Ammonium tungsten oxide generally refers to ammonium paratungstate (APT), a key compound in tungsten chemistry and industry. Its chemical formula is often represented as (NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O or (NH₄)₁₀W₁₂O₄₁·5H₂O, signifying its complex polyatomic structure. APT appears as white or slightly yellow crystalline solids, typically in fine powder form.

(ammonium tungsten oxide)

Its primary significance lies as an essential intermediate in tungsten metal and tungsten carbide production. The compound is industrially produced by digesting tungsten ore concentrates (like wolframite or scheelite) in alkaline solutions, followed by precipitation using ammonium salts. This purification step effectively isolates tungsten from impurities.

A critical property of APT is its behavior upon heating. When calcined under controlled conditions, it undergoes thermal decomposition. This process involves losing ammonia and water molecules, ultimately transforming into tungsten trioxide (WO₃), a crucial precursor for tungsten powder reduction. The purity and particle size of the resulting WO₃, and thus the final tungsten powder, are heavily influenced by the starting APT characteristics.

(ammonium tungsten oxide)

Beyond metal production, APT finds use as a catalyst precursor in various chemical reactions, particularly in petroleum refining and oxidation processes. Its decomposition products or derived tungsten compounds exhibit catalytic activity. Research also explores modified ammonium tungsten oxides (like ammonium tungsten bronzes) for applications in electrochromic devices, where their ability to change color with applied voltage is exploited for smart windows and displays. Handling requires care as APT can decompose to release ammonia gas under certain conditions. Its stability and solubility properties make it a fundamental material in the tungsten value chain.
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Tungsten trioxide, WO3, is a versatile inorganic compound. It appears as a yellow crystalline solid or powder. Key properties include semiconductor behavior and electrochromism, meaning it changes color reversibly under electrical charge. This makes it essential for smart windows that dynamically control light and heat. WO3 is also highly insoluble and stable under many conditions. Its photocatalytic activity is valuable for environmental applications like breaking down pollutants. WO3 effectively senses gases like nitrogen dioxide and ammonia, changing electrical resistance upon exposure, crucial for air quality monitors. Research explores WO3 in batteries, particularly cathodes for lithium-ion systems, and in photoelectrochemical cells for solar water splitting to produce hydrogen fuel. Nanostructured WO3 enhances surface area, boosting performance in sensing and catalysis. Future potential lies in optimizing nanostructures and composites for energy storage, conversion, and advanced electrochromic devices. Tungsten trioxide remains a key material for smart technologies and sustainable solutions.

(tungsten 6 oxide)

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Lithium tungsten oxide, often denoted as LixWO3 or LiyWO3+z, represents a class of materials within the tungsten bronze family. Its significance stems primarily from its electrochemical properties, making it relevant for energy storage research, particularly lithium-ion batteries. The structure is typically a distorted perovskite framework derived from WO3, where lithium ions can intercalate into the tunnels and cavities.

(lithium tungsten oxide)

The material exhibits interesting characteristics. It can achieve reasonably high theoretical specific capacities, potentially exceeding 200 mAh/g depending on the specific composition and structure. Lithium insertion/extraction occurs at relatively low voltages, often below 1.5 V vs. Li/Li+, which can be advantageous for certain cell configurations. This low voltage operation is linked to the reduction/oxidation of tungsten ions (W⁶⁺ ↔ W⁵⁺) during cycling.

However, lithium tungsten oxide faces significant challenges hindering widespread commercial battery use. A major issue is its electronic conductivity, which is generally poor in the pristine state. While lithium insertion improves conductivity, it often remains insufficient for high-rate applications without conductive additives or nanostructuring. Lithium-ion diffusion within the crystal lattice can also be slow, limiting power density. Furthermore, structural changes during deep lithium insertion can lead to capacity fading over cycles.

(lithium tungsten oxide)

Synthesis typically involves solid-state reactions, heating mixtures of lithium and tungsten precursors (like carbonates or oxides) at high temperatures (700-1000°C). Precise control over stoichiometry and crystal structure is crucial for optimizing performance. Despite the challenges, research continues due to its unique properties. It serves as a model system for studying intercalation chemistry and finds niche applications in electrochromic devices due to its color changes upon lithium insertion. Its stability compared to some other anode materials also attracts interest for specialized battery designs.
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Tungsten trioxide WO3 is a critical inorganic compound with unique properties driving diverse applications. It typically appears as a yellow crystalline solid or powder. WO3 is a wide bandgap semiconductor around 2.6-2.8 eV. Its electrical conductivity changes significantly with temperature and gas exposure making it a key material in chemiresistive gas sensors for detecting pollutants like NOx NH3 H2S and O3. Synthesis methods include calcining ammonium paratungstate or direct oxidation of tungsten metal. WO3 exhibits fascinating chromic properties. It is electrochromic meaning its optical transmission and color change reversibly upon charge insertion extraction under an applied voltage. This powers smart windows for energy saving. It also shows photochromism darkening under UV light. Photocatalysis is another major area. WO3 acts as a photocatalyst under visible light for applications like water splitting to produce hydrogen and degrading organic pollutants in water treatment. Its bandgap allows it to absorb a portion of the visible spectrum. Nanostructured WO3 like nanowires nanorods and nanoflowers enhances surface area improving performance in sensing electrochromic devices and photocatalysis. Thin films are crucial for electrochromic windows and displays. WO3 is also used in fireproofing fabrics as a pigment in ceramics and paints and historically in x-ray screens phosphors. Its stability non toxicity and tunable properties through doping or nanostructuring ensure its continued importance in advanced materials science for energy environmental and electronic technologies.

(wo3 tungsten)

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Tungsten oxide, chemical formula WO3, is a versatile inorganic compound. Commonly appearing as a yellow powder or crystalline solid, it’s an n-type semiconductor with a bandgap around 2.6-2.8 eV. Its properties make it crucial in several advanced technologies. A primary application is in electrochromic devices. WO3 thin films change color reversibly from transparent to deep blue upon lithium ion insertion and extraction. This principle is used in smart windows that dynamically control light and heat transmission in buildings, enhancing energy efficiency. WO3 is also a key material in gas sensors. Its electrical conductivity changes significantly upon exposure to specific gases like nitrogen oxides (NOx), ammonia (NH3), or hydrogen sulfide (H2S). This sensitivity allows for the detection of pollutants and hazardous gases in environmental monitoring and industrial safety. Furthermore, WO3 exhibits photocatalytic activity under visible light irradiation. It can degrade organic pollutants in water and air, contributing to environmental remediation efforts. Research also explores its potential in photocatalytic water splitting for hydrogen fuel production. The material is stable, relatively non-toxic, and can be synthesized in various nanostructured forms (nanoparticles, nanowires, nanorods) to enhance its surface area and reactivity. These nanostructures improve performance in sensing and catalysis. Tungsten oxide is also investigated for use in batteries, particularly as a cathode material in lithium-ion systems, and in solar cells. Ongoing research focuses on optimizing its nanostructure, doping it with other elements to modify its bandgap and electronic properties, and developing efficient composite materials to further boost its performance across all application areas, solidifying its role in sustainable technologies.

(tungsten oxide wo3)

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Tungsten carbide oxidation presents a significant challenge limiting its high-temperature applications. This hard, wear-resistant material excels in cutting tools, dies, and wear parts, but exposure to oxygen at elevated temperatures triggers degradation.

(tungsten carbide oxidation)

The oxidation process begins noticeably around 400-500°C. Atmospheric oxygen reacts chemically with the tungsten carbide grains. The primary reaction is WC + 5/2 O2 → WO3 + CO2. This forms tungsten trioxide (WO3), a voluminous, brittle oxide, and carbon dioxide gas.

This reaction has detrimental consequences. The formation of WO3 creates significant internal stresses due to its larger molar volume compared to WC. This leads to cracking and spallation of the oxide layer. Crucially, the escaping CO2 gas creates pores and voids within the material structure. This combination of oxide formation and gas evolution causes severe material loss, surface pitting, and a catastrophic disintegration phenomenon known as “pest oxidation” at certain temperatures, destroying structural integrity.

Oxidation significantly accelerates tool wear mechanisms like flank wear and crater wear in machining applications. It reduces hardness and strength, leading to premature failure. The rate increases dramatically with rising temperature.

(tungsten carbide oxidation)

Mitigation strategies are essential. Applying protective coatings (like Al2O3, TiAlN, TiCN) creates a barrier against oxygen diffusion. Alloying with elements forming stable oxides (e.g., chromium) can improve inherent oxidation resistance. Careful control of the cobalt binder phase chemistry and microstructure also plays a role. Limiting operating temperatures below the critical oxidation threshold remains the simplest, though often impractical, defense. Understanding and managing tungsten carbide oxidation is vital for extending component life in demanding environments.
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Tungsten(III) Oxide: The Unstable Blue-Grey Cousin

(tungsten iii oxide)

Formula: W₂O₃. Often non-stoichiometric, meaning slight deviations from the ideal ratio occur. Exists primarily as W₃O₈ or similar suboxides under ambient conditions.
Appearance: Typically manifests as a blue-grey or violet-black solid. This distinct color contrasts sharply with the yellow tungsten(VI) oxide (WO₃).
Properties: Highly unstable under atmospheric conditions. Prone to oxidation, readily converting back to higher oxides like WO₃ when exposed to air. This inherent instability makes handling difficult. Exhibits metallic conductivity due to partially filled d-orbitals in tungsten.
Synthesis: Cannot be made by direct combination of elements. Common methods involve controlled reduction of WO₃. Techniques include heating WO₃ with tungsten metal powder in vacuum or inert atmosphere, or carefully reducing WO₃ with hydrogen gas at specific temperatures. Requires precise conditions to avoid over-reduction to metal or under-reduction to WO₃.
Applications: Limited due to instability. Primary interest lies in catalysis research. Its unique electronic structure makes it a potential candidate for specific catalytic reactions, particularly where metallic conductivity combined with oxide character is beneficial. It may act as an intermediate in the reduction of WO₃ to tungsten metal powder. Also studied for its thermoelectric properties.
Challenges: Handling requires inert atmosphere techniques (glovebox, Schlenk line) to prevent oxidation. Its non-stoichiometric nature complicates precise characterization and property measurement. Synthesis reproducibility can be challenging.

(tungsten iii oxide)

Key Takeaway: Tungsten(III) oxide is a fascinating but temperamental material. Its instability restricts widespread use, but its unique properties, particularly conductivity and catalytic potential, drive niche research interest. Understanding its behavior requires careful synthesis and handling under oxygen-free conditions.
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Tungsten oxide, often called wolfram oxide (WO₃), is a significant inorganic compound. This yellow crystalline solid exhibits fascinating properties driven by its unique chemistry. A key characteristic is electrochromism: its ability to reversibly change color when subjected to an electrical voltage or charge insertion. This makes WO₃ the heart of smart window technology. Applying a small voltage triggers a reaction, turning the transparent oxide a deep blue. Reversing the voltage clears it. This dynamic control over light and heat transmission offers massive potential for energy-saving buildings by reducing reliance on heating and cooling systems.

(wolfram oxide)

Beyond smart windows, tungsten oxide finds diverse applications. Its sensitivity to gases like nitrogen dioxide (NO₂) and hydrogen sulfide (H₂S) makes it invaluable in gas sensors for environmental monitoring and industrial safety. WO₃ also acts as a photocatalyst under visible light, useful in applications like self-cleaning surfaces and air/water purification by breaking down organic pollutants. Furthermore, it serves as a crucial component in certain types of batteries and as a catalyst in industrial chemical processes, particularly in petroleum refining.

(wolfram oxide)

The material’s behavior is heavily influenced by its oxygen content and structure. Non-stoichiometric forms (WO₃₋ᵪ) are common and crucial for its electrical and optical properties. Researchers continuously explore nanostructuring WO₃ (nanowires, nanoparticles) to enhance its surface area and reactivity, boosting performance in sensing and catalytic applications. While challenges remain in optimizing long-term stability and large-scale manufacturing costs, tungsten oxide’s unique blend of optical, electrical, and chemical properties ensures its continued importance in advancing technologies focused on energy efficiency, environmental protection, and smart materials.
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Tungsten Trioxide Powder: Essential Properties and Uses

(tungsten trioxide powder)

Chemical Formula: WO3
Appearance: Fine yellow powder, odorless.
CAS Number: 1314-35-8
Key Properties: Insoluble in water. Good electrical conductivity under certain conditions. High chemical stability. Exhibits electrochromism (changes color with applied voltage). Photocatalytic activity. Semiconductor behavior. High melting point (~1473°C). Non-flammable.
Primary Production: Typically derived from ammonium paratungstate (APT) via thermal decomposition or acid precipitation followed by calcination.
Major Applications:
Electrochromic Devices: Crucial component in smart windows, mirrors, and displays. Enables controllable light and heat transmission by reversibly changing color (blue to transparent) with applied voltage.
Gas Sensors: Used in detecting toxic gases (e.g., NOx, H2S, NH3) due to conductivity changes upon gas adsorption. Offers good sensitivity and selectivity.
Photocatalysis: Acts as a photocatalyst under visible light for environmental remediation (degrading organic pollutants) and water splitting (hydrogen production).
Pigments: Provides a durable yellow pigment for ceramics, paints, and plastics.
Chemical Catalysis: Serves as a catalyst or catalyst support in various industrial chemical processes, including petroleum refining and oxidation reactions.
Other Uses: X-ray screens, fireproofing fabrics, ceramic glazes, corrosion inhibitors.
Handling & Safety: Low acute toxicity. Handle with standard industrial hygiene practices. Avoid inhalation of dust (use respirators in dusty conditions). Avoid contact with strong reducing agents. Store in a cool, dry place in tightly sealed containers. Refer to the Safety Data Sheet (SDS) for detailed handling and emergency procedures.

(tungsten trioxide powder)

Key Advantages: Versatile functional material. Stable. Relatively low cost for its applications. Tunable properties via doping or nanostructuring.
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Tungsten(IV) oxide, WO₂, is a compound of tungsten and oxygen. It appears as a bronze-colored solid with a metallic luster. Unlike the more common tungsten trioxide (WO₃), which is yellow, WO₂ features tungsten in a lower +4 oxidation state. Its crystal structure is typically a distorted rutile form, contributing to its unique properties.

(tungsten ii oxide)

WO₂ exhibits metallic electrical conductivity, a key characteristic distinguishing it from the insulating or semiconducting behavior of WO₃. This conductivity arises from the partially filled d-orbitals of tungsten(IV). WO₂ is often discussed within the context of the tungsten oxide bronzes, specifically the “tungsten bronze” phase, which refers to substoichiometric oxides like WO₃₋ₓ (where x represents oxygen deficiency). WO₂ itself can be considered part of the Magnéli phase series for tungsten oxides.

Synthesizing pure WO₂ can be challenging. Common methods include reducing WO₃ under controlled conditions using hydrogen gas or carbon monoxide at elevated temperatures (around 900-1000°C). Alternatively, thermal decomposition of ammonium paratungstate under reducing atmospheres is employed. Precise control of temperature and reducing agent concentration is vital to avoid over-reduction to tungsten metal or under-reduction to other oxides.

(tungsten ii oxide)

Chemically, WO₂ is relatively stable in air at room temperature but oxidizes slowly over time. It reacts with strong oxidizing agents and dissolves in concentrated acids. Its primary interest lies in its electrical properties. Research explores its potential in thermoelectric materials for converting heat to electricity, electrodes, and specific catalytic applications where its metallic conductivity and surface chemistry are advantageous. However, handling requires care due to its reactivity with acids and oxidizers. WO₂ represents a crucial intermediate state in tungsten oxide chemistry.
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