Search

The revised American Society for Gastrointestinal Endoscopy (ASGE) guideline 2019 provides the high-risk criteria for suspected common bile duct stones (CBDSs).To evaluate CBDS detection rates during endoscopic retrograde cholangiopancreatography (ERCP) in high-risk patients with suspected CBDSs based on the ASGE guideline 2019.This multicenter retrospective study included 1100 consecutive patients who underwent ERCP for suspected CBDSs with any high-risk criteria based on the revised ASGE guideline 2019: Criterion 1, CBDSs on imaging; Criterion 2, clinical ascending cholangitis; and Criterion 3, total bilirubin exceeding 4 mg/dL and dilated common bile duct on imaging. We compared CBDS detection rates during ERCP based on individual and combined high-risk criteria.The CBDS detection rates of patients who met any of the criteria, only Criterion 1, and Criteria 2 or 3 were 86.0% (946/1100), 93.4% (113/121), and 50.0% (106/212), respectively. In patients who met Criteria 1 and 2, 1 and 3, 2 and 3, and all criteria, CBDSs were confirmed during ERCP in 95.1% (490/515), 96.2% (25/26), 55.3% (26/47), and 98.4% (186/189), respectively. The CBDS detection rate during ERCP of patients with at least Criterion 1 significantly exceeded that of patients without at least Criterion 1 [95.7% (814/851) vs. 51.0% (132/259), respectively, P 0.001].Patients with CBDS visualization on imaging have very high CBDS detection rates during ERCP. However, performing ERCP on patients with only clinical predictors, such as cholangitis and dilated CBD with total bilirubin exceeding 4 mg/dL, often results in unnecessary ERCP.

Prophylaxis is important for post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP), which is the most common and serious complication of ERCP. Although the current guidelines include independent patient- and procedure-related risk factors for PEP and available PEP prophylactic measures, the synergistic effect of these risk factors on PEP should also be considered, given that patients often harbor multiple risk factors. Furthermore, a combination of prophylactic measures is often selected in clinical practice. However, established methods estimating the synergistic effect of independent risk factors on PEP incidence are lacking, and evidence on the impact of combining prophylactic measures on PEP should be discussed. Selection of appropriate candidate patients for ERCP is also important to reduce the incidence of PEP associated with unnecessary ERCP. ERCP indications in patients with asymptomatic common bile duct stones (CBDSs) and in those with suspected CBDSs with no imaging-based evidence of stones are controversial. Further studies are warranted to predict the synergistic effect of independent risk factors on PEP, determine the best prophylactic PEP measures, and identify appropriate candidates for ERCP in patients with asymptomatic CBDSs and those with suspected CBDSs.

As the aging population grows worldwide, the rates of endoscopic retrograde cholangiopancreatography (ERCP) for common bile duct stones (CBDS) in older patients with a poor performance status (PS) have been increasing. However, the data on the safety and efficacy of ERCP for CBDS in patients with a PS score of 3 or 4 are lacking, with only a few studies having investigated this issue among patients with poor PS.To examine the safety and efficacy of ERCP for CBDS in patients with a PS score of 3 or 4.This study utilized a retrospective multi-centered design of three institutions in Japan for 8 years to identify a total of 1343 patients with CBDS having native papillae who underwent therapeutic ERCP. As a result, 1113 patients with a PS 0-2 and 230 patients with a PS 3-4 were included. One-to-one propensity-score matching was performed to compare the safety and efficacy of ERCP for CBDS between patients with a PS 0-2 and those with a PS 3-4.The overall ERCP-related complication rates in all patients and propensity score-matched patients with a PS 0-2 and 3-4 were 9.0% (100/1113) and 7.0% (16/230;ERCP for CBDS can be effectively performed in patients with a PS 3 or 4. Nevertheless, the indication for ERCP in such patients should be carefully considered with prophylactic antibiotics.

Background/Aims: Difficult biliary cannulation is an important risk factor for post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP). Therefore, this study aimed to identify the factors that predict difficult cannulation for common bile duct stones (CBDS) to reduce the risk for PEP.Methods: This multicenter retrospective study included 1,406 consecutive patients with native papillae who underwent ERCP for CBDS. Factors predicting difficult cannulation for CBDS were identified using univariate and multivariate analyses.Results: Univariate analysis showed that six factors significantly predicted difficult cannulation: ERCP performed by non-expert endoscopists, low-volume center, absence of acute cholangitis, normal serum bilirubin, intradiverticular papilla, and type of major duodenal papilla. Multivariate analysis identified ERCP performed by non-expert endoscopists (odds ratio [OR], 2.5; p

Current guidelines for treating asymptomatic common bile duct stones (CBDS) recommend stone removal, with endoscopic retrograde cholangiopancreatography (ERCP) being the first treatment choice. When deciding on ERCP treatment for asymptomatic CBDS, the risk of ERCP-related complications and outcome of natural history of asymptomatic CBDS should be compared. The incidence rate of ERCP-related complications, particularly of post-ERCP pancreatitis for asymptomatic CBDS, was reportedly higher than that of symptomatic CBDS, increasing the risk of ERCP-related complications for asymptomatic CBDS compared with that previously reported for biliopancreatic diseases. Although studies have reported short- to middle-term outcomes of natural history of asymptomatic CBDS, its long-term natural history is not well known. Till date, there are no prospective studies that determined whether ERCP has a better outcome than no treatment in patients with asymptomatic CBDS or not. No randomized controlled trial has evaluated the risk of early and late ERCP-related complications vs the risk of biliary complications in the wait-and-see approach, suggesting that a change is needed in our perspective on endoscopic treatment for asymptomatic CBDS. Further studies examining long-term complication risks of ERCP and wait-and-see groups for asymptomatic CBDS are warranted to discuss whether routine endoscopic treatment for asymptomatic CBDS is justified or not.

Objective Endoscopic papillary large-balloon dilation (EPLBD) with limited endoscopic sphincterotomy (EST) is widely used for removing multiple large common bile duct (CBD) stones. However, the safety and effectiveness of immediate EPLBD after limited EST and EPLBD at an interval after limited EST is unclear. Thus, this multicenter retrospective study was conducted to examine this matter. Methods Propensity score-matching was performed to adjust the baseline characteristics between the immediate and interval EPLBD groups. We compared the incidence of post-endoscopic retrograde cholangiopancreatography (ERCP) complications and the early outcomes of ERCP between the 2 matched groups, which comprised 66 patients each. Results The complete stone clearance rate in each study group was 100%. The overall incidence of post-ERCP complications in the propensity score-matched interval and immediate EPLBD groups was 3/33 (9.1%) and 1/33 (3.0%), respectively (p=0.61). The immediate EPLBD group had significantly fewer mean ERCP sessions for complete stone removal and a significantly lower rate of endoscopic mechanical lithotripsy (EML) usage than the interval EPLBD group (1.6 vs. 2.4 sessions, p

Risk stratification of postendoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP) for common bile duct (CBD) stones is needed for clinicians to adequately explain to patients regarding the risk of PEP in advance of ERCP and to proactively take preventive measures in high-risk patients. To stratify the risk of PEP for CBD stones based on CBD-related diseases. A total of 1551 patients with naive papilla who underwent ERCP for CBD stones were divided into three groups: Group A: asymptomatic CBD stones, Group B: obstructive jaundice and elevated liver test values without cholangitis, and Group C: mild, moderate, and severe cholangitis. We stratified the risk of PEP by comparing its incidence among the three groups using the Holm’s method. Furthermore, we performed one-to-one propensity score matching between Group A and the other groups to examine the risk of PEP in Group A. The incidence rates in Groups A, B, and C were 13.7%, 7.3%, and 1.8%, respectively. The Holm-adjusted p values between Groups A and B, Groups A and C, and Groups B and C were 0.023

Stones in the common bile duct (CBD) are reported worldwide, and this condition is majorly managed through endoscopic retrograde cholangiopancreatography (ERCP). CBD stone recurrence is an important issue after endoscopic stone removal. Therefore, it is essential to identify its risk factors to determine the necessity of regular follow-up in patients who underwent endoscopic removal of CBD stones. The authors identified that the S and polyline morphological subtypes of CBD were associated with increased stone recurrence. New morphological subtypes of CBD presented by the authors can be important risk predictors of recurrence after endoscopic stone removal. Furthermore, the new morphological subtypes of CBD may predict the risk of residual CBD stones or technical difficulty in CBD stone removal. Further studies with a large sample size and longer follow-up durations are warranted to examine the usefulness of the newly identified morphological subtypes of CBD in predicting the outcomes of ERCP for CBD stone removal.

BACKGROUND AND AIM Choledocholithiasis is the most common indication for endoscopic retrograde cholangiopancreatography (ERCP). Identifying risk factors for post-ERCP pancreatitis (PEP) is important for reducing the risk of developing PEP after common bile duct (CBD) stone removal. However, studies examining the risk factors for PEP for CBD stones are scarce. The aim of this study was to examine whether the presence or absence of acute cholangitis is a clinical risk factor for PEP in patients with CBD stones. METHODS In this multicenter retrospective study, 1539 patients with naive papillae were divided into patients without and with acute cholangitis. We compared the incidence of PEP between the two groups using one-to-one propensity score matching to adjust for the potential confounding factors of PEP. RESULTS In the entire cohort, the rates of PEP in patients without and with acute cholangitis were 9.6% (52/542) and 1.8% (18/997), respectively (P

BACKGROUND AND AIM For asymptomatic common bile duct (CBD) stones, removal by endoscopic retrograde cholangiopancreatography (ERCP) is recommended in available guidelines. However, few studies have reported the risk of post-ERCP pancreatitis (PEP), which is the most common and serious ERCP-related complication for asymptomatic CBD stones. We performed a propensity score matching analysis to examine the risk of PEP in therapeutic ERCP for asymptomatic CBD stones. METHODS Information from medical databases of three institutions in Japan was collected over 6 years to identify 1113 patients with native papilla who underwent therapeutic ERCP for choledocholithiasis (excluding biliary pancreatitis). We compared the risk of PEP between asymptomatic and symptomatic groups by performing one-to-one propensity score matching. RESULTS PEP was present in 52 (4.7%) of the 1113 patients overall. Of the 949 symptomatic patients, 28 (3.0%) had PEP, and of the 164 asymptomatic patients, 24 (14.6%) had PEP. The incidence of PEP was significantly higher in the asymptomatic group than in the symptomatic group (3.0% vs 14.6%; P

OBJECTIVE Dual-layer spectral detector computed tomography (DLCT) can detect noncalcified biliary stones. The diagnostic ability of DLCT for detecting biliary stones may be comparable to that of magnetic resonance cholangiopancreatography (MRCP). This study seeks to compare the diagnostic ability for biliary stones between these two imaging modalities. METHODS This retrospective study included 102 cases with a diagnosis of biliary stones including gallstones (n = 66) and common bile duct (CBD) stones (n = 25) or spontaneously passing CBD stones (n = 11). The reference standard used was operative findings, endoscopic retrograde cholangiopancreatography or follow-up over 6 months. In DLCT, 120-kVp images, 40-keV virtual monoenergetic images and material decomposition images were created. We compared the diagnostic ability of DLCT and MRCP for biliary stones using the McNemar's test. RESULTS The sensitivity and specificity of DLCT versus MRCP for biliary stones were 91.2% versus 95.6% and 90.9% versus 90.9%. Thus, the sensitivity and specificity were not significantly different (P = 0.25 and P = 1.0). Although in small stones (

Objective Single-stage endoscopic stone removal for choledocholithiasis is an advantageous approach because it is associated with a shorter hospital stay; however, few studies have reported the incidence of complications related to this procedure in detail. The aim of this study was to examine the incidence of complications and efficacy of this procedure. Methods This retrospective study investigated the incidence of complications in 345 patients with naive papilla who underwent therapeutic endoscopic retrograde cholangiopancreatography (ERCP) for choledocholithiasis at three institutions between April 2014 and March 2016 by a propensity score analysis. The efficacy of single-stage endoscopic stone removal was assessed based on a hospital stay of within 7 days and the number of ERCP attempts. Results Among 114 patients who underwent single-stage endoscopic stone removal, 15 patients (13.2%) experienced complications. Among the remaining 231 patients in the two-stage endoscopic stone removal group, complications were observed in 17 patients (7.4%). The propensity score analysis, which was adjusted for confounding factors, revealed that single-stage endoscopic stone removal was not a significant risk factor for complications (p=0.52). In patients in whom >10 min was required for deep cannulation, single-stage endoscopic stone removal was not a significant risk factor for complications in the propensity score analysis (p=0.37). In the single-stage group, the proportion of patients with a hospital stay of within 7 days was significantly higher and the number of ERCP attempts was significantly lower in comparison to the two-stage group (p

Objective We examined the safety and efficacy of endoscopic stone removal for choledocholithiasis in elderly patients ≥90 years of age with native papilla and compared the outcomes with those in patients 75-89 years of age. Methods This multicenter retrospective study included 569 patients 75-89 years of age and 126 patients ≥90 years of age who had native papilla and underwent therapeutic endoscopic retrograde cholangiopancreatography (ERCP) for choledocholithiasis at 3 institutions in Japan between April 2012 and March 2018. The main outcomes assessed were the incidence of post-ERCP complications during hospitalization and outcomes of ERCP in patients ≥90 years of age. Results Biliary cannulation and subsequent endoscopic sphincterotomy, endoscopic balloon dilation, and endoscopic large balloon dilation were successful in 97.7% of patients 75-89 years of age and in 98.4% of patients ≥90 years of age. There was no significant difference in the incidence of post-ERCP complications between patients 75-89 years of age and those ≥90 years of age (7.7% vs. 9.5%, respectively; p=0.47). Although the rate of use of mechanical lithotripter was not significantly different, the rate of complete stone removal in patients ≥90 years of age was lower than that in patients 75-89 years of age (81.0% vs. 94.9%, respectively; p

In the present study, hypoeutectic Al–7 wt% Si and hypereutectic Al–17 wt% Si alloys were solidified using an electromagnetic stirring (EMS) technique. The microstructures were observed as a function of EMS imposition time for both alloys, showing that the primary aluminium solid solution (Al(ss)) in the Al–7 wt% Si alloy and the primary silicon solid solution (Si(ss)) in the Al–17 wt% Si alloy could be refined when EMS was imposed for a sufficiently long duration. In addition to the EMS-induced fluid flow, which plays an important role in promoting grain multiplication during solidification, a novel mechanism was proposed to explain the refinement upon considering the significant differences in electrical resistivity between the primary solid and remaining liquid. It was revealed that the primary Al(ss) in the Al–7 wt% Si alloy is mobile and leads the surrounding liquid, whereas the primary Si(ss) in the Al–17 wt% Si alloy is sluggish and lags the counterpart liquid, when EMS is imposed. Although the movement behaviours of these two solids differ greatly, both primary phases can be refined owing to uncoupled displacement, indicating that EMS is effective for refining the primary phases despite the differences in their crystal features. A supplementary quenching experiment of the Al–17 wt% Si alloy below liquidus indicated that even a low fraction of primary Si solid can provide sufficient crystal nuclei to produce refined Si(ss) grains.

Amount of waste from the electric motor is expected to increase by the spread of hybrid vehicles and electric vehicles. The pyro-recycle method, that is, separation and collection method of copper and rare earth elements by directly melting of a rotor of a motor, is expected as an efficient and low-cost method to recycle an electric motor. Cu and Fe are dissolved each other in the liquid phase, but they are separated by the addition of several percent carbons. In this study, we attempted to apply mechanical vibration to the melted magnet and copper to promote phase separation of Cu and Fe phase. Moreover, we investigated the distribution of rare earth elements in the copper and ferrous phase. By the results, the phase separation was promoted by applying feeble mechanical vibration such as 60 Hz, 0.75 G in a short time. Also, rare earth elements were concentrated in the copper phase.

The industrial 3xxx aluminum alloy was solidified in a superconducting magnet, in which electromagnetic vibration (EMV) was imposed throughout the entire solidification process. The microstructure was examined as a function of vibration frequency. It is revealed that the microstructure contains intermetallic compounds and aluminum solid solution (Al(ss)) regardless of solidification condition. For both structures, quantitative characterization shows that their average grain sizes decrease to minima when vibration frequency, f, increases and further increases of f leads to an increase of average grain sizes. Moreover, the general uniformity of intermetallic compound becomes poor when f goes beyond 1000 Hz. The microstructure transition behavior can be elucidated when considering the electrical resistivities of phases, i.e., Al(ss), intermetallic compounds and remaining liquid that coexist in mushy zone. The different electrical resistivities of these phases produce different Lorentz forces and thus lead to different vibration amplitudes and eventually generate uncoupled movement between the leading phase and sluggish phase during vibration. The microstructure transition can be clarified when the distance covered by the leading phase is revealed as a function of frequency. The morphological appearance of intermetallic compounds is dependent on f in EMV processing; however, their phase species and volume proportion are independent of processing conditions.

We have developed new type semi-solid injection process for magnesium alloy. This process does not require to use any cover gases and the special magnesium billet such as thixo-billet. In this study, plate specimens were produced by injecting the semi-solid billet with different fraction solid. The microstructure observation, detection of casting defects by an X-ray computed tomography scanner, and tensile test were carried out. With increasing fraction solid, the size and shape of α-Mg solid particles became smaller and more spherical. In the condition of low fraction solid or forming in liquid state, the casting defects were located in the center of the specimen at the thickness direction. Additionally, the volume fraction of the casting defect decreased with increasing fraction solid. Moreover, the casting defects can be reduced by preventing solidifying and clogging of the top of the nozzle. Then, the specimen which has few casting defects could be obtained by injecting the slurry of fraction solid 0.5. However, the tensile strength and yield strength were highest in fraction solid 0.4. It is contemplated that the composition of the solid solution component element in the matrix was increased in fraction solid of 50%, therefore the matrix became brittle.

Background and study aims Endoscopic removal of asymptomatic common bile duct stones (CBDS) is generally recommended. Although many reports have described the risk of complications in endoscopic retrograde cholangiopancreatography (ERCP), no studies have addressed this problem in the context of asymptomatic CBDS. This study examines the risk of complications arising in ERCP for asymptomatic CBDS. Patients and methods This retrospective study included 425 patients with naive papilla who underwent therapeutic ERCP for choledocholithiasis at 2 institutions in Japan for 2 years. The risk of complications was examined in patients who were divided into the asymptomatic and symptomatic CBDS groups. We used propensity score analysis to adjust for confounding effects. Results Complications were observed in 32 (7.5 %) of the 425 patients. Of the 358 patients with symptomatic CBDS, 14 patients (3.9 %) had complications. In contrast, of the 67 patients with asymptomatic CBDS, 18 patients (26.9 %) had complications. Propensity score analysis revealed that asymptomatic CBDS was a significant risk factor, with a significantly higher incidence of complications compared with symptomatic CBDS (odds ratio, 5.3). Moderate to severe complications were observed in 15 of 18 patients (83.3 %) in the asymptomatic CBDS group, with significantly more moderate to severe complications than those in the symptomatic CBDS (odds ratio, 6.7). Conclusions Asymptomatic CBDS carried a high risk of ERCP-related complications, and these were often more severe. In asymptomatic CBDS, endoscopic treatment should be carefully performed after considering the patient’s background, and detailed explanation of its possible complications should be given to patients in advance.

A TiB2-FeAl cermet was successfully fabricated by the mechanical milling of TiB2, Fe and Al powders, and subsequent pulsed current sintering. A FeAl phase was formed during the sintering process by the diffusive reaction of Fe and Al. The transverse rupture strength of the sintered sample depends on the milling condition. A suitable condition in this process was the revolution speed of 180 rpm and the milling time for 18 ks. The TiB2-40 mass% FeAl prepared from the powder milled by this condition shows a transverse rupture strength of 1370 MPa and a hardness of 86 HRA.

Effect of TiB2 substitution on thermal conductivity and hardness in TiC / Fe-Al cermets was investigated. The (70-x)TiC / xTiB2 / 26Fe-4Al mass % cermets were fabricated by mechanical milling and subsequent pulsed current sintering method. The high relative density compacts was formed by sintering at 1423 K under 25 MPa for 60 s. The sintered materials were mainly composed of TiC, TiB2 and Fe-Al intermetallic compound. In addition, small amounts of Fe2B surrounding TiB2 were formed. The thermal conductivity of the sintered compact lineally increased with increasing TiB2 volume fraction. However, the hardness of the sintered compacts of x = 20 – 40 were higher than that of x = 0. Therefore, the substitution of TiC to TiB2 in the TiC / Fe-Al based cermet is effective to improve the thermal conductivity without the degradation of hardness.

In the present study, Ti/Si/2TiC/ x Al ( x = 0, 0.05, 0.1, 0.15, and 0.2) powder mixtures were heated in vacuum for synthesis of Ti 3 SiC 2 powder. It was found that Al addition accelerated the synthesis reaction for Ti 3 SiC 2 . When Al of x = 0.2 was added, the synthesis temperature for single-phase Ti 3 SiC 2 was lowered to 1150 °C from 1500 °C. The mechanism of the accelerating effect of Al addition on Ti 3 SiC 2 formation was revealed to be that molten Al plays the role of deoxidation agent, which prompts the synthesis of Ti 3 SiC 2 through accelerating the formation of Ti 5 Si 3 intermediate phase. In addition, equations for quantitative evaluation of the contents of three coexisting phases (Ti 3 SiC 2 , Ti 5 Si 3 , and TiC) during the synthesis process were derived in this study based on experimental calibration.

The frozen mould which is produced by refrigerating the mixture of sand and water has the possibility to improve both the casting cost and the poor working environments such as noise, vibration and dust. The transition of mechanical properties of the frozen mould when it was transforming into thawed and dried states was examined. The compressive strength of the standard frozen mould consisting of only sand and water dramatically decreased when it was thawed and the strength was not recovered by drying. In contrast, the frozen mould produced by substituting colloidal silica solution for water showed some compressive strength even in thawed state and the strength was elevated by subsequent drying. The reusability of the sand mixture with colloidal silica solution was also evaluated. The compressive strengths did not deteriorate with any reclamation. The above results prove that the frozen mould with colloidal silica solution has an excellent industrial potential.

Powders of Ti, Al and TiC were mixed as starting materials for the synthesis of ternary compound Ti 3 AlC 2 at 1200–1400 °C by using pulse discharge sintering (PDS) technique. The fully dense and almost single-phase polycrystalline Ti 3 AlC 2 was obtained at 1300 °C for 15 min, when the molar ratio of the starting powder mixture was selected to be Ti:Al:TiC = 2:2:3. The typical microstructure of Ti 3 AlC 2 was found to consist of plate-like grains with size of about 3–5 μm in width and 20–50 μm in length. The intermediate phases of Ti 3 Al, TiAl and Ti 2 AlC were found during the reactive sintering process and the reactions for the Ti 3 AlC 2 phase formation were proposed.

Ternary compound Ti 3 SiC 2 was rapidly synthesized by pulse discharge sintering the powder mixture of 1TiH 2 /1Si/1.8TiC without preliminary dehydrogenation. Almost single-phase dense Ti 3 SiC 2 was synthesized at 1400 °C for 20 min. The grain size of synthesized Ti 3 SiC 2 strongly depends on sintering temperature. The synthesis mechanism of Ti 3 SiC 2 was revealed to be completed via the reactions among the intermediate phases of Ti 5 Si 3 , TiSi 2 and the other reactants in the starting powder. The Ti–Si liquid reaction occurring above the Ti–Ti 5 Si 3 eutectic temperature at 1330 °C was found to assist the synthesis reaction and densification of Ti 3 SiC 2 . The dehydrogenation of TiH 2 was accelerated by the synthesis reactions.

Synthesis of Ti 3 SiC 2 powder was carried out by heat treating powder mixtures of Si, TiC and coarse Ti (−150 μm) in a temperature range of 1000–1400 °C. The phase content of Ti 3 SiC 2 in the synthesized powder was improved to 99% when heat treated at 1400 °C for 4 h. Ti–Si liquid reaction was found to occur above the binary eutectic temperature, and this liquid reaction is believed to have assisted the synthesis reaction of Ti 3 SiC 2 .

Ti3AlC2 was rapidly synthesized by pulse discharge sintering Ti/Al/C (molar ratio 3:1.1:1.8) powder mixtures in a temperature range of 1200–1400 °C. The fully dense and single-phase Ti3AlC2 was obtained at sintering temperature 1250–1350 °C for 15 min and at 1300 °C for 15–60 min. The typical microstructure of polycrystalline bulk Ti3AlC2 consists of plate-like grains, and the grain size can be adjusted by choosing sintering temperature and time. The intermediate phases of AlTi3, AlTi, Ti3AlC and Ti2AlC were found during the reactive sintering process and the mechanisms for the Ti3AlC2 phase formation were proposed.

A powder blend of Ti, SiC and C at a molar ratio of Ti:SiC:C = 3:1:1 was compacted into cylinder and sintered in vacuum for the synthesis of Ti3SiC2. The microstructure of synthesized Ti3SiC2 showed unique morphology. Variation in phase and microstructural morphology with temperature during sintering was investigated by X-ray diffraction analysis and a scanning electron microscope equipped with an energy dispersive X-ray analyzer in order to elucidate reaction mechanism. Two kinds of powder blends, Ti/Si and Ti/C, were also compacted and sintered to confirm the effect of diffusion of Si and C atoms into Ti particles on the morphological change of Ti particles. As a result, we proposed the progress of synthesis as follows: (1) Si and C atoms start to diffuse into Ti particles from SiC and C particles over 1023 K, (2) the diffusion of Si and C atoms is enhanced rapidly over α/β phase transition temperature of Ti, which results in the formation of shell structure having ruffled surface composed of Ti5Si3 and TiC on Ti particle surfaces, (3) the shell grows and joins together with neighbor ones and pure Ti core in Ti particles reduces in size, (4) Ti3SiC2 is formed by the reaction of Ti5Si3 with TiC over 1623 K, (5) finally, Ti3SiC2 with TiC is synthesized over 1823 K. The joined shell structure having ruffled surface formed during sintering remained after the formation of Ti3SiC2, which resulted in the formation of the unique morphology.

Single-phase, nearly fully dense ternary compound Ti 3 SiC 2 was successfully synthesized by pulse discharge sintering (PDS) Ti/Si/TiC powder mixture, where coarse Ti powder (−0.15 mm) was used, at 1350–1400 °C for a short time of 20 min. Ti 3 SiC 2 was found to form through reaction among intermediate phases of Ti 5 Si 3 , TiSi 2 and the starting powders. Evidence of Ti–Si liquid reaction above Ti–Ti 5 Si 3 eutectic temperature was revealed by studying the shrinkage displacement curve, and this liquid reaction is believed to have greatly assisted the ternary phase synthesis reaction as well as densification.

Single-phase dense Ti3AlC2 was rapidly synthesized through pulse discharge sintering a TiH2/Al/TiC powder mixture. Dehydrogenation of TiH2 was rapidly accomplished during the synthesis process at the heating up stage below 800 °C. The formation of Ti3AlC2 was found to be achieved by the reactions among the intermediate phases of AlTi3, Al3Ti, AlTi and Ti2AlC, as well as the reactants in the starting powders.