Showing papers on "Active surface published in 1984"

Etching: A Two-Dimensional Mathematical Approach

Abstract: A mathematical model for the etching of a semi-infinite active surface is presented. The model assumes that the transport of the active species occurs solely by diffusion. It is shown that, when the diffusion field propagates much faster than the etched surface, the problem can be solved by a singular perturbation technique, which distinguishes a near field in the area where the moving surface and the non-etchable mask meet, and a far field where edge effects may be disregarded to first order. The leading terms of a composite expansion are given, from which the shape of the moving boundary can be determined at all times.

Surface structure of iron catalysts for ammonia synthesis

Abstract: A brief review of existing data on ammonia synthesis catalysts has resulted in a mathematical model which demonstrates that the active surface of the iron is that of the (111) face. 7 references.

Reactive metal battery having continuous supply of cathode reactant

Abstract: An improved porous cathode structure (11) for use in a battery having a reactive metal electrode and flowed electrolyte. The cathode (10) is preferably formed of an electrically conducting porous material with categorically active surface (12) at an interface with the electrolyte. Alternatively the cathode (10) may be of an electrochemically reducible porous material and defines an active surface (12). Structure is provided for delivering electrochemically reducible cathode reactant material continuously through the cathode (10) to the cathode active surface (12) during operation of the battery. The reactant material is delivered in an amount required to be reduced at the active surface (12) to maintain high energy discharge rate with minimum amount of reactant material being utilized. The reactant material, in the illustrated embodiment, is provided from a storage supply (16) and delivered to the porous cathode (11) as needed during operation of the battery. In one form, the cathode (10) is provided with distribution passages (14) for conducting the reactant material therethrough. In another form, the reactant material is introduced through one or more edge portions of the cathode porous body (11) for flow through the pores to the active surface (12).

Method of making FETs in GaAs by dual species implantation of silicon and boron

Abstract: A method of preparing an active surface layer on a semi-insulating GaAs substrate comprising the steps of ion implanting a surface layer with silicon to form an n-type active layer and ion implanting a buried diffusion layer beneath the active layer with boron to prevent defects in the substrate from influencing the active region. The method is particularly useful for GaAs MESFETs.

Solid state radiative heat pump

Abstract: A solid state radiative heat pump (10, 50, 70) operable at room temperature (300° K.) utilizes a semiconductor having a gap energy in the range of 0.03-0.25 eV and operated reversibly to produce an excess or deficit of charge carriers as compared to thermal equilibrium. In one form of the invention (10, 70) an infrared semiconductor photodiode (21, 71) is used, with forward or reverse bias, to emit an excess or deficit of infrared radiation. In another form of the invention (50), a homogeneous semiconductor (51) is subjected to orthogonal magnetic and electric fields to emit an excess or deficit of infrared radiation. Three methods of enhancing transmission of radiation through the active surface of the semiconductor are disclosed. In one method, an anti-reflection layer (19) is coated into the active surface (13) of the semiconductor (11), the anti-reflection layer (19) having an index of refraction equal to the square root of that of the semiconductor (11). In the second method, a passive layer (75) is spaced from the active surface (73) of the semiconductor (71) by a submicron vacuum gap, the passive layer having an index of refractive equal to that of the semiconductor. In the third method, a coupler (91) with a paraboloid reflecting surface (92) is in contact with the active surface (13, 53) of the semiconductor (11, 51), the coupler having an index of refraction about the same as that of the semiconductor.

Ultrasonic detector device

Abstract: This invention relates to a novel design of a microprobe for measuring intensity distribution, instantaneous intensity values and acoustic signal shapes of ultrasound. The probe consists of a rod-shaped electrode which is fixed with the aid of an electrically and acoustically insulating material in a sleeve-shaped electrical shield. To one end surface of said device is adhered a piezoelectric film such that the film will come in contact with the end surfaces of the electrode, the insulating material and the electrical shield. As only the outer surface of the piezoelectric film is covered by an electrically conductive layer, the rod-shaped electrode on the inner side of the film will determine the active surface of the probe.

Polarographic pO2 test probe

Abstract: A polarographic pO2 probe having a small active surface has, over the electrolyte space, an O2-permeable membrane which encloses the surface and is screened on its inner side from the electrolyte space in an O2-diffusion-tight manner, with one or more small holes being left free. In the vicinity of the holes, a large-area cathode is mounted on the membrane. The diffusion geometry consequently becomes independent of movements of the membrane, so that the probe becomes insensitive to mechanical disturbances or pressure disturbances.