The figure depicts an apparatus that pulverizes brittle material by means of a combination of ultrasonic and sonic vibration, hammering, and abrasion. The basic design of the apparatus could be specialized to be a portable version for use by a geologist in collecting powdered rock samples for analysis in the field or in a laboratory. Alternatively, a larger benchtop version could be designed for milling and mixing of precursor powders for such purposes as synthesis of ceramic and other polycrystalline materials or preparing powder samples for x-ray diffraction or x-ray fluorescence measurements to determine crystalline structures and compositions. Among the most attractive characteristics of this apparatus are its light weight and the ability to function without need for a large preload or a large power supply: It has been estimated that a portable version could have a mass <0.5 kg, would consume less than 1 W·h of energy in milling a 1-cm 3 volume of rock, and could operate at a preload <10 N.
The basic design and principle of operation of this apparatus are similar to those of other apparatuses described in a series of prior NASA Tech Briefs articles, the two most relevant being "Ultra- sonic/Sonic Drill/Corers With Inte- grated Sensors" (NPO-20856), Vol.25, No.1 (January 2001), page 38 and "Ultrasonic/Sonic Mechanisms for Deep Drilling and Coring" (NPO-30291), Vol. 27, No.9 (September 2003), page 65. As before, vibrations are excited by means of a piezoelectric actuator, an ultrasonic horn, and a mass that is free to move axially over a limited range. As before, the ultrasonic harmonic motion of the horn drives the free-mass in a combination of ultrasonic harmonic and lower-frequency hammering motion. In this case, the free-mass is confined within a hollow cylinder that serves as a crushing chamber, and the free-mass serves as a crushing or milling tool.
The hammering of the free-mass against a material sample at the lower end of the chamber grinds the sample into powder in a relatively short time. The restriction of the free-mass to axial motion only makes the grinding very efficient. The free-mass can be fabricated to have teeth on its lower face to enhance the grinding effect. Optionally, there can be a hole at the bottom of the chamber covered with a sieve to tailor the size distribution of the powder leaving the crushing chamber.
This work was done by Stewart Sherrit, Xiaoqi Bao, Yoseph Bar-Cohen, Benjamin Dolgin, and Zensheu Chang of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Machinery/Automation category. NPO-30682
This Brief includes a Technical Support Package (TSP).
Ultrasonic Apparatus for Pulverizing Brittle Material
(reference NPO30682) is currently available for download from the TSP library.
Don't have an account?
Overview
The document presents a technical support package for an innovative Ultrasonic Apparatus designed for crushing, milling, and powdering brittle materials, particularly rock samples. Developed by a team at NASA's Jet Propulsion Laboratory, the device utilizes ultrasonic technology, specifically a piezoelectric actuator coupled with an amplification horn, to create efficient grinding through low-frequency impacts.
The apparatus features a free mass that moves in a piston-like manner, delivering precise impacts to the rock sample within a confinement volume. This design allows for effective powder extraction through holes at the base of the chamber. The size of the resulting powder can be controlled by adjusting the duration of hammering, modifying the surface morphology of the free mass, or using screens to filter the powder size.
The document outlines the novelty of this device compared to prior art, emphasizing its efficiency and lightweight design, which makes it suitable for portable applications. This is particularly beneficial for field geologists and in-situ sample preparation for various NASA missions. The device operates with minimal power requirements, needing less than 1 watt-hour and a preload of less than 10 Newtons, making it energy-efficient.
Additionally, the document discusses potential modifications to enhance the device's commercial viability. These include integrating a compressed gas system to facilitate powder removal, designing the crushing volume to double as a powder container, and incorporating sensors for monitoring operational parameters. Other suggested improvements involve adjusting the power and duty cycle to manage powder temperature, using springs to enhance the efficiency of the free mass, and employing integrated sieves for better powder size selection.
Figures included in the document illustrate the device's components and operation, showcasing the solid design and functionality of the ultrasonic crusher. Overall, this technical support package highlights the advancements in material processing technology, with implications for both scientific research and commercial applications, reflecting NASA's commitment to innovation and technology transfer.
