Magnetic behaviors and magnetocaloric effects in rare earth high-entropy amorphous/nanocrystalline alloys

Rare earth high-entropy alloys(RE-HEAs)exhibit great potential to be applied as refrigerants due to their good comprehensive magnetocaloric properties.In this work,octary GdTbDyHoErTmCoAl and GdTbDyHoErTmCoNi RE-HEAs with amorphous/nanocrystalline structure exhibiting comparable magnetocaloric effect were synthesized.Both RE-HEAs show a second-order magnetic phase transition in the temperature range of hydrogen liquefaction.Due to the complex magnetic interactions,a spin glasslike behavior at low temperatures is observed in the RE-HEAs.A superior magnetocaloric effect is obtained in the nanocrystalline GdTbDyHoErTmCoNi high-entropy alloy that is multiphase attributed to a stronger magnetic exchange interaction when compared with the other that exhibits single amorphous structure.Despite heterogeneous microstructure,homogeneous chemical distributions are observed in the partially crystallized high-entropy alloy.In addition,the magnetocaloric effect and magnetic transition behavior of rare earth medium-and high-entropy alloys,including the RE-HEAs in this study,are summarized and discussed.The results in this work provide a helpful guide for the design of RE-HEAs for hydrogen liquefaction applications with excellent magnetocaloric effects.

Construction and application of an ontology-based domain-specific knowledge graph for petroleum exploration and development

The massive amount and multi-sourced,multi-structured data in the upstream petroleum industry impose great challenge on data integration and smart application.Knowledge graph,as an emerging technology,can potentially provide a way to tackle the challenges associated with oil and gas big data.This paper proposes an engineering-based method that can improve upon traditional natural language processing to construct the domain knowledge graph based on a petroleum exploration and development ontology.The exploration and development knowledge graph is constructed by assembling Sinopec’s multi-sourced heterogeneous database,and millions of nodes.The two applications based on the constructed knowledge graph are developed and validated for effectiveness and advantages in providing better knowledge services for the oil and gas industry.

Single-material-substrated triboelectric–electromagnetic hybrid generator for self-powered multifunctional sensing in intelligent greenhouse

The environmental micro-energy harvested by the triboelectric–electromagnetic hybrid generator(TEHG)can power sensors and Internet of Things(IoT)nodes in smart agriculture.However,the separation structure of traditional TEHG raises the complexity of form and material,which is harmful to the miniaturization of the device.Herein,a single-material-substrated triboelectric–electromagnetic hybrid generator(SMS-TEHG)based on the flexible magnets is designed to achieve the structural integration of triboelectric nanogenerator(TENG)and electromagnetic generator(EMG).The flexible magnets serve as the electropositive triboelectric materials for TENG and the magnetic materials for EMG,simplifying the structural complexity of TEHG.The open-circuit voltage(VOC)of the TENG and EMG are 187.2 and 9.0 V at 300 rpm,respectively.After 30,000 cycles of stability testing,the VOC of the TENG and EMG retain about 95.6%and 99.3%,respectively.Additionally,the self-powered applications driven by SMS-TEHG in intelligent greenhouse have been successfully demonstrated,such as crop light supplementation,rain monitoring,and wireless temperature and humidity sensing.This work provides a new design for TEHG and possibilities for applying TEHG and IoT in smart agriculture.

3D printed triboelectric nanogenerator as self-powered human–machine interactive sensor for breathing-based language expression

Human–machine interfaces(HMIs)are important windows for a human to communicate with the outside world.The current HMI devices such as cellphones,tablets,and computers can be used to help people with aphasia for language expression.However,these conventional HMI devices are not friendly to some particular groups who also lose their abilities of physical movements like in the intensive care unit(ICU)or vegetative patients to realize language expression.Herein,we report a breath-driven triboelectric nanogenerator(TENG)acting as a HMI sensor for language expression through human breathing without voice controls or manual operations.The TENG is integrated within a mask and fabricated via a three-dimensional(3D)printing method.When wearing the mask,the TENG can produce responsive electric signals corresponding to the airflow from breathing,which is capable of recognizing human breathing types with different intensities,lengths,and frequencies.On the basis of the breathing recognition ability,a breathing-based language expressing system is further developed through introducing the Morse code as a communication protocol.Compared with conventional language expressing devices,this system can extract subjective information of a person from breathing behaviors and output corresponding language text,which is not relying on voices or physical movements.This research for the first time introduces the self-powered breathing-based language expressing method to the field of HMI technology by using a 3D printed TENG,and could make HMI interactions become more friendly and fascinating.

Preparation,characterization,and tribological properties of silicananoparticle-reinforced B–N-co-doped reduced graphene oxide as a multifunctional additive for enhanced lubrication

Microwave-synthesized SiO_(2)-reinforced B–N-co-doped reduced graphene oxide(SiO_(2)–B–N–GO)nanocomposites were characterized by X-ray photon spectroscopy(XPS),X-ray diffraction(XRD),infrared(IR)spectroscopy,and transmission electron microscopy/energy dispersive X-ray(TEM/EDX)analysis.The tribological properties of the SiO2–B–N–GO prepared as anti-wear additives for enhanced lubrication were studied using a four-ball tester.The experiment results indicated that SiO_(2)–B–N–GO exhibits excellent load-carrying,anti-wear,and anti-friction properties in a base oil,especially at the optimal concentration of additives at 0.15 wt%.The wear scar diameter decreased from 0.70 to 0.37 mm and the coefficient of friction was reduced from 0.092 to 0.070,which reductions are attributed to the formation of B–N and graphene layer tribofilms of several tens of nanometers in thickness that prevented direct contact between metals.