Taiwanese researchers have produced new graphene composites that can effectively reduce the LED temperature and thus greatly increase the lifetime of the LED.
Light-emitting diodes (LEDs) are rapidly gaining popularity in the world. They are well-known for their high brightness, low power consumption and durability, and have replaced incandescent and fluorescent lamps in many applications. However, few people know that although LEDs do not radiate heat outward, they generate heat at the junction of the semiconductor, which reduces the life of the LED, even for low-power LEDs. With the demand for higher power of LED lights, how to control temperature has become a big challenge.
At present, Taiwan researchers have developed a kind of aluminum heat sink that can really replace heavy and hard aluminum. The research team claims that the use of a heat sink made of polyamide (PA) and reduced graphene oxide (rGO) enables more efficient heat dissipation inside the LED lamp.
The researchers used titanate coupling agents (TCA) as bridge molecules for the reduction of graphene oxide and polyamide, resulting in a 53% increase in thermal conductivity of dense nanocomposites compared to polymers used alone. They tested two different components (one with polyamide and the other with polyamide/titanate-graphene), applying both materials to the LED and using heat Imaging and thermocouples were analyzed.
The polyamide/titanate-graphene material has a higher equilibrium temperature, which indicates that the material has a faster heat transfer rate than the polyamide material. The researchers tested the durability of the composite and the results showed that the high temperature at the joint would degrade the performance of the LED during continuous use. The results show that the composite retains 95% of its light intensity, while the polyamide single component material retains only 69%.
In fact, the research team has developed a thermoplastic material that is comparable in thermal performance to more expensive graphene and can be molded using an injection molding process that is easy to control. This material helps to produce low cost, light weight, flexible LED heat sinks and also increases the life of the LEDs.
The research results have been published in Carbon.
Lead-acid is the oldest rechargeable Battery in existence. Invented by the French physician Gaston Planté in 1859, lead-acid was the first rechargeable battery for commercial use. 150 years later, we still have no cost-effective alternatives for cars, wheelchairs, scooters, golf carts and UPS systems. The lead-acid battery has retained a market share in applications where newer battery chemistries would either be too expensive.
Lead-acid does not lend itself to fast charging. Typical charge time is 8 to 16 hours. A periodic fully saturated charge is essential to prevent sulfation and the battery must always be stored in a charged state. Leaving the battery in a discharged condition causes sulfation and a recharge may not be possible.
Finding the ideal charge voltage limit is critical. A high voltage (above 2.40V/cell) produces good battery performance but shortens the service life due to grid corrosion on the positive plate. A low voltage limit is subject to sulfation on the negative plate. Leaving the battery on float charge for a prolonged time does not cause damage.
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