Papers by Author: Shen Dong

Abstract: The nose roundness is one of the most important indexes of lapping quality of rounded diamond cutting tools. Due to its special characters and requirements, a new measuring method was proposed based on atomic force microscope (AFM) and precision-revolution spindle. However, in the measurement the alignment errors of tools with the spindle axis have great influence on the measuring result. By a carefully deducting, the relations between the deviation and the alignment errors were presented. The deviation increases with the eccentric linearly, and has the same value with the eccentric. But it varies with θ dramatically and forms a parabola curve when the deflection angle is negative, otherwise, varies with θ gently and forms a flat Gaussian curve.

Abstract: Optics with free form surface can be achieve special imaging effects and reduce component amounts in optical systems. However, it is difficulty to fabricate high accuracy, damage-free optical surface with free form surfaces by conventional method. Atmospheric plasma machining is a non-contact chemical processing method which can fabricate optics without damaged layer. Numerical controlled atmospheric pressure plasma machining (NC-APPM) method is proposed to machine optical free form surfaces. A new atmospheric pressure plasma jet generator was designed to get Gaussian rotational symmetry removal spot and the spot maximum diameter is 1.5mm. Base on dwelling time algorithm, a sinusoidal wave structure, the pitch 2mm and the amplitude 500 nm, is fabricated on a pre-polished flat silica quartz surface using three-axis numerically controlled machine made by ourselves. The result shows that the amplitude error is 59 nm compare to the expectation value surfaces using numerical controlled atmospheric plasma machining method.

Abstract: As the dimensions of parts become smaller, understanding the mechanical properties of these small components was becoming more important. Till present day, the methods and technology used to investigate the deformation behavior in nanoscale were still lacking. In this paper, the specimens were single crystal copper wires with diameter in 50 microns. Atomic force microscope integrated with an in- situ tensile system were used to determine the mechanical behavior of copper wires and observe the surface topography deformation in nanoscale simultaneously. The results were as follows: the modulus of elasticity, tensile strength and failure strain of the sample were 167Gpa, 0.564GPa and 0.011, respectively. By using AFM, the separation process between the copper wire and impurities on it, such as oxide film, was observed. The nanoscale deformation process of the copper wire was also obtained.

Abstract: Parallel grinding is an effective method of aspheric moulds machining which is usually made of industrial ceramic such as silicon carbide (SiC) or tungsten carbide (WC), but if the spherical grinding wheel is not being with precision truing and dressing, the roughness and form accuracy of the ground aspheric surface should get worse, for this reason, in this paper, the influence factors of thoroughness and form accuracy induced by the wheel truing and dressing are studied firstly, and a new 3-axis CNC Ultra-precision grinding system which is based on the PMAC (Programmable Multi-axes Controller) is developed, through simultaneous motion of the controlled X, Z and B axis, the form errors which is induced by the grinding wheel can be improved theoretically, and the aspheric mould machining test shown that the surface roughness of Ra 0.025μm and the form accuracy of P-V 1.15μm are achieved.

Abstract: Mechanical scratching and chemical self-assembling can be combined to fabricate nano- or micro-scale functional structures on the oxide-coated silicon. The chemo-active species, such as NO2C6H4 groups, can be produce from aryldiazonium salt due to the breaking of chemical bond of silicon substrate when the diamond tool scratches the silicon sample in the presence of 4-benzoic nitryl diazonium tetrafluoroborate (NO2C6H4N2BF4). They may then induce grafting of an organic monolayer on the substrate via Si-C connection. The surface morphologies before and after chemomechanical reaction are characterized with Atomic Force Microscopy (AFM). We propose that chemomechanical reaction, which occurred during scratching the silicon surface, produce NO2C6H4 groups from aryldiazonium salt. The NO2C6H4 groups further bond with surface Si atoms via Si-C covalent bonds as confirmed from Infrared Spectroscopy (IR) results. To better understand the framework of the self-assembly monolayers (SAMs) on Si (100) surface, the first principles calculation at density functional theory levels has been employed to investigate the binding energy, bonds length and bonds angle. The reduced energy of system illuminates that the SAMs can be fabricated easily between aryldiazonium salt and Si (100) surface. The stability of system can be improved and SAMs can firmly stay on Si (100) surface.

Abstract: The equations correlated the normal load and the tip penetration depth were derived through the theoretical analysis of the penetration process of the diamond tip. Verified by experiments, the equations can reflect the penetration process of the scratching machining system and provide theoretical basis for the optimization of depth control algorithm. The control of scratching depth realized in AFM deflection mode can effectively restrain the system drift during scratching process.

Abstract: This study aimed to establish the coordinate transformation between the off-axis aspherics coordinate system σ and the axial symmetry aspherics coordinate system σ by transforming coordinates and present the computation models of asphericity in rectangular coordinate system and cylindrical coordinate system respectively. The asphericity expressions in both coordinate systems were applicable to the comparative sphere calculation of Off-axis aspherics with different figures. We selected an Initiation sphere in view of technology, along with equations in a right coordinate system for certain caliber and structure. Then, by numerical computation, we selected the best fitting sphere and simplifed the complex models by choosing a right coordinate system. At last, the solution for asphericity and the best fitting sphere curvature radius of off-axis aspherics were introduced by examples.

Abstract: Ultrathin block copolymer films are promising candidates for bottom-up nanotemplates in hybrid organic-inorganic electronic, optical, and magnetic devices. Key to many future applications is the long range ordering and precise placement of the phase-separated nanoscale domains. In this paper, a combined top-down/bottom-up hierarchical approach is presented on how to fabricate massive arrays of aligned nanoscale domains by means of the self-assembly of asymmetric poly (styrene-block-ethylene/butylenes-block-styrene) (SEBS) tirblock copolymers in confinement. The periodic arrays of the poly domains were orientated via the introduction of AFM micromachining technique as a tool for locally controlling the self-assembly process of triblock copolymers by the topography of the silicon nitride substrate. Using the controlled movement of 2- dimensional precision stage and the micro pressure force between the tip and the surface by computer control system, an artificial topographic pattern on the substrate can be fabricated precisely. Coupled with solvent annealing technique to direct the assembly of block copolymer, this method provides new routes for fabricating ordered nanostructure. This graphoepitaxial methodology can be exploited in hybrid hard/soft condensed matter systems for a variety of applications. Moreover, Pairing top-down and bottom-up techniques is a promising, and perhaps necessary, bridge between the parallel self-assembly of molecules and the structural control of current technology.

Abstract: As there are always certain defects on the final surface of large-scale lightweight mirrors, which are formed in traditional mechanical polishing process, such as microcracks, lattice disturbances, plastic deformation, and so on, an atmospheric pressure plasma polishing method is a good solution to this problem. As a key component, the design of the capacitance coupling atmospheric pressure radio-frequency plasma torch is introduced. The designed torch uses water cooled coaxial aluminium electrodes with special treatment to avoid arcing between them. In normal machining process, the mixture of reaction gas and plasma gas with optimum ratio is input into the plasma torch. Then, excited by radio-frequency power, reaction gas is ionized in the plasma so as to create high density and energy reactive radicals under atmospheric pressure. The radicals cause chemical reactions with the atoms on the part surface, which performs an effective atomscale removal process. As the machining process is chemical in nature, this method avoids surface/subsurface defects mentioned above. Furthermore, initial experiment data analysis has proved that the atmospheric pressure plasma polishing method is effective and reliable, as well as demonstrates the validity of the designed plasma torch.

Abstract: An advanced conditioning technique was developed to precisely and effectively condition the nickel electroplated mono-layer coarse-grained diamond grinding wheel of 46m and 91m grain size with an aim to fabricate Diamond Micro Tool Arrays (DMTA), to meet the high demands of form accuracy, surface quality and low subsurface damage in ductile machining of silicon carbide (SiC). The precision machining experiments on SiC were carried out on a precision grinder to determine the applicability of these fabricated diamond micro tool array (DMTA). The experimental result indicates that the newly developed DMTA is applicable and feasible to realize ductile machining on SiC with high efficiency and low diamond tool wear rate, which shows a good prospect to apply this new concept diamond tool type in precision machining of SiC, as well as the other brittle and hard-to-machine materials.