Hydrogen Reduction Process Research Articles

Hydrogen reduction and baking process of Pb-silicate microchannel plate and their performance studies

Microchannel plate (MCP) are honeycomb structures consisting of numerous parallel, hollow micro glass fiber channels renowned for their exceptional secondary electron multiplication. This paper investigates changes in MCP properties under hydrogen reduction temperatures ranging from 300 °C to 500 °C. The findings reveal that higher temperatures reduce surface metal oxides, which then accumulate within and darken the microchannels, affecting electron transport. Bulk resistance decreases before increasing, while gain increases and then decreases. At 350 °C, lead oxide begins to reduce to its conductive state, enhancing electron multiplication. However, increased temperatures cause clustering and roughening of the inner channel walls, which diminishes the efficiency of secondary electron release. These alterations are associated with the reduction dynamics of lead ions and temperature-induced microstructural changes. As the hydrogen reduction temperature increases, internal stresses shift outward, and the uniformity of gain varies, reaching its peak at 400 °C. Additionally, an aluminum oxide film enhances resistance to baking and ensures consistent bulk resistance. This study elucidates the relationship between MCP performance and reduction temperature, providing valuable insights for design improvement.

Self-sulfur doped mesoporous novel carbon electrodes derived from poly-anthraquinone sulfide for high-performance supercapacitors! A comparative study

Carbon materials are suitable electrode candidates in supercapacitors (SCs) because of their availability, well-defined microstructures, and ultrahigh surface areas. Herein, a universal chemical activation method was utilized to obtain activated carbon (C-KOH) from poly-anthraquinone sulfide (PAQS) at 850 °C and reduced activated carbon (C-KOH-H) from C-KOH via a mild hydrogen reduction process at low temperature. The electrochemical performances of the PAQS derived activated carbon electrodes were investigated by assembling electric double-layer capacitors (EDLCs). Electrodes fabricated from C-KOH and C-KOH-H showed 174 and 182.3 F g−1 specific capacitances at 0.5 A g−1 current density, respectively. Whereas their energy densities were 44 and 46 Wh kg−1 at 350 and 423 W kg−1 power densities, respectively. SCs assembled from C-KOH-H showed excellent rate performance, that retained 140 F g−1 even at high current density (20 A g−1), while the one assembled with C-KOH stored 54 F g−1. Furthermore, the C-KOH-H electrode retained 98 % of the initial capacitance at 1 A g−1 over 20,000 continuous cycles. The experimental results revealed that C-KOH-H showed the best electrochemical performance in SCs, which is attributed to the presence of less sulfur and oxygen than C-KOH after the mild reduction. These results prove that PAQS show excellent activation with KOH to produce well-organized porous activated carbons having high specific surface areas, which can be utilized as high-performance electrode materials in SCs.

The coexistence of highly dispersed Pt2+ and Pt0 co-catalysts on chemically oxidized g–C3N4 via metal-support interaction: The effect of reduction time on Pt species and hydrogen evolution of Pt/g-C3N4 photocatalysts

Platinum (Pt) cocatalyst greatly enhances the photoactivity of the graphitic carbon nitride (g-C3N4) photocatalyst for photocatalytic H2 evolution where the Pt properties are critical to determine the photocatalytic activity. In this study, highly dispersed Pt was successfully loaded onto chemically oxidized g–C3N4 (OCN) via a hydrogen reduction process over different reduction time. OCN photocatalysts containing highly dispersed Pt2+/Pt0 exhibited outstanding charge separation efficiency and photocatalytic performance. Symmetrical –CO groups on the OCN surface specifically interacted with atomic Pt2+, and the Pt2+ atoms were stably reduced to Pt0 atoms along with the generation of –OH groups over time. The coexistence of Pt0 and Pt2+ promoted superior photocatalytic performance because the photoinduced charge transfer was facilitated by the Pt0 atoms, which was evidenced by the DFT calculation and the EIS, PL, and photocurrent response results. Consequently, after the 24 h reduction, the highly stable and active Pt2+/Pt0 atoms were effectively distributed over OCN, resulting in the highest HER activity at 4091.3 µmol g−1 h−1.

Improving interfacial microstructure and mechanical properties of ODS-W/Cu joints via anodization treatment and spark plasma sintering

The bonding properties at the interface between the first wall oxide dispersion strengthened tungsten (ODS-W) and the heat sink copper (Cu) are vital for their application in future nuclear fusion reactors. However, the immiscibility and significant differences in the coefficient of thermal expansion between ODS-W and Cu pose considerable challenges for bonding these two materials. This study utilizes anodization and hydrogen reduction processes to form a nanoporous structure on the surface of ODS-W, thereby achieving effective bonding between ODS-W and Cu by spark plasma sintering (SPS). The effects of the anodization parameters on the surface characteristics of ODS-W, and the influence of the bonding temperature on the interfacial microstructure and mechanical properties of the ODS-W/Cu joints were investigated. The results demonstrate that under an anodization condition of 50 V for 40 min, a nanoporous structure with an average pore size of about 90 nm can forms on the surfaces of ODS-W. This significantly increases the surface roughness, thereby enhancing the interfacial bonding of ODS-W with Cu during SPS. As the bonding temperature increases, the interfacial microstructure changes from linear to serrated shape, effectively suppressing crack propagation and forming a stronger mechanical interlock between ODS-W and Cu. This significantly enhances the mechanical properties of the joints. Typically, at a bonding temperature of 1000 °C, the tensile strength of the anodized ODS-W/Cu joints reaches 245.2 MPa, which is 157.9 % higher than that of directly bonded joints. Additionally, the tensile fracture primarily occurs within the Cu substrate, transitioning from brittle to ductile fracture modes.

Parameter optimization of ultrafine molybdenum powder during hydrogen reduction of MoO2 based on central composite design method

The hydrogen reduction of MoO2 is a common method for preparing ultrafine molybdenum powder, which is an important basic material for manufacturing high-performance Mo-based alloys. However, its preparation parameters are usually hard to be controlled. To address this issue, the work conducted the parameter optimization research during the hydrogen reduction process with using central composite design method, and the influence of different parameters such as reaction temperature, yttrium content, and hydrogen flow rate, on the particle size and oxygen content of the prepared molybdenum powder were investigated. The findings showed that the particle size of the prepared molybdenum powder is gradually decreased with the increase of reaction temperature and yttrium content, while gradually increased with the increase of hydrogen flow rate. The oxygen content of the prepared molybdenum powder is gradually decreased with the increase of reaction temperature and hydrogen flow rate, while gradually increased with the increase of yttrium content. Reaction temperature and yttrium content have significant interactions on the particle size and oxygen content are also concluded, and their respective regression model equations are obtained. The result also demonstrated that the particle size and oxygen content of the prepared molybdenum powder had a certain contradictory relationship. Through the comprehensive analysis, the optimal parameters for preparing ultrafine molybdenum powder with a low oxygen content are deduced, that is, reaction temperature: 1200 K, yttrium content: 0.1 mass%, and hydrogen flow rate: 1000 mL/min. Under the conditions, the average particle size and oxygen content of the prepared molybdenum powder are 320 nm and 0.456 mass%, respectively.

Multi-site synergistic hydrogen evolution reactions on porous homogeneous FeCoNiCu high-entropy alloys fabricated by solution combustion synthesis and hydrogen reduction

A combination process of solution combustion synthesis and hydrogen reduction was proposed to prepare porous homogeneous FeCoNiCu high-entropy alloys (HEAs) for hydrogen evolution reaction (HER). Solution combustion synthesis was herein employed to obtain the multiple composite oxide precursor with tunable molar ratio of elements and pore structure, as well as uniform element distribution. The generated bulk porous HEAs composed of single-phase solid solution were achieved by hydrogen reduction of the oxide precursor at optimal temperature. The porous structure and specific surface area of oxide precursor and reduced HEA could be adjusted by varying the mass ratio of metal nitrates to glycine and the reduction temperature. The prepared FeCoNiCu0.5 HEA with enriched porosity and high specific surface area showed high catalytic activity and excellent electrochemical stability during alkaline HER. Density functional theory (DFT) calculation revealed the electronic interaction between Fe, Co, Ni and Cu elements facilitated the efficiency for H* adsorption and H2 desorption, and enhanced the catalytic activity of the Co/Ni sites. This work provided an approach to develop porous high-entropy alloy catalysts for HER and other applications.

Experimental study on strengthening the hydrogen reduction process of pyrite in the presence of alkaline oxide

ABSTRACT In this study, an innovative approach is proposed for the hydrogen reduction of pyrite in the presence of alkaline oxide, suitable for desulfurisation of high-sulfur bauxite and iron extraction from pyrite. This approach has the advantage of efficiently utilising high-sulfur bauxite, solving the issue of SO2 flue gas pollution. Stirred fluidised beds were used as reactors to promote uniform particle distribution. The impact of hydrogen concentration and spatial velocity of the gas on the reduction process of pyrite and the sticking behaviour between particles in a side-stirred fluidised bed were investigated using a single-factor experimental method. The effects of various experimental conditions on the pyrite reduction percentage, sticking ratio, phase composition, and microstructure of the reduction products were examined using chemical, XRD, and SEM analyses. The results demonstrated that, when agitated, modifying the hydrogen concentration and spatial velocity of the gas significantly enhanced the reduction of pyrite in the presence of alkaline oxide and increased the reduction efficiency. A hydrogen concentration of 37.5% and spatial velocity of the gas of 0.115 m·s−1 were the ideal values, respectively. In addition, kilogram-scale experiments were performed to confirm the viability of the approach.

Catalytic reduction of U(Ⅵ) to U(Ⅳ) using hydrogen as the sole reducing agent

Using hydrogen gas as a sole reducing agent to catalyze the reduction of hexavalent uranium to prepare tetravalent uranium can avoid the problem of pollutant poisoning catalysts caused by hydrazine reducing agents. However, research using only hydrogen as the sole reducing agent is very scarce. Herein, catalyst has been developed for catalytic hydrogen reduction to prepare uranium(Ⅳ) and a systematic study of the influence of process parameters such as catalyst carrier particle size, temperature, pressure, and acidity on the catalytic hydrogen reduction process for the preparation of uranium(Ⅳ) is presented. The effect of catalyst carrier particle size is particularly pronounced due to the differing rates of molecular diffusion. Fine particle-sized catalyst carriers exhibit faster catalytic reaction kinetics. Temperature exhibits an unusual phenomenon in its impact on the reaction process. As temperature increases, the reaction rate decreases, and an upper limit reaction temperature is observed. Furthermore, at excessively high reaction temperatures, an anomalous occurrence of uranium(Ⅳ) formation followed by disappearance was observed. Through an analysis of the reaction mechanism, the underlying reasons for this abnormal phenomenon are elucidated. Additionally, this paper also reveals that reaction rates increase with increasing reaction pressure and decrease with decreasing raw material acidity. Process parameters such as reaction temperature, pressure, and acidity exhibit coupled effects on the reaction process. Different reaction upper limit temperatures are observed under varying pressures and raw material acidities.

Significant augmentation of hydrogen and benzaldehyde production through mediator-free in-situ synthesis of CuNi/CN photocatalysts for benzyl alcohol splitting

Amidst growing concerns surrounding global warming and energy scarcity, there is an urgent demand for more efficient and environmentally friendly methods of hydrogen production. In response, we introduce a novel mediator-free in-situ approach for synthesizing CuNi/CN composite photocatalysts. This method entails the synthesis of copper and nickel complexes to fabricate bimetallic Cu and Ni nanoparticles on carbon nitride (CN). These catalysts are deployed for the photocatalytic dehydrogenation of benzyl alcohol, resulting in the generation of hydrogen and benzaldehyde. The CuNi bimetal-loaded CN structure provides ample active sites and demonstrates a low hydrogen reduction overpotential, thereby enhancing both charge separation and surface hydrogen reduction processes. In comparison to pure CN, the composite photocatalyst exhibits significantly improved photocatalytic activity. Notably, the composite 2 % Cu1Ni1/CN photocatalyst achieves a record-high hydrogen production rate of about 80 μmol g-1h−1, representing an impressive increase of approximately 533 times compared to pristine CN. Moreover, the catalyst offers cost-effectiveness, ease of preparation, and reusability, ensuring stable hydrogen production efficiency over multiple cycles. This precious metal-free composite photocatalyst not only facilitates the synthesis of valuable compounds but also promotes sustainable advancements in efficient hydrogen energy generation.

Unraveling grain growth of metallic tungsten: Investigating the nanoscale realm of hydrogen reduction of tungsten oxides

This paper focuses on the experimental observation of tungsten grain evolution during the process of hydrogen reduction of tungsten trioxide. The objective is to gain insights into the grain size distribution (GSD) evolution and morphology changes of metallic tungsten. The study employs an amalgamation of conventional characterization techniques – such as TGA, SEM-EDS, TEM and XRD – alongside cutting-edge techniques like phase contrast nano-tomography from synchrotron sources. Conducted as a quasi in-situ study, this research offers the opportunity to observe the transient evolution of the formed metallic tungsten phase within its precursor WO2 particles. The paper presents and discusses quantitative results concerning the evolution of GSD and morphological changes, encompassing growth rates of both crystallites and grains of the synthesized metallic phase. Additionally, the quasi in-situ study highlights the dependence of grain size on water concentration during the reduction process. The qualitative and quantitative findings contribute to a more nuanced understanding of the kinetics of grain growth of metallic tungsten and offer insights into the intricate interplay between reduction parameters, GSD evolution and morphological changes. Gaining a deeper understanding of the underlying mechanisms driving the changes in GSD establishes a foundation for predictive theory with immediate academic and industrial impact.

Kinetics of indium separation and recovery from In–Sn alloys in ITO waste target products via vacuum evaporation

The environmentally friendly recycling of ITO waste material to regenerate indium resources is crucial for sustainability. The hydrogen reduction process, particularly the green and low-carbon technique of vacuum distillation, is crucial in the production of In–Sn alloys. However, a thorough examination of the mechanics underlying its evaporation throughout this process has yet to be performed. These mechanics are investigated in the present study for 92In–8Sn alloys under specific conditions, including temperatures between 1173 and 1373 K, pressure of 5 Pa, and crucible depth of 25 mm. The relationship between temperature and the rate of volatilization is mathematically represented as ω = e(a+b∙T). Furthermore, the equation ω = A2 + (A1-A2)/(1 + e(h-h0)/dh) was used to predict the dependency of the volatilization rate on crucible depth, ranging from 25 to 65 mm at 1323 K and 5 Pa. The mass transfer coefficients for the alloy at different temperatures were calculated, and a theoretical kinetic model for evaporation behavior indicated that vapor-phase mass transfer is the limiting step in the process of vacuum distillation of this alloy. This study presents a theoretical basis for the retrieval of In from the In–Sn alloy using vacuum distillation.

Efficient Low-temperature Hydrogen Production by Electrochemical-assisted Methanol Steam Reforming.

Methanol steam reforming (MSR) provides an alternative way for efficient production and safe transportation of hydrogen but requires harsh conditions and complicated purification processes. In this work, an efficient electrochemical-assisted MSR reaction for pure H2 production at lower temperature (~140 °C) is developed by coupling the electrocatalysis reaction into the MSR in a polymer electrolyte membrane electrolysis reactor. By electrochemically assisted, the two critical steps including the methanol dehydrogenation and water-gas shift reaction are accelerated, which is attributed to decreasing the methanol dehydrogenation energy and promoting the dissociation of H2 O to OH* by the applied potential. Furthermore, the reduced H2 partial pressure by the hydrogen oxidation and reduction process further promotes MSR. The combination of these advantages not only efficiently decreases the MSR temperature but also achieves the high rate of hydrogen production of 505 mmol H2 g Pt -1 h-1 with exceptionally high H2 selectivity (99 %) at 180 °C and a low voltage (0.4 V), and the productivity is about 30-fold than that of traditional MSR. This study opens up a new avenue to design novel electrolysis cells for hydrogen production.

Efficient Low‐temperature Hydrogen Production by Electrochemical‐assisted Methanol Steam Reforming

AbstractMethanol steam reforming (MSR) provides an alternative way for efficient production and safe transportation of hydrogen but requires harsh conditions and complicated purification processes. In this work, an efficient electrochemical‐assisted MSR reaction for pure H2 production at lower temperature (~140 °C) is developed by coupling the electrocatalysis reaction into the MSR in a polymer electrolyte membrane electrolysis reactor. By electrochemically assisted, the two critical steps including the methanol dehydrogenation and water‐gas shift reaction are accelerated, which is attributed to decreasing the methanol dehydrogenation energy and promoting the dissociation of H2O to OH* by the applied potential. Furthermore, the reduced H2 partial pressure by the hydrogen oxidation and reduction process further promotes MSR. The combination of these advantages not only efficiently decreases the MSR temperature but also achieves the high rate of hydrogen production of 505 mmol H2 g Pt−1 h−1 with exceptionally high H2 selectivity (99 %) at 180 °C and a low voltage (0.4 V), and the productivity is about 30‐fold than that of traditional MSR. This study opens up a new avenue to design novel electrolysis cells for hydrogen production.

Recycling of Valuable Metals from the Priority Lithium Extraction Residue Obtained through Hydrogen Reduction of Spent Lithium Batteries

The selective separation of lithium from spent ternary positive materials is achieved through hydrogen reduction followed by water leaching. Almost 98% of the Li is transformed into soluble LiOH⋅H2O, while the Ni, Co and Mn species are all transformed into insoluble metals or their oxides, so the recovery of Ni, Co and Mn at this stage is challenging. The traditional acid leaching process has drawbacks such as high oxidant consumption, the low recovery of valuable metals and high production costs. Thus, sulfation roasting followed by water leaching was studied in this project. The leaching levels of Ni, Co, Mn and Al reached 87.13%, 99.87%, 96.21% and 94.95%, respectively, with 1.4 times the theoretical amount of sulfuric acid used at 180 °C for 120 min. To avoid the adverse effects of Mn and Al on the quality of the Ni and Co sulfate products, Mn2+ was first separated and precipitated via the KMnO4 oxidation–precipitation method, and >98% of the Mn was removed and precipitated within 30 min with a Kp/Kt (ratio of actual usage to theoretical usage of KMnO4) of 1.0 at pH = 2.0 and 25 °C. After removal of the Mn, the solvent extraction method was adopted by using P204 as an extractant to separate Al. More than 98% of the Al was extracted in 30 min with 20% (v/v) P204 + 10% (v/v) TBP with an A/O ratio of 1:1 at 30 °C. This optimized process for extracting lithium residues improved the hydrogen reduction process of waste lithium batteries and will enable industrialization of the developed processes.

Preparation of extra coarse-grained WC-Co cemented carbides by doping sodium in the ammonium tungstate solution during evaporation crystallization process

Coarse tungsten powders are usually used as raw material for preparing coarse grained WC-Co cemented carbides. Sodium can effectively promote the growth of tungsten powder during the reduction of tungsten oxide with hydrogen. Conventional addition of sodium salt into tungsten oxide powders by mechanical milling has the disadvantage of uneven distribution of sodium, which leads to abnormal growth of tungsten powders and affects the performance of WC-Co cemented carbides. In this study, uniform sodium doped ammonium paratungstate (APT) was prepared by adding sodium carbonate into ammonium tungstate solution during the evaporation and crystallization process based on the formation of ammonium-sodium paratungstate. Experimental results showed that sodium was uniformly distributed in the APT and promoted the growth of APT crystal. The sodium-doped APT was then used to produce coarse tungsten powders. Compared with tungsten powders obtained from tungsten trioxide with addition of sodium by mechanical milling, the coarse tungsten powders had larger average particle size and more uniform particle size distribution. The coarse tungsten powders were subsequently prepared into tungsten carbide powders and WC-Co cemented carbides by carburization and pressure sintering, respectively. Results showed that the obtained WC-Co cemented carbides had larger average WC grain size (6.8–7.2 μm), higher fracture toughness and transverse ruptures strength, and more uniform microstructure than that of WC-Co cemented carbides obtained by addition of sodium with mechanical milling. Moreover, sodium thoroughly volatilized during hydrogen reduction and carburization process, so that the purity of WC-Co cemented carbides was not reduced. Therefore, this study provided a new route for preparation of extra coarse-grained WC-Co cemented carbides.

Understanding the Improved Sodium Ion Storage in Wood-Derived Hard Carbon Anodes by Hydrogen Treatment

Biomass carbon, as a renewable resource, has the ability to be a hard carbon anode material for sodium-ion batteries. Its performance is highly reliant on the surface functional group. Through our work, successfully synthesized the high-performance hard carbon by the treatment of the hydrogen reduction process of rose willow. Moreover, the effects of hydrogen reduction on the evolution of functional groups and the relevant electrochemical performance have been investigated. After undergoing hydrogen reduction treatment, hard carbons’ surface features and layer spacing were greatly enhanced. In addition, the partial surface C=O group was reduced to C-O, which led to the Na+ adsorption active sites and pseudo-capacity increased, thus improving the dynamics of the electrode process. As anticipated, the resulting hard carbon exhibited a capacity of 325 mAh g−1, with an initial coulomb efficiency (ICE) of 80.84%. This study is in an effort to demonstrate the possibility of biomass-based carbon materials in preparation for future commercial applications of sodium-ion batteries.

Oxidation Mechanism of Tetravalent Uranium in Nitric Acid System Synthesized by Hydrogen Reduction Process

Oxidation Mechanism of Tetravalent Uranium in Nitric Acid System Synthesized by Hydrogen Reduction Process

Regulation of particle size and morphology of tungsten powders in bottom-blowing hydrogen reduction process

Particle size and morphology of tungsten powders determine the processing properties of tungsten products. The thermodynamic analysis indicates that the partial pressure of water vapor is an essential factor to regulate the hydrogen reduction of tungsten oxides. The investigation proposed a method of changing the particle size of tungsten powders by bottom blowing hydrogen pretreated by water bath at various temperatures. The experimental results manifested that the bottom-blowing hydrogen could eliminate discrepancies of the water vapor partial pressure in the solid powder layers, thus improving the uniformity of the tungsten powders in a crucible. The partial pressure of water vapor increased with temperatures of water bath increasing. As the water bath temperature raised from 50 °C to 80 °C, the average particle size of tungsten powders increased significantly from 3.8 μm to 12.0 μm. Chemical vapor transport was responsible for the increase in the average particle size of tungsten powders under the higher partial pressure of water vapor. In addition, the oxygen content of tungsten powders produced remained relatively stable at a lower level with the partial pressure of the water vapor increasing. This study provided theoretical foundation and technological reference for preparing the tungsten powders with superior properties (desirable homogeneity in the particle size and shape and low oxygen content).

Electrocrystallization and Morphology of Copper Coatings in the Presence of Organic Additives

Copper coatings with refined grains and smooth surface morphology were electrodeposited from electrolytes comprising a novel accelerator, the disodium salt of 4,4-dithiobenzene disulfonic acid (DBDA), with sodium chloride and polyethylene glycol (PEG) as inhibitors and 2-aminobenzothiazole (ABT) as a leveler. It was found that the morphology of the coatings strongly depends on the presence and type of additives. In the presence of only DBDA and NaCl, large crystallites are formed, whereas the addition of PEG and ABT significantly decreases their size, and the most fine-grained, smooth, and defect-free copper coating is formed with the combined use of all additives. To establish the correlation between the observed morphology and the kinetics of the additive-assisted copper electrocrystallization in the proposed electrolytes, the nucleation mechanism and its parameters were determined by transient electrochemical characterization. The extended nucleation model, which takes into account not only the copper deposition but also the electric double-layer charging and hydrogen reduction process, was used to establish the electrocrystallization kinetics in the presence of the additives. The results of such kinetic analyses can help to explain the morphological effect. By using the chronopotentiometry method, it was found that the addition of the disodium salt of 4,4-dithiobenzene disulfonic acid with chloride ions gives a catalytic effect, while the sequential introduction of polyethylene glycol and 2-aminobenzothiazole provides an increasing inhibitory effect. Voltamperometry and chronoamperometry tests showed that the process is controlled by the diffusion of ions to the growing three-dimensional cluster of a new phase. The introduction of additives into the electrolyte slows down the copper electroplating process at comparatively negative potentials and increases the probability of transition from instantaneous to progressive nucleation. Moreover, the rate of the process and the density of nucleation active sites increase (up to 2–3 times) with the addition of DBDA but decrease significantly (up to 5–8 times) in the presence of PEG and ABT, which additionally confirms their catalytic and inhibitory effects, respectively, and explains the significant smoothing effect on the morphology of the Cu-coatings.

Deep decarburization of molybdenum and tungsten powders by wet hydrogen

The control of residual carbon content is an urgent problem to be solved for the preparations of molybdenum and tungsten powders by method of carbothermic reduction of their oxides. In this paper, finer Mo (W) powder with a low residual carbon content was prepared by a two-step reduction process consisting of carbothermal pre-reduction of MoO3 (WO3) at 1050 °C and following deep hydrogen reduction. During the deep hydrogen reduction process, with the increases of hydrogen reduction temperature and dew point, the residual carbon contents of the finally prepared Mo and W powders gradually decreased, while the particle sizes of Mo and W powders gradually increased. The lowest residual carbon and oxygen contents of Mo and W powders obtained after hydrogen reduction at 1100 °C with the hydrogen dew point of 41 °C were 0.007 wt% (carbon content) and 0.104 wt% (oxygen content), as well as 0.010 wt% and 0.086 wt%, respectively. In addition, the mean particle sizes of them were 1032 nm and 998 nm under this condition, respectively.