Iranian Journal of Materials Science and Engineering

en Effect of Temperature-Time on simultaneous hydrogen reduction of molybdenum and tungsten oxides گروه استخراج Metallurgical Extraction and Processing Research Paper Research Paper The Mo-30 wt% W solid solution is a well-established molybdenum-based alloy. A recent approach to alloying Mo and W involves the simultaneous reduction of their oxides by hydrogen. Several studies have reported the production of Mo-W alloys via the reduction of mixed oxides. But the alloying mechanism and the effects of key reduction parameters on alloy formation remain uninvestigated. In the present study, the simultaneous hydrogen reduction of MoO₃–WO₃ mixed oxides was investigated as a potential route for producing pre-alloyed Mo–W powders. In this study pre-alloyed Mo-30 wt% W is. The effects of reduction temperature and holding time on phase evolution, morphology, and alloy formation were systematically examined. The chosen temperature range is 600-1050°C. The influence of time on phase formation and morphology during the hydrogen reduction of molybdenum and tungsten oxides is examined over a 30-360 minute period. Other parameters such as heating rate (20<m:omath><m:f><m:fpr><m:ctrlpr></m:ctrlpr></m:fpr><m:num><m:r><m:rpr><m:scr m:val="roman"><m:sty m:val="p"></m:sty></m:scr></m:rpr>℃</m:r></m:num><m:den><m:r>min</m:r></m:den></m:f></m:omath><img alt="" id="_x0000_i1025" src="data:image/png;base64,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" style="width:16.5pt; height:27.75pt" > ), bed height (10mm), H₂ flow rate (500<m:omath><m:f><m:fpr><m:ctrlpr></m:ctrlpr></m:fpr><m:num><m:r><m:rpr><m:scr m:val="roman"><m:sty m:val="p"></m:sty></m:scr></m:rpr>ml</m:r></m:num><m:den><m:r>min</m:r></m:den></m:f></m:omath><img alt="" id="_x0000_i1025" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABYAAAAlCAIAAADJOI5vAAAAAXNSR0IArs4c6QAAAAlwSFlzAAAOxAAADsQBlSsOGwAAARhJREFUSEvtVckNwjAQHFMMD0QF0AQvSoB24MuPDvgAHVACD6CXMOwkzhIUZBELIZEVipZ41nvYMwko0NEGHeMZ/uUt1kAAjq91cxbpvwlwaOKzN8IiWSoLnlY1L83h33fW6GIBrKxUPlm2VmlyUhsZWgyf46QTzzCL5/Fy2rJ4ZfmGrdHUYFx17Yd/vOBJ5/MRqB9nPbYMFzxtC5L91npaGU4EuJoKRBZJETydxDHyKiIFqNRk8FjYAhsTCOJOwMUxlVASdGQxEempXPKaIJ8nJhSjucRg+REpEbCXNs4zMLM8e2DuHOk9C6TJj8idhVBlyypUmKRRCZmNJr2neRH1APMznEgoiq7f5bSrpZZbrN+iHsxvzOIOFm57xwkMJ94AAAAASUVORK5CYII=" style="width:16.5pt; height:27.75pt" > ), and material weight (14.3g) were kept constant. The reduced samples are analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of temperature and time on the reduction processes are closely linked. Results indicate the formation of MoO₂ and WO₂ phases at 600°C after 60 minutes of hydrogen reduction. No Oxide phases were detected in XRD analysis of the sample that was reduced at 800°C for 180 minutes. Therefore, tungsten and molybdenum coexist in all particles of the samples. Mass transfer between Mo and W takes place during the reduction of oxides to the metallic phase. But isothermal reduction does not yield a homogeneous alloy. In these studies, for T > 800°C, increasing time has minimal effect on alloying these elements. At T=800°C, a significant change in morphology occurs at t>180 min. At T=800°C, a notable morphological change occurs after t>180 min. These changes are caused by the CVT mechanism. The optimal conditions for achieving chemical homogeneity in the alloy powder particles after reduction were identified as: 600°C for 60 min, 600 to 1050 for 240 min, and 180 min at 1050°C. This cycle leads to the formation of homogeneous alloy powder particles. The achieved homogeneity is attributed to providing sufficient time for mass transport between molybdenum and tungsten oxide particles through gaseous chemical species formed within this temperature range.   MoO₃–WO₃ mixture,hydrogen reduction,alloy formation,Temperature–Time effects 0 0 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-52-4&slc_lang=en&sid=1 Iman Babaei Nezhad imanbnz@hotmail.com 1800319475328460022561 1800319475328460022561 No Iran University of Science and Technology Hossein Aghajani haghajani@iust.ac.ir 1800319475328460022562 1800319475328460022562 Yes Iran University of Science and Technology Seyed Hossein Seyedein seyedein@iust.ac.ir 1800319475328460022563 1800319475328460022563 No Iran University of Science and Technology Mohammad Reza Aboutalebi mrezab@iust.ac.ir 1800319475328460022564 1800319475328460022564 No Iran University of Science and Technology