Search

The cutting temperature plays an important role in the machining process. Research on the real-time monitoring of cutting temperature and its effect on tool wear still faces many challenges. In this paper, a fiber-optic two-color pyrometer is proposed to obtain temperature of cutting edge during turning at real-time. The effects of the cutting speed, cutting depth and feed rate on the variation of cutting edge temperatures are investigated. Intermittent cutting experiments are performed to verify the effectiveness and dynamic responsiveness. The processed inserts show good durability. The cutting temperature change and its effect on tool wear are also investigated.

Silicon micro/nanostructures are promising building blocks for high-performance solar cells, lithium-ion batteries, sensors and so on. Great challenges like high cost and complex fabrication process still exist for the fabrication of silicon micro/nanostructures, especially for the fabrication of uniformly distributed silicon micro/nanostructures. In this study, the generally unwelcome failure of materials, nanopitting, was introduced and demonstrated to be effective in micro/nanofabrication for the first time. Together with wet chemical etching, uniformly distributed silicon micro/nanostructures were obtained. Ag islands were formed by the nanopitting of chloridion, which will be used as mask and catalyser in the chemical etching process. The silicon micro/nanostructures, especially, uniformly distributed p-type silicon micro/nanostructures were fabricated with the low-cost and facile fabrication approach. In addition, the application of the silicon micro/nanostructures was demonstrated as microsupercapacitive electrodes with the integration of MnO 2 nanostructures. The results show that the electrochemical performance of silicon micro/nanostructures was much better than that of silicon microstructures. The proposed approach is cost-effective to fabricate silicon micro/nanostructures, and the silicon micro/nanostructures have great potentials in miniaturised energy storage devices, sensors and photodevices.

Flexible perovskite solar cells (PSCs) such as inverted PSCs are gaining increasing attention due to their wide range of potential applications, while the selection of stable, high conductivity and energy level suitable hole transport layers (HTLs) is still challenging. Here we introduce dopant-free copper phthalocyanine (CuPc) as HTL in inverted planar PSCs, and demonstrate improved photovoltaic performance and increased stability with high reproducibility and uniformity compared to the PEDOT:PSS based devices. The champion efficiency of PSCs is achieved by 15.4% on rigid substrates and 12.8% on flexible substrates, respectively. The flexible devices also exhibit excellent bending stability, retaining ∼85% of the original power conversion efficiency (PCE) after 3000 bending cycles at r = 5 mm without encapsulation. Our study provides a new strategy for fabricating cost-effective, scalable and flexible PSCs with high efficiency, little hysteresis, and excellent stability.

Perovskite solar cells (PSCs) are one of the most promising lab-scale technologies to deliver inexpensive solar electricity. Low-temperature printable carbon counter electrode based planar-heterojunction PSCs are particularly suitable for future large-scale manufacturing, but suffer from an inferior efficiency. Here, we demonstrate a TiO2/SnO2 bilayer as the electron transport layer (ETL) for carbon counter electrode based planar-heterojunction PSCs together with micromolecule Cu-phthalocyanine (CuPc) as the hole transport layer (HTL), yielding a high power conversion efficiency of 15.39% and an excellent stability over 1200 h. The improved performances are attributed to a better energy level transition, a suppressed electron–hole recombination, and a wider depletion region of the TiO2/SnO2 bilayer. Our work represents a great advancement in the fabrication and popularization of carbon counter electrode based PSCs. More importantly, the whole devices are processed at a temperature below 200 °C, providing potential application of PSCs in monolithic tandem devices and paving the way for the development of carbon based flexible PSCs.

Heat flux during machining has received extensive attention due to its importance for understanding the cutting mechanism and promising prospects on intelligent manufacturing. Research on heat flux estimation by inverse heat conduction methods faces many challenges, including measurement error amplification, stability of the methods, and limitations for applications. In this paper, we introduce a long short-term memory (LSTM) based encoder-decoder (ED) scheme in online estimation of the heat flux imposed at the tool-chip region during turning. The math-physical model and finite element model are established to generate training datasets. Numerical tests using simulated heat flux and temperature data representing different machining conditions are carried out to evaluate the method performance. Compared with other artificial intelligence methods such as multilayer perceptron, convolutional neural networks and LSTM, the LSTM-ED model performs better at all tested noise levels ( 1 ≤ σ ≤ 20 K ) with acceptable time cost for online process. Effects of the location and number of sensors on the accuracy of heat flux estimations are also investigated. Experimental validations based on cutting temperature measurements by five thermocouples located in the insert are conducted. Both numerical and experimental tests indicate the potential of the LSTM-ED method for online heat flux monitoring in scientific research and industrial production.

We demonstrate a novel integration of carbon counter electrodes based perovskite solar cells (PSCs) and thermoelectric generators (TEs), which exhibits excellent thermal endurance and photo-electric conversion by use of good light-harvesting capabilities over the wide sunlight spectra. The carbon counter electrode based PSC owns a good prospect in development and commercialization, whereas photo-thermal effects induced thermal degradation will be more crucial due to notable photo-thermal conversion of the carbon. The photovoltaic performance of the PSCs will decline when the temperature increases and recover when decreasing. After integration with TEs, the carbon electrodes can act as the infrared light absorption layer for the TEs, which improve the photo-thermal ability and triple the output voltage of the thermoelectric devices, substantially compensating the thermal degradation of the PSCs. Electrical measurements reveal that the integrated devices exhibit much higher and more stable energy output. When tested in ambient air, the hybrid device exhibits obvious enhancement: the overall conversion efficiency increases from 9.88% to 12.6% after integration. When the cold side of the TE part is cooled by ice bath, the hybridization obtains a maximum VOC of 1.87 V under AM 1.5 G illumination with a temperature gradient of 15 °C, boosts a more than 124% increase of the photo-electric conversion efficiency (PCE), from 9.88% (photovoltaic) to 22.2% (photovoltaic-thermoelectric), and gets a higher maximum power output of 22.2 mW cm−2. By further optimization, larger improvements in PCE of the integration can be achieved. Our work opens up new avenues for the realization of high-performance, wide sunlight-harvesting photovoltaic-thermoelectric hybrid devices.

Power packs integrating both photovoltaic parts and energy storage parts have gained great scientific and technological attention due to the increasing demand for green energy and the tendency for miniaturization and multifunctionalization in electronics industry. In this study, we demonstrate novel integration of perovskite solar cell and solid-state supercapacitor for power packs. The perovskite solar cell is integrated with the supercapacitor based on common carbon electrodes to hybridize photoelectric conversion and energy storage. The power pack achieves a voltage of 0.84 V when the supercapacitor is charged by the perovskite solar cell under the AM 1.5G white light illumination with a 0.071 cm2 active area, reaching an energy storage proportion of 76% and an overall conversion efficiency of 5.26%. When the supercapacitor is precharged at 1.0 V, an instant overall output efficiency of 22.9% can be achieved if the perovskite solar cell and supercapacitor are connected in series, exhibiting great poten...

Due to harsh environment in the cutting area, access to the cutting region is still limited for the existing temperature sensors. As such, measuring temperature signals remains a challenge for real-time tool wear monitoring. In this paper, a polycrystalline cubic boron nitride (PCBN) cutting tool embedded with thin-film thermocouple (TFTC) was devised and used for tool wear monitoring during the cutting of hardened AISI O2 tool steel. A detailed manufacturing process of the smart tool was introduced. Performance tests for the smart insert were evaluated and results showed that the embedded TFTC had a sensitivity of 14.4 μV/℃, good dynamic response, and functional validity. Wear experiments were implemented under two sets of cutting parameters to explore the relationship between cutting temperature and tool wear. The results showed that the increased maximum cutting temperature could well reflect the progression of flank wear. Obvious fluctuation in temperature signal could also well reflect the abnormal condition of the tool. The devised smart tool will be useful for determining optimum cutting parameters and extending tool life.

Cutting temperature in machining process has received extensive attention due to its significant influence on tool life and workpiece quality. Research on real-time monitoring of the cutting temperature still faces many challenges, including rapidly changing temperature, high temperature gradient, limited installation space, and flowing chips and coolant. In this paper, a near-infrared fiber-optic two-color pyrometer system is proposed to obtain real-time temperature of the cutting edge during turning. A sensor probe is inserted into a micro-hole of the tool near the cutting edge. The infrared rays radiated from the hole is received by the sensor probe, led by the optical fiber to a plano-convex lens, and split into two identical rays by a beam splitter. Then the two rays passing through specific band filters are focused by two plano-convex lenses on two amplified photodetectors, and the electrical signals are acquired by a data acquisition card. Typical difficult-to-cut material is selected as workpiece in turning. The pyrometer system shows good stability and dynamic response in continuous cutting and interrupted cutting experiments, respectively. The measured cutting temperature is responsive to the changed cutting regime, increasing with the increase of the cutting speed, cutting depth and feed rate in continuous cutting. Repeated cutting experiments are performed for further validation. It is found that the rapid wear in the tool flank face is accompanied by an obvious increase in the cutting temperature, and the cutting temperature rises sharply before the tool breakage. These results indicate the potential of the pyrometer for real-time monitoring of the working tool and early warning of the tool damage.

Measurement of the temperature at the tool-chip interface is still a significant challenge especially for machining difficult-to-machine material like titanium alloys. In this paper, a versatile PCBN tool, starting with the existing tool shape, was devised by embedding thin-film thermocouples (TFTCs) into tool interior to monitor the temperature at the tool-chip interface while machining titanium alloy bar. A simplified process was developed to fabricate TFTC array with a degree of spatial resolution (100 μm). A diffusion bonding technique was realized between PCBN plates to achieve reliable sensor protection with shorter sintering time and lower sintering temperature while metallic interlayer like titanium film was adopted. The sensors exhibit an excellent linear response with a sensitivity of about 13 μV/℃. Dry cutting including interrupted and continuous cutting was implemented with the fabricated PCBN insert. Results show that TFTCs embedded into PCBN insert not only have a good transient perception by comparing with commercial sensors but also can stably monitor cutting temperature as close as 300 μm to tool-chip interface under different cutting conditions. The devised PCBN tool presented in this paper will also be helpful for the improvement of machining processes and better understanding of the tool-chip contact phenomena.

Metal halide perovskite solar cells (PSCs) have attracted extensive research interest for next-generation solution-processed photovoltaic devices because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication cost. Although the world’s best PSC successfully achieves a considerable PCE of over 20% within a very limited timeframe after intensive efforts, the stability, high cost, and up-scaling of PSCs still remain issues. Recently, inorganic perovskite material, CsPbBr3, is emerging as a promising photo-sensitizer with excellent durability and thermal stability, but the efficiency is still embarrassing. In this work, we intend to address these issues by exploiting CsPbBr3 as light absorber, accompanied by using Cu-phthalocyanine (CuPc) as hole transport material (HTM) and carbon as counter electrode. The optimal device acquires a decent PCE of 6.21%, over 60% higher than those of the HTM-free devices. The systematic characterization and analysis reveal a more effective charge transfer process and a suppressed charge recombination in PSCs after introducing CuPc as hole transfer layer. More importantly, our devices exhibit an outstanding durability and a promising thermal stability, making it rather meaningful in future fabrication and application of PSCs.