[en] In this study, we describe the effect of aging heat treatment on the microstructural response in laser welded joints of low thermal expansion superalloy GH909. This investigation was conducted using an optical microscope, scanning electron microscope, energy diffraction spectrum and other methodologies. The results demonstrated that part of strengthening phase γ' was transformed into ε phase in the interior of the grains and more precipitated particles were formed in the grain boundary after aging heat treatment of the welded joint, resulting in bending of the grain boundary. Laves phase formed in the grain boundary is rich in Si and Nb elements, which helps to restrict grain growth. The second-phase particles generated at the bottom of dimples enhance the mechanical properties of the welded joint. Microhardness and strength of the welded joints can be significantly improved due to the occurrence of the precipitated phase in the grain boundary and interior of the grains. However, the occurrence of liquated GB can weaken binding between the grains, with the result that the heat affected zone becomes the weakest zone in the joint

[en] Highlights: • (Al, Cd) codoped ZnO powders prepared by sol–gel method. • Cd worked effectively on ZnO band gap engineering for Cd content x < 6%. • Phase segregation appears at high Cd doping concentration x ⩾ 6%. - Abstract: The effect of Cd doping on structural and optical properties of 1 at.% Al-doped Zn_1_−_xCd_xO (x = 0–8%) powders prepared by sol–gel method was systematically investigated. X-ray diffraction (XRD) patterns revealed the powders retained a hexagonal wurtzite structure of ZnO below x = 6%, while cubic rocksalt CdO appeared when x = 8%. The bandgap and near band emission (NBE) energies determined from ultraviolet–visible (UV–vis) absorbance and photoluminescence (PL) spectra, respectively, decreased linearly with increasing Cd content up to x = 6%, it seemed that the Cd worked effectively on ZnO bandgap engineering. However, the Stokes shift unexpectedly decreased from 136 meV to 33 meV with increasing Cd content. According to the fluctuation of integrated intensity of Cd 3d_5_/_2 X-ray photoelectron spectroscopy (XPS), and redshift for x ⩽ 4% and then blueshift for x > 4% of the broadening A_1(LO)/E_1(LO) Raman mode, it was concluded that CdO impurity might also exist in the sample of x = 6% at least. The redshift of bandgap and NBE could not be simply ascribed to bandgap shrinkage of Zn_1_−_xCd_xO powders for x > 4%, but also due to the existence of CdO impurity with narrower bandgap of 2.3 eV

[en] Highlights: • Hf doping can enhance the crystallinity of ZnO significantly. • The ultraviolet emission band of HZO exhibits a blue shift. • The intensity of ultraviolet emission band rises with of Hf-doping density. • The resistivity of HZO film is 5.6 × 10"−"3 Ω cm, which is lower than AlZnO film. - Abstract: Hafnium doped zinc oxide (HZO) thin films with various Hf contents (0, 1, 3, 5, 7 at.%) at different solution concentrations (0.15–0.75 mol/L) were deposited on the glass substrates using sol–gel method. The structural, optical and electrical properties were investigated by means of XRD, PL and Hall-effect measurement. The results show that Hf ions could substitute Zn ions effectively and improve the crystallinity of ZnO significantly with highly preferred c-axis orientation. Based on photoluminescence and transmittance measurements, the strong ultraviolet emission band exhibits a blue shift and its intensity is found to rise with the increasing of Hf-doping density. Furthermore, the resistivity shows a bell curve and the minimum value is 5.6 × 10"−"3 Ω cm for the HZO film with 3 at.% Hf, which is lower than that of the typical Al-doped ZnO thin films using sol–gel method

[en] Four types of micro-organisms (B. pumilus E₆₀₁, S. aureus, B. pyocyaneus and B. coli) were exposed to ⁶⁰Co γ-radiation, and D₁₀ values were determined. Results indicate that D₁₀ values were 2.1, 0.17, 0.07 and 0.08 kGy, respectively for the four types of organisms. At 10 kGy levels of treatment Bezoar detoxification powder, the number of micro-organisms is zero

[en] In order to eliminate the harm of metal flying debris and the influence of abnormal deformation of cutting position in the process of underwater radial cutting of rod-shaped irradiation test pipe, we developed a rotary extrusion pipe cutting method;In this method, we invented a special cutting device for rotating rod bundle fuel test tube by using servo motor-worm gear drive structure, Linear Variable Differential Transformer (LVDT) displacement sensor control system and considering safety measures. The three-dimensional modeling and simulation analysis show that the device can ensure the radial cutting of the rod bundle test tube, the material at the notch deforms towards the tube, and there is no chip in the whole cutting process, which can ensure the safe underwater cutting of the test tube after irradiation. (authors)

[en] In this paper, we describe experimental laser welding of low-thermal-expansion superalloy GH909. The main welding defects of GH909 by laser in the weld are liquation cracks and porosities, including hydrogen and carbon monoxide porosity. The forming mechanism of laser welding defects was investigated. This investigation was conducted using an optical microscope, scanning electron microscope, energy diffraction spectrum, X-ray diffractometer and other methodologies. The results demonstrated that porosities appearing in the central weld were related to incomplete removal of oxide film on the surface of the welding samples. The porosities produced by these bubbles were formed as a result of residual hydrogen or oxygenium in the weld. These elements failed to escape from the weld since laser welding has both a rapid welding speed and cooling rate. The emerging crack in the heat affected zone is a liquation crack and extends along the grain boundary as a result of composition segregation. Laves–Ni₂Ti phase with low melting point is a harmful phase, and the stress causes grain boundaries to liquefy, migrate and even crack. Removing the oxides on the surface of the samples before welding and carefully controlling technological parameters can reduce welding defects and improve formation of the GH909 alloy weld. - Highlights: ► It is a new process for the forming of GH909 alloy via laser welding. ► The forming mechanism of laser welding defects in GH909 has been studied. ► It may be a means to improve the efficiency of aircraft engine production

[en] This paper uses a non-negative least-squares method based on sparse matrix, to solve the dwell time in computer controlled optical surfacing (CCOS) of optical elements with large diameter and microstructure, and the regularization of the method is researched. The simulation results reveal that the large-scale non-negative least-squares method based on sparse matrix has higher accuracy and efficiency, in contrast with the traditional non-negative least-squares method. The RMS of surface residual error converges to 0.067 wavelength, when the method is used to simulate the manufacturing of an optical workpiece with large diameter, microstructures and average surface amplitude of 1.1776 wavelength. (authors)

[en] With the application of modern technology represented by computer, in recent years, the probability of coal mine safety production accidents has been declining. However, the current coal mine water disasters still occur, and a considerable proportion of accidents are caused by water inrush from goaf. The destructive characteristics of coal mine goaf water make it necessary to carry out the relevant research on the occurrence law of coalmine goaf water. Based on this, this paper first analyses the characteristics of water disaster in the goaf of merger and reorganization coal mine, then studies the computer-based investigation and exploration mode of water accumulation in the goaf of merger and reorganization coal mine, and finally puts forward the prevention and control strategy of water accumulation in the goaf of merger and reorganization coal mine based on computer. (paper)

[en] Based on the ultrasonic phased array technology, the time delay law of ultrasonic deflection and focusing at the water-aluminium alloy interface is studied in this paper. By changing the delay time applied on each array element, the immersion ultrasonic phased array technology can realize the preset deflection angle and focusing depth, so as to detect different angles and depth positions of the work piece. The principles of ultrasonic phased array deflection and focusing are studied based on Huygens principle, and the time delay law is obtained when the sound beam is deflected and focused. When ultrasonic waves deflect and focus at the water-aluminium alloy interface, the Matlab software is used to simulate the time delay law and sound field distribution, which verifies the correctness of the design and calculation of the time delay law. (paper)

[en] With the gradual depletion of the upper resources of some coal mines with a long mining life, the operations of these coal mines gradually want to transfer to the lower coal seam. However, the mining activities of the upper coal seam have produced a large number of goafs, and due to human and natural factors, there are serious water problems in the goaf, and there is a big security risk. Based on this, this paper first studies the computer-based coal mining and overlying goaf exploration technology, and then gives the comprehensive prevention and control strategy of overlying goaf water under complex conditions based on computer. (paper)