Pulse Tunnel Effect: Prospects for Scaling Photocatalysts

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Introduction

Nanotechnology is not just one of the branches of high technology, but also a source of fundamentally new approaches, including the creation of nanostructures and products based on them. Nanomaterials possess unique properties, such as magnetic, optical, and electrical characteristics, induced by quantum effects, which significantly differentiate them from bulk counterparts. This opens up possibilities for improving the performance characteristics of materials by creating composites with nanoscale components. In recent years, there has been a rapid development of numerous nanoscale materials that have the potential for applications in various fields, from energy to medicine. This study investigates the synthesis of ceramic nanomaterial-based photocatalysts capable of converting solar radiation and other sources of energy into pulsed electromagnetic radiation with controllable parameters. Such photocatalysts have great potential for activating complex processes, such as water splitting using solar energy to produce hydrogen, as well as applications in resource-saving technologies, medicine, mining industry, and other fields. The key physical mechanism of operation for these photocatalysts is the impulse tunneling effect (ITE) [1–5]. However, there are certain challenges with scaling up the production of these materials in industrial volumes, and the mechanism of pulse generation by these photocatalysts is not fully understood.

In this regard, this study presents the results of comparative testing of film-ceramic composites based on the thermo-mechano-chemical approach, combined with sol-gel technology, and composite films made from functional ceramics obtained using a large solar furnace (LSF). The thermo-mechano-chemical method allows for the creation of amorphous inclusions in the crystalline ceramic matrix of photocatalysts, the composition of which is similar to the target crystalline phases. The main focus is on the development of synthesis techniques for nanocomposite powders and the study of the evolution of their microstructure upon the introduction of nanoscale additives of various compositions. Additionally, the work presents new approaches to the synthesis and formation of the microstructure of pulsed functional ceramics in the far-infrared range, similar to ceramics obtained using the large solar furnace at high temperatures. Special attention is given to the activation of the obtained materials through the impulse tunneling effect (ITE) generated by functional ceramics, with the aim of stabilizing metastable phases that play a key role in the impulse tunneling effect. The developed synthesis methods have high potential for scaling up and industrial applications. The results of comparative field testing of the obtained composites are provided.

Currently, a composite ceramic material based on zirconium oxide, aluminum, and lithium silicate has been developed, capable of generating pulsed radiation in the far-infrared (THz) region of the spectrum. This radiation is commonly referred to as terahertz (THz) radiation due to its frequency range of 0.1 to 10 THz. With its unique properties, it finds a wide range of practical applications, including energy conservation, medicine, engineering, as well as low-temperature sterilization and drying of agricultural products [6].

However, existing synthesis methods for this ceramic material, based on sol-gel technology, have several drawbacks and limitations. The material volumes obtained are insufficient for industrial production, and the methods themselves are small-scale. Nevertheless, the demand for such materials in industrially developed countries, according to preliminary estimates, exceeds millions of tons. Therefore, it is promising to search for more productive synthesis methods for this ceramic material, which would reduce costs and yield materials with the desired set of properties under the influence of pulsed terahertz radiation.

Terahertz radiation, or radiation in the far-infrared range, possesses a number of unique characteristics. Many common materials and biological tissues are transparent or semi-transparent to this spectral range and have specific terahertz signatures that allow for successful identification and study. Due to the low quantum energy of terahertz radiation, it is non-ionizing and, unlike X-ray radiation, does not cause damage to biomolecules [7–9].

The advantages of the impulse tunneling effect (ITE) when applied to different objects are as follows:

• precise adjustment of pulse parameters for specific objects or processes by controlling the rising front;
• high selectivity of action due to focusing all pulse energy into a narrow energy range;
• ability to overcome potential barriers even with energy lower than their height, ensuring effective interaction;
• utilization of all incident radiation energy, including low-energy quanta, by transforming them into the desired wavelength;
• achieving high energy density of the pulse for process intensification;
• reduction in process time and increased efficiency.

These are key advantages that make ITE a promising technology for interacting with various objects.

Impulse tunneling effect (ITE)

Impulse Tunneling Effect (ITE) is a quantum mechanical phenomenon wherein a particle or wave can overcome a potential barrier by accumulating significant momentum energy.

According to de Broglie's hypothesis, the momentum of any type defines its wavelength by the formula

$\lambda =\frac{h}{p},$

where λ – wavelength;

h – Planck constant;

p – the momentum of the object.

When a large amount of momentum energy is accumulated, for example, in the form of photons, the particle's wavelength significantly decreases.

These short-wavelength particles can tunnel through the potential barrier, overcoming it even with energy lower than the height of the barrier itself. Unlike the standard tunneling effect, ITE uses all the photons that hit the functional ceramics, converting them to the required wavelength. Thus, ITE allows for efficient use of radiation energy by focusing the momentum, exceeding the effective energy of the photons over their actual energy.

Furthermore, ITE provides a very narrow energy range associated with the rise front of the momentum. By precisely tuning the momentum front to match the energy of the target process, ITE operates highly selectively, directing all the impulse energy into the necessary narrow range. This allows for maximum efficiency of the selected processes by optimally matching the impulse characteristics with the required energy [1; 10].

Key points distinguishing ITE from standard tunneling effect:

1) utilization of all incoming photons, converting them to the required wavelength;

2) high efficiency of energy use by focusing the momentum;

3) high selectivity due to the ability to precisely tune the impulse front to the required energy of the process.

Combining these features allows ITE to achieve maximum efficiency in various practical applications.

In previous publications [11–13], the results of field tests on composite films ZB1 and ZB2 with a functional ceramic content of 0.1% by mass relative to polyethylene were presented. Additional information on temperature stabilization in greenhouses using the composites compared to regular polyethylene film (ZB0) is provided. The results are shown in Fig. 1.

 

Fig. 1. Results of temperature stabilization in greenhouses using composite films with a functional ceramic content of 0.1% (ZB1, ZB2) and conventional polyethylene film (ZB0)

 

As evident from the examples provided, even with such a small content of functional ceramic in the composites, the temperature inside the greenhouses is more stable. At high temperatures (40 °C), it is lower by 4–6 degrees, while at low temperatures (–15 °C), it is higher by nearly 20 degrees compared to the prototype. It should be noted that no heating was applied inside the greenhouses. Additionally, the composite films for greenhouses reduce moisture evaporation by 4–6% compared to regular polyethylene. This protects the greenhouses from condensation and ice formation on the film, which can fall and damage plants, leading to rapid film deterioration.

This allows for the cultivation of many vegetable crops under such composites during the winter, especially considering that the yield under them is 50–100% higher compared to regular films. If additional heating is used, fuel consumption can be reduced by 60–80%. Here are some vegetable crops that can grow at temperatures close to 0 °C:

• carrots – one of the most frost-resistant vegetable crops, seed germination occurs at 0–5 °C;
• seed germination of beets is possible at 0–7 °C;
• seeds germinate of radishes at 0–10 °C;
• onion (bulb) – one of the most frost-resistant onion varieties, germination occurs at 0–5 °C;
• some varieties (e.g., Sevenner) of lettuce can germinate at 2–5 °C;
• turnips germination occurs at 0–6 °C;
• garlic germination occurs at 0–7 °C, provided there is moisture in the soil;
• asparagus – one of the most cold-resistant vegetable crops, germination occurs at 0–5 °C;
• arugula, or rocket, can germinate at low temperatures, although germination may take longer than under warmer conditions;
• leeks can germinate at relatively low temperatures, such as 4–5 °C;
• spinach seeds can also germinate at low temperatures;
• cabbage, including varieties such as broccoli, cauliflower, and head cabbage, thrives well in low temperatures, they can tolerate cool weather and even light frosts;
• some lettuce varieties grow well in cool temperatures, they can be cultivated in early spring or late autumn;
• radishes thrive well in cool temperatures, they can be grown in cool weather during spring or autumn.
• some varieties of green onions, such as scallions and shallots, can be grown in cool conditions. They can be planted early in spring or late autumn.

Based on the obtained results, composite films were produced with a functional ceramic content of 0.5% by mass of the following types: ZB1/0.5%; ZB2/0.1%; ZB3/0.5% with an additional wavelength of 500–550 nm; ZBV/0.5% with functional ceramic manufactured using the thermomechanical chemical method, followed by ITE activation generated by the functional ceramic MC-1.

It should be noted that without ITE activation of the ceramic synthesized using the thermomechanical chemical method, the composites performed even worse than regular polyethylene films, primarily due to lower light transmittance, resulting in reduced photosynthesis.

Figure 2 shows plants (corn) grown under different composites.

 

Fig. 2. Development of corn under various composites

 

As can be seen from the results, the slowest development is observed under the ZB2/0.1% composite, although, as presented in previous publications, it performs significantly better than regular polyethylene, and its activity was even slightly higher than that of ZB1/0.1%. Increasing the ceramic content in the composite from 0.1 to 0.5% (ZB1/0.5%) had a significant impact on its activity. At this stage, plant growth under this composite surpasses the growth under ZB3/0.5%. The most remarkable result at this stage of development was demonstrated by the ZBV/0.5% composite, obtained using ceramics through the thermomechanical chemical method. Temperature data is not provided as during this period, the temperature remained within the normal range, indicating that the composite did not activate the temperature stabilization mode.

We consider it appropriate to present the data on the results of activating ITE of the functional ceramics used for manufacturing the ZBB/0.5% composite.

Undoubtedly, the activation process has a significant influence on the ceramic powders in the Cr₂O₃—SiO₂—Fe₂O₃—CaO—Al₂O₃—MgO—CuO system. To assess their ability to generate pulsed radiation, these powders were subjected to activation using pulsed infrared radiation generated by the functional ceramic MC-1, operating on the principles of ITE. These pulses had a short front and high intensity, reaching 320 W/cm².

Comparison of the X-ray spectra of activated and non-activated samples revealed significant changes in the crystalline structure and phase composition of the ceramics as a result of this process. Activation treatment resulted in the reduction of unreacted phases, indicating the completion of the main chemical processes.

It was determined that one of the key factors of activation was the redistribution of the phase composition of the synthesized composite. The proportion of the silicon oxide-based phase increased, while the proportion of spinel-structured solid solution-based phase decreased. It is assumed that the redistribution of phases occurred at the boundaries of their separation and was determined by the diffusion mobility of cations in this region. These non-equilibrium processes were accompanied by the formation of metastable compounds and solid solutions at the interfaces, which play a key role in the accumulation of phonons and the generation of simulated pulsed radiation.

As a result of activation, material modification occurred with an increase in its crystallinity, which is clearly visible in the X-ray spectrum of the activated sample with minor fluctuations of the background line, unlike the non-activated sample.

The increase in crystallinity after activation is also indicated by the pulse count, which is 800, in contrast to the pre-activated sample where it corresponds to 500 pulses.

Furthermore, the detailed analysis of specific regions of their X-ray spectra also indicates changes in the parameters of the crystalline structure of the ceramic powder samples after activation.

The analysis of X-ray diffraction patterns revealed a noticeable shift of reflections towards smaller diffraction angles, indicating an increase in the parameters of the crystal lattice for this phase. This effect could be attributed to the diffusion of cations from other crystalline phases into this phase, resulting in the expansion of its crystal lattice.

Microstructural investigations using electron microscopy and energy-dispersive analysis detected significant changes in the morphology and sizes of crystallites in different phases after activation of the sample. Specifically, a reduction in crystallite size and an increase in their density were observed, contributing to the formation of a well-developed network of interphase boundaries. It is presumed that such structural transformations serve as prerequisites for the occurrence of metastable compounds at the phase interfaces during the activation process.

The significant increase in the fraction of interphase boundaries observed as a result of sample activation likely contributed to the formation of a large number of metastable inclusions within the material. This effect could be one of the key factors initiating the generation of modulated infrared radiation in the investigated system.

The emergence of such metastable structures at interphase boundaries is likely due to the instability of the crystal structure during activation and accompanying structural transformations. Local distortions of the crystal lattice caused by diffusion processes and component redistribution may facilitate the formation of metastable phases, which, in turn, can lead to the emission of modulated infrared radiation.

Thus, the study shows that the activation of materials through pulsed tunneling can stimulate properties characteristic of functional ceramics obtained using a solar furnace.

The results of this study are consistent with previous work in the field of functional ceramics, confirming that the pulsed impact on a substance with a specific growth front can be described as the pulsed tunneling effect (PTE), which allows for the control of material properties without chemical or thermal intervention. The main findings on this topic have been published in the journal Computational Nanotechnology since 2015 and continue to be published.

In the case of wheat (see application, Fig. П1), the results differ from those obtained for the growth and development of maize (see application, Fig. П2–П5) under composite films. Firstly, under all composite films, the plants exhibited significantly enhanced development compared to the control film. Regarding the growth and development of wheat, the most pronounced acceleration was observed under the ZB1/0.5% and ZB3/0.5% composites. ZB2/0.1% and ZBВ/0.5% showed similar results. These results for maize and wheat were obtained on May 22, 2024.

The following results were obtained on May 31, 2024.

As indicated by the provided data, plants under the composite films exhibit rapid development and grow strong and healthy. The following results regarding the growth and development of plants, including tomatoes (see application, Fig. П6–П10), are from May 31, 2024.

The following photographs (see application, Fig. П11–П15) show the results of plant development under various films, taken on June 10, 2024.

According to the provided data, under the control film, tomato leaves curl due to insufficient moisture. This can be explained by the fact that composite films reduce water loss by 4-6 times, which is particularly important for regions facing water scarcity.

Conclusion

The conducted field tests of the composite films yielded the following findings:

• it has been established that activation through the pulsed tunneling effect leads to significant changes in the structure of materials and enables control over their properties;
• composite films facilitate rapid growth and development of plants;
• the thermo-mechano-chemical method combined with PTE activation shows promise for scaling functional materials.

 

Приложение

Application

 

Рис. П1. Развитие пшеницы под различными композитами

Fig. П1. Development of wheat under different composites

 

Рис. П2. Развитие кукурузы под композитом ZB1

Fig. П2. Development of corn under ZB1 composite

 

Рис. П3. Развитие кукурузы под композитом ZB2

Fig. П3. Development of corn under ZB2 composite

 

Рис. П4. Развитие кукурузы под композитом ZB3

Fig. П4. Development of corn under ZB3 composite

 

Рис. П5. Развитие кукурузы под композитом ZBB

Fig. П5. Development of corn under ZB3 composite

 

Рис. П6. Развитие томатов под обычной пленкой

Fig. П6. Development of tomatoes under regular film

 

Рис. П7. Развитие томатов под композитом ZB1

Fig. П7. Development of tomatoes under ZB1 composite

 

Рис. П8. Развитие томатов под композитом ZB2

Fig. П8. Development of tomatoes under ZB2 composite

 

Рис. П9. Развитие томатов под композитом ZB3

Fig. П9. Development of tomatoes under ZB3 composite

 

Рис. П10. Развитие томатов под композитом ZBB

Fig. П10. Development of tomatoes under ZBB composite

 

Рис. П11. Развитие растений под обычной пленкой

Fig. П11. Development of plants under ordinary film

 

Рис. П12. Развитие растений под ZB1

Fig. П12. Development of plants under ZB1

 

Рис. П13. Развитие растений под ZB2

Fig. П13. Development of plants under ZB2

 

Рис. П14. Развитие растений под ZBB

Fig. П14. Development of plants under ZBB

 

Рис. П15. Развитие растений под ZB3

Fig. П15. Development of plants under ZB3

About the authors

Rustam Kh. Rakhimov

Institute of Materials Science of the SPA “Physics-Sun” of the Academy of Science of Uzbekistan

Author for correspondence.
Email: rustam-shsul@yandex.com
ORCID iD: 0000-0001-6964-9260
SPIN-code: 3026-2619

Dr. Sci. (Eng.), Head, Laboratory No. 1

Uzbekistan, Tashkent

Vladimir V. Pankov

Belarusian State University

Email: pankovbsu@gmail.com
ORCID iD: 0000-0001-5478-0194

Dr. Sci. (Chem.), Professor

Belarus, Minsk

Vladimir P. Yermakov

Institute of Materials Science of the SPA “Physics-Sun” of the Academy of Science of Uzbekistan

Email: labimanod@uzsci.net
ORCID iD: 0000-0002-0632-6680
SPIN-code: 8907-1685

senior research, Laboratory No. 1

Uzbekistan, Tashkent

Temur S. Saidvaliev

Institute of Materials Science of the SPA “Physics-Sun” of the Academy of Science of Uzbekistan

Email: t.saidvaliyev@imssolar.uz
ORCID iD: 0009-0008-6473-9214

chief engineer

Uzbekistan, Tashkent

Zhasurkhon Kh. Rashidov

Institute of Materials Science of the SPA “Physics-Sun” of the Academy of Science of Uzbekistan

Email: labimanod@uzsci.net
ORCID iD: 0000-0001-5167-1312

junior researcher, Laboratory No. 1

Uzbekistan, Tashkent

Murod R. Rakhimov

Institute of Materials Science of the SPA “Physics-Sun” of the Academy of Science of Uzbekistan

Email: rustam-shsul@yandex.com
ORCID iD: 0000-0003-0686-5681

junior researcher, Laboratory No. 1

Uzbekistan, Tashkent

Khurshid K. Rashidov

Institute of Materials Science of the SPA “Physics-Sun” of the Academy of Science of Uzbekistan

Email: labimanod@uzsci.net
ORCID iD: 0000-0002-9744-6249

senior researcher, Laboratory No. 1

Uzbekistan, Tashkent

References

Supplementary files