Atmospheric pressure hydrolysis without stirring and a combustion–calcination method were utilized to fabricate magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods. First, the β-FeOOH nanorods were fabricated via hydrolysis, and the concentration of Fe3+, hydrolysis temperature, and hydrolysis time were optimized. The optimal fabrication conditions were as follows: a 0.1 M FeCl3 solution was hydrolyzed at 90 °C for 2 h. The average length and diameter of the β-FeOOH nanorods fabricated under the optimal conditions were approximately 216 and 58 nm, respectively. Subsequently, Fe3O4/α-Fe2O3 heterogeneous nanorods were fabricated via a combustion–calcination process. The volume of absolute ethanol, calcination temperature, and calcination time were investigated to optimize the fabrication conditions of Fe3O4/α-Fe2O3 heterogeneous nanorods under the following conditions: absolute ethanol: 50 mL; calcination temperature: 300 °C; and calcination time: 2 h. Magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods fabricated under optimal conditions were characterized with an average length of 199 nm, an average diameter of 51 nm, a zeta potential of +17.2 mV, and a saturation magnetization of 13 emu·g–1.

In order to convert the high pressure common rail system engine to CNG/Diesel dual fuel engine, an electronically controlled system is developed. The system includes a CNG fuel supply system, the CNG electronic control unit (ECU) and its matching harness etc. During starting and idle load conditions, the engine runs under pure diesel mode, when the speed and load reached a certain set point, the diesel ECU reduces the pilot diesel quantity, meanwhile, the CNG ECU increases the natural gas quantity, then the engine runs under dual fuel mode. The engine experiment data show that in different conditions, the highest substitution rate is 90% and the average substitution rate is 83%; the average savings ratio of operation cost per hour is 26%.