Hydrogen reduction of ammonium paratungstate into tungsten blue oxide—Part I: Literature review

The macromeritic tungsten powder was prepared by wet hydrogen reduction at medium temperature; the coarse powder of Ammonium paratungstate powder (APT) was used as raw material. It is obtained by evaporating and crystallizating adding alkalia metal salts in the solution of ammonium tungstate. The microstructure, phase composition and particle size of the macromeritic tungsten powder were investigated by SEM, XRD and test analysis sieves. The effects of kinds, contents of alkali metal salts and the temperature in the reduction were studied. The results revealed that ideal tungsten powder, with the good fluditity, spherical, integrate and well-distributed, could be obtained. The raw material is the solution of ammonium tungstate adding NaCl, Li2CO3 and KCl , the concentration of them are all 3g/L, and it is under the condition of 1000°C,180min in wet hydrogen atmosphere. The average particle size is 67μm, the maximum is 150μm, the biggest loose density is 13.41g/cm3, and the best powder flowability is 9s/50g.

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Sintering Behavior and Hardness of Tungsten Prepared by Hard Metal Sludge Recycling Process without Ammonium Paratungstate

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2022.60.1.53 ◽

2022 ◽

Vol 60 (1) ◽

pp. 53-61

Author(s):

Hanjung Kwon ◽

Jung-Min Shin

Keyword(s):

Grain Size ◽

Tungsten Oxide ◽

Hydrogen Reduction ◽

Hard Metal ◽

High Energy ◽

Tungstic Acid ◽

Sintering Behavior ◽

Recycling Process ◽

Ammonium Paratungstate ◽

Tungsten Powders

In this paper, we suggest a novel recycling process for hard metal sludge that does not use ammonium paratungstate. Ammonia, which in the conventional recycling process is essential for removing sodium and crystallized tungstate, was not used in the novel process. Instead of ammonia, acid was used to remove the sodium and crystallized tungstate resulting in the formation of tungstic acid (H2WO4). Tungsten powders were successfully synthesized by hydrogen reduction of the tungstic acid through H2O decomposition, WO3 to WO2 reduction, and tungsten metal formation. The tungsten powders prepared from tungstic acid were spherical in shape and had a higher sintering density than the facet-shaped tungsten powders prepared from tungsten oxide. The spherical shape of the tungsten powders enhanced their sinterability and resulted in an increase in the size of grains. This is a result of the high diffusion rate of the atoms along the particle surfaces. Despite having a higher density, the hardness of the sintered tungsten was lower than that of tungsten from tungsten oxide. High energy milling effectively reduced grain size and improved hardness. The hardness of the tungsten prepared from milled tungstic acid was enhanced to a value (max. 471 HV) higher than the best previously reported value (389 HV). In sum, tungsten can be hardened, thereby improving its sinterability and reducing grain size, with tungstic acid prepared using the proposed recycling process.

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Effect of Computerized Auditory Training on Speech Perception of Adults With Hearing Impairment

Perspectives on Aural Rehabilitation and Its Instrumentation ◽

10.1044/arri20.3.91 ◽

2013 ◽

Vol 20 (3) ◽

pp. 91-106 ◽

Cited By ~ 6

Author(s):

Rachel Pizarek ◽

Valeriy Shafiro ◽

Patricia McCarthy

Keyword(s):

Hearing Loss ◽

Speech Perception ◽

Literature Review ◽

Low Cost ◽

Experimental Designs ◽

Auditory Training ◽

Hearing Impairments ◽

Communicative Disorders ◽

And Training

Computerized auditory training (CAT) is a convenient, low-cost approach to improving communication of individuals with hearing loss or other communicative disorders. A number of CAT programs are being marketed to patients and audiologists. The present literature review is an examination of evidence for the effectiveness of CAT in improving speech perception in adults with hearing impairments. Six current CAT programs, used in 9 published studies, were reviewed. In all 9 studies, some benefit of CAT for speech perception was demonstrated. Although these results are encouraging, the overall quality of available evidence remains low, and many programs currently on the market have not yet been evaluated. Thus, caution is needed when selecting CAT programs for specific patients. It is hoped that future researchers will (a) examine a greater number of CAT programs using more rigorous experimental designs, (b) determine which program features and training regimens are most effective, and (c) indicate which patients may benefit from CAT the most.

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Taking Care of Children After Traumatic Brain Injury

Perspectives on School-Based Issues ◽

10.1044/sbi13.3.79 ◽

2012 ◽

Vol 13 (3) ◽

pp. 79-86 ◽

Cited By ~ 1

Author(s):

Julie Haarbauer-Krupa

Keyword(s):

Traumatic Brain Injury ◽

Brain Injury ◽

Literature Review ◽

School Setting ◽

Leadership Role ◽

Speech Language Pathologists ◽

Educational Information ◽

Taking Care

AbstractPurpose: The purpose of this article is to inform speech-language pathologists in the schools about issues related to the care of children with traumatic brain injury.Method: Literature review of characteristics, outcomes and issues related to the needs serving children.Results: Due to acquired changes in cognition, children with traumatic brain injury have unique needs in a school setting.Conclusions: Speech-Language Pathologists in the school can take a leadership role with taking care of children after a traumatic brain injury and coordination of medical and educational information.

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