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Proposing a simple strategy for developing full-color carbon quantum dots (CQDs) and exploring how the luminescence can be tuned and improved is attractive and encouraging. Herein, blue, green, yellow-green, and orange-red CQDs doped with heteroatoms were synthesized in one pot and separated by column chromatography, with emission peaks of 435 nm, 495 nm [photoluminescence quantum yield (PLQY) of 88.9%], 525 nm, and 595 nm (full width at half-maximum of 31 nm), respectively. The abundant C-O/C-O-C electron donor groups greatly improve the PLQY of green CQDs, and the expended effective conjugated domains (particle size, doped chlorine, and conjugated nitrogen) of CQDs boost the red-shifts of emission spectra. Energy transfer (ET) in a concentrated mixed solution of CQDs was discovered, and possible ET mechanisms are proposed. Furthermore, a high-efficiency white light-emitting diode with Commission Internationale de L'Eclairage coordinates of (0.361, 0.369), a correlated color temperature of 4534 K, and a high color rendering index of 90.8 was fabricated.

We propose a simple germanium Schottky photodiode, in which an ultrathin Al2O3 or HfO2 interlayer is inserted between the indium-doped tin oxide (ITO) and n-Ge contact, showing low dark current and ultra-high responsivity (gain). The introduction of 2 nm thick Al2O3 interlayer in a ITO/n-Ge Schottky photodetector results in 138 × reduction of dark current, and 16 × improvement of responsivity, exhibiting a low dark current density of 32 mA/cm2 and high responsivity of 12.5 A/W (external quantum efficiency: 1183%) for 1310 nm and 7.3 A/W (external quantum efficiency: 584%) for 1550 nm at − 4 V reverse bias, respectively. The large responsivity up to 18.5 A/W is obtained for 1310 nm at − 9 V for ITO/Al2O3(2 nm)/n-Ge diode, which corresponds to a large photoconductive gain of 24. Such a high photoconductive gain may be attributed to the capture of holes by the traps at the interface. These results are of significance for the fabrication of Ge photodetector with high performances.

In this paper, a kind of exhaust treatment device for drilling diesel engine with simple structure, low resistance, high filtration efficiency, wide collecting particle size range and low energy consumption was designed. Using RNG $$k - \varepsilon$$ turbulence model, the gas-phase flow field of the tail gas treatment unit and the gas-phase flow field of the conventional cyclone separator without corona pole were numerically calculated, and the three-dimensional velocity distribution law of the flow field in the tail gas treatment unit was studied. Compared with the conventional cyclone separator, the results show that the tangential velocity disturbance of the inner flow field is more obvious, the mean tangential velocity decreases, and the velocity in the outer vortex area decreases by 20%. Meanwhile, due to the influence of corona electrode, the eddy current flow in the treatment device is more disordered. The inner axial velocity of the processing device is slower in the down-flow area and larger in the up-flow area. Relatively speaking, the radial velocity magnitude is small, and the distribution is non-axisymmetric.

Strain evolution in SiGe-on-insulator fabricated by a modified germanium condensation technique was studied. As enrichment of Ge content, the condensation temperature was proposed to decrease from 1150 to 900 °C through five steps, rather than only two different temperatures (1150 °C and 900 °C) were used as reported previously. Compared to condensation recipe with only two different temperatures, the modified condensation recipe was beneficial to obtain more uniform SiGe layers with lower surface roughness, thus better material quality. As Ge content enriched to 0.54, the strain in SiGe is almost fully relaxed with surface roughness RMS of less than 0.59 nm at condensation temperature of ≥1050 °C. After further condensation at 900 °C, the strain in SiGe accumulated dramatically to −1.23% with a surface roughness RMS of 0.66 nm. At the final stage of Ge condensation process, most of the compressive strain was sustained in Ge-rich SiGe layer. However, when pure GOI was obtained, the compressive strain could be almost fully relaxed by intensive over-oxidation without surface deterioration. The fully relaxed SiGe-on-insulator and germanium-on-insulator with low surface roughness could be a good template for secondary growth of strained Si and Ge, respectively.

Single crystalline bismuth nanowire is recently considered as one of the most attractive low dimensional materials for the exploration of exotic higher-order topological properties. However, its growth mechanism by sputtering, which is regarded as one of the most cost-effective and simplest method, is still unrevealed. In this work, a bismuth nanowire growth model based on surface diffusion driven by chemical potential difference among crystal facets is proposed for sputtering method. The morphology evolution of bismuth nanowires is captured for the first time, and three corresponding growth stages are clearly discriminated. The possible self-catalyzed, stress-driven, and screw dislocation-driven nanowire growth mechanisms are precluded separately based on the theoretical and experimental data. The thoroughly understanding of growth mechanism is fundamental and necessary for fabrication of size-controllable bismuth nanowires and may pave the way for the preparation of other low dimensional materials and the investigation of novel physics.

The defect of pipe dent has a great threat to the safety of oil and gas pipe transportation. In this paper, the numerical calculation model of pipe extruded by cylindrical indenter at vertical and transverse direction was established. Effects of indenter displacement, indenter radius and internal pressure on the dent behavior were discussed. The results show that different action forms of the indenter would cause different dent behaviors. A large degree of plastic deformation is formed at the edge of the cylinder end of the indenter when indenter made a vertical action. The larger the indenter radius is, the larger the plastic deformation is. But when the indenter extrudes transversely, the change in the indenter radius has little influence. For pressure pipeline, the strain in the dent fluctuates in a certain degree, and the plastic strain is larger than that in the non-pressure pipeline, but the dent depth would be lower in the end. Under different conditions of internal pressure, the laws of dent with “non-pressure” and “loading pressure” are the same, and the dented laws of “pressure” and “unloading pressure” are consistent. The strain and the depth of the dent achieve an extreme point or maximum near the edge of the dent.

Corrosion and erosion are the main factors of pipes failure. Erosion wear characteristics of elbow pipe with corrosion defect are investigated in this paper. Initially, the erosion result of nondefect elbow pipe is calculated and compared to elbow pipe with corrosion defect. An elliptical erosion area with a V-shaped dent occurs at the extrados due to the particles' impact. The uniform corrosion defects change the structure of the pipe's inner surface. Therefore, the defect areas are more prone to be impacted by particles and then more severe erosion occurs. The maximum erosion rates of corrosion defect and noncorrosion area synchronously reach the maximum value as the corrosion defect located at 55 deg. The larger the particle mass flow rate is, the more severe the elbow pipe erosion is. As the flow rate increases, erosion rates of corrosion area and noncorrosion area increase, while the maximum erosion rate of corrosion area occurs at 55 deg. Structural parameters of corrosion defects affect the erosion. As the distance between two corrosion defects increases, the maximum erosion rate of lower corrosion defect increases. Considering the location, structure, and number of corrosion defect, a larger corrosion defect located in the middle of extrados has a worse effect on elbow pipe safety.

As electronic devices are becoming faster and incorporating more functions, they are simultaneously shrinking in size and weight. These factors suggest significant increases in the packaging densities and heat fluxes for the integrated circuits. Effective thermal management will be the key factor to ensure that these devices perform well with high efficiency and reliability. As the heat dissipation concentrates on tiny gate fingers, the operation of the GaN high-electron mobility transistor (HEMT) posts a huge challenge on thermal management. In order to enhance the heat dissipation capability of GaN power device, it is mostly soldered on the heat spreader with the AuSn solder. However, the thermal conductivity of the AuSn solder is only 57 W•K−1•m−1, which cannot fulfil the reliability requirements of future power electronic devices. New interconnection technologies have to be developed and one of them is a low-temperature pressure-less silver sintering paste with nano silver technology.The joining strength, thermal conduction, electric conductivity and long-term reliability of nano-silver soldering paste under low temperature without pressure are studied, and then compared with AuSn bonder. It forms a strong, highly electrically and thermally conductive bond. Chip shear tests show that 200 °C is already sufficient to generate bonds comparable to solder and high-strength welding interface if the remaining parameters (r, t and T, respectively) are set correctly. However, the strength of the welding interface is only a necessary criterion as chip performance comes into play. Therefore, reliability performance of thermal shock test, high temperature storage test and low temperature storage test are run, which return superior reliability of the sintered samples.In addition, the electrical performance of the GaN power chip is tested. The nano-silver bonded sample is compared with the AuSn sintered sample. The saturated signal output power of these two packaging processes can reach 41dBm, and the leakage current is in the normal range of 0.2A~0.3A. Through reliability test, there is no significant change in these samples, and they all achieve normal electrical performance of the power amplifier component.Besides, thermal performance is one of the important parameters affecting the reliability of high-power devices. In the field of electronic assembly, it is of vital importance to reduce the junction temperature. Ordinary conductive adhesives have lower thermal conductivity which generally below 10 W•K−1•m−1 compared with the AuSn solder. Considering that, it is not suitable to join GaN power devices with the AuSn solder and conductive adhesives. In order to verify the heat dissipation performance of the nano-sintered silver solder samples, 20 samples are prepared for thermal imaging experiments. By observing and comparing the temperature distribution on the surface of nano-silver solder paste sintered chips and the AuSn sintered chips. There are some fluctuations in the thermo-resistance of nano-silver solder paste sintered chips and the AuSn sintered chips. Although the thermo-resistance of both samples are concentrated in 1.00 °C•W−1to 1.20 °C•W−1 and heated by the same power, the nano-sintered silver solder achieves around 16.7% decrease in the maximum temperature of the test chip. With the attached heat spreader, 50 W power can be dissipated.

In this work, the Ge condensation effect of amorphous SiGe on a SiO2/Si substrate is systematically investigated. As Ge condensation proceeds, the Ge content gradually enriches from an initial 0.24–1.0 with improving crystal quality. The enlargement of the grain size results in gradual roughening of the surface roughness. As the Ge content reaches 0.36, a high hole mobility of ∼211 cm2 · V−1 · s−1 is achieved with a hole concentration of ∼3.7 × 1015 cm−3. As the Ge content further accumulates, the grain number increases resulting in a higher hole concentration. The film mobility gradually deteriorates probably due to the following factors: strong impurity scattering at high hole concentration, increase of grain boundaries, decrease of SiGe thickness, and increase of surface roughness. A polycrystalline Ge-on-insulator with a hole concentration of ∼5.1 × 1018 cm−3 and mobility of ∼15 cm2 · V−1 · s−1 is ultimately fabricated. The investigation provides a promising method to fabricate a high hole mobility SiGe-on-insulator platform from low-cost amorphous SiGe.

In this work, three-dimensional (3D) Ge condensation was carried out to explore the merits of Ge condensation method in fabricating low-dimensional SiGe-on-insulator (SGOI) and Ge-on-insulator (GOI) structures. Through varying the width of SGOI wires from 220 nm to 50 μm before Ge condensation, the Ge content of SiGe wires can be easily modulated from 1.0 to 0.55 after 3D Ge condensation facilitating fabrication of SiGe/Ge heterojunction nanowires (NWs). Based on the volume change of Si, Ge and SiO2 with consideration of a geometry factor, a simple 3D Ge condensation model was built. It is found that the enrichment of Ge content mainly comes from condensation effect along directions with small dimensions. The proposed 3D condensation model can be a guidance to design and fabricate low-dimensional SGOI, GOI and even SiGe/Ge heterostructures on insulator materials.

A 2.7% tensile strained Ge/SiGe heterostructure nanowire (NW) is in-situ fabricated by a three-dimensional Ge condensation method. The NW metal-semiconductor-metal (MSM) photodetector demonstrates an ultra-broadband detection wavelength of 400-2400 nm, showing a high responsivity of >3.46×102 A/W with a photocurrent gain of >4.32×102 at 1550 nm under −2 V. A high normalized photocurrent to dark current ratio (NPDR) of 1.88×1011 W−1 at 1550 nm under −1 V is achieved. The fully complementary metal-oxide-semiconductor (CMOS) compatible, simple and scalable process suggest that the Ge heterostructure NW is promising for low cost, high performance near-infrared or short wavelength infrared focal plane array applications.

In this article, a novel x-ray image intensifier is introduced. It is mainly composed of an x-ray intensifying screen and a low-light-level (L3) image intensifier. In order to obtain a bright enough image, the spectral compatibility among three different combinations of the x-ray intensifying screen and the photocathode is analyzed. The comparison indicates that a (Zn,Cd)S:Ag screen is superior to either a CaWO4 screen or a Gd2O2S:Tb screen when combined with the Super S25 photocathode and spectral compatibility analysis is a useful guide when designing an optoelectronic imaging device.