Electrospining Machine: Hollow hafnium oxide (HfO2) fibers: an effective combination of sol-gel, electrospinning, and thermal degradation approaches

Background

Hafnium oxide (HfO2) has the advantages of high dielectric constant, excellent mechanical properties, thermal stability, wide energy band, etc., and has been widely used in metal oxide semiconductor devices, optoelectronics, microelectronics and other fields. HfO2 materials with special morphology have been applied in different fields. For example, Qiu et al. applied the coating method of nano-hfO2 fibers to W-Re alloy, showing thermal shock resistance with high melting point (above 3000 K). In addition, Kahro et al. reported a HfO2 film grown by atomic layer deposition (ALD), revealing the application of resistive switching media. These applications are based on the physicochemical properties of HfO2 materials and the high surface area of nanostructures.

The main point of this paper

Preparation method of HfO2 materials:

In addition to bulk materials, HfO2 materials can be prepared by various methods such as atomic layer deposition, electrochemical anodization, thermal oxidation and sol-gel method to form materials with special morphology.

Application of HfO2:

These HfO2 materials with special morphology are used in applications such as Li-S batteries, gas sensors and high-performance field emitters.

Preparation of HfO2 hollow fibers:

The researchers proposed a method combining sol-gel and electrospinning to prepare HfO2 hollow fibers.

First, polystyrene (PS) fibers are formed by electrospinning technology.

Then, these PS fibers are coated with HfO2 precursor solution, and HfO2 coated PS fibers are formed after drying.

Through high-temperature heat treatment at 800℃, the HfO2 precursor condenses, the PS fibers are selectively pyrolyzed, and finally HfO2 hollow fibers are formed.

Characteristics of HfO2 hollow fibers:

Scanning electron microscopy (SEM) characterization showed that the surface of HfO2 hollow fibers was relatively rough and the diameter was reduced.

The molar ratio of the precursor solution affects the diameter of the fiber, and less precursor can obtain HfO2 fibers with smaller diameters.

Thermogravimetric analysis (TGA) and energy dispersive spectroscopy (EDS) were used to determine the composition of the material.

X-ray diffraction (XRD) analysis showed that the crystallinity of HfO2 hollow fibers annealed at 800°C was higher than that of fibers annealed at 400°C.

Surface properties of HfO2 hollow fibers:

The water contact angle (WCA) of HfO2 hollow fibers was 38.70±5.24°, showing hydrophilicity, which was caused by the removal of hydrophobic PS fibers.

Application potential of HfO2 hollow fibers:

Researchers believe that HfO2 hollow fibers have great application potential in filtration, energy storage, and storage devices.

Preparation of HfO2 hollow fibers by combining sol-gel method and electrospinning technology and their potential applications in filtration, energy storage and memory devices

Background of HfO2:

HfO2 has attracted attention due to its high dielectric constant, excellent thermal stability and high band gap.

Although bulk and thin film materials of HfO2 have been widely studied, there are few studies on HfO2 fibers, especially hollow fibers.

Preparation method:

The researchers proposed a method combining sol-gel method and electrospinning technology to prepare HfO2 hollow fibers.

First, polystyrene (PS) fibers were prepared by electrospinning technology.

Then the PS fibers were immersed in HfO2 precursor solution to form HfO2-coated PS fibers.

After heat treatment at 800℃, the PS fibers were pyrolyzed and the HfO2 precursor was condensed to finally form HfO2 hollow fibers.

Characteristics of HfO2 hollow fibers:

Scanning electron microscopy (SEM) characterization showed that the surface of HfO2 hollow fibers was rough and the diameter was reduced, which was due to the removal of PS fibers and the condensation of HfO2 precursors.

The study explored the effect of the molar ratio of the precursor solution and found that reducing the amount of precursor can produce HfO2 fibers with smaller diameters.

The composition of the materials was verified by thermogravimetric analysis (TGA) and energy dispersive spectroscopy (EDS).

X-ray diffraction (XRD) analysis showed that the crystallinity of HfO2 hollow fibers annealed at 800°C was higher than that of fibers annealed at 400°C.

Surface properties:

The water contact angle (WCA) of HfO2 hollow fibers was 38.70±5.24°, indicating a transition from hydrophobic PS fibers to hydrophilic HfO2 hollow fibers.

Summarize

In this work, we successfully synthesized HfO2 hollow fibers by combining sol-gel and electrospinning. After electrospinning into fibers, the HfO2 precursor solution was coated on the electrospun PS fibers to form HfO2-coated PS fibers. Through high temperature (800°C) heat treatment, the PS fibers were selectively pyrolyzed and the HfO2 precursor condensed to form HfO2 hollow fibers. The prepared materials were analyzed by scanning electron microscopy; the surface of the HfO2 hollow fibers was relatively rough and the diameter was reduced due to the disappearance of the PS fibers and the condensation of the HfO2 precursor. The effect of the molar ratio of the precursor solution was studied, indicating that the use of less precursor can obtain HfO2 fibers with smaller diameters. The composition of the prepared materials was determined by thermogravimetric analysis and energy spectrum analysis.

XRD results show that the crystallinity of the HfO2 hollow fibers annealed at 800°C is higher than that of the HfO2 hollow fibers annealed at 400°C. In addition, the WCA of HfO2 hollow fibers is 38.70 ± 5.24°, which is due to the removal of the hydrophobic PS fibers and the hydrophilic nature of HfO2. In the future, we will further study the surface properties of HfO2 hollow fibers and their applications in filtration, energy storage, and memory devices.