A novel fabrication method of copper–reduced graphene oxide composites with highly aligned reduced graphene oxide and highly anisotropic thermal conductivity

Recently, metals with graphene and graphene oxide have been extensively used to enhance the mechanical and anisotropic thermal properties of composites. A novel facile fabrication approach of layer by layer self-assembly followed by hot press sintering was adopted to make copper–reduced graphene oxide composites. The microstructure and heat dissipation properties of pure copper and copper–reduced graphene oxide composites were analyzed with the help of SEM and continuous laser machine analysis. Thermal diffusivity of pure copper and copper–reduced graphene oxide composites was examined in different directions to measure the anisotropic thermal properties by using different volumetric percentages of reduced graphene oxide in the composites. Extraordinarily high anisotropic thermal conductivity of the copper–reduced graphene oxide composites was obtained at a very low concentration of 0.8 vol% reduced graphene oxide, with the difference between the thermal conductivity in-plane and through-plane being a factor of 8.82. Laser test results confirmed the highly anisotropic behavior of our copper–reduced graphene oxide composite with the remarkable property of heat dissipation. The three point bending test was also performed to check the flexural strength of the composites. At 0.6 vol% rGO, the flexural strength was noted (∼127 MPa), and it is 22% higher than that of pure sintered Cu. The high value of anisotropic thermal conductivity and higher flexural strength exhibited by the copper–reduced graphene oxide composite produced using a simple two-step fabrication method give us new hope to use these materials as heat sinks in thermal packaging systems.

Highly aligned rGO with anisotropic thermal conductivity was obtained in this work.     

Micro-mechanical properties of a novel silicon nitride fiber reinforced silicon carbide matrix composite via in situ nano-indentation method

A novel Si₃N₄ fiber reinforced SiC matrix composite has been prepared and the micro-mechanical properties of the composites in situ have been explored. For the Si₃N₄ fibers, the micro-mechanical properties in situ remained almost unchanged with the increasing fabrication temperatures. In comparison, for the PCS derived SiC matrix, higher fabrication temperature could trigger more β-SiC formations, which led to enlarging the corresponding micro-mechanical properties. The microstructure analysis of the interfacial zones in the composites revealed strong interfacial reactions existing in the composites fabricated at ≥800 °C. Therefore, the interfacial shear strength of the composite was significantly increased from ∼420 MPa to ∼535 MPa with the fabrication temperature increasing from 800 °C to 1200 °C, thus impeding the toughening mechanisms of the composites. After introducing BN interphase, the interfacial shear strength was significantly reduced to ∼140 MPa and the flexural strength was increased from ∼140 MPa to ∼250 MPa. The work highlights the efficiency of introducing BN interphase to weaken the interfacial interaction, thus to enhance the macro-mechanical properties.

A novel Si₃N₄ fiber reinforced SiC matrix composite has been prepared and the micro-mechanical properties of the composites in situ have been explored.     

Fabrication of tough,anisotropic, chemical-crosslinker-free poly(vinyl alcohol) nanofibrous cryogels via electrospinning

PVA hydrogels with anisotropic structures have many biomedical applications; however, the hydrophilicity of PVA nanofibers degrades their mechanical properties, and the residual unreacted chemical crosslinkers are disadvantageous for medical use. Therefore, maintaining the stability of aqueous solutions without using crosslinkers is essential while synthesizing electrospun anisotropic PVA nanofibers. Herein, we developed a novel fabrication method for synthesizing tough, anisotropic, and chemical-crosslinker-free nanofibrous cryogels composed of poly(vinyl alcohol) (PVA) and glycerol (Gly) via electrospinning in conjunction with freeze–thawing treatment. Wide-angle X-ray diffraction, attenuated total reflection Fourier-transform infrared spectroscopy, and differential scanning calorimetry analysis revealed an enhanced crystallinity of the PVA and hydrogen bonds in the PVA/Gly nanofibers after freeze–thawing, thereby leading to improved stability of the PVA/Gly nanofiber in water. The scanning electron microscopy observation and tensile tests revealed that the addition of Gly improved both the orientation and the mechanical properties. The values of the toughness parallel and vertical to the fiber axis direction were 4.20 ± 0.63 MPa and 2.17 ± 0.27 MPa, respectively, thus revealing the anisotropy of this mechanical property. The PVA/Gly nanofibrous cryogel consisted of physically crosslinked biocompatible materials featuring toughness and mechanical anisotropy, which are favorable for medical applications including tissue engineering.

Fabrication of tough, anisotropic, and chemical crosslinker-free nanofibrous cryogels made from poly(vinyl alcohol) and glycerol via electrospinning in conjunction with freeze-thawing treatment which would be favorable for medical applications.     

Tunnable rectifying performance of in-plane metal–semiconductor junctions based on passivated zigzag phosphorene nanoribbons

Using first principles density functional theory, we perform a systematic study of the band structures of passivated zigzag phosphorene nanoribbons (ZPNRs) and the transport properties of in-plane metal–semiconductor junctions. It is found that the ZPNR passivated by H, Cl or F atoms is a semiconductor, and the ZPNR passivated by C, O or S atoms is a metal. Therefore, ZPNRs with different passivated atoms can be fabricated into an in-plane metal–semiconductor junction. The calculated current–voltage characteristics indicate that these in-plane metal–semiconductor junctions can exhibit excellent rectification behavior. More importantly, we find that the type of passivated atom plays a very important role in the rectification ratio of this in-plane metal–semiconductor junction. The findings are very useful for the further design of functional nanodevices based on ZPNRs.

Using first principles density functional theory, we perform a systematic study of the band structures of passivated zigzag phosphorene nanoribbons (ZPNRs) and the transport properties of in-plane metal–semiconductor junctions.     

A study of bioactive glass–ceramic's mechanical properties,apatite formation,and medical applications

Apparently, bioactive glass–ceramics are made by doing a number of steps, such as creating a microstructure from dispersed crystals within the residual glass, which provides high bending strength, and apatite crystallizes on surfaces of glass–ceramics when calcium ions are present in the blood. Apatite crystals grow on the glass and ceramic surfaces due to the hydrated silica. These materials are biocompatible with living bone in a matter of weeks, don''t weaken mechanically or histologically, and exhibit good osteointegration as well as mechanical properties that are therapeutically relevant, such as fracture toughness and flexural strength. As part of this study, we examined mechanical properties, process mechanisms involved in apatite formation, and potential applications for bioactive glass–ceramic in orthopedic surgery, including load-bearing devices.

Bioactive glass–ceramics are made by several steps, such as creating a microstructure from dispersed crystals within the residual glass, which provides high bending strength, and apatite crystallizes on surfaces of glass–ceramics with calcium ions.     

Feasibility of polyethylene composites reinforced by distillers dried fibers with solubles (DDFS) after different generations of ethanol fermentation

In order to effectively evaluate the distillers dried fibers with solubles (DDFS) obtained from biorefinery processes, sorghum distiller (SD), cassava distiller (CD) and corn cob distiller (CCD) residuals from different generation bioethanol plants were used as the reinforcing phase for polyethylene composites. The mechanical performances and the physical properties of the polyethylene/DDFS composites were evaluated. The results showed that the CCD reinforced specimen offered the best mechanical performances, with a flexural strength of 21.8 ± 2.2 MPa and a tensile strength of 39.7 ± 3.2 MPa. After multigelation, the retention ratios of the rupture modulus and the elasticity modulus of the CCD reinforced specimen reached 88.7 ± 6.7% and 84.1 ± 2.7%, while after 2000 h of xenon lamp weathering they reached 96.2 ± 4.7% and 82 ± 1.8%, respectively. Hybridizing the biorefinery process with the process of composites production was feasible.

Flowchart of the process for prepares polyethylene/DDFS composites. Solid residuals after 1 G, 1.5 G and 2 G SSF bioethanol plants were used as the reinforcement.     

Enhanced skin adhesive property of electrospun α-cyclodextrin/nonanyl group-modified poly(vinyl alcohol) inclusion complex fiber sheet

Many medical tapes on the market lack sufficient adhesive strength and breathability. Owing to its high biocompatibility, poly(vinyl alcohol) (PVA), a synthetic polymer, has attracted attention in the medical field. In this study, we aimed to prepare an inclusion complex fiber (ICFiber) using α-cyclodextrin (α-CD) and nonanyl-group-modified PVA (C9–PVA) for skin adhesion with improved performance. By changing the concentration of α-CD, six microfiber sheets were fabricated by electrospinning the α-CD/2.3C9–PVA inclusion complex solutions. The bonding strength and energy of the ICFiber sheets on the porcine skin were evaluated. Among the tested ICFiber sheets, the ICFiber-3 (molar ratio of α-CD/C9 groups was 0.612) sheet showed high tensile strength and break strain. The bonding strength and energy of ICFiber-3 sheet on porcine skin were 1.10 ± 0.11 N and 5.07 ± 0.94 J m⁻², respectively, in the presence of water. In addition, ICFiber-3 sheet showed a better water vapor transmission rate (0.95 ± 0.02 mL per day) than commercial tapes. These results demonstrate that the α-CD/2.3C9–PVA ICFiber sheet is a promising adhesive for wearable medical devices.

Inclusion complex fiber (ICFiber) sheets composed of α-cyclodextrin (α-CD) and nonanyl-group-modified poly(vinyl alcohol) (PVA) (C9–PVA) were developed for breathable skin adhesive.     

Biomechanical evaluation of the reconstruction of the calcar femorale in femoral neck fractures: a comparative finite element analysis

ObjectiveFemoral neck fractures are common. We evaluated the biomechanical performance of an internal fixation method based on traditional three cannulated screws (3CS) inserted from below the fracture in the direction of the calcar femorale in the treatment of Pauwels III femoral neck fracture.MethodsWe constructed and evaluated a three-dimensional model of a Pauwels III femoral neck fracture with four models of internal fixation (3CS, and 150°, 155°, and 160° nailing angles) for reconstruction of the calcar femorale, by finite element analysis (FEA).ResultsThe peak stress values at the fracture ends in the 3CS, 150°, 155°, and 160° nailing angle models were 30.052 MPa, 33.382 MPa, 34.012 MPa, and 29.858 MPa; peak stress values for internal fixed stress were 315.121 MPa, 228.819 MPa, 198.173 MPa, and 208.798 MPa; and the maximum displacement of the femoral head was 13.190 mm, 13.183 mm, 12.443 mm, and 12.896 mm, respectively.ConclusionFEA showed that the new nailing methods and the 160° nailing angle for reconstruction of the calcar femorale showed better performance in resisting shearing force for Pauwels III femoral neck fracture, with better mechanical properties, than those with the other three models. These findings can provide a clinical reference.     

Heat treatment effect on the mechanical properties,roughness and bone ingrowth capacity of 3D printing porous titanium alloy

The weak mechanical strength and biological inertia of Ti–6Al–4V porous titanium alloy limit its clinical application in the field of orthopedics. The present study investigated the influence of different solution temperatures (e.g. 800 °C, 950 °C and 1000 °C) on the mechanical properties, roughness and bone ingrowth capacity of Ti–6Al–4V porous titanium alloy prepared by Electron Beam Melting. It was found that the compressive and shear strength were promoted with the increase of solution temperature because of the transformed crystallinity of Ti–6Al–4V titanium alloy and phase changes from TiAl to TiAl + TiV. In addition, the topological morphology, surface roughness and wettability of the porous titanium alloy scaffolds were improved after heat treatment, and in turn, the adhesion rate and cell proliferation of bone marrow mesenchymal stem cells were enhanced. Compared with the scaffolds before and after heat treatment at 800 °C, the scaffolds heat-treated at 950 °C and 1000 °C achieved better bone ingrowth, extracellular matrix deposition and osseointegration. These findings indicate the great potential of heat treatment in possessing Ti–6Al–4V porous titanium alloy for orthopedic implant.

The weak mechanical strength and biological inertia of Ti–6Al–4V porous titanium alloy limit its clinical application in the field of orthopedics.     

Reaction mechanism,cure behavior and properties of a multifunctional epoxy resin,TGDDM, with latent curing agent dicyandiamide

A novel resin system was prepared using the glycidyl amide type multifunctional epoxy resin N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) and latent curing agent dicyandiamide (DICY). The curing reaction mechanism of the TGDDM/DICY system was studied by Fourier transform infrared (FTIR) spectrometry and the non-isothermal cure behaviors of the mixture were investigated with differential scanning calorimetry (DSC) measurements. The FTIR results demonstrated that there were two main reactions occurring in the curing process of the TGDDM/DICY system. The DSC thermogram of the blend exhibited two different cure regimes in the temperature range of 140–358 °C, and the system experienced two autocatalytic curing processes with α = 0.45 as the boundary; the corresponding average activation energies calculated by the Kissinger method were 69.7 and 88.7 kJ mol⁻¹, respectively. In addition, the correlation between activation energy E_a and fractional conversion α was determined by applying model-free isoconversional analysis with Flynn–Wall–Ozawa (FWO) and Starink methods. Results showed that both methods revealed similar trends and possessed approximately the same values at each fractional conversion. Activation energy varied greatly with fractional conversion and the possible causes behind the variations were analyzed in detail. The cured TGDDM/DICY exhibited outstanding mechanical and adhesive properties with tensile and shear strengths of 27.1 MPa at 25 °C and12.6 MPa at 200 °C, good dielectric properties with a low dielectric constant of 3.26 at 1000 kHz and a low water absorption of 0.41%.

The curing mechanism of the TGDDM/DICY system consisted of two main reactions and it experienced two autocatalytic curing processes.     

Carbonisation temperature dependence of electrochemical activity of nitrogen-doped carbon fibres from electrospinning as air-cathodes for aqueous-alkaline metal–air batteries

Poly-acrylonitrile (PAN)-derived carbon fibres were characterised as air electrode frameworks for aqueous-alkaline metal–air batteries, focussing on the influence of the carbonisation temperature on the structure and electrochemical properties. Elemental composition, (atomic) structure, electrical conductivity, and electrochemical performance related to the oxygen reduction were investigated for electrodes carbonised in the range from 300 °C to 1400 °C. Chemical and structural properties were analysed using elemental analysis, XPS, SEM, and Raman spectroscopy; electrical conductivities of the fibre networks were examined by four-point probe measurements. Electrochemical properties were evaluated using linear sweep voltammetry in 6 M KOH by the open circuit potentials, the cathodic current densities at given overpotentials, and required overpotentials at given current densities. The highest current density was obtained from fibres carbonised at 850 °C. The connection between the fibre characteristics and electrochemical properties are discussed, highlighting the importance of the nitrogen bonding state. The results provide a base for thedevelopment of high performance air electrodes.

Nitrogen-doped carbon fibres derived from electrospun poly-acrylonitrile display an optimum catalytic activity towards the oxygen reduction reaction in aqueous-alkaline metal–air batteries, when carbonised under argon at 850 °C.     

High strength composites from low-value animal coproducts and industrial waste sulfur

Herein we report high strength composites prepared by reaction of sulfur, plant oils (either canola oil or sunflower oil) and brown grease. Brown grease is a high-volume, low value animal fat rendering coproduct that represents one of the most underutilized products of agricultural animal processing. Chemically, brown grease is primarily comprised of triglycerides and fatty acids. The inverse vulcanization of the unsaturated units in triglycerides/fatty acids upon their reaction with sulfur yields CanBG_x or SunBG_x (x = wt% sulfur, varied from 85–90%). These composites were characterized by infrared spectroscopy, dynamic mechanical analysis (DMA), mechanical test stand analysis, elemental analysis, and powder X-ray diffraction. CanBG_x and SunBG_x composites exhibit impressive compressive strengths (28.7–35.9 MPa) when compared to other materials such as Portland cement, for which a compressive strength of ≥17 MPa is required for residential building. Stress–strain analysis revealed high flexural strengths of 6.5–8.5 MPa for CanBG_x and SunBG_x composites as well, again exceeding the range of ∼2–5 MPa for ordinary Portland cements. The thermal properties of the composites were assessed by thermogravimetric analysis, revealing decomposition temperatures ranging from 223–226 °C, and by differential scanning calorimetry. These composites represent a promising new application for low value animal coproducts having limited value to be used as organic crosslinkers in the atom-efficient inverse vulcanization process to yield high sulfur-content materials that have impressive mechanical properties.

Herein we report high strength composites prepared by reaction of sulfur, plant oils (either canola oil or sunflower oil) and brown grease.     

Preparation and characterization of a nanolignin phenol formaldehyde resin by replacing phenol partially with lignin nanoparticles

A new strategy for the preparation of a lignin phenol formaldehyde (LPF) resin has been developed. Nanolignin with high specific surface area and porous structure with an average particle size of about 300 nm was prepared, used as the raw material to substitute phenol partially, and combined with formaldehyde to produce a wood adhesive. The results show that the artificial board prepared with a nanolignin phenol formaldehyde (NLPF) resin with nanolignin substitution degree of 40% wt for phenol could give a dry bond strength of 1.30 ± 0.08 MPa, which is 1.85 times that of the Chinese national grade 1 plywood standard (0.7 MPa) and whose formaldehyde emission of 0.40 mg L⁻¹ meets the standard of GB/T 14732-2006 (E₀, 0.5 mg L⁻¹). TG and DSC analyses show that the replacement of phenol by nanolignin could improve the thermal stability and decrease the curing temperature of the prepared lignin-based resin, with the residual ratio of 40% NLPF being 45% wt at 800 °C and the curing exothermic peak being 145.4 °C, which are much better than that of the 40% LPF resin with the residual ratio being 40% wt and the exothermic peak being 186 °C, respectively. The present study provides a new thought for preparation of LPF resins.

A new strategy for the preparation of a lignin phenol formaldehyde (LPF) resin.     

Microstructure and properties of SiC ceramic brazed with Zr–Cu composite filler metal

The microstructure and properties of SiC ceramic brazed with Zr–Cu composite filler metal were investigated. Combined with the brazing experiment, the microstructure of the interface reaction layer and the brazed SiC ceramic joint was analyzed, and the shear strength was used to evaluate the mechanical properties of the joint. The results show that both Zr–Cu + SiC_p and Zr–Cu + Mo composite filler metals can braze SiC ceramic, and the products of the interface reaction layer are mainly ZrC and Zr₂Si. The addition of SiC_p and Mo to Zr–Cu-based composite filler metal improves the nuclear properties of the composite filler metal and its joint, reduces the coefficient of thermal expansion of the composite filler metal and SiC ceramic joint, and improves the mechanical properties of the joint. The shear properties of the joint increase with the increase of the content of SiCp and Mo in the Zr–Cu composite filler metals. The shear strength of the joint reaches the maximum (82 MPa) when the content of SiC particles is 10 vol% of the Zr–Cu + SiCp composite filler metal, and the average value of the shear strength reaches the maximum of 74 MPa when the content of Mo is 6 vol% of the Zr–Cu + Mo composite filler metal.

The microstructure and properties of SiC ceramic brazed with Zr–Cu composite filler metal were investigated.     

Structures and impact strength variation of chemically crosslinked high-density polyethylene: effect of crosslinking density

Impact strength of high-density polyethylene (HDPE), especially at low temperature, is crucial for its applications outdoors because of its poor impact strength. In order to improve the impact strength of HDPE, crosslinked HDPE was prepared by the addition of a peroxide crosslink agent, bis(tert-butyldioxyisopropyl)benzenehexane, and the effect of the crosslinking density on the microstructures and mechanical properties, especially impact strength between −60 °C and 23 °C, were investigated. The results show that the crosslinking density is controlled by varying the content of the crosslinking agent. It is found that, at room temperature, with increase in the content of crosslink agent from 0% to 0.5–0.7%, the impact strength increases from 4 kJ m⁻² to about 80 kJ m⁻² and the elongation at break increases from 20% to about 550%. With further increase in the content of crosslink agent to 1.5%, the impact strength and the elongation at break reduce to 64 kJ m⁻² and 360% respectively. With increase in crosslink agent, the flexural modulus, yield strength, crystallinity, mean lamellar thickness, crystal size and spherulitic size and the brittle–ductile transition temperature (BDTT) decrease, and the gel content, impact strength of the HDPE at low temperature, intensity of β transition increase significantly. In considering both the room temperature mechanical properties and low temperature impact strength, the optimized content of the crosslink agent is about 0.7%. Overall, crosslinking significantly improves the toughness and impact strength of HDPE and extends its application, especially at low temperature.

Crosslinking significantly improves the toughness and impact strength of HDPE and extends its application, especially at low temperature.     

Boron carbide composites with highly aligned graphene nanoplatelets: light-weight and efficient electromagnetic interference shielding materials at high temperatures

B₄C-based ceramic composites containing 0–2 vol% highly aligned graphene nanoplatelets (GNPs) are fabricated. The electromagnetic interference (EMI) shielding properties of the obtained composites are investigated at X-band (8.2–12.4 GHz) frequency range from room-temperature up to 800 °C. All composites exhibit outstanding EMI shielding properties with satisfactory frequency- and thermal-stability. The shielding effectiveness (SE) of GNP/B₄C composites increases monotonically with increasing GNP loading. Superior room-temperature SE close to 40 dB is achieved with only 2 vol% GNPs and high SE around 35 dB still persists at 800 °C. Considering their relatively low density, GNP/B₄C composites possess a high specific shielding effectiveness (SSE) of 16 dB cm³ g⁻¹ which is among the highest values in reported ceramic-based shielding composites. Especially, the GNP/B₄C composite with 2 vol% GNPs exhibits the highest SSE/t (SSE divided by thickness) values at temperatures above 200 °C for all reported shielding composites, indicating that GNP/B₄C composites belong to the most promising high-temperature shielding composites. The excellent shielding properties of GNP/B₄C composites arise mainly from the high electrical conductivity, high dielectric loss and the multiple reflections by the highly aligned and large-sized GNP layers.

The incorporation of a small amount of highly aligned graphene nanoplatelets into boron carbide leads to light-weight and efficient high-temperature electromagnetic interference shielding composites.     

Highly crystallized glass-ceramics from high content gold tailings via a one-step direct cooling method

Highly crystalline glass-ceramics were successfully manufactured via a one-step direct cooling method using Shuangqishan (Fujian, China) gold tailings as raw materials. A series of glass-ceramics were prepared by controlling the gold tailings addition and post-treatment. X-ray diffraction results show that the crystalline phase of glass-ceramics samples with high tailing addition content (65–80 wt%) is akermanite phase (Ca₂MgSi₂O₇). By contrast, the main phase of 60 wt% and 55 wt% tailings addition samples is diopside (CaMgSi₂O₆) crystalline phase. In addition, although glass-ceramics have typical fracture characteristics of brittle materials, the crack propagation in the fracture process is disturbed by grains, resulting in the deviation of the fracture path in terms of macroscopic and microcosmic observation. Based on the investigation of samples with different tailings additions, glass-ceramics with 60 wt% tailings contents show excellent mechanical properties with a density of 2.89 g cm⁻³, a Vickers hardness value of 8.17 GPa, and a flexural strength of 116 MPa after 950 °C heat treatment. This study further confirms the possibility of using Shuangqi Mountain gold tailings as the raw materials for highly crystalline glass-ceramics, which shows great potential for application in mass production.

Highly crystalline glass-ceramics were successfully manufactured via a one-step direct cooling method using Shuangqishan (Fujian, China) gold tailings as raw materials.     

Thoracic Coupled Motions of Korean Men in Good Health in Their 20s

[Purpose] The purpose of this study was to investigate thoracic coupled motions of 20 Korean young individuals. [Methods] Thoracic motion of twenty healthy male college students aged 23.2±3.1 was examined. The coupled motions of the thoracic regions T1–4, T4–8, T8–12 were measured using a three dimensional motion capture system. [Results] Coupled axial rotation in the same direction as lateral bending was observed in T1–T4 and T4–T8 in the neutral, flexed, and extended postures of the thoracic spine. In T8–T12, coupled axial rotation in the same direction as lateral bending were observed in the neutral and flexed postures, while coupled axial rotation in the opposite direction was observed in an extended posture. [Conclusion] The patterns of coupled motions in the thoracic spine demonstrated some variability between postures and regions in vivo. However, coupled motions in the same direction were predominantly lateral flexion or axial rotation in the three postures.Key words: Coupled motion, Three-dimensional motion capture system, Thoracic spine     

Humidity sensor based on poly(lactic acid)/PANI–ZnO composite electrospun fibers

The electrospinning technique has been successfully used to prepared micro-fibers of the poly(lactic acid)/polyaniline–zinc oxide (PLA/PANI–ZnO) composite. The polyaniline–zinc oxide (PANI–ZnO) nanocomposites are synthesized by hydrothermal and in situ polymerization methods. X-ray diffraction techniques are used to study the structural properties of the PLA/PANI–ZnO composite fibers and the PANI–ZnO nanocomposite. The average crystallite size of the PANI–ZnO nanocomposite is found to be 36 nm. The morphology and diameter of the composite fibers are analyzed by scanning electron microscopy (SEM). The average fiber diameter of the pure poly(lactic acid) (PLA) fiber is around 2.5 μm and that of the PLA/PANI–ZnO composite fiber is around 1.4 μm. Differential scanning calorimetry (DSC) provides the thermal properties of the PLA/PANI–ZnO composite fibers. The melting temperature (T_m) for the pure PLA is observed at 149.3 °C, and it is shifted to 153.0 °C for the PLA/PANI–ZnO composite fibers. The enhanced thermal properties of the composite fibers are due to the interaction between the polymer and the nanoparticles. The water contact angle measurements probe the surface hydrophilicity of the PLA/PANI–ZnO composite fibers. The role of the PANI–ZnO nanocomposite on the sensing behavior of PLA fibers has also been investigated. The humidity sensing properties of the composite fiber based sensor are studied in the relative humidity (RH) range of 20–90% RH. The experimental results show that the composite fiber exhibited good response (85 s) and recovery (120 s) times. These results indicate that the one-dimensional (1D) fiber structure enhances the humidity sensing properties.

The electrospinning technique has been successfully used to prepared micro-fibers of the poly(lactic acid)/polyaniline–zinc oxide (PLA/PANI–ZnO) composite for humidity sensor application.     

Enhancement of photocatalytic hydrogen evolution with catalysts based on carbonized MOF-5 and g-C3N4

The study presents enhancement of photocatalytic hydrogen generation after metal–organic framework (MOF5) carbonization at 700 °C and its utilization as a co-catalyst of graphitic carbon nitride (gCN). Thermal treatment of MOF5 affected the formation of ZnO nanoparticles which played the role of co-catalyst for H₂ evolution. Moreover, significant band-gap narrowing of MOF5 was observed, which also affected the narrowing of the hybrid band gap. The appropriate conduction band position of the carbonized MOF allowed photogenerated electron transfer from gCN to the carbonized MOF, hence, improving the separation of the charge carriers and reducing the overpotential for H₂ generation. The mechanism of the photocatalytic process was also discussed.

The study presents enhancement of photocatalytic hydrogen generation after metal–organic framework (MOF5) carbonization at 700 °C and its utilization as a co-catalyst of graphitic carbon nitride (gCN).