Recently, there has been growing interest in the green synthesis of zeolite (aluminosilicate) materials using solvent-free synthesis methods. Solid starting materials are typically ground for a period of time followed by thermal heating to synthesize crystalline ZSM-5 zeolite. These studies generally have focused on products formed after the thermal heating. However, very little is known about the reaction intermediates formed during the mechanochemical pre-reaction grinding step and how the pre-reaction impacts the subsequent synthetic success. In this study, the mechanochemical approach used to synthesize ZSM-5 and mordenite zeolite was investigated. Two types of solvent-free synthesis methods were investigated; templated solvent-free synthesis, and template-free and solvent-free synthesis. The effect of grinding time was investigated first to find the optimal grinding time that initiates pre-reactions between the starting materials. Controlled experiments were used to monitor chemical and physical changes occuring during the grinding step. Subsequently, the effect of different synthesis conditions such as time, temperature, template, SiO2/Al2O3, and Na2O/Al2O3 ratios, and different precursors were studied using the optimal grinding time. Both manual (mortar and pestle) and ball mill (FTS 1000) grinding were used in this study. The synthesized products were characterized using XRD, BET nitrogen adsorption, SEM, and ICP-OES. Finally, selected single-phase synthesized zeolite materials were evaluated for their catalytic performance in biomass conversion process of cellulose and glucose to useful chemicals such as hydroxymethylfurfural (HMF).

Doctor Educationis / Energy storage technologies are rapidly being developed due to the increased awareness of global warming and growing reliance of society on renewable energy sources. Among various electrochemical energy storage technologies, high power supercapacitors and lithium ion batteries with excellent energy density stand out in terms of their flexibility and scalability. However, supercapacitors are handicapped by low energy density and batteries lag behind in power. Supercapatteries have emerged as hybrid devices which synergize the merits of supercapacitors and batteries with the likelihood of becoming the ultimate power sources for multi-function electronic equipment and electric/hybrid vehicles in the future. But the need for new and advanced electrodes is key to enhancing the performance of supercapatteries. Leading edge technologies in material design such as nanoarchitectonics become very relevant in this regard. This work involves the preparation of vanadium pentoxide (V2O5), pristine and zinc doped lithium manganese silicate (Li2MnSiO4) nanoarchitectures as well as their composites with hydroxylated graphene (G-ol) and carbon nanotubes (CNT). / 2023-12-02

The present thesis work is focused on the low-temperature transformation of food industry wastes like mussel shells into nanocrystalline ions-substituted hydroxyapatite powder, having similarities with natural bone apatite, on the consolidation of such powder by cold sintering, and on the physicochemical characterization of the raw materials, synthesised powders and sintered pellets. Nonetheless the evaluation of the mechanical and biological properties was carried out to address cold sintered bodies to possible scaffolds for bone tissue engineering applications. Mussel shells, like other biogenic source of calcium carbonate/phosphate, have the attractive of being a “zero”-cost raw material because they are a waste, but also of having trace elements (Mg, Na, Sr, etc.) which, if found in a bioceramic, have a positive effect on the biological properties. Therefore, mussel shell-derived hydroxyapatite could resemble the mineralized bone tissue, being natural apatite nanometric, ion substituted and with low crystalline tenor. In the first part of the manuscript, two production methods were explored: mechanochemistry and dissolution-precipitation synthesis. Mechanochemistry was carried out at room temperature by directly mixing crushed mussel shells with phosphoric acid in a ball mill. Nanocrystalline multi-ions substituted hydroxyapatite was produced after 4 h of milling and drying at 150°C. Conversely, dissolution-precipitation synthesis was carried out in two steps: the dissolution of crushed mussel shells by adding phosphoric and chloric acid occurred at room temperature, whereas the precipitation of calcium phosphates induced by soda solution, occurred at 45°C. Dissolution-precipitation was further implemented to produce a homogeneous composite material in a single-step by introducing chitosan (in a 2/5/10 wt%) during the dissolution step. The idea was to produce a composite material able to mimic the natural bone tissue composition. In the second part of the manuscript, cold sintering was investigated for the consolidation of the synthesised hydroxyapatite and hydroxyapatite-based composites at a maximum temperature of 200 °C to avoid phase transformation, limit grain growth and preserve the osteoconduction of the bioceramic materials. The effect of the main process parameters such as solvent amount, pressure, temperature and holding time was discussed. Pressure-solution creep and plastic deformation were pointed out as the fundamental consolidation mechanisms in cold sintering, the pressure playing the major role. With a synergistic combination of pressure (600 MPa), temperature (200°C) and liquid phase (20 wt%) it was possible to consolidate hydroxyapatite above 80% relative density in only 15 min. Furthermore, pressure and temperature act a complementary agent during cold sintering. In fact, it was possible to consolidate nanometric HAp and HAp/chitosan composites above 90% relative density by increasing the applied pressure up to 1.5 GPa at room temperature. The mechanical properties of cold sintered pellets were investigated, and resulted in a flexural bending strength and Vickers microhardness, respectively, of 45 MPa and 1.1 GPa for pure hydroxyapatite and of 55 MPa and 0.8 GPa for HAp/chitosan composite. In the frame of bone tissue engineering applications, cold sintered bodies were also preliminarily tested in vitro to establish their bioactivity, their cellular viability through cytotoxicity assessment, and the ability to sustain cells adhesion, osteogenic differentiation. And extracellular matrix mineralization.

No / Mechanochemical chemoenzymatic peptide and amide bond formation catalysed by papain was studied by ball milling. Despite the high-energy mixing experienced inside the ball mill, the biocatalyst proved stable and highly efficient to catalyse the formation of α,α- and α,β-dipeptides. This strategy was further extended to the enzymatic acylation of amines by milling, and to the mechanosynthesis of a derivative of the valuable dipeptide L-alanyl-L-glutamine. / We thank RWTH Aachen University for support from the Distinguished Professorship Program funded by the Excellence Initiative of the German federal and state governments. EPSRC, grant no. EP/L019655/1.

Germanium nanoparticles (Ge NPs) may be fascinating for their electronic and optoelectronic properties, as the band gap of Ge NPs can be tuned from the infrared into the visible range of solar spectru. Further functionalization of those nanoparticles may potentially lead to numerous applications ranging from surface attachment, bioimaging, drug delivery and nanoparticles based devices. Blue luminescent germanium nanoparticles were synthesized from a novel top-down mechanochemical process using high energy ball milling (HEBM) of bulk germanium. Various reactive organic molecules (such as, alkynes, nitriles, azides) were used in this process to react with fresh surface and passivate the surface through Ge-C or Ge-N bond. Various purification process, such as gel permeation chromatography (GPC), Soxhlet dailysis etc. were introduced to purify nanoparticles from molecular impurities. A size separation technique was developed using GPC. The size separated Ge NPs were characterize by TEM, small angle X-ray scattering (SAXS), UV-vis absorption and photoluminescence (PL) emission spectroscopy to investigate their size selective properties. Germanium nanoparticles with alkyne termini group were prepared by HEBM of germanium with a mixture of n-alkynes and α, ω-diynes. Additional functionalization of those nanoparticles was achieved by copper(I) catalyzed azide-alkyne ""click"" reaction. A variety of organic and organometallic azides including biologically important glucals have been reacted in this manner resulting in nanopartilces adorned with ferrocenyl, trimethylsilyl, and glucal groups. Additional functionalization of those nanoparticles was achieved by reactions with various azides via a Cu(I) catalyzed azide-alkyne ""click"" reaction. Various azides, including PEG derivatives and cylcodextrin moiety, were grafted to the initially formed surface. Globular nanoparticle arrays were formed through interparticle linking via ""click"" chemistry or ""host-guest"" chemistry. Copper(I) catalyzed ""click"" chemistry also can be explored with azido-terminated Ge NPs which were synthesized by azidation of chloro-terminated Ge NPs. Water soluble PEGylated Ge NPs were synthesized by ""click"" reaction for biological application. PEGylated Ge NP clusters were prepared using α, ω-bis alkyno or bis-azido polyethylene glycol (PEG) derivatives by copper catalyzed ""click"" reaction via inter-particle linking. These nanoparticles were further functionalized by azido β-cyclodextrin (β-CD) and azido adamantane via alkyne-azide “click” reactions. Nanoparticle clusters were made from the functionalized Ge NPs by “host-guest” chemistry of β-CD functionalized Ge NPs either with adamantane functionalized Ge NPs or fullerene, C60. / acase@tulane.edu

The demand for efficient and clean fuel alternatives has been increasing in recent years and is expected to become more pronounced in the future. Utilization of hydrogen as a fuel is one of the most promising energy resources due to its easy production, abundance, regeneration and not creation of greenhouse gases during its combustion. Although gaseous hydrogen has a very high energy content per unit weight, its volumetric energy density is rather low. The large scale use of hydrogen as a fuel crucially depends on the development of compact hydrogen storage materials with a high mass content of hydrogen relative to total mass and to volume. Certain metals and alloys are capable of reversibly absorbing large amounts of hydrogen to form metal hydrides. They exhibit the highest volumetric densities of hydrogen and are very promising for hydrogen storage because of their efficiency, cost and safety. Some of the metal hydride families can also be used in hydrogen compressors. The objective of this work is to investigate the synthesis and characterization behavior of intermetallic alloys (ZrMn2, ZrNi) for hydrogen compression and of complex hydrides (Zn(BH4)2 ) for on-board hydrogen storage. An overview of hydrogen as a fuel and its storage means is provided, synthesis and characterization methods of metal hydrides are presented and the effect of mechanical milling and the catalytic doping of metal/complex hydrides are investigated in detail. The hydrogen storage alloys (hydrides) are extensively characterized using various analytical tools such as: XRD, SEM, EDS, TCD, FTIR and GC/MS. The thermal (heat flow and weight loss) and volumetric (storage capacity, kinetics, cycle life, etc) analysis have been carried out via DSC/TGA and high pressure PCT apparatus. Finally conclusions and recommendations for future work are provided to improve the absorption/desorption cycle of hydrogen storage in the compounds under investigation.

Previous work has shown that when inorganic compounds are milled with quartz in a high energy ball mill the elements are sequestered into the quartz matrix and cannot be easily recovered by simple extraction methods. In this study lead (II) oxide, copper (II) oxide, magnesium oxide, zinc oxide and sodium hydroxide were milled with quartz sand and the recoveries of the metals investigated in detail. The standard EPA3050B method (acid digestion of sediments, sludge and soils) for extractable metals was compared to exhaustive HF digestion method based on ASTM C146-94a (test methods for chemical analysis of glass sand) and UDC 666.123:543.06 (chemical analysis of soda-lime and borosilicate glass). From these two analyses the total recovery of metals was determined. It was found that the elements extracted by the EPA3050B method decreased in an approximately logarithmic way with milling time. The metals are apparently strongly sequestered into the fractured quartz. Total HF digestion of the insoluble matrix gave good recovery of the “lost” elements. A reliable analytical procedure has been developed and the mechanisms leading to this sequestering are discussed. Particle size analysis and electron microscopy of milled samples support a process of brittle alloy formation as the proposed mechanism whereby the elements are sequestered into the milled quartz.

Titanium diboride was produced both by volume combustion synthesis (VCS) and by mechanochemical synthesis through the reaction of TiO2, B2O3 and metallic Mg. Reaction products were expected to be composed of TiB2 and MgO. However, side products such as Mg2TiO4, Mg3B2O6, MgB2 and TiN were also present in the products obtained by volume combustion synthesis. Formation of TiN could be prevented by conducting the volume combustion synthesis under argon atmosphere. Mg2TiO4 did not form when 40% excess Mg was used. Wet ball milling of the products before leaching was found to be effective in removal of Mg3B2O6 during leaching in 1M HCl. When stoichiometric starting mixtures were used, all of the side products could be removed after wet ball milling in ethanol and leaching in 5 M HCl. Thus, pure TiB2 was obtained with a molar yield of 30%. Pure TiB2 could also be obtained at a molar yield of 45.6% by hot leaching of VCS products at 75oC in 5 M HCl, omitting the wet ball milling step. By mechanochemical processing, products containing only TiB2 and MgO were obtained after 15 hours of ball milling. Leaching in 0.5 M HCl for 3 minutes was found to be sufficient for elimination of MgO. Molar yield of TiB2 was 89.6%, much higher than that of TiB2 produced by volume combustion synthesis. According to scanning electron microscope analyses, produced TiB2 had average particle size of 0.27&plusmn / 0.08 &amp / #956 / m.

The aim of this study was to investigate synthesis of lithium borides by mechanochemical synthesis from oxides. Lithium borides have promising properties in the area of high energy additives and hydrogen storage. Lithium oxide (Li2O), boron oxide (B2O3) and Mg were used to synthesize lithium borides. Experiments were conducted in a planetary ball mill under argon atmosphere. Analyses of the products were done by X-ray diffraction and scanning electron microscopy. Trilithium tetradecaboride (Li3B14) peaks were observed in the product powder. Removal of other phases that were formed during experiments was done by leaching in HCl/water solution. Leaching in 0.5 M HCl/water solution for 10 minutes was found to be sufficient to remove / iron (Fe) and magnesium oxide (MgO). Effects of ball milling parameters such as milling speed, ball to powder ratio, milling duration were investigated and milling for 20 hours with 300 rpm and 30:1 ball to powder ratio was found to be the optimum conditions. Syntheses of other lithium borides (LiB4, Li2B6, LiB13) were also experimented with the same milling parameters. Formation of LiB4, Li2B6 and LiB13 was not observed in the product powders. However, the results of LiB4 and LiB13 production experiments showed also Li3B14 peaks in the product. Li2B6 synthesis experiments resulted in Li2B9 peaks in the product powders.

Previous work has shown that when inorganic compounds are milled with quartz in a high energy ball mill the elements are sequestered into the quartz matrix and cannot be easily recovered by simple extraction methods. In this study lead (II) oxide, copper (II) oxide, magnesium oxide, zinc oxide and sodium hydroxide were milled with quartz sand and the recoveries of the metals investigated in detail. The standard EPA3050B method (acid digestion of sediments, sludge and soils) for extractable metals was compared to exhaustive HF digestion method based on ASTM C146-94a (test methods for chemical analysis of glass sand) and UDC 666.123:543.06 (chemical analysis of soda-lime and borosilicate glass). From these two analyses the total recovery of metals was determined. It was found that the elements extracted by the EPA3050B method decreased in an approximately logarithmic way with milling time. The metals are apparently strongly sequestered into the fractured quartz. Total HF digestion of the insoluble matrix gave good recovery of the “lost” elements. A reliable analytical procedure has been developed and the mechanisms leading to this sequestering are discussed. Particle size analysis and electron microscopy of milled samples support a process of brittle alloy formation as the proposed mechanism whereby the elements are sequestered into the milled quartz.