Lower Crystallite Size Research Articles

Effects of hydroxyapatite nanorods prepared through Elaeagnus Angustifolia extract on modulating immunomodulatory/dentin-pulp regeneration genes in DPSCs.

Dental pulp stem cells (DPSCs) are a new type of mesenchymal stem cells (MSCs) found in the oral cavity with immunomodulation and tissue regeneration capacities. This study determined the impacts of nano-hydroxyapatite (nHA) prepared through Elaeagnus Angustifolia extract (EAE) to enhance the relative expression of immunomodulatory/dentin-pulp regeneration genes in DPSCs. To produce nHA and modified nHA via EAE (nHAEA), the sol-gel technique was used. The functional groups of nanoparticles (NPs), morphological, and optical features were determined using Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) together with energy-dispersive X-ray analysis (EDAX), and Transmission electron microscopy (TEM). The cell viability was then determined using the MTT method in the presence of various EAE, nHA, and nHAEA concentrations. Target gene expression was quantified using a real-time PCR procedure after treating DPSCs with an optimally non-toxic dose of EAE and NPs. The presence of the HA phase was reported with the XRD and FTIR results. According to the results of SEM and TEM, the rod-like NPs could be fabricated. nHAEAs were found to be characterized with low crystallite size, reduced diameter, lengthier, needle-like, and less agglomerated particles compared with nHA. The real-time PCR results demonstrated that nHAEA remarkably increased the expression of human leukocyte antigen-G5 (HLA-G5), vascular endothelial growth factor (VEGF), dentin sialophosphoprotein (DSPP), and interleukin6 (IL6) genes compared to the nHA group. These findings suggest that nHAEAs might have the potential application in the stemness capability of DPSCs for the treatment of inflamed/damaged pulp.

Room temperature operated composite SnS–ZnS heterojunction based sensor for sub-ppm ethanol detection

The present work demonstrates the potential of metal sulphide SnS–ZnS composite towards detection of low concentration (sub ppm) ethanol at room temperature (27 °C). The fabricated sensor has shown excellent performance in terms of % response of 56.58% at 100 ppb owing to the low crystallite size observed from the x-ray diffraction (XRD) characterization. The sensor has been exposed to ethanol under relative humidity (RH) range of 40% RH to 80% RH. The sensor has shown fast response and appreciable selectivity towards ethanol. The elemental composition and valence states of the composite formed are shown using energy dispersive x-ray analysis and x-ray photoelectron spectroscopy. The excellent sensing behavior is also supposed to be contributed due to SnS–ZnS p-n heterojunction formation. XRD of the prepared sample has been done to find the crystal structure and crystallite size. Further, field emission scanning electron microscopy results have confirmed the low particle size of the sample which complements the high sensitivity of the sensor.

Physico-chemical characterization of Grewia Monticola Sond (GMS) fibers for prospective application in biocomposites

ABSTRACT New fibers extracted from plant barks are a recent subject of investigation as possible fillers for polymer composites. In this work, Grewia Monticola Sond (GMS) fibers have been characterized from a morphological, chemical, and thermal point of view. This involved using a number of techniques, including Fourier infrared spectroscopy (FTIR), X-ray diffraction (×RD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and 13C nuclear magnetic resonance (NMR). Results indicated that GMS fibers have relatively high cellulose (55%), with 33.5% crystallinity index and a crystallite size of 4.89 nm, and lower hemicellulose (14%) and lignin (15%) contents. The fibers showed cellulose degradation onset at around 324°C, while kinetic activation energy (74.18 kJ/mol) is quite low. The roughness of the fibers was in the range expected for similar natural fibers, and they may be considered silky according to their kurtosis values. As for possible application in composites, they would definitely withstand process temperatures with thermoplastics. However, their not very high crystallinity and low crystallite size might suggest a limited strength, to be verified in future after optimizing GMS fiber extraction from bark.

Mechanical and tribological properties of carbon fiber‐reinforced polyetheretherketone composite coatings by flame‐spraying method

AbstractThe carbon fiber‐reinforced polyetheretherketone (CF/PEEK) composite coatings with two types of short CFs, that is, 300‐ and 600‐mesh, each in the contents of 10 and 30 wt% are deposited in comparison with the pure PEEK coatings by using a flame spraying method, respectively. The 300‐mesh CFs with intact morphology and the 600‐mesh CFs preserving fractured shape and higher graphitization degree are selected as the reinforced fillers in the CF/PEEK composite coatings. The flame‐sprayed CF/PEEK composite coatings show the increased porosity with the higher CF contents. The adding of CFs in the flame‐sprayed CF/PEEK composite coatings limits the thermal degradation of PEEK and restrains the PEEK crystallization showing low crystallinity degree and small crystallite size. The composite coatings in 10 wt% CF content exhibit the optimized nanoindentation behavior and tribological property. The 300‐mesh CFs with large length and intact morphology in flame‐sprayed CF/PEEK composite coatings lead to the increased surface hardness by 1.31 times over that of the pure PEEK coatings. The 600‐mesh CFs with higher graphitization degree contribute to better tribological property of flame‐sprayed CF/PEEK composite coatings with an order of magnitude lower specific wear rate.

Enhanced hardness and wear resistance of Al-based hybrid MMCs by using of composite metal boride reinforcement particles

Composite metal boride particles were synthesized and then used as the reinforcement material for fabricating Al-based hybrid metal matrix composites (MMCs). Mechanical alloying and pressureless sintering methods were used to produce the Al - 2 wt % Co–Ni–B/Co–Ti–B hybrid composites. Mechanically alloyed powders and sintered composites were characterized in terms of physical, microstructural and mechanical properties. The low crystallite size of Al particles and high density of the composites provided improved microstructures without needle-shaped secondary phases, and increased nanohardness values of Al matrix, and hence resulted in enhanced mechanical properties. The lowest indentation depths (both for matrix and reinforcement phases), the highest hardness (∼2 GPa) and the lowest wear volume loss (∼0.13 mm3) were obtained from the Al-based MMCs reinforced with Co–Ni–B particles containing CoB and Ni2Co0.67B0.33 phases. Studies revealed that the synergetic effect of the binary and ternary boride phases in the composite reinforcements had a positive role on the hardness and wear resistance of hybrid composites.

Fuel oxygenation as a novel method to reduce sooting propensity of fuels: An investigation with gasoline surrogate fuels

Blending transportation fuels like gasoline with biofuels reduce our reliance on fossil fuels and pollutant emission due to the presence of fuel-bound oxygen. However, biofuel availability is limited to regions with an abundance of biomass and land for energy crops. To gain the advantage of fuel-bound oxygen on emission reduction, this work explores the effect of replacing a fraction of soot-producing aromatics present in gasoline with oxygenated aromatics to check if a fuel formulation strategy, where a fraction of aromatics-rich stream in a refinery is catalytically oxygenated to form oxygenated aromatics before blending with other hydrocarbon streams to produce gasoline, could be advantageous in producing clean fuels. A gasoline surrogate containing 17% n-heptane, 47% isooctane, and 36% toluene, which closely predicted gasoline properties such as density, molecular weight, threshold sooting index, and octane number, is used for the experiments. To mimic the above fuel formulation strategy, a fraction of toluene in gasoline surrogate is replaced with oxygenated aromatics, benzyl alcohol and anisole that are structurally similar to toluene. The oxygenated blends showcased lower sooting tendency than the surrogate fuel. Soot particles, collected from the three fuel blends, are analyzed using TGA, XRD, HRTEM, and elemental analyzer, where soots from oxygenated blends are found to have higher reactivity with lower particle diameter and crystallite size. The results indicate that such fuel formulation can not only reduce soot emission, but also improve soot physicochemical properties to reduce its lifetime in the environment.

Elucidation of sensing mechanism through VOCs induced surface potential changes on graphene oxide/tin oxide nanocomposites

We report the use of a scanning Kelvin probe in measuring the gas adsorption induced change in contact potential difference (CPD) for the graphene-based binary nanocomposites towards various volatile organic compounds (VOCs) at room temperature. The binary nanocomposites (GO/SnO2) were prepared by one-step solvothermal (GS-I) and two-step mechanical mixing (GS-II) methods. The significant change in CPD upon visible light illumination for both the samples in the air medium enabled a room temperature interaction with VOCs. GS-I exhibited superior structural, optical and electrical properties in terms of lower crystallite size, defects, a higher percentage of surface atoms and visible light absorption. This appears to be consistent with the change in surface potential upon VOC interaction with a downward band bending for GS-I and upward bending for GS-II. These findings provided substantial details for understanding the interfacial modifications between graphene-based binary nanocomposites and assist in characterizing the mechanism of gas interaction.

Self-combustion Ni and Co-based perovskites as catalyst precursors for ammonia decomposition. Effect of Ce and Mg doping

LaCo1-xNixO3 perovskites have been synthesized by self-combustion, characterized, and examined as catalyst precursors for the COx-free hydrogen production from catalytic ammonia decomposition at low temperatures. The influence of the cobalt content as well as the addition of two dopant in different amount was studied and optimized. Small Ni crystallite size and high total basic sites were found to remarkably enhance the catalytic activity. Moreover, bimetallic perovskites generated cobalt/nickel in higher size, higher impurities and lower active sites than pure nickel perovskite, which decreased the ammonia conversion. On the other hand, the addition of dopant in adequate amount over pure Ni perovskite (La0.1A0.9NiO3; A = Ce or Mg) generated catalyst with low nickel crystallite size and high basicity delivering superior catalytic performance. Catalysts were demonstrated to be stable for at least 40 h. In fact, 96 % and 98 % ammonia conversion were achieved at low temperature (400 °C), when La0.1Ce0.9NiO3 and La0.1Mg0.9NiO3 were employed, resulting from the synergic effect between La-Ce and Ni-Mg-La. Presenting the Mg-doped perovskite the highest catalytic activity at the mild temperature of 350 °C.This study provides new insight in designing diverse catalyst precursors to develop economic and efficient catalysts to achieve high ammonia conversion (high hydrogen production) at low temperature and enhance the ammonia perspective as hydrogen carrier toward the ‘hydrogen economy’.

Spray pyrolysis developed Nd doped Co3O4 nanostructured thin films and their structural, and opto-nonlinear properties for optoelectronics applications

Herein we are reporting the facile spray pyrolysis fabrication of different Neodymium (Nd) contents loaded cobalt oxide (Co3O4) nanostructured thin films at 400 °C substrate temperature and investigated for opto-nonlinear applications. Structural and vibrational studies approve the cubic system of all films with the low crystallite size between 25 and 20 nm. FESEM e-mapping and EDX analyses further confirm the homogeneous Nd doping in Co3O4 films. FESEM study reveals that the grains are very fine and distributed throughout the films. The optical study reveals that the grown films possess two energy gaps which are between 2.03 and 2.15 eV and 1.49–1.55 eV. Photoluminescence study has been performed at three different excitation wavelengths and the mono-emission was noticed at 375, 500 and 754 nm. Furthermore, the linear absorption and refractive indices were determined along with dielectric and electrical properties. Also, the nonlinear susceptibility and refractive index were determined and found to be in range of 4 × 10-13 to 1.27 × 10-10 esu and 5.86 × 10-12 to 1.35 × 10-9 esu., respectively.

Structural, magnetic and electrical properties of La1-xMgxFeO3 perovskites

In this study, we synthesized La 1-x Mg x FeO 3 (x = 0.1, 0.2, and 0.3) powdered ceramics using sol − gel and sintering methods and their structure, magnetic and electrical properties have been investigated. All samples showed the Pbnm single phase, and structural analyses revealed a lattice distortion due to the addition of Mg that increases with increasing Mg content. Transmission electron microscopy revealed a decrease in particle size with increasing Mg content. The M − H hysteresis loops of the samples revealed that the samples with Mg substitution at the La site exhibits weak ferromagnetic behaviour, and the hysteresis loops increases with an increase in Mg content. The magnetisation increases as the Mg content is increased, which is might be related to the lower crystallite and particle sizes, as well as higher Fe 4+ /Fe 3+ ratio, as shown by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. Analysis of the electrical properties showed grain–grain boundary effect in the conduction mechanism and two relaxation mechanisms for low Mg contents (x ≤ 0.2), whereas only the grain effect and one relaxation mechanism were observed at higher Mg contents (x = 0.3). The temperature dependence of direct current conductivity obeys the Arrhenius law. The activation energy for the conduction mechanism decreased with an increase in the Mg content. These results contribute the important knowledge in promising the candidate electrode material in electrochemical application.

Improved Methane Production by Photocatalytic CO2 Conversion over Ag/In2O3/TiO2 Heterojunctions.

In this work, the role of In2O3 in a heterojunction with TiO2 is studied as a way of increasing the photocatalytic activity for gas-phase CO2 reduction using water as the electron donor and UV irradiation. Depending on the nature of the employed In2O3, different behaviors appear. Thus, with the high crystallite sizes of commercial In2O3, the activity is improved with respect to TiO2, with modest improvements in the selectivity to methane. On the other hand, when In2O3 obtained in the laboratory, with low crystallite size, is employed, there is a further change in selectivity toward CH4, even if the total conversion is lower than that obtained with TiO2. The selectivity improvement in the heterojunctions is attributed to an enhancement in the charge transfer and separation with the presence of In2O3, more pronounced when smaller particles are used as in the case of laboratory-made In2O3, as confirmed by time-resolved fluorescence measurements. Ternary systems formed by these heterojunctions with silver nanoparticles reflect a drastic change in selectivity toward methane, confirming the role of silver as an electron collector that favors the charge transfer to the reaction medium.

A Negative Effect of Niobium‐Doped Ceria on Soot Oxidation Activity‡

AbstractNiobium‐doped ceria catalysts were synthesized to study soot oxidation activity. X‐Ray diffraction (XRD) and Raman analysis of the samples revealed the presence of a fluorite structure of CeO2 for all the doped samples. The T50 temperature of the pure CeO2 sample was more significant than that of bare soot. The high catalytic activity of the CeO2 catalyst can be attributed to the low crystallite size, high facet ratio, and the large Brunauer‐Emmett‐Teller (BET) surface area as compared to Nb‐doped samples. The activation energy calculated by both Ozawa and KAS methods were found to be low for CeO2 when compared to Nb‐doped samples. CeO2 resulted in better soot oxidation activity with low activation energy.

Tuning the properties of ZnxS1-x nanoparticles by controlling reaction conditions

In this work, a modified synthesis method was deployed to obtain nanocrystalline zinc sulfide from zinc acetate. By utilizing the hydrothermal and sol gel method, the influence of: reaction time, solvent and temperature control were used to tune the properties of zinc sulfide. Our results showed that ZnS(B) (which was obtained by sol gel in water + hydrothermal) typified formation of increased sulfur vacancies while an increase in reaction time resulted in decreased sulfur vacancies. The introduction of chemical defects in ZnS(A) (which was obtained by sol gel in methanol + KOH) resulted in lower crystallite size. We observed that crystallinity improved with increased reaction time and utilization of water as solvent improved the crystallinity of the material as confirmed in ZnS(C) and ZnS(B). Furthermore, our result showed that reaction time influenced dislocation density of the material to a greater extent than type of solvent used. The crystallite size estimated by Scherer formula was in the range 1.35 nm – 18.64 nm while the band gap energy of the ZnS samples were calculated in the range 3.8 eV- 4.6 eV. Utilizing these novel syntheses methods can stimulate new directions in synthesizing ZnS crystals with options of choosing appropriate method for specific applications depending on properties to be traded off.

Catalytic activity of magnetite and its magnetic heating properties

Magnetite (Fe3O4) nanoparticles have been successfully synthesized using cetyltrimethylammonium bromide (CTAB). The stabilizing agent CTAB reduces agglomeration of magnetic nanoparticles in solution. The formation of Fe3O4 nanoparticles was confirmed by X-ray diffractometry, IR spectroscopy and Mössbauer spectroscopy. The average crystallite size of magnetite nanoparticles was found to be 14.41 nm. The catalytic activity of the obtained magnetite have been tested in a batch reactor. Due to favourable redox properties and low crystallite size, magnetite nanoparticles have high catalytic activity in the decomposition of H2O2. The degree of H2O2 decomposition was 77.41% in 120 min. The induction heating of synthesized Fe3O4 nanoparticles have been investigated. At magnetite concentration of 40 mg/ml, the specific absorption rate is equal 14.57 W/g.

Synthesis and characterization of sol–gel derived hydroxyapatite from a novel mix of two natural biowastes and their potentials for biomedical applications

The surge in meat and fish processing in Nigeria has resulted in a significant increase in biowaste production and these wastes can be salvaged, allowing for the extraction of calcium phosphates and a reduction in solid waste in the concerned industries. These biowastes, particularly animal bones and fish bones can be used as the precursors for the synthesis of hydroxyapatite (HAp), a very popular member of the family of calcium phosphates. In this present study, for the first time, we report the utilization of animal bone biowaste and catfish bone biowaste in mixed proportions to produce hydroxyapatite by using the sol–gel synthesis protocol. The conversion of the as-received deproteinized biowastes was conducted by calcining the powders independently at 900 °C, followed by a chemical mixing process (sol–gel) of the mixed powders in specified proportions (C100, BC 75/25, BC 50/50, BC 25/75, and B 100: C-catfish bones and B: animal bones). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the samples, while scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis were used to investigate the structure, size, and elemental composition of the derived mixed and stand-alone powders. The sample BC 50/50 exhibited a higher degree of crystallinity and a mean crystallite size of 80.42% and 27.3 nm, respectively. EDS analysis showed that the atomic Ca/P ratios of the as-synthesized HAp samples ranged from 2.379, to 3.10.The obtained products are Mg containing except for the BC 75/25 with B 100 having a higher Mg wt% of 1.538 and lowest reactivity potential by reason of its lowest crystallite size. Thus, sample B100 can be of higher potential for biomedical applications.

Ferroelectric properties of heterostructure Sr-=SUB=-0.5-=/SUB=-Ba-=SUB=-0.5-=/SUB=-Nb-=SUB=-2-=/SUB=-O-=SUB=-6-=/SUB=-/Ba-=SUB=-0.2-=/SUB=-Sr-=SUB=-0.8-=/SUB=-TiO-=SUB=-3-=/SUB=-/Si(001)

The properties of c-oriented thin films of Sr0.5Ba0.5Nb2O6 grown on a Si(001) (p-type) substrate with a pre-deposited Ba0.2Sr0.8TiO3 layer were studied using scanning probe microscopy and dielectric spectroscopy. It is established that the Sr0.5Ba0.5Nb2O6 films are characterized by low surface roughness (less than 6 nm) and average crystallite size of ~ 93 nm. It is shown that there is spontaneous polarization in the film directed from its surface to the substrate, which causes the manifestation of the field effect for the case of the Si substrate with p-type conductivity without the external field effect. Differences in the magnitudes of the surface potential signal for regions polarized by an external electric field of different polarities (+10 and -10 V), as well as in their relaxation to the initial state, are revealed. The reasons for the established patterns are discussed. Keywords: barium-strontium niobate, SBN, scanning probe microscopy, thin films

All-natural and biocompatible cellulose nanocrystals films with tunable supramolecular structure

Herein, nanocomposites films were prepared via the facile casting method by incorporating cellulose nanocrystals (CNCs) with arabinogalactan (AG), galactomannan (GM) or konjac glucomannan (KGM) respectively. The introduced polysaccharides maintained the transparency of CNCs films and promoted the UV blocking properties. In addition, mechanical strength of the nanocomposite films was greatly improved after the combination of polysaccharides. The interactions of hydroxyl-abundant macromolecules, smoother and tighter morphological structures, as well as the disturbed crystal structure were proved to be responsible for the improved properties. Hydrophilic lattice planes of cellulose crystallites were determined to interact with polysaccharides resulting in lower crystallite sizes and crystallinity. The cell culture assay revealed that the films had no cytotoxicity and presented a satisfactory cytocompatibility, because of the polysaccharides from plant cell walls introduced into the films. Therefore, the biocompatible nanocomposites films can be tuned by the addition of polysaccharides, which show great potentials for materials modification in optical, packaging and biomedical fields.

Lignin enhances cellulose dissolution in cold alkali

Aqueous sodium hydroxide solutions are extensively used as solvents for lignin in kraft pulping. These are also appealing systems for cellulose dissolution due to their inexpensiveness, ease to recycle and low toxicity. Cellulose dissolution occurs in a narrow concentration region and at low temperatures. Dissolution is often incomplete but additives, such as zinc oxide or urea, have been found to significantly improve cellulose dissolution. In this work, lignin was explored as a possible beneficial additive for cellulose dissolution. Lignin was found to improve cellulose dissolution in cold alkali, extending the NaOH concentration range to lower values. The regenerated cellulose material from the NaOH-lignin solvents was found to have a lower crystallinity and crystallite size than the samples prepared in the neat NaOH and NaOH-urea solvents. Beneficial lignin-cellulose interactions in solution state appear to be preserved under coagulation and regeneration, reducing the tendency of crystallization of cellulose.

Co-relation between mechanical properties and porosity in thick, thin and thinnest sections of stepped casted workpiece using A-356 Aluminum alloy

A-356 aluminum alloy stepped casted workpiece were prepared with step casting technique was investigated for the mechanical properties and porosity defects using various gating elements (ingate/runner) profiles. Similarly, casted workpieces were produced using single and double gating elements with circular (vortex free), square and rectangular runner and ingate profiles. Hardness (HV) and ultimate tensile strength (UTS) of the thick section prepared from single circular runner/ingate system was more in comparison to thin and thinnest sections extracted at respective heights. Similarly, hardness and tensile strengths of thick specimen prepared from double ingate/runner having circular shape was found greater in comparison to thin and thinnest sections accordingly. SEM images depicted increase of porosity levels in thin and thinnest sections prepared from single or double within workpiece manufactured from circular runner & ingate arrangements respectively. In addition, X-ray diffraction results further revealed increase in crystallite size, hardness and tensile strength for specimens manufactured through circular profiled single or double runner/ingate arrangement. The prepared specimens also follow inverse Hall-Petch and D 2/%P statistical fit with p < 0.05 between hardness and crystallite size. Hence, the specimen with lower crystallite size or finer grains depicted attenuated mechanical properties due to higher porosity levels. In other words, D 2/%P index ratio value <1.40 (≥95% data points follows) exhibited reductions in mechanical properties accompanied by decreasing crystallite size and vise-versa. Moreover, double gating runner & ingate combination exhibited comparatively lesser pores relative to single gating design. Hence, this study suggests double runner & ingate arrangement accompanied with circular cross-section are appropriate for large size step castings or complicated geometries production in foundries.

A systematic study of electrolyte effect on exfoliation efficiency and green synthesis of graphene oxide

A systematic study on the effect of the electrochemical exfoliation of graphite was conducted to provide new insights on the structure and material properties. Graphene-like structures are produced at scale currently using the wet chemical approaches, which is usually followed by an additional reduction step. The electrochemical exfoliation constitutes a promising alternative method for green, fast, and safe industrial exploitation, due to its low cost, mild conditions, basic equipment requirement and eco-friendlier electrolytes. Additionally, crystal structure of graphene related materials demonstrates less defective sights due to the high speed of exfoliation. A thorough investigation was conducted on critical parameters of the electrochemical process. The parameters of concentration, voltage, temperature and sonication assistance were studied using the randomized block design approach for various electrolytes. After the evaluation and screening of the materials with several characterization techniques, three optimization routes were selected, which included a modified Hummers' method, exfoliation based on the surface energy of pure DMF, and violent pH neutralization. The production of graphene oxide nanoplatelets was achieved, with high oxidation rates, high crystallinity and limited imperfections. The materials were consisted of less than 10 layers and up to 5 layers as demonstrated by the low crystallite size, which was also demonstrated for GO that underwent post-treatment optimization. Higher yields were achieved with electrolytes known for their strong oxidative effect, while the hydrogen peroxide electrolyte and the ionic liquid demonstrated lower exfoliation rates.