Preparation and characterization of boron carbide at low temperatures

Dissertant

Jabir, Husayn Ala

Thesis advisor

Chyad, Fadil A.
al-Tai, Muhammad H.

University

University of Technology

Faculty

-

Department

Department of Materials Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2013

English Abstract

Boron carbide is one of the ceramic materials has extreme hardness with low specific gravity; zirconia has high fracture toughness.

These properties promote to prepare boron carbide – zirconia composite.

In this study, boron carbide (BR4RC) has been prepared using boric acid as boron source, and three types of polymer materials as carbon source (glucose, polyvinyl alcohol (PVA) and corn starch) by utilizing the carbothermal process with using reduced gas (Ar/HR2R) flow.

Aqueous solutions of boric acid in the presence of one polymeric materials take a gel form.

Pyrolysis temperature 350°C was used after obtained the gel.

Then, the pyrolysed product is calcined at a range of (600 – 900)°C for (1 – 2) hours.

XRD analyses show that BR4RC is detected by using boric acid and PVA as raw materials after calcination at 800°C.

Also, the addition of magnesium sulfate into the mixture of reactants promotes the reaction and resulted in an increase of the boron carbide content.

Some of the produced BR4RC powders have been coated with yttria stabilized tetragonal zirconia polycrystalline (YTZP) (ZrOR2R – 6wt% YR2ROR3R) by using sol-gel method in order to obtain composite powder (BR4RC core/ YTZP shell, 1/1 wt%).

Zirconium oxychloride (ZrOClR2R.8HR2RO) and yttrium nitrate (Y(NOR3R)R3R.6HR2RO) have been used as the precursors for the synthesis of the YTZP compound.

Several characterizations such as, particle size distribution, XRD, SEM and EDX have been studied for both of prepared BR4RC powder and the composite powder.

The characterization results show that the prepared BR4RC powder has a median size of 460 nm, and the SEM images of the composite powder show the YTZP shell compound on the surface of BR4RC particles are well distributed.

The prepared boron carbide and composite powders were mixed with different percentages to produce BR4RC – YTZP composite materials.

The YTZP was added to BR4RC are in the range (0 – 12.5) wt%.

The samples are sintered using spark plasma sintering technique at (1800 and 1900)°C for 5 minutes.

Microstructure examinations after the sintering are revealed by XRD, SEM and EDX.

The physical and mechanical properties (density, porosity, Vickers hardness, Young's modulus, fracture toughness and splitting tensile strength) for the sintered samples are then measured.

The results showed that the YTZP addition to B4C enhance the physical and mechanical properties.

Furthermore, the YTZP addition as composite powder has an obvious effect on sintering and mechanical properties of B4C.

The best YTZP additions are ranged 5 – 7.5 wt% at 1900°C sintering.

When the YTZP content in B4C increases more, the most properties of the samples will be reduced as a result of the residual pores.

A statistical analysis has been implemented for the experimental part data during this work and regression equations for the ceramic composite properties are obtained by using SPSS software.

The results show, that the SPSS software creates regression equations for the ceramic composite properties with high regression accuracy, through comparison with the measured values.

Main Subjects

Materials Science , Minerals

Topics

• Temperatures

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-417983