Porosity Percentage Research Articles

Preparation of Nanosize Bone Powder from Waste and Development of Al Composite through Squeeze Casting Process

Al6061 alloy is most commonly used in automotive, marine, and aerospace applications to lighten the composite and increase its strength. Al6061 alloy is a precipitation-hardened aluminum alloy used as a matrix material. Beef bone is a biowaste that has polluted the environment and the people who live in the vicinity of its manufacturing and disposal sites. Biowaste has been used in a variety of ways by researchers in recent years, including activated carbon, water purification, reinforcement in composites, fillers, additives, etc. Beef bones that had been abandoned as waste were collected, cleaned, and grounded into a fine powder with a particle size of 50–100 nm and used as reinforcement. Squeeze casting process is used to create the newly created aluminum composite (Al6061 + 0%, 5%, 10% of bone powder). The aluminum composite was fabricated and three samples were successfully obtained for further testing and analysis. The prepared Al composites with nanopowder reinforcement are analyzed for surface morphology, elemental identification, hardness, porosity, tensile strength, and compression strength. The percentage of porosity in the composite is improved by 36.7% when compared to the Al6061 alloy. Similarly, the tensile strength of the produced composite is increased to 5.59%. A significant improvement is observed in the wear resistance and hardness of the composite as 54.55% and 48.65%, respectively.

Selective Laser Melting of (Fe-Si-B)/Cu Composite: Structure and Magnetic Properties Study

A mixture of original 1CP powder and 10 wt.% of pure Cu-powder was prepared and 1CP-Cu composite samples were obtained by selective laser melting using different process parameters. Comparison of pure 1CP and composite samples showed that addition of Cu halved the porosity percentage of the obtained material. Distribution of Cu-phase in 1CP-matrix can be recognized as uniform in all the samples. X-ray diffraction of samples showed the presence of α-Fe solid solution, iron boride Fe2B, and crystal Cu. Scanning electron microscopy analysis also allowed to discover ordered solid solution Fe3Si in samples microstructure. Differential scanning calorimetry data showed that composite sample contains amorphous phase as opposed to pure 1CP sample manufactured using the same process parameters. Magnetic properties of samples were studied, and it was found that addition of 10 wt.% of Cu allowed to reduce magnetic field energy losses by approximately four times.

Smart waste management perspective of COVID-19 healthy personal protective materials in concrete for decorative landscape pavements and artificial rocks

This paper presents a new method for determining the effect of healthy personal protective material (HPPM) stripes, such as surgical masks, protective suits, and overhead and foot covers, on the durability and physicomechanical characteristics of concrete for use in architectural forms. Because of the current global epidemic caused by coronavirus (COVID-19), the use of HPPM, such as surgical masks, protective suits, and overhead and foot covers, has increased considerably. COVID-19’s second and third waves are currently affecting various countries, necessitating the use of facemasks (FM). Consequently, millions of single FM have been discharged into the wild, washing up on beaches, floating beneath the seas, and ending up in hazardous locations. The effect of stripe fibers on the physicomechanical characteristics of concrete, such as the workability, Uniaxial Compressive Strength UCS, flexural strength, impact strength, spalling resistance, abrasion resistance, sorptivity, Water absorption Sw, porosity (ηe), water penetration, permeability, and economic and eco-friendly aspects, need to be determined. With a focus on HPPM, especially single-use facemasks, this study investigated an innovative way to incorporate pandemic waste into concrete structures. Scanning electron microscope and X-ray diffraction patterns were employed to analyze the microstructures and interfacial transition zones and to identify the elemental composition. The HPPM had a pore-blocking effect, which reduced the permeability and capillary porosity. Additionally, the best concentrations of HPPM, particularly of masks, were applied by volume at 0, 1, 1.5, 2.0, and 2.5%. The use of mixed fibers from different HPPMs increased the strength and overall performance of concrete samples. The tendency of growing strength began to disappear at approximately 2%. The results of this investigation showed that the stripe content had no effect on the compressive strength. However, the stripe is critical for determining the flexural strength of concrete. The UCS increased steadily between 1 and 1.5% before falling marginally at 2.5%, which indicates that incorporating HPPM into concrete had a significant impact on the UCS of the mixture. The addition of HPPM to the mixtures considerably modified the failure mode of concrete from brittle to ductile. Water absorption in hardened concrete is reduced when HPPM stripes and fibers were added separately in low-volume fractions to the concrete mixture. The concrete containing 2% HPPM fibers had the lowest water absorption and porosity percentage. The HPPM fibers were found to act as bridges across cracks, enhancing the transfer capability of the matrices. From a technological and environmental standpoint, this study found that using HPPM fibers in the production of concrete is viable.

Compressive strength of metamaterial bones fabricated by 3D printing with different porosities in cubic cells

This research focuses on the compressive strength of metamaterial bones, fabricated by 3D printing with different porosities in cubic cells. For this objective, compressive testing was done on standard samples besides bones, both 3D-printed and real ones. To fabricate a metamaterial bone, the cubic cell was chosen in this research. Since the yield strength and the ultimate stress of the vertical solid standard specimen had better performance than the horizontal solid standard one, the vertical metamaterial sample with a cubic cell was designed for four porosity states of 25%, 30%, 50%, and 55%. The obtained results illustrated that 30% of porosity was introduced as the optimal specimen. Therefore, this percentage of porosity was used to fabricate a metamaterial bone. In addition, the rabbit tibia bone in two solid and metamaterial states was prepared by 3D printing and compared with the real rabbit bone. The results showed that the real bones withstood more force compared to the solid and metamaterial 3D-printed bone samples. The weight of the metamaterial bone decreased by 5.97%, compared to the solid bone specimen. Finally, the quality of 3D printing was checked by microscopy. Then, the quality of 3D printing decreased by increasing the thickness of the strut.

Optimizing the Parameters of Long Short-Term Memory Networks Using the Bees Algorithm

Improving the performance of Deep Learning (DL) algorithms is a challenging problem. However, DL is applied to different types of Deep Neural Networks, and Long Short-Term Memory (LSTM) is one of them that deals with time series or sequential data. This paper attempts to overcome this problem by optimizing LSTM parameters using the Bees Algorithm (BA), which is a nature-inspired algorithm that mimics the foraging behavior of honey bees. In particular, it was used to optimize the adjustment factors of the learning rate in the forget, input, and output gates, in addition to cell candidate, in both forward and backward sides. Furthermore, the BA was used to optimize the learning rate factor in the fully connected layer. In this study, artificial porosity images were used for testing the algorithms; since the input data were images, a Convolutional Neural Network (CNN) was added in order to extract the features in the images to feed into the LSTM for predicting the percentage of porosity in the sequential layers of artificial porosity images that mimic real CT scan images of products manufactured by the Selective Laser Melting (SLM) process. Applying a Convolutional Neural Network Long Short-Term Memory (CNN-LSTM) yielded a porosity prediction accuracy of 93.17%. Although using Bayesian Optimization (BO) to optimize the LSTM parameters mentioned previously did not improve the performance of the LSTM, as the prediction accuracy was 93%, adding the BA to optimize the same LSTM parameters did improve its performance in predicting the porosity, with an accuracy of 95.17% where a hybrid Bees Algorithm Convolutional Neural Network Long Short-Term Memory (BA-CNN-LSTM) was used. Furthermore, the hybrid BA-CNN-LSTM algorithm was capable of dealing with classification problems as well. This was shown by applying it to Electrocardiogram (ECG) benchmark images, which improved the test set classification accuracy, which was 92.50% for the CNN-LSTM algorithm and 95% for both the BO-CNN-LSTM and BA-CNN-LSTM algorithms. In addition, the turbofan engine degradation simulation numerical dataset was used to predict the Remaining Useful Life (RUL) of the engines using the LSTM network. A CNN was not needed in this case, as there was no feature extraction for the images. However, adding the BA to optimize the LSTM parameters improved the prediction accuracy in the testing set for the LSTM and BO-LSTM, which increased from 74% to 77% for the hybrid BA-LSTM algorithm.

Morphological and Optical Study of Black P- Silicon Textured in KOH Bath

This paper reports the temperature and the concentration dependence of anisotropic etching for (100) p-Silicon in an aqueous KOH solution etching rate of wet etching has been experimentally determined with varying concentrations and the temperature of the KOH solution. The texturing process was managed at different etching durations ( 20 min, 40 min, and 60 min). XRD test showed that the lowest value of grain size was 5.0 nm (obtained with the highest porosity percentage of 50% with 4.5% KOH concentration for 60 min). FESEM test showed that the pore diameter increased with increasing etching time. The lowest reflectance value was (2.8 % at 550 nm wavelengths for samples treated with 4.5% KOH concentration for 60 min etching time. The refractive index value was 1.8 for the same black Si sample, also Hall test is introduced.

Analysis of amorphous structure with polycaprolactone-hydroxyapatite nanoparticles fabricated by 3D bioprinter technique for bone tissue engineering

New ceramic scaffolds have the ability to be designed to replace the hip bone with different shapes. In this research, the aim is to fabricate a porous scaffold by fused deposition modeling (FDM) with three geometric shapes of circle, multi-circle and square for bone replacement applications. Biological tests included immersing the samples in simulated body fluid (SBF) to monitor the apatite formation and phosphate buffer saline (PBS) to check weight loss and ion concentration changes. Morphological examination was evaluated by examining the surface of the sample before and after immersion in the SBF using scanning electron microscope (SEM) analysis. The obtained mechanical results such as elastic modulus and compressive strength were used in the finite element analysis (FEA). The mechanical results showed that the sample with a multi-circle structure have a higher elastic modulus under the compressive strength about 32 MPa. Also, the porosity percentage showed that the highest porosity belongs to the second sample. The stress-strain results show that the second sample has a compressive strength of about 2.6 MPa. The FEA of the samples show that the sample with square structure has the highest stress compared to the other sample. The apatite growth in all three samples had similar trend. The mechanical and morphological analysis shows the fracture surface of the bone scaffold under compressive loading for the third sample has porosity of about 42% and the lowest compressive strength of about 1.85 ± 0.8 MPa. In order to reduce the amount of remain stress, the first and second samples should be used for the pelvic bone repair.

Effect of induced plastic strain on the porosity of PA12 printed through selective laser sintering studied by X-ray computed micro-tomography

3D printing is a widespread technology in different fields, such as medicine, construction, ergonomics, and the transportation industry. Its diffusion is related to the ability of this technique to produce complex parts without needing for assembly of different components or post-processing. However, the quality of the parts produced by additive manufacturing could be affected by the fabrication process, thus leading to the development of different kinds of defects such as porosity or inclusions. Understanding the role played by these defects and promoting strategies that could help reduce their occurrence represents a key point to allow using 3D printing for structural applications. In this work, 3D printed parts have been subjected to porosity characterization by using experimental tests on dogbone samples subjected to plastic deformation. In particular, multiple loading-unloading steps have been carried out and, at the end of each step, the X-ray computed micro-tomography (μ-CT) has been employed for the identification of fabrication defects and for analyzing the crack growth mechanism that occurs after quasi-static loading tests. Sample analysis reveals the presence of a high porosity that could be attributed to the fabrication process. After the sample’s plastic deformation, it was found an increase in both porosity percentage and pore dimensions. Moreover, the crack propagation mechanism is affected by porosity.

Evaluation of Vitamin D isolated or Associated with Teriparatide in Peri-Implant Bone Repair in Tibia of Orchiectomized Rats.

(1) Background: The objective of this study was to evaluate the morphometry of peri-implant bone tissue in orchiectomized rats, treated with vitamin D isolated or associated with teriparatide. (2) Methods: 24 rats were divided into 4 groups: ORQ-orchiectomy, without drug treatment, ORQ+D-orchiectomy, treated with vitamin D, ORQTERI-orchiectomy, treated with teriparatide and ORQTERI+D-orchiectomy, treated with teriparatide + vitamin D. Each animal received an implant in the tibial metaphysis. Euthanasia occurred 60 days after implant surgery. Computed microtomography (micro-CT) was performed to evaluate the parameters of volume and percentage of bone volume (BV, BV/TV), trabecular thickness (Tb.Th), number and separation of trabeculae (Tb.N, Tb.Sp) and percentage of total porosity (Po-tot). Data were subjected to 1-way ANOVA and Tukey post-test, with a significance level of 5%. (3) Results: For the parameters BV, BV/TV, Tb.Th, the ORQTERI+D group showed the highest values in relation to the other groups and for Po-tot, the lowest values were for ORQTERI+D. For Tb.Sp and Tb.N, there was no statistically significant difference when comparing intragroup results (p > 0.05). (4) Conclusions: It was possible to conclude that treatment with vitamin D associated with teriparatide increases bone volume and improves bone quality.

The Effect of Electrospinning Parameters on Morphological and Mechanical Properties of PAN-based Nanofibers Membrane

The electrospun nanofibers membranes (ENMs) have gained great attention due to their superior performance. However, the low mechanical strength of ENMs, such as the rigidity and low strength, limits their applications in many aspects which need adequate strength, such as water filtration. This work investigates the impact of electrospinning parameters on the properties of ENMs fabricated from polyacrylonitrile (PAN) solved in N, N-Dimethylformamide (DMF). The studied electrospinning parameters were polymer concentration, solution flow rate, collector rotating speed, and the distance between the needle and collector. The fabricated ENMs were characterized using scanning electron microscopy (SEM) to understand the surface morphology and estimate the average fiber sizes. The membrane porosity percentage was measured using the dry-wet weight method. Also, a dynamic mechanical analyzer was used to determine the mechanical strength properties (tensile strength and Young's modulus) (DMA). The obtained results revealed that the polymer concentration and flow rate mainly affect the porosity and fiber size in ENMs. Increasing the polymer concentration improves the strength and flexibility, while the flow rate did not show a clear effect on the mechanical strength of ENMs. Both fibers collecting speed and spinning distance did not clearly impact the membrane morphology. ENMs flexibility significantly increased with increasing the collector speed and decreasing the spinning distance. Strong and flexible ENMs with small fibers can be fabricated using 10% PAN/DMF at a flow rate of 1 mL/h, collector speed of 140 rpm, and spinning distance of 13 cm.

Poly (l-lactic acid)-based modified nanofibrous membrane with dual drug release capability for GBR application

Electrospun multilayer nanofibers guided bone regeneration (GBR) with a new design were developed in this study. The synthesized multilayer GBR was composed of two distinct layers. Poly l-lactic acid (PLA) incorporated with simvastatin (SIM) was designed as PLA/SIM layer to contact with a bone defect. In addition, the hydrophilic gelatin (GT) containing thymol (THY) was fabricated as GT/THY layer to contact connective tissue, potentially for bacterial gathering. Due to the different chemical nature and weak cohesion of the hydrophilic and hydrophobic layers, hybrid fibers made of PLA/SIM and GT/THY were electrospun as cohesion promoters between these layers. The microstructure and characteristics of the synthesized multilayer substrate, named GT/PLA, were evaluated, and different fibrous monolayers were fabricated to determine the optimal concentrations of drugs.Scanning electron microscopy (SEM) images showed continuous, smooth, randomly aligned, and bead-free fibers. In addition, there were no drug particles on the fiber surfaces which displayed the good placement of those inside the fibers. The mats exhibited satisfactory tensile strength (4.60 ± 0.14 MPa) and favorable physicochemical properties, including proper porosity percentage (<50 %) and appropriate pore size. Suitable swelling behavior (293 ± 0.05 %) and adequate degradation rates were also approved by characterizing swelling and degradability in vitro. The GT/PLA membrane exhibited a prolonged and sustained SIM release and controlled THY release with high antibacterial efficiency. Cell viability, cell attachment assay, and nuclear staining using 4′,6-diamidino-2-phenylindole (DAPI) showed that the designed GT/PLA substrate had good biocompatibility and cell attachment. Cell infiltration testing also showed that the cells were finely prevented by the outer layer (GT/THY). Overall, the obtained results in this study indicated the great potential of the prepared GT/PLA for use as a GBR which can develop osteogenic and antibacterial biomimetic periosteum optimizing the clinical application of GBR strategies.

Biodegradable and antithrombogenic chitosan/elastin blended polyurethane electrospun membrane for vascular tissue integration.

Current commercialized vascular membranes to treat coronary heart disease (CHD) such as Dacron and expanded polytetrafluoroethylene (ePTFE) have been associated with biodegradable and thrombogenic issues that limit tissue integration. In this study, biodegradable vascular membranes were fabricated in a structure of electrospun nanofibers composed of polyurethane (PU), chitosan (CS) and elastin (0.5%, 1.0%, and 1.5%). The physicochemical properties of the membranes were analyzed, followed by the conduction of several test analyses. The blending of CS and elastin has increased the fiber diameter, pore size and porosity percentage with the appearance of identical chemical groups. The wettability of PU membranes was enhanced up to 39.6%, demonstrating higher degradation following the incorporation of both natural polymers. The PU/CS/elastin electrospun membranes exhibited a controlled release of CS (Higuchi and first-order mechanisms) and elastin (Higuchi and Korsmeyer-Peppas mechanisms). Delayed blood clotting time was observed through both activated partial thromboplastin time (APTT) and partial thromboplastin time (PT) analyses where significantly delay of 26.8% APTT was recorded on the PU membranes blended with CS and elastin, in comparison with the PU membranes, supporting the membrane's antithrombogenic properties. Besides, these membranes produced a minimum of 2.6 ± 0.1 low hemolytic percentage, projecting its hemocompatibility to be used as vascular membrane.

Properties Evaluation of Composite Materials Based on Gypsum Plaster and Posidonia Oceanica Fibers

Estimating the amount of material without significant losses at the end of hybrid casting is a problem addressed in this study. To minimize manufacturing costs and improve the accuracy of results, a correction factor (CF) was used in the formula to estimate the volume percent of the material in order to reduce material losses during the sample manufacturing stage, allowing for greater confidence between the approved blending plan and the results obtained. In this context, three material mixing schemes of different sizes and shapes (gypsum plaster, sand (0/2), gravel (2/4), and Posidonia oceanica fibers (PO)) were created to verify the efficiency of CF and more precisely study the physico-mechanical effects on the samples. The results show that the use of a CF can reduce mixing loss to almost 0%. The optimal compressive strength of the sample (S1B) with the lowest mixing loss was 7.50 MPa. Under optimal conditions, the addition of PO improves mix volume percent correction (negligible), flexural strength (5.45%), density (18%), and porosity (3.70%) compared with S1B. On the other hand, the addition of PO thermo-chemical treatment by NaOH increases the compressive strength (3.97%) compared with PO due to the removal of impurities on the fiber surface, as shown by scanning electron microscopy. We then determined the optimal mixture ratio (PO divided by a mixture of plaster, sand, and gravel), which equals 0.0321 because Tunisian gypsum contains small amounts of bassanite and calcite, as shown by the X-ray diffraction results.

Investigating of physical, mechanical, and biological properties of polyhydroxybutyrate-keratin/alumina electrospun scaffold utilized in bone tissue engineering

Electrospun nanofiber scaffolds have a similar structure to extracellular matrix, leading to increased cell adhesion, proliferation, and migration. In this study, 1–5wt % of alumina nanowires were added to polyhydroxybutyrate-keratin (PHB–K) solution, and the morphology of the electrospun scaffolds in terms of fiber diameter, porosity percentage, and the uniformity of the alumina nanowires distribution was evaluated by SEM. FTIR and raman tests were also used to evaluate the chemical bonds of nanofibers and the presence of alumina and keratin in electrospun scaffolds. The crystallinity of the scaffolds was also measured using DSC and confirmed by XRD. The increase of alumina augmented the crystallinity of scaffolds because alumina is a nucleating agent. The tensile strength of PHB-K scaffolds increased up to 3 fold in the presence of 3 wt % of alumina.The MG63 cells survived, and the secretion of alkaline phosphatase and mineralization due to the presence of alumina was significantly higher than PHB and PHB-K scaffolds. Based on the results, the electrospun PHB-K/AL2O3 scaffolds are potential candidates for bone tissue engineering.

Pore network characteristics as a function of diagenesis: Implications for epigenic karstification in shallow-water carbonates

Karst processes may be critical for developing secondary porosity and permeability within carbonate reservoirs and aquifers. Karstification can significantly influence reservoir storage capacity and subsurface fluid flow. This study investigates the interplay between fluid-flow pathways and diagenesis in an epigenic karst setting in Cretaceous shallow-water carbonate rocks, Potiguar Basin, Brazil. The results indicate that dissolution occurred at all diagenetic stages, but the last stage is the most important because it is related to the most recent subaerial exposure. Dissolution produced during the last karst stage occurred in the vadose and phreatic environments, leading to the precipitation of isopachous, blocky and syntaxial cements. Dissolution affected the original pore network within the matrix and localized on preexisting discontinuities such as stylolites, fractures, and bedding surfaces. The resulting karst cavities are classified as vugs, channels and caverns, varying from a few millimeters to hundreds of meters in size. In epigenic karst systems, high porosity percentages are commonly due to moldic, intragrain/intrafossil and intercrystal porosities. The results of our study show how such porosities can be connected to fractures, veins and stylolites at the microscale. Karst dissolution can further increase porosity and the overall rock permeability due to aragonite and calcite cement dissolution during eodiagenesis, microfractures and stylolites dissolution during mesodiagenesis and all cements, fractures and stylolites during telodiagenesis.

Determination of porosity and microstructure studies of wax-based Aluminium metal foam

Aluminium metal foams nowadays are popularly used because of their unique feature of high stiffness concerning low density in the order of 10-15% of the bulk Aluminium material. In this paper, Aluminium metal foam is developed using the powder metallurgy technique. The elements used in the composition are Aluminium metal powder and a foaming agent as a wax powder (3-9%). The porosity is calculated using the Archimedes principle and achieved a good percentage of porosity in the specimen with a blowing agent as wax powder and achieved maximum porosity of 60.41%. The Microstructure study has been done on the prepared specimens to check the uniform distribution of porosity on the entire specimen and to check if any foreign chemical factor is incorporated. It is found that there is no adequate result in the prepared specimen.

Atomoxetine and escitalopram migrate the derangement of the temporomandibular joint morphologic and histologic changes in rats exposed to stress-induced depression.

The purpose of this in vivo study was to determine the effects of stress-induced depression and antidepressants on depressive-like behavior, microstructure, and histomorphology of the temporomandibular joint (TMJ) using rats. Experimentally induced depression in rats was created before being treated with two antidepressants; escitalopram (selective-serotonin-reuptake inhibitors) and atomoxetine (norepinephrine-reuptake inhibitors). Micro-computed tomography (Micro-CT) was performed to measure the change in bone volume and bone porosity of the condyle. Further histological evaluation of the condylar cartilage was performed. Micro-CT scanning revealed a decrease in bone volume in the depression group. The bone porosity percentage significantly increased in both the escitalopram and atomoxetine groups compared with the control group and the depression group. Histopathological analysis showed increased thickness of cartilage layers in the depression group. In the atomoxetine group, there was a significant increase in the pre-hypertrophic and hypertrophic layer thickness and cell count, but a significant decrease in proteoglycans. The present study findings indicated the change in TMJ characteristics, especially on the superficial part of the condylar head in the depression group. Concerning the applicability of the different antidepressants, depression with the treatment of atomoxetine has the most disadvantages due to bone porosity and cartilaginous condyle changes.

The Effect of Prosopis juliflora (Fabaceae) on the Physical and Chemical Properties of Coastal Dune Soil in Western Mexico

Vargas-Lomelín, J.G.; Macías-Rodríguez, M.Á.; Zarazúa-Villaseñor, P.; Rodríguez-Zaragoza, F.A.; Neri-Luna, C., and Albuquerque, F., 2023. The effect of Prosopis juliflora (Fabaceae) on the physical and chemical properties of coastal dune soil in western Mexico. Journal of Coastal Research, 39(1), 63–72. Charlotte (North Carolina), ISSN 0749-0208. Prosopis juliflora (Fabaceae) is a dominant legume and potential ecosystem engineer in the dunes of Jalisco, western Mexico. The objective of the present study was to evaluate how P. juliflora modifies soil physical and chemical properties in three coastal dunes that belong to different watersheds. To determine the physical properties of the three sites, soil samples were taken inside the canopy of five P. juliflora trees and five soil samples were taken outside their canopies. The same trees and soil positions regarding the canopy of P. juliflora were considered to determine the chemical properties, but the samples were taken at two different depths. A multidimensional and permutational analysis of variance (PERMANOVA) was performed to evaluate differences in the physical properties among the sites and between the sampling positions relative to the canopy of P. juliflora. This PERMANOVA also evaluated differences among sites, sample depths, and the positions of the samples relative to the P. juliflora canopy. A test of homogeneity of dispersions was performed to determine the data dispersion type, whereas a similarity percentage analysis identified which variables contributed most to the observed differences. A principal coordinate analysis was performed to visualize the differences in the model. The results demonstrated that P. juliflora modified the soil physical properties, specifically the real density, total porosity percentage, and percentages of silt and clay. The soil physical properties also varied significantly among the three sites. In addition, P. juliflora modified the soil chemical properties, increasing the electrical conductivity, pH, and total nitrogen, iron, and available phosphorus content. The results show significant differences between the two soil depths, as well as among sites. Ultimately, this study contributes to understanding of the implications of soil property modifications by plants in coastal dunes, which will give guidelines for managing and conserving these ecosystems.

Mechanical and Tribological Properties Correlations of Die Cast and Spray Formed Aluminum 2.5wt.% Cu-2.5wt.% Mg - 5wt.% Zn Alloy

Aluminum with –2.5wt.% Cu–2.5wt.% Mg – 5wt.% Zn alloy was synthesized by die cast and spray formed technique. The average density of die cast and spray formed Al alloy was measured by water displacement method. The compression strength, hardness and tribological properties of the Al alloy produced by die cast and spray formed technique was studied as per the ASTM test standards and recorded the average values. The surface morphology of die cast Al alloy depicts the dendritic structures and spray formed Al alloy contains the equiaxed grains, coarse grains and fine grains across the surface. The elemental analysis of both die cast and spray formed Al alloy was measured by using scanning electron microscope. Average percentage of porosity of die cast and spray formed aluminum alloy is 1.79 ± 0.23 and 1.10 ± 0.3 respectively. The hardness of spray formed Al alloy is 10.54 % lesser than that of die cast Al alloy. Average ultimate compression strength of spray formed and die cast Al alloys are 360.07 ± 9.58 MPa and 353.33 ± 5.56 MPa respectively. The study also recorded the wear rate and coefficient of friction of die cast and spray formed Al alloy at different load and speed conditions. The precipitation strengthening mechanism is found to be involved in spray formed alloy.

Preparation of porous PCL-PEG-PCL scaffolds using supercritical carbon dioxide

In this study, the Supercritical Carbon Dioxide (scCO2) gas foaming procedure was used in the preparation of scaffolds containing the model drug dexamethasone (DXMT). The method used did not include an organic solvent thus making it a safe method. The ring-opening polymerization of PCL-PEG-PCL (PCEC) triblock was conducted using an organocatalyst [1,8 diazabicyclo [5.4.0] undec-7-ene (DBU)]. After mixing 5.0 g of DXMT with 50.0 g of PCEC, hydraulic pressure was applied to compress the mixed powder into disc-like tablets. The tablet-like scaffold of the triblock containing DXMT was inserted into a scCO2 gas-foaming device. The peak porosity percentage of the synthesized triblock was found to be 55.58 %. Pressure, temperature, soaking time and the time required to depressurize were recorded as 198 bar, 50 °C, 2.0 h, and 28 min respectively. After treatment with scCO2, the scaffolds experienced an almost full release of DXMT in vitro after 30 days (83.74 ± 1.54 % vs 52.24 ± 2.03 % before scCO2 treatment). In conclusion, the results proved that the scCO2 gas foaming procedure could be employed for constructing modifiable PCEC scaffolds with plausible porosity and structural and morphological features which can manipulate drug release.