WC and Co by the composition of tungsten cobalt-based carbide with excellent hardness and wear resistance and other properties, is a widely used tools, structural materials. However, there is a rejection phenomenon between the transverse rupture strength and the hardness in the tungsten-cobalt type cemented carbide, that is, the hoisting strength will damage the hardness, and the hardness will be weakened by the increase of the hardness. This is a technical problem that has been difficult to solve. The results show that the microstructure with ultra-fine grain characteristics of tungsten and cobalt type cemented carbide, can achieve strength and hardness of the synchronous upgrade; general requirements, the grain size of 0.2 to 0.5 microns of tungsten cobalt-based hard alloy can be called super Fine grain hard alloy. However, in the sintering stage of the preparation of WC-Co cemented carbide, grain growth occurs. In order to achieve tungsten cobalt-based carbide fine grain size, generally from two aspects. Conventional method is to WC and Co mixed powder as raw materials, milling after mixing granulation, and then press forming, and then pressure sintering. In order to avoid grain growth, the grain growth inhibitor such as VC and Cr2C3 was added to the mixed powder. Another idea is the use of small grain size of WC-Co composite powder as raw material. The WC-6% Co composite powder prepared by spray-transformation, calcination and low-temperature reduction carbonization process was used as the raw material. The average grain size was below 50 nm and the distribution was uniform. The ultrafine WC-Co tungsten carbide with grain size of about 400 nm was successfully prepared by wet grinding, forming and pressure sintering without adding grain growth inhibitor, and good results were obtained.

The microstructures of the composites prepared by the composite powders show that the size of WC grains is smaller than 0.5 micrometers, and the size distribution of WC grains is uniform. Bonding, bridging phenomenon is greatly reduced, part of the grain edges and corners dissolved dissolved, the edge is more smooth, so that the application of the alloy is not prone to excessive concentration of stress. These are beneficial to improve the mechanical properties of materials. However, the WC grains in the alloy prepared by the traditional method have abnormal growth phenomenon, which will seriously damage the mechanical properties of ultra-fine cemented carbide.

The strength and hardness of ultrafine WC-Co cemented carbide prepared by composite powder were higher than that of the traditional mixed powder preparation. The tensile strength of the composites was 4304N / mm2, which was much higher than that of the samples prepared with mixed powders (3200N / mm2). The hardness of the composite powders was 93.1HRA, which was also superior to that of the mixed powders The hardness of the sample was prepared (91.5 HRA). The results show that the grain size of the composite powder is small, the average grain size is below 50 nm and the distribution is uniform. The component distribution of the composite powder is uniform, and the distribution of W, C and Co is related to the molecular homogeneity. .

Their experiments also found that the composite powder prepared by ultrafine WC-Co cemented carbide prepared with the traditional method of the material in the coercivity value of the significant difference. According to the analysis, when the content of Co in the alloy is the same, as the grain size of WC decreases, the Co phase dispersion increases, the mean free path decreases and the coercive force increases. The coercivity of the composite powder was 34 kA / m, and the sample prepared by the conventional method was 26.7 kA / m. It is also proved that the WC grain size of the ultrafine WC-Co cemented carbide prepared by using composite powder as raw material is smaller than that of the traditional mixed powder.

The United States is pursuing more investigations into Chinese firms with North Korea  sanctions against a Chinese trading company suspected of supporting North Korea's nuclear weapons development.

Daniel Fried, the U.S. State Department's coordinator for sanctions policy, said the investigations are underway during a U.S. Senate hearing on East Asia and the Pacific, Yonhap reported.

"We're investigating. The Treasury and State are investigating firms around the world," Fried said. "There are no limits and there is no administration red line of exempt countries or companies. We go where the evidence takes us." Fried said it is very effective to convey to Chinese banks and companies that trade with North Korean firms under sanctions is dangerous and not worth the trouble, according to the report.

The State Department official also said sanctions measures are not mere slogans. "Our actions on Monday indicate that Chinese companies are not off limits. That news will spread around the Chinese community. We can also use various means to get the word out to Chinese businesses and banks that we are serious," he said.

On Monday the U.S. Treasury announced Hongxiang Industrial, suspected of sending banned material to North Korea, had been placed under unilateral sanctions. Washington is taking action against the company's chief executive Ma Xiaohong, a 44-year-old businesswoman who founded the company in 2000, and three other members of her organization.

Hongxiang Industrial is believed to have exported aluminum oxide, ammonium paratungstate, and tungsten trioxide to North Korea, dual-use items that could have been placed into military use. Aluminum oxide can be used in developing the centrifuges used in uranium enrichment.

Fried also said investigations are underway into Air Koryo, North Korea's commercial airliner.

An international research team has used tungsten oxide thermal metamaterial to control the emission of radiation at high temperatures, an advance that could bring devices able to efficiently harvest waste heat from power plants and factories. Roughly 50 to 60 percent of the energy generated in coal and oil-based power plants is wasted as heat. However, thermophotovoltaic devices that generate electricity from thermal radiation might be adapted to industrial pipes in factories and power plants, as well as on car engines and automotive exhaust systems, to recapture much of the wasted energy. In new findings, researchers demonstrated how to restrict emission of thermal radiation to a portion of the spectrum most needed for thermophotovoltaic technology.

"These devices require spectrally tailored thermal emission at high temperatures, and our research shows that intrinsic material properties can be controlled so that a very hot object glows only in certain colors," said Zubin Jacob, an assistant professor of electrical and computer engineering at Purdue University. "The main idea is to start controlling thermal emission at record high temperatures in ways that haven't been done before." The thermal metamaterial – nanoscale layers of tungsten oxide and hafnium oxide – was used to suppress the emission of one portion of the spectrum while enhancing emission in another.

The basic operating principle of a photovoltaic cell is that a semiconducting material is illuminated with light, causing electrons to move from one energy level to another. Electrons in the semiconductor occupy a region of energy called the valence band while the material is in the dark. But shining light on the material causes the electrons to absorb energy, elevating them into a region of higher energy called the conduction band. As the electrons move to the conduction band, they leave behind "holes" in the valance band. The region between both bands, where no electrons exist, is called the band gap.

Future research will include work to convert heat radiation from a thermal metamaterial to electron-hole pairs in a semiconducting material, a critical step in developing the technology. The thermophotovoltaic technology might be ready for commercialization within seven years, Jacob said.

The Treasury Department and Justice Department took the measures on Monday, saying that the company and the individuals conspired to aid North Korea’s nuclear weapons program in violation of US economic sanctions.

The measures were taken against 44-year-old Ma Xiaohong and her conglomerate based in China's frontier city of Dandong for money laundering and evading sanctions.

The Treasury Department accused the firm, Dandong Hongxiang, and a host of officials of making up a "key illicit network supporting North Korea's weapons proliferation."

Adam J. Szubin, acting undersecretary for terrorism and financial intelligence at the Treasury Department, said, “Treasury will take forceful action to pressure North Korea’s proliferation network and to protect the US financial system from abuse.”

Dandong Hongxiang had over $530 million worth of trade with North Korea from 2011 to 2015, according to a report by the Asian Institute for Policy Studies in Seoul and C4ADS in Washington. The amount could have been enough to help North Korea fund its uranium enrichment facilities, and to design, make, and test its nuclear weapons, the report said.

Among the items traded, there were aluminum ingots, aluminum oxide, ammonium paratungstate and tungsten trioxide as well as materials used in nuclear enrichment centrifuges and missile design.

Tungsten trioxide can be used in making more aerodynamically stable missiles, while aluminum oxide is used to resist corrosion in gas centrifuges during uranium enrichment, according to Asan. It said those could qualify as "potential military and nuclear dual use products" under U.S. Department of Commerce restrictions.

The three other individuals who were targeted include Zhou Jianshu, Hong Jinhua and Luo Chuanxu, who can no longer do business with American individuals or companies. The department also sought to seize 25 bank accounts controlled by Dandong Hongxiang, because it said they "represent property involved in money laundering."

The move came after Pyongyang conducted its fifth nuclear test on September 9. It also tested a submarine-launched ballistic missile in August. South Korean officials say the North is physically ready to conduct its sixth nuclear test.

Pyongyang says it will continue to develop nuclear weapons as a “deterrence” measure against America’s military aggression.