The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

/pdf/a-comprehensive-review-of-zno-materials-and-devices-21a3zjadem.pdf

A comprehensive review of zno materials and devices

Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

/pdf/diamond-like-amorphous-carbon-3pczopr0z7.pdf

Diamond-like amorphous carbon

Hydrotalcite-type anionic clays: Preparation, properties and applications.

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Titanium dioxide, TiO2, is an important photocatalytic material that exists as two main polymorphs, anatase and rutile. The presence of either or both of these phases impacts on the photocatalytic performance of the material. The present work reviews the anatase to rutile phase transformation. The synthesis and properties of anatase and rutile are examined, followed by a discussion of the thermodynamics of the phase transformation and the factors affecting its observation. A comprehensive analysis of the reported effects of dopants on the anatase to rutile phase transformation and the mechanisms by which these effects are brought about is presented in this review, yielding a plot of the cationic radius versus the valence characterised by a distinct boundary between inhibitors and promoters of the phase transformation. Further, the likely effects of dopant elements, including those for which experimental data are unavailable, on the phase transformation are deduced and presented on the basis of this analysis.

https://link.springer.com/content/pdf/10.1007%2Fs10853-010-5113-0.pdf

Review of the anatase to rutile phase transformation

Science Teachers and Recent Scientific Research

/pdf/ceramics-from-solutions-3r9zoftju4.pdf

Ceramics from Solutions

Beside chromium carbide and chromium nitride, chromium sesquioxide Cr 2 O 3 is a new candidate for hard and protective coatings. The reported bulk microhardness of Cr 2 O 3 is 29.5 GPa according to Samsonov (1982) and 28GPa according to Robertson and Manning (1990), making it second among all oxides, even above sapphire. The Mohs hardness is 8. The hardest oxide is the high pressure form of SiO 2 , stishovite, with 35 GPa (Haines and Lager (1998).

Remarkably Adherent, Thick And Tough Chromia (Cr2 O3) Coatings On Steel Made By A Laser Process

Candidate backfill materials such as montmorillonite and clinoptilolite with and without the presence of simulated nuclear waste solids such as borosilicate glass, glass ceramic, sintered ceramic and supercalcine ceramic were investigated under repository simulating conditions (=300°C and 30 MPa). Experiments were conducted under semi-wet as well as wet repository conditions. Montmorillonite and clinoptilolite did not seem to alter under both semi-wet and wet repository conditions as determined by XRD. However, the above backfill materials reacted extensively with wastes under both conditions. They altered to feldspar (oligoclase) in the presence of borosilicate glass and to analcime in the presence of particular ceramics under both semi-wet and wet repository conditions. Alteration of montmorillonite could not be detected either in the presence of the glass ceramic or supercalcine ceramic under both repository conditions. However, clinoptilolite altered to analcime in the presence of glass ceramic or supercalcine ceramic under wet repository conditions. Reactions of backfill materials with simulated wastes immobilized waste elements such as Cs, Mo, etc., by forming new phases such as analcime, oligoclase and powellite. In fact, analyses of product solutions from interaction runs indicated that the presence of backfill materials during the alteration of waste solids served to drastically reduce the concentration of some radionuclides in solutions. These results suggest that properly selected backfills can provide the simplest and most effective chemical (or thermodynamic) engineered barrier in an intelligently designed multibarrier system. Moreover, they indicate that the μ, P, and T in the usual leach tests (e.g. Paige, IAEA, etc.) are such that results of such tests cannot have any value in evaluating waste form behavior under repository conditions.

Backfill-Waste Interactions in Repository Simulating Tests

The desirability of the synthesis of materials at low temperatures is becoming evident in many major technologies. The principal obstacle is the slow kinetics of both combination and re-ordering to, and within, crystalline arrangements of ions at these low temperatures. This paper reviews several different methods, used by his group over the last 40 years. Results very recently developed in the author's laboratory are described in some detail. The methods for accelerating reactions in oxide materials at temperatures in the range of 0°-500°C include:
1.	
Utilizing precursors made via solution-sol-gel and, recently, epitaxy via nanocomposite gel routes.

2.	
Using low melting “fluxes.”

3.	

(a)	
Hydrothermal processes.

(b)	
Hydrothermal process with superimposed electric fields.

(c)	
Hydrothermal process with mechanical forces.




4.	
Mechano-chemical effects including very high uniaxial pressure and shear.

5.	
Acoustic wave stimulation (sonochemical).

6.	
Using of ionizing and non-ionizing radiation.

7.	
Hydrothermal process with microwave fields.




The results will show that several of these methods can accelerate reactions of the most common oxides by 1-2 orders of magnitude, and will therefore be technologically significant. The basic science behind the processes is still primitive.

Catalysis of low temperature synthesis of ceramics

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