When Sand Wears 'Nano Raincoat'

In the exhibition hall of Xi'an Meinan Biotechnology Co., Ltd. (Maenam High-Tech), an experiment catches visitors' eye: Water is poured onto ordinary sand and it quickly seeps through. But when poured onto water-resistant sand, the droplets roll across the surface of the grains without penetrating at all.

This independently developed micro- and nano-scale coating technology enables sand grains to prevent water loss while retaining and storing water, effectively giving each grain a "nano raincoat."

Tackling coating barriers

Lu Wei, founder and chairman of Maenam High-Tech, first encountered the challenge of preventing water leakage while working on tunnel construction projects early in his career.

Organic waterproof membranes are prone to rapid aging and leakage at joints, so Lu thought about developing a kind of waterproof material that is durable and environmentally friendly. The rainy engineering environment in Thailand reinforced this idea.

The R&D began in 2021. The biggest challenge was forming a dense, stable waterproof coating on the rough surfaces of sand grains — one that was robust and heat-resistant enough to withstand abrasion from windblown sand.

The team tried dozens of solutions, but in vain. The breakthrough came from optimizing the material formulation.

They mixed dozens of ore bodies in a certain proportion and achieved coordination effects by micro- and nano-scale grinding technology. Rather than adopting the conventional spraying methods, the team chose the physical, high-temperature and high-pressure technology to make sure that the waterproof coating adheres evenly to the surface of the sand grains.

By the end of 2022, the team managed to build a stable micro- and nano-scale coating structure on sand grains, and the key performance indicators, including water resistance, adhesion and durability, all met the required standards.

Exploring diverse application scenarios

The hydrated water-retaining agent developed by Maenam High-Tech can absorb more than 1,200 times its own weight in water. The innovative "waterproof sand + water-retaining agent" mode can firmly hold rainwater or irrigation water at the roots of plants, greatly reducing evaporation.

This solution has found its place in restoring ecology in extreme environments. Domestically, it has been adopted to address desertification in the Taklimakan Desert, northwest China's Xinjiang Uygur autonomous region, and the Kubuqi Desert in north China's Inner Mongolia autonomous region.

The products have also been sold to over 40 Belt and Road partner countries, including the United Arab Emirates, Saudi Arabia and Türkiye. A desert greening project in Dubai used a whole set of solutions provided by the company.

Li Xiaobo, general manager of Maenam High-Tech, said they launched a new product named "Mars Water-Retaining Sand," a new material specifically developed for extreme environment in deep space like Mars and the Moon.

Able to block, retain and store water, the material remains stable in super large temperature fluctuation between -90℃ and 250℃. This precisely matches the characteristics of soil on Mars and solves the problem of water control in extreme environments.

Customized service brings customers

Domestic customers were satisfied with their products and recommended them to overseas partners, Li said. That was how they gained cooperation opportunities with customers from Guyana in South America.

According to Li, customers in South America have two distinct requirements for the material: vibrant colors and durability. The company's waterproof colored sand meets both requirements.

Most of the waterproof materials in the market are organic, which eventually leads to problems like oxidation, paint peeling and cracking, Li said. Maenam High-Tech develops inorganic materials, with its products designed to last as long as the buildings themselves.

The exported waterproof-colored sand comes in a wide range of colors and has self-cleaning properties, allowing rainwater to wash away surface dirt and leave the walls looking fresh and clean.

During this year's spring Canton Fair in Guangzhou in south China, there were prospective customers from South Africa, the Middle East, Southeast Asia and part of Europe. "Our goal is clear: to become a global leader in the field of eco-friendly new materials and to let hard tech set the trend," Lu said.

Source: Science and Technology Daily