Bala Vaidhyanathan

Bala Vaidhyanathan
Loughborough University | Lough · Department of Materials

M.Sc., PhD., FHEA
Professor of Advanced Materials & Processing

About

104
Publications
23,153
Reads
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3,741
Citations
Citations since 2016
24 Research Items
1643 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
Introduction
Advanced Materials; Nanostructured Ceramics & composites; 3D printing of Ceramics; Field Assisted Processing of Materials AWARD: http://www.lboro.ac.uk/departments/materials/news/materials-professor-wins-verulam-medal-and-prize.html Outreach: BBC 4 features our research on 3D Printing of Bioceramic Implants - today 31st October, 2018, at 9 pm : www.bbc.co.uk/materials
Additional affiliations
September 2009 - present
Higher Education Academy
Position
  • Fellow
Description
  • FHEA
January 2006 - December 2011
Loughborough University
January 1997 - present
Pennsylvania State University
Position
  • Microwave Processing of Advanced Materials

Publications

Publications (104)
Article
BaTiO3 based multilayer ceramic capacitor (MLCC) is an important component in electronic devices. Achieving high dielectric performance, miniaturisation and cost effectiveness are still challenging. Co-sintering ceramic layers with metal electrodes and use of expensive Pt and high-Pd content compositions as electrodes are other key issues. Thus, th...
Chapter
Piezoelectric accelerometer sensors are widely used for testing and monitoring vibrations in automotive, aerospace or industrial applications. The temperature limitation of most piezoelectric accelerometers is below 500 °C, which meets the requirements of typical vibration measurement applications. However, in extreme cases such as engine monitorin...
Article
Low sintering temperature, ultra-low loss microwave ceramics are envisaged as future dielectrics for fabricating low temperature co-fired ceramic (LTCC) components for 5G applications. Low sintering temperature bismuth molybdate β-Bi2Mo2O9 ceramic powders have been synthesised using a solid-state reaction method. Their additive manufacture and resu...
Article
The ballistic impact performance of nanocrystalline zirconia-toughened alumina (nZTA) ceramics, comprising 15 wt% nano-yttria-stabilised zirconia in a sub-micron alumina matrix, have been studied through depth of penetration tests and compared to the results for monolithic alumina. The penetration resistance of each material was evaluated by fittin...
Article
Full-text available
Graphene-based advanced electrodes with improved electrochemical properties have received increasing attention for use in lithium ion batteries (LIBs). The conventional synthesis of graphene via liquid phase exfoliation or chemical reduction of graphene oxide (GO) approaches, however, either involves prolonged processing or leads to the retainment...
Article
Nanocrystalline BaTiO3 (BT) powder was synthesised using a polymer precursor route and the influence of conventional, microwave and combined hybrid heating methods on phase formation was investigated. A single-phase tetragonal BT (t-BT) nanocrystalline powder of about 20 nm primary particle size and decreased agglomeration were formed when high lev...
Article
Full-text available
Additive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based A...
Conference Paper
Full-text available
This paper presents 3D printed low temperature sintered (< 700 °C) ceramic materials for microwave applications. The advantages of using cold sintered ceramics include better material compatibility with conductive elements in future multi-material additive manufacturing for microwave devices. Molybdate based ceramics have been synthesized and prepa...
Article
Full-text available
Lanthanum/manganese doped barium titanate (BT) based PTCR functional heater elements/structures were fabricated with desirable electrical properties for the first time using Additive Manufacturing (AM). 3D printed components of varying size and shape and prototype honeycomb lattices with high density were achieved through AM. Aqueous, less organic...
Cover Page
Full-text available
BBC 4 - Materials of Modern Age - Documentary (Outreach) LU ceramics research - UKRI funded
Article
A rapid synthesis procedure for the preparation of nanocrystalline yttrium aluminium garnet (nYAG) particles has been developed, for the first time, using the combination of subcritical conditions and microwave irradiation. It is believed that the use of butanediol delayed the onset of pressure rise due to its low partial pressure, whilst the micro...
Article
Large scale 50 × 50 mm sintered nanostructured zirconia ceramics were fabricated via industrially viable dry pressing routes. The green bodies were sintered by a two-stage process and the optimised sintering conditions are reported. The suitability of nanostructured zirconia for demanding applications in petrochemical valve components was investiga...
Article
Full-text available
Towards achieving efficient waste water treatment, the degradation of a common water pollutant, Orange G azo dye, was studied using a new hybrid catalyst and microwave irradiation. The fabrication of a hybrid catalyst based on reduced graphene oxide–titania (rGO–TiO2), was first achieved in a single mode microwave cavity by reducing the precursor c...
Article
Full-text available
Room and high temperature flexural strength and coefficient of thermal expansion (CTE) of HfB2 ultra-high temperature ceramic (UHTC) particulate filled Cf/C composites are determined along with UHT oxidation behavior. Both room and high temperature strength of the composites were found to be broadly comparable to those of other thermal protection s...
Article
Full-text available
Granulation is a key factor towards improvement of the flowability of fine ceramic powders to make them suitable for industrial dry pressing. Controlled granulation of fine alumina particles with a primary particle size of ∼150 nm was carried out using spray-freeze drying, which led to the production of flowable granules with high crushability. The...
Article
Full-text available
Nanocrystalline alumina powder with an average crystallite size of ≤50 nm has been consolidated by spark plasma sintering (SPS) and hot pressing (HP) with a view to achieving dense, fine grained alumina bodies that display transparency. When as-synthesised powder was densified directly, excessive grain growth resulted from both the SPS and HP techn...
Article
Flash and field assisted sintering techniques (FAST) have been demonstrated in many singular ceramic systems. However, little has been done to thoroughly investigate this phenomenon in binary systems. Zirconia-alumina composites are of interest because of their widespread use in demanding situations for health care, petrochemical and energy applica...
Article
Cost effective and fast ultra-high-temperature testing methods such as oxyacetylene torch testing are extremely useful for the rapid screening of ultra-high-temperature ceramic (UHTC) materials for hypersonic applications. There is no report in the literature, however, of an organised study to measure the heat flux and how it varies with gas flow r...
Article
NanoYAG particles with spherical morphology have been synthesised using a solvothermal method; a structure sensitive reaction, where the chemical reaction and the particle growth kinetics are interdependent. It has been observed that the primary YAG particles agglomerated into ∼30 nm clusters via a self-assembled Ostwald ripening process along (2 1...
Article
The mechanism of anisotropic growth of HfB2 rods has been discussed in this study. HfB2 powder has been synthesized via a sol–gel-based route using phenolic resin, hafnium chloride, and boric acid as the source of carbon, hafnium, and boron respectively, though a small number of comparative experiments involved amorphous boron as the boron source....
Chapter
This chapter describes recent developments in the field of advanced ceramic composites for hypersonic applications. Ultra-high temperature ceramic (UHTC) composites are the most viable class of materials that can overcome the poor fracture toughness and thermal shock resistance of monolithic UHTC materials. The various techniques that have been exp...
Article
The present work describes a simple process to synthesise HfB2 powder with sub-micron sized particles. Hafnium chloride and boric acid were used as the elemental sources whilst several carbon sources including sucrose, graphite, carbon black, carbon nanotubes and liquid and powder phenolic resin were used. The carbon sources were characterised usin...
Article
Granulation of nanostructured 3 mol% yttria stabilised zirconia using spray freeze drying was investigated to achieve flowable and crushable granules for subsequent die pressing. Commercial nanosuspension consisting of ∼16 nm particles was concentrated to ∼55 wt% solids content via a patented technique, followed by spraying into liquid nitrogen usi...
Article
Full-text available
Alumina, 10% and 20% ZTA with 1.5 mol% yttria stabiliser were subjected to Vickers indentation testing with loads from 1 to 20 kg. Cr3+ fluorescence and Raman spectroscopy were applied to the indent centre and around the indentation in order to investigate the origin of the signal, the effect of indentation loads and zirconia phase transformation o...
Article
Two different synthesis methods, viz. precipitation and hydrothermal treatment, were used to synthesise ultra-fine α-alumina powders from aluminium chloride, ammonia solution and TEAH (tetraethyl ammonium hydroxide). XRD, BET surface area analysis, TEM and FEG-SEM were used to characterise the powders produced. The presence of industrial α-alumina...
Article
Hafnium diboride (HfB2) powder has been synthesized via a sol–gel-based route using phenolic resin, hafnium chloride, and boric acid as the source of carbon, hafnium, and boron, respectively, though a small number of comparative experiments involved amorphous boron as boron source. The effects of heat-treatment dwell time and hafnium:carbon (Hf:C)...
Article
Isotropically conductive adhesives (ICAs) and inks are widely used for interconnecting components and for printed circuits. Silver (Ag)-filled ICAs and inks are the most popular due to their high conductivity and good reliability. However, the price of Ag is a significant issue for the wider exploitation of these materials in low cost, high volume...
Article
Techniques based on vacuum bagging (VB) and electrophoretic impregnation (EPI) have been investigated for the impregnation of SiC powder into layered Nicalon SiC fabric preforms. The aim was to produce preimpregnated samples for subsequent chemical vapor infiltration (CVI) with reduced intertow porosity that arises from the construction of the fabr...
Article
Full-text available
Microwave assisted preparation has been shown to improve the performance of hematite photoelectrodes for solar driven water splitting. To understand the microwave heating process further, the distribution of the electromagnetic (EM) fields within the material is analysed using finite-difference time-domain (FDTD) EM software. The rate of the increa...
Article
A microwave heated methyl trichlorosilane based chemical vapour infiltration technique has been used to form SiCf/SiC composites from SiC fibre preforms preimpregnated with SiC powder using two different fabrication techniques. While infiltration rates obtained from samples loaded with powder were generally higher than for preforms without powder,...
Patent
Full-text available
A method of forming granules, the method including forming a suspension of a nanopowder such as a nano zirconia powder containing yttria. The powder is formed from a suspension, and freon is added directly to the suspension as an additive. The suspension is then granulated by spray freeze drying, and the freon subsequently removed by heat treatment...
Article
Full-text available
Tantalum carbide samples have been subjected to high-temperature testing at ∼2300°C using an oxyacetylene torch to evaluate their potential for ultra-high temperature applications. While large samples cracked during the rapid heating, indicating their inability to withstand thermal shock, small samples survived the severe test conditions. The oxida...
Article
Current generation carbon–carbon (C–C) and carbon–silicon carbide (C–SiC) materials are limited to service temperatures below 1800 °C and materials are sought that can withstand higher temperatures and ablative conditions for aerospace applications. One potential materials solution is carbon fibre-based composites with matrices composed of one or m...
Article
Nanocrystalline yttrium aluminium garnet (nYAG) powder has been synthesized via sol-gel and co-precipitation methods using nitrate precursors. Thermal evolution and crystallisation kinetics of both the methods were investigated. The optimised calcination condition for the formation of nYAG was also examined. It was found that a complete transformat...
Chapter
Hematite is the mineral form of iron(III) oxide (Fe2O3), one of several iron oxides. In this book, the authors present current research in the study of the sources, properties and applications of hematite. Topics discussed include nanostructured hematite for solar driven hydrogen generation; reactions at the hematite surface with Fe(II) and environ...
Article
Isotropically conductive adhesives (ICAs) and inks are seen as suitable candidates for interconnecting components and for printed circuits. Silver (Ag) filled ICAs and inks are the most popular due to their high conductivity and good reliability. However, the price of Ag is a significant issue for the wider exploitation of these materials in low co...
Article
Full-text available
Hypersonic vehicles need sharp leading edges to enable vehicle maneuverability during atmosphere exit and re-entry. Components, such as the leading edges, combustors and thermal protection systems, thus require materials that can withstand the high thermal, mechanical and shock-wave loadings that these aircraft will experience during flight. Develo...
Article
Full-text available
The brittle nature of ceramics can limit their ability to resist multiple ballistic impacts. The present work focuses on investigating the possibility of using a toughened nanostructured ceramic, viz. nano zirconia toughened alumina (ZTA), as a potential ceramic armour. The material comprises of 10 -20 wt% nano yttria stabilised zirconia (nanoYSZ)...
Article
Full-text available
The paper reports the synthesis, structural and high frequency dielectric properties of Ba(Zr x Ti1−x )O3,BZT, nanopowders where x = 0, 0.1, 0.2, 0.3. These powders were synthesized using both microwave assisted and conventional heating, with the former requiring lower temperature and shorter times compared to the latter, viz., 700 °C for 30 min ve...
Article
The influence of grain size and yttria content on the hydrothermal aging behavior of yttria-stabilized zirconia ceramics has been investigated via the preparation of genuine, fully dense nanozirconia ceramics with <100 nm grain size by two-step sintering. The samples were aged at different temperatures for varying periods of time and XRD and micro-...
Article
This paper investigates the effect of grain size within the nano to micron regime on ionic conductivity for yttria stabilised zirconia (YSZ) with various yttria levels. The samples were made using either slip casting or die pressing routes and were characterised via the use of 4-point electrical conductivity, AC impedance, high resolution transmiss...
Article
Full-text available
Micro?Raman spectroscopy has been employed as an effective technique to determine the phase transformations in nanostructured yttria stabilised zirconia (YSZ) ceramics with different yttria contents. Samples have been prepared with varying mean grain sizes by a slip casting route followed by a microwave assisted two?step sintering cycle starting wi...
Article
Nano-crystalline HfB 2 and HfC powders have been synthesized through a simple sol-gel route by using inorganic precursors like hafnium (IV) chloride (HfCl 4), boric acid (H 3BO 3) and phenolic resin as a source of hafnium, boron and carbon respectively. The resulting HfB 2 powders had an average crystallite size of ∼35 nm whilst the HfC powders wer...
Article
The study of hydrothermal degradation of 3 mol% yttria partially stabilized zirconia was carried out on various grain sizes with the target to prove the long term stability of nano sized 3YSZ applied in solid oxide fuel cells (SOFC5). Samples with grain sizes lower than 100 nm (nano) and higher than 100 nm (submicron) were produced by uniaxial pres...
Article
It is demonstrated for the first time that significant enhancement of photoelectrochemical performance could be achieved by using microwave-assisted annealing for the fabrication of α-Fe2O3 thin films. The process can also lead to significant energy savings (>60% when compared with conventional methods). Different types of Fe thin films were oxidiz...
Article
The processing of nanocrystalline yttria doped zirconia powder via dry forming routes has been investigated via the granulation of the powder using spray freeze drying (SFD). Free-flowing and crushable powders suitable for either die or isosatic pressing have been achieved via the combination of SFD with additions of up to 2 vol% of Freon 11; the l...
Article
Microwave sintering of multilayer capacitor/varistor-based integrated passive devices (IPDs) has been investigated for the first time. The sintered samples were characterized for density, microstructure, composition, and electrical performance. It was found that IPDs with varistor/capacitor formulations could be microwave sintered to fully dense de...
Article
There is a considerable current interest in learning how to process genuinely nanostructured ceramics as they offer the potential for significantly enhanced properties; however, it is often difficult to make large enough components to allow more than the most basic of property measurements. In this work, densified components measuring up to 50 mm i...
Chapter
This paper was published in Ceramic Engineering and Science Proceedings [© The American Ceramic Society] and details of the definitive version are available from: http://ceramics.org/acers-bookstore/cesp-ceramic-engineering-and-science-proceedings/ The feasibility of employing the microwave methodology for the processing of integrated passive devic...
Article
Si-doped nanostructured hematite (α-Fe2O3) has attracted significant attention as a low-cost, high-efficiency candidate material for photoelectrochemical water splitting. In this work, we investigated the effect of Si incorporation on the preparation and performance of α-Fe2O3 films produced by atmospheric pressure chemical vapor deposition (APCVD)...
Article
Nanostructured thin films of α-Fe2O3 were prepared through atmospheric chemical vapour deposition (APCVD) using ferrocene and iron pentacarbonyl as precursors. Higher optical absorption was observed for hematite films prepared using ferrocene, which was attributed to the higher packing density. Photoelectrochemical (PEC) studies of the films prepar...
Article
This article was published in the journal, Materials Science Forum [© Trans Tech Publications] and the definitive version is available at: http://www.scientific.net/MSF/ This paper attempts to shed light on why the stand alone microwave processing of technical ceramics, despite being one of the most popular field with respect to volume of research...
Article
Conventional ceramic forming routes have been adapted for the processing of ∼16 nm, 3 mol% yttria-stabilised zirconia nanopowders leading to the production of ∼99% dense nanostructured ceramics that display average grain sizes as fine as ∼65 nm. The precursor material is in the form of ∼5 vol.% solids content nanosuspensions produced commercially;...
Article
This is article was published in the journal, Journal of the European Ceramic Society [© Elsevier]. The definitive version (doi:10.1016/j.jeurceramsoc.2007.09.002) is available at: http://www.elsevier.com/locate/jeurceramsoc The processing of 3 mol% yttria-partially stabilised zirconia nanopowder into components has been investigated via slip casti...
Article
Full-text available
Nanostructured thin films of α-Fe 2 O 3 were prepared through atmospheric chemical vapour deposition (APCVD) using ferrocene and iron pentacarbonyl as precursors. Higher optical absorption was observed for hematite films prepared using ferrocene, which was attributed to the higher packing density. Photoelec-trochemical (PEC) studies of the films pr...
Article
This is a journal article. It was published in the journal, Thin solid films [© Elsevier]. The definitive version is available at: http://www.sciencedirect.com/science/journal/00406090 or at: doi:10.1016/j.tsf.2007.10.095 Alumina films prepared by the sol-gel method were sintered at 1160 °C and 1200 °C using a 2.45 GHz microwave / conventional hybr...
Article
Full-text available
Clear evidence for the microwave effect has been observed during experiments in which a variety of materials have been heated using experimental systems that allowed both conventional and conventional-microwave hybrid heating. A hybrid single mode cavity has been used to investigate the microwave effect during phase changes in silver iodide, barium...
Article
This is a pre-print of an article published in the journal, Journal of the American Ceramic Society [© Blackwell]. The definitive version: BINNER, J.G.P. ... et al, 2006. Evidence for the microwave effect during hybrid sintering. Journal of the American Ceramic Society,89 (6), pp. 1977-1984, is available at: http://www.blackwell-synergy.com/loi/jac...
Article
Full-text available
A calorimetric device intended to study the 'microwave effect' - an apparent acceleratio n in kinetics or lowering of transition temperatures in inorganic and organic systems under the influence of microwave radiation - is being developed. Previous studies have often compared experiments where the thermal energy has been supplied using conventional...
Article
A fast, near-net shape route for the production of advanced ceramic components has been developed that uses carboxylic acid derivatives as coagulants for electrosterically dispersed, high solids content ceramic suspensions. The time dependent in situ hydrolysis of the coagulant d-gulonic-γ-lactone progressively destabilises the suspension to form a...
Article
This is Restricted Access. This article was published in the journal, Advances in Science and Technology [© Trans Tech] and is available at: http://www.scientific.net. Radiant and hybrid sintering experiments have been performed on dry and wet processed nanocrystalline 3-YSZ using both a conventional single stage and a new two stage sintering cycle...