Inferior Mechanical Properties Research Articles

CNT and rGO reinforced PMMA based bone cement for fixation of load bearing implants: Mechanical property and biological response

Polymethyl methacrylate (PMMA) bone cements (BCs) have some drawbacks, including limited bioactivity and bone formation, as well as inferior mechanical properties, which may result in failure of the BC. To deal with the mentioned issues, novel bioactive polymethyl methacrylate-hardystonite (PMMA-HT) bone cement (BC) reinforced with 0.25 and 0.5 wt% of carbon nanotube (CNT) and reduced graphene oxide (rGO) was synthesized. In this context, the obtained bone cements were evaluated in terms of their mechanical and biological characteristics. The rGO reinforced bone cement exhibited better mechanical properties to the extent that the addition of 0.5 wt% of rGO where its compressive and tensile strength of bioactive PMMA-HT/rGO cement escalated from 92.07 ± 0.72 MPa, and 40.02 ± 0.71 MPa to 187.48 ± 5.79 MPa and 64.92 ± 0.75 MPa, respectively. Besides, the mechanisms of toughening, apatite formation, and cell interaction in CNT and rGO encapsulated PMMA have been studied. Results showed that the existence of CNT and rGO in BCs led to increase of MG63 osteoblast viability, and proliferation. However, rGO reinforced bone cement was more successful in supporting MG63 cell attachment compared to the CNT counterpart due to its wrinkled surface, which made a suitable substrate for cell adhesion. Based on the results, PMMA-HT/rGO can be a proper bone cement for the fixation of load-bearing implants.

Determination of Mechanical Properties and Physical Characterization of HA-ZnO-$$ {\mathbf{Fe}}_{3} {\mathbf{O}}_{4} $$ Composites for Implant Applications

The high biocompatibility of Hydroxyapatite (HA) makes it one of the most common ceramics used in bio-implants. However, its inferior mechanical properties can be improved through the formation of composites. In the present work, composites are fabricated by adding ZnO and Fe3O4 in HA through compaction and sintering in five different compositions to study their effect on HA. Their structural properties using scanning electron microscopy and x-ray diffraction are studied, while mechanical properties are studied using micro-hardness test and compression test. In experimental results, it was observed that 7.5% ZnO in HA has resulted in improved relative density (~ 99%), increased hardness (6.9 GPa) but with reduced compressive strength (25.6 MPa), hence it can be suitable for hard coatings on bio-implants. 20% porosity was observed in an HA-7.5%ZnO-20% $$ Fe_{3} O_{4} $$ composite with compressive strength (40 MPa) and hardness (4.1 GPa). Among all, this composition showed a maximum balance between mechanical properties and porosity.

Enhancing potential of hydrofracturing in mylonitic coal by biocementation

AbstractMylonite coal is a representative of tectonically deformed coal and is a result of crushing original coal into fine coal grains under strong shear or long‐low tectonic stress. Because of its granular nature and the resultant inferior mechanical property, it is difficult to initiate fluid‐driven fractures within mylonitic coal reservoirs for enhancing coalbed methane recovery. The following explores a biomineralization method of microbially mediated calcium carbonate precipitation (MICP) to enhance the structural integrity and mechanical strength of mylonitic coal, enabling potential success for hydrofracturing. The experimental results indicate that the mechanical properties of mylonite coal are significantly enhanced after a short period of MICP treatment with ten cycles of treatments yielding a maximum uniaxial compressive strength (UCS) of 8.7 MPa and a maximum brittleness index of 0.218 approaching that of the hard coal. The increments in UCS and brittleness of biocemented mylonite coal show a positive correlation with the generated calcium carbonate content. Scanning electron microscopy (SEM) imaging indicates that the generated calcium carbonate precipitates first randomly occur on the particle surfaces, and then occupies the interstitial space until particle‐particle bonds are developed. The irregular morphology of coal particles results in two contact relations between particles, point contact and planar contact, causing a significant difference in biocementation effectiveness. Two microfailure patterns of biocemented coal with uniaxial compression are observed. One is that the coal particles are crushed, and the other occurs at the biocemented interface between the coal particles and calcium carbonate crystals.

Solid wood property variations in early-age Acacia plantation trees grown in southern Vietnam

A high demand for woodchips has encouraged smallholder farmers in Vietnam to invest in short-rotation Acacia plantations to produce pulpwood that has a relatively quick, though often low, income return. Because of an expanding export furniture industry, the Vietnam Government has sought to increase sawlog production and, at the same time, improve returns to smallholder farmers. However, currently the quality and therefore market value of the timber from acacias under differing management strategies has not been well quantified. Acacia auriculiformis, both in its pure form and its hybrid with A. mangium (Acacia hybrid) are grown in plantations in Vietnam to produce merchantable timber, though the inferior mechanical properties of juvenile wood at an early age has impeded access to higher-value product markets. However, with thinning, there may be improvements in wood properties that could enhance sawlog values. This study examined how the wood properties of plantation grown Acacia hybrid change with stand age, explored differences in wood properties between Acacia hybrid and A. auriculiformis following different thinning treatments, and determined which of the two species is the most favourable for solid wood products. The potential to supply logs to produce sliced veneer for the furniture industry was also investigated. Logs from A. hybrid trees aged eight years could be processed to manufacture structural products, and at age five years for manufacturing utility furniture. Acacia auriculiformis thinned to 833 stems per hectare at age 4 years had mechanical wood properties indicating a potential for durable flooring products that can command a high value in the market. Because of dead knots, most sliced veneer samples were not acceptable for face veneer, though visual assessments indicated that with pruning, an attractive high-value product could potentially be produced. Tree species rather than age or thinning treatment had the most influence on wood properties.

Improvements in mechanical properties of aluminium alloy-titanium di boride and boron carbide hybrid composite produced through friction stir processing route

Aluminium alloys finds many applications in automotive, aerospace and ship building industries. Among all series AA 5083 alloys are commonly used in ship building industry but possess inferior mechanical properties which are replaced with aluminium alloy composites due to high strength to weight ratio. The present work is focussed to produce aluminium alloy composites with hybrid reinforcement Particles using friction stir processing route. The different proportions of boron carbide and titanium di boride particles are used as hybrid reinforcement particles. The aluminium alloy composites are fabricated by different proportions of reinforcement particles. The properties of fabricated composites such as ultimate tensile strength, micro Vickers hardness and impact strength are evaluated. The mechanical properties are improved and found that highest values of mechanical properties are obtained for 75% TiB2 + 25% B4C hybrid reinforced composite. The microstructural evaluations of composites are analysed using optical and scanning electron microscopy. It is found that hybrid reinforcement particles are uniformly distributed in the stirring zone without any micro defects.

Physico-Mechanical and Biological Durability of Citric Acid-Bonded Rubberwood Particleboard.

This study investigated the effects of different citric acid content on the physico-mechanical and biological durability of rubberwood particleboard. Particleboards with density of 700 kg/m3 were produced with three different citric acid contents, namely 10, 15 and 20 wt%. Particleboards made from 10 wt% urea formaldehyde (UF) resin were served as control for comparison purposes. FTIR analysis was carried out and the formation of ester linkages between -OH on cellulose and carbonyl groups of citric acid was confirmed. The peak intensity increased along with increasing citric content, which indicated that a higher amount of ester linkages were formed at higher citric acid content. Citric acid-bonded particleboard had inferior physical properties (water absorption and thickness swelling) and mechanical properties (internal bonding strength, modulus of rupture and modulus of elasticity) compared to that of the UF-bonded particleboard. However, the performance of particleboard was enhanced with increasing citric acid content. Meanwhile, citric acid-bonded particleboard displayed significantly better fungal and termite resistance than UF-bonded particleboard owing to the acidic nature of citric acid. It can be concluded that citric acid is a suitable green binder for particleboard but some improvement is needed during the particleboard production process.

Diminishing effects of mechanical loading over time during rat Achilles tendon healing.

Mechanical loading affects tendon healing and recovery. However, our understanding about how physical loading affects recovery of viscoelastic functions, collagen production and tissue organisation is limited. The objective of this study was to investigate how different magnitudes of loading affects biomechanical and collagen properties of healing Achilles tendons over time. Achilles tendon from female Sprague Dawley rats were cut transversely and divided into two groups; normal loading (control) and reduced loading by Botox (unloading). The rats were sacrificed at 1, 2- and 4-weeks post-injury and mechanical testing (creep test and load to failure), small angle x-ray scattering (SAXS) and histological analysis were performed. The effect of unloading was primarily seen at the early time points, with inferior mechanical and collagen properties (SAXS), and reduced histological maturation of the tissue in unloaded compared to loaded tendons. However, by 4 weeks no differences remained. SAXS and histology revealed heterogeneous tissue maturation with more mature tissue at the peripheral region compared to the center of the callus. Thus, mechanical loading advances Achilles tendon biomechanical and collagen properties earlier compared to unloaded tendons, and the spatial variation in tissue maturation and collagen organization across the callus suggests important regional (mechano-) biological activities that require more investigation.

Effect of the viscosity of polyvinyl chloride resin and weaving structures of polyester fabric on the off-axis mechanical properties of PVC coated fabric

PVC coated fabric is a useful structural material mainly used as a roof material because of its lightweight, flexibility. However, the main issues of this PVC coated fabric product is that it is damaged such as tensile failure, peel, and tear when exposed to extreme environments such as strong rain and wind owing to its inferior mechanical properties. Various studies have been reported to improve the mechanical properties of PVC coated fabric, there have been no significant improvement. Therefore, in this study, to improve the mechanical properties of the PVC coated fabrics, applied the low viscosity PVC resin and 4 [Formula: see text] 4 matt weave structure polyester fabric. In addition, the mechanical properties of PVC coated fabrics with various viscosity PVC resins (D10, D8, D5, D2 and D0) were investigated and the mechanical properties of PVC coated fabrics with various weaving structure such as plain weave structure (1 [Formula: see text] 1), matt weave structure (2 [Formula: see text] 2, 3[Formula: see text] 3, and 4 [Formula: see text] 4) were studied. The PVC coated fabric fabricated by low viscosity PVC resin (D10), the tensile strength, tear load, and peel strength improved about 3%, 11%, and 29% compared to the PVC coated fabric fabricated by high viscosity PVC resin (D0). The mechanical properties of the PVC coated fabric fabricated by 4 × 4 matt weave structure polyester fabric was superior to the 1 × 1 plain weave structure polyester fabric and 2 × 2, 3 × 3 matt weave structure polyester fabrics because of the low crimp rate and low intersection point of the warp yarn and weft yarn of the fabric.

Characterization of cellulose nano/microfibril reinforced polypropylene composites processed via solid‐state shear pulverization

AbstractPolypropylene (PP) composites with cellulose nanofibril (CNF), lignocellulose nanofibril (LCNF) or bleached kraft wood pulp (BWKP) cellulose microfibril compatibilized by maleic anhydride grafted polypropylene were produced by different approaches. Samples containing 10–30 wt% filler were prepared by mixing cellulose aqueous suspensions and PP through solid‐state shear pulverization. The flakes obtained were compounded by twin‐screw melt extrusion (MSE) followed by injection molding (IM) into standard specimens. Reference samples with 30 wt% CNF or LCNF were prepared through a standard procedure, which involved freeze‐drying of nanofibrils aqueous suspensions before MSE and IM, whereas a sample with 30 wt% BWKP was prepared directly by MSE and IM. Injection‐molded specimens were characterized by scanning electron microscopy, differential scanning calorimetry, thermogravimetry, and tensile and notched impact tests. The thermal behavior of the PP matrix in the composites was not significantly affected by the filler type and content and processing route as well. CNF and LCNF reinforced PP composites showed inferior mechanical properties, due to the formation of nanofibrils agglomerates in the PP matrix, regardless of the processing route adopted. Highly filled (30 wt%) BWKP composites presented superior mechanical properties with significant increase in the modulus, tensile strength, and impact strength due to the formation of well‐dispersed microfibrils bundles in the PP matrix. A comparative analysis showed that the composites developed in this study present similar or even superior mechanical performance for given filler content to other natural fiber reinforced PP composites reported in the literature.

Effect of Zinc Addition on Electrodeposition of Fe-W Alloys

Tungsten (W) and its alloys have been applied to various industrial fields for its excellent mechanical, tribological and chemical properties. Electrodeposition process is anticipated to be a economical and cost-effective method for preparing W-based alloys since W has the highest melting point among metals (3422 ℃). In general, electrodeposition of metal W from aqueous solution is difficult because it exists as oxyanions in a wide pH range. However, electrodeposition in the co-existence of iron group metals such as iron (Fe), nickel (Ni), and cobalt (Co), enables W to be reduced to metal state, which is so called the induced co-deposition. Recently, electrodeposited W alloys have gained increased attention due to their advanced properties such as high microhardness, thermal stability, wear resistance and corrosion resistance. Among them, binary Fe-W, Ni-W alloys have been most intensively studied. These alloys are expected to be promising substitute for hard chrome (Cr) plating due to its high hardness, abrasion resistance, heat resistance and corrosion resistance without the use of hazardous hexavalent chromium (Cr6+). Meanwhile, Ni has been reported as the one of the major elements in triggering skin allergies for humans. Therefore, we focused on Fe-W-based alloys that do not use Ni. Unfortunately, Fe-W alloys are reported to have inferior mechanical properties and corrosion resistance compared to Ni-W alloys. Thus, the addition of Zinc (Zn); an element that is widely used in anti-corrosion coatings, as a third element to the Fe-W binary alloy was considered for preparation of a ternary alloy with improved properties.This study reports the first experimental results of electrodeposition of ternary Fe-W-Zn alloy by incorporation of Zn to Fe-W alloys. Ternary Fe-W-Zn plating was prepared in citrate-ammonia aqueous solution heated to 80℃ by potentiostatic elcecrolysis range from -1.1 to -1.4V (vs. Ag/AgCl). Ternary alloys with the compositions of Fe-(28.8 to 37.1 at.%) W-(1.7 to 6.5 at.%) Zn were obtained with maximum current efficiency of 42%. The corrosion properties of the prepared ternary alloys were compared with those of Ni-W and Fe-W platings by a potentiodynamic polarization test in deaerated 1M sulfuric acid solution and 3 mass% sodium chloride solution. Although Zn has lower potential than Fe, ternary Fe-W-Zn alloys with relatively low Zn contents of 1.7 to 2.6 at.% showed better anti-corrosion properties than Ni-20 at.%W and Fe-33 at.%W alloys in acidic media. Addition of a small amount of Zn was found to be effective in tuning properties of Fe-W alloys. Acknowledgement This work was partially supported by the JST-OPERA Program, Japan [grant number JPMJOP1843]

Ductility Evaluation of Damaged Recycled Aggregate Concrete Columns Repaired With Carbon Fiber-Reinforced Polymer and Large Rupture Strain FRP

The inherent defects of recycled aggregate concrete (RAC) include the complex interfacial transition zone (ITZ) and the many micro-cracks that appear during its producing process, which result in some inferior mechanical properties compared with natural aggregate concrete (NAC). This drawback usually prevents RAC from being selected for structural purposes. Existing research has shown that the strength and ductility of damaged concrete in compression members can be significantly enhanced through external confinement using fiber-reinforced polymer (FRP) wraps. This application has been widely used in concrete structural repair and retrofitting technology. However, research on the effects of RAC damage coupled with different load damage conditions is rare, as is information on the mechanical properties of RAC reinforced with FRP jackets. This paper presents the results of an experimental study on the behavior of pre-damaged recycled aggregate concrete cylinders that were repaired with carbon fiber-reinforced polymer (CFRP) or large rupture strain (LRS)-FRP jackets. Tests were conducted on 58 concrete cylinders with variations in the replacement ratio, damage levels, and FRP properties. Test results demonstrated that the ultimate strain and strength of damaged recycled aggregate concrete could be significantly enhanced by FRP jackets and that aggregate quality plays a vital role in the strength of confined concrete. Also, the energy absorption of CFRP- and LRS-FRP-confined RAC were evaluated. The analysis indicated that, compared with CFRP-confined RAC, LRS-FRP can greatly improve the energy absorption capacity of RAC; thus, LRS-FRP confined concrete has a good potential to achieve a ductile design for concrete columns, especially when used in seismic reinforcement.

Tooth ultrastructure of a novel COL1A2 mutation expanding its genotypic and phenotypic spectra.

To investigate tooth ultrastructure and mutation of two patients in a family affected with osteogenesis imperfecta (OI) type IV and dentinogenesis imperfecta (DGI). Mutations were detected by whole exome and Sanger sequencing. The permanent second molar obtained from the proband (DGI1) and the primary first molar from his affected son (DGI2) were studied for their color, roughness, mineral density, hardness, elastic modulus, mineral content, and ultrastructure, compared to the controls. Two novel missense COL1A2 variants, c.752C>T (p.Ser251Phe) and c.758G>T (p.Gly253Val), were identified in both patients. The c.758G>T was predicted to be the causative mutation. Pulp cavities of DGI1 (permanent teeth) were obliterated while those of DGI2 (primary teeth) were wide. The patients' teeth had darker and redder colors; reduced dentin hardness; decreased, disorganized, and scattered dentinal tubules and collagen fibers; and irregular dentinoenamel junction (DEJ), compared to controls. Lacunae-like structures were present in DGI2. We reported the novel causative mutation, c.758G>T (p.Gly253Val), in COL1A2 for OI type IV and DGI. The DGI dentin demonstrated inferior mechanical property and ultrastructure, suggesting severe disturbances of dentin formation. These could contribute to fragility and prone to infection of DGI teeth. This study expands phenotypic and genotypic spectra of COL1A2 mutations.

Failure Mechanisms and Mitigation Measures of the G1006 Electricity Pylon Landslide in the Dam Area of the Jinping I Hydropower Station

On the 29th and 30th of August 2012, more than 100 geological disasters occurred near the dam area of Jinping I Hydropower Station, Xichang, China due to local intense rainstorm. The upper part of the left valley slope, which is 500 m upstream of the dam, failed and slid, exposing the C-pile of the G1006 electricity pylon and threatening the entire power transmission lines. Therefore, ensuring the stability of the residual rock masses in the rear of the main scarp and the safety of the G1006 electricity pylon became a primary emergency task. Field geological survey, topographic mapping, and the instability mechanism study of the G1006 electricity pylon landslide were conducted. Results revealed that the G1006 electricity pylon landslide (here after represented as the G1006 EPL) occurred in the middle block cut by two faults, and the rock masses had inferior mechanical properties. Intense unloading effects and frequent microseism events during the dam construction relaxed the rock mass structural planes and reduced the geotechnical parameters. Under the influence of intense rainfall, the failure mechanisms of the slope were a combination of slope surface effect from rainfall and lateral erosion and undercutting of the slope toe by high flooding. The residual rock masses and landslide deposits around the pylon foundation were unstable under natural conditions and during the rainstorm. To prevent the continuous damage and exposure of C-pile foundation and ensure the stability of pylon foundation, the mitigation measure of “retaining piles + platform + retaining wall” was arranged. Moreover, a check dam was added to stabilize the slope toe and prevent the landslide deposits, which are the starting material source of debris flow that threatens the safety of the arch dam.

Effect on Physical and Mechanical Properties of Conventional Glass Ionomer Luting Cements by Incorporation of All-Ceramic Additives: An In Vitro Study.

Introduction Glass ionomer cements (GICs) are commonly used for cementation of indirect restorations. However, one of their main drawbacks is their inferior mechanical properties. Aim Compositional modification of conventional glass ionomer luting cements by incorporating two types of all-ceramic powders in varying concentrations and evaluation of their film thickness, setting time, and strength. Material & Methods. Experimental GICs were prepared by adding different concentrations of two all-ceramic powders (5%, 10, and 15% by weight) to the powder of the glass ionomer luting cements, and their setting time, film thickness, and compressive strength were determined. The Differential Scanning Calorimetry analysis was done to evaluate the kinetics of the setting reaction of the samples. The average particle size of the all-ceramic and glass ionomer powders was determined with the help of a particle size analyzer. Results A significant increase in strength was observed in experimental GICs containing 10% all-ceramic powders. The experimental GICs with 5% all-ceramic powders showed no improvement in strength, whereas those containing 15% all-ceramic powders exhibited a marked decrease in strength. Setting time of all experimental GICs progressively increased with increasing concentration of all-ceramic powders. Film thickness of all experimental GICs was much higher than the recommended value for clinical application. Conclusion 10% concentration of the two all-ceramic powders can be regarded as the optimal concentration for enhancing the glass ionomer luting cements' strength. There was a significant increase in the setting time at this concentration, but it was within the limit specified by ISO 9917–1:2007 specifications for powder/liquid acid-base dental cements. Reducing the particle size of the all-ceramic powders may help in decreasing the film thickness, which is an essential parameter for the clinical performance of any luting cement.

Characterization of a Bioresorbable Magnesium-Reinforced PLA-Integrated GTR/GBR Membrane as Dental Applications.

Inferior mechanical properties have always been a limitation of the bioresorbable membranes in GBR/GTR. This study is aimed at fabricating a bioresorbable magnesium-reinforced polylactic acid- (PLA-) integrated membrane and investigating its mechanical properties, degradation rate, and biocompatibility. The uncoated and fluoride-coated magnesium alloys, AZ91, were made into strips. Then, magnesium-reinforced PLA-integrated membrane was made through integration. PLA strips were used in the control group instead of magnesium strips. Specimens were cut into rectangular shape and immersed in Hank's Balanced Salt Solution (HBSS) at 37°C for 4, 8, and 12 d. The weight loss of the AZ91 strips was measured. Three-point bending tests were conducted before and after the immersion to determine the maximum load on specimens. Potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were conducted on coated and uncoated AZ91 plates to examine corrosion resistance. Murine fibroblast and osteoblast cells were cultured on circular specimens and titanium disks for 1, 3, and 5 d. Thereafter, WST test was performed to examine cell proliferation. As a result, the coated and uncoated groups showed higher maximum loads than the control group at all time points. The weight loss of AZ91 strips used in the coated group was lower than that in the uncoated group. PDP, EIS, SEM, and EDS showed that the coated AZ91 had a better corrosion resistance than the uncoated AZ91. The cell proliferation test showed that the addition of AZ91 did not have an adverse effect on osteoblast cells. Conclusively, the magnesium-reinforced PLA-integrated membrane has excellent load capacity, corrosion resistance, cell affinity, and proper degradation rate. Moreover, it has great potential as a bioresorbable membrane in the GBR/GTR application.

Microstructural and mechanical properties of dissimilar nitinol and stainless steel wire joints produced by micro electron beam welding without filler material

Nitinol is a shape memory and superelastic alloy, respectively, and stainless steels are widely used materials in medical engineering, e.g., for implants and medical instruments. However, due to its high price and poor machinability, there is a high demand for dissimilar welding of nitinol components to stainless steel. During welding of titanium-containing alloys, like nitinol, to ferrous metals like stainless steel, intermetallic phases between titanium and iron may form. These phases are brittle and lead to rapid crack formation and/or inferior mechanical properties of the joint. In this study, superelastic nitinol wires are butt-welded with stainless steel wires by means of micro electron beam welding, providing good quality weld seams. Due to a very accurate beam alignment and fast beam deflection, the composition and the level of dilution in the weld metal can be precisely controlled, resulting in a significant reduction of fraction of intermetallic phases. The experiments show that it is possible to produce sound welds without the presence of any cracks on the surface as well as in the cross sections.

Behavior of FRP-Confined Recycled Brick Aggregate Concrete under Monotonic Compression

Brick waste is the second-largest source of China's construction and demolition waste. Reprocessing brick waste into recycled brick aggregate (RBA) to fabricate new concrete [i.e., recycled brick aggregate concrete (RBAC)] has proved to be an effective solution. RBAC is generally used as nonstructural concrete owing to its inferior mechanical and durability properties compared with natural aggregate concrete (NAC). To achieve substantially enhanced properties that would qualify RBAC for potential structural use, fiber-reinforced polymer (FRP) jacketing will be adopted in this study to provide confinement and corrosion resistance to the concrete core. A total of 60 standard cylinder specimens will be tested under monotonic axial compression with the replacement ratio of RBA (0%, 15%, 30%, 60%, and 100%) and the FRP jacket stiffness (0, 1, 2, and 3 plies) as variables. The test results will be analyzed and compared with existing strength and stress–strain models, and based on this it is concluded that although the compressive behavior of FRP-confined RBAC is similar to that of FRP-confined NAC, in general, a high RBA content tends to reduce the effectiveness of FRP confinement.

Termite Resistance of Furfuryl Alcohol and Imidacloprid Treated Fast-Growing Tropical Wood Species as Function of Field Test

In general fast-growing tree species harvested at a young age has substantial amount of sapwood. It also contains juvenile wood, which has undesirable inferior physical and mechanical properties. Having sapwood and juvenile wood in the trees makes them very susceptible to be attacked by biological deterioration specifically termites in a tropical environment. The main objective of this study was to investigate the termite resistance of four fast-growing Indonesian wood species treated with furfuryl alcohol and imidacloprid. Wood specimens from sengon (Falcataria moluccana), jabon (Anthocephalus cadamba), mangium (Acacia mangium), and pine (Pinus merkusii) were impregnated with furfuryl alcohol, using tartaric acid and heat as well as treated with imidacloprid for the polymerization process. All of the specimens were exposed to environmental conditions in the field for three months. Based on the findings in this work, the untreated control samples had higher weight loss values and lower protection levels than those of imidacloprid-treated and furfurylated samples of all four species. It appears that furfurylation and imidacloprid treatment of such fast-growing species had a significant impact regarding their resistance against termite so that their service life can be extended during their utilization.

Bioresorbable magnesium-reinforced PLA membrane for guided bone/tissue regeneration

Considering the inferior mechanical properties of the current bioresorbable polymers, a novel bioresorbable magnesium-reinforced polylactide (PLA) membrane was designed for the application in critical defect sites in guided bone/tissue regeneration. The PLA-FAZ91 membrane was fabricated by combining two PLA membranes with a fluoride-coated AZ91 (9 wt% Al, 1 wt% Zn) (FAZ91) magnesium alloy core by hot pressing. A combined double-layered PLA membrane was used as the control group. A three-point bending test was performed to compare their maximum load and stiffness. Samples were immersed in the HBSS for 20 weeks, and their weight loss percentages were recorded, and a three-point bending test was performed after immersion. An ion release test was performed by immersing samples in the HBSS for 4 weeks and determining the pH and ion concentrations of the HBSS. Cell viability was tested by culturing pre-osteoblast cells with sample extracts in the culture medium obtained from degraded samples. As a result, PLA-FAZ91 showed a significantly higher maximum load and stiffness than those of the non-reinforced PLA membrane. The weight loss of PLA-FAZ91 was much faster, as FAZ91 showed major degradation and was completely degraded after 16–20 weeks of immersion. The degradation of the PLA wrap was accelerated by FAZ91. The mechanical superiority of PLA-FAZ91 over PLA endured for at least 3 weeks during immersion. The pH, magnesium- and fluoride-ion concentration in the PLA-FAZ91 group increased at an appropriate rate. The cell viability was not adversely affected by the addition of FAZ91 to PLA. Therefore, the bioresorbable magnesium-reinforced PLA membrane has the potential to be used as a good alternative to pure PLA membrane in guided bone/tissue regeneration.

Alloying criteria and investigations on the properties of novel AM series alloy fabricated using stir casting

Abstract Magnesium alloys are being used in different sectors for several applications. The low density and high strength to weight ratio have made them indispensable. However, it is observed that Mg alloys are less preferred for the fabrication of critical and complex parts. The inferior mechanical and corrosive properties, along with high inflammability, limit their usage for several applications. The mechanical and physical properties can be enhanced by varying the weight percentage of alloying elements along with an appropriate process for its development. The paper discusses an approach for selection of the alloying elements and their weight percentage with the help of phase diagrams, vital inputs from past literature and properties of commercially available Mg alloys. The developed AM series alloy (Mg-7 wt%Al-0.9 wt%Mn) has shown improvement in the mechanical properties vis-a-vis the existing AM series alloys. The elastic modulus and hardness were observed 24.3% and 16.21% higher than the maximum values of existing AM alloys. For the development of alloy, a systemized stir casting setup was used, which ensured uniform mixing of alloying elements and essentially played an active role in enhancing the mechanical properties.