Volume 115, Issue 4

Environmental pollution seriously affects the survival of human beings. Semiconductor photocatalysis technology is considered to be one of the most effective ways to solve environmental pollution and energy shortage. The high degradation efficiency of nanometric photocatalysts has attracted extensive attention, but the photocatalysts are difficult to recycle and reuse, which limits their application. ZnFe 2 O 4 hollow nano-photocatalysts loaded with different contents of Ag were successfully prepared by template-assisted calcination and photoreduction, and can be conveniently separated from water in a magnetic environment. The results indicate that Ag–ZnFe 2 O 4 possess a hollow nano-shell structure with a particle size distribution of about 280 nm and a shell thickness of about 24 nm. Ag–ZnFe 2 O 4 shows the strongest photocurrent intensity and photocatalytic performance compared to bulk ZnFe 2 O 4 and nano ZnFe 2 O 4 . When the concentration of AgNO 3 solution is 0.2 mmol, Ag–ZnFe 2 O 4 has the strongest photodegradation efficiency to degrade RhB under visible light irradiation. After several photodegradation experiments, the photodegradation efficiency is only decreased by 2.8 %, further proving that Ag–ZnFe 2 O 4 possess good application value in wastewater treatment.

MnFe 2 O 4 nanoparticles were synthesized using the co-precipitation method with a wide range of molar concentrations of sodium hydroxide 0.76 M−3.0 M. X-ray diffraction, field effect scanning electron microscopy, transmission electron microscopy, and vibrating sample magne-tometry were employed to characterise the structural, morphological, and magnetic characteristics of nanoparticles. Field effect scanning electron microscopy and transmission electron microscopy images show that the particles were spherical in shape for all the samples except for sample prepared at a molar concentration of 1.3 M. Particle shape was found to depend on the molar concentration of NaOH. The hysteresis loops of the samples possessed a very small area and low coercivity. The crystallite size ( cs ), saturation magnetisation, coercivity, retentivity, squareness ratio and anisotropy constant were found to be dependent on the molar concentration on NaOH. M S was noted to be at a maximum of 64.4 emu g −1 at a molar concentration of 1.3 M. The ratio t / cs (where t is the thickness of the dead layer) was calculated to account for the variation in M S . H C was found to be maximum of ∼52 Oe at molar concentrations between 1.0 M and 2.0 M. M r and M r / M S were found to be a maximum of 8.95 emu g −1 and 0.15, respectively, for the molar concentration of 2.0 M.

We study the effect of the synthesis method on the structural and magnetic properties of La 0.7 Ca 0.2 Ba 0.1 Mn0 3 . The samples were synthesized by coprecipitation and solution combustion methods. X-ray diffraction and scanning electron microscopy were performed to investigate the crystallographic structure, showing that both methods produced La 0.7 Ca 0.2 Ba 0.1 Mn0 3 monophasic samples. From magnetization measurements a second-order, ferromagnetic to paramagnetic, phase transition was observed. The Curie temperature is found to be 272 K for the sample obtained by coprecipitation and 283 K for the sample obtained by solution combustion. There is a small magnetic hysteresis for both samples. The magnetocaloric parameters were obtained using a phenomenological model; the magnetic entropy change and relative cooling power factor are higher in the sample synthesized by combustion.

The field of biomaterials continually seeks novel materials to meet the requirements of bone tissue engineering. This manuscript explores polyvinyl alcohol (PVA)–combeite composites. The composites were characterized using X-ray diffraction and scanning electron microscopy. Notably, the X-ray diffraction patterns unveil a combination of amorphous and crystalline regions attributed to PVA and combeite, respectively. More importantly, PVA–combeite composites exhibit reduced swelling and degradation rates compared to pure PVA. The percentage swelling and degradation values (%) for the prepared materials fall within the range of 190–340 and 55–75, respectively. The spherical apatite structures formed post the immersion in Hanks’ Balanced Salt Solution indicate that these materials could be used in the field of bone tissue engineering.

Erbium doped zinc boro-tellurite (EZBT) glass samples with molar composition of (55 − x )TeO 2 –20ZnO–25B 2 O 3 – x Er 2 O 3 ( x = 0.0, 0.5, 1.0, 1.5 and 2.0 mol.%) were prepared by a conventional melt quenching technique. The prepared samples were characterised using X-ray diffraction, Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy techniques to investigate the structural, optical and dielectric properties. To study the radiation shielding capabilities, the parameters such as mass attenuation coefficient ( μ m ), half-value layer ( HVL ), effective atomic number ( Z eff ) etc., were evaluated using WinXCom software. Judd–Ofelt analysis was carried out to determine the intensity of electronic transitions and other radiative transition parameters within the 4f shell of erbium ions. The μ m values in a range of (108.5–0.03) cm 2  g −1 for energy range (0.01–10) MeV were obtained for 2.0 mol.% erbium-doped tellurite glass matrix. The μ m and HVL values were also compared with conventionally used ordinary concrete and specific lead borate glass at certain energies. The detailed investigation of this current EZBT glass matrix is very useful in the specific optical and radiation shielding applications of this EZBT glass.

In order to improve the corrosion resistance of welded joints, X90 pipeline steel joints were subjected to post-weld heat treatment at 610 °C, 640 °C, and 670 °C (holding time was 1 h). Through electrochemical corrosion and full immersion corrosion experiments, the corrosion resistance of welded joints under various conditions was tested, and the surface morphology and corrosion products of the corroded samples were analyzed by scanning electron microscopy and X-ray diffraction analysis. The experimental results show that the corrosion products of X90 pipeline steel welded joints in simulated soil solution mainly include Fe(OH) 3 , γ-FeOOH, α-Fe 2 O 3 , γ-Fe 2 O 3 , and a small amount of Fe 3 O 4 , FeCl 3 and Fe. After heat treatment at 610 °C, the corrosion current density of the parent metal, heat-affected zone, and weld metal of the joint changes from 1.081, 2.889, 2.079 (×10 −5  A cm −2 ) to 0.977, 2.211, 1.810 (×10 −5  A cm −2 ), respectively, the corrosion resistance is improved.

Vacuum electron beam welding was applied to a 50 mm-thick TA15 titanium alloy plate. Microstructure observation and microhardness testing were performed. Meanwhile, the residual stress on the surface at different distances from the weld centre was measured via the hole drilling method. A finite element model for electron beam welding of the TA15 titanium alloy plate was constructed on commercial finite element software. Experimental results showed that the microstructure of the weld zone consisted of a basket martensitic phase. The highest microhardness in the weld zone was 409 HV, and the microhardness of the base metal was the lowest. The maximum gradient change area was located at the HAZ near the base metal. The peak value of longitudinal residual stress from the simulation was 880 MPa, which was in the weld metal. The sharp change area of longitudinal residual stress gradient was located in the base metal near HAZ.