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The influence of P content on Curie temperature, magnetic properties and microstructures of Fe81.5Si3B10+xP3.5−xC0.2Cu0.8Nb1 (x = 0, 1, 2, and 3 at.%) alloys subjected to magnetic field annealing has been studied. Here, the decrease in P content can improve Curie temperature of alloys from about 575 to 584 K, which increases the operating temperature of magnetic device. Via optimal field annealing technique, the amorphous alloy with x = 3 exhibits good soft magnetic properties, including saturation magnetic flux density of 1.53 T, high effective permeability above 12,000, low coercivity below 3 A/m, and low core loss around 0.18 W/kg. The hysteresis loops show that tuning down the content of P relative to B can increase the saturation magnetic flux density of alloy system. Besides, the investigation about the microstructures of alloys annealed at optimal conditions indicates that longitudinal magnetic field annealing can improve the stability of amorphous phase, thereby ensuring the amorphous structure annealed at a higher annealing temperature compared with the general annealing for alloys.

Phosphorus (P) is a cheap and effective element that inhibits grain growth and improves soft magnetic properties in Fe-based nanocrystalline alloys. However, most alloys usually require high P content, leading to problems such as volatilization and oxidation during production process. In this paper, we study and report new findings regarding the effect of P microalloying on the magnetic properties, microstructure and magnetic domain structure of Fe77.8Si10B9−xCu0.6Nb2.6Px (x = 0 and 1) nanocrystalline alloys. The substitution of B by 1 at% P has little influence on the crystallization behavior, saturation magnetic flux density (Bs) and permeability (μ) of the alloy, while effectively reduces the coercivity (Hc) in a wide annealing temperature range. The reduced Hc can be attributed to the low magnetocrystalline anisotropy and wide magnetic domains caused by uniform and fine α-Fe(Si) grains. The mechanism of structural evolution induced by 1 at% P is also been discussed. The P microalloyed nanocrystalline alloy with high Bs of 1.43 T, high μ up to 27,000 at 1 kHz, and low Hc of 1.4 A/m is suitable for magnetic shielding piece of wireless charging.

The development of Fe-based nanocrystalline alloys with high saturation magnetization (Bs), excellent magnetic softness and good manufacturability is highly desirable. Here, the effect of substituting 1 at% P for B and Si on the thermal stability, microstructure and magnetic properties of Fe76Cu0.8Nb2.2B9Si12 alloy has been studied in detail. It was found that replacing B with P effectively reduces the coercivity (Hc) of the alloy without deteriorating the Bs and permeability (μ). However, replacing Si with P has little effect on the Hc and Bs, yet significantly reduces the μ. The variation in the magnetic properties can be well understood from the evolution of the microstructure and magnetic anisotropy induced by P microalloying. The Fe76Cu0.8Nb2.2B8Si12P1 alloy with a good processing window, a high Bs of 1.41 T, a great μ of 29,000 at 1 kHz and a low Hc of 0.6 A/m is suitable for high-power electronic devices.

The effect of Si/B ratio on the magnetic properties, microstructure, magnetic domain structure, and crystallization kinetics of Fe77Si10+xB9-xNb2Cu1Al1 (x=0, 1, 2 at%) nanocrystalline alloys has been investigated. The slight increase in Si/B ratio has minimal effect on the saturation magnetization of the alloys, but effectively increases the permeability and decreases the coercivity in a wide annealing temperature range. Substituting 2% Si for B significantly increases the activation energy of α-Fe(Si) growth and Fe3B precipitation, leading to the formation of uniform, fine and stable α-Fe(Si) grains. This structure is beneficial to reduce the magnetocrystalline anisotropy and magnetoelastic anisotropy of the alloy, and form wide and smooth-moving magnetic domains, thus significantly improving the soft magnetic properties.

There is abundant super heavy oil resource in the world, however, due to the very high viscosity and density, conventional steam stimulation process will result in high steam injection pressure and small heating area, leading to very bad development effect. To improve the development effect of steam injection in super heavy oil reservoirs, a compound stimulation enhanced thermal recovery technology is proposed. Steam injection is conducted through horizontal well assisted by carbon dioxide and oil-soluble composite dissolver, so this kind of technology is called HDCS for short. HDCS technology synthetically utilizes the physical and chemical characteristics of dissolver, carbon dioxide and steam, so that viscosity reduction, mixing and mass transfer, increasing energy and assisting cleanup of the three components are combined. In this paper, three-dimensional thermal recovery physical simulation experiment apparatus is used to conduct the comparison experiments between steam stimulation and HDCS stimulation, to analyze the development advantage and mechanisms of HDCS stimulation. Experimental results indicate that HDCS stimulation realizes the rolling replacement of viscosity reduction effect of dissolver, carbon dioxide and steam, keeping the oil in steam front with a low-viscosity, and enlarging the viscosity reduction range of super heavy oil by steam injection. Besides, the dissolver injection beforehand decreases the subsequent steam injection pressure, and the dissolution and release of carbon dioxide in super heavy oil can complement the reservoir energy. Compared with the condition after conventional steam stimulation, after HDCS stimulation the steam has larger swept volume and heating range, and the content of heavy component and viscosity of crude oil decreases by larger amplitude. The properties of super heavy oil are improved better than conventional steam stimulation. HDCS stimulation significantly improves the development effect of steam in super heavy oil reservoirs.