TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The metal substrate is copper, copper alloys, aluminum, aluminum alloys, stainless steel and/or iron alloys.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The concavities have depths of 0.2-10 mu m. The first coating layer has a thickness of 20-300 mu m. The first coating layer comprises a polyphenylene sulfide resin and titanium dioxide particles having an average diameter of 200-500 nm. The weight ratio of the polyphenylene sulfide resin to titanium dioxide is 1-15 (preferably 4-8). The second coating layer comprises a polyphenylene sulfide resin and an inorganic material comprising glass fibers, carbon fibers, aromatic polyamide fibers, calcium carbonate, magnesium carbonate, silicon dioxide and/or talcum powder. Preferred Composition: The mixture comprises a polyphenylene sulfide resin and an inorganic material. The slurry comprises a polyphenylene sulfide resin, an organic solvent, titanium dioxide, a coupling agent, and water. Preferred Process: The calcining step is performed under 300-350 degrees C for 10-60 minutes. EXAMPLE - A copper substrate was cut into a rectangular substrate with a size of 10 cm x 2 cm x 0.2 mm. The surface was polished with a 150 grit abrasive paper for 2 minutes. The substrate was immersed into ethanol, acetone or detergent solutions for 30 minutes. Then the substrate was cleaned with running water. The substrate was immersed into a sodium persulfate solution with a weight concentration of 25% for 3 minutes. The substrate was cleaned by running deionized water. The substrate was dried in air. Polyphenylene sulfide resin powder (7 g), titanium dioxide (5 g), ethanol (60 g), and deionized water (5 g) were mixed and dispersed by an ultrasonic machine to form a slurry. The slurry was sprayed onto the metal substrate by a spray gun with a nozzle diameter of 0.3 mm. The coating process was performed by more than one time under a pressure of 1.5 atmosphere, to form a coating layer of a thickness of 150 mu m. The metal substrate was calcined at 330 degrees C and an atmosphere of helium for 20 minutes. The substrate was quenched in water to provide a precast metal substrate. A polyphenylene sulfide resin, a glass fiber, and talcum powder were mixed at a weight ratio of 1:1:1. The mixture was granulated in a twin screw extruder to form a mixture. The substrate was placed in an injection molding machine and 70 g of the mixture was injected into the machine to provide a metal-resin composite.