Haucl4

Decoding HauCl4: Understanding and Handling Hafnium Tetrachloride

The world of advanced materials relies heavily on compounds with unique properties, and Hafnium Tetrachloride (HfCl₄) is no exception. This seemingly simple inorganic compound plays a crucial role in several high-technology applications, ranging from the production of high-purity hafnium metal to the fabrication of advanced electronic components. However, its handling and utilization require a thorough understanding of its physical and chemical characteristics, safety precautions, and relevant applications. This article aims to provide a comprehensive overview of HfCl₄, equipping readers with the knowledge necessary for safe and effective interaction with this powerful chemical.

I. Physical and Chemical Properties of HfCl₄

HfCl₄ is a white to slightly yellow crystalline solid, highly sensitive to moisture. Its defining characteristic is its high reactivity, particularly with water. Exposure to atmospheric moisture leads to rapid hydrolysis, producing hafnium oxychloride (HfOCl₂) and hydrogen chloride (HCl), a corrosive and toxic gas. This reaction is exothermic, generating heat, which can further accelerate the hydrolysis process.

Key Properties:

Molecular Weight: 320.26 g/mol
Melting Point: 432 °C (789.6 °F)
Boiling Point: 317 °C (603 °F) at 760 mmHg (sublimes)
Density: 4.8 g/cm³
Solubility: Soluble in non-polar solvents like benzene and toluene, but reacts violently with water.
Structure: It adopts a tetrahedral structure with hafnium at the center and four chlorine atoms surrounding it.

II. Synthesis and Production of HfCl₄

The primary method for producing HfCl₄ involves the chlorination of hafnium dioxide (HfO₂), a common hafnium-containing ore. The reaction typically occurs at high temperatures (around 500-800 °C) in the presence of chlorine gas (Cl₂) and a reducing agent, often carbon (C). The overall reaction can be represented as:

HfO₂ + 2Cl₂ + C → HfCl₄ + CO₂

The resulting HfCl₄ is then purified through processes like fractional distillation or sublimation to remove impurities and ensure high purity, which is crucial for many applications. The purity level is critical as even trace impurities can significantly impact the performance of the end product.

III. Applications of HfCl₄

HfCl₄'s unique properties dictate its primary applications, predominantly focused on the production of high-purity hafnium metal and the creation of advanced materials:

Hafnium Metal Production: The Kroll process, a widely used method for refining hafnium metal, relies heavily on HfCl₄. The chloride is reacted with magnesium or sodium in an inert atmosphere to reduce it to metallic hafnium. Subsequent purification steps yield high-purity hafnium, a crucial element in nuclear reactors and high-temperature applications.

Chemical Vapor Deposition (CVD): HfCl₄ is used as a precursor in CVD processes for depositing hafnium-containing thin films. These films are essential in microelectronics as high-k dielectric materials in advanced integrated circuits, helping to improve device performance and reduce leakage currents. For example, in the fabrication of DRAM chips, HfO₂ films derived from HfCl₄ are used as gate dielectrics.

Atomic Layer Deposition (ALD): Similar to CVD, ALD leverages HfCl₄ to precisely control the deposition of hafnium oxide films, offering exceptional thickness uniformity and control over film properties crucial for advanced semiconductor manufacturing.

Other Applications: HfCl₄ finds niche applications in catalyst preparation and specialized chemical syntheses, although these are less prevalent compared to its use in materials science and metal production.

IV. Safety Precautions and Handling

HfCl₄'s reactivity demands meticulous safety protocols during handling and storage. The following precautions are crucial:

Moisture Sensitivity: HfCl₄ must be kept in rigorously dry conditions. Exposure to moisture leads to the formation of HCl gas, posing significant respiratory hazards. Sealed containers under inert atmosphere (e.g., nitrogen or argon) are essential for storage.

Personal Protective Equipment (PPE): Appropriate PPE, including respirators, gloves, and eye protection, is mandatory when handling HfCl₄. Laboratory fume hoods equipped with efficient scrubbing systems are necessary to manage potential HCl emissions.

Emergency Procedures: Spill procedures should be established and clearly communicated. Neutralization with alkaline solutions (e.g., sodium hydroxide) followed by careful disposal of the neutralized waste according to local regulations is crucial.

Disposal: HfCl₄ waste must be handled according to stringent environmental regulations. Consult local environmental agencies for specific disposal procedures.

V. Conclusion

HfCl₄ is a powerful and versatile chemical with significant applications in materials science and related fields. Understanding its physical and chemical properties, synthesis methods, and crucial safety precautions is paramount for its safe and effective utilization. From enabling the production of high-purity hafnium to playing a critical role in advanced semiconductor manufacturing, HfCl₄'s impact on modern technology is undeniable. However, its reactivity demands careful handling and adherence to strict safety protocols to prevent accidents and protect both personnel and the environment.

FAQs

1. What are the health hazards associated with HfCl₄? Exposure to HfCl₄ and its hydrolysis products (HCl) can cause severe respiratory irritation, burns to skin and eyes, and potential long-term health problems. Proper PPE and ventilation are essential.

2. Can HfCl₄ be stored at room temperature? Yes, but only in tightly sealed containers under an inert atmosphere (nitrogen or argon) to prevent hydrolysis.

3. What is the difference between HfCl₄ and ZrCl₄ (Zirconium Tetrachloride)? While both are chemically similar, they differ significantly in their applications due to the differences in the properties of hafnium and zirconium. HfCl₄ is often preferred in high-k dielectric applications due to hafnium oxide's higher dielectric constant.

4. How is the purity of HfCl₄ determined? Purity analysis typically involves techniques such as Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or other advanced analytical methods to quantify the presence of impurities.

5. What are the environmental concerns associated with HfCl₄? Improper handling and disposal can lead to the release of HCl into the environment, causing acidification and potential harm to ecosystems. Adherence to strict disposal protocols is crucial.

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塩化金酸（HAuCl4）の酸解離定数（pKa）の値を知っている方 … 29 Jun 2012 · 塩化金酸（HAuCl4）の酸解離定数（pKa）の値を知っている方、また載っている文献を知っている方は教えて下さい。化学便覧などを調べたのですがどうしても分からないのです。よろしくお願いします。 HAuCl4→H^++AuCl4^-強酸だと思われます。だからpKa値は殆ど意味がないでしょう。根拠は、H^+と ...

electrochemistry - Gold Chloride as electroplating solution ... 31 Dec 2022 · $\begingroup$ Electrolysis of gold chloride solutions (or $\ce{HAuCl4^-}$) produces a rough, dusty and pulverulent gold deposit, which is not really adherent. To get a bright and continuous gold deposit, electrolysis must be carried out with gold cyanide, because in gold cyanide solutions, the concentration of $\ce{Au^{3+}}$ ions is extremely low.

Represent HAuCl4using stock notation. - BYJU'S Represent HAuCl4using stock notation.

Reactions involving gold have been of particular interest to … Reactions involving gold have been of particular interest to alchemists. Consider the following reactions, AuOH3 + 4 HCl → HAuCl4 + 3 H2O, H = 28 kcalAuOH3 + 4 HBr → HAuBr4 + 3 H2O, H = 36.8 kcalIn an experiment, there was an absorption of 0.44 kcal when one mole of HAuBr4 was mixed with 4 moles of HCl. Then, the fraction of HAuBr4 converted into HAuCl4 …

IUPAC name of H [AuCl4] - Chemistry Stack Exchange 23 Mar 2021 · The authoritative source Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 (Red Book) lists $\ce{H[AuCl4]}$ as an example of a salt in the subsection IR-4.4.3.4 Generalized salt formulae [1, pp. 61–62].

化学の金コロイド合成について。 - HAuCl4(塩化金酸)とNa3. 5 Apr 2016 · 化学の金コロイド合成について。 HAuCl4(塩化金酸)とNa3C6H5O7(クエン酸ナトリウム)を混ぜて金コロイドを合成するという実験をするのですが…調べてみたら、条件によって金コロイドの大きさも違うように書いていて、なぜ大きさが変わってくるのかが分かりません。また、分子レベルでこの2つの ...

inorganic chemistry - How pure gold is obtained back from … 1 Jul 2019 · You say: I searched everywhere, but I didn't get the answer. When I type youtube gold recovery from chloroauric acid into Google, the first link is to a Youtube video with a visible demonstration of converting chloroauric acid to gold.

Solubility of gold salt solution? - Chemistry Stack Exchange 6 Feb 2015 · $\bullet \ce{Au2S}$: insoluble (quite sure this is the precipitate formed in basic solution when sodium metabisulfite is added to $\ce{HAuCl4}$. Either that or $\ce{Au2S3}$). $\bullet \ce{AuCl3}$: highly soluble (can be formed by dehydrating and evaporating $\ce{HCl}$ from $\ce{HAuCl4}$, which is the product of $\ce{Au}$ dissolved in aqua regia).

What is the oxidation number of gold in the complex What is the oxidation number of gold in the complex [ AuCl 4] ?A. 4B. 3C. 2D. 1

Haucl4

Decoding HauCl4: Understanding and Handling Hafnium Tetrachloride

I. Physical and Chemical Properties of HfCl₄

II. Synthesis and Production of HfCl₄

III. Applications of HfCl₄

IV. Safety Precautions and Handling

V. Conclusion

FAQs

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