Expansion Valves are devices used to control the refrigerant flow in a refrigeration system. They remove pressure from the liquid refrigerant to allow expansion or change of state from a liquid to a vapor in the evaporator. Expansion valves serve two purposes: controlling the amount of refrigerant entering the evaporator and maintaining the pressure difference between the condenser (high-pressure side) and the evaporator (low-pressure side). Thermal Expansion Valve, Thermostatic Expansion Valve, Automatic Expansion Valve, Electronic Expansion Valve NINGBO BRANDO HARDWARE CO.,LTD , https://www.brandopneumatic.com
The main types of expansion valves are as follows.
1. Thermal Expansion Valve (TEV)
2. Electronic Expansion Valve
3. Automatic Expansion Valve
4. Manual Valve
5. Capillary Tube
6. Float Valve
**Abstract**
Synthetic diamonds in China have gone through 50 years of development. My mother, Guo Yongcun, and my father, Li Zhihua, have been working in this field for half a century. After graduating from university, I also joined the research and manufacturing of synthetic diamonds. Under the guidance of my mother’s father, my cousins, and other relatives, more than 100 people are involved in the diamond industry, which is known as a "diamond family." Examples like ours are numerous in the superhard materials industry. Here, I want to highlight the glorious history of synthetic diamond development in China through my family's story and personal experience.
Diamonds, due to their unique beauty and extreme hardness, have captured human attention since ancient times. They were primarily used for decoration. The earliest recorded discovery of diamonds dates back to around 3000 BC in India. The ancient Greeks were aware of diamonds before the 5th century BC, likely introduced through trade with India. Today, there is a bronze statue in the British Museum with eyes made of unprocessed diamonds, showing how valuable they were even then.
Due to its high hardness, low specific heat, good thermal conductivity, high mechanical strength, corrosion resistance, temperature stability, and semiconductor properties, diamond has extensive industrial applications. However, natural diamond resources are limited, and China lacks large-scale natural deposits. Despite reports about a massive Russian diamond mine, China still relies heavily on synthetic diamonds to meet industrial demands. Developing synthetic diamond technology is crucial to avoid dependency on external sources.
In 1797, British chemist S. Tennant burned a diamond in a sealed gold container filled with oxygen and identified carbon dioxide, proving that diamonds are made of pure carbon. This discovery was later confirmed by measuring the weight of the gas, which matched the original diamond. In the late 18th century, it was finally established that diamonds are an allotrope of carbon, a rare mineral composed of the same element found in coal.
The study of synthetic diamonds began long ago but remained theoretical until 1955 when General Electric successfully synthesized diamonds using high-pressure and high-temperature methods. Although China started later than the US and Sweden, it has developed rapidly and is now a global leader in the field.
My parents graduated from the Central South Institute of Mining and Metallurgy and were assigned to the Zhengzhou Abrasives Grinding Research Institute in the early 1960s. They contributed significantly to the development of superhard materials. My mother participated in projects such as diamond drill bits and circular saw blades, while my father worked on synthetic diamond sorting, purification, and catalyst development. Together with others, they published key texts like *Diamond Manufacturing* and *Synthesis and Application of Diamond*, laying the foundation for the industry.
The “121†project, launched in 1960, marked a milestone in China's synthetic diamond research. Jointly led by Zhengzhou Abrasives Grinding Research Institute, Hefei General Machinery Research Institute, and Beijing Institute of Geological Sciences, the team completed the first successful synthesis of artificial diamonds in 1963. Despite harsh conditions and limited resources, the team overcame challenges and laid the groundwork for future advancements.
The first synthetic diamonds were not visually impressive, appearing as small, dark particles under a microscope. However, through rigorous testing and analysis, the team confirmed their identity as true diamonds. This achievement marked the beginning of China's self-reliance in diamond production.
Over the decades, China's synthetic diamond industry has grown exponentially. Companies like Zhongnan Diamond Co., Ltd., Henan Huanghe Cyclone, and Shenzhen Yongcun Diamond Tools have become leaders in the field. Today, China produces over 90% of the world's synthetic diamonds, with applications ranging from industrial tools to consumer goods.
The development of superhard materials in China has followed three main stages: initial breakthroughs in the 1960s, expansion in the 1970s and 1980s, and rapid growth in the 1990s and beyond. The industry has evolved from small-scale operations to large, technologically advanced enterprises.
Looking ahead, continued investment in research and innovation will ensure China remains at the forefront of superhard materials. The spirit of perseverance, collaboration, and creativity displayed by the pioneers of this field continues to inspire new generations.
Author: Li Han, born in 1974, graduated from Shenzhen University in 1996 with a bachelor's degree in Control and Mechanical Engineering. He is currently the general manager of Shenzhen Yongcun Diamond Tools Co., Ltd.