Search query: The search for superhard materials: Doped boron

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abstract: Superhard materials have numerous industrial applications and are then the subject of intense investigations. The b rhombohedral polymorph of boron is the second hardest elemental crystal (HV ~34 GPa) It is also very light and a p type semiconductor. In the early seventies, it has been shown that the doping of boron with 3d transition elements enhances its hardness by about 25% We predict that, in general, heavily doped samples MBx, with x<=31 or equivalently a dopant concentration larger than 3.2 at. should be ultrahard, i.e. HV >43 GPa. The relevant dopants M are Al, Cu, Sc, Mn, Mg and Li. In addition to these properties, boron rich materials have a very low volatility, a high chemical inertness and high melting point >2400 degC) They are suitable for applications under extreme conditions and thermoelectric equipment.
author_names: Mohamed Hebbache
title: The search for superhard materials: Doped boron
year: 2009

abstract: The search for suitable additives for boron suboxide (B6O) materials which could improve densification, reduce sintering temperature and tailor the microstructure has been productive. B6O materials doped with 0 5 vol% cobalt addition were sintered at temperatures up to 1850 degC and pressure of 50 MPa for 20 min. Relationships between the formed phases, microstructures and mechanical properties of the sintered materials were investigated as a function of sintering conditions and added cobalt content. The hardness of the sintered B6O materials increases with sintering temperature, while the fracture toughness increases with increasing cobalt content and reduces with increasing sintering temperature.
author_names: O T Johnson

Iakovos Sigalas

Mathias Herrmann

Hans Joachim Kleebe
title: Densification and properties of superhard B6O materials with cobalt additions
year: 2012

abstract: The development of superhard materials is focused on two very different classes of compounds. The first contains only light, inexpensive main group elements and requires high pressures and temperatures for preparation whereas the second class combines a transition metal with light main group elements and in general tends to only need high reaction temperatures. Although the preparation conditions are simpler, the second class of compounds suffers from the transition metals used being expensive and exceedingly scarce. Thus, in the search for novel superhard compounds, synthetic accessibility, resource considerations, and material response must be balanced. The research presented here develops high information density plots drawn from high throughput first principle calculations and data mining to reveal the optimal composition space to synthesize new materials. This contribution includes analysis of the experimentally known Vickers hardness for materials as well as screening over 1100 compounds from first principle calculations to predict their intrinsic hardness. Both data sets are analyzed not only for their mechanical performance but also the compositional scarcity, and Herfindahl Hirschman index is calculated. Following this methodology, it is possible to ensure targeted materials are not only sustainable and accessible but that they will also have superb mechanical response.
author_names: Aria Mansouri Tehrani

Leila Ghadbeigi

Jakoah Brgoch

Taylor D Sparks
title: Balancing Mechanical Properties and Sustainability in the Search for Superhard Materials
venue: Integrating Materials and Manufacturing Innovation
year: 2017

abstract: Superhard boron carbon materials are of prime interest due to their non oxidizing properties at high temperatures compared to diamond based materials and their non reactivity with ferrous metals under extreme conditions. In this work, evolutionary algorithms combined with density functional theory have been utilized to predict stable structures and properties for the boron carbon system, including the elusive superhard BC5 compound. We report on the microwave plasma chemical vapor deposition on a silicon substrate of a series of composite materials containing amorphous boron doped graphitic carbon, boron doped diamond, and a cubic hard phase with a boron content as high as 7.7 at% The nanoindentation hardness of these composite materials can be tailored from 8 GPa to as high as 62 GPa depending on the growth conditions. These materials have been characterized by electron microscopy, X ray photoelectron spectroscopy, Raman spectroscopy, X ray diffraction, and nanoindentation hardness, and the experimental results are compared with theoretical predictions. Our studies show that a significant amount of boron up to 7.7 at% can be accommodated in the cubic phase of diamond and its phonon modes and mechanical properties can be accurately modeled by theory. This cubic hard phase can be incorporated into amorphous boron carbon matrices to yield superhard materials with tunable hardness values.
author_names: Paul A Baker

Shane A Catledge

Sumner B Harris

Kathryn J Ham

Wei-Chi Chen

Cheng-Chien Chen

Yogesh K Vohra
title: Computational Predictions and Microwave Plasma Synthesis of Superhard Boron Carbon Materials
venue: Materials
year: 2018

abstract: In the pursuit of materials with exceptional mechanical properties, a machine learning model is developed to direct the synthetic efforts toward compounds with high hardness by predicting the elastic moduli as a proxy. This approach screens 118 287 compounds compiled in crystal structure databases for the materials with the highest bulk and shear moduli determined by support vector machine regression. Following these models, a ternary rhenium tungsten carbide and a quaternary molybdenum tungsten borocarbide are selected and synthesized at ambient pressure. High pressure diamond anvil cell measurements corroborate the machine learning prediction of the bulk modulus with less than 10% error, as well as confirm the ultraincompressible nature of both compounds. Subsequent Vickers microhardness measurements reveal that each compound also has an extremely high hardness exceeding the superhard threshold of 40 GPa at low loads (0.49 N) These results show the effectiveness of materials development through state of the art machine learning techniques by identifying functional inorganic materials.
author_names: Aria Mansouri Tehrani

Anton O Oliynyk

Marcus Parry

Zeshan Rizvi

Samantha Couper

Feng Lin

Lowell Miyagi

Taylor D Sparks

Jakoah Brgoch
title: Machine Learning Directed Search for Ultraincompressible, Superhard Materials.
venue: Journal of the American Chemical Society
year: 2018

abstract: Superhard materials such as diamond or cubic boron nitride are widely used in industry for fast machining and drilling. A great challenge to scientists is to make a material which could be harder than diamond. A short review of the compounds predicted to be superhard is made. A new approach based on recent experimental high pressure results is to consider heavier atom compounds crystallizing in dense structures; possible new materials are proposed.
author_names: Jean-Michel Leger

J Haines
title: The search for superhard materials
year: 1997

abstract: As an extension of boron based materials, transition metal doped boron clusters deserve interest in controlling size dependent structural and electronic properties. Herein, using the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method and density functional theory (DFT) calculations, we have performed a global search for the lowest energy structures of ZrBQn (Q 0, 1) clusters with n 10 20. The results show that the ground state structures of the obtained clusters feature a distinctive structural evolution pattern, from half sandwich bowl to distorted drum like and then to Zr centered distorted tubular motifs. For the sake of validating the current ground state structures, photoelectron spectra are predicted from time dependent DFT calculations. More interestingly, the neutral and anionic ZrB12 clusters are found to possess enhanced stability in the size regime studied here. The stability of the closed shell half sandwich ZrB12 cluster is analyzed by intrinsic bond orbital (IBO) and Adaptive Natural Density Partitioning (AdNDP) methods, which indicates that the stability mechanism is caused by the dopant Zr atom breaking the boron bowl's triangle B3 unit to form a quasi linear B3 unit in B12 and strengthen both the interaction of the B B s bonds and the Zr B p bonds.
author_names: Weiguo Sun

Xinxin Xia

Cheng Lu

Xiaoyu Kuang

Andreas Hermann
title: Probing the structural and electronic properties of zirconium doped boron clusters: Zr distorted B12 ligand framework.
venue: Physical chemistry chemical physics PCCP
year: 2018

abstract: Electron emission signifies an important mechanism facilitating the enlargement of devices that have modernized large parts of science and technology. Today, the search for innovative electron emission devices for imaging, sensing, electronics, and high energy physics continues. Integrating two materials with dissimilar electronic properties into a hybrid material is an extremely sought after synergistic approach envisioning a superior field electron emission (FEE) material. An innovation is described regarding the fabrication of a nanostructured carbon hybrid resulting from the one step growth of boron doped nanocrystalline diamond (BNCD) and carbon nanospines (CNSs) by a microwave plasma enhanced chemical vapor deposition technique. Spectroscopic and microscopic tools are used to investigate the morphological, bonding, and microstructural characteristics related to the growth mechanism of these hybrids. Utilizing the benefits of both the sharp edges of the CNSs and the high stability of BNCD, a promising FEE performance with a lower turn on field of 1.3 V mm 1, a higher field enhancement factor of 6780, and a stable FEE current stability lasting for 780 min is obtained. The microplasma devices utilizing these hybrids as a cathode illustrate a superior plasma illumination behavior. Such hybrid carbon nanostructures, with superb electron emission characteristics, can encourage the enlargement of several electron emission device technologies.
author_names: Kamatchi Jothiramalingam Sankaran

Mateusz Ficek

Kalpataru Panda

C J Yeh

Miroslaw Sawczak

Jacek Ryl

Keh-Chyang Leou

Jeong Y Park

I-Nan Lin

Robert Bogdanowicz

Ken Haenen
title: Boron doped Nanocrystalline Diamond Carbon Nanospine Hybrid Electron Emission Source.
venue: ACS applied materials interfaces
year: 2019

abstract: We investigated the high pressure structures and properties of iron tetraborides (FeB4) using a combination of an ab initio high throughput search and a particle swarm optimization algorithm for crystal structure prediction. We found that, under compression, the boron sublattice in FeB4 from the buckled boron layer first polymerizes into B4 tetrahedral clusters and then forms cubo octahedral B12 clusters. At 55 GPa, the orthorhombic crystal structure with a Pnnm space group (58 FeB4) transforms into a tetragonal I41/acd structure (142 FeB4) which is stable within a wide pressure range up to 695 GPa. Then, a cubic Imm phase (229 FeB4) emerges at higher pressures up to at least 1 TPa. The computed Vicker's hardnesses of 58 142 and 229 FeB4 are 61.58, 47.44, and 50.87 GPa, respectively. All of them can be considered as superhard materials. Compared to the previously reported 58 FeB4 as a superhard superconductor, the B4 tetrahedral cluster based 142 FeB4 is a superhard semiconductor with an indirect band gap of 1.34 eV. The pressure induced metal to semiconductor transition can be related to a unique Fe B B three center covalent bond. Moreover, 229 FeB4, which is composed of cubo octahedral B12 clusters, is ferromagnetic with a magnetic moment of 0.929mB per Fe atom at ambient pressure. The magnetic moment will decrease rapidly with increasing pressure and be completely quenched as pressure exceeds 40 GPa. The pressure induced evolution of boron cluster units not only adds new features to boron chemistry, but also gives rise to novel superhard semiconductors or ferromagnetic materials. Moreover, our results may inspire further experimental and theoretical interest in designing new materials using clusters as pseudo atoms with expected properties.
author_names: Xuening Jiang

Jijun Zhao
title: Evolution of boron clusters in iron tetraborides under high pressure: semiconducting and ferromagnetic superhard materials
year: 2015

abstract: This review summarizes progress in electroanalysis of organic compounds and biomacromolecules by means of bare BDD based electrodes for the period of 2009 2018. New trends, which have emerged in the reported decade and which have improved their performance in batch voltammetric and amperometric methods and electrochemical detection in liquid flow techniques are commented. Importance of BDD surface termination, effect of boron doping level, and utilization of adsorption of analytes on BDD surfaces enabling development of adsorptive voltammetric techniques are addressed. Further, possibilities of simultaneous determination of analytes by means of voltammetric techniques utilizing computational approaches and multiple pulse amperometric detection are discussed. Strategies leading to enhancement of sensitivity such as nanostructuring of the BDD surface, fabrication of BDD based composite materials or new approaches in construction of microelectrodes and microelectrode arrays for biosensing represent another area of interest. Attention is paid to possibilities in detection of amino acids, peptides and proteins, nucleobases, nucleos(t)ides and DNA/RNA.
author_names: Simona Baluchova

Ales Danhel

Hana Dejmkova

Veronika Ostatna

Miroslav Fojta

Karolina Schwarzova-Peckova
title: Recent progress in the applications of boron doped diamond electrodes in electroanalysis of organic compounds and biomolecules A review.
venue: Analytica chimica acta
year: 2019