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Highly crystalline glass-ceramics were successfully manufactured via a one-step direct cooling method using Shuangqishan (Fujian, China) gold tailings as raw materials.

Background: The co-occurrence of depression and anxiety in adolescents is common and associated with suicide ideation. This study aimed to investigate the symptom-level relationship between suicide ideation and comorbidity of depression and anxiety. Methods: R was used for network analysis of depressive and anxiety symptoms from 716 adolescents (PHQ-9 ≥ 5 and GAD-7 ≥ 5). Participants were grouped into the suicide ideation group and the non-suicide ideation group. Network differences were compared between these two groups. Results: “Restlessness”, “Sad mood”, and “Trouble relaxing” were the most prominent central symptoms in this depressive-anxiety symptom network. “Restlessness”, “Nervousness”, and “Motor” were the bridge symptoms in this network. “Sad Mood” directly related to “Suicide Ideation” and explained the highest variance. The network structure was significantly different in network properties between adolescents who had suicide ideation and those who did not. “Restlessness” was the most central symptom in adolescents with suicide ideation. “Sad Mood” was the central and bridge symptom in adolescents with suicide ideation. Conclusion: “Restlessness” and “Sad Mood” might be interesting avenues for reducing depression and anxiety symptoms in adolescents with suicide ideation. Trial registration: The study received ethical approval from the Second Xiangya Hospital of Central South University on March 31, 2022.The number of Institutional Review Boards approval was 004.

Diabetic cardiomyopathy (DCM) is a common complication in diabetic patients. The molecular mechanisms of DCM remain to be fully elucidated. The intronic long noncoding RNA of DACH1 (lncDACH1) has been demonstrated to be closely associated with heart failure and cardiac regeneration. In this study, we investigated the role of lncDACH1 in DCM and the underlying molecular mechanisms. The expression of lncDACH1 was increased in DCM hearts and in high glucose-treated cardiomyocytes. Knockout of lncDACH1 reduced mitochondrial oxidative stress, cell apoptosis, cardiac fibrosis and hypertrophy, and improved cardiac function in DCM mice. Overexpression of lncDACH1 exacerbated mitochondria-derived reactive oxygen species (ROS) level and apoptosis, decreased activity of manganese superoxide dismutase (Mn-SOD); while silencing of lncDACH1 attenuated ROS production, mitochondrial dysfunction, cell apoptosis, and increased the activity of Mn-SOD in cardiomyocytes treated with high glucose. LncDACH1 directly bound to sirtuin3 (SIRT3) and facilitated its degradation by ubiquitination, therefore promoting mitochondrial oxidative injury and cell apoptosis in mouse hearts. In addition, SIRT3 silencing abrogated the protective effects of lncDACH1 deficiency in cardiomyocytes. In summary, lncDACH1 aggravates DCM by promoting mitochondrial oxidative stress and cell apoptosis via increasing ubiquitination-mediated SIRT3 degradation in mouse hearts. Inhibition of lncDACH1 represents a novel therapeutic strategy for the intervention of diabetic cardiomyopathy.

In order to solve the complex load transfer and structural design of the joint structures including skin, longeron and frame in the composite fuselage, the adhesively bonded integrated composite joint was designed. Static tensile test was performed and the strain-load curves and damage modes were obtained. Then the numerical simulation model of integrated composite joint was built. The damage initiation, propagation and failure process of integrated composite joint under tensile load were simulated and analyzed. Results show that: the first load drop and the ultimate failure load of the joint are 120.82 kN and 168.11 kN respectively; the initial damage occurs at the corner bend region of the lower-left corner-shaped preform, and extends across the radius bend region among short flange, long flange and web, and leads to the interface debonding of the upper and lower corner-shaped preform and the delamination of corner-shaped preform and L-shaped preform. Compared with the experimental results, the errors of the first load drop and the ultimate failure load from numerical calculated results are 6.68% and 2.61% respectively, which agree with each other very well.

Quasi-liquid solid electrolytes are a promising alternative for next-generation Li batteries. These systems combine the safety of solid electrolytes with the desired properties of liquids and are typically formed by solutions of Li salts in ionic liquids incorporated into solid matrices. Here, we present a fundamental understanding of the transport properties in solutions of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]), either in bulk form or incorporated in a boron nitride (BN) matrix. We performed a series of quasi-elastic neutron scattering experiments that, given the high incoherent neutron scattering cross section of hydrogen, allowed us to focus on the Emim+ dynamics. First, [Emim][TFSI]/LiTFSI solutions (0.5 and 2.5 mol·kg-1) were investigated and we show how the increase in the concentration reduces the Emim+ mobility and increases the activation energy of their long-range motions. Then, the 0.5 mol·kg-1 solution was incorporated into the BN matrix and we report that the diffusivities of the Emim+ cations that remain mobile under confinement are highly accelerated in comparison with the bulk sample and the activation energy of these motions is drastically reduced. We present the experimental evidence that this effect is related to the content of the Emim+ cations immobilized near the surfaces of the BN pores.

This research uses nanotechnology and molecular assembly technology, using biocompatible hydroxyapatite material as the inorganic filler, organically compound and assemble with the organic resin matrix to achieve the performance shear of the composite material, thus developing strength High-resistance, easy-to-process and good biocompatibility composite resin dental restoration materials, and the nano-composite resin material flexural strength, compressive strength and water absorption value were characterized in laboratory stage, the performance fully reached the current clinical use Various indicators of imported composite resin. This study analyzed the differences in the effects and friction properties of different prosthetic materials in oral repair. In order to better simulate the friction and wear performance of dental restoration materials in the oral environment, this paper studied under two conditions of oil lubrication and artificial saliva lubrication, and the wear mechanism from the macro aspects of friction coefficient, wear rate, wear resistance, etc. The research results show that the abrasion performance of the nanocomposite resin is closely related to its surface morphology and characteristics. The comparison with the performance of ceramic and composite resin restoration materials shows that nanocomposite resin materials have better mechanical properties and resistance than other dental restoration wear performance.

It has been confirmed that silicon (Si) fertilizer and humic acid (HA) could effectively decrease the heavy metals in soil. Nonetheless, the impact of these additives on soil aggregate characteristics was ignored. Therefore, the effects of Si fertilizer, HA, and their combinations on the physicochemical characteristics, availability of heavy metals (Cu, Cd, Pb, Zn), and fraction changes in soils and soil aggregates were investigated in this research. The results showed that Si fertilizer and HA significantly modified soil properties such as soil pH, electrical conductivity total organic carbon, water-soluble organic carbon, and nitrate‑nitrogen. HA and Si-HA (SHA) supplementation significantly decreased the availability of Cu, Cd, Pd, and Zn. Besides, there was no significant difference in physicochemical properties between soil and soil aggregates. The availability of Cu, Cd, Pd, and Zn in soil aggregates could be significantly inhibited by the addition of HA and SHA, and the content in microaggregates was greater than that in macroaggregates. After the addition of the three additives, the main fractions of heavy metals in different particle sizes were changed and eventually transformed to the residue state. These results indicated that Si fertilizer, HA, and SHA were influential in physicochemical properties and metal availability in soil aggregates. Therefore, it is of great scientific significance to study the impact of heavy metal pollution on the ecological environment in different aggregates, which will provide reference data for future sustainable management of heavy-metal polluted soils.

Dystrophin deficiency due to genetic mutations causes cardiac abnormalities in Duchenne's muscular dystrophy. Dystrophin is also shown to be downregulated in conventional failing hearts. Whether restoration of dystrophin expression possesses any therapeutic potential for conventional heart failure (HF) remains to be examined. HF mouse model was generated by transverse aortic constriction (TAC). In vivo activation of dystrophin transcription was achieved by tail-vein injection of adeno-associated virus 9 carrying CRISPR/dCas system for dystrophin. We found that activation of dystrophin expression in TAC mice significantly reduced the susceptibility to arrhythmia of TAC mice and the mortality rate. We further demonstrated that over-expression of dystrophin increased cardiac conduction of hearts in TAC mice by optical mapping evaluation. Activation of dystrophin expression also increased peak sodium current in isolated ventricular myocytes from hearts of TAC mice as recorded by the patch-clamp technique. Immunoblotting and immunofluorescence showed that increased dystrophin transcription restored the membrane distribution of Nav1.5 in the hearts of TAC mice. In summary, correction of dystrophin downregulation by the CRISPR-dCas9 system reduced the susceptibility to arrhythmia of conventional HF mice through restoring Nav1.5 membrane distribution. This study paved the way to develop a new therapeutic strategy for HF-related ventricular arrhythmia.

With the development of deep learning and the emergence of unmanned driving, fully convolutional networks are a feasible and effective for image semantic segmentation. DeepLab is an algorithm based on the fully convolutional networks. However, DeepLab algorithm still has room for improvement, and we design three improved methods: (1) the global context structure module, (2) highly efficient decoder module, and (3) multi-scale feature fusion module. The experimental results show that the three improved methods that we proposed in this paper can make the model obtain more expressive features and improve the accuracy of the algorithm. At the same time, we do some experiments on the Cityscapes dataset to further verify robustness and effectiveness of the improved algorithm. Finally, the improved algorithm is applied to the actual scene and has certain practical value.

Al-60wt.%Si composites were successfully prepared by semi-solid squeezing powder mixture of Al and Si at 700 °C. The appearance of about 50wt.% Al-Si metal liquid results that less than 4–5 MPa pressure can squeeze the Al-Si powder mixture to near full density at vacuum condition. The effects of Si particle size on the microstructure and properties of Al-60wt.%Si were investigated. The results show that the composites are consisted of only Si and Al. Si particles distribute evenly in aluminum matrix. Al matrix exhibits a certain preferred orientation under the condition of directional solidification. Si particles with 5 μm size tend to be aggregated into locally interconnected particles and can be effectively passivated. As Si particle size ranges from 10 to 20 μm, the corner passivation effect for Si particles is gradually suppressed. The fracture morphology of Al-60wt.%Si is composed of cleavage platforms of Si grains and fine tearing ridges of Al which tightly wraps Si grains. With the increase of Si particle size from 5 to 20 μm, the flexural strength of Al-60wt.%Si decreases from 270 MPa to 223 MPa, the thermal conductivity increase from 128 to 136 W·m−1·°C−1, and the average coefficient of thermal expansion from ambient temperature to 400 °C ranges from 9.49 to 9.97 × 10−6 °C−1.

Copper based composites with high graphite contents for pantograph sliders have been manufactured via an inexpensive powder metallurgy method. Large size cluster graphite is added into the matrix as solid lubricant to optimize the mechanical and wear performance of the composites. The mechanical performance and microstructure of graphite cluster/ copper-based (GC/Cu) composites are investigated. The highest graphite content in GC/Cu composites can reach up to 5 wt%. The graphite cluster/copper-based composites show an outstanding mechanical performance, in which the impact toughness can reach 4.8 J/cm2 with 5 wt% graphite cluster. The matrix is constituted with single α-phase Cu10Sn3with second phase particles CuNi2Sn. Moreover, friction and wear behavior with or without electric currency have been explored systematically, which indicates that the friction coefficient with 5 wt% graphite composites reached a minimum of 0.184 at a load of 25 N. It also exhibits the excellent friction performance under the effect of electric current. The smallest wear rate of 4.2×10−3 mg/m occurs in the sample with 2 wt% graphite at 30 A. Meanwhile, the interaction between pantographs and contact wire has been investigated based on elemental analysis and surface morphology. Oxidation and material transfer is found on the worn surface.

Diabetic cardiomyopathy (DCM) is a common complication in diabetic patients. The molecular mechanisms of DCM remain to be fully elucidated. The intronic long noncoding RNA of DACH1 (lncDACH1) has been demonstrated to be closely associated with heart failure and cardiac regeneration. In this study, we investigated the role of lncDACH1 in DCM and the underlying molecular mechanisms. The expression of lncDACH1 was increased in DCM hearts and in high glucose-treated cardiomyocytes. Knockout of lncDACH1 reduced mitochondrial oxidative stress, cell apoptosis, cardiac fibrosis and hypertrophy, and improved cardiac function in DCM mice. Overexpression of lncDACH1 exacerbated mitochondria-derived reactive oxygen species (ROS) level and apoptosis, decreased activity of manganese superoxide dismutase (Mn-SOD); while silencing of lncDACH1 attenuated ROS production, mitochondrial dysfunction, cell apoptosis, and increased the activity of Mn-SOD in cardiomyocytes treated with high glucose. LncDACH1 directly bound to sirtuin3 (SIRT3) and facilitated its degradation by ubiquitination, therefore promoting mitochondrial oxidative injury and cell apoptosis in mouse hearts. In addition, SIRT3 silencing abrogated the protective effects of lncDACH1 deficiency in cardiomyocytes. In summary, lncDACH1 aggravates DCM by promoting mitochondrial oxidative stress and cell apoptosis via increasing ubiquitination-mediated SIRT3 degradation in mouse hearts. Inhibition of lncDACH1 represents a novel therapeutic strategy for the intervention of diabetic cardiomyopathy.

Purpose: Cardiomyocyte senescence is associated with a progressive decline in cardiac physiological function and the risk of cardiovascular events. lncRNA H19 (H19), a well-known long noncoding RNA (lncRNA), is involved in the pathophysiological process of multiple cardiovascular disease such as heart failure, cardiac ischemia and fibrosis. However, the role of H19 in cardiomyocyte senescence remains to be further explored.Methods: Senescence-associated β-galactosidases (SA-β-gal) staining was used to detect cardiomyocyte senescence. Western blot, qRT-PCR and luciferase reporter assay were employed to evaluate the role of H19 in cardiomyocyte senescence and its underling molecular mechanism.Results: H19 level was significantly increased in high glucose-induced senescence cardiomyocytes and aged mouse hearts. Overexpression of H19 enhanced the number of SA-β-gal-positive cells, and the expression of senescence-related proteins p53 and p21, whereas H19 knockdown exerted the opposite effects. Mechanistically, H19 was demonstrated as a competing endogenous RNA (ceRNA) for microRNA-19a (miR-19a): H19 overexpression downregulated miR-19a level, while H19 knockdown upregulated miR-19a. The expression of SOSC1 was dramatically increased in senescence cardiomyocytes and aged mouse hearts. Further experiments identified SOCS1 as a downstream target of miR-19a. H19 upregulated SOCS1 expression and activated the p53/p21 pathway by targeting miR-19a, thus promoting the cardiomyocytes senescence.Conclusion: Our results show that H19 is a pro-senescence lncRNA in cardiomyocytes acting as a ceRNA to target the miR-19a/SOCS1/p53/p21 pathway. Our research reveals a molecular mechanism of cardiomyocyte senescence regulation and provides a novel target of the therapy for senescence-associated cardiac diseases.

Co-Cu composite powders with different Cu contents were synthesized via an ultra-rapid solution combustion synthesis (SCS) method and WC-10(Co/Cu) cemented carbides with an ultrafine grain size were prepared by microwave sintering the compacts of powder mixes of WC and the Co-Cu composite powders. The effects of Cu addition on the microstructure and properties of the microwave-sintered WC-Co cemented carbides were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), field emission transmission electron microscopy (FE-TEM) and mechanical properties tests. The results showed that the addition of a small amount of Cu instead of Co in the WC-Co cemented carbides enhances the sintering, restrains the WC grain growth and improves the mechanical properties. The average WC grain size decreases as Cu is added, and the grain size distribution narrows. The Rockwell hardness and fracture toughness of the WC-10(Co/Cu) alloys with a 0.5 wt% Cu addition reach 90.7 HRA and 14.3 MPa m−1/2, respectively. In addition, the transverse rupture strength (TRS) reaches 2544.7 MPa with a 1 wt% Cu content. The present results show that Cu-doped WC-Co cemented carbides have excellent comprehensive performances.

In this paper, high-Si reinforced Al matrix composites (H-Si/Al) with Si mass ratio 50–70% were successfully fabricated from the powder mixture of Si and Al by a novel route called as powder semi-solid squeeze. It is found that no Al–Si lamellar eutectic in the composites. As the Si content increases, fine Si particles in the H-Si/Al are reduced and the coarse Si particles may increase in size, or gather together to form twisted large particles and even form a space network structure. With the Si content ranging from 50% to 70%, The flexural strength varies between 248 and 179 MPa, the mean coefficient of thermal expansion from ambient temperature to 100 °C can be regulated between 11.32 and 7.55 × 10 −6 °C −1 , and the thermal conductivity varies between 140 and 120 W m −1 °C −1 , showing that H-Si/Al prepared by powder semi-solid squeeze have excellent mechanical and thermal properties.

Commercial F500 SiC powder and 6061 Al powder were chosen to fabricate the 50 vol.-% SiCp/6061Al composites via pressureless sintering. Effects of pre-treatment of the SiC powder and sintering temperature on the microstructures and properties of the composites were studied. Densification mechanism and interfacial reaction of the composites were also investigated. The results show that the composites have a high sintering ability and a low interfacial reaction activity. The density, bending strength and thermal conductivity of the composites are all sensitive to the sintering temperature. The composites sintered at 680°C are nearly fully dense and have the following optimal properties: the relative density of 98.5%, the bending strength of 495 MPa, the TC of 153 W/(m K) and the coefficient of thermal expansion of 8.1 × 10−6/°C (50–100°C), which are superior to most of the SiCp/Al composites of the similar composition reported previously.

High-performance copper-based pantograph slide materials play a crucial role in the rapid development of modern urban rail transit urgently. Herein, a full density graphite/copper-alloy matrix composite for pantograph slide has been successfully obtained by the hot powder forging process. The composite exhibits the full density when forging energy density is 307.6 J cm−3. In addition, the influence of different aging treatments on microstructure and mechanical performances of the composite has been studied in detail. The hardness and resistivity of the forged materials are greatly improved after an optimum aging treatment. Simultaneously, the friction and wear performances with or without currency current have been investigated, which demonstrates the friction coefficient can reach the minimum of 0.109 under 35 N. In current-carrying friction, the wear rate of the composite is an extremely small value of 5.5 × 10–5 mg m−1 after the aging treatment, indicating the outstanding anti-friction and self-lubricating performance. All the comprehensive analyses illustrate the full density graphite/copper-alloy matrix composite with excellent mechanical shows an enormous potential for pantograph slide.

Molecular dynamics simulations were performed to investigate the relationship between the molecular structure of perfluorosulfonic acid (PFSA) ionomers and the nanoscale morphology of the hydrated membranes. Three structural features are examined including (i) the length of the side chain to which the sulfonic acid group is attached, (ii) the equivalent weight (EW) of the electrolyte ionomer, and (iii) the molecular weight (MW) of the polymer electrolyte. Membrane morphologies are studied from the water content λ = 3 (λ represents number of water molecules per sulfonate group) to saturation (λ = 22). We find that with the longer side chain, there is more clustering of the sulfonate groups and more local water−water clustering, but a more poorly connected aqueous domain. When one decreases the equivalent weight (EW) in either the short side chain (SSC) PFSA or Nafion, there is more clustering of the sulfonate groups and more local water−water clustering and a better connected aqueous domain. Because connec...

Molecular dynamics simulations have been performed to study the structure and transport at the electrode/electrolyte interface in hydrogen-based proton exchange membrane fuel cells. We examine the wetting of catalyst surfaces that are not immediately adjacent to a Nafion membrane, but rather are separated from the membrane by a hydrophobic gap of carbon support surface (graphite). A mixture of Nafion, water and hydronium ions is able to wet small gaps (7.4 A) of graphite and reach the catalyst surface, providing a path for proton transport from the catalyst to the membrane. However, for gaps of 14.8 A, we observe no wetting of the graphite or the catalyst surface. Using a coarse-grained model, we found that the presence of a graphite gap of 7.4 A width slowed down the transport of water by at least an order of magnitude relative to a system with no gap. The implication is that catalyst particles that are not within nominally 1 nm of either the proton exchange membrane or recast ionomer in the electrode leading to the membrane do not possess a path for efficient proton transport to the membrane and consequently do not contribute significantly to power production in the fuel cell.

SiC/Al composites with uniformly distributed SiC particles were fabricated by pressureless infiltration of liquid AlSi7Mg alloy into SiC preforms with different porosity derived from SiC powders. The linear expansion of SiC preforms without any deformation was about 4% due to the oxidation of SiC powders during the sintering process. SiC preforms had no change in both shape and dimensions after infiltration so that near-net-shape composites were achieved. As SiC volume fraction varies from 39% to 62%, the thermal conductivity of SiC/Al composites with bending strength beyond 360 MPa and elastic modulus beyond 140 GPa varies from 146 to 118 W m−1 K−1 at room temperature, and the mean linear coefficient of thermal expansion from room temperature to 373 K varies from 10 × 10−6 to 7.69 × 10−6 K−1, agreeing better with the Turner's model.

The nanocrystalline β-SiC powder was successfully synthesized by ball milling the Si-50%C elemental powder. During ball milling, a solid solution of C in Si, Si(C), firstly forms, followed by SiC. The formation of SiC is controlled by the mixing mechanism of the gradual diffusion reaction(GDR) and the mechanically induced self-propagating reaction(MSR). The amount of β-SiC increases with milling time increasing. After 40 h milling, there exists only β-SiC in the milled powder. The grain size of β-SiC is about 6.4 nm after the powder is milled for 60 h. After the 60 h-milled Si-50%C elemental powder is heat treated at 1 100 °C for 1 h, the grain size of β-SiC does not change, but the lattice ordering degree of β-SiC increases.

Through the use of molecular dynamics simulation, we examine the structural and transport properties of water and hydronium ions at the interface of a Nafion polymer electrolyte membrane and a vapor phase. The effect of humidity was studied by examining water contents of 5%, 10%, 15%, and 20% by weight. We observe a region of water depletion in the membrane near the vapor interface. We report the vehicular diffusion of hydronium ions and water as components parallel and perpendicular to the interface. In the interfacial region, for hydronium ions, we find that the component of the vehicular diffusivity parallel to the interface is largely unchanged from that in the bulk hydrated membrane, but the component perpendicular to the interface has increased, due to local decrease in density. We find similar behavior with water in the interfacial region. On the basis of these diffusivities, we conclude that there is no observable additional resistance to mass transport of the vehicular component of water and hydronium ions due to the interface. In terms of structure at the interface, we find that there is a decrease in the fraction of fully hydrated hydronium ions. This translates into a lower probability of forming Eigen ions, which are necessary for structural diffusion. Finally, we observe that the hydronium ions display a preferential orientation at the interface with their oxygen atoms exposed to the vapor phase.

Molecular dynamics (MD) simulations were performed to investigate the structural and dynamical behavior of water and hydronium ions at the electrode/electrolyte interface of hydrogen polymer electrolyte membrane (PEM) fuel cells. Specifically, we have studied the hydrated Nafion membrane, humidified for four different water contents, 5, 10, 15, and 20%, at 300 K. We analyzed the three-phase interface where the hydrated PEM is in contact with the vapor phase and with either the catalyst surface (platinum in this paper) or the catalyst−support surface (graphite in this paper). These molecular simulations represent portions of interfaces that exist within the PEM fuel cells. We observed significant wetting of the catalyst surface by a mixture of polymer, water, and hydronium ions but not beyond a monolayer. We observed virtually no wetting of the graphite surface. On the catalyst surface, the degree of wetting of the catalyst surface depends strongly on the level of membrane humidity. The pair correlation fu...

A molecular dynamics simulation study of hydrated Nafion at water contents ranging from 5 to 20 wt % was performed to examine the structure and dynamics of the hydrated polyelectrolyte system. The simulations show that the system forms segregated hydrophobic regions consisting primarily of the polymer backbone and hydrophilic regions with an inhomogeneous water distribution. We find that the water clustering strongly depends on the water content. At low water content, only isolated small water clusters are formed. As the water content increases, it becomes increasingly possible that a predominant majority of water molecules form a single cluster, suggesting that the hydrophilic regions become connected. We characterize the atomic structures formed within the system by various atomic pair correlation functions. The water structure factor shows a peak at q values corresponding to an intercluster distance about 2.5 nm and greater. With increasing water content, the distance moves to larger values, consistent with findings from scattering experiments. We find that the degree of solvation of hydronium ions by water molecules is a strong function of water content. At 5 wt %, a majority of the hydronium ions are hydrated by no more than two water molecules, prohibiting structural diffusion. As water content increases, the hydronium ions continue to become increasingly hydrated, resulting in structures capable of forming eigen ions, a necessary step in structural diffusion. Addressing the experimentally observed fact that conductivity in these membranes abruptly drops near 5 wt %, we find that both the local structure of the poorly hydrated hydronium ions and the disconnected nature of the global morphology of the water nanonetwork at low water content should contribute to poor conductivity.

The TiC and TiB 2 powders were successfully synthesized by ball milling the Ti 50 C 50 and Ti 33 B 67 elemental powders, respectively. During ball milling the Ti 50 C 50 powder, a solid solution of C in Ti, Ti(C), was first formed, followed by TiC. After milling for 80 h, the powder was composed of TiC with grain size of 6 nm and a small amount of Ti(C) which was finally completely transformed to TiC after heat treatment. During ball milling the Ti 33 B 67 powder, a solid solution of B in Ti, Ti(B), was first formed followed by the formation of an amorphous structure which transformed into a hexagonal phase of TiB 2 with grain size of about 10 nm.

TiB2 nanocrystalline powder was synthesized by mechanical alloying of Ti-67B elemental powder. X-ray diffraction(XRD) and transmission electron microscopy(TEM) were used to study the structural evolution of the powder during ball milling. The effects of heat treatment on the structural evolution and thermal stability of the mechanically alloyed(MAed) Ti-67B powder were also discussed. During ball milling the Ti-67B powder, a solid solution of B in Ti, Ti(B) is firstly formed. When the powder is milled for 10 h, the amorphous transition of Ti(B) from the crystalline to the amorphous phase occurs. When the powder is milled for 20 h, nanocrystalline TiB2 is formed from the amorphous Ti(B). When the powder is milled for 60 h, only TiB2 is detected with grain size of 10 nm. The formation of TiB2 nanocrystalline is controlled by the gradual diffusion reaction mechanism. During heat-treatment of the MAed Ti-67B powder, the structural changes of TiB2, including grain growth and lattice ordering degree increasing may occur.

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