Stable Nd2Fe14B powders of refined grain size of 0.1-1.0 mu m were prepared using a combination of the rapid quenching (of the melt into thin ribbons), mechanical attrition and grain-surface passivation (or surface hardening) and coating by a thermally rigid, adhesive and corrosion-proof material in air. The ribbons (of 15-30 mu m thickness) were cut, crushed and milled under H-2 gas at approximately 1 bar and room temperature to give hydrided Nd2Fe14BHx less than or similar to 5, flakes of 1-5 mu m sizes, which are brittle and easily obtained in powder form by high-energy ball milling. The interstitial H atoms in the hydride sample were desorbed by slowly heating (5 degrees C min(-1)) the sample between 25 and 600 degrees C in N-2 gas (which helps the desorption of the H atoms without decomposition of the sample) in a reactor and then pumping off the total gas at 600 degrees C. The H-desorbed specimen, when annealed at 600-800 degrees C under a dynamic vacuum, results in a refined powder, showing a characteristically high remanence, J(r) of 9-12 kG, together with a high intrinsic coercivity, H-ci, of 10-28.3 kOe, depending on the size and surface structure of the grains. This powder is highly pyrophoric and catches fire in open air but can be stabilized by passivating and coating the grain surfaces with a mixture of carbon, AlN and Nd2O3 by milling the mixture in a suitable organic liquid (to allow the additives to adhere the sample without excess oxidation) followed by annealing at an elevated temperature in N-2 gas at approximately 1 bar. In this process, the separated Nd2Fe14B grains acquire a thin nitride-carbide (probably amorphous) stabilized surface passivation layer which prevents further oxidation of the sample in air at room temperature. The passivation layer, in combination with a thin film of the Nd-rich intergranular phases, if any, peculiarly appears to be non-magnetic compared with the main ferromagnetic Nd2Fe14B phase. It keeps the ferromagnetic Nd2Fe14B grains separated and thus inhibits mixing between the local magnetic lines of forces confined to them. As a result, they behave like ideal single-domain particles and therefore exhibit a reasonably improved H-ci value, without a significant decrease in the high J(r) or the high saturation magnetization M-s which are useful for the high-energy-density magnets and related devices and components. The results are modelled and discussed with microstructures, magnetic properties, thermal stability and loss, if any, in the mass of the specimens during exposure to ambient atmosphere.