samples were performed using X-ray diffractometer (XRD), TOPAS software, scanning electron microscope/energy dispersive spectrometer (SEM/EDS), X-ray fluorescence (XRF) spectrometer and particle size analyzer (PSA). Archimedes density and Vickers microhardness measurements, and sliding wear tests were also conducted on the sintered samples. The results showed that sequential milling enables the lowest average particle size (214.90 nm) and it is effective in inhibiting W grain coarsening during sintering. The cryomilled and sintered composite yielded a lower hardness value (5.80±0.23 GPa) and higher wear volume loss value (149.42 µm³) than that of the sintered sample after room temperature milling (6.66±0.39 GPa; 102.50 µm³). However, the sequentially milled and sintered sample had the highest relative density and microhardness values of 95.09% and 7.16±0.59 GPa and the lowest wear volume loss value of 66.0 µm³.     

Evaluation of the height 3D roughness parameters of concrete substrate and the adhesion to epoxy resin

In this work a newly designed three-dimensional (3D) scanner was used in order to evaluate and describe the morphology of selected concrete substrate surfaces. A special focus was placed on the advantages and disadvantages of the latter over the other scanners. The interseting results of such an investigation for 3 differently treated existing concrete substrates are selected and presented. It was found that with an increase of maximum aggregate grain size in concrete, the values of arithmetical mean height (Sa), the root mean square height (Sq) and skewness (Ssk) for the shotblasted surface also increase, while the value of the kurtosis (Sku) grows for ground surfaces and decreases for the shotblasted surface. It was also found that there is a relation between the values of height parameters Sku and the maximum height of peaks (Sp) with the pull-off adhesion (f_b) of the epoxy resin added layer and these surfaces.     

The effects of modified zinc oxide nanoparticles on the mechanical/thermal properties of epoxy resin

Characterized by its strength, durability, and thermal properties, epoxy resin has been widely used as an adhesive, paint, and coating in many applications in the aerospace, civil and automotive industries. Despite this, the thermoset polymer resin has been known for its brittleness and low fracture resistance. This study focuses on the reinforcement of an epoxy resin system (diglycidyl ether of bisphenol A) with zinc oxide (ZnO) nanoparticles in their pristine form and a further modified form. The modification took place in two ways: coating with polydopamine (PDA) and covalently functionalizing them with (3-aminopropyl)triethoxysilane (APTES) and (3-glycidoxypropyl)trimethoxysilane (GPTMS). Therefore, four different types of nanoparticles were used: pristine ZnO, ZnO/PDA, ZnO/GPTMS, and ZnO/APTES aiming to improve the interfacial bonding between the polymeric matrix and the reinforcement. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, and scanning electron microscopy characterization and imaging techniques were used to prove that the ZnO nanoparticles were successfully modified prior to manufacturing the epoxy composites. While tensile testing showed that using pristine ZnO increases the composite's strength by 32.14%, the fracture toughness of the resin was improved by 9.40% when reinforced with ZnO functionalized with APTES. TGA showed that the addition of functionalized nanoparticles increases the material's degradation temperature by at most 7.31 ± 4.9°C using ZnO/APTES. Differential scanning calorimetry and dynamic mechanical analysis testing proved that the addition of any type of nanoparticles increases the resin's glass transition temperature by as much as 7.83°C (ZnO/APTES).     

Structural,physicomechanical, and in vitro biodegradation studies on Sr-doped bioactive ceramic

This study aimed to investigate the effect of Sr substitution on the structure, mechanical properties, bioactivity, and biodegradation of akermanite (Ca₂MgSi₂O₇). Samples were synthesized through solid-state synthesis followed by heat treatment at 1200 °C and 1250 °C. X-ray diffraction patterns showed that Sr substitution did not change the Ca₂MgSi₂O₇ phase. Fourier transform infrared spectra demonstrated that the silicate structure of Ca₂MgSi₂O₇ also remained unchanged. The field emission scanning electron microscopy revealed that partial Sr substitution enhanced the density of Ca₂MgSi₂O₇ and reduced the grain size. The optimum dopant with the highest mechanical properties was 0.05Sr. However, the mechanical properties decreased beyond 0.05Sr because of the large grain size. The mechanical properties of Sr-substituted samples sintered at 1250 °C were lower due to high liquid phase formation. Sr substitution supported apatite formation and controlled Ca₂MgSi₂O₇ degradation after the samples were soaked in simulated body fluid solution (SBF).     

Understanding the effect of nanoparticles TiO2, Al2O3 and SiO2 on damage mechanisms of a polymer composite

In this paper, nanoparticles obtained by Sol-gel method have been incorporated as a filler in glass fiber/polyester composite in order to improve the mechanical properties of the resulting material. This work covered on the characterization and the study of the polymer matrix with 5 wt.%nano TiO₂, 5 wt.%nano Al₂O₃, 5 wt.%nano SiO₂.The results obtained revealed that sol-gel powders with a spherical morphology have excellent thermal stability. Acoustic emission analysis was used to investigate the microscopic damage mechanisms and progression in glass fiber reinforced nanocomposites. Thus, acoustic emission from four modes of approval has been identified: matrix cracking, matrix/fiber decohesion, delamination and fiber breakage. This study shows the increase of mechanical performance and the decrease of damage modes of @Polyester. From the SEM images, the good dispersion of nanofillers, absence of agglomerates, the good affinity with the improving of the interface compatibility were presented.     

Effect of polythiourethane hardener modification on the behaviour of epoxy resin

Polythiourethanes based on oligomeric polymercaptans were employed as curing agent of epoxy resin. The epoxy matrices, in the form of castings, were characterized for their mechanical properties such as tensile strength, elongation at break and unnotched Charpy impact strength as per ISO methods. Mechanical studies indicated that the incorporation of polythiourethane into epoxy resin improves the toughness and flexibility with reduction in tensile strength for samples cured at ambient conditions and influences the mechanical and thermal properties according to its percentage content for samples cured at 130°C. The high increase of impact strength was explained by the development of two-phase morphology during the cure process. The results of this study indicate that both the stoichiometry of the curing mixture and the initial thermal condition are of critical importance in governing the curing mechanism, structure of the network, morphology and the final properties of epoxy/polythiourethane compositions.     

High wear resistance white ceramic glaze containing needle like zircon single crystals by the addition of sepiolite n-ZrO2

Sepiolite with homogeneous zirconia nanoparticles distribution has been added to a transparent ceramic glaze to study opacification, mechanical and wear resistance properties. It has been observed that monodispersed zircon single crystals with needle-like shape have been formed in the ceramic glaze. These in situ zircon single crystals give white color and increase opacification (L = 94 vs L = 90), mechanical properties (hardness and toughness) and wear resistance by a factor of 4 compared to the commercial crystalline glaze containing a similar fraction of micrometer commercial zircon.     

Electrostatic deposition of silica nanoparticles between E‐glass fibers and an epoxy resin

The achievement of optimum adhesion between a thermoset and an inorganic material is an important goal for the composites and coatings industries. There is a growing interest in the use of structural surface modifiers, such as nanotubes, nanoparticles, and whiskers, to improve this adhesion. Here, a method for electrostatically depositing poly(ethylene imine)‐functionalized silica nanoparticles onto E‐glass fibers was developed. The deposition of 26‐nm functionalized particles onto glycidyloxypropyltrimethoxysilane (GPS)‐functionalized E‐glass fibers and then their embedding in a resin of diglycidyl ether of bisphenol A and m‐phenylene diamine increased the interfacial shear strength (IFSS) 35% over that of bare fibers and 8% over that of GPS‐functionalized fibers. IFSS was highly dependent on the particle size; the 16‐nm functionalized particles had little effect on the IFSS. When the particles size was increased to 71 and 100 nm, this led to increasingly poor IFSS values, whereas the 26‐nm particles produced the best results. Similar results were seen with the transverse flexural strength of the unidirectional composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41516.     

Improvement of structural/tribological properties and milling performances of tungsten carbide cutting tools by bilayer TiAlN/TiSiN and monolayer AlCrSiN ceramic films

In this study, bilayer TiAlN/TiSiN and monolayer AlCrSiN ceramic films were grown on carbide cutting tool material by cathodic arc physical vapor coating (CAPVD) method to improve the structural/tribological properties and milling performances. The ceramic films were applied on cylindrical test samples and carbide end mills. The coated materials' structural, mechanical, and tribological properties were determined via scanning electron microscope (SEM), X-ray diffraction meter (XRD), tribometer, microhardness tester, and optical profilometer. DIN 40CrMnNiMo8-6-4 steel workpieces were machined by using a CNC vertical machining center to determine the actual working performance of the coated and uncoated cutting tools. The wear performance of the cutting tools after machining was determined by measuring the flank wear widths and mass losses. The hardness and adhesion results of the coated sample with bilayer TiAlN/TiSiN were higher than the coated sample with monolayer AlCrSiN. According to the scratch test results, the best adhesion results were obtained for TiAlN/TiSiN coating. The critical load value was determined as about 105 N. As a result, the wear rate value of the TiAlN/TiSiN thin film coated sample was lower. After machining, the mass loss of TiAlN/TiSiN coated tools was lower than AlCrSiN coated tools. In addition, the surface roughness value of the workpiece machined by the cutting tool coated with AlCrSiN was higher than the cutting tool coated with TiAlN/TiSiN.     

Improved interfacial adhesion in carbon fiber/epoxy composites through a waterborne epoxy resin sizing agent

A series of self‐emulsified waterborne epoxy resin (WEP) emulsions were used as surface sizing for carbon fibers (CFs) to improve the interfacial adhesion between the CF and epoxy matrix. In this work, the hydrogenated bisphenol‐A epoxy resin (HBPAE) was modified by polyethylene glycol (PEG) with molecular weights of 400, 800, 1000, 1500, 2000, 4000, and 6000 g/mol. The properties of the WEP emulsion were examined by Fourier transform infrared spectroscopy, dynamic light scattering, and transmission electron microscopy. The surface characteristics of sized CFs were evaluated using scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy. Afterwards, CF/EP composites were prepared and their fracture surface and interlaminar shear strength (ILSS) were examined. The results indicated that PEG2000 modified HBPAE sizing had the optimum emulsion stability and film‐forming ability. Meanwhile, the results also demonstrated that a continuous and uniform sizing layer was formed on the surface of CFs and the surface sizing was excellent in improving the chemical activity of CFs. Compared with unsized CFs, the O1s/C1s composition ratio was observed to increase from 11.51% to 33.17% and the ILSS of CF/EP composites increased from 81.2 to 89.7 MPa, exhibiting better mechanical property than that of commercial Takemoto S64 sized CFs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44757.     

Development and characterization of novel DOPO based phosphorus tetraglycidyl epoxy nanocomposites for aerospace applications

A study was made in the present investigation on the development and characterization of 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) based phosphorus tetraglycidyl epoxy nanocomposites and to find its suitability for use in aerospace and high performance applications. Phosphorus-containing diamine (DOPO-NH₂) was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 4,4′-diaminobenzophenone (DABP), and this is utilized for the preparation of DOPO based phosphorus containing tetraglycidyl epoxy denoted as ‘D’. The synthesized resin was characterized by Fourier transform infrared spectra (FT-IR) and ¹H, ¹³C nuclear magnetic resonance (NMR) spectra. Nanoclay and polyhedral oligomeric silsesquioxane (POSS)-amine nano-reinforcements denoted as N1 and N2 were incorporated into the synthesized epoxy resin. Curing was done with diaminodiphenylmethane (DDM) and bis(3-aminophenyl) phenylphosphine oxide (BAPPO) curing agents denoted as X and Y respectively. Mechanical, thermal, flame retardant, water absorption behaviour and electrical properties of the epoxy nanocomposites were studied and the results are discussed.     

Influence of the interfacial composition on the adhesion between aggregates and bitumen: Investigations by EDX, XPS and peel tests

The study of the adhesion between aggregates and bitumen is necessary to enhance the lifetime of the roads. The purpose of this work concerns the interaction between the mineralogy of the aggregates and the adhesion force measured at the interface between bitumen and aggregate. The adhesion of bitumen was studied according to the mineralogy of the aggregates, which were made of dolomite rock or granite. A method was developed to measure the fracture energy during the peeling of the bitumen layer from the aggregate surface. The specific manufacturing of the samples ensured reproducible measurements using a constant thickness of the bitumen layer and by introducing a strengthened and flexible membrane into the bulk of bitumen. The peeling results demonstrated that the locus of the failure varied according to the mineralogy of the aggregate. The failure was cohesive during the peeling of the dolomite/bitumen system while the failure was partly interfacial concerning the granite/bitumen system. The interface between bitumen and minerals was characterized, before and after peeling. In case of the granite, the detection of sulfur by X-ray Photoelectron Spectroscopy (XPS) highlighted only the bitumen residues and allowed identifying the mineral compounds that weaken the interface between bitumen and granite. Finally, XPS analyses showed that the alkali feldspars of the granite induced a weak interface with bitumen.